xref: /rk3399_rockchip-uboot/README (revision adde435fa7c03c17c40e9f771eceed127fbbc251)
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			CONFIG_HIDE_LOGO_VERSION
844						do not display bootloader
845						version string
846
847		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
848		a limited number of ANSI escape sequences (cursor control,
849		erase functions and limited graphics rendition control).
850
851		When CONFIG_CFB_CONSOLE is defined, video console is
852		default i/o. Serial console can be forced with
853		environment 'console=serial'.
854
855		When CONFIG_SILENT_CONSOLE is defined, all console
856		messages (by U-Boot and Linux!) can be silenced with
857		the "silent" environment variable. See
858		doc/README.silent for more information.
859
860		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
861			is 0x00.
862		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
863			is 0xa0.
864
865- Console Baudrate:
866		CONFIG_BAUDRATE - in bps
867		Select one of the baudrates listed in
868		CONFIG_SYS_BAUDRATE_TABLE, see below.
869		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
870
871- Console Rx buffer length
872		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
873		the maximum receive buffer length for the SMC.
874		This option is actual only for 82xx and 8xx possible.
875		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
876		must be defined, to setup the maximum idle timeout for
877		the SMC.
878
879- Pre-Console Buffer:
880		Prior to the console being initialised (i.e. serial UART
881		initialised etc) all console output is silently discarded.
882		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
883		buffer any console messages prior to the console being
884		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
885		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
886		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
887		bytes are output before the console is initialised, the
888		earlier bytes are discarded.
889
890		Note that when printing the buffer a copy is made on the
891		stack so CONFIG_PRE_CON_BUF_SZ must fit on the stack.
892
893		'Sane' compilers will generate smaller code if
894		CONFIG_PRE_CON_BUF_SZ is a power of 2
895
896- Autoboot Command:
897		CONFIG_BOOTCOMMAND
898		Only needed when CONFIG_BOOTDELAY is enabled;
899		define a command string that is automatically executed
900		when no character is read on the console interface
901		within "Boot Delay" after reset.
902
903		CONFIG_BOOTARGS
904		This can be used to pass arguments to the bootm
905		command. The value of CONFIG_BOOTARGS goes into the
906		environment value "bootargs".
907
908		CONFIG_RAMBOOT and CONFIG_NFSBOOT
909		The value of these goes into the environment as
910		"ramboot" and "nfsboot" respectively, and can be used
911		as a convenience, when switching between booting from
912		RAM and NFS.
913
914- Bootcount:
915		CONFIG_BOOTCOUNT_LIMIT
916		Implements a mechanism for detecting a repeating reboot
917		cycle, see:
918		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
919
920		CONFIG_BOOTCOUNT_ENV
921		If no softreset save registers are found on the hardware
922		"bootcount" is stored in the environment. To prevent a
923		saveenv on all reboots, the environment variable
924		"upgrade_available" is used. If "upgrade_available" is
925		0, "bootcount" is always 0, if "upgrade_available" is
926		1 "bootcount" is incremented in the environment.
927		So the Userspace Applikation must set the "upgrade_available"
928		and "bootcount" variable to 0, if a boot was successfully.
929
930- Pre-Boot Commands:
931		CONFIG_PREBOOT
932
933		When this option is #defined, the existence of the
934		environment variable "preboot" will be checked
935		immediately before starting the CONFIG_BOOTDELAY
936		countdown and/or running the auto-boot command resp.
937		entering interactive mode.
938
939		This feature is especially useful when "preboot" is
940		automatically generated or modified. For an example
941		see the LWMON board specific code: here "preboot" is
942		modified when the user holds down a certain
943		combination of keys on the (special) keyboard when
944		booting the systems
945
946- Serial Download Echo Mode:
947		CONFIG_LOADS_ECHO
948		If defined to 1, all characters received during a
949		serial download (using the "loads" command) are
950		echoed back. This might be needed by some terminal
951		emulations (like "cu"), but may as well just take
952		time on others. This setting #define's the initial
953		value of the "loads_echo" environment variable.
954
955- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
956		CONFIG_KGDB_BAUDRATE
957		Select one of the baudrates listed in
958		CONFIG_SYS_BAUDRATE_TABLE, see below.
959
960- Monitor Functions:
961		Monitor commands can be included or excluded
962		from the build by using the #include files
963		<config_cmd_all.h> and #undef'ing unwanted
964		commands, or adding #define's for wanted commands.
965
966		The default command configuration includes all commands
967		except those marked below with a "*".
968
969		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
970		CONFIG_CMD_ASKENV	* ask for env variable
971		CONFIG_CMD_BDI		  bdinfo
972		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
973		CONFIG_CMD_BMP		* BMP support
974		CONFIG_CMD_BSP		* Board specific commands
975		CONFIG_CMD_BOOTD	  bootd
976		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
977		CONFIG_CMD_CACHE	* icache, dcache
978		CONFIG_CMD_CLK   	* clock command support
979		CONFIG_CMD_CONSOLE	  coninfo
980		CONFIG_CMD_CRC32	* crc32
981		CONFIG_CMD_DATE		* support for RTC, date/time...
982		CONFIG_CMD_DHCP		* DHCP support
983		CONFIG_CMD_DIAG		* Diagnostics
984		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
985		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
986		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
987		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
988		CONFIG_CMD_DTT		* Digital Therm and Thermostat
989		CONFIG_CMD_ECHO		  echo arguments
990		CONFIG_CMD_EDITENV	  edit env variable
991		CONFIG_CMD_EEPROM	* EEPROM read/write support
992		CONFIG_CMD_EEPROM_LAYOUT* EEPROM layout aware commands
993		CONFIG_CMD_ELF		* bootelf, bootvx
994		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
995		CONFIG_CMD_ENV_FLAGS	* display details about env flags
996		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
997		CONFIG_CMD_EXPORTENV	* export the environment
998		CONFIG_CMD_EXT2		* ext2 command support
999		CONFIG_CMD_EXT4		* ext4 command support
1000		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
1001					  that work for multiple fs types
1002		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
1003		CONFIG_CMD_SAVEENV	  saveenv
1004		CONFIG_CMD_FDC		* Floppy Disk Support
1005		CONFIG_CMD_FAT		* FAT command support
1006		CONFIG_CMD_FLASH	  flinfo, erase, protect
1007		CONFIG_CMD_FPGA		  FPGA device initialization support
1008		CONFIG_CMD_FUSE		* Device fuse support
1009		CONFIG_CMD_GETTIME	* Get time since boot
1010		CONFIG_CMD_GO		* the 'go' command (exec code)
1011		CONFIG_CMD_GREPENV	* search environment
1012		CONFIG_CMD_HASH		* calculate hash / digest
1013		CONFIG_CMD_I2C		* I2C serial bus support
1014		CONFIG_CMD_IDE		* IDE harddisk support
1015		CONFIG_CMD_IMI		  iminfo
1016		CONFIG_CMD_IMLS		  List all images found in NOR flash
1017		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
1018		CONFIG_CMD_IMMAP	* IMMR dump support
1019		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
1020		CONFIG_CMD_IMPORTENV	* import an environment
1021		CONFIG_CMD_INI		* import data from an ini file into the env
1022		CONFIG_CMD_IRQ		* irqinfo
1023		CONFIG_CMD_ITEST	  Integer/string test of 2 values
1024		CONFIG_CMD_JFFS2	* JFFS2 Support
1025		CONFIG_CMD_KGDB		* kgdb
1026		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
1027		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
1028					  (169.254.*.*)
1029		CONFIG_CMD_LOADB	  loadb
1030		CONFIG_CMD_LOADS	  loads
1031		CONFIG_CMD_MD5SUM	* print md5 message digest
1032					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
1033		CONFIG_CMD_MEMINFO	* Display detailed memory information
1034		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
1035					  loop, loopw
1036		CONFIG_CMD_MEMTEST	* mtest
1037		CONFIG_CMD_MISC		  Misc functions like sleep etc
1038		CONFIG_CMD_MMC		* MMC memory mapped support
1039		CONFIG_CMD_MII		* MII utility commands
1040		CONFIG_CMD_MTDPARTS	* MTD partition support
1041		CONFIG_CMD_NAND		* NAND support
1042		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1043		CONFIG_CMD_NFS		  NFS support
1044		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1045		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1046		CONFIG_CMD_PCI		* pciinfo
1047		CONFIG_CMD_PCMCIA		* PCMCIA support
1048		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1049					  host
1050		CONFIG_CMD_PORTIO	* Port I/O
1051		CONFIG_CMD_READ		* Read raw data from partition
1052		CONFIG_CMD_REGINFO	* Register dump
1053		CONFIG_CMD_RUN		  run command in env variable
1054		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1055		CONFIG_CMD_SAVES	* save S record dump
1056		CONFIG_SCSI		* SCSI Support
1057		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1058					  (requires CONFIG_CMD_I2C)
1059		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1060					  (4xx only)
1061		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1062		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1063					  (requires CONFIG_CMD_MEMORY)
1064		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1065		CONFIG_CMD_SOURCE	  "source" command Support
1066		CONFIG_CMD_SPI		* SPI serial bus support
1067		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1068		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1069		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1070		CONFIG_CMD_TIMER	* access to the system tick timer
1071		CONFIG_CMD_USB		* USB support
1072		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1073		CONFIG_CMD_MFSL		* Microblaze FSL support
1074		CONFIG_CMD_XIMG		  Load part of Multi Image
1075		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1076
1077		EXAMPLE: If you want all functions except of network
1078		support you can write:
1079
1080		#include "config_cmd_all.h"
1081		#undef CONFIG_CMD_NET
1082
1083	Other Commands:
1084		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1085
1086	Note:	Don't enable the "icache" and "dcache" commands
1087		(configuration option CONFIG_CMD_CACHE) unless you know
1088		what you (and your U-Boot users) are doing. Data
1089		cache cannot be enabled on systems like the 8xx or
1090		8260 (where accesses to the IMMR region must be
1091		uncached), and it cannot be disabled on all other
1092		systems where we (mis-) use the data cache to hold an
1093		initial stack and some data.
1094
1095
1096		XXX - this list needs to get updated!
1097
1098- Removal of commands
1099		If no commands are needed to boot, you can disable
1100		CONFIG_CMDLINE to remove them. In this case, the command line
1101		will not be available, and when U-Boot wants to execute the
1102		boot command (on start-up) it will call board_run_command()
1103		instead. This can reduce image size significantly for very
1104		simple boot procedures.
1105
1106- Regular expression support:
1107		CONFIG_REGEX
1108		If this variable is defined, U-Boot is linked against
1109		the SLRE (Super Light Regular Expression) library,
1110		which adds regex support to some commands, as for
1111		example "env grep" and "setexpr".
1112
1113- Device tree:
1114		CONFIG_OF_CONTROL
1115		If this variable is defined, U-Boot will use a device tree
1116		to configure its devices, instead of relying on statically
1117		compiled #defines in the board file. This option is
1118		experimental and only available on a few boards. The device
1119		tree is available in the global data as gd->fdt_blob.
1120
1121		U-Boot needs to get its device tree from somewhere. This can
1122		be done using one of the two options below:
1123
1124		CONFIG_OF_EMBED
1125		If this variable is defined, U-Boot will embed a device tree
1126		binary in its image. This device tree file should be in the
1127		board directory and called <soc>-<board>.dts. The binary file
1128		is then picked up in board_init_f() and made available through
1129		the global data structure as gd->blob.
1130
1131		CONFIG_OF_SEPARATE
1132		If this variable is defined, U-Boot will build a device tree
1133		binary. It will be called u-boot.dtb. Architecture-specific
1134		code will locate it at run-time. Generally this works by:
1135
1136			cat u-boot.bin u-boot.dtb >image.bin
1137
1138		and in fact, U-Boot does this for you, creating a file called
1139		u-boot-dtb.bin which is useful in the common case. You can
1140		still use the individual files if you need something more
1141		exotic.
1142
1143- Watchdog:
1144		CONFIG_WATCHDOG
1145		If this variable is defined, it enables watchdog
1146		support for the SoC. There must be support in the SoC
1147		specific code for a watchdog. For the 8xx and 8260
1148		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1149		register.  When supported for a specific SoC is
1150		available, then no further board specific code should
1151		be needed to use it.
1152
1153		CONFIG_HW_WATCHDOG
1154		When using a watchdog circuitry external to the used
1155		SoC, then define this variable and provide board
1156		specific code for the "hw_watchdog_reset" function.
1157
1158		CONFIG_AT91_HW_WDT_TIMEOUT
1159		specify the timeout in seconds. default 2 seconds.
1160
1161- U-Boot Version:
1162		CONFIG_VERSION_VARIABLE
1163		If this variable is defined, an environment variable
1164		named "ver" is created by U-Boot showing the U-Boot
1165		version as printed by the "version" command.
1166		Any change to this variable will be reverted at the
1167		next reset.
1168
1169- Real-Time Clock:
1170
1171		When CONFIG_CMD_DATE is selected, the type of the RTC
1172		has to be selected, too. Define exactly one of the
1173		following options:
1174
1175		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1176		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1177		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1178		CONFIG_RTC_MC146818	- use MC146818 RTC
1179		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1180		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1181		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1182		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1183		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1184		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1185		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1186		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1187		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1188					  RV3029 RTC.
1189
1190		Note that if the RTC uses I2C, then the I2C interface
1191		must also be configured. See I2C Support, below.
1192
1193- GPIO Support:
1194		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1195
1196		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1197		chip-ngpio pairs that tell the PCA953X driver the number of
1198		pins supported by a particular chip.
1199
1200		Note that if the GPIO device uses I2C, then the I2C interface
1201		must also be configured. See I2C Support, below.
1202
1203- I/O tracing:
1204		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1205		accesses and can checksum them or write a list of them out
1206		to memory. See the 'iotrace' command for details. This is
1207		useful for testing device drivers since it can confirm that
1208		the driver behaves the same way before and after a code
1209		change. Currently this is supported on sandbox and arm. To
1210		add support for your architecture, add '#include <iotrace.h>'
1211		to the bottom of arch/<arch>/include/asm/io.h and test.
1212
1213		Example output from the 'iotrace stats' command is below.
1214		Note that if the trace buffer is exhausted, the checksum will
1215		still continue to operate.
1216
1217			iotrace is enabled
1218			Start:  10000000	(buffer start address)
1219			Size:   00010000	(buffer size)
1220			Offset: 00000120	(current buffer offset)
1221			Output: 10000120	(start + offset)
1222			Count:  00000018	(number of trace records)
1223			CRC32:  9526fb66	(CRC32 of all trace records)
1224
1225- Timestamp Support:
1226
1227		When CONFIG_TIMESTAMP is selected, the timestamp
1228		(date and time) of an image is printed by image
1229		commands like bootm or iminfo. This option is
1230		automatically enabled when you select CONFIG_CMD_DATE .
1231
1232- Partition Labels (disklabels) Supported:
1233		Zero or more of the following:
1234		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1235		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1236				       Intel architecture, USB sticks, etc.
1237		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1238		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1239				       bootloader.  Note 2TB partition limit; see
1240				       disk/part_efi.c
1241		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1242
1243		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1244		CONFIG_SCSI) you must configure support for at
1245		least one non-MTD partition type as well.
1246
1247- IDE Reset method:
1248		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1249		board configurations files but used nowhere!
1250
1251		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1252		be performed by calling the function
1253			ide_set_reset(int reset)
1254		which has to be defined in a board specific file
1255
1256- ATAPI Support:
1257		CONFIG_ATAPI
1258
1259		Set this to enable ATAPI support.
1260
1261- LBA48 Support
1262		CONFIG_LBA48
1263
1264		Set this to enable support for disks larger than 137GB
1265		Also look at CONFIG_SYS_64BIT_LBA.
1266		Whithout these , LBA48 support uses 32bit variables and will 'only'
1267		support disks up to 2.1TB.
1268
1269		CONFIG_SYS_64BIT_LBA:
1270			When enabled, makes the IDE subsystem use 64bit sector addresses.
1271			Default is 32bit.
1272
1273- SCSI Support:
1274		At the moment only there is only support for the
1275		SYM53C8XX SCSI controller; define
1276		CONFIG_SCSI_SYM53C8XX to enable it.
1277
1278		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1279		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1280		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1281		maximum numbers of LUNs, SCSI ID's and target
1282		devices.
1283		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1284
1285		The environment variable 'scsidevs' is set to the number of
1286		SCSI devices found during the last scan.
1287
1288- NETWORK Support (PCI):
1289		CONFIG_E1000
1290		Support for Intel 8254x/8257x gigabit chips.
1291
1292		CONFIG_E1000_SPI
1293		Utility code for direct access to the SPI bus on Intel 8257x.
1294		This does not do anything useful unless you set at least one
1295		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1296
1297		CONFIG_E1000_SPI_GENERIC
1298		Allow generic access to the SPI bus on the Intel 8257x, for
1299		example with the "sspi" command.
1300
1301		CONFIG_CMD_E1000
1302		Management command for E1000 devices.  When used on devices
1303		with SPI support you can reprogram the EEPROM from U-Boot.
1304
1305		CONFIG_EEPRO100
1306		Support for Intel 82557/82559/82559ER chips.
1307		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1308		write routine for first time initialisation.
1309
1310		CONFIG_TULIP
1311		Support for Digital 2114x chips.
1312		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1313		modem chip initialisation (KS8761/QS6611).
1314
1315		CONFIG_NATSEMI
1316		Support for National dp83815 chips.
1317
1318		CONFIG_NS8382X
1319		Support for National dp8382[01] gigabit chips.
1320
1321- NETWORK Support (other):
1322
1323		CONFIG_DRIVER_AT91EMAC
1324		Support for AT91RM9200 EMAC.
1325
1326			CONFIG_RMII
1327			Define this to use reduced MII inteface
1328
1329			CONFIG_DRIVER_AT91EMAC_QUIET
1330			If this defined, the driver is quiet.
1331			The driver doen't show link status messages.
1332
1333		CONFIG_CALXEDA_XGMAC
1334		Support for the Calxeda XGMAC device
1335
1336		CONFIG_LAN91C96
1337		Support for SMSC's LAN91C96 chips.
1338
1339			CONFIG_LAN91C96_BASE
1340			Define this to hold the physical address
1341			of the LAN91C96's I/O space
1342
1343			CONFIG_LAN91C96_USE_32_BIT
1344			Define this to enable 32 bit addressing
1345
1346		CONFIG_SMC91111
1347		Support for SMSC's LAN91C111 chip
1348
1349			CONFIG_SMC91111_BASE
1350			Define this to hold the physical address
1351			of the device (I/O space)
1352
1353			CONFIG_SMC_USE_32_BIT
1354			Define this if data bus is 32 bits
1355
1356			CONFIG_SMC_USE_IOFUNCS
1357			Define this to use i/o functions instead of macros
1358			(some hardware wont work with macros)
1359
1360		CONFIG_DRIVER_TI_EMAC
1361		Support for davinci emac
1362
1363			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1364			Define this if you have more then 3 PHYs.
1365
1366		CONFIG_FTGMAC100
1367		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1368
1369			CONFIG_FTGMAC100_EGIGA
1370			Define this to use GE link update with gigabit PHY.
1371			Define this if FTGMAC100 is connected to gigabit PHY.
1372			If your system has 10/100 PHY only, it might not occur
1373			wrong behavior. Because PHY usually return timeout or
1374			useless data when polling gigabit status and gigabit
1375			control registers. This behavior won't affect the
1376			correctnessof 10/100 link speed update.
1377
1378		CONFIG_SMC911X
1379		Support for SMSC's LAN911x and LAN921x chips
1380
1381			CONFIG_SMC911X_BASE
1382			Define this to hold the physical address
1383			of the device (I/O space)
1384
1385			CONFIG_SMC911X_32_BIT
1386			Define this if data bus is 32 bits
1387
1388			CONFIG_SMC911X_16_BIT
1389			Define this if data bus is 16 bits. If your processor
1390			automatically converts one 32 bit word to two 16 bit
1391			words you may also try CONFIG_SMC911X_32_BIT.
1392
1393		CONFIG_SH_ETHER
1394		Support for Renesas on-chip Ethernet controller
1395
1396			CONFIG_SH_ETHER_USE_PORT
1397			Define the number of ports to be used
1398
1399			CONFIG_SH_ETHER_PHY_ADDR
1400			Define the ETH PHY's address
1401
1402			CONFIG_SH_ETHER_CACHE_WRITEBACK
1403			If this option is set, the driver enables cache flush.
1404
1405- PWM Support:
1406		CONFIG_PWM_IMX
1407		Support for PWM modul on the imx6.
1408
1409- TPM Support:
1410		CONFIG_TPM
1411		Support TPM devices.
1412
1413		CONFIG_TPM_TIS_INFINEON
1414		Support for Infineon i2c bus TPM devices. Only one device
1415		per system is supported at this time.
1416
1417			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1418			Define the burst count bytes upper limit
1419
1420		CONFIG_TPM_ST33ZP24
1421		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1422
1423			CONFIG_TPM_ST33ZP24_I2C
1424			Support for STMicroelectronics ST33ZP24 I2C devices.
1425			Requires TPM_ST33ZP24 and I2C.
1426
1427			CONFIG_TPM_ST33ZP24_SPI
1428			Support for STMicroelectronics ST33ZP24 SPI devices.
1429			Requires TPM_ST33ZP24 and SPI.
1430
1431		CONFIG_TPM_ATMEL_TWI
1432		Support for Atmel TWI TPM device. Requires I2C support.
1433
1434		CONFIG_TPM_TIS_LPC
1435		Support for generic parallel port TPM devices. Only one device
1436		per system is supported at this time.
1437
1438			CONFIG_TPM_TIS_BASE_ADDRESS
1439			Base address where the generic TPM device is mapped
1440			to. Contemporary x86 systems usually map it at
1441			0xfed40000.
1442
1443		CONFIG_CMD_TPM
1444		Add tpm monitor functions.
1445		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1446		provides monitor access to authorized functions.
1447
1448		CONFIG_TPM
1449		Define this to enable the TPM support library which provides
1450		functional interfaces to some TPM commands.
1451		Requires support for a TPM device.
1452
1453		CONFIG_TPM_AUTH_SESSIONS
1454		Define this to enable authorized functions in the TPM library.
1455		Requires CONFIG_TPM and CONFIG_SHA1.
1456
1457- USB Support:
1458		At the moment only the UHCI host controller is
1459		supported (PIP405, MIP405, MPC5200); define
1460		CONFIG_USB_UHCI to enable it.
1461		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1462		and define CONFIG_USB_STORAGE to enable the USB
1463		storage devices.
1464		Note:
1465		Supported are USB Keyboards and USB Floppy drives
1466		(TEAC FD-05PUB).
1467		MPC5200 USB requires additional defines:
1468			CONFIG_USB_CLOCK
1469				for 528 MHz Clock: 0x0001bbbb
1470			CONFIG_PSC3_USB
1471				for USB on PSC3
1472			CONFIG_USB_CONFIG
1473				for differential drivers: 0x00001000
1474				for single ended drivers: 0x00005000
1475				for differential drivers on PSC3: 0x00000100
1476				for single ended drivers on PSC3: 0x00004100
1477			CONFIG_SYS_USB_EVENT_POLL
1478				May be defined to allow interrupt polling
1479				instead of using asynchronous interrupts
1480
1481		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1482		txfilltuning field in the EHCI controller on reset.
1483
1484		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1485		HW module registers.
1486
1487- USB Device:
1488		Define the below if you wish to use the USB console.
1489		Once firmware is rebuilt from a serial console issue the
1490		command "setenv stdin usbtty; setenv stdout usbtty" and
1491		attach your USB cable. The Unix command "dmesg" should print
1492		it has found a new device. The environment variable usbtty
1493		can be set to gserial or cdc_acm to enable your device to
1494		appear to a USB host as a Linux gserial device or a
1495		Common Device Class Abstract Control Model serial device.
1496		If you select usbtty = gserial you should be able to enumerate
1497		a Linux host by
1498		# modprobe usbserial vendor=0xVendorID product=0xProductID
1499		else if using cdc_acm, simply setting the environment
1500		variable usbtty to be cdc_acm should suffice. The following
1501		might be defined in YourBoardName.h
1502
1503			CONFIG_USB_DEVICE
1504			Define this to build a UDC device
1505
1506			CONFIG_USB_TTY
1507			Define this to have a tty type of device available to
1508			talk to the UDC device
1509
1510			CONFIG_USBD_HS
1511			Define this to enable the high speed support for usb
1512			device and usbtty. If this feature is enabled, a routine
1513			int is_usbd_high_speed(void)
1514			also needs to be defined by the driver to dynamically poll
1515			whether the enumeration has succeded at high speed or full
1516			speed.
1517
1518			CONFIG_SYS_CONSOLE_IS_IN_ENV
1519			Define this if you want stdin, stdout &/or stderr to
1520			be set to usbtty.
1521
1522			mpc8xx:
1523				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1524				Derive USB clock from external clock "blah"
1525				- CONFIG_SYS_USB_EXTC_CLK 0x02
1526
1527				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1528				Derive USB clock from brgclk
1529				- CONFIG_SYS_USB_BRG_CLK 0x04
1530
1531		If you have a USB-IF assigned VendorID then you may wish to
1532		define your own vendor specific values either in BoardName.h
1533		or directly in usbd_vendor_info.h. If you don't define
1534		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1535		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1536		should pretend to be a Linux device to it's target host.
