xref: /openbmc/u-boot/README (revision 4bb656e9)
1#
2# (C) Copyright 2000 - 2013
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# SPDX-License-Identifier:	GPL-2.0+
6#
7
8Summary:
9========
10
11This directory contains the source code for U-Boot, a boot loader for
12Embedded boards based on PowerPC, ARM, MIPS and several other
13processors, which can be installed in a boot ROM and used to
14initialize and test the hardware or to download and run application
15code.
16
17The development of U-Boot is closely related to Linux: some parts of
18the source code originate in the Linux source tree, we have some
19header files in common, and special provision has been made to
20support booting of Linux images.
21
22Some attention has been paid to make this software easily
23configurable and extendable. For instance, all monitor commands are
24implemented with the same call interface, so that it's very easy to
25add new commands. Also, instead of permanently adding rarely used
26code (for instance hardware test utilities) to the monitor, you can
27load and run it dynamically.
28
29
30Status:
31=======
32
33In general, all boards for which a configuration option exists in the
34Makefile have been tested to some extent and can be considered
35"working". In fact, many of them are used in production systems.
36
37In case of problems see the CHANGELOG file to find out who contributed
38the specific port. In addition, there are various MAINTAINERS files
39scattered throughout the U-Boot source identifying the people or
40companies responsible for various boards and subsystems.
41
42Note: As of August, 2010, there is no longer a CHANGELOG file in the
43actual U-Boot source tree; however, it can be created dynamically
44from the Git log using:
45
46	make CHANGELOG
47
48
49Where to get help:
50==================
51
52In case you have questions about, problems with or contributions for
53U-Boot, you should send a message to the U-Boot mailing list at
54<u-boot@lists.denx.de>. There is also an archive of previous traffic
55on the mailing list - please search the archive before asking FAQ's.
56Please see http://lists.denx.de/pipermail/u-boot and
57http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
58
59
60Where to get source code:
61=========================
62
63The U-Boot source code is maintained in the Git repository at
64git://www.denx.de/git/u-boot.git ; you can browse it online at
65http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
66
67The "snapshot" links on this page allow you to download tarballs of
68any version you might be interested in. Official releases are also
69available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
70directory.
71
72Pre-built (and tested) images are available from
73ftp://ftp.denx.de/pub/u-boot/images/
74
75
76Where we come from:
77===================
78
79- start from 8xxrom sources
80- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
81- clean up code
82- make it easier to add custom boards
83- make it possible to add other [PowerPC] CPUs
84- extend functions, especially:
85  * Provide extended interface to Linux boot loader
86  * S-Record download
87  * network boot
88  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
89- create ARMBoot project (http://sourceforge.net/projects/armboot)
90- add other CPU families (starting with ARM)
91- create U-Boot project (http://sourceforge.net/projects/u-boot)
92- current project page: see http://www.denx.de/wiki/U-Boot
93
94
95Names and Spelling:
96===================
97
98The "official" name of this project is "Das U-Boot". The spelling
99"U-Boot" shall be used in all written text (documentation, comments
100in source files etc.). Example:
101
102	This is the README file for the U-Boot project.
103
104File names etc. shall be based on the string "u-boot". Examples:
105
106	include/asm-ppc/u-boot.h
107
108	#include <asm/u-boot.h>
109
110Variable names, preprocessor constants etc. shall be either based on
111the string "u_boot" or on "U_BOOT". Example:
112
113	U_BOOT_VERSION		u_boot_logo
114	IH_OS_U_BOOT		u_boot_hush_start
115
116
117Versioning:
118===========
119
120Starting with the release in October 2008, the names of the releases
121were changed from numerical release numbers without deeper meaning
122into a time stamp based numbering. Regular releases are identified by
123names consisting of the calendar year and month of the release date.
124Additional fields (if present) indicate release candidates or bug fix
125releases in "stable" maintenance trees.
126
127Examples:
128	U-Boot v2009.11	    - Release November 2009
129	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
130	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
131
132
133Directory Hierarchy:
134====================
135
136/arch			Architecture specific files
137  /arc			Files generic to ARC architecture
138  /arm			Files generic to ARM architecture
139  /avr32		Files generic to AVR32 architecture
140  /blackfin		Files generic to Analog Devices Blackfin architecture
141  /m68k			Files generic to m68k architecture
142  /microblaze		Files generic to microblaze architecture
143  /mips			Files generic to MIPS architecture
144  /nds32		Files generic to NDS32 architecture
145  /nios2		Files generic to Altera NIOS2 architecture
146  /openrisc		Files generic to OpenRISC architecture
147  /powerpc		Files generic to PowerPC architecture
148  /sandbox		Files generic to HW-independent "sandbox"
149  /sh			Files generic to SH architecture
150  /sparc		Files generic to SPARC architecture
151  /x86			Files generic to x86 architecture
152/api			Machine/arch independent API for external apps
153/board			Board dependent files
154/common			Misc architecture independent functions
155/configs		Board default configuration files
156/disk			Code for disk drive partition handling
157/doc			Documentation (don't expect too much)
158/drivers		Commonly used device drivers
159/dts			Contains Makefile for building internal U-Boot fdt.
160/examples		Example code for standalone applications, etc.
161/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
162/include		Header Files
163/lib			Library routines generic to all architectures
164/Licenses		Various license files
165/net			Networking code
166/post			Power On Self Test
167/scripts		Various build scripts and Makefiles
168/test			Various unit test files
169/tools			Tools to build S-Record or U-Boot images, etc.
170
171Software Configuration:
172=======================
173
174Configuration is usually done using C preprocessor defines; the
175rationale behind that is to avoid dead code whenever possible.
176
177There are two classes of configuration variables:
178
179* Configuration _OPTIONS_:
180  These are selectable by the user and have names beginning with
181  "CONFIG_".
182
183* Configuration _SETTINGS_:
184  These depend on the hardware etc. and should not be meddled with if
185  you don't know what you're doing; they have names beginning with
186  "CONFIG_SYS_".
187
188Previously, all configuration was done by hand, which involved creating
189symbolic links and editing configuration files manually. More recently,
190U-Boot has added the Kbuild infrastructure used by the Linux kernel,
191allowing you to use the "make menuconfig" command to configure your
192build.
193
194
195Selection of Processor Architecture and Board Type:
196---------------------------------------------------
197
198For all supported boards there are ready-to-use default
199configurations available; just type "make <board_name>_defconfig".
200
201Example: For a TQM823L module type:
202
203	cd u-boot
204	make TQM823L_defconfig
205
206Note: If you're looking for the default configuration file for a board
207you're sure used to be there but is now missing, check the file
208doc/README.scrapyard for a list of no longer supported boards.
209
210Sandbox Environment:
211--------------------
212
213U-Boot can be built natively to run on a Linux host using the 'sandbox'
214board. This allows feature development which is not board- or architecture-
215specific to be undertaken on a native platform. The sandbox is also used to
216run some of U-Boot's tests.
217
218See board/sandbox/README.sandbox for more details.
219
220
221Board Initialisation Flow:
222--------------------------
223
224This is the intended start-up flow for boards. This should apply for both
225SPL and U-Boot proper (i.e. they both follow the same rules).
226
227Note: "SPL" stands for "Secondary Program Loader," which is explained in
228more detail later in this file.
229
230At present, SPL mostly uses a separate code path, but the function names
231and roles of each function are the same. Some boards or architectures
232may not conform to this.  At least most ARM boards which use
233CONFIG_SPL_FRAMEWORK conform to this.
234
235Execution typically starts with an architecture-specific (and possibly
236CPU-specific) start.S file, such as:
237
238	- arch/arm/cpu/armv7/start.S
239	- arch/powerpc/cpu/mpc83xx/start.S
240	- arch/mips/cpu/start.S
241
242and so on. From there, three functions are called; the purpose and
243limitations of each of these functions are described below.
244
245lowlevel_init():
246	- purpose: essential init to permit execution to reach board_init_f()
247	- no global_data or BSS
248	- there is no stack (ARMv7 may have one but it will soon be removed)
249	- must not set up SDRAM or use console
250	- must only do the bare minimum to allow execution to continue to
251		board_init_f()
252	- this is almost never needed
253	- return normally from this function
254
255board_init_f():
256	- purpose: set up the machine ready for running board_init_r():
257		i.e. SDRAM and serial UART
258	- global_data is available
259	- stack is in SRAM
260	- BSS is not available, so you cannot use global/static variables,
261		only stack variables and global_data
262
263	Non-SPL-specific notes:
264	- dram_init() is called to set up DRAM. If already done in SPL this
265		can do nothing
266
267	SPL-specific notes:
268	- you can override the entire board_init_f() function with your own
269		version as needed.
270	- preloader_console_init() can be called here in extremis
271	- should set up SDRAM, and anything needed to make the UART work
272	- these is no need to clear BSS, it will be done by crt0.S
273	- must return normally from this function (don't call board_init_r()
274		directly)
275
276Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
277this point the stack and global_data are relocated to below
278CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
279memory.
280
281board_init_r():
282	- purpose: main execution, common code
283	- global_data is available
284	- SDRAM is available
285	- BSS is available, all static/global variables can be used
286	- execution eventually continues to main_loop()
287
288	Non-SPL-specific notes:
289	- U-Boot is relocated to the top of memory and is now running from
290		there.
291
292	SPL-specific notes:
293	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
294		CONFIG_SPL_STACK_R_ADDR points into SDRAM
295	- preloader_console_init() can be called here - typically this is
296		done by defining CONFIG_SPL_BOARD_INIT and then supplying a
297		spl_board_init() function containing this call
298	- loads U-Boot or (in falcon mode) Linux
299
300
301
302Configuration Options:
303----------------------
304
305Configuration depends on the combination of board and CPU type; all
306such information is kept in a configuration file
307"include/configs/<board_name>.h".
308
309Example: For a TQM823L module, all configuration settings are in
310"include/configs/TQM823L.h".
311
312
313Many of the options are named exactly as the corresponding Linux
314kernel configuration options. The intention is to make it easier to
315build a config tool - later.
316
317
318The following options need to be configured:
319
320- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
321
322- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
323
324- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
325		Define exactly one, e.g. CONFIG_ATSTK1002
326
327- CPU Module Type: (if CONFIG_COGENT is defined)
328		Define exactly one of
329		CONFIG_CMA286_60_OLD
330--- FIXME --- not tested yet:
331		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
332		CONFIG_CMA287_23, CONFIG_CMA287_50
333
334- Motherboard Type: (if CONFIG_COGENT is defined)
335		Define exactly one of
336		CONFIG_CMA101, CONFIG_CMA102
337
338- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
339		Define one or more of
340		CONFIG_CMA302
341
342- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
343		Define one or more of
344		CONFIG_LCD_HEARTBEAT	- update a character position on
345					  the LCD display every second with
346					  a "rotator" |\-/|\-/
347
348- Marvell Family Member
349		CONFIG_SYS_MVFS		- define it if you want to enable
350					  multiple fs option at one time
351					  for marvell soc family
352
353- 8xx CPU Options: (if using an MPC8xx CPU)
354		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
355					  get_gclk_freq() cannot work
356					  e.g. if there is no 32KHz
357					  reference PIT/RTC clock
358		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
359					  or XTAL/EXTAL)
360
361- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
362		CONFIG_SYS_8xx_CPUCLK_MIN
363		CONFIG_SYS_8xx_CPUCLK_MAX
364		CONFIG_8xx_CPUCLK_DEFAULT
365			See doc/README.MPC866
366
367		CONFIG_SYS_MEASURE_CPUCLK
368
369		Define this to measure the actual CPU clock instead
370		of relying on the correctness of the configured
371		values. Mostly useful for board bringup to make sure
372		the PLL is locked at the intended frequency. Note
373		that this requires a (stable) reference clock (32 kHz
374		RTC clock or CONFIG_SYS_8XX_XIN)
375
376		CONFIG_SYS_DELAYED_ICACHE
377
378		Define this option if you want to enable the
379		ICache only when Code runs from RAM.
380
381- 85xx CPU Options:
382		CONFIG_SYS_PPC64
383
384		Specifies that the core is a 64-bit PowerPC implementation (implements
385		the "64" category of the Power ISA). This is necessary for ePAPR
386		compliance, among other possible reasons.
387
388		CONFIG_SYS_FSL_TBCLK_DIV
389
390		Defines the core time base clock divider ratio compared to the
391		system clock.  On most PQ3 devices this is 8, on newer QorIQ
392		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
393
394		CONFIG_SYS_FSL_PCIE_COMPAT
395
396		Defines the string to utilize when trying to match PCIe device
397		tree nodes for the given platform.
398
399		CONFIG_SYS_PPC_E500_DEBUG_TLB
400
401		Enables a temporary TLB entry to be used during boot to work
402		around limitations in e500v1 and e500v2 external debugger
403		support. This reduces the portions of the boot code where
404		breakpoints and single stepping do not work.  The value of this
405		symbol should be set to the TLB1 entry to be used for this
406		purpose.
407
408		CONFIG_SYS_FSL_ERRATUM_A004510
409
410		Enables a workaround for erratum A004510.  If set,
411		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
412		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
413
414		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
415		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
416
417		Defines one or two SoC revisions (low 8 bits of SVR)
418		for which the A004510 workaround should be applied.
419
420		The rest of SVR is either not relevant to the decision
421		of whether the erratum is present (e.g. p2040 versus
422		p2041) or is implied by the build target, which controls
423		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
424
425		See Freescale App Note 4493 for more information about
426		this erratum.
427
428		CONFIG_A003399_NOR_WORKAROUND
429		Enables a workaround for IFC erratum A003399. It is only
430		required during NOR boot.
431
432		CONFIG_A008044_WORKAROUND
433		Enables a workaround for T1040/T1042 erratum A008044. It is only
434		required during NAND boot and valid for Rev 1.0 SoC revision
435
436		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
437
438		This is the value to write into CCSR offset 0x18600
439		according to the A004510 workaround.
440
441		CONFIG_SYS_FSL_DSP_DDR_ADDR
442		This value denotes start offset of DDR memory which is
443		connected exclusively to the DSP cores.
444
445		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
446		This value denotes start offset of M2 memory
447		which is directly connected to the DSP core.
448
449		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
450		This value denotes start offset of M3 memory which is directly
451		connected to the DSP core.
452
453		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
454		This value denotes start offset of DSP CCSR space.
455
456		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
457		Single Source Clock is clocking mode present in some of FSL SoC's.
458		In this mode, a single differential clock is used to supply
459		clocks to the sysclock, ddrclock and usbclock.
460
461		CONFIG_SYS_CPC_REINIT_F
462		This CONFIG is defined when the CPC is configured as SRAM at the
463		time of U-Boot entry and is required to be re-initialized.
464
465		CONFIG_DEEP_SLEEP
466		Indicates this SoC supports deep sleep feature. If deep sleep is
467		supported, core will start to execute uboot when wakes up.
468
469- Generic CPU options:
470		CONFIG_SYS_GENERIC_GLOBAL_DATA
471		Defines global data is initialized in generic board board_init_f().
472		If this macro is defined, global data is created and cleared in
473		generic board board_init_f(). Without this macro, architecture/board
474		should initialize global data before calling board_init_f().
475
476		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
477
478		Defines the endianess of the CPU. Implementation of those
479		values is arch specific.
480
481		CONFIG_SYS_FSL_DDR
482		Freescale DDR driver in use. This type of DDR controller is
483		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
484		SoCs.
485
486		CONFIG_SYS_FSL_DDR_ADDR
487		Freescale DDR memory-mapped register base.
488
489		CONFIG_SYS_FSL_DDR_EMU
490		Specify emulator support for DDR. Some DDR features such as
491		deskew training are not available.
492
493		CONFIG_SYS_FSL_DDRC_GEN1
494		Freescale DDR1 controller.
495
496		CONFIG_SYS_FSL_DDRC_GEN2
497		Freescale DDR2 controller.
498
499		CONFIG_SYS_FSL_DDRC_GEN3
500		Freescale DDR3 controller.
501
502		CONFIG_SYS_FSL_DDRC_GEN4
503		Freescale DDR4 controller.
504
505		CONFIG_SYS_FSL_DDRC_ARM_GEN3
506		Freescale DDR3 controller for ARM-based SoCs.
507
508		CONFIG_SYS_FSL_DDR1
509		Board config to use DDR1. It can be enabled for SoCs with
510		Freescale DDR1 or DDR2 controllers, depending on the board
511		implemetation.
512
513		CONFIG_SYS_FSL_DDR2
514		Board config to use DDR2. It can be eanbeld for SoCs with
515		Freescale DDR2 or DDR3 controllers, depending on the board
516		implementation.
517
518		CONFIG_SYS_FSL_DDR3
519		Board config to use DDR3. It can be enabled for SoCs with
520		Freescale DDR3 or DDR3L controllers.
521
522		CONFIG_SYS_FSL_DDR3L
523		Board config to use DDR3L. It can be enabled for SoCs with
524		DDR3L controllers.
525
526		CONFIG_SYS_FSL_DDR4
527		Board config to use DDR4. It can be enabled for SoCs with
528		DDR4 controllers.
529
530		CONFIG_SYS_FSL_IFC_BE
531		Defines the IFC controller register space as Big Endian
532
533		CONFIG_SYS_FSL_IFC_LE
534		Defines the IFC controller register space as Little Endian
535
536		CONFIG_SYS_FSL_PBL_PBI
537		It enables addition of RCW (Power on reset configuration) in built image.
538		Please refer doc/README.pblimage for more details
539
540		CONFIG_SYS_FSL_PBL_RCW
541		It adds PBI(pre-boot instructions) commands in u-boot build image.
542		PBI commands can be used to configure SoC before it starts the execution.
543		Please refer doc/README.pblimage for more details
544
545		CONFIG_SPL_FSL_PBL
546		It adds a target to create boot binary having SPL binary in PBI format
547		concatenated with u-boot binary.
548
549		CONFIG_SYS_FSL_DDR_BE
550		Defines the DDR controller register space as Big Endian
551
552		CONFIG_SYS_FSL_DDR_LE
553		Defines the DDR controller register space as Little Endian
554
555		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
556		Physical address from the view of DDR controllers. It is the
557		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
558		it could be different for ARM SoCs.
559
560		CONFIG_SYS_FSL_DDR_INTLV_256B
561		DDR controller interleaving on 256-byte. This is a special
562		interleaving mode, handled by Dickens for Freescale layerscape
563		SoCs with ARM core.
564
565		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
566		Number of controllers used as main memory.
567
568		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
569		Number of controllers used for other than main memory.
570
571		CONFIG_SYS_FSL_HAS_DP_DDR
572		Defines the SoC has DP-DDR used for DPAA.
573
574		CONFIG_SYS_FSL_SEC_BE
575		Defines the SEC controller register space as Big Endian
576
577		CONFIG_SYS_FSL_SEC_LE
578		Defines the SEC controller register space as Little Endian
579
580- Intel Monahans options:
581		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
582
583		Defines the Monahans run mode to oscillator
584		ratio. Valid values are 8, 16, 24, 31. The core
585		frequency is this value multiplied by 13 MHz.
586
587		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
588
589		Defines the Monahans turbo mode to oscillator
590		ratio. Valid values are 1 (default if undefined) and
591		2. The core frequency as calculated above is multiplied
592		by this value.
593
594- MIPS CPU options:
595		CONFIG_SYS_INIT_SP_OFFSET
596
597		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
598		pointer. This is needed for the temporary stack before
599		relocation.
600
601		CONFIG_SYS_MIPS_CACHE_MODE
602
603		Cache operation mode for the MIPS CPU.
604		See also arch/mips/include/asm/mipsregs.h.
605		Possible values are:
606			CONF_CM_CACHABLE_NO_WA
607			CONF_CM_CACHABLE_WA
608			CONF_CM_UNCACHED
609			CONF_CM_CACHABLE_NONCOHERENT
610			CONF_CM_CACHABLE_CE
611			CONF_CM_CACHABLE_COW
612			CONF_CM_CACHABLE_CUW
613			CONF_CM_CACHABLE_ACCELERATED
614
615		CONFIG_SYS_XWAY_EBU_BOOTCFG
616
617		Special option for Lantiq XWAY SoCs for booting from NOR flash.
618		See also arch/mips/cpu/mips32/start.S.
619
620		CONFIG_XWAY_SWAP_BYTES
621
622		Enable compilation of tools/xway-swap-bytes needed for Lantiq
623		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
624		be swapped if a flash programmer is used.
625
626- ARM options:
627		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
628
629		Select high exception vectors of the ARM core, e.g., do not
630		clear the V bit of the c1 register of CP15.
631
632		CONFIG_SYS_THUMB_BUILD
633
634		Use this flag to build U-Boot using the Thumb instruction
635		set for ARM architectures. Thumb instruction set provides
636		better code density. For ARM architectures that support
637		Thumb2 this flag will result in Thumb2 code generated by
638		GCC.
639
640		CONFIG_ARM_ERRATA_716044
641		CONFIG_ARM_ERRATA_742230
642		CONFIG_ARM_ERRATA_743622
643		CONFIG_ARM_ERRATA_751472
644		CONFIG_ARM_ERRATA_761320
645		CONFIG_ARM_ERRATA_773022
646		CONFIG_ARM_ERRATA_774769
647		CONFIG_ARM_ERRATA_794072
648
649		If set, the workarounds for these ARM errata are applied early
650		during U-Boot startup. Note that these options force the
651		workarounds to be applied; no CPU-type/version detection
652		exists, unlike the similar options in the Linux kernel. Do not
653		set these options unless they apply!
654
655		COUNTER_FREQUENCY
656		Generic timer clock source frequency.
657
658		COUNTER_FREQUENCY_REAL
659		Generic timer clock source frequency if the real clock is
660		different from COUNTER_FREQUENCY, and can only be determined
661		at run time.
662
663		NOTE: The following can be machine specific errata. These
664		do have ability to provide rudimentary version and machine
665		specific checks, but expect no product checks.
666		CONFIG_ARM_ERRATA_430973
667		CONFIG_ARM_ERRATA_454179
668		CONFIG_ARM_ERRATA_621766
669		CONFIG_ARM_ERRATA_798870
670		CONFIG_ARM_ERRATA_801819
671
672- Tegra SoC options:
673		CONFIG_TEGRA_SUPPORT_NON_SECURE
674
675		Support executing U-Boot in non-secure (NS) mode. Certain
676		impossible actions will be skipped if the CPU is in NS mode,
677		such as ARM architectural timer initialization.
678
679- Linux Kernel Interface:
680		CONFIG_CLOCKS_IN_MHZ
681
682		U-Boot stores all clock information in Hz
683		internally. For binary compatibility with older Linux
684		kernels (which expect the clocks passed in the
685		bd_info data to be in MHz) the environment variable
686		"clocks_in_mhz" can be defined so that U-Boot
687		converts clock data to MHZ before passing it to the
688		Linux kernel.
689		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
690		"clocks_in_mhz=1" is automatically included in the
691		default environment.
692
693		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
694
695		When transferring memsize parameter to Linux, some versions
696		expect it to be in bytes, others in MB.
697		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
698
699		CONFIG_OF_LIBFDT
700
701		New kernel versions are expecting firmware settings to be
702		passed using flattened device trees (based on open firmware
703		concepts).
704
705		CONFIG_OF_LIBFDT
706		 * New libfdt-based support
707		 * Adds the "fdt" command
708		 * The bootm command automatically updates the fdt
709
710		OF_CPU - The proper name of the cpus node (only required for
711			MPC512X and MPC5xxx based boards).
712		OF_SOC - The proper name of the soc node (only required for
713			MPC512X and MPC5xxx based boards).
714		OF_TBCLK - The timebase frequency.
715		OF_STDOUT_PATH - The path to the console device
716
717		boards with QUICC Engines require OF_QE to set UCC MAC
718		addresses
719
720		CONFIG_OF_BOARD_SETUP
721
722		Board code has addition modification that it wants to make
723		to the flat device tree before handing it off to the kernel
724
725		CONFIG_OF_SYSTEM_SETUP
726
727		Other code has addition modification that it wants to make
728		to the flat device tree before handing it off to the kernel.
729		This causes ft_system_setup() to be called before booting
730		the kernel.
731
732		CONFIG_OF_BOOT_CPU
733
734		This define fills in the correct boot CPU in the boot
735		param header, the default value is zero if undefined.
736
737		CONFIG_OF_IDE_FIXUP
738
739		U-Boot can detect if an IDE device is present or not.
740		If not, and this new config option is activated, U-Boot
741		removes the ATA node from the DTS before booting Linux,
742		so the Linux IDE driver does not probe the device and
743		crash. This is needed for buggy hardware (uc101) where
744		no pull down resistor is connected to the signal IDE5V_DD7.
745
746		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
747
748		This setting is mandatory for all boards that have only one
749		machine type and must be used to specify the machine type
750		number as it appears in the ARM machine registry
751		(see http://www.arm.linux.org.uk/developer/machines/).
752		Only boards that have multiple machine types supported
753		in a single configuration file and the machine type is
754		runtime discoverable, do not have to use this setting.
755
756- vxWorks boot parameters:
757
758		bootvx constructs a valid bootline using the following
759		environments variables: bootdev, bootfile, ipaddr, netmask,
760		serverip, gatewayip, hostname, othbootargs.
761		It loads the vxWorks image pointed bootfile.
762
763		Note: If a "bootargs" environment is defined, it will overwride
764		the defaults discussed just above.
765
766- Cache Configuration:
767		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
768		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
769		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
770
771- Cache Configuration for ARM:
772		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
773				      controller
774		CONFIG_SYS_PL310_BASE - Physical base address of PL310
775					controller register space
776
777- Serial Ports:
778		CONFIG_PL010_SERIAL
779
780		Define this if you want support for Amba PrimeCell PL010 UARTs.
781
782		CONFIG_PL011_SERIAL
783
784		Define this if you want support for Amba PrimeCell PL011 UARTs.
785
786		CONFIG_PL011_CLOCK
787
788		If you have Amba PrimeCell PL011 UARTs, set this variable to
789		the clock speed of the UARTs.
790
791		CONFIG_PL01x_PORTS
792
793		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
794		define this to a list of base addresses for each (supported)
795		port. See e.g. include/configs/versatile.h
796
797		CONFIG_SERIAL_HW_FLOW_CONTROL
798
799		Define this variable to enable hw flow control in serial driver.
800		Current user of this option is drivers/serial/nsl16550.c driver
801
802- Console Interface:
803		Depending on board, define exactly one serial port
804		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
805		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
806		console by defining CONFIG_8xx_CONS_NONE
807
808		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
809		port routines must be defined elsewhere
810		(i.e. serial_init(), serial_getc(), ...)
811
812		CONFIG_CFB_CONSOLE
813		Enables console device for a color framebuffer. Needs following
814		defines (cf. smiLynxEM, i8042)
815			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
816						(default big endian)
817			VIDEO_HW_RECTFILL	graphic chip supports
818						rectangle fill
819						(cf. smiLynxEM)
820			VIDEO_HW_BITBLT		graphic chip supports
821						bit-blit (cf. smiLynxEM)
822			VIDEO_VISIBLE_COLS	visible pixel columns
823						(cols=pitch)
824			VIDEO_VISIBLE_ROWS	visible pixel rows
825			VIDEO_PIXEL_SIZE	bytes per pixel
826			VIDEO_DATA_FORMAT	graphic data format
827						(0-5, cf. cfb_console.c)
828			VIDEO_FB_ADRS		framebuffer address
829			VIDEO_KBD_INIT_FCT	keyboard int fct
830						(i.e. rx51_kp_init())
831			VIDEO_TSTC_FCT		test char fct
832						(i.e. rx51_kp_tstc)
833			VIDEO_GETC_FCT		get char fct
834						(i.e. rx51_kp_getc)
835			CONFIG_VIDEO_LOGO	display Linux logo in
836						upper left corner
837			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
838						linux_logo.h for logo.
839						Requires CONFIG_VIDEO_LOGO
840			CONFIG_CONSOLE_EXTRA_INFO
841						additional board info beside
842						the logo
843
844		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
845		a limited number of ANSI escape sequences (cursor control,
846		erase functions and limited graphics rendition control).
847
848		When CONFIG_CFB_CONSOLE is defined, video console is
849		default i/o. Serial console can be forced with
850		environment 'console=serial'.
851
852		When CONFIG_SILENT_CONSOLE is defined, all console
853		messages (by U-Boot and Linux!) can be silenced with
854		the "silent" environment variable. See
855		doc/README.silent for more information.
856
857		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
858			is 0x00.
859		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
860			is 0xa0.
861
862- Console Baudrate:
863		CONFIG_BAUDRATE - in bps
864		Select one of the baudrates listed in
865		CONFIG_SYS_BAUDRATE_TABLE, see below.
866		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
867
868- Console Rx buffer length
869		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
870		the maximum receive buffer length for the SMC.
871		This option is actual only for 82xx and 8xx possible.
872		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
873		must be defined, to setup the maximum idle timeout for
874		the SMC.
