xref: /rk3399_rockchip-uboot/README (revision c6745195be700fa3f8a7221169a0f20df9c0e91f)
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- Marvell Family Member
329		CONFIG_SYS_MVFS		- define it if you want to enable
330					  multiple fs option at one time
331					  for marvell soc family
332
333- 8xx CPU Options: (if using an MPC8xx CPU)
334		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
335					  get_gclk_freq() cannot work
336					  e.g. if there is no 32KHz
337					  reference PIT/RTC clock
338		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
339					  or XTAL/EXTAL)
340
341- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
342		CONFIG_SYS_8xx_CPUCLK_MIN
343		CONFIG_SYS_8xx_CPUCLK_MAX
344		CONFIG_8xx_CPUCLK_DEFAULT
345			See doc/README.MPC866
346
347		CONFIG_SYS_MEASURE_CPUCLK
348
349		Define this to measure the actual CPU clock instead
350		of relying on the correctness of the configured
351		values. Mostly useful for board bringup to make sure
352		the PLL is locked at the intended frequency. Note
353		that this requires a (stable) reference clock (32 kHz
354		RTC clock or CONFIG_SYS_8XX_XIN)
355
356		CONFIG_SYS_DELAYED_ICACHE
357
358		Define this option if you want to enable the
359		ICache only when Code runs from RAM.
360
361- 85xx CPU Options:
362		CONFIG_SYS_PPC64
363
364		Specifies that the core is a 64-bit PowerPC implementation (implements
365		the "64" category of the Power ISA). This is necessary for ePAPR
366		compliance, among other possible reasons.
367
368		CONFIG_SYS_FSL_TBCLK_DIV
369
370		Defines the core time base clock divider ratio compared to the
371		system clock.  On most PQ3 devices this is 8, on newer QorIQ
372		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
373
374		CONFIG_SYS_FSL_PCIE_COMPAT
375
376		Defines the string to utilize when trying to match PCIe device
377		tree nodes for the given platform.
378
379		CONFIG_SYS_PPC_E500_DEBUG_TLB
380
381		Enables a temporary TLB entry to be used during boot to work
382		around limitations in e500v1 and e500v2 external debugger
383		support. This reduces the portions of the boot code where
384		breakpoints and single stepping do not work.  The value of this
385		symbol should be set to the TLB1 entry to be used for this
386		purpose.
387
388		CONFIG_SYS_FSL_ERRATUM_A004510
389
390		Enables a workaround for erratum A004510.  If set,
391		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
392		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
393
394		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
395		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
396
397		Defines one or two SoC revisions (low 8 bits of SVR)
398		for which the A004510 workaround should be applied.
399
400		The rest of SVR is either not relevant to the decision
401		of whether the erratum is present (e.g. p2040 versus
402		p2041) or is implied by the build target, which controls
403		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
404
405		See Freescale App Note 4493 for more information about
406		this erratum.
407
408		CONFIG_A003399_NOR_WORKAROUND
409		Enables a workaround for IFC erratum A003399. It is only
410		required during NOR boot.
411
412		CONFIG_A008044_WORKAROUND
413		Enables a workaround for T1040/T1042 erratum A008044. It is only
414		required during NAND boot and valid for Rev 1.0 SoC revision
415
416		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
417
418		This is the value to write into CCSR offset 0x18600
419		according to the A004510 workaround.
420
421		CONFIG_SYS_FSL_DSP_DDR_ADDR
422		This value denotes start offset of DDR memory which is
423		connected exclusively to the DSP cores.
424
425		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
426		This value denotes start offset of M2 memory
427		which is directly connected to the DSP core.
428
429		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
430		This value denotes start offset of M3 memory which is directly
431		connected to the DSP core.
432
433		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
434		This value denotes start offset of DSP CCSR space.
435
436		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
437		Single Source Clock is clocking mode present in some of FSL SoC's.
438		In this mode, a single differential clock is used to supply
439		clocks to the sysclock, ddrclock and usbclock.
440
441		CONFIG_SYS_CPC_REINIT_F
442		This CONFIG is defined when the CPC is configured as SRAM at the
443		time of U-Boot entry and is required to be re-initialized.
444
445		CONFIG_DEEP_SLEEP
446		Indicates this SoC supports deep sleep feature. If deep sleep is
447		supported, core will start to execute uboot when wakes up.
448
449- Generic CPU options:
450		CONFIG_SYS_GENERIC_GLOBAL_DATA
451		Defines global data is initialized in generic board board_init_f().
452		If this macro is defined, global data is created and cleared in
453		generic board board_init_f(). Without this macro, architecture/board
454		should initialize global data before calling board_init_f().