1537
1538			CONFIG_USBD_MANUFACTURER
1539			Define this string as the name of your company for
1540			- CONFIG_USBD_MANUFACTURER "my company"
1541
1542			CONFIG_USBD_PRODUCT_NAME
1543			Define this string as the name of your product
1544			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1545
1546			CONFIG_USBD_VENDORID
1547			Define this as your assigned Vendor ID from the USB
1548			Implementors Forum. This *must* be a genuine Vendor ID
1549			to avoid polluting the USB namespace.
1550			- CONFIG_USBD_VENDORID 0xFFFF
1551
1552			CONFIG_USBD_PRODUCTID
1553			Define this as the unique Product ID
1554			for your device
1555			- CONFIG_USBD_PRODUCTID 0xFFFF
1556
1557- ULPI Layer Support:
1558		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1559		the generic ULPI layer. The generic layer accesses the ULPI PHY
1560		via the platform viewport, so you need both the genric layer and
1561		the viewport enabled. Currently only Chipidea/ARC based
1562		viewport is supported.
1563		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1564		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1565		If your ULPI phy needs a different reference clock than the
1566		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1567		the appropriate value in Hz.
1568
1569- MMC Support:
1570		The MMC controller on the Intel PXA is supported. To
1571		enable this define CONFIG_MMC. The MMC can be
1572		accessed from the boot prompt by mapping the device
1573		to physical memory similar to flash. Command line is
1574		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1575		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1576
1577		CONFIG_SH_MMCIF
1578		Support for Renesas on-chip MMCIF controller
1579
1580			CONFIG_SH_MMCIF_ADDR
1581			Define the base address of MMCIF registers
1582
1583			CONFIG_SH_MMCIF_CLK
1584			Define the clock frequency for MMCIF
1585
1586		CONFIG_GENERIC_MMC
1587		Enable the generic MMC driver
1588
1589		CONFIG_SUPPORT_EMMC_BOOT
1590		Enable some additional features of the eMMC boot partitions.
1591
1592		CONFIG_SUPPORT_EMMC_RPMB
1593		Enable the commands for reading, writing and programming the
1594		key for the Replay Protection Memory Block partition in eMMC.
1595
1596- USB Device Firmware Update (DFU) class support:
1597		CONFIG_USB_FUNCTION_DFU
1598		This enables the USB portion of the DFU USB class
1599
1600		CONFIG_CMD_DFU
1601		This enables the command "dfu" which is used to have
1602		U-Boot create a DFU class device via USB.  This command
1603		requires that the "dfu_alt_info" environment variable be
1604		set and define the alt settings to expose to the host.
1605
1606		CONFIG_DFU_MMC
1607		This enables support for exposing (e)MMC devices via DFU.
1608
1609		CONFIG_DFU_NAND
1610		This enables support for exposing NAND devices via DFU.
1611
1612		CONFIG_DFU_RAM
1613		This enables support for exposing RAM via DFU.
1614		Note: DFU spec refer to non-volatile memory usage, but
1615		allow usages beyond the scope of spec - here RAM usage,
1616		one that would help mostly the developer.
1617
1618		CONFIG_SYS_DFU_DATA_BUF_SIZE
1619		Dfu transfer uses a buffer before writing data to the
1620		raw storage device. Make the size (in bytes) of this buffer
1621		configurable. The size of this buffer is also configurable
1622		through the "dfu_bufsiz" environment variable.
1623
1624		CONFIG_SYS_DFU_MAX_FILE_SIZE
1625		When updating files rather than the raw storage device,
1626		we use a static buffer to copy the file into and then write
1627		the buffer once we've been given the whole file.  Define
1628		this to the maximum filesize (in bytes) for the buffer.
1629		Default is 4 MiB if undefined.
1630
1631		DFU_DEFAULT_POLL_TIMEOUT
1632		Poll timeout [ms], is the timeout a device can send to the
1633		host. The host must wait for this timeout before sending
1634		a subsequent DFU_GET_STATUS request to the device.
1635
1636		DFU_MANIFEST_POLL_TIMEOUT
1637		Poll timeout [ms], which the device sends to the host when
1638		entering dfuMANIFEST state. Host waits this timeout, before
1639		sending again an USB request to the device.
1640
1641- USB Device Android Fastboot support:
1642		CONFIG_USB_FUNCTION_FASTBOOT
1643		This enables the USB part of the fastboot gadget
1644
1645		CONFIG_CMD_FASTBOOT
1646		This enables the command "fastboot" which enables the Android
1647		fastboot mode for the platform's USB device. Fastboot is a USB
1648		protocol for downloading images, flashing and device control
1649		used on Android devices.
1650		See doc/README.android-fastboot for more information.
1651
1652		CONFIG_ANDROID_BOOT_IMAGE
1653		This enables support for booting images which use the Android
1654		image format header.
1655
1656		CONFIG_FASTBOOT_BUF_ADDR
1657		The fastboot protocol requires a large memory buffer for
1658		downloads. Define this to the starting RAM address to use for
1659		downloaded images.
1660
1661		CONFIG_FASTBOOT_BUF_SIZE
1662		The fastboot protocol requires a large memory buffer for
1663		downloads. This buffer should be as large as possible for a
1664		platform. Define this to the size available RAM for fastboot.
1665
1666		CONFIG_FASTBOOT_FLASH
1667		The fastboot protocol includes a "flash" command for writing
1668		the downloaded image to a non-volatile storage device. Define
1669		this to enable the "fastboot flash" command.
1670
1671		CONFIG_FASTBOOT_FLASH_MMC_DEV
1672		The fastboot "flash" command requires additional information
1673		regarding the non-volatile storage device. Define this to
1674		the eMMC device that fastboot should use to store the image.
1675
1676		CONFIG_FASTBOOT_GPT_NAME
1677		The fastboot "flash" command supports writing the downloaded
1678		image to the Protective MBR and the Primary GUID Partition
1679		Table. (Additionally, this downloaded image is post-processed
1680		to generate and write the Backup GUID Partition Table.)
1681		This occurs when the specified "partition name" on the
1682		"fastboot flash" command line matches this value.
1683		Default is GPT_ENTRY_NAME (currently "gpt") if undefined.
1684
1685- Journaling Flash filesystem support:
1686		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1687		CONFIG_JFFS2_NAND_DEV
1688		Define these for a default partition on a NAND device
1689
1690		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1691		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1692		Define these for a default partition on a NOR device
1693
1694		CONFIG_SYS_JFFS_CUSTOM_PART
1695		Define this to create an own partition. You have to provide a
1696		function struct part_info* jffs2_part_info(int part_num)
1697
1698		If you define only one JFFS2 partition you may also want to
1699		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1700		to disable the command chpart. This is the default when you
1701		have not defined a custom partition
1702
1703- FAT(File Allocation Table) filesystem write function support:
1704		CONFIG_FAT_WRITE
1705
1706		Define this to enable support for saving memory data as a
1707		file in FAT formatted partition.
1708
1709		This will also enable the command "fatwrite" enabling the
1710		user to write files to FAT.
1711
1712CBFS (Coreboot Filesystem) support
1713		CONFIG_CMD_CBFS
1714
1715		Define this to enable support for reading from a Coreboot
1716		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1717		and cbfsload.
1718
1719- FAT(File Allocation Table) filesystem cluster size:
1720		CONFIG_FS_FAT_MAX_CLUSTSIZE
1721
1722		Define the max cluster size for fat operations else
1723		a default value of 65536 will be defined.
1724
1725- Keyboard Support:
1726		See Kconfig help for available keyboard drivers.
1727
1728		CONFIG_KEYBOARD
1729
1730		Define this to enable a custom keyboard support.
1731		This simply calls drv_keyboard_init() which must be
1732		defined in your board-specific files. This option is deprecated
1733		and is only used by novena. For new boards, use driver model
1734		instead.
1735
1736- Video support:
1737		CONFIG_VIDEO
1738
1739		Define this to enable video support (for output to
1740		video).
1741
1742		CONFIG_VIDEO_CT69000
1743
1744		Enable Chips & Technologies 69000 Video chip
1745
1746		CONFIG_VIDEO_SMI_LYNXEM
1747		Enable Silicon Motion SMI 712/710/810 Video chip. The
1748		video output is selected via environment 'videoout'
1749		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1750		assumed.
1751
1752		For the CT69000 and SMI_LYNXEM drivers, videomode is
1753		selected via environment 'videomode'. Two different ways
1754		are possible:
1755		- "videomode=num"   'num' is a standard LiLo mode numbers.
1756		Following standard modes are supported	(* is default):
1757
1758		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1759		-------------+---------------------------------------------
1760		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1761		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1762		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1763		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1764		-------------+---------------------------------------------
1765		(i.e. setenv videomode 317; saveenv; reset;)
1766
1767		- "videomode=bootargs" all the video parameters are parsed
1768		from the bootargs. (See drivers/video/videomodes.c)
1769
1770
1771		CONFIG_VIDEO_SED13806
1772		Enable Epson SED13806 driver. This driver supports 8bpp
1773		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1774		or CONFIG_VIDEO_SED13806_16BPP
1775
1776		CONFIG_FSL_DIU_FB
1777		Enable the Freescale DIU video driver.	Reference boards for
1778		SOCs that have a DIU should define this macro to enable DIU
1779		support, and should also define these other macros:
1780
1781			CONFIG_SYS_DIU_ADDR
1782			CONFIG_VIDEO
1783			CONFIG_CMD_BMP
1784			CONFIG_CFB_CONSOLE
1785			CONFIG_VIDEO_SW_CURSOR
1786			CONFIG_VGA_AS_SINGLE_DEVICE
1787			CONFIG_VIDEO_LOGO
1788			CONFIG_VIDEO_BMP_LOGO
1789
1790		The DIU driver will look for the 'video-mode' environment
1791		variable, and if defined, enable the DIU as a console during
1792		boot.  See the documentation file doc/README.video for a
1793		description of this variable.
1794
1795- LCD Support:	CONFIG_LCD
1796
1797		Define this to enable LCD support (for output to LCD
1798		display); also select one of the supported displays
1799		by defining one of these:
1800
1801		CONFIG_ATMEL_LCD:
1802
1803			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1804
1805		CONFIG_NEC_NL6448AC33:
1806
1807			NEC NL6448AC33-18. Active, color, single scan.
1808
1809		CONFIG_NEC_NL6448BC20
1810
1811			NEC NL6448BC20-08. 6.5", 640x480.
1812			Active, color, single scan.
1813
1814		CONFIG_NEC_NL6448BC33_54
1815
1816			NEC NL6448BC33-54. 10.4", 640x480.
1817			Active, color, single scan.
1818
1819		CONFIG_SHARP_16x9
1820
1821			Sharp 320x240. Active, color, single scan.
1822			It isn't 16x9, and I am not sure what it is.
1823
1824		CONFIG_SHARP_LQ64D341
1825
1826			Sharp LQ64D341 display, 640x480.
1827			Active, color, single scan.
1828
1829		CONFIG_HLD1045
1830
1831			HLD1045 display, 640x480.
1832			Active, color, single scan.
1833
1834		CONFIG_OPTREX_BW
1835
1836			Optrex	 CBL50840-2 NF-FW 99 22 M5
1837			or
1838			Hitachi	 LMG6912RPFC-00T
1839			or
1840			Hitachi	 SP14Q002
1841
1842			320x240. Black & white.
1843
1844		Normally display is black on white background; define
1845		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1846
1847		CONFIG_LCD_ALIGNMENT
1848
1849		Normally the LCD is page-aligned (typically 4KB). If this is
1850		defined then the LCD will be aligned to this value instead.
1851		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1852		here, since it is cheaper to change data cache settings on
1853		a per-section basis.
1854
1855		CONFIG_CONSOLE_SCROLL_LINES
1856
1857		When the console need to be scrolled, this is the number of
1858		lines to scroll by. It defaults to 1. Increasing this makes
1859		the console jump but can help speed up operation when scrolling
1860		is slow.
1861
1862		CONFIG_LCD_ROTATION
1863
1864		Sometimes, for example if the display is mounted in portrait
1865		mode or even if it's mounted landscape but rotated by 180degree,
1866		we need to rotate our content of the display relative to the
1867		framebuffer, so that user can read the messages which are
1868		printed out.
1869		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1870		initialized with a given rotation from "vl_rot" out of
1871		"vidinfo_t" which is provided by the board specific code.
1872		The value for vl_rot is coded as following (matching to
1873		fbcon=rotate:<n> linux-kernel commandline):
1874		0 = no rotation respectively 0 degree
1875		1 = 90 degree rotation
1876		2 = 180 degree rotation
1877		3 = 270 degree rotation
1878
1879		If CONFIG_LCD_ROTATION is not defined, the console will be
1880		initialized with 0degree rotation.
1881
1882		CONFIG_LCD_BMP_RLE8
1883
1884		Support drawing of RLE8-compressed bitmaps on the LCD.
1885
1886		CONFIG_I2C_EDID
1887
1888		Enables an 'i2c edid' command which can read EDID
1889		information over I2C from an attached LCD display.
1890
1891- Splash Screen Support: CONFIG_SPLASH_SCREEN
1892
1893		If this option is set, the environment is checked for
1894		a variable "splashimage". If found, the usual display
1895		of logo, copyright and system information on the LCD
1896		is suppressed and the BMP image at the address
1897		specified in "splashimage" is loaded instead. The
1898		console is redirected to the "nulldev", too. This
1899		allows for a "silent" boot where a splash screen is
1900		loaded very quickly after power-on.
1901
1902		CONFIG_SPLASHIMAGE_GUARD
1903
1904		If this option is set, then U-Boot will prevent the environment
1905		variable "splashimage" from being set to a problematic address
1906		(see doc/README.displaying-bmps).
1907		This option is useful for targets where, due to alignment
1908		restrictions, an improperly aligned BMP image will cause a data
1909		abort. If you think you will not have problems with unaligned
1910		accesses (for example because your toolchain prevents them)
1911		there is no need to set this option.
1912
1913		CONFIG_SPLASH_SCREEN_ALIGN
1914
1915		If this option is set the splash image can be freely positioned
1916		on the screen. Environment variable "splashpos" specifies the
1917		position as "x,y". If a positive number is given it is used as
1918		number of pixel from left/top. If a negative number is given it
1919		is used as number of pixel from right/bottom. You can also
1920		specify 'm' for centering the image.
1921
1922		Example:
1923		setenv splashpos m,m
1924			=> image at center of screen
1925
1926		setenv splashpos 30,20
1927			=> image at x = 30 and y = 20
1928
1929		setenv splashpos -10,m
1930			=> vertically centered image
1931			   at x = dspWidth - bmpWidth - 9
1932
1933- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1934
1935		If this option is set, additionally to standard BMP
1936		images, gzipped BMP images can be displayed via the
1937		splashscreen support or the bmp command.
1938
1939- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1940
1941		If this option is set, 8-bit RLE compressed BMP images
1942		can be displayed via the splashscreen support or the
1943		bmp command.
1944
1945- Do compressing for memory range:
1946		CONFIG_CMD_ZIP
1947
1948		If this option is set, it would use zlib deflate method
1949		to compress the specified memory at its best effort.
1950
1951- Compression support:
1952		CONFIG_GZIP
1953
1954		Enabled by default to support gzip compressed images.
1955
1956		CONFIG_BZIP2
1957
1958		If this option is set, support for bzip2 compressed
1959		images is included. If not, only uncompressed and gzip
1960		compressed images are supported.
1961
1962		NOTE: the bzip2 algorithm requires a lot of RAM, so
1963		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1964		be at least 4MB.
1965
1966		CONFIG_LZMA
1967
1968		If this option is set, support for lzma compressed
1969		images is included.
1970
1971		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1972		requires an amount of dynamic memory that is given by the
1973		formula:
1974
1975			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1976
1977		Where lc and lp stand for, respectively, Literal context bits
1978		and Literal pos bits.
1979
1980		This value is upper-bounded by 14MB in the worst case. Anyway,
1981		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1982		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1983		a very small buffer.
1984
1985		Use the lzmainfo tool to determinate the lc and lp values and
1986		then calculate the amount of needed dynamic memory (ensuring
1987		the appropriate CONFIG_SYS_MALLOC_LEN value).
1988
1989		CONFIG_LZO
1990
1991		If this option is set, support for LZO compressed images
1992		is included.
1993
1994- MII/PHY support:
1995		CONFIG_PHY_ADDR
1996
1997		The address of PHY on MII bus.
1998
1999		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
2000
2001		The clock frequency of the MII bus
2002
2003		CONFIG_PHY_GIGE
2004
2005		If this option is set, support for speed/duplex
2006		detection of gigabit PHY is included.
2007
2008		CONFIG_PHY_RESET_DELAY
2009
2010		Some PHY like Intel LXT971A need extra delay after
2011		reset before any MII register access is possible.
2012		For such PHY, set this option to the usec delay
2013		required. (minimum 300usec for LXT971A)
2014
2015		CONFIG_PHY_CMD_DELAY (ppc4xx)
2016
2017		Some PHY like Intel LXT971A need extra delay after
2018		command issued before MII status register can be read
2019
2020- IP address:
2021		CONFIG_IPADDR
2022
2023		Define a default value for the IP address to use for
2024		the default Ethernet interface, in case this is not
2025		determined through e.g. bootp.
2026		(Environment variable "ipaddr")
2027
2028- Server IP address:
2029		CONFIG_SERVERIP
2030
2031		Defines a default value for the IP address of a TFTP
2032		server to contact when using the "tftboot" command.
2033		(Environment variable "serverip")
2034
2035		CONFIG_KEEP_SERVERADDR
2036
2037		Keeps the server's MAC address, in the env 'serveraddr'
2038		for passing to bootargs (like Linux's netconsole option)
2039
2040- Gateway IP address:
2041		CONFIG_GATEWAYIP
2042
2043		Defines a default value for the IP address of the
2044		default router where packets to other networks are
2045		sent to.
2046		(Environment variable "gatewayip")
2047
2048- Subnet mask:
2049		CONFIG_NETMASK
2050
2051		Defines a default value for the subnet mask (or
2052		routing prefix) which is used to determine if an IP
2053		address belongs to the local subnet or needs to be
2054		forwarded through a router.
2055		(Environment variable "netmask")
2056
2057- Multicast TFTP Mode:
2058		CONFIG_MCAST_TFTP
2059
2060		Defines whether you want to support multicast TFTP as per
2061		rfc-2090; for example to work with atftp.  Lets lots of targets
2062		tftp down the same boot image concurrently.  Note: the Ethernet
2063		driver in use must provide a function: mcast() to join/leave a
2064		multicast group.
2065
2066- BOOTP Recovery Mode:
2067		CONFIG_BOOTP_RANDOM_DELAY
2068
2069		If you have many targets in a network that try to
2070		boot using BOOTP, you may want to avoid that all
2071		systems send out BOOTP requests at precisely the same
2072		moment (which would happen for instance at recovery
2073		from a power failure, when all systems will try to
2074		boot, thus flooding the BOOTP server. Defining
2075		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
2076		inserted before sending out BOOTP requests. The
2077		following delays are inserted then:
2078
2079		1st BOOTP request:	delay 0 ... 1 sec
2080		2nd BOOTP request:	delay 0 ... 2 sec
2081		3rd BOOTP request:	delay 0 ... 4 sec
2082		4th and following
2083		BOOTP requests:		delay 0 ... 8 sec
2084
2085		CONFIG_BOOTP_ID_CACHE_SIZE
2086
2087		BOOTP packets are uniquely identified using a 32-bit ID. The
2088		server will copy the ID from client requests to responses and
2089		U-Boot will use this to determine if it is the destination of
2090		an incoming response. Some servers will check that addresses
2091		aren't in use before handing them out (usually using an ARP
2092		ping) and therefore take up to a few hundred milliseconds to
2093		respond. Network congestion may also influence the time it
2094		takes for a response to make it back to the client. If that
2095		time is too long, U-Boot will retransmit requests. In order
2096		to allow earlier responses to still be accepted after these
2097		retransmissions, U-Boot's BOOTP client keeps a small cache of
2098		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
2099		cache. The default is to keep IDs for up to four outstanding
2100		requests. Increasing this will allow U-Boot to accept offers
2101		from a BOOTP client in networks with unusually high latency.
2102
2103- DHCP Advanced Options:
2104		You can fine tune the DHCP functionality by defining
2105		CONFIG_BOOTP_* symbols:
2106
2107		CONFIG_BOOTP_SUBNETMASK
2108		CONFIG_BOOTP_GATEWAY
2109		CONFIG_BOOTP_HOSTNAME
2110		CONFIG_BOOTP_NISDOMAIN
2111		CONFIG_BOOTP_BOOTPATH
2112		CONFIG_BOOTP_BOOTFILESIZE
2113		CONFIG_BOOTP_DNS
2114		CONFIG_BOOTP_DNS2
2115		CONFIG_BOOTP_SEND_HOSTNAME
2116		CONFIG_BOOTP_NTPSERVER
2117		CONFIG_BOOTP_TIMEOFFSET
2118		CONFIG_BOOTP_VENDOREX
2119		CONFIG_BOOTP_MAY_FAIL
2120
2121		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
2122		environment variable, not the BOOTP server.
2123
2124		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
2125		after the configured retry count, the call will fail
2126		instead of starting over.  This can be used to fail over
2127		to Link-local IP address configuration if the DHCP server
2128		is not available.
2129
2130		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
2131		serverip from a DHCP server, it is possible that more
2132		than one DNS serverip is offered to the client.
2133		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
2134		serverip will be stored in the additional environment
2135		variable "dnsip2". The first DNS serverip is always
2136		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2137		is defined.
2138
2139		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2140		to do a dynamic update of a DNS server. To do this, they
2141		need the hostname of the DHCP requester.
2142		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2143		of the "hostname" environment variable is passed as
2144		option 12 to the DHCP server.
2145
2146		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2147
2148		A 32bit value in microseconds for a delay between
2149		receiving a "DHCP Offer" and sending the "DHCP Request".
2150		This fixes a problem with certain DHCP servers that don't
2151		respond 100% of the time to a "DHCP request". E.g. On an
2152		AT91RM9200 processor running at 180MHz, this delay needed
2153		to be *at least* 15,000 usec before a Windows Server 2003
2154		DHCP server would reply 100% of the time. I recommend at
2155		least 50,000 usec to be safe. The alternative is to hope
2156		that one of the retries will be successful but note that
2157		the DHCP timeout and retry process takes a longer than
2158		this delay.
2159
2160 - Link-local IP address negotiation:
2161		Negotiate with other link-local clients on the local network
2162		for an address that doesn't require explicit configuration.
2163		This is especially useful if a DHCP server cannot be guaranteed
2164		to exist in all environments that the device must operate.
2165
2166		See doc/README.link-local for more information.
2167
2168 - CDP Options:
2169		CONFIG_CDP_DEVICE_ID
2170
2171		The device id used in CDP trigger frames.
2172
2173		CONFIG_CDP_DEVICE_ID_PREFIX
2174
2175		A two character string which is prefixed to the MAC address
2176		of the device.
2177
2178		CONFIG_CDP_PORT_ID
2179
2180		A printf format string which contains the ascii name of
2181		the port. Normally is set to "eth%d" which sets
2182		eth0 for the first Ethernet, eth1 for the second etc.
2183
2184		CONFIG_CDP_CAPABILITIES
2185
2186		A 32bit integer which indicates the device capabilities;
2187		0x00000010 for a normal host which does not forwards.
2188
2189		CONFIG_CDP_VERSION
2190
2191		An ascii string containing the version of the software.
2192
2193		CONFIG_CDP_PLATFORM
2194
2195		An ascii string containing the name of the platform.
2196
2197		CONFIG_CDP_TRIGGER
2198
2199		A 32bit integer sent on the trigger.
2200
2201		CONFIG_CDP_POWER_CONSUMPTION
2202
2203		A 16bit integer containing the power consumption of the
2204		device in .1 of milliwatts.
2205
2206		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2207
2208		A byte containing the id of the VLAN.
2209
2210- Status LED:	CONFIG_STATUS_LED
2211
2212		Several configurations allow to display the current
2213		status using a LED. For instance, the LED will blink
2214		fast while running U-Boot code, stop blinking as
2215		soon as a reply to a BOOTP request was received, and
2216		start blinking slow once the Linux kernel is running
2217		(supported by a status LED driver in the Linux
2218		kernel). Defining CONFIG_STATUS_LED enables this
2219		feature in U-Boot.
2220
2221		Additional options:
2222
2223		CONFIG_GPIO_LED
2224		The status LED can be connected to a GPIO pin.
2225		In such cases, the gpio_led driver can be used as a
2226		status LED backend implementation. Define CONFIG_GPIO_LED
2227		to include the gpio_led driver in the U-Boot binary.
2228
2229		CONFIG_GPIO_LED_INVERTED_TABLE
2230		Some GPIO connected LEDs may have inverted polarity in which
2231		case the GPIO high value corresponds to LED off state and
2232		GPIO low value corresponds to LED on state.
2233		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2234		with a list of GPIO LEDs that have inverted polarity.
2235
2236- CAN Support:	CONFIG_CAN_DRIVER
2237
2238		Defining CONFIG_CAN_DRIVER enables CAN driver support
2239		on those systems that support this (optional)
2240		feature, like the TQM8xxL modules.
