NameDateSize

..17-May-201940

.checkpatch.confH A D21-Jan-2018684

.gitignoreH A D18-Jul-2018878

.mailmapH A D30-Aug-20181.4 KiB

.travis.ymlH A D16-Nov-201814.9 KiB

api/H30-Jun-201813

arch/H06-Dec-201817

board/H26-Oct-2018191

cmd/H24-Nov-2018154

common/H24-Nov-201871

config.mkH A D19-Nov-20182.1 KiB

configs/H06-Dec-20181.3 KiB

disk/H16-Nov-201814

doc/H17-Nov-2018174

Documentation/H30-Aug-201813

drivers/H16-Nov-201863

dts/H03-Oct-20184

env/H17-Oct-201823

examples/H30-Jun-20185

fs/H17-Nov-201817

include/H24-Nov-2018438

KbuildH A D23-Aug-20161.8 KiB

KconfigH A D06-Dec-201817.1 KiB

lib/H24-Nov-201880

Licenses/H30-Jun-201815

MAINTAINERSH A D06-Dec-201818 KiB

MakefileH A D06-Dec-201862.4 KiB

net/H12-Oct-201833

post/H30-Jun-20188

READMEH A D06-Dec-2018176.7 KiB

scripts/H17-Nov-201844

test/H12-Oct-201824

tools/H17-Nov-2018107

README

1# SPDX-License-Identifier: GPL-2.0+
2#
3# (C) Copyright 2000 - 2013
4# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
5
6Summary:
7========
8
9This directory contains the source code for U-Boot, a boot loader for
10Embedded boards based on PowerPC, ARM, MIPS and several other
11processors, which can be installed in a boot ROM and used to
12initialize and test the hardware or to download and run application
13code.
14
15The development of U-Boot is closely related to Linux: some parts of
16the source code originate in the Linux source tree, we have some
17header files in common, and special provision has been made to
18support booting of Linux images.
19
20Some attention has been paid to make this software easily
21configurable and extendable. For instance, all monitor commands are
22implemented with the same call interface, so that it's very easy to
23add new commands. Also, instead of permanently adding rarely used
24code (for instance hardware test utilities) to the monitor, you can
25load and run it dynamically.
26
27
28Status:
29=======
30
31In general, all boards for which a configuration option exists in the
32Makefile have been tested to some extent and can be considered
33"working". In fact, many of them are used in production systems.
34
35In case of problems see the CHANGELOG file to find out who contributed
36the specific port. In addition, there are various MAINTAINERS files
37scattered throughout the U-Boot source identifying the people or
38companies responsible for various boards and subsystems.
39
40Note: As of August, 2010, there is no longer a CHANGELOG file in the
41actual U-Boot source tree; however, it can be created dynamically
42from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot, you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see http://lists.denx.de/pipermail/u-boot and
55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
56
57
58Where to get source code:
59=========================
60
61The U-Boot source code is maintained in the Git repository at
62git://www.denx.de/git/u-boot.git ; you can browse it online at
63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
64
65The "snapshot" links on this page allow you to download tarballs of
66any version you might be interested in. Official releases are also
67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
68directory.
69
70Pre-built (and tested) images are available from
71ftp://ftp.denx.de/pub/u-boot/images/
72
73
74Where we come from:
75===================
76
77- start from 8xxrom sources
78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
79- clean up code
80- make it easier to add custom boards
81- make it possible to add other [PowerPC] CPUs
82- extend functions, especially:
83  * Provide extended interface to Linux boot loader
84  * S-Record download
85  * network boot
86  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
87- create ARMBoot project (http://sourceforge.net/projects/armboot)
88- add other CPU families (starting with ARM)
89- create U-Boot project (http://sourceforge.net/projects/u-boot)
90- current project page: see http://www.denx.de/wiki/U-Boot
91
92
93Names and Spelling:
94===================
95
96The "official" name of this project is "Das U-Boot". The spelling
97"U-Boot" shall be used in all written text (documentation, comments
98in source files etc.). Example:
99
100	This is the README file for the U-Boot project.
101
102File names etc. shall be based on the string "u-boot". Examples:
103
104	include/asm-ppc/u-boot.h
105
106	#include <asm/u-boot.h>
107
108Variable names, preprocessor constants etc. shall be either based on
109the string "u_boot" or on "U_BOOT". Example:
110
111	U_BOOT_VERSION		u_boot_logo
112	IH_OS_U_BOOT		u_boot_hush_start
113
114
115Versioning:
116===========
117
118Starting with the release in October 2008, the names of the releases
119were changed from numerical release numbers without deeper meaning
120into a time stamp based numbering. Regular releases are identified by
121names consisting of the calendar year and month of the release date.
122Additional fields (if present) indicate release candidates or bug fix
123releases in "stable" maintenance trees.
124
125Examples:
126	U-Boot v2009.11	    - Release November 2009
127	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
128	U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
129
130
131Directory Hierarchy:
132====================
133
134/arch			Architecture specific files
135  /arc			Files generic to ARC architecture
136  /arm			Files generic to ARM architecture
137  /m68k			Files generic to m68k architecture
138  /microblaze		Files generic to microblaze architecture
139  /mips			Files generic to MIPS architecture
140  /nds32		Files generic to NDS32 architecture
141  /nios2		Files generic to Altera NIOS2 architecture
142  /openrisc		Files generic to OpenRISC architecture
143  /powerpc		Files generic to PowerPC architecture
144  /riscv		Files generic to RISC-V architecture
145  /sandbox		Files generic to HW-independent "sandbox"
146  /sh			Files generic to SH architecture
147  /x86			Files generic to x86 architecture
148/api			Machine/arch independent API for external apps
149/board			Board dependent files
150/cmd			U-Boot commands functions
151/common			Misc architecture independent functions
152/configs		Board default configuration files
153/disk			Code for disk drive partition handling
154/doc			Documentation (don't expect too much)
155/drivers		Commonly used device drivers
156/dts			Contains Makefile for building internal U-Boot fdt.
157/examples		Example code for standalone applications, etc.
158/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
159/include		Header Files
160/lib			Library routines generic to all architectures
161/Licenses		Various license files
162/net			Networking code
163/post			Power On Self Test
164/scripts		Various build scripts and Makefiles
165/test			Various unit test files
166/tools			Tools to build S-Record or U-Boot images, etc.
167
168Software Configuration:
169=======================
170
171Configuration is usually done using C preprocessor defines; the
172rationale behind that is to avoid dead code whenever possible.
173
174There are two classes of configuration variables:
175
176* Configuration _OPTIONS_:
177  These are selectable by the user and have names beginning with
178  "CONFIG_".
179
180* Configuration _SETTINGS_:
181  These depend on the hardware etc. and should not be meddled with if
182  you don't know what you're doing; they have names beginning with
183  "CONFIG_SYS_".
184
185Previously, all configuration was done by hand, which involved creating
186symbolic links and editing configuration files manually. More recently,
187U-Boot has added the Kbuild infrastructure used by the Linux kernel,
188allowing you to use the "make menuconfig" command to configure your
189build.
190
191
192Selection of Processor Architecture and Board Type:
193---------------------------------------------------
194
195For all supported boards there are ready-to-use default
196configurations available; just type "make <board_name>_defconfig".
197
198Example: For a TQM823L module type:
199
200	cd u-boot
201	make TQM823L_defconfig
202
203Note: If you're looking for the default configuration file for a board
204you're sure used to be there but is now missing, check the file
205doc/README.scrapyard for a list of no longer supported boards.
206
207Sandbox Environment:
208--------------------
209
210U-Boot can be built natively to run on a Linux host using the 'sandbox'
211board. This allows feature development which is not board- or architecture-
212specific to be undertaken on a native platform. The sandbox is also used to
213run some of U-Boot's tests.
214
215See board/sandbox/README.sandbox for more details.
216
217
218Board Initialisation Flow:
219--------------------------
220
221This is the intended start-up flow for boards. This should apply for both
222SPL and U-Boot proper (i.e. they both follow the same rules).
223
224Note: "SPL" stands for "Secondary Program Loader," which is explained in
225more detail later in this file.
226
227At present, SPL mostly uses a separate code path, but the function names
228and roles of each function are the same. Some boards or architectures
229may not conform to this.  At least most ARM boards which use
230CONFIG_SPL_FRAMEWORK conform to this.
231
232Execution typically starts with an architecture-specific (and possibly
233CPU-specific) start.S file, such as:
234
235	- arch/arm/cpu/armv7/start.S
236	- arch/powerpc/cpu/mpc83xx/start.S
237	- arch/mips/cpu/start.S
238
239and so on. From there, three functions are called; the purpose and
240limitations of each of these functions are described below.
241
242lowlevel_init():
243	- purpose: essential init to permit execution to reach board_init_f()
244	- no global_data or BSS
245	- there is no stack (ARMv7 may have one but it will soon be removed)
246	- must not set up SDRAM or use console
247	- must only do the bare minimum to allow execution to continue to
248		board_init_f()
249	- this is almost never needed
250	- return normally from this function
251
252board_init_f():
253	- purpose: set up the machine ready for running board_init_r():
254		i.e. SDRAM and serial UART
255	- global_data is available
256	- stack is in SRAM
257	- BSS is not available, so you cannot use global/static variables,
258		only stack variables and global_data
259
260	Non-SPL-specific notes:
261	- dram_init() is called to set up DRAM. If already done in SPL this
262		can do nothing
263
264	SPL-specific notes:
265	- you can override the entire board_init_f() function with your own
266		version as needed.
267	- preloader_console_init() can be called here in extremis
268	- should set up SDRAM, and anything needed to make the UART work
269	- these is no need to clear BSS, it will be done by crt0.S
270	- must return normally from this function (don't call board_init_r()
271		directly)
272
273Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
274this point the stack and global_data are relocated to below
275CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
276memory.
277
278board_init_r():
279	- purpose: main execution, common code
280	- global_data is available
281	- SDRAM is available
282	- BSS is available, all static/global variables can be used
283	- execution eventually continues to main_loop()
284
285	Non-SPL-specific notes:
286	- U-Boot is relocated to the top of memory and is now running from
287		there.
288
289	SPL-specific notes:
290	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
291		CONFIG_SPL_STACK_R_ADDR points into SDRAM
292	- preloader_console_init() can be called here - typically this is
293		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
294		spl_board_init() function containing this call
295	- loads U-Boot or (in falcon mode) Linux
296
297
298
299Configuration Options:
300----------------------
301
302Configuration depends on the combination of board and CPU type; all
303such information is kept in a configuration file
304"include/configs/<board_name>.h".
305
306Example: For a TQM823L module, all configuration settings are in
307"include/configs/TQM823L.h".
308
309
310Many of the options are named exactly as the corresponding Linux
311kernel configuration options. The intention is to make it easier to
312build a config tool - later.
313
314- ARM Platform Bus Type(CCI):
315		CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
316		provides full cache coherency between two clusters of multi-core
317		CPUs and I/O coherency for devices and I/O masters
318
319		CONFIG_SYS_FSL_HAS_CCI400
320
321		Defined For SoC that has cache coherent interconnect
322		CCN-400
323
324		CONFIG_SYS_FSL_HAS_CCN504
325
326		Defined for SoC that has cache coherent interconnect CCN-504
327
328The following options need to be configured:
329
330- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
331
332- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
333
334- 85xx CPU Options:
335		CONFIG_SYS_PPC64
336
337		Specifies that the core is a 64-bit PowerPC implementation (implements
338		the "64" category of the Power ISA). This is necessary for ePAPR
339		compliance, among other possible reasons.
340
341		CONFIG_SYS_FSL_TBCLK_DIV
342
343		Defines the core time base clock divider ratio compared to the
344		system clock.  On most PQ3 devices this is 8, on newer QorIQ
345		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
346
347		CONFIG_SYS_FSL_PCIE_COMPAT
348
349		Defines the string to utilize when trying to match PCIe device
350		tree nodes for the given platform.
351
352		CONFIG_SYS_FSL_ERRATUM_A004510
353
354		Enables a workaround for erratum A004510.  If set,
355		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
356		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
357
358		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
359		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
360
361		Defines one or two SoC revisions (low 8 bits of SVR)
362		for which the A004510 workaround should be applied.
363
364		The rest of SVR is either not relevant to the decision
365		of whether the erratum is present (e.g. p2040 versus
366		p2041) or is implied by the build target, which controls
367		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
368
369		See Freescale App Note 4493 for more information about
370		this erratum.
371
372		CONFIG_A003399_NOR_WORKAROUND
373		Enables a workaround for IFC erratum A003399. It is only
374		required during NOR boot.
375
376		CONFIG_A008044_WORKAROUND
377		Enables a workaround for T1040/T1042 erratum A008044. It is only
378		required during NAND boot and valid for Rev 1.0 SoC revision
379
380		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
381
382		This is the value to write into CCSR offset 0x18600
383		according to the A004510 workaround.
384
385		CONFIG_SYS_FSL_DSP_DDR_ADDR
386		This value denotes start offset of DDR memory which is
387		connected exclusively to the DSP cores.
388
389		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
390		This value denotes start offset of M2 memory
391		which is directly connected to the DSP core.
392
393		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
394		This value denotes start offset of M3 memory which is directly
395		connected to the DSP core.
396
397		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
398		This value denotes start offset of DSP CCSR space.
399
400		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
401		Single Source Clock is clocking mode present in some of FSL SoC's.
402		In this mode, a single differential clock is used to supply
403		clocks to the sysclock, ddrclock and usbclock.
404
405		CONFIG_SYS_CPC_REINIT_F
406		This CONFIG is defined when the CPC is configured as SRAM at the
407		time of U-Boot entry and is required to be re-initialized.
408
409		CONFIG_DEEP_SLEEP
410		Indicates this SoC supports deep sleep feature. If deep sleep is
411		supported, core will start to execute uboot when wakes up.
412
413- Generic CPU options:
414		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
415
416		Defines the endianess of the CPU. Implementation of those
417		values is arch specific.
418
419		CONFIG_SYS_FSL_DDR
420		Freescale DDR driver in use. This type of DDR controller is
421		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
422		SoCs.
423
424		CONFIG_SYS_FSL_DDR_ADDR
425		Freescale DDR memory-mapped register base.
426
427		CONFIG_SYS_FSL_DDR_EMU
428		Specify emulator support for DDR. Some DDR features such as
429		deskew training are not available.
430
431		CONFIG_SYS_FSL_DDRC_GEN1
432		Freescale DDR1 controller.
433
434		CONFIG_SYS_FSL_DDRC_GEN2
435		Freescale DDR2 controller.
436
437		CONFIG_SYS_FSL_DDRC_GEN3
438		Freescale DDR3 controller.
439
440		CONFIG_SYS_FSL_DDRC_GEN4
441		Freescale DDR4 controller.
442
443		CONFIG_SYS_FSL_DDRC_ARM_GEN3
444		Freescale DDR3 controller for ARM-based SoCs.
445
446		CONFIG_SYS_FSL_DDR1
447		Board config to use DDR1. It can be enabled for SoCs with
448		Freescale DDR1 or DDR2 controllers, depending on the board
449		implemetation.
450
451		CONFIG_SYS_FSL_DDR2
452		Board config to use DDR2. It can be enabled for SoCs with
453		Freescale DDR2 or DDR3 controllers, depending on the board
454		implementation.
455
456		CONFIG_SYS_FSL_DDR3
457		Board config to use DDR3. It can be enabled for SoCs with
458		Freescale DDR3 or DDR3L controllers.
459
460		CONFIG_SYS_FSL_DDR3L
461		Board config to use DDR3L. It can be enabled for SoCs with
462		DDR3L controllers.
463
464		CONFIG_SYS_FSL_DDR4
465		Board config to use DDR4. It can be enabled for SoCs with
466		DDR4 controllers.
467
468		CONFIG_SYS_FSL_IFC_BE
469		Defines the IFC controller register space as Big Endian
470
471		CONFIG_SYS_FSL_IFC_LE
472		Defines the IFC controller register space as Little Endian
473
474		CONFIG_SYS_FSL_IFC_CLK_DIV
475		Defines divider of platform clock(clock input to IFC controller).
476
477		CONFIG_SYS_FSL_LBC_CLK_DIV
478		Defines divider of platform clock(clock input to eLBC controller).
479
480		CONFIG_SYS_FSL_PBL_PBI
481		It enables addition of RCW (Power on reset configuration) in built image.
482		Please refer doc/README.pblimage for more details
483
484		CONFIG_SYS_FSL_PBL_RCW
485		It adds PBI(pre-boot instructions) commands in u-boot build image.
486		PBI commands can be used to configure SoC before it starts the execution.
487		Please refer doc/README.pblimage for more details
488
489		CONFIG_SPL_FSL_PBL
490		It adds a target to create boot binary having SPL binary in PBI format
491		concatenated with u-boot binary.
492
493		CONFIG_SYS_FSL_DDR_BE
494		Defines the DDR controller register space as Big Endian
495
496		CONFIG_SYS_FSL_DDR_LE
497		Defines the DDR controller register space as Little Endian
498
499		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
500		Physical address from the view of DDR controllers. It is the
501		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
502		it could be different for ARM SoCs.
503
504		CONFIG_SYS_FSL_DDR_INTLV_256B
505		DDR controller interleaving on 256-byte. This is a special
506		interleaving mode, handled by Dickens for Freescale layerscape
507		SoCs with ARM core.
508
509		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
510		Number of controllers used as main memory.
511
512		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
513		Number of controllers used for other than main memory.
514
515		CONFIG_SYS_FSL_HAS_DP_DDR
516		Defines the SoC has DP-DDR used for DPAA.
517
518		CONFIG_SYS_FSL_SEC_BE
519		Defines the SEC controller register space as Big Endian
520
521		CONFIG_SYS_FSL_SEC_LE
522		Defines the SEC controller register space as Little Endian
523
524- MIPS CPU options:
525		CONFIG_SYS_INIT_SP_OFFSET
526
527		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
528		pointer. This is needed for the temporary stack before
529		relocation.
530
531		CONFIG_XWAY_SWAP_BYTES
532
533		Enable compilation of tools/xway-swap-bytes needed for Lantiq
534		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
535		be swapped if a flash programmer is used.
536
537- ARM options:
538		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
539
540		Select high exception vectors of the ARM core, e.g., do not
541		clear the V bit of the c1 register of CP15.
542
543		COUNTER_FREQUENCY
544		Generic timer clock source frequency.
545
546		COUNTER_FREQUENCY_REAL
547		Generic timer clock source frequency if the real clock is
548		different from COUNTER_FREQUENCY, and can only be determined
549		at run time.
550
551- Tegra SoC options:
552		CONFIG_TEGRA_SUPPORT_NON_SECURE
553
554		Support executing U-Boot in non-secure (NS) mode. Certain
555		impossible actions will be skipped if the CPU is in NS mode,
556		such as ARM architectural timer initialization.
557
558- Linux Kernel Interface:
559		CONFIG_CLOCKS_IN_MHZ
560
561		U-Boot stores all clock information in Hz
562		internally. For binary compatibility with older Linux
563		kernels (which expect the clocks passed in the
564		bd_info data to be in MHz) the environment variable
565		"clocks_in_mhz" can be defined so that U-Boot
566		converts clock data to MHZ before passing it to the
567		Linux kernel.
568		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
569		"clocks_in_mhz=1" is automatically included in the
570		default environment.
571
572		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
573
574		When transferring memsize parameter to Linux, some versions
575		expect it to be in bytes, others in MB.
576		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
577
578		CONFIG_OF_LIBFDT
579
580		New kernel versions are expecting firmware settings to be
581		passed using flattened device trees (based on open firmware
582		concepts).
583
584		CONFIG_OF_LIBFDT
585		 * New libfdt-based support
586		 * Adds the "fdt" command
587		 * The bootm command automatically updates the fdt
588
589		OF_TBCLK - The timebase frequency.
590		OF_STDOUT_PATH - The path to the console device
591
592		boards with QUICC Engines require OF_QE to set UCC MAC
593		addresses
594
595		CONFIG_OF_BOARD_SETUP
596
597		Board code has addition modification that it wants to make
598		to the flat device tree before handing it off to the kernel
599
600		CONFIG_OF_SYSTEM_SETUP
601
602		Other code has addition modification that it wants to make
603		to the flat device tree before handing it off to the kernel.
604		This causes ft_system_setup() to be called before booting
605		the kernel.
606
607		CONFIG_OF_IDE_FIXUP
608
609		U-Boot can detect if an IDE device is present or not.
610		If not, and this new config option is activated, U-Boot
611		removes the ATA node from the DTS before booting Linux,
612		so the Linux IDE driver does not probe the device and
613		crash. This is needed for buggy hardware (uc101) where
614		no pull down resistor is connected to the signal IDE5V_DD7.
615
616		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
617
618		This setting is mandatory for all boards that have only one
619		machine type and must be used to specify the machine type
620		number as it appears in the ARM machine registry
621		(see http://www.arm.linux.org.uk/developer/machines/).
622		Only boards that have multiple machine types supported
623		in a single configuration file and the machine type is
624		runtime discoverable, do not have to use this setting.
625
626- vxWorks boot parameters:
627
628		bootvx constructs a valid bootline using the following
629		environments variables: bootdev, bootfile, ipaddr, netmask,
630		serverip, gatewayip, hostname, othbootargs.
631		It loads the vxWorks image pointed bootfile.
632
633		Note: If a "bootargs" environment is defined, it will overwride
634		the defaults discussed just above.
635
636- Cache Configuration:
637		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
638		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
639		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
640
641- Cache Configuration for ARM:
642		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
643				      controller
644		CONFIG_SYS_PL310_BASE - Physical base address of PL310
645					controller register space
646
647- Serial Ports:
648		CONFIG_PL010_SERIAL
649
650		Define this if you want support for Amba PrimeCell PL010 UARTs.
651
652		CONFIG_PL011_SERIAL
653
654		Define this if you want support for Amba PrimeCell PL011 UARTs.
655
656		CONFIG_PL011_CLOCK
657
658		If you have Amba PrimeCell PL011 UARTs, set this variable to
659		the clock speed of the UARTs.
660
661		CONFIG_PL01x_PORTS
662
663		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
664		define this to a list of base addresses for each (supported)
665		port. See e.g. include/configs/versatile.h
666
667		CONFIG_SERIAL_HW_FLOW_CONTROL
668
669		Define this variable to enable hw flow control in serial driver.
670		Current user of this option is drivers/serial/nsl16550.c driver
671