875
876- Pre-Console Buffer:
877		Prior to the console being initialised (i.e. serial UART
878		initialised etc) all console output is silently discarded.
879		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
880		buffer any console messages prior to the console being
881		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
882		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
883		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
884		bytes are output before the console is initialised, the
885		earlier bytes are discarded.
886
887		Note that when printing the buffer a copy is made on the
888		stack so CONFIG_PRE_CON_BUF_SZ must fit on the stack.
889
890		'Sane' compilers will generate smaller code if
891		CONFIG_PRE_CON_BUF_SZ is a power of 2
892
893- Boot Delay:	CONFIG_BOOTDELAY - in seconds
894		Delay before automatically booting the default image;
895		set to -1 to disable autoboot.
896		set to -2 to autoboot with no delay and not check for abort
897		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
898
899		See doc/README.autoboot for these options that
900		work with CONFIG_BOOTDELAY. None are required.
901		CONFIG_BOOT_RETRY_TIME
902		CONFIG_BOOT_RETRY_MIN
903		CONFIG_AUTOBOOT_KEYED
904		CONFIG_AUTOBOOT_PROMPT
905		CONFIG_AUTOBOOT_DELAY_STR
906		CONFIG_AUTOBOOT_STOP_STR
907		CONFIG_ZERO_BOOTDELAY_CHECK
908		CONFIG_RESET_TO_RETRY
909
910- Autoboot Command:
911		CONFIG_BOOTCOMMAND
912		Only needed when CONFIG_BOOTDELAY is enabled;
913		define a command string that is automatically executed
914		when no character is read on the console interface
915		within "Boot Delay" after reset.
916
917		CONFIG_BOOTARGS
918		This can be used to pass arguments to the bootm
919		command. The value of CONFIG_BOOTARGS goes into the
920		environment value "bootargs".
921
922		CONFIG_RAMBOOT and CONFIG_NFSBOOT
923		The value of these goes into the environment as
924		"ramboot" and "nfsboot" respectively, and can be used
925		as a convenience, when switching between booting from
926		RAM and NFS.
927
928- Bootcount:
929		CONFIG_BOOTCOUNT_LIMIT
930		Implements a mechanism for detecting a repeating reboot
931		cycle, see:
932		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
933
934		CONFIG_BOOTCOUNT_ENV
935		If no softreset save registers are found on the hardware
936		"bootcount" is stored in the environment. To prevent a
937		saveenv on all reboots, the environment variable
938		"upgrade_available" is used. If "upgrade_available" is
939		0, "bootcount" is always 0, if "upgrade_available" is
940		1 "bootcount" is incremented in the environment.
941		So the Userspace Applikation must set the "upgrade_available"
942		and "bootcount" variable to 0, if a boot was successfully.
943
944- Pre-Boot Commands:
945		CONFIG_PREBOOT
946
947		When this option is #defined, the existence of the
948		environment variable "preboot" will be checked
949		immediately before starting the CONFIG_BOOTDELAY
950		countdown and/or running the auto-boot command resp.
951		entering interactive mode.
952
953		This feature is especially useful when "preboot" is
954		automatically generated or modified. For an example
955		see the LWMON board specific code: here "preboot" is
956		modified when the user holds down a certain
957		combination of keys on the (special) keyboard when
958		booting the systems
959
960- Serial Download Echo Mode:
961		CONFIG_LOADS_ECHO
962		If defined to 1, all characters received during a
963		serial download (using the "loads" command) are
964		echoed back. This might be needed by some terminal
965		emulations (like "cu"), but may as well just take
966		time on others. This setting #define's the initial
967		value of the "loads_echo" environment variable.
968
969- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
970		CONFIG_KGDB_BAUDRATE
971		Select one of the baudrates listed in
972		CONFIG_SYS_BAUDRATE_TABLE, see below.
973
974- Monitor Functions:
975		Monitor commands can be included or excluded
976		from the build by using the #include files
977		<config_cmd_all.h> and #undef'ing unwanted
978		commands, or adding #define's for wanted commands.
979
980		The default command configuration includes all commands
981		except those marked below with a "*".
982
983		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
984		CONFIG_CMD_ASKENV	* ask for env variable
985		CONFIG_CMD_BDI		  bdinfo
986		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
987		CONFIG_CMD_BMP		* BMP support
988		CONFIG_CMD_BSP		* Board specific commands
989		CONFIG_CMD_BOOTD	  bootd
990		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
991		CONFIG_CMD_CACHE	* icache, dcache
992		CONFIG_CMD_CLK   	* clock command support
993		CONFIG_CMD_CONSOLE	  coninfo
994		CONFIG_CMD_CRC32	* crc32
995		CONFIG_CMD_DATE		* support for RTC, date/time...
996		CONFIG_CMD_DHCP		* DHCP support
997		CONFIG_CMD_DIAG		* Diagnostics
998		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
999		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
1000		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
1001		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
1002		CONFIG_CMD_DTT		* Digital Therm and Thermostat
1003		CONFIG_CMD_ECHO		  echo arguments
1004		CONFIG_CMD_EDITENV	  edit env variable
1005		CONFIG_CMD_EEPROM	* EEPROM read/write support
1006		CONFIG_CMD_ELF		* bootelf, bootvx
1007		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
1008		CONFIG_CMD_ENV_FLAGS	* display details about env flags
1009		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
1010		CONFIG_CMD_EXPORTENV	* export the environment
1011		CONFIG_CMD_EXT2		* ext2 command support
1012		CONFIG_CMD_EXT4		* ext4 command support
1013		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
1014					  that work for multiple fs types
1015		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
1016		CONFIG_CMD_SAVEENV	  saveenv
1017		CONFIG_CMD_FDC		* Floppy Disk Support
1018		CONFIG_CMD_FAT		* FAT command support
1019		CONFIG_CMD_FLASH	  flinfo, erase, protect
1020		CONFIG_CMD_FPGA		  FPGA device initialization support
1021		CONFIG_CMD_FUSE		* Device fuse support
1022		CONFIG_CMD_GETTIME	* Get time since boot
1023		CONFIG_CMD_GO		* the 'go' command (exec code)
1024		CONFIG_CMD_GREPENV	* search environment
1025		CONFIG_CMD_HASH		* calculate hash / digest
1026		CONFIG_CMD_I2C		* I2C serial bus support
1027		CONFIG_CMD_IDE		* IDE harddisk support
1028		CONFIG_CMD_IMI		  iminfo
1029		CONFIG_CMD_IMLS		  List all images found in NOR flash
1030		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
1031		CONFIG_CMD_IMMAP	* IMMR dump support
1032		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
1033		CONFIG_CMD_IMPORTENV	* import an environment
1034		CONFIG_CMD_INI		* import data from an ini file into the env
1035		CONFIG_CMD_IRQ		* irqinfo
1036		CONFIG_CMD_ITEST	  Integer/string test of 2 values
1037		CONFIG_CMD_JFFS2	* JFFS2 Support
1038		CONFIG_CMD_KGDB		* kgdb
1039		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
1040		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
1041					  (169.254.*.*)
1042		CONFIG_CMD_LOADB	  loadb
1043		CONFIG_CMD_LOADS	  loads
1044		CONFIG_CMD_MD5SUM	* print md5 message digest
1045					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
1046		CONFIG_CMD_MEMINFO	* Display detailed memory information
1047		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
1048					  loop, loopw
1049		CONFIG_CMD_MEMTEST	* mtest
1050		CONFIG_CMD_MISC		  Misc functions like sleep etc
1051		CONFIG_CMD_MMC		* MMC memory mapped support
1052		CONFIG_CMD_MII		* MII utility commands
1053		CONFIG_CMD_MTDPARTS	* MTD partition support
1054		CONFIG_CMD_NAND		* NAND support
1055		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1056		CONFIG_CMD_NFS		  NFS support
1057		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1058		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1059		CONFIG_CMD_PCI		* pciinfo
1060		CONFIG_CMD_PCMCIA		* PCMCIA support
1061		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1062					  host
1063		CONFIG_CMD_PORTIO	* Port I/O
1064		CONFIG_CMD_READ		* Read raw data from partition
1065		CONFIG_CMD_REGINFO	* Register dump
1066		CONFIG_CMD_RUN		  run command in env variable
1067		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1068		CONFIG_CMD_SAVES	* save S record dump
1069		CONFIG_CMD_SCSI		* SCSI Support
1070		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1071					  (requires CONFIG_CMD_I2C)
1072		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1073					  (4xx only)
1074		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1075		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1076					  (requires CONFIG_CMD_MEMORY)
1077		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1078		CONFIG_CMD_SOURCE	  "source" command Support
1079		CONFIG_CMD_SPI		* SPI serial bus support
1080		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1081		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1082		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1083		CONFIG_CMD_TIMER	* access to the system tick timer
1084		CONFIG_CMD_USB		* USB support
1085		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1086		CONFIG_CMD_MFSL		* Microblaze FSL support
1087		CONFIG_CMD_XIMG		  Load part of Multi Image
1088		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1089
1090		EXAMPLE: If you want all functions except of network
1091		support you can write:
1092
1093		#include "config_cmd_all.h"
1094		#undef CONFIG_CMD_NET
1095
1096	Other Commands:
1097		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1098
1099	Note:	Don't enable the "icache" and "dcache" commands
1100		(configuration option CONFIG_CMD_CACHE) unless you know
1101		what you (and your U-Boot users) are doing. Data
1102		cache cannot be enabled on systems like the 8xx or
1103		8260 (where accesses to the IMMR region must be
1104		uncached), and it cannot be disabled on all other
1105		systems where we (mis-) use the data cache to hold an
1106		initial stack and some data.
1107
1108
1109		XXX - this list needs to get updated!
1110
1111- Removal of commands
1112		If no commands are needed to boot, you can disable
1113		CONFIG_CMDLINE to remove them. In this case, the command line
1114		will not be available, and when U-Boot wants to execute the
1115		boot command (on start-up) it will call board_run_command()
1116		instead. This can reduce image size significantly for very
1117		simple boot procedures.
1118
1119- Regular expression support:
1120		CONFIG_REGEX
1121		If this variable is defined, U-Boot is linked against
1122		the SLRE (Super Light Regular Expression) library,
1123		which adds regex support to some commands, as for
1124		example "env grep" and "setexpr".
1125
1126- Device tree:
1127		CONFIG_OF_CONTROL
1128		If this variable is defined, U-Boot will use a device tree
1129		to configure its devices, instead of relying on statically
1130		compiled #defines in the board file. This option is
1131		experimental and only available on a few boards. The device
1132		tree is available in the global data as gd->fdt_blob.
1133
1134		U-Boot needs to get its device tree from somewhere. This can
1135		be done using one of the two options below:
1136
1137		CONFIG_OF_EMBED
1138		If this variable is defined, U-Boot will embed a device tree
1139		binary in its image. This device tree file should be in the
1140		board directory and called <soc>-<board>.dts. The binary file
1141		is then picked up in board_init_f() and made available through
1142		the global data structure as gd->blob.
1143
1144		CONFIG_OF_SEPARATE
1145		If this variable is defined, U-Boot will build a device tree
1146		binary. It will be called u-boot.dtb. Architecture-specific
1147		code will locate it at run-time. Generally this works by:
1148
1149			cat u-boot.bin u-boot.dtb >image.bin
1150
1151		and in fact, U-Boot does this for you, creating a file called
1152		u-boot-dtb.bin which is useful in the common case. You can
1153		still use the individual files if you need something more
1154		exotic.
1155
1156- Watchdog:
1157		CONFIG_WATCHDOG
1158		If this variable is defined, it enables watchdog
1159		support for the SoC. There must be support in the SoC
1160		specific code for a watchdog. For the 8xx and 8260
1161		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1162		register.  When supported for a specific SoC is
1163		available, then no further board specific code should
1164		be needed to use it.
1165
1166		CONFIG_HW_WATCHDOG
1167		When using a watchdog circuitry external to the used
1168		SoC, then define this variable and provide board
1169		specific code for the "hw_watchdog_reset" function.
1170
1171		CONFIG_AT91_HW_WDT_TIMEOUT
1172		specify the timeout in seconds. default 2 seconds.
1173
1174- U-Boot Version:
1175		CONFIG_VERSION_VARIABLE
1176		If this variable is defined, an environment variable
1177		named "ver" is created by U-Boot showing the U-Boot
1178		version as printed by the "version" command.
1179		Any change to this variable will be reverted at the
1180		next reset.
1181
1182- Real-Time Clock:
1183
1184		When CONFIG_CMD_DATE is selected, the type of the RTC
1185		has to be selected, too. Define exactly one of the
1186		following options:
1187
1188		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1189		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1190		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1191		CONFIG_RTC_MC146818	- use MC146818 RTC
1192		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1193		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1194		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1195		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1196		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1197		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1198		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1199		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1200		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1201					  RV3029 RTC.
1202
1203		Note that if the RTC uses I2C, then the I2C interface
1204		must also be configured. See I2C Support, below.
1205
1206- GPIO Support:
1207		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1208
1209		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1210		chip-ngpio pairs that tell the PCA953X driver the number of
1211		pins supported by a particular chip.
1212
1213		Note that if the GPIO device uses I2C, then the I2C interface
1214		must also be configured. See I2C Support, below.
1215
1216- I/O tracing:
1217		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1218		accesses and can checksum them or write a list of them out
1219		to memory. See the 'iotrace' command for details. This is
1220		useful for testing device drivers since it can confirm that
1221		the driver behaves the same way before and after a code
1222		change. Currently this is supported on sandbox and arm. To
1223		add support for your architecture, add '#include <iotrace.h>'
1224		to the bottom of arch/<arch>/include/asm/io.h and test.
1225
1226		Example output from the 'iotrace stats' command is below.
1227		Note that if the trace buffer is exhausted, the checksum will
1228		still continue to operate.
1229
1230			iotrace is enabled
1231			Start:  10000000	(buffer start address)
1232			Size:   00010000	(buffer size)
1233			Offset: 00000120	(current buffer offset)
1234			Output: 10000120	(start + offset)
1235			Count:  00000018	(number of trace records)
1236			CRC32:  9526fb66	(CRC32 of all trace records)
1237
1238- Timestamp Support:
1239
1240		When CONFIG_TIMESTAMP is selected, the timestamp
1241		(date and time) of an image is printed by image
1242		commands like bootm or iminfo. This option is
1243		automatically enabled when you select CONFIG_CMD_DATE .
1244
1245- Partition Labels (disklabels) Supported:
1246		Zero or more of the following:
1247		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1248		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1249				       Intel architecture, USB sticks, etc.
1250		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1251		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1252				       bootloader.  Note 2TB partition limit; see
1253				       disk/part_efi.c
1254		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1255
1256		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1257		CONFIG_CMD_SCSI) you must configure support for at
1258		least one non-MTD partition type as well.
1259
1260- IDE Reset method:
1261		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1262		board configurations files but used nowhere!
1263
1264		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1265		be performed by calling the function
1266			ide_set_reset(int reset)
1267		which has to be defined in a board specific file
1268
1269- ATAPI Support:
1270		CONFIG_ATAPI
1271
1272		Set this to enable ATAPI support.
1273
1274- LBA48 Support
1275		CONFIG_LBA48
1276
1277		Set this to enable support for disks larger than 137GB
1278		Also look at CONFIG_SYS_64BIT_LBA.
1279		Whithout these , LBA48 support uses 32bit variables and will 'only'
1280		support disks up to 2.1TB.
1281
1282		CONFIG_SYS_64BIT_LBA:
1283			When enabled, makes the IDE subsystem use 64bit sector addresses.
1284			Default is 32bit.
1285
1286- SCSI Support:
1287		At the moment only there is only support for the
1288		SYM53C8XX SCSI controller; define
1289		CONFIG_SCSI_SYM53C8XX to enable it.
1290
1291		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1292		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1293		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1294		maximum numbers of LUNs, SCSI ID's and target
1295		devices.
1296		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1297
1298		The environment variable 'scsidevs' is set to the number of
1299		SCSI devices found during the last scan.
1300
1301- NETWORK Support (PCI):
1302		CONFIG_E1000
1303		Support for Intel 8254x/8257x gigabit chips.
1304
1305		CONFIG_E1000_SPI
1306		Utility code for direct access to the SPI bus on Intel 8257x.
1307		This does not do anything useful unless you set at least one
1308		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1309
1310		CONFIG_E1000_SPI_GENERIC
1311		Allow generic access to the SPI bus on the Intel 8257x, for
1312		example with the "sspi" command.
1313
1314		CONFIG_CMD_E1000
1315		Management command for E1000 devices.  When used on devices
1316		with SPI support you can reprogram the EEPROM from U-Boot.
1317
1318		CONFIG_EEPRO100
1319		Support for Intel 82557/82559/82559ER chips.
1320		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1321		write routine for first time initialisation.
1322
1323		CONFIG_TULIP
1324		Support for Digital 2114x chips.
1325		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1326		modem chip initialisation (KS8761/QS6611).
1327
1328		CONFIG_NATSEMI
1329		Support for National dp83815 chips.
1330
1331		CONFIG_NS8382X
1332		Support for National dp8382[01] gigabit chips.
1333
1334- NETWORK Support (other):
1335
1336		CONFIG_DRIVER_AT91EMAC
1337		Support for AT91RM9200 EMAC.
1338
1339			CONFIG_RMII
1340			Define this to use reduced MII inteface
1341
1342			CONFIG_DRIVER_AT91EMAC_QUIET
1343			If this defined, the driver is quiet.
1344			The driver doen't show link status messages.
1345
1346		CONFIG_CALXEDA_XGMAC
1347		Support for the Calxeda XGMAC device
1348
1349		CONFIG_LAN91C96
1350		Support for SMSC's LAN91C96 chips.
1351
1352			CONFIG_LAN91C96_BASE
1353			Define this to hold the physical address
1354			of the LAN91C96's I/O space
1355
1356			CONFIG_LAN91C96_USE_32_BIT
1357			Define this to enable 32 bit addressing
1358
1359		CONFIG_SMC91111
1360		Support for SMSC's LAN91C111 chip
1361
1362			CONFIG_SMC91111_BASE
1363			Define this to hold the physical address
1364			of the device (I/O space)
1365
1366			CONFIG_SMC_USE_32_BIT
1367			Define this if data bus is 32 bits
1368
1369			CONFIG_SMC_USE_IOFUNCS
1370			Define this to use i/o functions instead of macros
1371			(some hardware wont work with macros)
1372
1373		CONFIG_DRIVER_TI_EMAC
1374		Support for davinci emac
1375
1376			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1377			Define this if you have more then 3 PHYs.
1378
1379		CONFIG_FTGMAC100
1380		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1381
1382			CONFIG_FTGMAC100_EGIGA
1383			Define this to use GE link update with gigabit PHY.
1384			Define this if FTGMAC100 is connected to gigabit PHY.
1385			If your system has 10/100 PHY only, it might not occur
1386			wrong behavior. Because PHY usually return timeout or
1387			useless data when polling gigabit status and gigabit
1388			control registers. This behavior won't affect the
1389			correctnessof 10/100 link speed update.
1390
1391		CONFIG_SMC911X
1392		Support for SMSC's LAN911x and LAN921x chips
1393
1394			CONFIG_SMC911X_BASE
1395			Define this to hold the physical address
1396			of the device (I/O space)
1397
1398			CONFIG_SMC911X_32_BIT
1399			Define this if data bus is 32 bits
1400
1401			CONFIG_SMC911X_16_BIT
1402			Define this if data bus is 16 bits. If your processor
1403			automatically converts one 32 bit word to two 16 bit
1404			words you may also try CONFIG_SMC911X_32_BIT.
1405
1406		CONFIG_SH_ETHER
1407		Support for Renesas on-chip Ethernet controller
1408
1409			CONFIG_SH_ETHER_USE_PORT
1410			Define the number of ports to be used
1411
1412			CONFIG_SH_ETHER_PHY_ADDR
1413			Define the ETH PHY's address
1414
1415			CONFIG_SH_ETHER_CACHE_WRITEBACK
1416			If this option is set, the driver enables cache flush.
1417
1418- PWM Support:
1419		CONFIG_PWM_IMX
1420		Support for PWM modul on the imx6.
1421
1422- TPM Support:
1423		CONFIG_TPM
1424		Support TPM devices.
1425
1426		CONFIG_TPM_TIS_INFINEON
1427		Support for Infineon i2c bus TPM devices. Only one device
1428		per system is supported at this time.
1429
1430			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1431			Define the burst count bytes upper limit
1432
1433		CONFIG_TPM_ST33ZP24
1434		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1435
1436			CONFIG_TPM_ST33ZP24_I2C
1437			Support for STMicroelectronics ST33ZP24 I2C devices.
1438			Requires TPM_ST33ZP24 and I2C.
1439
1440			CONFIG_TPM_ST33ZP24_SPI
1441			Support for STMicroelectronics ST33ZP24 SPI devices.
1442			Requires TPM_ST33ZP24 and SPI.
1443
1444		CONFIG_TPM_ATMEL_TWI
1445		Support for Atmel TWI TPM device. Requires I2C support.
1446
1447		CONFIG_TPM_TIS_LPC
1448		Support for generic parallel port TPM devices. Only one device
1449		per system is supported at this time.
1450
1451			CONFIG_TPM_TIS_BASE_ADDRESS
1452			Base address where the generic TPM device is mapped
1453			to. Contemporary x86 systems usually map it at
1454			0xfed40000.
1455
1456		CONFIG_CMD_TPM
1457		Add tpm monitor functions.
1458		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1459		provides monitor access to authorized functions.
1460
1461		CONFIG_TPM
1462		Define this to enable the TPM support library which provides
1463		functional interfaces to some TPM commands.
1464		Requires support for a TPM device.
1465
1466		CONFIG_TPM_AUTH_SESSIONS
1467		Define this to enable authorized functions in the TPM library.
1468		Requires CONFIG_TPM and CONFIG_SHA1.
1469
1470- USB Support:
1471		At the moment only the UHCI host controller is
1472		supported (PIP405, MIP405, MPC5200); define
1473		CONFIG_USB_UHCI to enable it.
1474		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1475		and define CONFIG_USB_STORAGE to enable the USB
1476		storage devices.
1477		Note:
1478		Supported are USB Keyboards and USB Floppy drives
1479		(TEAC FD-05PUB).
1480		MPC5200 USB requires additional defines:
1481			CONFIG_USB_CLOCK
1482				for 528 MHz Clock: 0x0001bbbb
1483			CONFIG_PSC3_USB
1484				for USB on PSC3
1485			CONFIG_USB_CONFIG
1486				for differential drivers: 0x00001000
1487				for single ended drivers: 0x00005000
1488				for differential drivers on PSC3: 0x00000100
1489				for single ended drivers on PSC3: 0x00004100
1490			CONFIG_SYS_USB_EVENT_POLL
1491				May be defined to allow interrupt polling
1492				instead of using asynchronous interrupts
1493
1494		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1495		txfilltuning field in the EHCI controller on reset.
1496
1497		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1498		HW module registers.
1499
1500- USB Device:
1501		Define the below if you wish to use the USB console.
1502		Once firmware is rebuilt from a serial console issue the
1503		command "setenv stdin usbtty; setenv stdout usbtty" and
1504		attach your USB cable. The Unix command "dmesg" should print
1505		it has found a new device. The environment variable usbtty
1506		can be set to gserial or cdc_acm to enable your device to
1507		appear to a USB host as a Linux gserial device or a
1508		Common Device Class Abstract Control Model serial device.
1509		If you select usbtty = gserial you should be able to enumerate
1510		a Linux host by
1511		# modprobe usbserial vendor=0xVendorID product=0xProductID
1512		else if using cdc_acm, simply setting the environment
1513		variable usbtty to be cdc_acm should suffice. The following
1514		might be defined in YourBoardName.h
1515
1516			CONFIG_USB_DEVICE
1517			Define this to build a UDC device
1518
1519			CONFIG_USB_TTY
1520			Define this to have a tty type of device available to
1521			talk to the UDC device
1522
1523			CONFIG_USBD_HS
1524			Define this to enable the high speed support for usb
1525			device and usbtty. If this feature is enabled, a routine
1526			int is_usbd_high_speed(void)
1527			also needs to be defined by the driver to dynamically poll
1528			whether the enumeration has succeded at high speed or full
1529			speed.
1530
1531			CONFIG_SYS_CONSOLE_IS_IN_ENV
1532			Define this if you want stdin, stdout &/or stderr to
1533			be set to usbtty.
1534
1535			mpc8xx:
1536				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1537				Derive USB clock from external clock "blah"
1538				- CONFIG_SYS_USB_EXTC_CLK 0x02
1539
1540				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1541				Derive USB clock from brgclk
1542				- CONFIG_SYS_USB_BRG_CLK 0x04
1543
1544		If you have a USB-IF assigned VendorID then you may wish to
1545		define your own vendor specific values either in BoardName.h
1546		or directly in usbd_vendor_info.h. If you don't define
1547		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1548		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1549		should pretend to be a Linux device to it's target host.
1550
1551			CONFIG_USBD_MANUFACTURER
1552			Define this string as the name of your company for
1553			- CONFIG_USBD_MANUFACTURER "my company"
1554
1555			CONFIG_USBD_PRODUCT_NAME
1556			Define this string as the name of your product
1557			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1558
1559			CONFIG_USBD_VENDORID
1560			Define this as your assigned Vendor ID from the USB
1561			Implementors Forum. This *must* be a genuine Vendor ID
1562			to avoid polluting the USB namespace.
1563			- CONFIG_USBD_VENDORID 0xFFFF
1564
1565			CONFIG_USBD_PRODUCTID
1566			Define this as the unique Product ID
1567			for your device
1568			- CONFIG_USBD_PRODUCTID 0xFFFF
1569
1570- ULPI Layer Support:
1571		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1572		the generic ULPI layer. The generic layer accesses the ULPI PHY
1573		via the platform viewport, so you need both the genric layer and
1574		the viewport enabled. Currently only Chipidea/ARC based
1575		viewport is supported.
1576		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1577		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1578		If your ULPI phy needs a different reference clock than the
1579		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1580		the appropriate value in Hz.
1581
1582- MMC Support:
1583		The MMC controller on the Intel PXA is supported. To
1584		enable this define CONFIG_MMC. The MMC can be
1585		accessed from the boot prompt by mapping the device
1586		to physical memory similar to flash. Command line is
1587		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1588		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1589
1590		CONFIG_SH_MMCIF
1591		Support for Renesas on-chip MMCIF controller
1592
1593			CONFIG_SH_MMCIF_ADDR
1594			Define the base address of MMCIF registers
1595
1596			CONFIG_SH_MMCIF_CLK
1597			Define the clock frequency for MMCIF
1598
1599		CONFIG_GENERIC_MMC
1600		Enable the generic MMC driver
1601
1602		CONFIG_SUPPORT_EMMC_BOOT
1603		Enable some additional features of the eMMC boot partitions.
1604
1605		CONFIG_SUPPORT_EMMC_RPMB
1606		Enable the commands for reading, writing and programming the
1607		key for the Replay Protection Memory Block partition in eMMC.
1608
1609- USB Device Firmware Update (DFU) class support:
1610		CONFIG_USB_FUNCTION_DFU
1611		This enables the USB portion of the DFU USB class
1612
1613		CONFIG_CMD_DFU
1614		This enables the command "dfu" which is used to have
1615		U-Boot create a DFU class device via USB.  This command
1616		requires that the "dfu_alt_info" environment variable be
1617		set and define the alt settings to expose to the host.
1618
1619		CONFIG_DFU_MMC
1620		This enables support for exposing (e)MMC devices via DFU.
1621
1622		CONFIG_DFU_NAND
1623		This enables support for exposing NAND devices via DFU.
1624
1625		CONFIG_DFU_RAM
1626		This enables support for exposing RAM via DFU.
1627		Note: DFU spec refer to non-volatile memory usage, but
1628		allow usages beyond the scope of spec - here RAM usage,
1629		one that would help mostly the developer.
1630
1631		CONFIG_SYS_DFU_DATA_BUF_SIZE
1632		Dfu transfer uses a buffer before writing data to the
1633		raw storage device. Make the size (in bytes) of this buffer
1634		configurable. The size of this buffer is also configurable
1635		through the "dfu_bufsiz" environment variable.
1636
1637		CONFIG_SYS_DFU_MAX_FILE_SIZE
1638		When updating files rather than the raw storage device,
1639		we use a static buffer to copy the file into and then write
1640		the buffer once we've been given the whole file.  Define
1641		this to the maximum filesize (in bytes) for the buffer.
1642		Default is 4 MiB if undefined.
1643
1644		DFU_DEFAULT_POLL_TIMEOUT
1645		Poll timeout [ms], is the timeout a device can send to the
1646		host. The host must wait for this timeout before sending
1647		a subsequent DFU_GET_STATUS request to the device.
1648
1649		DFU_MANIFEST_POLL_TIMEOUT
1650		Poll timeout [ms], which the device sends to the host when
1651		entering dfuMANIFEST state. Host waits this timeout, before
1652		sending again an USB request to the device.