2241
2242- I2C Support:	CONFIG_SYS_I2C
2243
2244		This enable the NEW i2c subsystem, and will allow you to use
2245		i2c commands at the u-boot command line (as long as you set
2246		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2247		based realtime clock chips or other i2c devices. See
2248		common/cmd_i2c.c for a description of the command line
2249		interface.
2250
2251		ported i2c driver to the new framework:
2252		- drivers/i2c/soft_i2c.c:
2253		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2254		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2255		    for defining speed and slave address
2256		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2257		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2258		    for defining speed and slave address
2259		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2260		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2261		    for defining speed and slave address
2262		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2263		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2264		    for defining speed and slave address
2265
2266		- drivers/i2c/fsl_i2c.c:
2267		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2268		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2269		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2270		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2271		    bus.
2272		  - If your board supports a second fsl i2c bus, define
2273		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2274		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2275		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2276		    second bus.
2277
2278		- drivers/i2c/tegra_i2c.c:
2279		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2280		  - This driver adds 4 i2c buses with a fix speed from
2281		    100000 and the slave addr 0!
2282
2283		- drivers/i2c/ppc4xx_i2c.c
2284		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2285		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2286		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2287
2288		- drivers/i2c/i2c_mxc.c
2289		  - activate this driver with CONFIG_SYS_I2C_MXC
2290		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
2291		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
2292		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
2293		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
2294		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2295		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2296		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2297		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2298		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2299		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2300		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
2301		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
2302		If those defines are not set, default value is 100000
2303		for speed, and 0 for slave.
2304
2305		- drivers/i2c/rcar_i2c.c:
2306		  - activate this driver with CONFIG_SYS_I2C_RCAR
2307		  - This driver adds 4 i2c buses
2308
2309		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2310		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2311		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2312		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2313		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2314		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2315		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2316		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2317		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2318
2319		- drivers/i2c/sh_i2c.c:
2320		  - activate this driver with CONFIG_SYS_I2C_SH
2321		  - This driver adds from 2 to 5 i2c buses
2322
2323		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2324		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2325		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2326		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2327		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2328		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2329		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2330		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2331		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2332		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2333		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2334		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2335		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2336
2337		- drivers/i2c/omap24xx_i2c.c
2338		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2339		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2340		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2341		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2342		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2343		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2344		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2345		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2346		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2347		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2348		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2349
2350		- drivers/i2c/zynq_i2c.c
2351		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2352		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2353		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2354
2355		- drivers/i2c/s3c24x0_i2c.c:
2356		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2357		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2358		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2359		    with a fix speed from 100000 and the slave addr 0!
2360
2361		- drivers/i2c/ihs_i2c.c
2362		  - activate this driver with CONFIG_SYS_I2C_IHS
2363		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2364		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2365		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2366		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2367		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2368		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2369		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2370		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2371		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2372		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2373		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2374		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2375		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
2376		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
2377		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
2378		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
2379		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
2380		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
2381		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
2382		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
2383		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
2384
2385		additional defines:
2386
2387		CONFIG_SYS_NUM_I2C_BUSES
2388		Hold the number of i2c buses you want to use. If you
2389		don't use/have i2c muxes on your i2c bus, this
2390		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2391		omit this define.
2392
2393		CONFIG_SYS_I2C_DIRECT_BUS
2394		define this, if you don't use i2c muxes on your hardware.
2395		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2396		omit this define.
2397
2398		CONFIG_SYS_I2C_MAX_HOPS
2399		define how many muxes are maximal consecutively connected
2400		on one i2c bus. If you not use i2c muxes, omit this
2401		define.
2402
2403		CONFIG_SYS_I2C_BUSES
2404		hold a list of buses you want to use, only used if
2405		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2406		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2407		CONFIG_SYS_NUM_I2C_BUSES = 9:
2408
2409		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2410					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2411					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2412					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2413					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2414					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2415					{1, {I2C_NULL_HOP}}, \
2416					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2417					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2418					}
2419
2420		which defines
2421			bus 0 on adapter 0 without a mux
2422			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2423			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2424			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2425			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2426			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2427			bus 6 on adapter 1 without a mux
2428			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2429			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2430
2431		If you do not have i2c muxes on your board, omit this define.
2432
2433- Legacy I2C Support:	CONFIG_HARD_I2C
2434
2435		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2436		provides the following compelling advantages:
2437
2438		- more than one i2c adapter is usable
2439		- approved multibus support
2440		- better i2c mux support
2441
2442		** Please consider updating your I2C driver now. **
2443
2444		These enable legacy I2C serial bus commands. Defining
2445		CONFIG_HARD_I2C will include the appropriate I2C driver
2446		for the selected CPU.
2447
2448		This will allow you to use i2c commands at the u-boot
2449		command line (as long as you set CONFIG_CMD_I2C in
2450		CONFIG_COMMANDS) and communicate with i2c based realtime
2451		clock chips. See common/cmd_i2c.c for a description of the
2452		command line interface.
2453
2454		CONFIG_HARD_I2C selects a hardware I2C controller.
2455
2456		There are several other quantities that must also be
2457		defined when you define CONFIG_HARD_I2C.
2458
2459		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2460		to be the frequency (in Hz) at which you wish your i2c bus
2461		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2462		the CPU's i2c node address).
2463
2464		Now, the u-boot i2c code for the mpc8xx
2465		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2466		and so its address should therefore be cleared to 0 (See,
2467		eg, MPC823e User's Manual p.16-473). So, set
2468		CONFIG_SYS_I2C_SLAVE to 0.
2469
2470		CONFIG_SYS_I2C_INIT_MPC5XXX
2471
2472		When a board is reset during an i2c bus transfer
2473		chips might think that the current transfer is still
2474		in progress.  Reset the slave devices by sending start
2475		commands until the slave device responds.
2476
2477		That's all that's required for CONFIG_HARD_I2C.
2478
2479		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2480		then the following macros need to be defined (examples are
2481		from include/configs/lwmon.h):
2482
2483		I2C_INIT
2484
2485		(Optional). Any commands necessary to enable the I2C
2486		controller or configure ports.
2487
2488		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2489
2490		I2C_PORT
2491
2492		(Only for MPC8260 CPU). The I/O port to use (the code
2493		assumes both bits are on the same port). Valid values
2494		are 0..3 for ports A..D.
2495
2496		I2C_ACTIVE
2497
2498		The code necessary to make the I2C data line active
2499		(driven).  If the data line is open collector, this
2500		define can be null.
2501
2502		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2503
2504		I2C_TRISTATE
2505
2506		The code necessary to make the I2C data line tri-stated
2507		(inactive).  If the data line is open collector, this
2508		define can be null.
2509
2510		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2511
2512		I2C_READ
2513
2514		Code that returns true if the I2C data line is high,
2515		false if it is low.
2516
2517		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2518
2519		I2C_SDA(bit)
2520
2521		If <bit> is true, sets the I2C data line high. If it
2522		is false, it clears it (low).
2523
2524		eg: #define I2C_SDA(bit) \
2525			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2526			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2527
2528		I2C_SCL(bit)
2529
2530		If <bit> is true, sets the I2C clock line high. If it
2531		is false, it clears it (low).
2532
2533		eg: #define I2C_SCL(bit) \
2534			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2535			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2536
2537		I2C_DELAY
2538
2539		This delay is invoked four times per clock cycle so this
2540		controls the rate of data transfer.  The data rate thus
2541		is 1 / (I2C_DELAY * 4). Often defined to be something
2542		like:
2543
2544		#define I2C_DELAY  udelay(2)
2545
2546		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2547
2548		If your arch supports the generic GPIO framework (asm/gpio.h),
2549		then you may alternatively define the two GPIOs that are to be
2550		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2551		have GPIO-based defaults assigned to them as appropriate.
2552
2553		You should define these to the GPIO value as given directly to
2554		the generic GPIO functions.
2555
2556		CONFIG_SYS_I2C_INIT_BOARD
2557
2558		When a board is reset during an i2c bus transfer
2559		chips might think that the current transfer is still
2560		in progress. On some boards it is possible to access
2561		the i2c SCLK line directly, either by using the
2562		processor pin as a GPIO or by having a second pin
2563		connected to the bus. If this option is defined a
2564		custom i2c_init_board() routine in boards/xxx/board.c
2565		is run early in the boot sequence.
2566
2567		CONFIG_SYS_I2C_BOARD_LATE_INIT
2568
2569		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2570		defined a custom i2c_board_late_init() routine in
2571		boards/xxx/board.c is run AFTER the operations in i2c_init()
2572		is completed. This callpoint can be used to unreset i2c bus
2573		using CPU i2c controller register accesses for CPUs whose i2c
2574		controller provide such a method. It is called at the end of
2575		i2c_init() to allow i2c_init operations to setup the i2c bus
2576		controller on the CPU (e.g. setting bus speed & slave address).
2577
2578		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2579
2580		This option enables configuration of bi_iic_fast[] flags
2581		in u-boot bd_info structure based on u-boot environment
2582		variable "i2cfast". (see also i2cfast)
2583
2584		CONFIG_I2C_MULTI_BUS
2585
2586		This option allows the use of multiple I2C buses, each of which
2587		must have a controller.	 At any point in time, only one bus is
2588		active.	 To switch to a different bus, use the 'i2c dev' command.
2589		Note that bus numbering is zero-based.
2590
2591		CONFIG_SYS_I2C_NOPROBES
2592
2593		This option specifies a list of I2C devices that will be skipped
2594		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2595		is set, specify a list of bus-device pairs.  Otherwise, specify
2596		a 1D array of device addresses
2597
2598		e.g.
2599			#undef	CONFIG_I2C_MULTI_BUS
2600			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2601
2602		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2603
2604			#define CONFIG_I2C_MULTI_BUS
2605			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2606
2607		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2608
2609		CONFIG_SYS_SPD_BUS_NUM
2610
2611		If defined, then this indicates the I2C bus number for DDR SPD.
2612		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2613
2614		CONFIG_SYS_RTC_BUS_NUM
2615
2616		If defined, then this indicates the I2C bus number for the RTC.
2617		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2618
2619		CONFIG_SYS_DTT_BUS_NUM
2620
2621		If defined, then this indicates the I2C bus number for the DTT.
2622		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2623
2624		CONFIG_SYS_I2C_DTT_ADDR:
2625
2626		If defined, specifies the I2C address of the DTT device.
2627		If not defined, then U-Boot uses predefined value for
2628		specified DTT device.
2629
2630		CONFIG_SOFT_I2C_READ_REPEATED_START
2631
2632		defining this will force the i2c_read() function in
2633		the soft_i2c driver to perform an I2C repeated start
2634		between writing the address pointer and reading the
2635		data.  If this define is omitted the default behaviour
2636		of doing a stop-start sequence will be used.  Most I2C
2637		devices can use either method, but some require one or
2638		the other.
2639
2640- SPI Support:	CONFIG_SPI
2641
2642		Enables SPI driver (so far only tested with
2643		SPI EEPROM, also an instance works with Crystal A/D and
2644		D/As on the SACSng board)
2645
2646		CONFIG_SH_SPI
2647
2648		Enables the driver for SPI controller on SuperH. Currently
2649		only SH7757 is supported.
2650
2651		CONFIG_SOFT_SPI
2652
2653		Enables a software (bit-bang) SPI driver rather than
2654		using hardware support. This is a general purpose
2655		driver that only requires three general I/O port pins
2656		(two outputs, one input) to function. If this is
2657		defined, the board configuration must define several
2658		SPI configuration items (port pins to use, etc). For
2659		an example, see include/configs/sacsng.h.
2660
2661		CONFIG_HARD_SPI
2662
2663		Enables a hardware SPI driver for general-purpose reads
2664		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2665		must define a list of chip-select function pointers.
2666		Currently supported on some MPC8xxx processors.	 For an
2667		example, see include/configs/mpc8349emds.h.
2668
2669		CONFIG_MXC_SPI
2670
2671		Enables the driver for the SPI controllers on i.MX and MXC
2672		SoCs. Currently i.MX31/35/51 are supported.
2673
2674		CONFIG_SYS_SPI_MXC_WAIT
2675		Timeout for waiting until spi transfer completed.
2676		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2677
2678- FPGA Support: CONFIG_FPGA
2679
2680		Enables FPGA subsystem.
2681
2682		CONFIG_FPGA_<vendor>
2683
2684		Enables support for specific chip vendors.
2685		(ALTERA, XILINX)
2686
2687		CONFIG_FPGA_<family>
2688
2689		Enables support for FPGA family.
2690		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2691
2692		CONFIG_FPGA_COUNT
2693
2694		Specify the number of FPGA devices to support.
2695
2696		CONFIG_CMD_FPGA_LOADMK
2697
2698		Enable support for fpga loadmk command
2699
2700		CONFIG_CMD_FPGA_LOADP
2701
2702		Enable support for fpga loadp command - load partial bitstream
2703
2704		CONFIG_CMD_FPGA_LOADBP
2705
2706		Enable support for fpga loadbp command - load partial bitstream
2707		(Xilinx only)
2708
2709		CONFIG_SYS_FPGA_PROG_FEEDBACK
2710
2711		Enable printing of hash marks during FPGA configuration.
2712
2713		CONFIG_SYS_FPGA_CHECK_BUSY
2714
2715		Enable checks on FPGA configuration interface busy
2716		status by the configuration function. This option
2717		will require a board or device specific function to
2718		be written.
2719
2720		CONFIG_FPGA_DELAY
2721
2722		If defined, a function that provides delays in the FPGA
2723		configuration driver.
2724
2725		CONFIG_SYS_FPGA_CHECK_CTRLC
2726		Allow Control-C to interrupt FPGA configuration
2727
2728		CONFIG_SYS_FPGA_CHECK_ERROR
2729
2730		Check for configuration errors during FPGA bitfile
2731		loading. For example, abort during Virtex II
2732		configuration if the INIT_B line goes low (which
2733		indicated a CRC error).
2734
2735		CONFIG_SYS_FPGA_WAIT_INIT
2736
2737		Maximum time to wait for the INIT_B line to de-assert
2738		after PROB_B has been de-asserted during a Virtex II
2739		FPGA configuration sequence. The default time is 500
2740		ms.
2741
2742		CONFIG_SYS_FPGA_WAIT_BUSY
2743
2744		Maximum time to wait for BUSY to de-assert during
2745		Virtex II FPGA configuration. The default is 5 ms.
2746
2747		CONFIG_SYS_FPGA_WAIT_CONFIG
2748
2749		Time to wait after FPGA configuration. The default is
2750		200 ms.
2751
2752- Configuration Management:
2753		CONFIG_BUILD_TARGET
2754
2755		Some SoCs need special image types (e.g. U-Boot binary
2756		with a special header) as build targets. By defining
2757		CONFIG_BUILD_TARGET in the SoC / board header, this
2758		special image will be automatically built upon calling
2759		make / MAKEALL.
2760
2761		CONFIG_IDENT_STRING
2762
2763		If defined, this string will be added to the U-Boot
2764		version information (U_BOOT_VERSION)
2765
2766- Vendor Parameter Protection:
2767
2768		U-Boot considers the values of the environment
2769		variables "serial#" (Board Serial Number) and
2770		"ethaddr" (Ethernet Address) to be parameters that
2771		are set once by the board vendor / manufacturer, and
2772		protects these variables from casual modification by
2773		the user. Once set, these variables are read-only,
2774		and write or delete attempts are rejected. You can
2775		change this behaviour:
2776
2777		If CONFIG_ENV_OVERWRITE is #defined in your config
2778		file, the write protection for vendor parameters is
2779		completely disabled. Anybody can change or delete
2780		these parameters.
2781
2782		Alternatively, if you define _both_ an ethaddr in the
2783		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2784		Ethernet address is installed in the environment,
2785		which can be changed exactly ONCE by the user. [The
2786		serial# is unaffected by this, i. e. it remains
2787		read-only.]
2788
2789		The same can be accomplished in a more flexible way
2790		for any variable by configuring the type of access
2791		to allow for those variables in the ".flags" variable
2792		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2793
2794- Protected RAM:
2795		CONFIG_PRAM
2796
2797		Define this variable to enable the reservation of
2798		"protected RAM", i. e. RAM which is not overwritten
2799		by U-Boot. Define CONFIG_PRAM to hold the number of
2800		kB you want to reserve for pRAM. You can overwrite
2801		this default value by defining an environment
2802		variable "pram" to the number of kB you want to
2803		reserve. Note that the board info structure will
2804		still show the full amount of RAM. If pRAM is
2805		reserved, a new environment variable "mem" will
2806		automatically be defined to hold the amount of
2807		remaining RAM in a form that can be passed as boot
2808		argument to Linux, for instance like that:
2809
2810			setenv bootargs ... mem=\${mem}
2811			saveenv
2812
2813		This way you can tell Linux not to use this memory,
2814		either, which results in a memory region that will
2815		not be affected by reboots.
2816
2817		*WARNING* If your board configuration uses automatic
2818		detection of the RAM size, you must make sure that
2819		this memory test is non-destructive. So far, the
2820		following board configurations are known to be
2821		"pRAM-clean":
2822
2823			IVMS8, IVML24, SPD8xx, TQM8xxL,
2824			HERMES, IP860, RPXlite, LWMON,
2825			FLAGADM, TQM8260
2826
2827- Access to physical memory region (> 4GB)
2828		Some basic support is provided for operations on memory not
2829		normally accessible to U-Boot - e.g. some architectures
2830		support access to more than 4GB of memory on 32-bit
2831		machines using physical address extension or similar.
2832		Define CONFIG_PHYSMEM to access this basic support, which
2833		currently only supports clearing the memory.
2834
2835- Error Recovery:
2836		CONFIG_PANIC_HANG
2837
2838		Define this variable to stop the system in case of a
2839		fatal error, so that you have to reset it manually.
2840		This is probably NOT a good idea for an embedded
2841		system where you want the system to reboot
2842		automatically as fast as possible, but it may be
2843		useful during development since you can try to debug
2844		the conditions that lead to the situation.
2845
2846		CONFIG_NET_RETRY_COUNT
2847
2848		This variable defines the number of retries for
2849		network operations like ARP, RARP, TFTP, or BOOTP
2850		before giving up the operation. If not defined, a
2851		default value of 5 is used.
2852
2853		CONFIG_ARP_TIMEOUT
2854
2855		Timeout waiting for an ARP reply in milliseconds.
2856
2857		CONFIG_NFS_TIMEOUT
2858
2859		Timeout in milliseconds used in NFS protocol.
2860		If you encounter "ERROR: Cannot umount" in nfs command,
2861		try longer timeout such as
2862		#define CONFIG_NFS_TIMEOUT 10000UL
2863
2864- Command Interpreter:
2865		CONFIG_AUTO_COMPLETE
2866
2867		Enable auto completion of commands using TAB.
2868
2869		CONFIG_SYS_PROMPT_HUSH_PS2
2870
2871		This defines the secondary prompt string, which is
2872		printed when the command interpreter needs more input
2873		to complete a command. Usually "> ".
2874
2875	Note:
2876
2877		In the current implementation, the local variables
2878		space and global environment variables space are
2879		separated. Local variables are those you define by
2880		simply typing `name=value'. To access a local
2881		variable later on, you have write `$name' or
2882		`${name}'; to execute the contents of a variable
2883		directly type `$name' at the command prompt.
2884
2885		Global environment variables are those you use
2886		setenv/printenv to work with. To run a command stored
2887		in such a variable, you need to use the run command,
2888		and you must not use the '$' sign to access them.
2889
2890		To store commands and special characters in a
2891		variable, please use double quotation marks
2892		surrounding the whole text of the variable, instead
2893		of the backslashes before semicolons and special
2894		symbols.
2895
2896- Command Line Editing and History:
2897		CONFIG_CMDLINE_EDITING
2898
2899		Enable editing and History functions for interactive
2900		command line input operations
2901
2902- Command Line PS1/PS2 support:
2903		CONFIG_CMDLINE_PS_SUPPORT
2904
2905		Enable support for changing the command prompt string
2906		at run-time. Only static string is supported so far.
2907		The string is obtained from environment variables PS1
2908		and PS2.
2909
2910- Default Environment:
2911		CONFIG_EXTRA_ENV_SETTINGS
2912
2913		Define this to contain any number of null terminated
2914		strings (variable = value pairs) that will be part of
2915		the default environment compiled into the boot image.
2916
2917		For example, place something like this in your
2918		board's config file:
2919
2920		#define CONFIG_EXTRA_ENV_SETTINGS \
2921			"myvar1=value1\0" \
2922			"myvar2=value2\0"
2923
2924		Warning: This method is based on knowledge about the
2925		internal format how the environment is stored by the
2926		U-Boot code. This is NOT an official, exported
2927		interface! Although it is unlikely that this format
2928		will change soon, there is no guarantee either.
2929		You better know what you are doing here.
2930
2931		Note: overly (ab)use of the default environment is
2932		discouraged. Make sure to check other ways to preset
2933		the environment like the "source" command or the
2934		boot command first.
2935
2936		CONFIG_ENV_VARS_UBOOT_CONFIG
2937
2938		Define this in order to add variables describing the
2939		U-Boot build configuration to the default environment.
2940		These will be named arch, cpu, board, vendor, and soc.
2941
2942		Enabling this option will cause the following to be defined:
2943
2944		- CONFIG_SYS_ARCH
2945		- CONFIG_SYS_CPU
2946		- CONFIG_SYS_BOARD
2947		- CONFIG_SYS_VENDOR
2948		- CONFIG_SYS_SOC
2949
2950		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2951
2952		Define this in order to add variables describing certain
2953		run-time determined information about the hardware to the
2954		environment.  These will be named board_name, board_rev.
2955
2956		CONFIG_DELAY_ENVIRONMENT
2957
2958		Normally the environment is loaded when the board is
2959		initialised so that it is available to U-Boot. This inhibits
2960		that so that the environment is not available until
2961		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2962		this is instead controlled by the value of
2963		/config/load-environment.
2964
2965- Parallel Flash support:
2966		CONFIG_SYS_NO_FLASH
2967
2968		Traditionally U-Boot was run on systems with parallel NOR
2969		flash. This option is used to disable support for parallel NOR
2970		flash. This option should be defined if the board does not have
2971		parallel flash.
2972
2973		If this option is not defined one of the generic flash drivers
2974		(e.g.  CONFIG_FLASH_CFI_DRIVER or CONFIG_ST_SMI) must be
2975		selected or the board must provide an implementation of the
2976		flash API (see include/flash.h).
2977
2978- DataFlash Support:
2979		CONFIG_HAS_DATAFLASH
2980
2981		Defining this option enables DataFlash features and
2982		allows to read/write in Dataflash via the standard
2983		commands cp, md...
2984
2985- Serial Flash support
2986		CONFIG_CMD_SF
2987
2988		Defining this option enables SPI flash commands
2989		'sf probe/read/write/erase/update'.
2990
2991		Usage requires an initial 'probe' to define the serial
2992		flash parameters, followed by read/write/erase/update
2993		commands.
2994
2995		The following defaults may be provided by the platform
2996		to handle the common case when only a single serial
2997		flash is present on the system.
2998
2999		CONFIG_SF_DEFAULT_BUS		Bus identifier
3000		CONFIG_SF_DEFAULT_CS		Chip-select
3001		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
3002		CONFIG_SF_DEFAULT_SPEED		in Hz
3003
3004		CONFIG_CMD_SF_TEST
3005
3006		Define this option to include a destructive SPI flash
3007		test ('sf test').
3008
3009		CONFIG_SF_DUAL_FLASH		Dual flash memories
3010
3011		Define this option to use dual flash support where two flash
3012		memories can be connected with a given cs line.
3013		Currently Xilinx Zynq qspi supports these type of connections.
3014
3015- SystemACE Support:
3016		CONFIG_SYSTEMACE
3017
3018		Adding this option adds support for Xilinx SystemACE
3019		chips attached via some sort of local bus. The address
3020		of the chip must also be defined in the
3021		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
3022
3023		#define CONFIG_SYSTEMACE
3024		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
3025
3026		When SystemACE support is added, the "ace" device type
3027		becomes available to the fat commands, i.e. fatls.
3028
3029- TFTP Fixed UDP Port:
3030		CONFIG_TFTP_PORT
3031
3032		If this is defined, the environment variable tftpsrcp
3033		is used to supply the TFTP UDP source port value.
3034		If tftpsrcp isn't defined, the normal pseudo-random port
3035		number generator is used.
3036
3037		Also, the environment variable tftpdstp is used to supply
3038		the TFTP UDP destination port value.  If tftpdstp isn't
3039		defined, the normal port 69 is used.
3040
3041		The purpose for tftpsrcp is to allow a TFTP server to
3042		blindly start the TFTP transfer using the pre-configured
3043		target IP address and UDP port. This has the effect of
3044		"punching through" the (Windows XP) firewall, allowing
3045		the remainder of the TFTP transfer to proceed normally.
3046		A better solution is to properly configure the firewall,
3047		but sometimes that is not allowed.
3048
3049- Hashing support:
3050		CONFIG_CMD_HASH
3051
3052		This enables a generic 'hash' command which can produce
3053		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
3054
3055		CONFIG_HASH_VERIFY
3056
3057		Enable the hash verify command (hash -v). This adds to code
3058		size a little.
3059
3060		CONFIG_SHA1 - This option enables support of hashing using SHA1
3061		algorithm. The hash is calculated in software.
3062		CONFIG_SHA256 - This option enables support of hashing using
3063		SHA256 algorithm. The hash is calculated in software.
3064		CONFIG_SHA_HW_ACCEL - This option enables hardware acceleration
3065		for SHA1/SHA256 hashing.
