xref: /rk3399_rockchip-uboot/README (revision 84777634621d13a75ea33c7c2ed1a7a76a609a93)
1#
2# (C) Copyright 2000 - 2013
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# SPDX-License-Identifier:	GPL-2.0+
6#
7
8Summary:
9========
10
11This directory contains the source code for U-Boot, a boot loader for
12Embedded boards based on PowerPC, ARM, MIPS and several other
13processors, which can be installed in a boot ROM and used to
14initialize and test the hardware or to download and run application
15code.
16
17The development of U-Boot is closely related to Linux: some parts of
18the source code originate in the Linux source tree, we have some
19header files in common, and special provision has been made to
20support booting of Linux images.
21
22Some attention has been paid to make this software easily
23configurable and extendable. For instance, all monitor commands are
24implemented with the same call interface, so that it's very easy to
25add new commands. Also, instead of permanently adding rarely used
26code (for instance hardware test utilities) to the monitor, you can
27load and run it dynamically.
28
29
30Status:
31=======
32
33In general, all boards for which a configuration option exists in the
34Makefile have been tested to some extent and can be considered
35"working". In fact, many of them are used in production systems.
36
37In case of problems see the CHANGELOG file to find out who contributed
38the specific port. In addition, there are various MAINTAINERS files
39scattered throughout the U-Boot source identifying the people or
40companies responsible for various boards and subsystems.
41
42Note: As of August, 2010, there is no longer a CHANGELOG file in the
43actual U-Boot source tree; however, it can be created dynamically
44from the Git log using:
45
46	make CHANGELOG
47
48
49Where to get help:
50==================
51
52In case you have questions about, problems with or contributions for
53U-Boot, you should send a message to the U-Boot mailing list at
54<u-boot@lists.denx.de>. There is also an archive of previous traffic
55on the mailing list - please search the archive before asking FAQ's.
56Please see http://lists.denx.de/pipermail/u-boot and
57http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
58
59
60Where to get source code:
61=========================
62
63The U-Boot source code is maintained in the Git repository at
64git://www.denx.de/git/u-boot.git ; you can browse it online at
65http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
66
67The "snapshot" links on this page allow you to download tarballs of
68any version you might be interested in. Official releases are also
69available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
70directory.
71
72Pre-built (and tested) images are available from
73ftp://ftp.denx.de/pub/u-boot/images/
74
75
76Where we come from:
77===================
78
79- start from 8xxrom sources
80- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
81- clean up code
82- make it easier to add custom boards
83- make it possible to add other [PowerPC] CPUs
84- extend functions, especially:
85  * Provide extended interface to Linux boot loader
86  * S-Record download
87  * network boot
88  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
89- create ARMBoot project (http://sourceforge.net/projects/armboot)
90- add other CPU families (starting with ARM)
91- create U-Boot project (http://sourceforge.net/projects/u-boot)
92- current project page: see http://www.denx.de/wiki/U-Boot
93
94
95Names and Spelling:
96===================
97
98The "official" name of this project is "Das U-Boot". The spelling
99"U-Boot" shall be used in all written text (documentation, comments
100in source files etc.). Example:
101
102	This is the README file for the U-Boot project.
103
104File names etc. shall be based on the string "u-boot". Examples:
105
106	include/asm-ppc/u-boot.h
107
108	#include <asm/u-boot.h>
109
110Variable names, preprocessor constants etc. shall be either based on
111the string "u_boot" or on "U_BOOT". Example:
112
113	U_BOOT_VERSION		u_boot_logo
114	IH_OS_U_BOOT		u_boot_hush_start
115
116
117Versioning:
118===========
119
120Starting with the release in October 2008, the names of the releases
121were changed from numerical release numbers without deeper meaning
122into a time stamp based numbering. Regular releases are identified by
123names consisting of the calendar year and month of the release date.
124Additional fields (if present) indicate release candidates or bug fix
125releases in "stable" maintenance trees.
126
127Examples:
128	U-Boot v2009.11	    - Release November 2009
129	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
130	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
131
132
133Directory Hierarchy:
134====================
135
136/arch			Architecture specific files
137  /arc			Files generic to ARC architecture
138  /arm			Files generic to ARM architecture
139  /avr32		Files generic to AVR32 architecture
140  /blackfin		Files generic to Analog Devices Blackfin architecture
141  /m68k			Files generic to m68k architecture
142  /microblaze		Files generic to microblaze architecture
143  /mips			Files generic to MIPS architecture
144  /nds32		Files generic to NDS32 architecture
145  /nios2		Files generic to Altera NIOS2 architecture
146  /openrisc		Files generic to OpenRISC architecture
147  /powerpc		Files generic to PowerPC architecture
148  /sandbox		Files generic to HW-independent "sandbox"
149  /sh			Files generic to SH architecture
150  /sparc		Files generic to SPARC architecture
151  /x86			Files generic to x86 architecture
152/api			Machine/arch independent API for external apps
153/board			Board dependent files
154/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- CPU Module Type: (if CONFIG_COGENT is defined)
329		Define exactly one of
330		CONFIG_CMA286_60_OLD
331--- FIXME --- not tested yet:
332		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
333		CONFIG_CMA287_23, CONFIG_CMA287_50
334
335- Motherboard Type: (if CONFIG_COGENT is defined)
336		Define exactly one of
337		CONFIG_CMA101, CONFIG_CMA102
338
339- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
340		Define one or more of
341		CONFIG_CMA302
342
343- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
344		Define one or more of
345		CONFIG_LCD_HEARTBEAT	- update a character position on
346					  the LCD display every second with
347					  a "rotator" |\-/|\-/
348
349- Marvell Family Member
350		CONFIG_SYS_MVFS		- define it if you want to enable
351					  multiple fs option at one time
352					  for marvell soc family
353
354- 8xx CPU Options: (if using an MPC8xx CPU)
355		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
356					  get_gclk_freq() cannot work
357					  e.g. if there is no 32KHz
358					  reference PIT/RTC clock
359		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
360					  or XTAL/EXTAL)
361
362- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
363		CONFIG_SYS_8xx_CPUCLK_MIN
364		CONFIG_SYS_8xx_CPUCLK_MAX
365		CONFIG_8xx_CPUCLK_DEFAULT
366			See doc/README.MPC866
367
368		CONFIG_SYS_MEASURE_CPUCLK
369
370		Define this to measure the actual CPU clock instead
371		of relying on the correctness of the configured
372		values. Mostly useful for board bringup to make sure
373		the PLL is locked at the intended frequency. Note
374		that this requires a (stable) reference clock (32 kHz
375		RTC clock or CONFIG_SYS_8XX_XIN)
376
377		CONFIG_SYS_DELAYED_ICACHE
378
379		Define this option if you want to enable the
380		ICache only when Code runs from RAM.
381
382- 85xx CPU Options:
383		CONFIG_SYS_PPC64
384
385		Specifies that the core is a 64-bit PowerPC implementation (implements
386		the "64" category of the Power ISA). This is necessary for ePAPR
387		compliance, among other possible reasons.
388
389		CONFIG_SYS_FSL_TBCLK_DIV
390
391		Defines the core time base clock divider ratio compared to the
392		system clock.  On most PQ3 devices this is 8, on newer QorIQ
393		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
394
395		CONFIG_SYS_FSL_PCIE_COMPAT
396
397		Defines the string to utilize when trying to match PCIe device
398		tree nodes for the given platform.
399
400		CONFIG_SYS_PPC_E500_DEBUG_TLB
401
402		Enables a temporary TLB entry to be used during boot to work
403		around limitations in e500v1 and e500v2 external debugger
404		support. This reduces the portions of the boot code where
405		breakpoints and single stepping do not work.  The value of this
406		symbol should be set to the TLB1 entry to be used for this
407		purpose.
408
409		CONFIG_SYS_FSL_ERRATUM_A004510
410
411		Enables a workaround for erratum A004510.  If set,
412		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
413		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
414
415		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
416		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
417
418		Defines one or two SoC revisions (low 8 bits of SVR)
419		for which the A004510 workaround should be applied.
420
421		The rest of SVR is either not relevant to the decision
422		of whether the erratum is present (e.g. p2040 versus
423		p2041) or is implied by the build target, which controls
424		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
425
426		See Freescale App Note 4493 for more information about
427		this erratum.
428
429		CONFIG_A003399_NOR_WORKAROUND
430		Enables a workaround for IFC erratum A003399. It is only
431		required during NOR boot.
432
433		CONFIG_A008044_WORKAROUND
434		Enables a workaround for T1040/T1042 erratum A008044. It is only
435		required during NAND boot and valid for Rev 1.0 SoC revision
436
437		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
438
439		This is the value to write into CCSR offset 0x18600
440		according to the A004510 workaround.
441
442		CONFIG_SYS_FSL_DSP_DDR_ADDR
443		This value denotes start offset of DDR memory which is
444		connected exclusively to the DSP cores.
445
446		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
447		This value denotes start offset of M2 memory
448		which is directly connected to the DSP core.
449
450		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
451		This value denotes start offset of M3 memory which is directly
452		connected to the DSP core.
453
454		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
455		This value denotes start offset of DSP CCSR space.
456
457		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
458		Single Source Clock is clocking mode present in some of FSL SoC's.
459		In this mode, a single differential clock is used to supply
460		clocks to the sysclock, ddrclock and usbclock.
461
462		CONFIG_SYS_CPC_REINIT_F
463		This CONFIG is defined when the CPC is configured as SRAM at the
464		time of U-Boot entry and is required to be re-initialized.
465
466		CONFIG_DEEP_SLEEP
467		Indicates this SoC supports deep sleep feature. If deep sleep is
468		supported, core will start to execute uboot when wakes up.
469
470- Generic CPU options:
471		CONFIG_SYS_GENERIC_GLOBAL_DATA
472		Defines global data is initialized in generic board board_init_f().
473		If this macro is defined, global data is created and cleared in
474		generic board board_init_f(). Without this macro, architecture/board
475		should initialize global data before calling board_init_f().
476
477		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
478
479		Defines the endianess of the CPU. Implementation of those
480		values is arch specific.
481
482		CONFIG_SYS_FSL_DDR
483		Freescale DDR driver in use. This type of DDR controller is
484		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
485		SoCs.
486
487		CONFIG_SYS_FSL_DDR_ADDR
488		Freescale DDR memory-mapped register base.
489
490		CONFIG_SYS_FSL_DDR_EMU
491		Specify emulator support for DDR. Some DDR features such as
492		deskew training are not available.
493
494		CONFIG_SYS_FSL_DDRC_GEN1
495		Freescale DDR1 controller.
496
497		CONFIG_SYS_FSL_DDRC_GEN2
498		Freescale DDR2 controller.
499
500		CONFIG_SYS_FSL_DDRC_GEN3
501		Freescale DDR3 controller.
502
503		CONFIG_SYS_FSL_DDRC_GEN4
504		Freescale DDR4 controller.
505
506		CONFIG_SYS_FSL_DDRC_ARM_GEN3
507		Freescale DDR3 controller for ARM-based SoCs.
508
509		CONFIG_SYS_FSL_DDR1
510		Board config to use DDR1. It can be enabled for SoCs with
511		Freescale DDR1 or DDR2 controllers, depending on the board
512		implemetation.
513
514		CONFIG_SYS_FSL_DDR2
515		Board config to use DDR2. It can be enabled for SoCs with
516		Freescale DDR2 or DDR3 controllers, depending on the board
517		implementation.
518
519		CONFIG_SYS_FSL_DDR3
520		Board config to use DDR3. It can be enabled for SoCs with
521		Freescale DDR3 or DDR3L controllers.
522
523		CONFIG_SYS_FSL_DDR3L
524		Board config to use DDR3L. It can be enabled for SoCs with
525		DDR3L controllers.
526
527		CONFIG_SYS_FSL_DDR4
528		Board config to use DDR4. It can be enabled for SoCs with
529		DDR4 controllers.
530
531		CONFIG_SYS_FSL_IFC_BE
532		Defines the IFC controller register space as Big Endian
533
534		CONFIG_SYS_FSL_IFC_LE
535		Defines the IFC controller register space as Little Endian
536
537		CONFIG_SYS_FSL_PBL_PBI
538		It enables addition of RCW (Power on reset configuration) in built image.
539		Please refer doc/README.pblimage for more details
540
541		CONFIG_SYS_FSL_PBL_RCW
542		It adds PBI(pre-boot instructions) commands in u-boot build image.
543		PBI commands can be used to configure SoC before it starts the execution.
544		Please refer doc/README.pblimage for more details
545
546		CONFIG_SPL_FSL_PBL
547		It adds a target to create boot binary having SPL binary in PBI format
548		concatenated with u-boot binary.
549
550		CONFIG_SYS_FSL_DDR_BE
551		Defines the DDR controller register space as Big Endian
552
553		CONFIG_SYS_FSL_DDR_LE
554		Defines the DDR controller register space as Little Endian
555
556		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
557		Physical address from the view of DDR controllers. It is the
558		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
559		it could be different for ARM SoCs.
560
561		CONFIG_SYS_FSL_DDR_INTLV_256B
562		DDR controller interleaving on 256-byte. This is a special
563		interleaving mode, handled by Dickens for Freescale layerscape
564		SoCs with ARM core.
565
566		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
567		Number of controllers used as main memory.
568
569		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
570		Number of controllers used for other than main memory.
571
572		CONFIG_SYS_FSL_HAS_DP_DDR
573		Defines the SoC has DP-DDR used for DPAA.
574
575		CONFIG_SYS_FSL_SEC_BE
576		Defines the SEC controller register space as Big Endian
577
578		CONFIG_SYS_FSL_SEC_LE
579		Defines the SEC controller register space as Little Endian
580
581- MIPS CPU options:
582		CONFIG_SYS_INIT_SP_OFFSET
583
584		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
585		pointer. This is needed for the temporary stack before
586		relocation.
587
588		CONFIG_SYS_MIPS_CACHE_MODE
589
590		Cache operation mode for the MIPS CPU.
591		See also arch/mips/include/asm/mipsregs.h.
592		Possible values are:
593			CONF_CM_CACHABLE_NO_WA
594			CONF_CM_CACHABLE_WA
595			CONF_CM_UNCACHED
596			CONF_CM_CACHABLE_NONCOHERENT
597			CONF_CM_CACHABLE_CE
598			CONF_CM_CACHABLE_COW
599			CONF_CM_CACHABLE_CUW
600			CONF_CM_CACHABLE_ACCELERATED
601
602		CONFIG_SYS_XWAY_EBU_BOOTCFG
603
604		Special option for Lantiq XWAY SoCs for booting from NOR flash.
605		See also arch/mips/cpu/mips32/start.S.
606
607		CONFIG_XWAY_SWAP_BYTES
608
609		Enable compilation of tools/xway-swap-bytes needed for Lantiq
610		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
611		be swapped if a flash programmer is used.
612
613- ARM options:
614		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
615
616		Select high exception vectors of the ARM core, e.g., do not
617		clear the V bit of the c1 register of CP15.
618
619		CONFIG_SYS_THUMB_BUILD
620
621		Use this flag to build U-Boot using the Thumb instruction
622		set for ARM architectures. Thumb instruction set provides
623		better code density. For ARM architectures that support
624		Thumb2 this flag will result in Thumb2 code generated by
625		GCC.
626
627		CONFIG_ARM_ERRATA_716044
628		CONFIG_ARM_ERRATA_742230
629		CONFIG_ARM_ERRATA_743622
630		CONFIG_ARM_ERRATA_751472
631		CONFIG_ARM_ERRATA_761320
632		CONFIG_ARM_ERRATA_773022
633		CONFIG_ARM_ERRATA_774769
634		CONFIG_ARM_ERRATA_794072
635
636		If set, the workarounds for these ARM errata are applied early
637		during U-Boot startup. Note that these options force the
638		workarounds to be applied; no CPU-type/version detection
639		exists, unlike the similar options in the Linux kernel. Do not
640		set these options unless they apply!
641
642		COUNTER_FREQUENCY
643		Generic timer clock source frequency.
644
645		COUNTER_FREQUENCY_REAL
646		Generic timer clock source frequency if the real clock is
647		different from COUNTER_FREQUENCY, and can only be determined
648		at run time.
649
650		NOTE: The following can be machine specific errata. These
651		do have ability to provide rudimentary version and machine
652		specific checks, but expect no product checks.
653		CONFIG_ARM_ERRATA_430973
654		CONFIG_ARM_ERRATA_454179
655		CONFIG_ARM_ERRATA_621766
656		CONFIG_ARM_ERRATA_798870
657		CONFIG_ARM_ERRATA_801819
658
659- Tegra SoC options:
660		CONFIG_TEGRA_SUPPORT_NON_SECURE
661
662		Support executing U-Boot in non-secure (NS) mode. Certain
663		impossible actions will be skipped if the CPU is in NS mode,
664		such as ARM architectural timer initialization.
665
666- Linux Kernel Interface:
667		CONFIG_CLOCKS_IN_MHZ
668
669		U-Boot stores all clock information in Hz
670		internally. For binary compatibility with older Linux
671		kernels (which expect the clocks passed in the
672		bd_info data to be in MHz) the environment variable
673		"clocks_in_mhz" can be defined so that U-Boot
674		converts clock data to MHZ before passing it to the
675		Linux kernel.
676		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
677		"clocks_in_mhz=1" is automatically included in the
678		default environment.
679
680		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
681
682		When transferring memsize parameter to Linux, some versions
683		expect it to be in bytes, others in MB.
684		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
685
686		CONFIG_OF_LIBFDT
687
688		New kernel versions are expecting firmware settings to be
689		passed using flattened device trees (based on open firmware
690		concepts).
691
692		CONFIG_OF_LIBFDT
693		 * New libfdt-based support
694		 * Adds the "fdt" command
695		 * The bootm command automatically updates the fdt
696
697		OF_CPU - The proper name of the cpus node (only required for
698			MPC512X and MPC5xxx based boards).
699		OF_SOC - The proper name of the soc node (only required for
700			MPC512X and MPC5xxx based boards).
701		OF_TBCLK - The timebase frequency.
702		OF_STDOUT_PATH - The path to the console device
703
704		boards with QUICC Engines require OF_QE to set UCC MAC
705		addresses
706
707		CONFIG_OF_BOARD_SETUP
708
709		Board code has addition modification that it wants to make
710		to the flat device tree before handing it off to the kernel
711
712		CONFIG_OF_SYSTEM_SETUP
713
714		Other code has addition modification that it wants to make
715		to the flat device tree before handing it off to the kernel.
716		This causes ft_system_setup() to be called before booting
717		the kernel.
718
719		CONFIG_OF_BOOT_CPU
720
721		This define fills in the correct boot CPU in the boot
722		param header, the default value is zero if undefined.
723
724		CONFIG_OF_IDE_FIXUP
725
726		U-Boot can detect if an IDE device is present or not.
727		If not, and this new config option is activated, U-Boot
728		removes the ATA node from the DTS before booting Linux,
729		so the Linux IDE driver does not probe the device and
730		crash. This is needed for buggy hardware (uc101) where
731		no pull down resistor is connected to the signal IDE5V_DD7.
732
733		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
734
735		This setting is mandatory for all boards that have only one
736		machine type and must be used to specify the machine type
737		number as it appears in the ARM machine registry
738		(see http://www.arm.linux.org.uk/developer/machines/).
739		Only boards that have multiple machine types supported
740		in a single configuration file and the machine type is
741		runtime discoverable, do not have to use this setting.
742
743- vxWorks boot parameters:
744
745		bootvx constructs a valid bootline using the following
746		environments variables: bootdev, bootfile, ipaddr, netmask,
747		serverip, gatewayip, hostname, othbootargs.
748		It loads the vxWorks image pointed bootfile.
749
750		Note: If a "bootargs" environment is defined, it will overwride
751		the defaults discussed just above.
752
753- Cache Configuration:
754		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
755		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
756		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
757
758- Cache Configuration for ARM:
759		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
760				      controller
761		CONFIG_SYS_PL310_BASE - Physical base address of PL310
762					controller register space
763
764- Serial Ports:
765		CONFIG_PL010_SERIAL
766
767		Define this if you want support for Amba PrimeCell PL010 UARTs.
768
769		CONFIG_PL011_SERIAL
770
771		Define this if you want support for Amba PrimeCell PL011 UARTs.
772
773		CONFIG_PL011_CLOCK
774
775		If you have Amba PrimeCell PL011 UARTs, set this variable to
776		the clock speed of the UARTs.
777
778		CONFIG_PL01x_PORTS
779
780		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
781		define this to a list of base addresses for each (supported)
782		port. See e.g. include/configs/versatile.h
783
784		CONFIG_SERIAL_HW_FLOW_CONTROL
785
786		Define this variable to enable hw flow control in serial driver.
787		Current user of this option is drivers/serial/nsl16550.c driver
788
789- Console Interface:
790		Depending on board, define exactly one serial port
791		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
792		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
793		console by defining CONFIG_8xx_CONS_NONE
794
795		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
796		port routines must be defined elsewhere
797		(i.e. serial_init(), serial_getc(), ...)
798
799		CONFIG_CFB_CONSOLE
800		Enables console device for a color framebuffer. Needs following
801		defines (cf. smiLynxEM, i8042)
802			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
803						(default big endian)
804			VIDEO_HW_RECTFILL	graphic chip supports
805						rectangle fill
806						(cf. smiLynxEM)
807			VIDEO_HW_BITBLT		graphic chip supports
808						bit-blit (cf. smiLynxEM)
809			VIDEO_VISIBLE_COLS	visible pixel columns
810						(cols=pitch)
811			VIDEO_VISIBLE_ROWS	visible pixel rows
812			VIDEO_PIXEL_SIZE	bytes per pixel
813			VIDEO_DATA_FORMAT	graphic data format
814						(0-5, cf. cfb_console.c)
815			VIDEO_FB_ADRS		framebuffer address
816			VIDEO_KBD_INIT_FCT	keyboard int fct
817						(i.e. rx51_kp_init())
818			VIDEO_TSTC_FCT		test char fct
819						(i.e. rx51_kp_tstc)
820			VIDEO_GETC_FCT		get char fct
821						(i.e. rx51_kp_getc)
822			CONFIG_VIDEO_LOGO	display Linux logo in
823						upper left corner
824			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
825						linux_logo.h for logo.
826						Requires CONFIG_VIDEO_LOGO
827			CONFIG_CONSOLE_EXTRA_INFO
828						additional board info beside
829						the logo
830			CONFIG_HIDE_LOGO_VERSION
831						do not display bootloader
832						version string
833
834		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
835		a limited number of ANSI escape sequences (cursor control,
836		erase functions and limited graphics rendition control).
837
838		When CONFIG_CFB_CONSOLE is defined, video console is
839		default i/o. Serial console can be forced with
840		environment 'console=serial'.
841
842		When CONFIG_SILENT_CONSOLE is defined, all console
843		messages (by U-Boot and Linux!) can be silenced with
844		the "silent" environment variable. See
845		doc/README.silent for more information.
846
847		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
848			is 0x00.
849		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
850			is 0xa0.
851
852- Console Baudrate:
853		CONFIG_BAUDRATE - in bps
854		Select one of the baudrates listed in
855		CONFIG_SYS_BAUDRATE_TABLE, see below.
856		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
857
858- Console Rx buffer length
859		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
860		the maximum receive buffer length for the SMC.
861		This option is actual only for 82xx and 8xx possible.
862		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
863		must be defined, to setup the maximum idle timeout for
864		the SMC.
865
866- Pre-Console Buffer:
867		Prior to the console being initialised (i.e. serial UART
868		initialised etc) all console output is silently discarded.
869		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
870		buffer any console messages prior to the console being
871		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
872		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
873		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
874		bytes are output before the console is initialised, the
875		earlier bytes are discarded.
876
877		Note that when printing the buffer a copy is made on the
878		stack so CONFIG_PRE_CON_BUF_SZ must fit on the stack.
879
880		'Sane' compilers will generate smaller code if
881		CONFIG_PRE_CON_BUF_SZ is a power of 2
882
883- Autoboot Command:
884		CONFIG_BOOTCOMMAND
885		Only needed when CONFIG_BOOTDELAY is enabled;
886		define a command string that is automatically executed
887		when no character is read on the console interface
888		within "Boot Delay" after reset.
889
890		CONFIG_BOOTARGS
891		This can be used to pass arguments to the bootm
892		command. The value of CONFIG_BOOTARGS goes into the
893		environment value "bootargs".
894
895		CONFIG_RAMBOOT and CONFIG_NFSBOOT
896		The value of these goes into the environment as
897		"ramboot" and "nfsboot" respectively, and can be used
898		as a convenience, when switching between booting from
899		RAM and NFS.
900
901- Bootcount:
902		CONFIG_BOOTCOUNT_LIMIT
903		Implements a mechanism for detecting a repeating reboot
904		cycle, see:
905		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
906
907		CONFIG_BOOTCOUNT_ENV
908		If no softreset save registers are found on the hardware
909		"bootcount" is stored in the environment. To prevent a
910		saveenv on all reboots, the environment variable
911		"upgrade_available" is used. If "upgrade_available" is
912		0, "bootcount" is always 0, if "upgrade_available" is
913		1 "bootcount" is incremented in the environment.
914		So the Userspace Applikation must set the "upgrade_available"
915		and "bootcount" variable to 0, if a boot was successfully.
916
917- Pre-Boot Commands:
918		CONFIG_PREBOOT
919
920		When this option is #defined, the existence of the
921		environment variable "preboot" will be checked
922		immediately before starting the CONFIG_BOOTDELAY
923		countdown and/or running the auto-boot command resp.
924		entering interactive mode.
925
926		This feature is especially useful when "preboot" is
927		automatically generated or modified. For an example
928		see the LWMON board specific code: here "preboot" is
929		modified when the user holds down a certain
930		combination of keys on the (special) keyboard when
931		booting the systems
932
933- Serial Download Echo Mode:
934		CONFIG_LOADS_ECHO
935		If defined to 1, all characters received during a
936		serial download (using the "loads" command) are
937		echoed back. This might be needed by some terminal
938		emulations (like "cu"), but may as well just take
939		time on others. This setting #define's the initial
940		value of the "loads_echo" environment variable.
941
942- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
943		CONFIG_KGDB_BAUDRATE
944		Select one of the baudrates listed in
945		CONFIG_SYS_BAUDRATE_TABLE, see below.
946
947- Monitor Functions:
948		Monitor commands can be included or excluded
949		from the build by using the #include files
950		<config_cmd_all.h> and #undef'ing unwanted
951		commands, or adding #define's for wanted commands.
952
953		The default command configuration includes all commands
954		except those marked below with a "*".
