xref: /openbmc/u-boot/README (revision 8149d114)
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 candidate 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/cmd			U-Boot commands functions
155/common			Misc architecture independent functions
156/configs		Board default configuration files
157/disk			Code for disk drive partition handling
158/doc			Documentation (don't expect too much)
159/drivers		Commonly used device drivers
160/dts			Contains Makefile for building internal U-Boot fdt.
161/examples		Example code for standalone applications, etc.
162/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
163/include		Header Files
164/lib			Library routines generic to all architectures
165/Licenses		Various license files
166/net			Networking code
167/post			Power On Self Test
168/scripts		Various build scripts and Makefiles
169/test			Various unit test files
170/tools			Tools to build S-Record or U-Boot images, etc.
171
172Software Configuration:
173=======================
174
175Configuration is usually done using C preprocessor defines; the
176rationale behind that is to avoid dead code whenever possible.
177
178There are two classes of configuration variables:
179
180* Configuration _OPTIONS_:
181  These are selectable by the user and have names beginning with
182  "CONFIG_".
183
184* Configuration _SETTINGS_:
185  These depend on the hardware etc. and should not be meddled with if
186  you don't know what you're doing; they have names beginning with
187  "CONFIG_SYS_".
188
189Previously, all configuration was done by hand, which involved creating
190symbolic links and editing configuration files manually. More recently,
191U-Boot has added the Kbuild infrastructure used by the Linux kernel,
192allowing you to use the "make menuconfig" command to configure your
193build.
194
195
196Selection of Processor Architecture and Board Type:
197---------------------------------------------------
198
199For all supported boards there are ready-to-use default
200configurations available; just type "make <board_name>_defconfig".
201
202Example: For a TQM823L module type:
203
204	cd u-boot
205	make TQM823L_defconfig
206
207Note: If you're looking for the default configuration file for a board
208you're sure used to be there but is now missing, check the file
209doc/README.scrapyard for a list of no longer supported boards.
210
211Sandbox Environment:
212--------------------
213
214U-Boot can be built natively to run on a Linux host using the 'sandbox'
215board. This allows feature development which is not board- or architecture-
216specific to be undertaken on a native platform. The sandbox is also used to
217run some of U-Boot's tests.
218
219See board/sandbox/README.sandbox for more details.
220
221
222Board Initialisation Flow:
223--------------------------
224
225This is the intended start-up flow for boards. This should apply for both
226SPL and U-Boot proper (i.e. they both follow the same rules).
227
228Note: "SPL" stands for "Secondary Program Loader," which is explained in
229more detail later in this file.
230
231At present, SPL mostly uses a separate code path, but the function names
232and roles of each function are the same. Some boards or architectures
233may not conform to this.  At least most ARM boards which use
234CONFIG_SPL_FRAMEWORK conform to this.
235
236Execution typically starts with an architecture-specific (and possibly
237CPU-specific) start.S file, such as:
238
239	- arch/arm/cpu/armv7/start.S
240	- arch/powerpc/cpu/mpc83xx/start.S
241	- arch/mips/cpu/start.S
242
243and so on. From there, three functions are called; the purpose and
244limitations of each of these functions are described below.
245
246lowlevel_init():
247	- purpose: essential init to permit execution to reach board_init_f()
248	- no global_data or BSS
249	- there is no stack (ARMv7 may have one but it will soon be removed)
250	- must not set up SDRAM or use console
251	- must only do the bare minimum to allow execution to continue to
252		board_init_f()
253	- this is almost never needed
254	- return normally from this function
255
256board_init_f():
257	- purpose: set up the machine ready for running board_init_r():
258		i.e. SDRAM and serial UART
259	- global_data is available
260	- stack is in SRAM
261	- BSS is not available, so you cannot use global/static variables,
262		only stack variables and global_data
263
264	Non-SPL-specific notes:
265	- dram_init() is called to set up DRAM. If already done in SPL this
266		can do nothing
267
268	SPL-specific notes:
269	- you can override the entire board_init_f() function with your own
270		version as needed.
271	- preloader_console_init() can be called here in extremis
272	- should set up SDRAM, and anything needed to make the UART work
273	- these is no need to clear BSS, it will be done by crt0.S
274	- must return normally from this function (don't call board_init_r()
275		directly)
276
277Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
278this point the stack and global_data are relocated to below
279CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
280memory.
281
282board_init_r():
283	- purpose: main execution, common code
284	- global_data is available
285	- SDRAM is available
286	- BSS is available, all static/global variables can be used
287	- execution eventually continues to main_loop()
288
289	Non-SPL-specific notes:
290	- U-Boot is relocated to the top of memory and is now running from
291		there.
292
293	SPL-specific notes:
294	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
295		CONFIG_SPL_STACK_R_ADDR points into SDRAM
296	- preloader_console_init() can be called here - typically this is
297		done by defining CONFIG_SPL_BOARD_INIT and then supplying a
298		spl_board_init() function containing this call
299	- loads U-Boot or (in falcon mode) Linux
300
301
302
303Configuration Options:
304----------------------
305
306Configuration depends on the combination of board and CPU type; all
307such information is kept in a configuration file
308"include/configs/<board_name>.h".
309
310Example: For a TQM823L module, all configuration settings are in
311"include/configs/TQM823L.h".
312
313
314Many of the options are named exactly as the corresponding Linux
315kernel configuration options. The intention is to make it easier to
316build a config tool - later.
317
318
319The following options need to be configured:
320
321- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
322
323- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
324
325- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
326		Define exactly one, e.g. CONFIG_ATSTK1002
327
328- Marvell Family Member
329		CONFIG_SYS_MVFS		- define it if you want to enable
330					  multiple fs option at one time
331					  for marvell soc family
332
333- 8xx CPU Options: (if using an MPC8xx CPU)
334		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
335					  get_gclk_freq() cannot work
336					  e.g. if there is no 32KHz
337					  reference PIT/RTC clock
338		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
339					  or XTAL/EXTAL)
340
341- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
342		CONFIG_SYS_8xx_CPUCLK_MIN
343		CONFIG_SYS_8xx_CPUCLK_MAX
344		CONFIG_8xx_CPUCLK_DEFAULT
345			See doc/README.MPC866
346
347		CONFIG_SYS_MEASURE_CPUCLK
348
349		Define this to measure the actual CPU clock instead
350		of relying on the correctness of the configured
351		values. Mostly useful for board bringup to make sure
352		the PLL is locked at the intended frequency. Note
353		that this requires a (stable) reference clock (32 kHz
354		RTC clock or CONFIG_SYS_8XX_XIN)
355
356		CONFIG_SYS_DELAYED_ICACHE
357
358		Define this option if you want to enable the
359		ICache only when Code runs from RAM.
360
361- 85xx CPU Options:
362		CONFIG_SYS_PPC64
363
364		Specifies that the core is a 64-bit PowerPC implementation (implements
365		the "64" category of the Power ISA). This is necessary for ePAPR
366		compliance, among other possible reasons.
367
368		CONFIG_SYS_FSL_TBCLK_DIV
369
370		Defines the core time base clock divider ratio compared to the
371		system clock.  On most PQ3 devices this is 8, on newer QorIQ
372		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
373
374		CONFIG_SYS_FSL_PCIE_COMPAT
375
376		Defines the string to utilize when trying to match PCIe device
377		tree nodes for the given platform.
378
379		CONFIG_SYS_FSL_ERRATUM_A004510
380
381		Enables a workaround for erratum A004510.  If set,
382		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
383		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
384
385		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
386		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
387
388		Defines one or two SoC revisions (low 8 bits of SVR)
389		for which the A004510 workaround should be applied.
390
391		The rest of SVR is either not relevant to the decision
392		of whether the erratum is present (e.g. p2040 versus
393		p2041) or is implied by the build target, which controls
394		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
395
396		See Freescale App Note 4493 for more information about
397		this erratum.
398
399		CONFIG_A003399_NOR_WORKAROUND
400		Enables a workaround for IFC erratum A003399. It is only
401		required during NOR boot.
402
403		CONFIG_A008044_WORKAROUND
404		Enables a workaround for T1040/T1042 erratum A008044. It is only
405		required during NAND boot and valid for Rev 1.0 SoC revision
406
407		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
408
409		This is the value to write into CCSR offset 0x18600
410		according to the A004510 workaround.
411
412		CONFIG_SYS_FSL_DSP_DDR_ADDR
413		This value denotes start offset of DDR memory which is
414		connected exclusively to the DSP cores.
415
416		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
417		This value denotes start offset of M2 memory
418		which is directly connected to the DSP core.
419
420		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
421		This value denotes start offset of M3 memory which is directly
422		connected to the DSP core.
423
424		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
425		This value denotes start offset of DSP CCSR space.
426
427		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
428		Single Source Clock is clocking mode present in some of FSL SoC's.
429		In this mode, a single differential clock is used to supply
430		clocks to the sysclock, ddrclock and usbclock.
431
432		CONFIG_SYS_CPC_REINIT_F
433		This CONFIG is defined when the CPC is configured as SRAM at the
434		time of U-Boot entry and is required to be re-initialized.
435
436		CONFIG_DEEP_SLEEP
437		Indicates this SoC supports deep sleep feature. If deep sleep is
438		supported, core will start to execute uboot when wakes up.
439
440- Generic CPU options:
441		CONFIG_SYS_GENERIC_GLOBAL_DATA
442		Defines global data is initialized in generic board board_init_f().
443		If this macro is defined, global data is created and cleared in
444		generic board board_init_f(). Without this macro, architecture/board
445		should initialize global data before calling board_init_f().
446
447		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
448
449		Defines the endianess of the CPU. Implementation of those
450		values is arch specific.
451
452		CONFIG_SYS_FSL_DDR
453		Freescale DDR driver in use. This type of DDR controller is
454		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
455		SoCs.
456
457		CONFIG_SYS_FSL_DDR_ADDR
458		Freescale DDR memory-mapped register base.
459
460		CONFIG_SYS_FSL_DDR_EMU
461		Specify emulator support for DDR. Some DDR features such as
462		deskew training are not available.
463
464		CONFIG_SYS_FSL_DDRC_GEN1
465		Freescale DDR1 controller.
466
467		CONFIG_SYS_FSL_DDRC_GEN2
468		Freescale DDR2 controller.
469
470		CONFIG_SYS_FSL_DDRC_GEN3
471		Freescale DDR3 controller.
472
473		CONFIG_SYS_FSL_DDRC_GEN4
474		Freescale DDR4 controller.
475
476		CONFIG_SYS_FSL_DDRC_ARM_GEN3
477		Freescale DDR3 controller for ARM-based SoCs.
478
479		CONFIG_SYS_FSL_DDR1
480		Board config to use DDR1. It can be enabled for SoCs with
481		Freescale DDR1 or DDR2 controllers, depending on the board
482		implemetation.
483
484		CONFIG_SYS_FSL_DDR2
485		Board config to use DDR2. It can be enabled for SoCs with
486		Freescale DDR2 or DDR3 controllers, depending on the board
487		implementation.
488
489		CONFIG_SYS_FSL_DDR3
490		Board config to use DDR3. It can be enabled for SoCs with
491		Freescale DDR3 or DDR3L controllers.
492
493		CONFIG_SYS_FSL_DDR3L
494		Board config to use DDR3L. It can be enabled for SoCs with
495		DDR3L controllers.
496
497		CONFIG_SYS_FSL_DDR4
498		Board config to use DDR4. It can be enabled for SoCs with
499		DDR4 controllers.
500
501		CONFIG_SYS_FSL_IFC_BE
502		Defines the IFC controller register space as Big Endian
503
504		CONFIG_SYS_FSL_IFC_LE
505		Defines the IFC controller register space as Little Endian
506
507		CONFIG_SYS_FSL_IFC_CLK_DIV
508		Defines divider of platform clock(clock input to IFC controller).
509
510		CONFIG_SYS_FSL_LBC_CLK_DIV
511		Defines divider of platform clock(clock input to eLBC controller).
512
513		CONFIG_SYS_FSL_PBL_PBI
514		It enables addition of RCW (Power on reset configuration) in built image.
515		Please refer doc/README.pblimage for more details
516
517		CONFIG_SYS_FSL_PBL_RCW
518		It adds PBI(pre-boot instructions) commands in u-boot build image.
519		PBI commands can be used to configure SoC before it starts the execution.
520		Please refer doc/README.pblimage for more details
521
522		CONFIG_SPL_FSL_PBL
523		It adds a target to create boot binary having SPL binary in PBI format
524		concatenated with u-boot binary.
525
526		CONFIG_SYS_FSL_DDR_BE
527		Defines the DDR controller register space as Big Endian
528
529		CONFIG_SYS_FSL_DDR_LE
530		Defines the DDR controller register space as Little Endian
531
532		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
533		Physical address from the view of DDR controllers. It is the
534		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
535		it could be different for ARM SoCs.
536
537		CONFIG_SYS_FSL_DDR_INTLV_256B
538		DDR controller interleaving on 256-byte. This is a special
539		interleaving mode, handled by Dickens for Freescale layerscape
540		SoCs with ARM core.
541
542		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
543		Number of controllers used as main memory.
544
545		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
546		Number of controllers used for other than main memory.
547
548		CONFIG_SYS_FSL_HAS_DP_DDR
549		Defines the SoC has DP-DDR used for DPAA.
550
551		CONFIG_SYS_FSL_SEC_BE
552		Defines the SEC controller register space as Big Endian
553
554		CONFIG_SYS_FSL_SEC_LE
555		Defines the SEC controller register space as Little Endian
556
557- MIPS CPU options:
558		CONFIG_SYS_INIT_SP_OFFSET
559
560		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
561		pointer. This is needed for the temporary stack before
562		relocation.
563
564		CONFIG_SYS_MIPS_CACHE_MODE
565
566		Cache operation mode for the MIPS CPU.
567		See also arch/mips/include/asm/mipsregs.h.
568		Possible values are:
569			CONF_CM_CACHABLE_NO_WA
570			CONF_CM_CACHABLE_WA
571			CONF_CM_UNCACHED
572			CONF_CM_CACHABLE_NONCOHERENT
573			CONF_CM_CACHABLE_CE
574			CONF_CM_CACHABLE_COW
575			CONF_CM_CACHABLE_CUW
576			CONF_CM_CACHABLE_ACCELERATED
577
578		CONFIG_SYS_XWAY_EBU_BOOTCFG
579
580		Special option for Lantiq XWAY SoCs for booting from NOR flash.
581		See also arch/mips/cpu/mips32/start.S.
582
583		CONFIG_XWAY_SWAP_BYTES
584
585		Enable compilation of tools/xway-swap-bytes needed for Lantiq
586		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
587		be swapped if a flash programmer is used.
588
589- ARM options:
590		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
591
592		Select high exception vectors of the ARM core, e.g., do not
593		clear the V bit of the c1 register of CP15.
594
595		CONFIG_SYS_THUMB_BUILD
596
597		Use this flag to build U-Boot using the Thumb instruction
598		set for ARM architectures. Thumb instruction set provides
599		better code density. For ARM architectures that support
600		Thumb2 this flag will result in Thumb2 code generated by
601		GCC.
602
603		CONFIG_ARM_ERRATA_716044
604		CONFIG_ARM_ERRATA_742230
605		CONFIG_ARM_ERRATA_743622
606		CONFIG_ARM_ERRATA_751472
607		CONFIG_ARM_ERRATA_761320
608		CONFIG_ARM_ERRATA_773022
609		CONFIG_ARM_ERRATA_774769
610		CONFIG_ARM_ERRATA_794072
611
612		If set, the workarounds for these ARM errata are applied early
613		during U-Boot startup. Note that these options force the
614		workarounds to be applied; no CPU-type/version detection
615		exists, unlike the similar options in the Linux kernel. Do not
616		set these options unless they apply!
617
618		COUNTER_FREQUENCY
619		Generic timer clock source frequency.
620
621		COUNTER_FREQUENCY_REAL
622		Generic timer clock source frequency if the real clock is
623		different from COUNTER_FREQUENCY, and can only be determined
624		at run time.
625
626		NOTE: The following can be machine specific errata. These
627		do have ability to provide rudimentary version and machine
628		specific checks, but expect no product checks.
629		CONFIG_ARM_ERRATA_430973
630		CONFIG_ARM_ERRATA_454179
631		CONFIG_ARM_ERRATA_621766
632		CONFIG_ARM_ERRATA_798870
633		CONFIG_ARM_ERRATA_801819
634
635- Tegra SoC options:
636		CONFIG_TEGRA_SUPPORT_NON_SECURE
637
638		Support executing U-Boot in non-secure (NS) mode. Certain
639		impossible actions will be skipped if the CPU is in NS mode,
640		such as ARM architectural timer initialization.
641
642- Linux Kernel Interface:
643		CONFIG_CLOCKS_IN_MHZ
644
645		U-Boot stores all clock information in Hz
646		internally. For binary compatibility with older Linux
647		kernels (which expect the clocks passed in the
648		bd_info data to be in MHz) the environment variable
649		"clocks_in_mhz" can be defined so that U-Boot
650		converts clock data to MHZ before passing it to the
651		Linux kernel.
652		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
653		"clocks_in_mhz=1" is automatically included in the
654		default environment.
655
656		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
657
658		When transferring memsize parameter to Linux, some versions
659		expect it to be in bytes, others in MB.
660		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
661
662		CONFIG_OF_LIBFDT
663
664		New kernel versions are expecting firmware settings to be
665		passed using flattened device trees (based on open firmware
666		concepts).
667
668		CONFIG_OF_LIBFDT
669		 * New libfdt-based support
670		 * Adds the "fdt" command
671		 * The bootm command automatically updates the fdt
672
673		OF_CPU - The proper name of the cpus node (only required for
674			MPC512X and MPC5xxx based boards).
675		OF_SOC - The proper name of the soc node (only required for
676			MPC512X and MPC5xxx based boards).
677		OF_TBCLK - The timebase frequency.
678		OF_STDOUT_PATH - The path to the console device
679
680		boards with QUICC Engines require OF_QE to set UCC MAC
681		addresses
682
683		CONFIG_OF_BOARD_SETUP
684
685		Board code has addition modification that it wants to make
686		to the flat device tree before handing it off to the kernel
687
688		CONFIG_OF_SYSTEM_SETUP
689
690		Other code has addition modification that it wants to make
691		to the flat device tree before handing it off to the kernel.
692		This causes ft_system_setup() to be called before booting
693		the kernel.
694
695		CONFIG_OF_IDE_FIXUP
696
697		U-Boot can detect if an IDE device is present or not.
698		If not, and this new config option is activated, U-Boot
699		removes the ATA node from the DTS before booting Linux,
700		so the Linux IDE driver does not probe the device and
701		crash. This is needed for buggy hardware (uc101) where
702		no pull down resistor is connected to the signal IDE5V_DD7.
703
704		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
705
706		This setting is mandatory for all boards that have only one
707		machine type and must be used to specify the machine type
708		number as it appears in the ARM machine registry
709		(see http://www.arm.linux.org.uk/developer/machines/).
710		Only boards that have multiple machine types supported
711		in a single configuration file and the machine type is
712		runtime discoverable, do not have to use this setting.
713
714- vxWorks boot parameters:
715
716		bootvx constructs a valid bootline using the following
717		environments variables: bootdev, bootfile, ipaddr, netmask,
718		serverip, gatewayip, hostname, othbootargs.
719		It loads the vxWorks image pointed bootfile.
720
721		Note: If a "bootargs" environment is defined, it will overwride
722		the defaults discussed just above.
723
724- Cache Configuration:
725		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
726		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
727		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
728
729- Cache Configuration for ARM:
730		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
731				      controller
732		CONFIG_SYS_PL310_BASE - Physical base address of PL310
733					controller register space
734
735- Serial Ports:
736		CONFIG_PL010_SERIAL
737
738		Define this if you want support for Amba PrimeCell PL010 UARTs.
739
740		CONFIG_PL011_SERIAL
741
742		Define this if you want support for Amba PrimeCell PL011 UARTs.
743
744		CONFIG_PL011_CLOCK
745
746		If you have Amba PrimeCell PL011 UARTs, set this variable to
747		the clock speed of the UARTs.
748
749		CONFIG_PL01x_PORTS
750
751		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
752		define this to a list of base addresses for each (supported)
753		port. See e.g. include/configs/versatile.h
754
755		CONFIG_SERIAL_HW_FLOW_CONTROL
756
757		Define this variable to enable hw flow control in serial driver.
758		Current user of this option is drivers/serial/nsl16550.c driver
759
760- Console Interface:
761		Depending on board, define exactly one serial port
762		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
763		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
764		console by defining CONFIG_8xx_CONS_NONE
765
766		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
767		port routines must be defined elsewhere
768		(i.e. serial_init(), serial_getc(), ...)
769
770- Console Baudrate:
771		CONFIG_BAUDRATE - in bps
772		Select one of the baudrates listed in
773		CONFIG_SYS_BAUDRATE_TABLE, see below.
774		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
775
776- Console Rx buffer length
777		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
778		the maximum receive buffer length for the SMC.
779		This option is actual only for 82xx and 8xx possible.
780		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
781		must be defined, to setup the maximum idle timeout for
782		the SMC.
783
784- Autoboot Command:
785		CONFIG_BOOTCOMMAND
786		Only needed when CONFIG_BOOTDELAY is enabled;
787		define a command string that is automatically executed
788		when no character is read on the console interface
789		within "Boot Delay" after reset.
790
791		CONFIG_BOOTARGS
792		This can be used to pass arguments to the bootm
793		command. The value of CONFIG_BOOTARGS goes into the
794		environment value "bootargs".
795
796		CONFIG_RAMBOOT and CONFIG_NFSBOOT
797		The value of these goes into the environment as
798		"ramboot" and "nfsboot" respectively, and can be used
799		as a convenience, when switching between booting from
800		RAM and NFS.
801
802- Bootcount:
803		CONFIG_BOOTCOUNT_LIMIT
804		Implements a mechanism for detecting a repeating reboot
805		cycle, see:
806		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
807
808		CONFIG_BOOTCOUNT_ENV
809		If no softreset save registers are found on the hardware
810		"bootcount" is stored in the environment. To prevent a
811		saveenv on all reboots, the environment variable
812		"upgrade_available" is used. If "upgrade_available" is
813		0, "bootcount" is always 0, if "upgrade_available" is
814		1 "bootcount" is incremented in the environment.
815		So the Userspace Applikation must set the "upgrade_available"
816		and "bootcount" variable to 0, if a boot was successfully.
817
818- Pre-Boot Commands:
819		CONFIG_PREBOOT
820
821		When this option is #defined, the existence of the
822		environment variable "preboot" will be checked
823		immediately before starting the CONFIG_BOOTDELAY
824		countdown and/or running the auto-boot command resp.
825		entering interactive mode.
826
827		This feature is especially useful when "preboot" is
828		automatically generated or modified. For an example
829		see the LWMON board specific code: here "preboot" is
830		modified when the user holds down a certain
831		combination of keys on the (special) keyboard when
832		booting the systems
833
834- Serial Download Echo Mode:
835		CONFIG_LOADS_ECHO
836		If defined to 1, all characters received during a
837		serial download (using the "loads" command) are
838		echoed back. This might be needed by some terminal
839		emulations (like "cu"), but may as well just take
840		time on others. This setting #define's the initial
841		value of the "loads_echo" environment variable.
842
843- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
844		CONFIG_KGDB_BAUDRATE
845		Select one of the baudrates listed in
846		CONFIG_SYS_BAUDRATE_TABLE, see below.
847
848- Monitor Functions:
849		Monitor commands can be included or excluded
850		from the build by using the #include files
851		<config_cmd_all.h> and #undef'ing unwanted
852		commands, or adding #define's for wanted commands.
853
854		The default command configuration includes all commands
855		except those marked below with a "*".
856
857		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
858		CONFIG_CMD_ASKENV	* ask for env variable
859		CONFIG_CMD_BDI		  bdinfo
860		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
861		CONFIG_CMD_BMP		* BMP support
862		CONFIG_CMD_BSP		* Board specific commands
863		CONFIG_CMD_BOOTD	  bootd
864		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
865		CONFIG_CMD_CACHE	* icache, dcache
866		CONFIG_CMD_CLK   	* clock command support
867		CONFIG_CMD_CONSOLE	  coninfo
868		CONFIG_CMD_CRC32	* crc32
869		CONFIG_CMD_DATE		* support for RTC, date/time...
870		CONFIG_CMD_DHCP		* DHCP support
871		CONFIG_CMD_DIAG		* Diagnostics
872		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
873		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
874		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
875		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
876		CONFIG_CMD_DTT		* Digital Therm and Thermostat
877		CONFIG_CMD_ECHO		  echo arguments
878		CONFIG_CMD_EDITENV	  edit env variable
879		CONFIG_CMD_EEPROM	* EEPROM read/write support
880		CONFIG_CMD_EEPROM_LAYOUT* EEPROM layout aware commands
881		CONFIG_CMD_ELF		* bootelf, bootvx
882		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
883		CONFIG_CMD_ENV_FLAGS	* display details about env flags
884		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
885		CONFIG_CMD_EXPORTENV	* export the environment
886		CONFIG_CMD_EXT2		* ext2 command support
887		CONFIG_CMD_EXT4		* ext4 command support
888		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
889					  that work for multiple fs types
890		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
891		CONFIG_CMD_SAVEENV	  saveenv
892		CONFIG_CMD_FDC		* Floppy Disk Support
893		CONFIG_CMD_FAT		* FAT command support
894		CONFIG_CMD_FLASH	  flinfo, erase, protect
895		CONFIG_CMD_FPGA		  FPGA device initialization support
896		CONFIG_CMD_FUSE		* Device fuse support
897		CONFIG_CMD_GETTIME	* Get time since boot
898		CONFIG_CMD_GO		* the 'go' command (exec code)
899		CONFIG_CMD_GREPENV	* search environment
900		CONFIG_CMD_HASH		* calculate hash / digest
901		CONFIG_CMD_I2C		* I2C serial bus support
902		CONFIG_CMD_IDE		* IDE harddisk support
903		CONFIG_CMD_IMI		  iminfo
904		CONFIG_CMD_IMLS		  List all images found in NOR flash
905		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
906		CONFIG_CMD_IMMAP	* IMMR dump support
907		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
908		CONFIG_CMD_IMPORTENV	* import an environment
909		CONFIG_CMD_INI		* import data from an ini file into the env
910		CONFIG_CMD_IRQ		* irqinfo
911		CONFIG_CMD_ITEST	  Integer/string test of 2 values
912		CONFIG_CMD_JFFS2	* JFFS2 Support
913		CONFIG_CMD_KGDB		* kgdb
914		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
915		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
916					  (169.254.*.*)
917		CONFIG_CMD_LOADB	  loadb
918		CONFIG_CMD_LOADS	  loads
919		CONFIG_CMD_MD5SUM	* print md5 message digest
920					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
921		CONFIG_CMD_MEMINFO	* Display detailed memory information
922		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
923					  loop, loopw
924		CONFIG_CMD_MEMTEST	* mtest
925		CONFIG_CMD_MISC		  Misc functions like sleep etc
926		CONFIG_CMD_MMC		* MMC memory mapped support
927		CONFIG_CMD_MII		* MII utility commands
928		CONFIG_CMD_MTDPARTS	* MTD partition support
929		CONFIG_CMD_NAND		* NAND support
930		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
931		CONFIG_CMD_NFS		  NFS support
932		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
933		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
934		CONFIG_CMD_PCI		* pciinfo
935		CONFIG_CMD_PCMCIA		* PCMCIA support
936		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
937					  host
938		CONFIG_CMD_PORTIO	* Port I/O
939		CONFIG_CMD_READ		* Read raw data from partition
940		CONFIG_CMD_REGINFO	* Register dump
941		CONFIG_CMD_RUN		  run command in env variable
942		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
943		CONFIG_CMD_SAVES	* save S record dump
944		CONFIG_SCSI		* SCSI Support
945		CONFIG_CMD_SDRAM	* print SDRAM configuration information
946					  (requires CONFIG_CMD_I2C)
947		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
948					  (4xx only)
949		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
950		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
951					  (requires CONFIG_CMD_MEMORY)
952		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
953		CONFIG_CMD_SOURCE	  "source" command Support
954		CONFIG_CMD_SPI		* SPI serial bus support
955		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
956		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
957		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
958		CONFIG_CMD_TIMER	* access to the system tick timer
959		CONFIG_CMD_USB		* USB support
960		CONFIG_CMD_CDP		* Cisco Discover Protocol support
961		CONFIG_CMD_MFSL		* Microblaze FSL support
962		CONFIG_CMD_XIMG		  Load part of Multi Image
963		CONFIG_CMD_UUID		* Generate random UUID or GUID string
964
965		EXAMPLE: If you want all functions except of network
966		support you can write:
967
968		#include "config_cmd_all.h"
969		#undef CONFIG_CMD_NET
970
971	Other Commands:
972		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
973
974	Note:	Don't enable the "icache" and "dcache" commands
975		(configuration option CONFIG_CMD_CACHE) unless you know
976		what you (and your U-Boot users) are doing. Data
977		cache cannot be enabled on systems like the 8xx or
978		8260 (where accesses to the IMMR region must be
979		uncached), and it cannot be disabled on all other
980		systems where we (mis-) use the data cache to hold an
981		initial stack and some data.