3066		This affects the 'hash' command and also the
3067		hash_lookup_algo() function.
3068		CONFIG_SHA_PROG_HW_ACCEL - This option enables
3069		hardware-acceleration for SHA1/SHA256 progressive hashing.
3070		Data can be streamed in a block at a time and the hashing
3071		is performed in hardware.
3072
3073		Note: There is also a sha1sum command, which should perhaps
3074		be deprecated in favour of 'hash sha1'.
3075
3076- Freescale i.MX specific commands:
3077		CONFIG_CMD_HDMIDETECT
3078		This enables 'hdmidet' command which returns true if an
3079		HDMI monitor is detected.  This command is i.MX 6 specific.
3080
3081		CONFIG_CMD_BMODE
3082		This enables the 'bmode' (bootmode) command for forcing
3083		a boot from specific media.
3084
3085		This is useful for forcing the ROM's usb downloader to
3086		activate upon a watchdog reset which is nice when iterating
3087		on U-Boot.  Using the reset button or running bmode normal
3088		will set it back to normal.  This command currently
3089		supports i.MX53 and i.MX6.
3090
3091- bootcount support:
3092		CONFIG_BOOTCOUNT_LIMIT
3093
3094		This enables the bootcounter support, see:
3095		http://www.denx.de/wiki/DULG/UBootBootCountLimit
3096
3097		CONFIG_AT91SAM9XE
3098		enable special bootcounter support on at91sam9xe based boards.
3099		CONFIG_BLACKFIN
3100		enable special bootcounter support on blackfin based boards.
3101		CONFIG_SOC_DA8XX
3102		enable special bootcounter support on da850 based boards.
3103		CONFIG_BOOTCOUNT_RAM
3104		enable support for the bootcounter in RAM
3105		CONFIG_BOOTCOUNT_I2C
3106		enable support for the bootcounter on an i2c (like RTC) device.
3107			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
3108			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
3109						    the bootcounter.
3110			CONFIG_BOOTCOUNT_ALEN = address len
3111
3112- Show boot progress:
3113		CONFIG_SHOW_BOOT_PROGRESS
3114
3115		Defining this option allows to add some board-
3116		specific code (calling a user-provided function
3117		"show_boot_progress(int)") that enables you to show
3118		the system's boot progress on some display (for
3119		example, some LED's) on your board. At the moment,
3120		the following checkpoints are implemented:
3121
3122
3123Legacy uImage format:
3124
3125  Arg	Where			When
3126    1	common/cmd_bootm.c	before attempting to boot an image
3127   -1	common/cmd_bootm.c	Image header has bad	 magic number
3128    2	common/cmd_bootm.c	Image header has correct magic number
3129   -2	common/cmd_bootm.c	Image header has bad	 checksum
3130    3	common/cmd_bootm.c	Image header has correct checksum
3131   -3	common/cmd_bootm.c	Image data   has bad	 checksum
3132    4	common/cmd_bootm.c	Image data   has correct checksum
3133   -4	common/cmd_bootm.c	Image is for unsupported architecture
3134    5	common/cmd_bootm.c	Architecture check OK
3135   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
3136    6	common/cmd_bootm.c	Image Type check OK
3137   -6	common/cmd_bootm.c	gunzip uncompression error
3138   -7	common/cmd_bootm.c	Unimplemented compression type
3139    7	common/cmd_bootm.c	Uncompression OK
3140    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3141   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3142
3143    9	common/image.c		Start initial ramdisk verification
3144  -10	common/image.c		Ramdisk header has bad	   magic number
3145  -11	common/image.c		Ramdisk header has bad	   checksum
3146   10	common/image.c		Ramdisk header is OK
3147  -12	common/image.c		Ramdisk data   has bad	   checksum
3148   11	common/image.c		Ramdisk data   has correct checksum
3149   12	common/image.c		Ramdisk verification complete, start loading
3150  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3151   13	common/image.c		Start multifile image verification
3152   14	common/image.c		No initial ramdisk, no multifile, continue.
3153
3154   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3155
3156  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3157  -31	post/post.c		POST test failed, detected by post_output_backlog()
3158  -32	post/post.c		POST test failed, detected by post_run_single()
3159
3160   34	common/cmd_doc.c	before loading a Image from a DOC device
3161  -35	common/cmd_doc.c	Bad usage of "doc" command
3162   35	common/cmd_doc.c	correct usage of "doc" command
3163  -36	common/cmd_doc.c	No boot device
3164   36	common/cmd_doc.c	correct boot device
3165  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3166   37	common/cmd_doc.c	correct chip ID found, device available
3167  -38	common/cmd_doc.c	Read Error on boot device
3168   38	common/cmd_doc.c	reading Image header from DOC device OK
3169  -39	common/cmd_doc.c	Image header has bad magic number
3170   39	common/cmd_doc.c	Image header has correct magic number
3171  -40	common/cmd_doc.c	Error reading Image from DOC device
3172   40	common/cmd_doc.c	Image header has correct magic number
3173   41	common/cmd_ide.c	before loading a Image from a IDE device
3174  -42	common/cmd_ide.c	Bad usage of "ide" command
3175   42	common/cmd_ide.c	correct usage of "ide" command
3176  -43	common/cmd_ide.c	No boot device
3177   43	common/cmd_ide.c	boot device found
3178  -44	common/cmd_ide.c	Device not available
3179   44	common/cmd_ide.c	Device available
3180  -45	common/cmd_ide.c	wrong partition selected
3181   45	common/cmd_ide.c	partition selected
3182  -46	common/cmd_ide.c	Unknown partition table
3183   46	common/cmd_ide.c	valid partition table found
3184  -47	common/cmd_ide.c	Invalid partition type
3185   47	common/cmd_ide.c	correct partition type
3186  -48	common/cmd_ide.c	Error reading Image Header on boot device
3187   48	common/cmd_ide.c	reading Image Header from IDE device OK
3188  -49	common/cmd_ide.c	Image header has bad magic number
3189   49	common/cmd_ide.c	Image header has correct magic number
3190  -50	common/cmd_ide.c	Image header has bad	 checksum
3191   50	common/cmd_ide.c	Image header has correct checksum
3192  -51	common/cmd_ide.c	Error reading Image from IDE device
3193   51	common/cmd_ide.c	reading Image from IDE device OK
3194   52	common/cmd_nand.c	before loading a Image from a NAND device
3195  -53	common/cmd_nand.c	Bad usage of "nand" command
3196   53	common/cmd_nand.c	correct usage of "nand" command
3197  -54	common/cmd_nand.c	No boot device
3198   54	common/cmd_nand.c	boot device found
3199  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3200   55	common/cmd_nand.c	correct chip ID found, device available
3201  -56	common/cmd_nand.c	Error reading Image Header on boot device
3202   56	common/cmd_nand.c	reading Image Header from NAND device OK
3203  -57	common/cmd_nand.c	Image header has bad magic number
3204   57	common/cmd_nand.c	Image header has correct magic number
3205  -58	common/cmd_nand.c	Error reading Image from NAND device
3206   58	common/cmd_nand.c	reading Image from NAND device OK
3207
3208  -60	common/env_common.c	Environment has a bad CRC, using default
3209
3210   64	net/eth.c		starting with Ethernet configuration.
3211  -64	net/eth.c		no Ethernet found.
3212   65	net/eth.c		Ethernet found.
3213
3214  -80	common/cmd_net.c	usage wrong
3215   80	common/cmd_net.c	before calling net_loop()
3216  -81	common/cmd_net.c	some error in net_loop() occurred
3217   81	common/cmd_net.c	net_loop() back without error
3218  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3219   82	common/cmd_net.c	trying automatic boot
3220   83	common/cmd_net.c	running "source" command
3221  -83	common/cmd_net.c	some error in automatic boot or "source" command
3222   84	common/cmd_net.c	end without errors
3223
3224FIT uImage format:
3225
3226  Arg	Where			When
3227  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3228 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3229  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3230 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3231  102	common/cmd_bootm.c	Kernel unit name specified
3232 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3233  103	common/cmd_bootm.c	Found configuration node
3234  104	common/cmd_bootm.c	Got kernel subimage node offset
3235 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3236  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3237 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3238  106	common/cmd_bootm.c	Architecture check OK
3239 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3240  107	common/cmd_bootm.c	Kernel subimage type OK
3241 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3242  108	common/cmd_bootm.c	Got kernel subimage data/size
3243 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3244 -109	common/cmd_bootm.c	Can't get kernel subimage type
3245 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3246 -111	common/cmd_bootm.c	Can't get kernel subimage os
3247 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3248 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3249
3250  120	common/image.c		Start initial ramdisk verification
3251 -120	common/image.c		Ramdisk FIT image has incorrect format
3252  121	common/image.c		Ramdisk FIT image has correct format
3253  122	common/image.c		No ramdisk subimage unit name, using configuration
3254 -122	common/image.c		Can't get configuration for ramdisk subimage
3255  123	common/image.c		Ramdisk unit name specified
3256 -124	common/image.c		Can't get ramdisk subimage node offset
3257  125	common/image.c		Got ramdisk subimage node offset
3258 -125	common/image.c		Ramdisk subimage hash verification failed
3259  126	common/image.c		Ramdisk subimage hash verification OK
3260 -126	common/image.c		Ramdisk subimage for unsupported architecture
3261  127	common/image.c		Architecture check OK
3262 -127	common/image.c		Can't get ramdisk subimage data/size
3263  128	common/image.c		Got ramdisk subimage data/size
3264  129	common/image.c		Can't get ramdisk load address
3265 -129	common/image.c		Got ramdisk load address
3266
3267 -130	common/cmd_doc.c	Incorrect FIT image format
3268  131	common/cmd_doc.c	FIT image format OK
3269
3270 -140	common/cmd_ide.c	Incorrect FIT image format
3271  141	common/cmd_ide.c	FIT image format OK
3272
3273 -150	common/cmd_nand.c	Incorrect FIT image format
3274  151	common/cmd_nand.c	FIT image format OK
3275
3276- legacy image format:
3277		CONFIG_IMAGE_FORMAT_LEGACY
3278		enables the legacy image format support in U-Boot.
3279
3280		Default:
3281		enabled if CONFIG_FIT_SIGNATURE is not defined.
3282
3283		CONFIG_DISABLE_IMAGE_LEGACY
3284		disable the legacy image format
3285
3286		This define is introduced, as the legacy image format is
3287		enabled per default for backward compatibility.
3288
3289- FIT image support:
3290		CONFIG_FIT_DISABLE_SHA256
3291		Supporting SHA256 hashes has quite an impact on binary size.
3292		For constrained systems sha256 hash support can be disabled
3293		with this option.
3294
3295		TODO(sjg@chromium.org): Adjust this option to be positive,
3296		and move it to Kconfig
3297
3298- Standalone program support:
3299		CONFIG_STANDALONE_LOAD_ADDR
3300
3301		This option defines a board specific value for the
3302		address where standalone program gets loaded, thus
3303		overwriting the architecture dependent default
3304		settings.
3305
3306- Frame Buffer Address:
3307		CONFIG_FB_ADDR
3308
3309		Define CONFIG_FB_ADDR if you want to use specific
3310		address for frame buffer.  This is typically the case
3311		when using a graphics controller has separate video
3312		memory.  U-Boot will then place the frame buffer at
3313		the given address instead of dynamically reserving it
3314		in system RAM by calling lcd_setmem(), which grabs
3315		the memory for the frame buffer depending on the
3316		configured panel size.
3317
3318		Please see board_init_f function.
3319
3320- Automatic software updates via TFTP server
3321		CONFIG_UPDATE_TFTP
3322		CONFIG_UPDATE_TFTP_CNT_MAX
3323		CONFIG_UPDATE_TFTP_MSEC_MAX
3324
3325		These options enable and control the auto-update feature;
3326		for a more detailed description refer to doc/README.update.
3327
3328- MTD Support (mtdparts command, UBI support)
3329		CONFIG_MTD_DEVICE
3330
3331		Adds the MTD device infrastructure from the Linux kernel.
3332		Needed for mtdparts command support.
3333
3334		CONFIG_MTD_PARTITIONS
3335
3336		Adds the MTD partitioning infrastructure from the Linux
3337		kernel. Needed for UBI support.
3338
3339- UBI support
3340		CONFIG_CMD_UBI
3341
3342		Adds commands for interacting with MTD partitions formatted
3343		with the UBI flash translation layer
3344
3345		Requires also defining CONFIG_RBTREE
3346
3347		CONFIG_UBI_SILENCE_MSG
3348
3349		Make the verbose messages from UBI stop printing.  This leaves
3350		warnings and errors enabled.
3351
3352
3353		CONFIG_MTD_UBI_WL_THRESHOLD
3354		This parameter defines the maximum difference between the highest
3355		erase counter value and the lowest erase counter value of eraseblocks
3356		of UBI devices. When this threshold is exceeded, UBI starts performing
3357		wear leveling by means of moving data from eraseblock with low erase
3358		counter to eraseblocks with high erase counter.
3359
3360		The default value should be OK for SLC NAND flashes, NOR flashes and
3361		other flashes which have eraseblock life-cycle 100000 or more.
3362		However, in case of MLC NAND flashes which typically have eraseblock
3363		life-cycle less than 10000, the threshold should be lessened (e.g.,
3364		to 128 or 256, although it does not have to be power of 2).
3365
3366		default: 4096
3367
3368		CONFIG_MTD_UBI_BEB_LIMIT
3369		This option specifies the maximum bad physical eraseblocks UBI
3370		expects on the MTD device (per 1024 eraseblocks). If the
3371		underlying flash does not admit of bad eraseblocks (e.g. NOR
3372		flash), this value is ignored.
3373
3374		NAND datasheets often specify the minimum and maximum NVM
3375		(Number of Valid Blocks) for the flashes' endurance lifetime.
3376		The maximum expected bad eraseblocks per 1024 eraseblocks
3377		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3378		which gives 20 for most NANDs (MaxNVB is basically the total
3379		count of eraseblocks on the chip).
3380
3381		To put it differently, if this value is 20, UBI will try to
3382		reserve about 1.9% of physical eraseblocks for bad blocks
3383		handling. And that will be 1.9% of eraseblocks on the entire
3384		NAND chip, not just the MTD partition UBI attaches. This means
3385		that if you have, say, a NAND flash chip admits maximum 40 bad
3386		eraseblocks, and it is split on two MTD partitions of the same
3387		size, UBI will reserve 40 eraseblocks when attaching a
3388		partition.
3389
3390		default: 20
3391
3392		CONFIG_MTD_UBI_FASTMAP
3393		Fastmap is a mechanism which allows attaching an UBI device
3394		in nearly constant time. Instead of scanning the whole MTD device it
3395		only has to locate a checkpoint (called fastmap) on the device.
3396		The on-flash fastmap contains all information needed to attach
3397		the device. Using fastmap makes only sense on large devices where
3398		attaching by scanning takes long. UBI will not automatically install
3399		a fastmap on old images, but you can set the UBI parameter
3400		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3401		that fastmap-enabled images are still usable with UBI implementations
3402		without	fastmap support. On typical flash devices the whole fastmap
3403		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3404
3405		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3406		Set this parameter to enable fastmap automatically on images
3407		without a fastmap.
3408		default: 0
3409
3410		CONFIG_MTD_UBI_FM_DEBUG
3411		Enable UBI fastmap debug
3412		default: 0
3413
3414- UBIFS support
3415		CONFIG_CMD_UBIFS
3416
3417		Adds commands for interacting with UBI volumes formatted as
3418		UBIFS.  UBIFS is read-only in u-boot.
3419
3420		Requires UBI support as well as CONFIG_LZO
3421
3422		CONFIG_UBIFS_SILENCE_MSG
3423
3424		Make the verbose messages from UBIFS stop printing.  This leaves
3425		warnings and errors enabled.
3426
3427- SPL framework
3428		CONFIG_SPL
3429		Enable building of SPL globally.
3430
3431		CONFIG_SPL_LDSCRIPT
3432		LDSCRIPT for linking the SPL binary.
3433
3434		CONFIG_SPL_MAX_FOOTPRINT
3435		Maximum size in memory allocated to the SPL, BSS included.
3436		When defined, the linker checks that the actual memory
3437		used by SPL from _start to __bss_end does not exceed it.
3438		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3439		must not be both defined at the same time.
3440
3441		CONFIG_SPL_MAX_SIZE
3442		Maximum size of the SPL image (text, data, rodata, and
3443		linker lists sections), BSS excluded.
3444		When defined, the linker checks that the actual size does
3445		not exceed it.
3446
3447		CONFIG_SPL_TEXT_BASE
3448		TEXT_BASE for linking the SPL binary.
3449
3450		CONFIG_SPL_RELOC_TEXT_BASE
3451		Address to relocate to.  If unspecified, this is equal to
3452		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3453
3454		CONFIG_SPL_BSS_START_ADDR
3455		Link address for the BSS within the SPL binary.
3456
3457		CONFIG_SPL_BSS_MAX_SIZE
3458		Maximum size in memory allocated to the SPL BSS.
3459		When defined, the linker checks that the actual memory used
3460		by SPL from __bss_start to __bss_end does not exceed it.
3461		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3462		must not be both defined at the same time.
3463
3464		CONFIG_SPL_STACK
3465		Adress of the start of the stack SPL will use
3466
3467		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3468		When defined, SPL will panic() if the image it has
3469		loaded does not have a signature.
3470		Defining this is useful when code which loads images
3471		in SPL cannot guarantee that absolutely all read errors
3472		will be caught.
3473		An example is the LPC32XX MLC NAND driver, which will
3474		consider that a completely unreadable NAND block is bad,
3475		and thus should be skipped silently.
3476
3477		CONFIG_SPL_ABORT_ON_RAW_IMAGE
3478		When defined, SPL will proceed to another boot method
3479		if the image it has loaded does not have a signature.
3480
3481		CONFIG_SPL_RELOC_STACK
3482		Adress of the start of the stack SPL will use after
3483		relocation.  If unspecified, this is equal to
3484		CONFIG_SPL_STACK.
3485
3486		CONFIG_SYS_SPL_MALLOC_START
3487		Starting address of the malloc pool used in SPL.
3488		When this option is set the full malloc is used in SPL and
3489		it is set up by spl_init() and before that, the simple malloc()
3490		can be used if CONFIG_SYS_MALLOC_F is defined.
3491
3492		CONFIG_SYS_SPL_MALLOC_SIZE
3493		The size of the malloc pool used in SPL.
3494
3495		CONFIG_SPL_FRAMEWORK
3496		Enable the SPL framework under common/.  This framework
3497		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3498		NAND loading of the Linux Kernel.
3499
3500		CONFIG_SPL_OS_BOOT
3501		Enable booting directly to an OS from SPL.
3502		See also: doc/README.falcon
3503
3504		CONFIG_SPL_DISPLAY_PRINT
3505		For ARM, enable an optional function to print more information
3506		about the running system.
3507
3508		CONFIG_SPL_INIT_MINIMAL
3509		Arch init code should be built for a very small image
3510
3511		CONFIG_SPL_LIBCOMMON_SUPPORT
3512		Support for common/libcommon.o in SPL binary
3513
3514		CONFIG_SPL_LIBDISK_SUPPORT
3515		Support for disk/libdisk.o in SPL binary
3516
3517		CONFIG_SPL_I2C_SUPPORT
3518		Support for drivers/i2c/libi2c.o in SPL binary
3519
3520		CONFIG_SPL_GPIO_SUPPORT
3521		Support for drivers/gpio/libgpio.o in SPL binary
3522
3523		CONFIG_SPL_MMC_SUPPORT
3524		Support for drivers/mmc/libmmc.o in SPL binary
3525
3526		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3527		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3528		Address and partition on the MMC to load U-Boot from
3529		when the MMC is being used in raw mode.
3530
3531		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3532		Partition on the MMC to load U-Boot from when the MMC is being
3533		used in raw mode
3534
3535		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3536		Sector to load kernel uImage from when MMC is being
3537		used in raw mode (for Falcon mode)
3538
3539		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3540		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3541		Sector and number of sectors to load kernel argument
3542		parameters from when MMC is being used in raw mode
3543		(for falcon mode)
3544
3545		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3546		Partition on the MMC to load U-Boot from when the MMC is being
3547		used in fs mode
3548
3549		CONFIG_SPL_FAT_SUPPORT
3550		Support for fs/fat/libfat.o in SPL binary
3551
3552		CONFIG_SPL_EXT_SUPPORT
3553		Support for EXT filesystem in SPL binary
3554
3555		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3556		Filename to read to load U-Boot when reading from filesystem
3557
3558		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3559		Filename to read to load kernel uImage when reading
3560		from filesystem (for Falcon mode)
3561
3562		CONFIG_SPL_FS_LOAD_ARGS_NAME
3563		Filename to read to load kernel argument parameters
3564		when reading from filesystem (for Falcon mode)
3565
3566		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3567		Set this for NAND SPL on PPC mpc83xx targets, so that
3568		start.S waits for the rest of the SPL to load before
3569		continuing (the hardware starts execution after just
3570		loading the first page rather than the full 4K).
3571
3572		CONFIG_SPL_SKIP_RELOCATE
3573		Avoid SPL relocation
3574
3575		CONFIG_SPL_NAND_BASE
3576		Include nand_base.c in the SPL.  Requires
3577		CONFIG_SPL_NAND_DRIVERS.
3578
3579		CONFIG_SPL_NAND_DRIVERS
3580		SPL uses normal NAND drivers, not minimal drivers.
3581
3582		CONFIG_SPL_NAND_ECC
3583		Include standard software ECC in the SPL
3584
3585		CONFIG_SPL_NAND_SIMPLE
3586		Support for NAND boot using simple NAND drivers that
3587		expose the cmd_ctrl() interface.
3588
3589		CONFIG_SPL_MTD_SUPPORT
3590		Support for the MTD subsystem within SPL.  Useful for
3591		environment on NAND support within SPL.
3592
3593		CONFIG_SPL_NAND_RAW_ONLY
3594		Support to boot only raw u-boot.bin images. Use this only
3595		if you need to save space.
3596
3597		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3598		Set for the SPL on PPC mpc8xxx targets, support for
3599		drivers/ddr/fsl/libddr.o in SPL binary.
3600
3601		CONFIG_SPL_COMMON_INIT_DDR
3602		Set for common ddr init with serial presence detect in
3603		SPL binary.
3604
3605		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3606		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3607		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3608		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3609		CONFIG_SYS_NAND_ECCBYTES
3610		Defines the size and behavior of the NAND that SPL uses
3611		to read U-Boot
3612
3613		CONFIG_SPL_NAND_BOOT
3614		Add support NAND boot
3615
3616		CONFIG_SYS_NAND_U_BOOT_OFFS
3617		Location in NAND to read U-Boot from
3618
3619		CONFIG_SYS_NAND_U_BOOT_DST
3620		Location in memory to load U-Boot to
3621
3622		CONFIG_SYS_NAND_U_BOOT_SIZE
3623		Size of image to load
3624
3625		CONFIG_SYS_NAND_U_BOOT_START
3626		Entry point in loaded image to jump to
3627
3628		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3629		Define this if you need to first read the OOB and then the
3630		data. This is used, for example, on davinci platforms.
3631
3632		CONFIG_SPL_OMAP3_ID_NAND
3633		Support for an OMAP3-specific set of functions to return the
3634		ID and MFR of the first attached NAND chip, if present.
3635
3636		CONFIG_SPL_SERIAL_SUPPORT
3637		Support for drivers/serial/libserial.o in SPL binary
3638
3639		CONFIG_SPL_SPI_FLASH_SUPPORT
3640		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3641
3642		CONFIG_SPL_SPI_SUPPORT
3643		Support for drivers/spi/libspi.o in SPL binary
3644
3645		CONFIG_SPL_RAM_DEVICE
3646		Support for running image already present in ram, in SPL binary
3647
3648		CONFIG_SPL_LIBGENERIC_SUPPORT
3649		Support for lib/libgeneric.o in SPL binary
3650
3651		CONFIG_SPL_ENV_SUPPORT
3652		Support for the environment operating in SPL binary
3653
3654		CONFIG_SPL_NET_SUPPORT
3655		Support for the net/libnet.o in SPL binary.
3656		It conflicts with SPL env from storage medium specified by
3657		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3658
3659		CONFIG_SPL_PAD_TO
3660		Image offset to which the SPL should be padded before appending
3661		the SPL payload. By default, this is defined as
3662		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3663		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3664		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3665
3666		CONFIG_SPL_TARGET
3667		Final target image containing SPL and payload.  Some SPLs
3668		use an arch-specific makefile fragment instead, for
3669		example if more than one image needs to be produced.
3670
3671		CONFIG_FIT_SPL_PRINT
3672		Printing information about a FIT image adds quite a bit of
3673		code to SPL. So this is normally disabled in SPL. Use this
3674		option to re-enable it. This will affect the output of the
3675		bootm command when booting a FIT image.
3676
3677- TPL framework
3678		CONFIG_TPL
3679		Enable building of TPL globally.
3680
3681		CONFIG_TPL_PAD_TO
3682		Image offset to which the TPL should be padded before appending
3683		the TPL payload. By default, this is defined as
3684		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3685		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3686		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3687
3688- Interrupt support (PPC):
3689
3690		There are common interrupt_init() and timer_interrupt()
3691		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3692		for CPU specific initialization. interrupt_init_cpu()
3693		should set decrementer_count to appropriate value. If
3694		CPU resets decrementer automatically after interrupt
3695		(ppc4xx) it should set decrementer_count to zero.