672- Console Baudrate:
673		CONFIG_BAUDRATE - in bps
674		Select one of the baudrates listed in
675		CONFIG_SYS_BAUDRATE_TABLE, see below.
676
677- Autoboot Command:
678		CONFIG_BOOTCOMMAND
679		Only needed when CONFIG_BOOTDELAY is enabled;
680		define a command string that is automatically executed
681		when no character is read on the console interface
682		within "Boot Delay" after reset.
683
684		CONFIG_RAMBOOT and CONFIG_NFSBOOT
685		The value of these goes into the environment as
686		"ramboot" and "nfsboot" respectively, and can be used
687		as a convenience, when switching between booting from
688		RAM and NFS.
689
690- Pre-Boot Commands:
691		CONFIG_PREBOOT
692
693		When this option is #defined, the existence of the
694		environment variable "preboot" will be checked
695		immediately before starting the CONFIG_BOOTDELAY
696		countdown and/or running the auto-boot command resp.
697		entering interactive mode.
698
699		This feature is especially useful when "preboot" is
700		automatically generated or modified. For an example
701		see the LWMON board specific code: here "preboot" is
702		modified when the user holds down a certain
703		combination of keys on the (special) keyboard when
704		booting the systems
705
706- Serial Download Echo Mode:
707		CONFIG_LOADS_ECHO
708		If defined to 1, all characters received during a
709		serial download (using the "loads" command) are
710		echoed back. This might be needed by some terminal
711		emulations (like "cu"), but may as well just take
712		time on others. This setting #define's the initial
713		value of the "loads_echo" environment variable.
714
715- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
716		CONFIG_KGDB_BAUDRATE
717		Select one of the baudrates listed in
718		CONFIG_SYS_BAUDRATE_TABLE, see below.
719
720- Removal of commands
721		If no commands are needed to boot, you can disable
722		CONFIG_CMDLINE to remove them. In this case, the command line
723		will not be available, and when U-Boot wants to execute the
724		boot command (on start-up) it will call board_run_command()
725		instead. This can reduce image size significantly for very
726		simple boot procedures.
727
728- Regular expression support:
729		CONFIG_REGEX
730		If this variable is defined, U-Boot is linked against
731		the SLRE (Super Light Regular Expression) library,
732		which adds regex support to some commands, as for
733		example "env grep" and "setexpr".
734
735- Device tree:
736		CONFIG_OF_CONTROL
737		If this variable is defined, U-Boot will use a device tree
738		to configure its devices, instead of relying on statically
739		compiled #defines in the board file. This option is
740		experimental and only available on a few boards. The device
741		tree is available in the global data as gd->fdt_blob.
742
743		U-Boot needs to get its device tree from somewhere. This can
744		be done using one of the three options below:
745
746		CONFIG_OF_EMBED
747		If this variable is defined, U-Boot will embed a device tree
748		binary in its image. This device tree file should be in the
749		board directory and called <soc>-<board>.dts. The binary file
750		is then picked up in board_init_f() and made available through
751		the global data structure as gd->fdt_blob.
752
753		CONFIG_OF_SEPARATE
754		If this variable is defined, U-Boot will build a device tree
755		binary. It will be called u-boot.dtb. Architecture-specific
756		code will locate it at run-time. Generally this works by:
757
758			cat u-boot.bin u-boot.dtb >image.bin
759
760		and in fact, U-Boot does this for you, creating a file called
761		u-boot-dtb.bin which is useful in the common case. You can
762		still use the individual files if you need something more
763		exotic.
764
765		CONFIG_OF_BOARD
766		If this variable is defined, U-Boot will use the device tree
767		provided by the board at runtime instead of embedding one with
768		the image. Only boards defining board_fdt_blob_setup() support
769		this option (see include/fdtdec.h file).
770
771- Watchdog:
772		CONFIG_WATCHDOG
773		If this variable is defined, it enables watchdog
774		support for the SoC. There must be support in the SoC
775		specific code for a watchdog. For the 8xx
776		CPUs, the SIU Watchdog feature is enabled in the SYPCR
777		register.  When supported for a specific SoC is
778		available, then no further board specific code should
779		be needed to use it.
780
781		CONFIG_HW_WATCHDOG
782		When using a watchdog circuitry external to the used
783		SoC, then define this variable and provide board
784		specific code for the "hw_watchdog_reset" function.
785
786		CONFIG_AT91_HW_WDT_TIMEOUT
787		specify the timeout in seconds. default 2 seconds.
788
789- Real-Time Clock:
790
791		When CONFIG_CMD_DATE is selected, the type of the RTC
792		has to be selected, too. Define exactly one of the
793		following options:
794
795		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
796		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
797		CONFIG_RTC_MC146818	- use MC146818 RTC
798		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
799		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
800		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
801		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
802		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
803		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
804		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
805		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
806		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
807					  RV3029 RTC.
808
809		Note that if the RTC uses I2C, then the I2C interface
810		must also be configured. See I2C Support, below.
811
812- GPIO Support:
813		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
814
815		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
816		chip-ngpio pairs that tell the PCA953X driver the number of
817		pins supported by a particular chip.
818
819		Note that if the GPIO device uses I2C, then the I2C interface
820		must also be configured. See I2C Support, below.
821
822- I/O tracing:
823		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
824		accesses and can checksum them or write a list of them out
825		to memory. See the 'iotrace' command for details. This is
826		useful for testing device drivers since it can confirm that
827		the driver behaves the same way before and after a code
828		change. Currently this is supported on sandbox and arm. To
829		add support for your architecture, add '#include <iotrace.h>'
830		to the bottom of arch/<arch>/include/asm/io.h and test.
831
832		Example output from the 'iotrace stats' command is below.
833		Note that if the trace buffer is exhausted, the checksum will
834		still continue to operate.
835
836			iotrace is enabled
837			Start:  10000000	(buffer start address)
838			Size:   00010000	(buffer size)
839			Offset: 00000120	(current buffer offset)
840			Output: 10000120	(start + offset)
841			Count:  00000018	(number of trace records)
842			CRC32:  9526fb66	(CRC32 of all trace records)
843
844- Timestamp Support:
845
846		When CONFIG_TIMESTAMP is selected, the timestamp
847		(date and time) of an image is printed by image
848		commands like bootm or iminfo. This option is
849		automatically enabled when you select CONFIG_CMD_DATE .
850
851- Partition Labels (disklabels) Supported:
852		Zero or more of the following:
853		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
854		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
855		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
856				       bootloader.  Note 2TB partition limit; see
857				       disk/part_efi.c
858		CONFIG_SCSI) you must configure support for at
859		least one non-MTD partition type as well.
860
861- IDE Reset method:
862		CONFIG_IDE_RESET_ROUTINE - this is defined in several
863		board configurations files but used nowhere!
864
865		CONFIG_IDE_RESET - is this is defined, IDE Reset will
866		be performed by calling the function
867			ide_set_reset(int reset)
868		which has to be defined in a board specific file
869
870- ATAPI Support:
871		CONFIG_ATAPI
872
873		Set this to enable ATAPI support.
874
875- LBA48 Support
876		CONFIG_LBA48
877
878		Set this to enable support for disks larger than 137GB
879		Also look at CONFIG_SYS_64BIT_LBA.
880		Whithout these , LBA48 support uses 32bit variables and will 'only'
881		support disks up to 2.1TB.
882
883		CONFIG_SYS_64BIT_LBA:
884			When enabled, makes the IDE subsystem use 64bit sector addresses.
885			Default is 32bit.
886
887- SCSI Support:
888		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
889		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
890		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
891		maximum numbers of LUNs, SCSI ID's and target
892		devices.
893
894		The environment variable 'scsidevs' is set to the number of
895		SCSI devices found during the last scan.
896
897- NETWORK Support (PCI):
898		CONFIG_E1000
899		Support for Intel 8254x/8257x gigabit chips.
900
901		CONFIG_E1000_SPI
902		Utility code for direct access to the SPI bus on Intel 8257x.
903		This does not do anything useful unless you set at least one
904		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
905
906		CONFIG_E1000_SPI_GENERIC
907		Allow generic access to the SPI bus on the Intel 8257x, for
908		example with the "sspi" command.
909
910		CONFIG_EEPRO100
911		Support for Intel 82557/82559/82559ER chips.
912		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
913		write routine for first time initialisation.
914
915		CONFIG_TULIP
916		Support for Digital 2114x chips.
917		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
918		modem chip initialisation (KS8761/QS6611).
919
920		CONFIG_NATSEMI
921		Support for National dp83815 chips.
922
923		CONFIG_NS8382X
924		Support for National dp8382[01] gigabit chips.
925
926- NETWORK Support (other):
927
928		CONFIG_DRIVER_AT91EMAC
929		Support for AT91RM9200 EMAC.
930
931			CONFIG_RMII
932			Define this to use reduced MII inteface
933
934			CONFIG_DRIVER_AT91EMAC_QUIET
935			If this defined, the driver is quiet.
936			The driver doen't show link status messages.
937
938		CONFIG_CALXEDA_XGMAC
939		Support for the Calxeda XGMAC device
940
941		CONFIG_LAN91C96
942		Support for SMSC's LAN91C96 chips.
943
944			CONFIG_LAN91C96_USE_32_BIT
945			Define this to enable 32 bit addressing
946
947		CONFIG_SMC91111
948		Support for SMSC's LAN91C111 chip
949
950			CONFIG_SMC91111_BASE
951			Define this to hold the physical address
952			of the device (I/O space)
953
954			CONFIG_SMC_USE_32_BIT
955			Define this if data bus is 32 bits
956
957			CONFIG_SMC_USE_IOFUNCS
958			Define this to use i/o functions instead of macros
959			(some hardware wont work with macros)
960
961			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
962			Define this if you have more then 3 PHYs.
963
964		CONFIG_FTGMAC100
965		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
966
967			CONFIG_FTGMAC100_EGIGA
968			Define this to use GE link update with gigabit PHY.
969			Define this if FTGMAC100 is connected to gigabit PHY.
970			If your system has 10/100 PHY only, it might not occur
971			wrong behavior. Because PHY usually return timeout or
972			useless data when polling gigabit status and gigabit
973			control registers. This behavior won't affect the
974			correctnessof 10/100 link speed update.
975
976		CONFIG_SH_ETHER
977		Support for Renesas on-chip Ethernet controller
978
979			CONFIG_SH_ETHER_USE_PORT
980			Define the number of ports to be used
981
982			CONFIG_SH_ETHER_PHY_ADDR
983			Define the ETH PHY's address
984
985			CONFIG_SH_ETHER_CACHE_WRITEBACK
986			If this option is set, the driver enables cache flush.
987
988- PWM Support:
989		CONFIG_PWM_IMX
990		Support for PWM module on the imx6.
991
992- TPM Support:
993		CONFIG_TPM
994		Support TPM devices.
995
996		CONFIG_TPM_TIS_INFINEON
997		Support for Infineon i2c bus TPM devices. Only one device
998		per system is supported at this time.
999
1000			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1001			Define the burst count bytes upper limit
1002
1003		CONFIG_TPM_ST33ZP24
1004		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1005
1006			CONFIG_TPM_ST33ZP24_I2C
1007			Support for STMicroelectronics ST33ZP24 I2C devices.
1008			Requires TPM_ST33ZP24 and I2C.
1009
1010			CONFIG_TPM_ST33ZP24_SPI
1011			Support for STMicroelectronics ST33ZP24 SPI devices.
1012			Requires TPM_ST33ZP24 and SPI.
1013
1014		CONFIG_TPM_ATMEL_TWI
1015		Support for Atmel TWI TPM device. Requires I2C support.
1016
1017		CONFIG_TPM_TIS_LPC
1018		Support for generic parallel port TPM devices. Only one device
1019		per system is supported at this time.
1020
1021			CONFIG_TPM_TIS_BASE_ADDRESS
1022			Base address where the generic TPM device is mapped
1023			to. Contemporary x86 systems usually map it at
1024			0xfed40000.
1025
1026		CONFIG_TPM
1027		Define this to enable the TPM support library which provides
1028		functional interfaces to some TPM commands.
1029		Requires support for a TPM device.
1030
1031		CONFIG_TPM_AUTH_SESSIONS
1032		Define this to enable authorized functions in the TPM library.
1033		Requires CONFIG_TPM and CONFIG_SHA1.
1034
1035- USB Support:
1036		At the moment only the UHCI host controller is
1037		supported (PIP405, MIP405); define
1038		CONFIG_USB_UHCI to enable it.
1039		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1040		and define CONFIG_USB_STORAGE to enable the USB
1041		storage devices.
1042		Note:
1043		Supported are USB Keyboards and USB Floppy drives
1044		(TEAC FD-05PUB).
1045
1046		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1047		txfilltuning field in the EHCI controller on reset.
1048
1049		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1050		HW module registers.
1051
1052- USB Device:
1053		Define the below if you wish to use the USB console.
1054		Once firmware is rebuilt from a serial console issue the
1055		command "setenv stdin usbtty; setenv stdout usbtty" and
1056		attach your USB cable. The Unix command "dmesg" should print
1057		it has found a new device. The environment variable usbtty
1058		can be set to gserial or cdc_acm to enable your device to
1059		appear to a USB host as a Linux gserial device or a
1060		Common Device Class Abstract Control Model serial device.
1061		If you select usbtty = gserial you should be able to enumerate
1062		a Linux host by
1063		# modprobe usbserial vendor=0xVendorID product=0xProductID
1064		else if using cdc_acm, simply setting the environment
1065		variable usbtty to be cdc_acm should suffice. The following
1066		might be defined in YourBoardName.h
1067
1068			CONFIG_USB_DEVICE
1069			Define this to build a UDC device
1070
1071			CONFIG_USB_TTY
1072			Define this to have a tty type of device available to
1073			talk to the UDC device
1074
1075			CONFIG_USBD_HS
1076			Define this to enable the high speed support for usb
1077			device and usbtty. If this feature is enabled, a routine
1078			int is_usbd_high_speed(void)
1079			also needs to be defined by the driver to dynamically poll
1080			whether the enumeration has succeded at high speed or full
1081			speed.
1082
1083			CONFIG_SYS_CONSOLE_IS_IN_ENV
1084			Define this if you want stdin, stdout &/or stderr to
1085			be set to usbtty.
1086
1087		If you have a USB-IF assigned VendorID then you may wish to
1088		define your own vendor specific values either in BoardName.h
1089		or directly in usbd_vendor_info.h. If you don't define
1090		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1091		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1092		should pretend to be a Linux device to it's target host.
1093
1094			CONFIG_USBD_MANUFACTURER
1095			Define this string as the name of your company for
1096			- CONFIG_USBD_MANUFACTURER "my company"
1097
1098			CONFIG_USBD_PRODUCT_NAME
1099			Define this string as the name of your product
1100			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1101
1102			CONFIG_USBD_VENDORID
1103			Define this as your assigned Vendor ID from the USB
1104			Implementors Forum. This *must* be a genuine Vendor ID
1105			to avoid polluting the USB namespace.
1106			- CONFIG_USBD_VENDORID 0xFFFF
1107
1108			CONFIG_USBD_PRODUCTID
1109			Define this as the unique Product ID
1110			for your device
1111			- CONFIG_USBD_PRODUCTID 0xFFFF
1112
1113- ULPI Layer Support:
1114		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1115		the generic ULPI layer. The generic layer accesses the ULPI PHY
1116		via the platform viewport, so you need both the genric layer and
1117		the viewport enabled. Currently only Chipidea/ARC based
1118		viewport is supported.
1119		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1120		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1121		If your ULPI phy needs a different reference clock than the
1122		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1123		the appropriate value in Hz.
1124
1125- MMC Support:
1126		The MMC controller on the Intel PXA is supported. To
1127		enable this define CONFIG_MMC. The MMC can be
1128		accessed from the boot prompt by mapping the device
1129		to physical memory similar to flash. Command line is
1130		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1131		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1132
1133		CONFIG_SH_MMCIF
1134		Support for Renesas on-chip MMCIF controller
1135
1136			CONFIG_SH_MMCIF_ADDR
1137			Define the base address of MMCIF registers
1138
1139			CONFIG_SH_MMCIF_CLK
1140			Define the clock frequency for MMCIF
1141
1142		CONFIG_SUPPORT_EMMC_BOOT
1143		Enable some additional features of the eMMC boot partitions.
1144
1145- USB Device Firmware Update (DFU) class support:
1146		CONFIG_DFU_OVER_USB
1147		This enables the USB portion of the DFU USB class
1148
1149		CONFIG_DFU_MMC
1150		This enables support for exposing (e)MMC devices via DFU.
1151
1152		CONFIG_DFU_NAND
1153		This enables support for exposing NAND devices via DFU.
1154
1155		CONFIG_DFU_RAM
1156		This enables support for exposing RAM via DFU.
1157		Note: DFU spec refer to non-volatile memory usage, but
1158		allow usages beyond the scope of spec - here RAM usage,
1159		one that would help mostly the developer.
1160
1161		CONFIG_SYS_DFU_DATA_BUF_SIZE
1162		Dfu transfer uses a buffer before writing data to the
1163		raw storage device. Make the size (in bytes) of this buffer
1164		configurable. The size of this buffer is also configurable
1165		through the "dfu_bufsiz" environment variable.
1166
1167		CONFIG_SYS_DFU_MAX_FILE_SIZE
1168		When updating files rather than the raw storage device,
1169		we use a static buffer to copy the file into and then write
1170		the buffer once we've been given the whole file.  Define
1171		this to the maximum filesize (in bytes) for the buffer.
1172		Default is 4 MiB if undefined.
1173
1174		DFU_DEFAULT_POLL_TIMEOUT
1175		Poll timeout [ms], is the timeout a device can send to the
1176		host. The host must wait for this timeout before sending
1177		a subsequent DFU_GET_STATUS request to the device.
1178
1179		DFU_MANIFEST_POLL_TIMEOUT
1180		Poll timeout [ms], which the device sends to the host when
1181		entering dfuMANIFEST state. Host waits this timeout, before
1182		sending again an USB request to the device.
1183
1184- Journaling Flash filesystem support:
1185		CONFIG_JFFS2_NAND
1186		Define these for a default partition on a NAND device
1187
1188		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1189		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1190		Define these for a default partition on a NOR device
1191
1192- Keyboard Support:
1193		See Kconfig help for available keyboard drivers.
1194
1195		CONFIG_KEYBOARD
1196
1197		Define this to enable a custom keyboard support.
1198		This simply calls drv_keyboard_init() which must be
1199		defined in your board-specific files. This option is deprecated
1200		and is only used by novena. For new boards, use driver model
1201		instead.
1202
1203- Video support:
1204		CONFIG_FSL_DIU_FB
1205		Enable the Freescale DIU video driver.	Reference boards for
1206		SOCs that have a DIU should define this macro to enable DIU
1207		support, and should also define these other macros:
1208
1209			CONFIG_SYS_DIU_ADDR
1210			CONFIG_VIDEO
1211			CONFIG_CFB_CONSOLE
1212			CONFIG_VIDEO_SW_CURSOR
1213			CONFIG_VGA_AS_SINGLE_DEVICE
1214			CONFIG_VIDEO_LOGO
1215			CONFIG_VIDEO_BMP_LOGO
1216
1217		The DIU driver will look for the 'video-mode' environment
1218		variable, and if defined, enable the DIU as a console during
1219		boot.  See the documentation file doc/README.video for a
1220		description of this variable.
1221
1222- LCD Support:	CONFIG_LCD
1223
1224		Define this to enable LCD support (for output to LCD
1225		display); also select one of the supported displays
1226		by defining one of these:
1227
1228		CONFIG_ATMEL_LCD:
1229
1230			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1231
1232		CONFIG_NEC_NL6448AC33:
1233
1234			NEC NL6448AC33-18. Active, color, single scan.
1235
1236		CONFIG_NEC_NL6448BC20
1237
1238			NEC NL6448BC20-08. 6.5", 640x480.
1239			Active, color, single scan.
1240
1241		CONFIG_NEC_NL6448BC33_54
1242
1243			NEC NL6448BC33-54. 10.4", 640x480.
1244			Active, color, single scan.
1245
1246		CONFIG_SHARP_16x9
1247
1248			Sharp 320x240. Active, color, single scan.
1249			It isn't 16x9, and I am not sure what it is.
1250
1251		CONFIG_SHARP_LQ64D341
1252
1253			Sharp LQ64D341 display, 640x480.
1254			Active, color, single scan.
1255
1256		CONFIG_HLD1045
1257
1258			HLD1045 display, 640x480.
1259			Active, color, single scan.
1260
1261		CONFIG_OPTREX_BW
1262
1263			Optrex	 CBL50840-2 NF-FW 99 22 M5
1264			or
1265			Hitachi	 LMG6912RPFC-00T
1266			or
1267			Hitachi	 SP14Q002
1268
1269			320x240. Black & white.
1270
1271		CONFIG_LCD_ALIGNMENT
1272
1273		Normally the LCD is page-aligned (typically 4KB). If this is
1274		defined then the LCD will be aligned to this value instead.
1275		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1276		here, since it is cheaper to change data cache settings on
1277		a per-section basis.
1278
1279
1280		CONFIG_LCD_ROTATION
1281
1282		Sometimes, for example if the display is mounted in portrait
1283		mode or even if it's mounted landscape but rotated by 180degree,
1284		we need to rotate our content of the display relative to the
1285		framebuffer, so that user can read the messages which are
1286		printed out.
1287		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1288		initialized with a given rotation from "vl_rot" out of
1289		"vidinfo_t" which is provided by the board specific code.
1290		The value for vl_rot is coded as following (matching to
1291		fbcon=rotate:<n> linux-kernel commandline):
1292		0 = no rotation respectively 0 degree
1293		1 = 90 degree rotation
1294		2 = 180 degree rotation
1295		3 = 270 degree rotation
1296
1297		If CONFIG_LCD_ROTATION is not defined, the console will be
1298		initialized with 0degree rotation.
1299
1300		CONFIG_LCD_BMP_RLE8
1301
1302		Support drawing of RLE8-compressed bitmaps on the LCD.
1303
1304		CONFIG_I2C_EDID
1305
1306		Enables an 'i2c edid' command which can read EDID
1307		information over I2C from an attached LCD display.
1308
1309- Splash Screen Support: CONFIG_SPLASH_SCREEN
1310
1311		If this option is set, the environment is checked for
1312		a variable "splashimage". If found, the usual display
1313		of logo, copyright and system information on the LCD
1314		is suppressed and the BMP image at the address
1315		specified in "splashimage" is loaded instead. The
1316		console is redirected to the "nulldev", too. This
1317		allows for a "silent" boot where a splash screen is
1318		loaded very quickly after power-on.
1319
1320		CONFIG_SPLASHIMAGE_GUARD
1321
1322		If this option is set, then U-Boot will prevent the environment
1323		variable "splashimage" from being set to a problematic address
1324		(see doc/README.displaying-bmps).
1325		This option is useful for targets where, due to alignment
1326		restrictions, an improperly aligned BMP image will cause a data
1327		abort. If you think you will not have problems with unaligned
1328		accesses (for example because your toolchain prevents them)
1329		there is no need to set this option.
1330
1331		CONFIG_SPLASH_SCREEN_ALIGN
1332
1333		If this option is set the splash image can be freely positioned
1334		on the screen. Environment variable "splashpos" specifies the
1335		position as "x,y". If a positive number is given it is used as
1336		number of pixel from left/top. If a negative number is given it
1337		is used as number of pixel from right/bottom. You can also
1338		specify 'm' for centering the image.
1339
1340		Example:
1341		setenv splashpos m,m
1342			=> image at center of screen
1343
1344		setenv splashpos 30,20