955
956		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
957		CONFIG_CMD_ASKENV	* ask for env variable
958		CONFIG_CMD_BDI		  bdinfo
959		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
960		CONFIG_CMD_BMP		* BMP support
961		CONFIG_CMD_BSP		* Board specific commands
962		CONFIG_CMD_BOOTD	  bootd
963		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
964		CONFIG_CMD_CACHE	* icache, dcache
965		CONFIG_CMD_CLK   	* clock command support
966		CONFIG_CMD_CONSOLE	  coninfo
967		CONFIG_CMD_CRC32	* crc32
968		CONFIG_CMD_DATE		* support for RTC, date/time...
969		CONFIG_CMD_DHCP		* DHCP support
970		CONFIG_CMD_DIAG		* Diagnostics
971		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
972		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
973		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
974		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
975		CONFIG_CMD_DTT		* Digital Therm and Thermostat
976		CONFIG_CMD_ECHO		  echo arguments
977		CONFIG_CMD_EDITENV	  edit env variable
978		CONFIG_CMD_EEPROM	* EEPROM read/write support
979		CONFIG_CMD_EEPROM_LAYOUT* EEPROM layout aware commands
980		CONFIG_CMD_ELF		* bootelf, bootvx
981		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
982		CONFIG_CMD_ENV_FLAGS	* display details about env flags
983		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
984		CONFIG_CMD_EXPORTENV	* export the environment
985		CONFIG_CMD_EXT2		* ext2 command support
986		CONFIG_CMD_EXT4		* ext4 command support
987		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
988					  that work for multiple fs types
989		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
990		CONFIG_CMD_SAVEENV	  saveenv
991		CONFIG_CMD_FDC		* Floppy Disk Support
992		CONFIG_CMD_FAT		* FAT command support
993		CONFIG_CMD_FLASH	  flinfo, erase, protect
994		CONFIG_CMD_FPGA		  FPGA device initialization support
995		CONFIG_CMD_FUSE		* Device fuse support
996		CONFIG_CMD_GETTIME	* Get time since boot
997		CONFIG_CMD_GO		* the 'go' command (exec code)
998		CONFIG_CMD_GREPENV	* search environment
999		CONFIG_CMD_HASH		* calculate hash / digest
1000		CONFIG_CMD_I2C		* I2C serial bus support
1001		CONFIG_CMD_IDE		* IDE harddisk support
1002		CONFIG_CMD_IMI		  iminfo
1003		CONFIG_CMD_IMLS		  List all images found in NOR flash
1004		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
1005		CONFIG_CMD_IMMAP	* IMMR dump support
1006		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
1007		CONFIG_CMD_IMPORTENV	* import an environment
1008		CONFIG_CMD_INI		* import data from an ini file into the env
1009		CONFIG_CMD_IRQ		* irqinfo
1010		CONFIG_CMD_ITEST	  Integer/string test of 2 values
1011		CONFIG_CMD_JFFS2	* JFFS2 Support
1012		CONFIG_CMD_KGDB		* kgdb
1013		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
1014		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
1015					  (169.254.*.*)
1016		CONFIG_CMD_LOADB	  loadb
1017		CONFIG_CMD_LOADS	  loads
1018		CONFIG_CMD_MD5SUM	* print md5 message digest
1019					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
1020		CONFIG_CMD_MEMINFO	* Display detailed memory information
1021		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
1022					  loop, loopw
1023		CONFIG_CMD_MEMTEST	* mtest
1024		CONFIG_CMD_MISC		  Misc functions like sleep etc
1025		CONFIG_CMD_MMC		* MMC memory mapped support
1026		CONFIG_CMD_MII		* MII utility commands
1027		CONFIG_CMD_MTDPARTS	* MTD partition support
1028		CONFIG_CMD_NAND		* NAND support
1029		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1030		CONFIG_CMD_NFS		  NFS support
1031		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1032		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1033		CONFIG_CMD_PCI		* pciinfo
1034		CONFIG_CMD_PCMCIA		* PCMCIA support
1035		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1036					  host
1037		CONFIG_CMD_PORTIO	* Port I/O
1038		CONFIG_CMD_READ		* Read raw data from partition
1039		CONFIG_CMD_REGINFO	* Register dump
1040		CONFIG_CMD_RUN		  run command in env variable
1041		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1042		CONFIG_CMD_SAVES	* save S record dump
1043		CONFIG_SCSI		* SCSI Support
1044		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1045					  (requires CONFIG_CMD_I2C)
1046		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1047					  (4xx only)
1048		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1049		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1050					  (requires CONFIG_CMD_MEMORY)
1051		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1052		CONFIG_CMD_SOURCE	  "source" command Support
1053		CONFIG_CMD_SPI		* SPI serial bus support
1054		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1055		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1056		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1057		CONFIG_CMD_TIMER	* access to the system tick timer
1058		CONFIG_CMD_USB		* USB support
1059		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1060		CONFIG_CMD_MFSL		* Microblaze FSL support
1061		CONFIG_CMD_XIMG		  Load part of Multi Image
1062		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1063
1064		EXAMPLE: If you want all functions except of network
1065		support you can write:
1066
1067		#include "config_cmd_all.h"
1068		#undef CONFIG_CMD_NET
1069
1070	Other Commands:
1071		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1072
1073	Note:	Don't enable the "icache" and "dcache" commands
1074		(configuration option CONFIG_CMD_CACHE) unless you know
1075		what you (and your U-Boot users) are doing. Data
1076		cache cannot be enabled on systems like the 8xx or
1077		8260 (where accesses to the IMMR region must be
1078		uncached), and it cannot be disabled on all other
1079		systems where we (mis-) use the data cache to hold an
1080		initial stack and some data.
1081
1082
1083		XXX - this list needs to get updated!
1084
1085- Removal of commands
1086		If no commands are needed to boot, you can disable
1087		CONFIG_CMDLINE to remove them. In this case, the command line
1088		will not be available, and when U-Boot wants to execute the
1089		boot command (on start-up) it will call board_run_command()
1090		instead. This can reduce image size significantly for very
1091		simple boot procedures.
1092
1093- Regular expression support:
1094		CONFIG_REGEX
1095		If this variable is defined, U-Boot is linked against
1096		the SLRE (Super Light Regular Expression) library,
1097		which adds regex support to some commands, as for
1098		example "env grep" and "setexpr".
1099
1100- Device tree:
1101		CONFIG_OF_CONTROL
1102		If this variable is defined, U-Boot will use a device tree
1103		to configure its devices, instead of relying on statically
1104		compiled #defines in the board file. This option is
1105		experimental and only available on a few boards. The device
1106		tree is available in the global data as gd->fdt_blob.
1107
1108		U-Boot needs to get its device tree from somewhere. This can
1109		be done using one of the two options below:
1110
1111		CONFIG_OF_EMBED
1112		If this variable is defined, U-Boot will embed a device tree
1113		binary in its image. This device tree file should be in the
1114		board directory and called <soc>-<board>.dts. The binary file
1115		is then picked up in board_init_f() and made available through
1116		the global data structure as gd->blob.
1117
1118		CONFIG_OF_SEPARATE
1119		If this variable is defined, U-Boot will build a device tree
1120		binary. It will be called u-boot.dtb. Architecture-specific
1121		code will locate it at run-time. Generally this works by:
1122
1123			cat u-boot.bin u-boot.dtb >image.bin
1124
1125		and in fact, U-Boot does this for you, creating a file called
1126		u-boot-dtb.bin which is useful in the common case. You can
1127		still use the individual files if you need something more
1128		exotic.
1129
1130- Watchdog:
1131		CONFIG_WATCHDOG
1132		If this variable is defined, it enables watchdog
1133		support for the SoC. There must be support in the SoC
1134		specific code for a watchdog. For the 8xx and 8260
1135		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1136		register.  When supported for a specific SoC is
1137		available, then no further board specific code should
1138		be needed to use it.
1139
1140		CONFIG_HW_WATCHDOG
1141		When using a watchdog circuitry external to the used
1142		SoC, then define this variable and provide board
1143		specific code for the "hw_watchdog_reset" function.
1144
1145		CONFIG_AT91_HW_WDT_TIMEOUT
1146		specify the timeout in seconds. default 2 seconds.
1147
1148- U-Boot Version:
1149		CONFIG_VERSION_VARIABLE
1150		If this variable is defined, an environment variable
1151		named "ver" is created by U-Boot showing the U-Boot
1152		version as printed by the "version" command.
1153		Any change to this variable will be reverted at the
1154		next reset.
1155
1156- Real-Time Clock:
1157
1158		When CONFIG_CMD_DATE is selected, the type of the RTC
1159		has to be selected, too. Define exactly one of the
1160		following options:
1161
1162		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1163		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1164		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1165		CONFIG_RTC_MC146818	- use MC146818 RTC
1166		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1167		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1168		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1169		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1170		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1171		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1172		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1173		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1174		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1175					  RV3029 RTC.
1176
1177		Note that if the RTC uses I2C, then the I2C interface
1178		must also be configured. See I2C Support, below.
1179
1180- GPIO Support:
1181		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1182
1183		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1184		chip-ngpio pairs that tell the PCA953X driver the number of
1185		pins supported by a particular chip.
1186
1187		Note that if the GPIO device uses I2C, then the I2C interface
1188		must also be configured. See I2C Support, below.
1189
1190- I/O tracing:
1191		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1192		accesses and can checksum them or write a list of them out
1193		to memory. See the 'iotrace' command for details. This is
1194		useful for testing device drivers since it can confirm that
1195		the driver behaves the same way before and after a code
1196		change. Currently this is supported on sandbox and arm. To
1197		add support for your architecture, add '#include <iotrace.h>'
1198		to the bottom of arch/<arch>/include/asm/io.h and test.
1199
1200		Example output from the 'iotrace stats' command is below.
1201		Note that if the trace buffer is exhausted, the checksum will
1202		still continue to operate.
1203
1204			iotrace is enabled
1205			Start:  10000000	(buffer start address)
1206			Size:   00010000	(buffer size)
1207			Offset: 00000120	(current buffer offset)
1208			Output: 10000120	(start + offset)
1209			Count:  00000018	(number of trace records)
1210			CRC32:  9526fb66	(CRC32 of all trace records)
1211
1212- Timestamp Support:
1213
1214		When CONFIG_TIMESTAMP is selected, the timestamp
1215		(date and time) of an image is printed by image
1216		commands like bootm or iminfo. This option is
1217		automatically enabled when you select CONFIG_CMD_DATE .
1218
1219- Partition Labels (disklabels) Supported:
1220		Zero or more of the following:
1221		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1222		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1223				       Intel architecture, USB sticks, etc.
1224		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1225		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1226				       bootloader.  Note 2TB partition limit; see
1227				       disk/part_efi.c
1228		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1229
1230		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1231		CONFIG_SCSI) you must configure support for at
1232		least one non-MTD partition type as well.
1233
1234- IDE Reset method:
1235		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1236		board configurations files but used nowhere!
1237
1238		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1239		be performed by calling the function
1240			ide_set_reset(int reset)
1241		which has to be defined in a board specific file
1242
1243- ATAPI Support:
1244		CONFIG_ATAPI
1245
1246		Set this to enable ATAPI support.
1247
1248- LBA48 Support
1249		CONFIG_LBA48
1250
1251		Set this to enable support for disks larger than 137GB
1252		Also look at CONFIG_SYS_64BIT_LBA.
1253		Whithout these , LBA48 support uses 32bit variables and will 'only'
1254		support disks up to 2.1TB.
1255
1256		CONFIG_SYS_64BIT_LBA:
1257			When enabled, makes the IDE subsystem use 64bit sector addresses.
1258			Default is 32bit.
1259
1260- SCSI Support:
1261		At the moment only there is only support for the
1262		SYM53C8XX SCSI controller; define
1263		CONFIG_SCSI_SYM53C8XX to enable it.
1264
1265		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1266		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1267		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1268		maximum numbers of LUNs, SCSI ID's and target
1269		devices.
1270		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1271
1272		The environment variable 'scsidevs' is set to the number of
1273		SCSI devices found during the last scan.
1274
1275- NETWORK Support (PCI):
1276		CONFIG_E1000
1277		Support for Intel 8254x/8257x gigabit chips.
1278
1279		CONFIG_E1000_SPI
1280		Utility code for direct access to the SPI bus on Intel 8257x.
1281		This does not do anything useful unless you set at least one
1282		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1283
1284		CONFIG_E1000_SPI_GENERIC
1285		Allow generic access to the SPI bus on the Intel 8257x, for
1286		example with the "sspi" command.
1287
1288		CONFIG_CMD_E1000
1289		Management command for E1000 devices.  When used on devices
1290		with SPI support you can reprogram the EEPROM from U-Boot.
1291
1292		CONFIG_EEPRO100
1293		Support for Intel 82557/82559/82559ER chips.
1294		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1295		write routine for first time initialisation.
1296
1297		CONFIG_TULIP
1298		Support for Digital 2114x chips.
1299		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1300		modem chip initialisation (KS8761/QS6611).
1301
1302		CONFIG_NATSEMI
1303		Support for National dp83815 chips.
1304
1305		CONFIG_NS8382X
1306		Support for National dp8382[01] gigabit chips.
1307
1308- NETWORK Support (other):
1309
1310		CONFIG_DRIVER_AT91EMAC
1311		Support for AT91RM9200 EMAC.
1312
1313			CONFIG_RMII
1314			Define this to use reduced MII inteface
1315
1316			CONFIG_DRIVER_AT91EMAC_QUIET
1317			If this defined, the driver is quiet.
1318			The driver doen't show link status messages.
1319
1320		CONFIG_CALXEDA_XGMAC
1321		Support for the Calxeda XGMAC device
1322
1323		CONFIG_LAN91C96
1324		Support for SMSC's LAN91C96 chips.
1325
1326			CONFIG_LAN91C96_BASE
1327			Define this to hold the physical address
1328			of the LAN91C96's I/O space
1329
1330			CONFIG_LAN91C96_USE_32_BIT
1331			Define this to enable 32 bit addressing
1332
1333		CONFIG_SMC91111
1334		Support for SMSC's LAN91C111 chip
1335
1336			CONFIG_SMC91111_BASE
1337			Define this to hold the physical address
1338			of the device (I/O space)
1339
1340			CONFIG_SMC_USE_32_BIT
1341			Define this if data bus is 32 bits
1342
1343			CONFIG_SMC_USE_IOFUNCS
1344			Define this to use i/o functions instead of macros
1345			(some hardware wont work with macros)
1346
1347		CONFIG_DRIVER_TI_EMAC
1348		Support for davinci emac
1349
1350			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1351			Define this if you have more then 3 PHYs.
1352
1353		CONFIG_FTGMAC100
1354		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1355
1356			CONFIG_FTGMAC100_EGIGA
1357			Define this to use GE link update with gigabit PHY.
1358			Define this if FTGMAC100 is connected to gigabit PHY.
1359			If your system has 10/100 PHY only, it might not occur
1360			wrong behavior. Because PHY usually return timeout or
1361			useless data when polling gigabit status and gigabit
1362			control registers. This behavior won't affect the
1363			correctnessof 10/100 link speed update.
1364
1365		CONFIG_SMC911X
1366		Support for SMSC's LAN911x and LAN921x chips
1367
1368			CONFIG_SMC911X_BASE
1369			Define this to hold the physical address
1370			of the device (I/O space)
1371
1372			CONFIG_SMC911X_32_BIT
1373			Define this if data bus is 32 bits
1374
1375			CONFIG_SMC911X_16_BIT
1376			Define this if data bus is 16 bits. If your processor
1377			automatically converts one 32 bit word to two 16 bit
1378			words you may also try CONFIG_SMC911X_32_BIT.
1379
1380		CONFIG_SH_ETHER
1381		Support for Renesas on-chip Ethernet controller
1382
1383			CONFIG_SH_ETHER_USE_PORT
1384			Define the number of ports to be used
1385
1386			CONFIG_SH_ETHER_PHY_ADDR
1387			Define the ETH PHY's address
1388
1389			CONFIG_SH_ETHER_CACHE_WRITEBACK
1390			If this option is set, the driver enables cache flush.
1391
1392- PWM Support:
1393		CONFIG_PWM_IMX
1394		Support for PWM modul on the imx6.
1395
1396- TPM Support:
1397		CONFIG_TPM
1398		Support TPM devices.
1399
1400		CONFIG_TPM_TIS_INFINEON
1401		Support for Infineon i2c bus TPM devices. Only one device
1402		per system is supported at this time.
1403
1404			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1405			Define the burst count bytes upper limit
1406
1407		CONFIG_TPM_ST33ZP24
1408		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1409
1410			CONFIG_TPM_ST33ZP24_I2C
1411			Support for STMicroelectronics ST33ZP24 I2C devices.
1412			Requires TPM_ST33ZP24 and I2C.
1413
1414			CONFIG_TPM_ST33ZP24_SPI
1415			Support for STMicroelectronics ST33ZP24 SPI devices.
1416			Requires TPM_ST33ZP24 and SPI.
1417
1418		CONFIG_TPM_ATMEL_TWI
1419		Support for Atmel TWI TPM device. Requires I2C support.
1420
1421		CONFIG_TPM_TIS_LPC
1422		Support for generic parallel port TPM devices. Only one device
1423		per system is supported at this time.
1424
1425			CONFIG_TPM_TIS_BASE_ADDRESS
1426			Base address where the generic TPM device is mapped
1427			to. Contemporary x86 systems usually map it at
1428			0xfed40000.
1429
1430		CONFIG_CMD_TPM
1431		Add tpm monitor functions.
1432		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1433		provides monitor access to authorized functions.
1434
1435		CONFIG_TPM
1436		Define this to enable the TPM support library which provides
1437		functional interfaces to some TPM commands.
1438		Requires support for a TPM device.
1439
1440		CONFIG_TPM_AUTH_SESSIONS
1441		Define this to enable authorized functions in the TPM library.
1442		Requires CONFIG_TPM and CONFIG_SHA1.
1443
1444- USB Support:
1445		At the moment only the UHCI host controller is
1446		supported (PIP405, MIP405, MPC5200); define
1447		CONFIG_USB_UHCI to enable it.
1448		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1449		and define CONFIG_USB_STORAGE to enable the USB
1450		storage devices.
1451		Note:
1452		Supported are USB Keyboards and USB Floppy drives
1453		(TEAC FD-05PUB).
1454		MPC5200 USB requires additional defines:
1455			CONFIG_USB_CLOCK
1456				for 528 MHz Clock: 0x0001bbbb
1457			CONFIG_PSC3_USB
1458				for USB on PSC3
1459			CONFIG_USB_CONFIG
1460				for differential drivers: 0x00001000
1461				for single ended drivers: 0x00005000
1462				for differential drivers on PSC3: 0x00000100
1463				for single ended drivers on PSC3: 0x00004100
1464			CONFIG_SYS_USB_EVENT_POLL
1465				May be defined to allow interrupt polling
1466				instead of using asynchronous interrupts
1467
1468		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1469		txfilltuning field in the EHCI controller on reset.
1470
1471		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1472		HW module registers.
1473
1474- USB Device:
1475		Define the below if you wish to use the USB console.
1476		Once firmware is rebuilt from a serial console issue the
1477		command "setenv stdin usbtty; setenv stdout usbtty" and
1478		attach your USB cable. The Unix command "dmesg" should print
1479		it has found a new device. The environment variable usbtty
1480		can be set to gserial or cdc_acm to enable your device to
1481		appear to a USB host as a Linux gserial device or a
1482		Common Device Class Abstract Control Model serial device.
1483		If you select usbtty = gserial you should be able to enumerate
1484		a Linux host by
1485		# modprobe usbserial vendor=0xVendorID product=0xProductID
1486		else if using cdc_acm, simply setting the environment
1487		variable usbtty to be cdc_acm should suffice. The following
1488		might be defined in YourBoardName.h
1489
1490			CONFIG_USB_DEVICE
1491			Define this to build a UDC device
1492
1493			CONFIG_USB_TTY
1494			Define this to have a tty type of device available to
1495			talk to the UDC device
1496
1497			CONFIG_USBD_HS
1498			Define this to enable the high speed support for usb
1499			device and usbtty. If this feature is enabled, a routine
1500			int is_usbd_high_speed(void)
1501			also needs to be defined by the driver to dynamically poll
1502			whether the enumeration has succeded at high speed or full
1503			speed.
1504
1505			CONFIG_SYS_CONSOLE_IS_IN_ENV
1506			Define this if you want stdin, stdout &/or stderr to
1507			be set to usbtty.
1508
1509			mpc8xx:
1510				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1511				Derive USB clock from external clock "blah"
1512				- CONFIG_SYS_USB_EXTC_CLK 0x02
1513
1514				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1515				Derive USB clock from brgclk
1516				- CONFIG_SYS_USB_BRG_CLK 0x04
1517
1518		If you have a USB-IF assigned VendorID then you may wish to
1519		define your own vendor specific values either in BoardName.h
1520		or directly in usbd_vendor_info.h. If you don't define
1521		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1522		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1523		should pretend to be a Linux device to it's target host.
1524
1525			CONFIG_USBD_MANUFACTURER
1526			Define this string as the name of your company for
1527			- CONFIG_USBD_MANUFACTURER "my company"
1528
1529			CONFIG_USBD_PRODUCT_NAME
1530			Define this string as the name of your product
1531			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1532
1533			CONFIG_USBD_VENDORID
1534			Define this as your assigned Vendor ID from the USB
1535			Implementors Forum. This *must* be a genuine Vendor ID
1536			to avoid polluting the USB namespace.
1537			- CONFIG_USBD_VENDORID 0xFFFF
1538
1539			CONFIG_USBD_PRODUCTID
1540			Define this as the unique Product ID
1541			for your device
1542			- CONFIG_USBD_PRODUCTID 0xFFFF
1543
1544- ULPI Layer Support:
1545		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1546		the generic ULPI layer. The generic layer accesses the ULPI PHY
1547		via the platform viewport, so you need both the genric layer and
1548		the viewport enabled. Currently only Chipidea/ARC based
1549		viewport is supported.
1550		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1551		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1552		If your ULPI phy needs a different reference clock than the
1553		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1554		the appropriate value in Hz.
1555
1556- MMC Support:
1557		The MMC controller on the Intel PXA is supported. To
1558		enable this define CONFIG_MMC. The MMC can be
1559		accessed from the boot prompt by mapping the device
1560		to physical memory similar to flash. Command line is
1561		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1562		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1563
1564		CONFIG_SH_MMCIF
1565		Support for Renesas on-chip MMCIF controller
1566
1567			CONFIG_SH_MMCIF_ADDR
1568			Define the base address of MMCIF registers
1569
1570			CONFIG_SH_MMCIF_CLK
1571			Define the clock frequency for MMCIF
1572
1573		CONFIG_GENERIC_MMC
1574		Enable the generic MMC driver
1575
1576		CONFIG_SUPPORT_EMMC_BOOT
1577		Enable some additional features of the eMMC boot partitions.
1578
1579		CONFIG_SUPPORT_EMMC_RPMB
1580		Enable the commands for reading, writing and programming the
1581		key for the Replay Protection Memory Block partition in eMMC.
1582
1583- USB Device Firmware Update (DFU) class support:
1584		CONFIG_USB_FUNCTION_DFU
1585		This enables the USB portion of the DFU USB class
1586
1587		CONFIG_CMD_DFU
1588		This enables the command "dfu" which is used to have
1589		U-Boot create a DFU class device via USB.  This command
1590		requires that the "dfu_alt_info" environment variable be
1591		set and define the alt settings to expose to the host.
1592
1593		CONFIG_DFU_MMC
1594		This enables support for exposing (e)MMC devices via DFU.
1595
1596		CONFIG_DFU_NAND
1597		This enables support for exposing NAND devices via DFU.
1598
1599		CONFIG_DFU_RAM
1600		This enables support for exposing RAM via DFU.
1601		Note: DFU spec refer to non-volatile memory usage, but
1602		allow usages beyond the scope of spec - here RAM usage,
1603		one that would help mostly the developer.
1604
1605		CONFIG_SYS_DFU_DATA_BUF_SIZE
1606		Dfu transfer uses a buffer before writing data to the
1607		raw storage device. Make the size (in bytes) of this buffer
1608		configurable. The size of this buffer is also configurable
1609		through the "dfu_bufsiz" environment variable.
1610
1611		CONFIG_SYS_DFU_MAX_FILE_SIZE
1612		When updating files rather than the raw storage device,
1613		we use a static buffer to copy the file into and then write
1614		the buffer once we've been given the whole file.  Define
1615		this to the maximum filesize (in bytes) for the buffer.
1616		Default is 4 MiB if undefined.
1617
1618		DFU_DEFAULT_POLL_TIMEOUT
1619		Poll timeout [ms], is the timeout a device can send to the
1620		host. The host must wait for this timeout before sending
1621		a subsequent DFU_GET_STATUS request to the device.
1622
1623		DFU_MANIFEST_POLL_TIMEOUT
1624		Poll timeout [ms], which the device sends to the host when
1625		entering dfuMANIFEST state. Host waits this timeout, before
1626		sending again an USB request to the device.
1627
1628- USB Device Android Fastboot support:
1629		CONFIG_USB_FUNCTION_FASTBOOT
1630		This enables the USB part of the fastboot gadget
1631
1632		CONFIG_CMD_FASTBOOT
1633		This enables the command "fastboot" which enables the Android
1634		fastboot mode for the platform's USB device. Fastboot is a USB
1635		protocol for downloading images, flashing and device control
1636		used on Android devices.
1637		See doc/README.android-fastboot for more information.
1638
1639		CONFIG_ANDROID_BOOT_IMAGE
1640		This enables support for booting images which use the Android
1641		image format header.
1642
1643		CONFIG_FASTBOOT_BUF_ADDR
1644		The fastboot protocol requires a large memory buffer for
1645		downloads. Define this to the starting RAM address to use for
1646		downloaded images.
1647
1648		CONFIG_FASTBOOT_BUF_SIZE
1649		The fastboot protocol requires a large memory buffer for
1650		downloads. This buffer should be as large as possible for a
1651		platform. Define this to the size available RAM for fastboot.
1652
1653		CONFIG_FASTBOOT_FLASH
1654		The fastboot protocol includes a "flash" command for writing
1655		the downloaded image to a non-volatile storage device. Define
1656		this to enable the "fastboot flash" command.
1657
1658		CONFIG_FASTBOOT_FLASH_MMC_DEV
1659		The fastboot "flash" command requires additional information
1660		regarding the non-volatile storage device. Define this to
1661		the eMMC device that fastboot should use to store the image.
1662
1663		CONFIG_FASTBOOT_GPT_NAME
1664		The fastboot "flash" command supports writing the downloaded
1665		image to the Protective MBR and the Primary GUID Partition
1666		Table. (Additionally, this downloaded image is post-processed
1667		to generate and write the Backup GUID Partition Table.)
1668		This occurs when the specified "partition name" on the
1669		"fastboot flash" command line matches this value.
1670		The default is "gpt" if undefined.
1671
1672		CONFIG_FASTBOOT_MBR_NAME
1673		The fastboot "flash" command supports writing the downloaded
1674		image to DOS MBR.
1675		This occurs when the "partition name" specified on the
1676		"fastboot flash" command line matches this value.
1677		If not defined the default value "mbr" is used.
1678
1679- Journaling Flash filesystem support:
1680		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1681		CONFIG_JFFS2_NAND_DEV
1682		Define these for a default partition on a NAND device
1683
1684		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1685		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1686		Define these for a default partition on a NOR device
1687
1688		CONFIG_SYS_JFFS_CUSTOM_PART
1689		Define this to create an own partition. You have to provide a
1690		function struct part_info* jffs2_part_info(int part_num)
1691
1692		If you define only one JFFS2 partition you may also want to
1693		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1694		to disable the command chpart. This is the default when you
1695		have not defined a custom partition
1696
1697- FAT(File Allocation Table) filesystem write function support:
1698		CONFIG_FAT_WRITE
1699
1700		Define this to enable support for saving memory data as a
1701		file in FAT formatted partition.
1702
1703		This will also enable the command "fatwrite" enabling the
1704		user to write files to FAT.
1705
1706CBFS (Coreboot Filesystem) support
1707		CONFIG_CMD_CBFS
1708
1709		Define this to enable support for reading from a Coreboot
1710		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1711		and cbfsload.
1712
1713- FAT(File Allocation Table) filesystem cluster size:
1714		CONFIG_FS_FAT_MAX_CLUSTSIZE
1715
1716		Define the max cluster size for fat operations else
1717		a default value of 65536 will be defined.
1718
1719- Keyboard Support:
1720		See Kconfig help for available keyboard drivers.
1721
1722		CONFIG_KEYBOARD
1723
1724		Define this to enable a custom keyboard support.
1725		This simply calls drv_keyboard_init() which must be
1726		defined in your board-specific files. This option is deprecated
1727		and is only used by novena. For new boards, use driver model
1728		instead.