455
456		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
457
458		Defines the endianess of the CPU. Implementation of those
459		values is arch specific.
460
461		CONFIG_SYS_FSL_DDR
462		Freescale DDR driver in use. This type of DDR controller is
463		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
464		SoCs.
465
466		CONFIG_SYS_FSL_DDR_ADDR
467		Freescale DDR memory-mapped register base.
468
469		CONFIG_SYS_FSL_DDR_EMU
470		Specify emulator support for DDR. Some DDR features such as
471		deskew training are not available.
472
473		CONFIG_SYS_FSL_DDRC_GEN1
474		Freescale DDR1 controller.
475
476		CONFIG_SYS_FSL_DDRC_GEN2
477		Freescale DDR2 controller.
478
479		CONFIG_SYS_FSL_DDRC_GEN3
480		Freescale DDR3 controller.
481
482		CONFIG_SYS_FSL_DDRC_GEN4
483		Freescale DDR4 controller.
484
485		CONFIG_SYS_FSL_DDRC_ARM_GEN3
486		Freescale DDR3 controller for ARM-based SoCs.
487
488		CONFIG_SYS_FSL_DDR1
489		Board config to use DDR1. It can be enabled for SoCs with
490		Freescale DDR1 or DDR2 controllers, depending on the board
491		implemetation.
492
493		CONFIG_SYS_FSL_DDR2
494		Board config to use DDR2. It can be enabled for SoCs with
495		Freescale DDR2 or DDR3 controllers, depending on the board
496		implementation.
497
498		CONFIG_SYS_FSL_DDR3
499		Board config to use DDR3. It can be enabled for SoCs with
500		Freescale DDR3 or DDR3L controllers.
501
502		CONFIG_SYS_FSL_DDR3L
503		Board config to use DDR3L. It can be enabled for SoCs with
504		DDR3L controllers.
505
506		CONFIG_SYS_FSL_DDR4
507		Board config to use DDR4. It can be enabled for SoCs with
508		DDR4 controllers.
509
510		CONFIG_SYS_FSL_IFC_BE
511		Defines the IFC controller register space as Big Endian
512
513		CONFIG_SYS_FSL_IFC_LE
514		Defines the IFC controller register space as Little Endian
515
516		CONFIG_SYS_FSL_PBL_PBI
517		It enables addition of RCW (Power on reset configuration) in built image.
518		Please refer doc/README.pblimage for more details
519
520		CONFIG_SYS_FSL_PBL_RCW
521		It adds PBI(pre-boot instructions) commands in u-boot build image.
522		PBI commands can be used to configure SoC before it starts the execution.
523		Please refer doc/README.pblimage for more details
524
525		CONFIG_SPL_FSL_PBL
526		It adds a target to create boot binary having SPL binary in PBI format
527		concatenated with u-boot binary.
528
529		CONFIG_SYS_FSL_DDR_BE
530		Defines the DDR controller register space as Big Endian
531
532		CONFIG_SYS_FSL_DDR_LE
533		Defines the DDR controller register space as Little Endian
534
535		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
536		Physical address from the view of DDR controllers. It is the
537		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
538		it could be different for ARM SoCs.
539
540		CONFIG_SYS_FSL_DDR_INTLV_256B
541		DDR controller interleaving on 256-byte. This is a special
542		interleaving mode, handled by Dickens for Freescale layerscape
543		SoCs with ARM core.
544
545		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
546		Number of controllers used as main memory.
547
548		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
549		Number of controllers used for other than main memory.
550
551		CONFIG_SYS_FSL_HAS_DP_DDR
552		Defines the SoC has DP-DDR used for DPAA.
553
554		CONFIG_SYS_FSL_SEC_BE
555		Defines the SEC controller register space as Big Endian
556
557		CONFIG_SYS_FSL_SEC_LE
558		Defines the SEC controller register space as Little Endian
559
560- MIPS CPU options:
561		CONFIG_SYS_INIT_SP_OFFSET
562
563		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
564		pointer. This is needed for the temporary stack before
565		relocation.