1653
1654- USB Device Android Fastboot support:
1655		CONFIG_USB_FUNCTION_FASTBOOT
1656		This enables the USB part of the fastboot gadget
1657
1658		CONFIG_CMD_FASTBOOT
1659		This enables the command "fastboot" which enables the Android
1660		fastboot mode for the platform's USB device. Fastboot is a USB
1661		protocol for downloading images, flashing and device control
1662		used on Android devices.
1663		See doc/README.android-fastboot for more information.
1664
1665		CONFIG_ANDROID_BOOT_IMAGE
1666		This enables support for booting images which use the Android
1667		image format header.
1668
1669		CONFIG_FASTBOOT_BUF_ADDR
1670		The fastboot protocol requires a large memory buffer for
1671		downloads. Define this to the starting RAM address to use for
1672		downloaded images.
1673
1674		CONFIG_FASTBOOT_BUF_SIZE
1675		The fastboot protocol requires a large memory buffer for
1676		downloads. This buffer should be as large as possible for a
1677		platform. Define this to the size available RAM for fastboot.
1678
1679		CONFIG_FASTBOOT_FLASH
1680		The fastboot protocol includes a "flash" command for writing
1681		the downloaded image to a non-volatile storage device. Define
1682		this to enable the "fastboot flash" command.
1683
1684		CONFIG_FASTBOOT_FLASH_MMC_DEV
1685		The fastboot "flash" command requires additional information
1686		regarding the non-volatile storage device. Define this to
1687		the eMMC device that fastboot should use to store the image.
1688
1689		CONFIG_FASTBOOT_GPT_NAME
1690		The fastboot "flash" command supports writing the downloaded
1691		image to the Protective MBR and the Primary GUID Partition
1692		Table. (Additionally, this downloaded image is post-processed
1693		to generate and write the Backup GUID Partition Table.)
1694		This occurs when the specified "partition name" on the
1695		"fastboot flash" command line matches this value.
1696		Default is GPT_ENTRY_NAME (currently "gpt") if undefined.
1697
1698- Journaling Flash filesystem support:
1699		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1700		CONFIG_JFFS2_NAND_DEV
1701		Define these for a default partition on a NAND device
1702
1703		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1704		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1705		Define these for a default partition on a NOR device
1706
1707		CONFIG_SYS_JFFS_CUSTOM_PART
1708		Define this to create an own partition. You have to provide a
1709		function struct part_info* jffs2_part_info(int part_num)
1710
1711		If you define only one JFFS2 partition you may also want to
1712		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1713		to disable the command chpart. This is the default when you
1714		have not defined a custom partition
1715
1716- FAT(File Allocation Table) filesystem write function support:
1717		CONFIG_FAT_WRITE
1718
1719		Define this to enable support for saving memory data as a
1720		file in FAT formatted partition.
1721
1722		This will also enable the command "fatwrite" enabling the
1723		user to write files to FAT.
1724
1725CBFS (Coreboot Filesystem) support
1726		CONFIG_CMD_CBFS
1727
1728		Define this to enable support for reading from a Coreboot
1729		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1730		and cbfsload.
1731
1732- FAT(File Allocation Table) filesystem cluster size:
1733		CONFIG_FS_FAT_MAX_CLUSTSIZE
1734
1735		Define the max cluster size for fat operations else
1736		a default value of 65536 will be defined.
1737
1738- Keyboard Support:
1739		See Kconfig help for available keyboard drivers.
1740
1741		CONFIG_KEYBOARD
1742
1743		Define this to enable a custom keyboard support.
1744		This simply calls drv_keyboard_init() which must be
1745		defined in your board-specific files. This option is deprecated
1746		and is only used by novena. For new boards, use driver model
1747		instead.
1748
1749- Video support:
1750		CONFIG_VIDEO
1751
1752		Define this to enable video support (for output to
1753		video).
1754
1755		CONFIG_VIDEO_CT69000
1756
1757		Enable Chips & Technologies 69000 Video chip
1758
1759		CONFIG_VIDEO_SMI_LYNXEM
1760		Enable Silicon Motion SMI 712/710/810 Video chip. The
1761		video output is selected via environment 'videoout'
1762		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1763		assumed.
1764
1765		For the CT69000 and SMI_LYNXEM drivers, videomode is
1766		selected via environment 'videomode'. Two different ways
1767		are possible:
1768		- "videomode=num"   'num' is a standard LiLo mode numbers.
1769		Following standard modes are supported	(* is default):
1770
1771		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1772		-------------+---------------------------------------------
1773		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1774		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1775		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1776		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1777		-------------+---------------------------------------------
1778		(i.e. setenv videomode 317; saveenv; reset;)
1779
1780		- "videomode=bootargs" all the video parameters are parsed
1781		from the bootargs. (See drivers/video/videomodes.c)
1782
1783
1784		CONFIG_VIDEO_SED13806
1785		Enable Epson SED13806 driver. This driver supports 8bpp
1786		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1787		or CONFIG_VIDEO_SED13806_16BPP
1788
1789		CONFIG_FSL_DIU_FB
1790		Enable the Freescale DIU video driver.	Reference boards for
1791		SOCs that have a DIU should define this macro to enable DIU
1792		support, and should also define these other macros:
1793
1794			CONFIG_SYS_DIU_ADDR
1795			CONFIG_VIDEO
1796			CONFIG_CMD_BMP
1797			CONFIG_CFB_CONSOLE
1798			CONFIG_VIDEO_SW_CURSOR
1799			CONFIG_VGA_AS_SINGLE_DEVICE
1800			CONFIG_VIDEO_LOGO
1801			CONFIG_VIDEO_BMP_LOGO
1802
1803		The DIU driver will look for the 'video-mode' environment
1804		variable, and if defined, enable the DIU as a console during
1805		boot.  See the documentation file README.video for a
1806		description of this variable.
1807
1808- LCD Support:	CONFIG_LCD
1809
1810		Define this to enable LCD support (for output to LCD
1811		display); also select one of the supported displays
1812		by defining one of these:
1813
1814		CONFIG_ATMEL_LCD:
1815
1816			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1817
1818		CONFIG_NEC_NL6448AC33:
1819
1820			NEC NL6448AC33-18. Active, color, single scan.
1821
1822		CONFIG_NEC_NL6448BC20
1823
1824			NEC NL6448BC20-08. 6.5", 640x480.
1825			Active, color, single scan.
1826
1827		CONFIG_NEC_NL6448BC33_54
1828
1829			NEC NL6448BC33-54. 10.4", 640x480.
1830			Active, color, single scan.
1831
1832		CONFIG_SHARP_16x9
1833
1834			Sharp 320x240. Active, color, single scan.
1835			It isn't 16x9, and I am not sure what it is.
1836
1837		CONFIG_SHARP_LQ64D341
1838
1839			Sharp LQ64D341 display, 640x480.
1840			Active, color, single scan.
1841
1842		CONFIG_HLD1045
1843
1844			HLD1045 display, 640x480.
1845			Active, color, single scan.
1846
1847		CONFIG_OPTREX_BW
1848
1849			Optrex	 CBL50840-2 NF-FW 99 22 M5
1850			or
1851			Hitachi	 LMG6912RPFC-00T
1852			or
1853			Hitachi	 SP14Q002
1854
1855			320x240. Black & white.
1856
1857		Normally display is black on white background; define
1858		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1859
1860		CONFIG_LCD_ALIGNMENT
1861
1862		Normally the LCD is page-aligned (typically 4KB). If this is
1863		defined then the LCD will be aligned to this value instead.
1864		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1865		here, since it is cheaper to change data cache settings on
1866		a per-section basis.
1867
1868		CONFIG_CONSOLE_SCROLL_LINES
1869
1870		When the console need to be scrolled, this is the number of
1871		lines to scroll by. It defaults to 1. Increasing this makes
1872		the console jump but can help speed up operation when scrolling
1873		is slow.
1874
1875		CONFIG_LCD_ROTATION
1876
1877		Sometimes, for example if the display is mounted in portrait
1878		mode or even if it's mounted landscape but rotated by 180degree,
1879		we need to rotate our content of the display relative to the
1880		framebuffer, so that user can read the messages which are
1881		printed out.
1882		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1883		initialized with a given rotation from "vl_rot" out of
1884		"vidinfo_t" which is provided by the board specific code.
1885		The value for vl_rot is coded as following (matching to
1886		fbcon=rotate:<n> linux-kernel commandline):
1887		0 = no rotation respectively 0 degree
1888		1 = 90 degree rotation
1889		2 = 180 degree rotation
1890		3 = 270 degree rotation
1891
1892		If CONFIG_LCD_ROTATION is not defined, the console will be
1893		initialized with 0degree rotation.
1894
1895		CONFIG_LCD_BMP_RLE8
1896
1897		Support drawing of RLE8-compressed bitmaps on the LCD.
1898
1899		CONFIG_I2C_EDID
1900
1901		Enables an 'i2c edid' command which can read EDID
1902		information over I2C from an attached LCD display.
1903
1904- Splash Screen Support: CONFIG_SPLASH_SCREEN
1905
1906		If this option is set, the environment is checked for
1907		a variable "splashimage". If found, the usual display
1908		of logo, copyright and system information on the LCD
1909		is suppressed and the BMP image at the address
1910		specified in "splashimage" is loaded instead. The
1911		console is redirected to the "nulldev", too. This
1912		allows for a "silent" boot where a splash screen is
1913		loaded very quickly after power-on.
1914
1915		CONFIG_SPLASHIMAGE_GUARD
1916
1917		If this option is set, then U-Boot will prevent the environment
1918		variable "splashimage" from being set to a problematic address
1919		(see README.displaying-bmps).
1920		This option is useful for targets where, due to alignment
1921		restrictions, an improperly aligned BMP image will cause a data
1922		abort. If you think you will not have problems with unaligned
1923		accesses (for example because your toolchain prevents them)
1924		there is no need to set this option.
1925
1926		CONFIG_SPLASH_SCREEN_ALIGN
1927
1928		If this option is set the splash image can be freely positioned
1929		on the screen. Environment variable "splashpos" specifies the
1930		position as "x,y". If a positive number is given it is used as
1931		number of pixel from left/top. If a negative number is given it
1932		is used as number of pixel from right/bottom. You can also
1933		specify 'm' for centering the image.
1934
1935		Example:
1936		setenv splashpos m,m
1937			=> image at center of screen
1938
1939		setenv splashpos 30,20
1940			=> image at x = 30 and y = 20
1941
1942		setenv splashpos -10,m
1943			=> vertically centered image
1944			   at x = dspWidth - bmpWidth - 9
1945
1946- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1947
1948		If this option is set, additionally to standard BMP
1949		images, gzipped BMP images can be displayed via the
1950		splashscreen support or the bmp command.
1951
1952- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1953
1954		If this option is set, 8-bit RLE compressed BMP images
1955		can be displayed via the splashscreen support or the
1956		bmp command.
1957
1958- Do compressing for memory range:
1959		CONFIG_CMD_ZIP
1960
1961		If this option is set, it would use zlib deflate method
1962		to compress the specified memory at its best effort.
1963
1964- Compression support:
1965		CONFIG_GZIP
1966
1967		Enabled by default to support gzip compressed images.
1968
1969		CONFIG_BZIP2
1970
1971		If this option is set, support for bzip2 compressed
1972		images is included. If not, only uncompressed and gzip
1973		compressed images are supported.
1974
1975		NOTE: the bzip2 algorithm requires a lot of RAM, so
1976		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1977		be at least 4MB.
1978
1979		CONFIG_LZMA
1980
1981		If this option is set, support for lzma compressed
1982		images is included.
1983
1984		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1985		requires an amount of dynamic memory that is given by the
1986		formula:
1987
1988			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1989
1990		Where lc and lp stand for, respectively, Literal context bits
1991		and Literal pos bits.
1992
1993		This value is upper-bounded by 14MB in the worst case. Anyway,
1994		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1995		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1996		a very small buffer.
1997
1998		Use the lzmainfo tool to determinate the lc and lp values and
1999		then calculate the amount of needed dynamic memory (ensuring
2000		the appropriate CONFIG_SYS_MALLOC_LEN value).
2001
2002		CONFIG_LZO
2003
2004		If this option is set, support for LZO compressed images
2005		is included.
2006
2007- MII/PHY support:
2008		CONFIG_PHY_ADDR
2009
2010		The address of PHY on MII bus.
2011
2012		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
2013
2014		The clock frequency of the MII bus
2015
2016		CONFIG_PHY_GIGE
2017
2018		If this option is set, support for speed/duplex
2019		detection of gigabit PHY is included.
2020
2021		CONFIG_PHY_RESET_DELAY
2022
2023		Some PHY like Intel LXT971A need extra delay after
2024		reset before any MII register access is possible.
2025		For such PHY, set this option to the usec delay
2026		required. (minimum 300usec for LXT971A)
2027
2028		CONFIG_PHY_CMD_DELAY (ppc4xx)
2029
2030		Some PHY like Intel LXT971A need extra delay after
2031		command issued before MII status register can be read
2032
2033- IP address:
2034		CONFIG_IPADDR
2035
2036		Define a default value for the IP address to use for
2037		the default Ethernet interface, in case this is not
2038		determined through e.g. bootp.
2039		(Environment variable "ipaddr")
2040
2041- Server IP address:
2042		CONFIG_SERVERIP
2043
2044		Defines a default value for the IP address of a TFTP
2045		server to contact when using the "tftboot" command.
2046		(Environment variable "serverip")
2047
2048		CONFIG_KEEP_SERVERADDR
2049
2050		Keeps the server's MAC address, in the env 'serveraddr'
2051		for passing to bootargs (like Linux's netconsole option)
2052
2053- Gateway IP address:
2054		CONFIG_GATEWAYIP
2055
2056		Defines a default value for the IP address of the
2057		default router where packets to other networks are
2058		sent to.
2059		(Environment variable "gatewayip")
2060
2061- Subnet mask:
2062		CONFIG_NETMASK
2063
2064		Defines a default value for the subnet mask (or
2065		routing prefix) which is used to determine if an IP
2066		address belongs to the local subnet or needs to be
2067		forwarded through a router.
2068		(Environment variable "netmask")
2069
2070- Multicast TFTP Mode:
2071		CONFIG_MCAST_TFTP
2072
2073		Defines whether you want to support multicast TFTP as per
2074		rfc-2090; for example to work with atftp.  Lets lots of targets
2075		tftp down the same boot image concurrently.  Note: the Ethernet
2076		driver in use must provide a function: mcast() to join/leave a
2077		multicast group.
2078
2079- BOOTP Recovery Mode:
2080		CONFIG_BOOTP_RANDOM_DELAY
2081
2082		If you have many targets in a network that try to
2083		boot using BOOTP, you may want to avoid that all
2084		systems send out BOOTP requests at precisely the same
2085		moment (which would happen for instance at recovery
2086		from a power failure, when all systems will try to
2087		boot, thus flooding the BOOTP server. Defining
2088		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
2089		inserted before sending out BOOTP requests. The
2090		following delays are inserted then:
2091
2092		1st BOOTP request:	delay 0 ... 1 sec
2093		2nd BOOTP request:	delay 0 ... 2 sec
2094		3rd BOOTP request:	delay 0 ... 4 sec
2095		4th and following
2096		BOOTP requests:		delay 0 ... 8 sec
2097
2098		CONFIG_BOOTP_ID_CACHE_SIZE
2099
2100		BOOTP packets are uniquely identified using a 32-bit ID. The
2101		server will copy the ID from client requests to responses and
2102		U-Boot will use this to determine if it is the destination of
2103		an incoming response. Some servers will check that addresses
2104		aren't in use before handing them out (usually using an ARP
2105		ping) and therefore take up to a few hundred milliseconds to
2106		respond. Network congestion may also influence the time it
2107		takes for a response to make it back to the client. If that
2108		time is too long, U-Boot will retransmit requests. In order
2109		to allow earlier responses to still be accepted after these
2110		retransmissions, U-Boot's BOOTP client keeps a small cache of
2111		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
2112		cache. The default is to keep IDs for up to four outstanding
2113		requests. Increasing this will allow U-Boot to accept offers
2114		from a BOOTP client in networks with unusually high latency.
2115
2116- DHCP Advanced Options:
2117		You can fine tune the DHCP functionality by defining
2118		CONFIG_BOOTP_* symbols:
2119
2120		CONFIG_BOOTP_SUBNETMASK
2121		CONFIG_BOOTP_GATEWAY
2122		CONFIG_BOOTP_HOSTNAME
2123		CONFIG_BOOTP_NISDOMAIN
2124		CONFIG_BOOTP_BOOTPATH
2125		CONFIG_BOOTP_BOOTFILESIZE
2126		CONFIG_BOOTP_DNS
2127		CONFIG_BOOTP_DNS2
2128		CONFIG_BOOTP_SEND_HOSTNAME
2129		CONFIG_BOOTP_NTPSERVER
2130		CONFIG_BOOTP_TIMEOFFSET
2131		CONFIG_BOOTP_VENDOREX
2132		CONFIG_BOOTP_MAY_FAIL
2133
2134		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
2135		environment variable, not the BOOTP server.
2136
2137		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
2138		after the configured retry count, the call will fail
2139		instead of starting over.  This can be used to fail over
2140		to Link-local IP address configuration if the DHCP server
2141		is not available.
2142
2143		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
2144		serverip from a DHCP server, it is possible that more
2145		than one DNS serverip is offered to the client.
2146		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
2147		serverip will be stored in the additional environment
2148		variable "dnsip2". The first DNS serverip is always
2149		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2150		is defined.
2151
2152		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2153		to do a dynamic update of a DNS server. To do this, they
2154		need the hostname of the DHCP requester.
2155		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2156		of the "hostname" environment variable is passed as
2157		option 12 to the DHCP server.
2158
2159		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2160
2161		A 32bit value in microseconds for a delay between
2162		receiving a "DHCP Offer" and sending the "DHCP Request".
2163		This fixes a problem with certain DHCP servers that don't
2164		respond 100% of the time to a "DHCP request". E.g. On an
2165		AT91RM9200 processor running at 180MHz, this delay needed
2166		to be *at least* 15,000 usec before a Windows Server 2003
2167		DHCP server would reply 100% of the time. I recommend at
2168		least 50,000 usec to be safe. The alternative is to hope
2169		that one of the retries will be successful but note that
2170		the DHCP timeout and retry process takes a longer than
2171		this delay.
2172
2173 - Link-local IP address negotiation:
2174		Negotiate with other link-local clients on the local network
2175		for an address that doesn't require explicit configuration.
2176		This is especially useful if a DHCP server cannot be guaranteed
2177		to exist in all environments that the device must operate.
2178
2179		See doc/README.link-local for more information.
2180
2181 - CDP Options:
2182		CONFIG_CDP_DEVICE_ID
2183
2184		The device id used in CDP trigger frames.
2185
2186		CONFIG_CDP_DEVICE_ID_PREFIX
2187
2188		A two character string which is prefixed to the MAC address
2189		of the device.
2190
2191		CONFIG_CDP_PORT_ID
2192
2193		A printf format string which contains the ascii name of
2194		the port. Normally is set to "eth%d" which sets
2195		eth0 for the first Ethernet, eth1 for the second etc.
2196
2197		CONFIG_CDP_CAPABILITIES
2198
2199		A 32bit integer which indicates the device capabilities;
2200		0x00000010 for a normal host which does not forwards.
2201
2202		CONFIG_CDP_VERSION
2203
2204		An ascii string containing the version of the software.
2205
2206		CONFIG_CDP_PLATFORM
2207
2208		An ascii string containing the name of the platform.
2209
2210		CONFIG_CDP_TRIGGER
2211
2212		A 32bit integer sent on the trigger.
2213
2214		CONFIG_CDP_POWER_CONSUMPTION
2215
2216		A 16bit integer containing the power consumption of the
2217		device in .1 of milliwatts.
2218
2219		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2220
2221		A byte containing the id of the VLAN.
2222
2223- Status LED:	CONFIG_STATUS_LED
2224
2225		Several configurations allow to display the current
2226		status using a LED. For instance, the LED will blink
2227		fast while running U-Boot code, stop blinking as
2228		soon as a reply to a BOOTP request was received, and
2229		start blinking slow once the Linux kernel is running
2230		(supported by a status LED driver in the Linux
2231		kernel). Defining CONFIG_STATUS_LED enables this
2232		feature in U-Boot.
2233
2234		Additional options:
2235
2236		CONFIG_GPIO_LED
2237		The status LED can be connected to a GPIO pin.
2238		In such cases, the gpio_led driver can be used as a
2239		status LED backend implementation. Define CONFIG_GPIO_LED
2240		to include the gpio_led driver in the U-Boot binary.
2241
2242		CONFIG_GPIO_LED_INVERTED_TABLE
2243		Some GPIO connected LEDs may have inverted polarity in which
2244		case the GPIO high value corresponds to LED off state and
2245		GPIO low value corresponds to LED on state.
2246		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2247		with a list of GPIO LEDs that have inverted polarity.
2248
2249- CAN Support:	CONFIG_CAN_DRIVER
2250
2251		Defining CONFIG_CAN_DRIVER enables CAN driver support
2252		on those systems that support this (optional)
2253		feature, like the TQM8xxL modules.
2254
2255- I2C Support:	CONFIG_SYS_I2C
2256
2257		This enable the NEW i2c subsystem, and will allow you to use
2258		i2c commands at the u-boot command line (as long as you set
2259		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2260		based realtime clock chips or other i2c devices. See
2261		common/cmd_i2c.c for a description of the command line
2262		interface.
2263
2264		ported i2c driver to the new framework:
2265		- drivers/i2c/soft_i2c.c:
2266		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2267		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2268		    for defining speed and slave address
2269		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2270		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2271		    for defining speed and slave address
2272		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2273		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2274		    for defining speed and slave address
2275		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2276		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2277		    for defining speed and slave address
2278
2279		- drivers/i2c/fsl_i2c.c:
2280		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2281		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2282		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2283		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2284		    bus.
2285		  - If your board supports a second fsl i2c bus, define
2286		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2287		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2288		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2289		    second bus.
2290
2291		- drivers/i2c/tegra_i2c.c:
2292		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2293		  - This driver adds 4 i2c buses with a fix speed from
2294		    100000 and the slave addr 0!
2295
2296		- drivers/i2c/ppc4xx_i2c.c
2297		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2298		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2299		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2300
2301		- drivers/i2c/i2c_mxc.c
2302		  - activate this driver with CONFIG_SYS_I2C_MXC
2303		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
2304		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
2305		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
2306		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
2307		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2308		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2309		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2310		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2311		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2312		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2313		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
2314		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
2315		If those defines are not set, default value is 100000
2316		for speed, and 0 for slave.
2317
2318		- drivers/i2c/rcar_i2c.c:
2319		  - activate this driver with CONFIG_SYS_I2C_RCAR
2320		  - This driver adds 4 i2c buses
2321
2322		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2323		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2324		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2325		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2326		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2327		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2328		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2329		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2330		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2331
2332		- drivers/i2c/sh_i2c.c:
2333		  - activate this driver with CONFIG_SYS_I2C_SH
2334		  - This driver adds from 2 to 5 i2c buses
2335
2336		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2337		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2338		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2339		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2340		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2341		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2342		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2343		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2344		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2345		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2346		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2347		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2348		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2349
2350		- drivers/i2c/omap24xx_i2c.c
2351		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2352		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2353		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2354		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2355		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2356		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2357		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2358		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2359		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2360		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2361		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2362
2363		- drivers/i2c/zynq_i2c.c
2364		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2365		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2366		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2367
2368		- drivers/i2c/s3c24x0_i2c.c:
2369		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2370		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2371		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2372		    with a fix speed from 100000 and the slave addr 0!
2373
2374		- drivers/i2c/ihs_i2c.c
2375		  - activate this driver with CONFIG_SYS_I2C_IHS
2376		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2377		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2378		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2379		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2380		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2381		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2382		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2383		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2384		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2385		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2386		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2387		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2388		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
2389		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
2390		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
2391		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
2392		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
2393		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
2394		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
2395		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
2396		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
2397
2398		additional defines:
2399
2400		CONFIG_SYS_NUM_I2C_BUSES
2401		Hold the number of i2c buses you want to use. If you
2402		don't use/have i2c muxes on your i2c bus, this
2403		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2404		omit this define.
2405
2406		CONFIG_SYS_I2C_DIRECT_BUS
2407		define this, if you don't use i2c muxes on your hardware.
2408		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2409		omit this define.
2410
2411		CONFIG_SYS_I2C_MAX_HOPS
2412		define how many muxes are maximal consecutively connected
2413		on one i2c bus. If you not use i2c muxes, omit this
2414		define.
2415
2416		CONFIG_SYS_I2C_BUSES
2417		hold a list of buses you want to use, only used if
2418		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2419		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2420		CONFIG_SYS_NUM_I2C_BUSES = 9:
2421
2422		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2423					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2424					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2425					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2426					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2427					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2428					{1, {I2C_NULL_HOP}}, \
2429					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2430					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2431					}
2432
2433		which defines
2434			bus 0 on adapter 0 without a mux
2435			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2436			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2437			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2438			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2439			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2440			bus 6 on adapter 1 without a mux
2441			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2442			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2443
2444		If you do not have i2c muxes on your board, omit this define.
2445
2446- Legacy I2C Support:	CONFIG_HARD_I2C
2447
2448		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2449		provides the following compelling advantages:
2450
2451		- more than one i2c adapter is usable
2452		- approved multibus support
2453		- better i2c mux support
2454
2455		** Please consider updating your I2C driver now. **
2456
2457		These enable legacy I2C serial bus commands. Defining
2458		CONFIG_HARD_I2C will include the appropriate I2C driver
2459		for the selected CPU.
2460
2461		This will allow you to use i2c commands at the u-boot
2462		command line (as long as you set CONFIG_CMD_I2C in
2463		CONFIG_COMMANDS) and communicate with i2c based realtime
2464		clock chips. See common/cmd_i2c.c for a description of the
2465		command line interface.
2466
2467		CONFIG_HARD_I2C selects a hardware I2C controller.
2468
2469		There are several other quantities that must also be
2470		defined when you define CONFIG_HARD_I2C.
2471
2472		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2473		to be the frequency (in Hz) at which you wish your i2c bus
2474		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2475		the CPU's i2c node address).
2476
2477		Now, the u-boot i2c code for the mpc8xx
2478		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2479		and so its address should therefore be cleared to 0 (See,
2480		eg, MPC823e User's Manual p.16-473). So, set
2481		CONFIG_SYS_I2C_SLAVE to 0.
2482
2483		CONFIG_SYS_I2C_INIT_MPC5XXX
2484
2485		When a board is reset during an i2c bus transfer
2486		chips might think that the current transfer is still
2487		in progress.  Reset the slave devices by sending start
2488		commands until the slave device responds.
2489
2490		That's all that's required for CONFIG_HARD_I2C.
2491
2492		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2493		then the following macros need to be defined (examples are
2494		from include/configs/lwmon.h):
2495
2496		I2C_INIT
2497
2498		(Optional). Any commands necessary to enable the I2C
2499		controller or configure ports.
2500
2501		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2502
2503		I2C_PORT
2504
2505		(Only for MPC8260 CPU). The I/O port to use (the code
2506		assumes both bits are on the same port). Valid values
2507		are 0..3 for ports A..D.
2508
2509		I2C_ACTIVE
2510
2511		The code necessary to make the I2C data line active
2512		(driven).  If the data line is open collector, this
2513		define can be null.
2514
2515		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2516
2517		I2C_TRISTATE
2518
2519		The code necessary to make the I2C data line tri-stated
2520		(inactive).  If the data line is open collector, this
2521		define can be null.
2522
2523		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2524
2525		I2C_READ
2526
2527		Code that returns true if the I2C data line is high,
2528		false if it is low.
2529
2530		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2531
2532		I2C_SDA(bit)
2533
2534		If <bit> is true, sets the I2C data line high. If it
2535		is false, it clears it (low).
2536
2537		eg: #define I2C_SDA(bit) \
2538			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2539			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2540
2541		I2C_SCL(bit)
2542
2543		If <bit> is true, sets the I2C clock line high. If it
2544		is false, it clears it (low).
2545
2546		eg: #define I2C_SCL(bit) \
2547			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2548			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2549
2550		I2C_DELAY
2551
2552		This delay is invoked four times per clock cycle so this
2553		controls the rate of data transfer.  The data rate thus
2554		is 1 / (I2C_DELAY * 4). Often defined to be something
2555		like:
2556
2557		#define I2C_DELAY  udelay(2)
2558
2559		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2560
2561		If your arch supports the generic GPIO framework (asm/gpio.h),
2562		then you may alternatively define the two GPIOs that are to be
2563		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2564		have GPIO-based defaults assigned to them as appropriate.
2565
2566		You should define these to the GPIO value as given directly to
2567		the generic GPIO functions.