1729
1730- Video support:
1731		CONFIG_VIDEO
1732
1733		Define this to enable video support (for output to
1734		video).
1735
1736		CONFIG_VIDEO_CT69000
1737
1738		Enable Chips & Technologies 69000 Video chip
1739
1740		CONFIG_VIDEO_SMI_LYNXEM
1741		Enable Silicon Motion SMI 712/710/810 Video chip. The
1742		video output is selected via environment 'videoout'
1743		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1744		assumed.
1745
1746		For the CT69000 and SMI_LYNXEM drivers, videomode is
1747		selected via environment 'videomode'. Two different ways
1748		are possible:
1749		- "videomode=num"   'num' is a standard LiLo mode numbers.
1750		Following standard modes are supported	(* is default):
1751
1752		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1753		-------------+---------------------------------------------
1754		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1755		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1756		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1757		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1758		-------------+---------------------------------------------
1759		(i.e. setenv videomode 317; saveenv; reset;)
1760
1761		- "videomode=bootargs" all the video parameters are parsed
1762		from the bootargs. (See drivers/video/videomodes.c)
1763
1764
1765		CONFIG_VIDEO_SED13806
1766		Enable Epson SED13806 driver. This driver supports 8bpp
1767		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1768		or CONFIG_VIDEO_SED13806_16BPP
1769
1770		CONFIG_FSL_DIU_FB
1771		Enable the Freescale DIU video driver.	Reference boards for
1772		SOCs that have a DIU should define this macro to enable DIU
1773		support, and should also define these other macros:
1774
1775			CONFIG_SYS_DIU_ADDR
1776			CONFIG_VIDEO
1777			CONFIG_CMD_BMP
1778			CONFIG_CFB_CONSOLE
1779			CONFIG_VIDEO_SW_CURSOR
1780			CONFIG_VGA_AS_SINGLE_DEVICE
1781			CONFIG_VIDEO_LOGO
1782			CONFIG_VIDEO_BMP_LOGO
1783
1784		The DIU driver will look for the 'video-mode' environment
1785		variable, and if defined, enable the DIU as a console during
1786		boot.  See the documentation file doc/README.video for a
1787		description of this variable.
1788
1789- LCD Support:	CONFIG_LCD
1790
1791		Define this to enable LCD support (for output to LCD
1792		display); also select one of the supported displays
1793		by defining one of these:
1794
1795		CONFIG_ATMEL_LCD:
1796
1797			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1798
1799		CONFIG_NEC_NL6448AC33:
1800
1801			NEC NL6448AC33-18. Active, color, single scan.
1802
1803		CONFIG_NEC_NL6448BC20
1804
1805			NEC NL6448BC20-08. 6.5", 640x480.
1806			Active, color, single scan.
1807
1808		CONFIG_NEC_NL6448BC33_54
1809
1810			NEC NL6448BC33-54. 10.4", 640x480.
1811			Active, color, single scan.
1812
1813		CONFIG_SHARP_16x9
1814
1815			Sharp 320x240. Active, color, single scan.
1816			It isn't 16x9, and I am not sure what it is.
1817
1818		CONFIG_SHARP_LQ64D341
1819
1820			Sharp LQ64D341 display, 640x480.
1821			Active, color, single scan.
1822
1823		CONFIG_HLD1045
1824
1825			HLD1045 display, 640x480.
1826			Active, color, single scan.
1827
1828		CONFIG_OPTREX_BW
1829
1830			Optrex	 CBL50840-2 NF-FW 99 22 M5
1831			or
1832			Hitachi	 LMG6912RPFC-00T
1833			or
1834			Hitachi	 SP14Q002
1835
1836			320x240. Black & white.
1837
1838		Normally display is black on white background; define
1839		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1840
1841		CONFIG_LCD_ALIGNMENT
1842
1843		Normally the LCD is page-aligned (typically 4KB). If this is
1844		defined then the LCD will be aligned to this value instead.
1845		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1846		here, since it is cheaper to change data cache settings on
1847		a per-section basis.
1848
1849		CONFIG_CONSOLE_SCROLL_LINES
1850
1851		When the console need to be scrolled, this is the number of
1852		lines to scroll by. It defaults to 1. Increasing this makes
1853		the console jump but can help speed up operation when scrolling
1854		is slow.
1855
1856		CONFIG_LCD_ROTATION
1857
1858		Sometimes, for example if the display is mounted in portrait
1859		mode or even if it's mounted landscape but rotated by 180degree,
1860		we need to rotate our content of the display relative to the
1861		framebuffer, so that user can read the messages which are
1862		printed out.
1863		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1864		initialized with a given rotation from "vl_rot" out of
1865		"vidinfo_t" which is provided by the board specific code.
1866		The value for vl_rot is coded as following (matching to
1867		fbcon=rotate:<n> linux-kernel commandline):
1868		0 = no rotation respectively 0 degree
1869		1 = 90 degree rotation
1870		2 = 180 degree rotation
1871		3 = 270 degree rotation
1872
1873		If CONFIG_LCD_ROTATION is not defined, the console will be
1874		initialized with 0degree rotation.
1875
1876		CONFIG_LCD_BMP_RLE8
1877
1878		Support drawing of RLE8-compressed bitmaps on the LCD.
1879
1880		CONFIG_I2C_EDID
1881
1882		Enables an 'i2c edid' command which can read EDID
1883		information over I2C from an attached LCD display.
1884
1885- Splash Screen Support: CONFIG_SPLASH_SCREEN
1886
1887		If this option is set, the environment is checked for
1888		a variable "splashimage". If found, the usual display
1889		of logo, copyright and system information on the LCD
1890		is suppressed and the BMP image at the address
1891		specified in "splashimage" is loaded instead. The
1892		console is redirected to the "nulldev", too. This
1893		allows for a "silent" boot where a splash screen is
1894		loaded very quickly after power-on.
1895
1896		CONFIG_SPLASHIMAGE_GUARD
1897
1898		If this option is set, then U-Boot will prevent the environment
1899		variable "splashimage" from being set to a problematic address
1900		(see doc/README.displaying-bmps).
1901		This option is useful for targets where, due to alignment
1902		restrictions, an improperly aligned BMP image will cause a data
1903		abort. If you think you will not have problems with unaligned
1904		accesses (for example because your toolchain prevents them)
1905		there is no need to set this option.
1906
1907		CONFIG_SPLASH_SCREEN_ALIGN
1908
1909		If this option is set the splash image can be freely positioned
1910		on the screen. Environment variable "splashpos" specifies the
1911		position as "x,y". If a positive number is given it is used as
1912		number of pixel from left/top. If a negative number is given it
1913		is used as number of pixel from right/bottom. You can also
1914		specify 'm' for centering the image.
1915
1916		Example:
1917		setenv splashpos m,m
1918			=> image at center of screen
1919
1920		setenv splashpos 30,20
1921			=> image at x = 30 and y = 20
1922
1923		setenv splashpos -10,m
1924			=> vertically centered image
1925			   at x = dspWidth - bmpWidth - 9
1926
1927- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1928
1929		If this option is set, additionally to standard BMP
1930		images, gzipped BMP images can be displayed via the
1931		splashscreen support or the bmp command.
1932
1933- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1934
1935		If this option is set, 8-bit RLE compressed BMP images
1936		can be displayed via the splashscreen support or the
1937		bmp command.
1938
1939- Do compressing for memory range:
1940		CONFIG_CMD_ZIP
1941
1942		If this option is set, it would use zlib deflate method
1943		to compress the specified memory at its best effort.
1944
1945- Compression support:
1946		CONFIG_GZIP
1947
1948		Enabled by default to support gzip compressed images.
1949
1950		CONFIG_BZIP2
1951
1952		If this option is set, support for bzip2 compressed
1953		images is included. If not, only uncompressed and gzip
1954		compressed images are supported.
1955
1956		NOTE: the bzip2 algorithm requires a lot of RAM, so
1957		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1958		be at least 4MB.
1959
1960		CONFIG_LZMA
1961
1962		If this option is set, support for lzma compressed
1963		images is included.
1964
1965		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1966		requires an amount of dynamic memory that is given by the
1967		formula:
1968
1969			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1970
1971		Where lc and lp stand for, respectively, Literal context bits
1972		and Literal pos bits.
1973
1974		This value is upper-bounded by 14MB in the worst case. Anyway,
1975		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1976		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1977		a very small buffer.
1978
1979		Use the lzmainfo tool to determinate the lc and lp values and
1980		then calculate the amount of needed dynamic memory (ensuring
1981		the appropriate CONFIG_SYS_MALLOC_LEN value).
1982
1983		CONFIG_LZO
1984
1985		If this option is set, support for LZO compressed images
1986		is included.
1987
1988- MII/PHY support:
1989		CONFIG_PHY_ADDR
1990
1991		The address of PHY on MII bus.
1992
1993		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1994
1995		The clock frequency of the MII bus
1996
1997		CONFIG_PHY_GIGE
1998
1999		If this option is set, support for speed/duplex
2000		detection of gigabit PHY is included.
2001
2002		CONFIG_PHY_RESET_DELAY
2003
2004		Some PHY like Intel LXT971A need extra delay after
2005		reset before any MII register access is possible.
2006		For such PHY, set this option to the usec delay
2007		required. (minimum 300usec for LXT971A)
2008
2009		CONFIG_PHY_CMD_DELAY (ppc4xx)
2010
2011		Some PHY like Intel LXT971A need extra delay after
2012		command issued before MII status register can be read
2013
2014- IP address:
2015		CONFIG_IPADDR
2016
2017		Define a default value for the IP address to use for
2018		the default Ethernet interface, in case this is not
2019		determined through e.g. bootp.
2020		(Environment variable "ipaddr")
2021
2022- Server IP address:
2023		CONFIG_SERVERIP
2024
2025		Defines a default value for the IP address of a TFTP
2026		server to contact when using the "tftboot" command.
2027		(Environment variable "serverip")
2028
2029		CONFIG_KEEP_SERVERADDR
2030
2031		Keeps the server's MAC address, in the env 'serveraddr'
2032		for passing to bootargs (like Linux's netconsole option)
2033
2034- Gateway IP address:
2035		CONFIG_GATEWAYIP
2036
2037		Defines a default value for the IP address of the
2038		default router where packets to other networks are
2039		sent to.
2040		(Environment variable "gatewayip")
2041
2042- Subnet mask:
2043		CONFIG_NETMASK
2044
2045		Defines a default value for the subnet mask (or
2046		routing prefix) which is used to determine if an IP
2047		address belongs to the local subnet or needs to be
2048		forwarded through a router.
2049		(Environment variable "netmask")
2050
2051- Multicast TFTP Mode:
2052		CONFIG_MCAST_TFTP
2053
2054		Defines whether you want to support multicast TFTP as per
2055		rfc-2090; for example to work with atftp.  Lets lots of targets
2056		tftp down the same boot image concurrently.  Note: the Ethernet
2057		driver in use must provide a function: mcast() to join/leave a
2058		multicast group.
2059
2060- BOOTP Recovery Mode:
2061		CONFIG_BOOTP_RANDOM_DELAY
2062
2063		If you have many targets in a network that try to
2064		boot using BOOTP, you may want to avoid that all
2065		systems send out BOOTP requests at precisely the same
2066		moment (which would happen for instance at recovery
2067		from a power failure, when all systems will try to
2068		boot, thus flooding the BOOTP server. Defining
2069		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
2070		inserted before sending out BOOTP requests. The
2071		following delays are inserted then:
2072
2073		1st BOOTP request:	delay 0 ... 1 sec
2074		2nd BOOTP request:	delay 0 ... 2 sec
2075		3rd BOOTP request:	delay 0 ... 4 sec
2076		4th and following
2077		BOOTP requests:		delay 0 ... 8 sec
2078
2079		CONFIG_BOOTP_ID_CACHE_SIZE
2080
2081		BOOTP packets are uniquely identified using a 32-bit ID. The
2082		server will copy the ID from client requests to responses and
2083		U-Boot will use this to determine if it is the destination of
2084		an incoming response. Some servers will check that addresses
2085		aren't in use before handing them out (usually using an ARP
2086		ping) and therefore take up to a few hundred milliseconds to
2087		respond. Network congestion may also influence the time it
2088		takes for a response to make it back to the client. If that
2089		time is too long, U-Boot will retransmit requests. In order
2090		to allow earlier responses to still be accepted after these
2091		retransmissions, U-Boot's BOOTP client keeps a small cache of
2092		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
2093		cache. The default is to keep IDs for up to four outstanding
2094		requests. Increasing this will allow U-Boot to accept offers
2095		from a BOOTP client in networks with unusually high latency.
2096
2097- DHCP Advanced Options:
2098		You can fine tune the DHCP functionality by defining
2099		CONFIG_BOOTP_* symbols:
2100
2101		CONFIG_BOOTP_SUBNETMASK
2102		CONFIG_BOOTP_GATEWAY
2103		CONFIG_BOOTP_HOSTNAME
2104		CONFIG_BOOTP_NISDOMAIN
2105		CONFIG_BOOTP_BOOTPATH
2106		CONFIG_BOOTP_BOOTFILESIZE
2107		CONFIG_BOOTP_DNS
2108		CONFIG_BOOTP_DNS2
2109		CONFIG_BOOTP_SEND_HOSTNAME
2110		CONFIG_BOOTP_NTPSERVER
2111		CONFIG_BOOTP_TIMEOFFSET
2112		CONFIG_BOOTP_VENDOREX
2113		CONFIG_BOOTP_MAY_FAIL
2114
2115		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
2116		environment variable, not the BOOTP server.
2117
2118		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
2119		after the configured retry count, the call will fail
2120		instead of starting over.  This can be used to fail over
2121		to Link-local IP address configuration if the DHCP server
2122		is not available.
2123
2124		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
2125		serverip from a DHCP server, it is possible that more
2126		than one DNS serverip is offered to the client.
2127		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
2128		serverip will be stored in the additional environment
2129		variable "dnsip2". The first DNS serverip is always
2130		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2131		is defined.
2132
2133		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2134		to do a dynamic update of a DNS server. To do this, they
2135		need the hostname of the DHCP requester.
2136		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2137		of the "hostname" environment variable is passed as
2138		option 12 to the DHCP server.
2139
2140		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2141
2142		A 32bit value in microseconds for a delay between
2143		receiving a "DHCP Offer" and sending the "DHCP Request".
2144		This fixes a problem with certain DHCP servers that don't
2145		respond 100% of the time to a "DHCP request". E.g. On an
2146		AT91RM9200 processor running at 180MHz, this delay needed
2147		to be *at least* 15,000 usec before a Windows Server 2003
2148		DHCP server would reply 100% of the time. I recommend at
2149		least 50,000 usec to be safe. The alternative is to hope
2150		that one of the retries will be successful but note that
2151		the DHCP timeout and retry process takes a longer than
2152		this delay.
2153
2154 - Link-local IP address negotiation:
2155		Negotiate with other link-local clients on the local network
2156		for an address that doesn't require explicit configuration.
2157		This is especially useful if a DHCP server cannot be guaranteed
2158		to exist in all environments that the device must operate.
2159
2160		See doc/README.link-local for more information.
2161
2162 - CDP Options:
2163		CONFIG_CDP_DEVICE_ID
2164
2165		The device id used in CDP trigger frames.
2166
2167		CONFIG_CDP_DEVICE_ID_PREFIX
2168
2169		A two character string which is prefixed to the MAC address
2170		of the device.
2171
2172		CONFIG_CDP_PORT_ID
2173
2174		A printf format string which contains the ascii name of
2175		the port. Normally is set to "eth%d" which sets
2176		eth0 for the first Ethernet, eth1 for the second etc.
2177
2178		CONFIG_CDP_CAPABILITIES
2179
2180		A 32bit integer which indicates the device capabilities;
2181		0x00000010 for a normal host which does not forwards.
2182
2183		CONFIG_CDP_VERSION
2184
2185		An ascii string containing the version of the software.
2186
2187		CONFIG_CDP_PLATFORM
2188
2189		An ascii string containing the name of the platform.
2190
2191		CONFIG_CDP_TRIGGER
2192
2193		A 32bit integer sent on the trigger.
2194
2195		CONFIG_CDP_POWER_CONSUMPTION
2196
2197		A 16bit integer containing the power consumption of the
2198		device in .1 of milliwatts.
2199
2200		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2201
2202		A byte containing the id of the VLAN.
2203
2204- Status LED:	CONFIG_STATUS_LED
2205
2206		Several configurations allow to display the current
2207		status using a LED. For instance, the LED will blink
2208		fast while running U-Boot code, stop blinking as
2209		soon as a reply to a BOOTP request was received, and
2210		start blinking slow once the Linux kernel is running
2211		(supported by a status LED driver in the Linux
2212		kernel). Defining CONFIG_STATUS_LED enables this
2213		feature in U-Boot.
2214
2215		Additional options:
2216
2217		CONFIG_GPIO_LED
2218		The status LED can be connected to a GPIO pin.
2219		In such cases, the gpio_led driver can be used as a
2220		status LED backend implementation. Define CONFIG_GPIO_LED
2221		to include the gpio_led driver in the U-Boot binary.
2222
2223		CONFIG_GPIO_LED_INVERTED_TABLE
2224		Some GPIO connected LEDs may have inverted polarity in which
2225		case the GPIO high value corresponds to LED off state and
2226		GPIO low value corresponds to LED on state.
2227		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2228		with a list of GPIO LEDs that have inverted polarity.
2229
2230- CAN Support:	CONFIG_CAN_DRIVER
2231
2232		Defining CONFIG_CAN_DRIVER enables CAN driver support
2233		on those systems that support this (optional)
2234		feature, like the TQM8xxL modules.
2235
2236- I2C Support:	CONFIG_SYS_I2C
2237
2238		This enable the NEW i2c subsystem, and will allow you to use
2239		i2c commands at the u-boot command line (as long as you set
2240		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2241		based realtime clock chips or other i2c devices. See
2242		common/cmd_i2c.c for a description of the command line
2243		interface.
2244
2245		ported i2c driver to the new framework:
2246		- drivers/i2c/soft_i2c.c:
2247		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2248		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2249		    for defining speed and slave address
2250		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2251		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2252		    for defining speed and slave address
2253		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2254		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2255		    for defining speed and slave address
2256		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2257		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2258		    for defining speed and slave address
2259
2260		- drivers/i2c/fsl_i2c.c:
2261		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2262		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2263		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2264		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2265		    bus.
2266		  - If your board supports a second fsl i2c bus, define
2267		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2268		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2269		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2270		    second bus.
2271
2272		- drivers/i2c/tegra_i2c.c:
2273		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2274		  - This driver adds 4 i2c buses with a fix speed from
2275		    100000 and the slave addr 0!
2276
2277		- drivers/i2c/ppc4xx_i2c.c
2278		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2279		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2280		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2281
2282		- drivers/i2c/i2c_mxc.c
2283		  - activate this driver with CONFIG_SYS_I2C_MXC
2284		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
2285		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
2286		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
2287		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
2288		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2289		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2290		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2291		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2292		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2293		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2294		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
2295		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
2296		If those defines are not set, default value is 100000
2297		for speed, and 0 for slave.
2298
2299		- drivers/i2c/rcar_i2c.c:
2300		  - activate this driver with CONFIG_SYS_I2C_RCAR
2301		  - This driver adds 4 i2c buses
2302
2303		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2304		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2305		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2306		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2307		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2308		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2309		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2310		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2311		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2312
2313		- drivers/i2c/sh_i2c.c:
2314		  - activate this driver with CONFIG_SYS_I2C_SH
2315		  - This driver adds from 2 to 5 i2c buses
2316
2317		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2318		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2319		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2320		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2321		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2322		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2323		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2324		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2325		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2326		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2327		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2328		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2329		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2330
2331		- drivers/i2c/omap24xx_i2c.c
2332		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2333		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2334		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2335		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2336		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2337		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2338		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2339		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2340		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2341		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2342		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2343
2344		- drivers/i2c/zynq_i2c.c
2345		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2346		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2347		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2348
2349		- drivers/i2c/s3c24x0_i2c.c:
2350		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2351		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2352		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2353		    with a fix speed from 100000 and the slave addr 0!
2354
2355		- drivers/i2c/ihs_i2c.c
2356		  - activate this driver with CONFIG_SYS_I2C_IHS
2357		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2358		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2359		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2360		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2361		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2362		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2363		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2364		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2365		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2366		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2367		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2368		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2369		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
2370		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
2371		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
2372		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
2373		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
2374		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
2375		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
2376		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
2377		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
2378
2379		additional defines:
2380
2381		CONFIG_SYS_NUM_I2C_BUSES
2382		Hold the number of i2c buses you want to use. If you
2383		don't use/have i2c muxes on your i2c bus, this
2384		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2385		omit this define.
2386
2387		CONFIG_SYS_I2C_DIRECT_BUS
2388		define this, if you don't use i2c muxes on your hardware.
2389		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2390		omit this define.
2391
2392		CONFIG_SYS_I2C_MAX_HOPS
2393		define how many muxes are maximal consecutively connected
2394		on one i2c bus. If you not use i2c muxes, omit this
2395		define.
2396
2397		CONFIG_SYS_I2C_BUSES
2398		hold a list of buses you want to use, only used if
2399		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2400		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2401		CONFIG_SYS_NUM_I2C_BUSES = 9:
2402
2403		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2404					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2405					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2406					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2407					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2408					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2409					{1, {I2C_NULL_HOP}}, \
2410					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2411					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2412					}
2413
2414		which defines
2415			bus 0 on adapter 0 without a mux
2416			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2417			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2418			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2419			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2420			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2421			bus 6 on adapter 1 without a mux
2422			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2423			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2424
2425		If you do not have i2c muxes on your board, omit this define.
2426
2427- Legacy I2C Support:	CONFIG_HARD_I2C
2428
2429		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2430		provides the following compelling advantages:
2431
2432		- more than one i2c adapter is usable
2433		- approved multibus support
2434		- better i2c mux support
2435
2436		** Please consider updating your I2C driver now. **
2437
2438		These enable legacy I2C serial bus commands. Defining
2439		CONFIG_HARD_I2C will include the appropriate I2C driver
2440		for the selected CPU.
2441
2442		This will allow you to use i2c commands at the u-boot
2443		command line (as long as you set CONFIG_CMD_I2C in
2444		CONFIG_COMMANDS) and communicate with i2c based realtime
2445		clock chips. See common/cmd_i2c.c for a description of the
2446		command line interface.
2447
2448		CONFIG_HARD_I2C selects a hardware I2C controller.
2449
2450		There are several other quantities that must also be
2451		defined when you define CONFIG_HARD_I2C.
2452
2453		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2454		to be the frequency (in Hz) at which you wish your i2c bus
2455		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2456		the CPU's i2c node address).
2457
2458		Now, the u-boot i2c code for the mpc8xx
2459		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2460		and so its address should therefore be cleared to 0 (See,
2461		eg, MPC823e User's Manual p.16-473). So, set
2462		CONFIG_SYS_I2C_SLAVE to 0.
2463
2464		CONFIG_SYS_I2C_INIT_MPC5XXX
2465
2466		When a board is reset during an i2c bus transfer
2467		chips might think that the current transfer is still
2468		in progress.  Reset the slave devices by sending start
2469		commands until the slave device responds.
2470
2471		That's all that's required for CONFIG_HARD_I2C.
2472
2473		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2474		then the following macros need to be defined (examples are
2475		from include/configs/lwmon.h):
2476
2477		I2C_INIT
2478
2479		(Optional). Any commands necessary to enable the I2C
2480		controller or configure ports.
2481
2482		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2483
2484		I2C_PORT
2485
2486		(Only for MPC8260 CPU). The I/O port to use (the code
2487		assumes both bits are on the same port). Valid values
2488		are 0..3 for ports A..D.
2489
2490		I2C_ACTIVE
2491
2492		The code necessary to make the I2C data line active
2493		(driven).  If the data line is open collector, this
2494		define can be null.
2495
2496		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2497
2498		I2C_TRISTATE
2499
2500		The code necessary to make the I2C data line tri-stated
2501		(inactive).  If the data line is open collector, this
2502		define can be null.
2503
2504		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2505
2506		I2C_READ
2507
2508		Code that returns true if the I2C data line is high,
2509		false if it is low.
2510
2511		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2512
2513		I2C_SDA(bit)
2514
2515		If <bit> is true, sets the I2C data line high. If it
2516		is false, it clears it (low).
2517
2518		eg: #define I2C_SDA(bit) \
2519			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2520			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2521
2522		I2C_SCL(bit)
2523
2524		If <bit> is true, sets the I2C clock line high. If it
2525		is false, it clears it (low).
2526
2527		eg: #define I2C_SCL(bit) \
2528			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2529			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2530
2531		I2C_DELAY
2532
2533		This delay is invoked four times per clock cycle so this
2534		controls the rate of data transfer.  The data rate thus
2535		is 1 / (I2C_DELAY * 4). Often defined to be something
2536		like:
2537
2538		#define I2C_DELAY  udelay(2)
2539
2540		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2541
2542		If your arch supports the generic GPIO framework (asm/gpio.h),
2543		then you may alternatively define the two GPIOs that are to be
2544		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2545		have GPIO-based defaults assigned to them as appropriate.
2546
2547		You should define these to the GPIO value as given directly to
2548		the generic GPIO functions.
2549
2550		CONFIG_SYS_I2C_INIT_BOARD
2551
2552		When a board is reset during an i2c bus transfer
2553		chips might think that the current transfer is still
2554		in progress. On some boards it is possible to access
2555		the i2c SCLK line directly, either by using the
2556		processor pin as a GPIO or by having a second pin
2557		connected to the bus. If this option is defined a
2558		custom i2c_init_board() routine in boards/xxx/board.c
2559		is run early in the boot sequence.
2560
2561		CONFIG_SYS_I2C_BOARD_LATE_INIT
2562
2563		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2564		defined a custom i2c_board_late_init() routine in
2565		boards/xxx/board.c is run AFTER the operations in i2c_init()
2566		is completed. This callpoint can be used to unreset i2c bus
2567		using CPU i2c controller register accesses for CPUs whose i2c
2568		controller provide such a method. It is called at the end of
2569		i2c_init() to allow i2c_init operations to setup the i2c bus
2570		controller on the CPU (e.g. setting bus speed & slave address).
2571
2572		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2573
2574		This option enables configuration of bi_iic_fast[] flags
2575		in u-boot bd_info structure based on u-boot environment
2576		variable "i2cfast". (see also i2cfast)
2577
2578		CONFIG_I2C_MULTI_BUS
2579
2580		This option allows the use of multiple I2C buses, each of which
2581		must have a controller.	 At any point in time, only one bus is
2582		active.	 To switch to a different bus, use the 'i2c dev' command.
2583		Note that bus numbering is zero-based.
2584
2585		CONFIG_SYS_I2C_NOPROBES
2586
2587		This option specifies a list of I2C devices that will be skipped
2588		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2589		is set, specify a list of bus-device pairs.  Otherwise, specify
2590		a 1D array of device addresses
2591
2592		e.g.
2593			#undef	CONFIG_I2C_MULTI_BUS
2594			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2595
2596		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2597
2598			#define CONFIG_I2C_MULTI_BUS
2599			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2600
2601		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2602
2603		CONFIG_SYS_SPD_BUS_NUM
2604
2605		If defined, then this indicates the I2C bus number for DDR SPD.
2606		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2607
2608		CONFIG_SYS_RTC_BUS_NUM
2609
2610		If defined, then this indicates the I2C bus number for the RTC.
2611		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2612
2613		CONFIG_SYS_DTT_BUS_NUM
2614
2615		If defined, then this indicates the I2C bus number for the DTT.
2616		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2617
2618		CONFIG_SYS_I2C_DTT_ADDR:
2619
2620		If defined, specifies the I2C address of the DTT device.
2621		If not defined, then U-Boot uses predefined value for
2622		specified DTT device.