3696		timer_interrupt() calls timer_interrupt_cpu() for CPU
3697		specific handling. If board has watchdog / status_led
3698		/ other_activity_monitor it works automatically from
3699		general timer_interrupt().
3700
3701
3702Board initialization settings:
3703------------------------------
3704
3705During Initialization u-boot calls a number of board specific functions
3706to allow the preparation of board specific prerequisites, e.g. pin setup
3707before drivers are initialized. To enable these callbacks the
3708following configuration macros have to be defined. Currently this is
3709architecture specific, so please check arch/your_architecture/lib/board.c
3710typically in board_init_f() and board_init_r().
3711
3712- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3713- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3714- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3715- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3716
3717Configuration Settings:
3718-----------------------
3719
3720- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3721		Optionally it can be defined to support 64-bit memory commands.
3722
3723- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3724		undefine this when you're short of memory.
3725
3726- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3727		width of the commands listed in the 'help' command output.
3728
3729- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3730		prompt for user input.
3731
3732- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3733
3734- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3735
3736- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3737
3738- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3739		the application (usually a Linux kernel) when it is
3740		booted
3741
3742- CONFIG_SYS_BAUDRATE_TABLE:
3743		List of legal baudrate settings for this board.
3744
3745- CONFIG_SYS_CONSOLE_INFO_QUIET
3746		Suppress display of console information at boot.
3747
3748- CONFIG_SYS_CONSOLE_IS_IN_ENV
3749		If the board specific function
3750			extern int overwrite_console (void);
3751		returns 1, the stdin, stderr and stdout are switched to the
3752		serial port, else the settings in the environment are used.
3753
3754- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3755		Enable the call to overwrite_console().
3756
3757- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3758		Enable overwrite of previous console environment settings.
3759
3760- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3761		Begin and End addresses of the area used by the
3762		simple memory test.
3763
3764- CONFIG_SYS_ALT_MEMTEST:
3765		Enable an alternate, more extensive memory test.
3766
3767- CONFIG_SYS_MEMTEST_SCRATCH:
3768		Scratch address used by the alternate memory test
3769		You only need to set this if address zero isn't writeable
3770
3771- CONFIG_SYS_MEM_RESERVE_SECURE
3772		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
3773		is substracted from total RAM and won't be reported to OS.
3774		This memory can be used as secure memory. A variable
3775		gd->secure_ram is used to track the location. In systems
3776		the RAM base is not zero, or RAM is divided into banks,
3777		this variable needs to be recalcuated to get the address.
3778
3779- CONFIG_SYS_MEM_TOP_HIDE:
3780		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3781		this specified memory area will get subtracted from the top
3782		(end) of RAM and won't get "touched" at all by U-Boot. By
3783		fixing up gd->ram_size the Linux kernel should gets passed
3784		the now "corrected" memory size and won't touch it either.
3785		This should work for arch/ppc and arch/powerpc. Only Linux
3786		board ports in arch/powerpc with bootwrapper support that
3787		recalculate the memory size from the SDRAM controller setup
3788		will have to get fixed in Linux additionally.
3789
3790		This option can be used as a workaround for the 440EPx/GRx
3791		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3792		be touched.
3793
3794		WARNING: Please make sure that this value is a multiple of
3795		the Linux page size (normally 4k). If this is not the case,
3796		then the end address of the Linux memory will be located at a
3797		non page size aligned address and this could cause major
3798		problems.
3799
3800- CONFIG_SYS_LOADS_BAUD_CHANGE:
3801		Enable temporary baudrate change while serial download
3802
3803- CONFIG_SYS_SDRAM_BASE:
3804		Physical start address of SDRAM. _Must_ be 0 here.
3805
3806- CONFIG_SYS_MBIO_BASE:
3807		Physical start address of Motherboard I/O (if using a
3808		Cogent motherboard)
3809
3810- CONFIG_SYS_FLASH_BASE:
3811		Physical start address of Flash memory.
3812
3813- CONFIG_SYS_MONITOR_BASE:
3814		Physical start address of boot monitor code (set by
3815		make config files to be same as the text base address
3816		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3817		CONFIG_SYS_FLASH_BASE when booting from flash.
3818
3819- CONFIG_SYS_MONITOR_LEN:
3820		Size of memory reserved for monitor code, used to
3821		determine _at_compile_time_ (!) if the environment is
3822		embedded within the U-Boot image, or in a separate
3823		flash sector.
3824
3825- CONFIG_SYS_MALLOC_LEN:
3826		Size of DRAM reserved for malloc() use.
3827
3828- CONFIG_SYS_MALLOC_F_LEN
3829		Size of the malloc() pool for use before relocation. If
3830		this is defined, then a very simple malloc() implementation
3831		will become available before relocation. The address is just
3832		below the global data, and the stack is moved down to make
3833		space.
3834
3835		This feature allocates regions with increasing addresses
3836		within the region. calloc() is supported, but realloc()
3837		is not available. free() is supported but does nothing.
3838		The memory will be freed (or in fact just forgotten) when
3839		U-Boot relocates itself.
3840
3841		Pre-relocation malloc() is only supported on ARM and sandbox
3842		at present but is fairly easy to enable for other archs.
3843
3844- CONFIG_SYS_MALLOC_SIMPLE
3845		Provides a simple and small malloc() and calloc() for those
3846		boards which do not use the full malloc in SPL (which is
3847		enabled with CONFIG_SYS_SPL_MALLOC_START).
3848
3849- CONFIG_SYS_NONCACHED_MEMORY:
3850		Size of non-cached memory area. This area of memory will be
3851		typically located right below the malloc() area and mapped
3852		uncached in the MMU. This is useful for drivers that would
3853		otherwise require a lot of explicit cache maintenance. For
3854		some drivers it's also impossible to properly maintain the
3855		cache. For example if the regions that need to be flushed
3856		are not a multiple of the cache-line size, *and* padding
3857		cannot be allocated between the regions to align them (i.e.
3858		if the HW requires a contiguous array of regions, and the
3859		size of each region is not cache-aligned), then a flush of
3860		one region may result in overwriting data that hardware has
3861		written to another region in the same cache-line. This can
3862		happen for example in network drivers where descriptors for
3863		buffers are typically smaller than the CPU cache-line (e.g.
3864		16 bytes vs. 32 or 64 bytes).
3865
3866		Non-cached memory is only supported on 32-bit ARM at present.
3867
3868- CONFIG_SYS_BOOTM_LEN:
3869		Normally compressed uImages are limited to an
3870		uncompressed size of 8 MBytes. If this is not enough,
3871		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3872		to adjust this setting to your needs.
3873
3874- CONFIG_SYS_BOOTMAPSZ:
3875		Maximum size of memory mapped by the startup code of
3876		the Linux kernel; all data that must be processed by
3877		the Linux kernel (bd_info, boot arguments, FDT blob if
3878		used) must be put below this limit, unless "bootm_low"
3879		environment variable is defined and non-zero. In such case
3880		all data for the Linux kernel must be between "bootm_low"
3881		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3882		variable "bootm_mapsize" will override the value of
3883		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3884		then the value in "bootm_size" will be used instead.
3885
3886- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3887		Enable initrd_high functionality.  If defined then the
3888		initrd_high feature is enabled and the bootm ramdisk subcommand
3889		is enabled.
3890
3891- CONFIG_SYS_BOOT_GET_CMDLINE:
3892		Enables allocating and saving kernel cmdline in space between
3893		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3894
3895- CONFIG_SYS_BOOT_GET_KBD:
3896		Enables allocating and saving a kernel copy of the bd_info in
3897		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3898
3899- CONFIG_SYS_MAX_FLASH_BANKS:
3900		Max number of Flash memory banks
3901
3902- CONFIG_SYS_MAX_FLASH_SECT:
3903		Max number of sectors on a Flash chip
3904
3905- CONFIG_SYS_FLASH_ERASE_TOUT:
3906		Timeout for Flash erase operations (in ms)
3907
3908- CONFIG_SYS_FLASH_WRITE_TOUT:
3909		Timeout for Flash write operations (in ms)
3910
3911- CONFIG_SYS_FLASH_LOCK_TOUT
3912		Timeout for Flash set sector lock bit operation (in ms)
3913
3914- CONFIG_SYS_FLASH_UNLOCK_TOUT
3915		Timeout for Flash clear lock bits operation (in ms)
3916
3917- CONFIG_SYS_FLASH_PROTECTION
3918		If defined, hardware flash sectors protection is used
3919		instead of U-Boot software protection.
3920
3921- CONFIG_SYS_DIRECT_FLASH_TFTP:
3922
3923		Enable TFTP transfers directly to flash memory;
3924		without this option such a download has to be
3925		performed in two steps: (1) download to RAM, and (2)
3926		copy from RAM to flash.
3927
3928		The two-step approach is usually more reliable, since
3929		you can check if the download worked before you erase
3930		the flash, but in some situations (when system RAM is
3931		too limited to allow for a temporary copy of the
3932		downloaded image) this option may be very useful.
3933
3934- CONFIG_SYS_FLASH_CFI:
3935		Define if the flash driver uses extra elements in the
3936		common flash structure for storing flash geometry.
3937
3938- CONFIG_FLASH_CFI_DRIVER
3939		This option also enables the building of the cfi_flash driver
3940		in the drivers directory
3941
3942- CONFIG_FLASH_CFI_MTD
3943		This option enables the building of the cfi_mtd driver
3944		in the drivers directory. The driver exports CFI flash
3945		to the MTD layer.
3946
3947- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3948		Use buffered writes to flash.
3949
3950- CONFIG_FLASH_SPANSION_S29WS_N
3951		s29ws-n MirrorBit flash has non-standard addresses for buffered
3952		write commands.
3953
3954- CONFIG_SYS_FLASH_QUIET_TEST
3955		If this option is defined, the common CFI flash doesn't
3956		print it's warning upon not recognized FLASH banks. This
3957		is useful, if some of the configured banks are only
3958		optionally available.
3959
3960- CONFIG_FLASH_SHOW_PROGRESS
3961		If defined (must be an integer), print out countdown
3962		digits and dots.  Recommended value: 45 (9..1) for 80
3963		column displays, 15 (3..1) for 40 column displays.
3964
3965- CONFIG_FLASH_VERIFY
3966		If defined, the content of the flash (destination) is compared
3967		against the source after the write operation. An error message
3968		will be printed when the contents are not identical.
3969		Please note that this option is useless in nearly all cases,
3970		since such flash programming errors usually are detected earlier
3971		while unprotecting/erasing/programming. Please only enable
3972		this option if you really know what you are doing.
3973
3974- CONFIG_SYS_RX_ETH_BUFFER:
3975		Defines the number of Ethernet receive buffers. On some
3976		Ethernet controllers it is recommended to set this value
3977		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3978		buffers can be full shortly after enabling the interface
3979		on high Ethernet traffic.
3980		Defaults to 4 if not defined.
3981
3982- CONFIG_ENV_MAX_ENTRIES
3983
3984	Maximum number of entries in the hash table that is used
3985	internally to store the environment settings. The default
3986	setting is supposed to be generous and should work in most
3987	cases. This setting can be used to tune behaviour; see
3988	lib/hashtable.c for details.
3989
3990- CONFIG_ENV_FLAGS_LIST_DEFAULT
3991- CONFIG_ENV_FLAGS_LIST_STATIC
3992	Enable validation of the values given to environment variables when
3993	calling env set.  Variables can be restricted to only decimal,
3994	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3995	the variables can also be restricted to IP address or MAC address.
3996
3997	The format of the list is:
3998		type_attribute = [s|d|x|b|i|m]
3999		access_attribute = [a|r|o|c]
4000		attributes = type_attribute[access_attribute]
4001		entry = variable_name[:attributes]
4002		list = entry[,list]
4003
4004	The type attributes are:
4005		s - String (default)
4006		d - Decimal
4007		x - Hexadecimal
4008		b - Boolean ([1yYtT|0nNfF])
4009		i - IP address
4010		m - MAC address
4011
4012	The access attributes are:
4013		a - Any (default)
4014		r - Read-only
4015		o - Write-once
4016		c - Change-default
4017
4018	- CONFIG_ENV_FLAGS_LIST_DEFAULT
4019		Define this to a list (string) to define the ".flags"
4020		environment variable in the default or embedded environment.
4021
4022	- CONFIG_ENV_FLAGS_LIST_STATIC
4023		Define this to a list (string) to define validation that
4024		should be done if an entry is not found in the ".flags"
4025		environment variable.  To override a setting in the static
4026		list, simply add an entry for the same variable name to the
4027		".flags" variable.
4028
4029	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4030	regular expression. This allows multiple variables to define the same
4031	flags without explicitly listing them for each variable.
4032
4033- CONFIG_ENV_ACCESS_IGNORE_FORCE
4034	If defined, don't allow the -f switch to env set override variable
4035	access flags.
4036
4037- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
4038	This is set by OMAP boards for the max time that reset should
4039	be asserted. See doc/README.omap-reset-time for details on how
4040	the value can be calculated on a given board.
4041
4042- CONFIG_USE_STDINT
4043	If stdint.h is available with your toolchain you can define this
4044	option to enable it. You can provide option 'USE_STDINT=1' when
4045	building U-Boot to enable this.
4046
4047The following definitions that deal with the placement and management
4048of environment data (variable area); in general, we support the
4049following configurations:
4050
4051- CONFIG_BUILD_ENVCRC:
4052
4053	Builds up envcrc with the target environment so that external utils
4054	may easily extract it and embed it in final U-Boot images.
4055
4056- CONFIG_ENV_IS_IN_FLASH:
4057
4058	Define this if the environment is in flash memory.
4059
4060	a) The environment occupies one whole flash sector, which is
4061	   "embedded" in the text segment with the U-Boot code. This
4062	   happens usually with "bottom boot sector" or "top boot
4063	   sector" type flash chips, which have several smaller
4064	   sectors at the start or the end. For instance, such a
4065	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
4066	   such a case you would place the environment in one of the
4067	   4 kB sectors - with U-Boot code before and after it. With
4068	   "top boot sector" type flash chips, you would put the
4069	   environment in one of the last sectors, leaving a gap
4070	   between U-Boot and the environment.
4071
4072	- CONFIG_ENV_OFFSET:
4073
4074	   Offset of environment data (variable area) to the
4075	   beginning of flash memory; for instance, with bottom boot
4076	   type flash chips the second sector can be used: the offset
4077	   for this sector is given here.
4078
4079	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
4080
4081	- CONFIG_ENV_ADDR:
4082
4083	   This is just another way to specify the start address of
4084	   the flash sector containing the environment (instead of
4085	   CONFIG_ENV_OFFSET).
4086
4087	- CONFIG_ENV_SECT_SIZE:
4088
4089	   Size of the sector containing the environment.
4090
4091
4092	b) Sometimes flash chips have few, equal sized, BIG sectors.
4093	   In such a case you don't want to spend a whole sector for
4094	   the environment.
4095
4096	- CONFIG_ENV_SIZE:
4097
4098	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
4099	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
4100	   of this flash sector for the environment. This saves
4101	   memory for the RAM copy of the environment.
4102
4103	   It may also save flash memory if you decide to use this
4104	   when your environment is "embedded" within U-Boot code,
4105	   since then the remainder of the flash sector could be used
4106	   for U-Boot code. It should be pointed out that this is
4107	   STRONGLY DISCOURAGED from a robustness point of view:
4108	   updating the environment in flash makes it always
4109	   necessary to erase the WHOLE sector. If something goes
4110	   wrong before the contents has been restored from a copy in
4111	   RAM, your target system will be dead.
4112
4113	- CONFIG_ENV_ADDR_REDUND
4114	  CONFIG_ENV_SIZE_REDUND
4115
4116	   These settings describe a second storage area used to hold
4117	   a redundant copy of the environment data, so that there is
4118	   a valid backup copy in case there is a power failure during
4119	   a "saveenv" operation.
4120
4121BE CAREFUL! Any changes to the flash layout, and some changes to the
4122source code will make it necessary to adapt <board>/u-boot.lds*
4123accordingly!
4124
4125
4126- CONFIG_ENV_IS_IN_NVRAM:
4127
4128	Define this if you have some non-volatile memory device
4129	(NVRAM, battery buffered SRAM) which you want to use for the
4130	environment.
4131
4132	- CONFIG_ENV_ADDR:
4133	- CONFIG_ENV_SIZE:
4134
4135	  These two #defines are used to determine the memory area you
4136	  want to use for environment. It is assumed that this memory
4137	  can just be read and written to, without any special
4138	  provision.
4139
4140BE CAREFUL! The first access to the environment happens quite early
4141in U-Boot initialization (when we try to get the setting of for the
4142console baudrate). You *MUST* have mapped your NVRAM area then, or
4143U-Boot will hang.
4144
4145Please note that even with NVRAM we still use a copy of the
4146environment in RAM: we could work on NVRAM directly, but we want to
4147keep settings there always unmodified except somebody uses "saveenv"
4148to save the current settings.
4149
4150
4151- CONFIG_ENV_IS_IN_EEPROM:
4152
4153	Use this if you have an EEPROM or similar serial access
4154	device and a driver for it.
4155
4156	- CONFIG_ENV_OFFSET:
4157	- CONFIG_ENV_SIZE:
4158
4159	  These two #defines specify the offset and size of the
4160	  environment area within the total memory of your EEPROM.
4161
4162	- CONFIG_SYS_I2C_EEPROM_ADDR:
4163	  If defined, specified the chip address of the EEPROM device.
4164	  The default address is zero.
4165
4166	- CONFIG_SYS_I2C_EEPROM_BUS:
4167	  If defined, specified the i2c bus of the EEPROM device.
4168
4169	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
4170	  If defined, the number of bits used to address bytes in a
4171	  single page in the EEPROM device.  A 64 byte page, for example
4172	  would require six bits.
4173
4174	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
4175	  If defined, the number of milliseconds to delay between
4176	  page writes.	The default is zero milliseconds.
4177
4178	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
4179	  The length in bytes of the EEPROM memory array address.  Note
4180	  that this is NOT the chip address length!
4181
4182	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
4183	  EEPROM chips that implement "address overflow" are ones
4184	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
4185	  address and the extra bits end up in the "chip address" bit
4186	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
4187	  byte chips.
4188
4189	  Note that we consider the length of the address field to
4190	  still be one byte because the extra address bits are hidden
4191	  in the chip address.
4192
4193	- CONFIG_SYS_EEPROM_SIZE:
4194	  The size in bytes of the EEPROM device.
4195
4196	- CONFIG_ENV_EEPROM_IS_ON_I2C
4197	  define this, if you have I2C and SPI activated, and your
4198	  EEPROM, which holds the environment, is on the I2C bus.
4199
4200	- CONFIG_I2C_ENV_EEPROM_BUS
4201	  if you have an Environment on an EEPROM reached over
4202	  I2C muxes, you can define here, how to reach this
4203	  EEPROM. For example:
4204
4205	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
4206
4207	  EEPROM which holds the environment, is reached over
4208	  a pca9547 i2c mux with address 0x70, channel 3.
4209
4210- CONFIG_ENV_IS_IN_DATAFLASH:
4211
4212	Define this if you have a DataFlash memory device which you
4213	want to use for the environment.
4214
4215	- CONFIG_ENV_OFFSET:
4216	- CONFIG_ENV_ADDR:
4217	- CONFIG_ENV_SIZE:
4218
4219	  These three #defines specify the offset and size of the
4220	  environment area within the total memory of your DataFlash placed
4221	  at the specified address.
4222
4223- CONFIG_ENV_IS_IN_SPI_FLASH:
4224
4225	Define this if you have a SPI Flash memory device which you
4226	want to use for the environment.
4227
4228	- CONFIG_ENV_OFFSET:
4229	- CONFIG_ENV_SIZE:
4230
4231	  These two #defines specify the offset and size of the
4232	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
4233	  aligned to an erase sector boundary.
4234
4235	- CONFIG_ENV_SECT_SIZE:
4236
4237	  Define the SPI flash's sector size.
4238
4239	- CONFIG_ENV_OFFSET_REDUND (optional):
4240
4241	  This setting describes a second storage area of CONFIG_ENV_SIZE
4242	  size used to hold a redundant copy of the environment data, so
4243	  that there is a valid backup copy in case there is a power failure
4244	  during a "saveenv" operation. CONFIG_ENV_OFFSET_RENDUND must be
4245	  aligned to an erase sector boundary.
4246
4247	- CONFIG_ENV_SPI_BUS (optional):
4248	- CONFIG_ENV_SPI_CS (optional):
4249
4250	  Define the SPI bus and chip select. If not defined they will be 0.
4251
4252	- CONFIG_ENV_SPI_MAX_HZ (optional):
4253
4254	  Define the SPI max work clock. If not defined then use 1MHz.
4255
4256	- CONFIG_ENV_SPI_MODE (optional):
4257
4258	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4259
4260- CONFIG_ENV_IS_IN_REMOTE:
4261
4262	Define this if you have a remote memory space which you
4263	want to use for the local device's environment.
4264
4265	- CONFIG_ENV_ADDR:
4266	- CONFIG_ENV_SIZE:
4267
4268	  These two #defines specify the address and size of the
4269	  environment area within the remote memory space. The
4270	  local device can get the environment from remote memory
4271	  space by SRIO or PCIE links.
4272
4273BE CAREFUL! For some special cases, the local device can not use
4274"saveenv" command. For example, the local device will get the
4275environment stored in a remote NOR flash by SRIO or PCIE link,
4276but it can not erase, write this NOR flash by SRIO or PCIE interface.
4277
4278- CONFIG_ENV_IS_IN_NAND:
4279
4280	Define this if you have a NAND device which you want to use
4281	for the environment.
4282
4283	- CONFIG_ENV_OFFSET:
4284	- CONFIG_ENV_SIZE:
4285
4286	  These two #defines specify the offset and size of the environment
4287	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4288	  aligned to an erase block boundary.
4289
4290	- CONFIG_ENV_OFFSET_REDUND (optional):
4291
4292	  This setting describes a second storage area of CONFIG_ENV_SIZE
4293	  size used to hold a redundant copy of the environment data, so
4294	  that there is a valid backup copy in case there is a power failure
4295	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
4296	  aligned to an erase block boundary.
4297
4298	- CONFIG_ENV_RANGE (optional):
4299
4300	  Specifies the length of the region in which the environment
4301	  can be written.  This should be a multiple of the NAND device's
4302	  block size.  Specifying a range with more erase blocks than
4303	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4304	  the range to be avoided.
4305
4306	- CONFIG_ENV_OFFSET_OOB (optional):
4307
4308	  Enables support for dynamically retrieving the offset of the
4309	  environment from block zero's out-of-band data.  The
4310	  "nand env.oob" command can be used to record this offset.
4311	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4312	  using CONFIG_ENV_OFFSET_OOB.
4313
4314- CONFIG_NAND_ENV_DST
4315
4316	Defines address in RAM to which the nand_spl code should copy the
4317	environment. If redundant environment is used, it will be copied to
4318	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4319
4320- CONFIG_ENV_IS_IN_UBI:
4321
4322	Define this if you have an UBI volume that you want to use for the
4323	environment.  This has the benefit of wear-leveling the environment
4324	accesses, which is important on NAND.
4325
4326	- CONFIG_ENV_UBI_PART:
4327
4328	  Define this to a string that is the mtd partition containing the UBI.
4329
4330	- CONFIG_ENV_UBI_VOLUME:
4331
4332	  Define this to the name of the volume that you want to store the
4333	  environment in.
4334
4335	- CONFIG_ENV_UBI_VOLUME_REDUND:
4336
4337	  Define this to the name of another volume to store a second copy of
4338	  the environment in.  This will enable redundant environments in UBI.
4339	  It is assumed that both volumes are in the same MTD partition.
4340
4341	- CONFIG_UBI_SILENCE_MSG
4342	- CONFIG_UBIFS_SILENCE_MSG
4343
4344	  You will probably want to define these to avoid a really noisy system
4345	  when storing the env in UBI.
4346
4347- CONFIG_ENV_IS_IN_FAT:
4348       Define this if you want to use the FAT file system for the environment.
4349
4350       - FAT_ENV_INTERFACE:
4351
4352         Define this to a string that is the name of the block device.
4353
4354       - FAT_ENV_DEV_AND_PART:
4355
4356         Define this to a string to specify the partition of the device. It can
4357         be as following:
4358
4359           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4360               - "D:P": device D partition P. Error occurs if device D has no
4361                        partition table.
4362               - "D:0": device D.
4363               - "D" or "D:": device D partition 1 if device D has partition
4364                              table, or the whole device D if has no partition
4365                              table.
4366               - "D:auto": first partition in device D with bootable flag set.
4367                           If none, first valid partition in device D. If no
4368                           partition table then means device D.
4369
4370       - FAT_ENV_FILE:
4371
4372         It's a string of the FAT file name. This file use to store the
4373         environment.
4374
4375       - CONFIG_FAT_WRITE:
4376         This should be defined. Otherwise it cannot save the environment file.
4377
4378- CONFIG_ENV_IS_IN_MMC:
4379
4380	Define this if you have an MMC device which you want to use for the
4381	environment.