982
983
984		XXX - this list needs to get updated!
985
986- Removal of commands
987		If no commands are needed to boot, you can disable
988		CONFIG_CMDLINE to remove them. In this case, the command line
989		will not be available, and when U-Boot wants to execute the
990		boot command (on start-up) it will call board_run_command()
991		instead. This can reduce image size significantly for very
992		simple boot procedures.
993
994- Regular expression support:
995		CONFIG_REGEX
996		If this variable is defined, U-Boot is linked against
997		the SLRE (Super Light Regular Expression) library,
998		which adds regex support to some commands, as for
999		example "env grep" and "setexpr".
1000
1001- Device tree:
1002		CONFIG_OF_CONTROL
1003		If this variable is defined, U-Boot will use a device tree
1004		to configure its devices, instead of relying on statically
1005		compiled #defines in the board file. This option is
1006		experimental and only available on a few boards. The device
1007		tree is available in the global data as gd->fdt_blob.
1008
1009		U-Boot needs to get its device tree from somewhere. This can
1010		be done using one of the two options below:
1011
1012		CONFIG_OF_EMBED
1013		If this variable is defined, U-Boot will embed a device tree
1014		binary in its image. This device tree file should be in the
1015		board directory and called <soc>-<board>.dts. The binary file
1016		is then picked up in board_init_f() and made available through
1017		the global data structure as gd->blob.
1018
1019		CONFIG_OF_SEPARATE
1020		If this variable is defined, U-Boot will build a device tree
1021		binary. It will be called u-boot.dtb. Architecture-specific
1022		code will locate it at run-time. Generally this works by:
1023
1024			cat u-boot.bin u-boot.dtb >image.bin
1025
1026		and in fact, U-Boot does this for you, creating a file called
1027		u-boot-dtb.bin which is useful in the common case. You can
1028		still use the individual files if you need something more
1029		exotic.
1030
1031- Watchdog:
1032		CONFIG_WATCHDOG
1033		If this variable is defined, it enables watchdog
1034		support for the SoC. There must be support in the SoC
1035		specific code for a watchdog. For the 8xx and 8260
1036		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1037		register.  When supported for a specific SoC is
1038		available, then no further board specific code should
1039		be needed to use it.
1040
1041		CONFIG_HW_WATCHDOG
1042		When using a watchdog circuitry external to the used
1043		SoC, then define this variable and provide board
1044		specific code for the "hw_watchdog_reset" function.
1045
1046		CONFIG_AT91_HW_WDT_TIMEOUT
1047		specify the timeout in seconds. default 2 seconds.
1048
1049- U-Boot Version:
1050		CONFIG_VERSION_VARIABLE
1051		If this variable is defined, an environment variable
1052		named "ver" is created by U-Boot showing the U-Boot
1053		version as printed by the "version" command.
1054		Any change to this variable will be reverted at the
1055		next reset.
1056
1057- Real-Time Clock:
1058
1059		When CONFIG_CMD_DATE is selected, the type of the RTC
1060		has to be selected, too. Define exactly one of the
1061		following options:
1062
1063		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1064		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1065		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1066		CONFIG_RTC_MC146818	- use MC146818 RTC
1067		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1068		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1069		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1070		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1071		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1072		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1073		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1074		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1075		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1076					  RV3029 RTC.
1077
1078		Note that if the RTC uses I2C, then the I2C interface
1079		must also be configured. See I2C Support, below.
1080
1081- GPIO Support:
1082		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1083
1084		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1085		chip-ngpio pairs that tell the PCA953X driver the number of
1086		pins supported by a particular chip.
1087
1088		Note that if the GPIO device uses I2C, then the I2C interface
1089		must also be configured. See I2C Support, below.
1090
1091- I/O tracing:
1092		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1093		accesses and can checksum them or write a list of them out
1094		to memory. See the 'iotrace' command for details. This is
1095		useful for testing device drivers since it can confirm that
1096		the driver behaves the same way before and after a code
1097		change. Currently this is supported on sandbox and arm. To
1098		add support for your architecture, add '#include <iotrace.h>'
1099		to the bottom of arch/<arch>/include/asm/io.h and test.
1100
1101		Example output from the 'iotrace stats' command is below.
1102		Note that if the trace buffer is exhausted, the checksum will
1103		still continue to operate.
1104
1105			iotrace is enabled
1106			Start:  10000000	(buffer start address)
1107			Size:   00010000	(buffer size)
1108			Offset: 00000120	(current buffer offset)
1109			Output: 10000120	(start + offset)
1110			Count:  00000018	(number of trace records)
1111			CRC32:  9526fb66	(CRC32 of all trace records)
1112
1113- Timestamp Support:
1114
1115		When CONFIG_TIMESTAMP is selected, the timestamp
1116		(date and time) of an image is printed by image
1117		commands like bootm or iminfo. This option is
1118		automatically enabled when you select CONFIG_CMD_DATE .
1119
1120- Partition Labels (disklabels) Supported:
1121		Zero or more of the following:
1122		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1123		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1124				       Intel architecture, USB sticks, etc.
1125		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1126		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1127				       bootloader.  Note 2TB partition limit; see
1128				       disk/part_efi.c
1129		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1130
1131		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1132		CONFIG_SCSI) you must configure support for at
1133		least one non-MTD partition type as well.
1134
1135- IDE Reset method:
1136		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1137		board configurations files but used nowhere!
1138
1139		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1140		be performed by calling the function
1141			ide_set_reset(int reset)
1142		which has to be defined in a board specific file
1143
1144- ATAPI Support:
1145		CONFIG_ATAPI
1146
1147		Set this to enable ATAPI support.
1148
1149- LBA48 Support
1150		CONFIG_LBA48
1151
1152		Set this to enable support for disks larger than 137GB
1153		Also look at CONFIG_SYS_64BIT_LBA.
1154		Whithout these , LBA48 support uses 32bit variables and will 'only'
1155		support disks up to 2.1TB.
1156
1157		CONFIG_SYS_64BIT_LBA:
1158			When enabled, makes the IDE subsystem use 64bit sector addresses.
1159			Default is 32bit.
1160
1161- SCSI Support:
1162		At the moment only there is only support for the
1163		SYM53C8XX SCSI controller; define
1164		CONFIG_SCSI_SYM53C8XX to enable it.
1165
1166		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1167		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1168		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1169		maximum numbers of LUNs, SCSI ID's and target
1170		devices.
1171		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1172
1173		The environment variable 'scsidevs' is set to the number of
1174		SCSI devices found during the last scan.
1175
1176- NETWORK Support (PCI):
1177		CONFIG_E1000
1178		Support for Intel 8254x/8257x gigabit chips.
1179
1180		CONFIG_E1000_SPI
1181		Utility code for direct access to the SPI bus on Intel 8257x.
1182		This does not do anything useful unless you set at least one
1183		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1184
1185		CONFIG_E1000_SPI_GENERIC
1186		Allow generic access to the SPI bus on the Intel 8257x, for
1187		example with the "sspi" command.
1188
1189		CONFIG_CMD_E1000
1190		Management command for E1000 devices.  When used on devices
1191		with SPI support you can reprogram the EEPROM from U-Boot.
1192
1193		CONFIG_EEPRO100
1194		Support for Intel 82557/82559/82559ER chips.
1195		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1196		write routine for first time initialisation.
1197
1198		CONFIG_TULIP
1199		Support for Digital 2114x chips.
1200		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1201		modem chip initialisation (KS8761/QS6611).
1202
1203		CONFIG_NATSEMI
1204		Support for National dp83815 chips.
1205
1206		CONFIG_NS8382X
1207		Support for National dp8382[01] gigabit chips.
1208
1209- NETWORK Support (other):
1210
1211		CONFIG_DRIVER_AT91EMAC
1212		Support for AT91RM9200 EMAC.
1213
1214			CONFIG_RMII
1215			Define this to use reduced MII inteface
1216
1217			CONFIG_DRIVER_AT91EMAC_QUIET
1218			If this defined, the driver is quiet.
1219			The driver doen't show link status messages.
1220
1221		CONFIG_CALXEDA_XGMAC
1222		Support for the Calxeda XGMAC device
1223
1224		CONFIG_LAN91C96
1225		Support for SMSC's LAN91C96 chips.
1226
1227			CONFIG_LAN91C96_USE_32_BIT
1228			Define this to enable 32 bit addressing
1229
1230		CONFIG_SMC91111
1231		Support for SMSC's LAN91C111 chip
1232
1233			CONFIG_SMC91111_BASE
1234			Define this to hold the physical address
1235			of the device (I/O space)
1236
1237			CONFIG_SMC_USE_32_BIT
1238			Define this if data bus is 32 bits
1239
1240			CONFIG_SMC_USE_IOFUNCS
1241			Define this to use i/o functions instead of macros
1242			(some hardware wont work with macros)
1243
1244		CONFIG_DRIVER_TI_EMAC
1245		Support for davinci emac
1246
1247			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1248			Define this if you have more then 3 PHYs.
1249
1250		CONFIG_FTGMAC100
1251		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1252
1253			CONFIG_FTGMAC100_EGIGA
1254			Define this to use GE link update with gigabit PHY.
1255			Define this if FTGMAC100 is connected to gigabit PHY.
1256			If your system has 10/100 PHY only, it might not occur
1257			wrong behavior. Because PHY usually return timeout or
1258			useless data when polling gigabit status and gigabit
1259			control registers. This behavior won't affect the
1260			correctnessof 10/100 link speed update.
1261
1262		CONFIG_SMC911X
1263		Support for SMSC's LAN911x and LAN921x chips
1264
1265			CONFIG_SMC911X_BASE
1266			Define this to hold the physical address
1267			of the device (I/O space)
1268
1269			CONFIG_SMC911X_32_BIT
1270			Define this if data bus is 32 bits
1271
1272			CONFIG_SMC911X_16_BIT
1273			Define this if data bus is 16 bits. If your processor
1274			automatically converts one 32 bit word to two 16 bit
1275			words you may also try CONFIG_SMC911X_32_BIT.
1276
1277		CONFIG_SH_ETHER
1278		Support for Renesas on-chip Ethernet controller
1279
1280			CONFIG_SH_ETHER_USE_PORT
1281			Define the number of ports to be used
1282
1283			CONFIG_SH_ETHER_PHY_ADDR
1284			Define the ETH PHY's address
1285
1286			CONFIG_SH_ETHER_CACHE_WRITEBACK
1287			If this option is set, the driver enables cache flush.
1288
1289- PWM Support:
1290		CONFIG_PWM_IMX
1291		Support for PWM module on the imx6.
1292
1293- TPM Support:
1294		CONFIG_TPM
1295		Support TPM devices.
1296
1297		CONFIG_TPM_TIS_INFINEON
1298		Support for Infineon i2c bus TPM devices. Only one device
1299		per system is supported at this time.
1300
1301			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1302			Define the burst count bytes upper limit
1303
1304		CONFIG_TPM_ST33ZP24
1305		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1306
1307			CONFIG_TPM_ST33ZP24_I2C
1308			Support for STMicroelectronics ST33ZP24 I2C devices.
1309			Requires TPM_ST33ZP24 and I2C.
1310
1311			CONFIG_TPM_ST33ZP24_SPI
1312			Support for STMicroelectronics ST33ZP24 SPI devices.
1313			Requires TPM_ST33ZP24 and SPI.
1314
1315		CONFIG_TPM_ATMEL_TWI
1316		Support for Atmel TWI TPM device. Requires I2C support.
1317
1318		CONFIG_TPM_TIS_LPC
1319		Support for generic parallel port TPM devices. Only one device
1320		per system is supported at this time.
1321
1322			CONFIG_TPM_TIS_BASE_ADDRESS
1323			Base address where the generic TPM device is mapped
1324			to. Contemporary x86 systems usually map it at
1325			0xfed40000.
1326
1327		CONFIG_CMD_TPM
1328		Add tpm monitor functions.
1329		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1330		provides monitor access to authorized functions.
1331
1332		CONFIG_TPM
1333		Define this to enable the TPM support library which provides
1334		functional interfaces to some TPM commands.
1335		Requires support for a TPM device.
1336
1337		CONFIG_TPM_AUTH_SESSIONS
1338		Define this to enable authorized functions in the TPM library.
1339		Requires CONFIG_TPM and CONFIG_SHA1.
1340
1341- USB Support:
1342		At the moment only the UHCI host controller is
1343		supported (PIP405, MIP405, MPC5200); define
1344		CONFIG_USB_UHCI to enable it.
1345		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1346		and define CONFIG_USB_STORAGE to enable the USB
1347		storage devices.
1348		Note:
1349		Supported are USB Keyboards and USB Floppy drives
1350		(TEAC FD-05PUB).
1351		MPC5200 USB requires additional defines:
1352			CONFIG_USB_CLOCK
1353				for 528 MHz Clock: 0x0001bbbb
1354			CONFIG_PSC3_USB
1355				for USB on PSC3
1356			CONFIG_USB_CONFIG
1357				for differential drivers: 0x00001000
1358				for single ended drivers: 0x00005000
1359				for differential drivers on PSC3: 0x00000100
1360				for single ended drivers on PSC3: 0x00004100
1361			CONFIG_SYS_USB_EVENT_POLL
1362				May be defined to allow interrupt polling
1363				instead of using asynchronous interrupts
1364
1365		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1366		txfilltuning field in the EHCI controller on reset.
1367
1368		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1369		HW module registers.
1370
1371- USB Device:
1372		Define the below if you wish to use the USB console.
1373		Once firmware is rebuilt from a serial console issue the
1374		command "setenv stdin usbtty; setenv stdout usbtty" and
1375		attach your USB cable. The Unix command "dmesg" should print
1376		it has found a new device. The environment variable usbtty
1377		can be set to gserial or cdc_acm to enable your device to
1378		appear to a USB host as a Linux gserial device or a
1379		Common Device Class Abstract Control Model serial device.
1380		If you select usbtty = gserial you should be able to enumerate
1381		a Linux host by
1382		# modprobe usbserial vendor=0xVendorID product=0xProductID
1383		else if using cdc_acm, simply setting the environment
1384		variable usbtty to be cdc_acm should suffice. The following
1385		might be defined in YourBoardName.h
1386
1387			CONFIG_USB_DEVICE
1388			Define this to build a UDC device
1389
1390			CONFIG_USB_TTY
1391			Define this to have a tty type of device available to
1392			talk to the UDC device
1393
1394			CONFIG_USBD_HS
1395			Define this to enable the high speed support for usb
1396			device and usbtty. If this feature is enabled, a routine
1397			int is_usbd_high_speed(void)
1398			also needs to be defined by the driver to dynamically poll
1399			whether the enumeration has succeded at high speed or full
1400			speed.
1401
1402			CONFIG_SYS_CONSOLE_IS_IN_ENV
1403			Define this if you want stdin, stdout &/or stderr to
1404			be set to usbtty.
1405
1406			mpc8xx:
1407				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1408				Derive USB clock from external clock "blah"
1409				- CONFIG_SYS_USB_EXTC_CLK 0x02
1410
1411		If you have a USB-IF assigned VendorID then you may wish to
1412		define your own vendor specific values either in BoardName.h
1413		or directly in usbd_vendor_info.h. If you don't define
1414		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1415		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1416		should pretend to be a Linux device to it's target host.
1417
1418			CONFIG_USBD_MANUFACTURER
1419			Define this string as the name of your company for
1420			- CONFIG_USBD_MANUFACTURER "my company"
1421
1422			CONFIG_USBD_PRODUCT_NAME
1423			Define this string as the name of your product
1424			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1425
1426			CONFIG_USBD_VENDORID
1427			Define this as your assigned Vendor ID from the USB
1428			Implementors Forum. This *must* be a genuine Vendor ID
1429			to avoid polluting the USB namespace.
1430			- CONFIG_USBD_VENDORID 0xFFFF
1431
1432			CONFIG_USBD_PRODUCTID
1433			Define this as the unique Product ID
1434			for your device
1435			- CONFIG_USBD_PRODUCTID 0xFFFF
1436
1437- ULPI Layer Support:
1438		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1439		the generic ULPI layer. The generic layer accesses the ULPI PHY
1440		via the platform viewport, so you need both the genric layer and
1441		the viewport enabled. Currently only Chipidea/ARC based
1442		viewport is supported.
1443		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1444		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1445		If your ULPI phy needs a different reference clock than the
1446		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1447		the appropriate value in Hz.
1448
1449- MMC Support:
1450		The MMC controller on the Intel PXA is supported. To
1451		enable this define CONFIG_MMC. The MMC can be
1452		accessed from the boot prompt by mapping the device
1453		to physical memory similar to flash. Command line is
1454		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1455		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1456
1457		CONFIG_SH_MMCIF
1458		Support for Renesas on-chip MMCIF controller
1459
1460			CONFIG_SH_MMCIF_ADDR
1461			Define the base address of MMCIF registers
1462
1463			CONFIG_SH_MMCIF_CLK
1464			Define the clock frequency for MMCIF
1465
1466		CONFIG_SUPPORT_EMMC_BOOT
1467		Enable some additional features of the eMMC boot partitions.
1468
1469		CONFIG_SUPPORT_EMMC_RPMB
1470		Enable the commands for reading, writing and programming the
1471		key for the Replay Protection Memory Block partition in eMMC.
1472
1473- USB Device Firmware Update (DFU) class support:
1474		CONFIG_USB_FUNCTION_DFU
1475		This enables the USB portion of the DFU USB class
1476
1477		CONFIG_CMD_DFU
1478		This enables the command "dfu" which is used to have
1479		U-Boot create a DFU class device via USB.  This command
1480		requires that the "dfu_alt_info" environment variable be
1481		set and define the alt settings to expose to the host.
1482
1483		CONFIG_DFU_MMC
1484		This enables support for exposing (e)MMC devices via DFU.
1485
1486		CONFIG_DFU_NAND
1487		This enables support for exposing NAND devices via DFU.
1488
1489		CONFIG_DFU_RAM
1490		This enables support for exposing RAM via DFU.
1491		Note: DFU spec refer to non-volatile memory usage, but
1492		allow usages beyond the scope of spec - here RAM usage,
1493		one that would help mostly the developer.
1494
1495		CONFIG_SYS_DFU_DATA_BUF_SIZE
1496		Dfu transfer uses a buffer before writing data to the
1497		raw storage device. Make the size (in bytes) of this buffer
1498		configurable. The size of this buffer is also configurable
1499		through the "dfu_bufsiz" environment variable.
1500
1501		CONFIG_SYS_DFU_MAX_FILE_SIZE
1502		When updating files rather than the raw storage device,
1503		we use a static buffer to copy the file into and then write
1504		the buffer once we've been given the whole file.  Define
1505		this to the maximum filesize (in bytes) for the buffer.
1506		Default is 4 MiB if undefined.
1507
1508		DFU_DEFAULT_POLL_TIMEOUT
1509		Poll timeout [ms], is the timeout a device can send to the
1510		host. The host must wait for this timeout before sending
1511		a subsequent DFU_GET_STATUS request to the device.
1512
1513		DFU_MANIFEST_POLL_TIMEOUT
1514		Poll timeout [ms], which the device sends to the host when
1515		entering dfuMANIFEST state. Host waits this timeout, before
1516		sending again an USB request to the device.
1517
1518- USB Device Android Fastboot support:
1519		CONFIG_USB_FUNCTION_FASTBOOT
1520		This enables the USB part of the fastboot gadget
1521
1522		CONFIG_CMD_FASTBOOT
1523		This enables the command "fastboot" which enables the Android
1524		fastboot mode for the platform's USB device. Fastboot is a USB
1525		protocol for downloading images, flashing and device control
1526		used on Android devices.
1527		See doc/README.android-fastboot for more information.
1528
1529		CONFIG_ANDROID_BOOT_IMAGE
1530		This enables support for booting images which use the Android
1531		image format header.
1532
1533		CONFIG_FASTBOOT_BUF_ADDR
1534		The fastboot protocol requires a large memory buffer for
1535		downloads. Define this to the starting RAM address to use for
1536		downloaded images.
1537
1538		CONFIG_FASTBOOT_BUF_SIZE
1539		The fastboot protocol requires a large memory buffer for
1540		downloads. This buffer should be as large as possible for a
1541		platform. Define this to the size available RAM for fastboot.
1542
1543		CONFIG_FASTBOOT_FLASH
1544		The fastboot protocol includes a "flash" command for writing
1545		the downloaded image to a non-volatile storage device. Define
1546		this to enable the "fastboot flash" command.
1547
1548		CONFIG_FASTBOOT_FLASH_MMC_DEV
1549		The fastboot "flash" command requires additional information
1550		regarding the non-volatile storage device. Define this to
1551		the eMMC device that fastboot should use to store the image.
1552
1553		CONFIG_FASTBOOT_GPT_NAME
1554		The fastboot "flash" command supports writing the downloaded
1555		image to the Protective MBR and the Primary GUID Partition
1556		Table. (Additionally, this downloaded image is post-processed
1557		to generate and write the Backup GUID Partition Table.)
1558		This occurs when the specified "partition name" on the
1559		"fastboot flash" command line matches this value.
1560		The default is "gpt" if undefined.
1561
1562		CONFIG_FASTBOOT_MBR_NAME
1563		The fastboot "flash" command supports writing the downloaded
1564		image to DOS MBR.
1565		This occurs when the "partition name" specified on the
1566		"fastboot flash" command line matches this value.
1567		If not defined the default value "mbr" is used.
1568
1569- Journaling Flash filesystem support:
1570		CONFIG_JFFS2_NAND
1571		Define these for a default partition on a NAND device
1572
1573		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1574		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1575		Define these for a default partition on a NOR device
1576
1577- FAT(File Allocation Table) filesystem write function support:
1578		CONFIG_FAT_WRITE
1579
1580		Define this to enable support for saving memory data as a
1581		file in FAT formatted partition.
1582
1583		This will also enable the command "fatwrite" enabling the
1584		user to write files to FAT.
1585
1586- CBFS (Coreboot Filesystem) support:
1587		CONFIG_CMD_CBFS
1588
1589		Define this to enable support for reading from a Coreboot
1590		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1591		and cbfsload.
1592
1593- FAT(File Allocation Table) filesystem cluster size:
1594		CONFIG_FS_FAT_MAX_CLUSTSIZE
1595
1596		Define the max cluster size for fat operations else
1597		a default value of 65536 will be defined.
1598
1599- Keyboard Support:
1600		See Kconfig help for available keyboard drivers.
1601
1602		CONFIG_KEYBOARD
1603
1604		Define this to enable a custom keyboard support.
1605		This simply calls drv_keyboard_init() which must be
1606		defined in your board-specific files. This option is deprecated
1607		and is only used by novena. For new boards, use driver model
1608		instead.
1609
1610- Video support:
1611		CONFIG_FSL_DIU_FB
1612		Enable the Freescale DIU video driver.	Reference boards for
1613		SOCs that have a DIU should define this macro to enable DIU
1614		support, and should also define these other macros:
1615
1616			CONFIG_SYS_DIU_ADDR
1617			CONFIG_VIDEO
1618			CONFIG_CMD_BMP
1619			CONFIG_CFB_CONSOLE
1620			CONFIG_VIDEO_SW_CURSOR
1621			CONFIG_VGA_AS_SINGLE_DEVICE
1622			CONFIG_VIDEO_LOGO
1623			CONFIG_VIDEO_BMP_LOGO
1624
1625		The DIU driver will look for the 'video-mode' environment
1626		variable, and if defined, enable the DIU as a console during
1627		boot.  See the documentation file doc/README.video for a
1628		description of this variable.
1629
1630- LCD Support:	CONFIG_LCD
1631
1632		Define this to enable LCD support (for output to LCD
1633		display); also select one of the supported displays
1634		by defining one of these:
1635
1636		CONFIG_ATMEL_LCD:
1637
1638			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1639
1640		CONFIG_NEC_NL6448AC33:
1641
1642			NEC NL6448AC33-18. Active, color, single scan.
1643
1644		CONFIG_NEC_NL6448BC20
1645
1646			NEC NL6448BC20-08. 6.5", 640x480.
1647			Active, color, single scan.
1648
1649		CONFIG_NEC_NL6448BC33_54
1650
1651			NEC NL6448BC33-54. 10.4", 640x480.
1652			Active, color, single scan.
1653
1654		CONFIG_SHARP_16x9
1655
1656			Sharp 320x240. Active, color, single scan.
1657			It isn't 16x9, and I am not sure what it is.
1658
1659		CONFIG_SHARP_LQ64D341
1660
1661			Sharp LQ64D341 display, 640x480.
1662			Active, color, single scan.
1663
1664		CONFIG_HLD1045
1665
1666			HLD1045 display, 640x480.
1667			Active, color, single scan.
1668
1669		CONFIG_OPTREX_BW
1670
1671			Optrex	 CBL50840-2 NF-FW 99 22 M5
1672			or
1673			Hitachi	 LMG6912RPFC-00T
1674			or
1675			Hitachi	 SP14Q002
1676
1677			320x240. Black & white.
