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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  * 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 doc/arch/index.rst 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	- for specific scenarios on certain architectures an early BSS *can*
271	  be made available (via CONFIG_SPL_EARLY_BSS by moving the clearing
272	  of BSS prior to entering board_init_f()) but doing so is discouraged.
273	  Instead it is strongly recommended to architect any code changes
274	  or additions such to not depend on the availability of BSS during
275	  board_init_f() as indicated in other sections of this README to
276	  maintain compatibility and consistency across the entire code base.
277	- must return normally from this function (don't call board_init_r()
278		directly)
279
280Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
281this point the stack and global_data are relocated to below
282CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
283memory.
284
285board_init_r():
286	- purpose: main execution, common code
287	- global_data is available
288	- SDRAM is available
289	- BSS is available, all static/global variables can be used
290	- execution eventually continues to main_loop()
291
292	Non-SPL-specific notes:
293	- U-Boot is relocated to the top of memory and is now running from
294		there.
295
296	SPL-specific notes:
297	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
298		CONFIG_SPL_STACK_R_ADDR points into SDRAM
299	- preloader_console_init() can be called here - typically this is
300		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
301		spl_board_init() function containing this call
302	- loads U-Boot or (in falcon mode) Linux
303
304
305
306Configuration Options:
307----------------------
308
309Configuration depends on the combination of board and CPU type; all
310such information is kept in a configuration file
311"include/configs/<board_name>.h".
312
313Example: For a TQM823L module, all configuration settings are in
314"include/configs/TQM823L.h".
315
316
317Many of the options are named exactly as the corresponding Linux
318kernel configuration options. The intention is to make it easier to
319build a config tool - later.
320
321- ARM Platform Bus Type(CCI):
322		CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
323		provides full cache coherency between two clusters of multi-core
324		CPUs and I/O coherency for devices and I/O masters
325
326		CONFIG_SYS_FSL_HAS_CCI400
327
328		Defined For SoC that has cache coherent interconnect
329		CCN-400
330
331		CONFIG_SYS_FSL_HAS_CCN504
332
333		Defined for SoC that has cache coherent interconnect CCN-504
334
335The following options need to be configured:
336
337- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
338
339- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
340
341- 85xx CPU Options:
342		CONFIG_SYS_PPC64
343
344		Specifies that the core is a 64-bit PowerPC implementation (implements
345		the "64" category of the Power ISA). This is necessary for ePAPR
346		compliance, among other possible reasons.
347
348		CONFIG_SYS_FSL_TBCLK_DIV
349
350		Defines the core time base clock divider ratio compared to the
351		system clock.  On most PQ3 devices this is 8, on newer QorIQ
352		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
353
354		CONFIG_SYS_FSL_PCIE_COMPAT
355
356		Defines the string to utilize when trying to match PCIe device
357		tree nodes for the given platform.
358
359		CONFIG_SYS_FSL_ERRATUM_A004510
360
361		Enables a workaround for erratum A004510.  If set,
362		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
363		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
364
365		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
366		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
367
368		Defines one or two SoC revisions (low 8 bits of SVR)
369		for which the A004510 workaround should be applied.
370
371		The rest of SVR is either not relevant to the decision
372		of whether the erratum is present (e.g. p2040 versus
373		p2041) or is implied by the build target, which controls
374		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
375
376		See Freescale App Note 4493 for more information about
377		this erratum.
378
379		CONFIG_A003399_NOR_WORKAROUND
380		Enables a workaround for IFC erratum A003399. It is only
381		required during NOR boot.
382
383		CONFIG_A008044_WORKAROUND
384		Enables a workaround for T1040/T1042 erratum A008044. It is only
385		required during NAND boot and valid for Rev 1.0 SoC revision
386
387		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
388
389		This is the value to write into CCSR offset 0x18600
390		according to the A004510 workaround.
391
392		CONFIG_SYS_FSL_DSP_DDR_ADDR
393		This value denotes start offset of DDR memory which is
394		connected exclusively to the DSP cores.
395
396		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
397		This value denotes start offset of M2 memory
398		which is directly connected to the DSP core.
399
400		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
401		This value denotes start offset of M3 memory which is directly
402		connected to the DSP core.
403
404		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
405		This value denotes start offset of DSP CCSR space.
406
407		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
408		Single Source Clock is clocking mode present in some of FSL SoC's.
409		In this mode, a single differential clock is used to supply
410		clocks to the sysclock, ddrclock and usbclock.
411
412		CONFIG_SYS_CPC_REINIT_F
413		This CONFIG is defined when the CPC is configured as SRAM at the
414		time of U-Boot entry and is required to be re-initialized.
415
416		CONFIG_DEEP_SLEEP
417		Indicates this SoC supports deep sleep feature. If deep sleep is
418		supported, core will start to execute uboot when wakes up.
419
420- Generic CPU options:
421		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
422
423		Defines the endianess of the CPU. Implementation of those
424		values is arch specific.
425
426		CONFIG_SYS_FSL_DDR
427		Freescale DDR driver in use. This type of DDR controller is
428		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
429		SoCs.
430
431		CONFIG_SYS_FSL_DDR_ADDR
432		Freescale DDR memory-mapped register base.
433
434		CONFIG_SYS_FSL_DDR_EMU
435		Specify emulator support for DDR. Some DDR features such as
436		deskew training are not available.
437
438		CONFIG_SYS_FSL_DDRC_GEN1
439		Freescale DDR1 controller.
440
441		CONFIG_SYS_FSL_DDRC_GEN2
442		Freescale DDR2 controller.
443
444		CONFIG_SYS_FSL_DDRC_GEN3
445		Freescale DDR3 controller.
446
447		CONFIG_SYS_FSL_DDRC_GEN4
448		Freescale DDR4 controller.
449
450		CONFIG_SYS_FSL_DDRC_ARM_GEN3
451		Freescale DDR3 controller for ARM-based SoCs.
452
453		CONFIG_SYS_FSL_DDR1
454		Board config to use DDR1. It can be enabled for SoCs with
455		Freescale DDR1 or DDR2 controllers, depending on the board
456		implemetation.
457
458		CONFIG_SYS_FSL_DDR2
459		Board config to use DDR2. It can be enabled for SoCs with
460		Freescale DDR2 or DDR3 controllers, depending on the board
461		implementation.
462
463		CONFIG_SYS_FSL_DDR3
464		Board config to use DDR3. It can be enabled for SoCs with
465		Freescale DDR3 or DDR3L controllers.
466
467		CONFIG_SYS_FSL_DDR3L
468		Board config to use DDR3L. It can be enabled for SoCs with
469		DDR3L controllers.
470
471		CONFIG_SYS_FSL_DDR4
472		Board config to use DDR4. It can be enabled for SoCs with
473		DDR4 controllers.
474
475		CONFIG_SYS_FSL_IFC_BE
476		Defines the IFC controller register space as Big Endian
477
478		CONFIG_SYS_FSL_IFC_LE
479		Defines the IFC controller register space as Little Endian
480
481		CONFIG_SYS_FSL_IFC_CLK_DIV
482		Defines divider of platform clock(clock input to IFC controller).
483
484		CONFIG_SYS_FSL_LBC_CLK_DIV
485		Defines divider of platform clock(clock input to eLBC controller).
486
487		CONFIG_SYS_FSL_PBL_PBI
488		It enables addition of RCW (Power on reset configuration) in built image.
489		Please refer doc/README.pblimage for more details
490
491		CONFIG_SYS_FSL_PBL_RCW
492		It adds PBI(pre-boot instructions) commands in u-boot build image.
493		PBI commands can be used to configure SoC before it starts the execution.
494		Please refer doc/README.pblimage for more details
495
496		CONFIG_SYS_FSL_DDR_BE
497		Defines the DDR controller register space as Big Endian
498
499		CONFIG_SYS_FSL_DDR_LE
500		Defines the DDR controller register space as Little Endian
501
502		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
503		Physical address from the view of DDR controllers. It is the
504		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
505		it could be different for ARM SoCs.
506
507		CONFIG_SYS_FSL_DDR_INTLV_256B
508		DDR controller interleaving on 256-byte. This is a special
509		interleaving mode, handled by Dickens for Freescale layerscape
510		SoCs with ARM core.
511
512		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
513		Number of controllers used as main memory.
514
515		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
516		Number of controllers used for other than main memory.
517
518		CONFIG_SYS_FSL_HAS_DP_DDR
519		Defines the SoC has DP-DDR used for DPAA.
520
521		CONFIG_SYS_FSL_SEC_BE
522		Defines the SEC controller register space as Big Endian
523
524		CONFIG_SYS_FSL_SEC_LE
525		Defines the SEC controller register space as Little Endian
526
527- MIPS CPU options:
528		CONFIG_SYS_INIT_SP_OFFSET
529
530		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
531		pointer. This is needed for the temporary stack before
532		relocation.
533
534		CONFIG_XWAY_SWAP_BYTES
535
536		Enable compilation of tools/xway-swap-bytes needed for Lantiq
537		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
538		be swapped if a flash programmer is used.
539
540- ARM options:
541		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
542
543		Select high exception vectors of the ARM core, e.g., do not
544		clear the V bit of the c1 register of CP15.
545
546		COUNTER_FREQUENCY
547		Generic timer clock source frequency.
548
549		COUNTER_FREQUENCY_REAL
550		Generic timer clock source frequency if the real clock is
551		different from COUNTER_FREQUENCY, and can only be determined
552		at run time.
553
554- Tegra SoC options:
555		CONFIG_TEGRA_SUPPORT_NON_SECURE
556
557		Support executing U-Boot in non-secure (NS) mode. Certain
558		impossible actions will be skipped if the CPU is in NS mode,
559		such as ARM architectural timer initialization.
560
561- Linux Kernel Interface:
562		CONFIG_CLOCKS_IN_MHZ
563
564		U-Boot stores all clock information in Hz
565		internally. For binary compatibility with older Linux
566		kernels (which expect the clocks passed in the
567		bd_info data to be in MHz) the environment variable
568		"clocks_in_mhz" can be defined so that U-Boot
569		converts clock data to MHZ before passing it to the
570		Linux kernel.
571		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
572		"clocks_in_mhz=1" is automatically included in the
573		default environment.
574
575		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
576
577		When transferring memsize parameter to Linux, some versions
578		expect it to be in bytes, others in MB.
579		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
580
581		CONFIG_OF_LIBFDT
582
583		New kernel versions are expecting firmware settings to be
584		passed using flattened device trees (based on open firmware
585		concepts).
586
587		CONFIG_OF_LIBFDT
588		 * New libfdt-based support
589		 * Adds the "fdt" command
590		 * The bootm command automatically updates the fdt
591
592		OF_TBCLK - The timebase frequency.
593		OF_STDOUT_PATH - The path to the console device
594
595		boards with QUICC Engines require OF_QE to set UCC MAC
596		addresses
597
598		CONFIG_OF_BOARD_SETUP
599
600		Board code has addition modification that it wants to make
601		to the flat device tree before handing it off to the kernel
602
603		CONFIG_OF_SYSTEM_SETUP
604
605		Other code has addition modification that it wants to make
606		to the flat device tree before handing it off to the kernel.
607		This causes ft_system_setup() to be called before booting
608		the kernel.
609
610		CONFIG_OF_IDE_FIXUP
611
612		U-Boot can detect if an IDE device is present or not.
613		If not, and this new config option is activated, U-Boot
614		removes the ATA node from the DTS before booting Linux,
615		so the Linux IDE driver does not probe the device and
616		crash. This is needed for buggy hardware (uc101) where
617		no pull down resistor is connected to the signal IDE5V_DD7.
618
619		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
620
621		This setting is mandatory for all boards that have only one
622		machine type and must be used to specify the machine type
623		number as it appears in the ARM machine registry
624		(see http://www.arm.linux.org.uk/developer/machines/).
625		Only boards that have multiple machine types supported
626		in a single configuration file and the machine type is
627		runtime discoverable, do not have to use this setting.
628
629- vxWorks boot parameters:
630
631		bootvx constructs a valid bootline using the following
632		environments variables: bootdev, bootfile, ipaddr, netmask,
633		serverip, gatewayip, hostname, othbootargs.
634		It loads the vxWorks image pointed bootfile.
635
636		Note: If a "bootargs" environment is defined, it will overwride
637		the defaults discussed just above.
638
639- Cache Configuration:
640		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
641
642- Cache Configuration for ARM:
643		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
644				      controller
645		CONFIG_SYS_PL310_BASE - Physical base address of PL310
646					controller register space
647
648- Serial Ports:
649		CONFIG_PL010_SERIAL
650
651		Define this if you want support for Amba PrimeCell PL010 UARTs.
652
653		CONFIG_PL011_SERIAL
654
655		Define this if you want support for Amba PrimeCell PL011 UARTs.
656
657		CONFIG_PL011_CLOCK
658
659		If you have Amba PrimeCell PL011 UARTs, set this variable to
660		the clock speed of the UARTs.
661
662		CONFIG_PL01x_PORTS
663
664		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
665		define this to a list of base addresses for each (supported)
666		port. See e.g. include/configs/versatile.h
667
668		CONFIG_SERIAL_HW_FLOW_CONTROL
669
670		Define this variable to enable hw flow control in serial driver.
671		Current user of this option is drivers/serial/nsl16550.c driver
672
673- Console Baudrate:
674		CONFIG_BAUDRATE - in bps
675		Select one of the baudrates listed in
676		CONFIG_SYS_BAUDRATE_TABLE, see below.
677
678- Autoboot Command:
679		CONFIG_BOOTCOMMAND
680		Only needed when CONFIG_BOOTDELAY is enabled;
681		define a command string that is automatically executed
682		when no character is read on the console interface
683		within "Boot Delay" after reset.
684
685		CONFIG_RAMBOOT and CONFIG_NFSBOOT
686		The value of these goes into the environment as
687		"ramboot" and "nfsboot" respectively, and can be used
688		as a convenience, when switching between booting from
689		RAM and NFS.
690
691- Serial Download Echo Mode:
692		CONFIG_LOADS_ECHO
693		If defined to 1, all characters received during a
694		serial download (using the "loads" command) are
695		echoed back. This might be needed by some terminal
696		emulations (like "cu"), but may as well just take
697		time on others. This setting #define's the initial
698		value of the "loads_echo" environment variable.
699
700- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
701		CONFIG_KGDB_BAUDRATE
702		Select one of the baudrates listed in
703		CONFIG_SYS_BAUDRATE_TABLE, see below.
704
705- Removal of commands
706		If no commands are needed to boot, you can disable
707		CONFIG_CMDLINE to remove them. In this case, the command line
708		will not be available, and when U-Boot wants to execute the
709		boot command (on start-up) it will call board_run_command()
710		instead. This can reduce image size significantly for very
711		simple boot procedures.
712
713- Regular expression support:
714		CONFIG_REGEX
715		If this variable is defined, U-Boot is linked against
716		the SLRE (Super Light Regular Expression) library,
717		which adds regex support to some commands, as for
718		example "env grep" and "setexpr".
719
720- Device tree:
721		CONFIG_OF_CONTROL
722		If this variable is defined, U-Boot will use a device tree
723		to configure its devices, instead of relying on statically
724		compiled #defines in the board file. This option is
725		experimental and only available on a few boards. The device
726		tree is available in the global data as gd->fdt_blob.
727
728		U-Boot needs to get its device tree from somewhere. This can
729		be done using one of the three options below:
730
731		CONFIG_OF_EMBED
732		If this variable is defined, U-Boot will embed a device tree
733		binary in its image. This device tree file should be in the
734		board directory and called <soc>-<board>.dts. The binary file
735		is then picked up in board_init_f() and made available through
736		the global data structure as gd->fdt_blob.
737
738		CONFIG_OF_SEPARATE
739		If this variable is defined, U-Boot will build a device tree
740		binary. It will be called u-boot.dtb. Architecture-specific
741		code will locate it at run-time. Generally this works by:
742
743			cat u-boot.bin u-boot.dtb >image.bin
744
745		and in fact, U-Boot does this for you, creating a file called
746		u-boot-dtb.bin which is useful in the common case. You can
747		still use the individual files if you need something more
748		exotic.
749
750		CONFIG_OF_BOARD
751		If this variable is defined, U-Boot will use the device tree
752		provided by the board at runtime instead of embedding one with
753		the image. Only boards defining board_fdt_blob_setup() support
754		this option (see include/fdtdec.h file).
755
756- Watchdog:
757		CONFIG_WATCHDOG
758		If this variable is defined, it enables watchdog
759		support for the SoC. There must be support in the SoC
760		specific code for a watchdog. For the 8xx
761		CPUs, the SIU Watchdog feature is enabled in the SYPCR
762		register.  When supported for a specific SoC is
763		available, then no further board specific code should
764		be needed to use it.
765
766		CONFIG_HW_WATCHDOG
767		When using a watchdog circuitry external to the used
768		SoC, then define this variable and provide board
769		specific code for the "hw_watchdog_reset" function.
770
771- Real-Time Clock:
772
773		When CONFIG_CMD_DATE is selected, the type of the RTC
774		has to be selected, too. Define exactly one of the
775		following options:
776
777		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
778		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
779		CONFIG_RTC_MC146818	- use MC146818 RTC
780		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
781		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
782		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
783		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
784		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
785		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
786		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
787		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
788		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
789					  RV3029 RTC.
790
791		Note that if the RTC uses I2C, then the I2C interface
792		must also be configured. See I2C Support, below.
793
794- GPIO Support:
795		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
796
797		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
798		chip-ngpio pairs that tell the PCA953X driver the number of
799		pins supported by a particular chip.
800
801		Note that if the GPIO device uses I2C, then the I2C interface
802		must also be configured. See I2C Support, below.
803
804- I/O tracing:
805		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
806		accesses and can checksum them or write a list of them out
807		to memory. See the 'iotrace' command for details. This is
808		useful for testing device drivers since it can confirm that
809		the driver behaves the same way before and after a code
810		change. Currently this is supported on sandbox and arm. To
811		add support for your architecture, add '#include <iotrace.h>'
812		to the bottom of arch/<arch>/include/asm/io.h and test.
813
814		Example output from the 'iotrace stats' command is below.
815		Note that if the trace buffer is exhausted, the checksum will
816		still continue to operate.
817
818			iotrace is enabled
819			Start:  10000000	(buffer start address)
820			Size:   00010000	(buffer size)
821			Offset: 00000120	(current buffer offset)
822			Output: 10000120	(start + offset)
823			Count:  00000018	(number of trace records)
824			CRC32:  9526fb66	(CRC32 of all trace records)
825
826- Timestamp Support:
827
828		When CONFIG_TIMESTAMP is selected, the timestamp
829		(date and time) of an image is printed by image
830		commands like bootm or iminfo. This option is
831		automatically enabled when you select CONFIG_CMD_DATE .
832
833- Partition Labels (disklabels) Supported:
834		Zero or more of the following:
835		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
836		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
837		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
838				       bootloader.  Note 2TB partition limit; see
839				       disk/part_efi.c
840		CONFIG_SCSI) you must configure support for at
841		least one non-MTD partition type as well.
842
843- IDE Reset method:
844		CONFIG_IDE_RESET_ROUTINE - this is defined in several
845		board configurations files but used nowhere!
846
847		CONFIG_IDE_RESET - is this is defined, IDE Reset will
848		be performed by calling the function
849			ide_set_reset(int reset)
850		which has to be defined in a board specific file
851
852- ATAPI Support:
853		CONFIG_ATAPI
854
855		Set this to enable ATAPI support.
856
857- LBA48 Support
858		CONFIG_LBA48
859
860		Set this to enable support for disks larger than 137GB
861		Also look at CONFIG_SYS_64BIT_LBA.
862		Whithout these , LBA48 support uses 32bit variables and will 'only'
863		support disks up to 2.1TB.