4382
4383	- CONFIG_SYS_MMC_ENV_DEV:
4384
4385	  Specifies which MMC device the environment is stored in.
4386
4387	- CONFIG_SYS_MMC_ENV_PART (optional):
4388
4389	  Specifies which MMC partition the environment is stored in. If not
4390	  set, defaults to partition 0, the user area. Common values might be
4391	  1 (first MMC boot partition), 2 (second MMC boot partition).
4392
4393	- CONFIG_ENV_OFFSET:
4394	- CONFIG_ENV_SIZE:
4395
4396	  These two #defines specify the offset and size of the environment
4397	  area within the specified MMC device.
4398
4399	  If offset is positive (the usual case), it is treated as relative to
4400	  the start of the MMC partition. If offset is negative, it is treated
4401	  as relative to the end of the MMC partition. This can be useful if
4402	  your board may be fitted with different MMC devices, which have
4403	  different sizes for the MMC partitions, and you always want the
4404	  environment placed at the very end of the partition, to leave the
4405	  maximum possible space before it, to store other data.
4406
4407	  These two values are in units of bytes, but must be aligned to an
4408	  MMC sector boundary.
4409
4410	- CONFIG_ENV_OFFSET_REDUND (optional):
4411
4412	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4413	  hold a redundant copy of the environment data. This provides a
4414	  valid backup copy in case the other copy is corrupted, e.g. due
4415	  to a power failure during a "saveenv" operation.
4416
4417	  This value may also be positive or negative; this is handled in the
4418	  same way as CONFIG_ENV_OFFSET.
4419
4420	  This value is also in units of bytes, but must also be aligned to
4421	  an MMC sector boundary.
4422
4423	- CONFIG_ENV_SIZE_REDUND (optional):
4424
4425	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4426	  set. If this value is set, it must be set to the same value as
4427	  CONFIG_ENV_SIZE.
4428
4429- CONFIG_SYS_SPI_INIT_OFFSET
4430
4431	Defines offset to the initial SPI buffer area in DPRAM. The
4432	area is used at an early stage (ROM part) if the environment
4433	is configured to reside in the SPI EEPROM: We need a 520 byte
4434	scratch DPRAM area. It is used between the two initialization
4435	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4436	to be a good choice since it makes it far enough from the
4437	start of the data area as well as from the stack pointer.
4438
4439Please note that the environment is read-only until the monitor
4440has been relocated to RAM and a RAM copy of the environment has been
4441created; also, when using EEPROM you will have to use getenv_f()
4442until then to read environment variables.
4443
4444The environment is protected by a CRC32 checksum. Before the monitor
4445is relocated into RAM, as a result of a bad CRC you will be working
4446with the compiled-in default environment - *silently*!!! [This is
4447necessary, because the first environment variable we need is the
4448"baudrate" setting for the console - if we have a bad CRC, we don't
4449have any device yet where we could complain.]
4450
4451Note: once the monitor has been relocated, then it will complain if
4452the default environment is used; a new CRC is computed as soon as you
4453use the "saveenv" command to store a valid environment.
4454
4455- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4456		Echo the inverted Ethernet link state to the fault LED.
4457
4458		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4459		      also needs to be defined.
4460
4461- CONFIG_SYS_FAULT_MII_ADDR:
4462		MII address of the PHY to check for the Ethernet link state.
4463
4464- CONFIG_NS16550_MIN_FUNCTIONS:
4465		Define this if you desire to only have use of the NS16550_init
4466		and NS16550_putc functions for the serial driver located at
4467		drivers/serial/ns16550.c.  This option is useful for saving
4468		space for already greatly restricted images, including but not
4469		limited to NAND_SPL configurations.
4470
4471- CONFIG_DISPLAY_BOARDINFO
4472		Display information about the board that U-Boot is running on
4473		when U-Boot starts up. The board function checkboard() is called
4474		to do this.
4475
4476- CONFIG_DISPLAY_BOARDINFO_LATE
4477		Similar to the previous option, but display this information
4478		later, once stdio is running and output goes to the LCD, if
4479		present.
4480
4481- CONFIG_BOARD_SIZE_LIMIT:
4482		Maximum size of the U-Boot image. When defined, the
4483		build system checks that the actual size does not
4484		exceed it.
4485
4486Low Level (hardware related) configuration options:
4487---------------------------------------------------
4488
4489- CONFIG_SYS_CACHELINE_SIZE:
4490		Cache Line Size of the CPU.
4491
4492- CONFIG_SYS_DEFAULT_IMMR:
4493		Default address of the IMMR after system reset.
4494
4495		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4496		and RPXsuper) to be able to adjust the position of
4497		the IMMR register after a reset.
4498
4499- CONFIG_SYS_CCSRBAR_DEFAULT:
4500		Default (power-on reset) physical address of CCSR on Freescale
4501		PowerPC SOCs.
4502
4503- CONFIG_SYS_CCSRBAR:
4504		Virtual address of CCSR.  On a 32-bit build, this is typically
4505		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4506
4507		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4508		for cross-platform code that uses that macro instead.
4509
4510- CONFIG_SYS_CCSRBAR_PHYS:
4511		Physical address of CCSR.  CCSR can be relocated to a new
4512		physical address, if desired.  In this case, this macro should
4513		be set to that address.	 Otherwise, it should be set to the
4514		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4515		is typically relocated on 36-bit builds.  It is recommended
4516		that this macro be defined via the _HIGH and _LOW macros:
4517
4518		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4519			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4520
4521- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4522		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4523		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4524		used in assembly code, so it must not contain typecasts or
4525		integer size suffixes (e.g. "ULL").
4526
4527- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4528		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4529		used in assembly code, so it must not contain typecasts or
4530		integer size suffixes (e.g. "ULL").
4531
4532- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4533		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4534		forced to a value that ensures that CCSR is not relocated.
4535
4536- Floppy Disk Support:
4537		CONFIG_SYS_FDC_DRIVE_NUMBER
4538
4539		the default drive number (default value 0)
4540
4541		CONFIG_SYS_ISA_IO_STRIDE
4542
4543		defines the spacing between FDC chipset registers
4544		(default value 1)
4545
4546		CONFIG_SYS_ISA_IO_OFFSET
4547
4548		defines the offset of register from address. It
4549		depends on which part of the data bus is connected to
4550		the FDC chipset. (default value 0)
4551
4552		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4553		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4554		default value.
4555
4556		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4557		fdc_hw_init() is called at the beginning of the FDC
4558		setup. fdc_hw_init() must be provided by the board
4559		source code. It is used to make hardware-dependent
4560		initializations.
4561
4562- CONFIG_IDE_AHB:
4563		Most IDE controllers were designed to be connected with PCI
4564		interface. Only few of them were designed for AHB interface.
4565		When software is doing ATA command and data transfer to
4566		IDE devices through IDE-AHB controller, some additional
4567		registers accessing to these kind of IDE-AHB controller
4568		is required.
4569
4570- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4571		DO NOT CHANGE unless you know exactly what you're
4572		doing! (11-4) [MPC8xx/82xx systems only]
4573
4574- CONFIG_SYS_INIT_RAM_ADDR:
4575
4576		Start address of memory area that can be used for
4577		initial data and stack; please note that this must be
4578		writable memory that is working WITHOUT special
4579		initialization, i. e. you CANNOT use normal RAM which
4580		will become available only after programming the
4581		memory controller and running certain initialization
4582		sequences.
4583
4584		U-Boot uses the following memory types:
4585		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4586		- MPC824X: data cache
4587		- PPC4xx:  data cache
4588
4589- CONFIG_SYS_GBL_DATA_OFFSET:
4590
4591		Offset of the initial data structure in the memory
4592		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4593		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4594		data is located at the end of the available space
4595		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4596		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4597		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4598		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4599
4600	Note:
4601		On the MPC824X (or other systems that use the data
4602		cache for initial memory) the address chosen for
4603		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4604		point to an otherwise UNUSED address space between
4605		the top of RAM and the start of the PCI space.
4606
4607- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4608
4609- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4610
4611- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4612
4613- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4614
4615- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4616
4617- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4618
4619- CONFIG_SYS_OR_TIMING_SDRAM:
4620		SDRAM timing
4621
4622- CONFIG_SYS_MAMR_PTA:
4623		periodic timer for refresh
4624
4625- CONFIG_SYS_DER:	Debug Event Register (37-47)
4626
4627- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4628  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4629  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4630  CONFIG_SYS_BR1_PRELIM:
4631		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4632
4633- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4634  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4635  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4636		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4637
4638- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4639  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4640		Machine Mode Register and Memory Periodic Timer
4641		Prescaler definitions (SDRAM timing)
4642
4643- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4644		enable I2C microcode relocation patch (MPC8xx);
4645		define relocation offset in DPRAM [DSP2]
4646
4647- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4648		enable SMC microcode relocation patch (MPC8xx);
4649		define relocation offset in DPRAM [SMC1]
4650
4651- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4652		enable SPI microcode relocation patch (MPC8xx);
4653		define relocation offset in DPRAM [SCC4]
4654
4655- CONFIG_SYS_USE_OSCCLK:
4656		Use OSCM clock mode on MBX8xx board. Be careful,
4657		wrong setting might damage your board. Read
4658		doc/README.MBX before setting this variable!
4659
4660- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4661		Offset of the bootmode word in DPRAM used by post
4662		(Power On Self Tests). This definition overrides
4663		#define'd default value in commproc.h resp.
4664		cpm_8260.h.
4665
4666- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4667  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4668  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4669  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4670  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4671  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4672  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4673  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4674		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4675
4676- CONFIG_PCI_DISABLE_PCIE:
4677		Disable PCI-Express on systems where it is supported but not
4678		required.
4679
4680- CONFIG_PCI_ENUM_ONLY
4681		Only scan through and get the devices on the buses.
4682		Don't do any setup work, presumably because someone or
4683		something has already done it, and we don't need to do it
4684		a second time.	Useful for platforms that are pre-booted
4685		by coreboot or similar.
4686
4687- CONFIG_PCI_INDIRECT_BRIDGE:
4688		Enable support for indirect PCI bridges.
4689
4690- CONFIG_SYS_SRIO:
4691		Chip has SRIO or not
4692
4693- CONFIG_SRIO1:
4694		Board has SRIO 1 port available
4695
4696- CONFIG_SRIO2:
4697		Board has SRIO 2 port available
4698
4699- CONFIG_SRIO_PCIE_BOOT_MASTER
4700		Board can support master function for Boot from SRIO and PCIE
4701
4702- CONFIG_SYS_SRIOn_MEM_VIRT:
4703		Virtual Address of SRIO port 'n' memory region
4704
4705- CONFIG_SYS_SRIOn_MEM_PHYS:
4706		Physical Address of SRIO port 'n' memory region
4707
4708- CONFIG_SYS_SRIOn_MEM_SIZE:
4709		Size of SRIO port 'n' memory region
4710
4711- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4712		Defined to tell the NAND controller that the NAND chip is using
4713		a 16 bit bus.
4714		Not all NAND drivers use this symbol.
4715		Example of drivers that use it:
4716		- drivers/mtd/nand/ndfc.c
4717		- drivers/mtd/nand/mxc_nand.c
4718
4719- CONFIG_SYS_NDFC_EBC0_CFG
4720		Sets the EBC0_CFG register for the NDFC. If not defined
4721		a default value will be used.
4722
4723- CONFIG_SPD_EEPROM
4724		Get DDR timing information from an I2C EEPROM. Common
4725		with pluggable memory modules such as SODIMMs
4726
4727  SPD_EEPROM_ADDRESS
4728		I2C address of the SPD EEPROM
4729
4730- CONFIG_SYS_SPD_BUS_NUM
4731		If SPD EEPROM is on an I2C bus other than the first
4732		one, specify here. Note that the value must resolve
4733		to something your driver can deal with.
4734
4735- CONFIG_SYS_DDR_RAW_TIMING
4736		Get DDR timing information from other than SPD. Common with
4737		soldered DDR chips onboard without SPD. DDR raw timing
4738		parameters are extracted from datasheet and hard-coded into
4739		header files or board specific files.
4740
4741- CONFIG_FSL_DDR_INTERACTIVE
4742		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4743
4744- CONFIG_FSL_DDR_SYNC_REFRESH
4745		Enable sync of refresh for multiple controllers.
4746
4747- CONFIG_FSL_DDR_BIST
4748		Enable built-in memory test for Freescale DDR controllers.
4749
4750- CONFIG_SYS_83XX_DDR_USES_CS0
4751		Only for 83xx systems. If specified, then DDR should
4752		be configured using CS0 and CS1 instead of CS2 and CS3.
4753
4754- CONFIG_ETHER_ON_FEC[12]
4755		Define to enable FEC[12] on a 8xx series processor.
4756
4757- CONFIG_FEC[12]_PHY
4758		Define to the hardcoded PHY address which corresponds
4759		to the given FEC; i. e.
4760			#define CONFIG_FEC1_PHY 4
4761		means that the PHY with address 4 is connected to FEC1
4762
4763		When set to -1, means to probe for first available.
4764
4765- CONFIG_FEC[12]_PHY_NORXERR
4766		The PHY does not have a RXERR line (RMII only).
4767		(so program the FEC to ignore it).
4768
4769- CONFIG_RMII
4770		Enable RMII mode for all FECs.
4771		Note that this is a global option, we can't
4772		have one FEC in standard MII mode and another in RMII mode.
4773
4774- CONFIG_CRC32_VERIFY
4775		Add a verify option to the crc32 command.
4776		The syntax is:
4777
4778		=> crc32 -v <address> <count> <crc32>
4779
4780		Where address/count indicate a memory area
4781		and crc32 is the correct crc32 which the
4782		area should have.
4783
4784- CONFIG_LOOPW
4785		Add the "loopw" memory command. This only takes effect if
4786		the memory commands are activated globally (CONFIG_CMD_MEM).
4787
4788- CONFIG_MX_CYCLIC
4789		Add the "mdc" and "mwc" memory commands. These are cyclic
4790		"md/mw" commands.
4791		Examples:
4792
4793		=> mdc.b 10 4 500
4794		This command will print 4 bytes (10,11,12,13) each 500 ms.
4795
4796		=> mwc.l 100 12345678 10
4797		This command will write 12345678 to address 100 all 10 ms.
4798
4799		This only takes effect if the memory commands are activated
4800		globally (CONFIG_CMD_MEM).
4801
4802- CONFIG_SKIP_LOWLEVEL_INIT
4803		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4804		low level initializations (like setting up the memory
4805		controller) are omitted and/or U-Boot does not
4806		relocate itself into RAM.
4807
4808		Normally this variable MUST NOT be defined. The only
4809		exception is when U-Boot is loaded (to RAM) by some
4810		other boot loader or by a debugger which performs
4811		these initializations itself.
4812
4813- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
4814		[ARM926EJ-S only] This allows just the call to lowlevel_init()
4815		to be skipped. The normal CPU15 init (such as enabling the
4816		instruction cache) is still performed.
4817
4818- CONFIG_SPL_BUILD
4819		Modifies the behaviour of start.S when compiling a loader
4820		that is executed before the actual U-Boot. E.g. when
4821		compiling a NAND SPL.
4822
4823- CONFIG_TPL_BUILD
4824		Modifies the behaviour of start.S  when compiling a loader
4825		that is executed after the SPL and before the actual U-Boot.
4826		It is loaded by the SPL.
4827
4828- CONFIG_SYS_MPC85XX_NO_RESETVEC
4829		Only for 85xx systems. If this variable is specified, the section
4830		.resetvec is not kept and the section .bootpg is placed in the
4831		previous 4k of the .text section.
4832
4833- CONFIG_ARCH_MAP_SYSMEM
4834		Generally U-Boot (and in particular the md command) uses
4835		effective address. It is therefore not necessary to regard
4836		U-Boot address as virtual addresses that need to be translated
4837		to physical addresses. However, sandbox requires this, since
4838		it maintains its own little RAM buffer which contains all
4839		addressable memory. This option causes some memory accesses
4840		to be mapped through map_sysmem() / unmap_sysmem().
4841
4842- CONFIG_USE_ARCH_MEMCPY
4843  CONFIG_USE_ARCH_MEMSET
4844		If these options are used a optimized version of memcpy/memset will
4845		be used if available. These functions may be faster under some
4846		conditions but may increase the binary size.
4847
4848- CONFIG_X86_RESET_VECTOR
4849		If defined, the x86 reset vector code is included. This is not
4850		needed when U-Boot is running from Coreboot.
4851
4852- CONFIG_SYS_MPUCLK
4853		Defines the MPU clock speed (in MHz).
4854
4855		NOTE : currently only supported on AM335x platforms.
4856
4857- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4858		Enables the RTC32K OSC on AM33xx based plattforms
4859
4860- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4861		Option to disable subpage write in NAND driver
4862		driver that uses this:
4863		drivers/mtd/nand/davinci_nand.c
4864
4865Freescale QE/FMAN Firmware Support:
4866-----------------------------------
4867
4868The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4869loading of "firmware", which is encoded in the QE firmware binary format.
4870This firmware often needs to be loaded during U-Boot booting, so macros
4871are used to identify the storage device (NOR flash, SPI, etc) and the address
4872within that device.
4873
4874- CONFIG_SYS_FMAN_FW_ADDR
4875	The address in the storage device where the FMAN microcode is located.  The
4876	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4877	is also specified.
4878
4879- CONFIG_SYS_QE_FW_ADDR
4880	The address in the storage device where the QE microcode is located.  The
4881	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4882	is also specified.
4883
4884- CONFIG_SYS_QE_FMAN_FW_LENGTH
4885	The maximum possible size of the firmware.  The firmware binary format
4886	has a field that specifies the actual size of the firmware, but it
4887	might not be possible to read any part of the firmware unless some
4888	local storage is allocated to hold the entire firmware first.
4889
4890- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4891	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4892	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4893	virtual address in NOR flash.
4894
4895- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4896	Specifies that QE/FMAN firmware is located in NAND flash.
4897	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4898
4899- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4900	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4901	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4902
4903- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4904	Specifies that QE/FMAN firmware is located on the primary SPI
4905	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4906
4907- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4908	Specifies that QE/FMAN firmware is located in the remote (master)
4909	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4910	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4911	window->master inbound window->master LAW->the ucode address in
4912	master's memory space.
4913
4914Freescale Layerscape Management Complex Firmware Support:
4915---------------------------------------------------------
4916The Freescale Layerscape Management Complex (MC) supports the loading of
4917"firmware".
4918This firmware often needs to be loaded during U-Boot booting, so macros
4919are used to identify the storage device (NOR flash, SPI, etc) and the address
4920within that device.
4921
4922- CONFIG_FSL_MC_ENET
4923	Enable the MC driver for Layerscape SoCs.
4924
4925- CONFIG_SYS_LS_MC_FW_ADDR
4926	The address in the storage device where the firmware is located.  The
4927	meaning of this address depends on which CONFIG_SYS_LS_MC_FW_IN_xxx macro
4928	is also specified.
4929
4930- CONFIG_SYS_LS_MC_FW_LENGTH
4931	The maximum possible size of the firmware.  The firmware binary format
4932	has a field that specifies the actual size of the firmware, but it
4933	might not be possible to read any part of the firmware unless some
4934	local storage is allocated to hold the entire firmware first.
4935
4936- CONFIG_SYS_LS_MC_FW_IN_NOR
4937	Specifies that MC firmware is located in NOR flash, mapped as
4938	normal addressable memory via the LBC. CONFIG_SYS_LS_MC_FW_ADDR is the
4939	virtual address in NOR flash.
4940
4941Freescale Layerscape Debug Server Support:
4942-------------------------------------------
4943The Freescale Layerscape Debug Server Support supports the loading of
4944"Debug Server firmware" and triggering SP boot-rom.
4945This firmware often needs to be loaded during U-Boot booting.
4946
4947- CONFIG_FSL_DEBUG_SERVER
4948	Enable the Debug Server for Layerscape SoCs.
4949
4950- CONFIG_SYS_DEBUG_SERVER_DRAM_BLOCK_MIN_SIZE
4951	Define minimum DDR size required for debug server image
4952
4953- CONFIG_SYS_MC_RSV_MEM_ALIGN
4954	Define alignment of reserved memory MC requires
4955
4956Reproducible builds
4957-------------------
4958
4959In order to achieve reproducible builds, timestamps used in the U-Boot build
4960process have to be set to a fixed value.
4961
4962This is done using the SOURCE_DATE_EPOCH environment variable.
4963SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
4964option for U-Boot or an environment variable in U-Boot.
4965
4966SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
4967
4968Building the Software:
4969======================
4970
4971Building U-Boot has been tested in several native build environments
4972and in many different cross environments. Of course we cannot support
4973all possibly existing versions of cross development tools in all
4974(potentially obsolete) versions. In case of tool chain problems we
4975recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4976which is extensively used to build and test U-Boot.
4977
4978If you are not using a native environment, it is assumed that you
4979have GNU cross compiling tools available in your path. In this case,
4980you must set the environment variable CROSS_COMPILE in your shell.
4981Note that no changes to the Makefile or any other source files are
4982necessary. For example using the ELDK on a 4xx CPU, please enter:
4983
4984	$ CROSS_COMPILE=ppc_4xx-
4985	$ export CROSS_COMPILE
4986
4987Note: If you wish to generate Windows versions of the utilities in
4988      the tools directory you can use the MinGW toolchain
4989      (http://www.mingw.org).  Set your HOST tools to the MinGW
4990      toolchain and execute 'make tools'.  For example:
4991
4992       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4993
4994      Binaries such as tools/mkimage.exe will be created which can
4995      be executed on computers running Windows.
4996
4997U-Boot is intended to be simple to build. After installing the
4998sources you must configure U-Boot for one specific board type. This
4999is done by typing:
5000
5001	make NAME_defconfig
5002
5003where "NAME_defconfig" is the name of one of the existing configu-
5004rations; see boards.cfg for supported names.
5005
5006Note: for some board special configuration names may exist; check if
5007      additional information is available from the board vendor; for
5008      instance, the TQM823L systems are available without (standard)
5009      or with LCD support. You can select such additional "features"
5010      when choosing the configuration, i. e.
5011
5012      make TQM823L_defconfig
5013	- will configure for a plain TQM823L, i. e. no LCD support
5014
5015      make TQM823L_LCD_defconfig
5016	- will configure for a TQM823L with U-Boot console on LCD
5017
5018      etc.
5019
5020
5021Finally, type "make all", and you should get some working U-Boot
5022images ready for download to / installation on your system:
5023
5024- "u-boot.bin" is a raw binary image
5025- "u-boot" is an image in ELF binary format
5026- "u-boot.srec" is in Motorola S-Record format
5027
5028By default the build is performed locally and the objects are saved
5029in the source directory. One of the two methods can be used to change
5030this behavior and build U-Boot to some external directory:
5031
50321. Add O= to the make command line invocations:
5033
5034	make O=/tmp/build distclean
5035	make O=/tmp/build NAME_defconfig
5036	make O=/tmp/build all
5037
50382. Set environment variable KBUILD_OUTPUT to point to the desired location:
5039
5040	export KBUILD_OUTPUT=/tmp/build
5041	make distclean
5042	make NAME_defconfig
5043	make all
5044
5045Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
5046variable.
5047
5048
5049Please be aware that the Makefiles assume you are using GNU make, so
5050for instance on NetBSD you might need to use "gmake" instead of
5051native "make".
5052
5053
5054If the system board that you have is not listed, then you will need
5055to port U-Boot to your hardware platform. To do this, follow these
5056steps:
5057
50581.  Create a new directory to hold your board specific code. Add any
5059    files you need. In your board directory, you will need at least
5060    the "Makefile" and a "<board>.c".
50612.  Create a new configuration file "include/configs/<board>.h" for
5062    your board.
50633.  If you're porting U-Boot to a new CPU, then also create a new
5064    directory to hold your CPU specific code. Add any files you need.
50654.  Run "make <board>_defconfig" with your new name.
50665.  Type "make", and you should get a working "u-boot.srec" file
5067    to be installed on your target system.
50686.  Debug and solve any problems that might arise.
5069    [Of course, this last step is much harder than it sounds.]
5070
5071
5072Testing of U-Boot Modifications, Ports to New Hardware, etc.:
5073==============================================================
5074
5075If you have modified U-Boot sources (for instance added a new board
5076or support for new devices, a new CPU, etc.) you are expected to
5077provide feedback to the other developers. The feedback normally takes
5078the form of a "patch", i. e. a context diff against a certain (latest
5079official or latest in the git repository) version of U-Boot sources.
5080
5081But before you submit such a patch, please verify that your modifi-
5082cation did not break existing code. At least make sure that *ALL* of
5083the supported boards compile WITHOUT ANY compiler warnings. To do so,
5084just run the "MAKEALL" script, which will configure and build U-Boot
5085for ALL supported system. Be warned, this will take a while. You can
5086select which (cross) compiler to use by passing a `CROSS_COMPILE'
5087environment variable to the script, i. e. to use the ELDK cross tools
5088you can type
5089
5090	CROSS_COMPILE=ppc_8xx- MAKEALL
5091
5092or to build on a native PowerPC system you can type
5093
5094	CROSS_COMPILE=' ' MAKEALL
5095
5096When using the MAKEALL script, the default behaviour is to build
5097U-Boot in the source directory. This location can be changed by
5098setting the BUILD_DIR environment variable. Also, for each target
5099built, the MAKEALL script saves two log files (<target>.ERR and
5100<target>.MAKEALL) in the <source dir>/LOG directory. This default
5101location can be changed by setting the MAKEALL_LOGDIR environment
5102variable. For example:
5103
5104	export BUILD_DIR=/tmp/build
5105	export MAKEALL_LOGDIR=/tmp/log
5106	CROSS_COMPILE=ppc_8xx- MAKEALL
5107
5108With the above settings build objects are saved in the /tmp/build,
5109log files are saved in the /tmp/log and the source tree remains clean
5110during the whole build process.