566
567		CONFIG_SYS_MIPS_CACHE_MODE
568
569		Cache operation mode for the MIPS CPU.
570		See also arch/mips/include/asm/mipsregs.h.
571		Possible values are:
572			CONF_CM_CACHABLE_NO_WA
573			CONF_CM_CACHABLE_WA
574			CONF_CM_UNCACHED
575			CONF_CM_CACHABLE_NONCOHERENT
576			CONF_CM_CACHABLE_CE
577			CONF_CM_CACHABLE_COW
578			CONF_CM_CACHABLE_CUW
579			CONF_CM_CACHABLE_ACCELERATED
580
581		CONFIG_SYS_XWAY_EBU_BOOTCFG
582
583		Special option for Lantiq XWAY SoCs for booting from NOR flash.
584		See also arch/mips/cpu/mips32/start.S.
585
586		CONFIG_XWAY_SWAP_BYTES
587
588		Enable compilation of tools/xway-swap-bytes needed for Lantiq
589		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
590		be swapped if a flash programmer is used.
591
592- ARM options:
593		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
594
595		Select high exception vectors of the ARM core, e.g., do not
596		clear the V bit of the c1 register of CP15.
597
598		CONFIG_SYS_THUMB_BUILD
599
600		Use this flag to build U-Boot using the Thumb instruction
601		set for ARM architectures. Thumb instruction set provides
602		better code density. For ARM architectures that support
603		Thumb2 this flag will result in Thumb2 code generated by
604		GCC.
605
606		CONFIG_ARM_ERRATA_716044
607		CONFIG_ARM_ERRATA_742230
608		CONFIG_ARM_ERRATA_743622
609		CONFIG_ARM_ERRATA_751472
610		CONFIG_ARM_ERRATA_761320
611		CONFIG_ARM_ERRATA_773022
612		CONFIG_ARM_ERRATA_774769
613		CONFIG_ARM_ERRATA_794072
614
615		If set, the workarounds for these ARM errata are applied early
616		during U-Boot startup. Note that these options force the
617		workarounds to be applied; no CPU-type/version detection
618		exists, unlike the similar options in the Linux kernel. Do not
619		set these options unless they apply!
620
621		COUNTER_FREQUENCY
622		Generic timer clock source frequency.
623
624		COUNTER_FREQUENCY_REAL
625		Generic timer clock source frequency if the real clock is
626		different from COUNTER_FREQUENCY, and can only be determined
627		at run time.
628
629		NOTE: The following can be machine specific errata. These
630		do have ability to provide rudimentary version and machine
631		specific checks, but expect no product checks.
632		CONFIG_ARM_ERRATA_430973
633		CONFIG_ARM_ERRATA_454179
634		CONFIG_ARM_ERRATA_621766
635		CONFIG_ARM_ERRATA_798870
636		CONFIG_ARM_ERRATA_801819
637
638- Tegra SoC options:
639		CONFIG_TEGRA_SUPPORT_NON_SECURE
640
641		Support executing U-Boot in non-secure (NS) mode. Certain
642		impossible actions will be skipped if the CPU is in NS mode,
643		such as ARM architectural timer initialization.
644
645- Linux Kernel Interface:
646		CONFIG_CLOCKS_IN_MHZ
647
648		U-Boot stores all clock information in Hz
649		internally. For binary compatibility with older Linux
650		kernels (which expect the clocks passed in the
651		bd_info data to be in MHz) the environment variable
652		"clocks_in_mhz" can be defined so that U-Boot
653		converts clock data to MHZ before passing it to the
654		Linux kernel.
655		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
656		"clocks_in_mhz=1" is automatically included in the
657		default environment.
658
659		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
660
661		When transferring memsize parameter to Linux, some versions
662		expect it to be in bytes, others in MB.
663		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
664
665		CONFIG_OF_LIBFDT
666
667		New kernel versions are expecting firmware settings to be
668		passed using flattened device trees (based on open firmware
669		concepts).
670
671		CONFIG_OF_LIBFDT
672		 * New libfdt-based support
673		 * Adds the "fdt" command
674		 * The bootm command automatically updates the fdt
675
676		OF_CPU - The proper name of the cpus node (only required for
677			MPC512X and MPC5xxx based boards).
678		OF_SOC - The proper name of the soc node (only required for
679			MPC512X and MPC5xxx based boards).
680		OF_TBCLK - The timebase frequency.
681		OF_STDOUT_PATH - The path to the console device
682
683		boards with QUICC Engines require OF_QE to set UCC MAC
684		addresses
685
686		CONFIG_OF_BOARD_SETUP
687
688		Board code has addition modification that it wants to make
689		to the flat device tree before handing it off to the kernel
690
691		CONFIG_OF_SYSTEM_SETUP
692
693		Other code has addition modification that it wants to make
694		to the flat device tree before handing it off to the kernel.