2623
2624		CONFIG_SOFT_I2C_READ_REPEATED_START
2625
2626		defining this will force the i2c_read() function in
2627		the soft_i2c driver to perform an I2C repeated start
2628		between writing the address pointer and reading the
2629		data.  If this define is omitted the default behaviour
2630		of doing a stop-start sequence will be used.  Most I2C
2631		devices can use either method, but some require one or
2632		the other.
2633
2634- SPI Support:	CONFIG_SPI
2635
2636		Enables SPI driver (so far only tested with
2637		SPI EEPROM, also an instance works with Crystal A/D and
2638		D/As on the SACSng board)
2639
2640		CONFIG_SH_SPI
2641
2642		Enables the driver for SPI controller on SuperH. Currently
2643		only SH7757 is supported.
2644
2645		CONFIG_SOFT_SPI
2646
2647		Enables a software (bit-bang) SPI driver rather than
2648		using hardware support. This is a general purpose
2649		driver that only requires three general I/O port pins
2650		(two outputs, one input) to function. If this is
2651		defined, the board configuration must define several
2652		SPI configuration items (port pins to use, etc). For
2653		an example, see include/configs/sacsng.h.
2654
2655		CONFIG_HARD_SPI
2656
2657		Enables a hardware SPI driver for general-purpose reads
2658		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2659		must define a list of chip-select function pointers.
2660		Currently supported on some MPC8xxx processors.	 For an
2661		example, see include/configs/mpc8349emds.h.
2662
2663		CONFIG_MXC_SPI
2664
2665		Enables the driver for the SPI controllers on i.MX and MXC
2666		SoCs. Currently i.MX31/35/51 are supported.
2667
2668		CONFIG_SYS_SPI_MXC_WAIT
2669		Timeout for waiting until spi transfer completed.
2670		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2671
2672- FPGA Support: CONFIG_FPGA
2673
2674		Enables FPGA subsystem.
2675
2676		CONFIG_FPGA_<vendor>
2677
2678		Enables support for specific chip vendors.
2679		(ALTERA, XILINX)
2680
2681		CONFIG_FPGA_<family>
2682
2683		Enables support for FPGA family.
2684		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2685
2686		CONFIG_FPGA_COUNT
2687
2688		Specify the number of FPGA devices to support.
2689
2690		CONFIG_CMD_FPGA_LOADMK
2691
2692		Enable support for fpga loadmk command
2693
2694		CONFIG_CMD_FPGA_LOADP
2695
2696		Enable support for fpga loadp command - load partial bitstream
2697
2698		CONFIG_CMD_FPGA_LOADBP
2699
2700		Enable support for fpga loadbp command - load partial bitstream
2701		(Xilinx only)
2702
2703		CONFIG_SYS_FPGA_PROG_FEEDBACK
2704
2705		Enable printing of hash marks during FPGA configuration.
2706
2707		CONFIG_SYS_FPGA_CHECK_BUSY
2708
2709		Enable checks on FPGA configuration interface busy
2710		status by the configuration function. This option
2711		will require a board or device specific function to
2712		be written.
2713
2714		CONFIG_FPGA_DELAY
2715
2716		If defined, a function that provides delays in the FPGA
2717		configuration driver.
2718
2719		CONFIG_SYS_FPGA_CHECK_CTRLC
2720		Allow Control-C to interrupt FPGA configuration
2721
2722		CONFIG_SYS_FPGA_CHECK_ERROR
2723
2724		Check for configuration errors during FPGA bitfile
2725		loading. For example, abort during Virtex II
2726		configuration if the INIT_B line goes low (which
2727		indicated a CRC error).
2728
2729		CONFIG_SYS_FPGA_WAIT_INIT
2730
2731		Maximum time to wait for the INIT_B line to de-assert
2732		after PROB_B has been de-asserted during a Virtex II
2733		FPGA configuration sequence. The default time is 500
2734		ms.
2735
2736		CONFIG_SYS_FPGA_WAIT_BUSY
2737
2738		Maximum time to wait for BUSY to de-assert during
2739		Virtex II FPGA configuration. The default is 5 ms.
2740
2741		CONFIG_SYS_FPGA_WAIT_CONFIG
2742
2743		Time to wait after FPGA configuration. The default is
2744		200 ms.
2745
2746- Configuration Management:
2747		CONFIG_BUILD_TARGET
2748
2749		Some SoCs need special image types (e.g. U-Boot binary
2750		with a special header) as build targets. By defining
2751		CONFIG_BUILD_TARGET in the SoC / board header, this
2752		special image will be automatically built upon calling
2753		make / buildman.
2754
2755		CONFIG_IDENT_STRING
2756
2757		If defined, this string will be added to the U-Boot
2758		version information (U_BOOT_VERSION)
2759
2760- Vendor Parameter Protection:
2761
2762		U-Boot considers the values of the environment
2763		variables "serial#" (Board Serial Number) and
2764		"ethaddr" (Ethernet Address) to be parameters that
2765		are set once by the board vendor / manufacturer, and
2766		protects these variables from casual modification by
2767		the user. Once set, these variables are read-only,
2768		and write or delete attempts are rejected. You can
2769		change this behaviour:
2770
2771		If CONFIG_ENV_OVERWRITE is #defined in your config
2772		file, the write protection for vendor parameters is
2773		completely disabled. Anybody can change or delete
2774		these parameters.
2775
2776		Alternatively, if you define _both_ an ethaddr in the
2777		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2778		Ethernet address is installed in the environment,
2779		which can be changed exactly ONCE by the user. [The
2780		serial# is unaffected by this, i. e. it remains
2781		read-only.]
2782
2783		The same can be accomplished in a more flexible way
2784		for any variable by configuring the type of access
2785		to allow for those variables in the ".flags" variable
2786		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2787
2788- Protected RAM:
2789		CONFIG_PRAM
2790
2791		Define this variable to enable the reservation of
2792		"protected RAM", i. e. RAM which is not overwritten
2793		by U-Boot. Define CONFIG_PRAM to hold the number of
2794		kB you want to reserve for pRAM. You can overwrite
2795		this default value by defining an environment
2796		variable "pram" to the number of kB you want to
2797		reserve. Note that the board info structure will
2798		still show the full amount of RAM. If pRAM is
2799		reserved, a new environment variable "mem" will
2800		automatically be defined to hold the amount of
2801		remaining RAM in a form that can be passed as boot
2802		argument to Linux, for instance like that:
2803
2804			setenv bootargs ... mem=\${mem}
2805			saveenv
2806
2807		This way you can tell Linux not to use this memory,
2808		either, which results in a memory region that will
2809		not be affected by reboots.
2810
2811		*WARNING* If your board configuration uses automatic
2812		detection of the RAM size, you must make sure that
2813		this memory test is non-destructive. So far, the
2814		following board configurations are known to be
2815		"pRAM-clean":
2816
2817			IVMS8, IVML24, SPD8xx, TQM8xxL,
2818			HERMES, IP860, RPXlite, LWMON,
2819			FLAGADM, TQM8260
2820
2821- Access to physical memory region (> 4GB)
2822		Some basic support is provided for operations on memory not
2823		normally accessible to U-Boot - e.g. some architectures
2824		support access to more than 4GB of memory on 32-bit
2825		machines using physical address extension or similar.
2826		Define CONFIG_PHYSMEM to access this basic support, which
2827		currently only supports clearing the memory.
2828
2829- Error Recovery:
2830		CONFIG_PANIC_HANG
2831
2832		Define this variable to stop the system in case of a
2833		fatal error, so that you have to reset it manually.
2834		This is probably NOT a good idea for an embedded
2835		system where you want the system to reboot
2836		automatically as fast as possible, but it may be
2837		useful during development since you can try to debug
2838		the conditions that lead to the situation.
2839
2840		CONFIG_NET_RETRY_COUNT
2841
2842		This variable defines the number of retries for
2843		network operations like ARP, RARP, TFTP, or BOOTP
2844		before giving up the operation. If not defined, a
2845		default value of 5 is used.
2846
2847		CONFIG_ARP_TIMEOUT
2848
2849		Timeout waiting for an ARP reply in milliseconds.
2850
2851		CONFIG_NFS_TIMEOUT
2852
2853		Timeout in milliseconds used in NFS protocol.
2854		If you encounter "ERROR: Cannot umount" in nfs command,
2855		try longer timeout such as
2856		#define CONFIG_NFS_TIMEOUT 10000UL
2857
2858- Command Interpreter:
2859		CONFIG_AUTO_COMPLETE
2860
2861		Enable auto completion of commands using TAB.
2862
2863		CONFIG_SYS_PROMPT_HUSH_PS2
2864
2865		This defines the secondary prompt string, which is
2866		printed when the command interpreter needs more input
2867		to complete a command. Usually "> ".
2868
2869	Note:
2870
2871		In the current implementation, the local variables
2872		space and global environment variables space are
2873		separated. Local variables are those you define by
2874		simply typing `name=value'. To access a local
2875		variable later on, you have write `$name' or
2876		`${name}'; to execute the contents of a variable
2877		directly type `$name' at the command prompt.
2878
2879		Global environment variables are those you use
2880		setenv/printenv to work with. To run a command stored
2881		in such a variable, you need to use the run command,
2882		and you must not use the '$' sign to access them.
2883
2884		To store commands and special characters in a
2885		variable, please use double quotation marks
2886		surrounding the whole text of the variable, instead
2887		of the backslashes before semicolons and special
2888		symbols.
2889
2890- Command Line Editing and History:
2891		CONFIG_CMDLINE_EDITING
2892
2893		Enable editing and History functions for interactive
2894		command line input operations
2895
2896- Command Line PS1/PS2 support:
2897		CONFIG_CMDLINE_PS_SUPPORT
2898
2899		Enable support for changing the command prompt string
2900		at run-time. Only static string is supported so far.
2901		The string is obtained from environment variables PS1
2902		and PS2.
2903
2904- Default Environment:
2905		CONFIG_EXTRA_ENV_SETTINGS
2906
2907		Define this to contain any number of null terminated
2908		strings (variable = value pairs) that will be part of
2909		the default environment compiled into the boot image.
2910
2911		For example, place something like this in your
2912		board's config file:
2913
2914		#define CONFIG_EXTRA_ENV_SETTINGS \
2915			"myvar1=value1\0" \
2916			"myvar2=value2\0"
2917
2918		Warning: This method is based on knowledge about the
2919		internal format how the environment is stored by the
2920		U-Boot code. This is NOT an official, exported
2921		interface! Although it is unlikely that this format
2922		will change soon, there is no guarantee either.
2923		You better know what you are doing here.
2924
2925		Note: overly (ab)use of the default environment is
2926		discouraged. Make sure to check other ways to preset
2927		the environment like the "source" command or the
2928		boot command first.
2929
2930		CONFIG_ENV_VARS_UBOOT_CONFIG
2931
2932		Define this in order to add variables describing the
2933		U-Boot build configuration to the default environment.
2934		These will be named arch, cpu, board, vendor, and soc.
2935
2936		Enabling this option will cause the following to be defined:
2937
2938		- CONFIG_SYS_ARCH
2939		- CONFIG_SYS_CPU
2940		- CONFIG_SYS_BOARD
2941		- CONFIG_SYS_VENDOR
2942		- CONFIG_SYS_SOC
2943
2944		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2945
2946		Define this in order to add variables describing certain
2947		run-time determined information about the hardware to the
2948		environment.  These will be named board_name, board_rev.
2949
2950		CONFIG_DELAY_ENVIRONMENT
2951
2952		Normally the environment is loaded when the board is
2953		initialised so that it is available to U-Boot. This inhibits
2954		that so that the environment is not available until
2955		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2956		this is instead controlled by the value of
2957		/config/load-environment.
2958
2959- Parallel Flash support:
2960		CONFIG_SYS_NO_FLASH
2961
2962		Traditionally U-Boot was run on systems with parallel NOR
2963		flash. This option is used to disable support for parallel NOR
2964		flash. This option should be defined if the board does not have
2965		parallel flash.
2966
2967		If this option is not defined one of the generic flash drivers
2968		(e.g.  CONFIG_FLASH_CFI_DRIVER or CONFIG_ST_SMI) must be
2969		selected or the board must provide an implementation of the
2970		flash API (see include/flash.h).
2971
2972- DataFlash Support:
2973		CONFIG_HAS_DATAFLASH
2974
2975		Defining this option enables DataFlash features and
2976		allows to read/write in Dataflash via the standard
2977		commands cp, md...
2978
2979- Serial Flash support
2980		CONFIG_CMD_SF
2981
2982		Defining this option enables SPI flash commands
2983		'sf probe/read/write/erase/update'.
2984
2985		Usage requires an initial 'probe' to define the serial
2986		flash parameters, followed by read/write/erase/update
2987		commands.
2988
2989		The following defaults may be provided by the platform
2990		to handle the common case when only a single serial
2991		flash is present on the system.
2992
2993		CONFIG_SF_DEFAULT_BUS		Bus identifier
2994		CONFIG_SF_DEFAULT_CS		Chip-select
2995		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2996		CONFIG_SF_DEFAULT_SPEED		in Hz
2997
2998		CONFIG_CMD_SF_TEST
2999
3000		Define this option to include a destructive SPI flash
3001		test ('sf test').
3002
3003		CONFIG_SF_DUAL_FLASH		Dual flash memories
3004
3005		Define this option to use dual flash support where two flash
3006		memories can be connected with a given cs line.
3007		Currently Xilinx Zynq qspi supports these type of connections.
3008
3009- SystemACE Support:
3010		CONFIG_SYSTEMACE
3011
3012		Adding this option adds support for Xilinx SystemACE
3013		chips attached via some sort of local bus. The address
3014		of the chip must also be defined in the
3015		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
3016
3017		#define CONFIG_SYSTEMACE
3018		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
3019
3020		When SystemACE support is added, the "ace" device type
3021		becomes available to the fat commands, i.e. fatls.
3022
3023- TFTP Fixed UDP Port:
3024		CONFIG_TFTP_PORT
3025
3026		If this is defined, the environment variable tftpsrcp
3027		is used to supply the TFTP UDP source port value.
3028		If tftpsrcp isn't defined, the normal pseudo-random port
3029		number generator is used.
3030
3031		Also, the environment variable tftpdstp is used to supply
3032		the TFTP UDP destination port value.  If tftpdstp isn't
3033		defined, the normal port 69 is used.
3034
3035		The purpose for tftpsrcp is to allow a TFTP server to
3036		blindly start the TFTP transfer using the pre-configured
3037		target IP address and UDP port. This has the effect of
3038		"punching through" the (Windows XP) firewall, allowing
3039		the remainder of the TFTP transfer to proceed normally.
3040		A better solution is to properly configure the firewall,
3041		but sometimes that is not allowed.
3042
3043- Hashing support:
3044		CONFIG_CMD_HASH
3045
3046		This enables a generic 'hash' command which can produce
3047		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
3048
3049		CONFIG_HASH_VERIFY
3050
3051		Enable the hash verify command (hash -v). This adds to code
3052		size a little.
3053
3054		CONFIG_SHA1 - This option enables support of hashing using SHA1
3055		algorithm. The hash is calculated in software.
3056		CONFIG_SHA256 - This option enables support of hashing using
3057		SHA256 algorithm. The hash is calculated in software.
3058		CONFIG_SHA_HW_ACCEL - This option enables hardware acceleration
3059		for SHA1/SHA256 hashing.
3060		This affects the 'hash' command and also the
3061		hash_lookup_algo() function.
3062		CONFIG_SHA_PROG_HW_ACCEL - This option enables
3063		hardware-acceleration for SHA1/SHA256 progressive hashing.
3064		Data can be streamed in a block at a time and the hashing
3065		is performed in hardware.
3066
3067		Note: There is also a sha1sum command, which should perhaps
3068		be deprecated in favour of 'hash sha1'.
3069
3070- Freescale i.MX specific commands:
3071		CONFIG_CMD_HDMIDETECT
3072		This enables 'hdmidet' command which returns true if an
3073		HDMI monitor is detected.  This command is i.MX 6 specific.
3074
3075		CONFIG_CMD_BMODE
3076		This enables the 'bmode' (bootmode) command for forcing
3077		a boot from specific media.
3078
3079		This is useful for forcing the ROM's usb downloader to
3080		activate upon a watchdog reset which is nice when iterating
3081		on U-Boot.  Using the reset button or running bmode normal
3082		will set it back to normal.  This command currently
3083		supports i.MX53 and i.MX6.
3084
3085- bootcount support:
3086		CONFIG_BOOTCOUNT_LIMIT
3087
3088		This enables the bootcounter support, see:
3089		http://www.denx.de/wiki/DULG/UBootBootCountLimit
3090
3091		CONFIG_AT91SAM9XE
3092		enable special bootcounter support on at91sam9xe based boards.
3093		CONFIG_BLACKFIN
3094		enable special bootcounter support on blackfin based boards.
3095		CONFIG_SOC_DA8XX
3096		enable special bootcounter support on da850 based boards.
3097		CONFIG_BOOTCOUNT_RAM
3098		enable support for the bootcounter in RAM
3099		CONFIG_BOOTCOUNT_I2C
3100		enable support for the bootcounter on an i2c (like RTC) device.
3101			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
3102			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
3103						    the bootcounter.
3104			CONFIG_BOOTCOUNT_ALEN = address len
3105
3106- Show boot progress:
3107		CONFIG_SHOW_BOOT_PROGRESS
3108
3109		Defining this option allows to add some board-
3110		specific code (calling a user-provided function
3111		"show_boot_progress(int)") that enables you to show
3112		the system's boot progress on some display (for
3113		example, some LED's) on your board. At the moment,
3114		the following checkpoints are implemented:
3115
3116
3117Legacy uImage format:
3118
3119  Arg	Where			When
3120    1	common/cmd_bootm.c	before attempting to boot an image
3121   -1	common/cmd_bootm.c	Image header has bad	 magic number
3122    2	common/cmd_bootm.c	Image header has correct magic number
3123   -2	common/cmd_bootm.c	Image header has bad	 checksum
3124    3	common/cmd_bootm.c	Image header has correct checksum
3125   -3	common/cmd_bootm.c	Image data   has bad	 checksum
3126    4	common/cmd_bootm.c	Image data   has correct checksum
3127   -4	common/cmd_bootm.c	Image is for unsupported architecture
3128    5	common/cmd_bootm.c	Architecture check OK
3129   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
3130    6	common/cmd_bootm.c	Image Type check OK
3131   -6	common/cmd_bootm.c	gunzip uncompression error
3132   -7	common/cmd_bootm.c	Unimplemented compression type
3133    7	common/cmd_bootm.c	Uncompression OK
3134    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3135   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3136
3137    9	common/image.c		Start initial ramdisk verification
3138  -10	common/image.c		Ramdisk header has bad	   magic number
3139  -11	common/image.c		Ramdisk header has bad	   checksum
3140   10	common/image.c		Ramdisk header is OK
3141  -12	common/image.c		Ramdisk data   has bad	   checksum
3142   11	common/image.c		Ramdisk data   has correct checksum
3143   12	common/image.c		Ramdisk verification complete, start loading
3144  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3145   13	common/image.c		Start multifile image verification
3146   14	common/image.c		No initial ramdisk, no multifile, continue.
3147
3148   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3149
3150  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3151  -31	post/post.c		POST test failed, detected by post_output_backlog()
3152  -32	post/post.c		POST test failed, detected by post_run_single()
3153
3154   34	common/cmd_doc.c	before loading a Image from a DOC device
3155  -35	common/cmd_doc.c	Bad usage of "doc" command
3156   35	common/cmd_doc.c	correct usage of "doc" command
3157  -36	common/cmd_doc.c	No boot device
3158   36	common/cmd_doc.c	correct boot device
3159  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3160   37	common/cmd_doc.c	correct chip ID found, device available
3161  -38	common/cmd_doc.c	Read Error on boot device
3162   38	common/cmd_doc.c	reading Image header from DOC device OK
3163  -39	common/cmd_doc.c	Image header has bad magic number
3164   39	common/cmd_doc.c	Image header has correct magic number
3165  -40	common/cmd_doc.c	Error reading Image from DOC device
3166   40	common/cmd_doc.c	Image header has correct magic number
3167   41	common/cmd_ide.c	before loading a Image from a IDE device
3168  -42	common/cmd_ide.c	Bad usage of "ide" command
3169   42	common/cmd_ide.c	correct usage of "ide" command
3170  -43	common/cmd_ide.c	No boot device
3171   43	common/cmd_ide.c	boot device found
3172  -44	common/cmd_ide.c	Device not available
3173   44	common/cmd_ide.c	Device available
3174  -45	common/cmd_ide.c	wrong partition selected
3175   45	common/cmd_ide.c	partition selected
3176  -46	common/cmd_ide.c	Unknown partition table
3177   46	common/cmd_ide.c	valid partition table found
3178  -47	common/cmd_ide.c	Invalid partition type
3179   47	common/cmd_ide.c	correct partition type
3180  -48	common/cmd_ide.c	Error reading Image Header on boot device
3181   48	common/cmd_ide.c	reading Image Header from IDE device OK
3182  -49	common/cmd_ide.c	Image header has bad magic number
3183   49	common/cmd_ide.c	Image header has correct magic number
3184  -50	common/cmd_ide.c	Image header has bad	 checksum
3185   50	common/cmd_ide.c	Image header has correct checksum
3186  -51	common/cmd_ide.c	Error reading Image from IDE device
3187   51	common/cmd_ide.c	reading Image from IDE device OK
3188   52	common/cmd_nand.c	before loading a Image from a NAND device
3189  -53	common/cmd_nand.c	Bad usage of "nand" command
3190   53	common/cmd_nand.c	correct usage of "nand" command
3191  -54	common/cmd_nand.c	No boot device
3192   54	common/cmd_nand.c	boot device found
3193  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3194   55	common/cmd_nand.c	correct chip ID found, device available
3195  -56	common/cmd_nand.c	Error reading Image Header on boot device
3196   56	common/cmd_nand.c	reading Image Header from NAND device OK
3197  -57	common/cmd_nand.c	Image header has bad magic number
3198   57	common/cmd_nand.c	Image header has correct magic number
3199  -58	common/cmd_nand.c	Error reading Image from NAND device
3200   58	common/cmd_nand.c	reading Image from NAND device OK
3201
3202  -60	common/env_common.c	Environment has a bad CRC, using default
3203
3204   64	net/eth.c		starting with Ethernet configuration.
3205  -64	net/eth.c		no Ethernet found.
3206   65	net/eth.c		Ethernet found.
3207
3208  -80	common/cmd_net.c	usage wrong
3209   80	common/cmd_net.c	before calling net_loop()
3210  -81	common/cmd_net.c	some error in net_loop() occurred
3211   81	common/cmd_net.c	net_loop() back without error
3212  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3213   82	common/cmd_net.c	trying automatic boot
3214   83	common/cmd_net.c	running "source" command
3215  -83	common/cmd_net.c	some error in automatic boot or "source" command
3216   84	common/cmd_net.c	end without errors
3217
3218FIT uImage format:
3219
3220  Arg	Where			When
3221  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3222 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3223  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3224 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3225  102	common/cmd_bootm.c	Kernel unit name specified
3226 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3227  103	common/cmd_bootm.c	Found configuration node
3228  104	common/cmd_bootm.c	Got kernel subimage node offset
3229 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3230  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3231 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3232  106	common/cmd_bootm.c	Architecture check OK
3233 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3234  107	common/cmd_bootm.c	Kernel subimage type OK
3235 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3236  108	common/cmd_bootm.c	Got kernel subimage data/size
3237 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3238 -109	common/cmd_bootm.c	Can't get kernel subimage type
3239 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3240 -111	common/cmd_bootm.c	Can't get kernel subimage os
3241 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3242 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3243
3244  120	common/image.c		Start initial ramdisk verification
3245 -120	common/image.c		Ramdisk FIT image has incorrect format
3246  121	common/image.c		Ramdisk FIT image has correct format
3247  122	common/image.c		No ramdisk subimage unit name, using configuration
3248 -122	common/image.c		Can't get configuration for ramdisk subimage
3249  123	common/image.c		Ramdisk unit name specified
3250 -124	common/image.c		Can't get ramdisk subimage node offset
3251  125	common/image.c		Got ramdisk subimage node offset
3252 -125	common/image.c		Ramdisk subimage hash verification failed
3253  126	common/image.c		Ramdisk subimage hash verification OK
3254 -126	common/image.c		Ramdisk subimage for unsupported architecture
3255  127	common/image.c		Architecture check OK
3256 -127	common/image.c		Can't get ramdisk subimage data/size
3257  128	common/image.c		Got ramdisk subimage data/size
3258  129	common/image.c		Can't get ramdisk load address
3259 -129	common/image.c		Got ramdisk load address
3260
3261 -130	common/cmd_doc.c	Incorrect FIT image format
3262  131	common/cmd_doc.c	FIT image format OK
3263
3264 -140	common/cmd_ide.c	Incorrect FIT image format
3265  141	common/cmd_ide.c	FIT image format OK
3266
3267 -150	common/cmd_nand.c	Incorrect FIT image format
3268  151	common/cmd_nand.c	FIT image format OK
3269
3270- legacy image format:
3271		CONFIG_IMAGE_FORMAT_LEGACY
3272		enables the legacy image format support in U-Boot.
3273
3274		Default:
3275		enabled if CONFIG_FIT_SIGNATURE is not defined.
3276
3277		CONFIG_DISABLE_IMAGE_LEGACY
3278		disable the legacy image format
3279
3280		This define is introduced, as the legacy image format is
3281		enabled per default for backward compatibility.
3282
3283- FIT image support:
3284		CONFIG_FIT_DISABLE_SHA256
3285		Supporting SHA256 hashes has quite an impact on binary size.
3286		For constrained systems sha256 hash support can be disabled
3287		with this option.
3288
3289		TODO(sjg@chromium.org): Adjust this option to be positive,
3290		and move it to Kconfig
3291
3292- Standalone program support:
3293		CONFIG_STANDALONE_LOAD_ADDR
3294
3295		This option defines a board specific value for the
3296		address where standalone program gets loaded, thus
3297		overwriting the architecture dependent default
3298		settings.
3299
3300- Frame Buffer Address:
3301		CONFIG_FB_ADDR
3302
3303		Define CONFIG_FB_ADDR if you want to use specific
3304		address for frame buffer.  This is typically the case
3305		when using a graphics controller has separate video
3306		memory.  U-Boot will then place the frame buffer at
3307		the given address instead of dynamically reserving it
3308		in system RAM by calling lcd_setmem(), which grabs
3309		the memory for the frame buffer depending on the
3310		configured panel size.
3311
3312		Please see board_init_f function.
3313
3314- Automatic software updates via TFTP server
3315		CONFIG_UPDATE_TFTP
3316		CONFIG_UPDATE_TFTP_CNT_MAX
3317		CONFIG_UPDATE_TFTP_MSEC_MAX
3318
3319		These options enable and control the auto-update feature;
3320		for a more detailed description refer to doc/README.update.
3321
3322- MTD Support (mtdparts command, UBI support)
3323		CONFIG_MTD_DEVICE
3324
3325		Adds the MTD device infrastructure from the Linux kernel.
3326		Needed for mtdparts command support.
3327
3328		CONFIG_MTD_PARTITIONS
3329
3330		Adds the MTD partitioning infrastructure from the Linux
3331		kernel. Needed for UBI support.
3332
3333- UBI support
3334		CONFIG_CMD_UBI
3335
3336		Adds commands for interacting with MTD partitions formatted
3337		with the UBI flash translation layer
3338
3339		Requires also defining CONFIG_RBTREE
3340
3341		CONFIG_UBI_SILENCE_MSG
3342
3343		Make the verbose messages from UBI stop printing.  This leaves
3344		warnings and errors enabled.