1345			=> image at x = 30 and y = 20
1346
1347		setenv splashpos -10,m
1348			=> vertically centered image
1349			   at x = dspWidth - bmpWidth - 9
1350
1351- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1352
1353		If this option is set, additionally to standard BMP
1354		images, gzipped BMP images can be displayed via the
1355		splashscreen support or the bmp command.
1356
1357- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1358
1359		If this option is set, 8-bit RLE compressed BMP images
1360		can be displayed via the splashscreen support or the
1361		bmp command.
1362
1363- Compression support:
1364		CONFIG_GZIP
1365
1366		Enabled by default to support gzip compressed images.
1367
1368		CONFIG_BZIP2
1369
1370		If this option is set, support for bzip2 compressed
1371		images is included. If not, only uncompressed and gzip
1372		compressed images are supported.
1373
1374		NOTE: the bzip2 algorithm requires a lot of RAM, so
1375		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1376		be at least 4MB.
1377
1378- MII/PHY support:
1379		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1380
1381		The clock frequency of the MII bus
1382
1383		CONFIG_PHY_RESET_DELAY
1384
1385		Some PHY like Intel LXT971A need extra delay after
1386		reset before any MII register access is possible.
1387		For such PHY, set this option to the usec delay
1388		required. (minimum 300usec for LXT971A)
1389
1390		CONFIG_PHY_CMD_DELAY (ppc4xx)
1391
1392		Some PHY like Intel LXT971A need extra delay after
1393		command issued before MII status register can be read
1394
1395- IP address:
1396		CONFIG_IPADDR
1397
1398		Define a default value for the IP address to use for
1399		the default Ethernet interface, in case this is not
1400		determined through e.g. bootp.
1401		(Environment variable "ipaddr")
1402
1403- Server IP address:
1404		CONFIG_SERVERIP
1405
1406		Defines a default value for the IP address of a TFTP
1407		server to contact when using the "tftboot" command.
1408		(Environment variable "serverip")
1409
1410		CONFIG_KEEP_SERVERADDR
1411
1412		Keeps the server's MAC address, in the env 'serveraddr'
1413		for passing to bootargs (like Linux's netconsole option)
1414
1415- Gateway IP address:
1416		CONFIG_GATEWAYIP
1417
1418		Defines a default value for the IP address of the
1419		default router where packets to other networks are
1420		sent to.
1421		(Environment variable "gatewayip")
1422
1423- Subnet mask:
1424		CONFIG_NETMASK
1425
1426		Defines a default value for the subnet mask (or
1427		routing prefix) which is used to determine if an IP
1428		address belongs to the local subnet or needs to be
1429		forwarded through a router.
1430		(Environment variable "netmask")
1431
1432- Multicast TFTP Mode:
1433		CONFIG_MCAST_TFTP
1434
1435		Defines whether you want to support multicast TFTP as per
1436		rfc-2090; for example to work with atftp.  Lets lots of targets
1437		tftp down the same boot image concurrently.  Note: the Ethernet
1438		driver in use must provide a function: mcast() to join/leave a
1439		multicast group.
1440
1441- BOOTP Recovery Mode:
1442		CONFIG_BOOTP_RANDOM_DELAY
1443
1444		If you have many targets in a network that try to
1445		boot using BOOTP, you may want to avoid that all
1446		systems send out BOOTP requests at precisely the same
1447		moment (which would happen for instance at recovery
1448		from a power failure, when all systems will try to
1449		boot, thus flooding the BOOTP server. Defining
1450		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1451		inserted before sending out BOOTP requests. The
1452		following delays are inserted then:
1453
1454		1st BOOTP request:	delay 0 ... 1 sec
1455		2nd BOOTP request:	delay 0 ... 2 sec
1456		3rd BOOTP request:	delay 0 ... 4 sec
1457		4th and following
1458		BOOTP requests:		delay 0 ... 8 sec
1459
1460		CONFIG_BOOTP_ID_CACHE_SIZE
1461
1462		BOOTP packets are uniquely identified using a 32-bit ID. The
1463		server will copy the ID from client requests to responses and
1464		U-Boot will use this to determine if it is the destination of
1465		an incoming response. Some servers will check that addresses
1466		aren't in use before handing them out (usually using an ARP
1467		ping) and therefore take up to a few hundred milliseconds to
1468		respond. Network congestion may also influence the time it
1469		takes for a response to make it back to the client. If that
1470		time is too long, U-Boot will retransmit requests. In order
1471		to allow earlier responses to still be accepted after these
1472		retransmissions, U-Boot's BOOTP client keeps a small cache of
1473		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1474		cache. The default is to keep IDs for up to four outstanding
1475		requests. Increasing this will allow U-Boot to accept offers
1476		from a BOOTP client in networks with unusually high latency.
1477
1478- DHCP Advanced Options:
1479		You can fine tune the DHCP functionality by defining
1480		CONFIG_BOOTP_* symbols:
1481
1482		CONFIG_BOOTP_NISDOMAIN
1483		CONFIG_BOOTP_BOOTFILESIZE
1484		CONFIG_BOOTP_SEND_HOSTNAME
1485		CONFIG_BOOTP_NTPSERVER
1486		CONFIG_BOOTP_TIMEOFFSET
1487		CONFIG_BOOTP_VENDOREX
1488		CONFIG_BOOTP_MAY_FAIL
1489
1490		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1491		environment variable, not the BOOTP server.
1492
1493		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1494		after the configured retry count, the call will fail
1495		instead of starting over.  This can be used to fail over
1496		to Link-local IP address configuration if the DHCP server
1497		is not available.
1498
1499		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1500		to do a dynamic update of a DNS server. To do this, they
1501		need the hostname of the DHCP requester.
1502		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1503		of the "hostname" environment variable is passed as
1504		option 12 to the DHCP server.
1505
1506		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1507
1508		A 32bit value in microseconds for a delay between
1509		receiving a "DHCP Offer" and sending the "DHCP Request".
1510		This fixes a problem with certain DHCP servers that don't
1511		respond 100% of the time to a "DHCP request". E.g. On an
1512		AT91RM9200 processor running at 180MHz, this delay needed
1513		to be *at least* 15,000 usec before a Windows Server 2003
1514		DHCP server would reply 100% of the time. I recommend at
1515		least 50,000 usec to be safe. The alternative is to hope
1516		that one of the retries will be successful but note that
1517		the DHCP timeout and retry process takes a longer than
1518		this delay.
1519
1520 - Link-local IP address negotiation:
1521		Negotiate with other link-local clients on the local network
1522		for an address that doesn't require explicit configuration.
1523		This is especially useful if a DHCP server cannot be guaranteed
1524		to exist in all environments that the device must operate.
1525
1526		See doc/README.link-local for more information.
1527
1528 - MAC address from environment variables
1529
1530		FDT_SEQ_MACADDR_FROM_ENV
1531
1532		Fix-up device tree with MAC addresses fetched sequentially from
1533		environment variables. This config work on assumption that
1534		non-usable ethernet node of device-tree are either not present
1535		or their status has been marked as "disabled".
1536
1537 - CDP Options:
1538		CONFIG_CDP_DEVICE_ID
1539
1540		The device id used in CDP trigger frames.
1541
1542		CONFIG_CDP_DEVICE_ID_PREFIX
1543
1544		A two character string which is prefixed to the MAC address
1545		of the device.
1546
1547		CONFIG_CDP_PORT_ID
1548
1549		A printf format string which contains the ascii name of
1550		the port. Normally is set to "eth%d" which sets
1551		eth0 for the first Ethernet, eth1 for the second etc.
1552
1553		CONFIG_CDP_CAPABILITIES
1554
1555		A 32bit integer which indicates the device capabilities;
1556		0x00000010 for a normal host which does not forwards.
1557
1558		CONFIG_CDP_VERSION
1559
1560		An ascii string containing the version of the software.
1561
1562		CONFIG_CDP_PLATFORM
1563
1564		An ascii string containing the name of the platform.
1565
1566		CONFIG_CDP_TRIGGER
1567
1568		A 32bit integer sent on the trigger.
1569
1570		CONFIG_CDP_POWER_CONSUMPTION
1571
1572		A 16bit integer containing the power consumption of the
1573		device in .1 of milliwatts.
1574
1575		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1576
1577		A byte containing the id of the VLAN.
1578
1579- Status LED:	CONFIG_LED_STATUS
1580
1581		Several configurations allow to display the current
1582		status using a LED. For instance, the LED will blink
1583		fast while running U-Boot code, stop blinking as
1584		soon as a reply to a BOOTP request was received, and
1585		start blinking slow once the Linux kernel is running
1586		(supported by a status LED driver in the Linux
1587		kernel). Defining CONFIG_LED_STATUS enables this
1588		feature in U-Boot.
1589
1590		Additional options:
1591
1592		CONFIG_LED_STATUS_GPIO
1593		The status LED can be connected to a GPIO pin.
1594		In such cases, the gpio_led driver can be used as a
1595		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1596		to include the gpio_led driver in the U-Boot binary.
1597
1598		CONFIG_GPIO_LED_INVERTED_TABLE
1599		Some GPIO connected LEDs may have inverted polarity in which
1600		case the GPIO high value corresponds to LED off state and
1601		GPIO low value corresponds to LED on state.
1602		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1603		with a list of GPIO LEDs that have inverted polarity.
1604
1605- I2C Support:	CONFIG_SYS_I2C
1606
1607		This enable the NEW i2c subsystem, and will allow you to use
1608		i2c commands at the u-boot command line (as long as you set
1609		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1610		based realtime clock chips or other i2c devices. See
1611		common/cmd_i2c.c for a description of the command line
1612		interface.
1613
1614		ported i2c driver to the new framework:
1615		- drivers/i2c/soft_i2c.c:
1616		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1617		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1618		    for defining speed and slave address
1619		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1620		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1621		    for defining speed and slave address
1622		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1623		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1624		    for defining speed and slave address
1625		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1626		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1627		    for defining speed and slave address
1628
1629		- drivers/i2c/fsl_i2c.c:
1630		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1631		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1632		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1633		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1634		    bus.
1635		  - If your board supports a second fsl i2c bus, define
1636		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1637		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1638		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1639		    second bus.
1640
1641		- drivers/i2c/tegra_i2c.c:
1642		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1643		  - This driver adds 4 i2c buses with a fix speed from
1644		    100000 and the slave addr 0!
1645
1646		- drivers/i2c/ppc4xx_i2c.c
1647		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1648		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1649		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1650
1651		- drivers/i2c/i2c_mxc.c
1652		  - activate this driver with CONFIG_SYS_I2C_MXC
1653		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1654		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1655		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1656		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1657		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1658		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1659		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1660		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1661		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1662		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1663		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1664		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1665		If those defines are not set, default value is 100000
1666		for speed, and 0 for slave.
1667
1668		- drivers/i2c/rcar_i2c.c:
1669		  - activate this driver with CONFIG_SYS_I2C_RCAR
1670		  - This driver adds 4 i2c buses
1671
1672		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1673		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1674		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1675		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1676		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1677		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1678		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1679		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1680		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1681
1682		- drivers/i2c/sh_i2c.c:
1683		  - activate this driver with CONFIG_SYS_I2C_SH
1684		  - This driver adds from 2 to 5 i2c buses
1685
1686		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1687		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1688		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1689		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1690		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1691		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1692		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1693		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1694		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1695		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1696		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1697
1698		- drivers/i2c/omap24xx_i2c.c
1699		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1700		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1701		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1702		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1703		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1704		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1705		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1706		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1707		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1708		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1709		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1710
1711		- drivers/i2c/zynq_i2c.c
1712		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1713		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1714		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1715
1716		- drivers/i2c/s3c24x0_i2c.c:
1717		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1718		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1719		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1720		    with a fix speed from 100000 and the slave addr 0!
1721
1722		- drivers/i2c/ihs_i2c.c
1723		  - activate this driver with CONFIG_SYS_I2C_IHS
1724		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1725		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1726		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1727		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1728		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1729		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1730		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1731		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1732		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1733		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1734		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1735		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1736		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1737		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1738		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1739		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1740		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1741		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1742		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1743		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1744		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1745
1746		additional defines:
1747
1748		CONFIG_SYS_NUM_I2C_BUSES
1749		Hold the number of i2c buses you want to use.
1750
1751		CONFIG_SYS_I2C_DIRECT_BUS
1752		define this, if you don't use i2c muxes on your hardware.
1753		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1754		omit this define.
1755
1756		CONFIG_SYS_I2C_MAX_HOPS
1757		define how many muxes are maximal consecutively connected
1758		on one i2c bus. If you not use i2c muxes, omit this
1759		define.
1760
1761		CONFIG_SYS_I2C_BUSES
1762		hold a list of buses you want to use, only used if
1763		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1764		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1765		CONFIG_SYS_NUM_I2C_BUSES = 9:
1766
1767		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1768					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1769					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1770					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1771					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1772					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1773					{1, {I2C_NULL_HOP}}, \
1774					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1775					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1776					}
1777
1778		which defines
1779			bus 0 on adapter 0 without a mux
1780			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1781			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1782			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1783			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1784			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1785			bus 6 on adapter 1 without a mux
1786			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1787			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1788
1789		If you do not have i2c muxes on your board, omit this define.
1790
1791- Legacy I2C Support:
1792		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1793		then the following macros need to be defined (examples are
1794		from include/configs/lwmon.h):
1795
1796		I2C_INIT
1797
1798		(Optional). Any commands necessary to enable the I2C
1799		controller or configure ports.
1800
1801		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1802
1803		I2C_ACTIVE
1804
1805		The code necessary to make the I2C data line active
1806		(driven).  If the data line is open collector, this
1807		define can be null.
1808
1809		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1810
1811		I2C_TRISTATE
1812
1813		The code necessary to make the I2C data line tri-stated
1814		(inactive).  If the data line is open collector, this
1815		define can be null.
1816
1817		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1818
1819		I2C_READ
1820
1821		Code that returns true if the I2C data line is high,
1822		false if it is low.
1823
1824		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1825
1826		I2C_SDA(bit)
1827
1828		If <bit> is true, sets the I2C data line high. If it
1829		is false, it clears it (low).
1830
1831		eg: #define I2C_SDA(bit) \
1832			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1833			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1834
1835		I2C_SCL(bit)
1836
1837		If <bit> is true, sets the I2C clock line high. If it
1838		is false, it clears it (low).
1839
1840		eg: #define I2C_SCL(bit) \
1841			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1842			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1843
1844		I2C_DELAY
1845
1846		This delay is invoked four times per clock cycle so this
1847		controls the rate of data transfer.  The data rate thus
1848		is 1 / (I2C_DELAY * 4). Often defined to be something
1849		like:
1850
1851		#define I2C_DELAY  udelay(2)
1852
1853		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1854
1855		If your arch supports the generic GPIO framework (asm/gpio.h),
1856		then you may alternatively define the two GPIOs that are to be
1857		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1858		have GPIO-based defaults assigned to them as appropriate.
1859
1860		You should define these to the GPIO value as given directly to
1861		the generic GPIO functions.
1862
1863		CONFIG_SYS_I2C_INIT_BOARD
1864
1865		When a board is reset during an i2c bus transfer
1866		chips might think that the current transfer is still
1867		in progress. On some boards it is possible to access
1868		the i2c SCLK line directly, either by using the
1869		processor pin as a GPIO or by having a second pin
1870		connected to the bus. If this option is defined a
1871		custom i2c_init_board() routine in boards/xxx/board.c
1872		is run early in the boot sequence.
1873
1874		CONFIG_I2C_MULTI_BUS
1875
1876		This option allows the use of multiple I2C buses, each of which
1877		must have a controller.	 At any point in time, only one bus is
1878		active.	 To switch to a different bus, use the 'i2c dev' command.
1879		Note that bus numbering is zero-based.
1880
1881		CONFIG_SYS_I2C_NOPROBES
1882
1883		This option specifies a list of I2C devices that will be skipped
1884		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1885		is set, specify a list of bus-device pairs.  Otherwise, specify
1886		a 1D array of device addresses
1887
1888		e.g.
1889			#undef	CONFIG_I2C_MULTI_BUS
1890			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1891
1892		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1893
1894			#define CONFIG_I2C_MULTI_BUS
1895			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1896
1897		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1898
1899		CONFIG_SYS_SPD_BUS_NUM
1900
1901		If defined, then this indicates the I2C bus number for DDR SPD.
1902		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1903
1904		CONFIG_SYS_RTC_BUS_NUM
1905
1906		If defined, then this indicates the I2C bus number for the RTC.
1907		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1908
1909		CONFIG_SOFT_I2C_READ_REPEATED_START
1910
1911		defining this will force the i2c_read() function in
1912		the soft_i2c driver to perform an I2C repeated start
1913		between writing the address pointer and reading the
1914		data.  If this define is omitted the default behaviour
1915		of doing a stop-start sequence will be used.  Most I2C
1916		devices can use either method, but some require one or
1917		the other.
1918
1919- SPI Support:	CONFIG_SPI
1920
1921		Enables SPI driver (so far only tested with
1922		SPI EEPROM, also an instance works with Crystal A/D and
1923		D/As on the SACSng board)
1924
1925		CONFIG_SOFT_SPI
1926
1927		Enables a software (bit-bang) SPI driver rather than
1928		using hardware support. This is a general purpose
1929		driver that only requires three general I/O port pins
1930		(two outputs, one input) to function. If this is
1931		defined, the board configuration must define several
1932		SPI configuration items (port pins to use, etc). For
1933		an example, see include/configs/sacsng.h.
1934
1935		CONFIG_SYS_SPI_MXC_WAIT
1936		Timeout for waiting until spi transfer completed.
1937		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1938
1939- FPGA Support: CONFIG_FPGA
1940
1941		Enables FPGA subsystem.
1942
1943		CONFIG_FPGA_<vendor>
1944
1945		Enables support for specific chip vendors.
1946		(ALTERA, XILINX)
1947
1948		CONFIG_FPGA_<family>
1949
1950		Enables support for FPGA family.
1951		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1952
1953		CONFIG_FPGA_COUNT
1954
1955		Specify the number of FPGA devices to support.
1956
1957		CONFIG_SYS_FPGA_PROG_FEEDBACK
1958
1959		Enable printing of hash marks during FPGA configuration.
1960
1961		CONFIG_SYS_FPGA_CHECK_BUSY
1962
1963		Enable checks on FPGA configuration interface busy
1964		status by the configuration function. This option
1965		will require a board or device specific function to
1966		be written.
1967
1968		CONFIG_FPGA_DELAY
1969
1970		If defined, a function that provides delays in the FPGA
1971		configuration driver.
1972
1973		CONFIG_SYS_FPGA_CHECK_CTRLC
1974		Allow Control-C to interrupt FPGA configuration
1975
1976		CONFIG_SYS_FPGA_CHECK_ERROR
1977
1978		Check for configuration errors during FPGA bitfile
1979		loading. For example, abort during Virtex II
1980		configuration if the INIT_B line goes low (which
1981		indicated a CRC error).
1982
1983		CONFIG_SYS_FPGA_WAIT_INIT
1984