1678
1679		Normally display is black on white background; define
1680		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1681
1682		CONFIG_LCD_ALIGNMENT
1683
1684		Normally the LCD is page-aligned (typically 4KB). If this is
1685		defined then the LCD will be aligned to this value instead.
1686		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1687		here, since it is cheaper to change data cache settings on
1688		a per-section basis.
1689
1690
1691		CONFIG_LCD_ROTATION
1692
1693		Sometimes, for example if the display is mounted in portrait
1694		mode or even if it's mounted landscape but rotated by 180degree,
1695		we need to rotate our content of the display relative to the
1696		framebuffer, so that user can read the messages which are
1697		printed out.
1698		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1699		initialized with a given rotation from "vl_rot" out of
1700		"vidinfo_t" which is provided by the board specific code.
1701		The value for vl_rot is coded as following (matching to
1702		fbcon=rotate:<n> linux-kernel commandline):
1703		0 = no rotation respectively 0 degree
1704		1 = 90 degree rotation
1705		2 = 180 degree rotation
1706		3 = 270 degree rotation
1707
1708		If CONFIG_LCD_ROTATION is not defined, the console will be
1709		initialized with 0degree rotation.
1710
1711		CONFIG_LCD_BMP_RLE8
1712
1713		Support drawing of RLE8-compressed bitmaps on the LCD.
1714
1715		CONFIG_I2C_EDID
1716
1717		Enables an 'i2c edid' command which can read EDID
1718		information over I2C from an attached LCD display.
1719
1720- Splash Screen Support: CONFIG_SPLASH_SCREEN
1721
1722		If this option is set, the environment is checked for
1723		a variable "splashimage". If found, the usual display
1724		of logo, copyright and system information on the LCD
1725		is suppressed and the BMP image at the address
1726		specified in "splashimage" is loaded instead. The
1727		console is redirected to the "nulldev", too. This
1728		allows for a "silent" boot where a splash screen is
1729		loaded very quickly after power-on.
1730
1731		CONFIG_SPLASHIMAGE_GUARD
1732
1733		If this option is set, then U-Boot will prevent the environment
1734		variable "splashimage" from being set to a problematic address
1735		(see doc/README.displaying-bmps).
1736		This option is useful for targets where, due to alignment
1737		restrictions, an improperly aligned BMP image will cause a data
1738		abort. If you think you will not have problems with unaligned
1739		accesses (for example because your toolchain prevents them)
1740		there is no need to set this option.
1741
1742		CONFIG_SPLASH_SCREEN_ALIGN
1743
1744		If this option is set the splash image can be freely positioned
1745		on the screen. Environment variable "splashpos" specifies the
1746		position as "x,y". If a positive number is given it is used as
1747		number of pixel from left/top. If a negative number is given it
1748		is used as number of pixel from right/bottom. You can also
1749		specify 'm' for centering the image.
1750
1751		Example:
1752		setenv splashpos m,m
1753			=> image at center of screen
1754
1755		setenv splashpos 30,20
1756			=> image at x = 30 and y = 20
1757
1758		setenv splashpos -10,m
1759			=> vertically centered image
1760			   at x = dspWidth - bmpWidth - 9
1761
1762- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1763
1764		If this option is set, additionally to standard BMP
1765		images, gzipped BMP images can be displayed via the
1766		splashscreen support or the bmp command.
1767
1768- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1769
1770		If this option is set, 8-bit RLE compressed BMP images
1771		can be displayed via the splashscreen support or the
1772		bmp command.
1773
1774- Do compressing for memory range:
1775		CONFIG_CMD_ZIP
1776
1777		If this option is set, it would use zlib deflate method
1778		to compress the specified memory at its best effort.
1779
1780- Compression support:
1781		CONFIG_GZIP
1782
1783		Enabled by default to support gzip compressed images.
1784
1785		CONFIG_BZIP2
1786
1787		If this option is set, support for bzip2 compressed
1788		images is included. If not, only uncompressed and gzip
1789		compressed images are supported.
1790
1791		NOTE: the bzip2 algorithm requires a lot of RAM, so
1792		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1793		be at least 4MB.
1794
1795		CONFIG_LZMA
1796
1797		If this option is set, support for lzma compressed
1798		images is included.
1799
1800		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1801		requires an amount of dynamic memory that is given by the
1802		formula:
1803
1804			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1805
1806		Where lc and lp stand for, respectively, Literal context bits
1807		and Literal pos bits.
1808
1809		This value is upper-bounded by 14MB in the worst case. Anyway,
1810		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1811		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1812		a very small buffer.
1813
1814		Use the lzmainfo tool to determinate the lc and lp values and
1815		then calculate the amount of needed dynamic memory (ensuring
1816		the appropriate CONFIG_SYS_MALLOC_LEN value).
1817
1818		CONFIG_LZO
1819
1820		If this option is set, support for LZO compressed images
1821		is included.
1822
1823- MII/PHY support:
1824		CONFIG_PHY_ADDR
1825
1826		The address of PHY on MII bus.
1827
1828		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1829
1830		The clock frequency of the MII bus
1831
1832		CONFIG_PHY_GIGE
1833
1834		If this option is set, support for speed/duplex
1835		detection of gigabit PHY is included.
1836
1837		CONFIG_PHY_RESET_DELAY
1838
1839		Some PHY like Intel LXT971A need extra delay after
1840		reset before any MII register access is possible.
1841		For such PHY, set this option to the usec delay
1842		required. (minimum 300usec for LXT971A)
1843
1844		CONFIG_PHY_CMD_DELAY (ppc4xx)
1845
1846		Some PHY like Intel LXT971A need extra delay after
1847		command issued before MII status register can be read
1848
1849- IP address:
1850		CONFIG_IPADDR
1851
1852		Define a default value for the IP address to use for
1853		the default Ethernet interface, in case this is not
1854		determined through e.g. bootp.
1855		(Environment variable "ipaddr")
1856
1857- Server IP address:
1858		CONFIG_SERVERIP
1859
1860		Defines a default value for the IP address of a TFTP
1861		server to contact when using the "tftboot" command.
1862		(Environment variable "serverip")
1863
1864		CONFIG_KEEP_SERVERADDR
1865
1866		Keeps the server's MAC address, in the env 'serveraddr'
1867		for passing to bootargs (like Linux's netconsole option)
1868
1869- Gateway IP address:
1870		CONFIG_GATEWAYIP
1871
1872		Defines a default value for the IP address of the
1873		default router where packets to other networks are
1874		sent to.
1875		(Environment variable "gatewayip")
1876
1877- Subnet mask:
1878		CONFIG_NETMASK
1879
1880		Defines a default value for the subnet mask (or
1881		routing prefix) which is used to determine if an IP
1882		address belongs to the local subnet or needs to be
1883		forwarded through a router.
1884		(Environment variable "netmask")
1885
1886- Multicast TFTP Mode:
1887		CONFIG_MCAST_TFTP
1888
1889		Defines whether you want to support multicast TFTP as per
1890		rfc-2090; for example to work with atftp.  Lets lots of targets
1891		tftp down the same boot image concurrently.  Note: the Ethernet
1892		driver in use must provide a function: mcast() to join/leave a
1893		multicast group.
1894
1895- BOOTP Recovery Mode:
1896		CONFIG_BOOTP_RANDOM_DELAY
1897
1898		If you have many targets in a network that try to
1899		boot using BOOTP, you may want to avoid that all
1900		systems send out BOOTP requests at precisely the same
1901		moment (which would happen for instance at recovery
1902		from a power failure, when all systems will try to
1903		boot, thus flooding the BOOTP server. Defining
1904		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1905		inserted before sending out BOOTP requests. The
1906		following delays are inserted then:
1907
1908		1st BOOTP request:	delay 0 ... 1 sec
1909		2nd BOOTP request:	delay 0 ... 2 sec
1910		3rd BOOTP request:	delay 0 ... 4 sec
1911		4th and following
1912		BOOTP requests:		delay 0 ... 8 sec
1913
1914		CONFIG_BOOTP_ID_CACHE_SIZE
1915
1916		BOOTP packets are uniquely identified using a 32-bit ID. The
1917		server will copy the ID from client requests to responses and
1918		U-Boot will use this to determine if it is the destination of
1919		an incoming response. Some servers will check that addresses
1920		aren't in use before handing them out (usually using an ARP
1921		ping) and therefore take up to a few hundred milliseconds to
1922		respond. Network congestion may also influence the time it
1923		takes for a response to make it back to the client. If that
1924		time is too long, U-Boot will retransmit requests. In order
1925		to allow earlier responses to still be accepted after these
1926		retransmissions, U-Boot's BOOTP client keeps a small cache of
1927		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1928		cache. The default is to keep IDs for up to four outstanding
1929		requests. Increasing this will allow U-Boot to accept offers
1930		from a BOOTP client in networks with unusually high latency.
1931
1932- DHCP Advanced Options:
1933		You can fine tune the DHCP functionality by defining
1934		CONFIG_BOOTP_* symbols:
1935
1936		CONFIG_BOOTP_SUBNETMASK
1937		CONFIG_BOOTP_GATEWAY
1938		CONFIG_BOOTP_HOSTNAME
1939		CONFIG_BOOTP_NISDOMAIN
1940		CONFIG_BOOTP_BOOTPATH
1941		CONFIG_BOOTP_BOOTFILESIZE
1942		CONFIG_BOOTP_DNS
1943		CONFIG_BOOTP_DNS2
1944		CONFIG_BOOTP_SEND_HOSTNAME
1945		CONFIG_BOOTP_NTPSERVER
1946		CONFIG_BOOTP_TIMEOFFSET
1947		CONFIG_BOOTP_VENDOREX
1948		CONFIG_BOOTP_MAY_FAIL
1949
1950		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1951		environment variable, not the BOOTP server.
1952
1953		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1954		after the configured retry count, the call will fail
1955		instead of starting over.  This can be used to fail over
1956		to Link-local IP address configuration if the DHCP server
1957		is not available.
1958
1959		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1960		serverip from a DHCP server, it is possible that more
1961		than one DNS serverip is offered to the client.
1962		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1963		serverip will be stored in the additional environment
1964		variable "dnsip2". The first DNS serverip is always
1965		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1966		is defined.
1967
1968		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1969		to do a dynamic update of a DNS server. To do this, they
1970		need the hostname of the DHCP requester.
1971		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1972		of the "hostname" environment variable is passed as
1973		option 12 to the DHCP server.
1974
1975		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1976
1977		A 32bit value in microseconds for a delay between
1978		receiving a "DHCP Offer" and sending the "DHCP Request".
1979		This fixes a problem with certain DHCP servers that don't
1980		respond 100% of the time to a "DHCP request". E.g. On an
1981		AT91RM9200 processor running at 180MHz, this delay needed
1982		to be *at least* 15,000 usec before a Windows Server 2003
1983		DHCP server would reply 100% of the time. I recommend at
1984		least 50,000 usec to be safe. The alternative is to hope
1985		that one of the retries will be successful but note that
1986		the DHCP timeout and retry process takes a longer than
1987		this delay.
1988
1989 - Link-local IP address negotiation:
1990		Negotiate with other link-local clients on the local network
1991		for an address that doesn't require explicit configuration.
1992		This is especially useful if a DHCP server cannot be guaranteed
1993		to exist in all environments that the device must operate.
1994
1995		See doc/README.link-local for more information.
1996
1997 - CDP Options:
1998		CONFIG_CDP_DEVICE_ID
1999
2000		The device id used in CDP trigger frames.
2001
2002		CONFIG_CDP_DEVICE_ID_PREFIX
2003
2004		A two character string which is prefixed to the MAC address
2005		of the device.
2006
2007		CONFIG_CDP_PORT_ID
2008
2009		A printf format string which contains the ascii name of
2010		the port. Normally is set to "eth%d" which sets
2011		eth0 for the first Ethernet, eth1 for the second etc.
2012
2013		CONFIG_CDP_CAPABILITIES
2014
2015		A 32bit integer which indicates the device capabilities;
2016		0x00000010 for a normal host which does not forwards.
2017
2018		CONFIG_CDP_VERSION
2019
2020		An ascii string containing the version of the software.
2021
2022		CONFIG_CDP_PLATFORM
2023
2024		An ascii string containing the name of the platform.
2025
2026		CONFIG_CDP_TRIGGER
2027
2028		A 32bit integer sent on the trigger.
2029
2030		CONFIG_CDP_POWER_CONSUMPTION
2031
2032		A 16bit integer containing the power consumption of the
2033		device in .1 of milliwatts.
2034
2035		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2036
2037		A byte containing the id of the VLAN.
2038
2039- Status LED:	CONFIG_LED_STATUS
2040
2041		Several configurations allow to display the current
2042		status using a LED. For instance, the LED will blink
2043		fast while running U-Boot code, stop blinking as
2044		soon as a reply to a BOOTP request was received, and
2045		start blinking slow once the Linux kernel is running
2046		(supported by a status LED driver in the Linux
2047		kernel). Defining CONFIG_LED_STATUS enables this
2048		feature in U-Boot.
2049
2050		Additional options:
2051
2052		CONFIG_LED_STATUS_GPIO
2053		The status LED can be connected to a GPIO pin.
2054		In such cases, the gpio_led driver can be used as a
2055		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
2056		to include the gpio_led driver in the U-Boot binary.
2057
2058		CONFIG_GPIO_LED_INVERTED_TABLE
2059		Some GPIO connected LEDs may have inverted polarity in which
2060		case the GPIO high value corresponds to LED off state and
2061		GPIO low value corresponds to LED on state.
2062		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2063		with a list of GPIO LEDs that have inverted polarity.
2064
2065- CAN Support:	CONFIG_CAN_DRIVER
2066
2067		Defining CONFIG_CAN_DRIVER enables CAN driver support
2068		on those systems that support this (optional)
2069		feature, like the TQM8xxL modules.
2070
2071- I2C Support:	CONFIG_SYS_I2C
2072
2073		This enable the NEW i2c subsystem, and will allow you to use
2074		i2c commands at the u-boot command line (as long as you set
2075		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2076		based realtime clock chips or other i2c devices. See
2077		common/cmd_i2c.c for a description of the command line
2078		interface.
2079
2080		ported i2c driver to the new framework:
2081		- drivers/i2c/soft_i2c.c:
2082		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2083		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2084		    for defining speed and slave address
2085		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2086		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2087		    for defining speed and slave address
2088		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2089		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2090		    for defining speed and slave address
2091		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2092		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2093		    for defining speed and slave address
2094
2095		- drivers/i2c/fsl_i2c.c:
2096		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2097		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2098		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2099		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2100		    bus.
2101		  - If your board supports a second fsl i2c bus, define
2102		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2103		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2104		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2105		    second bus.
2106
2107		- drivers/i2c/tegra_i2c.c:
2108		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2109		  - This driver adds 4 i2c buses with a fix speed from
2110		    100000 and the slave addr 0!
2111
2112		- drivers/i2c/ppc4xx_i2c.c
2113		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2114		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2115		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2116
2117		- drivers/i2c/i2c_mxc.c
2118		  - activate this driver with CONFIG_SYS_I2C_MXC
2119		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
2120		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
2121		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
2122		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
2123		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2124		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2125		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2126		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2127		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2128		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2129		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
2130		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
2131		If those defines are not set, default value is 100000
2132		for speed, and 0 for slave.
2133
2134		- drivers/i2c/rcar_i2c.c:
2135		  - activate this driver with CONFIG_SYS_I2C_RCAR
2136		  - This driver adds 4 i2c buses
2137
2138		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2139		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2140		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2141		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2142		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2143		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2144		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2145		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2146		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2147
2148		- drivers/i2c/sh_i2c.c:
2149		  - activate this driver with CONFIG_SYS_I2C_SH
2150		  - This driver adds from 2 to 5 i2c buses
2151
2152		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2153		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2154		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2155		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2156		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2157		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2158		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2159		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2160		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2161		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2162		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2163
2164		- drivers/i2c/omap24xx_i2c.c
2165		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2166		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2167		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2168		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2169		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2170		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2171		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2172		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2173		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2174		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2175		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2176
2177		- drivers/i2c/zynq_i2c.c
2178		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2179		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2180		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2181
2182		- drivers/i2c/s3c24x0_i2c.c:
2183		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2184		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2185		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2186		    with a fix speed from 100000 and the slave addr 0!
2187
2188		- drivers/i2c/ihs_i2c.c
2189		  - activate this driver with CONFIG_SYS_I2C_IHS
2190		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2191		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2192		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2193		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2194		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2195		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2196		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2197		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2198		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2199		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2200		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2201		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2202		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
2203		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
2204		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
2205		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
2206		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
2207		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
2208		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
2209		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
2210		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
2211
2212		additional defines:
2213
2214		CONFIG_SYS_NUM_I2C_BUSES
2215		Hold the number of i2c buses you want to use.
2216
2217		CONFIG_SYS_I2C_DIRECT_BUS
2218		define this, if you don't use i2c muxes on your hardware.
2219		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2220		omit this define.
2221
2222		CONFIG_SYS_I2C_MAX_HOPS
2223		define how many muxes are maximal consecutively connected
2224		on one i2c bus. If you not use i2c muxes, omit this
2225		define.
2226
2227		CONFIG_SYS_I2C_BUSES
2228		hold a list of buses you want to use, only used if
2229		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2230		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2231		CONFIG_SYS_NUM_I2C_BUSES = 9:
2232
2233		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2234					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2235					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2236					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2237					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2238					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2239					{1, {I2C_NULL_HOP}}, \
2240					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2241					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2242					}
2243
2244		which defines
2245			bus 0 on adapter 0 without a mux
2246			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2247			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2248			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2249			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2250			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2251			bus 6 on adapter 1 without a mux
2252			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2253			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2254
2255		If you do not have i2c muxes on your board, omit this define.
2256
2257- Legacy I2C Support:	CONFIG_HARD_I2C
2258
2259		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2260		provides the following compelling advantages:
2261
2262		- more than one i2c adapter is usable
2263		- approved multibus support
2264		- better i2c mux support
2265
2266		** Please consider updating your I2C driver now. **
2267
2268		These enable legacy I2C serial bus commands. Defining
2269		CONFIG_HARD_I2C will include the appropriate I2C driver
2270		for the selected CPU.
2271
2272		This will allow you to use i2c commands at the u-boot
2273		command line (as long as you set CONFIG_CMD_I2C in
2274		CONFIG_COMMANDS) and communicate with i2c based realtime
2275		clock chips. See common/cmd_i2c.c for a description of the
2276		command line interface.
2277
2278		CONFIG_HARD_I2C selects a hardware I2C controller.
2279
2280		There are several other quantities that must also be
2281		defined when you define CONFIG_HARD_I2C.
2282
2283		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2284		to be the frequency (in Hz) at which you wish your i2c bus
2285		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2286		the CPU's i2c node address).
2287
2288		Now, the u-boot i2c code for the mpc8xx
2289		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2290		and so its address should therefore be cleared to 0 (See,
2291		eg, MPC823e User's Manual p.16-473). So, set
2292		CONFIG_SYS_I2C_SLAVE to 0.
2293
2294		CONFIG_SYS_I2C_INIT_MPC5XXX
2295
2296		When a board is reset during an i2c bus transfer
2297		chips might think that the current transfer is still
2298		in progress.  Reset the slave devices by sending start
2299		commands until the slave device responds.
2300
2301		That's all that's required for CONFIG_HARD_I2C.
2302
2303		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2304		then the following macros need to be defined (examples are
2305		from include/configs/lwmon.h):
2306
2307		I2C_INIT
2308
2309		(Optional). Any commands necessary to enable the I2C
2310		controller or configure ports.
2311
2312		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2313
2314		I2C_PORT
2315
2316		(Only for MPC8260 CPU). The I/O port to use (the code
2317		assumes both bits are on the same port). Valid values
2318		are 0..3 for ports A..D.
2319
2320		I2C_ACTIVE
2321
2322		The code necessary to make the I2C data line active
2323		(driven).  If the data line is open collector, this
2324		define can be null.
2325
2326		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2327
2328		I2C_TRISTATE
2329
2330		The code necessary to make the I2C data line tri-stated
2331		(inactive).  If the data line is open collector, this
2332		define can be null.
2333
2334		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2335
2336		I2C_READ
2337
2338		Code that returns true if the I2C data line is high,
2339		false if it is low.
2340
2341		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2342
2343		I2C_SDA(bit)
2344
2345		If <bit> is true, sets the I2C data line high. If it
2346		is false, it clears it (low).
2347
2348		eg: #define I2C_SDA(bit) \
2349			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2350			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2351
2352		I2C_SCL(bit)
2353
2354		If <bit> is true, sets the I2C clock line high. If it
2355		is false, it clears it (low).
2356
2357		eg: #define I2C_SCL(bit) \
2358			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2359			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2360
2361		I2C_DELAY
2362
2363		This delay is invoked four times per clock cycle so this
2364		controls the rate of data transfer.  The data rate thus
2365		is 1 / (I2C_DELAY * 4). Often defined to be something
2366		like:
2367
2368		#define I2C_DELAY  udelay(2)
2369
2370		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2371
2372		If your arch supports the generic GPIO framework (asm/gpio.h),
2373		then you may alternatively define the two GPIOs that are to be
2374		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2375		have GPIO-based defaults assigned to them as appropriate.
2376
2377		You should define these to the GPIO value as given directly to
2378		the generic GPIO functions.
2379
2380		CONFIG_SYS_I2C_INIT_BOARD
2381
2382		When a board is reset during an i2c bus transfer
2383		chips might think that the current transfer is still
2384		in progress. On some boards it is possible to access
2385		the i2c SCLK line directly, either by using the
2386		processor pin as a GPIO or by having a second pin
2387		connected to the bus. If this option is defined a
2388		custom i2c_init_board() routine in boards/xxx/board.c
2389		is run early in the boot sequence.
2390
2391		CONFIG_SYS_I2C_BOARD_LATE_INIT
2392
2393		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2394		defined a custom i2c_board_late_init() routine in
2395		boards/xxx/board.c is run AFTER the operations in i2c_init()
2396		is completed. This callpoint can be used to unreset i2c bus
2397		using CPU i2c controller register accesses for CPUs whose i2c
2398		controller provide such a method. It is called at the end of
2399		i2c_init() to allow i2c_init operations to setup the i2c bus
2400		controller on the CPU (e.g. setting bus speed & slave address).
2401
2402		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2403
2404		This option enables configuration of bi_iic_fast[] flags
2405		in u-boot bd_info structure based on u-boot environment
2406		variable "i2cfast". (see also i2cfast)
2407
2408		CONFIG_I2C_MULTI_BUS
2409
2410		This option allows the use of multiple I2C buses, each of which
2411		must have a controller.	 At any point in time, only one bus is
2412		active.	 To switch to a different bus, use the 'i2c dev' command.
2413		Note that bus numbering is zero-based.
2414
2415		CONFIG_SYS_I2C_NOPROBES
2416
2417		This option specifies a list of I2C devices that will be skipped
2418		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2419		is set, specify a list of bus-device pairs.  Otherwise, specify
2420		a 1D array of device addresses
2421
2422		e.g.
2423			#undef	CONFIG_I2C_MULTI_BUS
2424			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2425
2426		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2427
2428			#define CONFIG_I2C_MULTI_BUS
2429			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2430
2431		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2432
2433		CONFIG_SYS_SPD_BUS_NUM
2434
2435		If defined, then this indicates the I2C bus number for DDR SPD.
2436		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2437
2438		CONFIG_SYS_RTC_BUS_NUM
2439
2440		If defined, then this indicates the I2C bus number for the RTC.
2441		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2442
2443		CONFIG_SYS_DTT_BUS_NUM
2444
2445		If defined, then this indicates the I2C bus number for the DTT.
2446		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2447
2448		CONFIG_SYS_I2C_DTT_ADDR:
2449
2450		If defined, specifies the I2C address of the DTT device.
2451		If not defined, then U-Boot uses predefined value for
2452		specified DTT device.
2453
2454		CONFIG_SOFT_I2C_READ_REPEATED_START
2455
2456		defining this will force the i2c_read() function in
2457		the soft_i2c driver to perform an I2C repeated start
2458		between writing the address pointer and reading the
2459		data.  If this define is omitted the default behaviour
2460		of doing a stop-start sequence will be used.  Most I2C
2461		devices can use either method, but some require one or
2462		the other.
2463
2464- SPI Support:	CONFIG_SPI
2465
2466		Enables SPI driver (so far only tested with
2467		SPI EEPROM, also an instance works with Crystal A/D and
2468		D/As on the SACSng board)
2469
2470		CONFIG_SH_SPI
2471
2472		Enables the driver for SPI controller on SuperH. Currently
2473		only SH7757 is supported.
2474
2475		CONFIG_SOFT_SPI
2476
2477		Enables a software (bit-bang) SPI driver rather than
2478		using hardware support. This is a general purpose
2479		driver that only requires three general I/O port pins
2480		(two outputs, one input) to function. If this is
2481		defined, the board configuration must define several
2482		SPI configuration items (port pins to use, etc). For
2483		an example, see include/configs/sacsng.h.
2484
2485		CONFIG_HARD_SPI
2486
2487		Enables a hardware SPI driver for general-purpose reads
2488		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2489		must define a list of chip-select function pointers.
2490		Currently supported on some MPC8xxx processors.	 For an
2491		example, see include/configs/mpc8349emds.h.