3345
3346
3347		CONFIG_MTD_UBI_WL_THRESHOLD
3348		This parameter defines the maximum difference between the highest
3349		erase counter value and the lowest erase counter value of eraseblocks
3350		of UBI devices. When this threshold is exceeded, UBI starts performing
3351		wear leveling by means of moving data from eraseblock with low erase
3352		counter to eraseblocks with high erase counter.
3353
3354		The default value should be OK for SLC NAND flashes, NOR flashes and
3355		other flashes which have eraseblock life-cycle 100000 or more.
3356		However, in case of MLC NAND flashes which typically have eraseblock
3357		life-cycle less than 10000, the threshold should be lessened (e.g.,
3358		to 128 or 256, although it does not have to be power of 2).
3359
3360		default: 4096
3361
3362		CONFIG_MTD_UBI_BEB_LIMIT
3363		This option specifies the maximum bad physical eraseblocks UBI
3364		expects on the MTD device (per 1024 eraseblocks). If the
3365		underlying flash does not admit of bad eraseblocks (e.g. NOR
3366		flash), this value is ignored.
3367
3368		NAND datasheets often specify the minimum and maximum NVM
3369		(Number of Valid Blocks) for the flashes' endurance lifetime.
3370		The maximum expected bad eraseblocks per 1024 eraseblocks
3371		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3372		which gives 20 for most NANDs (MaxNVB is basically the total
3373		count of eraseblocks on the chip).
3374
3375		To put it differently, if this value is 20, UBI will try to
3376		reserve about 1.9% of physical eraseblocks for bad blocks
3377		handling. And that will be 1.9% of eraseblocks on the entire
3378		NAND chip, not just the MTD partition UBI attaches. This means
3379		that if you have, say, a NAND flash chip admits maximum 40 bad
3380		eraseblocks, and it is split on two MTD partitions of the same
3381		size, UBI will reserve 40 eraseblocks when attaching a
3382		partition.
3383
3384		default: 20
3385
3386		CONFIG_MTD_UBI_FASTMAP
3387		Fastmap is a mechanism which allows attaching an UBI device
3388		in nearly constant time. Instead of scanning the whole MTD device it
3389		only has to locate a checkpoint (called fastmap) on the device.
3390		The on-flash fastmap contains all information needed to attach
3391		the device. Using fastmap makes only sense on large devices where
3392		attaching by scanning takes long. UBI will not automatically install
3393		a fastmap on old images, but you can set the UBI parameter
3394		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3395		that fastmap-enabled images are still usable with UBI implementations
3396		without	fastmap support. On typical flash devices the whole fastmap
3397		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3398
3399		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3400		Set this parameter to enable fastmap automatically on images
3401		without a fastmap.
3402		default: 0
3403
3404		CONFIG_MTD_UBI_FM_DEBUG
3405		Enable UBI fastmap debug
3406		default: 0
3407
3408- UBIFS support
3409		CONFIG_CMD_UBIFS
3410
3411		Adds commands for interacting with UBI volumes formatted as
3412		UBIFS.  UBIFS is read-only in u-boot.
3413
3414		Requires UBI support as well as CONFIG_LZO
3415
3416		CONFIG_UBIFS_SILENCE_MSG
3417
3418		Make the verbose messages from UBIFS stop printing.  This leaves
3419		warnings and errors enabled.
3420
3421- SPL framework
3422		CONFIG_SPL
3423		Enable building of SPL globally.
3424
3425		CONFIG_SPL_LDSCRIPT
3426		LDSCRIPT for linking the SPL binary.
3427
3428		CONFIG_SPL_MAX_FOOTPRINT
3429		Maximum size in memory allocated to the SPL, BSS included.
3430		When defined, the linker checks that the actual memory
3431		used by SPL from _start to __bss_end does not exceed it.
3432		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3433		must not be both defined at the same time.
3434
3435		CONFIG_SPL_MAX_SIZE
3436		Maximum size of the SPL image (text, data, rodata, and
3437		linker lists sections), BSS excluded.
3438		When defined, the linker checks that the actual size does
3439		not exceed it.
3440
3441		CONFIG_SPL_TEXT_BASE
3442		TEXT_BASE for linking the SPL binary.
3443
3444		CONFIG_SPL_RELOC_TEXT_BASE
3445		Address to relocate to.  If unspecified, this is equal to
3446		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3447
3448		CONFIG_SPL_BSS_START_ADDR
3449		Link address for the BSS within the SPL binary.
3450
3451		CONFIG_SPL_BSS_MAX_SIZE
3452		Maximum size in memory allocated to the SPL BSS.
3453		When defined, the linker checks that the actual memory used
3454		by SPL from __bss_start to __bss_end does not exceed it.
3455		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3456		must not be both defined at the same time.
3457
3458		CONFIG_SPL_STACK
3459		Adress of the start of the stack SPL will use
3460
3461		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3462		When defined, SPL will panic() if the image it has
3463		loaded does not have a signature.
3464		Defining this is useful when code which loads images
3465		in SPL cannot guarantee that absolutely all read errors
3466		will be caught.
3467		An example is the LPC32XX MLC NAND driver, which will
3468		consider that a completely unreadable NAND block is bad,
3469		and thus should be skipped silently.
3470
3471		CONFIG_SPL_ABORT_ON_RAW_IMAGE
3472		When defined, SPL will proceed to another boot method
3473		if the image it has loaded does not have a signature.
3474
3475		CONFIG_SPL_RELOC_STACK
3476		Adress of the start of the stack SPL will use after
3477		relocation.  If unspecified, this is equal to
3478		CONFIG_SPL_STACK.
3479
3480		CONFIG_SYS_SPL_MALLOC_START
3481		Starting address of the malloc pool used in SPL.
3482		When this option is set the full malloc is used in SPL and
3483		it is set up by spl_init() and before that, the simple malloc()
3484		can be used if CONFIG_SYS_MALLOC_F is defined.
3485
3486		CONFIG_SYS_SPL_MALLOC_SIZE
3487		The size of the malloc pool used in SPL.
3488
3489		CONFIG_SPL_FRAMEWORK
3490		Enable the SPL framework under common/.  This framework
3491		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3492		NAND loading of the Linux Kernel.
3493
3494		CONFIG_SPL_OS_BOOT
3495		Enable booting directly to an OS from SPL.
3496		See also: doc/README.falcon
3497
3498		CONFIG_SPL_DISPLAY_PRINT
3499		For ARM, enable an optional function to print more information
3500		about the running system.
3501
3502		CONFIG_SPL_INIT_MINIMAL
3503		Arch init code should be built for a very small image
3504
3505		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3506		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3507		Address and partition on the MMC to load U-Boot from
3508		when the MMC is being used in raw mode.
3509
3510		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3511		Partition on the MMC to load U-Boot from when the MMC is being
3512		used in raw mode
3513
3514		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3515		Sector to load kernel uImage from when MMC is being
3516		used in raw mode (for Falcon mode)
3517
3518		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3519		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3520		Sector and number of sectors to load kernel argument
3521		parameters from when MMC is being used in raw mode
3522		(for falcon mode)
3523
3524		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3525		Partition on the MMC to load U-Boot from when the MMC is being
3526		used in fs mode
3527
3528		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3529		Filename to read to load U-Boot when reading from filesystem
3530
3531		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3532		Filename to read to load kernel uImage when reading
3533		from filesystem (for Falcon mode)
3534
3535		CONFIG_SPL_FS_LOAD_ARGS_NAME
3536		Filename to read to load kernel argument parameters
3537		when reading from filesystem (for Falcon mode)
3538
3539		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3540		Set this for NAND SPL on PPC mpc83xx targets, so that
3541		start.S waits for the rest of the SPL to load before
3542		continuing (the hardware starts execution after just
3543		loading the first page rather than the full 4K).
3544
3545		CONFIG_SPL_SKIP_RELOCATE
3546		Avoid SPL relocation
3547
3548		CONFIG_SPL_NAND_BASE
3549		Include nand_base.c in the SPL.  Requires
3550		CONFIG_SPL_NAND_DRIVERS.
3551
3552		CONFIG_SPL_NAND_DRIVERS
3553		SPL uses normal NAND drivers, not minimal drivers.
3554
3555		CONFIG_SPL_NAND_ECC
3556		Include standard software ECC in the SPL
3557
3558		CONFIG_SPL_NAND_SIMPLE
3559		Support for NAND boot using simple NAND drivers that
3560		expose the cmd_ctrl() interface.
3561
3562		CONFIG_SPL_UBI
3563		Support for a lightweight UBI (fastmap) scanner and
3564		loader
3565
3566		CONFIG_SPL_NAND_RAW_ONLY
3567		Support to boot only raw u-boot.bin images. Use this only
3568		if you need to save space.
3569
3570		CONFIG_SPL_COMMON_INIT_DDR
3571		Set for common ddr init with serial presence detect in
3572		SPL binary.
3573
3574		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3575		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3576		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3577		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3578		CONFIG_SYS_NAND_ECCBYTES
3579		Defines the size and behavior of the NAND that SPL uses
3580		to read U-Boot
3581
3582		CONFIG_SPL_NAND_BOOT
3583		Add support NAND boot
3584
3585		CONFIG_SYS_NAND_U_BOOT_OFFS
3586		Location in NAND to read U-Boot from
3587
3588		CONFIG_SYS_NAND_U_BOOT_DST
3589		Location in memory to load U-Boot to
3590
3591		CONFIG_SYS_NAND_U_BOOT_SIZE
3592		Size of image to load
3593
3594		CONFIG_SYS_NAND_U_BOOT_START
3595		Entry point in loaded image to jump to
3596
3597		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3598		Define this if you need to first read the OOB and then the
3599		data. This is used, for example, on davinci platforms.
3600
3601		CONFIG_SPL_OMAP3_ID_NAND
3602		Support for an OMAP3-specific set of functions to return the
3603		ID and MFR of the first attached NAND chip, if present.
3604
3605		CONFIG_SPL_RAM_DEVICE
3606		Support for running image already present in ram, in SPL binary
3607
3608		CONFIG_SPL_PAD_TO
3609		Image offset to which the SPL should be padded before appending
3610		the SPL payload. By default, this is defined as
3611		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3612		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3613		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3614
3615		CONFIG_SPL_TARGET
3616		Final target image containing SPL and payload.  Some SPLs
3617		use an arch-specific makefile fragment instead, for
3618		example if more than one image needs to be produced.
3619
3620		CONFIG_FIT_SPL_PRINT
3621		Printing information about a FIT image adds quite a bit of
3622		code to SPL. So this is normally disabled in SPL. Use this
3623		option to re-enable it. This will affect the output of the
3624		bootm command when booting a FIT image.
3625
3626- TPL framework
3627		CONFIG_TPL
3628		Enable building of TPL globally.
3629
3630		CONFIG_TPL_PAD_TO
3631		Image offset to which the TPL should be padded before appending
3632		the TPL payload. By default, this is defined as
3633		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3634		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3635		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3636
3637- Interrupt support (PPC):
3638
3639		There are common interrupt_init() and timer_interrupt()
3640		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3641		for CPU specific initialization. interrupt_init_cpu()
3642		should set decrementer_count to appropriate value. If
3643		CPU resets decrementer automatically after interrupt
3644		(ppc4xx) it should set decrementer_count to zero.
3645		timer_interrupt() calls timer_interrupt_cpu() for CPU
3646		specific handling. If board has watchdog / status_led
3647		/ other_activity_monitor it works automatically from
3648		general timer_interrupt().
3649
3650
3651Board initialization settings:
3652------------------------------
3653
3654During Initialization u-boot calls a number of board specific functions
3655to allow the preparation of board specific prerequisites, e.g. pin setup
3656before drivers are initialized. To enable these callbacks the
3657following configuration macros have to be defined. Currently this is
3658architecture specific, so please check arch/your_architecture/lib/board.c
3659typically in board_init_f() and board_init_r().
3660
3661- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3662- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3663- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3664- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3665
3666Configuration Settings:
3667-----------------------
3668
3669- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3670		Optionally it can be defined to support 64-bit memory commands.
3671
3672- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3673		undefine this when you're short of memory.
3674
3675- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3676		width of the commands listed in the 'help' command output.
3677
3678- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3679		prompt for user input.
3680
3681- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3682
3683- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3684
3685- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3686
3687- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3688		the application (usually a Linux kernel) when it is
3689		booted
3690
3691- CONFIG_SYS_BAUDRATE_TABLE:
3692		List of legal baudrate settings for this board.
3693
3694- CONFIG_SYS_CONSOLE_INFO_QUIET
3695		Suppress display of console information at boot.
3696
3697- CONFIG_SYS_CONSOLE_IS_IN_ENV
3698		If the board specific function
3699			extern int overwrite_console (void);
3700		returns 1, the stdin, stderr and stdout are switched to the
3701		serial port, else the settings in the environment are used.
3702
3703- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3704		Enable the call to overwrite_console().
3705
3706- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3707		Enable overwrite of previous console environment settings.
3708
3709- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3710		Begin and End addresses of the area used by the
3711		simple memory test.
3712
3713- CONFIG_SYS_ALT_MEMTEST:
3714		Enable an alternate, more extensive memory test.
3715
3716- CONFIG_SYS_MEMTEST_SCRATCH:
3717		Scratch address used by the alternate memory test
3718		You only need to set this if address zero isn't writeable
3719
3720- CONFIG_SYS_MEM_RESERVE_SECURE
3721		Only implemented for ARMv8 for now.
3722		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
3723		is substracted from total RAM and won't be reported to OS.
3724		This memory can be used as secure memory. A variable
3725		gd->arch.secure_ram is used to track the location. In systems
3726		the RAM base is not zero, or RAM is divided into banks,
3727		this variable needs to be recalcuated to get the address.
3728
3729- CONFIG_SYS_MEM_TOP_HIDE:
3730		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3731		this specified memory area will get subtracted from the top
3732		(end) of RAM and won't get "touched" at all by U-Boot. By
3733		fixing up gd->ram_size the Linux kernel should gets passed
3734		the now "corrected" memory size and won't touch it either.
3735		This should work for arch/ppc and arch/powerpc. Only Linux
3736		board ports in arch/powerpc with bootwrapper support that
3737		recalculate the memory size from the SDRAM controller setup
3738		will have to get fixed in Linux additionally.
3739
3740		This option can be used as a workaround for the 440EPx/GRx
3741		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3742		be touched.
3743
3744		WARNING: Please make sure that this value is a multiple of
3745		the Linux page size (normally 4k). If this is not the case,
3746		then the end address of the Linux memory will be located at a
3747		non page size aligned address and this could cause major
3748		problems.
3749
3750- CONFIG_SYS_LOADS_BAUD_CHANGE:
3751		Enable temporary baudrate change while serial download
3752
3753- CONFIG_SYS_SDRAM_BASE:
3754		Physical start address of SDRAM. _Must_ be 0 here.
3755
3756- CONFIG_SYS_MBIO_BASE:
3757		Physical start address of Motherboard I/O (if using a
3758		Cogent motherboard)
3759
3760- CONFIG_SYS_FLASH_BASE:
3761		Physical start address of Flash memory.
3762
3763- CONFIG_SYS_MONITOR_BASE:
3764		Physical start address of boot monitor code (set by
3765		make config files to be same as the text base address
3766		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3767		CONFIG_SYS_FLASH_BASE when booting from flash.
3768
3769- CONFIG_SYS_MONITOR_LEN:
3770		Size of memory reserved for monitor code, used to
3771		determine _at_compile_time_ (!) if the environment is
3772		embedded within the U-Boot image, or in a separate
3773		flash sector.
3774
3775- CONFIG_SYS_MALLOC_LEN:
3776		Size of DRAM reserved for malloc() use.
3777
3778- CONFIG_SYS_MALLOC_F_LEN
3779		Size of the malloc() pool for use before relocation. If
3780		this is defined, then a very simple malloc() implementation
3781		will become available before relocation. The address is just
3782		below the global data, and the stack is moved down to make
3783		space.
3784
3785		This feature allocates regions with increasing addresses
3786		within the region. calloc() is supported, but realloc()
3787		is not available. free() is supported but does nothing.
3788		The memory will be freed (or in fact just forgotten) when
3789		U-Boot relocates itself.
3790
3791- CONFIG_SYS_MALLOC_SIMPLE
3792		Provides a simple and small malloc() and calloc() for those
3793		boards which do not use the full malloc in SPL (which is
3794		enabled with CONFIG_SYS_SPL_MALLOC_START).
3795
3796- CONFIG_SYS_NONCACHED_MEMORY:
3797		Size of non-cached memory area. This area of memory will be
3798		typically located right below the malloc() area and mapped
3799		uncached in the MMU. This is useful for drivers that would
3800		otherwise require a lot of explicit cache maintenance. For
3801		some drivers it's also impossible to properly maintain the
3802		cache. For example if the regions that need to be flushed
3803		are not a multiple of the cache-line size, *and* padding
3804		cannot be allocated between the regions to align them (i.e.
3805		if the HW requires a contiguous array of regions, and the
3806		size of each region is not cache-aligned), then a flush of
3807		one region may result in overwriting data that hardware has
3808		written to another region in the same cache-line. This can
3809		happen for example in network drivers where descriptors for
3810		buffers are typically smaller than the CPU cache-line (e.g.
3811		16 bytes vs. 32 or 64 bytes).
3812
3813		Non-cached memory is only supported on 32-bit ARM at present.
3814
3815- CONFIG_SYS_BOOTM_LEN:
3816		Normally compressed uImages are limited to an
3817		uncompressed size of 8 MBytes. If this is not enough,
3818		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3819		to adjust this setting to your needs.
3820
3821- CONFIG_SYS_BOOTMAPSZ:
3822		Maximum size of memory mapped by the startup code of
3823		the Linux kernel; all data that must be processed by
3824		the Linux kernel (bd_info, boot arguments, FDT blob if
3825		used) must be put below this limit, unless "bootm_low"
3826		environment variable is defined and non-zero. In such case
3827		all data for the Linux kernel must be between "bootm_low"
3828		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3829		variable "bootm_mapsize" will override the value of
3830		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3831		then the value in "bootm_size" will be used instead.
3832
3833- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3834		Enable initrd_high functionality.  If defined then the
3835		initrd_high feature is enabled and the bootm ramdisk subcommand
3836		is enabled.
3837
3838- CONFIG_SYS_BOOT_GET_CMDLINE:
3839		Enables allocating and saving kernel cmdline in space between
3840		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3841
3842- CONFIG_SYS_BOOT_GET_KBD:
3843		Enables allocating and saving a kernel copy of the bd_info in
3844		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3845
3846- CONFIG_SYS_MAX_FLASH_BANKS:
3847		Max number of Flash memory banks
3848
3849- CONFIG_SYS_MAX_FLASH_SECT:
3850		Max number of sectors on a Flash chip
3851
3852- CONFIG_SYS_FLASH_ERASE_TOUT:
3853		Timeout for Flash erase operations (in ms)
3854
3855- CONFIG_SYS_FLASH_WRITE_TOUT:
3856		Timeout for Flash write operations (in ms)
3857
3858- CONFIG_SYS_FLASH_LOCK_TOUT
3859		Timeout for Flash set sector lock bit operation (in ms)
3860
3861- CONFIG_SYS_FLASH_UNLOCK_TOUT
3862		Timeout for Flash clear lock bits operation (in ms)
3863
3864- CONFIG_SYS_FLASH_PROTECTION
3865		If defined, hardware flash sectors protection is used
3866		instead of U-Boot software protection.
3867
3868- CONFIG_SYS_DIRECT_FLASH_TFTP:
3869
3870		Enable TFTP transfers directly to flash memory;
3871		without this option such a download has to be
3872		performed in two steps: (1) download to RAM, and (2)
3873		copy from RAM to flash.
3874
3875		The two-step approach is usually more reliable, since
3876		you can check if the download worked before you erase
3877		the flash, but in some situations (when system RAM is
3878		too limited to allow for a temporary copy of the
3879		downloaded image) this option may be very useful.
3880
3881- CONFIG_SYS_FLASH_CFI:
3882		Define if the flash driver uses extra elements in the
3883		common flash structure for storing flash geometry.
3884
3885- CONFIG_FLASH_CFI_DRIVER
3886		This option also enables the building of the cfi_flash driver
3887		in the drivers directory
3888
3889- CONFIG_FLASH_CFI_MTD
3890		This option enables the building of the cfi_mtd driver
3891		in the drivers directory. The driver exports CFI flash
3892		to the MTD layer.
3893
3894- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3895		Use buffered writes to flash.
3896
3897- CONFIG_FLASH_SPANSION_S29WS_N
3898		s29ws-n MirrorBit flash has non-standard addresses for buffered
3899		write commands.
3900
3901- CONFIG_SYS_FLASH_QUIET_TEST
3902		If this option is defined, the common CFI flash doesn't
3903		print it's warning upon not recognized FLASH banks. This
3904		is useful, if some of the configured banks are only
3905		optionally available.
3906
3907- CONFIG_FLASH_SHOW_PROGRESS
3908		If defined (must be an integer), print out countdown
3909		digits and dots.  Recommended value: 45 (9..1) for 80
3910		column displays, 15 (3..1) for 40 column displays.
3911
3912- CONFIG_FLASH_VERIFY
3913		If defined, the content of the flash (destination) is compared
3914		against the source after the write operation. An error message
3915		will be printed when the contents are not identical.
3916		Please note that this option is useless in nearly all cases,
3917		since such flash programming errors usually are detected earlier
3918		while unprotecting/erasing/programming. Please only enable
3919		this option if you really know what you are doing.
3920
3921- CONFIG_SYS_RX_ETH_BUFFER:
3922		Defines the number of Ethernet receive buffers. On some
3923		Ethernet controllers it is recommended to set this value
3924		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3925		buffers can be full shortly after enabling the interface
3926		on high Ethernet traffic.
3927		Defaults to 4 if not defined.
3928
3929- CONFIG_ENV_MAX_ENTRIES
3930
3931	Maximum number of entries in the hash table that is used
3932	internally to store the environment settings. The default
3933	setting is supposed to be generous and should work in most
3934	cases. This setting can be used to tune behaviour; see
3935	lib/hashtable.c for details.
3936
3937- CONFIG_ENV_FLAGS_LIST_DEFAULT
3938- CONFIG_ENV_FLAGS_LIST_STATIC
3939	Enable validation of the values given to environment variables when
3940	calling env set.  Variables can be restricted to only decimal,
3941	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3942	the variables can also be restricted to IP address or MAC address.
3943
3944	The format of the list is:
3945		type_attribute = [s|d|x|b|i|m]
3946		access_attribute = [a|r|o|c]
3947		attributes = type_attribute[access_attribute]
3948		entry = variable_name[:attributes]
3949		list = entry[,list]
3950
3951	The type attributes are:
3952		s - String (default)
3953		d - Decimal
3954		x - Hexadecimal
3955		b - Boolean ([1yYtT|0nNfF])
3956		i - IP address
3957		m - MAC address
3958
3959	The access attributes are:
3960		a - Any (default)
3961		r - Read-only
3962		o - Write-once
3963		c - Change-default
3964
3965	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3966		Define this to a list (string) to define the ".flags"
3967		environment variable in the default or embedded environment.
3968
3969	- CONFIG_ENV_FLAGS_LIST_STATIC
3970		Define this to a list (string) to define validation that
3971		should be done if an entry is not found in the ".flags"
3972		environment variable.  To override a setting in the static
3973		list, simply add an entry for the same variable name to the
3974		".flags" variable.
3975
3976	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3977	regular expression. This allows multiple variables to define the same
3978	flags without explicitly listing them for each variable.
3979
3980- CONFIG_ENV_ACCESS_IGNORE_FORCE
3981	If defined, don't allow the -f switch to env set override variable
3982	access flags.
3983
3984- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3985	This is set by OMAP boards for the max time that reset should
3986	be asserted. See doc/README.omap-reset-time for details on how
3987	the value can be calculated on a given board.
3988
3989- CONFIG_USE_STDINT
3990	If stdint.h is available with your toolchain you can define this
3991	option to enable it. You can provide option 'USE_STDINT=1' when
3992	building U-Boot to enable this.
3993
3994The following definitions that deal with the placement and management
3995of environment data (variable area); in general, we support the
3996following configurations:
3997
3998- CONFIG_BUILD_ENVCRC:
3999
4000	Builds up envcrc with the target environment so that external utils
4001	may easily extract it and embed it in final U-Boot images.
4002
4003- CONFIG_ENV_IS_IN_FLASH:
4004
4005	Define this if the environment is in flash memory.
4006
4007	a) The environment occupies one whole flash sector, which is
4008	   "embedded" in the text segment with the U-Boot code. This
4009	   happens usually with "bottom boot sector" or "top boot
4010	   sector" type flash chips, which have several smaller
4011	   sectors at the start or the end. For instance, such a
4012	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
4013	   such a case you would place the environment in one of the
4014	   4 kB sectors - with U-Boot code before and after it. With
4015	   "top boot sector" type flash chips, you would put the
4016	   environment in one of the last sectors, leaving a gap
4017	   between U-Boot and the environment.
4018
4019	- CONFIG_ENV_OFFSET:
4020
4021	   Offset of environment data (variable area) to the
4022	   beginning of flash memory; for instance, with bottom boot
4023	   type flash chips the second sector can be used: the offset
4024	   for this sector is given here.
4025
4026	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
4027
4028	- CONFIG_ENV_ADDR:
4029
4030	   This is just another way to specify the start address of
4031	   the flash sector containing the environment (instead of
4032	   CONFIG_ENV_OFFSET).
4033
4034	- CONFIG_ENV_SECT_SIZE:
4035
4036	   Size of the sector containing the environment.
4037
4038
4039	b) Sometimes flash chips have few, equal sized, BIG sectors.
4040	   In such a case you don't want to spend a whole sector for
4041	   the environment.
4042
4043	- CONFIG_ENV_SIZE:
4044
4045	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
4046	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
4047	   of this flash sector for the environment. This saves
4048	   memory for the RAM copy of the environment.
4049
4050	   It may also save flash memory if you decide to use this
4051	   when your environment is "embedded" within U-Boot code,
4052	   since then the remainder of the flash sector could be used
4053	   for U-Boot code. It should be pointed out that this is
4054	   STRONGLY DISCOURAGED from a robustness point of view:
4055	   updating the environment in flash makes it always
4056	   necessary to erase the WHOLE sector. If something goes
4057	   wrong before the contents has been restored from a copy in
4058	   RAM, your target system will be dead.
4059
4060	- CONFIG_ENV_ADDR_REDUND
4061	  CONFIG_ENV_SIZE_REDUND
4062
4063	   These settings describe a second storage area used to hold
4064	   a redundant copy of the environment data, so that there is
4065	   a valid backup copy in case there is a power failure during
4066	   a "saveenv" operation.
4067
4068BE CAREFUL! Any changes to the flash layout, and some changes to the
4069source code will make it necessary to adapt <board>/u-boot.lds*
4070accordingly!
4071
4072
4073- CONFIG_ENV_IS_IN_NVRAM:
4074
4075	Define this if you have some non-volatile memory device
4076	(NVRAM, battery buffered SRAM) which you want to use for the
4077	environment.
4078
4079	- CONFIG_ENV_ADDR:
4080	- CONFIG_ENV_SIZE:
4081
4082	  These two #defines are used to determine the memory area you
4083	  want to use for environment. It is assumed that this memory
4084	  can just be read and written to, without any special
4085	  provision.
4086
4087BE CAREFUL! The first access to the environment happens quite early
4088in U-Boot initialization (when we try to get the setting of for the
4089console baudrate). You *MUST* have mapped your NVRAM area then, or
4090U-Boot will hang.