1985		Maximum time to wait for the INIT_B line to de-assert
1986		after PROB_B has been de-asserted during a Virtex II
1987		FPGA configuration sequence. The default time is 500
1988		ms.
1989
1990		CONFIG_SYS_FPGA_WAIT_BUSY
1991
1992		Maximum time to wait for BUSY to de-assert during
1993		Virtex II FPGA configuration. The default is 5 ms.
1994
1995		CONFIG_SYS_FPGA_WAIT_CONFIG
1996
1997		Time to wait after FPGA configuration. The default is
1998		200 ms.
1999
2000- Configuration Management:
2001		CONFIG_BUILD_TARGET
2002
2003		Some SoCs need special image types (e.g. U-Boot binary
2004		with a special header) as build targets. By defining
2005		CONFIG_BUILD_TARGET in the SoC / board header, this
2006		special image will be automatically built upon calling
2007		make / buildman.
2008
2009		CONFIG_IDENT_STRING
2010
2011		If defined, this string will be added to the U-Boot
2012		version information (U_BOOT_VERSION)
2013
2014- Vendor Parameter Protection:
2015
2016		U-Boot considers the values of the environment
2017		variables "serial#" (Board Serial Number) and
2018		"ethaddr" (Ethernet Address) to be parameters that
2019		are set once by the board vendor / manufacturer, and
2020		protects these variables from casual modification by
2021		the user. Once set, these variables are read-only,
2022		and write or delete attempts are rejected. You can
2023		change this behaviour:
2024
2025		If CONFIG_ENV_OVERWRITE is #defined in your config
2026		file, the write protection for vendor parameters is
2027		completely disabled. Anybody can change or delete
2028		these parameters.
2029
2030		Alternatively, if you define _both_ an ethaddr in the
2031		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2032		Ethernet address is installed in the environment,
2033		which can be changed exactly ONCE by the user. [The
2034		serial# is unaffected by this, i. e. it remains
2035		read-only.]
2036
2037		The same can be accomplished in a more flexible way
2038		for any variable by configuring the type of access
2039		to allow for those variables in the ".flags" variable
2040		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2041
2042- Protected RAM:
2043		CONFIG_PRAM
2044
2045		Define this variable to enable the reservation of
2046		"protected RAM", i. e. RAM which is not overwritten
2047		by U-Boot. Define CONFIG_PRAM to hold the number of
2048		kB you want to reserve for pRAM. You can overwrite
2049		this default value by defining an environment
2050		variable "pram" to the number of kB you want to
2051		reserve. Note that the board info structure will
2052		still show the full amount of RAM. If pRAM is
2053		reserved, a new environment variable "mem" will
2054		automatically be defined to hold the amount of
2055		remaining RAM in a form that can be passed as boot
2056		argument to Linux, for instance like that:
2057
2058			setenv bootargs ... mem=\${mem}
2059			saveenv
2060
2061		This way you can tell Linux not to use this memory,
2062		either, which results in a memory region that will
2063		not be affected by reboots.
2064
2065		*WARNING* If your board configuration uses automatic
2066		detection of the RAM size, you must make sure that
2067		this memory test is non-destructive. So far, the
2068		following board configurations are known to be
2069		"pRAM-clean":
2070
2071			IVMS8, IVML24, SPD8xx,
2072			HERMES, IP860, RPXlite, LWMON,
2073			FLAGADM
2074
2075- Access to physical memory region (> 4GB)
2076		Some basic support is provided for operations on memory not
2077		normally accessible to U-Boot - e.g. some architectures
2078		support access to more than 4GB of memory on 32-bit
2079		machines using physical address extension or similar.
2080		Define CONFIG_PHYSMEM to access this basic support, which
2081		currently only supports clearing the memory.
2082
2083- Error Recovery:
2084		CONFIG_NET_RETRY_COUNT
2085
2086		This variable defines the number of retries for
2087		network operations like ARP, RARP, TFTP, or BOOTP
2088		before giving up the operation. If not defined, a
2089		default value of 5 is used.
2090
2091		CONFIG_ARP_TIMEOUT
2092
2093		Timeout waiting for an ARP reply in milliseconds.
2094
2095		CONFIG_NFS_TIMEOUT
2096
2097		Timeout in milliseconds used in NFS protocol.
2098		If you encounter "ERROR: Cannot umount" in nfs command,
2099		try longer timeout such as
2100		#define CONFIG_NFS_TIMEOUT 10000UL
2101
2102- Command Interpreter:
2103		CONFIG_SYS_PROMPT_HUSH_PS2
2104
2105		This defines the secondary prompt string, which is
2106		printed when the command interpreter needs more input
2107		to complete a command. Usually "> ".
2108
2109	Note:
2110
2111		In the current implementation, the local variables
2112		space and global environment variables space are
2113		separated. Local variables are those you define by
2114		simply typing `name=value'. To access a local
2115		variable later on, you have write `$name' or
2116		`${name}'; to execute the contents of a variable
2117		directly type `$name' at the command prompt.
2118
2119		Global environment variables are those you use
2120		setenv/printenv to work with. To run a command stored
2121		in such a variable, you need to use the run command,
2122		and you must not use the '$' sign to access them.
2123
2124		To store commands and special characters in a
2125		variable, please use double quotation marks
2126		surrounding the whole text of the variable, instead
2127		of the backslashes before semicolons and special
2128		symbols.
2129
2130- Command Line Editing and History:
2131		CONFIG_CMDLINE_PS_SUPPORT
2132
2133		Enable support for changing the command prompt string
2134		at run-time. Only static string is supported so far.
2135		The string is obtained from environment variables PS1
2136		and PS2.
2137
2138- Default Environment:
2139		CONFIG_EXTRA_ENV_SETTINGS
2140
2141		Define this to contain any number of null terminated
2142		strings (variable = value pairs) that will be part of
2143		the default environment compiled into the boot image.
2144
2145		For example, place something like this in your
2146		board's config file:
2147
2148		#define CONFIG_EXTRA_ENV_SETTINGS \
2149			"myvar1=value1\0" \
2150			"myvar2=value2\0"
2151
2152		Warning: This method is based on knowledge about the
2153		internal format how the environment is stored by the
2154		U-Boot code. This is NOT an official, exported
2155		interface! Although it is unlikely that this format
2156		will change soon, there is no guarantee either.
2157		You better know what you are doing here.
2158
2159		Note: overly (ab)use of the default environment is
2160		discouraged. Make sure to check other ways to preset
2161		the environment like the "source" command or the
2162		boot command first.
2163
2164		CONFIG_DELAY_ENVIRONMENT
2165
2166		Normally the environment is loaded when the board is
2167		initialised so that it is available to U-Boot. This inhibits
2168		that so that the environment is not available until
2169		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2170		this is instead controlled by the value of
2171		/config/load-environment.
2172
2173- Serial Flash support
2174		Usage requires an initial 'sf probe' to define the serial
2175		flash parameters, followed by read/write/erase/update
2176		commands.
2177
2178		The following defaults may be provided by the platform
2179		to handle the common case when only a single serial
2180		flash is present on the system.
2181
2182		CONFIG_SF_DEFAULT_BUS		Bus identifier
2183		CONFIG_SF_DEFAULT_CS		Chip-select
2184		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2185		CONFIG_SF_DEFAULT_SPEED		in Hz
2186
2187
2188- TFTP Fixed UDP Port:
2189		CONFIG_TFTP_PORT
2190
2191		If this is defined, the environment variable tftpsrcp
2192		is used to supply the TFTP UDP source port value.
2193		If tftpsrcp isn't defined, the normal pseudo-random port
2194		number generator is used.
2195
2196		Also, the environment variable tftpdstp is used to supply
2197		the TFTP UDP destination port value.  If tftpdstp isn't
2198		defined, the normal port 69 is used.
2199
2200		The purpose for tftpsrcp is to allow a TFTP server to
2201		blindly start the TFTP transfer using the pre-configured
2202		target IP address and UDP port. This has the effect of
2203		"punching through" the (Windows XP) firewall, allowing
2204		the remainder of the TFTP transfer to proceed normally.
2205		A better solution is to properly configure the firewall,
2206		but sometimes that is not allowed.
2207
2208- Show boot progress:
2209		CONFIG_SHOW_BOOT_PROGRESS
2210
2211		Defining this option allows to add some board-
2212		specific code (calling a user-provided function
2213		"show_boot_progress(int)") that enables you to show
2214		the system's boot progress on some display (for
2215		example, some LED's) on your board. At the moment,
2216		the following checkpoints are implemented:
2217
2218
2219Legacy uImage format:
2220
2221  Arg	Where			When
2222    1	common/cmd_bootm.c	before attempting to boot an image
2223   -1	common/cmd_bootm.c	Image header has bad	 magic number
2224    2	common/cmd_bootm.c	Image header has correct magic number
2225   -2	common/cmd_bootm.c	Image header has bad	 checksum
2226    3	common/cmd_bootm.c	Image header has correct checksum
2227   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2228    4	common/cmd_bootm.c	Image data   has correct checksum
2229   -4	common/cmd_bootm.c	Image is for unsupported architecture
2230    5	common/cmd_bootm.c	Architecture check OK
2231   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2232    6	common/cmd_bootm.c	Image Type check OK
2233   -6	common/cmd_bootm.c	gunzip uncompression error
2234   -7	common/cmd_bootm.c	Unimplemented compression type
2235    7	common/cmd_bootm.c	Uncompression OK
2236    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2237   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2238
2239    9	common/image.c		Start initial ramdisk verification
2240  -10	common/image.c		Ramdisk header has bad	   magic number
2241  -11	common/image.c		Ramdisk header has bad	   checksum
2242   10	common/image.c		Ramdisk header is OK
2243  -12	common/image.c		Ramdisk data   has bad	   checksum
2244   11	common/image.c		Ramdisk data   has correct checksum
2245   12	common/image.c		Ramdisk verification complete, start loading
2246  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2247   13	common/image.c		Start multifile image verification
2248   14	common/image.c		No initial ramdisk, no multifile, continue.
2249
2250   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2251
2252  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2253  -31	post/post.c		POST test failed, detected by post_output_backlog()
2254  -32	post/post.c		POST test failed, detected by post_run_single()
2255
2256   34	common/cmd_doc.c	before loading a Image from a DOC device
2257  -35	common/cmd_doc.c	Bad usage of "doc" command
2258   35	common/cmd_doc.c	correct usage of "doc" command
2259  -36	common/cmd_doc.c	No boot device
2260   36	common/cmd_doc.c	correct boot device
2261  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2262   37	common/cmd_doc.c	correct chip ID found, device available
2263  -38	common/cmd_doc.c	Read Error on boot device
2264   38	common/cmd_doc.c	reading Image header from DOC device OK
2265  -39	common/cmd_doc.c	Image header has bad magic number
2266   39	common/cmd_doc.c	Image header has correct magic number
2267  -40	common/cmd_doc.c	Error reading Image from DOC device
2268   40	common/cmd_doc.c	Image header has correct magic number
2269   41	common/cmd_ide.c	before loading a Image from a IDE device
2270  -42	common/cmd_ide.c	Bad usage of "ide" command
2271   42	common/cmd_ide.c	correct usage of "ide" command
2272  -43	common/cmd_ide.c	No boot device
2273   43	common/cmd_ide.c	boot device found
2274  -44	common/cmd_ide.c	Device not available
2275   44	common/cmd_ide.c	Device available
2276  -45	common/cmd_ide.c	wrong partition selected
2277   45	common/cmd_ide.c	partition selected
2278  -46	common/cmd_ide.c	Unknown partition table
2279   46	common/cmd_ide.c	valid partition table found
2280  -47	common/cmd_ide.c	Invalid partition type
2281   47	common/cmd_ide.c	correct partition type
2282  -48	common/cmd_ide.c	Error reading Image Header on boot device
2283   48	common/cmd_ide.c	reading Image Header from IDE device OK
2284  -49	common/cmd_ide.c	Image header has bad magic number
2285   49	common/cmd_ide.c	Image header has correct magic number
2286  -50	common/cmd_ide.c	Image header has bad	 checksum
2287   50	common/cmd_ide.c	Image header has correct checksum
2288  -51	common/cmd_ide.c	Error reading Image from IDE device
2289   51	common/cmd_ide.c	reading Image from IDE device OK
2290   52	common/cmd_nand.c	before loading a Image from a NAND device
2291  -53	common/cmd_nand.c	Bad usage of "nand" command
2292   53	common/cmd_nand.c	correct usage of "nand" command
2293  -54	common/cmd_nand.c	No boot device
2294   54	common/cmd_nand.c	boot device found
2295  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2296   55	common/cmd_nand.c	correct chip ID found, device available
2297  -56	common/cmd_nand.c	Error reading Image Header on boot device
2298   56	common/cmd_nand.c	reading Image Header from NAND device OK
2299  -57	common/cmd_nand.c	Image header has bad magic number
2300   57	common/cmd_nand.c	Image header has correct magic number
2301  -58	common/cmd_nand.c	Error reading Image from NAND device
2302   58	common/cmd_nand.c	reading Image from NAND device OK
2303
2304  -60	common/env_common.c	Environment has a bad CRC, using default
2305
2306   64	net/eth.c		starting with Ethernet configuration.
2307  -64	net/eth.c		no Ethernet found.
2308   65	net/eth.c		Ethernet found.
2309
2310  -80	common/cmd_net.c	usage wrong
2311   80	common/cmd_net.c	before calling net_loop()
2312  -81	common/cmd_net.c	some error in net_loop() occurred
2313   81	common/cmd_net.c	net_loop() back without error
2314  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2315   82	common/cmd_net.c	trying automatic boot
2316   83	common/cmd_net.c	running "source" command
2317  -83	common/cmd_net.c	some error in automatic boot or "source" command
2318   84	common/cmd_net.c	end without errors
2319
2320FIT uImage format:
2321
2322  Arg	Where			When
2323  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2324 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2325  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2326 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2327  102	common/cmd_bootm.c	Kernel unit name specified
2328 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2329  103	common/cmd_bootm.c	Found configuration node
2330  104	common/cmd_bootm.c	Got kernel subimage node offset
2331 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2332  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2333 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2334  106	common/cmd_bootm.c	Architecture check OK
2335 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2336  107	common/cmd_bootm.c	Kernel subimage type OK
2337 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2338  108	common/cmd_bootm.c	Got kernel subimage data/size
2339 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2340 -109	common/cmd_bootm.c	Can't get kernel subimage type
2341 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2342 -111	common/cmd_bootm.c	Can't get kernel subimage os
2343 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2344 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2345
2346  120	common/image.c		Start initial ramdisk verification
2347 -120	common/image.c		Ramdisk FIT image has incorrect format
2348  121	common/image.c		Ramdisk FIT image has correct format
2349  122	common/image.c		No ramdisk subimage unit name, using configuration
2350 -122	common/image.c		Can't get configuration for ramdisk subimage
2351  123	common/image.c		Ramdisk unit name specified
2352 -124	common/image.c		Can't get ramdisk subimage node offset
2353  125	common/image.c		Got ramdisk subimage node offset
2354 -125	common/image.c		Ramdisk subimage hash verification failed
2355  126	common/image.c		Ramdisk subimage hash verification OK
2356 -126	common/image.c		Ramdisk subimage for unsupported architecture
2357  127	common/image.c		Architecture check OK
2358 -127	common/image.c		Can't get ramdisk subimage data/size
2359  128	common/image.c		Got ramdisk subimage data/size
2360  129	common/image.c		Can't get ramdisk load address
2361 -129	common/image.c		Got ramdisk load address
2362
2363 -130	common/cmd_doc.c	Incorrect FIT image format
2364  131	common/cmd_doc.c	FIT image format OK
2365
2366 -140	common/cmd_ide.c	Incorrect FIT image format
2367  141	common/cmd_ide.c	FIT image format OK
2368
2369 -150	common/cmd_nand.c	Incorrect FIT image format
2370  151	common/cmd_nand.c	FIT image format OK
2371
2372- Standalone program support:
2373		CONFIG_STANDALONE_LOAD_ADDR
2374
2375		This option defines a board specific value for the
2376		address where standalone program gets loaded, thus
2377		overwriting the architecture dependent default
2378		settings.
2379
2380- Frame Buffer Address:
2381		CONFIG_FB_ADDR
2382
2383		Define CONFIG_FB_ADDR if you want to use specific
2384		address for frame buffer.  This is typically the case
2385		when using a graphics controller has separate video
2386		memory.  U-Boot will then place the frame buffer at
2387		the given address instead of dynamically reserving it
2388		in system RAM by calling lcd_setmem(), which grabs
2389		the memory for the frame buffer depending on the
2390		configured panel size.
2391
2392		Please see board_init_f function.
2393
2394- Automatic software updates via TFTP server
2395		CONFIG_UPDATE_TFTP
2396		CONFIG_UPDATE_TFTP_CNT_MAX
2397		CONFIG_UPDATE_TFTP_MSEC_MAX
2398
2399		These options enable and control the auto-update feature;
2400		for a more detailed description refer to doc/README.update.
2401
2402- MTD Support (mtdparts command, UBI support)
2403		CONFIG_MTD_UBI_WL_THRESHOLD
2404		This parameter defines the maximum difference between the highest
2405		erase counter value and the lowest erase counter value of eraseblocks
2406		of UBI devices. When this threshold is exceeded, UBI starts performing
2407		wear leveling by means of moving data from eraseblock with low erase
2408		counter to eraseblocks with high erase counter.
2409
2410		The default value should be OK for SLC NAND flashes, NOR flashes and
2411		other flashes which have eraseblock life-cycle 100000 or more.
2412		However, in case of MLC NAND flashes which typically have eraseblock
2413		life-cycle less than 10000, the threshold should be lessened (e.g.,
2414		to 128 or 256, although it does not have to be power of 2).
2415
2416		default: 4096
2417
2418		CONFIG_MTD_UBI_BEB_LIMIT
2419		This option specifies the maximum bad physical eraseblocks UBI
2420		expects on the MTD device (per 1024 eraseblocks). If the
2421		underlying flash does not admit of bad eraseblocks (e.g. NOR
2422		flash), this value is ignored.
2423
2424		NAND datasheets often specify the minimum and maximum NVM
2425		(Number of Valid Blocks) for the flashes' endurance lifetime.
2426		The maximum expected bad eraseblocks per 1024 eraseblocks
2427		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2428		which gives 20 for most NANDs (MaxNVB is basically the total
2429		count of eraseblocks on the chip).
2430
2431		To put it differently, if this value is 20, UBI will try to
2432		reserve about 1.9% of physical eraseblocks for bad blocks
2433		handling. And that will be 1.9% of eraseblocks on the entire
2434		NAND chip, not just the MTD partition UBI attaches. This means
2435		that if you have, say, a NAND flash chip admits maximum 40 bad
2436		eraseblocks, and it is split on two MTD partitions of the same
2437		size, UBI will reserve 40 eraseblocks when attaching a
2438		partition.
2439
2440		default: 20
2441
2442		CONFIG_MTD_UBI_FASTMAP
2443		Fastmap is a mechanism which allows attaching an UBI device
2444		in nearly constant time. Instead of scanning the whole MTD device it
2445		only has to locate a checkpoint (called fastmap) on the device.
2446		The on-flash fastmap contains all information needed to attach
2447		the device. Using fastmap makes only sense on large devices where
2448		attaching by scanning takes long. UBI will not automatically install
2449		a fastmap on old images, but you can set the UBI parameter
2450		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2451		that fastmap-enabled images are still usable with UBI implementations
2452		without	fastmap support. On typical flash devices the whole fastmap
2453		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2454
2455		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2456		Set this parameter to enable fastmap automatically on images
2457		without a fastmap.
2458		default: 0
2459
2460		CONFIG_MTD_UBI_FM_DEBUG
2461		Enable UBI fastmap debug
2462		default: 0
2463
2464- SPL framework
2465		CONFIG_SPL
2466		Enable building of SPL globally.
2467
2468		CONFIG_SPL_LDSCRIPT
2469		LDSCRIPT for linking the SPL binary.
2470
2471		CONFIG_SPL_MAX_FOOTPRINT
2472		Maximum size in memory allocated to the SPL, BSS included.
2473		When defined, the linker checks that the actual memory
2474		used by SPL from _start to __bss_end does not exceed it.
2475		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2476		must not be both defined at the same time.
2477
2478		CONFIG_SPL_MAX_SIZE
2479		Maximum size of the SPL image (text, data, rodata, and
2480		linker lists sections), BSS excluded.
2481		When defined, the linker checks that the actual size does
2482		not exceed it.
2483
2484		CONFIG_SPL_TEXT_BASE
2485		TEXT_BASE for linking the SPL binary.
2486
2487		CONFIG_SPL_RELOC_TEXT_BASE
2488		Address to relocate to.  If unspecified, this is equal to
2489		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2490
2491		CONFIG_SPL_BSS_START_ADDR
2492		Link address for the BSS within the SPL binary.
2493
2494		CONFIG_SPL_BSS_MAX_SIZE
2495		Maximum size in memory allocated to the SPL BSS.
2496		When defined, the linker checks that the actual memory used
2497		by SPL from __bss_start to __bss_end does not exceed it.
2498		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2499		must not be both defined at the same time.
2500
2501		CONFIG_SPL_STACK
2502		Adress of the start of the stack SPL will use
2503
2504		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2505		When defined, SPL will panic() if the image it has
2506		loaded does not have a signature.
2507		Defining this is useful when code which loads images
2508		in SPL cannot guarantee that absolutely all read errors
2509		will be caught.
2510		An example is the LPC32XX MLC NAND driver, which will
2511		consider that a completely unreadable NAND block is bad,
2512		and thus should be skipped silently.
2513
2514		CONFIG_SPL_RELOC_STACK
2515		Adress of the start of the stack SPL will use after
2516		relocation.  If unspecified, this is equal to
2517		CONFIG_SPL_STACK.
2518
2519		CONFIG_SYS_SPL_MALLOC_START
2520		Starting address of the malloc pool used in SPL.
2521		When this option is set the full malloc is used in SPL and
2522		it is set up by spl_init() and before that, the simple malloc()
2523		can be used if CONFIG_SYS_MALLOC_F is defined.
2524
2525		CONFIG_SYS_SPL_MALLOC_SIZE
2526		The size of the malloc pool used in SPL.
2527
2528		CONFIG_SPL_OS_BOOT
2529		Enable booting directly to an OS from SPL.
2530		See also: doc/README.falcon
2531
2532		CONFIG_SPL_DISPLAY_PRINT
2533		For ARM, enable an optional function to print more information
2534		about the running system.
2535
2536		CONFIG_SPL_INIT_MINIMAL
2537		Arch init code should be built for a very small image
2538
2539		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2540		Partition on the MMC to load U-Boot from when the MMC is being
2541		used in raw mode
2542
2543		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2544		Sector to load kernel uImage from when MMC is being
2545		used in raw mode (for Falcon mode)
2546
2547		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2548		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2549		Sector and number of sectors to load kernel argument
2550		parameters from when MMC is being used in raw mode
2551		(for falcon mode)
2552
2553		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2554		Partition on the MMC to load U-Boot from when the MMC is being
2555		used in fs mode
2556
2557		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2558		Filename to read to load U-Boot when reading from filesystem
2559
2560		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2561		Filename to read to load kernel uImage when reading
2562		from filesystem (for Falcon mode)
2563
2564		CONFIG_SPL_FS_LOAD_ARGS_NAME