864
865		CONFIG_SYS_64BIT_LBA:
866			When enabled, makes the IDE subsystem use 64bit sector addresses.
867			Default is 32bit.
868
869- SCSI Support:
870		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
871		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
872		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
873		maximum numbers of LUNs, SCSI ID's and target
874		devices.
875
876		The environment variable 'scsidevs' is set to the number of
877		SCSI devices found during the last scan.
878
879- NETWORK Support (PCI):
880		CONFIG_E1000
881		Support for Intel 8254x/8257x gigabit chips.
882
883		CONFIG_E1000_SPI
884		Utility code for direct access to the SPI bus on Intel 8257x.
885		This does not do anything useful unless you set at least one
886		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
887
888		CONFIG_E1000_SPI_GENERIC
889		Allow generic access to the SPI bus on the Intel 8257x, for
890		example with the "sspi" command.
891
892		CONFIG_EEPRO100
893		Support for Intel 82557/82559/82559ER chips.
894		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
895		write routine for first time initialisation.
896
897		CONFIG_TULIP
898		Support for Digital 2114x chips.
899		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
900		modem chip initialisation (KS8761/QS6611).
901
902		CONFIG_NATSEMI
903		Support for National dp83815 chips.
904
905		CONFIG_NS8382X
906		Support for National dp8382[01] gigabit chips.
907
908- NETWORK Support (other):
909
910		CONFIG_DRIVER_AT91EMAC
911		Support for AT91RM9200 EMAC.
912
913			CONFIG_RMII
914			Define this to use reduced MII inteface
915
916			CONFIG_DRIVER_AT91EMAC_QUIET
917			If this defined, the driver is quiet.
918			The driver doen't show link status messages.
919
920		CONFIG_CALXEDA_XGMAC
921		Support for the Calxeda XGMAC device
922
923		CONFIG_LAN91C96
924		Support for SMSC's LAN91C96 chips.
925
926			CONFIG_LAN91C96_USE_32_BIT
927			Define this to enable 32 bit addressing
928
929		CONFIG_SMC91111
930		Support for SMSC's LAN91C111 chip
931
932			CONFIG_SMC91111_BASE
933			Define this to hold the physical address
934			of the device (I/O space)
935
936			CONFIG_SMC_USE_32_BIT
937			Define this if data bus is 32 bits
938
939			CONFIG_SMC_USE_IOFUNCS
940			Define this to use i/o functions instead of macros
941			(some hardware wont work with macros)
942
943			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
944			Define this if you have more then 3 PHYs.
945
946		CONFIG_FTGMAC100
947		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
948
949			CONFIG_FTGMAC100_EGIGA
950			Define this to use GE link update with gigabit PHY.
951			Define this if FTGMAC100 is connected to gigabit PHY.
952			If your system has 10/100 PHY only, it might not occur
953			wrong behavior. Because PHY usually return timeout or
954			useless data when polling gigabit status and gigabit
955			control registers. This behavior won't affect the
956			correctnessof 10/100 link speed update.
957
958		CONFIG_SH_ETHER
959		Support for Renesas on-chip Ethernet controller
960
961			CONFIG_SH_ETHER_USE_PORT
962			Define the number of ports to be used
963
964			CONFIG_SH_ETHER_PHY_ADDR
965			Define the ETH PHY's address
966
967			CONFIG_SH_ETHER_CACHE_WRITEBACK
968			If this option is set, the driver enables cache flush.
969
970- TPM Support:
971		CONFIG_TPM
972		Support TPM devices.
973
974		CONFIG_TPM_TIS_INFINEON
975		Support for Infineon i2c bus TPM devices. Only one device
976		per system is supported at this time.
977
978			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
979			Define the burst count bytes upper limit
980
981		CONFIG_TPM_ST33ZP24
982		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
983
984			CONFIG_TPM_ST33ZP24_I2C
985			Support for STMicroelectronics ST33ZP24 I2C devices.
986			Requires TPM_ST33ZP24 and I2C.
987
988			CONFIG_TPM_ST33ZP24_SPI
989			Support for STMicroelectronics ST33ZP24 SPI devices.
990			Requires TPM_ST33ZP24 and SPI.
991
992		CONFIG_TPM_ATMEL_TWI
993		Support for Atmel TWI TPM device. Requires I2C support.
994
995		CONFIG_TPM_TIS_LPC
996		Support for generic parallel port TPM devices. Only one device
997		per system is supported at this time.
998
999			CONFIG_TPM_TIS_BASE_ADDRESS
1000			Base address where the generic TPM device is mapped
1001			to. Contemporary x86 systems usually map it at
1002			0xfed40000.
1003
1004		CONFIG_TPM
1005		Define this to enable the TPM support library which provides
1006		functional interfaces to some TPM commands.
1007		Requires support for a TPM device.
1008
1009		CONFIG_TPM_AUTH_SESSIONS
1010		Define this to enable authorized functions in the TPM library.
1011		Requires CONFIG_TPM and CONFIG_SHA1.
1012
1013- USB Support:
1014		At the moment only the UHCI host controller is
1015		supported (PIP405, MIP405); define
1016		CONFIG_USB_UHCI to enable it.
1017		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1018		and define CONFIG_USB_STORAGE to enable the USB
1019		storage devices.
1020		Note:
1021		Supported are USB Keyboards and USB Floppy drives
1022		(TEAC FD-05PUB).
1023
1024		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1025		txfilltuning field in the EHCI controller on reset.
1026
1027		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1028		HW module registers.
1029
1030- USB Device:
1031		Define the below if you wish to use the USB console.
1032		Once firmware is rebuilt from a serial console issue the
1033		command "setenv stdin usbtty; setenv stdout usbtty" and
1034		attach your USB cable. The Unix command "dmesg" should print
1035		it has found a new device. The environment variable usbtty
1036		can be set to gserial or cdc_acm to enable your device to
1037		appear to a USB host as a Linux gserial device or a
1038		Common Device Class Abstract Control Model serial device.
1039		If you select usbtty = gserial you should be able to enumerate
1040		a Linux host by
1041		# modprobe usbserial vendor=0xVendorID product=0xProductID
1042		else if using cdc_acm, simply setting the environment
1043		variable usbtty to be cdc_acm should suffice. The following
1044		might be defined in YourBoardName.h
1045
1046			CONFIG_USB_DEVICE
1047			Define this to build a UDC device
1048
1049			CONFIG_USB_TTY
1050			Define this to have a tty type of device available to
1051			talk to the UDC device
1052
1053			CONFIG_USBD_HS
1054			Define this to enable the high speed support for usb
1055			device and usbtty. If this feature is enabled, a routine
1056			int is_usbd_high_speed(void)
1057			also needs to be defined by the driver to dynamically poll
1058			whether the enumeration has succeded at high speed or full
1059			speed.
1060
1061			CONFIG_SYS_CONSOLE_IS_IN_ENV
1062			Define this if you want stdin, stdout &/or stderr to
1063			be set to usbtty.
1064
1065		If you have a USB-IF assigned VendorID then you may wish to
1066		define your own vendor specific values either in BoardName.h
1067		or directly in usbd_vendor_info.h. If you don't define
1068		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1069		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1070		should pretend to be a Linux device to it's target host.
1071
1072			CONFIG_USBD_MANUFACTURER
1073			Define this string as the name of your company for
1074			- CONFIG_USBD_MANUFACTURER "my company"
1075
1076			CONFIG_USBD_PRODUCT_NAME
1077			Define this string as the name of your product
1078			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1079
1080			CONFIG_USBD_VENDORID
1081			Define this as your assigned Vendor ID from the USB
1082			Implementors Forum. This *must* be a genuine Vendor ID
1083			to avoid polluting the USB namespace.
1084			- CONFIG_USBD_VENDORID 0xFFFF
1085
1086			CONFIG_USBD_PRODUCTID
1087			Define this as the unique Product ID
1088			for your device
1089			- CONFIG_USBD_PRODUCTID 0xFFFF
1090
1091- ULPI Layer Support:
1092		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1093		the generic ULPI layer. The generic layer accesses the ULPI PHY
1094		via the platform viewport, so you need both the genric layer and
1095		the viewport enabled. Currently only Chipidea/ARC based
1096		viewport is supported.
1097		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1098		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1099		If your ULPI phy needs a different reference clock than the
1100		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1101		the appropriate value in Hz.
1102
1103- MMC Support:
1104		The MMC controller on the Intel PXA is supported. To
1105		enable this define CONFIG_MMC. The MMC can be
1106		accessed from the boot prompt by mapping the device
1107		to physical memory similar to flash. Command line is
1108		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1109		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1110
1111		CONFIG_SH_MMCIF
1112		Support for Renesas on-chip MMCIF controller
1113
1114			CONFIG_SH_MMCIF_ADDR
1115			Define the base address of MMCIF registers
1116
1117			CONFIG_SH_MMCIF_CLK
1118			Define the clock frequency for MMCIF
1119
1120- USB Device Firmware Update (DFU) class support:
1121		CONFIG_DFU_OVER_USB
1122		This enables the USB portion of the DFU USB class
1123
1124		CONFIG_DFU_NAND
1125		This enables support for exposing NAND devices via DFU.
1126
1127		CONFIG_DFU_RAM
1128		This enables support for exposing RAM via DFU.
1129		Note: DFU spec refer to non-volatile memory usage, but
1130		allow usages beyond the scope of spec - here RAM usage,
1131		one that would help mostly the developer.
1132
1133		CONFIG_SYS_DFU_DATA_BUF_SIZE
1134		Dfu transfer uses a buffer before writing data to the
1135		raw storage device. Make the size (in bytes) of this buffer
1136		configurable. The size of this buffer is also configurable
1137		through the "dfu_bufsiz" environment variable.
1138
1139		CONFIG_SYS_DFU_MAX_FILE_SIZE
1140		When updating files rather than the raw storage device,
1141		we use a static buffer to copy the file into and then write
1142		the buffer once we've been given the whole file.  Define
1143		this to the maximum filesize (in bytes) for the buffer.
1144		Default is 4 MiB if undefined.
1145
1146		DFU_DEFAULT_POLL_TIMEOUT
1147		Poll timeout [ms], is the timeout a device can send to the
1148		host. The host must wait for this timeout before sending
1149		a subsequent DFU_GET_STATUS request to the device.
1150
1151		DFU_MANIFEST_POLL_TIMEOUT
1152		Poll timeout [ms], which the device sends to the host when
1153		entering dfuMANIFEST state. Host waits this timeout, before
1154		sending again an USB request to the device.
1155
1156- Journaling Flash filesystem support:
1157		CONFIG_JFFS2_NAND
1158		Define these for a default partition on a NAND device
1159
1160		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1161		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1162		Define these for a default partition on a NOR device
1163
1164- Keyboard Support:
1165		See Kconfig help for available keyboard drivers.
1166
1167		CONFIG_KEYBOARD
1168
1169		Define this to enable a custom keyboard support.
1170		This simply calls drv_keyboard_init() which must be
1171		defined in your board-specific files. This option is deprecated
1172		and is only used by novena. For new boards, use driver model
1173		instead.
1174
1175- Video support:
1176		CONFIG_FSL_DIU_FB
1177		Enable the Freescale DIU video driver.	Reference boards for
1178		SOCs that have a DIU should define this macro to enable DIU
1179		support, and should also define these other macros:
1180
1181			CONFIG_SYS_DIU_ADDR
1182			CONFIG_VIDEO
1183			CONFIG_CFB_CONSOLE
1184			CONFIG_VIDEO_SW_CURSOR
1185			CONFIG_VGA_AS_SINGLE_DEVICE
1186			CONFIG_VIDEO_LOGO
1187			CONFIG_VIDEO_BMP_LOGO
1188
1189		The DIU driver will look for the 'video-mode' environment
1190		variable, and if defined, enable the DIU as a console during
1191		boot.  See the documentation file doc/README.video for a
1192		description of this variable.
1193
1194- LCD Support:	CONFIG_LCD
1195
1196		Define this to enable LCD support (for output to LCD
1197		display); also select one of the supported displays
1198		by defining one of these:
1199
1200		CONFIG_ATMEL_LCD:
1201
1202			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1203
1204		CONFIG_NEC_NL6448AC33:
1205
1206			NEC NL6448AC33-18. Active, color, single scan.
1207
1208		CONFIG_NEC_NL6448BC20
1209
1210			NEC NL6448BC20-08. 6.5", 640x480.
1211			Active, color, single scan.
1212
1213		CONFIG_NEC_NL6448BC33_54
1214
1215			NEC NL6448BC33-54. 10.4", 640x480.
1216			Active, color, single scan.
1217
1218		CONFIG_SHARP_16x9
1219
1220			Sharp 320x240. Active, color, single scan.
1221			It isn't 16x9, and I am not sure what it is.
1222
1223		CONFIG_SHARP_LQ64D341
1224
1225			Sharp LQ64D341 display, 640x480.
1226			Active, color, single scan.
1227
1228		CONFIG_HLD1045
1229
1230			HLD1045 display, 640x480.
1231			Active, color, single scan.
1232
1233		CONFIG_OPTREX_BW
1234
1235			Optrex	 CBL50840-2 NF-FW 99 22 M5
1236			or
1237			Hitachi	 LMG6912RPFC-00T
1238			or
1239			Hitachi	 SP14Q002
1240
1241			320x240. Black & white.
1242
1243		CONFIG_LCD_ALIGNMENT
1244
1245		Normally the LCD is page-aligned (typically 4KB). If this is
1246		defined then the LCD will be aligned to this value instead.
1247		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1248		here, since it is cheaper to change data cache settings on
1249		a per-section basis.
1250
1251
1252		CONFIG_LCD_ROTATION
1253
1254		Sometimes, for example if the display is mounted in portrait
1255		mode or even if it's mounted landscape but rotated by 180degree,
1256		we need to rotate our content of the display relative to the
1257		framebuffer, so that user can read the messages which are
1258		printed out.
1259		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1260		initialized with a given rotation from "vl_rot" out of
1261		"vidinfo_t" which is provided by the board specific code.
1262		The value for vl_rot is coded as following (matching to
1263		fbcon=rotate:<n> linux-kernel commandline):
1264		0 = no rotation respectively 0 degree
1265		1 = 90 degree rotation
1266		2 = 180 degree rotation
1267		3 = 270 degree rotation
1268
1269		If CONFIG_LCD_ROTATION is not defined, the console will be
1270		initialized with 0degree rotation.
1271
1272		CONFIG_LCD_BMP_RLE8
1273
1274		Support drawing of RLE8-compressed bitmaps on the LCD.
1275
1276		CONFIG_I2C_EDID
1277
1278		Enables an 'i2c edid' command which can read EDID
1279		information over I2C from an attached LCD display.
1280
1281- Splash Screen Support: CONFIG_SPLASH_SCREEN
1282
1283		If this option is set, the environment is checked for
1284		a variable "splashimage". If found, the usual display
1285		of logo, copyright and system information on the LCD
1286		is suppressed and the BMP image at the address
1287		specified in "splashimage" is loaded instead. The
1288		console is redirected to the "nulldev", too. This
1289		allows for a "silent" boot where a splash screen is
1290		loaded very quickly after power-on.
1291
1292		CONFIG_SPLASHIMAGE_GUARD
1293
1294		If this option is set, then U-Boot will prevent the environment
1295		variable "splashimage" from being set to a problematic address
1296		(see doc/README.displaying-bmps).
1297		This option is useful for targets where, due to alignment
1298		restrictions, an improperly aligned BMP image will cause a data
1299		abort. If you think you will not have problems with unaligned
1300		accesses (for example because your toolchain prevents them)
1301		there is no need to set this option.
1302
1303		CONFIG_SPLASH_SCREEN_ALIGN
1304
1305		If this option is set the splash image can be freely positioned
1306		on the screen. Environment variable "splashpos" specifies the
1307		position as "x,y". If a positive number is given it is used as
1308		number of pixel from left/top. If a negative number is given it
1309		is used as number of pixel from right/bottom. You can also
1310		specify 'm' for centering the image.
1311
1312		Example:
1313		setenv splashpos m,m
1314			=> image at center of screen
1315
1316		setenv splashpos 30,20
1317			=> image at x = 30 and y = 20
1318
1319		setenv splashpos -10,m
1320			=> vertically centered image
1321			   at x = dspWidth - bmpWidth - 9
1322
1323- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1324
1325		If this option is set, additionally to standard BMP
1326		images, gzipped BMP images can be displayed via the
1327		splashscreen support or the bmp command.
1328
1329- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1330
1331		If this option is set, 8-bit RLE compressed BMP images
1332		can be displayed via the splashscreen support or the
1333		bmp command.
1334
1335- Compression support:
1336		CONFIG_GZIP
1337
1338		Enabled by default to support gzip compressed images.
1339
1340		CONFIG_BZIP2
1341
1342		If this option is set, support for bzip2 compressed
1343		images is included. If not, only uncompressed and gzip
1344		compressed images are supported.
1345
1346		NOTE: the bzip2 algorithm requires a lot of RAM, so
1347		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1348		be at least 4MB.
1349
1350- MII/PHY support:
1351		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1352
1353		The clock frequency of the MII bus
1354
1355		CONFIG_PHY_RESET_DELAY
1356
1357		Some PHY like Intel LXT971A need extra delay after
1358		reset before any MII register access is possible.
1359		For such PHY, set this option to the usec delay
1360		required. (minimum 300usec for LXT971A)
1361
1362		CONFIG_PHY_CMD_DELAY (ppc4xx)
1363
1364		Some PHY like Intel LXT971A need extra delay after
1365		command issued before MII status register can be read
1366
1367- IP address:
1368		CONFIG_IPADDR
1369
1370		Define a default value for the IP address to use for
1371		the default Ethernet interface, in case this is not
1372		determined through e.g. bootp.
1373		(Environment variable "ipaddr")
1374
1375- Server IP address:
1376		CONFIG_SERVERIP
1377
1378		Defines a default value for the IP address of a TFTP
1379		server to contact when using the "tftboot" command.
1380		(Environment variable "serverip")
1381
1382		CONFIG_KEEP_SERVERADDR
1383
1384		Keeps the server's MAC address, in the env 'serveraddr'
1385		for passing to bootargs (like Linux's netconsole option)
1386
1387- Gateway IP address:
1388		CONFIG_GATEWAYIP
1389
1390		Defines a default value for the IP address of the
1391		default router where packets to other networks are
1392		sent to.
1393		(Environment variable "gatewayip")
1394
1395- Subnet mask:
1396		CONFIG_NETMASK
1397
1398		Defines a default value for the subnet mask (or
1399		routing prefix) which is used to determine if an IP
1400		address belongs to the local subnet or needs to be
1401		forwarded through a router.