4091
4092Please note that even with NVRAM we still use a copy of the
4093environment in RAM: we could work on NVRAM directly, but we want to
4094keep settings there always unmodified except somebody uses "saveenv"
4095to save the current settings.
4096
4097
4098- CONFIG_ENV_IS_IN_EEPROM:
4099
4100	Use this if you have an EEPROM or similar serial access
4101	device and a driver for it.
4102
4103	- CONFIG_ENV_OFFSET:
4104	- CONFIG_ENV_SIZE:
4105
4106	  These two #defines specify the offset and size of the
4107	  environment area within the total memory of your EEPROM.
4108
4109	- CONFIG_SYS_I2C_EEPROM_ADDR:
4110	  If defined, specified the chip address of the EEPROM device.
4111	  The default address is zero.
4112
4113	- CONFIG_SYS_I2C_EEPROM_BUS:
4114	  If defined, specified the i2c bus of the EEPROM device.
4115
4116	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
4117	  If defined, the number of bits used to address bytes in a
4118	  single page in the EEPROM device.  A 64 byte page, for example
4119	  would require six bits.
4120
4121	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
4122	  If defined, the number of milliseconds to delay between
4123	  page writes.	The default is zero milliseconds.
4124
4125	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
4126	  The length in bytes of the EEPROM memory array address.  Note
4127	  that this is NOT the chip address length!
4128
4129	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
4130	  EEPROM chips that implement "address overflow" are ones
4131	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
4132	  address and the extra bits end up in the "chip address" bit
4133	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
4134	  byte chips.
4135
4136	  Note that we consider the length of the address field to
4137	  still be one byte because the extra address bits are hidden
4138	  in the chip address.
4139
4140	- CONFIG_SYS_EEPROM_SIZE:
4141	  The size in bytes of the EEPROM device.
4142
4143	- CONFIG_ENV_EEPROM_IS_ON_I2C
4144	  define this, if you have I2C and SPI activated, and your
4145	  EEPROM, which holds the environment, is on the I2C bus.
4146
4147	- CONFIG_I2C_ENV_EEPROM_BUS
4148	  if you have an Environment on an EEPROM reached over
4149	  I2C muxes, you can define here, how to reach this
4150	  EEPROM. For example:
4151
4152	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
4153
4154	  EEPROM which holds the environment, is reached over
4155	  a pca9547 i2c mux with address 0x70, channel 3.
4156
4157- CONFIG_ENV_IS_IN_DATAFLASH:
4158
4159	Define this if you have a DataFlash memory device which you
4160	want to use for the environment.
4161
4162	- CONFIG_ENV_OFFSET:
4163	- CONFIG_ENV_ADDR:
4164	- CONFIG_ENV_SIZE:
4165
4166	  These three #defines specify the offset and size of the
4167	  environment area within the total memory of your DataFlash placed
4168	  at the specified address.
4169
4170- CONFIG_ENV_IS_IN_SPI_FLASH:
4171
4172	Define this if you have a SPI Flash memory device which you
4173	want to use for the environment.
4174
4175	- CONFIG_ENV_OFFSET:
4176	- CONFIG_ENV_SIZE:
4177
4178	  These two #defines specify the offset and size of the
4179	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
4180	  aligned to an erase sector boundary.
4181
4182	- CONFIG_ENV_SECT_SIZE:
4183
4184	  Define the SPI flash's sector size.
4185
4186	- CONFIG_ENV_OFFSET_REDUND (optional):
4187
4188	  This setting describes a second storage area of CONFIG_ENV_SIZE
4189	  size used to hold a redundant copy of the environment data, so
4190	  that there is a valid backup copy in case there is a power failure
4191	  during a "saveenv" operation. CONFIG_ENV_OFFSET_RENDUND must be
4192	  aligned to an erase sector boundary.
4193
4194	- CONFIG_ENV_SPI_BUS (optional):
4195	- CONFIG_ENV_SPI_CS (optional):
4196
4197	  Define the SPI bus and chip select. If not defined they will be 0.
4198
4199	- CONFIG_ENV_SPI_MAX_HZ (optional):
4200
4201	  Define the SPI max work clock. If not defined then use 1MHz.
4202
4203	- CONFIG_ENV_SPI_MODE (optional):
4204
4205	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4206
4207- CONFIG_ENV_IS_IN_REMOTE:
4208
4209	Define this if you have a remote memory space which you
4210	want to use for the local device's environment.
4211
4212	- CONFIG_ENV_ADDR:
4213	- CONFIG_ENV_SIZE:
4214
4215	  These two #defines specify the address and size of the
4216	  environment area within the remote memory space. The
4217	  local device can get the environment from remote memory
4218	  space by SRIO or PCIE links.
4219
4220BE CAREFUL! For some special cases, the local device can not use
4221"saveenv" command. For example, the local device will get the
4222environment stored in a remote NOR flash by SRIO or PCIE link,
4223but it can not erase, write this NOR flash by SRIO or PCIE interface.
4224
4225- CONFIG_ENV_IS_IN_NAND:
4226
4227	Define this if you have a NAND device which you want to use
4228	for the environment.
4229
4230	- CONFIG_ENV_OFFSET:
4231	- CONFIG_ENV_SIZE:
4232
4233	  These two #defines specify the offset and size of the environment
4234	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4235	  aligned to an erase block boundary.
4236
4237	- CONFIG_ENV_OFFSET_REDUND (optional):
4238
4239	  This setting describes a second storage area of CONFIG_ENV_SIZE
4240	  size used to hold a redundant copy of the environment data, so
4241	  that there is a valid backup copy in case there is a power failure
4242	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
4243	  aligned to an erase block boundary.
4244
4245	- CONFIG_ENV_RANGE (optional):
4246
4247	  Specifies the length of the region in which the environment
4248	  can be written.  This should be a multiple of the NAND device's
4249	  block size.  Specifying a range with more erase blocks than
4250	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4251	  the range to be avoided.
4252
4253	- CONFIG_ENV_OFFSET_OOB (optional):
4254
4255	  Enables support for dynamically retrieving the offset of the
4256	  environment from block zero's out-of-band data.  The
4257	  "nand env.oob" command can be used to record this offset.
4258	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4259	  using CONFIG_ENV_OFFSET_OOB.
4260
4261- CONFIG_NAND_ENV_DST
4262
4263	Defines address in RAM to which the nand_spl code should copy the
4264	environment. If redundant environment is used, it will be copied to
4265	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4266
4267- CONFIG_ENV_IS_IN_UBI:
4268
4269	Define this if you have an UBI volume that you want to use for the
4270	environment.  This has the benefit of wear-leveling the environment
4271	accesses, which is important on NAND.
4272
4273	- CONFIG_ENV_UBI_PART:
4274
4275	  Define this to a string that is the mtd partition containing the UBI.
4276
4277	- CONFIG_ENV_UBI_VOLUME:
4278
4279	  Define this to the name of the volume that you want to store the
4280	  environment in.
4281
4282	- CONFIG_ENV_UBI_VOLUME_REDUND:
4283
4284	  Define this to the name of another volume to store a second copy of
4285	  the environment in.  This will enable redundant environments in UBI.
4286	  It is assumed that both volumes are in the same MTD partition.
4287
4288	- CONFIG_UBI_SILENCE_MSG
4289	- CONFIG_UBIFS_SILENCE_MSG
4290
4291	  You will probably want to define these to avoid a really noisy system
4292	  when storing the env in UBI.
4293
4294- CONFIG_ENV_IS_IN_FAT:
4295       Define this if you want to use the FAT file system for the environment.
4296
4297       - FAT_ENV_INTERFACE:
4298
4299         Define this to a string that is the name of the block device.
4300
4301       - FAT_ENV_DEV_AND_PART:
4302
4303         Define this to a string to specify the partition of the device. It can
4304         be as following:
4305
4306           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4307               - "D:P": device D partition P. Error occurs if device D has no
4308                        partition table.
4309               - "D:0": device D.
4310               - "D" or "D:": device D partition 1 if device D has partition
4311                              table, or the whole device D if has no partition
4312                              table.
4313               - "D:auto": first partition in device D with bootable flag set.
4314                           If none, first valid partition in device D. If no
4315                           partition table then means device D.
4316
4317       - FAT_ENV_FILE:
4318
4319         It's a string of the FAT file name. This file use to store the
4320         environment.
4321
4322       - CONFIG_FAT_WRITE:
4323         This should be defined. Otherwise it cannot save the environment file.
4324
4325- CONFIG_ENV_IS_IN_MMC:
4326
4327	Define this if you have an MMC device which you want to use for the
4328	environment.
4329
4330	- CONFIG_SYS_MMC_ENV_DEV:
4331
4332	  Specifies which MMC device the environment is stored in.
4333
4334	- CONFIG_SYS_MMC_ENV_PART (optional):
4335
4336	  Specifies which MMC partition the environment is stored in. If not
4337	  set, defaults to partition 0, the user area. Common values might be
4338	  1 (first MMC boot partition), 2 (second MMC boot partition).
4339
4340	- CONFIG_ENV_OFFSET:
4341	- CONFIG_ENV_SIZE:
4342
4343	  These two #defines specify the offset and size of the environment
4344	  area within the specified MMC device.
4345
4346	  If offset is positive (the usual case), it is treated as relative to
4347	  the start of the MMC partition. If offset is negative, it is treated
4348	  as relative to the end of the MMC partition. This can be useful if
4349	  your board may be fitted with different MMC devices, which have
4350	  different sizes for the MMC partitions, and you always want the
4351	  environment placed at the very end of the partition, to leave the
4352	  maximum possible space before it, to store other data.
4353
4354	  These two values are in units of bytes, but must be aligned to an
4355	  MMC sector boundary.
4356
4357	- CONFIG_ENV_OFFSET_REDUND (optional):
4358
4359	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4360	  hold a redundant copy of the environment data. This provides a
4361	  valid backup copy in case the other copy is corrupted, e.g. due
4362	  to a power failure during a "saveenv" operation.
4363
4364	  This value may also be positive or negative; this is handled in the
4365	  same way as CONFIG_ENV_OFFSET.
4366
4367	  This value is also in units of bytes, but must also be aligned to
4368	  an MMC sector boundary.
4369
4370	- CONFIG_ENV_SIZE_REDUND (optional):
4371
4372	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4373	  set. If this value is set, it must be set to the same value as
4374	  CONFIG_ENV_SIZE.
4375
4376- CONFIG_SYS_SPI_INIT_OFFSET
4377
4378	Defines offset to the initial SPI buffer area in DPRAM. The
4379	area is used at an early stage (ROM part) if the environment
4380	is configured to reside in the SPI EEPROM: We need a 520 byte
4381	scratch DPRAM area. It is used between the two initialization
4382	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4383	to be a good choice since it makes it far enough from the
4384	start of the data area as well as from the stack pointer.
4385
4386Please note that the environment is read-only until the monitor
4387has been relocated to RAM and a RAM copy of the environment has been
4388created; also, when using EEPROM you will have to use getenv_f()
4389until then to read environment variables.
4390
4391The environment is protected by a CRC32 checksum. Before the monitor
4392is relocated into RAM, as a result of a bad CRC you will be working
4393with the compiled-in default environment - *silently*!!! [This is
4394necessary, because the first environment variable we need is the
4395"baudrate" setting for the console - if we have a bad CRC, we don't
4396have any device yet where we could complain.]
4397
4398Note: once the monitor has been relocated, then it will complain if
4399the default environment is used; a new CRC is computed as soon as you
4400use the "saveenv" command to store a valid environment.
4401
4402- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4403		Echo the inverted Ethernet link state to the fault LED.
4404
4405		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4406		      also needs to be defined.
4407
4408- CONFIG_SYS_FAULT_MII_ADDR:
4409		MII address of the PHY to check for the Ethernet link state.
4410
4411- CONFIG_NS16550_MIN_FUNCTIONS:
4412		Define this if you desire to only have use of the NS16550_init
4413		and NS16550_putc functions for the serial driver located at
4414		drivers/serial/ns16550.c.  This option is useful for saving
4415		space for already greatly restricted images, including but not
4416		limited to NAND_SPL configurations.
4417
4418- CONFIG_DISPLAY_BOARDINFO
4419		Display information about the board that U-Boot is running on
4420		when U-Boot starts up. The board function checkboard() is called
4421		to do this.
4422
4423- CONFIG_DISPLAY_BOARDINFO_LATE
4424		Similar to the previous option, but display this information
4425		later, once stdio is running and output goes to the LCD, if
4426		present.
4427
4428- CONFIG_BOARD_SIZE_LIMIT:
4429		Maximum size of the U-Boot image. When defined, the
4430		build system checks that the actual size does not
4431		exceed it.
4432
4433Low Level (hardware related) configuration options:
4434---------------------------------------------------
4435
4436- CONFIG_SYS_CACHELINE_SIZE:
4437		Cache Line Size of the CPU.
4438
4439- CONFIG_SYS_DEFAULT_IMMR:
4440		Default address of the IMMR after system reset.
4441
4442		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4443		and RPXsuper) to be able to adjust the position of
4444		the IMMR register after a reset.
4445
4446- CONFIG_SYS_CCSRBAR_DEFAULT:
4447		Default (power-on reset) physical address of CCSR on Freescale
4448		PowerPC SOCs.
4449
4450- CONFIG_SYS_CCSRBAR:
4451		Virtual address of CCSR.  On a 32-bit build, this is typically
4452		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4453
4454		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4455		for cross-platform code that uses that macro instead.
4456
4457- CONFIG_SYS_CCSRBAR_PHYS:
4458		Physical address of CCSR.  CCSR can be relocated to a new
4459		physical address, if desired.  In this case, this macro should
4460		be set to that address.	 Otherwise, it should be set to the
4461		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4462		is typically relocated on 36-bit builds.  It is recommended
4463		that this macro be defined via the _HIGH and _LOW macros:
4464
4465		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4466			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4467
4468- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4469		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4470		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4471		used in assembly code, so it must not contain typecasts or
4472		integer size suffixes (e.g. "ULL").
4473
4474- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4475		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4476		used in assembly code, so it must not contain typecasts or
4477		integer size suffixes (e.g. "ULL").
4478
4479- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4480		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4481		forced to a value that ensures that CCSR is not relocated.
4482
4483- Floppy Disk Support:
4484		CONFIG_SYS_FDC_DRIVE_NUMBER
4485
4486		the default drive number (default value 0)
4487
4488		CONFIG_SYS_ISA_IO_STRIDE
4489
4490		defines the spacing between FDC chipset registers
4491		(default value 1)
4492
4493		CONFIG_SYS_ISA_IO_OFFSET
4494
4495		defines the offset of register from address. It
4496		depends on which part of the data bus is connected to
4497		the FDC chipset. (default value 0)
4498
4499		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4500		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4501		default value.
4502
4503		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4504		fdc_hw_init() is called at the beginning of the FDC
4505		setup. fdc_hw_init() must be provided by the board
4506		source code. It is used to make hardware-dependent
4507		initializations.
4508
4509- CONFIG_IDE_AHB:
4510		Most IDE controllers were designed to be connected with PCI
4511		interface. Only few of them were designed for AHB interface.
4512		When software is doing ATA command and data transfer to
4513		IDE devices through IDE-AHB controller, some additional
4514		registers accessing to these kind of IDE-AHB controller
4515		is required.
4516
4517- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4518		DO NOT CHANGE unless you know exactly what you're
4519		doing! (11-4) [MPC8xx/82xx systems only]
4520
4521- CONFIG_SYS_INIT_RAM_ADDR:
4522
4523		Start address of memory area that can be used for
4524		initial data and stack; please note that this must be
4525		writable memory that is working WITHOUT special
4526		initialization, i. e. you CANNOT use normal RAM which
4527		will become available only after programming the
4528		memory controller and running certain initialization
4529		sequences.
4530
4531		U-Boot uses the following memory types:
4532		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4533		- MPC824X: data cache
4534		- PPC4xx:  data cache
4535
4536- CONFIG_SYS_GBL_DATA_OFFSET:
4537
4538		Offset of the initial data structure in the memory
4539		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4540		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4541		data is located at the end of the available space
4542		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4543		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4544		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4545		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4546
4547	Note:
4548		On the MPC824X (or other systems that use the data
4549		cache for initial memory) the address chosen for
4550		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4551		point to an otherwise UNUSED address space between
4552		the top of RAM and the start of the PCI space.
4553
4554- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4555
4556- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4557
4558- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4559
4560- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4561
4562- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4563
4564- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4565
4566- CONFIG_SYS_OR_TIMING_SDRAM:
4567		SDRAM timing
4568
4569- CONFIG_SYS_MAMR_PTA:
4570		periodic timer for refresh
4571
4572- CONFIG_SYS_DER:	Debug Event Register (37-47)
4573
4574- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4575  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4576  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4577  CONFIG_SYS_BR1_PRELIM:
4578		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4579
4580- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4581  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4582  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4583		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4584
4585- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4586  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4587		Machine Mode Register and Memory Periodic Timer
4588		Prescaler definitions (SDRAM timing)
4589
4590- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4591		enable I2C microcode relocation patch (MPC8xx);
4592		define relocation offset in DPRAM [DSP2]
4593
4594- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4595		enable SMC microcode relocation patch (MPC8xx);
4596		define relocation offset in DPRAM [SMC1]
4597
4598- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4599		enable SPI microcode relocation patch (MPC8xx);
4600		define relocation offset in DPRAM [SCC4]
4601
4602- CONFIG_SYS_USE_OSCCLK:
4603		Use OSCM clock mode on MBX8xx board. Be careful,
4604		wrong setting might damage your board. Read
4605		doc/README.MBX before setting this variable!
4606
4607- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4608		Offset of the bootmode word in DPRAM used by post
4609		(Power On Self Tests). This definition overrides
4610		#define'd default value in commproc.h resp.
4611		cpm_8260.h.
4612
4613- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4614  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4615  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4616  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4617  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4618  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4619  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4620  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4621		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4622
4623- CONFIG_PCI_DISABLE_PCIE:
4624		Disable PCI-Express on systems where it is supported but not
4625		required.
4626
4627- CONFIG_PCI_ENUM_ONLY
4628		Only scan through and get the devices on the buses.
4629		Don't do any setup work, presumably because someone or
4630		something has already done it, and we don't need to do it
4631		a second time.	Useful for platforms that are pre-booted
4632		by coreboot or similar.
4633
4634- CONFIG_PCI_INDIRECT_BRIDGE:
4635		Enable support for indirect PCI bridges.
4636
4637- CONFIG_SYS_SRIO:
4638		Chip has SRIO or not
4639
4640- CONFIG_SRIO1:
4641		Board has SRIO 1 port available
4642
4643- CONFIG_SRIO2:
4644		Board has SRIO 2 port available
4645
4646- CONFIG_SRIO_PCIE_BOOT_MASTER
4647		Board can support master function for Boot from SRIO and PCIE
4648
4649- CONFIG_SYS_SRIOn_MEM_VIRT:
4650		Virtual Address of SRIO port 'n' memory region
4651
4652- CONFIG_SYS_SRIOn_MEM_PHYS:
4653		Physical Address of SRIO port 'n' memory region
4654
4655- CONFIG_SYS_SRIOn_MEM_SIZE:
4656		Size of SRIO port 'n' memory region
4657
4658- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4659		Defined to tell the NAND controller that the NAND chip is using
4660		a 16 bit bus.
4661		Not all NAND drivers use this symbol.
4662		Example of drivers that use it:
4663		- drivers/mtd/nand/ndfc.c
4664		- drivers/mtd/nand/mxc_nand.c
4665
4666- CONFIG_SYS_NDFC_EBC0_CFG
4667		Sets the EBC0_CFG register for the NDFC. If not defined
4668		a default value will be used.
4669
4670- CONFIG_SPD_EEPROM
4671		Get DDR timing information from an I2C EEPROM. Common
4672		with pluggable memory modules such as SODIMMs
4673
4674  SPD_EEPROM_ADDRESS
4675		I2C address of the SPD EEPROM
4676
4677- CONFIG_SYS_SPD_BUS_NUM
4678		If SPD EEPROM is on an I2C bus other than the first
4679		one, specify here. Note that the value must resolve
4680		to something your driver can deal with.
4681
4682- CONFIG_SYS_DDR_RAW_TIMING
4683		Get DDR timing information from other than SPD. Common with
4684		soldered DDR chips onboard without SPD. DDR raw timing
4685		parameters are extracted from datasheet and hard-coded into
4686		header files or board specific files.
4687
4688- CONFIG_FSL_DDR_INTERACTIVE
4689		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4690
4691- CONFIG_FSL_DDR_SYNC_REFRESH
4692		Enable sync of refresh for multiple controllers.
4693
4694- CONFIG_FSL_DDR_BIST
4695		Enable built-in memory test for Freescale DDR controllers.
4696
4697- CONFIG_SYS_83XX_DDR_USES_CS0
4698		Only for 83xx systems. If specified, then DDR should
4699		be configured using CS0 and CS1 instead of CS2 and CS3.
4700
4701- CONFIG_ETHER_ON_FEC[12]
4702		Define to enable FEC[12] on a 8xx series processor.
4703
4704- CONFIG_FEC[12]_PHY
4705		Define to the hardcoded PHY address which corresponds
4706		to the given FEC; i. e.
4707			#define CONFIG_FEC1_PHY 4
4708		means that the PHY with address 4 is connected to FEC1
4709
4710		When set to -1, means to probe for first available.
4711
4712- CONFIG_FEC[12]_PHY_NORXERR
4713		The PHY does not have a RXERR line (RMII only).
4714		(so program the FEC to ignore it).
4715
4716- CONFIG_RMII
4717		Enable RMII mode for all FECs.
4718		Note that this is a global option, we can't
4719		have one FEC in standard MII mode and another in RMII mode.
4720
4721- CONFIG_CRC32_VERIFY
4722		Add a verify option to the crc32 command.
4723		The syntax is:
4724
4725		=> crc32 -v <address> <count> <crc32>
4726
4727		Where address/count indicate a memory area
4728		and crc32 is the correct crc32 which the
4729		area should have.
4730
4731- CONFIG_LOOPW
4732		Add the "loopw" memory command. This only takes effect if
4733		the memory commands are activated globally (CONFIG_CMD_MEM).
4734
4735- CONFIG_MX_CYCLIC
4736		Add the "mdc" and "mwc" memory commands. These are cyclic
4737		"md/mw" commands.
4738		Examples:
4739
4740		=> mdc.b 10 4 500
4741		This command will print 4 bytes (10,11,12,13) each 500 ms.
4742
4743		=> mwc.l 100 12345678 10
4744		This command will write 12345678 to address 100 all 10 ms.
4745
4746		This only takes effect if the memory commands are activated
4747		globally (CONFIG_CMD_MEM).
4748
4749- CONFIG_SKIP_LOWLEVEL_INIT
4750		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4751		low level initializations (like setting up the memory
4752		controller) are omitted and/or U-Boot does not
4753		relocate itself into RAM.
4754
4755		Normally this variable MUST NOT be defined. The only
4756		exception is when U-Boot is loaded (to RAM) by some
4757		other boot loader or by a debugger which performs
4758		these initializations itself.
4759
4760- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
4761		[ARM926EJ-S only] This allows just the call to lowlevel_init()
4762		to be skipped. The normal CP15 init (such as enabling the
4763		instruction cache) is still performed.
4764
4765- CONFIG_SPL_BUILD
4766		Modifies the behaviour of start.S when compiling a loader
4767		that is executed before the actual U-Boot. E.g. when
4768		compiling a NAND SPL.
4769
4770- CONFIG_TPL_BUILD
4771		Modifies the behaviour of start.S  when compiling a loader
4772		that is executed after the SPL and before the actual U-Boot.
4773		It is loaded by the SPL.
4774
4775- CONFIG_SYS_MPC85XX_NO_RESETVEC
4776		Only for 85xx systems. If this variable is specified, the section
4777		.resetvec is not kept and the section .bootpg is placed in the
4778		previous 4k of the .text section.
4779
4780- CONFIG_ARCH_MAP_SYSMEM
4781		Generally U-Boot (and in particular the md command) uses
4782		effective address. It is therefore not necessary to regard
4783		U-Boot address as virtual addresses that need to be translated
4784		to physical addresses. However, sandbox requires this, since
4785		it maintains its own little RAM buffer which contains all
4786		addressable memory. This option causes some memory accesses
4787		to be mapped through map_sysmem() / unmap_sysmem().
4788
4789- CONFIG_USE_ARCH_MEMCPY
4790  CONFIG_USE_ARCH_MEMSET
4791		If these options are used a optimized version of memcpy/memset will
4792		be used if available. These functions may be faster under some
4793		conditions but may increase the binary size.
4794
4795- CONFIG_X86_RESET_VECTOR
4796		If defined, the x86 reset vector code is included. This is not
4797		needed when U-Boot is running from Coreboot.
4798
4799- CONFIG_SYS_MPUCLK
4800		Defines the MPU clock speed (in MHz).
4801
4802		NOTE : currently only supported on AM335x platforms.
4803
4804- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4805		Enables the RTC32K OSC on AM33xx based plattforms
4806
4807- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4808		Option to disable subpage write in NAND driver
4809		driver that uses this:
4810		drivers/mtd/nand/davinci_nand.c
4811
4812Freescale QE/FMAN Firmware Support:
4813-----------------------------------
4814
4815The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4816loading of "firmware", which is encoded in the QE firmware binary format.
4817This firmware often needs to be loaded during U-Boot booting, so macros
4818are used to identify the storage device (NOR flash, SPI, etc) and the address
4819within that device.
4820
4821- CONFIG_SYS_FMAN_FW_ADDR
4822	The address in the storage device where the FMAN microcode is located.  The
4823	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4824	is also specified.
4825
4826- CONFIG_SYS_QE_FW_ADDR
4827	The address in the storage device where the QE microcode is located.  The
4828	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4829	is also specified.
4830
4831- CONFIG_SYS_QE_FMAN_FW_LENGTH
4832	The maximum possible size of the firmware.  The firmware binary format
4833	has a field that specifies the actual size of the firmware, but it
4834	might not be possible to read any part of the firmware unless some
4835	local storage is allocated to hold the entire firmware first.
4836
4837- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4838	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4839	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4840	virtual address in NOR flash.
4841
4842- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4843	Specifies that QE/FMAN firmware is located in NAND flash.
4844	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4845
4846- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4847	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4848	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4849
4850- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4851	Specifies that QE/FMAN firmware is located on the primary SPI
4852	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4853
4854- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4855	Specifies that QE/FMAN firmware is located in the remote (master)
4856	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4857	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4858	window->master inbound window->master LAW->the ucode address in
4859	master's memory space.
4860
4861Freescale Layerscape Management Complex Firmware Support:
4862---------------------------------------------------------
4863The Freescale Layerscape Management Complex (MC) supports the loading of
4864"firmware".
4865This firmware often needs to be loaded during U-Boot booting, so macros
4866are used to identify the storage device (NOR flash, SPI, etc) and the address
4867within that device.
4868
4869- CONFIG_FSL_MC_ENET
4870	Enable the MC driver for Layerscape SoCs.
4871
4872- CONFIG_SYS_LS_MC_FW_ADDR
4873	The address in the storage device where the firmware is located.  The
4874	meaning of this address depends on which CONFIG_SYS_LS_MC_FW_IN_xxx macro
4875	is also specified.
4876
4877- CONFIG_SYS_LS_MC_FW_LENGTH
4878	The maximum possible size of the firmware.  The firmware binary format
4879	has a field that specifies the actual size of the firmware, but it
4880	might not be possible to read any part of the firmware unless some
4881	local storage is allocated to hold the entire firmware first.
4882
4883- CONFIG_SYS_LS_MC_FW_IN_NOR
4884	Specifies that MC firmware is located in NOR flash, mapped as
4885	normal addressable memory via the LBC. CONFIG_SYS_LS_MC_FW_ADDR is the
4886	virtual address in NOR flash.