695		This causes ft_system_setup() to be called before booting
696		the kernel.
697
698		CONFIG_OF_IDE_FIXUP
699
700		U-Boot can detect if an IDE device is present or not.
701		If not, and this new config option is activated, U-Boot
702		removes the ATA node from the DTS before booting Linux,
703		so the Linux IDE driver does not probe the device and
704		crash. This is needed for buggy hardware (uc101) where
705		no pull down resistor is connected to the signal IDE5V_DD7.
706
707		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
708
709		This setting is mandatory for all boards that have only one
710		machine type and must be used to specify the machine type
711		number as it appears in the ARM machine registry
712		(see http://www.arm.linux.org.uk/developer/machines/).
713		Only boards that have multiple machine types supported
714		in a single configuration file and the machine type is
715		runtime discoverable, do not have to use this setting.
716
717- vxWorks boot parameters:
718
719		bootvx constructs a valid bootline using the following
720		environments variables: bootdev, bootfile, ipaddr, netmask,
721		serverip, gatewayip, hostname, othbootargs.
722		It loads the vxWorks image pointed bootfile.
723
724		Note: If a "bootargs" environment is defined, it will overwride
725		the defaults discussed just above.
726
727- Cache Configuration:
728		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
729		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
730		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
731
732- Cache Configuration for ARM:
733		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
734				      controller
735		CONFIG_SYS_PL310_BASE - Physical base address of PL310
736					controller register space
737
738- Serial Ports:
739		CONFIG_PL010_SERIAL
740
741		Define this if you want support for Amba PrimeCell PL010 UARTs.
742
743		CONFIG_PL011_SERIAL
744
745		Define this if you want support for Amba PrimeCell PL011 UARTs.
746
747		CONFIG_PL011_CLOCK
748
749		If you have Amba PrimeCell PL011 UARTs, set this variable to
750		the clock speed of the UARTs.
751
752		CONFIG_PL01x_PORTS
753
754		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
755		define this to a list of base addresses for each (supported)
756		port. See e.g. include/configs/versatile.h
757
758		CONFIG_SERIAL_HW_FLOW_CONTROL
759
760		Define this variable to enable hw flow control in serial driver.
761		Current user of this option is drivers/serial/nsl16550.c driver
762
763- Console Interface:
764		Depending on board, define exactly one serial port
765		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
766		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
767		console by defining CONFIG_8xx_CONS_NONE
768
769		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
770		port routines must be defined elsewhere
771		(i.e. serial_init(), serial_getc(), ...)
772
773		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
774			is 0x00.
775		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
776			is 0xa0.
777
778- Console Baudrate:
779		CONFIG_BAUDRATE - in bps
780		Select one of the baudrates listed in
781		CONFIG_SYS_BAUDRATE_TABLE, see below.
782		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
783
784- Console Rx buffer length
785		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
786		the maximum receive buffer length for the SMC.
787		This option is actual only for 82xx and 8xx possible.
788		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
789		must be defined, to setup the maximum idle timeout for
790		the SMC.
791
792- Autoboot Command:
793		CONFIG_BOOTCOMMAND
794		Only needed when CONFIG_BOOTDELAY is enabled;
795		define a command string that is automatically executed
796		when no character is read on the console interface
797		within "Boot Delay" after reset.
798
799		CONFIG_BOOTARGS
800		This can be used to pass arguments to the bootm
801		command. The value of CONFIG_BOOTARGS goes into the
802		environment value "bootargs".
803
804		CONFIG_RAMBOOT and CONFIG_NFSBOOT
805		The value of these goes into the environment as
806		"ramboot" and "nfsboot" respectively, and can be used
807		as a convenience, when switching between booting from
808		RAM and NFS.
809
810- Bootcount:
811		CONFIG_BOOTCOUNT_LIMIT
812		Implements a mechanism for detecting a repeating reboot
813		cycle, see:
814		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
815
816		CONFIG_BOOTCOUNT_ENV
817		If no softreset save registers are found on the hardware
818		"bootcount" is stored in the environment. To prevent a
819		saveenv on all reboots, the environment variable
820		"upgrade_available" is used. If "upgrade_available" is
821		0, "bootcount" is always 0, if "upgrade_available" is
822		1 "bootcount" is incremented in the environment.
823		So the Userspace Applikation must set the "upgrade_available"
824		and "bootcount" variable to 0, if a boot was successfully.
825
826- Pre-Boot Commands:
827		CONFIG_PREBOOT
828
829		When this option is #defined, the existence of the
830		environment variable "preboot" will be checked
831		immediately before starting the CONFIG_BOOTDELAY
832		countdown and/or running the auto-boot command resp.