2492
2493		CONFIG_MXC_SPI
2494
2495		Enables the driver for the SPI controllers on i.MX and MXC
2496		SoCs. Currently i.MX31/35/51 are supported.
2497
2498		CONFIG_SYS_SPI_MXC_WAIT
2499		Timeout for waiting until spi transfer completed.
2500		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2501
2502- FPGA Support: CONFIG_FPGA
2503
2504		Enables FPGA subsystem.
2505
2506		CONFIG_FPGA_<vendor>
2507
2508		Enables support for specific chip vendors.
2509		(ALTERA, XILINX)
2510
2511		CONFIG_FPGA_<family>
2512
2513		Enables support for FPGA family.
2514		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2515
2516		CONFIG_FPGA_COUNT
2517
2518		Specify the number of FPGA devices to support.
2519
2520		CONFIG_CMD_FPGA_LOADMK
2521
2522		Enable support for fpga loadmk command
2523
2524		CONFIG_CMD_FPGA_LOADP
2525
2526		Enable support for fpga loadp command - load partial bitstream
2527
2528		CONFIG_CMD_FPGA_LOADBP
2529
2530		Enable support for fpga loadbp command - load partial bitstream
2531		(Xilinx only)
2532
2533		CONFIG_SYS_FPGA_PROG_FEEDBACK
2534
2535		Enable printing of hash marks during FPGA configuration.
2536
2537		CONFIG_SYS_FPGA_CHECK_BUSY
2538
2539		Enable checks on FPGA configuration interface busy
2540		status by the configuration function. This option
2541		will require a board or device specific function to
2542		be written.
2543
2544		CONFIG_FPGA_DELAY
2545
2546		If defined, a function that provides delays in the FPGA
2547		configuration driver.
2548
2549		CONFIG_SYS_FPGA_CHECK_CTRLC
2550		Allow Control-C to interrupt FPGA configuration
2551
2552		CONFIG_SYS_FPGA_CHECK_ERROR
2553
2554		Check for configuration errors during FPGA bitfile
2555		loading. For example, abort during Virtex II
2556		configuration if the INIT_B line goes low (which
2557		indicated a CRC error).
2558
2559		CONFIG_SYS_FPGA_WAIT_INIT
2560
2561		Maximum time to wait for the INIT_B line to de-assert
2562		after PROB_B has been de-asserted during a Virtex II
2563		FPGA configuration sequence. The default time is 500
2564		ms.
2565
2566		CONFIG_SYS_FPGA_WAIT_BUSY
2567
2568		Maximum time to wait for BUSY to de-assert during
2569		Virtex II FPGA configuration. The default is 5 ms.
2570
2571		CONFIG_SYS_FPGA_WAIT_CONFIG
2572
2573		Time to wait after FPGA configuration. The default is
2574		200 ms.
2575
2576- Configuration Management:
2577		CONFIG_BUILD_TARGET
2578
2579		Some SoCs need special image types (e.g. U-Boot binary
2580		with a special header) as build targets. By defining
2581		CONFIG_BUILD_TARGET in the SoC / board header, this
2582		special image will be automatically built upon calling
2583		make / buildman.
2584
2585		CONFIG_IDENT_STRING
2586
2587		If defined, this string will be added to the U-Boot
2588		version information (U_BOOT_VERSION)
2589
2590- Vendor Parameter Protection:
2591
2592		U-Boot considers the values of the environment
2593		variables "serial#" (Board Serial Number) and
2594		"ethaddr" (Ethernet Address) to be parameters that
2595		are set once by the board vendor / manufacturer, and
2596		protects these variables from casual modification by
2597		the user. Once set, these variables are read-only,
2598		and write or delete attempts are rejected. You can
2599		change this behaviour:
2600
2601		If CONFIG_ENV_OVERWRITE is #defined in your config
2602		file, the write protection for vendor parameters is
2603		completely disabled. Anybody can change or delete
2604		these parameters.
2605
2606		Alternatively, if you define _both_ an ethaddr in the
2607		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2608		Ethernet address is installed in the environment,
2609		which can be changed exactly ONCE by the user. [The
2610		serial# is unaffected by this, i. e. it remains
2611		read-only.]
2612
2613		The same can be accomplished in a more flexible way
2614		for any variable by configuring the type of access
2615		to allow for those variables in the ".flags" variable
2616		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2617
2618- Protected RAM:
2619		CONFIG_PRAM
2620
2621		Define this variable to enable the reservation of
2622		"protected RAM", i. e. RAM which is not overwritten
2623		by U-Boot. Define CONFIG_PRAM to hold the number of
2624		kB you want to reserve for pRAM. You can overwrite
2625		this default value by defining an environment
2626		variable "pram" to the number of kB you want to
2627		reserve. Note that the board info structure will
2628		still show the full amount of RAM. If pRAM is
2629		reserved, a new environment variable "mem" will
2630		automatically be defined to hold the amount of
2631		remaining RAM in a form that can be passed as boot
2632		argument to Linux, for instance like that:
2633
2634			setenv bootargs ... mem=\${mem}
2635			saveenv
2636
2637		This way you can tell Linux not to use this memory,
2638		either, which results in a memory region that will
2639		not be affected by reboots.
2640
2641		*WARNING* If your board configuration uses automatic
2642		detection of the RAM size, you must make sure that
2643		this memory test is non-destructive. So far, the
2644		following board configurations are known to be
2645		"pRAM-clean":
2646
2647			IVMS8, IVML24, SPD8xx, TQM8xxL,
2648			HERMES, IP860, RPXlite, LWMON,
2649			FLAGADM, TQM8260
2650
2651- Access to physical memory region (> 4GB)
2652		Some basic support is provided for operations on memory not
2653		normally accessible to U-Boot - e.g. some architectures
2654		support access to more than 4GB of memory on 32-bit
2655		machines using physical address extension or similar.
2656		Define CONFIG_PHYSMEM to access this basic support, which
2657		currently only supports clearing the memory.
2658
2659- Error Recovery:
2660		CONFIG_PANIC_HANG
2661
2662		Define this variable to stop the system in case of a
2663		fatal error, so that you have to reset it manually.
2664		This is probably NOT a good idea for an embedded
2665		system where you want the system to reboot
2666		automatically as fast as possible, but it may be
2667		useful during development since you can try to debug
2668		the conditions that lead to the situation.
2669
2670		CONFIG_NET_RETRY_COUNT
2671
2672		This variable defines the number of retries for
2673		network operations like ARP, RARP, TFTP, or BOOTP
2674		before giving up the operation. If not defined, a
2675		default value of 5 is used.
2676
2677		CONFIG_ARP_TIMEOUT
2678
2679		Timeout waiting for an ARP reply in milliseconds.
2680
2681		CONFIG_NFS_TIMEOUT
2682
2683		Timeout in milliseconds used in NFS protocol.
2684		If you encounter "ERROR: Cannot umount" in nfs command,
2685		try longer timeout such as
2686		#define CONFIG_NFS_TIMEOUT 10000UL
2687
2688- Command Interpreter:
2689		CONFIG_AUTO_COMPLETE
2690
2691		Enable auto completion of commands using TAB.
2692
2693		CONFIG_SYS_PROMPT_HUSH_PS2
2694
2695		This defines the secondary prompt string, which is
2696		printed when the command interpreter needs more input
2697		to complete a command. Usually "> ".
2698
2699	Note:
2700
2701		In the current implementation, the local variables
2702		space and global environment variables space are
2703		separated. Local variables are those you define by
2704		simply typing `name=value'. To access a local
2705		variable later on, you have write `$name' or
2706		`${name}'; to execute the contents of a variable
2707		directly type `$name' at the command prompt.
2708
2709		Global environment variables are those you use
2710		setenv/printenv to work with. To run a command stored
2711		in such a variable, you need to use the run command,
2712		and you must not use the '$' sign to access them.
2713
2714		To store commands and special characters in a
2715		variable, please use double quotation marks
2716		surrounding the whole text of the variable, instead
2717		of the backslashes before semicolons and special
2718		symbols.
2719
2720- Command Line Editing and History:
2721		CONFIG_CMDLINE_EDITING
2722
2723		Enable editing and History functions for interactive
2724		command line input operations
2725
2726- Command Line PS1/PS2 support:
2727		CONFIG_CMDLINE_PS_SUPPORT
2728
2729		Enable support for changing the command prompt string
2730		at run-time. Only static string is supported so far.
2731		The string is obtained from environment variables PS1
2732		and PS2.
2733
2734- Default Environment:
2735		CONFIG_EXTRA_ENV_SETTINGS
2736
2737		Define this to contain any number of null terminated
2738		strings (variable = value pairs) that will be part of
2739		the default environment compiled into the boot image.
2740
2741		For example, place something like this in your
2742		board's config file:
2743
2744		#define CONFIG_EXTRA_ENV_SETTINGS \
2745			"myvar1=value1\0" \
2746			"myvar2=value2\0"
2747
2748		Warning: This method is based on knowledge about the
2749		internal format how the environment is stored by the
2750		U-Boot code. This is NOT an official, exported
2751		interface! Although it is unlikely that this format
2752		will change soon, there is no guarantee either.
2753		You better know what you are doing here.
2754
2755		Note: overly (ab)use of the default environment is
2756		discouraged. Make sure to check other ways to preset
2757		the environment like the "source" command or the
2758		boot command first.
2759
2760		CONFIG_ENV_VARS_UBOOT_CONFIG
2761
2762		Define this in order to add variables describing the
2763		U-Boot build configuration to the default environment.
2764		These will be named arch, cpu, board, vendor, and soc.
2765
2766		Enabling this option will cause the following to be defined:
2767
2768		- CONFIG_SYS_ARCH
2769		- CONFIG_SYS_CPU
2770		- CONFIG_SYS_BOARD
2771		- CONFIG_SYS_VENDOR
2772		- CONFIG_SYS_SOC
2773
2774		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2775
2776		Define this in order to add variables describing certain
2777		run-time determined information about the hardware to the
2778		environment.  These will be named board_name, board_rev.
2779
2780		CONFIG_DELAY_ENVIRONMENT
2781
2782		Normally the environment is loaded when the board is
2783		initialised so that it is available to U-Boot. This inhibits
2784		that so that the environment is not available until
2785		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2786		this is instead controlled by the value of
2787		/config/load-environment.
2788
2789- Parallel Flash support:
2790		CONFIG_SYS_NO_FLASH
2791
2792		Traditionally U-Boot was run on systems with parallel NOR
2793		flash. This option is used to disable support for parallel NOR
2794		flash. This option should be defined if the board does not have
2795		parallel flash.
2796
2797		If this option is not defined one of the generic flash drivers
2798		(e.g.  CONFIG_FLASH_CFI_DRIVER or CONFIG_ST_SMI) must be
2799		selected or the board must provide an implementation of the
2800		flash API (see include/flash.h).
2801
2802- DataFlash Support:
2803		CONFIG_HAS_DATAFLASH
2804
2805		Defining this option enables DataFlash features and
2806		allows to read/write in Dataflash via the standard
2807		commands cp, md...
2808
2809- Serial Flash support
2810		CONFIG_CMD_SF
2811
2812		Defining this option enables SPI flash commands
2813		'sf probe/read/write/erase/update'.
2814
2815		Usage requires an initial 'probe' to define the serial
2816		flash parameters, followed by read/write/erase/update
2817		commands.
2818
2819		The following defaults may be provided by the platform
2820		to handle the common case when only a single serial
2821		flash is present on the system.
2822
2823		CONFIG_SF_DEFAULT_BUS		Bus identifier
2824		CONFIG_SF_DEFAULT_CS		Chip-select
2825		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2826		CONFIG_SF_DEFAULT_SPEED		in Hz
2827
2828		CONFIG_CMD_SF_TEST
2829
2830		Define this option to include a destructive SPI flash
2831		test ('sf test').
2832
2833		CONFIG_SF_DUAL_FLASH		Dual flash memories
2834
2835		Define this option to use dual flash support where two flash
2836		memories can be connected with a given cs line.
2837		Currently Xilinx Zynq qspi supports these type of connections.
2838
2839- SystemACE Support:
2840		CONFIG_SYSTEMACE
2841
2842		Adding this option adds support for Xilinx SystemACE
2843		chips attached via some sort of local bus. The address
2844		of the chip must also be defined in the
2845		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2846
2847		#define CONFIG_SYSTEMACE
2848		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2849
2850		When SystemACE support is added, the "ace" device type
2851		becomes available to the fat commands, i.e. fatls.
2852
2853- TFTP Fixed UDP Port:
2854		CONFIG_TFTP_PORT
2855
2856		If this is defined, the environment variable tftpsrcp
2857		is used to supply the TFTP UDP source port value.
2858		If tftpsrcp isn't defined, the normal pseudo-random port
2859		number generator is used.
2860
2861		Also, the environment variable tftpdstp is used to supply
2862		the TFTP UDP destination port value.  If tftpdstp isn't
2863		defined, the normal port 69 is used.
2864
2865		The purpose for tftpsrcp is to allow a TFTP server to
2866		blindly start the TFTP transfer using the pre-configured
2867		target IP address and UDP port. This has the effect of
2868		"punching through" the (Windows XP) firewall, allowing
2869		the remainder of the TFTP transfer to proceed normally.
2870		A better solution is to properly configure the firewall,
2871		but sometimes that is not allowed.
2872
2873- Hashing support:
2874		CONFIG_CMD_HASH
2875
2876		This enables a generic 'hash' command which can produce
2877		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2878
2879		CONFIG_HASH_VERIFY
2880
2881		Enable the hash verify command (hash -v). This adds to code
2882		size a little.
2883
2884		CONFIG_SHA1 - This option enables support of hashing using SHA1
2885		algorithm. The hash is calculated in software.
2886		CONFIG_SHA256 - This option enables support of hashing using
2887		SHA256 algorithm. The hash is calculated in software.
2888		CONFIG_SHA_HW_ACCEL - This option enables hardware acceleration
2889		for SHA1/SHA256 hashing.
2890		This affects the 'hash' command and also the
2891		hash_lookup_algo() function.
2892		CONFIG_SHA_PROG_HW_ACCEL - This option enables
2893		hardware-acceleration for SHA1/SHA256 progressive hashing.
2894		Data can be streamed in a block at a time and the hashing
2895		is performed in hardware.
2896
2897		Note: There is also a sha1sum command, which should perhaps
2898		be deprecated in favour of 'hash sha1'.
2899
2900- Freescale i.MX specific commands:
2901		CONFIG_CMD_HDMIDETECT
2902		This enables 'hdmidet' command which returns true if an
2903		HDMI monitor is detected.  This command is i.MX 6 specific.
2904
2905		CONFIG_CMD_BMODE
2906		This enables the 'bmode' (bootmode) command for forcing
2907		a boot from specific media.
2908
2909		This is useful for forcing the ROM's usb downloader to
2910		activate upon a watchdog reset which is nice when iterating
2911		on U-Boot.  Using the reset button or running bmode normal
2912		will set it back to normal.  This command currently
2913		supports i.MX53 and i.MX6.
2914
2915- bootcount support:
2916		CONFIG_BOOTCOUNT_LIMIT
2917
2918		This enables the bootcounter support, see:
2919		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2920
2921		CONFIG_AT91SAM9XE
2922		enable special bootcounter support on at91sam9xe based boards.
2923		CONFIG_BLACKFIN
2924		enable special bootcounter support on blackfin based boards.
2925		CONFIG_SOC_DA8XX
2926		enable special bootcounter support on da850 based boards.
2927		CONFIG_BOOTCOUNT_RAM
2928		enable support for the bootcounter in RAM
2929		CONFIG_BOOTCOUNT_I2C
2930		enable support for the bootcounter on an i2c (like RTC) device.
2931			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2932			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2933						    the bootcounter.
2934			CONFIG_BOOTCOUNT_ALEN = address len
2935
2936- Show boot progress:
2937		CONFIG_SHOW_BOOT_PROGRESS
2938
2939		Defining this option allows to add some board-
2940		specific code (calling a user-provided function
2941		"show_boot_progress(int)") that enables you to show
2942		the system's boot progress on some display (for
2943		example, some LED's) on your board. At the moment,
2944		the following checkpoints are implemented:
2945
2946
2947Legacy uImage format:
2948
2949  Arg	Where			When
2950    1	common/cmd_bootm.c	before attempting to boot an image
2951   -1	common/cmd_bootm.c	Image header has bad	 magic number
2952    2	common/cmd_bootm.c	Image header has correct magic number
2953   -2	common/cmd_bootm.c	Image header has bad	 checksum
2954    3	common/cmd_bootm.c	Image header has correct checksum
2955   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2956    4	common/cmd_bootm.c	Image data   has correct checksum
2957   -4	common/cmd_bootm.c	Image is for unsupported architecture
2958    5	common/cmd_bootm.c	Architecture check OK
2959   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2960    6	common/cmd_bootm.c	Image Type check OK
2961   -6	common/cmd_bootm.c	gunzip uncompression error
2962   -7	common/cmd_bootm.c	Unimplemented compression type
2963    7	common/cmd_bootm.c	Uncompression OK
2964    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2965   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2966
2967    9	common/image.c		Start initial ramdisk verification
2968  -10	common/image.c		Ramdisk header has bad	   magic number
2969  -11	common/image.c		Ramdisk header has bad	   checksum
2970   10	common/image.c		Ramdisk header is OK
2971  -12	common/image.c		Ramdisk data   has bad	   checksum
2972   11	common/image.c		Ramdisk data   has correct checksum
2973   12	common/image.c		Ramdisk verification complete, start loading
2974  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2975   13	common/image.c		Start multifile image verification
2976   14	common/image.c		No initial ramdisk, no multifile, continue.
2977
2978   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2979
2980  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2981  -31	post/post.c		POST test failed, detected by post_output_backlog()
2982  -32	post/post.c		POST test failed, detected by post_run_single()
2983
2984   34	common/cmd_doc.c	before loading a Image from a DOC device
2985  -35	common/cmd_doc.c	Bad usage of "doc" command
2986   35	common/cmd_doc.c	correct usage of "doc" command
2987  -36	common/cmd_doc.c	No boot device
2988   36	common/cmd_doc.c	correct boot device
2989  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2990   37	common/cmd_doc.c	correct chip ID found, device available
2991  -38	common/cmd_doc.c	Read Error on boot device
2992   38	common/cmd_doc.c	reading Image header from DOC device OK
2993  -39	common/cmd_doc.c	Image header has bad magic number
2994   39	common/cmd_doc.c	Image header has correct magic number
2995  -40	common/cmd_doc.c	Error reading Image from DOC device
2996   40	common/cmd_doc.c	Image header has correct magic number
2997   41	common/cmd_ide.c	before loading a Image from a IDE device
2998  -42	common/cmd_ide.c	Bad usage of "ide" command
2999   42	common/cmd_ide.c	correct usage of "ide" command
3000  -43	common/cmd_ide.c	No boot device
3001   43	common/cmd_ide.c	boot device found
3002  -44	common/cmd_ide.c	Device not available
3003   44	common/cmd_ide.c	Device available
3004  -45	common/cmd_ide.c	wrong partition selected
3005   45	common/cmd_ide.c	partition selected
3006  -46	common/cmd_ide.c	Unknown partition table
3007   46	common/cmd_ide.c	valid partition table found
3008  -47	common/cmd_ide.c	Invalid partition type
3009   47	common/cmd_ide.c	correct partition type
3010  -48	common/cmd_ide.c	Error reading Image Header on boot device
3011   48	common/cmd_ide.c	reading Image Header from IDE device OK
3012  -49	common/cmd_ide.c	Image header has bad magic number
3013   49	common/cmd_ide.c	Image header has correct magic number
3014  -50	common/cmd_ide.c	Image header has bad	 checksum
3015   50	common/cmd_ide.c	Image header has correct checksum
3016  -51	common/cmd_ide.c	Error reading Image from IDE device
3017   51	common/cmd_ide.c	reading Image from IDE device OK
3018   52	common/cmd_nand.c	before loading a Image from a NAND device
3019  -53	common/cmd_nand.c	Bad usage of "nand" command
3020   53	common/cmd_nand.c	correct usage of "nand" command
3021  -54	common/cmd_nand.c	No boot device
3022   54	common/cmd_nand.c	boot device found
3023  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3024   55	common/cmd_nand.c	correct chip ID found, device available
3025  -56	common/cmd_nand.c	Error reading Image Header on boot device
3026   56	common/cmd_nand.c	reading Image Header from NAND device OK
3027  -57	common/cmd_nand.c	Image header has bad magic number
3028   57	common/cmd_nand.c	Image header has correct magic number
3029  -58	common/cmd_nand.c	Error reading Image from NAND device
3030   58	common/cmd_nand.c	reading Image from NAND device OK
3031
3032  -60	common/env_common.c	Environment has a bad CRC, using default
3033
3034   64	net/eth.c		starting with Ethernet configuration.
3035  -64	net/eth.c		no Ethernet found.
3036   65	net/eth.c		Ethernet found.
3037
3038  -80	common/cmd_net.c	usage wrong
3039   80	common/cmd_net.c	before calling net_loop()
3040  -81	common/cmd_net.c	some error in net_loop() occurred
3041   81	common/cmd_net.c	net_loop() back without error
3042  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3043   82	common/cmd_net.c	trying automatic boot
3044   83	common/cmd_net.c	running "source" command
3045  -83	common/cmd_net.c	some error in automatic boot or "source" command
3046   84	common/cmd_net.c	end without errors
3047
3048FIT uImage format:
3049
3050  Arg	Where			When
3051  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3052 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3053  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3054 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3055  102	common/cmd_bootm.c	Kernel unit name specified
3056 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3057  103	common/cmd_bootm.c	Found configuration node
3058  104	common/cmd_bootm.c	Got kernel subimage node offset
3059 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3060  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3061 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3062  106	common/cmd_bootm.c	Architecture check OK
3063 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3064  107	common/cmd_bootm.c	Kernel subimage type OK
3065 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3066  108	common/cmd_bootm.c	Got kernel subimage data/size
3067 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3068 -109	common/cmd_bootm.c	Can't get kernel subimage type
3069 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3070 -111	common/cmd_bootm.c	Can't get kernel subimage os
3071 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3072 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3073
3074  120	common/image.c		Start initial ramdisk verification
3075 -120	common/image.c		Ramdisk FIT image has incorrect format
3076  121	common/image.c		Ramdisk FIT image has correct format
3077  122	common/image.c		No ramdisk subimage unit name, using configuration
3078 -122	common/image.c		Can't get configuration for ramdisk subimage
3079  123	common/image.c		Ramdisk unit name specified
3080 -124	common/image.c		Can't get ramdisk subimage node offset
3081  125	common/image.c		Got ramdisk subimage node offset
3082 -125	common/image.c		Ramdisk subimage hash verification failed
3083  126	common/image.c		Ramdisk subimage hash verification OK
3084 -126	common/image.c		Ramdisk subimage for unsupported architecture
3085  127	common/image.c		Architecture check OK
3086 -127	common/image.c		Can't get ramdisk subimage data/size
3087  128	common/image.c		Got ramdisk subimage data/size
3088  129	common/image.c		Can't get ramdisk load address
3089 -129	common/image.c		Got ramdisk load address
3090
3091 -130	common/cmd_doc.c	Incorrect FIT image format
3092  131	common/cmd_doc.c	FIT image format OK
3093
3094 -140	common/cmd_ide.c	Incorrect FIT image format
3095  141	common/cmd_ide.c	FIT image format OK
3096
3097 -150	common/cmd_nand.c	Incorrect FIT image format
3098  151	common/cmd_nand.c	FIT image format OK
3099
3100- legacy image format:
3101		CONFIG_IMAGE_FORMAT_LEGACY
3102		enables the legacy image format support in U-Boot.
3103
3104		Default:
3105		enabled if CONFIG_FIT_SIGNATURE is not defined.
3106
3107		CONFIG_DISABLE_IMAGE_LEGACY
3108		disable the legacy image format
3109
3110		This define is introduced, as the legacy image format is
3111		enabled per default for backward compatibility.
3112
3113- FIT image support:
3114		CONFIG_FIT_DISABLE_SHA256
3115		Supporting SHA256 hashes has quite an impact on binary size.
3116		For constrained systems sha256 hash support can be disabled
3117		with this option.
3118
3119		TODO(sjg@chromium.org): Adjust this option to be positive,
3120		and move it to Kconfig
3121
3122- Standalone program support:
3123		CONFIG_STANDALONE_LOAD_ADDR
3124
3125		This option defines a board specific value for the
3126		address where standalone program gets loaded, thus
3127		overwriting the architecture dependent default
3128		settings.
3129
3130- Frame Buffer Address:
3131		CONFIG_FB_ADDR
3132
3133		Define CONFIG_FB_ADDR if you want to use specific
3134		address for frame buffer.  This is typically the case
3135		when using a graphics controller has separate video
3136		memory.  U-Boot will then place the frame buffer at
3137		the given address instead of dynamically reserving it
3138		in system RAM by calling lcd_setmem(), which grabs
3139		the memory for the frame buffer depending on the
3140		configured panel size.
3141
3142		Please see board_init_f function.
3143
3144- Automatic software updates via TFTP server
3145		CONFIG_UPDATE_TFTP
3146		CONFIG_UPDATE_TFTP_CNT_MAX
3147		CONFIG_UPDATE_TFTP_MSEC_MAX
3148
3149		These options enable and control the auto-update feature;
3150		for a more detailed description refer to doc/README.update.
3151
3152- MTD Support (mtdparts command, UBI support)
3153		CONFIG_MTD_DEVICE
3154
3155		Adds the MTD device infrastructure from the Linux kernel.
3156		Needed for mtdparts command support.
3157
3158		CONFIG_MTD_PARTITIONS
3159
3160		Adds the MTD partitioning infrastructure from the Linux
3161		kernel. Needed for UBI support.
3162
3163- UBI support
3164		CONFIG_CMD_UBI
3165
3166		Adds commands for interacting with MTD partitions formatted
3167		with the UBI flash translation layer
3168
3169		Requires also defining CONFIG_RBTREE
3170
3171		CONFIG_UBI_SILENCE_MSG
3172
3173		Make the verbose messages from UBI stop printing.  This leaves
3174		warnings and errors enabled.
3175
3176
3177		CONFIG_MTD_UBI_WL_THRESHOLD
3178		This parameter defines the maximum difference between the highest
3179		erase counter value and the lowest erase counter value of eraseblocks
3180		of UBI devices. When this threshold is exceeded, UBI starts performing
3181		wear leveling by means of moving data from eraseblock with low erase
3182		counter to eraseblocks with high erase counter.
3183
3184		The default value should be OK for SLC NAND flashes, NOR flashes and
3185		other flashes which have eraseblock life-cycle 100000 or more.
3186		However, in case of MLC NAND flashes which typically have eraseblock
3187		life-cycle less than 10000, the threshold should be lessened (e.g.,
3188		to 128 or 256, although it does not have to be power of 2).
3189
3190		default: 4096
3191
3192		CONFIG_MTD_UBI_BEB_LIMIT
3193		This option specifies the maximum bad physical eraseblocks UBI
3194		expects on the MTD device (per 1024 eraseblocks). If the
3195		underlying flash does not admit of bad eraseblocks (e.g. NOR
3196		flash), this value is ignored.
3197
3198		NAND datasheets often specify the minimum and maximum NVM
3199		(Number of Valid Blocks) for the flashes' endurance lifetime.
3200		The maximum expected bad eraseblocks per 1024 eraseblocks
3201		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3202		which gives 20 for most NANDs (MaxNVB is basically the total
3203		count of eraseblocks on the chip).