4887
4888Freescale Layerscape Debug Server Support:
4889-------------------------------------------
4890The Freescale Layerscape Debug Server Support supports the loading of
4891"Debug Server firmware" and triggering SP boot-rom.
4892This firmware often needs to be loaded during U-Boot booting.
4893
4894- CONFIG_SYS_MC_RSV_MEM_ALIGN
4895	Define alignment of reserved memory MC requires
4896
4897Reproducible builds
4898-------------------
4899
4900In order to achieve reproducible builds, timestamps used in the U-Boot build
4901process have to be set to a fixed value.
4902
4903This is done using the SOURCE_DATE_EPOCH environment variable.
4904SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
4905option for U-Boot or an environment variable in U-Boot.
4906
4907SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
4908
4909Building the Software:
4910======================
4911
4912Building U-Boot has been tested in several native build environments
4913and in many different cross environments. Of course we cannot support
4914all possibly existing versions of cross development tools in all
4915(potentially obsolete) versions. In case of tool chain problems we
4916recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4917which is extensively used to build and test U-Boot.
4918
4919If you are not using a native environment, it is assumed that you
4920have GNU cross compiling tools available in your path. In this case,
4921you must set the environment variable CROSS_COMPILE in your shell.
4922Note that no changes to the Makefile or any other source files are
4923necessary. For example using the ELDK on a 4xx CPU, please enter:
4924
4925	$ CROSS_COMPILE=ppc_4xx-
4926	$ export CROSS_COMPILE
4927
4928Note: If you wish to generate Windows versions of the utilities in
4929      the tools directory you can use the MinGW toolchain
4930      (http://www.mingw.org).  Set your HOST tools to the MinGW
4931      toolchain and execute 'make tools'.  For example:
4932
4933       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4934
4935      Binaries such as tools/mkimage.exe will be created which can
4936      be executed on computers running Windows.
4937
4938U-Boot is intended to be simple to build. After installing the
4939sources you must configure U-Boot for one specific board type. This
4940is done by typing:
4941
4942	make NAME_defconfig
4943
4944where "NAME_defconfig" is the name of one of the existing configu-
4945rations; see boards.cfg for supported names.
4946
4947Note: for some board special configuration names may exist; check if
4948      additional information is available from the board vendor; for
4949      instance, the TQM823L systems are available without (standard)
4950      or with LCD support. You can select such additional "features"
4951      when choosing the configuration, i. e.
4952
4953      make TQM823L_defconfig
4954	- will configure for a plain TQM823L, i. e. no LCD support
4955
4956      make TQM823L_LCD_defconfig
4957	- will configure for a TQM823L with U-Boot console on LCD
4958
4959      etc.
4960
4961
4962Finally, type "make all", and you should get some working U-Boot
4963images ready for download to / installation on your system:
4964
4965- "u-boot.bin" is a raw binary image
4966- "u-boot" is an image in ELF binary format
4967- "u-boot.srec" is in Motorola S-Record format
4968
4969By default the build is performed locally and the objects are saved
4970in the source directory. One of the two methods can be used to change
4971this behavior and build U-Boot to some external directory:
4972
49731. Add O= to the make command line invocations:
4974
4975	make O=/tmp/build distclean
4976	make O=/tmp/build NAME_defconfig
4977	make O=/tmp/build all
4978
49792. Set environment variable KBUILD_OUTPUT to point to the desired location:
4980
4981	export KBUILD_OUTPUT=/tmp/build
4982	make distclean
4983	make NAME_defconfig
4984	make all
4985
4986Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
4987variable.
4988
4989
4990Please be aware that the Makefiles assume you are using GNU make, so
4991for instance on NetBSD you might need to use "gmake" instead of
4992native "make".
4993
4994
4995If the system board that you have is not listed, then you will need
4996to port U-Boot to your hardware platform. To do this, follow these
4997steps:
4998
49991.  Create a new directory to hold your board specific code. Add any
5000    files you need. In your board directory, you will need at least
5001    the "Makefile" and a "<board>.c".
50022.  Create a new configuration file "include/configs/<board>.h" for
5003    your board.
50043.  If you're porting U-Boot to a new CPU, then also create a new
5005    directory to hold your CPU specific code. Add any files you need.
50064.  Run "make <board>_defconfig" with your new name.
50075.  Type "make", and you should get a working "u-boot.srec" file
5008    to be installed on your target system.
50096.  Debug and solve any problems that might arise.
5010    [Of course, this last step is much harder than it sounds.]
5011
5012
5013Testing of U-Boot Modifications, Ports to New Hardware, etc.:
5014==============================================================
5015
5016If you have modified U-Boot sources (for instance added a new board
5017or support for new devices, a new CPU, etc.) you are expected to
5018provide feedback to the other developers. The feedback normally takes
5019the form of a "patch", i. e. a context diff against a certain (latest
5020official or latest in the git repository) version of U-Boot sources.
5021
5022But before you submit such a patch, please verify that your modifi-
5023cation did not break existing code. At least make sure that *ALL* of
5024the supported boards compile WITHOUT ANY compiler warnings. To do so,
5025just run the buildman script (tools/buildman/buildman), which will
5026configure and build U-Boot for ALL supported system. Be warned, this
5027will take a while. Please see the buildman README, or run 'buildman -H'
5028for documentation.
5029
5030
5031See also "U-Boot Porting Guide" below.
5032
5033
5034Monitor Commands - Overview:
5035============================
5036
5037go	- start application at address 'addr'
5038run	- run commands in an environment variable
5039bootm	- boot application image from memory
5040bootp	- boot image via network using BootP/TFTP protocol
5041bootz   - boot zImage from memory
5042tftpboot- boot image via network using TFTP protocol
5043	       and env variables "ipaddr" and "serverip"
5044	       (and eventually "gatewayip")
5045tftpput - upload a file via network using TFTP protocol
5046rarpboot- boot image via network using RARP/TFTP protocol
5047diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
5048loads	- load S-Record file over serial line
5049loadb	- load binary file over serial line (kermit mode)
5050md	- memory display
5051mm	- memory modify (auto-incrementing)
5052nm	- memory modify (constant address)
5053mw	- memory write (fill)
5054cp	- memory copy
5055cmp	- memory compare
5056crc32	- checksum calculation
5057i2c	- I2C sub-system
5058sspi	- SPI utility commands
5059base	- print or set address offset
5060printenv- print environment variables
5061setenv	- set environment variables
5062saveenv - save environment variables to persistent storage
5063protect - enable or disable FLASH write protection
5064erase	- erase FLASH memory
5065flinfo	- print FLASH memory information
5066nand	- NAND memory operations (see doc/README.nand)
5067bdinfo	- print Board Info structure
5068iminfo	- print header information for application image
5069coninfo - print console devices and informations
5070ide	- IDE sub-system
5071loop	- infinite loop on address range
5072loopw	- infinite write loop on address range
5073mtest	- simple RAM test
5074icache	- enable or disable instruction cache
5075dcache	- enable or disable data cache
5076reset	- Perform RESET of the CPU
5077echo	- echo args to console
5078version - print monitor version
5079help	- print online help
5080?	- alias for 'help'
5081
5082
5083Monitor Commands - Detailed Description:
5084========================================
5085
5086TODO.
5087
5088For now: just type "help <command>".
5089
5090
5091Environment Variables:
5092======================
5093
5094U-Boot supports user configuration using Environment Variables which
5095can be made persistent by saving to Flash memory.
5096
5097Environment Variables are set using "setenv", printed using
5098"printenv", and saved to Flash using "saveenv". Using "setenv"
5099without a value can be used to delete a variable from the
5100environment. As long as you don't save the environment you are
5101working with an in-memory copy. In case the Flash area containing the
5102environment is erased by accident, a default environment is provided.
5103
5104Some configuration options can be set using Environment Variables.
5105
5106List of environment variables (most likely not complete):
5107
5108  baudrate	- see CONFIG_BAUDRATE
5109
5110  bootdelay	- see CONFIG_BOOTDELAY
5111
5112  bootcmd	- see CONFIG_BOOTCOMMAND
5113
5114  bootargs	- Boot arguments when booting an RTOS image
5115
5116  bootfile	- Name of the image to load with TFTP
5117
5118  bootm_low	- Memory range available for image processing in the bootm
5119		  command can be restricted. This variable is given as
5120		  a hexadecimal number and defines lowest address allowed
5121		  for use by the bootm command. See also "bootm_size"
5122		  environment variable. Address defined by "bootm_low" is
5123		  also the base of the initial memory mapping for the Linux
5124		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
5125		  bootm_mapsize.
5126
5127  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
5128		  This variable is given as a hexadecimal number and it
5129		  defines the size of the memory region starting at base
5130		  address bootm_low that is accessible by the Linux kernel
5131		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
5132		  as the default value if it is defined, and bootm_size is
5133		  used otherwise.
5134
5135  bootm_size	- Memory range available for image processing in the bootm
5136		  command can be restricted. This variable is given as
5137		  a hexadecimal number and defines the size of the region
5138		  allowed for use by the bootm command. See also "bootm_low"
5139		  environment variable.
5140
5141  updatefile	- Location of the software update file on a TFTP server, used
5142		  by the automatic software update feature. Please refer to
5143		  documentation in doc/README.update for more details.
5144
5145  autoload	- if set to "no" (any string beginning with 'n'),
5146		  "bootp" will just load perform a lookup of the
5147		  configuration from the BOOTP server, but not try to
5148		  load any image using TFTP
5149
5150  autostart	- if set to "yes", an image loaded using the "bootp",
5151		  "rarpboot", "tftpboot" or "diskboot" commands will
5152		  be automatically started (by internally calling
5153		  "bootm")
5154
5155		  If set to "no", a standalone image passed to the
5156		  "bootm" command will be copied to the load address
5157		  (and eventually uncompressed), but NOT be started.
5158		  This can be used to load and uncompress arbitrary
5159		  data.
5160
5161  fdt_high	- if set this restricts the maximum address that the
5162		  flattened device tree will be copied into upon boot.
5163		  For example, if you have a system with 1 GB memory
5164		  at physical address 0x10000000, while Linux kernel
5165		  only recognizes the first 704 MB as low memory, you
5166		  may need to set fdt_high as 0x3C000000 to have the
5167		  device tree blob be copied to the maximum address
5168		  of the 704 MB low memory, so that Linux kernel can
5169		  access it during the boot procedure.
5170
5171		  If this is set to the special value 0xFFFFFFFF then
5172		  the fdt will not be copied at all on boot.  For this
5173		  to work it must reside in writable memory, have
5174		  sufficient padding on the end of it for u-boot to
5175		  add the information it needs into it, and the memory
5176		  must be accessible by the kernel.
5177
5178  fdtcontroladdr- if set this is the address of the control flattened
5179		  device tree used by U-Boot when CONFIG_OF_CONTROL is
5180		  defined.
5181
5182  i2cfast	- (PPC405GP|PPC405EP only)
5183		  if set to 'y' configures Linux I2C driver for fast
5184		  mode (400kHZ). This environment variable is used in
5185		  initialization code. So, for changes to be effective
5186		  it must be saved and board must be reset.
5187
5188  initrd_high	- restrict positioning of initrd images:
5189		  If this variable is not set, initrd images will be
5190		  copied to the highest possible address in RAM; this
5191		  is usually what you want since it allows for
5192		  maximum initrd size. If for some reason you want to
5193		  make sure that the initrd image is loaded below the
5194		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
5195		  variable to a value of "no" or "off" or "0".
5196		  Alternatively, you can set it to a maximum upper
5197		  address to use (U-Boot will still check that it
5198		  does not overwrite the U-Boot stack and data).
5199
5200		  For instance, when you have a system with 16 MB
5201		  RAM, and want to reserve 4 MB from use by Linux,
5202		  you can do this by adding "mem=12M" to the value of
5203		  the "bootargs" variable. However, now you must make
5204		  sure that the initrd image is placed in the first
5205		  12 MB as well - this can be done with
5206
5207		  setenv initrd_high 00c00000
5208
5209		  If you set initrd_high to 0xFFFFFFFF, this is an
5210		  indication to U-Boot that all addresses are legal
5211		  for the Linux kernel, including addresses in flash
5212		  memory. In this case U-Boot will NOT COPY the
5213		  ramdisk at all. This may be useful to reduce the
5214		  boot time on your system, but requires that this
5215		  feature is supported by your Linux kernel.
5216
5217  ipaddr	- IP address; needed for tftpboot command
5218
5219  loadaddr	- Default load address for commands like "bootp",
5220		  "rarpboot", "tftpboot", "loadb" or "diskboot"
5221
5222  loads_echo	- see CONFIG_LOADS_ECHO
5223
5224  serverip	- TFTP server IP address; needed for tftpboot command
5225
5226  bootretry	- see CONFIG_BOOT_RETRY_TIME
5227
5228  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5229
5230  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5231
5232  ethprime	- controls which interface is used first.
5233
5234  ethact	- controls which interface is currently active.
5235		  For example you can do the following
5236
5237		  => setenv ethact FEC
5238		  => ping 192.168.0.1 # traffic sent on FEC
5239		  => setenv ethact SCC
5240		  => ping 10.0.0.1 # traffic sent on SCC
5241
5242  ethrotate	- When set to "no" U-Boot does not go through all
5243		  available network interfaces.
5244		  It just stays at the currently selected interface.
5245
5246  netretry	- When set to "no" each network operation will
5247		  either succeed or fail without retrying.
5248		  When set to "once" the network operation will
5249		  fail when all the available network interfaces
5250		  are tried once without success.
5251		  Useful on scripts which control the retry operation
5252		  themselves.
5253
5254  npe_ucode	- set load address for the NPE microcode
5255
5256  silent_linux  - If set then Linux will be told to boot silently, by
5257		  changing the console to be empty. If "yes" it will be
5258		  made silent. If "no" it will not be made silent. If
5259		  unset, then it will be made silent if the U-Boot console
5260		  is silent.
5261
5262  tftpsrcp	- If this is set, the value is used for TFTP's
5263		  UDP source port.
5264
5265  tftpdstp	- If this is set, the value is used for TFTP's UDP
5266		  destination port instead of the Well Know Port 69.
5267
5268  tftpblocksize - Block size to use for TFTP transfers; if not set,
5269		  we use the TFTP server's default block size
5270
5271  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5272		  seconds, minimum value is 1000 = 1 second). Defines
5273		  when a packet is considered to be lost so it has to
5274		  be retransmitted. The default is 5000 = 5 seconds.
5275		  Lowering this value may make downloads succeed
5276		  faster in networks with high packet loss rates or
5277		  with unreliable TFTP servers.
5278
5279  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
5280		  unit, minimum value = 0). Defines how many timeouts
5281		  can happen during a single file transfer before that
5282		  transfer is aborted. The default is 10, and 0 means
5283		  'no timeouts allowed'. Increasing this value may help
5284		  downloads succeed with high packet loss rates, or with
5285		  unreliable TFTP servers or client hardware.
5286
5287  vlan		- When set to a value < 4095 the traffic over
5288		  Ethernet is encapsulated/received over 802.1q
5289		  VLAN tagged frames.
5290
5291  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
5292		  Unsigned value, in milliseconds. If not set, the period will
5293		  be either the default (28000), or a value based on
5294		  CONFIG_NET_RETRY_COUNT, if defined. This value has
5295		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
5296
5297The following image location variables contain the location of images
5298used in booting. The "Image" column gives the role of the image and is
5299not an environment variable name. The other columns are environment
5300variable names. "File Name" gives the name of the file on a TFTP
5301server, "RAM Address" gives the location in RAM the image will be
5302loaded to, and "Flash Location" gives the image's address in NOR
5303flash or offset in NAND flash.
5304
5305*Note* - these variables don't have to be defined for all boards, some
5306boards currently use other variables for these purposes, and some
5307boards use these variables for other purposes.
5308
5309Image		    File Name	     RAM Address       Flash Location
5310-----		    ---------	     -----------       --------------
5311u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5312Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5313device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5314ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5315
5316The following environment variables may be used and automatically
5317updated by the network boot commands ("bootp" and "rarpboot"),
5318depending the information provided by your boot server:
5319
5320  bootfile	- see above
5321  dnsip		- IP address of your Domain Name Server
5322  dnsip2	- IP address of your secondary Domain Name Server
5323  gatewayip	- IP address of the Gateway (Router) to use
5324  hostname	- Target hostname
5325  ipaddr	- see above
5326  netmask	- Subnet Mask
5327  rootpath	- Pathname of the root filesystem on the NFS server
5328  serverip	- see above
5329
5330
5331There are two special Environment Variables:
5332
5333  serial#	- contains hardware identification information such
5334		  as type string and/or serial number
5335  ethaddr	- Ethernet address
5336
5337These variables can be set only once (usually during manufacturing of
5338the board). U-Boot refuses to delete or overwrite these variables
5339once they have been set once.
5340
5341
5342Further special Environment Variables:
5343
5344  ver		- Contains the U-Boot version string as printed
5345		  with the "version" command. This variable is
5346		  readonly (see CONFIG_VERSION_VARIABLE).
5347
5348
5349Please note that changes to some configuration parameters may take
5350only effect after the next boot (yes, that's just like Windoze :-).
5351
5352
5353Callback functions for environment variables:
5354---------------------------------------------
5355
5356For some environment variables, the behavior of u-boot needs to change
5357when their values are changed.  This functionality allows functions to
5358be associated with arbitrary variables.  On creation, overwrite, or
5359deletion, the callback will provide the opportunity for some side
5360effect to happen or for the change to be rejected.
5361
5362The callbacks are named and associated with a function using the
5363U_BOOT_ENV_CALLBACK macro in your board or driver code.
5364
5365These callbacks are associated with variables in one of two ways.  The
5366static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5367in the board configuration to a string that defines a list of
5368associations.  The list must be in the following format:
5369
5370	entry = variable_name[:callback_name]
5371	list = entry[,list]
5372
5373If the callback name is not specified, then the callback is deleted.
5374Spaces are also allowed anywhere in the list.
5375
5376Callbacks can also be associated by defining the ".callbacks" variable
5377with the same list format above.  Any association in ".callbacks" will
5378override any association in the static list. You can define
5379CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5380".callbacks" environment variable in the default or embedded environment.
5381
5382If CONFIG_REGEX is defined, the variable_name above is evaluated as a
5383regular expression. This allows multiple variables to be connected to
5384the same callback without explicitly listing them all out.
5385
5386
5387Command Line Parsing:
5388=====================
5389
5390There are two different command line parsers available with U-Boot:
5391the old "simple" one, and the much more powerful "hush" shell:
5392
5393Old, simple command line parser:
5394--------------------------------
5395
5396- supports environment variables (through setenv / saveenv commands)
5397- several commands on one line, separated by ';'
5398- variable substitution using "... ${name} ..." syntax
5399- special characters ('$', ';') can be escaped by prefixing with '\',
5400  for example:
5401	setenv bootcmd bootm \${address}
5402- You can also escape text by enclosing in single apostrophes, for example:
5403	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5404
5405Hush shell:
5406-----------
5407
5408- similar to Bourne shell, with control structures like
5409  if...then...else...fi, for...do...done; while...do...done,
5410  until...do...done, ...
5411- supports environment ("global") variables (through setenv / saveenv
5412  commands) and local shell variables (through standard shell syntax
5413  "name=value"); only environment variables can be used with "run"
5414  command
5415
5416General rules:
5417--------------
5418
5419(1) If a command line (or an environment variable executed by a "run"
5420    command) contains several commands separated by semicolon, and
5421    one of these commands fails, then the remaining commands will be
5422    executed anyway.
5423
5424(2) If you execute several variables with one call to run (i. e.
5425    calling run with a list of variables as arguments), any failing
5426    command will cause "run" to terminate, i. e. the remaining
5427    variables are not executed.
5428
5429Note for Redundant Ethernet Interfaces:
5430=======================================
5431
5432Some boards come with redundant Ethernet interfaces; U-Boot supports
5433such configurations and is capable of automatic selection of a
5434"working" interface when needed. MAC assignment works as follows:
5435
5436Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5437MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5438"eth1addr" (=>eth1), "eth2addr", ...
5439
5440If the network interface stores some valid MAC address (for instance
5441in SROM), this is used as default address if there is NO correspon-
5442ding setting in the environment; if the corresponding environment
5443variable is set, this overrides the settings in the card; that means:
5444
5445o If the SROM has a valid MAC address, and there is no address in the
5446  environment, the SROM's address is used.
5447
5448o If there is no valid address in the SROM, and a definition in the
5449  environment exists, then the value from the environment variable is
5450  used.
5451
5452o If both the SROM and the environment contain a MAC address, and
5453  both addresses are the same, this MAC address is used.
5454
5455o If both the SROM and the environment contain a MAC address, and the
5456  addresses differ, the value from the environment is used and a
5457  warning is printed.
5458
5459o If neither SROM nor the environment contain a MAC address, an error
5460  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
5461  a random, locally-assigned MAC is used.
5462
5463If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5464will be programmed into hardware as part of the initialization process.	 This
5465may be skipped by setting the appropriate 'ethmacskip' environment variable.
5466The naming convention is as follows:
5467"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5468
5469Image Formats:
5470==============
5471
5472U-Boot is capable of booting (and performing other auxiliary operations on)
5473images in two formats:
5474
5475New uImage format (FIT)
5476-----------------------
5477
5478Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5479to Flattened Device Tree). It allows the use of images with multiple
5480components (several kernels, ramdisks, etc.), with contents protected by
5481SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5482
5483
5484Old uImage format
5485-----------------
5486
5487Old image format is based on binary files which can be basically anything,
5488preceded by a special header; see the definitions in include/image.h for
5489details; basically, the header defines the following image properties:
5490
5491* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5492  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5493  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5494  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5495  INTEGRITY).
5496* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5497  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5498  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5499* Compression Type (uncompressed, gzip, bzip2)
5500* Load Address
5501* Entry Point
5502* Image Name
5503* Image Timestamp
5504
5505The header is marked by a special Magic Number, and both the header
5506and the data portions of the image are secured against corruption by
5507CRC32 checksums.
5508
5509
5510Linux Support:
5511==============
5512
5513Although U-Boot should support any OS or standalone application
5514easily, the main focus has always been on Linux during the design of
5515U-Boot.
5516
5517U-Boot includes many features that so far have been part of some
5518special "boot loader" code within the Linux kernel. Also, any
5519"initrd" images to be used are no longer part of one big Linux image;
5520instead, kernel and "initrd" are separate images. This implementation
5521serves several purposes:
5522
5523- the same features can be used for other OS or standalone
5524  applications (for instance: using compressed images to reduce the
5525  Flash memory footprint)
5526
5527- it becomes much easier to port new Linux kernel versions because
5528  lots of low-level, hardware dependent stuff are done by U-Boot
5529
5530- the same Linux kernel image can now be used with different "initrd"
5531  images; of course this also means that different kernel images can
5532  be run with the same "initrd". This makes testing easier (you don't
5533  have to build a new "zImage.initrd" Linux image when you just
5534  change a file in your "initrd"). Also, a field-upgrade of the
5535  software is easier now.
5536
5537
5538Linux HOWTO:
5539============
5540
5541Porting Linux to U-Boot based systems:
5542---------------------------------------
5543
5544U-Boot cannot save you from doing all the necessary modifications to
5545configure the Linux device drivers for use with your target hardware
5546(no, we don't intend to provide a full virtual machine interface to
5547Linux :-).
5548
5549But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5550
5551Just make sure your machine specific header file (for instance
5552include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5553Information structure as we define in include/asm-<arch>/u-boot.h,
5554and make sure that your definition of IMAP_ADDR uses the same value
5555as your U-Boot configuration in CONFIG_SYS_IMMR.
5556
5557Note that U-Boot now has a driver model, a unified model for drivers.
5558If you are adding a new driver, plumb it into driver model. If there
5559is no uclass available, you are encouraged to create one. See
5560doc/driver-model.
5561
5562
5563Configuring the Linux kernel:
5564-----------------------------
5565
5566No specific requirements for U-Boot. Make sure you have some root
5567device (initial ramdisk, NFS) for your target system.
5568
5569
5570Building a Linux Image:
5571-----------------------
5572
5573With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5574not used. If you use recent kernel source, a new build target
5575"uImage" will exist which automatically builds an image usable by
5576U-Boot. Most older kernels also have support for a "pImage" target,
5577which was introduced for our predecessor project PPCBoot and uses a
5578100% compatible format.
5579
5580Example:
5581
5582	make TQM850L_defconfig
5583	make oldconfig
5584	make dep
5585	make uImage
5586
5587The "uImage" build target uses a special tool (in 'tools/mkimage') to
5588encapsulate a compressed Linux kernel image with header	 information,
5589CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5590
5591* build a standard "vmlinux" kernel image (in ELF binary format):
5592
5593* convert the kernel into a raw binary image:
5594
5595	${CROSS_COMPILE}-objcopy -O binary \
5596				 -R .note -R .comment \
5597				 -S vmlinux linux.bin
5598
5599* compress the binary image:
5600
5601	gzip -9 linux.bin
5602
5603* package compressed binary image for U-Boot:
5604
5605	mkimage -A ppc -O linux -T kernel -C gzip \
5606		-a 0 -e 0 -n "Linux Kernel Image" \
5607		-d linux.bin.gz uImage
5608
5609
5610The "mkimage" tool can also be used to create ramdisk images for use
5611with U-Boot, either separated from the Linux kernel image, or
5612combined into one file. "mkimage" encapsulates the images with a 64
5613byte header containing information about target architecture,
5614operating system, image type, compression method, entry points, time
5615stamp, CRC32 checksums, etc.
5616
5617"mkimage" can be called in two ways: to verify existing images and
5618print the header information, or to build new images.
5619
5620In the first form (with "-l" option) mkimage lists the information
5621contained in the header of an existing U-Boot image; this includes
5622checksum verification:
5623
5624	tools/mkimage -l image
5625	  -l ==> list image header information
5626
5627The second form (with "-d" option) is used to build a U-Boot image
5628from a "data file" which is used as image payload:
5629
5630	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5631		      -n name -d data_file image
5632	  -A ==> set architecture to 'arch'
5633	  -O ==> set operating system to 'os'
5634	  -T ==> set image type to 'type'
5635	  -C ==> set compression type 'comp'
5636	  -a ==> set load address to 'addr' (hex)
5637	  -e ==> set entry point to 'ep' (hex)
5638	  -n ==> set image name to 'name'
5639	  -d ==> use image data from 'datafile'
5640
5641Right now, all Linux kernels for PowerPC systems use the same load
5642address (0x00000000), but the entry point address depends on the
5643kernel version:
5644
5645- 2.2.x kernels have the entry point at 0x0000000C,
5646- 2.3.x and later kernels have the entry point at 0x00000000.