2565		Filename to read to load kernel argument parameters
2566		when reading from filesystem (for Falcon mode)
2567
2568		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2569		Set this for NAND SPL on PPC mpc83xx targets, so that
2570		start.S waits for the rest of the SPL to load before
2571		continuing (the hardware starts execution after just
2572		loading the first page rather than the full 4K).
2573
2574		CONFIG_SPL_SKIP_RELOCATE
2575		Avoid SPL relocation
2576
2577		CONFIG_SPL_NAND_BASE
2578		Include nand_base.c in the SPL.  Requires
2579		CONFIG_SPL_NAND_DRIVERS.
2580
2581		CONFIG_SPL_NAND_DRIVERS
2582		SPL uses normal NAND drivers, not minimal drivers.
2583
2584		CONFIG_SPL_NAND_IDENT
2585		SPL uses the chip ID list to identify the NAND flash.
2586		Requires CONFIG_SPL_NAND_BASE.
2587
2588		CONFIG_SPL_NAND_ECC
2589		Include standard software ECC in the SPL
2590
2591		CONFIG_SPL_NAND_SIMPLE
2592		Support for NAND boot using simple NAND drivers that
2593		expose the cmd_ctrl() interface.
2594
2595		CONFIG_SPL_UBI
2596		Support for a lightweight UBI (fastmap) scanner and
2597		loader
2598
2599		CONFIG_SPL_NAND_RAW_ONLY
2600		Support to boot only raw u-boot.bin images. Use this only
2601		if you need to save space.
2602
2603		CONFIG_SPL_COMMON_INIT_DDR
2604		Set for common ddr init with serial presence detect in
2605		SPL binary.
2606
2607		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2608		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2609		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2610		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2611		CONFIG_SYS_NAND_ECCBYTES
2612		Defines the size and behavior of the NAND that SPL uses
2613		to read U-Boot
2614
2615		CONFIG_SPL_NAND_BOOT
2616		Add support NAND boot
2617
2618		CONFIG_SYS_NAND_U_BOOT_OFFS
2619		Location in NAND to read U-Boot from
2620
2621		CONFIG_SYS_NAND_U_BOOT_DST
2622		Location in memory to load U-Boot to
2623
2624		CONFIG_SYS_NAND_U_BOOT_SIZE
2625		Size of image to load
2626
2627		CONFIG_SYS_NAND_U_BOOT_START
2628		Entry point in loaded image to jump to
2629
2630		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2631		Define this if you need to first read the OOB and then the
2632		data. This is used, for example, on davinci platforms.
2633
2634		CONFIG_SPL_RAM_DEVICE
2635		Support for running image already present in ram, in SPL binary
2636
2637		CONFIG_SPL_PAD_TO
2638		Image offset to which the SPL should be padded before appending
2639		the SPL payload. By default, this is defined as
2640		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2641		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2642		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2643
2644		CONFIG_SPL_TARGET
2645		Final target image containing SPL and payload.  Some SPLs
2646		use an arch-specific makefile fragment instead, for
2647		example if more than one image needs to be produced.
2648
2649		CONFIG_SPL_FIT_PRINT
2650		Printing information about a FIT image adds quite a bit of
2651		code to SPL. So this is normally disabled in SPL. Use this
2652		option to re-enable it. This will affect the output of the
2653		bootm command when booting a FIT image.
2654
2655- TPL framework
2656		CONFIG_TPL
2657		Enable building of TPL globally.
2658
2659		CONFIG_TPL_PAD_TO
2660		Image offset to which the TPL should be padded before appending
2661		the TPL payload. By default, this is defined as
2662		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2663		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2664		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2665
2666- Interrupt support (PPC):
2667
2668		There are common interrupt_init() and timer_interrupt()
2669		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2670		for CPU specific initialization. interrupt_init_cpu()
2671		should set decrementer_count to appropriate value. If
2672		CPU resets decrementer automatically after interrupt
2673		(ppc4xx) it should set decrementer_count to zero.
2674		timer_interrupt() calls timer_interrupt_cpu() for CPU
2675		specific handling. If board has watchdog / status_led
2676		/ other_activity_monitor it works automatically from
2677		general timer_interrupt().
2678
2679
2680Board initialization settings:
2681------------------------------
2682
2683During Initialization u-boot calls a number of board specific functions
2684to allow the preparation of board specific prerequisites, e.g. pin setup
2685before drivers are initialized. To enable these callbacks the
2686following configuration macros have to be defined. Currently this is
2687architecture specific, so please check arch/your_architecture/lib/board.c
2688typically in board_init_f() and board_init_r().
2689
2690- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2691- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2692- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2693- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2694
2695Configuration Settings:
2696-----------------------
2697
2698- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2699		Optionally it can be defined to support 64-bit memory commands.
2700
2701- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2702		undefine this when you're short of memory.
2703
2704- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2705		width of the commands listed in the 'help' command output.
2706
2707- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2708		prompt for user input.
2709
2710- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2711
2712- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2713
2714- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2715
2716- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2717		the application (usually a Linux kernel) when it is
2718		booted
2719
2720- CONFIG_SYS_BAUDRATE_TABLE:
2721		List of legal baudrate settings for this board.
2722
2723- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2724		Begin and End addresses of the area used by the
2725		simple memory test.
2726
2727- CONFIG_SYS_MEMTEST_SCRATCH:
2728		Scratch address used by the alternate memory test
2729		You only need to set this if address zero isn't writeable
2730
2731- CONFIG_SYS_MEM_RESERVE_SECURE
2732		Only implemented for ARMv8 for now.
2733		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2734		is substracted from total RAM and won't be reported to OS.
2735		This memory can be used as secure memory. A variable
2736		gd->arch.secure_ram is used to track the location. In systems
2737		the RAM base is not zero, or RAM is divided into banks,
2738		this variable needs to be recalcuated to get the address.
2739
2740- CONFIG_SYS_MEM_TOP_HIDE:
2741		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2742		this specified memory area will get subtracted from the top
2743		(end) of RAM and won't get "touched" at all by U-Boot. By
2744		fixing up gd->ram_size the Linux kernel should gets passed
2745		the now "corrected" memory size and won't touch it either.
2746		This should work for arch/ppc and arch/powerpc. Only Linux
2747		board ports in arch/powerpc with bootwrapper support that
2748		recalculate the memory size from the SDRAM controller setup
2749		will have to get fixed in Linux additionally.
2750
2751		This option can be used as a workaround for the 440EPx/GRx
2752		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2753		be touched.
2754
2755		WARNING: Please make sure that this value is a multiple of
2756		the Linux page size (normally 4k). If this is not the case,
2757		then the end address of the Linux memory will be located at a
2758		non page size aligned address and this could cause major
2759		problems.
2760
2761- CONFIG_SYS_LOADS_BAUD_CHANGE:
2762		Enable temporary baudrate change while serial download
2763
2764- CONFIG_SYS_SDRAM_BASE:
2765		Physical start address of SDRAM. _Must_ be 0 here.
2766
2767- CONFIG_SYS_FLASH_BASE:
2768		Physical start address of Flash memory.
2769
2770- CONFIG_SYS_MONITOR_BASE:
2771		Physical start address of boot monitor code (set by
2772		make config files to be same as the text base address
2773		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2774		CONFIG_SYS_FLASH_BASE when booting from flash.
2775
2776- CONFIG_SYS_MONITOR_LEN:
2777		Size of memory reserved for monitor code, used to
2778		determine _at_compile_time_ (!) if the environment is
2779		embedded within the U-Boot image, or in a separate
2780		flash sector.
2781
2782- CONFIG_SYS_MALLOC_LEN:
2783		Size of DRAM reserved for malloc() use.
2784
2785- CONFIG_SYS_MALLOC_F_LEN
2786		Size of the malloc() pool for use before relocation. If
2787		this is defined, then a very simple malloc() implementation
2788		will become available before relocation. The address is just
2789		below the global data, and the stack is moved down to make
2790		space.
2791
2792		This feature allocates regions with increasing addresses
2793		within the region. calloc() is supported, but realloc()
2794		is not available. free() is supported but does nothing.
2795		The memory will be freed (or in fact just forgotten) when
2796		U-Boot relocates itself.
2797
2798- CONFIG_SYS_MALLOC_SIMPLE
2799		Provides a simple and small malloc() and calloc() for those
2800		boards which do not use the full malloc in SPL (which is
2801		enabled with CONFIG_SYS_SPL_MALLOC_START).
2802
2803- CONFIG_SYS_NONCACHED_MEMORY:
2804		Size of non-cached memory area. This area of memory will be
2805		typically located right below the malloc() area and mapped
2806		uncached in the MMU. This is useful for drivers that would
2807		otherwise require a lot of explicit cache maintenance. For
2808		some drivers it's also impossible to properly maintain the
2809		cache. For example if the regions that need to be flushed
2810		are not a multiple of the cache-line size, *and* padding
2811		cannot be allocated between the regions to align them (i.e.
2812		if the HW requires a contiguous array of regions, and the
2813		size of each region is not cache-aligned), then a flush of
2814		one region may result in overwriting data that hardware has
2815		written to another region in the same cache-line. This can
2816		happen for example in network drivers where descriptors for
2817		buffers are typically smaller than the CPU cache-line (e.g.
2818		16 bytes vs. 32 or 64 bytes).
2819
2820		Non-cached memory is only supported on 32-bit ARM at present.
2821
2822- CONFIG_SYS_BOOTM_LEN:
2823		Normally compressed uImages are limited to an
2824		uncompressed size of 8 MBytes. If this is not enough,
2825		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2826		to adjust this setting to your needs.
2827
2828- CONFIG_SYS_BOOTMAPSZ:
2829		Maximum size of memory mapped by the startup code of
2830		the Linux kernel; all data that must be processed by
2831		the Linux kernel (bd_info, boot arguments, FDT blob if
2832		used) must be put below this limit, unless "bootm_low"
2833		environment variable is defined and non-zero. In such case
2834		all data for the Linux kernel must be between "bootm_low"
2835		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2836		variable "bootm_mapsize" will override the value of
2837		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2838		then the value in "bootm_size" will be used instead.
2839
2840- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2841		Enable initrd_high functionality.  If defined then the
2842		initrd_high feature is enabled and the bootm ramdisk subcommand
2843		is enabled.
2844
2845- CONFIG_SYS_BOOT_GET_CMDLINE:
2846		Enables allocating and saving kernel cmdline in space between
2847		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2848
2849- CONFIG_SYS_BOOT_GET_KBD:
2850		Enables allocating and saving a kernel copy of the bd_info in
2851		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2852
2853- CONFIG_SYS_MAX_FLASH_BANKS:
2854		Max number of Flash memory banks
2855
2856- CONFIG_SYS_MAX_FLASH_SECT:
2857		Max number of sectors on a Flash chip
2858
2859- CONFIG_SYS_FLASH_ERASE_TOUT:
2860		Timeout for Flash erase operations (in ms)
2861
2862- CONFIG_SYS_FLASH_WRITE_TOUT:
2863		Timeout for Flash write operations (in ms)
2864
2865- CONFIG_SYS_FLASH_LOCK_TOUT
2866		Timeout for Flash set sector lock bit operation (in ms)
2867
2868- CONFIG_SYS_FLASH_UNLOCK_TOUT
2869		Timeout for Flash clear lock bits operation (in ms)
2870
2871- CONFIG_SYS_FLASH_PROTECTION
2872		If defined, hardware flash sectors protection is used
2873		instead of U-Boot software protection.
2874
2875- CONFIG_SYS_DIRECT_FLASH_TFTP:
2876
2877		Enable TFTP transfers directly to flash memory;
2878		without this option such a download has to be
2879		performed in two steps: (1) download to RAM, and (2)
2880		copy from RAM to flash.
2881
2882		The two-step approach is usually more reliable, since
2883		you can check if the download worked before you erase
2884		the flash, but in some situations (when system RAM is
2885		too limited to allow for a temporary copy of the
2886		downloaded image) this option may be very useful.
2887
2888- CONFIG_SYS_FLASH_CFI:
2889		Define if the flash driver uses extra elements in the
2890		common flash structure for storing flash geometry.
2891
2892- CONFIG_FLASH_CFI_DRIVER
2893		This option also enables the building of the cfi_flash driver
2894		in the drivers directory
2895
2896- CONFIG_FLASH_CFI_MTD
2897		This option enables the building of the cfi_mtd driver
2898		in the drivers directory. The driver exports CFI flash
2899		to the MTD layer.
2900
2901- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2902		Use buffered writes to flash.
2903
2904- CONFIG_FLASH_SPANSION_S29WS_N
2905		s29ws-n MirrorBit flash has non-standard addresses for buffered
2906		write commands.
2907
2908- CONFIG_SYS_FLASH_QUIET_TEST
2909		If this option is defined, the common CFI flash doesn't
2910		print it's warning upon not recognized FLASH banks. This
2911		is useful, if some of the configured banks are only
2912		optionally available.
2913
2914- CONFIG_FLASH_SHOW_PROGRESS
2915		If defined (must be an integer), print out countdown
2916		digits and dots.  Recommended value: 45 (9..1) for 80
2917		column displays, 15 (3..1) for 40 column displays.
2918
2919- CONFIG_FLASH_VERIFY
2920		If defined, the content of the flash (destination) is compared
2921		against the source after the write operation. An error message
2922		will be printed when the contents are not identical.
2923		Please note that this option is useless in nearly all cases,
2924		since such flash programming errors usually are detected earlier
2925		while unprotecting/erasing/programming. Please only enable
2926		this option if you really know what you are doing.
2927
2928- CONFIG_SYS_RX_ETH_BUFFER:
2929		Defines the number of Ethernet receive buffers. On some
2930		Ethernet controllers it is recommended to set this value
2931		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2932		buffers can be full shortly after enabling the interface
2933		on high Ethernet traffic.
2934		Defaults to 4 if not defined.
2935
2936- CONFIG_ENV_MAX_ENTRIES
2937
2938	Maximum number of entries in the hash table that is used
2939	internally to store the environment settings. The default
2940	setting is supposed to be generous and should work in most
2941	cases. This setting can be used to tune behaviour; see
2942	lib/hashtable.c for details.
2943
2944- CONFIG_ENV_FLAGS_LIST_DEFAULT
2945- CONFIG_ENV_FLAGS_LIST_STATIC
2946	Enable validation of the values given to environment variables when
2947	calling env set.  Variables can be restricted to only decimal,
2948	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2949	the variables can also be restricted to IP address or MAC address.
2950
2951	The format of the list is:
2952		type_attribute = [s|d|x|b|i|m]
2953		access_attribute = [a|r|o|c]
2954		attributes = type_attribute[access_attribute]
2955		entry = variable_name[:attributes]
2956		list = entry[,list]
2957
2958	The type attributes are:
2959		s - String (default)
2960		d - Decimal
2961		x - Hexadecimal
2962		b - Boolean ([1yYtT|0nNfF])
2963		i - IP address
2964		m - MAC address
2965
2966	The access attributes are:
2967		a - Any (default)
2968		r - Read-only
2969		o - Write-once
2970		c - Change-default
2971
2972	- CONFIG_ENV_FLAGS_LIST_DEFAULT
2973		Define this to a list (string) to define the ".flags"
2974		environment variable in the default or embedded environment.
2975
2976	- CONFIG_ENV_FLAGS_LIST_STATIC
2977		Define this to a list (string) to define validation that
2978		should be done if an entry is not found in the ".flags"
2979		environment variable.  To override a setting in the static
2980		list, simply add an entry for the same variable name to the
2981		".flags" variable.
2982
2983	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2984	regular expression. This allows multiple variables to define the same
2985	flags without explicitly listing them for each variable.
2986
2987- CONFIG_ENV_ACCESS_IGNORE_FORCE
2988	If defined, don't allow the -f switch to env set override variable
2989	access flags.
2990
2991The following definitions that deal with the placement and management
2992of environment data (variable area); in general, we support the
2993following configurations:
2994
2995- CONFIG_BUILD_ENVCRC:
2996
2997	Builds up envcrc with the target environment so that external utils
2998	may easily extract it and embed it in final U-Boot images.
2999
3000BE CAREFUL! The first access to the environment happens quite early
3001in U-Boot initialization (when we try to get the setting of for the
3002console baudrate). You *MUST* have mapped your NVRAM area then, or
3003U-Boot will hang.
3004
3005Please note that even with NVRAM we still use a copy of the
3006environment in RAM: we could work on NVRAM directly, but we want to
3007keep settings there always unmodified except somebody uses "saveenv"
3008to save the current settings.
3009
3010BE CAREFUL! For some special cases, the local device can not use
3011"saveenv" command. For example, the local device will get the
3012environment stored in a remote NOR flash by SRIO or PCIE link,
3013but it can not erase, write this NOR flash by SRIO or PCIE interface.
3014
3015- CONFIG_NAND_ENV_DST
3016
3017	Defines address in RAM to which the nand_spl code should copy the
3018	environment. If redundant environment is used, it will be copied to
3019	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3020
3021Please note that the environment is read-only until the monitor
3022has been relocated to RAM and a RAM copy of the environment has been
3023created; also, when using EEPROM you will have to use env_get_f()
3024until then to read environment variables.
3025
3026The environment is protected by a CRC32 checksum. Before the monitor
3027is relocated into RAM, as a result of a bad CRC you will be working
3028with the compiled-in default environment - *silently*!!! [This is
3029necessary, because the first environment variable we need is the
3030"baudrate" setting for the console - if we have a bad CRC, we don't
3031have any device yet where we could complain.]
3032
3033Note: once the monitor has been relocated, then it will complain if
3034the default environment is used; a new CRC is computed as soon as you
3035use the "saveenv" command to store a valid environment.
3036
3037- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3038		Echo the inverted Ethernet link state to the fault LED.
3039
3040		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3041		      also needs to be defined.
3042
3043- CONFIG_SYS_FAULT_MII_ADDR:
3044		MII address of the PHY to check for the Ethernet link state.
3045
3046- CONFIG_NS16550_MIN_FUNCTIONS:
3047		Define this if you desire to only have use of the NS16550_init
3048		and NS16550_putc functions for the serial driver located at
3049		drivers/serial/ns16550.c.  This option is useful for saving
3050		space for already greatly restricted images, including but not
3051		limited to NAND_SPL configurations.
3052
3053- CONFIG_DISPLAY_BOARDINFO
3054		Display information about the board that U-Boot is running on
3055		when U-Boot starts up. The board function checkboard() is called
3056		to do this.
3057
3058- CONFIG_DISPLAY_BOARDINFO_LATE
3059		Similar to the previous option, but display this information
3060		later, once stdio is running and output goes to the LCD, if
3061		present.
3062
3063- CONFIG_BOARD_SIZE_LIMIT:
3064		Maximum size of the U-Boot image. When defined, the
3065		build system checks that the actual size does not
3066		exceed it.
3067
3068Low Level (hardware related) configuration options:
3069---------------------------------------------------
3070
3071- CONFIG_SYS_CACHELINE_SIZE:
3072		Cache Line Size of the CPU.
3073
3074- CONFIG_SYS_CCSRBAR_DEFAULT:
3075		Default (power-on reset) physical address of CCSR on Freescale
3076		PowerPC SOCs.
3077
3078- CONFIG_SYS_CCSRBAR:
3079		Virtual address of CCSR.  On a 32-bit build, this is typically
3080		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3081
3082- CONFIG_SYS_CCSRBAR_PHYS:
3083		Physical address of CCSR.  CCSR can be relocated to a new
3084		physical address, if desired.  In this case, this macro should
3085		be set to that address.	 Otherwise, it should be set to the
3086		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3087		is typically relocated on 36-bit builds.  It is recommended
3088		that this macro be defined via the _HIGH and _LOW macros:
3089
3090		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3091			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3092
3093- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3094		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3095		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3096		used in assembly code, so it must not contain typecasts or
3097		integer size suffixes (e.g. "ULL").
3098
3099- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3100		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3101		used in assembly code, so it must not contain typecasts or
3102		integer size suffixes (e.g. "ULL").
3103
3104- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3105		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3106		forced to a value that ensures that CCSR is not relocated.
3107
3108- Floppy Disk Support:
3109		CONFIG_SYS_FDC_DRIVE_NUMBER
3110
3111		the default drive number (default value 0)
3112
3113		CONFIG_SYS_ISA_IO_STRIDE
3114
3115		defines the spacing between FDC chipset registers
3116		(default value 1)
3117
3118		CONFIG_SYS_ISA_IO_OFFSET
3119
3120		defines the offset of register from address. It
3121		depends on which part of the data bus is connected to
3122		the FDC chipset. (default value 0)
3123
3124		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3125		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3126		default value.
3127
3128		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3129		fdc_hw_init() is called at the beginning of the FDC
3130		setup. fdc_hw_init() must be provided by the board
3131		source code. It is used to make hardware-dependent
3132		initializations.
3133
3134- CONFIG_IDE_AHB:
3135		Most IDE controllers were designed to be connected with PCI
3136		interface. Only few of them were designed for AHB interface.
3137		When software is doing ATA command and data transfer to
3138		IDE devices through IDE-AHB controller, some additional
3139		registers accessing to these kind of IDE-AHB controller
3140		is required.
3141
3142- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3143		DO NOT CHANGE unless you know exactly what you're
3144		doing! (11-4) [MPC8xx systems only]
3145
3146- CONFIG_SYS_INIT_RAM_ADDR:
3147
3148		Start address of memory area that can be used for
3149		initial data and stack; please note that this must be
3150		writable memory that is working WITHOUT special
3151		initialization, i. e. you CANNOT use normal RAM which
3152		will become available only after programming the
3153		memory controller and running certain initialization
3154		sequences.
3155
3156		U-Boot uses the following memory types:
3157		- MPC8xx: IMMR (internal memory of the CPU)
3158
3159- CONFIG_SYS_GBL_DATA_OFFSET:
3160
3161		Offset of the initial data structure in the memory
3162		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3163		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3164		data is located at the end of the available space
3165		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3166		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3167		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3168		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3169
3170	Note:
3171		On the MPC824X (or other systems that use the data
3172		cache for initial memory) the address chosen for
3173		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3174		point to an otherwise UNUSED address space between