5111
5112
5113See also "U-Boot Porting Guide" below.
5114
5115
5116Monitor Commands - Overview:
5117============================
5118
5119go	- start application at address 'addr'
5120run	- run commands in an environment variable
5121bootm	- boot application image from memory
5122bootp	- boot image via network using BootP/TFTP protocol
5123bootz   - boot zImage from memory
5124tftpboot- boot image via network using TFTP protocol
5125	       and env variables "ipaddr" and "serverip"
5126	       (and eventually "gatewayip")
5127tftpput - upload a file via network using TFTP protocol
5128rarpboot- boot image via network using RARP/TFTP protocol
5129diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
5130loads	- load S-Record file over serial line
5131loadb	- load binary file over serial line (kermit mode)
5132md	- memory display
5133mm	- memory modify (auto-incrementing)
5134nm	- memory modify (constant address)
5135mw	- memory write (fill)
5136cp	- memory copy
5137cmp	- memory compare
5138crc32	- checksum calculation
5139i2c	- I2C sub-system
5140sspi	- SPI utility commands
5141base	- print or set address offset
5142printenv- print environment variables
5143setenv	- set environment variables
5144saveenv - save environment variables to persistent storage
5145protect - enable or disable FLASH write protection
5146erase	- erase FLASH memory
5147flinfo	- print FLASH memory information
5148nand	- NAND memory operations (see doc/README.nand)
5149bdinfo	- print Board Info structure
5150iminfo	- print header information for application image
5151coninfo - print console devices and informations
5152ide	- IDE sub-system
5153loop	- infinite loop on address range
5154loopw	- infinite write loop on address range
5155mtest	- simple RAM test
5156icache	- enable or disable instruction cache
5157dcache	- enable or disable data cache
5158reset	- Perform RESET of the CPU
5159echo	- echo args to console
5160version - print monitor version
5161help	- print online help
5162?	- alias for 'help'
5163
5164
5165Monitor Commands - Detailed Description:
5166========================================
5167
5168TODO.
5169
5170For now: just type "help <command>".
5171
5172
5173Environment Variables:
5174======================
5175
5176U-Boot supports user configuration using Environment Variables which
5177can be made persistent by saving to Flash memory.
5178
5179Environment Variables are set using "setenv", printed using
5180"printenv", and saved to Flash using "saveenv". Using "setenv"
5181without a value can be used to delete a variable from the
5182environment. As long as you don't save the environment you are
5183working with an in-memory copy. In case the Flash area containing the
5184environment is erased by accident, a default environment is provided.
5185
5186Some configuration options can be set using Environment Variables.
5187
5188List of environment variables (most likely not complete):
5189
5190  baudrate	- see CONFIG_BAUDRATE
5191
5192  bootdelay	- see CONFIG_BOOTDELAY
5193
5194  bootcmd	- see CONFIG_BOOTCOMMAND
5195
5196  bootargs	- Boot arguments when booting an RTOS image
5197
5198  bootfile	- Name of the image to load with TFTP
5199
5200  bootm_low	- Memory range available for image processing in the bootm
5201		  command can be restricted. This variable is given as
5202		  a hexadecimal number and defines lowest address allowed
5203		  for use by the bootm command. See also "bootm_size"
5204		  environment variable. Address defined by "bootm_low" is
5205		  also the base of the initial memory mapping for the Linux
5206		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
5207		  bootm_mapsize.
5208
5209  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
5210		  This variable is given as a hexadecimal number and it
5211		  defines the size of the memory region starting at base
5212		  address bootm_low that is accessible by the Linux kernel
5213		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
5214		  as the default value if it is defined, and bootm_size is
5215		  used otherwise.
5216
5217  bootm_size	- Memory range available for image processing in the bootm
5218		  command can be restricted. This variable is given as
5219		  a hexadecimal number and defines the size of the region
5220		  allowed for use by the bootm command. See also "bootm_low"
5221		  environment variable.
5222
5223  updatefile	- Location of the software update file on a TFTP server, used
5224		  by the automatic software update feature. Please refer to
5225		  documentation in doc/README.update for more details.
5226
5227  autoload	- if set to "no" (any string beginning with 'n'),
5228		  "bootp" will just load perform a lookup of the
5229		  configuration from the BOOTP server, but not try to
5230		  load any image using TFTP
5231
5232  autostart	- if set to "yes", an image loaded using the "bootp",
5233		  "rarpboot", "tftpboot" or "diskboot" commands will
5234		  be automatically started (by internally calling
5235		  "bootm")
5236
5237		  If set to "no", a standalone image passed to the
5238		  "bootm" command will be copied to the load address
5239		  (and eventually uncompressed), but NOT be started.
5240		  This can be used to load and uncompress arbitrary
5241		  data.
5242
5243  fdt_high	- if set this restricts the maximum address that the
5244		  flattened device tree will be copied into upon boot.
5245		  For example, if you have a system with 1 GB memory
5246		  at physical address 0x10000000, while Linux kernel
5247		  only recognizes the first 704 MB as low memory, you
5248		  may need to set fdt_high as 0x3C000000 to have the
5249		  device tree blob be copied to the maximum address
5250		  of the 704 MB low memory, so that Linux kernel can
5251		  access it during the boot procedure.
5252
5253		  If this is set to the special value 0xFFFFFFFF then
5254		  the fdt will not be copied at all on boot.  For this
5255		  to work it must reside in writable memory, have
5256		  sufficient padding on the end of it for u-boot to
5257		  add the information it needs into it, and the memory
5258		  must be accessible by the kernel.
5259
5260  fdtcontroladdr- if set this is the address of the control flattened
5261		  device tree used by U-Boot when CONFIG_OF_CONTROL is
5262		  defined.
5263
5264  i2cfast	- (PPC405GP|PPC405EP only)
5265		  if set to 'y' configures Linux I2C driver for fast
5266		  mode (400kHZ). This environment variable is used in
5267		  initialization code. So, for changes to be effective
5268		  it must be saved and board must be reset.
5269
5270  initrd_high	- restrict positioning of initrd images:
5271		  If this variable is not set, initrd images will be
5272		  copied to the highest possible address in RAM; this
5273		  is usually what you want since it allows for
5274		  maximum initrd size. If for some reason you want to
5275		  make sure that the initrd image is loaded below the
5276		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
5277		  variable to a value of "no" or "off" or "0".
5278		  Alternatively, you can set it to a maximum upper
5279		  address to use (U-Boot will still check that it
5280		  does not overwrite the U-Boot stack and data).
5281
5282		  For instance, when you have a system with 16 MB
5283		  RAM, and want to reserve 4 MB from use by Linux,
5284		  you can do this by adding "mem=12M" to the value of
5285		  the "bootargs" variable. However, now you must make
5286		  sure that the initrd image is placed in the first
5287		  12 MB as well - this can be done with
5288
5289		  setenv initrd_high 00c00000
5290
5291		  If you set initrd_high to 0xFFFFFFFF, this is an
5292		  indication to U-Boot that all addresses are legal
5293		  for the Linux kernel, including addresses in flash
5294		  memory. In this case U-Boot will NOT COPY the
5295		  ramdisk at all. This may be useful to reduce the
5296		  boot time on your system, but requires that this
5297		  feature is supported by your Linux kernel.
5298
5299  ipaddr	- IP address; needed for tftpboot command
5300
5301  loadaddr	- Default load address for commands like "bootp",
5302		  "rarpboot", "tftpboot", "loadb" or "diskboot"
5303
5304  loads_echo	- see CONFIG_LOADS_ECHO
5305
5306  serverip	- TFTP server IP address; needed for tftpboot command
5307
5308  bootretry	- see CONFIG_BOOT_RETRY_TIME
5309
5310  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5311
5312  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5313
5314  ethprime	- controls which interface is used first.
5315
5316  ethact	- controls which interface is currently active.
5317		  For example you can do the following
5318
5319		  => setenv ethact FEC
5320		  => ping 192.168.0.1 # traffic sent on FEC
5321		  => setenv ethact SCC
5322		  => ping 10.0.0.1 # traffic sent on SCC
5323
5324  ethrotate	- When set to "no" U-Boot does not go through all
5325		  available network interfaces.
5326		  It just stays at the currently selected interface.
5327
5328  netretry	- When set to "no" each network operation will
5329		  either succeed or fail without retrying.
5330		  When set to "once" the network operation will
5331		  fail when all the available network interfaces
5332		  are tried once without success.
5333		  Useful on scripts which control the retry operation
5334		  themselves.
5335
5336  npe_ucode	- set load address for the NPE microcode
5337
5338  silent_linux  - If set then Linux will be told to boot silently, by
5339		  changing the console to be empty. If "yes" it will be
5340		  made silent. If "no" it will not be made silent. If
5341		  unset, then it will be made silent if the U-Boot console
5342		  is silent.
5343
5344  tftpsrcp	- If this is set, the value is used for TFTP's
5345		  UDP source port.
5346
5347  tftpdstp	- If this is set, the value is used for TFTP's UDP
5348		  destination port instead of the Well Know Port 69.
5349
5350  tftpblocksize - Block size to use for TFTP transfers; if not set,
5351		  we use the TFTP server's default block size
5352
5353  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5354		  seconds, minimum value is 1000 = 1 second). Defines
5355		  when a packet is considered to be lost so it has to
5356		  be retransmitted. The default is 5000 = 5 seconds.
5357		  Lowering this value may make downloads succeed
5358		  faster in networks with high packet loss rates or
5359		  with unreliable TFTP servers.
5360
5361  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
5362		  unit, minimum value = 0). Defines how many timeouts
5363		  can happen during a single file transfer before that
5364		  transfer is aborted. The default is 10, and 0 means
5365		  'no timeouts allowed'. Increasing this value may help
5366		  downloads succeed with high packet loss rates, or with
5367		  unreliable TFTP servers or client hardware.
5368
5369  vlan		- When set to a value < 4095 the traffic over
5370		  Ethernet is encapsulated/received over 802.1q
5371		  VLAN tagged frames.
5372
5373  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
5374		  Unsigned value, in milliseconds. If not set, the period will
5375		  be either the default (28000), or a value based on
5376		  CONFIG_NET_RETRY_COUNT, if defined. This value has
5377		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
5378
5379The following image location variables contain the location of images
5380used in booting. The "Image" column gives the role of the image and is
5381not an environment variable name. The other columns are environment
5382variable names. "File Name" gives the name of the file on a TFTP
5383server, "RAM Address" gives the location in RAM the image will be
5384loaded to, and "Flash Location" gives the image's address in NOR
5385flash or offset in NAND flash.
5386
5387*Note* - these variables don't have to be defined for all boards, some
5388boards currently use other variables for these purposes, and some
5389boards use these variables for other purposes.
5390
5391Image		    File Name	     RAM Address       Flash Location
5392-----		    ---------	     -----------       --------------
5393u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5394Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5395device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5396ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5397
5398The following environment variables may be used and automatically
5399updated by the network boot commands ("bootp" and "rarpboot"),
5400depending the information provided by your boot server:
5401
5402  bootfile	- see above
5403  dnsip		- IP address of your Domain Name Server
5404  dnsip2	- IP address of your secondary Domain Name Server
5405  gatewayip	- IP address of the Gateway (Router) to use
5406  hostname	- Target hostname
5407  ipaddr	- see above
5408  netmask	- Subnet Mask
5409  rootpath	- Pathname of the root filesystem on the NFS server
5410  serverip	- see above
5411
5412
5413There are two special Environment Variables:
5414
5415  serial#	- contains hardware identification information such
5416		  as type string and/or serial number
5417  ethaddr	- Ethernet address
5418
5419These variables can be set only once (usually during manufacturing of
5420the board). U-Boot refuses to delete or overwrite these variables
5421once they have been set once.
5422
5423
5424Further special Environment Variables:
5425
5426  ver		- Contains the U-Boot version string as printed
5427		  with the "version" command. This variable is
5428		  readonly (see CONFIG_VERSION_VARIABLE).
5429
5430
5431Please note that changes to some configuration parameters may take
5432only effect after the next boot (yes, that's just like Windoze :-).
5433
5434
5435Callback functions for environment variables:
5436---------------------------------------------
5437
5438For some environment variables, the behavior of u-boot needs to change
5439when their values are changed.  This functionality allows functions to
5440be associated with arbitrary variables.  On creation, overwrite, or
5441deletion, the callback will provide the opportunity for some side
5442effect to happen or for the change to be rejected.
5443
5444The callbacks are named and associated with a function using the
5445U_BOOT_ENV_CALLBACK macro in your board or driver code.
5446
5447These callbacks are associated with variables in one of two ways.  The
5448static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5449in the board configuration to a string that defines a list of
5450associations.  The list must be in the following format:
5451
5452	entry = variable_name[:callback_name]
5453	list = entry[,list]
5454
5455If the callback name is not specified, then the callback is deleted.
5456Spaces are also allowed anywhere in the list.
5457
5458Callbacks can also be associated by defining the ".callbacks" variable
5459with the same list format above.  Any association in ".callbacks" will
5460override any association in the static list. You can define
5461CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5462".callbacks" environment variable in the default or embedded environment.
5463
5464If CONFIG_REGEX is defined, the variable_name above is evaluated as a
5465regular expression. This allows multiple variables to be connected to
5466the same callback without explicitly listing them all out.
5467
5468
5469Command Line Parsing:
5470=====================
5471
5472There are two different command line parsers available with U-Boot:
5473the old "simple" one, and the much more powerful "hush" shell:
5474
5475Old, simple command line parser:
5476--------------------------------
5477
5478- supports environment variables (through setenv / saveenv commands)
5479- several commands on one line, separated by ';'
5480- variable substitution using "... ${name} ..." syntax
5481- special characters ('$', ';') can be escaped by prefixing with '\',
5482  for example:
5483	setenv bootcmd bootm \${address}
5484- You can also escape text by enclosing in single apostrophes, for example:
5485	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5486
5487Hush shell:
5488-----------
5489
5490- similar to Bourne shell, with control structures like
5491  if...then...else...fi, for...do...done; while...do...done,
5492  until...do...done, ...
5493- supports environment ("global") variables (through setenv / saveenv
5494  commands) and local shell variables (through standard shell syntax
5495  "name=value"); only environment variables can be used with "run"
5496  command
5497
5498General rules:
5499--------------
5500
5501(1) If a command line (or an environment variable executed by a "run"
5502    command) contains several commands separated by semicolon, and
5503    one of these commands fails, then the remaining commands will be
5504    executed anyway.
5505
5506(2) If you execute several variables with one call to run (i. e.
5507    calling run with a list of variables as arguments), any failing
5508    command will cause "run" to terminate, i. e. the remaining
5509    variables are not executed.
5510
5511Note for Redundant Ethernet Interfaces:
5512=======================================
5513
5514Some boards come with redundant Ethernet interfaces; U-Boot supports
5515such configurations and is capable of automatic selection of a
5516"working" interface when needed. MAC assignment works as follows:
5517
5518Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5519MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5520"eth1addr" (=>eth1), "eth2addr", ...
5521
5522If the network interface stores some valid MAC address (for instance
5523in SROM), this is used as default address if there is NO correspon-
5524ding setting in the environment; if the corresponding environment
5525variable is set, this overrides the settings in the card; that means:
5526
5527o If the SROM has a valid MAC address, and there is no address in the
5528  environment, the SROM's address is used.
5529
5530o If there is no valid address in the SROM, and a definition in the
5531  environment exists, then the value from the environment variable is
5532  used.
5533
5534o If both the SROM and the environment contain a MAC address, and
5535  both addresses are the same, this MAC address is used.
5536
5537o If both the SROM and the environment contain a MAC address, and the
5538  addresses differ, the value from the environment is used and a
5539  warning is printed.
5540
5541o If neither SROM nor the environment contain a MAC address, an error
5542  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
5543  a random, locally-assigned MAC is used.
5544
5545If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5546will be programmed into hardware as part of the initialization process.	 This
5547may be skipped by setting the appropriate 'ethmacskip' environment variable.
5548The naming convention is as follows:
5549"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5550
5551Image Formats:
5552==============
5553
5554U-Boot is capable of booting (and performing other auxiliary operations on)
5555images in two formats:
5556
5557New uImage format (FIT)
5558-----------------------
5559
5560Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5561to Flattened Device Tree). It allows the use of images with multiple
5562components (several kernels, ramdisks, etc.), with contents protected by
5563SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5564
5565
5566Old uImage format
5567-----------------
5568
5569Old image format is based on binary files which can be basically anything,
5570preceded by a special header; see the definitions in include/image.h for
5571details; basically, the header defines the following image properties:
5572
5573* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5574  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5575  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5576  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5577  INTEGRITY).
5578* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5579  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5580  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5581* Compression Type (uncompressed, gzip, bzip2)
5582* Load Address
5583* Entry Point
5584* Image Name
5585* Image Timestamp
5586
5587The header is marked by a special Magic Number, and both the header
5588and the data portions of the image are secured against corruption by
5589CRC32 checksums.
5590
5591
5592Linux Support:
5593==============
5594
5595Although U-Boot should support any OS or standalone application
5596easily, the main focus has always been on Linux during the design of
5597U-Boot.
5598
5599U-Boot includes many features that so far have been part of some
5600special "boot loader" code within the Linux kernel. Also, any
5601"initrd" images to be used are no longer part of one big Linux image;
5602instead, kernel and "initrd" are separate images. This implementation
5603serves several purposes:
5604
5605- the same features can be used for other OS or standalone
5606  applications (for instance: using compressed images to reduce the
5607  Flash memory footprint)
5608
5609- it becomes much easier to port new Linux kernel versions because
5610  lots of low-level, hardware dependent stuff are done by U-Boot
5611
5612- the same Linux kernel image can now be used with different "initrd"
5613  images; of course this also means that different kernel images can
5614  be run with the same "initrd". This makes testing easier (you don't
5615  have to build a new "zImage.initrd" Linux image when you just
5616  change a file in your "initrd"). Also, a field-upgrade of the
5617  software is easier now.
5618
5619
5620Linux HOWTO:
5621============
5622
5623Porting Linux to U-Boot based systems:
5624---------------------------------------
5625
5626U-Boot cannot save you from doing all the necessary modifications to
5627configure the Linux device drivers for use with your target hardware
5628(no, we don't intend to provide a full virtual machine interface to
5629Linux :-).
5630
5631But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5632
5633Just make sure your machine specific header file (for instance
5634include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5635Information structure as we define in include/asm-<arch>/u-boot.h,
5636and make sure that your definition of IMAP_ADDR uses the same value
5637as your U-Boot configuration in CONFIG_SYS_IMMR.
5638
5639Note that U-Boot now has a driver model, a unified model for drivers.
5640If you are adding a new driver, plumb it into driver model. If there
5641is no uclass available, you are encouraged to create one. See
5642doc/driver-model.
5643
5644
5645Configuring the Linux kernel:
5646-----------------------------
5647
5648No specific requirements for U-Boot. Make sure you have some root
5649device (initial ramdisk, NFS) for your target system.
5650
5651
5652Building a Linux Image:
5653-----------------------
5654
5655With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5656not used. If you use recent kernel source, a new build target
5657"uImage" will exist which automatically builds an image usable by
5658U-Boot. Most older kernels also have support for a "pImage" target,
5659which was introduced for our predecessor project PPCBoot and uses a
5660100% compatible format.
5661
5662Example:
5663
5664	make TQM850L_defconfig
5665	make oldconfig
5666	make dep
5667	make uImage
5668
5669The "uImage" build target uses a special tool (in 'tools/mkimage') to
5670encapsulate a compressed Linux kernel image with header	 information,
5671CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5672
5673* build a standard "vmlinux" kernel image (in ELF binary format):
5674
5675* convert the kernel into a raw binary image:
5676
5677	${CROSS_COMPILE}-objcopy -O binary \
5678				 -R .note -R .comment \
5679				 -S vmlinux linux.bin
5680
5681* compress the binary image:
5682
5683	gzip -9 linux.bin
5684
5685* package compressed binary image for U-Boot:
5686
5687	mkimage -A ppc -O linux -T kernel -C gzip \
5688		-a 0 -e 0 -n "Linux Kernel Image" \
5689		-d linux.bin.gz uImage
5690
5691
5692The "mkimage" tool can also be used to create ramdisk images for use
5693with U-Boot, either separated from the Linux kernel image, or
5694combined into one file. "mkimage" encapsulates the images with a 64
5695byte header containing information about target architecture,
5696operating system, image type, compression method, entry points, time
5697stamp, CRC32 checksums, etc.
5698
5699"mkimage" can be called in two ways: to verify existing images and
5700print the header information, or to build new images.
5701
5702In the first form (with "-l" option) mkimage lists the information
5703contained in the header of an existing U-Boot image; this includes
5704checksum verification:
5705
5706	tools/mkimage -l image
5707	  -l ==> list image header information
5708
5709The second form (with "-d" option) is used to build a U-Boot image
5710from a "data file" which is used as image payload:
5711
5712	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5713		      -n name -d data_file image
5714	  -A ==> set architecture to 'arch'
5715	  -O ==> set operating system to 'os'
5716	  -T ==> set image type to 'type'
5717	  -C ==> set compression type 'comp'
5718	  -a ==> set load address to 'addr' (hex)
5719	  -e ==> set entry point to 'ep' (hex)
5720	  -n ==> set image name to 'name'
5721	  -d ==> use image data from 'datafile'
5722
5723Right now, all Linux kernels for PowerPC systems use the same load
5724address (0x00000000), but the entry point address depends on the
5725kernel version:
5726
5727- 2.2.x kernels have the entry point at 0x0000000C,
5728- 2.3.x and later kernels have the entry point at 0x00000000.
5729
5730So a typical call to build a U-Boot image would read:
5731
5732	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5733	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5734	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5735	> examples/uImage.TQM850L
5736	Image Name:   2.4.4 kernel for TQM850L
5737	Created:      Wed Jul 19 02:34:59 2000
5738	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5739	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5740	Load Address: 0x00000000
5741	Entry Point:  0x00000000
5742
5743To verify the contents of the image (or check for corruption):
5744
5745	-> tools/mkimage -l examples/uImage.TQM850L
5746	Image Name:   2.4.4 kernel for TQM850L
5747	Created:      Wed Jul 19 02:34:59 2000
5748	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5749	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5750	Load Address: 0x00000000
5751	Entry Point:  0x00000000
5752
5753NOTE: for embedded systems where boot time is critical you can trade
5754speed for memory and install an UNCOMPRESSED image instead: this
5755needs more space in Flash, but boots much faster since it does not
5756need to be uncompressed:
5757
5758	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5759	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5760	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5761	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5762	> examples/uImage.TQM850L-uncompressed
5763	Image Name:   2.4.4 kernel for TQM850L
5764	Created:      Wed Jul 19 02:34:59 2000
5765	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5766	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5767	Load Address: 0x00000000
5768	Entry Point:  0x00000000
5769
5770
5771Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5772when your kernel is intended to use an initial ramdisk:
5773
5774	-> tools/mkimage -n 'Simple Ramdisk Image' \
5775	> -A ppc -O linux -T ramdisk -C gzip \
5776	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5777	Image Name:   Simple Ramdisk Image
5778	Created:      Wed Jan 12 14:01:50 2000
5779	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5780	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5781	Load Address: 0x00000000
5782	Entry Point:  0x00000000
5783
5784The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5785option performs the converse operation of the mkimage's second form (the "-d"
5786option). Given an image built by mkimage, the dumpimage extracts a "data file"
5787from the image:
5788
5789	tools/dumpimage -i image -T type -p position data_file
5790	  -i ==> extract from the 'image' a specific 'data_file'
5791	  -T ==> set image type to 'type'
5792	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5793
5794
5795Installing a Linux Image:
5796-------------------------
5797
5798To downloading a U-Boot image over the serial (console) interface,
5799you must convert the image to S-Record format:
5800
5801	objcopy -I binary -O srec examples/image examples/image.srec
5802
5803The 'objcopy' does not understand the information in the U-Boot
5804image header, so the resulting S-Record file will be relative to
5805address 0x00000000. To load it to a given address, you need to
5806specify the target address as 'offset' parameter with the 'loads'
5807command.
5808
5809Example: install the image to address 0x40100000 (which on the
5810TQM8xxL is in the first Flash bank):
5811
5812	=> erase 40100000 401FFFFF
5813
5814	.......... done
5815	Erased 8 sectors
5816
5817	=> loads 40100000
5818	## Ready for S-Record download ...
5819	~>examples/image.srec
5820	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5821	...
5822	15989 15990 15991 15992
5823	[file transfer complete]
5824	[connected]
5825	## Start Addr = 0x00000000
5826
5827
5828You can check the success of the download using the 'iminfo' command;
5829this includes a checksum verification so you can be sure no data
5830corruption happened:
5831
5832	=> imi 40100000
5833
5834	## Checking Image at 40100000 ...