2568
2569		CONFIG_SYS_I2C_INIT_BOARD
2570
2571		When a board is reset during an i2c bus transfer
2572		chips might think that the current transfer is still
2573		in progress. On some boards it is possible to access
2574		the i2c SCLK line directly, either by using the
2575		processor pin as a GPIO or by having a second pin
2576		connected to the bus. If this option is defined a
2577		custom i2c_init_board() routine in boards/xxx/board.c
2578		is run early in the boot sequence.
2579
2580		CONFIG_SYS_I2C_BOARD_LATE_INIT
2581
2582		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2583		defined a custom i2c_board_late_init() routine in
2584		boards/xxx/board.c is run AFTER the operations in i2c_init()
2585		is completed. This callpoint can be used to unreset i2c bus
2586		using CPU i2c controller register accesses for CPUs whose i2c
2587		controller provide such a method. It is called at the end of
2588		i2c_init() to allow i2c_init operations to setup the i2c bus
2589		controller on the CPU (e.g. setting bus speed & slave address).
2590
2591		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2592
2593		This option enables configuration of bi_iic_fast[] flags
2594		in u-boot bd_info structure based on u-boot environment
2595		variable "i2cfast". (see also i2cfast)
2596
2597		CONFIG_I2C_MULTI_BUS
2598
2599		This option allows the use of multiple I2C buses, each of which
2600		must have a controller.	 At any point in time, only one bus is
2601		active.	 To switch to a different bus, use the 'i2c dev' command.
2602		Note that bus numbering is zero-based.
2603
2604		CONFIG_SYS_I2C_NOPROBES
2605
2606		This option specifies a list of I2C devices that will be skipped
2607		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2608		is set, specify a list of bus-device pairs.  Otherwise, specify
2609		a 1D array of device addresses
2610
2611		e.g.
2612			#undef	CONFIG_I2C_MULTI_BUS
2613			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2614
2615		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2616
2617			#define CONFIG_I2C_MULTI_BUS
2618			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2619
2620		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2621
2622		CONFIG_SYS_SPD_BUS_NUM
2623
2624		If defined, then this indicates the I2C bus number for DDR SPD.
2625		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2626
2627		CONFIG_SYS_RTC_BUS_NUM
2628
2629		If defined, then this indicates the I2C bus number for the RTC.
2630		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2631
2632		CONFIG_SYS_DTT_BUS_NUM
2633
2634		If defined, then this indicates the I2C bus number for the DTT.
2635		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2636
2637		CONFIG_SYS_I2C_DTT_ADDR:
2638
2639		If defined, specifies the I2C address of the DTT device.
2640		If not defined, then U-Boot uses predefined value for
2641		specified DTT device.
2642
2643		CONFIG_SOFT_I2C_READ_REPEATED_START
2644
2645		defining this will force the i2c_read() function in
2646		the soft_i2c driver to perform an I2C repeated start
2647		between writing the address pointer and reading the
2648		data.  If this define is omitted the default behaviour
2649		of doing a stop-start sequence will be used.  Most I2C
2650		devices can use either method, but some require one or
2651		the other.
2652
2653- SPI Support:	CONFIG_SPI
2654
2655		Enables SPI driver (so far only tested with
2656		SPI EEPROM, also an instance works with Crystal A/D and
2657		D/As on the SACSng board)
2658
2659		CONFIG_SH_SPI
2660
2661		Enables the driver for SPI controller on SuperH. Currently
2662		only SH7757 is supported.
2663
2664		CONFIG_SOFT_SPI
2665
2666		Enables a software (bit-bang) SPI driver rather than
2667		using hardware support. This is a general purpose
2668		driver that only requires three general I/O port pins
2669		(two outputs, one input) to function. If this is
2670		defined, the board configuration must define several
2671		SPI configuration items (port pins to use, etc). For
2672		an example, see include/configs/sacsng.h.
2673
2674		CONFIG_HARD_SPI
2675
2676		Enables a hardware SPI driver for general-purpose reads
2677		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2678		must define a list of chip-select function pointers.
2679		Currently supported on some MPC8xxx processors.	 For an
2680		example, see include/configs/mpc8349emds.h.
2681
2682		CONFIG_MXC_SPI
2683
2684		Enables the driver for the SPI controllers on i.MX and MXC
2685		SoCs. Currently i.MX31/35/51 are supported.
2686
2687		CONFIG_SYS_SPI_MXC_WAIT
2688		Timeout for waiting until spi transfer completed.
2689		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2690
2691- FPGA Support: CONFIG_FPGA
2692
2693		Enables FPGA subsystem.
2694
2695		CONFIG_FPGA_<vendor>
2696
2697		Enables support for specific chip vendors.
2698		(ALTERA, XILINX)
2699
2700		CONFIG_FPGA_<family>
2701
2702		Enables support for FPGA family.
2703		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2704
2705		CONFIG_FPGA_COUNT
2706
2707		Specify the number of FPGA devices to support.
2708
2709		CONFIG_CMD_FPGA_LOADMK
2710
2711		Enable support for fpga loadmk command
2712
2713		CONFIG_CMD_FPGA_LOADP
2714
2715		Enable support for fpga loadp command - load partial bitstream
2716
2717		CONFIG_CMD_FPGA_LOADBP
2718
2719		Enable support for fpga loadbp command - load partial bitstream
2720		(Xilinx only)
2721
2722		CONFIG_SYS_FPGA_PROG_FEEDBACK
2723
2724		Enable printing of hash marks during FPGA configuration.
2725
2726		CONFIG_SYS_FPGA_CHECK_BUSY
2727
2728		Enable checks on FPGA configuration interface busy
2729		status by the configuration function. This option
2730		will require a board or device specific function to
2731		be written.
2732
2733		CONFIG_FPGA_DELAY
2734
2735		If defined, a function that provides delays in the FPGA
2736		configuration driver.
2737
2738		CONFIG_SYS_FPGA_CHECK_CTRLC
2739		Allow Control-C to interrupt FPGA configuration
2740
2741		CONFIG_SYS_FPGA_CHECK_ERROR
2742
2743		Check for configuration errors during FPGA bitfile
2744		loading. For example, abort during Virtex II
2745		configuration if the INIT_B line goes low (which
2746		indicated a CRC error).
2747
2748		CONFIG_SYS_FPGA_WAIT_INIT
2749
2750		Maximum time to wait for the INIT_B line to de-assert
2751		after PROB_B has been de-asserted during a Virtex II
2752		FPGA configuration sequence. The default time is 500
2753		ms.
2754
2755		CONFIG_SYS_FPGA_WAIT_BUSY
2756
2757		Maximum time to wait for BUSY to de-assert during
2758		Virtex II FPGA configuration. The default is 5 ms.
2759
2760		CONFIG_SYS_FPGA_WAIT_CONFIG
2761
2762		Time to wait after FPGA configuration. The default is
2763		200 ms.
2764
2765- Configuration Management:
2766		CONFIG_BUILD_TARGET
2767
2768		Some SoCs need special image types (e.g. U-Boot binary
2769		with a special header) as build targets. By defining
2770		CONFIG_BUILD_TARGET in the SoC / board header, this
2771		special image will be automatically built upon calling
2772		make / MAKEALL.
2773
2774		CONFIG_IDENT_STRING
2775
2776		If defined, this string will be added to the U-Boot
2777		version information (U_BOOT_VERSION)
2778
2779- Vendor Parameter Protection:
2780
2781		U-Boot considers the values of the environment
2782		variables "serial#" (Board Serial Number) and
2783		"ethaddr" (Ethernet Address) to be parameters that
2784		are set once by the board vendor / manufacturer, and
2785		protects these variables from casual modification by
2786		the user. Once set, these variables are read-only,
2787		and write or delete attempts are rejected. You can
2788		change this behaviour:
2789
2790		If CONFIG_ENV_OVERWRITE is #defined in your config
2791		file, the write protection for vendor parameters is
2792		completely disabled. Anybody can change or delete
2793		these parameters.
2794
2795		Alternatively, if you define _both_ an ethaddr in the
2796		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2797		Ethernet address is installed in the environment,
2798		which can be changed exactly ONCE by the user. [The
2799		serial# is unaffected by this, i. e. it remains
2800		read-only.]
2801
2802		The same can be accomplished in a more flexible way
2803		for any variable by configuring the type of access
2804		to allow for those variables in the ".flags" variable
2805		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2806
2807- Protected RAM:
2808		CONFIG_PRAM
2809
2810		Define this variable to enable the reservation of
2811		"protected RAM", i. e. RAM which is not overwritten
2812		by U-Boot. Define CONFIG_PRAM to hold the number of
2813		kB you want to reserve for pRAM. You can overwrite
2814		this default value by defining an environment
2815		variable "pram" to the number of kB you want to
2816		reserve. Note that the board info structure will
2817		still show the full amount of RAM. If pRAM is
2818		reserved, a new environment variable "mem" will
2819		automatically be defined to hold the amount of
2820		remaining RAM in a form that can be passed as boot
2821		argument to Linux, for instance like that:
2822
2823			setenv bootargs ... mem=\${mem}
2824			saveenv
2825
2826		This way you can tell Linux not to use this memory,
2827		either, which results in a memory region that will
2828		not be affected by reboots.
2829
2830		*WARNING* If your board configuration uses automatic
2831		detection of the RAM size, you must make sure that
2832		this memory test is non-destructive. So far, the
2833		following board configurations are known to be
2834		"pRAM-clean":
2835
2836			IVMS8, IVML24, SPD8xx, TQM8xxL,
2837			HERMES, IP860, RPXlite, LWMON,
2838			FLAGADM, TQM8260
2839
2840- Access to physical memory region (> 4GB)
2841		Some basic support is provided for operations on memory not
2842		normally accessible to U-Boot - e.g. some architectures
2843		support access to more than 4GB of memory on 32-bit
2844		machines using physical address extension or similar.
2845		Define CONFIG_PHYSMEM to access this basic support, which
2846		currently only supports clearing the memory.
2847
2848- Error Recovery:
2849		CONFIG_PANIC_HANG
2850
2851		Define this variable to stop the system in case of a
2852		fatal error, so that you have to reset it manually.
2853		This is probably NOT a good idea for an embedded
2854		system where you want the system to reboot
2855		automatically as fast as possible, but it may be
2856		useful during development since you can try to debug
2857		the conditions that lead to the situation.
2858
2859		CONFIG_NET_RETRY_COUNT
2860
2861		This variable defines the number of retries for
2862		network operations like ARP, RARP, TFTP, or BOOTP
2863		before giving up the operation. If not defined, a
2864		default value of 5 is used.
2865
2866		CONFIG_ARP_TIMEOUT
2867
2868		Timeout waiting for an ARP reply in milliseconds.
2869
2870		CONFIG_NFS_TIMEOUT
2871
2872		Timeout in milliseconds used in NFS protocol.
2873		If you encounter "ERROR: Cannot umount" in nfs command,
2874		try longer timeout such as
2875		#define CONFIG_NFS_TIMEOUT 10000UL
2876
2877- Command Interpreter:
2878		CONFIG_AUTO_COMPLETE
2879
2880		Enable auto completion of commands using TAB.
2881
2882		CONFIG_SYS_PROMPT_HUSH_PS2
2883
2884		This defines the secondary prompt string, which is
2885		printed when the command interpreter needs more input
2886		to complete a command. Usually "> ".
2887
2888	Note:
2889
2890		In the current implementation, the local variables
2891		space and global environment variables space are
2892		separated. Local variables are those you define by
2893		simply typing `name=value'. To access a local
2894		variable later on, you have write `$name' or
2895		`${name}'; to execute the contents of a variable
2896		directly type `$name' at the command prompt.
2897
2898		Global environment variables are those you use
2899		setenv/printenv to work with. To run a command stored
2900		in such a variable, you need to use the run command,
2901		and you must not use the '$' sign to access them.
2902
2903		To store commands and special characters in a
2904		variable, please use double quotation marks
2905		surrounding the whole text of the variable, instead
2906		of the backslashes before semicolons and special
2907		symbols.
2908
2909- Command Line Editing and History:
2910		CONFIG_CMDLINE_EDITING
2911
2912		Enable editing and History functions for interactive
2913		command line input operations
2914
2915- Command Line PS1/PS2 support:
2916		CONFIG_CMDLINE_PS_SUPPORT
2917
2918		Enable support for changing the command prompt string
2919		at run-time. Only static string is supported so far.
2920		The string is obtained from environment variables PS1
2921		and PS2.
2922
2923- Default Environment:
2924		CONFIG_EXTRA_ENV_SETTINGS
2925
2926		Define this to contain any number of null terminated
2927		strings (variable = value pairs) that will be part of
2928		the default environment compiled into the boot image.
2929
2930		For example, place something like this in your
2931		board's config file:
2932
2933		#define CONFIG_EXTRA_ENV_SETTINGS \
2934			"myvar1=value1\0" \
2935			"myvar2=value2\0"
2936
2937		Warning: This method is based on knowledge about the
2938		internal format how the environment is stored by the
2939		U-Boot code. This is NOT an official, exported
2940		interface! Although it is unlikely that this format
2941		will change soon, there is no guarantee either.
2942		You better know what you are doing here.
2943
2944		Note: overly (ab)use of the default environment is
2945		discouraged. Make sure to check other ways to preset
2946		the environment like the "source" command or the
2947		boot command first.
2948
2949		CONFIG_ENV_VARS_UBOOT_CONFIG
2950
2951		Define this in order to add variables describing the
2952		U-Boot build configuration to the default environment.
2953		These will be named arch, cpu, board, vendor, and soc.
2954
2955		Enabling this option will cause the following to be defined:
2956
2957		- CONFIG_SYS_ARCH
2958		- CONFIG_SYS_CPU
2959		- CONFIG_SYS_BOARD
2960		- CONFIG_SYS_VENDOR
2961		- CONFIG_SYS_SOC
2962
2963		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2964
2965		Define this in order to add variables describing certain
2966		run-time determined information about the hardware to the
2967		environment.  These will be named board_name, board_rev.
2968
2969		CONFIG_DELAY_ENVIRONMENT
2970
2971		Normally the environment is loaded when the board is
2972		initialised so that it is available to U-Boot. This inhibits
2973		that so that the environment is not available until
2974		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2975		this is instead controlled by the value of
2976		/config/load-environment.
2977
2978- Parallel Flash support:
2979		CONFIG_SYS_NO_FLASH
2980
2981		Traditionally U-Boot was run on systems with parallel NOR
2982		flash. This option is used to disable support for parallel NOR
2983		flash. This option should be defined if the board does not have
2984		parallel flash.
2985
2986		If this option is not defined one of the generic flash drivers
2987		(e.g.  CONFIG_FLASH_CFI_DRIVER or CONFIG_ST_SMI) must be
2988		selected or the board must provide an implementation of the
2989		flash API (see include/flash.h).
2990
2991- DataFlash Support:
2992		CONFIG_HAS_DATAFLASH
2993
2994		Defining this option enables DataFlash features and
2995		allows to read/write in Dataflash via the standard
2996		commands cp, md...
2997
2998- Serial Flash support
2999		CONFIG_CMD_SF
3000
3001		Defining this option enables SPI flash commands
3002		'sf probe/read/write/erase/update'.
3003
3004		Usage requires an initial 'probe' to define the serial
3005		flash parameters, followed by read/write/erase/update
3006		commands.
3007
3008		The following defaults may be provided by the platform
3009		to handle the common case when only a single serial
3010		flash is present on the system.
3011
3012		CONFIG_SF_DEFAULT_BUS		Bus identifier
3013		CONFIG_SF_DEFAULT_CS		Chip-select
3014		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
3015		CONFIG_SF_DEFAULT_SPEED		in Hz
3016
3017		CONFIG_CMD_SF_TEST
3018
3019		Define this option to include a destructive SPI flash
3020		test ('sf test').
3021
3022		CONFIG_SF_DUAL_FLASH		Dual flash memories
3023
3024		Define this option to use dual flash support where two flash
3025		memories can be connected with a given cs line.
3026		Currently Xilinx Zynq qspi supports these type of connections.
3027
3028- SystemACE Support:
3029		CONFIG_SYSTEMACE
3030
3031		Adding this option adds support for Xilinx SystemACE
3032		chips attached via some sort of local bus. The address
3033		of the chip must also be defined in the
3034		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
3035
3036		#define CONFIG_SYSTEMACE
3037		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
3038
3039		When SystemACE support is added, the "ace" device type
3040		becomes available to the fat commands, i.e. fatls.
3041
3042- TFTP Fixed UDP Port:
3043		CONFIG_TFTP_PORT
3044
3045		If this is defined, the environment variable tftpsrcp
3046		is used to supply the TFTP UDP source port value.
3047		If tftpsrcp isn't defined, the normal pseudo-random port
3048		number generator is used.
3049
3050		Also, the environment variable tftpdstp is used to supply
3051		the TFTP UDP destination port value.  If tftpdstp isn't
3052		defined, the normal port 69 is used.
3053
3054		The purpose for tftpsrcp is to allow a TFTP server to
3055		blindly start the TFTP transfer using the pre-configured
3056		target IP address and UDP port. This has the effect of
3057		"punching through" the (Windows XP) firewall, allowing
3058		the remainder of the TFTP transfer to proceed normally.
3059		A better solution is to properly configure the firewall,
3060		but sometimes that is not allowed.
3061
3062- Hashing support:
3063		CONFIG_CMD_HASH
3064
3065		This enables a generic 'hash' command which can produce
3066		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
3067
3068		CONFIG_HASH_VERIFY
3069
3070		Enable the hash verify command (hash -v). This adds to code
3071		size a little.
3072
3073		CONFIG_SHA1 - This option enables support of hashing using SHA1
3074		algorithm. The hash is calculated in software.
3075		CONFIG_SHA256 - This option enables support of hashing using
3076		SHA256 algorithm. The hash is calculated in software.
3077		CONFIG_SHA_HW_ACCEL - This option enables hardware acceleration
3078		for SHA1/SHA256 hashing.
3079		This affects the 'hash' command and also the
3080		hash_lookup_algo() function.
3081		CONFIG_SHA_PROG_HW_ACCEL - This option enables
3082		hardware-acceleration for SHA1/SHA256 progressive hashing.
3083		Data can be streamed in a block at a time and the hashing
3084		is performed in hardware.
3085
3086		Note: There is also a sha1sum command, which should perhaps
3087		be deprecated in favour of 'hash sha1'.
3088
3089- Freescale i.MX specific commands:
3090		CONFIG_CMD_HDMIDETECT
3091		This enables 'hdmidet' command which returns true if an
3092		HDMI monitor is detected.  This command is i.MX 6 specific.
3093
3094		CONFIG_CMD_BMODE
3095		This enables the 'bmode' (bootmode) command for forcing
3096		a boot from specific media.
3097
3098		This is useful for forcing the ROM's usb downloader to
3099		activate upon a watchdog reset which is nice when iterating
3100		on U-Boot.  Using the reset button or running bmode normal
3101		will set it back to normal.  This command currently
3102		supports i.MX53 and i.MX6.
3103
3104- bootcount support:
3105		CONFIG_BOOTCOUNT_LIMIT
3106
3107		This enables the bootcounter support, see:
3108		http://www.denx.de/wiki/DULG/UBootBootCountLimit
3109
3110		CONFIG_AT91SAM9XE
3111		enable special bootcounter support on at91sam9xe based boards.
3112		CONFIG_BLACKFIN
3113		enable special bootcounter support on blackfin based boards.
3114		CONFIG_SOC_DA8XX
3115		enable special bootcounter support on da850 based boards.
3116		CONFIG_BOOTCOUNT_RAM
3117		enable support for the bootcounter in RAM
3118		CONFIG_BOOTCOUNT_I2C
3119		enable support for the bootcounter on an i2c (like RTC) device.
3120			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
3121			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
3122						    the bootcounter.
3123			CONFIG_BOOTCOUNT_ALEN = address len
3124
3125- Show boot progress:
3126		CONFIG_SHOW_BOOT_PROGRESS
3127
3128		Defining this option allows to add some board-
3129		specific code (calling a user-provided function
3130		"show_boot_progress(int)") that enables you to show
3131		the system's boot progress on some display (for
3132		example, some LED's) on your board. At the moment,
3133		the following checkpoints are implemented:
3134
3135
3136Legacy uImage format:
3137
3138  Arg	Where			When
3139    1	common/cmd_bootm.c	before attempting to boot an image
3140   -1	common/cmd_bootm.c	Image header has bad	 magic number
3141    2	common/cmd_bootm.c	Image header has correct magic number
3142   -2	common/cmd_bootm.c	Image header has bad	 checksum
3143    3	common/cmd_bootm.c	Image header has correct checksum
3144   -3	common/cmd_bootm.c	Image data   has bad	 checksum
3145    4	common/cmd_bootm.c	Image data   has correct checksum
3146   -4	common/cmd_bootm.c	Image is for unsupported architecture
3147    5	common/cmd_bootm.c	Architecture check OK
3148   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
3149    6	common/cmd_bootm.c	Image Type check OK
3150   -6	common/cmd_bootm.c	gunzip uncompression error
3151   -7	common/cmd_bootm.c	Unimplemented compression type
3152    7	common/cmd_bootm.c	Uncompression OK
3153    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3154   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3155
3156    9	common/image.c		Start initial ramdisk verification
3157  -10	common/image.c		Ramdisk header has bad	   magic number
3158  -11	common/image.c		Ramdisk header has bad	   checksum
3159   10	common/image.c		Ramdisk header is OK
3160  -12	common/image.c		Ramdisk data   has bad	   checksum
3161   11	common/image.c		Ramdisk data   has correct checksum
3162   12	common/image.c		Ramdisk verification complete, start loading
3163  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3164   13	common/image.c		Start multifile image verification
3165   14	common/image.c		No initial ramdisk, no multifile, continue.
3166
3167   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3168
3169  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3170  -31	post/post.c		POST test failed, detected by post_output_backlog()
3171  -32	post/post.c		POST test failed, detected by post_run_single()
3172
3173   34	common/cmd_doc.c	before loading a Image from a DOC device
3174  -35	common/cmd_doc.c	Bad usage of "doc" command
3175   35	common/cmd_doc.c	correct usage of "doc" command
3176  -36	common/cmd_doc.c	No boot device
3177   36	common/cmd_doc.c	correct boot device
3178  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3179   37	common/cmd_doc.c	correct chip ID found, device available
3180  -38	common/cmd_doc.c	Read Error on boot device
3181   38	common/cmd_doc.c	reading Image header from DOC device OK
3182  -39	common/cmd_doc.c	Image header has bad magic number
3183   39	common/cmd_doc.c	Image header has correct magic number
3184  -40	common/cmd_doc.c	Error reading Image from DOC device
3185   40	common/cmd_doc.c	Image header has correct magic number
3186   41	common/cmd_ide.c	before loading a Image from a IDE device
3187  -42	common/cmd_ide.c	Bad usage of "ide" command
3188   42	common/cmd_ide.c	correct usage of "ide" command
3189  -43	common/cmd_ide.c	No boot device
3190   43	common/cmd_ide.c	boot device found
3191  -44	common/cmd_ide.c	Device not available
3192   44	common/cmd_ide.c	Device available
3193  -45	common/cmd_ide.c	wrong partition selected
3194   45	common/cmd_ide.c	partition selected
3195  -46	common/cmd_ide.c	Unknown partition table
3196   46	common/cmd_ide.c	valid partition table found
3197  -47	common/cmd_ide.c	Invalid partition type
3198   47	common/cmd_ide.c	correct partition type
3199  -48	common/cmd_ide.c	Error reading Image Header on boot device
3200   48	common/cmd_ide.c	reading Image Header from IDE device OK
3201  -49	common/cmd_ide.c	Image header has bad magic number
3202   49	common/cmd_ide.c	Image header has correct magic number
3203  -50	common/cmd_ide.c	Image header has bad	 checksum
3204   50	common/cmd_ide.c	Image header has correct checksum
3205  -51	common/cmd_ide.c	Error reading Image from IDE device
3206   51	common/cmd_ide.c	reading Image from IDE device OK
3207   52	common/cmd_nand.c	before loading a Image from a NAND device
3208  -53	common/cmd_nand.c	Bad usage of "nand" command
3209   53	common/cmd_nand.c	correct usage of "nand" command
3210  -54	common/cmd_nand.c	No boot device
3211   54	common/cmd_nand.c	boot device found
3212  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3213   55	common/cmd_nand.c	correct chip ID found, device available
3214  -56	common/cmd_nand.c	Error reading Image Header on boot device
3215   56	common/cmd_nand.c	reading Image Header from NAND device OK
3216  -57	common/cmd_nand.c	Image header has bad magic number
3217   57	common/cmd_nand.c	Image header has correct magic number
3218  -58	common/cmd_nand.c	Error reading Image from NAND device
3219   58	common/cmd_nand.c	reading Image from NAND device OK
3220
3221  -60	common/env_common.c	Environment has a bad CRC, using default
3222
3223   64	net/eth.c		starting with Ethernet configuration.
3224  -64	net/eth.c		no Ethernet found.
3225   65	net/eth.c		Ethernet found.
3226
3227  -80	common/cmd_net.c	usage wrong
3228   80	common/cmd_net.c	before calling net_loop()
3229  -81	common/cmd_net.c	some error in net_loop() occurred
3230   81	common/cmd_net.c	net_loop() back without error
3231  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3232   82	common/cmd_net.c	trying automatic boot
3233   83	common/cmd_net.c	running "source" command
3234  -83	common/cmd_net.c	some error in automatic boot or "source" command
3235   84	common/cmd_net.c	end without errors
3236
3237FIT uImage format:
3238
3239  Arg	Where			When
3240  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3241 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3242  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3243 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3244  102	common/cmd_bootm.c	Kernel unit name specified
3245 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3246  103	common/cmd_bootm.c	Found configuration node
3247  104	common/cmd_bootm.c	Got kernel subimage node offset
3248 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3249  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3250 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3251  106	common/cmd_bootm.c	Architecture check OK
3252 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3253  107	common/cmd_bootm.c	Kernel subimage type OK
3254 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3255  108	common/cmd_bootm.c	Got kernel subimage data/size
3256 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3257 -109	common/cmd_bootm.c	Can't get kernel subimage type
3258 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3259 -111	common/cmd_bootm.c	Can't get kernel subimage os
3260 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3261 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3262
3263  120	common/image.c		Start initial ramdisk verification
3264 -120	common/image.c		Ramdisk FIT image has incorrect format
3265  121	common/image.c		Ramdisk FIT image has correct format
3266  122	common/image.c		No ramdisk subimage unit name, using configuration
3267 -122	common/image.c		Can't get configuration for ramdisk subimage
3268  123	common/image.c		Ramdisk unit name specified
3269 -124	common/image.c		Can't get ramdisk subimage node offset
3270  125	common/image.c		Got ramdisk subimage node offset
3271 -125	common/image.c		Ramdisk subimage hash verification failed
3272  126	common/image.c		Ramdisk subimage hash verification OK
3273 -126	common/image.c		Ramdisk subimage for unsupported architecture
3274  127	common/image.c		Architecture check OK
3275 -127	common/image.c		Can't get ramdisk subimage data/size
3276  128	common/image.c		Got ramdisk subimage data/size
3277  129	common/image.c		Can't get ramdisk load address
3278 -129	common/image.c		Got ramdisk load address
3279
3280 -130	common/cmd_doc.c	Incorrect FIT image format
3281  131	common/cmd_doc.c	FIT image format OK
3282
3283 -140	common/cmd_ide.c	Incorrect FIT image format
3284  141	common/cmd_ide.c	FIT image format OK
3285
3286 -150	common/cmd_nand.c	Incorrect FIT image format
3287  151	common/cmd_nand.c	FIT image format OK
3288
3289- legacy image format:
3290		CONFIG_IMAGE_FORMAT_LEGACY
3291		enables the legacy image format support in U-Boot.
3292
3293		Default:
3294		enabled if CONFIG_FIT_SIGNATURE is not defined.
3295
3296		CONFIG_DISABLE_IMAGE_LEGACY
3297		disable the legacy image format
3298
3299		This define is introduced, as the legacy image format is
3300		enabled per default for backward compatibility.
3301
3302- FIT image support:
3303		CONFIG_FIT_DISABLE_SHA256
3304		Supporting SHA256 hashes has quite an impact on binary size.
3305		For constrained systems sha256 hash support can be disabled
3306		with this option.
3307
3308		TODO(sjg@chromium.org): Adjust this option to be positive,
3309		and move it to Kconfig
3310
3311- Standalone program support:
3312		CONFIG_STANDALONE_LOAD_ADDR
3313
3314		This option defines a board specific value for the
3315		address where standalone program gets loaded, thus
3316		overwriting the architecture dependent default
3317		settings.