3204
3205		To put it differently, if this value is 20, UBI will try to
3206		reserve about 1.9% of physical eraseblocks for bad blocks
3207		handling. And that will be 1.9% of eraseblocks on the entire
3208		NAND chip, not just the MTD partition UBI attaches. This means
3209		that if you have, say, a NAND flash chip admits maximum 40 bad
3210		eraseblocks, and it is split on two MTD partitions of the same
3211		size, UBI will reserve 40 eraseblocks when attaching a
3212		partition.
3213
3214		default: 20
3215
3216		CONFIG_MTD_UBI_FASTMAP
3217		Fastmap is a mechanism which allows attaching an UBI device
3218		in nearly constant time. Instead of scanning the whole MTD device it
3219		only has to locate a checkpoint (called fastmap) on the device.
3220		The on-flash fastmap contains all information needed to attach
3221		the device. Using fastmap makes only sense on large devices where
3222		attaching by scanning takes long. UBI will not automatically install
3223		a fastmap on old images, but you can set the UBI parameter
3224		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3225		that fastmap-enabled images are still usable with UBI implementations
3226		without	fastmap support. On typical flash devices the whole fastmap
3227		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3228
3229		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3230		Set this parameter to enable fastmap automatically on images
3231		without a fastmap.
3232		default: 0
3233
3234		CONFIG_MTD_UBI_FM_DEBUG
3235		Enable UBI fastmap debug
3236		default: 0
3237
3238- UBIFS support
3239		CONFIG_CMD_UBIFS
3240
3241		Adds commands for interacting with UBI volumes formatted as
3242		UBIFS.  UBIFS is read-only in u-boot.
3243
3244		Requires UBI support as well as CONFIG_LZO
3245
3246		CONFIG_UBIFS_SILENCE_MSG
3247
3248		Make the verbose messages from UBIFS stop printing.  This leaves
3249		warnings and errors enabled.
3250
3251- SPL framework
3252		CONFIG_SPL
3253		Enable building of SPL globally.
3254
3255		CONFIG_SPL_LDSCRIPT
3256		LDSCRIPT for linking the SPL binary.
3257
3258		CONFIG_SPL_MAX_FOOTPRINT
3259		Maximum size in memory allocated to the SPL, BSS included.
3260		When defined, the linker checks that the actual memory
3261		used by SPL from _start to __bss_end does not exceed it.
3262		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3263		must not be both defined at the same time.
3264
3265		CONFIG_SPL_MAX_SIZE
3266		Maximum size of the SPL image (text, data, rodata, and
3267		linker lists sections), BSS excluded.
3268		When defined, the linker checks that the actual size does
3269		not exceed it.
3270
3271		CONFIG_SPL_TEXT_BASE
3272		TEXT_BASE for linking the SPL binary.
3273
3274		CONFIG_SPL_RELOC_TEXT_BASE
3275		Address to relocate to.  If unspecified, this is equal to
3276		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3277
3278		CONFIG_SPL_BSS_START_ADDR
3279		Link address for the BSS within the SPL binary.
3280
3281		CONFIG_SPL_BSS_MAX_SIZE
3282		Maximum size in memory allocated to the SPL BSS.
3283		When defined, the linker checks that the actual memory used
3284		by SPL from __bss_start to __bss_end does not exceed it.
3285		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3286		must not be both defined at the same time.
3287
3288		CONFIG_SPL_STACK
3289		Adress of the start of the stack SPL will use
3290
3291		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3292		When defined, SPL will panic() if the image it has
3293		loaded does not have a signature.
3294		Defining this is useful when code which loads images
3295		in SPL cannot guarantee that absolutely all read errors
3296		will be caught.
3297		An example is the LPC32XX MLC NAND driver, which will
3298		consider that a completely unreadable NAND block is bad,
3299		and thus should be skipped silently.
3300
3301		CONFIG_SPL_ABORT_ON_RAW_IMAGE
3302		When defined, SPL will proceed to another boot method
3303		if the image it has loaded does not have a signature.
3304
3305		CONFIG_SPL_RELOC_STACK
3306		Adress of the start of the stack SPL will use after
3307		relocation.  If unspecified, this is equal to
3308		CONFIG_SPL_STACK.
3309
3310		CONFIG_SYS_SPL_MALLOC_START
3311		Starting address of the malloc pool used in SPL.
3312		When this option is set the full malloc is used in SPL and
3313		it is set up by spl_init() and before that, the simple malloc()
3314		can be used if CONFIG_SYS_MALLOC_F is defined.
3315
3316		CONFIG_SYS_SPL_MALLOC_SIZE
3317		The size of the malloc pool used in SPL.
3318
3319		CONFIG_SPL_FRAMEWORK
3320		Enable the SPL framework under common/.  This framework
3321		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3322		NAND loading of the Linux Kernel.
3323
3324		CONFIG_SPL_OS_BOOT
3325		Enable booting directly to an OS from SPL.
3326		See also: doc/README.falcon
3327
3328		CONFIG_SPL_DISPLAY_PRINT
3329		For ARM, enable an optional function to print more information
3330		about the running system.
3331
3332		CONFIG_SPL_INIT_MINIMAL
3333		Arch init code should be built for a very small image
3334
3335		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3336		Partition on the MMC to load U-Boot from when the MMC is being
3337		used in raw mode
3338
3339		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3340		Sector to load kernel uImage from when MMC is being
3341		used in raw mode (for Falcon mode)
3342
3343		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3344		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3345		Sector and number of sectors to load kernel argument
3346		parameters from when MMC is being used in raw mode
3347		(for falcon mode)
3348
3349		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3350		Partition on the MMC to load U-Boot from when the MMC is being
3351		used in fs mode
3352
3353		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3354		Filename to read to load U-Boot when reading from filesystem
3355
3356		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3357		Filename to read to load kernel uImage when reading
3358		from filesystem (for Falcon mode)
3359
3360		CONFIG_SPL_FS_LOAD_ARGS_NAME
3361		Filename to read to load kernel argument parameters
3362		when reading from filesystem (for Falcon mode)
3363
3364		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3365		Set this for NAND SPL on PPC mpc83xx targets, so that
3366		start.S waits for the rest of the SPL to load before
3367		continuing (the hardware starts execution after just
3368		loading the first page rather than the full 4K).
3369
3370		CONFIG_SPL_SKIP_RELOCATE
3371		Avoid SPL relocation
3372
3373		CONFIG_SPL_NAND_BASE
3374		Include nand_base.c in the SPL.  Requires
3375		CONFIG_SPL_NAND_DRIVERS.
3376
3377		CONFIG_SPL_NAND_DRIVERS
3378		SPL uses normal NAND drivers, not minimal drivers.
3379
3380		CONFIG_SPL_NAND_ECC
3381		Include standard software ECC in the SPL
3382
3383		CONFIG_SPL_NAND_SIMPLE
3384		Support for NAND boot using simple NAND drivers that
3385		expose the cmd_ctrl() interface.
3386
3387		CONFIG_SPL_UBI
3388		Support for a lightweight UBI (fastmap) scanner and
3389		loader
3390
3391		CONFIG_SPL_NAND_RAW_ONLY
3392		Support to boot only raw u-boot.bin images. Use this only
3393		if you need to save space.
3394
3395		CONFIG_SPL_COMMON_INIT_DDR
3396		Set for common ddr init with serial presence detect in
3397		SPL binary.
3398
3399		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3400		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3401		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3402		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3403		CONFIG_SYS_NAND_ECCBYTES
3404		Defines the size and behavior of the NAND that SPL uses
3405		to read U-Boot
3406
3407		CONFIG_SPL_NAND_BOOT
3408		Add support NAND boot
3409
3410		CONFIG_SYS_NAND_U_BOOT_OFFS
3411		Location in NAND to read U-Boot from
3412
3413		CONFIG_SYS_NAND_U_BOOT_DST
3414		Location in memory to load U-Boot to
3415
3416		CONFIG_SYS_NAND_U_BOOT_SIZE
3417		Size of image to load
3418
3419		CONFIG_SYS_NAND_U_BOOT_START
3420		Entry point in loaded image to jump to
3421
3422		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3423		Define this if you need to first read the OOB and then the
3424		data. This is used, for example, on davinci platforms.
3425
3426		CONFIG_SPL_OMAP3_ID_NAND
3427		Support for an OMAP3-specific set of functions to return the
3428		ID and MFR of the first attached NAND chip, if present.
3429
3430		CONFIG_SPL_RAM_DEVICE
3431		Support for running image already present in ram, in SPL binary
3432
3433		CONFIG_SPL_PAD_TO
3434		Image offset to which the SPL should be padded before appending
3435		the SPL payload. By default, this is defined as
3436		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3437		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3438		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3439
3440		CONFIG_SPL_TARGET
3441		Final target image containing SPL and payload.  Some SPLs
3442		use an arch-specific makefile fragment instead, for
3443		example if more than one image needs to be produced.
3444
3445		CONFIG_FIT_SPL_PRINT
3446		Printing information about a FIT image adds quite a bit of
3447		code to SPL. So this is normally disabled in SPL. Use this
3448		option to re-enable it. This will affect the output of the
3449		bootm command when booting a FIT image.
3450
3451- TPL framework
3452		CONFIG_TPL
3453		Enable building of TPL globally.
3454
3455		CONFIG_TPL_PAD_TO
3456		Image offset to which the TPL should be padded before appending
3457		the TPL payload. By default, this is defined as
3458		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3459		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3460		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3461
3462- Interrupt support (PPC):
3463
3464		There are common interrupt_init() and timer_interrupt()
3465		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3466		for CPU specific initialization. interrupt_init_cpu()
3467		should set decrementer_count to appropriate value. If
3468		CPU resets decrementer automatically after interrupt
3469		(ppc4xx) it should set decrementer_count to zero.
3470		timer_interrupt() calls timer_interrupt_cpu() for CPU
3471		specific handling. If board has watchdog / status_led
3472		/ other_activity_monitor it works automatically from
3473		general timer_interrupt().
3474
3475
3476Board initialization settings:
3477------------------------------
3478
3479During Initialization u-boot calls a number of board specific functions
3480to allow the preparation of board specific prerequisites, e.g. pin setup
3481before drivers are initialized. To enable these callbacks the
3482following configuration macros have to be defined. Currently this is
3483architecture specific, so please check arch/your_architecture/lib/board.c
3484typically in board_init_f() and board_init_r().
3485
3486- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3487- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3488- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3489- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3490
3491Configuration Settings:
3492-----------------------
3493
3494- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3495		Optionally it can be defined to support 64-bit memory commands.
3496
3497- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3498		undefine this when you're short of memory.
3499
3500- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3501		width of the commands listed in the 'help' command output.
3502
3503- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3504		prompt for user input.
3505
3506- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3507
3508- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3509
3510- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3511
3512- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3513		the application (usually a Linux kernel) when it is
3514		booted
3515
3516- CONFIG_SYS_BAUDRATE_TABLE:
3517		List of legal baudrate settings for this board.
3518
3519- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3520		Begin and End addresses of the area used by the
3521		simple memory test.
3522
3523- CONFIG_SYS_ALT_MEMTEST:
3524		Enable an alternate, more extensive memory test.
3525
3526- CONFIG_SYS_MEMTEST_SCRATCH:
3527		Scratch address used by the alternate memory test
3528		You only need to set this if address zero isn't writeable
3529
3530- CONFIG_SYS_MEM_RESERVE_SECURE
3531		Only implemented for ARMv8 for now.
3532		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
3533		is substracted from total RAM and won't be reported to OS.
3534		This memory can be used as secure memory. A variable
3535		gd->arch.secure_ram is used to track the location. In systems
3536		the RAM base is not zero, or RAM is divided into banks,
3537		this variable needs to be recalcuated to get the address.
3538
3539- CONFIG_SYS_MEM_TOP_HIDE:
3540		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3541		this specified memory area will get subtracted from the top
3542		(end) of RAM and won't get "touched" at all by U-Boot. By
3543		fixing up gd->ram_size the Linux kernel should gets passed
3544		the now "corrected" memory size and won't touch it either.
3545		This should work for arch/ppc and arch/powerpc. Only Linux
3546		board ports in arch/powerpc with bootwrapper support that
3547		recalculate the memory size from the SDRAM controller setup
3548		will have to get fixed in Linux additionally.
3549
3550		This option can be used as a workaround for the 440EPx/GRx
3551		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3552		be touched.
3553
3554		WARNING: Please make sure that this value is a multiple of
3555		the Linux page size (normally 4k). If this is not the case,
3556		then the end address of the Linux memory will be located at a
3557		non page size aligned address and this could cause major
3558		problems.
3559
3560- CONFIG_SYS_LOADS_BAUD_CHANGE:
3561		Enable temporary baudrate change while serial download
3562
3563- CONFIG_SYS_SDRAM_BASE:
3564		Physical start address of SDRAM. _Must_ be 0 here.
3565
3566- CONFIG_SYS_FLASH_BASE:
3567		Physical start address of Flash memory.
3568
3569- CONFIG_SYS_MONITOR_BASE:
3570		Physical start address of boot monitor code (set by
3571		make config files to be same as the text base address
3572		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3573		CONFIG_SYS_FLASH_BASE when booting from flash.
3574
3575- CONFIG_SYS_MONITOR_LEN:
3576		Size of memory reserved for monitor code, used to
3577		determine _at_compile_time_ (!) if the environment is
3578		embedded within the U-Boot image, or in a separate
3579		flash sector.
3580
3581- CONFIG_SYS_MALLOC_LEN:
3582		Size of DRAM reserved for malloc() use.
3583
3584- CONFIG_SYS_MALLOC_F_LEN
3585		Size of the malloc() pool for use before relocation. If
3586		this is defined, then a very simple malloc() implementation
3587		will become available before relocation. The address is just
3588		below the global data, and the stack is moved down to make
3589		space.
3590
3591		This feature allocates regions with increasing addresses
3592		within the region. calloc() is supported, but realloc()
3593		is not available. free() is supported but does nothing.
3594		The memory will be freed (or in fact just forgotten) when
3595		U-Boot relocates itself.
3596
3597- CONFIG_SYS_MALLOC_SIMPLE
3598		Provides a simple and small malloc() and calloc() for those
3599		boards which do not use the full malloc in SPL (which is
3600		enabled with CONFIG_SYS_SPL_MALLOC_START).
3601
3602- CONFIG_SYS_NONCACHED_MEMORY:
3603		Size of non-cached memory area. This area of memory will be
3604		typically located right below the malloc() area and mapped
3605		uncached in the MMU. This is useful for drivers that would
3606		otherwise require a lot of explicit cache maintenance. For
3607		some drivers it's also impossible to properly maintain the
3608		cache. For example if the regions that need to be flushed
3609		are not a multiple of the cache-line size, *and* padding
3610		cannot be allocated between the regions to align them (i.e.
3611		if the HW requires a contiguous array of regions, and the
3612		size of each region is not cache-aligned), then a flush of
3613		one region may result in overwriting data that hardware has
3614		written to another region in the same cache-line. This can
3615		happen for example in network drivers where descriptors for
3616		buffers are typically smaller than the CPU cache-line (e.g.
3617		16 bytes vs. 32 or 64 bytes).
3618
3619		Non-cached memory is only supported on 32-bit ARM at present.
3620
3621- CONFIG_SYS_BOOTM_LEN:
3622		Normally compressed uImages are limited to an
3623		uncompressed size of 8 MBytes. If this is not enough,
3624		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3625		to adjust this setting to your needs.
3626
3627- CONFIG_SYS_BOOTMAPSZ:
3628		Maximum size of memory mapped by the startup code of
3629		the Linux kernel; all data that must be processed by
3630		the Linux kernel (bd_info, boot arguments, FDT blob if
3631		used) must be put below this limit, unless "bootm_low"
3632		environment variable is defined and non-zero. In such case
3633		all data for the Linux kernel must be between "bootm_low"
3634		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3635		variable "bootm_mapsize" will override the value of
3636		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3637		then the value in "bootm_size" will be used instead.
3638
3639- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3640		Enable initrd_high functionality.  If defined then the
3641		initrd_high feature is enabled and the bootm ramdisk subcommand
3642		is enabled.
3643
3644- CONFIG_SYS_BOOT_GET_CMDLINE:
3645		Enables allocating and saving kernel cmdline in space between
3646		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3647
3648- CONFIG_SYS_BOOT_GET_KBD:
3649		Enables allocating and saving a kernel copy of the bd_info in
3650		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3651
3652- CONFIG_SYS_MAX_FLASH_BANKS:
3653		Max number of Flash memory banks
3654
3655- CONFIG_SYS_MAX_FLASH_SECT:
3656		Max number of sectors on a Flash chip
3657
3658- CONFIG_SYS_FLASH_ERASE_TOUT:
3659		Timeout for Flash erase operations (in ms)
3660
3661- CONFIG_SYS_FLASH_WRITE_TOUT:
3662		Timeout for Flash write operations (in ms)
3663
3664- CONFIG_SYS_FLASH_LOCK_TOUT
3665		Timeout for Flash set sector lock bit operation (in ms)
3666
3667- CONFIG_SYS_FLASH_UNLOCK_TOUT
3668		Timeout for Flash clear lock bits operation (in ms)
3669
3670- CONFIG_SYS_FLASH_PROTECTION
3671		If defined, hardware flash sectors protection is used
3672		instead of U-Boot software protection.
3673
3674- CONFIG_SYS_DIRECT_FLASH_TFTP:
3675
3676		Enable TFTP transfers directly to flash memory;
3677		without this option such a download has to be
3678		performed in two steps: (1) download to RAM, and (2)
3679		copy from RAM to flash.
3680
3681		The two-step approach is usually more reliable, since
3682		you can check if the download worked before you erase
3683		the flash, but in some situations (when system RAM is
3684		too limited to allow for a temporary copy of the
3685		downloaded image) this option may be very useful.
3686
3687- CONFIG_SYS_FLASH_CFI:
3688		Define if the flash driver uses extra elements in the
3689		common flash structure for storing flash geometry.
3690
3691- CONFIG_FLASH_CFI_DRIVER
3692		This option also enables the building of the cfi_flash driver
3693		in the drivers directory
3694
3695- CONFIG_FLASH_CFI_MTD
3696		This option enables the building of the cfi_mtd driver
3697		in the drivers directory. The driver exports CFI flash
3698		to the MTD layer.
3699
3700- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3701		Use buffered writes to flash.
3702
3703- CONFIG_FLASH_SPANSION_S29WS_N
3704		s29ws-n MirrorBit flash has non-standard addresses for buffered
3705		write commands.
3706
3707- CONFIG_SYS_FLASH_QUIET_TEST
3708		If this option is defined, the common CFI flash doesn't
3709		print it's warning upon not recognized FLASH banks. This
3710		is useful, if some of the configured banks are only
3711		optionally available.
3712
3713- CONFIG_FLASH_SHOW_PROGRESS
3714		If defined (must be an integer), print out countdown
3715		digits and dots.  Recommended value: 45 (9..1) for 80
3716		column displays, 15 (3..1) for 40 column displays.
3717
3718- CONFIG_FLASH_VERIFY
3719		If defined, the content of the flash (destination) is compared
3720		against the source after the write operation. An error message
3721		will be printed when the contents are not identical.
3722		Please note that this option is useless in nearly all cases,
3723		since such flash programming errors usually are detected earlier
3724		while unprotecting/erasing/programming. Please only enable
3725		this option if you really know what you are doing.
3726
3727- CONFIG_SYS_RX_ETH_BUFFER:
3728		Defines the number of Ethernet receive buffers. On some
3729		Ethernet controllers it is recommended to set this value
3730		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3731		buffers can be full shortly after enabling the interface
3732		on high Ethernet traffic.
3733		Defaults to 4 if not defined.
3734
3735- CONFIG_ENV_MAX_ENTRIES
3736
3737	Maximum number of entries in the hash table that is used
3738	internally to store the environment settings. The default
3739	setting is supposed to be generous and should work in most
3740	cases. This setting can be used to tune behaviour; see
3741	lib/hashtable.c for details.
3742
3743- CONFIG_ENV_FLAGS_LIST_DEFAULT
3744- CONFIG_ENV_FLAGS_LIST_STATIC
3745	Enable validation of the values given to environment variables when
3746	calling env set.  Variables can be restricted to only decimal,
3747	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3748	the variables can also be restricted to IP address or MAC address.
3749
3750	The format of the list is:
3751		type_attribute = [s|d|x|b|i|m]
3752		access_attribute = [a|r|o|c]
3753		attributes = type_attribute[access_attribute]
3754		entry = variable_name[:attributes]
3755		list = entry[,list]
3756
3757	The type attributes are:
3758		s - String (default)
3759		d - Decimal
3760		x - Hexadecimal
3761		b - Boolean ([1yYtT|0nNfF])
3762		i - IP address
3763		m - MAC address
3764
3765	The access attributes are:
3766		a - Any (default)
3767		r - Read-only
3768		o - Write-once
3769		c - Change-default
3770
3771	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3772		Define this to a list (string) to define the ".flags"
3773		environment variable in the default or embedded environment.
3774
3775	- CONFIG_ENV_FLAGS_LIST_STATIC
3776		Define this to a list (string) to define validation that
3777		should be done if an entry is not found in the ".flags"
3778		environment variable.  To override a setting in the static
3779		list, simply add an entry for the same variable name to the
3780		".flags" variable.
3781
3782	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3783	regular expression. This allows multiple variables to define the same
3784	flags without explicitly listing them for each variable.
3785
3786- CONFIG_ENV_ACCESS_IGNORE_FORCE
3787	If defined, don't allow the -f switch to env set override variable
3788	access flags.
3789
3790- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3791	This is set by OMAP boards for the max time that reset should
3792	be asserted. See doc/README.omap-reset-time for details on how
3793	the value can be calculated on a given board.
3794
3795- CONFIG_USE_STDINT
3796	If stdint.h is available with your toolchain you can define this
3797	option to enable it. You can provide option 'USE_STDINT=1' when
3798	building U-Boot to enable this.
3799
3800The following definitions that deal with the placement and management
3801of environment data (variable area); in general, we support the
3802following configurations:
3803
3804- CONFIG_BUILD_ENVCRC:
3805
3806	Builds up envcrc with the target environment so that external utils
3807	may easily extract it and embed it in final U-Boot images.
3808
3809- CONFIG_ENV_IS_IN_FLASH:
3810
3811	Define this if the environment is in flash memory.
3812
3813	a) The environment occupies one whole flash sector, which is
3814	   "embedded" in the text segment with the U-Boot code. This
3815	   happens usually with "bottom boot sector" or "top boot
3816	   sector" type flash chips, which have several smaller
3817	   sectors at the start or the end. For instance, such a
3818	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3819	   such a case you would place the environment in one of the
3820	   4 kB sectors - with U-Boot code before and after it. With
3821	   "top boot sector" type flash chips, you would put the
3822	   environment in one of the last sectors, leaving a gap
3823	   between U-Boot and the environment.
3824
3825	- CONFIG_ENV_OFFSET:
3826
3827	   Offset of environment data (variable area) to the
3828	   beginning of flash memory; for instance, with bottom boot
3829	   type flash chips the second sector can be used: the offset
3830	   for this sector is given here.
3831
3832	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3833
3834	- CONFIG_ENV_ADDR:
3835
3836	   This is just another way to specify the start address of
3837	   the flash sector containing the environment (instead of
3838	   CONFIG_ENV_OFFSET).
3839
3840	- CONFIG_ENV_SECT_SIZE:
3841
3842	   Size of the sector containing the environment.
3843
3844
3845	b) Sometimes flash chips have few, equal sized, BIG sectors.
3846	   In such a case you don't want to spend a whole sector for
3847	   the environment.
3848
3849	- CONFIG_ENV_SIZE:
3850
3851	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3852	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3853	   of this flash sector for the environment. This saves
3854	   memory for the RAM copy of the environment.
3855
3856	   It may also save flash memory if you decide to use this
3857	   when your environment is "embedded" within U-Boot code,
3858	   since then the remainder of the flash sector could be used
3859	   for U-Boot code. It should be pointed out that this is
3860	   STRONGLY DISCOURAGED from a robustness point of view:
3861	   updating the environment in flash makes it always
3862	   necessary to erase the WHOLE sector. If something goes
3863	   wrong before the contents has been restored from a copy in
3864	   RAM, your target system will be dead.
3865
3866	- CONFIG_ENV_ADDR_REDUND
3867	  CONFIG_ENV_SIZE_REDUND
3868
3869	   These settings describe a second storage area used to hold
3870	   a redundant copy of the environment data, so that there is
3871	   a valid backup copy in case there is a power failure during
3872	   a "saveenv" operation.
3873
3874BE CAREFUL! Any changes to the flash layout, and some changes to the
3875source code will make it necessary to adapt <board>/u-boot.lds*
3876accordingly!
3877
3878
3879- CONFIG_ENV_IS_IN_NVRAM:
3880
3881	Define this if you have some non-volatile memory device
3882	(NVRAM, battery buffered SRAM) which you want to use for the
3883	environment.
3884
3885	- CONFIG_ENV_ADDR:
3886	- CONFIG_ENV_SIZE:
3887
3888	  These two #defines are used to determine the memory area you
3889	  want to use for environment. It is assumed that this memory
3890	  can just be read and written to, without any special
3891	  provision.
3892
3893BE CAREFUL! The first access to the environment happens quite early
3894in U-Boot initialization (when we try to get the setting of for the
3895console baudrate). You *MUST* have mapped your NVRAM area then, or
3896U-Boot will hang.
3897
3898Please note that even with NVRAM we still use a copy of the
3899environment in RAM: we could work on NVRAM directly, but we want to
3900keep settings there always unmodified except somebody uses "saveenv"
3901to save the current settings.
3902
3903
3904- CONFIG_ENV_IS_IN_EEPROM:
3905
3906	Use this if you have an EEPROM or similar serial access
3907	device and a driver for it.
3908
3909	- CONFIG_ENV_OFFSET:
3910	- CONFIG_ENV_SIZE:
3911
3912	  These two #defines specify the offset and size of the
3913	  environment area within the total memory of your EEPROM.
3914
3915	- CONFIG_SYS_I2C_EEPROM_ADDR:
3916	  If defined, specified the chip address of the EEPROM device.
3917	  The default address is zero.
3918
3919	- CONFIG_SYS_I2C_EEPROM_BUS:
3920	  If defined, specified the i2c bus of the EEPROM device.
3921
3922	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3923	  If defined, the number of bits used to address bytes in a
3924	  single page in the EEPROM device.  A 64 byte page, for example
3925	  would require six bits.
3926
3927	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3928	  If defined, the number of milliseconds to delay between
3929	  page writes.	The default is zero milliseconds.