1402		(Environment variable "netmask")
1403
1404- BOOTP Recovery Mode:
1405		CONFIG_BOOTP_RANDOM_DELAY
1406
1407		If you have many targets in a network that try to
1408		boot using BOOTP, you may want to avoid that all
1409		systems send out BOOTP requests at precisely the same
1410		moment (which would happen for instance at recovery
1411		from a power failure, when all systems will try to
1412		boot, thus flooding the BOOTP server. Defining
1413		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1414		inserted before sending out BOOTP requests. The
1415		following delays are inserted then:
1416
1417		1st BOOTP request:	delay 0 ... 1 sec
1418		2nd BOOTP request:	delay 0 ... 2 sec
1419		3rd BOOTP request:	delay 0 ... 4 sec
1420		4th and following
1421		BOOTP requests:		delay 0 ... 8 sec
1422
1423		CONFIG_BOOTP_ID_CACHE_SIZE
1424
1425		BOOTP packets are uniquely identified using a 32-bit ID. The
1426		server will copy the ID from client requests to responses and
1427		U-Boot will use this to determine if it is the destination of
1428		an incoming response. Some servers will check that addresses
1429		aren't in use before handing them out (usually using an ARP
1430		ping) and therefore take up to a few hundred milliseconds to
1431		respond. Network congestion may also influence the time it
1432		takes for a response to make it back to the client. If that
1433		time is too long, U-Boot will retransmit requests. In order
1434		to allow earlier responses to still be accepted after these
1435		retransmissions, U-Boot's BOOTP client keeps a small cache of
1436		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1437		cache. The default is to keep IDs for up to four outstanding
1438		requests. Increasing this will allow U-Boot to accept offers
1439		from a BOOTP client in networks with unusually high latency.
1440
1441- DHCP Advanced Options:
1442		You can fine tune the DHCP functionality by defining
1443		CONFIG_BOOTP_* symbols:
1444
1445		CONFIG_BOOTP_NISDOMAIN
1446		CONFIG_BOOTP_BOOTFILESIZE
1447		CONFIG_BOOTP_SEND_HOSTNAME
1448		CONFIG_BOOTP_NTPSERVER
1449		CONFIG_BOOTP_TIMEOFFSET
1450		CONFIG_BOOTP_VENDOREX
1451		CONFIG_BOOTP_MAY_FAIL
1452
1453		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1454		environment variable, not the BOOTP server.
1455
1456		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1457		after the configured retry count, the call will fail
1458		instead of starting over.  This can be used to fail over
1459		to Link-local IP address configuration if the DHCP server
1460		is not available.
1461
1462		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1463		to do a dynamic update of a DNS server. To do this, they
1464		need the hostname of the DHCP requester.
1465		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1466		of the "hostname" environment variable is passed as
1467		option 12 to the DHCP server.
1468
1469		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1470
1471		A 32bit value in microseconds for a delay between
1472		receiving a "DHCP Offer" and sending the "DHCP Request".
1473		This fixes a problem with certain DHCP servers that don't
1474		respond 100% of the time to a "DHCP request". E.g. On an
1475		AT91RM9200 processor running at 180MHz, this delay needed
1476		to be *at least* 15,000 usec before a Windows Server 2003
1477		DHCP server would reply 100% of the time. I recommend at
1478		least 50,000 usec to be safe. The alternative is to hope
1479		that one of the retries will be successful but note that
1480		the DHCP timeout and retry process takes a longer than
1481		this delay.
1482
1483 - Link-local IP address negotiation:
1484		Negotiate with other link-local clients on the local network
1485		for an address that doesn't require explicit configuration.
1486		This is especially useful if a DHCP server cannot be guaranteed
1487		to exist in all environments that the device must operate.
1488
1489		See doc/README.link-local for more information.
1490
1491 - MAC address from environment variables
1492
1493		FDT_SEQ_MACADDR_FROM_ENV
1494
1495		Fix-up device tree with MAC addresses fetched sequentially from
1496		environment variables. This config work on assumption that
1497		non-usable ethernet node of device-tree are either not present
1498		or their status has been marked as "disabled".
1499
1500 - CDP Options:
1501		CONFIG_CDP_DEVICE_ID
1502
1503		The device id used in CDP trigger frames.
1504
1505		CONFIG_CDP_DEVICE_ID_PREFIX
1506
1507		A two character string which is prefixed to the MAC address
1508		of the device.
1509
1510		CONFIG_CDP_PORT_ID
1511
1512		A printf format string which contains the ascii name of
1513		the port. Normally is set to "eth%d" which sets
1514		eth0 for the first Ethernet, eth1 for the second etc.
1515
1516		CONFIG_CDP_CAPABILITIES
1517
1518		A 32bit integer which indicates the device capabilities;
1519		0x00000010 for a normal host which does not forwards.
1520
1521		CONFIG_CDP_VERSION
1522
1523		An ascii string containing the version of the software.
1524
1525		CONFIG_CDP_PLATFORM
1526
1527		An ascii string containing the name of the platform.
1528
1529		CONFIG_CDP_TRIGGER
1530
1531		A 32bit integer sent on the trigger.
1532
1533		CONFIG_CDP_POWER_CONSUMPTION
1534
1535		A 16bit integer containing the power consumption of the
1536		device in .1 of milliwatts.
1537
1538		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1539
1540		A byte containing the id of the VLAN.
1541
1542- Status LED:	CONFIG_LED_STATUS
1543
1544		Several configurations allow to display the current
1545		status using a LED. For instance, the LED will blink
1546		fast while running U-Boot code, stop blinking as
1547		soon as a reply to a BOOTP request was received, and
1548		start blinking slow once the Linux kernel is running
1549		(supported by a status LED driver in the Linux
1550		kernel). Defining CONFIG_LED_STATUS enables this
1551		feature in U-Boot.
1552
1553		Additional options:
1554
1555		CONFIG_LED_STATUS_GPIO
1556		The status LED can be connected to a GPIO pin.
1557		In such cases, the gpio_led driver can be used as a
1558		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1559		to include the gpio_led driver in the U-Boot binary.
1560
1561		CONFIG_GPIO_LED_INVERTED_TABLE
1562		Some GPIO connected LEDs may have inverted polarity in which
1563		case the GPIO high value corresponds to LED off state and
1564		GPIO low value corresponds to LED on state.
1565		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1566		with a list of GPIO LEDs that have inverted polarity.
1567
1568- I2C Support:	CONFIG_SYS_I2C
1569
1570		This enable the NEW i2c subsystem, and will allow you to use
1571		i2c commands at the u-boot command line (as long as you set
1572		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1573		based realtime clock chips or other i2c devices. See
1574		common/cmd_i2c.c for a description of the command line
1575		interface.
1576
1577		ported i2c driver to the new framework:
1578		- drivers/i2c/soft_i2c.c:
1579		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1580		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1581		    for defining speed and slave address
1582		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1583		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1584		    for defining speed and slave address
1585		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1586		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1587		    for defining speed and slave address
1588		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1589		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1590		    for defining speed and slave address
1591
1592		- drivers/i2c/fsl_i2c.c:
1593		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1594		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1595		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1596		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1597		    bus.
1598		  - If your board supports a second fsl i2c bus, define
1599		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1600		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1601		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1602		    second bus.
1603
1604		- drivers/i2c/tegra_i2c.c:
1605		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1606		  - This driver adds 4 i2c buses with a fix speed from
1607		    100000 and the slave addr 0!
1608
1609		- drivers/i2c/ppc4xx_i2c.c
1610		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1611		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1612		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1613
1614		- drivers/i2c/i2c_mxc.c
1615		  - activate this driver with CONFIG_SYS_I2C_MXC
1616		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1617		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1618		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1619		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1620		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1621		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1622		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1623		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1624		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1625		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1626		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1627		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1628		If those defines are not set, default value is 100000
1629		for speed, and 0 for slave.
1630
1631		- drivers/i2c/rcar_i2c.c:
1632		  - activate this driver with CONFIG_SYS_I2C_RCAR
1633		  - This driver adds 4 i2c buses
1634
1635		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1636		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1637		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1638		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1639		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1640		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1641		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1642		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1643		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1644
1645		- drivers/i2c/sh_i2c.c:
1646		  - activate this driver with CONFIG_SYS_I2C_SH
1647		  - This driver adds from 2 to 5 i2c buses
1648
1649		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1650		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1651		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1652		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1653		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1654		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1655		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1656		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1657		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1658		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1659		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1660
1661		- drivers/i2c/omap24xx_i2c.c
1662		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1663		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1664		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1665		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1666		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1667		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1668		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1669		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1670		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1671		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1672		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1673
1674		- drivers/i2c/s3c24x0_i2c.c:
1675		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1676		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1677		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1678		    with a fix speed from 100000 and the slave addr 0!
1679
1680		- drivers/i2c/ihs_i2c.c
1681		  - activate this driver with CONFIG_SYS_I2C_IHS
1682		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1683		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1684		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1685		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1686		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1687		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1688		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1689		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1690		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1691		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1692		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1693		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1694		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1695		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1696		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1697		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1698		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1699		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1700		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1701		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1702		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1703
1704		additional defines:
1705
1706		CONFIG_SYS_NUM_I2C_BUSES
1707		Hold the number of i2c buses you want to use.
1708
1709		CONFIG_SYS_I2C_DIRECT_BUS
1710		define this, if you don't use i2c muxes on your hardware.
1711		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1712		omit this define.
1713
1714		CONFIG_SYS_I2C_MAX_HOPS
1715		define how many muxes are maximal consecutively connected
1716		on one i2c bus. If you not use i2c muxes, omit this
1717		define.
1718
1719		CONFIG_SYS_I2C_BUSES
1720		hold a list of buses you want to use, only used if
1721		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1722		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1723		CONFIG_SYS_NUM_I2C_BUSES = 9:
1724
1725		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1726					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1727					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1728					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1729					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1730					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1731					{1, {I2C_NULL_HOP}}, \
1732					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1733					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1734					}
1735
1736		which defines
1737			bus 0 on adapter 0 without a mux
1738			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1739			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1740			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1741			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1742			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1743			bus 6 on adapter 1 without a mux
1744			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1745			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1746
1747		If you do not have i2c muxes on your board, omit this define.
1748
1749- Legacy I2C Support:
1750		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1751		then the following macros need to be defined (examples are
1752		from include/configs/lwmon.h):
1753
1754		I2C_INIT
1755
1756		(Optional). Any commands necessary to enable the I2C
1757		controller or configure ports.
1758
1759		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1760
1761		I2C_ACTIVE
1762
1763		The code necessary to make the I2C data line active
1764		(driven).  If the data line is open collector, this
1765		define can be null.
1766
1767		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1768
1769		I2C_TRISTATE
1770
1771		The code necessary to make the I2C data line tri-stated
1772		(inactive).  If the data line is open collector, this
1773		define can be null.
1774
1775		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1776
1777		I2C_READ
1778
1779		Code that returns true if the I2C data line is high,
1780		false if it is low.
1781
1782		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1783
1784		I2C_SDA(bit)
1785
1786		If <bit> is true, sets the I2C data line high. If it
1787		is false, it clears it (low).
1788
1789		eg: #define I2C_SDA(bit) \
1790			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1791			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1792
1793		I2C_SCL(bit)
1794
1795		If <bit> is true, sets the I2C clock line high. If it
1796		is false, it clears it (low).
1797
1798		eg: #define I2C_SCL(bit) \
1799			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1800			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1801
1802		I2C_DELAY
1803
1804		This delay is invoked four times per clock cycle so this
1805		controls the rate of data transfer.  The data rate thus
1806		is 1 / (I2C_DELAY * 4). Often defined to be something
1807		like:
1808
1809		#define I2C_DELAY  udelay(2)
1810
1811		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1812
1813		If your arch supports the generic GPIO framework (asm/gpio.h),
1814		then you may alternatively define the two GPIOs that are to be
1815		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1816		have GPIO-based defaults assigned to them as appropriate.
1817
1818		You should define these to the GPIO value as given directly to
1819		the generic GPIO functions.
1820
1821		CONFIG_SYS_I2C_INIT_BOARD
1822
1823		When a board is reset during an i2c bus transfer
1824		chips might think that the current transfer is still
1825		in progress. On some boards it is possible to access
1826		the i2c SCLK line directly, either by using the
1827		processor pin as a GPIO or by having a second pin
1828		connected to the bus. If this option is defined a
1829		custom i2c_init_board() routine in boards/xxx/board.c
1830		is run early in the boot sequence.
1831
1832		CONFIG_I2C_MULTI_BUS
1833
1834		This option allows the use of multiple I2C buses, each of which
1835		must have a controller.	 At any point in time, only one bus is
1836		active.	 To switch to a different bus, use the 'i2c dev' command.
1837		Note that bus numbering is zero-based.
1838
1839		CONFIG_SYS_I2C_NOPROBES
1840
1841		This option specifies a list of I2C devices that will be skipped
1842		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1843		is set, specify a list of bus-device pairs.  Otherwise, specify
1844		a 1D array of device addresses
1845
1846		e.g.
1847			#undef	CONFIG_I2C_MULTI_BUS
1848			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1849
1850		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1851
1852			#define CONFIG_I2C_MULTI_BUS
1853			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1854
1855		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1856
1857		CONFIG_SYS_SPD_BUS_NUM
1858
1859		If defined, then this indicates the I2C bus number for DDR SPD.
1860		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1861
1862		CONFIG_SYS_RTC_BUS_NUM
1863
1864		If defined, then this indicates the I2C bus number for the RTC.
1865		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1866
1867		CONFIG_SOFT_I2C_READ_REPEATED_START
1868
1869		defining this will force the i2c_read() function in
1870		the soft_i2c driver to perform an I2C repeated start
1871		between writing the address pointer and reading the
1872		data.  If this define is omitted the default behaviour
1873		of doing a stop-start sequence will be used.  Most I2C
1874		devices can use either method, but some require one or
1875		the other.
1876
1877- SPI Support:	CONFIG_SPI
1878
1879		Enables SPI driver (so far only tested with
1880		SPI EEPROM, also an instance works with Crystal A/D and
1881		D/As on the SACSng board)
1882
1883		CONFIG_SOFT_SPI
1884
1885		Enables a software (bit-bang) SPI driver rather than
1886		using hardware support. This is a general purpose
1887		driver that only requires three general I/O port pins
1888		(two outputs, one input) to function. If this is
1889		defined, the board configuration must define several
1890		SPI configuration items (port pins to use, etc). For
1891		an example, see include/configs/sacsng.h.
1892
1893		CONFIG_SYS_SPI_MXC_WAIT
1894		Timeout for waiting until spi transfer completed.
1895		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1896
1897- FPGA Support: CONFIG_FPGA
1898
1899		Enables FPGA subsystem.
1900
1901		CONFIG_FPGA_<vendor>
1902
1903		Enables support for specific chip vendors.
1904		(ALTERA, XILINX)
1905
1906		CONFIG_FPGA_<family>
1907
1908		Enables support for FPGA family.
1909		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1910
1911		CONFIG_FPGA_COUNT
1912
1913		Specify the number of FPGA devices to support.
1914
1915		CONFIG_SYS_FPGA_PROG_FEEDBACK
1916
1917		Enable printing of hash marks during FPGA configuration.
1918
1919		CONFIG_SYS_FPGA_CHECK_BUSY
1920
1921		Enable checks on FPGA configuration interface busy
1922		status by the configuration function. This option
1923		will require a board or device specific function to
1924		be written.
1925
1926		CONFIG_FPGA_DELAY
1927
1928		If defined, a function that provides delays in the FPGA
1929		configuration driver.
1930
1931		CONFIG_SYS_FPGA_CHECK_CTRLC
1932		Allow Control-C to interrupt FPGA configuration
1933
1934		CONFIG_SYS_FPGA_CHECK_ERROR
1935
1936		Check for configuration errors during FPGA bitfile
1937		loading. For example, abort during Virtex II
1938		configuration if the INIT_B line goes low (which
1939		indicated a CRC error).
1940
1941		CONFIG_SYS_FPGA_WAIT_INIT
1942
1943		Maximum time to wait for the INIT_B line to de-assert
1944		after PROB_B has been de-asserted during a Virtex II
1945		FPGA configuration sequence. The default time is 500
1946		ms.
1947
1948		CONFIG_SYS_FPGA_WAIT_BUSY
1949
1950		Maximum time to wait for BUSY to de-assert during
1951		Virtex II FPGA configuration. The default is 5 ms.
1952
1953		CONFIG_SYS_FPGA_WAIT_CONFIG
1954
1955		Time to wait after FPGA configuration. The default is
1956		200 ms.
1957
1958- Configuration Management:
1959
1960		CONFIG_IDENT_STRING
1961
1962		If defined, this string will be added to the U-Boot
1963		version information (U_BOOT_VERSION)
1964
1965- Vendor Parameter Protection:
1966
1967		U-Boot considers the values of the environment
1968		variables "serial#" (Board Serial Number) and
1969		"ethaddr" (Ethernet Address) to be parameters that
1970		are set once by the board vendor / manufacturer, and
1971		protects these variables from casual modification by
1972		the user. Once set, these variables are read-only,
1973		and write or delete attempts are rejected. You can
1974		change this behaviour:
1975
1976		If CONFIG_ENV_OVERWRITE is #defined in your config
1977		file, the write protection for vendor parameters is
1978		completely disabled. Anybody can change or delete
1979		these parameters.
1980
1981		Alternatively, if you define _both_ an ethaddr in the
1982		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1983		Ethernet address is installed in the environment,
1984		which can be changed exactly ONCE by the user. [The
1985		serial# is unaffected by this, i. e. it remains
1986		read-only.]
1987
1988		The same can be accomplished in a more flexible way
1989		for any variable by configuring the type of access
1990		to allow for those variables in the ".flags" variable
1991		or define CONFIG_ENV_FLAGS_LIST_STATIC.
1992
1993- Protected RAM:
1994		CONFIG_PRAM
1995
1996		Define this variable to enable the reservation of
1997		"protected RAM", i. e. RAM which is not overwritten
1998		by U-Boot. Define CONFIG_PRAM to hold the number of
1999		kB you want to reserve for pRAM. You can overwrite
2000		this default value by defining an environment
2001		variable "pram" to the number of kB you want to
2002		reserve. Note that the board info structure will
2003		still show the full amount of RAM. If pRAM is
2004		reserved, a new environment variable "mem" will
2005		automatically be defined to hold the amount of
2006		remaining RAM in a form that can be passed as boot
2007		argument to Linux, for instance like that:
2008
2009			setenv bootargs ... mem=\${mem}
2010			saveenv
2011
2012		This way you can tell Linux not to use this memory,
2013		either, which results in a memory region that will
2014		not be affected by reboots.
2015
2016		*WARNING* If your board configuration uses automatic
2017		detection of the RAM size, you must make sure that
2018		this memory test is non-destructive. So far, the
2019		following board configurations are known to be
2020		"pRAM-clean":
2021
2022			IVMS8, IVML24, SPD8xx,
2023			HERMES, IP860, RPXlite, LWMON,
2024			FLAGADM
2025
2026- Access to physical memory region (> 4GB)
2027		Some basic support is provided for operations on memory not
2028		normally accessible to U-Boot - e.g. some architectures
2029		support access to more than 4GB of memory on 32-bit
2030		machines using physical address extension or similar.
2031		Define CONFIG_PHYSMEM to access this basic support, which
2032		currently only supports clearing the memory.
2033
2034- Error Recovery:
2035		CONFIG_NET_RETRY_COUNT
2036
2037		This variable defines the number of retries for
2038		network operations like ARP, RARP, TFTP, or BOOTP
2039		before giving up the operation. If not defined, a
2040		default value of 5 is used.
2041
2042		CONFIG_ARP_TIMEOUT
2043
2044		Timeout waiting for an ARP reply in milliseconds.
2045
2046		CONFIG_NFS_TIMEOUT
2047
2048		Timeout in milliseconds used in NFS protocol.
2049		If you encounter "ERROR: Cannot umount" in nfs command,
2050		try longer timeout such as
2051		#define CONFIG_NFS_TIMEOUT 10000UL
2052
2053- Command Interpreter:
2054		CONFIG_SYS_PROMPT_HUSH_PS2
2055
2056		This defines the secondary prompt string, which is
2057		printed when the command interpreter needs more input
2058		to complete a command. Usually "> ".