3318
3319- Frame Buffer Address:
3320		CONFIG_FB_ADDR
3321
3322		Define CONFIG_FB_ADDR if you want to use specific
3323		address for frame buffer.  This is typically the case
3324		when using a graphics controller has separate video
3325		memory.  U-Boot will then place the frame buffer at
3326		the given address instead of dynamically reserving it
3327		in system RAM by calling lcd_setmem(), which grabs
3328		the memory for the frame buffer depending on the
3329		configured panel size.
3330
3331		Please see board_init_f function.
3332
3333- Automatic software updates via TFTP server
3334		CONFIG_UPDATE_TFTP
3335		CONFIG_UPDATE_TFTP_CNT_MAX
3336		CONFIG_UPDATE_TFTP_MSEC_MAX
3337
3338		These options enable and control the auto-update feature;
3339		for a more detailed description refer to doc/README.update.
3340
3341- MTD Support (mtdparts command, UBI support)
3342		CONFIG_MTD_DEVICE
3343
3344		Adds the MTD device infrastructure from the Linux kernel.
3345		Needed for mtdparts command support.
3346
3347		CONFIG_MTD_PARTITIONS
3348
3349		Adds the MTD partitioning infrastructure from the Linux
3350		kernel. Needed for UBI support.
3351
3352- UBI support
3353		CONFIG_CMD_UBI
3354
3355		Adds commands for interacting with MTD partitions formatted
3356		with the UBI flash translation layer
3357
3358		Requires also defining CONFIG_RBTREE
3359
3360		CONFIG_UBI_SILENCE_MSG
3361
3362		Make the verbose messages from UBI stop printing.  This leaves
3363		warnings and errors enabled.
3364
3365
3366		CONFIG_MTD_UBI_WL_THRESHOLD
3367		This parameter defines the maximum difference between the highest
3368		erase counter value and the lowest erase counter value of eraseblocks
3369		of UBI devices. When this threshold is exceeded, UBI starts performing
3370		wear leveling by means of moving data from eraseblock with low erase
3371		counter to eraseblocks with high erase counter.
3372
3373		The default value should be OK for SLC NAND flashes, NOR flashes and
3374		other flashes which have eraseblock life-cycle 100000 or more.
3375		However, in case of MLC NAND flashes which typically have eraseblock
3376		life-cycle less than 10000, the threshold should be lessened (e.g.,
3377		to 128 or 256, although it does not have to be power of 2).
3378
3379		default: 4096
3380
3381		CONFIG_MTD_UBI_BEB_LIMIT
3382		This option specifies the maximum bad physical eraseblocks UBI
3383		expects on the MTD device (per 1024 eraseblocks). If the
3384		underlying flash does not admit of bad eraseblocks (e.g. NOR
3385		flash), this value is ignored.
3386
3387		NAND datasheets often specify the minimum and maximum NVM
3388		(Number of Valid Blocks) for the flashes' endurance lifetime.
3389		The maximum expected bad eraseblocks per 1024 eraseblocks
3390		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3391		which gives 20 for most NANDs (MaxNVB is basically the total
3392		count of eraseblocks on the chip).
3393
3394		To put it differently, if this value is 20, UBI will try to
3395		reserve about 1.9% of physical eraseblocks for bad blocks
3396		handling. And that will be 1.9% of eraseblocks on the entire
3397		NAND chip, not just the MTD partition UBI attaches. This means
3398		that if you have, say, a NAND flash chip admits maximum 40 bad
3399		eraseblocks, and it is split on two MTD partitions of the same
3400		size, UBI will reserve 40 eraseblocks when attaching a
3401		partition.
3402
3403		default: 20
3404
3405		CONFIG_MTD_UBI_FASTMAP
3406		Fastmap is a mechanism which allows attaching an UBI device
3407		in nearly constant time. Instead of scanning the whole MTD device it
3408		only has to locate a checkpoint (called fastmap) on the device.
3409		The on-flash fastmap contains all information needed to attach
3410		the device. Using fastmap makes only sense on large devices where
3411		attaching by scanning takes long. UBI will not automatically install
3412		a fastmap on old images, but you can set the UBI parameter
3413		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3414		that fastmap-enabled images are still usable with UBI implementations
3415		without	fastmap support. On typical flash devices the whole fastmap
3416		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3417
3418		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3419		Set this parameter to enable fastmap automatically on images
3420		without a fastmap.
3421		default: 0
3422
3423		CONFIG_MTD_UBI_FM_DEBUG
3424		Enable UBI fastmap debug
3425		default: 0
3426
3427- UBIFS support
3428		CONFIG_CMD_UBIFS
3429
3430		Adds commands for interacting with UBI volumes formatted as
3431		UBIFS.  UBIFS is read-only in u-boot.
3432
3433		Requires UBI support as well as CONFIG_LZO
3434
3435		CONFIG_UBIFS_SILENCE_MSG
3436
3437		Make the verbose messages from UBIFS stop printing.  This leaves
3438		warnings and errors enabled.
3439
3440- SPL framework
3441		CONFIG_SPL
3442		Enable building of SPL globally.
3443
3444		CONFIG_SPL_LDSCRIPT
3445		LDSCRIPT for linking the SPL binary.
3446
3447		CONFIG_SPL_MAX_FOOTPRINT
3448		Maximum size in memory allocated to the SPL, BSS included.
3449		When defined, the linker checks that the actual memory
3450		used by SPL from _start to __bss_end does not exceed it.
3451		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3452		must not be both defined at the same time.
3453
3454		CONFIG_SPL_MAX_SIZE
3455		Maximum size of the SPL image (text, data, rodata, and
3456		linker lists sections), BSS excluded.
3457		When defined, the linker checks that the actual size does
3458		not exceed it.
3459
3460		CONFIG_SPL_TEXT_BASE
3461		TEXT_BASE for linking the SPL binary.
3462
3463		CONFIG_SPL_RELOC_TEXT_BASE
3464		Address to relocate to.  If unspecified, this is equal to
3465		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3466
3467		CONFIG_SPL_BSS_START_ADDR
3468		Link address for the BSS within the SPL binary.
3469
3470		CONFIG_SPL_BSS_MAX_SIZE
3471		Maximum size in memory allocated to the SPL BSS.
3472		When defined, the linker checks that the actual memory used
3473		by SPL from __bss_start to __bss_end does not exceed it.
3474		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3475		must not be both defined at the same time.
3476
3477		CONFIG_SPL_STACK
3478		Adress of the start of the stack SPL will use
3479
3480		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3481		When defined, SPL will panic() if the image it has
3482		loaded does not have a signature.
3483		Defining this is useful when code which loads images
3484		in SPL cannot guarantee that absolutely all read errors
3485		will be caught.
3486		An example is the LPC32XX MLC NAND driver, which will
3487		consider that a completely unreadable NAND block is bad,
3488		and thus should be skipped silently.
3489
3490		CONFIG_SPL_RELOC_STACK
3491		Adress of the start of the stack SPL will use after
3492		relocation.  If unspecified, this is equal to
3493		CONFIG_SPL_STACK.
3494
3495		CONFIG_SYS_SPL_MALLOC_START
3496		Starting address of the malloc pool used in SPL.
3497		When this option is set the full malloc is used in SPL and
3498		it is set up by spl_init() and before that, the simple malloc()
3499		can be used if CONFIG_SYS_MALLOC_F is defined.
3500
3501		CONFIG_SYS_SPL_MALLOC_SIZE
3502		The size of the malloc pool used in SPL.
3503
3504		CONFIG_SPL_FRAMEWORK
3505		Enable the SPL framework under common/.  This framework
3506		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3507		NAND loading of the Linux Kernel.
3508
3509		CONFIG_SPL_OS_BOOT
3510		Enable booting directly to an OS from SPL.
3511		See also: doc/README.falcon
3512
3513		CONFIG_SPL_DISPLAY_PRINT
3514		For ARM, enable an optional function to print more information
3515		about the running system.
3516
3517		CONFIG_SPL_INIT_MINIMAL
3518		Arch init code should be built for a very small image
3519
3520		CONFIG_SPL_LIBCOMMON_SUPPORT
3521		Support for common/libcommon.o in SPL binary
3522
3523		CONFIG_SPL_LIBDISK_SUPPORT
3524		Support for disk/libdisk.o in SPL binary
3525
3526		CONFIG_SPL_I2C_SUPPORT
3527		Support for drivers/i2c/libi2c.o in SPL binary
3528
3529		CONFIG_SPL_GPIO_SUPPORT
3530		Support for drivers/gpio/libgpio.o in SPL binary
3531
3532		CONFIG_SPL_MMC_SUPPORT
3533		Support for drivers/mmc/libmmc.o in SPL binary
3534
3535		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3536		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3537		Address and partition on the MMC to load U-Boot from
3538		when the MMC is being used in raw mode.
3539
3540		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3541		Partition on the MMC to load U-Boot from when the MMC is being
3542		used in raw mode
3543
3544		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3545		Sector to load kernel uImage from when MMC is being
3546		used in raw mode (for Falcon mode)
3547
3548		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3549		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3550		Sector and number of sectors to load kernel argument
3551		parameters from when MMC is being used in raw mode
3552		(for falcon mode)
3553
3554		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3555		Partition on the MMC to load U-Boot from when the MMC is being
3556		used in fs mode
3557
3558		CONFIG_SPL_FAT_SUPPORT
3559		Support for fs/fat/libfat.o in SPL binary
3560
3561		CONFIG_SPL_EXT_SUPPORT
3562		Support for EXT filesystem in SPL binary
3563
3564		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3565		Filename to read to load U-Boot when reading from filesystem
3566
3567		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3568		Filename to read to load kernel uImage when reading
3569		from filesystem (for Falcon mode)
3570
3571		CONFIG_SPL_FS_LOAD_ARGS_NAME
3572		Filename to read to load kernel argument parameters
3573		when reading from filesystem (for Falcon mode)
3574
3575		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3576		Set this for NAND SPL on PPC mpc83xx targets, so that
3577		start.S waits for the rest of the SPL to load before
3578		continuing (the hardware starts execution after just
3579		loading the first page rather than the full 4K).
3580
3581		CONFIG_SPL_SKIP_RELOCATE
3582		Avoid SPL relocation
3583
3584		CONFIG_SPL_NAND_BASE
3585		Include nand_base.c in the SPL.  Requires
3586		CONFIG_SPL_NAND_DRIVERS.
3587
3588		CONFIG_SPL_NAND_DRIVERS
3589		SPL uses normal NAND drivers, not minimal drivers.
3590
3591		CONFIG_SPL_NAND_ECC
3592		Include standard software ECC in the SPL
3593
3594		CONFIG_SPL_NAND_SIMPLE
3595		Support for NAND boot using simple NAND drivers that
3596		expose the cmd_ctrl() interface.
3597
3598		CONFIG_SPL_MTD_SUPPORT
3599		Support for the MTD subsystem within SPL.  Useful for
3600		environment on NAND support within SPL.
3601
3602		CONFIG_SPL_NAND_RAW_ONLY
3603		Support to boot only raw u-boot.bin images. Use this only
3604		if you need to save space.
3605
3606		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3607		Set for the SPL on PPC mpc8xxx targets, support for
3608		drivers/ddr/fsl/libddr.o in SPL binary.
3609
3610		CONFIG_SPL_COMMON_INIT_DDR
3611		Set for common ddr init with serial presence detect in
3612		SPL binary.
3613
3614		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3615		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3616		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3617		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3618		CONFIG_SYS_NAND_ECCBYTES
3619		Defines the size and behavior of the NAND that SPL uses
3620		to read U-Boot
3621
3622		CONFIG_SPL_NAND_BOOT
3623		Add support NAND boot
3624
3625		CONFIG_SYS_NAND_U_BOOT_OFFS
3626		Location in NAND to read U-Boot from
3627
3628		CONFIG_SYS_NAND_U_BOOT_DST
3629		Location in memory to load U-Boot to
3630
3631		CONFIG_SYS_NAND_U_BOOT_SIZE
3632		Size of image to load
3633
3634		CONFIG_SYS_NAND_U_BOOT_START
3635		Entry point in loaded image to jump to
3636
3637		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3638		Define this if you need to first read the OOB and then the
3639		data. This is used, for example, on davinci platforms.
3640
3641		CONFIG_SPL_OMAP3_ID_NAND
3642		Support for an OMAP3-specific set of functions to return the
3643		ID and MFR of the first attached NAND chip, if present.
3644
3645		CONFIG_SPL_SERIAL_SUPPORT
3646		Support for drivers/serial/libserial.o in SPL binary
3647
3648		CONFIG_SPL_SPI_FLASH_SUPPORT
3649		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3650
3651		CONFIG_SPL_SPI_SUPPORT
3652		Support for drivers/spi/libspi.o in SPL binary
3653
3654		CONFIG_SPL_RAM_DEVICE
3655		Support for running image already present in ram, in SPL binary
3656
3657		CONFIG_SPL_LIBGENERIC_SUPPORT
3658		Support for lib/libgeneric.o in SPL binary
3659
3660		CONFIG_SPL_ENV_SUPPORT
3661		Support for the environment operating in SPL binary
3662
3663		CONFIG_SPL_NET_SUPPORT
3664		Support for the net/libnet.o in SPL binary.
3665		It conflicts with SPL env from storage medium specified by
3666		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3667
3668		CONFIG_SPL_PAD_TO
3669		Image offset to which the SPL should be padded before appending
3670		the SPL payload. By default, this is defined as
3671		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3672		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3673		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3674
3675		CONFIG_SPL_TARGET
3676		Final target image containing SPL and payload.  Some SPLs
3677		use an arch-specific makefile fragment instead, for
3678		example if more than one image needs to be produced.
3679
3680		CONFIG_FIT_SPL_PRINT
3681		Printing information about a FIT image adds quite a bit of
3682		code to SPL. So this is normally disabled in SPL. Use this
3683		option to re-enable it. This will affect the output of the
3684		bootm command when booting a FIT image.
3685
3686- TPL framework
3687		CONFIG_TPL
3688		Enable building of TPL globally.
3689
3690		CONFIG_TPL_PAD_TO
3691		Image offset to which the TPL should be padded before appending
3692		the TPL payload. By default, this is defined as
3693		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3694		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3695		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3696
3697- Interrupt support (PPC):
3698
3699		There are common interrupt_init() and timer_interrupt()
3700		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3701		for CPU specific initialization. interrupt_init_cpu()
3702		should set decrementer_count to appropriate value. If
3703		CPU resets decrementer automatically after interrupt
3704		(ppc4xx) it should set decrementer_count to zero.
3705		timer_interrupt() calls timer_interrupt_cpu() for CPU
3706		specific handling. If board has watchdog / status_led
3707		/ other_activity_monitor it works automatically from
3708		general timer_interrupt().
3709
3710
3711Board initialization settings:
3712------------------------------
3713
3714During Initialization u-boot calls a number of board specific functions
3715to allow the preparation of board specific prerequisites, e.g. pin setup
3716before drivers are initialized. To enable these callbacks the
3717following configuration macros have to be defined. Currently this is
3718architecture specific, so please check arch/your_architecture/lib/board.c
3719typically in board_init_f() and board_init_r().
3720
3721- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3722- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3723- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3724- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3725
3726Configuration Settings:
3727-----------------------
3728
3729- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3730		Optionally it can be defined to support 64-bit memory commands.
3731
3732- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3733		undefine this when you're short of memory.
3734
3735- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3736		width of the commands listed in the 'help' command output.
3737
3738- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3739		prompt for user input.
3740
3741- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3742
3743- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3744
3745- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3746
3747- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3748		the application (usually a Linux kernel) when it is
3749		booted
3750
3751- CONFIG_SYS_BAUDRATE_TABLE:
3752		List of legal baudrate settings for this board.
3753
3754- CONFIG_SYS_CONSOLE_INFO_QUIET
3755		Suppress display of console information at boot.
3756
3757- CONFIG_SYS_CONSOLE_IS_IN_ENV
3758		If the board specific function
3759			extern int overwrite_console (void);
3760		returns 1, the stdin, stderr and stdout are switched to the
3761		serial port, else the settings in the environment are used.
3762
3763- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3764		Enable the call to overwrite_console().
3765
3766- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3767		Enable overwrite of previous console environment settings.
3768
3769- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3770		Begin and End addresses of the area used by the
3771		simple memory test.
3772
3773- CONFIG_SYS_ALT_MEMTEST:
3774		Enable an alternate, more extensive memory test.
3775
3776- CONFIG_SYS_MEMTEST_SCRATCH:
3777		Scratch address used by the alternate memory test
3778		You only need to set this if address zero isn't writeable
3779
3780- CONFIG_SYS_MEM_RESERVE_SECURE
3781		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
3782		is substracted from total RAM and won't be reported to OS.
3783		This memory can be used as secure memory. A variable
3784		gd->secure_ram is used to track the location. In systems
3785		the RAM base is not zero, or RAM is divided into banks,
3786		this variable needs to be recalcuated to get the address.
3787
3788- CONFIG_SYS_MEM_TOP_HIDE:
3789		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3790		this specified memory area will get subtracted from the top
3791		(end) of RAM and won't get "touched" at all by U-Boot. By
3792		fixing up gd->ram_size the Linux kernel should gets passed
3793		the now "corrected" memory size and won't touch it either.
3794		This should work for arch/ppc and arch/powerpc. Only Linux
3795		board ports in arch/powerpc with bootwrapper support that
3796		recalculate the memory size from the SDRAM controller setup
3797		will have to get fixed in Linux additionally.
3798
3799		This option can be used as a workaround for the 440EPx/GRx
3800		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3801		be touched.
3802
3803		WARNING: Please make sure that this value is a multiple of
3804		the Linux page size (normally 4k). If this is not the case,
3805		then the end address of the Linux memory will be located at a
3806		non page size aligned address and this could cause major
3807		problems.
3808
3809- CONFIG_SYS_LOADS_BAUD_CHANGE:
3810		Enable temporary baudrate change while serial download
3811
3812- CONFIG_SYS_SDRAM_BASE:
3813		Physical start address of SDRAM. _Must_ be 0 here.
3814
3815- CONFIG_SYS_MBIO_BASE:
3816		Physical start address of Motherboard I/O (if using a
3817		Cogent motherboard)
3818
3819- CONFIG_SYS_FLASH_BASE:
3820		Physical start address of Flash memory.
3821
3822- CONFIG_SYS_MONITOR_BASE:
3823		Physical start address of boot monitor code (set by
3824		make config files to be same as the text base address
3825		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3826		CONFIG_SYS_FLASH_BASE when booting from flash.
3827
3828- CONFIG_SYS_MONITOR_LEN:
3829		Size of memory reserved for monitor code, used to
3830		determine _at_compile_time_ (!) if the environment is
3831		embedded within the U-Boot image, or in a separate
3832		flash sector.
3833
3834- CONFIG_SYS_MALLOC_LEN:
3835		Size of DRAM reserved for malloc() use.
3836
3837- CONFIG_SYS_MALLOC_F_LEN
3838		Size of the malloc() pool for use before relocation. If
3839		this is defined, then a very simple malloc() implementation
3840		will become available before relocation. The address is just
3841		below the global data, and the stack is moved down to make
3842		space.
3843
3844		This feature allocates regions with increasing addresses
3845		within the region. calloc() is supported, but realloc()
3846		is not available. free() is supported but does nothing.
3847		The memory will be freed (or in fact just forgotten) when
3848		U-Boot relocates itself.
3849
3850		Pre-relocation malloc() is only supported on ARM and sandbox
3851		at present but is fairly easy to enable for other archs.
3852
3853- CONFIG_SYS_MALLOC_SIMPLE
3854		Provides a simple and small malloc() and calloc() for those
3855		boards which do not use the full malloc in SPL (which is
3856		enabled with CONFIG_SYS_SPL_MALLOC_START).
3857
3858- CONFIG_SYS_NONCACHED_MEMORY:
3859		Size of non-cached memory area. This area of memory will be
3860		typically located right below the malloc() area and mapped
3861		uncached in the MMU. This is useful for drivers that would
3862		otherwise require a lot of explicit cache maintenance. For
3863		some drivers it's also impossible to properly maintain the
3864		cache. For example if the regions that need to be flushed
3865		are not a multiple of the cache-line size, *and* padding
3866		cannot be allocated between the regions to align them (i.e.
3867		if the HW requires a contiguous array of regions, and the
3868		size of each region is not cache-aligned), then a flush of
3869		one region may result in overwriting data that hardware has
3870		written to another region in the same cache-line. This can
3871		happen for example in network drivers where descriptors for
3872		buffers are typically smaller than the CPU cache-line (e.g.
3873		16 bytes vs. 32 or 64 bytes).
3874
3875		Non-cached memory is only supported on 32-bit ARM at present.
3876
3877- CONFIG_SYS_BOOTM_LEN:
3878		Normally compressed uImages are limited to an
3879		uncompressed size of 8 MBytes. If this is not enough,
3880		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3881		to adjust this setting to your needs.
3882
3883- CONFIG_SYS_BOOTMAPSZ:
3884		Maximum size of memory mapped by the startup code of
3885		the Linux kernel; all data that must be processed by
3886		the Linux kernel (bd_info, boot arguments, FDT blob if
3887		used) must be put below this limit, unless "bootm_low"
3888		environment variable is defined and non-zero. In such case
3889		all data for the Linux kernel must be between "bootm_low"
3890		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3891		variable "bootm_mapsize" will override the value of
3892		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3893		then the value in "bootm_size" will be used instead.
3894
3895- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3896		Enable initrd_high functionality.  If defined then the
3897		initrd_high feature is enabled and the bootm ramdisk subcommand
3898		is enabled.
3899
3900- CONFIG_SYS_BOOT_GET_CMDLINE:
3901		Enables allocating and saving kernel cmdline in space between
3902		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3903
3904- CONFIG_SYS_BOOT_GET_KBD:
3905		Enables allocating and saving a kernel copy of the bd_info in
3906		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3907
3908- CONFIG_SYS_MAX_FLASH_BANKS:
3909		Max number of Flash memory banks
3910
3911- CONFIG_SYS_MAX_FLASH_SECT:
3912		Max number of sectors on a Flash chip
3913
3914- CONFIG_SYS_FLASH_ERASE_TOUT:
3915		Timeout for Flash erase operations (in ms)
3916
3917- CONFIG_SYS_FLASH_WRITE_TOUT:
3918		Timeout for Flash write operations (in ms)
3919
3920- CONFIG_SYS_FLASH_LOCK_TOUT
3921		Timeout for Flash set sector lock bit operation (in ms)
3922
3923- CONFIG_SYS_FLASH_UNLOCK_TOUT
3924		Timeout for Flash clear lock bits operation (in ms)
3925
3926- CONFIG_SYS_FLASH_PROTECTION
3927		If defined, hardware flash sectors protection is used
3928		instead of U-Boot software protection.
3929
3930- CONFIG_SYS_DIRECT_FLASH_TFTP:
3931
3932		Enable TFTP transfers directly to flash memory;
3933		without this option such a download has to be
3934		performed in two steps: (1) download to RAM, and (2)
3935		copy from RAM to flash.
3936
3937		The two-step approach is usually more reliable, since
3938		you can check if the download worked before you erase
3939		the flash, but in some situations (when system RAM is
3940		too limited to allow for a temporary copy of the
3941		downloaded image) this option may be very useful.
3942
3943- CONFIG_SYS_FLASH_CFI:
3944		Define if the flash driver uses extra elements in the
3945		common flash structure for storing flash geometry.
3946
3947- CONFIG_FLASH_CFI_DRIVER
3948		This option also enables the building of the cfi_flash driver
3949		in the drivers directory
3950
3951- CONFIG_FLASH_CFI_MTD
3952		This option enables the building of the cfi_mtd driver
3953		in the drivers directory. The driver exports CFI flash
3954		to the MTD layer.
3955
3956- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3957		Use buffered writes to flash.
3958
3959- CONFIG_FLASH_SPANSION_S29WS_N
3960		s29ws-n MirrorBit flash has non-standard addresses for buffered
3961		write commands.
3962
3963- CONFIG_SYS_FLASH_QUIET_TEST
3964		If this option is defined, the common CFI flash doesn't
3965		print it's warning upon not recognized FLASH banks. This
3966		is useful, if some of the configured banks are only
3967		optionally available.
3968
3969- CONFIG_FLASH_SHOW_PROGRESS
3970		If defined (must be an integer), print out countdown
3971		digits and dots.  Recommended value: 45 (9..1) for 80
3972		column displays, 15 (3..1) for 40 column displays.
3973
3974- CONFIG_FLASH_VERIFY
3975		If defined, the content of the flash (destination) is compared
3976		against the source after the write operation. An error message
3977		will be printed when the contents are not identical.
3978		Please note that this option is useless in nearly all cases,
3979		since such flash programming errors usually are detected earlier
3980		while unprotecting/erasing/programming. Please only enable
3981		this option if you really know what you are doing.
3982
3983- CONFIG_SYS_RX_ETH_BUFFER:
3984		Defines the number of Ethernet receive buffers. On some
3985		Ethernet controllers it is recommended to set this value
3986		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3987		buffers can be full shortly after enabling the interface
3988		on high Ethernet traffic.
3989		Defaults to 4 if not defined.
3990
3991- CONFIG_ENV_MAX_ENTRIES
3992
3993	Maximum number of entries in the hash table that is used
3994	internally to store the environment settings. The default
3995	setting is supposed to be generous and should work in most
3996	cases. This setting can be used to tune behaviour; see
3997	lib/hashtable.c for details.
3998
3999- CONFIG_ENV_FLAGS_LIST_DEFAULT
4000- CONFIG_ENV_FLAGS_LIST_STATIC
4001	Enable validation of the values given to environment variables when
4002	calling env set.  Variables can be restricted to only decimal,
4003	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
4004	the variables can also be restricted to IP address or MAC address.
4005
4006	The format of the list is:
4007		type_attribute = [s|d|x|b|i|m]
4008		access_attribute = [a|r|o|c]
4009		attributes = type_attribute[access_attribute]
4010		entry = variable_name[:attributes]
4011		list = entry[,list]
4012
4013	The type attributes are:
4014		s - String (default)
4015		d - Decimal
4016		x - Hexadecimal
4017		b - Boolean ([1yYtT|0nNfF])
4018		i - IP address
4019		m - MAC address
4020
4021	The access attributes are:
4022		a - Any (default)
4023		r - Read-only
4024		o - Write-once
4025		c - Change-default
4026
4027	- CONFIG_ENV_FLAGS_LIST_DEFAULT
4028		Define this to a list (string) to define the ".flags"
4029		environment variable in the default or embedded environment.
4030
4031	- CONFIG_ENV_FLAGS_LIST_STATIC
4032		Define this to a list (string) to define validation that
4033		should be done if an entry is not found in the ".flags"
4034		environment variable.  To override a setting in the static
4035		list, simply add an entry for the same variable name to the
4036		".flags" variable.
4037
4038	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4039	regular expression. This allows multiple variables to define the same
4040	flags without explicitly listing them for each variable.
4041
4042- CONFIG_ENV_ACCESS_IGNORE_FORCE
4043	If defined, don't allow the -f switch to env set override variable
4044	access flags.
4045
4046- CONFIG_SYS_GENERIC_BOARD
4047	This selects the architecture-generic board system instead of the
4048	architecture-specific board files. It is intended to move boards
4049	to this new framework over time. Defining this will disable the
4050	arch/foo/lib/board.c file and use common/board_f.c and
4051	common/board_r.c instead. To use this option your architecture
4052	must support it (i.e. must select HAVE_GENERIC_BOARD in arch/Kconfig).
4053	If you find problems enabling this option on your board please report
4054	the problem and send patches!
4055
4056- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
4057	This is set by OMAP boards for the max time that reset should
4058	be asserted. See doc/README.omap-reset-time for details on how
4059	the value can be calculated on a given board.
4060
4061- CONFIG_USE_STDINT
4062	If stdint.h is available with your toolchain you can define this
4063	option to enable it. You can provide option 'USE_STDINT=1' when
4064	building U-Boot to enable this.
4065
4066The following definitions that deal with the placement and management
4067of environment data (variable area); in general, we support the
4068following configurations:
4069
4070- CONFIG_BUILD_ENVCRC:
4071
4072	Builds up envcrc with the target environment so that external utils
4073	may easily extract it and embed it in final U-Boot images.
4074
4075- CONFIG_ENV_IS_IN_FLASH:
4076
4077	Define this if the environment is in flash memory.
4078
4079	a) The environment occupies one whole flash sector, which is
4080	   "embedded" in the text segment with the U-Boot code. This
4081	   happens usually with "bottom boot sector" or "top boot
4082	   sector" type flash chips, which have several smaller
4083	   sectors at the start or the end. For instance, such a
4084	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
4085	   such a case you would place the environment in one of the
4086	   4 kB sectors - with U-Boot code before and after it. With
4087	   "top boot sector" type flash chips, you would put the
4088	   environment in one of the last sectors, leaving a gap
4089	   between U-Boot and the environment.
4090
4091	- CONFIG_ENV_OFFSET:
4092
4093	   Offset of environment data (variable area) to the
4094	   beginning of flash memory; for instance, with bottom boot
4095	   type flash chips the second sector can be used: the offset
4096	   for this sector is given here.