5835	   Image Name:	 2.2.13 for initrd on TQM850L
5836	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5837	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5838	   Load Address: 00000000
5839	   Entry Point:	 0000000c
5840	   Verifying Checksum ... OK
5841
5842
5843Boot Linux:
5844-----------
5845
5846The "bootm" command is used to boot an application that is stored in
5847memory (RAM or Flash). In case of a Linux kernel image, the contents
5848of the "bootargs" environment variable is passed to the kernel as
5849parameters. You can check and modify this variable using the
5850"printenv" and "setenv" commands:
5851
5852
5853	=> printenv bootargs
5854	bootargs=root=/dev/ram
5855
5856	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5857
5858	=> printenv bootargs
5859	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5860
5861	=> bootm 40020000
5862	## Booting Linux kernel at 40020000 ...
5863	   Image Name:	 2.2.13 for NFS on TQM850L
5864	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5865	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5866	   Load Address: 00000000
5867	   Entry Point:	 0000000c
5868	   Verifying Checksum ... OK
5869	   Uncompressing Kernel Image ... OK
5870	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
5871	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5872	time_init: decrementer frequency = 187500000/60
5873	Calibrating delay loop... 49.77 BogoMIPS
5874	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5875	...
5876
5877If you want to boot a Linux kernel with initial RAM disk, you pass
5878the memory addresses of both the kernel and the initrd image (PPBCOOT
5879format!) to the "bootm" command:
5880
5881	=> imi 40100000 40200000
5882
5883	## Checking Image at 40100000 ...
5884	   Image Name:	 2.2.13 for initrd on TQM850L
5885	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5886	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5887	   Load Address: 00000000
5888	   Entry Point:	 0000000c
5889	   Verifying Checksum ... OK
5890
5891	## Checking Image at 40200000 ...
5892	   Image Name:	 Simple Ramdisk Image
5893	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5894	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5895	   Load Address: 00000000
5896	   Entry Point:	 00000000
5897	   Verifying Checksum ... OK
5898
5899	=> bootm 40100000 40200000
5900	## Booting Linux kernel at 40100000 ...
5901	   Image Name:	 2.2.13 for initrd on TQM850L
5902	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5903	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5904	   Load Address: 00000000
5905	   Entry Point:	 0000000c
5906	   Verifying Checksum ... OK
5907	   Uncompressing Kernel Image ... OK
5908	## Loading RAMDisk Image at 40200000 ...
5909	   Image Name:	 Simple Ramdisk Image
5910	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5911	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5912	   Load Address: 00000000
5913	   Entry Point:	 00000000
5914	   Verifying Checksum ... OK
5915	   Loading Ramdisk ... OK
5916	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
5917	Boot arguments: root=/dev/ram
5918	time_init: decrementer frequency = 187500000/60
5919	Calibrating delay loop... 49.77 BogoMIPS
5920	...
5921	RAMDISK: Compressed image found at block 0
5922	VFS: Mounted root (ext2 filesystem).
5923
5924	bash#
5925
5926Boot Linux and pass a flat device tree:
5927-----------
5928
5929First, U-Boot must be compiled with the appropriate defines. See the section
5930titled "Linux Kernel Interface" above for a more in depth explanation. The
5931following is an example of how to start a kernel and pass an updated
5932flat device tree:
5933
5934=> print oftaddr
5935oftaddr=0x300000
5936=> print oft
5937oft=oftrees/mpc8540ads.dtb
5938=> tftp $oftaddr $oft
5939Speed: 1000, full duplex
5940Using TSEC0 device
5941TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5942Filename 'oftrees/mpc8540ads.dtb'.
5943Load address: 0x300000
5944Loading: #
5945done
5946Bytes transferred = 4106 (100a hex)
5947=> tftp $loadaddr $bootfile
5948Speed: 1000, full duplex
5949Using TSEC0 device
5950TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5951Filename 'uImage'.
5952Load address: 0x200000
5953Loading:############
5954done
5955Bytes transferred = 1029407 (fb51f hex)
5956=> print loadaddr
5957loadaddr=200000
5958=> print oftaddr
5959oftaddr=0x300000
5960=> bootm $loadaddr - $oftaddr
5961## Booting image at 00200000 ...
5962   Image Name:	 Linux-2.6.17-dirty
5963   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5964   Data Size:	 1029343 Bytes = 1005.2 kB
5965   Load Address: 00000000
5966   Entry Point:	 00000000
5967   Verifying Checksum ... OK
5968   Uncompressing Kernel Image ... OK
5969Booting using flat device tree at 0x300000
5970Using MPC85xx ADS machine description
5971Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5972[snip]
5973
5974
5975More About U-Boot Image Types:
5976------------------------------
5977
5978U-Boot supports the following image types:
5979
5980   "Standalone Programs" are directly runnable in the environment
5981	provided by U-Boot; it is expected that (if they behave
5982	well) you can continue to work in U-Boot after return from
5983	the Standalone Program.
5984   "OS Kernel Images" are usually images of some Embedded OS which
5985	will take over control completely. Usually these programs
5986	will install their own set of exception handlers, device
5987	drivers, set up the MMU, etc. - this means, that you cannot
5988	expect to re-enter U-Boot except by resetting the CPU.
5989   "RAMDisk Images" are more or less just data blocks, and their
5990	parameters (address, size) are passed to an OS kernel that is
5991	being started.
5992   "Multi-File Images" contain several images, typically an OS
5993	(Linux) kernel image and one or more data images like
5994	RAMDisks. This construct is useful for instance when you want
5995	to boot over the network using BOOTP etc., where the boot
5996	server provides just a single image file, but you want to get
5997	for instance an OS kernel and a RAMDisk image.
5998
5999	"Multi-File Images" start with a list of image sizes, each
6000	image size (in bytes) specified by an "uint32_t" in network
6001	byte order. This list is terminated by an "(uint32_t)0".
6002	Immediately after the terminating 0 follow the images, one by
6003	one, all aligned on "uint32_t" boundaries (size rounded up to
6004	a multiple of 4 bytes).
6005
6006   "Firmware Images" are binary images containing firmware (like
6007	U-Boot or FPGA images) which usually will be programmed to
6008	flash memory.
6009
6010   "Script files" are command sequences that will be executed by
6011	U-Boot's command interpreter; this feature is especially
6012	useful when you configure U-Boot to use a real shell (hush)
6013	as command interpreter.
6014
6015Booting the Linux zImage:
6016-------------------------
6017
6018On some platforms, it's possible to boot Linux zImage. This is done
6019using the "bootz" command. The syntax of "bootz" command is the same
6020as the syntax of "bootm" command.
6021
6022Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
6023kernel with raw initrd images. The syntax is slightly different, the
6024address of the initrd must be augmented by it's size, in the following
6025format: "<initrd addres>:<initrd size>".
6026
6027
6028Standalone HOWTO:
6029=================
6030
6031One of the features of U-Boot is that you can dynamically load and
6032run "standalone" applications, which can use some resources of
6033U-Boot like console I/O functions or interrupt services.
6034
6035Two simple examples are included with the sources:
6036
6037"Hello World" Demo:
6038-------------------
6039
6040'examples/hello_world.c' contains a small "Hello World" Demo
6041application; it is automatically compiled when you build U-Boot.
6042It's configured to run at address 0x00040004, so you can play with it
6043like that:
6044
6045	=> loads
6046	## Ready for S-Record download ...
6047	~>examples/hello_world.srec
6048	1 2 3 4 5 6 7 8 9 10 11 ...
6049	[file transfer complete]
6050	[connected]
6051	## Start Addr = 0x00040004
6052
6053	=> go 40004 Hello World! This is a test.
6054	## Starting application at 0x00040004 ...
6055	Hello World
6056	argc = 7
6057	argv[0] = "40004"
6058	argv[1] = "Hello"
6059	argv[2] = "World!"
6060	argv[3] = "This"
6061	argv[4] = "is"
6062	argv[5] = "a"
6063	argv[6] = "test."
6064	argv[7] = "<NULL>"
6065	Hit any key to exit ...
6066
6067	## Application terminated, rc = 0x0
6068
6069Another example, which demonstrates how to register a CPM interrupt
6070handler with the U-Boot code, can be found in 'examples/timer.c'.
6071Here, a CPM timer is set up to generate an interrupt every second.
6072The interrupt service routine is trivial, just printing a '.'
6073character, but this is just a demo program. The application can be
6074controlled by the following keys:
6075
6076	? - print current values og the CPM Timer registers
6077	b - enable interrupts and start timer
6078	e - stop timer and disable interrupts
6079	q - quit application
6080
6081	=> loads
6082	## Ready for S-Record download ...
6083	~>examples/timer.srec
6084	1 2 3 4 5 6 7 8 9 10 11 ...
6085	[file transfer complete]
6086	[connected]
6087	## Start Addr = 0x00040004
6088
6089	=> go 40004
6090	## Starting application at 0x00040004 ...
6091	TIMERS=0xfff00980
6092	Using timer 1
6093	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
6094
6095Hit 'b':
6096	[q, b, e, ?] Set interval 1000000 us
6097	Enabling timer
6098Hit '?':
6099	[q, b, e, ?] ........
6100	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
6101Hit '?':
6102	[q, b, e, ?] .
6103	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
6104Hit '?':
6105	[q, b, e, ?] .
6106	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
6107Hit '?':
6108	[q, b, e, ?] .
6109	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
6110Hit 'e':
6111	[q, b, e, ?] ...Stopping timer
6112Hit 'q':
6113	[q, b, e, ?] ## Application terminated, rc = 0x0
6114
6115
6116Minicom warning:
6117================
6118
6119Over time, many people have reported problems when trying to use the
6120"minicom" terminal emulation program for serial download. I (wd)
6121consider minicom to be broken, and recommend not to use it. Under
6122Unix, I recommend to use C-Kermit for general purpose use (and
6123especially for kermit binary protocol download ("loadb" command), and
6124use "cu" for S-Record download ("loads" command).  See
6125http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
6126for help with kermit.
6127
6128
6129Nevertheless, if you absolutely want to use it try adding this
6130configuration to your "File transfer protocols" section:
6131
6132	   Name	   Program			Name U/D FullScr IO-Red. Multi
6133	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
6134	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
6135
6136
6137NetBSD Notes:
6138=============
6139
6140Starting at version 0.9.2, U-Boot supports NetBSD both as host
6141(build U-Boot) and target system (boots NetBSD/mpc8xx).
6142
6143Building requires a cross environment; it is known to work on
6144NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
6145need gmake since the Makefiles are not compatible with BSD make).
6146Note that the cross-powerpc package does not install include files;
6147attempting to build U-Boot will fail because <machine/ansi.h> is
6148missing.  This file has to be installed and patched manually:
6149
6150	# cd /usr/pkg/cross/powerpc-netbsd/include
6151	# mkdir powerpc
6152	# ln -s powerpc machine
6153	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
6154	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
6155
6156Native builds *don't* work due to incompatibilities between native
6157and U-Boot include files.
6158
6159Booting assumes that (the first part of) the image booted is a
6160stage-2 loader which in turn loads and then invokes the kernel
6161proper. Loader sources will eventually appear in the NetBSD source
6162tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
6163meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
6164
6165
6166Implementation Internals:
6167=========================
6168
6169The following is not intended to be a complete description of every
6170implementation detail. However, it should help to understand the
6171inner workings of U-Boot and make it easier to port it to custom
6172hardware.
6173
6174
6175Initial Stack, Global Data:
6176---------------------------
6177
6178The implementation of U-Boot is complicated by the fact that U-Boot
6179starts running out of ROM (flash memory), usually without access to
6180system RAM (because the memory controller is not initialized yet).
6181This means that we don't have writable Data or BSS segments, and BSS
6182is not initialized as zero. To be able to get a C environment working
6183at all, we have to allocate at least a minimal stack. Implementation
6184options for this are defined and restricted by the CPU used: Some CPU
6185models provide on-chip memory (like the IMMR area on MPC8xx and
6186MPC826x processors), on others (parts of) the data cache can be
6187locked as (mis-) used as memory, etc.
6188
6189	Chris Hallinan posted a good summary of these issues to the
6190	U-Boot mailing list:
6191
6192	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
6193	From: "Chris Hallinan" <clh@net1plus.com>
6194	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
6195	...
6196
6197	Correct me if I'm wrong, folks, but the way I understand it
6198	is this: Using DCACHE as initial RAM for Stack, etc, does not
6199	require any physical RAM backing up the cache. The cleverness
6200	is that the cache is being used as a temporary supply of
6201	necessary storage before the SDRAM controller is setup. It's
6202	beyond the scope of this list to explain the details, but you
6203	can see how this works by studying the cache architecture and
6204	operation in the architecture and processor-specific manuals.
6205
6206	OCM is On Chip Memory, which I believe the 405GP has 4K. It
6207	is another option for the system designer to use as an
6208	initial stack/RAM area prior to SDRAM being available. Either
6209	option should work for you. Using CS 4 should be fine if your
6210	board designers haven't used it for something that would
6211	cause you grief during the initial boot! It is frequently not
6212	used.
6213
6214	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
6215	with your processor/board/system design. The default value
6216	you will find in any recent u-boot distribution in
6217	walnut.h should work for you. I'd set it to a value larger
6218	than your SDRAM module. If you have a 64MB SDRAM module, set
6219	it above 400_0000. Just make sure your board has no resources
6220	that are supposed to respond to that address! That code in
6221	start.S has been around a while and should work as is when
6222	you get the config right.
6223
6224	-Chris Hallinan
6225	DS4.COM, Inc.
6226
6227It is essential to remember this, since it has some impact on the C
6228code for the initialization procedures:
6229
6230* Initialized global data (data segment) is read-only. Do not attempt
6231  to write it.
6232
6233* Do not use any uninitialized global data (or implicitly initialized
6234  as zero data - BSS segment) at all - this is undefined, initiali-
6235  zation is performed later (when relocating to RAM).
6236
6237* Stack space is very limited. Avoid big data buffers or things like
6238  that.
6239
6240Having only the stack as writable memory limits means we cannot use
6241normal global data to share information between the code. But it
6242turned out that the implementation of U-Boot can be greatly
6243simplified by making a global data structure (gd_t) available to all
6244functions. We could pass a pointer to this data as argument to _all_
6245functions, but this would bloat the code. Instead we use a feature of
6246the GCC compiler (Global Register Variables) to share the data: we
6247place a pointer (gd) to the global data into a register which we
6248reserve for this purpose.
6249
6250When choosing a register for such a purpose we are restricted by the
6251relevant  (E)ABI  specifications for the current architecture, and by
6252GCC's implementation.
6253
6254For PowerPC, the following registers have specific use:
6255	R1:	stack pointer
6256	R2:	reserved for system use
6257	R3-R4:	parameter passing and return values
6258	R5-R10: parameter passing
6259	R13:	small data area pointer
6260	R30:	GOT pointer
6261	R31:	frame pointer
6262
6263	(U-Boot also uses R12 as internal GOT pointer. r12
6264	is a volatile register so r12 needs to be reset when
6265	going back and forth between asm and C)
6266
6267    ==> U-Boot will use R2 to hold a pointer to the global data
6268
6269    Note: on PPC, we could use a static initializer (since the
6270    address of the global data structure is known at compile time),
6271    but it turned out that reserving a register results in somewhat
6272    smaller code - although the code savings are not that big (on
6273    average for all boards 752 bytes for the whole U-Boot image,
6274    624 text + 127 data).
6275
6276On Blackfin, the normal C ABI (except for P3) is followed as documented here:
6277	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
6278
6279    ==> U-Boot will use P3 to hold a pointer to the global data
6280
6281On ARM, the following registers are used:
6282
6283	R0:	function argument word/integer result
6284	R1-R3:	function argument word
6285	R9:	platform specific
6286	R10:	stack limit (used only if stack checking is enabled)
6287	R11:	argument (frame) pointer
6288	R12:	temporary workspace
6289	R13:	stack pointer
6290	R14:	link register
6291	R15:	program counter
6292
6293    ==> U-Boot will use R9 to hold a pointer to the global data
6294
6295    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
6296
6297On Nios II, the ABI is documented here:
6298	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
6299
6300    ==> U-Boot will use gp to hold a pointer to the global data
6301
6302    Note: on Nios II, we give "-G0" option to gcc and don't use gp
6303    to access small data sections, so gp is free.
6304
6305On NDS32, the following registers are used:
6306
6307	R0-R1:	argument/return
6308	R2-R5:	argument
6309	R15:	temporary register for assembler
6310	R16:	trampoline register
6311	R28:	frame pointer (FP)
6312	R29:	global pointer (GP)
6313	R30:	link register (LP)
6314	R31:	stack pointer (SP)
6315	PC:	program counter (PC)
6316
6317    ==> U-Boot will use R10 to hold a pointer to the global data
6318
6319NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6320or current versions of GCC may "optimize" the code too much.
6321
6322Memory Management:
6323------------------
6324
6325U-Boot runs in system state and uses physical addresses, i.e. the
6326MMU is not used either for address mapping nor for memory protection.
6327
6328The available memory is mapped to fixed addresses using the memory
6329controller. In this process, a contiguous block is formed for each
6330memory type (Flash, SDRAM, SRAM), even when it consists of several
6331physical memory banks.
6332
6333U-Boot is installed in the first 128 kB of the first Flash bank (on
6334TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6335booting and sizing and initializing DRAM, the code relocates itself
6336to the upper end of DRAM. Immediately below the U-Boot code some
6337memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6338configuration setting]. Below that, a structure with global Board
6339Info data is placed, followed by the stack (growing downward).
6340
6341Additionally, some exception handler code is copied to the low 8 kB
6342of DRAM (0x00000000 ... 0x00001FFF).
6343
6344So a typical memory configuration with 16 MB of DRAM could look like
6345this:
6346
6347	0x0000 0000	Exception Vector code
6348	      :
6349	0x0000 1FFF
6350	0x0000 2000	Free for Application Use
6351	      :
6352	      :
6353
6354	      :
6355	      :
6356	0x00FB FF20	Monitor Stack (Growing downward)
6357	0x00FB FFAC	Board Info Data and permanent copy of global data
6358	0x00FC 0000	Malloc Arena
6359	      :
6360	0x00FD FFFF
6361	0x00FE 0000	RAM Copy of Monitor Code
6362	...		eventually: LCD or video framebuffer
6363	...		eventually: pRAM (Protected RAM - unchanged by reset)
6364	0x00FF FFFF	[End of RAM]
6365
6366
6367System Initialization:
6368----------------------
6369
6370In the reset configuration, U-Boot starts at the reset entry point
6371(on most PowerPC systems at address 0x00000100). Because of the reset
6372configuration for CS0# this is a mirror of the on board Flash memory.
6373To be able to re-map memory U-Boot then jumps to its link address.
6374To be able to implement the initialization code in C, a (small!)
6375initial stack is set up in the internal Dual Ported RAM (in case CPUs
6376which provide such a feature like MPC8xx or MPC8260), or in a locked
6377part of the data cache. After that, U-Boot initializes the CPU core,
6378the caches and the SIU.
6379
6380Next, all (potentially) available memory banks are mapped using a
6381preliminary mapping. For example, we put them on 512 MB boundaries
6382(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6383on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6384programmed for SDRAM access. Using the temporary configuration, a
6385simple memory test is run that determines the size of the SDRAM
6386banks.
6387
6388When there is more than one SDRAM bank, and the banks are of
6389different size, the largest is mapped first. For equal size, the first
6390bank (CS2#) is mapped first. The first mapping is always for address
63910x00000000, with any additional banks following immediately to create
6392contiguous memory starting from 0.
6393
6394Then, the monitor installs itself at the upper end of the SDRAM area
6395and allocates memory for use by malloc() and for the global Board
6396Info data; also, the exception vector code is copied to the low RAM
6397pages, and the final stack is set up.
6398
6399Only after this relocation will you have a "normal" C environment;
6400until that you are restricted in several ways, mostly because you are
6401running from ROM, and because the code will have to be relocated to a
6402new address in RAM.
6403
6404
6405U-Boot Porting Guide:
6406----------------------
6407
6408[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6409list, October 2002]
6410
6411
6412int main(int argc, char *argv[])
6413{
6414	sighandler_t no_more_time;
6415
6416	signal(SIGALRM, no_more_time);
6417	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6418
6419	if (available_money > available_manpower) {
6420		Pay consultant to port U-Boot;
6421		return 0;
6422	}
6423
6424	Download latest U-Boot source;
6425
6426	Subscribe to u-boot mailing list;
6427
6428	if (clueless)
6429		email("Hi, I am new to U-Boot, how do I get started?");
6430
6431	while (learning) {
6432		Read the README file in the top level directory;
6433		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6434		Read applicable doc/*.README;
6435		Read the source, Luke;
6436		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6437	}
6438
6439	if (available_money > toLocalCurrency ($2500))
6440		Buy a BDI3000;
6441	else
6442		Add a lot of aggravation and time;
6443
6444	if (a similar board exists) {	/* hopefully... */
6445		cp -a board/<similar> board/<myboard>
6446		cp include/configs/<similar>.h include/configs/<myboard>.h
6447	} else {
6448		Create your own board support subdirectory;
6449		Create your own board include/configs/<myboard>.h file;
6450	}
6451	Edit new board/<myboard> files
6452	Edit new include/configs/<myboard>.h
6453
6454	while (!accepted) {
6455		while (!running) {
6456			do {
6457				Add / modify source code;
6458			} until (compiles);
6459			Debug;
6460			if (clueless)
6461				email("Hi, I am having problems...");
6462		}
6463		Send patch file to the U-Boot email list;
6464		if (reasonable critiques)
6465			Incorporate improvements from email list code review;
6466		else
6467			Defend code as written;
6468	}
6469
6470	return 0;
6471}
6472
6473void no_more_time (int sig)
6474{
6475      hire_a_guru();
6476}
6477
6478
6479Coding Standards:
6480-----------------
6481
6482All contributions to U-Boot should conform to the Linux kernel
6483coding style; see the file "Documentation/CodingStyle" and the script
6484"scripts/Lindent" in your Linux kernel source directory.
6485
6486Source files originating from a different project (for example the
6487MTD subsystem) are generally exempt from these guidelines and are not
6488reformatted to ease subsequent migration to newer versions of those
6489sources.
6490
6491Please note that U-Boot is implemented in C (and to some small parts in
6492Assembler); no C++ is used, so please do not use C++ style comments (//)
6493in your code.
6494
6495Please also stick to the following formatting rules:
6496- remove any trailing white space
6497- use TAB characters for indentation and vertical alignment, not spaces
6498- make sure NOT to use DOS '\r\n' line feeds
6499- do not add more than 2 consecutive empty lines to source files
6500- do not add trailing empty lines to source files
6501
6502Submissions which do not conform to the standards may be returned
6503with a request to reformat the changes.
6504
6505
6506Submitting Patches:
6507-------------------
6508
6509Since the number of patches for U-Boot is growing, we need to
6510establish some rules. Submissions which do not conform to these rules
6511may be rejected, even when they contain important and valuable stuff.
6512
6513Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6514
6515Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6516see http://lists.denx.de/mailman/listinfo/u-boot
6517
6518When you send a patch, please include the following information with
6519it:
6520
6521* For bug fixes: a description of the bug and how your patch fixes
6522  this bug. Please try to include a way of demonstrating that the
6523  patch actually fixes something.
6524
6525* For new features: a description of the feature and your
6526  implementation.
6527
6528* A CHANGELOG entry as plaintext (separate from the patch)
6529
6530* For major contributions, add a MAINTAINERS file with your
6531  information and associated file and directory references.
6532
6533* When you add support for a new board, don't forget to add a
6534  maintainer e-mail address to the boards.cfg file, too.
6535
6536* If your patch adds new configuration options, don't forget to
6537  document these in the README file.
6538
6539* The patch itself. If you are using git (which is *strongly*
6540  recommended) you can easily generate the patch using the
6541  "git format-patch". If you then use "git send-email" to send it to
6542  the U-Boot mailing list, you will avoid most of the common problems
6543  with some other mail clients.
6544
6545  If you cannot use git, use "diff -purN OLD NEW". If your version of
6546  diff does not support these options, then get the latest version of
6547  GNU diff.
6548
6549  The current directory when running this command shall be the parent
6550  directory of the U-Boot source tree (i. e. please make sure that
6551  your patch includes sufficient directory information for the
6552  affected files).
6553
6554  We prefer patches as plain text. MIME attachments are discouraged,
6555  and compressed attachments must not be used.
6556
6557* If one logical set of modifications affects or creates several
6558  files, all these changes shall be submitted in a SINGLE patch file.
6559
6560* Changesets that contain different, unrelated modifications shall be
6561  submitted as SEPARATE patches, one patch per changeset.
6562
6563
6564Notes:
6565
6566* Before sending the patch, run the MAKEALL script on your patched
6567  source tree and make sure that no errors or warnings are reported
6568  for any of the boards.
6569
6570* Keep your modifications to the necessary minimum: A patch
6571  containing several unrelated changes or arbitrary reformats will be
6572  returned with a request to re-formatting / split it.
6573
6574* If you modify existing code, make sure that your new code does not
6575  add to the memory footprint of the code ;-) Small is beautiful!
6576  When adding new features, these should compile conditionally only
6577  (using #ifdef), and the resulting code with the new feature
6578  disabled must not need more memory than the old code without your
6579  modification.
6580
6581* Remember that there is a size limit of 100 kB per message on the
6582  u-boot mailing list. Bigger patches will be moderated. If they are
6583  reasonable and not too big, they will be acknowledged. But patches
6584  bigger than the size limit should be avoided.
6585