2059
2060	Note:
2061
2062		In the current implementation, the local variables
2063		space and global environment variables space are
2064		separated. Local variables are those you define by
2065		simply typing `name=value'. To access a local
2066		variable later on, you have write `$name' or
2067		`${name}'; to execute the contents of a variable
2068		directly type `$name' at the command prompt.
2069
2070		Global environment variables are those you use
2071		setenv/printenv to work with. To run a command stored
2072		in such a variable, you need to use the run command,
2073		and you must not use the '$' sign to access them.
2074
2075		To store commands and special characters in a
2076		variable, please use double quotation marks
2077		surrounding the whole text of the variable, instead
2078		of the backslashes before semicolons and special
2079		symbols.
2080
2081- Command Line Editing and History:
2082		CONFIG_CMDLINE_PS_SUPPORT
2083
2084		Enable support for changing the command prompt string
2085		at run-time. Only static string is supported so far.
2086		The string is obtained from environment variables PS1
2087		and PS2.
2088
2089- Default Environment:
2090		CONFIG_EXTRA_ENV_SETTINGS
2091
2092		Define this to contain any number of null terminated
2093		strings (variable = value pairs) that will be part of
2094		the default environment compiled into the boot image.
2095
2096		For example, place something like this in your
2097		board's config file:
2098
2099		#define CONFIG_EXTRA_ENV_SETTINGS \
2100			"myvar1=value1\0" \
2101			"myvar2=value2\0"
2102
2103		Warning: This method is based on knowledge about the
2104		internal format how the environment is stored by the
2105		U-Boot code. This is NOT an official, exported
2106		interface! Although it is unlikely that this format
2107		will change soon, there is no guarantee either.
2108		You better know what you are doing here.
2109
2110		Note: overly (ab)use of the default environment is
2111		discouraged. Make sure to check other ways to preset
2112		the environment like the "source" command or the
2113		boot command first.
2114
2115		CONFIG_DELAY_ENVIRONMENT
2116
2117		Normally the environment is loaded when the board is
2118		initialised so that it is available to U-Boot. This inhibits
2119		that so that the environment is not available until
2120		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2121		this is instead controlled by the value of
2122		/config/load-environment.
2123
2124- TFTP Fixed UDP Port:
2125		CONFIG_TFTP_PORT
2126
2127		If this is defined, the environment variable tftpsrcp
2128		is used to supply the TFTP UDP source port value.
2129		If tftpsrcp isn't defined, the normal pseudo-random port
2130		number generator is used.
2131
2132		Also, the environment variable tftpdstp is used to supply
2133		the TFTP UDP destination port value.  If tftpdstp isn't
2134		defined, the normal port 69 is used.
2135
2136		The purpose for tftpsrcp is to allow a TFTP server to
2137		blindly start the TFTP transfer using the pre-configured
2138		target IP address and UDP port. This has the effect of
2139		"punching through" the (Windows XP) firewall, allowing
2140		the remainder of the TFTP transfer to proceed normally.
2141		A better solution is to properly configure the firewall,
2142		but sometimes that is not allowed.
2143
2144		CONFIG_STANDALONE_LOAD_ADDR
2145
2146		This option defines a board specific value for the
2147		address where standalone program gets loaded, thus
2148		overwriting the architecture dependent default
2149		settings.
2150
2151- Frame Buffer Address:
2152		CONFIG_FB_ADDR
2153
2154		Define CONFIG_FB_ADDR if you want to use specific
2155		address for frame buffer.  This is typically the case
2156		when using a graphics controller has separate video
2157		memory.  U-Boot will then place the frame buffer at
2158		the given address instead of dynamically reserving it
2159		in system RAM by calling lcd_setmem(), which grabs
2160		the memory for the frame buffer depending on the
2161		configured panel size.
2162
2163		Please see board_init_f function.
2164
2165- Automatic software updates via TFTP server
2166		CONFIG_UPDATE_TFTP
2167		CONFIG_UPDATE_TFTP_CNT_MAX
2168		CONFIG_UPDATE_TFTP_MSEC_MAX
2169
2170		These options enable and control the auto-update feature;
2171		for a more detailed description refer to doc/README.update.
2172
2173- MTD Support (mtdparts command, UBI support)
2174		CONFIG_MTD_UBI_WL_THRESHOLD
2175		This parameter defines the maximum difference between the highest
2176		erase counter value and the lowest erase counter value of eraseblocks
2177		of UBI devices. When this threshold is exceeded, UBI starts performing
2178		wear leveling by means of moving data from eraseblock with low erase
2179		counter to eraseblocks with high erase counter.
2180
2181		The default value should be OK for SLC NAND flashes, NOR flashes and
2182		other flashes which have eraseblock life-cycle 100000 or more.
2183		However, in case of MLC NAND flashes which typically have eraseblock
2184		life-cycle less than 10000, the threshold should be lessened (e.g.,
2185		to 128 or 256, although it does not have to be power of 2).
2186
2187		default: 4096
2188
2189		CONFIG_MTD_UBI_BEB_LIMIT
2190		This option specifies the maximum bad physical eraseblocks UBI
2191		expects on the MTD device (per 1024 eraseblocks). If the
2192		underlying flash does not admit of bad eraseblocks (e.g. NOR
2193		flash), this value is ignored.
2194
2195		NAND datasheets often specify the minimum and maximum NVM
2196		(Number of Valid Blocks) for the flashes' endurance lifetime.
2197		The maximum expected bad eraseblocks per 1024 eraseblocks
2198		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2199		which gives 20 for most NANDs (MaxNVB is basically the total
2200		count of eraseblocks on the chip).
2201
2202		To put it differently, if this value is 20, UBI will try to
2203		reserve about 1.9% of physical eraseblocks for bad blocks
2204		handling. And that will be 1.9% of eraseblocks on the entire
2205		NAND chip, not just the MTD partition UBI attaches. This means
2206		that if you have, say, a NAND flash chip admits maximum 40 bad
2207		eraseblocks, and it is split on two MTD partitions of the same
2208		size, UBI will reserve 40 eraseblocks when attaching a
2209		partition.
2210
2211		default: 20
2212
2213		CONFIG_MTD_UBI_FASTMAP
2214		Fastmap is a mechanism which allows attaching an UBI device
2215		in nearly constant time. Instead of scanning the whole MTD device it
2216		only has to locate a checkpoint (called fastmap) on the device.
2217		The on-flash fastmap contains all information needed to attach
2218		the device. Using fastmap makes only sense on large devices where
2219		attaching by scanning takes long. UBI will not automatically install
2220		a fastmap on old images, but you can set the UBI parameter
2221		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2222		that fastmap-enabled images are still usable with UBI implementations
2223		without	fastmap support. On typical flash devices the whole fastmap
2224		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2225
2226		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2227		Set this parameter to enable fastmap automatically on images
2228		without a fastmap.
2229		default: 0
2230
2231		CONFIG_MTD_UBI_FM_DEBUG
2232		Enable UBI fastmap debug
2233		default: 0
2234
2235- SPL framework
2236		CONFIG_SPL
2237		Enable building of SPL globally.
2238
2239		CONFIG_SPL_LDSCRIPT
2240		LDSCRIPT for linking the SPL binary.
2241
2242		CONFIG_SPL_MAX_FOOTPRINT
2243		Maximum size in memory allocated to the SPL, BSS included.
2244		When defined, the linker checks that the actual memory
2245		used by SPL from _start to __bss_end does not exceed it.
2246		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2247		must not be both defined at the same time.
2248
2249		CONFIG_SPL_MAX_SIZE
2250		Maximum size of the SPL image (text, data, rodata, and
2251		linker lists sections), BSS excluded.
2252		When defined, the linker checks that the actual size does
2253		not exceed it.
2254
2255		CONFIG_SPL_RELOC_TEXT_BASE
2256		Address to relocate to.  If unspecified, this is equal to
2257		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2258
2259		CONFIG_SPL_BSS_START_ADDR
2260		Link address for the BSS within the SPL binary.
2261
2262		CONFIG_SPL_BSS_MAX_SIZE
2263		Maximum size in memory allocated to the SPL BSS.
2264		When defined, the linker checks that the actual memory used
2265		by SPL from __bss_start to __bss_end does not exceed it.
2266		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2267		must not be both defined at the same time.
2268
2269		CONFIG_SPL_STACK
2270		Adress of the start of the stack SPL will use
2271
2272		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2273		When defined, SPL will panic() if the image it has
2274		loaded does not have a signature.
2275		Defining this is useful when code which loads images
2276		in SPL cannot guarantee that absolutely all read errors
2277		will be caught.
2278		An example is the LPC32XX MLC NAND driver, which will
2279		consider that a completely unreadable NAND block is bad,
2280		and thus should be skipped silently.
2281
2282		CONFIG_SPL_RELOC_STACK
2283		Adress of the start of the stack SPL will use after
2284		relocation.  If unspecified, this is equal to
2285		CONFIG_SPL_STACK.
2286
2287		CONFIG_SYS_SPL_MALLOC_START
2288		Starting address of the malloc pool used in SPL.
2289		When this option is set the full malloc is used in SPL and
2290		it is set up by spl_init() and before that, the simple malloc()
2291		can be used if CONFIG_SYS_MALLOC_F is defined.
2292
2293		CONFIG_SYS_SPL_MALLOC_SIZE
2294		The size of the malloc pool used in SPL.
2295
2296		CONFIG_SPL_OS_BOOT
2297		Enable booting directly to an OS from SPL.
2298		See also: doc/README.falcon
2299
2300		CONFIG_SPL_DISPLAY_PRINT
2301		For ARM, enable an optional function to print more information
2302		about the running system.
2303
2304		CONFIG_SPL_INIT_MINIMAL
2305		Arch init code should be built for a very small image
2306
2307		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2308		Partition on the MMC to load U-Boot from when the MMC is being
2309		used in raw mode
2310
2311		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2312		Sector to load kernel uImage from when MMC is being
2313		used in raw mode (for Falcon mode)
2314
2315		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2316		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2317		Sector and number of sectors to load kernel argument
2318		parameters from when MMC is being used in raw mode
2319		(for falcon mode)
2320
2321		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2322		Partition on the MMC to load U-Boot from when the MMC is being
2323		used in fs mode
2324
2325		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2326		Filename to read to load U-Boot when reading from filesystem
2327
2328		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2329		Filename to read to load kernel uImage when reading
2330		from filesystem (for Falcon mode)
2331
2332		CONFIG_SPL_FS_LOAD_ARGS_NAME
2333		Filename to read to load kernel argument parameters
2334		when reading from filesystem (for Falcon mode)
2335
2336		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2337		Set this for NAND SPL on PPC mpc83xx targets, so that
2338		start.S waits for the rest of the SPL to load before
2339		continuing (the hardware starts execution after just
2340		loading the first page rather than the full 4K).
2341
2342		CONFIG_SPL_SKIP_RELOCATE
2343		Avoid SPL relocation
2344
2345		CONFIG_SPL_NAND_BASE
2346		Include nand_base.c in the SPL.  Requires
2347		CONFIG_SPL_NAND_DRIVERS.
2348
2349		CONFIG_SPL_NAND_DRIVERS
2350		SPL uses normal NAND drivers, not minimal drivers.
2351
2352		CONFIG_SPL_NAND_IDENT
2353		SPL uses the chip ID list to identify the NAND flash.
2354		Requires CONFIG_SPL_NAND_BASE.
2355
2356		CONFIG_SPL_NAND_ECC
2357		Include standard software ECC in the SPL
2358
2359		CONFIG_SPL_NAND_SIMPLE
2360		Support for NAND boot using simple NAND drivers that
2361		expose the cmd_ctrl() interface.
2362
2363		CONFIG_SPL_UBI
2364		Support for a lightweight UBI (fastmap) scanner and
2365		loader
2366
2367		CONFIG_SPL_NAND_RAW_ONLY
2368		Support to boot only raw u-boot.bin images. Use this only
2369		if you need to save space.
2370
2371		CONFIG_SPL_COMMON_INIT_DDR
2372		Set for common ddr init with serial presence detect in
2373		SPL binary.
2374
2375		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2376		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2377		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2378		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2379		CONFIG_SYS_NAND_ECCBYTES
2380		Defines the size and behavior of the NAND that SPL uses
2381		to read U-Boot
2382
2383		CONFIG_SYS_NAND_U_BOOT_OFFS
2384		Location in NAND to read U-Boot from
2385
2386		CONFIG_SYS_NAND_U_BOOT_DST
2387		Location in memory to load U-Boot to
2388
2389		CONFIG_SYS_NAND_U_BOOT_SIZE
2390		Size of image to load
2391
2392		CONFIG_SYS_NAND_U_BOOT_START
2393		Entry point in loaded image to jump to
2394
2395		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2396		Define this if you need to first read the OOB and then the
2397		data. This is used, for example, on davinci platforms.
2398
2399		CONFIG_SPL_RAM_DEVICE
2400		Support for running image already present in ram, in SPL binary
2401
2402		CONFIG_SPL_PAD_TO
2403		Image offset to which the SPL should be padded before appending
2404		the SPL payload. By default, this is defined as
2405		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2406		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2407		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2408
2409		CONFIG_SPL_TARGET
2410		Final target image containing SPL and payload.  Some SPLs
2411		use an arch-specific makefile fragment instead, for
2412		example if more than one image needs to be produced.
2413
2414		CONFIG_SPL_FIT_PRINT
2415		Printing information about a FIT image adds quite a bit of
2416		code to SPL. So this is normally disabled in SPL. Use this
2417		option to re-enable it. This will affect the output of the
2418		bootm command when booting a FIT image.
2419
2420- TPL framework
2421		CONFIG_TPL
2422		Enable building of TPL globally.
2423
2424		CONFIG_TPL_PAD_TO
2425		Image offset to which the TPL should be padded before appending
2426		the TPL payload. By default, this is defined as
2427		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2428		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2429		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2430
2431- Interrupt support (PPC):
2432
2433		There are common interrupt_init() and timer_interrupt()
2434		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2435		for CPU specific initialization. interrupt_init_cpu()
2436		should set decrementer_count to appropriate value. If
2437		CPU resets decrementer automatically after interrupt
2438		(ppc4xx) it should set decrementer_count to zero.
2439		timer_interrupt() calls timer_interrupt_cpu() for CPU
2440		specific handling. If board has watchdog / status_led
2441		/ other_activity_monitor it works automatically from
2442		general timer_interrupt().
2443
2444
2445Board initialization settings:
2446------------------------------
2447
2448During Initialization u-boot calls a number of board specific functions
2449to allow the preparation of board specific prerequisites, e.g. pin setup
2450before drivers are initialized. To enable these callbacks the
2451following configuration macros have to be defined. Currently this is
2452architecture specific, so please check arch/your_architecture/lib/board.c
2453typically in board_init_f() and board_init_r().
2454
2455- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2456- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2457- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2458- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2459
2460Configuration Settings:
2461-----------------------
2462
2463- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2464		Optionally it can be defined to support 64-bit memory commands.
2465
2466- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2467		undefine this when you're short of memory.
2468
2469- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2470		width of the commands listed in the 'help' command output.
2471
2472- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2473		prompt for user input.
2474
2475- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2476
2477- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2478
2479- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2480
2481- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2482		the application (usually a Linux kernel) when it is
2483		booted
2484
2485- CONFIG_SYS_BAUDRATE_TABLE:
2486		List of legal baudrate settings for this board.
2487
2488- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2489		Begin and End addresses of the area used by the
2490		simple memory test.
2491
2492- CONFIG_SYS_MEMTEST_SCRATCH:
2493		Scratch address used by the alternate memory test
2494		You only need to set this if address zero isn't writeable
2495
2496- CONFIG_SYS_MEM_RESERVE_SECURE
2497		Only implemented for ARMv8 for now.
2498		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2499		is substracted from total RAM and won't be reported to OS.
2500		This memory can be used as secure memory. A variable
2501		gd->arch.secure_ram is used to track the location. In systems
2502		the RAM base is not zero, or RAM is divided into banks,
2503		this variable needs to be recalcuated to get the address.
2504
2505- CONFIG_SYS_MEM_TOP_HIDE:
2506		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2507		this specified memory area will get subtracted from the top
2508		(end) of RAM and won't get "touched" at all by U-Boot. By
2509		fixing up gd->ram_size the Linux kernel should gets passed
2510		the now "corrected" memory size and won't touch it either.
2511		This should work for arch/ppc and arch/powerpc. Only Linux
2512		board ports in arch/powerpc with bootwrapper support that
2513		recalculate the memory size from the SDRAM controller setup
2514		will have to get fixed in Linux additionally.
2515
2516		This option can be used as a workaround for the 440EPx/GRx
2517		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2518		be touched.
2519
2520		WARNING: Please make sure that this value is a multiple of
2521		the Linux page size (normally 4k). If this is not the case,
2522		then the end address of the Linux memory will be located at a
2523		non page size aligned address and this could cause major
2524		problems.
2525
2526- CONFIG_SYS_LOADS_BAUD_CHANGE:
2527		Enable temporary baudrate change while serial download
2528
2529- CONFIG_SYS_SDRAM_BASE:
2530		Physical start address of SDRAM. _Must_ be 0 here.
2531
2532- CONFIG_SYS_FLASH_BASE:
2533		Physical start address of Flash memory.
2534
2535- CONFIG_SYS_MONITOR_BASE:
2536		Physical start address of boot monitor code (set by
2537		make config files to be same as the text base address
2538		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2539		CONFIG_SYS_FLASH_BASE when booting from flash.
2540
2541- CONFIG_SYS_MONITOR_LEN:
2542		Size of memory reserved for monitor code, used to
2543		determine _at_compile_time_ (!) if the environment is
2544		embedded within the U-Boot image, or in a separate
2545		flash sector.
2546
2547- CONFIG_SYS_MALLOC_LEN:
2548		Size of DRAM reserved for malloc() use.
2549
2550- CONFIG_SYS_MALLOC_F_LEN
2551		Size of the malloc() pool for use before relocation. If
2552		this is defined, then a very simple malloc() implementation
2553		will become available before relocation. The address is just
2554		below the global data, and the stack is moved down to make
2555		space.
2556
2557		This feature allocates regions with increasing addresses
2558		within the region. calloc() is supported, but realloc()
2559		is not available. free() is supported but does nothing.
2560		The memory will be freed (or in fact just forgotten) when
2561		U-Boot relocates itself.
2562
2563- CONFIG_SYS_MALLOC_SIMPLE
2564		Provides a simple and small malloc() and calloc() for those
2565		boards which do not use the full malloc in SPL (which is
2566		enabled with CONFIG_SYS_SPL_MALLOC_START).
2567
2568- CONFIG_SYS_NONCACHED_MEMORY:
2569		Size of non-cached memory area. This area of memory will be
2570		typically located right below the malloc() area and mapped
2571		uncached in the MMU. This is useful for drivers that would
2572		otherwise require a lot of explicit cache maintenance. For
2573		some drivers it's also impossible to properly maintain the
2574		cache. For example if the regions that need to be flushed
2575		are not a multiple of the cache-line size, *and* padding
2576		cannot be allocated between the regions to align them (i.e.
2577		if the HW requires a contiguous array of regions, and the
2578		size of each region is not cache-aligned), then a flush of
2579		one region may result in overwriting data that hardware has
2580		written to another region in the same cache-line. This can
2581		happen for example in network drivers where descriptors for
2582		buffers are typically smaller than the CPU cache-line (e.g.