3175		the top of RAM and the start of the PCI space.
3176
3177- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3178
3179- CONFIG_SYS_OR_TIMING_SDRAM:
3180		SDRAM timing
3181
3182- CONFIG_SYS_MAMR_PTA:
3183		periodic timer for refresh
3184
3185- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3186  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3187  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3188  CONFIG_SYS_BR1_PRELIM:
3189		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3190
3191- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3192  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3193  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3194		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3195
3196- CONFIG_PCI_ENUM_ONLY
3197		Only scan through and get the devices on the buses.
3198		Don't do any setup work, presumably because someone or
3199		something has already done it, and we don't need to do it
3200		a second time.	Useful for platforms that are pre-booted
3201		by coreboot or similar.
3202
3203- CONFIG_PCI_INDIRECT_BRIDGE:
3204		Enable support for indirect PCI bridges.
3205
3206- CONFIG_SYS_SRIO:
3207		Chip has SRIO or not
3208
3209- CONFIG_SRIO1:
3210		Board has SRIO 1 port available
3211
3212- CONFIG_SRIO2:
3213		Board has SRIO 2 port available
3214
3215- CONFIG_SRIO_PCIE_BOOT_MASTER
3216		Board can support master function for Boot from SRIO and PCIE
3217
3218- CONFIG_SYS_SRIOn_MEM_VIRT:
3219		Virtual Address of SRIO port 'n' memory region
3220
3221- CONFIG_SYS_SRIOn_MEM_PHYS:
3222		Physical Address of SRIO port 'n' memory region
3223
3224- CONFIG_SYS_SRIOn_MEM_SIZE:
3225		Size of SRIO port 'n' memory region
3226
3227- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3228		Defined to tell the NAND controller that the NAND chip is using
3229		a 16 bit bus.
3230		Not all NAND drivers use this symbol.
3231		Example of drivers that use it:
3232		- drivers/mtd/nand/raw/ndfc.c
3233		- drivers/mtd/nand/raw/mxc_nand.c
3234
3235- CONFIG_SYS_NDFC_EBC0_CFG
3236		Sets the EBC0_CFG register for the NDFC. If not defined
3237		a default value will be used.
3238
3239- CONFIG_SPD_EEPROM
3240		Get DDR timing information from an I2C EEPROM. Common
3241		with pluggable memory modules such as SODIMMs
3242
3243  SPD_EEPROM_ADDRESS
3244		I2C address of the SPD EEPROM
3245
3246- CONFIG_SYS_SPD_BUS_NUM
3247		If SPD EEPROM is on an I2C bus other than the first
3248		one, specify here. Note that the value must resolve
3249		to something your driver can deal with.
3250
3251- CONFIG_SYS_DDR_RAW_TIMING
3252		Get DDR timing information from other than SPD. Common with
3253		soldered DDR chips onboard without SPD. DDR raw timing
3254		parameters are extracted from datasheet and hard-coded into
3255		header files or board specific files.
3256
3257- CONFIG_FSL_DDR_INTERACTIVE
3258		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3259
3260- CONFIG_FSL_DDR_SYNC_REFRESH
3261		Enable sync of refresh for multiple controllers.
3262
3263- CONFIG_FSL_DDR_BIST
3264		Enable built-in memory test for Freescale DDR controllers.
3265
3266- CONFIG_SYS_83XX_DDR_USES_CS0
3267		Only for 83xx systems. If specified, then DDR should
3268		be configured using CS0 and CS1 instead of CS2 and CS3.
3269
3270- CONFIG_RMII
3271		Enable RMII mode for all FECs.
3272		Note that this is a global option, we can't
3273		have one FEC in standard MII mode and another in RMII mode.
3274
3275- CONFIG_CRC32_VERIFY
3276		Add a verify option to the crc32 command.
3277		The syntax is:
3278
3279		=> crc32 -v <address> <count> <crc32>
3280
3281		Where address/count indicate a memory area
3282		and crc32 is the correct crc32 which the
3283		area should have.
3284
3285- CONFIG_LOOPW
3286		Add the "loopw" memory command. This only takes effect if
3287		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3288
3289- CONFIG_MX_CYCLIC
3290		Add the "mdc" and "mwc" memory commands. These are cyclic
3291		"md/mw" commands.
3292		Examples:
3293
3294		=> mdc.b 10 4 500
3295		This command will print 4 bytes (10,11,12,13) each 500 ms.
3296
3297		=> mwc.l 100 12345678 10
3298		This command will write 12345678 to address 100 all 10 ms.
3299
3300		This only takes effect if the memory commands are activated
3301		globally (CONFIG_CMD_MEMORY).
3302
3303- CONFIG_SKIP_LOWLEVEL_INIT
3304		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3305		low level initializations (like setting up the memory
3306		controller) are omitted and/or U-Boot does not
3307		relocate itself into RAM.
3308
3309		Normally this variable MUST NOT be defined. The only
3310		exception is when U-Boot is loaded (to RAM) by some
3311		other boot loader or by a debugger which performs
3312		these initializations itself.
3313
3314- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3315		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3316		to be skipped. The normal CP15 init (such as enabling the
3317		instruction cache) is still performed.
3318
3319- CONFIG_SPL_BUILD
3320		Modifies the behaviour of start.S when compiling a loader
3321		that is executed before the actual U-Boot. E.g. when
3322		compiling a NAND SPL.
3323
3324- CONFIG_TPL_BUILD
3325		Modifies the behaviour of start.S  when compiling a loader
3326		that is executed after the SPL and before the actual U-Boot.
3327		It is loaded by the SPL.
3328
3329- CONFIG_SYS_MPC85XX_NO_RESETVEC
3330		Only for 85xx systems. If this variable is specified, the section
3331		.resetvec is not kept and the section .bootpg is placed in the
3332		previous 4k of the .text section.
3333
3334- CONFIG_ARCH_MAP_SYSMEM
3335		Generally U-Boot (and in particular the md command) uses
3336		effective address. It is therefore not necessary to regard
3337		U-Boot address as virtual addresses that need to be translated
3338		to physical addresses. However, sandbox requires this, since
3339		it maintains its own little RAM buffer which contains all
3340		addressable memory. This option causes some memory accesses
3341		to be mapped through map_sysmem() / unmap_sysmem().
3342
3343- CONFIG_X86_RESET_VECTOR
3344		If defined, the x86 reset vector code is included. This is not
3345		needed when U-Boot is running from Coreboot.
3346
3347- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3348		Option to disable subpage write in NAND driver
3349		driver that uses this:
3350		drivers/mtd/nand/raw/davinci_nand.c
3351
3352Freescale QE/FMAN Firmware Support:
3353-----------------------------------
3354
3355The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3356loading of "firmware", which is encoded in the QE firmware binary format.
3357This firmware often needs to be loaded during U-Boot booting, so macros
3358are used to identify the storage device (NOR flash, SPI, etc) and the address
3359within that device.
3360
3361- CONFIG_SYS_FMAN_FW_ADDR
3362	The address in the storage device where the FMAN microcode is located.  The
3363	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3364	is also specified.
3365
3366- CONFIG_SYS_QE_FW_ADDR
3367	The address in the storage device where the QE microcode is located.  The
3368	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3369	is also specified.
3370
3371- CONFIG_SYS_QE_FMAN_FW_LENGTH
3372	The maximum possible size of the firmware.  The firmware binary format
3373	has a field that specifies the actual size of the firmware, but it
3374	might not be possible to read any part of the firmware unless some
3375	local storage is allocated to hold the entire firmware first.
3376
3377- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3378	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3379	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3380	virtual address in NOR flash.
3381
3382- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3383	Specifies that QE/FMAN firmware is located in NAND flash.
3384	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3385
3386- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3387	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3388	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3389
3390- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3391	Specifies that QE/FMAN firmware is located in the remote (master)
3392	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3393	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3394	window->master inbound window->master LAW->the ucode address in
3395	master's memory space.
3396
3397Freescale Layerscape Management Complex Firmware Support:
3398---------------------------------------------------------
3399The Freescale Layerscape Management Complex (MC) supports the loading of
3400"firmware".
3401This firmware often needs to be loaded during U-Boot booting, so macros
3402are used to identify the storage device (NOR flash, SPI, etc) and the address
3403within that device.
3404
3405- CONFIG_FSL_MC_ENET
3406	Enable the MC driver for Layerscape SoCs.
3407
3408Freescale Layerscape Debug Server Support:
3409-------------------------------------------
3410The Freescale Layerscape Debug Server Support supports the loading of
3411"Debug Server firmware" and triggering SP boot-rom.
3412This firmware often needs to be loaded during U-Boot booting.
3413
3414- CONFIG_SYS_MC_RSV_MEM_ALIGN
3415	Define alignment of reserved memory MC requires
3416
3417Reproducible builds
3418-------------------
3419
3420In order to achieve reproducible builds, timestamps used in the U-Boot build
3421process have to be set to a fixed value.
3422
3423This is done using the SOURCE_DATE_EPOCH environment variable.
3424SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3425option for U-Boot or an environment variable in U-Boot.
3426
3427SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3428
3429Building the Software:
3430======================
3431
3432Building U-Boot has been tested in several native build environments
3433and in many different cross environments. Of course we cannot support
3434all possibly existing versions of cross development tools in all
3435(potentially obsolete) versions. In case of tool chain problems we
3436recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3437which is extensively used to build and test U-Boot.
3438
3439If you are not using a native environment, it is assumed that you
3440have GNU cross compiling tools available in your path. In this case,
3441you must set the environment variable CROSS_COMPILE in your shell.
3442Note that no changes to the Makefile or any other source files are
3443necessary. For example using the ELDK on a 4xx CPU, please enter:
3444
3445	$ CROSS_COMPILE=ppc_4xx-
3446	$ export CROSS_COMPILE
3447
3448Note: If you wish to generate Windows versions of the utilities in
3449      the tools directory you can use the MinGW toolchain
3450      (http://www.mingw.org).  Set your HOST tools to the MinGW
3451      toolchain and execute 'make tools'.  For example:
3452
3453       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3454
3455      Binaries such as tools/mkimage.exe will be created which can
3456      be executed on computers running Windows.
3457
3458U-Boot is intended to be simple to build. After installing the
3459sources you must configure U-Boot for one specific board type. This
3460is done by typing:
3461
3462	make NAME_defconfig
3463
3464where "NAME_defconfig" is the name of one of the existing configu-
3465rations; see boards.cfg for supported names.
3466
3467Note: for some board special configuration names may exist; check if
3468      additional information is available from the board vendor; for
3469      instance, the TQM823L systems are available without (standard)
3470      or with LCD support. You can select such additional "features"
3471      when choosing the configuration, i. e.
3472
3473      make TQM823L_defconfig
3474	- will configure for a plain TQM823L, i. e. no LCD support
3475
3476      make TQM823L_LCD_defconfig
3477	- will configure for a TQM823L with U-Boot console on LCD
3478
3479      etc.
3480
3481
3482Finally, type "make all", and you should get some working U-Boot
3483images ready for download to / installation on your system:
3484
3485- "u-boot.bin" is a raw binary image
3486- "u-boot" is an image in ELF binary format
3487- "u-boot.srec" is in Motorola S-Record format
3488
3489By default the build is performed locally and the objects are saved
3490in the source directory. One of the two methods can be used to change
3491this behavior and build U-Boot to some external directory:
3492
34931. Add O= to the make command line invocations:
3494
3495	make O=/tmp/build distclean
3496	make O=/tmp/build NAME_defconfig
3497	make O=/tmp/build all
3498
34992. Set environment variable KBUILD_OUTPUT to point to the desired location:
3500
3501	export KBUILD_OUTPUT=/tmp/build
3502	make distclean
3503	make NAME_defconfig
3504	make all
3505
3506Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3507variable.
3508
3509User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3510setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3511For example to treat all compiler warnings as errors:
3512
3513	make KCFLAGS=-Werror
3514
3515Please be aware that the Makefiles assume you are using GNU make, so
3516for instance on NetBSD you might need to use "gmake" instead of
3517native "make".
3518
3519
3520If the system board that you have is not listed, then you will need
3521to port U-Boot to your hardware platform. To do this, follow these
3522steps:
3523
35241.  Create a new directory to hold your board specific code. Add any
3525    files you need. In your board directory, you will need at least
3526    the "Makefile" and a "<board>.c".
35272.  Create a new configuration file "include/configs/<board>.h" for
3528    your board.
35293.  If you're porting U-Boot to a new CPU, then also create a new
3530    directory to hold your CPU specific code. Add any files you need.
35314.  Run "make <board>_defconfig" with your new name.
35325.  Type "make", and you should get a working "u-boot.srec" file
3533    to be installed on your target system.
35346.  Debug and solve any problems that might arise.
3535    [Of course, this last step is much harder than it sounds.]
3536
3537
3538Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3539==============================================================
3540
3541If you have modified U-Boot sources (for instance added a new board
3542or support for new devices, a new CPU, etc.) you are expected to
3543provide feedback to the other developers. The feedback normally takes
3544the form of a "patch", i. e. a context diff against a certain (latest
3545official or latest in the git repository) version of U-Boot sources.
3546
3547But before you submit such a patch, please verify that your modifi-
3548cation did not break existing code. At least make sure that *ALL* of
3549the supported boards compile WITHOUT ANY compiler warnings. To do so,
3550just run the buildman script (tools/buildman/buildman), which will
3551configure and build U-Boot for ALL supported system. Be warned, this
3552will take a while. Please see the buildman README, or run 'buildman -H'
3553for documentation.
3554
3555
3556See also "U-Boot Porting Guide" below.
3557
3558
3559Monitor Commands - Overview:
3560============================
3561
3562go	- start application at address 'addr'
3563run	- run commands in an environment variable
3564bootm	- boot application image from memory
3565bootp	- boot image via network using BootP/TFTP protocol
3566bootz   - boot zImage from memory
3567tftpboot- boot image via network using TFTP protocol
3568	       and env variables "ipaddr" and "serverip"
3569	       (and eventually "gatewayip")
3570tftpput - upload a file via network using TFTP protocol
3571rarpboot- boot image via network using RARP/TFTP protocol
3572diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3573loads	- load S-Record file over serial line
3574loadb	- load binary file over serial line (kermit mode)
3575md	- memory display
3576mm	- memory modify (auto-incrementing)
3577nm	- memory modify (constant address)
3578mw	- memory write (fill)
3579cp	- memory copy
3580cmp	- memory compare
3581crc32	- checksum calculation
3582i2c	- I2C sub-system
3583sspi	- SPI utility commands
3584base	- print or set address offset
3585printenv- print environment variables
3586setenv	- set environment variables
3587saveenv - save environment variables to persistent storage
3588protect - enable or disable FLASH write protection
3589erase	- erase FLASH memory
3590flinfo	- print FLASH memory information
3591nand	- NAND memory operations (see doc/README.nand)
3592bdinfo	- print Board Info structure
3593iminfo	- print header information for application image
3594coninfo - print console devices and informations
3595ide	- IDE sub-system
3596loop	- infinite loop on address range
3597loopw	- infinite write loop on address range
3598mtest	- simple RAM test
3599icache	- enable or disable instruction cache
3600dcache	- enable or disable data cache
3601reset	- Perform RESET of the CPU
3602echo	- echo args to console
3603version - print monitor version
3604help	- print online help
3605?	- alias for 'help'
3606
3607
3608Monitor Commands - Detailed Description:
3609========================================
3610
3611TODO.
3612
3613For now: just type "help <command>".
3614
3615
3616Environment Variables:
3617======================
3618
3619U-Boot supports user configuration using Environment Variables which
3620can be made persistent by saving to Flash memory.
3621
3622Environment Variables are set using "setenv", printed using
3623"printenv", and saved to Flash using "saveenv". Using "setenv"
3624without a value can be used to delete a variable from the
3625environment. As long as you don't save the environment you are
3626working with an in-memory copy. In case the Flash area containing the
3627environment is erased by accident, a default environment is provided.
3628
3629Some configuration options can be set using Environment Variables.
3630
3631List of environment variables (most likely not complete):
3632
3633  baudrate	- see CONFIG_BAUDRATE
3634
3635  bootdelay	- see CONFIG_BOOTDELAY
3636
3637  bootcmd	- see CONFIG_BOOTCOMMAND
3638
3639  bootargs	- Boot arguments when booting an RTOS image
3640
3641  bootfile	- Name of the image to load with TFTP
3642
3643  bootm_low	- Memory range available for image processing in the bootm
3644		  command can be restricted. This variable is given as
3645		  a hexadecimal number and defines lowest address allowed
3646		  for use by the bootm command. See also "bootm_size"
3647		  environment variable. Address defined by "bootm_low" is
3648		  also the base of the initial memory mapping for the Linux
3649		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3650		  bootm_mapsize.
3651
3652  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3653		  This variable is given as a hexadecimal number and it
3654		  defines the size of the memory region starting at base
3655		  address bootm_low that is accessible by the Linux kernel
3656		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3657		  as the default value if it is defined, and bootm_size is
3658		  used otherwise.
3659
3660  bootm_size	- Memory range available for image processing in the bootm
3661		  command can be restricted. This variable is given as
3662		  a hexadecimal number and defines the size of the region
3663		  allowed for use by the bootm command. See also "bootm_low"
3664		  environment variable.
3665
3666  updatefile	- Location of the software update file on a TFTP server, used
3667		  by the automatic software update feature. Please refer to
3668		  documentation in doc/README.update for more details.
3669
3670  autoload	- if set to "no" (any string beginning with 'n'),
3671		  "bootp" will just load perform a lookup of the
3672		  configuration from the BOOTP server, but not try to
3673		  load any image using TFTP
3674
3675  autostart	- if set to "yes", an image loaded using the "bootp",
3676		  "rarpboot", "tftpboot" or "diskboot" commands will
3677		  be automatically started (by internally calling
3678		  "bootm")
3679
3680		  If set to "no", a standalone image passed to the
3681		  "bootm" command will be copied to the load address
3682		  (and eventually uncompressed), but NOT be started.
3683		  This can be used to load and uncompress arbitrary
3684		  data.
3685
3686  fdt_high	- if set this restricts the maximum address that the
3687		  flattened device tree will be copied into upon boot.
3688		  For example, if you have a system with 1 GB memory
3689		  at physical address 0x10000000, while Linux kernel
3690		  only recognizes the first 704 MB as low memory, you
3691		  may need to set fdt_high as 0x3C000000 to have the
3692		  device tree blob be copied to the maximum address
3693		  of the 704 MB low memory, so that Linux kernel can
3694		  access it during the boot procedure.
3695
3696		  If this is set to the special value 0xFFFFFFFF then
3697		  the fdt will not be copied at all on boot.  For this
3698		  to work it must reside in writable memory, have
3699		  sufficient padding on the end of it for u-boot to
3700		  add the information it needs into it, and the memory
3701		  must be accessible by the kernel.
3702
3703  fdtcontroladdr- if set this is the address of the control flattened
3704		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3705		  defined.
3706
3707  i2cfast	- (PPC405GP|PPC405EP only)
3708		  if set to 'y' configures Linux I2C driver for fast
3709		  mode (400kHZ). This environment variable is used in
3710		  initialization code. So, for changes to be effective
3711		  it must be saved and board must be reset.
3712
3713  initrd_high	- restrict positioning of initrd images:
3714		  If this variable is not set, initrd images will be
3715		  copied to the highest possible address in RAM; this
3716		  is usually what you want since it allows for
3717		  maximum initrd size. If for some reason you want to
3718		  make sure that the initrd image is loaded below the
3719		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3720		  variable to a value of "no" or "off" or "0".
3721		  Alternatively, you can set it to a maximum upper
3722		  address to use (U-Boot will still check that it
3723		  does not overwrite the U-Boot stack and data).
3724
3725		  For instance, when you have a system with 16 MB
3726		  RAM, and want to reserve 4 MB from use by Linux,
3727		  you can do this by adding "mem=12M" to the value of
3728		  the "bootargs" variable. However, now you must make
3729		  sure that the initrd image is placed in the first
3730		  12 MB as well - this can be done with
3731
3732		  setenv initrd_high 00c00000
3733
3734		  If you set initrd_high to 0xFFFFFFFF, this is an
3735		  indication to U-Boot that all addresses are legal
3736		  for the Linux kernel, including addresses in flash
3737		  memory. In this case U-Boot will NOT COPY the
3738		  ramdisk at all. This may be useful to reduce the
3739		  boot time on your system, but requires that this
3740		  feature is supported by your Linux kernel.
3741
3742  ipaddr	- IP address; needed for tftpboot command
3743
3744  loadaddr	- Default load address for commands like "bootp",
3745		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3746
3747  loads_echo	- see CONFIG_LOADS_ECHO
3748
3749  serverip	- TFTP server IP address; needed for tftpboot command
3750
3751  bootretry	- see CONFIG_BOOT_RETRY_TIME
3752
3753  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3754
3755  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3756
3757  ethprime	- controls which interface is used first.
3758
3759  ethact	- controls which interface is currently active.
3760		  For example you can do the following
3761
3762		  => setenv ethact FEC
3763		  => ping 192.168.0.1 # traffic sent on FEC
3764		  => setenv ethact SCC
3765		  => ping 10.0.0.1 # traffic sent on SCC
3766
3767  ethrotate	- When set to "no" U-Boot does not go through all
3768		  available network interfaces.
3769		  It just stays at the currently selected interface.
3770
3771  netretry	- When set to "no" each network operation will
3772		  either succeed or fail without retrying.
3773		  When set to "once" the network operation will
3774		  fail when all the available network interfaces
3775		  are tried once without success.
3776		  Useful on scripts which control the retry operation
3777		  themselves.
3778
3779  npe_ucode	- set load address for the NPE microcode
3780
3781  silent_linux  - If set then Linux will be told to boot silently, by
3782		  changing the console to be empty. If "yes" it will be
3783		  made silent. If "no" it will not be made silent. If
3784		  unset, then it will be made silent if the U-Boot console
3785		  is silent.