3930
3931	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3932	  The length in bytes of the EEPROM memory array address.  Note
3933	  that this is NOT the chip address length!
3934
3935	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3936	  EEPROM chips that implement "address overflow" are ones
3937	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3938	  address and the extra bits end up in the "chip address" bit
3939	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3940	  byte chips.
3941
3942	  Note that we consider the length of the address field to
3943	  still be one byte because the extra address bits are hidden
3944	  in the chip address.
3945
3946	- CONFIG_SYS_EEPROM_SIZE:
3947	  The size in bytes of the EEPROM device.
3948
3949	- CONFIG_ENV_EEPROM_IS_ON_I2C
3950	  define this, if you have I2C and SPI activated, and your
3951	  EEPROM, which holds the environment, is on the I2C bus.
3952
3953	- CONFIG_I2C_ENV_EEPROM_BUS
3954	  if you have an Environment on an EEPROM reached over
3955	  I2C muxes, you can define here, how to reach this
3956	  EEPROM. For example:
3957
3958	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3959
3960	  EEPROM which holds the environment, is reached over
3961	  a pca9547 i2c mux with address 0x70, channel 3.
3962
3963- CONFIG_ENV_IS_IN_DATAFLASH:
3964
3965	Define this if you have a DataFlash memory device which you
3966	want to use for the environment.
3967
3968	- CONFIG_ENV_OFFSET:
3969	- CONFIG_ENV_ADDR:
3970	- CONFIG_ENV_SIZE:
3971
3972	  These three #defines specify the offset and size of the
3973	  environment area within the total memory of your DataFlash placed
3974	  at the specified address.
3975
3976- CONFIG_ENV_IS_IN_SPI_FLASH:
3977
3978	Define this if you have a SPI Flash memory device which you
3979	want to use for the environment.
3980
3981	- CONFIG_ENV_OFFSET:
3982	- CONFIG_ENV_SIZE:
3983
3984	  These two #defines specify the offset and size of the
3985	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
3986	  aligned to an erase sector boundary.
3987
3988	- CONFIG_ENV_SECT_SIZE:
3989
3990	  Define the SPI flash's sector size.
3991
3992	- CONFIG_ENV_OFFSET_REDUND (optional):
3993
3994	  This setting describes a second storage area of CONFIG_ENV_SIZE
3995	  size used to hold a redundant copy of the environment data, so
3996	  that there is a valid backup copy in case there is a power failure
3997	  during a "saveenv" operation. CONFIG_ENV_OFFSET_REDUND must be
3998	  aligned to an erase sector boundary.
3999
4000	- CONFIG_ENV_SPI_BUS (optional):
4001	- CONFIG_ENV_SPI_CS (optional):
4002
4003	  Define the SPI bus and chip select. If not defined they will be 0.
4004
4005	- CONFIG_ENV_SPI_MAX_HZ (optional):
4006
4007	  Define the SPI max work clock. If not defined then use 1MHz.
4008
4009	- CONFIG_ENV_SPI_MODE (optional):
4010
4011	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4012
4013- CONFIG_ENV_IS_IN_REMOTE:
4014
4015	Define this if you have a remote memory space which you
4016	want to use for the local device's environment.
4017
4018	- CONFIG_ENV_ADDR:
4019	- CONFIG_ENV_SIZE:
4020
4021	  These two #defines specify the address and size of the
4022	  environment area within the remote memory space. The
4023	  local device can get the environment from remote memory
4024	  space by SRIO or PCIE links.
4025
4026BE CAREFUL! For some special cases, the local device can not use
4027"saveenv" command. For example, the local device will get the
4028environment stored in a remote NOR flash by SRIO or PCIE link,
4029but it can not erase, write this NOR flash by SRIO or PCIE interface.
4030
4031- CONFIG_ENV_IS_IN_NAND:
4032
4033	Define this if you have a NAND device which you want to use
4034	for the environment.
4035
4036	- CONFIG_ENV_OFFSET:
4037	- CONFIG_ENV_SIZE:
4038
4039	  These two #defines specify the offset and size of the environment
4040	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4041	  aligned to an erase block boundary.
4042
4043	- CONFIG_ENV_OFFSET_REDUND (optional):
4044
4045	  This setting describes a second storage area of CONFIG_ENV_SIZE
4046	  size used to hold a redundant copy of the environment data, so
4047	  that there is a valid backup copy in case there is a power failure
4048	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_REDUND must be
4049	  aligned to an erase block boundary.
4050
4051	- CONFIG_ENV_RANGE (optional):
4052
4053	  Specifies the length of the region in which the environment
4054	  can be written.  This should be a multiple of the NAND device's
4055	  block size.  Specifying a range with more erase blocks than
4056	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4057	  the range to be avoided.
4058
4059	- CONFIG_ENV_OFFSET_OOB (optional):
4060
4061	  Enables support for dynamically retrieving the offset of the
4062	  environment from block zero's out-of-band data.  The
4063	  "nand env.oob" command can be used to record this offset.
4064	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4065	  using CONFIG_ENV_OFFSET_OOB.
4066
4067- CONFIG_NAND_ENV_DST
4068
4069	Defines address in RAM to which the nand_spl code should copy the
4070	environment. If redundant environment is used, it will be copied to
4071	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4072
4073- CONFIG_ENV_IS_IN_UBI:
4074
4075	Define this if you have an UBI volume that you want to use for the
4076	environment.  This has the benefit of wear-leveling the environment
4077	accesses, which is important on NAND.
4078
4079	- CONFIG_ENV_UBI_PART:
4080
4081	  Define this to a string that is the mtd partition containing the UBI.
4082
4083	- CONFIG_ENV_UBI_VOLUME:
4084
4085	  Define this to the name of the volume that you want to store the
4086	  environment in.
4087
4088	- CONFIG_ENV_UBI_VOLUME_REDUND:
4089
4090	  Define this to the name of another volume to store a second copy of
4091	  the environment in.  This will enable redundant environments in UBI.
4092	  It is assumed that both volumes are in the same MTD partition.
4093
4094	- CONFIG_UBI_SILENCE_MSG
4095	- CONFIG_UBIFS_SILENCE_MSG
4096
4097	  You will probably want to define these to avoid a really noisy system
4098	  when storing the env in UBI.
4099
4100- CONFIG_ENV_IS_IN_FAT:
4101       Define this if you want to use the FAT file system for the environment.
4102
4103       - FAT_ENV_INTERFACE:
4104
4105         Define this to a string that is the name of the block device.
4106
4107       - FAT_ENV_DEVICE_AND_PART:
4108
4109         Define this to a string to specify the partition of the device. It can
4110         be as following:
4111
4112           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4113               - "D:P": device D partition P. Error occurs if device D has no
4114                        partition table.
4115               - "D:0": device D.
4116               - "D" or "D:": device D partition 1 if device D has partition
4117                              table, or the whole device D if has no partition
4118                              table.
4119               - "D:auto": first partition in device D with bootable flag set.
4120                           If none, first valid partition in device D. If no
4121                           partition table then means device D.
4122
4123       - FAT_ENV_FILE:
4124
4125         It's a string of the FAT file name. This file use to store the
4126         environment.
4127
4128       - CONFIG_FAT_WRITE:
4129         This should be defined. Otherwise it cannot save the environment file.
4130
4131- CONFIG_ENV_IS_IN_MMC:
4132
4133	Define this if you have an MMC device which you want to use for the
4134	environment.
4135
4136	- CONFIG_SYS_MMC_ENV_DEV:
4137
4138	  Specifies which MMC device the environment is stored in.
4139
4140	- CONFIG_SYS_MMC_ENV_PART (optional):
4141
4142	  Specifies which MMC partition the environment is stored in. If not
4143	  set, defaults to partition 0, the user area. Common values might be
4144	  1 (first MMC boot partition), 2 (second MMC boot partition).
4145
4146	- CONFIG_ENV_OFFSET:
4147	- CONFIG_ENV_SIZE:
4148
4149	  These two #defines specify the offset and size of the environment
4150	  area within the specified MMC device.
4151
4152	  If offset is positive (the usual case), it is treated as relative to
4153	  the start of the MMC partition. If offset is negative, it is treated
4154	  as relative to the end of the MMC partition. This can be useful if
4155	  your board may be fitted with different MMC devices, which have
4156	  different sizes for the MMC partitions, and you always want the
4157	  environment placed at the very end of the partition, to leave the
4158	  maximum possible space before it, to store other data.
4159
4160	  These two values are in units of bytes, but must be aligned to an
4161	  MMC sector boundary.
4162
4163	- CONFIG_ENV_OFFSET_REDUND (optional):
4164
4165	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4166	  hold a redundant copy of the environment data. This provides a
4167	  valid backup copy in case the other copy is corrupted, e.g. due
4168	  to a power failure during a "saveenv" operation.
4169
4170	  This value may also be positive or negative; this is handled in the
4171	  same way as CONFIG_ENV_OFFSET.
4172
4173	  This value is also in units of bytes, but must also be aligned to
4174	  an MMC sector boundary.
4175
4176	- CONFIG_ENV_SIZE_REDUND (optional):
4177
4178	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4179	  set. If this value is set, it must be set to the same value as
4180	  CONFIG_ENV_SIZE.
4181
4182- CONFIG_SYS_SPI_INIT_OFFSET
4183
4184	Defines offset to the initial SPI buffer area in DPRAM. The
4185	area is used at an early stage (ROM part) if the environment
4186	is configured to reside in the SPI EEPROM: We need a 520 byte
4187	scratch DPRAM area. It is used between the two initialization
4188	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4189	to be a good choice since it makes it far enough from the
4190	start of the data area as well as from the stack pointer.
4191
4192Please note that the environment is read-only until the monitor
4193has been relocated to RAM and a RAM copy of the environment has been
4194created; also, when using EEPROM you will have to use getenv_f()
4195until then to read environment variables.
4196
4197The environment is protected by a CRC32 checksum. Before the monitor
4198is relocated into RAM, as a result of a bad CRC you will be working
4199with the compiled-in default environment - *silently*!!! [This is
4200necessary, because the first environment variable we need is the
4201"baudrate" setting for the console - if we have a bad CRC, we don't
4202have any device yet where we could complain.]
4203
4204Note: once the monitor has been relocated, then it will complain if
4205the default environment is used; a new CRC is computed as soon as you
4206use the "saveenv" command to store a valid environment.
4207
4208- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4209		Echo the inverted Ethernet link state to the fault LED.
4210
4211		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4212		      also needs to be defined.
4213
4214- CONFIG_SYS_FAULT_MII_ADDR:
4215		MII address of the PHY to check for the Ethernet link state.
4216
4217- CONFIG_NS16550_MIN_FUNCTIONS:
4218		Define this if you desire to only have use of the NS16550_init
4219		and NS16550_putc functions for the serial driver located at
4220		drivers/serial/ns16550.c.  This option is useful for saving
4221		space for already greatly restricted images, including but not
4222		limited to NAND_SPL configurations.
4223
4224- CONFIG_DISPLAY_BOARDINFO
4225		Display information about the board that U-Boot is running on
4226		when U-Boot starts up. The board function checkboard() is called
4227		to do this.
4228
4229- CONFIG_DISPLAY_BOARDINFO_LATE
4230		Similar to the previous option, but display this information
4231		later, once stdio is running and output goes to the LCD, if
4232		present.
4233
4234- CONFIG_BOARD_SIZE_LIMIT:
4235		Maximum size of the U-Boot image. When defined, the
4236		build system checks that the actual size does not
4237		exceed it.
4238
4239Low Level (hardware related) configuration options:
4240---------------------------------------------------
4241
4242- CONFIG_SYS_CACHELINE_SIZE:
4243		Cache Line Size of the CPU.
4244
4245- CONFIG_SYS_DEFAULT_IMMR:
4246		Default address of the IMMR after system reset.
4247
4248		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4249		and RPXsuper) to be able to adjust the position of
4250		the IMMR register after a reset.
4251
4252- CONFIG_SYS_CCSRBAR_DEFAULT:
4253		Default (power-on reset) physical address of CCSR on Freescale
4254		PowerPC SOCs.
4255
4256- CONFIG_SYS_CCSRBAR:
4257		Virtual address of CCSR.  On a 32-bit build, this is typically
4258		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4259
4260		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4261		for cross-platform code that uses that macro instead.
4262
4263- CONFIG_SYS_CCSRBAR_PHYS:
4264		Physical address of CCSR.  CCSR can be relocated to a new
4265		physical address, if desired.  In this case, this macro should
4266		be set to that address.	 Otherwise, it should be set to the
4267		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4268		is typically relocated on 36-bit builds.  It is recommended
4269		that this macro be defined via the _HIGH and _LOW macros:
4270
4271		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4272			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4273
4274- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4275		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4276		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4277		used in assembly code, so it must not contain typecasts or
4278		integer size suffixes (e.g. "ULL").
4279
4280- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4281		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4282		used in assembly code, so it must not contain typecasts or
4283		integer size suffixes (e.g. "ULL").
4284
4285- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4286		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4287		forced to a value that ensures that CCSR is not relocated.
4288
4289- Floppy Disk Support:
4290		CONFIG_SYS_FDC_DRIVE_NUMBER
4291
4292		the default drive number (default value 0)
4293
4294		CONFIG_SYS_ISA_IO_STRIDE
4295
4296		defines the spacing between FDC chipset registers
4297		(default value 1)
4298
4299		CONFIG_SYS_ISA_IO_OFFSET
4300
4301		defines the offset of register from address. It
4302		depends on which part of the data bus is connected to
4303		the FDC chipset. (default value 0)
4304
4305		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4306		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4307		default value.
4308
4309		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4310		fdc_hw_init() is called at the beginning of the FDC
4311		setup. fdc_hw_init() must be provided by the board
4312		source code. It is used to make hardware-dependent
4313		initializations.
4314
4315- CONFIG_IDE_AHB:
4316		Most IDE controllers were designed to be connected with PCI
4317		interface. Only few of them were designed for AHB interface.
4318		When software is doing ATA command and data transfer to
4319		IDE devices through IDE-AHB controller, some additional
4320		registers accessing to these kind of IDE-AHB controller
4321		is required.
4322
4323- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4324		DO NOT CHANGE unless you know exactly what you're
4325		doing! (11-4) [MPC8xx/82xx systems only]
4326
4327- CONFIG_SYS_INIT_RAM_ADDR:
4328
4329		Start address of memory area that can be used for
4330		initial data and stack; please note that this must be
4331		writable memory that is working WITHOUT special
4332		initialization, i. e. you CANNOT use normal RAM which
4333		will become available only after programming the
4334		memory controller and running certain initialization
4335		sequences.
4336
4337		U-Boot uses the following memory types:
4338		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4339		- MPC824X: data cache
4340		- PPC4xx:  data cache
4341
4342- CONFIG_SYS_GBL_DATA_OFFSET:
4343
4344		Offset of the initial data structure in the memory
4345		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4346		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4347		data is located at the end of the available space
4348		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4349		GENERATED_GBL_DATA_SIZE), and the initial stack is just
4350		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4351		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4352
4353	Note:
4354		On the MPC824X (or other systems that use the data
4355		cache for initial memory) the address chosen for
4356		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4357		point to an otherwise UNUSED address space between
4358		the top of RAM and the start of the PCI space.
4359
4360- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4361
4362- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4363
4364- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4365
4366- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4367
4368- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4369
4370- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4371
4372- CONFIG_SYS_OR_TIMING_SDRAM:
4373		SDRAM timing
4374
4375- CONFIG_SYS_MAMR_PTA:
4376		periodic timer for refresh
4377
4378- CONFIG_SYS_DER:	Debug Event Register (37-47)
4379
4380- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4381  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4382  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4383  CONFIG_SYS_BR1_PRELIM:
4384		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4385
4386- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4387  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4388  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4389		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4390
4391- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4392  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4393		Machine Mode Register and Memory Periodic Timer
4394		Prescaler definitions (SDRAM timing)
4395
4396- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4397		enable I2C microcode relocation patch (MPC8xx);
4398		define relocation offset in DPRAM [DSP2]
4399
4400- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4401		enable SMC microcode relocation patch (MPC8xx);
4402		define relocation offset in DPRAM [SMC1]
4403
4404- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4405		enable SPI microcode relocation patch (MPC8xx);
4406		define relocation offset in DPRAM [SCC4]
4407
4408- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4409		Offset of the bootmode word in DPRAM used by post
4410		(Power On Self Tests). This definition overrides
4411		#define'd default value in commproc.h resp.
4412		cpm_8260.h.
4413
4414- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4415  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4416  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4417  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4418  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4419  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4420  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4421  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4422		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4423
4424- CONFIG_PCI_DISABLE_PCIE:
4425		Disable PCI-Express on systems where it is supported but not
4426		required.
4427
4428- CONFIG_PCI_ENUM_ONLY
4429		Only scan through and get the devices on the buses.
4430		Don't do any setup work, presumably because someone or
4431		something has already done it, and we don't need to do it
4432		a second time.	Useful for platforms that are pre-booted
4433		by coreboot or similar.
4434
4435- CONFIG_PCI_INDIRECT_BRIDGE:
4436		Enable support for indirect PCI bridges.
4437
4438- CONFIG_SYS_SRIO:
4439		Chip has SRIO or not
4440
4441- CONFIG_SRIO1:
4442		Board has SRIO 1 port available
4443
4444- CONFIG_SRIO2:
4445		Board has SRIO 2 port available
4446
4447- CONFIG_SRIO_PCIE_BOOT_MASTER
4448		Board can support master function for Boot from SRIO and PCIE
4449
4450- CONFIG_SYS_SRIOn_MEM_VIRT:
4451		Virtual Address of SRIO port 'n' memory region
4452
4453- CONFIG_SYS_SRIOn_MEM_PHYS:
4454		Physical Address of SRIO port 'n' memory region
4455
4456- CONFIG_SYS_SRIOn_MEM_SIZE:
4457		Size of SRIO port 'n' memory region
4458
4459- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4460		Defined to tell the NAND controller that the NAND chip is using
4461		a 16 bit bus.
4462		Not all NAND drivers use this symbol.
4463		Example of drivers that use it:
4464		- drivers/mtd/nand/ndfc.c
4465		- drivers/mtd/nand/mxc_nand.c
4466
4467- CONFIG_SYS_NDFC_EBC0_CFG
4468		Sets the EBC0_CFG register for the NDFC. If not defined
4469		a default value will be used.
4470
4471- CONFIG_SPD_EEPROM
4472		Get DDR timing information from an I2C EEPROM. Common
4473		with pluggable memory modules such as SODIMMs
4474
4475  SPD_EEPROM_ADDRESS
4476		I2C address of the SPD EEPROM
4477
4478- CONFIG_SYS_SPD_BUS_NUM
4479		If SPD EEPROM is on an I2C bus other than the first
4480		one, specify here. Note that the value must resolve
4481		to something your driver can deal with.
4482
4483- CONFIG_SYS_DDR_RAW_TIMING
4484		Get DDR timing information from other than SPD. Common with
4485		soldered DDR chips onboard without SPD. DDR raw timing
4486		parameters are extracted from datasheet and hard-coded into
4487		header files or board specific files.
4488
4489- CONFIG_FSL_DDR_INTERACTIVE
4490		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4491
4492- CONFIG_FSL_DDR_SYNC_REFRESH
4493		Enable sync of refresh for multiple controllers.
4494
4495- CONFIG_FSL_DDR_BIST
4496		Enable built-in memory test for Freescale DDR controllers.
4497
4498- CONFIG_SYS_83XX_DDR_USES_CS0
4499		Only for 83xx systems. If specified, then DDR should
4500		be configured using CS0 and CS1 instead of CS2 and CS3.
4501
4502- CONFIG_ETHER_ON_FEC[12]
4503		Define to enable FEC[12] on a 8xx series processor.
4504
4505- CONFIG_FEC[12]_PHY
4506		Define to the hardcoded PHY address which corresponds
4507		to the given FEC; i. e.
4508			#define CONFIG_FEC1_PHY 4
4509		means that the PHY with address 4 is connected to FEC1
4510
4511		When set to -1, means to probe for first available.
4512
4513- CONFIG_FEC[12]_PHY_NORXERR
4514		The PHY does not have a RXERR line (RMII only).
4515		(so program the FEC to ignore it).
4516
4517- CONFIG_RMII
4518		Enable RMII mode for all FECs.
4519		Note that this is a global option, we can't
4520		have one FEC in standard MII mode and another in RMII mode.
4521
4522- CONFIG_CRC32_VERIFY
4523		Add a verify option to the crc32 command.
4524		The syntax is:
4525
4526		=> crc32 -v <address> <count> <crc32>
4527
4528		Where address/count indicate a memory area
4529		and crc32 is the correct crc32 which the
4530		area should have.
4531
4532- CONFIG_LOOPW
4533		Add the "loopw" memory command. This only takes effect if
4534		the memory commands are activated globally (CONFIG_CMD_MEM).
4535
4536- CONFIG_MX_CYCLIC
4537		Add the "mdc" and "mwc" memory commands. These are cyclic
4538		"md/mw" commands.
4539		Examples:
4540
4541		=> mdc.b 10 4 500
4542		This command will print 4 bytes (10,11,12,13) each 500 ms.
4543
4544		=> mwc.l 100 12345678 10
4545		This command will write 12345678 to address 100 all 10 ms.
4546
4547		This only takes effect if the memory commands are activated
4548		globally (CONFIG_CMD_MEM).
4549
4550- CONFIG_SKIP_LOWLEVEL_INIT
4551		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4552		low level initializations (like setting up the memory
4553		controller) are omitted and/or U-Boot does not
4554		relocate itself into RAM.
4555
4556		Normally this variable MUST NOT be defined. The only
4557		exception is when U-Boot is loaded (to RAM) by some
4558		other boot loader or by a debugger which performs
4559		these initializations itself.
4560
4561- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
4562		[ARM926EJ-S only] This allows just the call to lowlevel_init()
4563		to be skipped. The normal CP15 init (such as enabling the
4564		instruction cache) is still performed.
4565
4566- CONFIG_SPL_BUILD
4567		Modifies the behaviour of start.S when compiling a loader
4568		that is executed before the actual U-Boot. E.g. when
4569		compiling a NAND SPL.
4570
4571- CONFIG_TPL_BUILD
4572		Modifies the behaviour of start.S  when compiling a loader
4573		that is executed after the SPL and before the actual U-Boot.
4574		It is loaded by the SPL.
4575
4576- CONFIG_SYS_MPC85XX_NO_RESETVEC
4577		Only for 85xx systems. If this variable is specified, the section
4578		.resetvec is not kept and the section .bootpg is placed in the
4579		previous 4k of the .text section.
4580
4581- CONFIG_ARCH_MAP_SYSMEM
4582		Generally U-Boot (and in particular the md command) uses
4583		effective address. It is therefore not necessary to regard
4584		U-Boot address as virtual addresses that need to be translated
4585		to physical addresses. However, sandbox requires this, since
4586		it maintains its own little RAM buffer which contains all
4587		addressable memory. This option causes some memory accesses
4588		to be mapped through map_sysmem() / unmap_sysmem().
4589
4590- CONFIG_X86_RESET_VECTOR
4591		If defined, the x86 reset vector code is included. This is not
4592		needed when U-Boot is running from Coreboot.
4593
4594- CONFIG_SYS_MPUCLK
4595		Defines the MPU clock speed (in MHz).
4596
4597		NOTE : currently only supported on AM335x platforms.
4598
4599- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4600		Enables the RTC32K OSC on AM33xx based plattforms
4601
4602- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4603		Option to disable subpage write in NAND driver
4604		driver that uses this:
4605		drivers/mtd/nand/davinci_nand.c
4606
4607Freescale QE/FMAN Firmware Support:
4608-----------------------------------
4609
4610The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4611loading of "firmware", which is encoded in the QE firmware binary format.
4612This firmware often needs to be loaded during U-Boot booting, so macros
4613are used to identify the storage device (NOR flash, SPI, etc) and the address
4614within that device.
4615
4616- CONFIG_SYS_FMAN_FW_ADDR
4617	The address in the storage device where the FMAN microcode is located.  The
4618	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4619	is also specified.
4620
4621- CONFIG_SYS_QE_FW_ADDR
4622	The address in the storage device where the QE microcode is located.  The
4623	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4624	is also specified.
4625
4626- CONFIG_SYS_QE_FMAN_FW_LENGTH
4627	The maximum possible size of the firmware.  The firmware binary format
4628	has a field that specifies the actual size of the firmware, but it
4629	might not be possible to read any part of the firmware unless some
4630	local storage is allocated to hold the entire firmware first.
4631
4632- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4633	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4634	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4635	virtual address in NOR flash.
4636
4637- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4638	Specifies that QE/FMAN firmware is located in NAND flash.
4639	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4640
4641- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4642	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4643	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4644
4645- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4646	Specifies that QE/FMAN firmware is located in the remote (master)
4647	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4648	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4649	window->master inbound window->master LAW->the ucode address in
4650	master's memory space.
4651
4652Freescale Layerscape Management Complex Firmware Support:
4653---------------------------------------------------------
4654The Freescale Layerscape Management Complex (MC) supports the loading of
4655"firmware".
4656This firmware often needs to be loaded during U-Boot booting, so macros
4657are used to identify the storage device (NOR flash, SPI, etc) and the address
4658within that device.
4659
4660- CONFIG_FSL_MC_ENET
4661	Enable the MC driver for Layerscape SoCs.
4662
4663Freescale Layerscape Debug Server Support:
4664-------------------------------------------
4665The Freescale Layerscape Debug Server Support supports the loading of
4666"Debug Server firmware" and triggering SP boot-rom.
4667This firmware often needs to be loaded during U-Boot booting.
4668
4669- CONFIG_SYS_MC_RSV_MEM_ALIGN
4670	Define alignment of reserved memory MC requires
4671
4672Reproducible builds
4673-------------------
4674
4675In order to achieve reproducible builds, timestamps used in the U-Boot build
4676process have to be set to a fixed value.
4677
4678This is done using the SOURCE_DATE_EPOCH environment variable.
4679SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
4680option for U-Boot or an environment variable in U-Boot.
4681
4682SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
4683
4684Building the Software:
4685======================
4686
4687Building U-Boot has been tested in several native build environments
4688and in many different cross environments. Of course we cannot support
4689all possibly existing versions of cross development tools in all
4690(potentially obsolete) versions. In case of tool chain problems we
4691recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4692which is extensively used to build and test U-Boot.
4693
4694If you are not using a native environment, it is assumed that you
4695have GNU cross compiling tools available in your path. In this case,
4696you must set the environment variable CROSS_COMPILE in your shell.