2583		16 bytes vs. 32 or 64 bytes).
2584
2585		Non-cached memory is only supported on 32-bit ARM at present.
2586
2587- CONFIG_SYS_BOOTM_LEN:
2588		Normally compressed uImages are limited to an
2589		uncompressed size of 8 MBytes. If this is not enough,
2590		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2591		to adjust this setting to your needs.
2592
2593- CONFIG_SYS_BOOTMAPSZ:
2594		Maximum size of memory mapped by the startup code of
2595		the Linux kernel; all data that must be processed by
2596		the Linux kernel (bd_info, boot arguments, FDT blob if
2597		used) must be put below this limit, unless "bootm_low"
2598		environment variable is defined and non-zero. In such case
2599		all data for the Linux kernel must be between "bootm_low"
2600		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2601		variable "bootm_mapsize" will override the value of
2602		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2603		then the value in "bootm_size" will be used instead.
2604
2605- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2606		Enable initrd_high functionality.  If defined then the
2607		initrd_high feature is enabled and the bootm ramdisk subcommand
2608		is enabled.
2609
2610- CONFIG_SYS_BOOT_GET_CMDLINE:
2611		Enables allocating and saving kernel cmdline in space between
2612		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2613
2614- CONFIG_SYS_BOOT_GET_KBD:
2615		Enables allocating and saving a kernel copy of the bd_info in
2616		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2617
2618- CONFIG_SYS_MAX_FLASH_BANKS:
2619		Max number of Flash memory banks
2620
2621- CONFIG_SYS_MAX_FLASH_SECT:
2622		Max number of sectors on a Flash chip
2623
2624- CONFIG_SYS_FLASH_ERASE_TOUT:
2625		Timeout for Flash erase operations (in ms)
2626
2627- CONFIG_SYS_FLASH_WRITE_TOUT:
2628		Timeout for Flash write operations (in ms)
2629
2630- CONFIG_SYS_FLASH_LOCK_TOUT
2631		Timeout for Flash set sector lock bit operation (in ms)
2632
2633- CONFIG_SYS_FLASH_UNLOCK_TOUT
2634		Timeout for Flash clear lock bits operation (in ms)
2635
2636- CONFIG_SYS_FLASH_PROTECTION
2637		If defined, hardware flash sectors protection is used
2638		instead of U-Boot software protection.
2639
2640- CONFIG_SYS_DIRECT_FLASH_TFTP:
2641
2642		Enable TFTP transfers directly to flash memory;
2643		without this option such a download has to be
2644		performed in two steps: (1) download to RAM, and (2)
2645		copy from RAM to flash.
2646
2647		The two-step approach is usually more reliable, since
2648		you can check if the download worked before you erase
2649		the flash, but in some situations (when system RAM is
2650		too limited to allow for a temporary copy of the
2651		downloaded image) this option may be very useful.
2652
2653- CONFIG_SYS_FLASH_CFI:
2654		Define if the flash driver uses extra elements in the
2655		common flash structure for storing flash geometry.
2656
2657- CONFIG_FLASH_CFI_DRIVER
2658		This option also enables the building of the cfi_flash driver
2659		in the drivers directory
2660
2661- CONFIG_FLASH_CFI_MTD
2662		This option enables the building of the cfi_mtd driver
2663		in the drivers directory. The driver exports CFI flash
2664		to the MTD layer.
2665
2666- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2667		Use buffered writes to flash.
2668
2669- CONFIG_FLASH_SPANSION_S29WS_N
2670		s29ws-n MirrorBit flash has non-standard addresses for buffered
2671		write commands.
2672
2673- CONFIG_SYS_FLASH_QUIET_TEST
2674		If this option is defined, the common CFI flash doesn't
2675		print it's warning upon not recognized FLASH banks. This
2676		is useful, if some of the configured banks are only
2677		optionally available.
2678
2679- CONFIG_FLASH_SHOW_PROGRESS
2680		If defined (must be an integer), print out countdown
2681		digits and dots.  Recommended value: 45 (9..1) for 80
2682		column displays, 15 (3..1) for 40 column displays.
2683
2684- CONFIG_FLASH_VERIFY
2685		If defined, the content of the flash (destination) is compared
2686		against the source after the write operation. An error message
2687		will be printed when the contents are not identical.
2688		Please note that this option is useless in nearly all cases,
2689		since such flash programming errors usually are detected earlier
2690		while unprotecting/erasing/programming. Please only enable
2691		this option if you really know what you are doing.
2692
2693- CONFIG_SYS_RX_ETH_BUFFER:
2694		Defines the number of Ethernet receive buffers. On some
2695		Ethernet controllers it is recommended to set this value
2696		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2697		buffers can be full shortly after enabling the interface
2698		on high Ethernet traffic.
2699		Defaults to 4 if not defined.
2700
2701- CONFIG_ENV_MAX_ENTRIES
2702
2703	Maximum number of entries in the hash table that is used
2704	internally to store the environment settings. The default
2705	setting is supposed to be generous and should work in most
2706	cases. This setting can be used to tune behaviour; see
2707	lib/hashtable.c for details.
2708
2709- CONFIG_ENV_FLAGS_LIST_DEFAULT
2710- CONFIG_ENV_FLAGS_LIST_STATIC
2711	Enable validation of the values given to environment variables when
2712	calling env set.  Variables can be restricted to only decimal,
2713	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2714	the variables can also be restricted to IP address or MAC address.
2715
2716	The format of the list is:
2717		type_attribute = [s|d|x|b|i|m]
2718		access_attribute = [a|r|o|c]
2719		attributes = type_attribute[access_attribute]
2720		entry = variable_name[:attributes]
2721		list = entry[,list]
2722
2723	The type attributes are:
2724		s - String (default)
2725		d - Decimal
2726		x - Hexadecimal
2727		b - Boolean ([1yYtT|0nNfF])
2728		i - IP address
2729		m - MAC address
2730
2731	The access attributes are:
2732		a - Any (default)
2733		r - Read-only
2734		o - Write-once
2735		c - Change-default
2736
2737	- CONFIG_ENV_FLAGS_LIST_DEFAULT
2738		Define this to a list (string) to define the ".flags"
2739		environment variable in the default or embedded environment.
2740
2741	- CONFIG_ENV_FLAGS_LIST_STATIC
2742		Define this to a list (string) to define validation that
2743		should be done if an entry is not found in the ".flags"
2744		environment variable.  To override a setting in the static
2745		list, simply add an entry for the same variable name to the
2746		".flags" variable.
2747
2748	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2749	regular expression. This allows multiple variables to define the same
2750	flags without explicitly listing them for each variable.
2751
2752- CONFIG_ENV_ACCESS_IGNORE_FORCE
2753	If defined, don't allow the -f switch to env set override variable
2754	access flags.
2755
2756The following definitions that deal with the placement and management
2757of environment data (variable area); in general, we support the
2758following configurations:
2759
2760- CONFIG_BUILD_ENVCRC:
2761
2762	Builds up envcrc with the target environment so that external utils
2763	may easily extract it and embed it in final U-Boot images.
2764
2765BE CAREFUL! The first access to the environment happens quite early
2766in U-Boot initialization (when we try to get the setting of for the
2767console baudrate). You *MUST* have mapped your NVRAM area then, or
2768U-Boot will hang.
2769
2770Please note that even with NVRAM we still use a copy of the
2771environment in RAM: we could work on NVRAM directly, but we want to
2772keep settings there always unmodified except somebody uses "saveenv"
2773to save the current settings.
2774
2775BE CAREFUL! For some special cases, the local device can not use
2776"saveenv" command. For example, the local device will get the
2777environment stored in a remote NOR flash by SRIO or PCIE link,
2778but it can not erase, write this NOR flash by SRIO or PCIE interface.
2779
2780- CONFIG_NAND_ENV_DST
2781
2782	Defines address in RAM to which the nand_spl code should copy the
2783	environment. If redundant environment is used, it will be copied to
2784	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2785
2786Please note that the environment is read-only until the monitor
2787has been relocated to RAM and a RAM copy of the environment has been
2788created; also, when using EEPROM you will have to use env_get_f()
2789until then to read environment variables.
2790
2791The environment is protected by a CRC32 checksum. Before the monitor
2792is relocated into RAM, as a result of a bad CRC you will be working
2793with the compiled-in default environment - *silently*!!! [This is
2794necessary, because the first environment variable we need is the
2795"baudrate" setting for the console - if we have a bad CRC, we don't
2796have any device yet where we could complain.]
2797
2798Note: once the monitor has been relocated, then it will complain if
2799the default environment is used; a new CRC is computed as soon as you
2800use the "saveenv" command to store a valid environment.
2801
2802- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
2803		Echo the inverted Ethernet link state to the fault LED.
2804
2805		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
2806		      also needs to be defined.
2807
2808- CONFIG_SYS_FAULT_MII_ADDR:
2809		MII address of the PHY to check for the Ethernet link state.
2810
2811- CONFIG_NS16550_MIN_FUNCTIONS:
2812		Define this if you desire to only have use of the NS16550_init
2813		and NS16550_putc functions for the serial driver located at
2814		drivers/serial/ns16550.c.  This option is useful for saving
2815		space for already greatly restricted images, including but not
2816		limited to NAND_SPL configurations.
2817
2818- CONFIG_DISPLAY_BOARDINFO
2819		Display information about the board that U-Boot is running on
2820		when U-Boot starts up. The board function checkboard() is called
2821		to do this.
2822
2823- CONFIG_DISPLAY_BOARDINFO_LATE
2824		Similar to the previous option, but display this information
2825		later, once stdio is running and output goes to the LCD, if
2826		present.
2827
2828- CONFIG_BOARD_SIZE_LIMIT:
2829		Maximum size of the U-Boot image. When defined, the
2830		build system checks that the actual size does not
2831		exceed it.
2832
2833Low Level (hardware related) configuration options:
2834---------------------------------------------------
2835
2836- CONFIG_SYS_CACHELINE_SIZE:
2837		Cache Line Size of the CPU.
2838
2839- CONFIG_SYS_CCSRBAR_DEFAULT:
2840		Default (power-on reset) physical address of CCSR on Freescale
2841		PowerPC SOCs.
2842
2843- CONFIG_SYS_CCSRBAR:
2844		Virtual address of CCSR.  On a 32-bit build, this is typically
2845		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
2846
2847- CONFIG_SYS_CCSRBAR_PHYS:
2848		Physical address of CCSR.  CCSR can be relocated to a new
2849		physical address, if desired.  In this case, this macro should
2850		be set to that address.	 Otherwise, it should be set to the
2851		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
2852		is typically relocated on 36-bit builds.  It is recommended
2853		that this macro be defined via the _HIGH and _LOW macros:
2854
2855		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
2856			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
2857
2858- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
2859		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
2860		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
2861		used in assembly code, so it must not contain typecasts or
2862		integer size suffixes (e.g. "ULL").
2863
2864- CONFIG_SYS_CCSRBAR_PHYS_LOW:
2865		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
2866		used in assembly code, so it must not contain typecasts or
2867		integer size suffixes (e.g. "ULL").
2868
2869- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
2870		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
2871		forced to a value that ensures that CCSR is not relocated.
2872
2873- Floppy Disk Support:
2874		CONFIG_SYS_FDC_DRIVE_NUMBER
2875
2876		the default drive number (default value 0)
2877
2878		CONFIG_SYS_ISA_IO_STRIDE
2879
2880		defines the spacing between FDC chipset registers
2881		(default value 1)
2882
2883		CONFIG_SYS_ISA_IO_OFFSET
2884
2885		defines the offset of register from address. It
2886		depends on which part of the data bus is connected to
2887		the FDC chipset. (default value 0)
2888
2889		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
2890		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
2891		default value.
2892
2893		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
2894		fdc_hw_init() is called at the beginning of the FDC
2895		setup. fdc_hw_init() must be provided by the board
2896		source code. It is used to make hardware-dependent
2897		initializations.
2898
2899- CONFIG_IDE_AHB:
2900		Most IDE controllers were designed to be connected with PCI
2901		interface. Only few of them were designed for AHB interface.
2902		When software is doing ATA command and data transfer to
2903		IDE devices through IDE-AHB controller, some additional
2904		registers accessing to these kind of IDE-AHB controller
2905		is required.
2906
2907- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
2908		DO NOT CHANGE unless you know exactly what you're
2909		doing! (11-4) [MPC8xx systems only]
2910
2911- CONFIG_SYS_INIT_RAM_ADDR:
2912
2913		Start address of memory area that can be used for
2914		initial data and stack; please note that this must be
2915		writable memory that is working WITHOUT special
2916		initialization, i. e. you CANNOT use normal RAM which
2917		will become available only after programming the
2918		memory controller and running certain initialization
2919		sequences.
2920
2921		U-Boot uses the following memory types:
2922		- MPC8xx: IMMR (internal memory of the CPU)
2923
2924- CONFIG_SYS_GBL_DATA_OFFSET:
2925
2926		Offset of the initial data structure in the memory
2927		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
2928		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
2929		data is located at the end of the available space
2930		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
2931		GENERATED_GBL_DATA_SIZE), and the initial stack is just
2932		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
2933		CONFIG_SYS_GBL_DATA_OFFSET) downward.
2934
2935	Note:
2936		On the MPC824X (or other systems that use the data
2937		cache for initial memory) the address chosen for
2938		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
2939		point to an otherwise UNUSED address space between
2940		the top of RAM and the start of the PCI space.
2941
2942- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
2943
2944- CONFIG_SYS_OR_TIMING_SDRAM:
2945		SDRAM timing
2946
2947- CONFIG_SYS_MAMR_PTA:
2948		periodic timer for refresh
2949
2950- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
2951  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
2952  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
2953  CONFIG_SYS_BR1_PRELIM:
2954		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
2955
2956- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
2957  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
2958  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
2959		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
2960
2961- CONFIG_PCI_ENUM_ONLY
2962		Only scan through and get the devices on the buses.
2963		Don't do any setup work, presumably because someone or
2964		something has already done it, and we don't need to do it
2965		a second time.	Useful for platforms that are pre-booted
2966		by coreboot or similar.
2967
2968- CONFIG_PCI_INDIRECT_BRIDGE:
2969		Enable support for indirect PCI bridges.
2970
2971- CONFIG_SYS_SRIO:
2972		Chip has SRIO or not
2973
2974- CONFIG_SRIO1:
2975		Board has SRIO 1 port available
2976
2977- CONFIG_SRIO2:
2978		Board has SRIO 2 port available
2979
2980- CONFIG_SRIO_PCIE_BOOT_MASTER
2981		Board can support master function for Boot from SRIO and PCIE
2982
2983- CONFIG_SYS_SRIOn_MEM_VIRT:
2984		Virtual Address of SRIO port 'n' memory region
2985
2986- CONFIG_SYS_SRIOn_MEM_PHYS:
2987		Physical Address of SRIO port 'n' memory region
2988
2989- CONFIG_SYS_SRIOn_MEM_SIZE:
2990		Size of SRIO port 'n' memory region
2991
2992- CONFIG_SYS_NAND_BUSWIDTH_16BIT
2993		Defined to tell the NAND controller that the NAND chip is using
2994		a 16 bit bus.
2995		Not all NAND drivers use this symbol.
2996		Example of drivers that use it:
2997		- drivers/mtd/nand/raw/ndfc.c
2998		- drivers/mtd/nand/raw/mxc_nand.c
2999
3000- CONFIG_SYS_NDFC_EBC0_CFG
3001		Sets the EBC0_CFG register for the NDFC. If not defined
3002		a default value will be used.
3003
3004- CONFIG_SPD_EEPROM
3005		Get DDR timing information from an I2C EEPROM. Common
3006		with pluggable memory modules such as SODIMMs
3007
3008  SPD_EEPROM_ADDRESS
3009		I2C address of the SPD EEPROM
3010
3011- CONFIG_SYS_SPD_BUS_NUM
3012		If SPD EEPROM is on an I2C bus other than the first
3013		one, specify here. Note that the value must resolve
3014		to something your driver can deal with.
3015
3016- CONFIG_SYS_DDR_RAW_TIMING
3017		Get DDR timing information from other than SPD. Common with
3018		soldered DDR chips onboard without SPD. DDR raw timing
3019		parameters are extracted from datasheet and hard-coded into
3020		header files or board specific files.
3021
3022- CONFIG_FSL_DDR_INTERACTIVE
3023		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3024
3025- CONFIG_FSL_DDR_SYNC_REFRESH
3026		Enable sync of refresh for multiple controllers.
3027
3028- CONFIG_FSL_DDR_BIST
3029		Enable built-in memory test for Freescale DDR controllers.
3030
3031- CONFIG_SYS_83XX_DDR_USES_CS0
3032		Only for 83xx systems. If specified, then DDR should
3033		be configured using CS0 and CS1 instead of CS2 and CS3.
3034
3035- CONFIG_RMII
3036		Enable RMII mode for all FECs.
3037		Note that this is a global option, we can't
3038		have one FEC in standard MII mode and another in RMII mode.
3039
3040- CONFIG_CRC32_VERIFY
3041		Add a verify option to the crc32 command.
3042		The syntax is:
3043
3044		=> crc32 -v <address> <count> <crc32>
3045
3046		Where address/count indicate a memory area
3047		and crc32 is the correct crc32 which the
3048		area should have.
3049
3050- CONFIG_LOOPW
3051		Add the "loopw" memory command. This only takes effect if
3052		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3053
3054- CONFIG_MX_CYCLIC
3055		Add the "mdc" and "mwc" memory commands. These are cyclic
3056		"md/mw" commands.
3057		Examples:
3058
3059		=> mdc.b 10 4 500
3060		This command will print 4 bytes (10,11,12,13) each 500 ms.
3061
3062		=> mwc.l 100 12345678 10
3063		This command will write 12345678 to address 100 all 10 ms.
3064
3065		This only takes effect if the memory commands are activated
3066		globally (CONFIG_CMD_MEMORY).
3067
3068- CONFIG_SKIP_LOWLEVEL_INIT
3069		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3070		low level initializations (like setting up the memory
3071		controller) are omitted and/or U-Boot does not
3072		relocate itself into RAM.
3073
3074		Normally this variable MUST NOT be defined. The only
3075		exception is when U-Boot is loaded (to RAM) by some
3076		other boot loader or by a debugger which performs
3077		these initializations itself.
3078
3079- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3080		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3081		to be skipped. The normal CP15 init (such as enabling the
3082		instruction cache) is still performed.
3083
3084- CONFIG_SPL_BUILD
3085		Modifies the behaviour of start.S when compiling a loader
3086		that is executed before the actual U-Boot. E.g. when
3087		compiling a NAND SPL.
3088
3089- CONFIG_TPL_BUILD
3090		Modifies the behaviour of start.S  when compiling a loader
3091		that is executed after the SPL and before the actual U-Boot.
3092		It is loaded by the SPL.
3093
3094- CONFIG_SYS_MPC85XX_NO_RESETVEC
3095		Only for 85xx systems. If this variable is specified, the section
3096		.resetvec is not kept and the section .bootpg is placed in the
3097		previous 4k of the .text section.
3098
3099- CONFIG_ARCH_MAP_SYSMEM
3100		Generally U-Boot (and in particular the md command) uses
3101		effective address. It is therefore not necessary to regard
3102		U-Boot address as virtual addresses that need to be translated
3103		to physical addresses. However, sandbox requires this, since
3104		it maintains its own little RAM buffer which contains all
3105		addressable memory. This option causes some memory accesses
3106		to be mapped through map_sysmem() / unmap_sysmem().