3786
3787  tftpsrcp	- If this is set, the value is used for TFTP's
3788		  UDP source port.
3789
3790  tftpdstp	- If this is set, the value is used for TFTP's UDP
3791		  destination port instead of the Well Know Port 69.
3792
3793  tftpblocksize - Block size to use for TFTP transfers; if not set,
3794		  we use the TFTP server's default block size
3795
3796  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3797		  seconds, minimum value is 1000 = 1 second). Defines
3798		  when a packet is considered to be lost so it has to
3799		  be retransmitted. The default is 5000 = 5 seconds.
3800		  Lowering this value may make downloads succeed
3801		  faster in networks with high packet loss rates or
3802		  with unreliable TFTP servers.
3803
3804  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3805		  unit, minimum value = 0). Defines how many timeouts
3806		  can happen during a single file transfer before that
3807		  transfer is aborted. The default is 10, and 0 means
3808		  'no timeouts allowed'. Increasing this value may help
3809		  downloads succeed with high packet loss rates, or with
3810		  unreliable TFTP servers or client hardware.
3811
3812  vlan		- When set to a value < 4095 the traffic over
3813		  Ethernet is encapsulated/received over 802.1q
3814		  VLAN tagged frames.
3815
3816  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3817		  Unsigned value, in milliseconds. If not set, the period will
3818		  be either the default (28000), or a value based on
3819		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3820		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3821
3822The following image location variables contain the location of images
3823used in booting. The "Image" column gives the role of the image and is
3824not an environment variable name. The other columns are environment
3825variable names. "File Name" gives the name of the file on a TFTP
3826server, "RAM Address" gives the location in RAM the image will be
3827loaded to, and "Flash Location" gives the image's address in NOR
3828flash or offset in NAND flash.
3829
3830*Note* - these variables don't have to be defined for all boards, some
3831boards currently use other variables for these purposes, and some
3832boards use these variables for other purposes.
3833
3834Image		    File Name	     RAM Address       Flash Location
3835-----		    ---------	     -----------       --------------
3836u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3837Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3838device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3839ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3840
3841The following environment variables may be used and automatically
3842updated by the network boot commands ("bootp" and "rarpboot"),
3843depending the information provided by your boot server:
3844
3845  bootfile	- see above
3846  dnsip		- IP address of your Domain Name Server
3847  dnsip2	- IP address of your secondary Domain Name Server
3848  gatewayip	- IP address of the Gateway (Router) to use
3849  hostname	- Target hostname
3850  ipaddr	- see above
3851  netmask	- Subnet Mask
3852  rootpath	- Pathname of the root filesystem on the NFS server
3853  serverip	- see above
3854
3855
3856There are two special Environment Variables:
3857
3858  serial#	- contains hardware identification information such
3859		  as type string and/or serial number
3860  ethaddr	- Ethernet address
3861
3862These variables can be set only once (usually during manufacturing of
3863the board). U-Boot refuses to delete or overwrite these variables
3864once they have been set once.
3865
3866
3867Further special Environment Variables:
3868
3869  ver		- Contains the U-Boot version string as printed
3870		  with the "version" command. This variable is
3871		  readonly (see CONFIG_VERSION_VARIABLE).
3872
3873
3874Please note that changes to some configuration parameters may take
3875only effect after the next boot (yes, that's just like Windoze :-).
3876
3877
3878Callback functions for environment variables:
3879---------------------------------------------
3880
3881For some environment variables, the behavior of u-boot needs to change
3882when their values are changed.  This functionality allows functions to
3883be associated with arbitrary variables.  On creation, overwrite, or
3884deletion, the callback will provide the opportunity for some side
3885effect to happen or for the change to be rejected.
3886
3887The callbacks are named and associated with a function using the
3888U_BOOT_ENV_CALLBACK macro in your board or driver code.
3889
3890These callbacks are associated with variables in one of two ways.  The
3891static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3892in the board configuration to a string that defines a list of
3893associations.  The list must be in the following format:
3894
3895	entry = variable_name[:callback_name]
3896	list = entry[,list]
3897
3898If the callback name is not specified, then the callback is deleted.
3899Spaces are also allowed anywhere in the list.
3900
3901Callbacks can also be associated by defining the ".callbacks" variable
3902with the same list format above.  Any association in ".callbacks" will
3903override any association in the static list. You can define
3904CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3905".callbacks" environment variable in the default or embedded environment.
3906
3907If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3908regular expression. This allows multiple variables to be connected to
3909the same callback without explicitly listing them all out.
3910
3911The signature of the callback functions is:
3912
3913    int callback(const char *name, const char *value, enum env_op op, int flags)
3914
3915* name - changed environment variable
3916* value - new value of the environment variable
3917* op - operation (create, overwrite, or delete)
3918* flags - attributes of the environment variable change, see flags H_* in
3919  include/search.h
3920
3921The return value is 0 if the variable change is accepted and 1 otherwise.
3922
3923Command Line Parsing:
3924=====================
3925
3926There are two different command line parsers available with U-Boot:
3927the old "simple" one, and the much more powerful "hush" shell:
3928
3929Old, simple command line parser:
3930--------------------------------
3931
3932- supports environment variables (through setenv / saveenv commands)
3933- several commands on one line, separated by ';'
3934- variable substitution using "... ${name} ..." syntax
3935- special characters ('$', ';') can be escaped by prefixing with '\',
3936  for example:
3937	setenv bootcmd bootm \${address}
3938- You can also escape text by enclosing in single apostrophes, for example:
3939	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3940
3941Hush shell:
3942-----------
3943
3944- similar to Bourne shell, with control structures like
3945  if...then...else...fi, for...do...done; while...do...done,
3946  until...do...done, ...
3947- supports environment ("global") variables (through setenv / saveenv
3948  commands) and local shell variables (through standard shell syntax
3949  "name=value"); only environment variables can be used with "run"
3950  command
3951
3952General rules:
3953--------------
3954
3955(1) If a command line (or an environment variable executed by a "run"
3956    command) contains several commands separated by semicolon, and
3957    one of these commands fails, then the remaining commands will be
3958    executed anyway.
3959
3960(2) If you execute several variables with one call to run (i. e.
3961    calling run with a list of variables as arguments), any failing
3962    command will cause "run" to terminate, i. e. the remaining
3963    variables are not executed.
3964
3965Note for Redundant Ethernet Interfaces:
3966=======================================
3967
3968Some boards come with redundant Ethernet interfaces; U-Boot supports
3969such configurations and is capable of automatic selection of a
3970"working" interface when needed. MAC assignment works as follows:
3971
3972Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3973MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3974"eth1addr" (=>eth1), "eth2addr", ...
3975
3976If the network interface stores some valid MAC address (for instance
3977in SROM), this is used as default address if there is NO correspon-
3978ding setting in the environment; if the corresponding environment
3979variable is set, this overrides the settings in the card; that means:
3980
3981o If the SROM has a valid MAC address, and there is no address in the
3982  environment, the SROM's address is used.
3983
3984o If there is no valid address in the SROM, and a definition in the
3985  environment exists, then the value from the environment variable is
3986  used.
3987
3988o If both the SROM and the environment contain a MAC address, and
3989  both addresses are the same, this MAC address is used.
3990
3991o If both the SROM and the environment contain a MAC address, and the
3992  addresses differ, the value from the environment is used and a
3993  warning is printed.
3994
3995o If neither SROM nor the environment contain a MAC address, an error
3996  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
3997  a random, locally-assigned MAC is used.
3998
3999If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4000will be programmed into hardware as part of the initialization process.	 This
4001may be skipped by setting the appropriate 'ethmacskip' environment variable.
4002The naming convention is as follows:
4003"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4004
4005Image Formats:
4006==============
4007
4008U-Boot is capable of booting (and performing other auxiliary operations on)
4009images in two formats:
4010
4011New uImage format (FIT)
4012-----------------------
4013
4014Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4015to Flattened Device Tree). It allows the use of images with multiple
4016components (several kernels, ramdisks, etc.), with contents protected by
4017SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4018
4019
4020Old uImage format
4021-----------------
4022
4023Old image format is based on binary files which can be basically anything,
4024preceded by a special header; see the definitions in include/image.h for
4025details; basically, the header defines the following image properties:
4026
4027* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4028  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4029  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4030  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4031  INTEGRITY).
4032* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4033  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4034  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4035* Compression Type (uncompressed, gzip, bzip2)
4036* Load Address
4037* Entry Point
4038* Image Name
4039* Image Timestamp
4040
4041The header is marked by a special Magic Number, and both the header
4042and the data portions of the image are secured against corruption by
4043CRC32 checksums.
4044
4045
4046Linux Support:
4047==============
4048
4049Although U-Boot should support any OS or standalone application
4050easily, the main focus has always been on Linux during the design of
4051U-Boot.
4052
4053U-Boot includes many features that so far have been part of some
4054special "boot loader" code within the Linux kernel. Also, any
4055"initrd" images to be used are no longer part of one big Linux image;
4056instead, kernel and "initrd" are separate images. This implementation
4057serves several purposes:
4058
4059- the same features can be used for other OS or standalone
4060  applications (for instance: using compressed images to reduce the
4061  Flash memory footprint)
4062
4063- it becomes much easier to port new Linux kernel versions because
4064  lots of low-level, hardware dependent stuff are done by U-Boot
4065
4066- the same Linux kernel image can now be used with different "initrd"
4067  images; of course this also means that different kernel images can
4068  be run with the same "initrd". This makes testing easier (you don't
4069  have to build a new "zImage.initrd" Linux image when you just
4070  change a file in your "initrd"). Also, a field-upgrade of the
4071  software is easier now.
4072
4073
4074Linux HOWTO:
4075============
4076
4077Porting Linux to U-Boot based systems:
4078---------------------------------------
4079
4080U-Boot cannot save you from doing all the necessary modifications to
4081configure the Linux device drivers for use with your target hardware
4082(no, we don't intend to provide a full virtual machine interface to
4083Linux :-).
4084
4085But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4086
4087Just make sure your machine specific header file (for instance
4088include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4089Information structure as we define in include/asm-<arch>/u-boot.h,
4090and make sure that your definition of IMAP_ADDR uses the same value
4091as your U-Boot configuration in CONFIG_SYS_IMMR.
4092
4093Note that U-Boot now has a driver model, a unified model for drivers.
4094If you are adding a new driver, plumb it into driver model. If there
4095is no uclass available, you are encouraged to create one. See
4096doc/driver-model.
4097
4098
4099Configuring the Linux kernel:
4100-----------------------------
4101
4102No specific requirements for U-Boot. Make sure you have some root
4103device (initial ramdisk, NFS) for your target system.
4104
4105
4106Building a Linux Image:
4107-----------------------
4108
4109With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4110not used. If you use recent kernel source, a new build target
4111"uImage" will exist which automatically builds an image usable by
4112U-Boot. Most older kernels also have support for a "pImage" target,
4113which was introduced for our predecessor project PPCBoot and uses a
4114100% compatible format.
4115
4116Example:
4117
4118	make TQM850L_defconfig
4119	make oldconfig
4120	make dep
4121	make uImage
4122
4123The "uImage" build target uses a special tool (in 'tools/mkimage') to
4124encapsulate a compressed Linux kernel image with header	 information,
4125CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4126
4127* build a standard "vmlinux" kernel image (in ELF binary format):
4128
4129* convert the kernel into a raw binary image:
4130
4131	${CROSS_COMPILE}-objcopy -O binary \
4132				 -R .note -R .comment \
4133				 -S vmlinux linux.bin
4134
4135* compress the binary image:
4136
4137	gzip -9 linux.bin
4138
4139* package compressed binary image for U-Boot:
4140
4141	mkimage -A ppc -O linux -T kernel -C gzip \
4142		-a 0 -e 0 -n "Linux Kernel Image" \
4143		-d linux.bin.gz uImage
4144
4145
4146The "mkimage" tool can also be used to create ramdisk images for use
4147with U-Boot, either separated from the Linux kernel image, or
4148combined into one file. "mkimage" encapsulates the images with a 64
4149byte header containing information about target architecture,
4150operating system, image type, compression method, entry points, time
4151stamp, CRC32 checksums, etc.
4152
4153"mkimage" can be called in two ways: to verify existing images and
4154print the header information, or to build new images.
4155
4156In the first form (with "-l" option) mkimage lists the information
4157contained in the header of an existing U-Boot image; this includes
4158checksum verification:
4159
4160	tools/mkimage -l image
4161	  -l ==> list image header information
4162
4163The second form (with "-d" option) is used to build a U-Boot image
4164from a "data file" which is used as image payload:
4165
4166	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4167		      -n name -d data_file image
4168	  -A ==> set architecture to 'arch'
4169	  -O ==> set operating system to 'os'
4170	  -T ==> set image type to 'type'
4171	  -C ==> set compression type 'comp'
4172	  -a ==> set load address to 'addr' (hex)
4173	  -e ==> set entry point to 'ep' (hex)
4174	  -n ==> set image name to 'name'
4175	  -d ==> use image data from 'datafile'
4176
4177Right now, all Linux kernels for PowerPC systems use the same load
4178address (0x00000000), but the entry point address depends on the
4179kernel version:
4180
4181- 2.2.x kernels have the entry point at 0x0000000C,
4182- 2.3.x and later kernels have the entry point at 0x00000000.
4183
4184So a typical call to build a U-Boot image would read:
4185
4186	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4187	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4188	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4189	> examples/uImage.TQM850L
4190	Image Name:   2.4.4 kernel for TQM850L
4191	Created:      Wed Jul 19 02:34:59 2000
4192	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4193	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4194	Load Address: 0x00000000
4195	Entry Point:  0x00000000
4196
4197To verify the contents of the image (or check for corruption):
4198
4199	-> tools/mkimage -l examples/uImage.TQM850L
4200	Image Name:   2.4.4 kernel for TQM850L
4201	Created:      Wed Jul 19 02:34:59 2000
4202	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4203	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4204	Load Address: 0x00000000
4205	Entry Point:  0x00000000
4206
4207NOTE: for embedded systems where boot time is critical you can trade
4208speed for memory and install an UNCOMPRESSED image instead: this
4209needs more space in Flash, but boots much faster since it does not
4210need to be uncompressed:
4211
4212	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4213	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4214	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4215	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4216	> examples/uImage.TQM850L-uncompressed
4217	Image Name:   2.4.4 kernel for TQM850L
4218	Created:      Wed Jul 19 02:34:59 2000
4219	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4220	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4221	Load Address: 0x00000000
4222	Entry Point:  0x00000000
4223
4224
4225Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4226when your kernel is intended to use an initial ramdisk:
4227
4228	-> tools/mkimage -n 'Simple Ramdisk Image' \
4229	> -A ppc -O linux -T ramdisk -C gzip \
4230	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4231	Image Name:   Simple Ramdisk Image
4232	Created:      Wed Jan 12 14:01:50 2000
4233	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4234	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4235	Load Address: 0x00000000
4236	Entry Point:  0x00000000
4237
4238The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4239option performs the converse operation of the mkimage's second form (the "-d"
4240option). Given an image built by mkimage, the dumpimage extracts a "data file"
4241from the image:
4242
4243	tools/dumpimage -i image -T type -p position data_file
4244	  -i ==> extract from the 'image' a specific 'data_file'
4245	  -T ==> set image type to 'type'
4246	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4247
4248
4249Installing a Linux Image:
4250-------------------------
4251
4252To downloading a U-Boot image over the serial (console) interface,
4253you must convert the image to S-Record format:
4254
4255	objcopy -I binary -O srec examples/image examples/image.srec
4256
4257The 'objcopy' does not understand the information in the U-Boot
4258image header, so the resulting S-Record file will be relative to
4259address 0x00000000. To load it to a given address, you need to
4260specify the target address as 'offset' parameter with the 'loads'
4261command.
4262
4263Example: install the image to address 0x40100000 (which on the
4264TQM8xxL is in the first Flash bank):
4265
4266	=> erase 40100000 401FFFFF
4267
4268	.......... done
4269	Erased 8 sectors
4270
4271	=> loads 40100000
4272	## Ready for S-Record download ...
4273	~>examples/image.srec
4274	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4275	...
4276	15989 15990 15991 15992
4277	[file transfer complete]
4278	[connected]
4279	## Start Addr = 0x00000000
4280
4281
4282You can check the success of the download using the 'iminfo' command;
4283this includes a checksum verification so you can be sure no data
4284corruption happened:
4285
4286	=> imi 40100000
4287
4288	## Checking Image at 40100000 ...
4289	   Image Name:	 2.2.13 for initrd on TQM850L
4290	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4291	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4292	   Load Address: 00000000
4293	   Entry Point:	 0000000c
4294	   Verifying Checksum ... OK
4295
4296
4297Boot Linux:
4298-----------
4299
4300The "bootm" command is used to boot an application that is stored in
4301memory (RAM or Flash). In case of a Linux kernel image, the contents
4302of the "bootargs" environment variable is passed to the kernel as
4303parameters. You can check and modify this variable using the
4304"printenv" and "setenv" commands:
4305
4306
4307	=> printenv bootargs
4308	bootargs=root=/dev/ram
4309
4310	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4311
4312	=> printenv bootargs
4313	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4314
4315	=> bootm 40020000
4316	## Booting Linux kernel at 40020000 ...
4317	   Image Name:	 2.2.13 for NFS on TQM850L
4318	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4319	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4320	   Load Address: 00000000
4321	   Entry Point:	 0000000c
4322	   Verifying Checksum ... OK
4323	   Uncompressing Kernel Image ... OK
4324	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
4325	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4326	time_init: decrementer frequency = 187500000/60
4327	Calibrating delay loop... 49.77 BogoMIPS
4328	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4329	...
4330
4331If you want to boot a Linux kernel with initial RAM disk, you pass
4332the memory addresses of both the kernel and the initrd image (PPBCOOT
4333format!) to the "bootm" command:
4334
4335	=> imi 40100000 40200000
4336
4337	## Checking Image at 40100000 ...
4338	   Image Name:	 2.2.13 for initrd on TQM850L
4339	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4340	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4341	   Load Address: 00000000
4342	   Entry Point:	 0000000c
4343	   Verifying Checksum ... OK
4344
4345	## Checking Image at 40200000 ...
4346	   Image Name:	 Simple Ramdisk Image
4347	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4348	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4349	   Load Address: 00000000
4350	   Entry Point:	 00000000
4351	   Verifying Checksum ... OK
4352
4353	=> bootm 40100000 40200000
4354	## Booting Linux kernel at 40100000 ...
4355	   Image Name:	 2.2.13 for initrd on TQM850L
4356	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4357	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4358	   Load Address: 00000000
4359	   Entry Point:	 0000000c
4360	   Verifying Checksum ... OK
4361	   Uncompressing Kernel Image ... OK
4362	## Loading RAMDisk Image at 40200000 ...
4363	   Image Name:	 Simple Ramdisk Image
4364	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4365	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4366	   Load Address: 00000000
4367	   Entry Point:	 00000000
4368	   Verifying Checksum ... OK
4369	   Loading Ramdisk ... OK
4370	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000
4371	Boot arguments: root=/dev/ram
4372	time_init: decrementer frequency = 187500000/60
4373	Calibrating delay loop... 49.77 BogoMIPS
4374	...
4375	RAMDISK: Compressed image found at block 0
4376	VFS: Mounted root (ext2 filesystem).
4377
4378	bash#
4379
4380Boot Linux and pass a flat device tree:
4381-----------
4382
4383First, U-Boot must be compiled with the appropriate defines. See the section
4384titled "Linux Kernel Interface" above for a more in depth explanation. The
4385following is an example of how to start a kernel and pass an updated
4386flat device tree:
4387
4388=> print oftaddr
4389oftaddr=0x300000
4390=> print oft
4391oft=oftrees/mpc8540ads.dtb
4392=> tftp $oftaddr $oft
4393Speed: 1000, full duplex
4394Using TSEC0 device
4395TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4396Filename 'oftrees/mpc8540ads.dtb'.
4397Load address: 0x300000
4398Loading: #
4399done
4400Bytes transferred = 4106 (100a hex)
4401=> tftp $loadaddr $bootfile
4402Speed: 1000, full duplex
4403Using TSEC0 device
4404TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4405Filename 'uImage'.
4406Load address: 0x200000
4407Loading:############
4408done
4409Bytes transferred = 1029407 (fb51f hex)