4697Note that no changes to the Makefile or any other source files are
4698necessary. For example using the ELDK on a 4xx CPU, please enter:
4699
4700	$ CROSS_COMPILE=ppc_4xx-
4701	$ export CROSS_COMPILE
4702
4703Note: If you wish to generate Windows versions of the utilities in
4704      the tools directory you can use the MinGW toolchain
4705      (http://www.mingw.org).  Set your HOST tools to the MinGW
4706      toolchain and execute 'make tools'.  For example:
4707
4708       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4709
4710      Binaries such as tools/mkimage.exe will be created which can
4711      be executed on computers running Windows.
4712
4713U-Boot is intended to be simple to build. After installing the
4714sources you must configure U-Boot for one specific board type. This
4715is done by typing:
4716
4717	make NAME_defconfig
4718
4719where "NAME_defconfig" is the name of one of the existing configu-
4720rations; see boards.cfg for supported names.
4721
4722Note: for some board special configuration names may exist; check if
4723      additional information is available from the board vendor; for
4724      instance, the TQM823L systems are available without (standard)
4725      or with LCD support. You can select such additional "features"
4726      when choosing the configuration, i. e.
4727
4728      make TQM823L_defconfig
4729	- will configure for a plain TQM823L, i. e. no LCD support
4730
4731      make TQM823L_LCD_defconfig
4732	- will configure for a TQM823L with U-Boot console on LCD
4733
4734      etc.
4735
4736
4737Finally, type "make all", and you should get some working U-Boot
4738images ready for download to / installation on your system:
4739
4740- "u-boot.bin" is a raw binary image
4741- "u-boot" is an image in ELF binary format
4742- "u-boot.srec" is in Motorola S-Record format
4743
4744By default the build is performed locally and the objects are saved
4745in the source directory. One of the two methods can be used to change
4746this behavior and build U-Boot to some external directory:
4747
47481. Add O= to the make command line invocations:
4749
4750	make O=/tmp/build distclean
4751	make O=/tmp/build NAME_defconfig
4752	make O=/tmp/build all
4753
47542. Set environment variable KBUILD_OUTPUT to point to the desired location:
4755
4756	export KBUILD_OUTPUT=/tmp/build
4757	make distclean
4758	make NAME_defconfig
4759	make all
4760
4761Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
4762variable.
4763
4764
4765Please be aware that the Makefiles assume you are using GNU make, so
4766for instance on NetBSD you might need to use "gmake" instead of
4767native "make".
4768
4769
4770If the system board that you have is not listed, then you will need
4771to port U-Boot to your hardware platform. To do this, follow these
4772steps:
4773
47741.  Create a new directory to hold your board specific code. Add any
4775    files you need. In your board directory, you will need at least
4776    the "Makefile" and a "<board>.c".
47772.  Create a new configuration file "include/configs/<board>.h" for
4778    your board.
47793.  If you're porting U-Boot to a new CPU, then also create a new
4780    directory to hold your CPU specific code. Add any files you need.
47814.  Run "make <board>_defconfig" with your new name.
47825.  Type "make", and you should get a working "u-boot.srec" file
4783    to be installed on your target system.
47846.  Debug and solve any problems that might arise.
4785    [Of course, this last step is much harder than it sounds.]
4786
4787
4788Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4789==============================================================
4790
4791If you have modified U-Boot sources (for instance added a new board
4792or support for new devices, a new CPU, etc.) you are expected to
4793provide feedback to the other developers. The feedback normally takes
4794the form of a "patch", i. e. a context diff against a certain (latest
4795official or latest in the git repository) version of U-Boot sources.
4796
4797But before you submit such a patch, please verify that your modifi-
4798cation did not break existing code. At least make sure that *ALL* of
4799the supported boards compile WITHOUT ANY compiler warnings. To do so,
4800just run the buildman script (tools/buildman/buildman), which will
4801configure and build U-Boot for ALL supported system. Be warned, this
4802will take a while. Please see the buildman README, or run 'buildman -H'
4803for documentation.
4804
4805
4806See also "U-Boot Porting Guide" below.
4807
4808
4809Monitor Commands - Overview:
4810============================
4811
4812go	- start application at address 'addr'
4813run	- run commands in an environment variable
4814bootm	- boot application image from memory
4815bootp	- boot image via network using BootP/TFTP protocol
4816bootz   - boot zImage from memory
4817tftpboot- boot image via network using TFTP protocol
4818	       and env variables "ipaddr" and "serverip"
4819	       (and eventually "gatewayip")
4820tftpput - upload a file via network using TFTP protocol
4821rarpboot- boot image via network using RARP/TFTP protocol
4822diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4823loads	- load S-Record file over serial line
4824loadb	- load binary file over serial line (kermit mode)
4825md	- memory display
4826mm	- memory modify (auto-incrementing)
4827nm	- memory modify (constant address)
4828mw	- memory write (fill)
4829cp	- memory copy
4830cmp	- memory compare
4831crc32	- checksum calculation
4832i2c	- I2C sub-system
4833sspi	- SPI utility commands
4834base	- print or set address offset
4835printenv- print environment variables
4836setenv	- set environment variables
4837saveenv - save environment variables to persistent storage
4838protect - enable or disable FLASH write protection
4839erase	- erase FLASH memory
4840flinfo	- print FLASH memory information
4841nand	- NAND memory operations (see doc/README.nand)
4842bdinfo	- print Board Info structure
4843iminfo	- print header information for application image
4844coninfo - print console devices and informations
4845ide	- IDE sub-system
4846loop	- infinite loop on address range
4847loopw	- infinite write loop on address range
4848mtest	- simple RAM test
4849icache	- enable or disable instruction cache
4850dcache	- enable or disable data cache
4851reset	- Perform RESET of the CPU
4852echo	- echo args to console
4853version - print monitor version
4854help	- print online help
4855?	- alias for 'help'
4856
4857
4858Monitor Commands - Detailed Description:
4859========================================
4860
4861TODO.
4862
4863For now: just type "help <command>".
4864
4865
4866Environment Variables:
4867======================
4868
4869U-Boot supports user configuration using Environment Variables which
4870can be made persistent by saving to Flash memory.
4871
4872Environment Variables are set using "setenv", printed using
4873"printenv", and saved to Flash using "saveenv". Using "setenv"
4874without a value can be used to delete a variable from the
4875environment. As long as you don't save the environment you are
4876working with an in-memory copy. In case the Flash area containing the
4877environment is erased by accident, a default environment is provided.
4878
4879Some configuration options can be set using Environment Variables.
4880
4881List of environment variables (most likely not complete):
4882
4883  baudrate	- see CONFIG_BAUDRATE
4884
4885  bootdelay	- see CONFIG_BOOTDELAY
4886
4887  bootcmd	- see CONFIG_BOOTCOMMAND
4888
4889  bootargs	- Boot arguments when booting an RTOS image
4890
4891  bootfile	- Name of the image to load with TFTP
4892
4893  bootm_low	- Memory range available for image processing in the bootm
4894		  command can be restricted. This variable is given as
4895		  a hexadecimal number and defines lowest address allowed
4896		  for use by the bootm command. See also "bootm_size"
4897		  environment variable. Address defined by "bootm_low" is
4898		  also the base of the initial memory mapping for the Linux
4899		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4900		  bootm_mapsize.
4901
4902  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4903		  This variable is given as a hexadecimal number and it
4904		  defines the size of the memory region starting at base
4905		  address bootm_low that is accessible by the Linux kernel
4906		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4907		  as the default value if it is defined, and bootm_size is
4908		  used otherwise.
4909
4910  bootm_size	- Memory range available for image processing in the bootm
4911		  command can be restricted. This variable is given as
4912		  a hexadecimal number and defines the size of the region
4913		  allowed for use by the bootm command. See also "bootm_low"
4914		  environment variable.
4915
4916  updatefile	- Location of the software update file on a TFTP server, used
4917		  by the automatic software update feature. Please refer to
4918		  documentation in doc/README.update for more details.
4919
4920  autoload	- if set to "no" (any string beginning with 'n'),
4921		  "bootp" will just load perform a lookup of the
4922		  configuration from the BOOTP server, but not try to
4923		  load any image using TFTP
4924
4925  autostart	- if set to "yes", an image loaded using the "bootp",
4926		  "rarpboot", "tftpboot" or "diskboot" commands will
4927		  be automatically started (by internally calling
4928		  "bootm")
4929
4930		  If set to "no", a standalone image passed to the
4931		  "bootm" command will be copied to the load address
4932		  (and eventually uncompressed), but NOT be started.
4933		  This can be used to load and uncompress arbitrary
4934		  data.
4935
4936  fdt_high	- if set this restricts the maximum address that the
4937		  flattened device tree will be copied into upon boot.
4938		  For example, if you have a system with 1 GB memory
4939		  at physical address 0x10000000, while Linux kernel
4940		  only recognizes the first 704 MB as low memory, you
4941		  may need to set fdt_high as 0x3C000000 to have the
4942		  device tree blob be copied to the maximum address
4943		  of the 704 MB low memory, so that Linux kernel can
4944		  access it during the boot procedure.
4945
4946		  If this is set to the special value 0xFFFFFFFF then
4947		  the fdt will not be copied at all on boot.  For this
4948		  to work it must reside in writable memory, have
4949		  sufficient padding on the end of it for u-boot to
4950		  add the information it needs into it, and the memory
4951		  must be accessible by the kernel.
4952
4953  fdtcontroladdr- if set this is the address of the control flattened
4954		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4955		  defined.
4956
4957  i2cfast	- (PPC405GP|PPC405EP only)
4958		  if set to 'y' configures Linux I2C driver for fast
4959		  mode (400kHZ). This environment variable is used in
4960		  initialization code. So, for changes to be effective
4961		  it must be saved and board must be reset.
4962
4963  initrd_high	- restrict positioning of initrd images:
4964		  If this variable is not set, initrd images will be
4965		  copied to the highest possible address in RAM; this
4966		  is usually what you want since it allows for
4967		  maximum initrd size. If for some reason you want to
4968		  make sure that the initrd image is loaded below the
4969		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4970		  variable to a value of "no" or "off" or "0".
4971		  Alternatively, you can set it to a maximum upper
4972		  address to use (U-Boot will still check that it
4973		  does not overwrite the U-Boot stack and data).
4974
4975		  For instance, when you have a system with 16 MB
4976		  RAM, and want to reserve 4 MB from use by Linux,
4977		  you can do this by adding "mem=12M" to the value of
4978		  the "bootargs" variable. However, now you must make
4979		  sure that the initrd image is placed in the first
4980		  12 MB as well - this can be done with
4981
4982		  setenv initrd_high 00c00000
4983
4984		  If you set initrd_high to 0xFFFFFFFF, this is an
4985		  indication to U-Boot that all addresses are legal
4986		  for the Linux kernel, including addresses in flash
4987		  memory. In this case U-Boot will NOT COPY the
4988		  ramdisk at all. This may be useful to reduce the
4989		  boot time on your system, but requires that this
4990		  feature is supported by your Linux kernel.
4991
4992  ipaddr	- IP address; needed for tftpboot command
4993
4994  loadaddr	- Default load address for commands like "bootp",
4995		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4996
4997  loads_echo	- see CONFIG_LOADS_ECHO
4998
4999  serverip	- TFTP server IP address; needed for tftpboot command
5000
5001  bootretry	- see CONFIG_BOOT_RETRY_TIME
5002
5003  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5004
5005  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5006
5007  ethprime	- controls which interface is used first.
5008
5009  ethact	- controls which interface is currently active.
5010		  For example you can do the following
5011
5012		  => setenv ethact FEC
5013		  => ping 192.168.0.1 # traffic sent on FEC
5014		  => setenv ethact SCC
5015		  => ping 10.0.0.1 # traffic sent on SCC
5016
5017  ethrotate	- When set to "no" U-Boot does not go through all
5018		  available network interfaces.
5019		  It just stays at the currently selected interface.
5020
5021  netretry	- When set to "no" each network operation will
5022		  either succeed or fail without retrying.
5023		  When set to "once" the network operation will
5024		  fail when all the available network interfaces
5025		  are tried once without success.
5026		  Useful on scripts which control the retry operation
5027		  themselves.
5028
5029  npe_ucode	- set load address for the NPE microcode
5030
5031  silent_linux  - If set then Linux will be told to boot silently, by
5032		  changing the console to be empty. If "yes" it will be
5033		  made silent. If "no" it will not be made silent. If
5034		  unset, then it will be made silent if the U-Boot console
5035		  is silent.
5036
5037  tftpsrcp	- If this is set, the value is used for TFTP's
5038		  UDP source port.
5039
5040  tftpdstp	- If this is set, the value is used for TFTP's UDP
5041		  destination port instead of the Well Know Port 69.
5042
5043  tftpblocksize - Block size to use for TFTP transfers; if not set,
5044		  we use the TFTP server's default block size
5045
5046  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5047		  seconds, minimum value is 1000 = 1 second). Defines
5048		  when a packet is considered to be lost so it has to
5049		  be retransmitted. The default is 5000 = 5 seconds.
5050		  Lowering this value may make downloads succeed
5051		  faster in networks with high packet loss rates or
5052		  with unreliable TFTP servers.
5053
5054  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
5055		  unit, minimum value = 0). Defines how many timeouts
5056		  can happen during a single file transfer before that
5057		  transfer is aborted. The default is 10, and 0 means
5058		  'no timeouts allowed'. Increasing this value may help
5059		  downloads succeed with high packet loss rates, or with
5060		  unreliable TFTP servers or client hardware.
5061
5062  vlan		- When set to a value < 4095 the traffic over
5063		  Ethernet is encapsulated/received over 802.1q
5064		  VLAN tagged frames.
5065
5066  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
5067		  Unsigned value, in milliseconds. If not set, the period will
5068		  be either the default (28000), or a value based on
5069		  CONFIG_NET_RETRY_COUNT, if defined. This value has
5070		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
5071
5072The following image location variables contain the location of images
5073used in booting. The "Image" column gives the role of the image and is
5074not an environment variable name. The other columns are environment
5075variable names. "File Name" gives the name of the file on a TFTP
5076server, "RAM Address" gives the location in RAM the image will be
5077loaded to, and "Flash Location" gives the image's address in NOR
5078flash or offset in NAND flash.
5079
5080*Note* - these variables don't have to be defined for all boards, some
5081boards currently use other variables for these purposes, and some
5082boards use these variables for other purposes.
5083
5084Image		    File Name	     RAM Address       Flash Location
5085-----		    ---------	     -----------       --------------
5086u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5087Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5088device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5089ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5090
5091The following environment variables may be used and automatically
5092updated by the network boot commands ("bootp" and "rarpboot"),
5093depending the information provided by your boot server:
5094
5095  bootfile	- see above
5096  dnsip		- IP address of your Domain Name Server
5097  dnsip2	- IP address of your secondary Domain Name Server
5098  gatewayip	- IP address of the Gateway (Router) to use
5099  hostname	- Target hostname
5100  ipaddr	- see above
5101  netmask	- Subnet Mask
5102  rootpath	- Pathname of the root filesystem on the NFS server
5103  serverip	- see above
5104
5105
5106There are two special Environment Variables:
5107
5108  serial#	- contains hardware identification information such
5109		  as type string and/or serial number
5110  ethaddr	- Ethernet address
5111
5112These variables can be set only once (usually during manufacturing of
5113the board). U-Boot refuses to delete or overwrite these variables
5114once they have been set once.
5115
5116
5117Further special Environment Variables:
5118
5119  ver		- Contains the U-Boot version string as printed
5120		  with the "version" command. This variable is
5121		  readonly (see CONFIG_VERSION_VARIABLE).
5122
5123
5124Please note that changes to some configuration parameters may take
5125only effect after the next boot (yes, that's just like Windoze :-).
5126
5127
5128Callback functions for environment variables:
5129---------------------------------------------
5130
5131For some environment variables, the behavior of u-boot needs to change
5132when their values are changed.  This functionality allows functions to
5133be associated with arbitrary variables.  On creation, overwrite, or
5134deletion, the callback will provide the opportunity for some side
5135effect to happen or for the change to be rejected.
5136
5137The callbacks are named and associated with a function using the
5138U_BOOT_ENV_CALLBACK macro in your board or driver code.
5139
5140These callbacks are associated with variables in one of two ways.  The
5141static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5142in the board configuration to a string that defines a list of
5143associations.  The list must be in the following format:
5144
5145	entry = variable_name[:callback_name]
5146	list = entry[,list]
5147
5148If the callback name is not specified, then the callback is deleted.
5149Spaces are also allowed anywhere in the list.
5150
5151Callbacks can also be associated by defining the ".callbacks" variable
5152with the same list format above.  Any association in ".callbacks" will
5153override any association in the static list. You can define
5154CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5155".callbacks" environment variable in the default or embedded environment.
5156
5157If CONFIG_REGEX is defined, the variable_name above is evaluated as a
5158regular expression. This allows multiple variables to be connected to
5159the same callback without explicitly listing them all out.
5160
5161
5162Command Line Parsing:
5163=====================
5164
5165There are two different command line parsers available with U-Boot:
5166the old "simple" one, and the much more powerful "hush" shell:
5167
5168Old, simple command line parser:
5169--------------------------------
5170
5171- supports environment variables (through setenv / saveenv commands)
5172- several commands on one line, separated by ';'
5173- variable substitution using "... ${name} ..." syntax
5174- special characters ('$', ';') can be escaped by prefixing with '\',
5175  for example:
5176	setenv bootcmd bootm \${address}
5177- You can also escape text by enclosing in single apostrophes, for example:
5178	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5179
5180Hush shell:
5181-----------
5182
5183- similar to Bourne shell, with control structures like
5184  if...then...else...fi, for...do...done; while...do...done,
5185  until...do...done, ...
5186- supports environment ("global") variables (through setenv / saveenv
5187  commands) and local shell variables (through standard shell syntax
5188  "name=value"); only environment variables can be used with "run"
5189  command
5190
5191General rules:
5192--------------
5193
5194(1) If a command line (or an environment variable executed by a "run"
5195    command) contains several commands separated by semicolon, and
5196    one of these commands fails, then the remaining commands will be
5197    executed anyway.
5198
5199(2) If you execute several variables with one call to run (i. e.
5200    calling run with a list of variables as arguments), any failing
5201    command will cause "run" to terminate, i. e. the remaining
5202    variables are not executed.
5203
5204Note for Redundant Ethernet Interfaces:
5205=======================================
5206
5207Some boards come with redundant Ethernet interfaces; U-Boot supports
5208such configurations and is capable of automatic selection of a
5209"working" interface when needed. MAC assignment works as follows:
5210
5211Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5212MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5213"eth1addr" (=>eth1), "eth2addr", ...
5214
5215If the network interface stores some valid MAC address (for instance
5216in SROM), this is used as default address if there is NO correspon-
5217ding setting in the environment; if the corresponding environment
5218variable is set, this overrides the settings in the card; that means:
5219
5220o If the SROM has a valid MAC address, and there is no address in the
5221  environment, the SROM's address is used.
5222
5223o If there is no valid address in the SROM, and a definition in the
5224  environment exists, then the value from the environment variable is
5225  used.
5226
5227o If both the SROM and the environment contain a MAC address, and
5228  both addresses are the same, this MAC address is used.
5229
5230o If both the SROM and the environment contain a MAC address, and the
5231  addresses differ, the value from the environment is used and a
5232  warning is printed.
5233
5234o If neither SROM nor the environment contain a MAC address, an error
5235  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
5236  a random, locally-assigned MAC is used.
5237
5238If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5239will be programmed into hardware as part of the initialization process.	 This
5240may be skipped by setting the appropriate 'ethmacskip' environment variable.
5241The naming convention is as follows:
5242"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5243
5244Image Formats:
5245==============
5246
5247U-Boot is capable of booting (and performing other auxiliary operations on)
5248images in two formats:
5249
5250New uImage format (FIT)
5251-----------------------
5252
5253Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5254to Flattened Device Tree). It allows the use of images with multiple
5255components (several kernels, ramdisks, etc.), with contents protected by
5256SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5257
5258
5259Old uImage format
5260-----------------
5261
5262Old image format is based on binary files which can be basically anything,
5263preceded by a special header; see the definitions in include/image.h for
5264details; basically, the header defines the following image properties:
5265
5266* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5267  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5268  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5269  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5270  INTEGRITY).
5271* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5272  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5273  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5274* Compression Type (uncompressed, gzip, bzip2)
5275* Load Address
5276* Entry Point
5277* Image Name
5278* Image Timestamp
5279
5280The header is marked by a special Magic Number, and both the header
5281and the data portions of the image are secured against corruption by
5282CRC32 checksums.
5283
5284
5285Linux Support:
5286==============
5287
5288Although U-Boot should support any OS or standalone application
5289easily, the main focus has always been on Linux during the design of
5290U-Boot.
5291
5292U-Boot includes many features that so far have been part of some
5293special "boot loader" code within the Linux kernel. Also, any
5294"initrd" images to be used are no longer part of one big Linux image;
5295instead, kernel and "initrd" are separate images. This implementation
5296serves several purposes:
5297
5298- the same features can be used for other OS or standalone
5299  applications (for instance: using compressed images to reduce the
5300  Flash memory footprint)
5301
5302- it becomes much easier to port new Linux kernel versions because
5303  lots of low-level, hardware dependent stuff are done by U-Boot
5304
5305- the same Linux kernel image can now be used with different "initrd"
5306  images; of course this also means that different kernel images can
5307  be run with the same "initrd". This makes testing easier (you don't
5308  have to build a new "zImage.initrd" Linux image when you just
5309  change a file in your "initrd"). Also, a field-upgrade of the
5310  software is easier now.
5311
5312
5313Linux HOWTO:
5314============
5315
5316Porting Linux to U-Boot based systems:
5317---------------------------------------
5318
5319U-Boot cannot save you from doing all the necessary modifications to
5320configure the Linux device drivers for use with your target hardware
5321(no, we don't intend to provide a full virtual machine interface to
5322Linux :-).
5323
5324But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5325
5326Just make sure your machine specific header file (for instance
5327include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5328Information structure as we define in include/asm-<arch>/u-boot.h,
5329and make sure that your definition of IMAP_ADDR uses the same value
5330as your U-Boot configuration in CONFIG_SYS_IMMR.
5331
5332Note that U-Boot now has a driver model, a unified model for drivers.
5333If you are adding a new driver, plumb it into driver model. If there
5334is no uclass available, you are encouraged to create one. See
5335doc/driver-model.
5336
5337
5338Configuring the Linux kernel:
5339-----------------------------
5340
5341No specific requirements for U-Boot. Make sure you have some root
5342device (initial ramdisk, NFS) for your target system.
5343
5344
5345Building a Linux Image:
5346-----------------------
5347
5348With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5349not used. If you use recent kernel source, a new build target
5350"uImage" will exist which automatically builds an image usable by
5351U-Boot. Most older kernels also have support for a "pImage" target,
5352which was introduced for our predecessor project PPCBoot and uses a
5353100% compatible format.
5354
5355Example:
5356
5357	make TQM850L_defconfig
5358	make oldconfig
5359	make dep
5360	make uImage
5361
5362The "uImage" build target uses a special tool (in 'tools/mkimage') to
5363encapsulate a compressed Linux kernel image with header	 information,
5364CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5365
5366* build a standard "vmlinux" kernel image (in ELF binary format):
5367
5368* convert the kernel into a raw binary image:
5369
5370	${CROSS_COMPILE}-objcopy -O binary \
5371				 -R .note -R .comment \
5372				 -S vmlinux linux.bin
5373
5374* compress the binary image:
5375
5376	gzip -9 linux.bin
5377
5378* package compressed binary image for U-Boot:
5379
5380	mkimage -A ppc -O linux -T kernel -C gzip \
5381		-a 0 -e 0 -n "Linux Kernel Image" \
5382		-d linux.bin.gz uImage
5383
5384
5385The "mkimage" tool can also be used to create ramdisk images for use
5386with U-Boot, either separated from the Linux kernel image, or
5387combined into one file. "mkimage" encapsulates the images with a 64
5388byte header containing information about target architecture,
5389operating system, image type, compression method, entry points, time
5390stamp, CRC32 checksums, etc.
5391
5392"mkimage" can be called in two ways: to verify existing images and
5393print the header information, or to build new images.
5394
5395In the first form (with "-l" option) mkimage lists the information
5396contained in the header of an existing U-Boot image; this includes
5397checksum verification:
5398
5399	tools/mkimage -l image
5400	  -l ==> list image header information
5401
5402The second form (with "-d" option) is used to build a U-Boot image
5403from a "data file" which is used as image payload:
5404
5405	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5406		      -n name -d data_file image
5407	  -A ==> set architecture to 'arch'
5408	  -O ==> set operating system to 'os'
5409	  -T ==> set image type to 'type'
5410	  -C ==> set compression type 'comp'
5411	  -a ==> set load address to 'addr' (hex)
5412	  -e ==> set entry point to 'ep' (hex)
5413	  -n ==> set image name to 'name'
5414	  -d ==> use image data from 'datafile'
5415
5416Right now, all Linux kernels for PowerPC systems use the same load
5417address (0x00000000), but the entry point address depends on the
5418kernel version:
5419
5420- 2.2.x kernels have the entry point at 0x0000000C,
5421- 2.3.x and later kernels have the entry point at 0x00000000.
5422
5423So a typical call to build a U-Boot image would read:
5424
5425	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5426	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5427	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5428	> examples/uImage.TQM850L
5429	Image Name:   2.4.4 kernel for TQM850L
5430	Created:      Wed Jul 19 02:34:59 2000
5431	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5432	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5433	Load Address: 0x00000000
5434	Entry Point:  0x00000000
5435
5436To verify the contents of the image (or check for corruption):
5437
5438	-> tools/mkimage -l examples/uImage.TQM850L
5439	Image Name:   2.4.4 kernel for TQM850L
5440	Created:      Wed Jul 19 02:34:59 2000
5441	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5442	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5443	Load Address: 0x00000000
5444	Entry Point:  0x00000000
5445
5446NOTE: for embedded systems where boot time is critical you can trade
5447speed for memory and install an UNCOMPRESSED image instead: this
5448needs more space in Flash, but boots much faster since it does not
5449need to be uncompressed:
5450
5451	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5452	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5453	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5454	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5455	> examples/uImage.TQM850L-uncompressed
5456	Image Name:   2.4.4 kernel for TQM850L
5457	Created:      Wed Jul 19 02:34:59 2000
5458	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5459	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5460	Load Address: 0x00000000
5461	Entry Point:  0x00000000
5462
5463
5464Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5465when your kernel is intended to use an initial ramdisk:
5466
5467	-> tools/mkimage -n 'Simple Ramdisk Image' \
5468	> -A ppc -O linux -T ramdisk -C gzip \
5469	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5470	Image Name:   Simple Ramdisk Image
5471	Created:      Wed Jan 12 14:01:50 2000
5472	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5473	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5474	Load Address: 0x00000000
5475	Entry Point:  0x00000000
5476
5477The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5478option performs the converse operation of the mkimage's second form (the "-d"
5479option). Given an image built by mkimage, the dumpimage extracts a "data file"
5480from the image:
5481
5482	tools/dumpimage -i image -T type -p position data_file
5483	  -i ==> extract from the 'image' a specific 'data_file'
5484	  -T ==> set image type to 'type'
5485	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5486
5487
5488Installing a Linux Image:
5489-------------------------
5490
5491To downloading a U-Boot image over the serial (console) interface,
5492you must convert the image to S-Record format:
5493
5494	objcopy -I binary -O srec examples/image examples/image.srec
5495
5496The 'objcopy' does not understand the information in the U-Boot
5497image header, so the resulting S-Record file will be relative to
5498address 0x00000000. To load it to a given address, you need to
5499specify the target address as 'offset' parameter with the 'loads'
5500command.