3107
3108- CONFIG_X86_RESET_VECTOR
3109		If defined, the x86 reset vector code is included. This is not
3110		needed when U-Boot is running from Coreboot.
3111
3112- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3113		Option to disable subpage write in NAND driver
3114		driver that uses this:
3115		drivers/mtd/nand/raw/davinci_nand.c
3116
3117Freescale QE/FMAN Firmware Support:
3118-----------------------------------
3119
3120The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3121loading of "firmware", which is encoded in the QE firmware binary format.
3122This firmware often needs to be loaded during U-Boot booting, so macros
3123are used to identify the storage device (NOR flash, SPI, etc) and the address
3124within that device.
3125
3126- CONFIG_SYS_FMAN_FW_ADDR
3127	The address in the storage device where the FMAN microcode is located.  The
3128	meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
3129	is also specified.
3130
3131- CONFIG_SYS_QE_FW_ADDR
3132	The address in the storage device where the QE microcode is located.  The
3133	meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
3134	is also specified.
3135
3136- CONFIG_SYS_QE_FMAN_FW_LENGTH
3137	The maximum possible size of the firmware.  The firmware binary format
3138	has a field that specifies the actual size of the firmware, but it
3139	might not be possible to read any part of the firmware unless some
3140	local storage is allocated to hold the entire firmware first.
3141
3142- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3143	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3144	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3145	virtual address in NOR flash.
3146
3147- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3148	Specifies that QE/FMAN firmware is located in NAND flash.
3149	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3150
3151- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3152	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3153	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3154
3155- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3156	Specifies that QE/FMAN firmware is located in the remote (master)
3157	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3158	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3159	window->master inbound window->master LAW->the ucode address in
3160	master's memory space.
3161
3162Freescale Layerscape Management Complex Firmware Support:
3163---------------------------------------------------------
3164The Freescale Layerscape Management Complex (MC) supports the loading of
3165"firmware".
3166This firmware often needs to be loaded during U-Boot booting, so macros
3167are used to identify the storage device (NOR flash, SPI, etc) and the address
3168within that device.
3169
3170- CONFIG_FSL_MC_ENET
3171	Enable the MC driver for Layerscape SoCs.
3172
3173Freescale Layerscape Debug Server Support:
3174-------------------------------------------
3175The Freescale Layerscape Debug Server Support supports the loading of
3176"Debug Server firmware" and triggering SP boot-rom.
3177This firmware often needs to be loaded during U-Boot booting.
3178
3179- CONFIG_SYS_MC_RSV_MEM_ALIGN
3180	Define alignment of reserved memory MC requires
3181
3182Reproducible builds
3183-------------------
3184
3185In order to achieve reproducible builds, timestamps used in the U-Boot build
3186process have to be set to a fixed value.
3187
3188This is done using the SOURCE_DATE_EPOCH environment variable.
3189SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3190option for U-Boot or an environment variable in U-Boot.
3191
3192SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3193
3194Building the Software:
3195======================
3196
3197Building U-Boot has been tested in several native build environments
3198and in many different cross environments. Of course we cannot support
3199all possibly existing versions of cross development tools in all
3200(potentially obsolete) versions. In case of tool chain problems we
3201recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3202which is extensively used to build and test U-Boot.
3203
3204If you are not using a native environment, it is assumed that you
3205have GNU cross compiling tools available in your path. In this case,
3206you must set the environment variable CROSS_COMPILE in your shell.
3207Note that no changes to the Makefile or any other source files are
3208necessary. For example using the ELDK on a 4xx CPU, please enter:
3209
3210	$ CROSS_COMPILE=ppc_4xx-
3211	$ export CROSS_COMPILE
3212
3213Note: If you wish to generate Windows versions of the utilities in
3214      the tools directory you can use the MinGW toolchain
3215      (http://www.mingw.org).  Set your HOST tools to the MinGW
3216      toolchain and execute 'make tools'.  For example:
3217
3218       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3219
3220      Binaries such as tools/mkimage.exe will be created which can
3221      be executed on computers running Windows.
3222
3223U-Boot is intended to be simple to build. After installing the
3224sources you must configure U-Boot for one specific board type. This
3225is done by typing:
3226
3227	make NAME_defconfig
3228
3229where "NAME_defconfig" is the name of one of the existing configu-
3230rations; see boards.cfg for supported names.
3231
3232Note: for some board special configuration names may exist; check if
3233      additional information is available from the board vendor; for
3234      instance, the TQM823L systems are available without (standard)
3235      or with LCD support. You can select such additional "features"
3236      when choosing the configuration, i. e.
3237
3238      make TQM823L_defconfig
3239	- will configure for a plain TQM823L, i. e. no LCD support
3240
3241      make TQM823L_LCD_defconfig
3242	- will configure for a TQM823L with U-Boot console on LCD
3243
3244      etc.
3245
3246
3247Finally, type "make all", and you should get some working U-Boot
3248images ready for download to / installation on your system:
3249
3250- "u-boot.bin" is a raw binary image
3251- "u-boot" is an image in ELF binary format
3252- "u-boot.srec" is in Motorola S-Record format
3253
3254By default the build is performed locally and the objects are saved
3255in the source directory. One of the two methods can be used to change
3256this behavior and build U-Boot to some external directory:
3257
32581. Add O= to the make command line invocations:
3259
3260	make O=/tmp/build distclean
3261	make O=/tmp/build NAME_defconfig
3262	make O=/tmp/build all
3263
32642. Set environment variable KBUILD_OUTPUT to point to the desired location:
3265
3266	export KBUILD_OUTPUT=/tmp/build
3267	make distclean
3268	make NAME_defconfig
3269	make all
3270
3271Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3272variable.
3273
3274User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3275setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3276For example to treat all compiler warnings as errors:
3277
3278	make KCFLAGS=-Werror
3279
3280Please be aware that the Makefiles assume you are using GNU make, so
3281for instance on NetBSD you might need to use "gmake" instead of
3282native "make".
3283
3284
3285If the system board that you have is not listed, then you will need
3286to port U-Boot to your hardware platform. To do this, follow these
3287steps:
3288
32891.  Create a new directory to hold your board specific code. Add any
3290    files you need. In your board directory, you will need at least
3291    the "Makefile" and a "<board>.c".
32922.  Create a new configuration file "include/configs/<board>.h" for
3293    your board.
32943.  If you're porting U-Boot to a new CPU, then also create a new
3295    directory to hold your CPU specific code. Add any files you need.
32964.  Run "make <board>_defconfig" with your new name.
32975.  Type "make", and you should get a working "u-boot.srec" file
3298    to be installed on your target system.
32996.  Debug and solve any problems that might arise.
3300    [Of course, this last step is much harder than it sounds.]
3301
3302
3303Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3304==============================================================
3305
3306If you have modified U-Boot sources (for instance added a new board
3307or support for new devices, a new CPU, etc.) you are expected to
3308provide feedback to the other developers. The feedback normally takes
3309the form of a "patch", i. e. a context diff against a certain (latest
3310official or latest in the git repository) version of U-Boot sources.
3311
3312But before you submit such a patch, please verify that your modifi-
3313cation did not break existing code. At least make sure that *ALL* of
3314the supported boards compile WITHOUT ANY compiler warnings. To do so,
3315just run the buildman script (tools/buildman/buildman), which will
3316configure and build U-Boot for ALL supported system. Be warned, this
3317will take a while. Please see the buildman README, or run 'buildman -H'
3318for documentation.
3319
3320
3321See also "U-Boot Porting Guide" below.
3322
3323
3324Monitor Commands - Overview:
3325============================
3326
3327go	- start application at address 'addr'
3328run	- run commands in an environment variable
3329bootm	- boot application image from memory
3330bootp	- boot image via network using BootP/TFTP protocol
3331bootz   - boot zImage from memory
3332tftpboot- boot image via network using TFTP protocol
3333	       and env variables "ipaddr" and "serverip"
3334	       (and eventually "gatewayip")
3335tftpput - upload a file via network using TFTP protocol
3336rarpboot- boot image via network using RARP/TFTP protocol
3337diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3338loads	- load S-Record file over serial line
3339loadb	- load binary file over serial line (kermit mode)
3340md	- memory display
3341mm	- memory modify (auto-incrementing)
3342nm	- memory modify (constant address)
3343mw	- memory write (fill)
3344cp	- memory copy
3345cmp	- memory compare
3346crc32	- checksum calculation
3347i2c	- I2C sub-system
3348sspi	- SPI utility commands
3349base	- print or set address offset
3350printenv- print environment variables
3351setenv	- set environment variables
3352saveenv - save environment variables to persistent storage
3353protect - enable or disable FLASH write protection
3354erase	- erase FLASH memory
3355flinfo	- print FLASH memory information
3356nand	- NAND memory operations (see doc/README.nand)
3357bdinfo	- print Board Info structure
3358iminfo	- print header information for application image
3359coninfo - print console devices and informations
3360ide	- IDE sub-system
3361loop	- infinite loop on address range
3362loopw	- infinite write loop on address range
3363mtest	- simple RAM test
3364icache	- enable or disable instruction cache
3365dcache	- enable or disable data cache
3366reset	- Perform RESET of the CPU
3367echo	- echo args to console
3368version - print monitor version
3369help	- print online help
3370?	- alias for 'help'
3371
3372
3373Monitor Commands - Detailed Description:
3374========================================
3375
3376TODO.
3377
3378For now: just type "help <command>".
3379
3380
3381Environment Variables:
3382======================
3383
3384U-Boot supports user configuration using Environment Variables which
3385can be made persistent by saving to Flash memory.
3386
3387Environment Variables are set using "setenv", printed using
3388"printenv", and saved to Flash using "saveenv". Using "setenv"
3389without a value can be used to delete a variable from the
3390environment. As long as you don't save the environment you are
3391working with an in-memory copy. In case the Flash area containing the
3392environment is erased by accident, a default environment is provided.
3393
3394Some configuration options can be set using Environment Variables.
3395
3396List of environment variables (most likely not complete):
3397
3398  baudrate	- see CONFIG_BAUDRATE
3399
3400  bootdelay	- see CONFIG_BOOTDELAY
3401
3402  bootcmd	- see CONFIG_BOOTCOMMAND
3403
3404  bootargs	- Boot arguments when booting an RTOS image
3405
3406  bootfile	- Name of the image to load with TFTP
3407
3408  bootm_low	- Memory range available for image processing in the bootm
3409		  command can be restricted. This variable is given as
3410		  a hexadecimal number and defines lowest address allowed
3411		  for use by the bootm command. See also "bootm_size"
3412		  environment variable. Address defined by "bootm_low" is
3413		  also the base of the initial memory mapping for the Linux
3414		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3415		  bootm_mapsize.
3416
3417  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3418		  This variable is given as a hexadecimal number and it
3419		  defines the size of the memory region starting at base
3420		  address bootm_low that is accessible by the Linux kernel
3421		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3422		  as the default value if it is defined, and bootm_size is
3423		  used otherwise.
3424
3425  bootm_size	- Memory range available for image processing in the bootm
3426		  command can be restricted. This variable is given as
3427		  a hexadecimal number and defines the size of the region
3428		  allowed for use by the bootm command. See also "bootm_low"
3429		  environment variable.
3430
3431  bootstopkeysha256, bootdelaykey, bootstopkey	- See README.autoboot
3432
3433  updatefile	- Location of the software update file on a TFTP server, used
3434		  by the automatic software update feature. Please refer to
3435		  documentation in doc/README.update for more details.
3436
3437  autoload	- if set to "no" (any string beginning with 'n'),
3438		  "bootp" will just load perform a lookup of the
3439		  configuration from the BOOTP server, but not try to
3440		  load any image using TFTP
3441
3442  autostart	- if set to "yes", an image loaded using the "bootp",
3443		  "rarpboot", "tftpboot" or "diskboot" commands will
3444		  be automatically started (by internally calling
3445		  "bootm")
3446
3447		  If set to "no", a standalone image passed to the
3448		  "bootm" command will be copied to the load address
3449		  (and eventually uncompressed), but NOT be started.
3450		  This can be used to load and uncompress arbitrary
3451		  data.
3452
3453  fdt_high	- if set this restricts the maximum address that the
3454		  flattened device tree will be copied into upon boot.
3455		  For example, if you have a system with 1 GB memory
3456		  at physical address 0x10000000, while Linux kernel
3457		  only recognizes the first 704 MB as low memory, you
3458		  may need to set fdt_high as 0x3C000000 to have the
3459		  device tree blob be copied to the maximum address
3460		  of the 704 MB low memory, so that Linux kernel can
3461		  access it during the boot procedure.
3462
3463		  If this is set to the special value 0xFFFFFFFF then
3464		  the fdt will not be copied at all on boot.  For this
3465		  to work it must reside in writable memory, have
3466		  sufficient padding on the end of it for u-boot to
3467		  add the information it needs into it, and the memory
3468		  must be accessible by the kernel.
3469
3470  fdtcontroladdr- if set this is the address of the control flattened
3471		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3472		  defined.
3473
3474  i2cfast	- (PPC405GP|PPC405EP only)
3475		  if set to 'y' configures Linux I2C driver for fast
3476		  mode (400kHZ). This environment variable is used in
3477		  initialization code. So, for changes to be effective
3478		  it must be saved and board must be reset.
3479
3480  initrd_high	- restrict positioning of initrd images:
3481		  If this variable is not set, initrd images will be
3482		  copied to the highest possible address in RAM; this
3483		  is usually what you want since it allows for
3484		  maximum initrd size. If for some reason you want to
3485		  make sure that the initrd image is loaded below the
3486		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3487		  variable to a value of "no" or "off" or "0".
3488		  Alternatively, you can set it to a maximum upper
3489		  address to use (U-Boot will still check that it
3490		  does not overwrite the U-Boot stack and data).
3491
3492		  For instance, when you have a system with 16 MB
3493		  RAM, and want to reserve 4 MB from use by Linux,
3494		  you can do this by adding "mem=12M" to the value of
3495		  the "bootargs" variable. However, now you must make
3496		  sure that the initrd image is placed in the first
3497		  12 MB as well - this can be done with
3498
3499		  setenv initrd_high 00c00000
3500
3501		  If you set initrd_high to 0xFFFFFFFF, this is an
3502		  indication to U-Boot that all addresses are legal
3503		  for the Linux kernel, including addresses in flash
3504		  memory. In this case U-Boot will NOT COPY the
3505		  ramdisk at all. This may be useful to reduce the
3506		  boot time on your system, but requires that this
3507		  feature is supported by your Linux kernel.
3508
3509  ipaddr	- IP address; needed for tftpboot command
3510
3511  loadaddr	- Default load address for commands like "bootp",
3512		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3513
3514  loads_echo	- see CONFIG_LOADS_ECHO
3515
3516  serverip	- TFTP server IP address; needed for tftpboot command
3517
3518  bootretry	- see CONFIG_BOOT_RETRY_TIME
3519
3520  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3521
3522  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3523
3524  ethprime	- controls which interface is used first.
3525
3526  ethact	- controls which interface is currently active.
3527		  For example you can do the following
3528
3529		  => setenv ethact FEC
3530		  => ping 192.168.0.1 # traffic sent on FEC
3531		  => setenv ethact SCC
3532		  => ping 10.0.0.1 # traffic sent on SCC
3533
3534  ethrotate	- When set to "no" U-Boot does not go through all
3535		  available network interfaces.
3536		  It just stays at the currently selected interface.
3537
3538  netretry	- When set to "no" each network operation will
3539		  either succeed or fail without retrying.
3540		  When set to "once" the network operation will
3541		  fail when all the available network interfaces
3542		  are tried once without success.
3543		  Useful on scripts which control the retry operation
3544		  themselves.
3545
3546  npe_ucode	- set load address for the NPE microcode
3547
3548  silent_linux  - If set then Linux will be told to boot silently, by
3549		  changing the console to be empty. If "yes" it will be
3550		  made silent. If "no" it will not be made silent. If
3551		  unset, then it will be made silent if the U-Boot console
3552		  is silent.
3553
3554  tftpsrcp	- If this is set, the value is used for TFTP's
3555		  UDP source port.
3556
3557  tftpdstp	- If this is set, the value is used for TFTP's UDP
3558		  destination port instead of the Well Know Port 69.
3559
3560  tftpblocksize - Block size to use for TFTP transfers; if not set,
3561		  we use the TFTP server's default block size
3562
3563  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3564		  seconds, minimum value is 1000 = 1 second). Defines
3565		  when a packet is considered to be lost so it has to
3566		  be retransmitted. The default is 5000 = 5 seconds.
3567		  Lowering this value may make downloads succeed
3568		  faster in networks with high packet loss rates or
3569		  with unreliable TFTP servers.
3570
3571  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3572		  unit, minimum value = 0). Defines how many timeouts
3573		  can happen during a single file transfer before that
3574		  transfer is aborted. The default is 10, and 0 means
3575		  'no timeouts allowed'. Increasing this value may help
3576		  downloads succeed with high packet loss rates, or with
3577		  unreliable TFTP servers or client hardware.
3578
3579  vlan		- When set to a value < 4095 the traffic over
3580		  Ethernet is encapsulated/received over 802.1q
3581		  VLAN tagged frames.
3582
3583  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3584		  Unsigned value, in milliseconds. If not set, the period will
3585		  be either the default (28000), or a value based on
3586		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3587		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3588
3589The following image location variables contain the location of images
3590used in booting. The "Image" column gives the role of the image and is
3591not an environment variable name. The other columns are environment
3592variable names. "File Name" gives the name of the file on a TFTP
3593server, "RAM Address" gives the location in RAM the image will be
3594loaded to, and "Flash Location" gives the image's address in NOR
3595flash or offset in NAND flash.
3596
3597*Note* - these variables don't have to be defined for all boards, some
3598boards currently use other variables for these purposes, and some
3599boards use these variables for other purposes.
3600
3601Image		    File Name	     RAM Address       Flash Location
3602-----		    ---------	     -----------       --------------
3603u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3604Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3605device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3606ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3607
3608The following environment variables may be used and automatically
3609updated by the network boot commands ("bootp" and "rarpboot"),
3610depending the information provided by your boot server:
3611
3612  bootfile	- see above
3613  dnsip		- IP address of your Domain Name Server
3614  dnsip2	- IP address of your secondary Domain Name Server
3615  gatewayip	- IP address of the Gateway (Router) to use
3616  hostname	- Target hostname
3617  ipaddr	- see above
3618  netmask	- Subnet Mask
3619  rootpath	- Pathname of the root filesystem on the NFS server
3620  serverip	- see above
3621
3622
3623There are two special Environment Variables:
3624
3625  serial#	- contains hardware identification information such
3626		  as type string and/or serial number
3627  ethaddr	- Ethernet address
3628
3629These variables can be set only once (usually during manufacturing of
3630the board). U-Boot refuses to delete or overwrite these variables
3631once they have been set once.
3632
3633
3634Further special Environment Variables:
3635
3636  ver		- Contains the U-Boot version string as printed
3637		  with the "version" command. This variable is
3638		  readonly (see CONFIG_VERSION_VARIABLE).
3639
3640
3641Please note that changes to some configuration parameters may take
3642only effect after the next boot (yes, that's just like Windoze :-).
3643
3644
3645Callback functions for environment variables:
3646---------------------------------------------
3647
3648For some environment variables, the behavior of u-boot needs to change
3649when their values are changed.  This functionality allows functions to
3650be associated with arbitrary variables.  On creation, overwrite, or
3651deletion, the callback will provide the opportunity for some side
3652effect to happen or for the change to be rejected.
3653
3654The callbacks are named and associated with a function using the
3655U_BOOT_ENV_CALLBACK macro in your board or driver code.