4410=> print loadaddr
4411loadaddr=200000
4412=> print oftaddr
4413oftaddr=0x300000
4414=> bootm $loadaddr - $oftaddr
4415## Booting image at 00200000 ...
4416   Image Name:	 Linux-2.6.17-dirty
4417   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4418   Data Size:	 1029343 Bytes = 1005.2 kB
4419   Load Address: 00000000
4420   Entry Point:	 00000000
4421   Verifying Checksum ... OK
4422   Uncompressing Kernel Image ... OK
4423Booting using flat device tree at 0x300000
4424Using MPC85xx ADS machine description
4425Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4426[snip]
4427
4428
4429More About U-Boot Image Types:
4430------------------------------
4431
4432U-Boot supports the following image types:
4433
4434   "Standalone Programs" are directly runnable in the environment
4435	provided by U-Boot; it is expected that (if they behave
4436	well) you can continue to work in U-Boot after return from
4437	the Standalone Program.
4438   "OS Kernel Images" are usually images of some Embedded OS which
4439	will take over control completely. Usually these programs
4440	will install their own set of exception handlers, device
4441	drivers, set up the MMU, etc. - this means, that you cannot
4442	expect to re-enter U-Boot except by resetting the CPU.
4443   "RAMDisk Images" are more or less just data blocks, and their
4444	parameters (address, size) are passed to an OS kernel that is
4445	being started.
4446   "Multi-File Images" contain several images, typically an OS
4447	(Linux) kernel image and one or more data images like
4448	RAMDisks. This construct is useful for instance when you want
4449	to boot over the network using BOOTP etc., where the boot
4450	server provides just a single image file, but you want to get
4451	for instance an OS kernel and a RAMDisk image.
4452
4453	"Multi-File Images" start with a list of image sizes, each
4454	image size (in bytes) specified by an "uint32_t" in network
4455	byte order. This list is terminated by an "(uint32_t)0".
4456	Immediately after the terminating 0 follow the images, one by
4457	one, all aligned on "uint32_t" boundaries (size rounded up to
4458	a multiple of 4 bytes).
4459
4460   "Firmware Images" are binary images containing firmware (like
4461	U-Boot or FPGA images) which usually will be programmed to
4462	flash memory.
4463
4464   "Script files" are command sequences that will be executed by
4465	U-Boot's command interpreter; this feature is especially
4466	useful when you configure U-Boot to use a real shell (hush)
4467	as command interpreter.
4468
4469Booting the Linux zImage:
4470-------------------------
4471
4472On some platforms, it's possible to boot Linux zImage. This is done
4473using the "bootz" command. The syntax of "bootz" command is the same
4474as the syntax of "bootm" command.
4475
4476Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4477kernel with raw initrd images. The syntax is slightly different, the
4478address of the initrd must be augmented by it's size, in the following
4479format: "<initrd addres>:<initrd size>".
4480
4481
4482Standalone HOWTO:
4483=================
4484
4485One of the features of U-Boot is that you can dynamically load and
4486run "standalone" applications, which can use some resources of
4487U-Boot like console I/O functions or interrupt services.
4488
4489Two simple examples are included with the sources:
4490
4491"Hello World" Demo:
4492-------------------
4493
4494'examples/hello_world.c' contains a small "Hello World" Demo
4495application; it is automatically compiled when you build U-Boot.
4496It's configured to run at address 0x00040004, so you can play with it
4497like that:
4498
4499	=> loads
4500	## Ready for S-Record download ...
4501	~>examples/hello_world.srec
4502	1 2 3 4 5 6 7 8 9 10 11 ...
4503	[file transfer complete]
4504	[connected]
4505	## Start Addr = 0x00040004
4506
4507	=> go 40004 Hello World! This is a test.
4508	## Starting application at 0x00040004 ...
4509	Hello World
4510	argc = 7
4511	argv[0] = "40004"
4512	argv[1] = "Hello"
4513	argv[2] = "World!"
4514	argv[3] = "This"
4515	argv[4] = "is"
4516	argv[5] = "a"
4517	argv[6] = "test."
4518	argv[7] = "<NULL>"
4519	Hit any key to exit ...
4520
4521	## Application terminated, rc = 0x0
4522
4523Another example, which demonstrates how to register a CPM interrupt
4524handler with the U-Boot code, can be found in 'examples/timer.c'.
4525Here, a CPM timer is set up to generate an interrupt every second.
4526The interrupt service routine is trivial, just printing a '.'
4527character, but this is just a demo program. The application can be
4528controlled by the following keys:
4529
4530	? - print current values og the CPM Timer registers
4531	b - enable interrupts and start timer
4532	e - stop timer and disable interrupts
4533	q - quit application
4534
4535	=> loads
4536	## Ready for S-Record download ...
4537	~>examples/timer.srec
4538	1 2 3 4 5 6 7 8 9 10 11 ...
4539	[file transfer complete]
4540	[connected]
4541	## Start Addr = 0x00040004
4542
4543	=> go 40004
4544	## Starting application at 0x00040004 ...
4545	TIMERS=0xfff00980
4546	Using timer 1
4547	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4548
4549Hit 'b':
4550	[q, b, e, ?] Set interval 1000000 us
4551	Enabling timer
4552Hit '?':
4553	[q, b, e, ?] ........
4554	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4555Hit '?':
4556	[q, b, e, ?] .
4557	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4558Hit '?':
4559	[q, b, e, ?] .
4560	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4561Hit '?':
4562	[q, b, e, ?] .
4563	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4564Hit 'e':
4565	[q, b, e, ?] ...Stopping timer
4566Hit 'q':
4567	[q, b, e, ?] ## Application terminated, rc = 0x0
4568
4569
4570Minicom warning:
4571================
4572
4573Over time, many people have reported problems when trying to use the
4574"minicom" terminal emulation program for serial download. I (wd)
4575consider minicom to be broken, and recommend not to use it. Under
4576Unix, I recommend to use C-Kermit for general purpose use (and
4577especially for kermit binary protocol download ("loadb" command), and
4578use "cu" for S-Record download ("loads" command).  See
4579http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4580for help with kermit.
4581
4582
4583Nevertheless, if you absolutely want to use it try adding this
4584configuration to your "File transfer protocols" section:
4585
4586	   Name	   Program			Name U/D FullScr IO-Red. Multi
4587	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4588	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4589
4590
4591NetBSD Notes:
4592=============
4593
4594Starting at version 0.9.2, U-Boot supports NetBSD both as host
4595(build U-Boot) and target system (boots NetBSD/mpc8xx).
4596
4597Building requires a cross environment; it is known to work on
4598NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4599need gmake since the Makefiles are not compatible with BSD make).
4600Note that the cross-powerpc package does not install include files;
4601attempting to build U-Boot will fail because <machine/ansi.h> is
4602missing.  This file has to be installed and patched manually:
4603
4604	# cd /usr/pkg/cross/powerpc-netbsd/include
4605	# mkdir powerpc
4606	# ln -s powerpc machine
4607	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4608	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4609
4610Native builds *don't* work due to incompatibilities between native
4611and U-Boot include files.
4612
4613Booting assumes that (the first part of) the image booted is a
4614stage-2 loader which in turn loads and then invokes the kernel
4615proper. Loader sources will eventually appear in the NetBSD source
4616tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4617meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4618
4619
4620Implementation Internals:
4621=========================
4622
4623The following is not intended to be a complete description of every
4624implementation detail. However, it should help to understand the
4625inner workings of U-Boot and make it easier to port it to custom
4626hardware.
4627
4628
4629Initial Stack, Global Data:
4630---------------------------
4631
4632The implementation of U-Boot is complicated by the fact that U-Boot
4633starts running out of ROM (flash memory), usually without access to
4634system RAM (because the memory controller is not initialized yet).
4635This means that we don't have writable Data or BSS segments, and BSS
4636is not initialized as zero. To be able to get a C environment working
4637at all, we have to allocate at least a minimal stack. Implementation
4638options for this are defined and restricted by the CPU used: Some CPU
4639models provide on-chip memory (like the IMMR area on MPC8xx and
4640MPC826x processors), on others (parts of) the data cache can be
4641locked as (mis-) used as memory, etc.
4642
4643	Chris Hallinan posted a good summary of these issues to the
4644	U-Boot mailing list:
4645
4646	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4647	From: "Chris Hallinan" <clh@net1plus.com>
4648	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4649	...
4650
4651	Correct me if I'm wrong, folks, but the way I understand it
4652	is this: Using DCACHE as initial RAM for Stack, etc, does not
4653	require any physical RAM backing up the cache. The cleverness
4654	is that the cache is being used as a temporary supply of
4655	necessary storage before the SDRAM controller is setup. It's
4656	beyond the scope of this list to explain the details, but you
4657	can see how this works by studying the cache architecture and
4658	operation in the architecture and processor-specific manuals.
4659
4660	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4661	is another option for the system designer to use as an
4662	initial stack/RAM area prior to SDRAM being available. Either
4663	option should work for you. Using CS 4 should be fine if your
4664	board designers haven't used it for something that would
4665	cause you grief during the initial boot! It is frequently not
4666	used.
4667
4668	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4669	with your processor/board/system design. The default value
4670	you will find in any recent u-boot distribution in
4671	walnut.h should work for you. I'd set it to a value larger
4672	than your SDRAM module. If you have a 64MB SDRAM module, set
4673	it above 400_0000. Just make sure your board has no resources
4674	that are supposed to respond to that address! That code in
4675	start.S has been around a while and should work as is when
4676	you get the config right.
4677
4678	-Chris Hallinan
4679	DS4.COM, Inc.
4680
4681It is essential to remember this, since it has some impact on the C
4682code for the initialization procedures:
4683
4684* Initialized global data (data segment) is read-only. Do not attempt
4685  to write it.
4686
4687* Do not use any uninitialized global data (or implicitly initialized
4688  as zero data - BSS segment) at all - this is undefined, initiali-
4689  zation is performed later (when relocating to RAM).
4690
4691* Stack space is very limited. Avoid big data buffers or things like
4692  that.
4693
4694Having only the stack as writable memory limits means we cannot use
4695normal global data to share information between the code. But it
4696turned out that the implementation of U-Boot can be greatly
4697simplified by making a global data structure (gd_t) available to all
4698functions. We could pass a pointer to this data as argument to _all_
4699functions, but this would bloat the code. Instead we use a feature of
4700the GCC compiler (Global Register Variables) to share the data: we
4701place a pointer (gd) to the global data into a register which we
4702reserve for this purpose.
4703
4704When choosing a register for such a purpose we are restricted by the
4705relevant  (E)ABI  specifications for the current architecture, and by
4706GCC's implementation.
4707
4708For PowerPC, the following registers have specific use:
4709	R1:	stack pointer
4710	R2:	reserved for system use
4711	R3-R4:	parameter passing and return values
4712	R5-R10: parameter passing
4713	R13:	small data area pointer
4714	R30:	GOT pointer
4715	R31:	frame pointer
4716
4717	(U-Boot also uses R12 as internal GOT pointer. r12
4718	is a volatile register so r12 needs to be reset when
4719	going back and forth between asm and C)
4720
4721    ==> U-Boot will use R2 to hold a pointer to the global data
4722
4723    Note: on PPC, we could use a static initializer (since the
4724    address of the global data structure is known at compile time),
4725    but it turned out that reserving a register results in somewhat
4726    smaller code - although the code savings are not that big (on
4727    average for all boards 752 bytes for the whole U-Boot image,
4728    624 text + 127 data).
4729
4730On ARM, the following registers are used:
4731
4732	R0:	function argument word/integer result
4733	R1-R3:	function argument word
4734	R9:	platform specific
4735	R10:	stack limit (used only if stack checking is enabled)
4736	R11:	argument (frame) pointer
4737	R12:	temporary workspace
4738	R13:	stack pointer
4739	R14:	link register
4740	R15:	program counter
4741
4742    ==> U-Boot will use R9 to hold a pointer to the global data
4743
4744    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4745
4746On Nios II, the ABI is documented here:
4747	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4748
4749    ==> U-Boot will use gp to hold a pointer to the global data
4750
4751    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4752    to access small data sections, so gp is free.
4753
4754On NDS32, the following registers are used:
4755
4756	R0-R1:	argument/return
4757	R2-R5:	argument
4758	R15:	temporary register for assembler
4759	R16:	trampoline register
4760	R28:	frame pointer (FP)
4761	R29:	global pointer (GP)
4762	R30:	link register (LP)
4763	R31:	stack pointer (SP)
4764	PC:	program counter (PC)
4765
4766    ==> U-Boot will use R10 to hold a pointer to the global data
4767
4768NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4769or current versions of GCC may "optimize" the code too much.
4770
4771On RISC-V, the following registers are used:
4772
4773	x0: hard-wired zero (zero)
4774	x1: return address (ra)
4775	x2:	stack pointer (sp)
4776	x3:	global pointer (gp)
4777	x4:	thread pointer (tp)
4778	x5:	link register (t0)
4779	x8:	frame pointer (fp)
4780	x10-x11:	arguments/return values (a0-1)
4781	x12-x17:	arguments (a2-7)
4782	x28-31:	 temporaries (t3-6)
4783	pc:	program counter (pc)
4784
4785    ==> U-Boot will use gp to hold a pointer to the global data
4786
4787Memory Management:
4788------------------
4789
4790U-Boot runs in system state and uses physical addresses, i.e. the
4791MMU is not used either for address mapping nor for memory protection.
4792
4793The available memory is mapped to fixed addresses using the memory
4794controller. In this process, a contiguous block is formed for each
4795memory type (Flash, SDRAM, SRAM), even when it consists of several
4796physical memory banks.
4797
4798U-Boot is installed in the first 128 kB of the first Flash bank (on
4799TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4800booting and sizing and initializing DRAM, the code relocates itself
4801to the upper end of DRAM. Immediately below the U-Boot code some
4802memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4803configuration setting]. Below that, a structure with global Board
4804Info data is placed, followed by the stack (growing downward).
4805
4806Additionally, some exception handler code is copied to the low 8 kB
4807of DRAM (0x00000000 ... 0x00001FFF).
4808
4809So a typical memory configuration with 16 MB of DRAM could look like
4810this:
4811
4812	0x0000 0000	Exception Vector code
4813	      :
4814	0x0000 1FFF
4815	0x0000 2000	Free for Application Use
4816	      :
4817	      :
4818
4819	      :
4820	      :
4821	0x00FB FF20	Monitor Stack (Growing downward)
4822	0x00FB FFAC	Board Info Data and permanent copy of global data
4823	0x00FC 0000	Malloc Arena
4824	      :
4825	0x00FD FFFF
4826	0x00FE 0000	RAM Copy of Monitor Code
4827	...		eventually: LCD or video framebuffer
4828	...		eventually: pRAM (Protected RAM - unchanged by reset)
4829	0x00FF FFFF	[End of RAM]
4830
4831
4832System Initialization:
4833----------------------
4834
4835In the reset configuration, U-Boot starts at the reset entry point
4836(on most PowerPC systems at address 0x00000100). Because of the reset
4837configuration for CS0# this is a mirror of the on board Flash memory.
4838To be able to re-map memory U-Boot then jumps to its link address.
4839To be able to implement the initialization code in C, a (small!)
4840initial stack is set up in the internal Dual Ported RAM (in case CPUs
4841which provide such a feature like), or in a locked part of the data
4842cache. After that, U-Boot initializes the CPU core, the caches and
4843the SIU.
4844
4845Next, all (potentially) available memory banks are mapped using a
4846preliminary mapping. For example, we put them on 512 MB boundaries
4847(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4848on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4849programmed for SDRAM access. Using the temporary configuration, a
4850simple memory test is run that determines the size of the SDRAM
4851banks.
4852
4853When there is more than one SDRAM bank, and the banks are of
4854different size, the largest is mapped first. For equal size, the first
4855bank (CS2#) is mapped first. The first mapping is always for address
48560x00000000, with any additional banks following immediately to create
4857contiguous memory starting from 0.
4858
4859Then, the monitor installs itself at the upper end of the SDRAM area
4860and allocates memory for use by malloc() and for the global Board
4861Info data; also, the exception vector code is copied to the low RAM
4862pages, and the final stack is set up.
4863
4864Only after this relocation will you have a "normal" C environment;
4865until that you are restricted in several ways, mostly because you are
4866running from ROM, and because the code will have to be relocated to a
4867new address in RAM.
4868
4869
4870U-Boot Porting Guide:
4871----------------------
4872
4873[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4874list, October 2002]
4875
4876
4877int main(int argc, char *argv[])
4878{
4879	sighandler_t no_more_time;
4880
4881	signal(SIGALRM, no_more_time);
4882	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4883
4884	if (available_money > available_manpower) {
4885		Pay consultant to port U-Boot;
4886		return 0;
4887	}
4888
4889	Download latest U-Boot source;
4890
4891	Subscribe to u-boot mailing list;
4892
4893	if (clueless)
4894		email("Hi, I am new to U-Boot, how do I get started?");
4895
4896	while (learning) {
4897		Read the README file in the top level directory;
4898		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4899		Read applicable doc/*.README;
4900		Read the source, Luke;
4901		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4902	}
4903
4904	if (available_money > toLocalCurrency ($2500))
4905		Buy a BDI3000;
4906	else
4907		Add a lot of aggravation and time;
4908
4909	if (a similar board exists) {	/* hopefully... */
4910		cp -a board/<similar> board/<myboard>
4911		cp include/configs/<similar>.h include/configs/<myboard>.h
4912	} else {
4913		Create your own board support subdirectory;
4914		Create your own board include/configs/<myboard>.h file;
4915	}
4916	Edit new board/<myboard> files
4917	Edit new include/configs/<myboard>.h
4918
4919	while (!accepted) {
4920		while (!running) {
4921			do {
4922				Add / modify source code;
4923			} until (compiles);
4924			Debug;
4925			if (clueless)
4926				email("Hi, I am having problems...");
4927		}
4928		Send patch file to the U-Boot email list;
4929		if (reasonable critiques)
4930			Incorporate improvements from email list code review;
4931		else
4932			Defend code as written;
4933	}
4934
4935	return 0;
4936}
4937
4938void no_more_time (int sig)
4939{
4940      hire_a_guru();
4941}
4942
4943
4944Coding Standards:
4945-----------------
4946
4947All contributions to U-Boot should conform to the Linux kernel
4948coding style; see the kernel coding style guide at
4949https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4950script "scripts/Lindent" in your Linux kernel source directory.
4951
4952Source files originating from a different project (for example the
4953MTD subsystem) are generally exempt from these guidelines and are not
4954reformatted to ease subsequent migration to newer versions of those
4955sources.
4956
4957Please note that U-Boot is implemented in C (and to some small parts in
4958Assembler); no C++ is used, so please do not use C++ style comments (//)
4959in your code.
4960
4961Please also stick to the following formatting rules:
4962- remove any trailing white space
4963- use TAB characters for indentation and vertical alignment, not spaces
4964- make sure NOT to use DOS '\r\n' line feeds
4965- do not add more than 2 consecutive empty lines to source files
4966- do not add trailing empty lines to source files
4967
4968Submissions which do not conform to the standards may be returned
4969with a request to reformat the changes.
4970
4971
4972Submitting Patches:
4973-------------------
4974
4975Since the number of patches for U-Boot is growing, we need to
4976establish some rules. Submissions which do not conform to these rules
4977may be rejected, even when they contain important and valuable stuff.
4978
4979Please see http://www.denx.de/wiki/U-Boot/Patches for details.
4980
4981Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4982see https://lists.denx.de/listinfo/u-boot
4983
4984When you send a patch, please include the following information with
4985it:
4986
4987* For bug fixes: a description of the bug and how your patch fixes
4988  this bug. Please try to include a way of demonstrating that the
4989  patch actually fixes something.
4990
4991* For new features: a description of the feature and your
4992  implementation.
4993
4994* A CHANGELOG entry as plaintext (separate from the patch)
4995
4996* For major contributions, add a MAINTAINERS file with your
4997  information and associated file and directory references.
4998
4999* When you add support for a new board, don't forget to add a
5000  maintainer e-mail address to the boards.cfg file, too.
5001
5002* If your patch adds new configuration options, don't forget to
5003  document these in the README file.
5004
5005* The patch itself. If you are using git (which is *strongly*
5006  recommended) you can easily generate the patch using the
5007  "git format-patch". If you then use "git send-email" to send it to
5008  the U-Boot mailing list, you will avoid most of the common problems
5009  with some other mail clients.
5010
5011  If you cannot use git, use "diff -purN OLD NEW". If your version of
5012  diff does not support these options, then get the latest version of
5013  GNU diff.
5014
5015  The current directory when running this command shall be the parent
5016  directory of the U-Boot source tree (i. e. please make sure that
5017  your patch includes sufficient directory information for the
5018  affected files).
5019
5020  We prefer patches as plain text. MIME attachments are discouraged,
5021  and compressed attachments must not be used.
5022
5023* If one logical set of modifications affects or creates several
5024  files, all these changes shall be submitted in a SINGLE patch file.
5025
5026* Changesets that contain different, unrelated modifications shall be
5027  submitted as SEPARATE patches, one patch per changeset.
5028
5029
5030Notes:
5031
5032* Before sending the patch, run the buildman script on your patched
5033  source tree and make sure that no errors or warnings are reported
5034  for any of the boards.
5035
5036* Keep your modifications to the necessary minimum: A patch
5037  containing several unrelated changes or arbitrary reformats will be
5038  returned with a request to re-formatting / split it.
5039
5040* If you modify existing code, make sure that your new code does not
5041  add to the memory footprint of the code ;-) Small is beautiful!
5042  When adding new features, these should compile conditionally only
5043  (using #ifdef), and the resulting code with the new feature
5044  disabled must not need more memory than the old code without your
5045  modification.
5046
5047* Remember that there is a size limit of 100 kB per message on the
5048  u-boot mailing list. Bigger patches will be moderated. If they are
5049  reasonable and not too big, they will be acknowledged. But patches
5050  bigger than the size limit should be avoided.
5051