4097
4098	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
4099
4100	- CONFIG_ENV_ADDR:
4101
4102	   This is just another way to specify the start address of
4103	   the flash sector containing the environment (instead of
4104	   CONFIG_ENV_OFFSET).
4105
4106	- CONFIG_ENV_SECT_SIZE:
4107
4108	   Size of the sector containing the environment.
4109
4110
4111	b) Sometimes flash chips have few, equal sized, BIG sectors.
4112	   In such a case you don't want to spend a whole sector for
4113	   the environment.
4114
4115	- CONFIG_ENV_SIZE:
4116
4117	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
4118	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
4119	   of this flash sector for the environment. This saves
4120	   memory for the RAM copy of the environment.
4121
4122	   It may also save flash memory if you decide to use this
4123	   when your environment is "embedded" within U-Boot code,
4124	   since then the remainder of the flash sector could be used
4125	   for U-Boot code. It should be pointed out that this is
4126	   STRONGLY DISCOURAGED from a robustness point of view:
4127	   updating the environment in flash makes it always
4128	   necessary to erase the WHOLE sector. If something goes
4129	   wrong before the contents has been restored from a copy in
4130	   RAM, your target system will be dead.
4131
4132	- CONFIG_ENV_ADDR_REDUND
4133	  CONFIG_ENV_SIZE_REDUND
4134
4135	   These settings describe a second storage area used to hold
4136	   a redundant copy of the environment data, so that there is
4137	   a valid backup copy in case there is a power failure during
4138	   a "saveenv" operation.
4139
4140BE CAREFUL! Any changes to the flash layout, and some changes to the
4141source code will make it necessary to adapt <board>/u-boot.lds*
4142accordingly!
4143
4144
4145- CONFIG_ENV_IS_IN_NVRAM:
4146
4147	Define this if you have some non-volatile memory device
4148	(NVRAM, battery buffered SRAM) which you want to use for the
4149	environment.
4150
4151	- CONFIG_ENV_ADDR:
4152	- CONFIG_ENV_SIZE:
4153
4154	  These two #defines are used to determine the memory area you
4155	  want to use for environment. It is assumed that this memory
4156	  can just be read and written to, without any special
4157	  provision.
4158
4159BE CAREFUL! The first access to the environment happens quite early
4160in U-Boot initialization (when we try to get the setting of for the
4161console baudrate). You *MUST* have mapped your NVRAM area then, or
4162U-Boot will hang.
4163
4164Please note that even with NVRAM we still use a copy of the
4165environment in RAM: we could work on NVRAM directly, but we want to
4166keep settings there always unmodified except somebody uses "saveenv"
4167to save the current settings.
4168
4169
4170- CONFIG_ENV_IS_IN_EEPROM:
4171
4172	Use this if you have an EEPROM or similar serial access
4173	device and a driver for it.
4174
4175	- CONFIG_ENV_OFFSET:
4176	- CONFIG_ENV_SIZE:
4177
4178	  These two #defines specify the offset and size of the
4179	  environment area within the total memory of your EEPROM.
4180
4181	- CONFIG_SYS_I2C_EEPROM_ADDR:
4182	  If defined, specified the chip address of the EEPROM device.
4183	  The default address is zero.
4184
4185	- CONFIG_SYS_I2C_EEPROM_BUS:
4186	  If defined, specified the i2c bus of the EEPROM device.
4187
4188	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
4189	  If defined, the number of bits used to address bytes in a
4190	  single page in the EEPROM device.  A 64 byte page, for example
4191	  would require six bits.
4192
4193	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
4194	  If defined, the number of milliseconds to delay between
4195	  page writes.	The default is zero milliseconds.
4196
4197	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
4198	  The length in bytes of the EEPROM memory array address.  Note
4199	  that this is NOT the chip address length!
4200
4201	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
4202	  EEPROM chips that implement "address overflow" are ones
4203	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
4204	  address and the extra bits end up in the "chip address" bit
4205	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
4206	  byte chips.
4207
4208	  Note that we consider the length of the address field to
4209	  still be one byte because the extra address bits are hidden
4210	  in the chip address.
4211
4212	- CONFIG_SYS_EEPROM_SIZE:
4213	  The size in bytes of the EEPROM device.
4214
4215	- CONFIG_ENV_EEPROM_IS_ON_I2C
4216	  define this, if you have I2C and SPI activated, and your
4217	  EEPROM, which holds the environment, is on the I2C bus.
4218
4219	- CONFIG_I2C_ENV_EEPROM_BUS
4220	  if you have an Environment on an EEPROM reached over
4221	  I2C muxes, you can define here, how to reach this
4222	  EEPROM. For example:
4223
4224	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
4225
4226	  EEPROM which holds the environment, is reached over
4227	  a pca9547 i2c mux with address 0x70, channel 3.
4228
4229- CONFIG_ENV_IS_IN_DATAFLASH:
4230
4231	Define this if you have a DataFlash memory device which you
4232	want to use for the environment.
4233
4234	- CONFIG_ENV_OFFSET:
4235	- CONFIG_ENV_ADDR:
4236	- CONFIG_ENV_SIZE:
4237
4238	  These three #defines specify the offset and size of the
4239	  environment area within the total memory of your DataFlash placed
4240	  at the specified address.
4241
4242- CONFIG_ENV_IS_IN_SPI_FLASH:
4243
4244	Define this if you have a SPI Flash memory device which you
4245	want to use for the environment.
4246
4247	- CONFIG_ENV_OFFSET:
4248	- CONFIG_ENV_SIZE:
4249
4250	  These two #defines specify the offset and size of the
4251	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
4252	  aligned to an erase sector boundary.
4253
4254	- CONFIG_ENV_SECT_SIZE:
4255
4256	  Define the SPI flash's sector size.
4257
4258	- CONFIG_ENV_OFFSET_REDUND (optional):
4259
4260	  This setting describes a second storage area of CONFIG_ENV_SIZE
4261	  size used to hold a redundant copy of the environment data, so
4262	  that there is a valid backup copy in case there is a power failure
4263	  during a "saveenv" operation. CONFIG_ENV_OFFSET_RENDUND must be
4264	  aligned to an erase sector boundary.
4265
4266	- CONFIG_ENV_SPI_BUS (optional):
4267	- CONFIG_ENV_SPI_CS (optional):
4268
4269	  Define the SPI bus and chip select. If not defined they will be 0.
4270
4271	- CONFIG_ENV_SPI_MAX_HZ (optional):
4272
4273	  Define the SPI max work clock. If not defined then use 1MHz.
4274
4275	- CONFIG_ENV_SPI_MODE (optional):
4276
4277	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4278
4279- CONFIG_ENV_IS_IN_REMOTE:
4280
4281	Define this if you have a remote memory space which you
4282	want to use for the local device's environment.
4283
4284	- CONFIG_ENV_ADDR:
4285	- CONFIG_ENV_SIZE:
4286
4287	  These two #defines specify the address and size of the
4288	  environment area within the remote memory space. The
4289	  local device can get the environment from remote memory
4290	  space by SRIO or PCIE links.
4291
4292BE CAREFUL! For some special cases, the local device can not use
4293"saveenv" command. For example, the local device will get the
4294environment stored in a remote NOR flash by SRIO or PCIE link,
4295but it can not erase, write this NOR flash by SRIO or PCIE interface.
4296
4297- CONFIG_ENV_IS_IN_NAND:
4298
4299	Define this if you have a NAND device which you want to use
4300	for the environment.
4301
4302	- CONFIG_ENV_OFFSET:
4303	- CONFIG_ENV_SIZE:
4304
4305	  These two #defines specify the offset and size of the environment
4306	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4307	  aligned to an erase block boundary.
4308
4309	- CONFIG_ENV_OFFSET_REDUND (optional):
4310
4311	  This setting describes a second storage area of CONFIG_ENV_SIZE
4312	  size used to hold a redundant copy of the environment data, so
4313	  that there is a valid backup copy in case there is a power failure
4314	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
4315	  aligned to an erase block boundary.
4316
4317	- CONFIG_ENV_RANGE (optional):
4318
4319	  Specifies the length of the region in which the environment
4320	  can be written.  This should be a multiple of the NAND device's
4321	  block size.  Specifying a range with more erase blocks than
4322	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4323	  the range to be avoided.
4324
4325	- CONFIG_ENV_OFFSET_OOB (optional):
4326
4327	  Enables support for dynamically retrieving the offset of the
4328	  environment from block zero's out-of-band data.  The
4329	  "nand env.oob" command can be used to record this offset.
4330	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4331	  using CONFIG_ENV_OFFSET_OOB.
4332
4333- CONFIG_NAND_ENV_DST
4334
4335	Defines address in RAM to which the nand_spl code should copy the
4336	environment. If redundant environment is used, it will be copied to
4337	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4338
4339- CONFIG_ENV_IS_IN_UBI:
4340
4341	Define this if you have an UBI volume that you want to use for the
4342	environment.  This has the benefit of wear-leveling the environment
4343	accesses, which is important on NAND.
4344
4345	- CONFIG_ENV_UBI_PART:
4346
4347	  Define this to a string that is the mtd partition containing the UBI.
4348
4349	- CONFIG_ENV_UBI_VOLUME:
4350
4351	  Define this to the name of the volume that you want to store the
4352	  environment in.
4353
4354	- CONFIG_ENV_UBI_VOLUME_REDUND:
4355
4356	  Define this to the name of another volume to store a second copy of
4357	  the environment in.  This will enable redundant environments in UBI.
4358	  It is assumed that both volumes are in the same MTD partition.
4359
4360	- CONFIG_UBI_SILENCE_MSG
4361	- CONFIG_UBIFS_SILENCE_MSG
4362
4363	  You will probably want to define these to avoid a really noisy system
4364	  when storing the env in UBI.
4365
4366- CONFIG_ENV_IS_IN_FAT:
4367       Define this if you want to use the FAT file system for the environment.
4368
4369       - FAT_ENV_INTERFACE:
4370
4371         Define this to a string that is the name of the block device.
4372
4373       - FAT_ENV_DEV_AND_PART:
4374
4375         Define this to a string to specify the partition of the device. It can
4376         be as following:
4377
4378           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4379               - "D:P": device D partition P. Error occurs if device D has no
4380                        partition table.
4381               - "D:0": device D.
4382               - "D" or "D:": device D partition 1 if device D has partition
4383                              table, or the whole device D if has no partition
4384                              table.
4385               - "D:auto": first partition in device D with bootable flag set.
4386                           If none, first valid partition in device D. If no
4387                           partition table then means device D.
4388
4389       - FAT_ENV_FILE:
4390
4391         It's a string of the FAT file name. This file use to store the
4392         environment.
4393
4394       - CONFIG_FAT_WRITE:
4395         This should be defined. Otherwise it cannot save the environment file.
4396
4397- CONFIG_ENV_IS_IN_MMC:
4398
4399	Define this if you have an MMC device which you want to use for the
4400	environment.
4401
4402	- CONFIG_SYS_MMC_ENV_DEV:
4403
4404	  Specifies which MMC device the environment is stored in.
4405
4406	- CONFIG_SYS_MMC_ENV_PART (optional):
4407
4408	  Specifies which MMC partition the environment is stored in. If not
4409	  set, defaults to partition 0, the user area. Common values might be
4410	  1 (first MMC boot partition), 2 (second MMC boot partition).
4411
4412	- CONFIG_ENV_OFFSET:
4413	- CONFIG_ENV_SIZE:
4414
4415	  These two #defines specify the offset and size of the environment
4416	  area within the specified MMC device.
4417
4418	  If offset is positive (the usual case), it is treated as relative to
4419	  the start of the MMC partition. If offset is negative, it is treated
4420	  as relative to the end of the MMC partition. This can be useful if
4421	  your board may be fitted with different MMC devices, which have
4422	  different sizes for the MMC partitions, and you always want the
4423	  environment placed at the very end of the partition, to leave the
4424	  maximum possible space before it, to store other data.
4425
4426	  These two values are in units of bytes, but must be aligned to an
4427	  MMC sector boundary.
4428
4429	- CONFIG_ENV_OFFSET_REDUND (optional):
4430
4431	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4432	  hold a redundant copy of the environment data. This provides a
4433	  valid backup copy in case the other copy is corrupted, e.g. due
4434	  to a power failure during a "saveenv" operation.
4435
4436	  This value may also be positive or negative; this is handled in the
4437	  same way as CONFIG_ENV_OFFSET.
4438
4439	  This value is also in units of bytes, but must also be aligned to
4440	  an MMC sector boundary.
4441
4442	- CONFIG_ENV_SIZE_REDUND (optional):
4443
4444	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4445	  set. If this value is set, it must be set to the same value as
4446	  CONFIG_ENV_SIZE.
4447
4448- CONFIG_SYS_SPI_INIT_OFFSET
4449
4450	Defines offset to the initial SPI buffer area in DPRAM. The
4451	area is used at an early stage (ROM part) if the environment
4452	is configured to reside in the SPI EEPROM: We need a 520 byte
4453	scratch DPRAM area. It is used between the two initialization
4454	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4455	to be a good choice since it makes it far enough from the
4456	start of the data area as well as from the stack pointer.
4457
4458Please note that the environment is read-only until the monitor
4459has been relocated to RAM and a RAM copy of the environment has been
4460created; also, when using EEPROM you will have to use getenv_f()
4461until then to read environment variables.
4462
4463The environment is protected by a CRC32 checksum. Before the monitor
4464is relocated into RAM, as a result of a bad CRC you will be working
4465with the compiled-in default environment - *silently*!!! [This is
4466necessary, because the first environment variable we need is the
4467"baudrate" setting for the console - if we have a bad CRC, we don't
4468have any device yet where we could complain.]
4469
4470Note: once the monitor has been relocated, then it will complain if
4471the default environment is used; a new CRC is computed as soon as you
4472use the "saveenv" command to store a valid environment.
4473
4474- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4475		Echo the inverted Ethernet link state to the fault LED.
4476
4477		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4478		      also needs to be defined.
4479
4480- CONFIG_SYS_FAULT_MII_ADDR:
4481		MII address of the PHY to check for the Ethernet link state.
4482
4483- CONFIG_NS16550_MIN_FUNCTIONS:
4484		Define this if you desire to only have use of the NS16550_init
4485		and NS16550_putc functions for the serial driver located at
4486		drivers/serial/ns16550.c.  This option is useful for saving
4487		space for already greatly restricted images, including but not
4488		limited to NAND_SPL configurations.
4489
4490- CONFIG_DISPLAY_BOARDINFO
4491		Display information about the board that U-Boot is running on
4492		when U-Boot starts up. The board function checkboard() is called
4493		to do this.
4494
4495- CONFIG_DISPLAY_BOARDINFO_LATE
4496		Similar to the previous option, but display this information
4497		later, once stdio is running and output goes to the LCD, if
4498		present.
4499
4500- CONFIG_BOARD_SIZE_LIMIT:
4501		Maximum size of the U-Boot image. When defined, the
4502		build system checks that the actual size does not
4503		exceed it.
4504
4505Low Level (hardware related) configuration options:
4506---------------------------------------------------
4507
4508- CONFIG_SYS_CACHELINE_SIZE:
4509		Cache Line Size of the CPU.
4510
4511- CONFIG_SYS_DEFAULT_IMMR:
4512		Default address of the IMMR after system reset.
4513
4514		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4515		and RPXsuper) to be able to adjust the position of
4516		the IMMR register after a reset.
4517
4518- CONFIG_SYS_CCSRBAR_DEFAULT:
4519		Default (power-on reset) physical address of CCSR on Freescale
4520		PowerPC SOCs.
4521
4522- CONFIG_SYS_CCSRBAR:
4523		Virtual address of CCSR.  On a 32-bit build, this is typically
4524		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4525
4526		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4527		for cross-platform code that uses that macro instead.
4528
4529- CONFIG_SYS_CCSRBAR_PHYS:
4530		Physical address of CCSR.  CCSR can be relocated to a new
4531		physical address, if desired.  In this case, this macro should
4532		be set to that address.	 Otherwise, it should be set to the
4533		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4534		is typically relocated on 36-bit builds.  It is recommended
4535		that this macro be defined via the _HIGH and _LOW macros:
4536
4537		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4538			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4539
4540- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4541		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4542		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4543		used in assembly code, so it must not contain typecasts or
4544		integer size suffixes (e.g. "ULL").
4545
4546- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4547		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4548		used in assembly code, so it must not contain typecasts or
4549		integer size suffixes (e.g. "ULL").
4550
4551- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4552		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4553		forced to a value that ensures that CCSR is not relocated.
4554
4555- Floppy Disk Support:
4556		CONFIG_SYS_FDC_DRIVE_NUMBER
4557
4558		the default drive number (default value 0)
4559
4560		CONFIG_SYS_ISA_IO_STRIDE
4561
4562		defines the spacing between FDC chipset registers
4563		(default value 1)
4564
4565		CONFIG_SYS_ISA_IO_OFFSET
4566
4567		defines the offset of register from address. It
4568		depends on which part of the data bus is connected to
4569		the FDC chipset. (default value 0)
4570
4571		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4572		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4573		default value.
4574
4575		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4576		fdc_hw_init() is called at the beginning of the FDC
4577		setup. fdc_hw_init() must be provided by the board
4578		source code. It is used to make hardware-dependent
4579		initializations.
4580
4581- CONFIG_IDE_AHB:
4582		Most IDE controllers were designed to be connected with PCI
4583		interface. Only few of them were designed for AHB interface.
4584		When software is doing ATA command and data transfer to
4585		IDE devices through IDE-AHB controller, some additional
4586		registers accessing to these kind of IDE-AHB controller
4587		is required.
4588
4589- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4590		DO NOT CHANGE unless you know exactly what you're
4591		doing! (11-4) [MPC8xx/82xx systems only]
4592
4593- CONFIG_SYS_INIT_RAM_ADDR:
4594
4595		Start address of memory area that can be used for
4596		initial data and stack; please note that this must be
4597		writable memory that is working WITHOUT special
4598		initialization, i. e. you CANNOT use normal RAM which
4599		will become available only after programming the
4600		memory controller and running certain initialization
4601		sequences.
4602
4603		U-Boot uses the following memory types:
4604		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4605		- MPC824X: data cache
4606		- PPC4xx:  data cache
4607
4608- CONFIG_SYS_GBL_DATA_OFFSET:
4609
4610		Offset of the initial data structure in the memory
4611		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4612		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4613		data is located at the end of the available space
4614		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4615		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4616		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4617		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4618
4619	Note:
4620		On the MPC824X (or other systems that use the data
4621		cache for initial memory) the address chosen for
4622		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4623		point to an otherwise UNUSED address space between
4624		the top of RAM and the start of the PCI space.
4625
4626- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4627
4628- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4629
4630- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4631
4632- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4633
4634- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4635
4636- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4637
4638- CONFIG_SYS_OR_TIMING_SDRAM:
4639		SDRAM timing
4640
4641- CONFIG_SYS_MAMR_PTA:
4642		periodic timer for refresh
4643
4644- CONFIG_SYS_DER:	Debug Event Register (37-47)
4645
4646- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4647  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4648  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4649  CONFIG_SYS_BR1_PRELIM:
4650		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4651
4652- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4653  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4654  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4655		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4656
4657- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4658  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4659		Machine Mode Register and Memory Periodic Timer
4660		Prescaler definitions (SDRAM timing)
4661
4662- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4663		enable I2C microcode relocation patch (MPC8xx);
4664		define relocation offset in DPRAM [DSP2]
4665
4666- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4667		enable SMC microcode relocation patch (MPC8xx);
4668		define relocation offset in DPRAM [SMC1]
4669
4670- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4671		enable SPI microcode relocation patch (MPC8xx);
4672		define relocation offset in DPRAM [SCC4]
4673
4674- CONFIG_SYS_USE_OSCCLK:
4675		Use OSCM clock mode on MBX8xx board. Be careful,
4676		wrong setting might damage your board. Read
4677		doc/README.MBX before setting this variable!
4678
4679- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4680		Offset of the bootmode word in DPRAM used by post
4681		(Power On Self Tests). This definition overrides
4682		#define'd default value in commproc.h resp.
4683		cpm_8260.h.
4684
4685- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4686  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4687  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4688  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4689  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4690  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4691  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4692  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4693		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4694
4695- CONFIG_PCI_DISABLE_PCIE:
4696		Disable PCI-Express on systems where it is supported but not
4697		required.
4698
4699- CONFIG_PCI_ENUM_ONLY
4700		Only scan through and get the devices on the buses.
4701		Don't do any setup work, presumably because someone or
4702		something has already done it, and we don't need to do it
4703		a second time.	Useful for platforms that are pre-booted
4704		by coreboot or similar.
4705
4706- CONFIG_PCI_INDIRECT_BRIDGE:
4707		Enable support for indirect PCI bridges.
4708
4709- CONFIG_SYS_SRIO:
4710		Chip has SRIO or not
4711
4712- CONFIG_SRIO1:
4713		Board has SRIO 1 port available
4714
4715- CONFIG_SRIO2:
4716		Board has SRIO 2 port available
4717
4718- CONFIG_SRIO_PCIE_BOOT_MASTER
4719		Board can support master function for Boot from SRIO and PCIE
4720
4721- CONFIG_SYS_SRIOn_MEM_VIRT:
4722		Virtual Address of SRIO port 'n' memory region
4723
4724- CONFIG_SYS_SRIOn_MEM_PHYS:
4725		Physical Address of SRIO port 'n' memory region
4726
4727- CONFIG_SYS_SRIOn_MEM_SIZE:
4728		Size of SRIO port 'n' memory region
4729
4730- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4731		Defined to tell the NAND controller that the NAND chip is using
4732		a 16 bit bus.
4733		Not all NAND drivers use this symbol.
4734		Example of drivers that use it:
4735		- drivers/mtd/nand/ndfc.c
4736		- drivers/mtd/nand/mxc_nand.c
4737
4738- CONFIG_SYS_NDFC_EBC0_CFG
4739		Sets the EBC0_CFG register for the NDFC. If not defined
4740		a default value will be used.
4741
4742- CONFIG_SPD_EEPROM
4743		Get DDR timing information from an I2C EEPROM. Common
4744		with pluggable memory modules such as SODIMMs
4745
4746  SPD_EEPROM_ADDRESS
4747		I2C address of the SPD EEPROM
4748
4749- CONFIG_SYS_SPD_BUS_NUM
4750		If SPD EEPROM is on an I2C bus other than the first
4751		one, specify here. Note that the value must resolve
4752		to something your driver can deal with.
4753
4754- CONFIG_SYS_DDR_RAW_TIMING
4755		Get DDR timing information from other than SPD. Common with
4756		soldered DDR chips onboard without SPD. DDR raw timing
4757		parameters are extracted from datasheet and hard-coded into
4758		header files or board specific files.
4759
4760- CONFIG_FSL_DDR_INTERACTIVE
4761		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4762
4763- CONFIG_FSL_DDR_SYNC_REFRESH
4764		Enable sync of refresh for multiple controllers.
4765
4766- CONFIG_FSL_DDR_BIST
4767		Enable built-in memory test for Freescale DDR controllers.
4768
4769- CONFIG_SYS_83XX_DDR_USES_CS0
4770		Only for 83xx systems. If specified, then DDR should
4771		be configured using CS0 and CS1 instead of CS2 and CS3.
4772
4773- CONFIG_ETHER_ON_FEC[12]
4774		Define to enable FEC[12] on a 8xx series processor.
4775
4776- CONFIG_FEC[12]_PHY
4777		Define to the hardcoded PHY address which corresponds
4778		to the given FEC; i. e.
4779			#define CONFIG_FEC1_PHY 4
4780		means that the PHY with address 4 is connected to FEC1
4781
4782		When set to -1, means to probe for first available.
4783
4784- CONFIG_FEC[12]_PHY_NORXERR
4785		The PHY does not have a RXERR line (RMII only).
4786		(so program the FEC to ignore it).
4787
4788- CONFIG_RMII
4789		Enable RMII mode for all FECs.
4790		Note that this is a global option, we can't
4791		have one FEC in standard MII mode and another in RMII mode.
4792
4793- CONFIG_CRC32_VERIFY
4794		Add a verify option to the crc32 command.
4795		The syntax is:
4796
4797		=> crc32 -v <address> <count> <crc32>
4798
4799		Where address/count indicate a memory area
4800		and crc32 is the correct crc32 which the
4801		area should have.
4802
4803- CONFIG_LOOPW
4804		Add the "loopw" memory command. This only takes effect if
4805		the memory commands are activated globally (CONFIG_CMD_MEM).
4806
4807- CONFIG_MX_CYCLIC
4808		Add the "mdc" and "mwc" memory commands. These are cyclic
4809		"md/mw" commands.
4810		Examples:
4811
4812		=> mdc.b 10 4 500
4813		This command will print 4 bytes (10,11,12,13) each 500 ms.
4814
4815		=> mwc.l 100 12345678 10
4816		This command will write 12345678 to address 100 all 10 ms.
4817
4818		This only takes effect if the memory commands are activated
4819		globally (CONFIG_CMD_MEM).
4820
4821- CONFIG_SKIP_LOWLEVEL_INIT
4822		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4823		low level initializations (like setting up the memory
4824		controller) are omitted and/or U-Boot does not
4825		relocate itself into RAM.
4826
4827		Normally this variable MUST NOT be defined. The only
4828		exception is when U-Boot is loaded (to RAM) by some
4829		other boot loader or by a debugger which performs
4830		these initializations itself.
4831
4832- CONFIG_SPL_BUILD
4833		Modifies the behaviour of start.S when compiling a loader
4834		that is executed before the actual U-Boot. E.g. when
4835		compiling a NAND SPL.
4836
4837- CONFIG_TPL_BUILD
4838		Modifies the behaviour of start.S  when compiling a loader
4839		that is executed after the SPL and before the actual U-Boot.
4840		It is loaded by the SPL.
4841
4842- CONFIG_SYS_MPC85XX_NO_RESETVEC
4843		Only for 85xx systems. If this variable is specified, the section
4844		.resetvec is not kept and the section .bootpg is placed in the
4845		previous 4k of the .text section.
4846
4847- CONFIG_ARCH_MAP_SYSMEM
4848		Generally U-Boot (and in particular the md command) uses
4849		effective address. It is therefore not necessary to regard
4850		U-Boot address as virtual addresses that need to be translated
4851		to physical addresses. However, sandbox requires this, since
4852		it maintains its own little RAM buffer which contains all
4853		addressable memory. This option causes some memory accesses
4854		to be mapped through map_sysmem() / unmap_sysmem().
4855
4856- CONFIG_USE_ARCH_MEMCPY
4857  CONFIG_USE_ARCH_MEMSET
4858		If these options are used a optimized version of memcpy/memset will
4859		be used if available. These functions may be faster under some
4860		conditions but may increase the binary size.
4861
4862- CONFIG_X86_RESET_VECTOR
4863		If defined, the x86 reset vector code is included. This is not
4864		needed when U-Boot is running from Coreboot.
4865
4866- CONFIG_SYS_MPUCLK
4867		Defines the MPU clock speed (in MHz).
4868
4869		NOTE : currently only supported on AM335x platforms.
4870
4871- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4872		Enables the RTC32K OSC on AM33xx based plattforms
4873
4874- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4875		Option to disable subpage write in NAND driver
4876		driver that uses this:
4877		drivers/mtd/nand/davinci_nand.c
4878
4879Freescale QE/FMAN Firmware Support:
4880-----------------------------------
4881
4882The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4883loading of "firmware", which is encoded in the QE firmware binary format.
4884This firmware often needs to be loaded during U-Boot booting, so macros
4885are used to identify the storage device (NOR flash, SPI, etc) and the address
4886within that device.
4887
4888- CONFIG_SYS_FMAN_FW_ADDR
4889	The address in the storage device where the FMAN microcode is located.  The
4890	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4891	is also specified.
4892
4893- CONFIG_SYS_QE_FW_ADDR
4894	The address in the storage device where the QE microcode is located.  The
4895	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4896	is also specified.
4897
4898- CONFIG_SYS_QE_FMAN_FW_LENGTH
4899	The maximum possible size of the firmware.  The firmware binary format
4900	has a field that specifies the actual size of the firmware, but it
4901	might not be possible to read any part of the firmware unless some
4902	local storage is allocated to hold the entire firmware first.
4903
4904- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4905	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4906	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4907	virtual address in NOR flash.
4908
4909- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4910	Specifies that QE/FMAN firmware is located in NAND flash.
4911	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4912
4913- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4914	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4915	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4916
4917- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4918	Specifies that QE/FMAN firmware is located on the primary SPI
4919	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4920
4921- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4922	Specifies that QE/FMAN firmware is located in the remote (master)
4923	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4924	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4925	window->master inbound window->master LAW->the ucode address in
4926	master's memory space.
4927
4928Freescale Layerscape Management Complex Firmware Support:
4929---------------------------------------------------------
4930The Freescale Layerscape Management Complex (MC) supports the loading of
4931"firmware".