5647
5648So a typical call to build a U-Boot image would read:
5649
5650	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5651	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5652	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5653	> examples/uImage.TQM850L
5654	Image Name:   2.4.4 kernel for TQM850L
5655	Created:      Wed Jul 19 02:34:59 2000
5656	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5657	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5658	Load Address: 0x00000000
5659	Entry Point:  0x00000000
5660
5661To verify the contents of the image (or check for corruption):
5662
5663	-> tools/mkimage -l examples/uImage.TQM850L
5664	Image Name:   2.4.4 kernel for TQM850L
5665	Created:      Wed Jul 19 02:34:59 2000
5666	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5667	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5668	Load Address: 0x00000000
5669	Entry Point:  0x00000000
5670
5671NOTE: for embedded systems where boot time is critical you can trade
5672speed for memory and install an UNCOMPRESSED image instead: this
5673needs more space in Flash, but boots much faster since it does not
5674need to be uncompressed:
5675
5676	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5677	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5678	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5679	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5680	> examples/uImage.TQM850L-uncompressed
5681	Image Name:   2.4.4 kernel for TQM850L
5682	Created:      Wed Jul 19 02:34:59 2000
5683	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5684	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5685	Load Address: 0x00000000
5686	Entry Point:  0x00000000
5687
5688
5689Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5690when your kernel is intended to use an initial ramdisk:
5691
5692	-> tools/mkimage -n 'Simple Ramdisk Image' \
5693	> -A ppc -O linux -T ramdisk -C gzip \
5694	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5695	Image Name:   Simple Ramdisk Image
5696	Created:      Wed Jan 12 14:01:50 2000
5697	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5698	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5699	Load Address: 0x00000000
5700	Entry Point:  0x00000000
5701
5702The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5703option performs the converse operation of the mkimage's second form (the "-d"
5704option). Given an image built by mkimage, the dumpimage extracts a "data file"
5705from the image:
5706
5707	tools/dumpimage -i image -T type -p position data_file
5708	  -i ==> extract from the 'image' a specific 'data_file'
5709	  -T ==> set image type to 'type'
5710	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5711
5712
5713Installing a Linux Image:
5714-------------------------
5715
5716To downloading a U-Boot image over the serial (console) interface,
5717you must convert the image to S-Record format:
5718
5719	objcopy -I binary -O srec examples/image examples/image.srec
5720
5721The 'objcopy' does not understand the information in the U-Boot
5722image header, so the resulting S-Record file will be relative to
5723address 0x00000000. To load it to a given address, you need to
5724specify the target address as 'offset' parameter with the 'loads'
5725command.
5726
5727Example: install the image to address 0x40100000 (which on the
5728TQM8xxL is in the first Flash bank):
5729
5730	=> erase 40100000 401FFFFF
5731
5732	.......... done
5733	Erased 8 sectors
5734
5735	=> loads 40100000
5736	## Ready for S-Record download ...
5737	~>examples/image.srec
5738	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5739	...
5740	15989 15990 15991 15992
5741	[file transfer complete]
5742	[connected]
5743	## Start Addr = 0x00000000
5744
5745
5746You can check the success of the download using the 'iminfo' command;
5747this includes a checksum verification so you can be sure no data
5748corruption happened:
5749
5750	=> imi 40100000
5751
5752	## Checking Image at 40100000 ...
5753	   Image Name:	 2.2.13 for initrd on TQM850L
5754	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5755	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5756	   Load Address: 00000000
5757	   Entry Point:	 0000000c
5758	   Verifying Checksum ... OK
5759
5760
5761Boot Linux:
5762-----------
5763
5764The "bootm" command is used to boot an application that is stored in
5765memory (RAM or Flash). In case of a Linux kernel image, the contents
5766of the "bootargs" environment variable is passed to the kernel as
5767parameters. You can check and modify this variable using the
5768"printenv" and "setenv" commands:
5769
5770
5771	=> printenv bootargs
5772	bootargs=root=/dev/ram
5773
5774	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5775
5776	=> printenv bootargs
5777	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5778
5779	=> bootm 40020000
5780	## Booting Linux kernel at 40020000 ...
5781	   Image Name:	 2.2.13 for NFS on TQM850L
5782	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5783	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5784	   Load Address: 00000000
5785	   Entry Point:	 0000000c
5786	   Verifying Checksum ... OK
5787	   Uncompressing Kernel Image ... OK
5788	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
5789	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5790	time_init: decrementer frequency = 187500000/60
5791	Calibrating delay loop... 49.77 BogoMIPS
5792	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5793	...
5794
5795If you want to boot a Linux kernel with initial RAM disk, you pass
5796the memory addresses of both the kernel and the initrd image (PPBCOOT
5797format!) to the "bootm" command:
5798
5799	=> imi 40100000 40200000
5800
5801	## Checking Image at 40100000 ...
5802	   Image Name:	 2.2.13 for initrd on TQM850L
5803	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5804	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5805	   Load Address: 00000000
5806	   Entry Point:	 0000000c
5807	   Verifying Checksum ... OK
5808
5809	## Checking Image at 40200000 ...
5810	   Image Name:	 Simple Ramdisk Image
5811	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5812	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5813	   Load Address: 00000000
5814	   Entry Point:	 00000000
5815	   Verifying Checksum ... OK
5816
5817	=> bootm 40100000 40200000
5818	## Booting Linux kernel at 40100000 ...
5819	   Image Name:	 2.2.13 for initrd on TQM850L
5820	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5821	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5822	   Load Address: 00000000
5823	   Entry Point:	 0000000c
5824	   Verifying Checksum ... OK
5825	   Uncompressing Kernel Image ... OK
5826	## Loading RAMDisk Image at 40200000 ...
5827	   Image Name:	 Simple Ramdisk Image
5828	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5829	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5830	   Load Address: 00000000
5831	   Entry Point:	 00000000
5832	   Verifying Checksum ... OK
5833	   Loading Ramdisk ... OK
5834	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
5835	Boot arguments: root=/dev/ram
5836	time_init: decrementer frequency = 187500000/60
5837	Calibrating delay loop... 49.77 BogoMIPS
5838	...
5839	RAMDISK: Compressed image found at block 0
5840	VFS: Mounted root (ext2 filesystem).
5841
5842	bash#
5843
5844Boot Linux and pass a flat device tree:
5845-----------
5846
5847First, U-Boot must be compiled with the appropriate defines. See the section
5848titled "Linux Kernel Interface" above for a more in depth explanation. The
5849following is an example of how to start a kernel and pass an updated
5850flat device tree:
5851
5852=> print oftaddr
5853oftaddr=0x300000
5854=> print oft
5855oft=oftrees/mpc8540ads.dtb
5856=> tftp $oftaddr $oft
5857Speed: 1000, full duplex
5858Using TSEC0 device
5859TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5860Filename 'oftrees/mpc8540ads.dtb'.
5861Load address: 0x300000
5862Loading: #
5863done
5864Bytes transferred = 4106 (100a hex)
5865=> tftp $loadaddr $bootfile
5866Speed: 1000, full duplex
5867Using TSEC0 device
5868TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5869Filename 'uImage'.
5870Load address: 0x200000
5871Loading:############
5872done
5873Bytes transferred = 1029407 (fb51f hex)
5874=> print loadaddr
5875loadaddr=200000
5876=> print oftaddr
5877oftaddr=0x300000
5878=> bootm $loadaddr - $oftaddr
5879## Booting image at 00200000 ...
5880   Image Name:	 Linux-2.6.17-dirty
5881   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5882   Data Size:	 1029343 Bytes = 1005.2 kB
5883   Load Address: 00000000
5884   Entry Point:	 00000000
5885   Verifying Checksum ... OK
5886   Uncompressing Kernel Image ... OK
5887Booting using flat device tree at 0x300000
5888Using MPC85xx ADS machine description
5889Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5890[snip]
5891
5892
5893More About U-Boot Image Types:
5894------------------------------
5895
5896U-Boot supports the following image types:
5897
5898   "Standalone Programs" are directly runnable in the environment
5899	provided by U-Boot; it is expected that (if they behave
5900	well) you can continue to work in U-Boot after return from
5901	the Standalone Program.
5902   "OS Kernel Images" are usually images of some Embedded OS which
5903	will take over control completely. Usually these programs
5904	will install their own set of exception handlers, device
5905	drivers, set up the MMU, etc. - this means, that you cannot
5906	expect to re-enter U-Boot except by resetting the CPU.
5907   "RAMDisk Images" are more or less just data blocks, and their
5908	parameters (address, size) are passed to an OS kernel that is
5909	being started.
5910   "Multi-File Images" contain several images, typically an OS
5911	(Linux) kernel image and one or more data images like
5912	RAMDisks. This construct is useful for instance when you want
5913	to boot over the network using BOOTP etc., where the boot
5914	server provides just a single image file, but you want to get
5915	for instance an OS kernel and a RAMDisk image.
5916
5917	"Multi-File Images" start with a list of image sizes, each
5918	image size (in bytes) specified by an "uint32_t" in network
5919	byte order. This list is terminated by an "(uint32_t)0".
5920	Immediately after the terminating 0 follow the images, one by
5921	one, all aligned on "uint32_t" boundaries (size rounded up to
5922	a multiple of 4 bytes).
5923
5924   "Firmware Images" are binary images containing firmware (like
5925	U-Boot or FPGA images) which usually will be programmed to
5926	flash memory.
5927
5928   "Script files" are command sequences that will be executed by
5929	U-Boot's command interpreter; this feature is especially
5930	useful when you configure U-Boot to use a real shell (hush)
5931	as command interpreter.
5932
5933Booting the Linux zImage:
5934-------------------------
5935
5936On some platforms, it's possible to boot Linux zImage. This is done
5937using the "bootz" command. The syntax of "bootz" command is the same
5938as the syntax of "bootm" command.
5939
5940Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5941kernel with raw initrd images. The syntax is slightly different, the
5942address of the initrd must be augmented by it's size, in the following
5943format: "<initrd addres>:<initrd size>".
5944
5945
5946Standalone HOWTO:
5947=================
5948
5949One of the features of U-Boot is that you can dynamically load and
5950run "standalone" applications, which can use some resources of
5951U-Boot like console I/O functions or interrupt services.
5952
5953Two simple examples are included with the sources:
5954
5955"Hello World" Demo:
5956-------------------
5957
5958'examples/hello_world.c' contains a small "Hello World" Demo
5959application; it is automatically compiled when you build U-Boot.
5960It's configured to run at address 0x00040004, so you can play with it
5961like that:
5962
5963	=> loads
5964	## Ready for S-Record download ...
5965	~>examples/hello_world.srec
5966	1 2 3 4 5 6 7 8 9 10 11 ...
5967	[file transfer complete]
5968	[connected]
5969	## Start Addr = 0x00040004
5970
5971	=> go 40004 Hello World! This is a test.
5972	## Starting application at 0x00040004 ...
5973	Hello World
5974	argc = 7
5975	argv[0] = "40004"
5976	argv[1] = "Hello"
5977	argv[2] = "World!"
5978	argv[3] = "This"
5979	argv[4] = "is"
5980	argv[5] = "a"
5981	argv[6] = "test."
5982	argv[7] = "<NULL>"
5983	Hit any key to exit ...
5984
5985	## Application terminated, rc = 0x0
5986
5987Another example, which demonstrates how to register a CPM interrupt
5988handler with the U-Boot code, can be found in 'examples/timer.c'.
5989Here, a CPM timer is set up to generate an interrupt every second.
5990The interrupt service routine is trivial, just printing a '.'
5991character, but this is just a demo program. The application can be
5992controlled by the following keys:
5993
5994	? - print current values og the CPM Timer registers
5995	b - enable interrupts and start timer
5996	e - stop timer and disable interrupts
5997	q - quit application
5998
5999	=> loads
6000	## Ready for S-Record download ...
6001	~>examples/timer.srec
6002	1 2 3 4 5 6 7 8 9 10 11 ...
6003	[file transfer complete]
6004	[connected]
6005	## Start Addr = 0x00040004
6006
6007	=> go 40004
6008	## Starting application at 0x00040004 ...
6009	TIMERS=0xfff00980
6010	Using timer 1
6011	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
6012
6013Hit 'b':
6014	[q, b, e, ?] Set interval 1000000 us
6015	Enabling timer
6016Hit '?':
6017	[q, b, e, ?] ........
6018	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
6019Hit '?':
6020	[q, b, e, ?] .
6021	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
6022Hit '?':
6023	[q, b, e, ?] .
6024	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
6025Hit '?':
6026	[q, b, e, ?] .
6027	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
6028Hit 'e':
6029	[q, b, e, ?] ...Stopping timer
6030Hit 'q':
6031	[q, b, e, ?] ## Application terminated, rc = 0x0
6032
6033
6034Minicom warning:
6035================
6036
6037Over time, many people have reported problems when trying to use the
6038"minicom" terminal emulation program for serial download. I (wd)
6039consider minicom to be broken, and recommend not to use it. Under
6040Unix, I recommend to use C-Kermit for general purpose use (and
6041especially for kermit binary protocol download ("loadb" command), and
6042use "cu" for S-Record download ("loads" command).  See
6043http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
6044for help with kermit.
6045
6046
6047Nevertheless, if you absolutely want to use it try adding this
6048configuration to your "File transfer protocols" section:
6049
6050	   Name	   Program			Name U/D FullScr IO-Red. Multi
6051	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
6052	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
6053
6054
6055NetBSD Notes:
6056=============
6057
6058Starting at version 0.9.2, U-Boot supports NetBSD both as host
6059(build U-Boot) and target system (boots NetBSD/mpc8xx).
6060
6061Building requires a cross environment; it is known to work on
6062NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
6063need gmake since the Makefiles are not compatible with BSD make).
6064Note that the cross-powerpc package does not install include files;
6065attempting to build U-Boot will fail because <machine/ansi.h> is
6066missing.  This file has to be installed and patched manually:
6067
6068	# cd /usr/pkg/cross/powerpc-netbsd/include
6069	# mkdir powerpc
6070	# ln -s powerpc machine
6071	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
6072	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
6073
6074Native builds *don't* work due to incompatibilities between native
6075and U-Boot include files.
6076
6077Booting assumes that (the first part of) the image booted is a
6078stage-2 loader which in turn loads and then invokes the kernel
6079proper. Loader sources will eventually appear in the NetBSD source
6080tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
6081meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
6082
6083
6084Implementation Internals:
6085=========================
6086
6087The following is not intended to be a complete description of every
6088implementation detail. However, it should help to understand the
6089inner workings of U-Boot and make it easier to port it to custom
6090hardware.
6091
6092
6093Initial Stack, Global Data:
6094---------------------------
6095
6096The implementation of U-Boot is complicated by the fact that U-Boot
6097starts running out of ROM (flash memory), usually without access to
6098system RAM (because the memory controller is not initialized yet).
6099This means that we don't have writable Data or BSS segments, and BSS
6100is not initialized as zero. To be able to get a C environment working
6101at all, we have to allocate at least a minimal stack. Implementation
6102options for this are defined and restricted by the CPU used: Some CPU
6103models provide on-chip memory (like the IMMR area on MPC8xx and
6104MPC826x processors), on others (parts of) the data cache can be
6105locked as (mis-) used as memory, etc.
6106
6107	Chris Hallinan posted a good summary of these issues to the
6108	U-Boot mailing list:
6109
6110	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
6111	From: "Chris Hallinan" <clh@net1plus.com>
6112	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
6113	...
6114
6115	Correct me if I'm wrong, folks, but the way I understand it
6116	is this: Using DCACHE as initial RAM for Stack, etc, does not
6117	require any physical RAM backing up the cache. The cleverness
6118	is that the cache is being used as a temporary supply of
6119	necessary storage before the SDRAM controller is setup. It's
6120	beyond the scope of this list to explain the details, but you
6121	can see how this works by studying the cache architecture and
6122	operation in the architecture and processor-specific manuals.
6123
6124	OCM is On Chip Memory, which I believe the 405GP has 4K. It
6125	is another option for the system designer to use as an
6126	initial stack/RAM area prior to SDRAM being available. Either
6127	option should work for you. Using CS 4 should be fine if your
6128	board designers haven't used it for something that would
6129	cause you grief during the initial boot! It is frequently not
6130	used.
6131
6132	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
6133	with your processor/board/system design. The default value
6134	you will find in any recent u-boot distribution in
6135	walnut.h should work for you. I'd set it to a value larger
6136	than your SDRAM module. If you have a 64MB SDRAM module, set
6137	it above 400_0000. Just make sure your board has no resources
6138	that are supposed to respond to that address! That code in
6139	start.S has been around a while and should work as is when
6140	you get the config right.
6141
6142	-Chris Hallinan
6143	DS4.COM, Inc.
6144
6145It is essential to remember this, since it has some impact on the C
6146code for the initialization procedures:
6147
6148* Initialized global data (data segment) is read-only. Do not attempt
6149  to write it.
6150
6151* Do not use any uninitialized global data (or implicitly initialized
6152  as zero data - BSS segment) at all - this is undefined, initiali-
6153  zation is performed later (when relocating to RAM).
6154
6155* Stack space is very limited. Avoid big data buffers or things like
6156  that.
6157
6158Having only the stack as writable memory limits means we cannot use
6159normal global data to share information between the code. But it
6160turned out that the implementation of U-Boot can be greatly
6161simplified by making a global data structure (gd_t) available to all
6162functions. We could pass a pointer to this data as argument to _all_
6163functions, but this would bloat the code. Instead we use a feature of
6164the GCC compiler (Global Register Variables) to share the data: we
6165place a pointer (gd) to the global data into a register which we
6166reserve for this purpose.
6167
6168When choosing a register for such a purpose we are restricted by the
6169relevant  (E)ABI  specifications for the current architecture, and by
6170GCC's implementation.
6171
6172For PowerPC, the following registers have specific use:
6173	R1:	stack pointer
6174	R2:	reserved for system use
6175	R3-R4:	parameter passing and return values
6176	R5-R10: parameter passing
6177	R13:	small data area pointer
6178	R30:	GOT pointer
6179	R31:	frame pointer
6180
6181	(U-Boot also uses R12 as internal GOT pointer. r12
6182	is a volatile register so r12 needs to be reset when
6183	going back and forth between asm and C)
6184
6185    ==> U-Boot will use R2 to hold a pointer to the global data
6186
6187    Note: on PPC, we could use a static initializer (since the
6188    address of the global data structure is known at compile time),
6189    but it turned out that reserving a register results in somewhat
6190    smaller code - although the code savings are not that big (on
6191    average for all boards 752 bytes for the whole U-Boot image,
6192    624 text + 127 data).
6193
6194On Blackfin, the normal C ABI (except for P3) is followed as documented here:
6195	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
6196
6197    ==> U-Boot will use P3 to hold a pointer to the global data
6198
6199On ARM, the following registers are used:
6200
6201	R0:	function argument word/integer result
6202	R1-R3:	function argument word
6203	R9:	platform specific
6204	R10:	stack limit (used only if stack checking is enabled)
6205	R11:	argument (frame) pointer
6206	R12:	temporary workspace
6207	R13:	stack pointer
6208	R14:	link register
6209	R15:	program counter
6210
6211    ==> U-Boot will use R9 to hold a pointer to the global data
6212
6213    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
6214
6215On Nios II, the ABI is documented here:
6216	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
6217
6218    ==> U-Boot will use gp to hold a pointer to the global data
6219
6220    Note: on Nios II, we give "-G0" option to gcc and don't use gp
6221    to access small data sections, so gp is free.
6222
6223On NDS32, the following registers are used:
6224
6225	R0-R1:	argument/return
6226	R2-R5:	argument
6227	R15:	temporary register for assembler
6228	R16:	trampoline register
6229	R28:	frame pointer (FP)
6230	R29:	global pointer (GP)
6231	R30:	link register (LP)
6232	R31:	stack pointer (SP)
6233	PC:	program counter (PC)
6234
6235    ==> U-Boot will use R10 to hold a pointer to the global data
6236
6237NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6238or current versions of GCC may "optimize" the code too much.
6239
6240Memory Management:
6241------------------
6242
6243U-Boot runs in system state and uses physical addresses, i.e. the
6244MMU is not used either for address mapping nor for memory protection.
6245
6246The available memory is mapped to fixed addresses using the memory
6247controller. In this process, a contiguous block is formed for each
6248memory type (Flash, SDRAM, SRAM), even when it consists of several
6249physical memory banks.
6250
6251U-Boot is installed in the first 128 kB of the first Flash bank (on
6252TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6253booting and sizing and initializing DRAM, the code relocates itself
6254to the upper end of DRAM. Immediately below the U-Boot code some
6255memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6256configuration setting]. Below that, a structure with global Board
6257Info data is placed, followed by the stack (growing downward).
6258
6259Additionally, some exception handler code is copied to the low 8 kB
6260of DRAM (0x00000000 ... 0x00001FFF).
6261
6262So a typical memory configuration with 16 MB of DRAM could look like
6263this:
6264
6265	0x0000 0000	Exception Vector code
6266	      :
6267	0x0000 1FFF
6268	0x0000 2000	Free for Application Use
6269	      :
6270	      :
6271
6272	      :
6273	      :
6274	0x00FB FF20	Monitor Stack (Growing downward)
6275	0x00FB FFAC	Board Info Data and permanent copy of global data
6276	0x00FC 0000	Malloc Arena
6277	      :
6278	0x00FD FFFF
6279	0x00FE 0000	RAM Copy of Monitor Code
6280	...		eventually: LCD or video framebuffer
6281	...		eventually: pRAM (Protected RAM - unchanged by reset)
6282	0x00FF FFFF	[End of RAM]
6283
6284
6285System Initialization:
6286----------------------
6287
6288In the reset configuration, U-Boot starts at the reset entry point
6289(on most PowerPC systems at address 0x00000100). Because of the reset
6290configuration for CS0# this is a mirror of the on board Flash memory.
6291To be able to re-map memory U-Boot then jumps to its link address.
6292To be able to implement the initialization code in C, a (small!)
6293initial stack is set up in the internal Dual Ported RAM (in case CPUs
6294which provide such a feature like MPC8xx or MPC8260), or in a locked
6295part of the data cache. After that, U-Boot initializes the CPU core,
6296the caches and the SIU.
6297
6298Next, all (potentially) available memory banks are mapped using a
6299preliminary mapping. For example, we put them on 512 MB boundaries
6300(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6301on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6302programmed for SDRAM access. Using the temporary configuration, a
6303simple memory test is run that determines the size of the SDRAM
6304banks.
6305
6306When there is more than one SDRAM bank, and the banks are of
6307different size, the largest is mapped first. For equal size, the first
6308bank (CS2#) is mapped first. The first mapping is always for address
63090x00000000, with any additional banks following immediately to create
6310contiguous memory starting from 0.
6311
6312Then, the monitor installs itself at the upper end of the SDRAM area
6313and allocates memory for use by malloc() and for the global Board
6314Info data; also, the exception vector code is copied to the low RAM
6315pages, and the final stack is set up.
6316
6317Only after this relocation will you have a "normal" C environment;
6318until that you are restricted in several ways, mostly because you are
6319running from ROM, and because the code will have to be relocated to a
6320new address in RAM.
6321
6322
6323U-Boot Porting Guide:
6324----------------------
6325
6326[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6327list, October 2002]
6328
6329
6330int main(int argc, char *argv[])
6331{
6332	sighandler_t no_more_time;
6333
6334	signal(SIGALRM, no_more_time);
6335	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6336
6337	if (available_money > available_manpower) {
6338		Pay consultant to port U-Boot;
6339		return 0;
6340	}
6341
6342	Download latest U-Boot source;
6343
6344	Subscribe to u-boot mailing list;
6345
6346	if (clueless)
6347		email("Hi, I am new to U-Boot, how do I get started?");
6348
6349	while (learning) {
6350		Read the README file in the top level directory;
6351		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6352		Read applicable doc/*.README;
6353		Read the source, Luke;
6354		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6355	}
6356
6357	if (available_money > toLocalCurrency ($2500))
6358		Buy a BDI3000;
6359	else
6360		Add a lot of aggravation and time;
6361
6362	if (a similar board exists) {	/* hopefully... */
6363		cp -a board/<similar> board/<myboard>
6364		cp include/configs/<similar>.h include/configs/<myboard>.h
6365	} else {
6366		Create your own board support subdirectory;
6367		Create your own board include/configs/<myboard>.h file;
6368	}
6369	Edit new board/<myboard> files
6370	Edit new include/configs/<myboard>.h
6371
6372	while (!accepted) {
6373		while (!running) {
6374			do {
6375				Add / modify source code;
6376			} until (compiles);
6377			Debug;
6378			if (clueless)
6379				email("Hi, I am having problems...");
6380		}
6381		Send patch file to the U-Boot email list;
6382		if (reasonable critiques)
6383			Incorporate improvements from email list code review;
6384		else
6385			Defend code as written;
6386	}
6387
6388	return 0;
6389}
6390
6391void no_more_time (int sig)
6392{
6393      hire_a_guru();
6394}
6395
6396
6397Coding Standards:
6398-----------------
6399
6400All contributions to U-Boot should conform to the Linux kernel
6401coding style; see the file "Documentation/CodingStyle" and the script
6402"scripts/Lindent" in your Linux kernel source directory.
6403
6404Source files originating from a different project (for example the
6405MTD subsystem) are generally exempt from these guidelines and are not
6406reformatted to ease subsequent migration to newer versions of those
6407sources.
6408
6409Please note that U-Boot is implemented in C (and to some small parts in
6410Assembler); no C++ is used, so please do not use C++ style comments (//)
6411in your code.
6412
6413Please also stick to the following formatting rules:
6414- remove any trailing white space
6415- use TAB characters for indentation and vertical alignment, not spaces
6416- make sure NOT to use DOS '\r\n' line feeds
6417- do not add more than 2 consecutive empty lines to source files
6418- do not add trailing empty lines to source files
6419
6420Submissions which do not conform to the standards may be returned
6421with a request to reformat the changes.
6422
6423
6424Submitting Patches:
6425-------------------
6426
6427Since the number of patches for U-Boot is growing, we need to
6428establish some rules. Submissions which do not conform to these rules
6429may be rejected, even when they contain important and valuable stuff.
6430
6431Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6432
6433Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6434see http://lists.denx.de/mailman/listinfo/u-boot
6435
6436When you send a patch, please include the following information with
6437it:
6438
6439* For bug fixes: a description of the bug and how your patch fixes
6440  this bug. Please try to include a way of demonstrating that the
6441  patch actually fixes something.
6442
6443* For new features: a description of the feature and your
6444  implementation.
6445
6446* A CHANGELOG entry as plaintext (separate from the patch)
6447
6448* For major contributions, add a MAINTAINERS file with your
6449  information and associated file and directory references.
6450
6451* When you add support for a new board, don't forget to add a
6452  maintainer e-mail address to the boards.cfg file, too.
6453
6454* If your patch adds new configuration options, don't forget to
6455  document these in the README file.
6456
6457* The patch itself. If you are using git (which is *strongly*
6458  recommended) you can easily generate the patch using the
6459  "git format-patch". If you then use "git send-email" to send it to
6460  the U-Boot mailing list, you will avoid most of the common problems
6461  with some other mail clients.
6462
6463  If you cannot use git, use "diff -purN OLD NEW". If your version of
6464  diff does not support these options, then get the latest version of
6465  GNU diff.
6466
6467  The current directory when running this command shall be the parent
6468  directory of the U-Boot source tree (i. e. please make sure that
6469  your patch includes sufficient directory information for the
6470  affected files).
6471
6472  We prefer patches as plain text. MIME attachments are discouraged,
6473  and compressed attachments must not be used.
6474
6475* If one logical set of modifications affects or creates several
6476  files, all these changes shall be submitted in a SINGLE patch file.
6477
6478* Changesets that contain different, unrelated modifications shall be
6479  submitted as SEPARATE patches, one patch per changeset.
6480
6481
6482Notes:
6483
6484* Before sending the patch, run the buildman script on your patched
6485  source tree and make sure that no errors or warnings are reported
6486  for any of the boards.
6487
6488* Keep your modifications to the necessary minimum: A patch
6489  containing several unrelated changes or arbitrary reformats will be
6490  returned with a request to re-formatting / split it.
6491
6492* If you modify existing code, make sure that your new code does not
6493  add to the memory footprint of the code ;-) Small is beautiful!
6494  When adding new features, these should compile conditionally only
6495  (using #ifdef), and the resulting code with the new feature
6496  disabled must not need more memory than the old code without your
6497  modification.
6498
6499* Remember that there is a size limit of 100 kB per message on the
6500  u-boot mailing list. Bigger patches will be moderated. If they are
6501  reasonable and not too big, they will be acknowledged. But patches
6502  bigger than the size limit should be avoided.
6503