3656
3657These callbacks are associated with variables in one of two ways.  The
3658static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3659in the board configuration to a string that defines a list of
3660associations.  The list must be in the following format:
3661
3662	entry = variable_name[:callback_name]
3663	list = entry[,list]
3664
3665If the callback name is not specified, then the callback is deleted.
3666Spaces are also allowed anywhere in the list.
3667
3668Callbacks can also be associated by defining the ".callbacks" variable
3669with the same list format above.  Any association in ".callbacks" will
3670override any association in the static list. You can define
3671CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3672".callbacks" environment variable in the default or embedded environment.
3673
3674If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3675regular expression. This allows multiple variables to be connected to
3676the same callback without explicitly listing them all out.
3677
3678The signature of the callback functions is:
3679
3680    int callback(const char *name, const char *value, enum env_op op, int flags)
3681
3682* name - changed environment variable
3683* value - new value of the environment variable
3684* op - operation (create, overwrite, or delete)
3685* flags - attributes of the environment variable change, see flags H_* in
3686  include/search.h
3687
3688The return value is 0 if the variable change is accepted and 1 otherwise.
3689
3690Command Line Parsing:
3691=====================
3692
3693There are two different command line parsers available with U-Boot:
3694the old "simple" one, and the much more powerful "hush" shell:
3695
3696Old, simple command line parser:
3697--------------------------------
3698
3699- supports environment variables (through setenv / saveenv commands)
3700- several commands on one line, separated by ';'
3701- variable substitution using "... ${name} ..." syntax
3702- special characters ('$', ';') can be escaped by prefixing with '\',
3703  for example:
3704	setenv bootcmd bootm \${address}
3705- You can also escape text by enclosing in single apostrophes, for example:
3706	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3707
3708Hush shell:
3709-----------
3710
3711- similar to Bourne shell, with control structures like
3712  if...then...else...fi, for...do...done; while...do...done,
3713  until...do...done, ...
3714- supports environment ("global") variables (through setenv / saveenv
3715  commands) and local shell variables (through standard shell syntax
3716  "name=value"); only environment variables can be used with "run"
3717  command
3718
3719General rules:
3720--------------
3721
3722(1) If a command line (or an environment variable executed by a "run"
3723    command) contains several commands separated by semicolon, and
3724    one of these commands fails, then the remaining commands will be
3725    executed anyway.
3726
3727(2) If you execute several variables with one call to run (i. e.
3728    calling run with a list of variables as arguments), any failing
3729    command will cause "run" to terminate, i. e. the remaining
3730    variables are not executed.
3731
3732Note for Redundant Ethernet Interfaces:
3733=======================================
3734
3735Some boards come with redundant Ethernet interfaces; U-Boot supports
3736such configurations and is capable of automatic selection of a
3737"working" interface when needed. MAC assignment works as follows:
3738
3739Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3740MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3741"eth1addr" (=>eth1), "eth2addr", ...
3742
3743If the network interface stores some valid MAC address (for instance
3744in SROM), this is used as default address if there is NO correspon-
3745ding setting in the environment; if the corresponding environment
3746variable is set, this overrides the settings in the card; that means:
3747
3748o If the SROM has a valid MAC address, and there is no address in the
3749  environment, the SROM's address is used.
3750
3751o If there is no valid address in the SROM, and a definition in the
3752  environment exists, then the value from the environment variable is
3753  used.
3754
3755o If both the SROM and the environment contain a MAC address, and
3756  both addresses are the same, this MAC address is used.
3757
3758o If both the SROM and the environment contain a MAC address, and the
3759  addresses differ, the value from the environment is used and a
3760  warning is printed.
3761
3762o If neither SROM nor the environment contain a MAC address, an error
3763  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
3764  a random, locally-assigned MAC is used.
3765
3766If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
3767will be programmed into hardware as part of the initialization process.	 This
3768may be skipped by setting the appropriate 'ethmacskip' environment variable.
3769The naming convention is as follows:
3770"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
3771
3772Image Formats:
3773==============
3774
3775U-Boot is capable of booting (and performing other auxiliary operations on)
3776images in two formats:
3777
3778New uImage format (FIT)
3779-----------------------
3780
3781Flexible and powerful format based on Flattened Image Tree -- FIT (similar
3782to Flattened Device Tree). It allows the use of images with multiple
3783components (several kernels, ramdisks, etc.), with contents protected by
3784SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
3785
3786
3787Old uImage format
3788-----------------
3789
3790Old image format is based on binary files which can be basically anything,
3791preceded by a special header; see the definitions in include/image.h for
3792details; basically, the header defines the following image properties:
3793
3794* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
3795  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
3796  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
3797  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
3798  INTEGRITY).
3799* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
3800  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
3801  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
3802* Compression Type (uncompressed, gzip, bzip2)
3803* Load Address
3804* Entry Point
3805* Image Name
3806* Image Timestamp
3807
3808The header is marked by a special Magic Number, and both the header
3809and the data portions of the image are secured against corruption by
3810CRC32 checksums.
3811
3812
3813Linux Support:
3814==============
3815
3816Although U-Boot should support any OS or standalone application
3817easily, the main focus has always been on Linux during the design of
3818U-Boot.
3819
3820U-Boot includes many features that so far have been part of some
3821special "boot loader" code within the Linux kernel. Also, any
3822"initrd" images to be used are no longer part of one big Linux image;
3823instead, kernel and "initrd" are separate images. This implementation
3824serves several purposes:
3825
3826- the same features can be used for other OS or standalone
3827  applications (for instance: using compressed images to reduce the
3828  Flash memory footprint)
3829
3830- it becomes much easier to port new Linux kernel versions because
3831  lots of low-level, hardware dependent stuff are done by U-Boot
3832
3833- the same Linux kernel image can now be used with different "initrd"
3834  images; of course this also means that different kernel images can
3835  be run with the same "initrd". This makes testing easier (you don't
3836  have to build a new "zImage.initrd" Linux image when you just
3837  change a file in your "initrd"). Also, a field-upgrade of the
3838  software is easier now.
3839
3840
3841Linux HOWTO:
3842============
3843
3844Porting Linux to U-Boot based systems:
3845---------------------------------------
3846
3847U-Boot cannot save you from doing all the necessary modifications to
3848configure the Linux device drivers for use with your target hardware
3849(no, we don't intend to provide a full virtual machine interface to
3850Linux :-).
3851
3852But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
3853
3854Just make sure your machine specific header file (for instance
3855include/asm-ppc/tqm8xx.h) includes the same definition of the Board
3856Information structure as we define in include/asm-<arch>/u-boot.h,
3857and make sure that your definition of IMAP_ADDR uses the same value
3858as your U-Boot configuration in CONFIG_SYS_IMMR.
3859
3860Note that U-Boot now has a driver model, a unified model for drivers.
3861If you are adding a new driver, plumb it into driver model. If there
3862is no uclass available, you are encouraged to create one. See
3863doc/driver-model.
3864
3865
3866Configuring the Linux kernel:
3867-----------------------------
3868
3869No specific requirements for U-Boot. Make sure you have some root
3870device (initial ramdisk, NFS) for your target system.
3871
3872
3873Building a Linux Image:
3874-----------------------
3875
3876With U-Boot, "normal" build targets like "zImage" or "bzImage" are
3877not used. If you use recent kernel source, a new build target
3878"uImage" will exist which automatically builds an image usable by
3879U-Boot. Most older kernels also have support for a "pImage" target,
3880which was introduced for our predecessor project PPCBoot and uses a
3881100% compatible format.
3882
3883Example:
3884
3885	make TQM850L_defconfig
3886	make oldconfig
3887	make dep
3888	make uImage
3889
3890The "uImage" build target uses a special tool (in 'tools/mkimage') to
3891encapsulate a compressed Linux kernel image with header	 information,
3892CRC32 checksum etc. for use with U-Boot. This is what we are doing:
3893
3894* build a standard "vmlinux" kernel image (in ELF binary format):
3895
3896* convert the kernel into a raw binary image:
3897
3898	${CROSS_COMPILE}-objcopy -O binary \
3899				 -R .note -R .comment \
3900				 -S vmlinux linux.bin
3901
3902* compress the binary image:
3903
3904	gzip -9 linux.bin
3905
3906* package compressed binary image for U-Boot:
3907
3908	mkimage -A ppc -O linux -T kernel -C gzip \
3909		-a 0 -e 0 -n "Linux Kernel Image" \
3910		-d linux.bin.gz uImage
3911
3912
3913The "mkimage" tool can also be used to create ramdisk images for use
3914with U-Boot, either separated from the Linux kernel image, or
3915combined into one file. "mkimage" encapsulates the images with a 64
3916byte header containing information about target architecture,
3917operating system, image type, compression method, entry points, time
3918stamp, CRC32 checksums, etc.
3919
3920"mkimage" can be called in two ways: to verify existing images and
3921print the header information, or to build new images.
3922
3923In the first form (with "-l" option) mkimage lists the information
3924contained in the header of an existing U-Boot image; this includes
3925checksum verification:
3926
3927	tools/mkimage -l image
3928	  -l ==> list image header information
3929
3930The second form (with "-d" option) is used to build a U-Boot image
3931from a "data file" which is used as image payload:
3932
3933	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
3934		      -n name -d data_file image
3935	  -A ==> set architecture to 'arch'
3936	  -O ==> set operating system to 'os'
3937	  -T ==> set image type to 'type'
3938	  -C ==> set compression type 'comp'
3939	  -a ==> set load address to 'addr' (hex)
3940	  -e ==> set entry point to 'ep' (hex)
3941	  -n ==> set image name to 'name'
3942	  -d ==> use image data from 'datafile'
3943
3944Right now, all Linux kernels for PowerPC systems use the same load
3945address (0x00000000), but the entry point address depends on the
3946kernel version:
3947
3948- 2.2.x kernels have the entry point at 0x0000000C,
3949- 2.3.x and later kernels have the entry point at 0x00000000.
3950
3951So a typical call to build a U-Boot image would read:
3952
3953	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3954	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
3955	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
3956	> examples/uImage.TQM850L
3957	Image Name:   2.4.4 kernel for TQM850L
3958	Created:      Wed Jul 19 02:34:59 2000
3959	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3960	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3961	Load Address: 0x00000000
3962	Entry Point:  0x00000000
3963
3964To verify the contents of the image (or check for corruption):
3965
3966	-> tools/mkimage -l examples/uImage.TQM850L
3967	Image Name:   2.4.4 kernel for TQM850L
3968	Created:      Wed Jul 19 02:34:59 2000
3969	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3970	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3971	Load Address: 0x00000000
3972	Entry Point:  0x00000000
3973
3974NOTE: for embedded systems where boot time is critical you can trade
3975speed for memory and install an UNCOMPRESSED image instead: this
3976needs more space in Flash, but boots much faster since it does not
3977need to be uncompressed:
3978
3979	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
3980	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3981	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
3982	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
3983	> examples/uImage.TQM850L-uncompressed
3984	Image Name:   2.4.4 kernel for TQM850L
3985	Created:      Wed Jul 19 02:34:59 2000
3986	Image Type:   PowerPC Linux Kernel Image (uncompressed)
3987	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
3988	Load Address: 0x00000000
3989	Entry Point:  0x00000000
3990
3991
3992Similar you can build U-Boot images from a 'ramdisk.image.gz' file
3993when your kernel is intended to use an initial ramdisk:
3994
3995	-> tools/mkimage -n 'Simple Ramdisk Image' \
3996	> -A ppc -O linux -T ramdisk -C gzip \
3997	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
3998	Image Name:   Simple Ramdisk Image
3999	Created:      Wed Jan 12 14:01:50 2000
4000	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4001	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4002	Load Address: 0x00000000
4003	Entry Point:  0x00000000
4004
4005The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4006option performs the converse operation of the mkimage's second form (the "-d"
4007option). Given an image built by mkimage, the dumpimage extracts a "data file"
4008from the image:
4009
4010	tools/dumpimage -i image -T type -p position data_file
4011	  -i ==> extract from the 'image' a specific 'data_file'
4012	  -T ==> set image type to 'type'
4013	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4014
4015
4016Installing a Linux Image:
4017-------------------------
4018
4019To downloading a U-Boot image over the serial (console) interface,
4020you must convert the image to S-Record format:
4021
4022	objcopy -I binary -O srec examples/image examples/image.srec
4023
4024The 'objcopy' does not understand the information in the U-Boot
4025image header, so the resulting S-Record file will be relative to
4026address 0x00000000. To load it to a given address, you need to
4027specify the target address as 'offset' parameter with the 'loads'
4028command.
4029
4030Example: install the image to address 0x40100000 (which on the
4031TQM8xxL is in the first Flash bank):
4032
4033	=> erase 40100000 401FFFFF
4034
4035	.......... done
4036	Erased 8 sectors
4037
4038	=> loads 40100000
4039	## Ready for S-Record download ...
4040	~>examples/image.srec
4041	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4042	...
4043	15989 15990 15991 15992
4044	[file transfer complete]
4045	[connected]
4046	## Start Addr = 0x00000000
4047
4048
4049You can check the success of the download using the 'iminfo' command;
4050this includes a checksum verification so you can be sure no data
4051corruption happened:
4052
4053	=> imi 40100000
4054
4055	## Checking Image at 40100000 ...
4056	   Image Name:	 2.2.13 for initrd on TQM850L
4057	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4058	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4059	   Load Address: 00000000
4060	   Entry Point:	 0000000c
4061	   Verifying Checksum ... OK
4062
4063
4064Boot Linux:
4065-----------
4066
4067The "bootm" command is used to boot an application that is stored in
4068memory (RAM or Flash). In case of a Linux kernel image, the contents
4069of the "bootargs" environment variable is passed to the kernel as
4070parameters. You can check and modify this variable using the
4071"printenv" and "setenv" commands:
4072
4073
4074	=> printenv bootargs
4075	bootargs=root=/dev/ram
4076
4077	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4078
4079	=> printenv bootargs
4080	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4081
4082	=> bootm 40020000
4083	## Booting Linux kernel at 40020000 ...
4084	   Image Name:	 2.2.13 for NFS on TQM850L
4085	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4086	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4087	   Load Address: 00000000
4088	   Entry Point:	 0000000c
4089	   Verifying Checksum ... OK
4090	   Uncompressing Kernel Image ... OK
4091	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
4092	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4093	time_init: decrementer frequency = 187500000/60
4094	Calibrating delay loop... 49.77 BogoMIPS
4095	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4096	...
4097
4098If you want to boot a Linux kernel with initial RAM disk, you pass
4099the memory addresses of both the kernel and the initrd image (PPBCOOT
4100format!) to the "bootm" command:
4101
4102	=> imi 40100000 40200000
4103
4104	## Checking Image at 40100000 ...
4105	   Image Name:	 2.2.13 for initrd on TQM850L
4106	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4107	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4108	   Load Address: 00000000
4109	   Entry Point:	 0000000c
4110	   Verifying Checksum ... OK
4111
4112	## Checking Image at 40200000 ...
4113	   Image Name:	 Simple Ramdisk Image
4114	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4115	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4116	   Load Address: 00000000
4117	   Entry Point:	 00000000
4118	   Verifying Checksum ... OK
4119
4120	=> bootm 40100000 40200000
4121	## Booting Linux kernel at 40100000 ...
4122	   Image Name:	 2.2.13 for initrd on TQM850L
4123	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4124	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4125	   Load Address: 00000000
4126	   Entry Point:	 0000000c
4127	   Verifying Checksum ... OK
4128	   Uncompressing Kernel Image ... OK
4129	## Loading RAMDisk Image at 40200000 ...
4130	   Image Name:	 Simple Ramdisk Image
4131	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4132	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4133	   Load Address: 00000000
4134	   Entry Point:	 00000000
4135	   Verifying Checksum ... OK
4136	   Loading Ramdisk ... OK
4137	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
4138	Boot arguments: root=/dev/ram
4139	time_init: decrementer frequency = 187500000/60
4140	Calibrating delay loop... 49.77 BogoMIPS
4141	...
4142	RAMDISK: Compressed image found at block 0
4143	VFS: Mounted root (ext2 filesystem).
4144
4145	bash#
4146
4147Boot Linux and pass a flat device tree:
4148-----------
4149
4150First, U-Boot must be compiled with the appropriate defines. See the section
4151titled "Linux Kernel Interface" above for a more in depth explanation. The
4152following is an example of how to start a kernel and pass an updated
4153flat device tree:
4154
4155=> print oftaddr
4156oftaddr=0x300000
4157=> print oft
4158oft=oftrees/mpc8540ads.dtb
4159=> tftp $oftaddr $oft
4160Speed: 1000, full duplex
4161Using TSEC0 device
4162TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4163Filename 'oftrees/mpc8540ads.dtb'.
4164Load address: 0x300000
4165Loading: #
4166done
4167Bytes transferred = 4106 (100a hex)
4168=> tftp $loadaddr $bootfile
4169Speed: 1000, full duplex
4170Using TSEC0 device
4171TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4172Filename 'uImage'.
4173Load address: 0x200000
4174Loading:############
4175done
4176Bytes transferred = 1029407 (fb51f hex)
4177=> print loadaddr
4178loadaddr=200000
4179=> print oftaddr
4180oftaddr=0x300000
4181=> bootm $loadaddr - $oftaddr
4182## Booting image at 00200000 ...
4183   Image Name:	 Linux-2.6.17-dirty
4184   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4185   Data Size:	 1029343 Bytes = 1005.2 kB
4186   Load Address: 00000000
4187   Entry Point:	 00000000
4188   Verifying Checksum ... OK
4189   Uncompressing Kernel Image ... OK
4190Booting using flat device tree at 0x300000
4191Using MPC85xx ADS machine description
4192Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4193[snip]
4194
4195
4196More About U-Boot Image Types:
4197------------------------------
4198
4199U-Boot supports the following image types:
4200
4201   "Standalone Programs" are directly runnable in the environment
4202	provided by U-Boot; it is expected that (if they behave
4203	well) you can continue to work in U-Boot after return from
4204	the Standalone Program.
4205   "OS Kernel Images" are usually images of some Embedded OS which
4206	will take over control completely. Usually these programs
4207	will install their own set of exception handlers, device
4208	drivers, set up the MMU, etc. - this means, that you cannot
4209	expect to re-enter U-Boot except by resetting the CPU.
4210   "RAMDisk Images" are more or less just data blocks, and their
4211	parameters (address, size) are passed to an OS kernel that is
4212	being started.
4213   "Multi-File Images" contain several images, typically an OS
4214	(Linux) kernel image and one or more data images like
4215	RAMDisks. This construct is useful for instance when you want
4216	to boot over the network using BOOTP etc., where the boot
4217	server provides just a single image file, but you want to get
4218	for instance an OS kernel and a RAMDisk image.
4219
4220	"Multi-File Images" start with a list of image sizes, each
4221	image size (in bytes) specified by an "uint32_t" in network
4222	byte order. This list is terminated by an "(uint32_t)0".
4223	Immediately after the terminating 0 follow the images, one by
4224	one, all aligned on "uint32_t" boundaries (size rounded up to
4225	a multiple of 4 bytes).
4226
4227   "Firmware Images" are binary images containing firmware (like
4228	U-Boot or FPGA images) which usually will be programmed to
4229	flash memory.
4230
4231   "Script files" are command sequences that will be executed by
4232	U-Boot's command interpreter; this feature is especially
4233	useful when you configure U-Boot to use a real shell (hush)
4234	as command interpreter.