4932This firmware often needs to be loaded during U-Boot booting, so macros
4933are used to identify the storage device (NOR flash, SPI, etc) and the address
4934within that device.
4935
4936- CONFIG_FSL_MC_ENET
4937	Enable the MC driver for Layerscape SoCs.
4938
4939- CONFIG_SYS_LS_MC_FW_ADDR
4940	The address in the storage device where the firmware is located.  The
4941	meaning of this address depends on which CONFIG_SYS_LS_MC_FW_IN_xxx macro
4942	is also specified.
4943
4944- CONFIG_SYS_LS_MC_FW_LENGTH
4945	The maximum possible size of the firmware.  The firmware binary format
4946	has a field that specifies the actual size of the firmware, but it
4947	might not be possible to read any part of the firmware unless some
4948	local storage is allocated to hold the entire firmware first.
4949
4950- CONFIG_SYS_LS_MC_FW_IN_NOR
4951	Specifies that MC firmware is located in NOR flash, mapped as
4952	normal addressable memory via the LBC. CONFIG_SYS_LS_MC_FW_ADDR is the
4953	virtual address in NOR flash.
4954
4955Freescale Layerscape Debug Server Support:
4956-------------------------------------------
4957The Freescale Layerscape Debug Server Support supports the loading of
4958"Debug Server firmware" and triggering SP boot-rom.
4959This firmware often needs to be loaded during U-Boot booting.
4960
4961- CONFIG_FSL_DEBUG_SERVER
4962	Enable the Debug Server for Layerscape SoCs.
4963
4964- CONFIG_SYS_DEBUG_SERVER_DRAM_BLOCK_MIN_SIZE
4965	Define minimum DDR size required for debug server image
4966
4967- CONFIG_SYS_MC_RSV_MEM_ALIGN
4968	Define alignment of reserved memory MC requires
4969
4970Reproducible builds
4971-------------------
4972
4973In order to achieve reproducible builds, timestamps used in the U-Boot build
4974process have to be set to a fixed value.
4975
4976This is done using the SOURCE_DATE_EPOCH environment variable.
4977SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
4978option for U-Boot or an environment variable in U-Boot.
4979
4980SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
4981
4982Building the Software:
4983======================
4984
4985Building U-Boot has been tested in several native build environments
4986and in many different cross environments. Of course we cannot support
4987all possibly existing versions of cross development tools in all
4988(potentially obsolete) versions. In case of tool chain problems we
4989recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4990which is extensively used to build and test U-Boot.
4991
4992If you are not using a native environment, it is assumed that you
4993have GNU cross compiling tools available in your path. In this case,
4994you must set the environment variable CROSS_COMPILE in your shell.
4995Note that no changes to the Makefile or any other source files are
4996necessary. For example using the ELDK on a 4xx CPU, please enter:
4997
4998	$ CROSS_COMPILE=ppc_4xx-
4999	$ export CROSS_COMPILE
5000
5001Note: If you wish to generate Windows versions of the utilities in
5002      the tools directory you can use the MinGW toolchain
5003      (http://www.mingw.org).  Set your HOST tools to the MinGW
5004      toolchain and execute 'make tools'.  For example:
5005
5006       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
5007
5008      Binaries such as tools/mkimage.exe will be created which can
5009      be executed on computers running Windows.
5010
5011U-Boot is intended to be simple to build. After installing the
5012sources you must configure U-Boot for one specific board type. This
5013is done by typing:
5014
5015	make NAME_defconfig
5016
5017where "NAME_defconfig" is the name of one of the existing configu-
5018rations; see boards.cfg for supported names.
5019
5020Note: for some board special configuration names may exist; check if
5021      additional information is available from the board vendor; for
5022      instance, the TQM823L systems are available without (standard)
5023      or with LCD support. You can select such additional "features"
5024      when choosing the configuration, i. e.
5025
5026      make TQM823L_defconfig
5027	- will configure for a plain TQM823L, i. e. no LCD support
5028
5029      make TQM823L_LCD_defconfig
5030	- will configure for a TQM823L with U-Boot console on LCD
5031
5032      etc.
5033
5034
5035Finally, type "make all", and you should get some working U-Boot
5036images ready for download to / installation on your system:
5037
5038- "u-boot.bin" is a raw binary image
5039- "u-boot" is an image in ELF binary format
5040- "u-boot.srec" is in Motorola S-Record format
5041
5042By default the build is performed locally and the objects are saved
5043in the source directory. One of the two methods can be used to change
5044this behavior and build U-Boot to some external directory:
5045
50461. Add O= to the make command line invocations:
5047
5048	make O=/tmp/build distclean
5049	make O=/tmp/build NAME_defconfig
5050	make O=/tmp/build all
5051
50522. Set environment variable KBUILD_OUTPUT to point to the desired location:
5053
5054	export KBUILD_OUTPUT=/tmp/build
5055	make distclean
5056	make NAME_defconfig
5057	make all
5058
5059Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
5060variable.
5061
5062
5063Please be aware that the Makefiles assume you are using GNU make, so
5064for instance on NetBSD you might need to use "gmake" instead of
5065native "make".
5066
5067
5068If the system board that you have is not listed, then you will need
5069to port U-Boot to your hardware platform. To do this, follow these
5070steps:
5071
50721.  Create a new directory to hold your board specific code. Add any
5073    files you need. In your board directory, you will need at least
5074    the "Makefile" and a "<board>.c".
50752.  Create a new configuration file "include/configs/<board>.h" for
5076    your board.
50773.  If you're porting U-Boot to a new CPU, then also create a new
5078    directory to hold your CPU specific code. Add any files you need.
50794.  Run "make <board>_defconfig" with your new name.
50805.  Type "make", and you should get a working "u-boot.srec" file
5081    to be installed on your target system.
50826.  Debug and solve any problems that might arise.
5083    [Of course, this last step is much harder than it sounds.]
5084
5085
5086Testing of U-Boot Modifications, Ports to New Hardware, etc.:
5087==============================================================
5088
5089If you have modified U-Boot sources (for instance added a new board
5090or support for new devices, a new CPU, etc.) you are expected to
5091provide feedback to the other developers. The feedback normally takes
5092the form of a "patch", i. e. a context diff against a certain (latest
5093official or latest in the git repository) version of U-Boot sources.
5094
5095But before you submit such a patch, please verify that your modifi-
5096cation did not break existing code. At least make sure that *ALL* of
5097the supported boards compile WITHOUT ANY compiler warnings. To do so,
5098just run the "MAKEALL" script, which will configure and build U-Boot
5099for ALL supported system. Be warned, this will take a while. You can
5100select which (cross) compiler to use by passing a `CROSS_COMPILE'
5101environment variable to the script, i. e. to use the ELDK cross tools
5102you can type
5103
5104	CROSS_COMPILE=ppc_8xx- MAKEALL
5105
5106or to build on a native PowerPC system you can type
5107
5108	CROSS_COMPILE=' ' MAKEALL
5109
5110When using the MAKEALL script, the default behaviour is to build
5111U-Boot in the source directory. This location can be changed by
5112setting the BUILD_DIR environment variable. Also, for each target
5113built, the MAKEALL script saves two log files (<target>.ERR and
5114<target>.MAKEALL) in the <source dir>/LOG directory. This default
5115location can be changed by setting the MAKEALL_LOGDIR environment
5116variable. For example:
5117
5118	export BUILD_DIR=/tmp/build
5119	export MAKEALL_LOGDIR=/tmp/log
5120	CROSS_COMPILE=ppc_8xx- MAKEALL
5121
5122With the above settings build objects are saved in the /tmp/build,
5123log files are saved in the /tmp/log and the source tree remains clean
5124during the whole build process.
5125
5126
5127See also "U-Boot Porting Guide" below.
5128
5129
5130Monitor Commands - Overview:
5131============================
5132
5133go	- start application at address 'addr'
5134run	- run commands in an environment variable
5135bootm	- boot application image from memory
5136bootp	- boot image via network using BootP/TFTP protocol
5137bootz   - boot zImage from memory
5138tftpboot- boot image via network using TFTP protocol
5139	       and env variables "ipaddr" and "serverip"
5140	       (and eventually "gatewayip")
5141tftpput - upload a file via network using TFTP protocol
5142rarpboot- boot image via network using RARP/TFTP protocol
5143diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
5144loads	- load S-Record file over serial line
5145loadb	- load binary file over serial line (kermit mode)
5146md	- memory display
5147mm	- memory modify (auto-incrementing)
5148nm	- memory modify (constant address)
5149mw	- memory write (fill)
5150cp	- memory copy
5151cmp	- memory compare
5152crc32	- checksum calculation
5153i2c	- I2C sub-system
5154sspi	- SPI utility commands
5155base	- print or set address offset
5156printenv- print environment variables
5157setenv	- set environment variables
5158saveenv - save environment variables to persistent storage
5159protect - enable or disable FLASH write protection
5160erase	- erase FLASH memory
5161flinfo	- print FLASH memory information
5162nand	- NAND memory operations (see doc/README.nand)
5163bdinfo	- print Board Info structure
5164iminfo	- print header information for application image
5165coninfo - print console devices and informations
5166ide	- IDE sub-system
5167loop	- infinite loop on address range
5168loopw	- infinite write loop on address range
5169mtest	- simple RAM test
5170icache	- enable or disable instruction cache
5171dcache	- enable or disable data cache
5172reset	- Perform RESET of the CPU
5173echo	- echo args to console
5174version - print monitor version
5175help	- print online help
5176?	- alias for 'help'
5177
5178
5179Monitor Commands - Detailed Description:
5180========================================
5181
5182TODO.
5183
5184For now: just type "help <command>".
5185
5186
5187Environment Variables:
5188======================
5189
5190U-Boot supports user configuration using Environment Variables which
5191can be made persistent by saving to Flash memory.
5192
5193Environment Variables are set using "setenv", printed using
5194"printenv", and saved to Flash using "saveenv". Using "setenv"
5195without a value can be used to delete a variable from the
5196environment. As long as you don't save the environment you are
5197working with an in-memory copy. In case the Flash area containing the
5198environment is erased by accident, a default environment is provided.
5199
5200Some configuration options can be set using Environment Variables.
5201
5202List of environment variables (most likely not complete):
5203
5204  baudrate	- see CONFIG_BAUDRATE
5205
5206  bootdelay	- see CONFIG_BOOTDELAY
5207
5208  bootcmd	- see CONFIG_BOOTCOMMAND
5209
5210  bootargs	- Boot arguments when booting an RTOS image
5211
5212  bootfile	- Name of the image to load with TFTP
5213
5214  bootm_low	- Memory range available for image processing in the bootm
5215		  command can be restricted. This variable is given as
5216		  a hexadecimal number and defines lowest address allowed
5217		  for use by the bootm command. See also "bootm_size"
5218		  environment variable. Address defined by "bootm_low" is
5219		  also the base of the initial memory mapping for the Linux
5220		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
5221		  bootm_mapsize.
5222
5223  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
5224		  This variable is given as a hexadecimal number and it
5225		  defines the size of the memory region starting at base
5226		  address bootm_low that is accessible by the Linux kernel
5227		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
5228		  as the default value if it is defined, and bootm_size is
5229		  used otherwise.
5230
5231  bootm_size	- Memory range available for image processing in the bootm
5232		  command can be restricted. This variable is given as
5233		  a hexadecimal number and defines the size of the region
5234		  allowed for use by the bootm command. See also "bootm_low"
5235		  environment variable.
5236
5237  updatefile	- Location of the software update file on a TFTP server, used
5238		  by the automatic software update feature. Please refer to
5239		  documentation in doc/README.update for more details.
5240
5241  autoload	- if set to "no" (any string beginning with 'n'),
5242		  "bootp" will just load perform a lookup of the
5243		  configuration from the BOOTP server, but not try to
5244		  load any image using TFTP
5245
5246  autostart	- if set to "yes", an image loaded using the "bootp",
5247		  "rarpboot", "tftpboot" or "diskboot" commands will
5248		  be automatically started (by internally calling
5249		  "bootm")
5250
5251		  If set to "no", a standalone image passed to the
5252		  "bootm" command will be copied to the load address
5253		  (and eventually uncompressed), but NOT be started.
5254		  This can be used to load and uncompress arbitrary
5255		  data.
5256
5257  fdt_high	- if set this restricts the maximum address that the
5258		  flattened device tree will be copied into upon boot.
5259		  For example, if you have a system with 1 GB memory
5260		  at physical address 0x10000000, while Linux kernel
5261		  only recognizes the first 704 MB as low memory, you
5262		  may need to set fdt_high as 0x3C000000 to have the
5263		  device tree blob be copied to the maximum address
5264		  of the 704 MB low memory, so that Linux kernel can
5265		  access it during the boot procedure.
5266
5267		  If this is set to the special value 0xFFFFFFFF then
5268		  the fdt will not be copied at all on boot.  For this
5269		  to work it must reside in writable memory, have
5270		  sufficient padding on the end of it for u-boot to
5271		  add the information it needs into it, and the memory
5272		  must be accessible by the kernel.
5273
5274  fdtcontroladdr- if set this is the address of the control flattened
5275		  device tree used by U-Boot when CONFIG_OF_CONTROL is
5276		  defined.
5277
5278  i2cfast	- (PPC405GP|PPC405EP only)
5279		  if set to 'y' configures Linux I2C driver for fast
5280		  mode (400kHZ). This environment variable is used in
5281		  initialization code. So, for changes to be effective
5282		  it must be saved and board must be reset.
5283
5284  initrd_high	- restrict positioning of initrd images:
5285		  If this variable is not set, initrd images will be
5286		  copied to the highest possible address in RAM; this
5287		  is usually what you want since it allows for
5288		  maximum initrd size. If for some reason you want to
5289		  make sure that the initrd image is loaded below the
5290		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
5291		  variable to a value of "no" or "off" or "0".
5292		  Alternatively, you can set it to a maximum upper
5293		  address to use (U-Boot will still check that it
5294		  does not overwrite the U-Boot stack and data).
5295
5296		  For instance, when you have a system with 16 MB
5297		  RAM, and want to reserve 4 MB from use by Linux,
5298		  you can do this by adding "mem=12M" to the value of
5299		  the "bootargs" variable. However, now you must make
5300		  sure that the initrd image is placed in the first
5301		  12 MB as well - this can be done with
5302
5303		  setenv initrd_high 00c00000
5304
5305		  If you set initrd_high to 0xFFFFFFFF, this is an
5306		  indication to U-Boot that all addresses are legal
5307		  for the Linux kernel, including addresses in flash
5308		  memory. In this case U-Boot will NOT COPY the
5309		  ramdisk at all. This may be useful to reduce the
5310		  boot time on your system, but requires that this
5311		  feature is supported by your Linux kernel.
5312
5313  ipaddr	- IP address; needed for tftpboot command
5314
5315  loadaddr	- Default load address for commands like "bootp",
5316		  "rarpboot", "tftpboot", "loadb" or "diskboot"
5317
5318  loads_echo	- see CONFIG_LOADS_ECHO
5319
5320  serverip	- TFTP server IP address; needed for tftpboot command
5321
5322  bootretry	- see CONFIG_BOOT_RETRY_TIME
5323
5324  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5325
5326  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5327
5328  ethprime	- controls which interface is used first.
5329
5330  ethact	- controls which interface is currently active.
5331		  For example you can do the following
5332
5333		  => setenv ethact FEC
5334		  => ping 192.168.0.1 # traffic sent on FEC
5335		  => setenv ethact SCC
5336		  => ping 10.0.0.1 # traffic sent on SCC
5337
5338  ethrotate	- When set to "no" U-Boot does not go through all
5339		  available network interfaces.
5340		  It just stays at the currently selected interface.
5341
5342  netretry	- When set to "no" each network operation will
5343		  either succeed or fail without retrying.
5344		  When set to "once" the network operation will
5345		  fail when all the available network interfaces
5346		  are tried once without success.
5347		  Useful on scripts which control the retry operation
5348		  themselves.
5349
5350  npe_ucode	- set load address for the NPE microcode
5351
5352  silent_linux  - If set then Linux will be told to boot silently, by
5353		  changing the console to be empty. If "yes" it will be
5354		  made silent. If "no" it will not be made silent. If
5355		  unset, then it will be made silent if the U-Boot console
5356		  is silent.
5357
5358  tftpsrcp	- If this is set, the value is used for TFTP's
5359		  UDP source port.
5360
5361  tftpdstp	- If this is set, the value is used for TFTP's UDP
5362		  destination port instead of the Well Know Port 69.
5363
5364  tftpblocksize - Block size to use for TFTP transfers; if not set,
5365		  we use the TFTP server's default block size
5366
5367  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5368		  seconds, minimum value is 1000 = 1 second). Defines
5369		  when a packet is considered to be lost so it has to
5370		  be retransmitted. The default is 5000 = 5 seconds.
5371		  Lowering this value may make downloads succeed
5372		  faster in networks with high packet loss rates or
5373		  with unreliable TFTP servers.
5374
5375  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
5376		  unit, minimum value = 0). Defines how many timeouts
5377		  can happen during a single file transfer before that
5378		  transfer is aborted. The default is 10, and 0 means
5379		  'no timeouts allowed'. Increasing this value may help
5380		  downloads succeed with high packet loss rates, or with
5381		  unreliable TFTP servers or client hardware.
5382
5383  vlan		- When set to a value < 4095 the traffic over
5384		  Ethernet is encapsulated/received over 802.1q
5385		  VLAN tagged frames.
5386
5387  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
5388		  Unsigned value, in milliseconds. If not set, the period will
5389		  be either the default (28000), or a value based on
5390		  CONFIG_NET_RETRY_COUNT, if defined. This value has
5391		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
5392
5393The following image location variables contain the location of images
5394used in booting. The "Image" column gives the role of the image and is
5395not an environment variable name. The other columns are environment
5396variable names. "File Name" gives the name of the file on a TFTP
5397server, "RAM Address" gives the location in RAM the image will be
5398loaded to, and "Flash Location" gives the image's address in NOR
5399flash or offset in NAND flash.
5400
5401*Note* - these variables don't have to be defined for all boards, some
5402boards currently use other variables for these purposes, and some
5403boards use these variables for other purposes.
5404
5405Image		    File Name	     RAM Address       Flash Location
5406-----		    ---------	     -----------       --------------
5407u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5408Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5409device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5410ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5411
5412The following environment variables may be used and automatically
5413updated by the network boot commands ("bootp" and "rarpboot"),
5414depending the information provided by your boot server:
5415
5416  bootfile	- see above
5417  dnsip		- IP address of your Domain Name Server
5418  dnsip2	- IP address of your secondary Domain Name Server
5419  gatewayip	- IP address of the Gateway (Router) to use
5420  hostname	- Target hostname
5421  ipaddr	- see above
5422  netmask	- Subnet Mask
5423  rootpath	- Pathname of the root filesystem on the NFS server
5424  serverip	- see above
5425
5426
5427There are two special Environment Variables:
5428
5429  serial#	- contains hardware identification information such
5430		  as type string and/or serial number
5431  ethaddr	- Ethernet address
5432
5433These variables can be set only once (usually during manufacturing of
5434the board). U-Boot refuses to delete or overwrite these variables
5435once they have been set once.
5436
5437
5438Further special Environment Variables:
5439
5440  ver		- Contains the U-Boot version string as printed
5441		  with the "version" command. This variable is
5442		  readonly (see CONFIG_VERSION_VARIABLE).
5443
5444
5445Please note that changes to some configuration parameters may take
5446only effect after the next boot (yes, that's just like Windoze :-).
5447
5448
5449Callback functions for environment variables:
5450---------------------------------------------
5451
5452For some environment variables, the behavior of u-boot needs to change
5453when their values are changed.  This functionality allows functions to
5454be associated with arbitrary variables.  On creation, overwrite, or
5455deletion, the callback will provide the opportunity for some side
5456effect to happen or for the change to be rejected.
5457
5458The callbacks are named and associated with a function using the
5459U_BOOT_ENV_CALLBACK macro in your board or driver code.
5460
5461These callbacks are associated with variables in one of two ways.  The
5462static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5463in the board configuration to a string that defines a list of
5464associations.  The list must be in the following format:
5465
5466	entry = variable_name[:callback_name]
5467	list = entry[,list]
5468
5469If the callback name is not specified, then the callback is deleted.
5470Spaces are also allowed anywhere in the list.
5471
5472Callbacks can also be associated by defining the ".callbacks" variable
5473with the same list format above.  Any association in ".callbacks" will
5474override any association in the static list. You can define
5475CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5476".callbacks" environment variable in the default or embedded environment.
5477
5478If CONFIG_REGEX is defined, the variable_name above is evaluated as a
5479regular expression. This allows multiple variables to be connected to
5480the same callback without explicitly listing them all out.
5481
5482
5483Command Line Parsing:
5484=====================
5485
5486There are two different command line parsers available with U-Boot:
5487the old "simple" one, and the much more powerful "hush" shell:
5488
5489Old, simple command line parser:
5490--------------------------------
5491
5492- supports environment variables (through setenv / saveenv commands)
5493- several commands on one line, separated by ';'
5494- variable substitution using "... ${name} ..." syntax
5495- special characters ('$', ';') can be escaped by prefixing with '\',
5496  for example:
5497	setenv bootcmd bootm \${address}
5498- You can also escape text by enclosing in single apostrophes, for example:
5499	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5500
5501Hush shell:
5502-----------
5503
5504- similar to Bourne shell, with control structures like
5505  if...then...else...fi, for...do...done; while...do...done,
5506  until...do...done, ...
5507- supports environment ("global") variables (through setenv / saveenv
5508  commands) and local shell variables (through standard shell syntax
5509  "name=value"); only environment variables can be used with "run"
5510  command
5511
5512General rules:
5513--------------
5514
5515(1) If a command line (or an environment variable executed by a "run"
5516    command) contains several commands separated by semicolon, and
5517    one of these commands fails, then the remaining commands will be
5518    executed anyway.
5519
5520(2) If you execute several variables with one call to run (i. e.
5521    calling run with a list of variables as arguments), any failing
5522    command will cause "run" to terminate, i. e. the remaining
5523    variables are not executed.
5524
5525Note for Redundant Ethernet Interfaces:
5526=======================================
5527
5528Some boards come with redundant Ethernet interfaces; U-Boot supports
5529such configurations and is capable of automatic selection of a
5530"working" interface when needed. MAC assignment works as follows:
5531
5532Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5533MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5534"eth1addr" (=>eth1), "eth2addr", ...
5535
5536If the network interface stores some valid MAC address (for instance
5537in SROM), this is used as default address if there is NO correspon-
5538ding setting in the environment; if the corresponding environment
5539variable is set, this overrides the settings in the card; that means:
5540
5541o If the SROM has a valid MAC address, and there is no address in the
5542  environment, the SROM's address is used.
5543
5544o If there is no valid address in the SROM, and a definition in the
5545  environment exists, then the value from the environment variable is
5546  used.
5547
5548o If both the SROM and the environment contain a MAC address, and
5549  both addresses are the same, this MAC address is used.
5550
5551o If both the SROM and the environment contain a MAC address, and the
5552  addresses differ, the value from the environment is used and a
5553  warning is printed.
5554
5555o If neither SROM nor the environment contain a MAC address, an error
5556  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
5557  a random, locally-assigned MAC is used.
5558
5559If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5560will be programmed into hardware as part of the initialization process.	 This
5561may be skipped by setting the appropriate 'ethmacskip' environment variable.
5562The naming convention is as follows:
5563"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5564
5565Image Formats:
5566==============
5567
5568U-Boot is capable of booting (and performing other auxiliary operations on)
5569images in two formats:
5570
5571New uImage format (FIT)
5572-----------------------
5573
5574Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5575to Flattened Device Tree). It allows the use of images with multiple
5576components (several kernels, ramdisks, etc.), with contents protected by
5577SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5578
5579
5580Old uImage format
5581-----------------
5582
5583Old image format is based on binary files which can be basically anything,
5584preceded by a special header; see the definitions in include/image.h for
5585details; basically, the header defines the following image properties:
5586
5587* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5588  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5589  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5590  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5591  INTEGRITY).
5592* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5593  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5594  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5595* Compression Type (uncompressed, gzip, bzip2)
5596* Load Address
5597* Entry Point
5598* Image Name
5599* Image Timestamp
5600
5601The header is marked by a special Magic Number, and both the header
5602and the data portions of the image are secured against corruption by
5603CRC32 checksums.
5604
5605
5606Linux Support:
5607==============
5608
5609Although U-Boot should support any OS or standalone application
5610easily, the main focus has always been on Linux during the design of
5611U-Boot.
5612
5613U-Boot includes many features that so far have been part of some
5614special "boot loader" code within the Linux kernel. Also, any
5615"initrd" images to be used are no longer part of one big Linux image;
5616instead, kernel and "initrd" are separate images. This implementation
5617serves several purposes:
5618
5619- the same features can be used for other OS or standalone
5620  applications (for instance: using compressed images to reduce the
5621  Flash memory footprint)
5622
5623- it becomes much easier to port new Linux kernel versions because
5624  lots of low-level, hardware dependent stuff are done by U-Boot
5625
5626- the same Linux kernel image can now be used with different "initrd"
5627  images; of course this also means that different kernel images can
5628  be run with the same "initrd". This makes testing easier (you don't
5629  have to build a new "zImage.initrd" Linux image when you just
5630  change a file in your "initrd"). Also, a field-upgrade of the
5631  software is easier now.
5632
5633
5634Linux HOWTO:
5635============
5636
5637Porting Linux to U-Boot based systems:
5638---------------------------------------
5639
5640U-Boot cannot save you from doing all the necessary modifications to
5641configure the Linux device drivers for use with your target hardware
5642(no, we don't intend to provide a full virtual machine interface to
5643Linux :-).
5644
5645But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5646
5647Just make sure your machine specific header file (for instance
5648include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5649Information structure as we define in include/asm-<arch>/u-boot.h,
5650and make sure that your definition of IMAP_ADDR uses the same value
5651as your U-Boot configuration in CONFIG_SYS_IMMR.
5652
5653Note that U-Boot now has a driver model, a unified model for drivers.
5654If you are adding a new driver, plumb it into driver model. If there
5655is no uclass available, you are encouraged to create one. See
5656doc/driver-model.
5657
5658
5659Configuring the Linux kernel:
5660-----------------------------
5661
5662No specific requirements for U-Boot. Make sure you have some root
5663device (initial ramdisk, NFS) for your target system.
5664
5665
5666Building a Linux Image:
5667-----------------------
5668
5669With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5670not used. If you use recent kernel source, a new build target
5671"uImage" will exist which automatically builds an image usable by
5672U-Boot. Most older kernels also have support for a "pImage" target,
5673which was introduced for our predecessor project PPCBoot and uses a
5674100% compatible format.
5675
5676Example:
5677
5678	make TQM850L_defconfig
5679	make oldconfig
5680	make dep
5681	make uImage
5682
5683The "uImage" build target uses a special tool (in 'tools/mkimage') to
5684encapsulate a compressed Linux kernel image with header	 information,
5685CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5686
5687* build a standard "vmlinux" kernel image (in ELF binary format):
5688
5689* convert the kernel into a raw binary image:
5690
5691	${CROSS_COMPILE}-objcopy -O binary \
5692				 -R .note -R .comment \
5693				 -S vmlinux linux.bin
5694
5695* compress the binary image:
5696
5697	gzip -9 linux.bin
5698
5699* package compressed binary image for U-Boot:
5700
5701	mkimage -A ppc -O linux -T kernel -C gzip \
5702		-a 0 -e 0 -n "Linux Kernel Image" \
5703		-d linux.bin.gz uImage
5704
5705
5706The "mkimage" tool can also be used to create ramdisk images for use
5707with U-Boot, either separated from the Linux kernel image, or
5708combined into one file. "mkimage" encapsulates the images with a 64
5709byte header containing information about target architecture,
5710operating system, image type, compression method, entry points, time
5711stamp, CRC32 checksums, etc.
5712
5713"mkimage" can be called in two ways: to verify existing images and
5714print the header information, or to build new images.
5715
5716In the first form (with "-l" option) mkimage lists the information
5717contained in the header of an existing U-Boot image; this includes
5718checksum verification:
5719
5720	tools/mkimage -l image
5721	  -l ==> list image header information
5722
5723The second form (with "-d" option) is used to build a U-Boot image
5724from a "data file" which is used as image payload:
5725
5726	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5727		      -n name -d data_file image
5728	  -A ==> set architecture to 'arch'
5729	  -O ==> set operating system to 'os'
5730	  -T ==> set image type to 'type'
5731	  -C ==> set compression type 'comp'
5732	  -a ==> set load address to 'addr' (hex)
5733	  -e ==> set entry point to 'ep' (hex)
5734	  -n ==> set image name to 'name'
5735	  -d ==> use image data from 'datafile'
5736
5737Right now, all Linux kernels for PowerPC systems use the same load
5738address (0x00000000), but the entry point address depends on the
5739kernel version:
5740
5741- 2.2.x kernels have the entry point at 0x0000000C,
5742- 2.3.x and later kernels have the entry point at 0x00000000.