5501
5502Example: install the image to address 0x40100000 (which on the
5503TQM8xxL is in the first Flash bank):
5504
5505	=> erase 40100000 401FFFFF
5506
5507	.......... done
5508	Erased 8 sectors
5509
5510	=> loads 40100000
5511	## Ready for S-Record download ...
5512	~>examples/image.srec
5513	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5514	...
5515	15989 15990 15991 15992
5516	[file transfer complete]
5517	[connected]
5518	## Start Addr = 0x00000000
5519
5520
5521You can check the success of the download using the 'iminfo' command;
5522this includes a checksum verification so you can be sure no data
5523corruption happened:
5524
5525	=> imi 40100000
5526
5527	## Checking Image at 40100000 ...
5528	   Image Name:	 2.2.13 for initrd on TQM850L
5529	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5530	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5531	   Load Address: 00000000
5532	   Entry Point:	 0000000c
5533	   Verifying Checksum ... OK
5534
5535
5536Boot Linux:
5537-----------
5538
5539The "bootm" command is used to boot an application that is stored in
5540memory (RAM or Flash). In case of a Linux kernel image, the contents
5541of the "bootargs" environment variable is passed to the kernel as
5542parameters. You can check and modify this variable using the
5543"printenv" and "setenv" commands:
5544
5545
5546	=> printenv bootargs
5547	bootargs=root=/dev/ram
5548
5549	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5550
5551	=> printenv bootargs
5552	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5553
5554	=> bootm 40020000
5555	## Booting Linux kernel at 40020000 ...
5556	   Image Name:	 2.2.13 for NFS on TQM850L
5557	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5558	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5559	   Load Address: 00000000
5560	   Entry Point:	 0000000c
5561	   Verifying Checksum ... OK
5562	   Uncompressing Kernel Image ... OK
5563	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
5564	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5565	time_init: decrementer frequency = 187500000/60
5566	Calibrating delay loop... 49.77 BogoMIPS
5567	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5568	...
5569
5570If you want to boot a Linux kernel with initial RAM disk, you pass
5571the memory addresses of both the kernel and the initrd image (PPBCOOT
5572format!) to the "bootm" command:
5573
5574	=> imi 40100000 40200000
5575
5576	## Checking Image at 40100000 ...
5577	   Image Name:	 2.2.13 for initrd on TQM850L
5578	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5579	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5580	   Load Address: 00000000
5581	   Entry Point:	 0000000c
5582	   Verifying Checksum ... OK
5583
5584	## Checking Image at 40200000 ...
5585	   Image Name:	 Simple Ramdisk Image
5586	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5587	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5588	   Load Address: 00000000
5589	   Entry Point:	 00000000
5590	   Verifying Checksum ... OK
5591
5592	=> bootm 40100000 40200000
5593	## Booting Linux kernel at 40100000 ...
5594	   Image Name:	 2.2.13 for initrd on TQM850L
5595	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5596	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5597	   Load Address: 00000000
5598	   Entry Point:	 0000000c
5599	   Verifying Checksum ... OK
5600	   Uncompressing Kernel Image ... OK
5601	## Loading RAMDisk Image at 40200000 ...
5602	   Image Name:	 Simple Ramdisk Image
5603	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5604	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5605	   Load Address: 00000000
5606	   Entry Point:	 00000000
5607	   Verifying Checksum ... OK
5608	   Loading Ramdisk ... OK
5609	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
5610	Boot arguments: root=/dev/ram
5611	time_init: decrementer frequency = 187500000/60
5612	Calibrating delay loop... 49.77 BogoMIPS
5613	...
5614	RAMDISK: Compressed image found at block 0
5615	VFS: Mounted root (ext2 filesystem).
5616
5617	bash#
5618
5619Boot Linux and pass a flat device tree:
5620-----------
5621
5622First, U-Boot must be compiled with the appropriate defines. See the section
5623titled "Linux Kernel Interface" above for a more in depth explanation. The
5624following is an example of how to start a kernel and pass an updated
5625flat device tree:
5626
5627=> print oftaddr
5628oftaddr=0x300000
5629=> print oft
5630oft=oftrees/mpc8540ads.dtb
5631=> tftp $oftaddr $oft
5632Speed: 1000, full duplex
5633Using TSEC0 device
5634TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5635Filename 'oftrees/mpc8540ads.dtb'.
5636Load address: 0x300000
5637Loading: #
5638done
5639Bytes transferred = 4106 (100a hex)
5640=> tftp $loadaddr $bootfile
5641Speed: 1000, full duplex
5642Using TSEC0 device
5643TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5644Filename 'uImage'.
5645Load address: 0x200000
5646Loading:############
5647done
5648Bytes transferred = 1029407 (fb51f hex)
5649=> print loadaddr
5650loadaddr=200000
5651=> print oftaddr
5652oftaddr=0x300000
5653=> bootm $loadaddr - $oftaddr
5654## Booting image at 00200000 ...
5655   Image Name:	 Linux-2.6.17-dirty
5656   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5657   Data Size:	 1029343 Bytes = 1005.2 kB
5658   Load Address: 00000000
5659   Entry Point:	 00000000
5660   Verifying Checksum ... OK
5661   Uncompressing Kernel Image ... OK
5662Booting using flat device tree at 0x300000
5663Using MPC85xx ADS machine description
5664Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5665[snip]
5666
5667
5668More About U-Boot Image Types:
5669------------------------------
5670
5671U-Boot supports the following image types:
5672
5673   "Standalone Programs" are directly runnable in the environment
5674	provided by U-Boot; it is expected that (if they behave
5675	well) you can continue to work in U-Boot after return from
5676	the Standalone Program.
5677   "OS Kernel Images" are usually images of some Embedded OS which
5678	will take over control completely. Usually these programs
5679	will install their own set of exception handlers, device
5680	drivers, set up the MMU, etc. - this means, that you cannot
5681	expect to re-enter U-Boot except by resetting the CPU.
5682   "RAMDisk Images" are more or less just data blocks, and their
5683	parameters (address, size) are passed to an OS kernel that is
5684	being started.
5685   "Multi-File Images" contain several images, typically an OS
5686	(Linux) kernel image and one or more data images like
5687	RAMDisks. This construct is useful for instance when you want
5688	to boot over the network using BOOTP etc., where the boot
5689	server provides just a single image file, but you want to get
5690	for instance an OS kernel and a RAMDisk image.
5691
5692	"Multi-File Images" start with a list of image sizes, each
5693	image size (in bytes) specified by an "uint32_t" in network
5694	byte order. This list is terminated by an "(uint32_t)0".
5695	Immediately after the terminating 0 follow the images, one by
5696	one, all aligned on "uint32_t" boundaries (size rounded up to
5697	a multiple of 4 bytes).
5698
5699   "Firmware Images" are binary images containing firmware (like
5700	U-Boot or FPGA images) which usually will be programmed to
5701	flash memory.
5702
5703   "Script files" are command sequences that will be executed by
5704	U-Boot's command interpreter; this feature is especially
5705	useful when you configure U-Boot to use a real shell (hush)
5706	as command interpreter.
5707
5708Booting the Linux zImage:
5709-------------------------
5710
5711On some platforms, it's possible to boot Linux zImage. This is done
5712using the "bootz" command. The syntax of "bootz" command is the same
5713as the syntax of "bootm" command.
5714
5715Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5716kernel with raw initrd images. The syntax is slightly different, the
5717address of the initrd must be augmented by it's size, in the following
5718format: "<initrd addres>:<initrd size>".
5719
5720
5721Standalone HOWTO:
5722=================
5723
5724One of the features of U-Boot is that you can dynamically load and
5725run "standalone" applications, which can use some resources of
5726U-Boot like console I/O functions or interrupt services.
5727
5728Two simple examples are included with the sources:
5729
5730"Hello World" Demo:
5731-------------------
5732
5733'examples/hello_world.c' contains a small "Hello World" Demo
5734application; it is automatically compiled when you build U-Boot.
5735It's configured to run at address 0x00040004, so you can play with it
5736like that:
5737
5738	=> loads
5739	## Ready for S-Record download ...
5740	~>examples/hello_world.srec
5741	1 2 3 4 5 6 7 8 9 10 11 ...
5742	[file transfer complete]
5743	[connected]
5744	## Start Addr = 0x00040004
5745
5746	=> go 40004 Hello World! This is a test.
5747	## Starting application at 0x00040004 ...
5748	Hello World
5749	argc = 7
5750	argv[0] = "40004"
5751	argv[1] = "Hello"
5752	argv[2] = "World!"
5753	argv[3] = "This"
5754	argv[4] = "is"
5755	argv[5] = "a"
5756	argv[6] = "test."
5757	argv[7] = "<NULL>"
5758	Hit any key to exit ...
5759
5760	## Application terminated, rc = 0x0
5761
5762Another example, which demonstrates how to register a CPM interrupt
5763handler with the U-Boot code, can be found in 'examples/timer.c'.
5764Here, a CPM timer is set up to generate an interrupt every second.
5765The interrupt service routine is trivial, just printing a '.'
5766character, but this is just a demo program. The application can be
5767controlled by the following keys:
5768
5769	? - print current values og the CPM Timer registers
5770	b - enable interrupts and start timer
5771	e - stop timer and disable interrupts
5772	q - quit application
5773
5774	=> loads
5775	## Ready for S-Record download ...
5776	~>examples/timer.srec
5777	1 2 3 4 5 6 7 8 9 10 11 ...
5778	[file transfer complete]
5779	[connected]
5780	## Start Addr = 0x00040004
5781
5782	=> go 40004
5783	## Starting application at 0x00040004 ...
5784	TIMERS=0xfff00980
5785	Using timer 1
5786	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5787
5788Hit 'b':
5789	[q, b, e, ?] Set interval 1000000 us
5790	Enabling timer
5791Hit '?':
5792	[q, b, e, ?] ........
5793	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5794Hit '?':
5795	[q, b, e, ?] .
5796	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5797Hit '?':
5798	[q, b, e, ?] .
5799	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5800Hit '?':
5801	[q, b, e, ?] .
5802	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5803Hit 'e':
5804	[q, b, e, ?] ...Stopping timer
5805Hit 'q':
5806	[q, b, e, ?] ## Application terminated, rc = 0x0
5807
5808
5809Minicom warning:
5810================
5811
5812Over time, many people have reported problems when trying to use the
5813"minicom" terminal emulation program for serial download. I (wd)
5814consider minicom to be broken, and recommend not to use it. Under
5815Unix, I recommend to use C-Kermit for general purpose use (and
5816especially for kermit binary protocol download ("loadb" command), and
5817use "cu" for S-Record download ("loads" command).  See
5818http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5819for help with kermit.
5820
5821
5822Nevertheless, if you absolutely want to use it try adding this
5823configuration to your "File transfer protocols" section:
5824
5825	   Name	   Program			Name U/D FullScr IO-Red. Multi
5826	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5827	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5828
5829
5830NetBSD Notes:
5831=============
5832
5833Starting at version 0.9.2, U-Boot supports NetBSD both as host
5834(build U-Boot) and target system (boots NetBSD/mpc8xx).
5835
5836Building requires a cross environment; it is known to work on
5837NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5838need gmake since the Makefiles are not compatible with BSD make).
5839Note that the cross-powerpc package does not install include files;
5840attempting to build U-Boot will fail because <machine/ansi.h> is
5841missing.  This file has to be installed and patched manually:
5842
5843	# cd /usr/pkg/cross/powerpc-netbsd/include
5844	# mkdir powerpc
5845	# ln -s powerpc machine
5846	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5847	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5848
5849Native builds *don't* work due to incompatibilities between native
5850and U-Boot include files.
5851
5852Booting assumes that (the first part of) the image booted is a
5853stage-2 loader which in turn loads and then invokes the kernel
5854proper. Loader sources will eventually appear in the NetBSD source
5855tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5856meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5857
5858
5859Implementation Internals:
5860=========================
5861
5862The following is not intended to be a complete description of every
5863implementation detail. However, it should help to understand the
5864inner workings of U-Boot and make it easier to port it to custom
5865hardware.
5866
5867
5868Initial Stack, Global Data:
5869---------------------------
5870
5871The implementation of U-Boot is complicated by the fact that U-Boot
5872starts running out of ROM (flash memory), usually without access to
5873system RAM (because the memory controller is not initialized yet).
5874This means that we don't have writable Data or BSS segments, and BSS
5875is not initialized as zero. To be able to get a C environment working
5876at all, we have to allocate at least a minimal stack. Implementation
5877options for this are defined and restricted by the CPU used: Some CPU
5878models provide on-chip memory (like the IMMR area on MPC8xx and
5879MPC826x processors), on others (parts of) the data cache can be
5880locked as (mis-) used as memory, etc.
5881
5882	Chris Hallinan posted a good summary of these issues to the
5883	U-Boot mailing list:
5884
5885	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5886	From: "Chris Hallinan" <clh@net1plus.com>
5887	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5888	...
5889
5890	Correct me if I'm wrong, folks, but the way I understand it
5891	is this: Using DCACHE as initial RAM for Stack, etc, does not
5892	require any physical RAM backing up the cache. The cleverness
5893	is that the cache is being used as a temporary supply of
5894	necessary storage before the SDRAM controller is setup. It's
5895	beyond the scope of this list to explain the details, but you
5896	can see how this works by studying the cache architecture and
5897	operation in the architecture and processor-specific manuals.
5898
5899	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5900	is another option for the system designer to use as an
5901	initial stack/RAM area prior to SDRAM being available. Either
5902	option should work for you. Using CS 4 should be fine if your
5903	board designers haven't used it for something that would
5904	cause you grief during the initial boot! It is frequently not
5905	used.
5906
5907	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5908	with your processor/board/system design. The default value
5909	you will find in any recent u-boot distribution in
5910	walnut.h should work for you. I'd set it to a value larger
5911	than your SDRAM module. If you have a 64MB SDRAM module, set
5912	it above 400_0000. Just make sure your board has no resources
5913	that are supposed to respond to that address! That code in
5914	start.S has been around a while and should work as is when
5915	you get the config right.
5916
5917	-Chris Hallinan
5918	DS4.COM, Inc.
5919
5920It is essential to remember this, since it has some impact on the C
5921code for the initialization procedures:
5922
5923* Initialized global data (data segment) is read-only. Do not attempt
5924  to write it.
5925
5926* Do not use any uninitialized global data (or implicitly initialized
5927  as zero data - BSS segment) at all - this is undefined, initiali-
5928  zation is performed later (when relocating to RAM).
5929
5930* Stack space is very limited. Avoid big data buffers or things like
5931  that.
5932
5933Having only the stack as writable memory limits means we cannot use
5934normal global data to share information between the code. But it
5935turned out that the implementation of U-Boot can be greatly
5936simplified by making a global data structure (gd_t) available to all
5937functions. We could pass a pointer to this data as argument to _all_
5938functions, but this would bloat the code. Instead we use a feature of
5939the GCC compiler (Global Register Variables) to share the data: we
5940place a pointer (gd) to the global data into a register which we
5941reserve for this purpose.
5942
5943When choosing a register for such a purpose we are restricted by the
5944relevant  (E)ABI  specifications for the current architecture, and by
5945GCC's implementation.
5946
5947For PowerPC, the following registers have specific use:
5948	R1:	stack pointer
5949	R2:	reserved for system use
5950	R3-R4:	parameter passing and return values
5951	R5-R10: parameter passing
5952	R13:	small data area pointer
5953	R30:	GOT pointer
5954	R31:	frame pointer
5955
5956	(U-Boot also uses R12 as internal GOT pointer. r12
5957	is a volatile register so r12 needs to be reset when
5958	going back and forth between asm and C)
5959
5960    ==> U-Boot will use R2 to hold a pointer to the global data
5961
5962    Note: on PPC, we could use a static initializer (since the
5963    address of the global data structure is known at compile time),
5964    but it turned out that reserving a register results in somewhat
5965    smaller code - although the code savings are not that big (on
5966    average for all boards 752 bytes for the whole U-Boot image,
5967    624 text + 127 data).
5968
5969On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5970	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5971
5972    ==> U-Boot will use P3 to hold a pointer to the global data
5973
5974On ARM, the following registers are used:
5975
5976	R0:	function argument word/integer result
5977	R1-R3:	function argument word
5978	R9:	platform specific
5979	R10:	stack limit (used only if stack checking is enabled)
5980	R11:	argument (frame) pointer
5981	R12:	temporary workspace
5982	R13:	stack pointer
5983	R14:	link register
5984	R15:	program counter
5985
5986    ==> U-Boot will use R9 to hold a pointer to the global data
5987
5988    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5989
5990On Nios II, the ABI is documented here:
5991	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5992
5993    ==> U-Boot will use gp to hold a pointer to the global data
5994
5995    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5996    to access small data sections, so gp is free.
5997
5998On NDS32, the following registers are used:
5999
6000	R0-R1:	argument/return
6001	R2-R5:	argument
6002	R15:	temporary register for assembler
6003	R16:	trampoline register
6004	R28:	frame pointer (FP)
6005	R29:	global pointer (GP)
6006	R30:	link register (LP)
6007	R31:	stack pointer (SP)
6008	PC:	program counter (PC)
6009
6010    ==> U-Boot will use R10 to hold a pointer to the global data
6011
6012NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6013or current versions of GCC may "optimize" the code too much.
6014
6015Memory Management:
6016------------------
6017
6018U-Boot runs in system state and uses physical addresses, i.e. the
6019MMU is not used either for address mapping nor for memory protection.
6020
6021The available memory is mapped to fixed addresses using the memory
6022controller. In this process, a contiguous block is formed for each
6023memory type (Flash, SDRAM, SRAM), even when it consists of several
6024physical memory banks.
6025
6026U-Boot is installed in the first 128 kB of the first Flash bank (on
6027TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6028booting and sizing and initializing DRAM, the code relocates itself
6029to the upper end of DRAM. Immediately below the U-Boot code some
6030memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6031configuration setting]. Below that, a structure with global Board
6032Info data is placed, followed by the stack (growing downward).
6033
6034Additionally, some exception handler code is copied to the low 8 kB
6035of DRAM (0x00000000 ... 0x00001FFF).
6036
6037So a typical memory configuration with 16 MB of DRAM could look like
6038this:
6039
6040	0x0000 0000	Exception Vector code
6041	      :
6042	0x0000 1FFF
6043	0x0000 2000	Free for Application Use
6044	      :
6045	      :
6046
6047	      :
6048	      :
6049	0x00FB FF20	Monitor Stack (Growing downward)
6050	0x00FB FFAC	Board Info Data and permanent copy of global data
6051	0x00FC 0000	Malloc Arena
6052	      :
6053	0x00FD FFFF
6054	0x00FE 0000	RAM Copy of Monitor Code
6055	...		eventually: LCD or video framebuffer
6056	...		eventually: pRAM (Protected RAM - unchanged by reset)
6057	0x00FF FFFF	[End of RAM]
6058
6059
6060System Initialization:
6061----------------------
6062
6063In the reset configuration, U-Boot starts at the reset entry point
6064(on most PowerPC systems at address 0x00000100). Because of the reset
6065configuration for CS0# this is a mirror of the on board Flash memory.
6066To be able to re-map memory U-Boot then jumps to its link address.
6067To be able to implement the initialization code in C, a (small!)
6068initial stack is set up in the internal Dual Ported RAM (in case CPUs
6069which provide such a feature like MPC8xx or MPC8260), or in a locked
6070part of the data cache. After that, U-Boot initializes the CPU core,
6071the caches and the SIU.
6072
6073Next, all (potentially) available memory banks are mapped using a
6074preliminary mapping. For example, we put them on 512 MB boundaries
6075(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6076on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6077programmed for SDRAM access. Using the temporary configuration, a
6078simple memory test is run that determines the size of the SDRAM
6079banks.
6080
6081When there is more than one SDRAM bank, and the banks are of
6082different size, the largest is mapped first. For equal size, the first
6083bank (CS2#) is mapped first. The first mapping is always for address
60840x00000000, with any additional banks following immediately to create
6085contiguous memory starting from 0.
6086
6087Then, the monitor installs itself at the upper end of the SDRAM area
6088and allocates memory for use by malloc() and for the global Board
6089Info data; also, the exception vector code is copied to the low RAM
6090pages, and the final stack is set up.
6091
6092Only after this relocation will you have a "normal" C environment;
6093until that you are restricted in several ways, mostly because you are
6094running from ROM, and because the code will have to be relocated to a
6095new address in RAM.
6096
6097
6098U-Boot Porting Guide:
6099----------------------
6100
6101[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6102list, October 2002]
6103
6104
6105int main(int argc, char *argv[])
6106{
6107	sighandler_t no_more_time;
6108
6109	signal(SIGALRM, no_more_time);
6110	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6111
6112	if (available_money > available_manpower) {
6113		Pay consultant to port U-Boot;
6114		return 0;
6115	}
6116
6117	Download latest U-Boot source;
6118
6119	Subscribe to u-boot mailing list;
6120
6121	if (clueless)
6122		email("Hi, I am new to U-Boot, how do I get started?");
6123
6124	while (learning) {
6125		Read the README file in the top level directory;
6126		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6127		Read applicable doc/*.README;
6128		Read the source, Luke;
6129		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6130	}
6131
6132	if (available_money > toLocalCurrency ($2500))
6133		Buy a BDI3000;
6134	else
6135		Add a lot of aggravation and time;
6136
6137	if (a similar board exists) {	/* hopefully... */
6138		cp -a board/<similar> board/<myboard>
6139		cp include/configs/<similar>.h include/configs/<myboard>.h
6140	} else {
6141		Create your own board support subdirectory;
6142		Create your own board include/configs/<myboard>.h file;
6143	}
6144	Edit new board/<myboard> files
6145	Edit new include/configs/<myboard>.h
6146
6147	while (!accepted) {
6148		while (!running) {
6149			do {
6150				Add / modify source code;
6151			} until (compiles);
6152			Debug;
6153			if (clueless)
6154				email("Hi, I am having problems...");
6155		}
6156		Send patch file to the U-Boot email list;
6157		if (reasonable critiques)
6158			Incorporate improvements from email list code review;
6159		else
6160			Defend code as written;
6161	}
6162
6163	return 0;
6164}
6165
6166void no_more_time (int sig)
6167{
6168      hire_a_guru();
6169}
6170
6171
6172Coding Standards:
6173-----------------
6174
6175All contributions to U-Boot should conform to the Linux kernel
6176coding style; see the file "Documentation/CodingStyle" and the script
6177"scripts/Lindent" in your Linux kernel source directory.
6178
6179Source files originating from a different project (for example the
6180MTD subsystem) are generally exempt from these guidelines and are not
6181reformatted to ease subsequent migration to newer versions of those
6182sources.
6183
6184Please note that U-Boot is implemented in C (and to some small parts in
6185Assembler); no C++ is used, so please do not use C++ style comments (//)
6186in your code.
6187
6188Please also stick to the following formatting rules:
6189- remove any trailing white space
6190- use TAB characters for indentation and vertical alignment, not spaces
6191- make sure NOT to use DOS '\r\n' line feeds
6192- do not add more than 2 consecutive empty lines to source files
6193- do not add trailing empty lines to source files
6194
6195Submissions which do not conform to the standards may be returned
6196with a request to reformat the changes.
6197
6198
6199Submitting Patches:
6200-------------------
6201
6202Since the number of patches for U-Boot is growing, we need to
6203establish some rules. Submissions which do not conform to these rules
6204may be rejected, even when they contain important and valuable stuff.
6205
6206Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6207
6208Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6209see http://lists.denx.de/mailman/listinfo/u-boot
6210
6211When you send a patch, please include the following information with
6212it:
6213
6214* For bug fixes: a description of the bug and how your patch fixes
6215  this bug. Please try to include a way of demonstrating that the
6216  patch actually fixes something.
6217
6218* For new features: a description of the feature and your
6219  implementation.
6220
6221* A CHANGELOG entry as plaintext (separate from the patch)
6222
6223* For major contributions, add a MAINTAINERS file with your
6224  information and associated file and directory references.
6225
6226* When you add support for a new board, don't forget to add a
6227  maintainer e-mail address to the boards.cfg file, too.
6228
6229* If your patch adds new configuration options, don't forget to
6230  document these in the README file.
6231
6232* The patch itself. If you are using git (which is *strongly*
6233  recommended) you can easily generate the patch using the
6234  "git format-patch". If you then use "git send-email" to send it to
6235  the U-Boot mailing list, you will avoid most of the common problems
6236  with some other mail clients.
6237
6238  If you cannot use git, use "diff -purN OLD NEW". If your version of
6239  diff does not support these options, then get the latest version of
6240  GNU diff.
6241
6242  The current directory when running this command shall be the parent
6243  directory of the U-Boot source tree (i. e. please make sure that
6244  your patch includes sufficient directory information for the
6245  affected files).
6246
6247  We prefer patches as plain text. MIME attachments are discouraged,
6248  and compressed attachments must not be used.
6249
6250* If one logical set of modifications affects or creates several
6251  files, all these changes shall be submitted in a SINGLE patch file.
6252
6253* Changesets that contain different, unrelated modifications shall be
6254  submitted as SEPARATE patches, one patch per changeset.
6255
6256
6257Notes:
6258
6259* Before sending the patch, run the buildman script on your patched
6260  source tree and make sure that no errors or warnings are reported
6261  for any of the boards.
6262
6263* Keep your modifications to the necessary minimum: A patch
6264  containing several unrelated changes or arbitrary reformats will be
6265  returned with a request to re-formatting / split it.
6266
6267* If you modify existing code, make sure that your new code does not
6268  add to the memory footprint of the code ;-) Small is beautiful!
6269  When adding new features, these should compile conditionally only
6270  (using #ifdef), and the resulting code with the new feature
6271  disabled must not need more memory than the old code without your
6272  modification.
6273
6274* Remember that there is a size limit of 100 kB per message on the
6275  u-boot mailing list. Bigger patches will be moderated. If they are
6276  reasonable and not too big, they will be acknowledged. But patches
6277  bigger than the size limit should be avoided.
6278