4235
4236Booting the Linux zImage:
4237-------------------------
4238
4239On some platforms, it's possible to boot Linux zImage. This is done
4240using the "bootz" command. The syntax of "bootz" command is the same
4241as the syntax of "bootm" command.
4242
4243Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4244kernel with raw initrd images. The syntax is slightly different, the
4245address of the initrd must be augmented by it's size, in the following
4246format: "<initrd addres>:<initrd size>".
4247
4248
4249Standalone HOWTO:
4250=================
4251
4252One of the features of U-Boot is that you can dynamically load and
4253run "standalone" applications, which can use some resources of
4254U-Boot like console I/O functions or interrupt services.
4255
4256Two simple examples are included with the sources:
4257
4258"Hello World" Demo:
4259-------------------
4260
4261'examples/hello_world.c' contains a small "Hello World" Demo
4262application; it is automatically compiled when you build U-Boot.
4263It's configured to run at address 0x00040004, so you can play with it
4264like that:
4265
4266	=> loads
4267	## Ready for S-Record download ...
4268	~>examples/hello_world.srec
4269	1 2 3 4 5 6 7 8 9 10 11 ...
4270	[file transfer complete]
4271	[connected]
4272	## Start Addr = 0x00040004
4273
4274	=> go 40004 Hello World! This is a test.
4275	## Starting application at 0x00040004 ...
4276	Hello World
4277	argc = 7
4278	argv[0] = "40004"
4279	argv[1] = "Hello"
4280	argv[2] = "World!"
4281	argv[3] = "This"
4282	argv[4] = "is"
4283	argv[5] = "a"
4284	argv[6] = "test."
4285	argv[7] = "<NULL>"
4286	Hit any key to exit ...
4287
4288	## Application terminated, rc = 0x0
4289
4290Another example, which demonstrates how to register a CPM interrupt
4291handler with the U-Boot code, can be found in 'examples/timer.c'.
4292Here, a CPM timer is set up to generate an interrupt every second.
4293The interrupt service routine is trivial, just printing a '.'
4294character, but this is just a demo program. The application can be
4295controlled by the following keys:
4296
4297	? - print current values og the CPM Timer registers
4298	b - enable interrupts and start timer
4299	e - stop timer and disable interrupts
4300	q - quit application
4301
4302	=> loads
4303	## Ready for S-Record download ...
4304	~>examples/timer.srec
4305	1 2 3 4 5 6 7 8 9 10 11 ...
4306	[file transfer complete]
4307	[connected]
4308	## Start Addr = 0x00040004
4309
4310	=> go 40004
4311	## Starting application at 0x00040004 ...
4312	TIMERS=0xfff00980
4313	Using timer 1
4314	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4315
4316Hit 'b':
4317	[q, b, e, ?] Set interval 1000000 us
4318	Enabling timer
4319Hit '?':
4320	[q, b, e, ?] ........
4321	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4322Hit '?':
4323	[q, b, e, ?] .
4324	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4325Hit '?':
4326	[q, b, e, ?] .
4327	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4328Hit '?':
4329	[q, b, e, ?] .
4330	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4331Hit 'e':
4332	[q, b, e, ?] ...Stopping timer
4333Hit 'q':
4334	[q, b, e, ?] ## Application terminated, rc = 0x0
4335
4336
4337Minicom warning:
4338================
4339
4340Over time, many people have reported problems when trying to use the
4341"minicom" terminal emulation program for serial download. I (wd)
4342consider minicom to be broken, and recommend not to use it. Under
4343Unix, I recommend to use C-Kermit for general purpose use (and
4344especially for kermit binary protocol download ("loadb" command), and
4345use "cu" for S-Record download ("loads" command).  See
4346http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4347for help with kermit.
4348
4349
4350Nevertheless, if you absolutely want to use it try adding this
4351configuration to your "File transfer protocols" section:
4352
4353	   Name	   Program			Name U/D FullScr IO-Red. Multi
4354	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4355	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4356
4357
4358NetBSD Notes:
4359=============
4360
4361Starting at version 0.9.2, U-Boot supports NetBSD both as host
4362(build U-Boot) and target system (boots NetBSD/mpc8xx).
4363
4364Building requires a cross environment; it is known to work on
4365NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4366need gmake since the Makefiles are not compatible with BSD make).
4367Note that the cross-powerpc package does not install include files;
4368attempting to build U-Boot will fail because <machine/ansi.h> is
4369missing.  This file has to be installed and patched manually:
4370
4371	# cd /usr/pkg/cross/powerpc-netbsd/include
4372	# mkdir powerpc
4373	# ln -s powerpc machine
4374	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4375	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4376
4377Native builds *don't* work due to incompatibilities between native
4378and U-Boot include files.
4379
4380Booting assumes that (the first part of) the image booted is a
4381stage-2 loader which in turn loads and then invokes the kernel
4382proper. Loader sources will eventually appear in the NetBSD source
4383tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4384meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4385
4386
4387Implementation Internals:
4388=========================
4389
4390The following is not intended to be a complete description of every
4391implementation detail. However, it should help to understand the
4392inner workings of U-Boot and make it easier to port it to custom
4393hardware.
4394
4395
4396Initial Stack, Global Data:
4397---------------------------
4398
4399The implementation of U-Boot is complicated by the fact that U-Boot
4400starts running out of ROM (flash memory), usually without access to
4401system RAM (because the memory controller is not initialized yet).
4402This means that we don't have writable Data or BSS segments, and BSS
4403is not initialized as zero. To be able to get a C environment working
4404at all, we have to allocate at least a minimal stack. Implementation
4405options for this are defined and restricted by the CPU used: Some CPU
4406models provide on-chip memory (like the IMMR area on MPC8xx and
4407MPC826x processors), on others (parts of) the data cache can be
4408locked as (mis-) used as memory, etc.
4409
4410	Chris Hallinan posted a good summary of these issues to the
4411	U-Boot mailing list:
4412
4413	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4414	From: "Chris Hallinan" <clh@net1plus.com>
4415	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4416	...
4417
4418	Correct me if I'm wrong, folks, but the way I understand it
4419	is this: Using DCACHE as initial RAM for Stack, etc, does not
4420	require any physical RAM backing up the cache. The cleverness
4421	is that the cache is being used as a temporary supply of
4422	necessary storage before the SDRAM controller is setup. It's
4423	beyond the scope of this list to explain the details, but you
4424	can see how this works by studying the cache architecture and
4425	operation in the architecture and processor-specific manuals.
4426
4427	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4428	is another option for the system designer to use as an
4429	initial stack/RAM area prior to SDRAM being available. Either
4430	option should work for you. Using CS 4 should be fine if your
4431	board designers haven't used it for something that would
4432	cause you grief during the initial boot! It is frequently not
4433	used.
4434
4435	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4436	with your processor/board/system design. The default value
4437	you will find in any recent u-boot distribution in
4438	walnut.h should work for you. I'd set it to a value larger
4439	than your SDRAM module. If you have a 64MB SDRAM module, set
4440	it above 400_0000. Just make sure your board has no resources
4441	that are supposed to respond to that address! That code in
4442	start.S has been around a while and should work as is when
4443	you get the config right.
4444
4445	-Chris Hallinan
4446	DS4.COM, Inc.
4447
4448It is essential to remember this, since it has some impact on the C
4449code for the initialization procedures:
4450
4451* Initialized global data (data segment) is read-only. Do not attempt
4452  to write it.
4453
4454* Do not use any uninitialized global data (or implicitly initialized
4455  as zero data - BSS segment) at all - this is undefined, initiali-
4456  zation is performed later (when relocating to RAM).
4457
4458* Stack space is very limited. Avoid big data buffers or things like
4459  that.
4460
4461Having only the stack as writable memory limits means we cannot use
4462normal global data to share information between the code. But it
4463turned out that the implementation of U-Boot can be greatly
4464simplified by making a global data structure (gd_t) available to all
4465functions. We could pass a pointer to this data as argument to _all_
4466functions, but this would bloat the code. Instead we use a feature of
4467the GCC compiler (Global Register Variables) to share the data: we
4468place a pointer (gd) to the global data into a register which we
4469reserve for this purpose.
4470
4471When choosing a register for such a purpose we are restricted by the
4472relevant  (E)ABI  specifications for the current architecture, and by
4473GCC's implementation.
4474
4475For PowerPC, the following registers have specific use:
4476	R1:	stack pointer
4477	R2:	reserved for system use
4478	R3-R4:	parameter passing and return values
4479	R5-R10: parameter passing
4480	R13:	small data area pointer
4481	R30:	GOT pointer
4482	R31:	frame pointer
4483
4484	(U-Boot also uses R12 as internal GOT pointer. r12
4485	is a volatile register so r12 needs to be reset when
4486	going back and forth between asm and C)
4487
4488    ==> U-Boot will use R2 to hold a pointer to the global data
4489
4490    Note: on PPC, we could use a static initializer (since the
4491    address of the global data structure is known at compile time),
4492    but it turned out that reserving a register results in somewhat
4493    smaller code - although the code savings are not that big (on
4494    average for all boards 752 bytes for the whole U-Boot image,
4495    624 text + 127 data).
4496
4497On ARM, the following registers are used:
4498
4499	R0:	function argument word/integer result
4500	R1-R3:	function argument word
4501	R9:	platform specific
4502	R10:	stack limit (used only if stack checking is enabled)
4503	R11:	argument (frame) pointer
4504	R12:	temporary workspace
4505	R13:	stack pointer
4506	R14:	link register
4507	R15:	program counter
4508
4509    ==> U-Boot will use R9 to hold a pointer to the global data
4510
4511    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4512
4513On Nios II, the ABI is documented here:
4514	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4515
4516    ==> U-Boot will use gp to hold a pointer to the global data
4517
4518    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4519    to access small data sections, so gp is free.
4520
4521On NDS32, the following registers are used:
4522
4523	R0-R1:	argument/return
4524	R2-R5:	argument
4525	R15:	temporary register for assembler
4526	R16:	trampoline register
4527	R28:	frame pointer (FP)
4528	R29:	global pointer (GP)
4529	R30:	link register (LP)
4530	R31:	stack pointer (SP)
4531	PC:	program counter (PC)
4532
4533    ==> U-Boot will use R10 to hold a pointer to the global data
4534
4535NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4536or current versions of GCC may "optimize" the code too much.
4537
4538On RISC-V, the following registers are used:
4539
4540	x0: hard-wired zero (zero)
4541	x1: return address (ra)
4542	x2:	stack pointer (sp)
4543	x3:	global pointer (gp)
4544	x4:	thread pointer (tp)
4545	x5:	link register (t0)
4546	x8:	frame pointer (fp)
4547	x10-x11:	arguments/return values (a0-1)
4548	x12-x17:	arguments (a2-7)
4549	x28-31:	 temporaries (t3-6)
4550	pc:	program counter (pc)
4551
4552    ==> U-Boot will use gp to hold a pointer to the global data
4553
4554Memory Management:
4555------------------
4556
4557U-Boot runs in system state and uses physical addresses, i.e. the
4558MMU is not used either for address mapping nor for memory protection.
4559
4560The available memory is mapped to fixed addresses using the memory
4561controller. In this process, a contiguous block is formed for each
4562memory type (Flash, SDRAM, SRAM), even when it consists of several
4563physical memory banks.
4564
4565U-Boot is installed in the first 128 kB of the first Flash bank (on
4566TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4567booting and sizing and initializing DRAM, the code relocates itself
4568to the upper end of DRAM. Immediately below the U-Boot code some
4569memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4570configuration setting]. Below that, a structure with global Board
4571Info data is placed, followed by the stack (growing downward).
4572
4573Additionally, some exception handler code is copied to the low 8 kB
4574of DRAM (0x00000000 ... 0x00001FFF).
4575
4576So a typical memory configuration with 16 MB of DRAM could look like
4577this:
4578
4579	0x0000 0000	Exception Vector code
4580	      :
4581	0x0000 1FFF
4582	0x0000 2000	Free for Application Use
4583	      :
4584	      :
4585
4586	      :
4587	      :
4588	0x00FB FF20	Monitor Stack (Growing downward)
4589	0x00FB FFAC	Board Info Data and permanent copy of global data
4590	0x00FC 0000	Malloc Arena
4591	      :
4592	0x00FD FFFF
4593	0x00FE 0000	RAM Copy of Monitor Code
4594	...		eventually: LCD or video framebuffer
4595	...		eventually: pRAM (Protected RAM - unchanged by reset)
4596	0x00FF FFFF	[End of RAM]
4597
4598
4599System Initialization:
4600----------------------
4601
4602In the reset configuration, U-Boot starts at the reset entry point
4603(on most PowerPC systems at address 0x00000100). Because of the reset
4604configuration for CS0# this is a mirror of the on board Flash memory.
4605To be able to re-map memory U-Boot then jumps to its link address.
4606To be able to implement the initialization code in C, a (small!)
4607initial stack is set up in the internal Dual Ported RAM (in case CPUs
4608which provide such a feature like), or in a locked part of the data
4609cache. After that, U-Boot initializes the CPU core, the caches and
4610the SIU.
4611
4612Next, all (potentially) available memory banks are mapped using a
4613preliminary mapping. For example, we put them on 512 MB boundaries
4614(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4615on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4616programmed for SDRAM access. Using the temporary configuration, a
4617simple memory test is run that determines the size of the SDRAM
4618banks.
4619
4620When there is more than one SDRAM bank, and the banks are of
4621different size, the largest is mapped first. For equal size, the first
4622bank (CS2#) is mapped first. The first mapping is always for address
46230x00000000, with any additional banks following immediately to create
4624contiguous memory starting from 0.
4625
4626Then, the monitor installs itself at the upper end of the SDRAM area
4627and allocates memory for use by malloc() and for the global Board
4628Info data; also, the exception vector code is copied to the low RAM
4629pages, and the final stack is set up.
4630
4631Only after this relocation will you have a "normal" C environment;
4632until that you are restricted in several ways, mostly because you are
4633running from ROM, and because the code will have to be relocated to a
4634new address in RAM.
4635
4636
4637U-Boot Porting Guide:
4638----------------------
4639
4640[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4641list, October 2002]
4642
4643
4644int main(int argc, char *argv[])
4645{
4646	sighandler_t no_more_time;
4647
4648	signal(SIGALRM, no_more_time);
4649	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4650
4651	if (available_money > available_manpower) {
4652		Pay consultant to port U-Boot;
4653		return 0;
4654	}
4655
4656	Download latest U-Boot source;
4657
4658	Subscribe to u-boot mailing list;
4659
4660	if (clueless)
4661		email("Hi, I am new to U-Boot, how do I get started?");
4662
4663	while (learning) {
4664		Read the README file in the top level directory;
4665		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4666		Read applicable doc/*.README;
4667		Read the source, Luke;
4668		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4669	}
4670
4671	if (available_money > toLocalCurrency ($2500))
4672		Buy a BDI3000;
4673	else
4674		Add a lot of aggravation and time;
4675
4676	if (a similar board exists) {	/* hopefully... */
4677		cp -a board/<similar> board/<myboard>
4678		cp include/configs/<similar>.h include/configs/<myboard>.h
4679	} else {
4680		Create your own board support subdirectory;
4681		Create your own board include/configs/<myboard>.h file;
4682	}
4683	Edit new board/<myboard> files
4684	Edit new include/configs/<myboard>.h
4685
4686	while (!accepted) {
4687		while (!running) {
4688			do {
4689				Add / modify source code;
4690			} until (compiles);
4691			Debug;
4692			if (clueless)
4693				email("Hi, I am having problems...");
4694		}
4695		Send patch file to the U-Boot email list;
4696		if (reasonable critiques)
4697			Incorporate improvements from email list code review;
4698		else
4699			Defend code as written;
4700	}
4701
4702	return 0;
4703}
4704
4705void no_more_time (int sig)
4706{
4707      hire_a_guru();
4708}
4709
4710
4711Coding Standards:
4712-----------------
4713
4714All contributions to U-Boot should conform to the Linux kernel
4715coding style; see the kernel coding style guide at
4716https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4717script "scripts/Lindent" in your Linux kernel source directory.
4718
4719Source files originating from a different project (for example the
4720MTD subsystem) are generally exempt from these guidelines and are not
4721reformatted to ease subsequent migration to newer versions of those
4722sources.
4723
4724Please note that U-Boot is implemented in C (and to some small parts in
4725Assembler); no C++ is used, so please do not use C++ style comments (//)
4726in your code.
4727
4728Please also stick to the following formatting rules:
4729- remove any trailing white space
4730- use TAB characters for indentation and vertical alignment, not spaces
4731- make sure NOT to use DOS '\r\n' line feeds
4732- do not add more than 2 consecutive empty lines to source files
4733- do not add trailing empty lines to source files
4734
4735Submissions which do not conform to the standards may be returned
4736with a request to reformat the changes.
4737
4738
4739Submitting Patches:
4740-------------------
4741
4742Since the number of patches for U-Boot is growing, we need to
4743establish some rules. Submissions which do not conform to these rules
4744may be rejected, even when they contain important and valuable stuff.
4745
4746Please see http://www.denx.de/wiki/U-Boot/Patches for details.
4747
4748Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4749see https://lists.denx.de/listinfo/u-boot
4750
4751When you send a patch, please include the following information with
4752it:
4753
4754* For bug fixes: a description of the bug and how your patch fixes
4755  this bug. Please try to include a way of demonstrating that the
4756  patch actually fixes something.
4757
4758* For new features: a description of the feature and your
4759  implementation.
4760
4761* A CHANGELOG entry as plaintext (separate from the patch)
4762
4763* For major contributions, add a MAINTAINERS file with your
4764  information and associated file and directory references.
4765
4766* When you add support for a new board, don't forget to add a
4767  maintainer e-mail address to the boards.cfg file, too.
4768
4769* If your patch adds new configuration options, don't forget to
4770  document these in the README file.
4771
4772* The patch itself. If you are using git (which is *strongly*
4773  recommended) you can easily generate the patch using the
4774  "git format-patch". If you then use "git send-email" to send it to
4775  the U-Boot mailing list, you will avoid most of the common problems
4776  with some other mail clients.
4777
4778  If you cannot use git, use "diff -purN OLD NEW". If your version of
4779  diff does not support these options, then get the latest version of
4780  GNU diff.
4781
4782  The current directory when running this command shall be the parent
4783  directory of the U-Boot source tree (i. e. please make sure that
4784  your patch includes sufficient directory information for the
4785  affected files).
4786
4787  We prefer patches as plain text. MIME attachments are discouraged,
4788  and compressed attachments must not be used.
4789
4790* If one logical set of modifications affects or creates several
4791  files, all these changes shall be submitted in a SINGLE patch file.
4792
4793* Changesets that contain different, unrelated modifications shall be
4794  submitted as SEPARATE patches, one patch per changeset.
4795
4796
4797Notes:
4798
4799* Before sending the patch, run the buildman script on your patched
4800  source tree and make sure that no errors or warnings are reported
4801  for any of the boards.
4802
4803* Keep your modifications to the necessary minimum: A patch
4804  containing several unrelated changes or arbitrary reformats will be
4805  returned with a request to re-formatting / split it.
4806
4807* If you modify existing code, make sure that your new code does not
4808  add to the memory footprint of the code ;-) Small is beautiful!
4809  When adding new features, these should compile conditionally only
4810  (using #ifdef), and the resulting code with the new feature
4811  disabled must not need more memory than the old code without your
4812  modification.
4813
4814* Remember that there is a size limit of 100 kB per message on the
4815  u-boot mailing list. Bigger patches will be moderated. If they are
4816  reasonable and not too big, they will be acknowledged. But patches
4817  bigger than the size limit should be avoided.
4818