5743
5744So a typical call to build a U-Boot image would read:
5745
5746	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5747	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5748	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5749	> examples/uImage.TQM850L
5750	Image Name:   2.4.4 kernel for TQM850L
5751	Created:      Wed Jul 19 02:34:59 2000
5752	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5753	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5754	Load Address: 0x00000000
5755	Entry Point:  0x00000000
5756
5757To verify the contents of the image (or check for corruption):
5758
5759	-> tools/mkimage -l examples/uImage.TQM850L
5760	Image Name:   2.4.4 kernel for TQM850L
5761	Created:      Wed Jul 19 02:34:59 2000
5762	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5763	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5764	Load Address: 0x00000000
5765	Entry Point:  0x00000000
5766
5767NOTE: for embedded systems where boot time is critical you can trade
5768speed for memory and install an UNCOMPRESSED image instead: this
5769needs more space in Flash, but boots much faster since it does not
5770need to be uncompressed:
5771
5772	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5773	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5774	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5775	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5776	> examples/uImage.TQM850L-uncompressed
5777	Image Name:   2.4.4 kernel for TQM850L
5778	Created:      Wed Jul 19 02:34:59 2000
5779	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5780	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5781	Load Address: 0x00000000
5782	Entry Point:  0x00000000
5783
5784
5785Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5786when your kernel is intended to use an initial ramdisk:
5787
5788	-> tools/mkimage -n 'Simple Ramdisk Image' \
5789	> -A ppc -O linux -T ramdisk -C gzip \
5790	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5791	Image Name:   Simple Ramdisk Image
5792	Created:      Wed Jan 12 14:01:50 2000
5793	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5794	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5795	Load Address: 0x00000000
5796	Entry Point:  0x00000000
5797
5798The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5799option performs the converse operation of the mkimage's second form (the "-d"
5800option). Given an image built by mkimage, the dumpimage extracts a "data file"
5801from the image:
5802
5803	tools/dumpimage -i image -T type -p position data_file
5804	  -i ==> extract from the 'image' a specific 'data_file'
5805	  -T ==> set image type to 'type'
5806	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5807
5808
5809Installing a Linux Image:
5810-------------------------
5811
5812To downloading a U-Boot image over the serial (console) interface,
5813you must convert the image to S-Record format:
5814
5815	objcopy -I binary -O srec examples/image examples/image.srec
5816
5817The 'objcopy' does not understand the information in the U-Boot
5818image header, so the resulting S-Record file will be relative to
5819address 0x00000000. To load it to a given address, you need to
5820specify the target address as 'offset' parameter with the 'loads'
5821command.
5822
5823Example: install the image to address 0x40100000 (which on the
5824TQM8xxL is in the first Flash bank):
5825
5826	=> erase 40100000 401FFFFF
5827
5828	.......... done
5829	Erased 8 sectors
5830
5831	=> loads 40100000
5832	## Ready for S-Record download ...
5833	~>examples/image.srec
5834	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5835	...
5836	15989 15990 15991 15992
5837	[file transfer complete]
5838	[connected]
5839	## Start Addr = 0x00000000
5840
5841
5842You can check the success of the download using the 'iminfo' command;
5843this includes a checksum verification so you can be sure no data
5844corruption happened:
5845
5846	=> imi 40100000
5847
5848	## Checking Image at 40100000 ...
5849	   Image Name:	 2.2.13 for initrd on TQM850L
5850	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5851	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5852	   Load Address: 00000000
5853	   Entry Point:	 0000000c
5854	   Verifying Checksum ... OK
5855
5856
5857Boot Linux:
5858-----------
5859
5860The "bootm" command is used to boot an application that is stored in
5861memory (RAM or Flash). In case of a Linux kernel image, the contents
5862of the "bootargs" environment variable is passed to the kernel as
5863parameters. You can check and modify this variable using the
5864"printenv" and "setenv" commands:
5865
5866
5867	=> printenv bootargs
5868	bootargs=root=/dev/ram
5869
5870	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5871
5872	=> printenv bootargs
5873	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5874
5875	=> bootm 40020000
5876	## Booting Linux kernel at 40020000 ...
5877	   Image Name:	 2.2.13 for NFS on TQM850L
5878	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5879	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5880	   Load Address: 00000000
5881	   Entry Point:	 0000000c
5882	   Verifying Checksum ... OK
5883	   Uncompressing Kernel Image ... OK
5884	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
5885	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5886	time_init: decrementer frequency = 187500000/60
5887	Calibrating delay loop... 49.77 BogoMIPS
5888	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5889	...
5890
5891If you want to boot a Linux kernel with initial RAM disk, you pass
5892the memory addresses of both the kernel and the initrd image (PPBCOOT
5893format!) to the "bootm" command:
5894
5895	=> imi 40100000 40200000
5896
5897	## Checking Image at 40100000 ...
5898	   Image Name:	 2.2.13 for initrd on TQM850L
5899	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5900	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5901	   Load Address: 00000000
5902	   Entry Point:	 0000000c
5903	   Verifying Checksum ... OK
5904
5905	## Checking Image at 40200000 ...
5906	   Image Name:	 Simple Ramdisk Image
5907	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5908	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5909	   Load Address: 00000000
5910	   Entry Point:	 00000000
5911	   Verifying Checksum ... OK
5912
5913	=> bootm 40100000 40200000
5914	## Booting Linux kernel at 40100000 ...
5915	   Image Name:	 2.2.13 for initrd on TQM850L
5916	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5917	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5918	   Load Address: 00000000
5919	   Entry Point:	 0000000c
5920	   Verifying Checksum ... OK
5921	   Uncompressing Kernel Image ... OK
5922	## Loading RAMDisk Image at 40200000 ...
5923	   Image Name:	 Simple Ramdisk Image
5924	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5925	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5926	   Load Address: 00000000
5927	   Entry Point:	 00000000
5928	   Verifying Checksum ... OK
5929	   Loading Ramdisk ... OK
5930	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
5931	Boot arguments: root=/dev/ram
5932	time_init: decrementer frequency = 187500000/60
5933	Calibrating delay loop... 49.77 BogoMIPS
5934	...
5935	RAMDISK: Compressed image found at block 0
5936	VFS: Mounted root (ext2 filesystem).
5937
5938	bash#
5939
5940Boot Linux and pass a flat device tree:
5941-----------
5942
5943First, U-Boot must be compiled with the appropriate defines. See the section
5944titled "Linux Kernel Interface" above for a more in depth explanation. The
5945following is an example of how to start a kernel and pass an updated
5946flat device tree:
5947
5948=> print oftaddr
5949oftaddr=0x300000
5950=> print oft
5951oft=oftrees/mpc8540ads.dtb
5952=> tftp $oftaddr $oft
5953Speed: 1000, full duplex
5954Using TSEC0 device
5955TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5956Filename 'oftrees/mpc8540ads.dtb'.
5957Load address: 0x300000
5958Loading: #
5959done
5960Bytes transferred = 4106 (100a hex)
5961=> tftp $loadaddr $bootfile
5962Speed: 1000, full duplex
5963Using TSEC0 device
5964TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5965Filename 'uImage'.
5966Load address: 0x200000
5967Loading:############
5968done
5969Bytes transferred = 1029407 (fb51f hex)
5970=> print loadaddr
5971loadaddr=200000
5972=> print oftaddr
5973oftaddr=0x300000
5974=> bootm $loadaddr - $oftaddr
5975## Booting image at 00200000 ...
5976   Image Name:	 Linux-2.6.17-dirty
5977   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5978   Data Size:	 1029343 Bytes = 1005.2 kB
5979   Load Address: 00000000
5980   Entry Point:	 00000000
5981   Verifying Checksum ... OK
5982   Uncompressing Kernel Image ... OK
5983Booting using flat device tree at 0x300000
5984Using MPC85xx ADS machine description
5985Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5986[snip]
5987
5988
5989More About U-Boot Image Types:
5990------------------------------
5991
5992U-Boot supports the following image types:
5993
5994   "Standalone Programs" are directly runnable in the environment
5995	provided by U-Boot; it is expected that (if they behave
5996	well) you can continue to work in U-Boot after return from
5997	the Standalone Program.
5998   "OS Kernel Images" are usually images of some Embedded OS which
5999	will take over control completely. Usually these programs
6000	will install their own set of exception handlers, device
6001	drivers, set up the MMU, etc. - this means, that you cannot
6002	expect to re-enter U-Boot except by resetting the CPU.
6003   "RAMDisk Images" are more or less just data blocks, and their
6004	parameters (address, size) are passed to an OS kernel that is
6005	being started.
6006   "Multi-File Images" contain several images, typically an OS
6007	(Linux) kernel image and one or more data images like
6008	RAMDisks. This construct is useful for instance when you want
6009	to boot over the network using BOOTP etc., where the boot
6010	server provides just a single image file, but you want to get
6011	for instance an OS kernel and a RAMDisk image.
6012
6013	"Multi-File Images" start with a list of image sizes, each
6014	image size (in bytes) specified by an "uint32_t" in network
6015	byte order. This list is terminated by an "(uint32_t)0".
6016	Immediately after the terminating 0 follow the images, one by
6017	one, all aligned on "uint32_t" boundaries (size rounded up to
6018	a multiple of 4 bytes).
6019
6020   "Firmware Images" are binary images containing firmware (like
6021	U-Boot or FPGA images) which usually will be programmed to
6022	flash memory.
6023
6024   "Script files" are command sequences that will be executed by
6025	U-Boot's command interpreter; this feature is especially
6026	useful when you configure U-Boot to use a real shell (hush)
6027	as command interpreter.
6028
6029Booting the Linux zImage:
6030-------------------------
6031
6032On some platforms, it's possible to boot Linux zImage. This is done
6033using the "bootz" command. The syntax of "bootz" command is the same
6034as the syntax of "bootm" command.
6035
6036Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
6037kernel with raw initrd images. The syntax is slightly different, the
6038address of the initrd must be augmented by it's size, in the following
6039format: "<initrd addres>:<initrd size>".
6040
6041
6042Standalone HOWTO:
6043=================
6044
6045One of the features of U-Boot is that you can dynamically load and
6046run "standalone" applications, which can use some resources of
6047U-Boot like console I/O functions or interrupt services.
6048
6049Two simple examples are included with the sources:
6050
6051"Hello World" Demo:
6052-------------------
6053
6054'examples/hello_world.c' contains a small "Hello World" Demo
6055application; it is automatically compiled when you build U-Boot.
6056It's configured to run at address 0x00040004, so you can play with it
6057like that:
6058
6059	=> loads
6060	## Ready for S-Record download ...
6061	~>examples/hello_world.srec
6062	1 2 3 4 5 6 7 8 9 10 11 ...
6063	[file transfer complete]
6064	[connected]
6065	## Start Addr = 0x00040004
6066
6067	=> go 40004 Hello World! This is a test.
6068	## Starting application at 0x00040004 ...
6069	Hello World
6070	argc = 7
6071	argv[0] = "40004"
6072	argv[1] = "Hello"
6073	argv[2] = "World!"
6074	argv[3] = "This"
6075	argv[4] = "is"
6076	argv[5] = "a"
6077	argv[6] = "test."
6078	argv[7] = "<NULL>"
6079	Hit any key to exit ...
6080
6081	## Application terminated, rc = 0x0
6082
6083Another example, which demonstrates how to register a CPM interrupt
6084handler with the U-Boot code, can be found in 'examples/timer.c'.
6085Here, a CPM timer is set up to generate an interrupt every second.
6086The interrupt service routine is trivial, just printing a '.'
6087character, but this is just a demo program. The application can be
6088controlled by the following keys:
6089
6090	? - print current values og the CPM Timer registers
6091	b - enable interrupts and start timer
6092	e - stop timer and disable interrupts
6093	q - quit application
6094
6095	=> loads
6096	## Ready for S-Record download ...
6097	~>examples/timer.srec
6098	1 2 3 4 5 6 7 8 9 10 11 ...
6099	[file transfer complete]
6100	[connected]
6101	## Start Addr = 0x00040004
6102
6103	=> go 40004
6104	## Starting application at 0x00040004 ...
6105	TIMERS=0xfff00980
6106	Using timer 1
6107	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
6108
6109Hit 'b':
6110	[q, b, e, ?] Set interval 1000000 us
6111	Enabling timer
6112Hit '?':
6113	[q, b, e, ?] ........
6114	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
6115Hit '?':
6116	[q, b, e, ?] .
6117	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
6118Hit '?':
6119	[q, b, e, ?] .
6120	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
6121Hit '?':
6122	[q, b, e, ?] .
6123	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
6124Hit 'e':
6125	[q, b, e, ?] ...Stopping timer
6126Hit 'q':
6127	[q, b, e, ?] ## Application terminated, rc = 0x0
6128
6129
6130Minicom warning:
6131================
6132
6133Over time, many people have reported problems when trying to use the
6134"minicom" terminal emulation program for serial download. I (wd)
6135consider minicom to be broken, and recommend not to use it. Under
6136Unix, I recommend to use C-Kermit for general purpose use (and
6137especially for kermit binary protocol download ("loadb" command), and
6138use "cu" for S-Record download ("loads" command).  See
6139http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
6140for help with kermit.
6141
6142
6143Nevertheless, if you absolutely want to use it try adding this
6144configuration to your "File transfer protocols" section:
6145
6146	   Name	   Program			Name U/D FullScr IO-Red. Multi
6147	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
6148	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
6149
6150
6151NetBSD Notes:
6152=============
6153
6154Starting at version 0.9.2, U-Boot supports NetBSD both as host
6155(build U-Boot) and target system (boots NetBSD/mpc8xx).
6156
6157Building requires a cross environment; it is known to work on
6158NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
6159need gmake since the Makefiles are not compatible with BSD make).
6160Note that the cross-powerpc package does not install include files;
6161attempting to build U-Boot will fail because <machine/ansi.h> is
6162missing.  This file has to be installed and patched manually:
6163
6164	# cd /usr/pkg/cross/powerpc-netbsd/include
6165	# mkdir powerpc
6166	# ln -s powerpc machine
6167	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
6168	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
6169
6170Native builds *don't* work due to incompatibilities between native
6171and U-Boot include files.
6172
6173Booting assumes that (the first part of) the image booted is a
6174stage-2 loader which in turn loads and then invokes the kernel
6175proper. Loader sources will eventually appear in the NetBSD source
6176tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
6177meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
6178
6179
6180Implementation Internals:
6181=========================
6182
6183The following is not intended to be a complete description of every
6184implementation detail. However, it should help to understand the
6185inner workings of U-Boot and make it easier to port it to custom
6186hardware.
6187
6188
6189Initial Stack, Global Data:
6190---------------------------
6191
6192The implementation of U-Boot is complicated by the fact that U-Boot
6193starts running out of ROM (flash memory), usually without access to
6194system RAM (because the memory controller is not initialized yet).
6195This means that we don't have writable Data or BSS segments, and BSS
6196is not initialized as zero. To be able to get a C environment working
6197at all, we have to allocate at least a minimal stack. Implementation
6198options for this are defined and restricted by the CPU used: Some CPU
6199models provide on-chip memory (like the IMMR area on MPC8xx and
6200MPC826x processors), on others (parts of) the data cache can be
6201locked as (mis-) used as memory, etc.
6202
6203	Chris Hallinan posted a good summary of these issues to the
6204	U-Boot mailing list:
6205
6206	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
6207	From: "Chris Hallinan" <clh@net1plus.com>
6208	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
6209	...
6210
6211	Correct me if I'm wrong, folks, but the way I understand it
6212	is this: Using DCACHE as initial RAM for Stack, etc, does not
6213	require any physical RAM backing up the cache. The cleverness
6214	is that the cache is being used as a temporary supply of
6215	necessary storage before the SDRAM controller is setup. It's
6216	beyond the scope of this list to explain the details, but you
6217	can see how this works by studying the cache architecture and
6218	operation in the architecture and processor-specific manuals.
6219
6220	OCM is On Chip Memory, which I believe the 405GP has 4K. It
6221	is another option for the system designer to use as an
6222	initial stack/RAM area prior to SDRAM being available. Either
6223	option should work for you. Using CS 4 should be fine if your
6224	board designers haven't used it for something that would
6225	cause you grief during the initial boot! It is frequently not
6226	used.
6227
6228	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
6229	with your processor/board/system design. The default value
6230	you will find in any recent u-boot distribution in
6231	walnut.h should work for you. I'd set it to a value larger
6232	than your SDRAM module. If you have a 64MB SDRAM module, set
6233	it above 400_0000. Just make sure your board has no resources
6234	that are supposed to respond to that address! That code in
6235	start.S has been around a while and should work as is when
6236	you get the config right.
6237
6238	-Chris Hallinan
6239	DS4.COM, Inc.
6240
6241It is essential to remember this, since it has some impact on the C
6242code for the initialization procedures:
6243
6244* Initialized global data (data segment) is read-only. Do not attempt
6245  to write it.
6246
6247* Do not use any uninitialized global data (or implicitly initialized
6248  as zero data - BSS segment) at all - this is undefined, initiali-
6249  zation is performed later (when relocating to RAM).
6250
6251* Stack space is very limited. Avoid big data buffers or things like
6252  that.
6253
6254Having only the stack as writable memory limits means we cannot use
6255normal global data to share information between the code. But it
6256turned out that the implementation of U-Boot can be greatly
6257simplified by making a global data structure (gd_t) available to all
6258functions. We could pass a pointer to this data as argument to _all_
6259functions, but this would bloat the code. Instead we use a feature of
6260the GCC compiler (Global Register Variables) to share the data: we
6261place a pointer (gd) to the global data into a register which we
6262reserve for this purpose.
6263
6264When choosing a register for such a purpose we are restricted by the
6265relevant  (E)ABI  specifications for the current architecture, and by
6266GCC's implementation.
6267
6268For PowerPC, the following registers have specific use:
6269	R1:	stack pointer
6270	R2:	reserved for system use
6271	R3-R4:	parameter passing and return values
6272	R5-R10: parameter passing
6273	R13:	small data area pointer
6274	R30:	GOT pointer
6275	R31:	frame pointer
6276
6277	(U-Boot also uses R12 as internal GOT pointer. r12
6278	is a volatile register so r12 needs to be reset when
6279	going back and forth between asm and C)
6280
6281    ==> U-Boot will use R2 to hold a pointer to the global data
6282
6283    Note: on PPC, we could use a static initializer (since the
6284    address of the global data structure is known at compile time),
6285    but it turned out that reserving a register results in somewhat
6286    smaller code - although the code savings are not that big (on
6287    average for all boards 752 bytes for the whole U-Boot image,
6288    624 text + 127 data).
6289
6290On Blackfin, the normal C ABI (except for P3) is followed as documented here:
6291	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
6292
6293    ==> U-Boot will use P3 to hold a pointer to the global data
6294
6295On ARM, the following registers are used:
6296
6297	R0:	function argument word/integer result
6298	R1-R3:	function argument word
6299	R9:	platform specific
6300	R10:	stack limit (used only if stack checking is enabled)
6301	R11:	argument (frame) pointer
6302	R12:	temporary workspace
6303	R13:	stack pointer
6304	R14:	link register
6305	R15:	program counter
6306
6307    ==> U-Boot will use R9 to hold a pointer to the global data
6308
6309    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
6310
6311On Nios II, the ABI is documented here:
6312	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
6313
6314    ==> U-Boot will use gp to hold a pointer to the global data
6315
6316    Note: on Nios II, we give "-G0" option to gcc and don't use gp
6317    to access small data sections, so gp is free.
6318
6319On NDS32, the following registers are used:
6320
6321	R0-R1:	argument/return
6322	R2-R5:	argument
6323	R15:	temporary register for assembler
6324	R16:	trampoline register
6325	R28:	frame pointer (FP)
6326	R29:	global pointer (GP)
6327	R30:	link register (LP)
6328	R31:	stack pointer (SP)
6329	PC:	program counter (PC)
6330
6331    ==> U-Boot will use R10 to hold a pointer to the global data
6332
6333NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6334or current versions of GCC may "optimize" the code too much.
6335
6336Memory Management:
6337------------------
6338
6339U-Boot runs in system state and uses physical addresses, i.e. the
6340MMU is not used either for address mapping nor for memory protection.
6341
6342The available memory is mapped to fixed addresses using the memory
6343controller. In this process, a contiguous block is formed for each
6344memory type (Flash, SDRAM, SRAM), even when it consists of several
6345physical memory banks.
6346
6347U-Boot is installed in the first 128 kB of the first Flash bank (on
6348TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6349booting and sizing and initializing DRAM, the code relocates itself
6350to the upper end of DRAM. Immediately below the U-Boot code some
6351memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6352configuration setting]. Below that, a structure with global Board
6353Info data is placed, followed by the stack (growing downward).
6354
6355Additionally, some exception handler code is copied to the low 8 kB
6356of DRAM (0x00000000 ... 0x00001FFF).
6357
6358So a typical memory configuration with 16 MB of DRAM could look like
6359this:
6360
6361	0x0000 0000	Exception Vector code
6362	      :
6363	0x0000 1FFF
6364	0x0000 2000	Free for Application Use
6365	      :
6366	      :
6367
6368	      :
6369	      :
6370	0x00FB FF20	Monitor Stack (Growing downward)
6371	0x00FB FFAC	Board Info Data and permanent copy of global data
6372	0x00FC 0000	Malloc Arena
6373	      :
6374	0x00FD FFFF
6375	0x00FE 0000	RAM Copy of Monitor Code
6376	...		eventually: LCD or video framebuffer
6377	...		eventually: pRAM (Protected RAM - unchanged by reset)
6378	0x00FF FFFF	[End of RAM]
6379
6380
6381System Initialization:
6382----------------------
6383
6384In the reset configuration, U-Boot starts at the reset entry point
6385(on most PowerPC systems at address 0x00000100). Because of the reset
6386configuration for CS0# this is a mirror of the on board Flash memory.
6387To be able to re-map memory U-Boot then jumps to its link address.
6388To be able to implement the initialization code in C, a (small!)
6389initial stack is set up in the internal Dual Ported RAM (in case CPUs
6390which provide such a feature like MPC8xx or MPC8260), or in a locked
6391part of the data cache. After that, U-Boot initializes the CPU core,
6392the caches and the SIU.
6393
6394Next, all (potentially) available memory banks are mapped using a
6395preliminary mapping. For example, we put them on 512 MB boundaries
6396(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6397on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6398programmed for SDRAM access. Using the temporary configuration, a
6399simple memory test is run that determines the size of the SDRAM
6400banks.
6401
6402When there is more than one SDRAM bank, and the banks are of
6403different size, the largest is mapped first. For equal size, the first
6404bank (CS2#) is mapped first. The first mapping is always for address
64050x00000000, with any additional banks following immediately to create
6406contiguous memory starting from 0.
6407
6408Then, the monitor installs itself at the upper end of the SDRAM area
6409and allocates memory for use by malloc() and for the global Board
6410Info data; also, the exception vector code is copied to the low RAM
6411pages, and the final stack is set up.
6412
6413Only after this relocation will you have a "normal" C environment;
6414until that you are restricted in several ways, mostly because you are
6415running from ROM, and because the code will have to be relocated to a
6416new address in RAM.
6417
6418
6419U-Boot Porting Guide:
6420----------------------
6421
6422[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6423list, October 2002]
6424
6425
6426int main(int argc, char *argv[])
6427{
6428	sighandler_t no_more_time;
6429
6430	signal(SIGALRM, no_more_time);
6431	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6432
6433	if (available_money > available_manpower) {
6434		Pay consultant to port U-Boot;
6435		return 0;
6436	}
6437
6438	Download latest U-Boot source;
6439
6440	Subscribe to u-boot mailing list;
6441
6442	if (clueless)
6443		email("Hi, I am new to U-Boot, how do I get started?");
6444
6445	while (learning) {
6446		Read the README file in the top level directory;
6447		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6448		Read applicable doc/*.README;
6449		Read the source, Luke;
6450		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6451	}
6452
6453	if (available_money > toLocalCurrency ($2500))
6454		Buy a BDI3000;
6455	else
6456		Add a lot of aggravation and time;
6457
6458	if (a similar board exists) {	/* hopefully... */
6459		cp -a board/<similar> board/<myboard>
6460		cp include/configs/<similar>.h include/configs/<myboard>.h
6461	} else {
6462		Create your own board support subdirectory;
6463		Create your own board include/configs/<myboard>.h file;
6464	}
6465	Edit new board/<myboard> files
6466	Edit new include/configs/<myboard>.h
6467
6468	while (!accepted) {
6469		while (!running) {
6470			do {
6471				Add / modify source code;
6472			} until (compiles);
6473			Debug;
6474			if (clueless)
6475				email("Hi, I am having problems...");
6476		}
6477		Send patch file to the U-Boot email list;
6478		if (reasonable critiques)
6479			Incorporate improvements from email list code review;
6480		else
6481			Defend code as written;
6482	}
6483
6484	return 0;
6485}
6486
6487void no_more_time (int sig)
6488{
6489      hire_a_guru();
6490}
6491
6492
6493Coding Standards:
6494-----------------
6495
6496All contributions to U-Boot should conform to the Linux kernel
6497coding style; see the file "Documentation/CodingStyle" and the script
6498"scripts/Lindent" in your Linux kernel source directory.
6499
6500Source files originating from a different project (for example the
6501MTD subsystem) are generally exempt from these guidelines and are not
6502reformatted to ease subsequent migration to newer versions of those
6503sources.
6504
6505Please note that U-Boot is implemented in C (and to some small parts in
6506Assembler); no C++ is used, so please do not use C++ style comments (//)
6507in your code.
6508
6509Please also stick to the following formatting rules:
6510- remove any trailing white space
6511- use TAB characters for indentation and vertical alignment, not spaces
6512- make sure NOT to use DOS '\r\n' line feeds
6513- do not add more than 2 consecutive empty lines to source files
6514- do not add trailing empty lines to source files
6515
6516Submissions which do not conform to the standards may be returned
6517with a request to reformat the changes.
6518
6519
6520Submitting Patches:
6521-------------------
6522
6523Since the number of patches for U-Boot is growing, we need to
6524establish some rules. Submissions which do not conform to these rules
6525may be rejected, even when they contain important and valuable stuff.
6526
6527Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6528
6529Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6530see http://lists.denx.de/mailman/listinfo/u-boot
6531
6532When you send a patch, please include the following information with
6533it:
6534
6535* For bug fixes: a description of the bug and how your patch fixes
6536  this bug. Please try to include a way of demonstrating that the
6537  patch actually fixes something.
6538
6539* For new features: a description of the feature and your
6540  implementation.
6541
6542* A CHANGELOG entry as plaintext (separate from the patch)
6543
6544* For major contributions, add a MAINTAINERS file with your
6545  information and associated file and directory references.
6546
6547* When you add support for a new board, don't forget to add a
6548  maintainer e-mail address to the boards.cfg file, too.
6549
6550* If your patch adds new configuration options, don't forget to
6551  document these in the README file.
6552
6553* The patch itself. If you are using git (which is *strongly*
6554  recommended) you can easily generate the patch using the
6555  "git format-patch". If you then use "git send-email" to send it to
6556  the U-Boot mailing list, you will avoid most of the common problems
6557  with some other mail clients.
6558
6559  If you cannot use git, use "diff -purN OLD NEW". If your version of
6560  diff does not support these options, then get the latest version of
6561  GNU diff.
6562
6563  The current directory when running this command shall be the parent
6564  directory of the U-Boot source tree (i. e. please make sure that
6565  your patch includes sufficient directory information for the
6566  affected files).
6567
6568  We prefer patches as plain text. MIME attachments are discouraged,
6569  and compressed attachments must not be used.
6570
6571* If one logical set of modifications affects or creates several
6572  files, all these changes shall be submitted in a SINGLE patch file.
6573
6574* Changesets that contain different, unrelated modifications shall be
6575  submitted as SEPARATE patches, one patch per changeset.
6576
6577
6578Notes:
6579
6580* Before sending the patch, run the MAKEALL script on your patched
6581  source tree and make sure that no errors or warnings are reported
6582  for any of the boards.
6583
6584* Keep your modifications to the necessary minimum: A patch
6585  containing several unrelated changes or arbitrary reformats will be
6586  returned with a request to re-formatting / split it.
6587
6588* If you modify existing code, make sure that your new code does not
6589  add to the memory footprint of the code ;-) Small is beautiful!
6590  When adding new features, these should compile conditionally only
6591  (using #ifdef), and the resulting code with the new feature
6592  disabled must not need more memory than the old code without your
6593  modification.
6594
6595* Remember that there is a size limit of 100 kB per message on the
6596  u-boot mailing list. Bigger patches will be moderated. If they are
6597  reasonable and not too big, they will be acknowledged. But patches
6598  bigger than the size limit should be avoided.
6599