833		entering interactive mode.
834
835		This feature is especially useful when "preboot" is
836		automatically generated or modified. For an example
837		see the LWMON board specific code: here "preboot" is
838		modified when the user holds down a certain
839		combination of keys on the (special) keyboard when
840		booting the systems
841
842- Serial Download Echo Mode:
843		CONFIG_LOADS_ECHO
844		If defined to 1, all characters received during a
845		serial download (using the "loads" command) are
846		echoed back. This might be needed by some terminal
847		emulations (like "cu"), but may as well just take
848		time on others. This setting #define's the initial
849		value of the "loads_echo" environment variable.
850
851- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
852		CONFIG_KGDB_BAUDRATE
853		Select one of the baudrates listed in
854		CONFIG_SYS_BAUDRATE_TABLE, see below.
855
856- Monitor Functions:
857		Monitor commands can be included or excluded
858		from the build by using the #include files
859		<config_cmd_all.h> and #undef'ing unwanted
860		commands, or adding #define's for wanted commands.
861
862		The default command configuration includes all commands
863		except those marked below with a "*".
864
865		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
866		CONFIG_CMD_ASKENV	* ask for env variable
867		CONFIG_CMD_BDI		  bdinfo
868		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
869		CONFIG_CMD_BMP		* BMP support
870		CONFIG_CMD_BSP		* Board specific commands
871		CONFIG_CMD_BOOTD	  bootd
872		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
873		CONFIG_CMD_CACHE	* icache, dcache
874		CONFIG_CMD_CLK   	* clock command support
875		CONFIG_CMD_CONSOLE	  coninfo
876		CONFIG_CMD_CRC32	* crc32
877		CONFIG_CMD_DATE		* support for RTC, date/time...
878		CONFIG_CMD_DHCP		* DHCP support
879		CONFIG_CMD_DIAG		* Diagnostics
880		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
881		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
882		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
883		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
884		CONFIG_CMD_DTT		* Digital Therm and Thermostat
885		CONFIG_CMD_ECHO		  echo arguments
886		CONFIG_CMD_EDITENV	  edit env variable
887		CONFIG_CMD_EEPROM	* EEPROM read/write support
888		CONFIG_CMD_EEPROM_LAYOUT* EEPROM layout aware commands
889		CONFIG_CMD_ELF		* bootelf, bootvx
890		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
891		CONFIG_CMD_ENV_FLAGS	* display details about env flags
892		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
893		CONFIG_CMD_EXPORTENV	* export the environment
894		CONFIG_CMD_EXT2		* ext2 command support
895		CONFIG_CMD_EXT4		* ext4 command support
896		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
897					  that work for multiple fs types
898		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
899		CONFIG_CMD_SAVEENV	  saveenv
900		CONFIG_CMD_FDC		* Floppy Disk Support
901		CONFIG_CMD_FAT		* FAT command support
902		CONFIG_CMD_FLASH	  flinfo, erase, protect
903		CONFIG_CMD_FPGA		  FPGA device initialization support
904		CONFIG_CMD_FUSE		* Device fuse support
905		CONFIG_CMD_GETTIME	* Get time since boot
906		CONFIG_CMD_GO		* the 'go' command (exec code)
907		CONFIG_CMD_GREPENV	* search environment
908		CONFIG_CMD_HASH		* calculate hash / digest
909		CONFIG_CMD_I2C		* I2C serial bus support
910		CONFIG_CMD_IDE		* IDE harddisk support
911		CONFIG_CMD_IMI		  iminfo
912		CONFIG_CMD_IMLS		  List all images found in NOR flash
913		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
914		CONFIG_CMD_IMMAP	* IMMR dump support
915		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
916		CONFIG_CMD_IMPORTENV	* import an environment
917		CONFIG_CMD_INI		* import data from an ini file into the env
918		CONFIG_CMD_IRQ		* irqinfo
919		CONFIG_CMD_ITEST	  Integer/string test of 2 values
920		CONFIG_CMD_JFFS2	* JFFS2 Support
921		CONFIG_CMD_KGDB		* kgdb
922		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
923		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
924					  (169.254.*.*)
925		CONFIG_CMD_LOADB	  loadb
926		CONFIG_CMD_LOADS	  loads
927		CONFIG_CMD_MD5SUM	* print md5 message digest
928					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
929		CONFIG_CMD_MEMINFO	* Display detailed memory information
930		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
931					  loop, loopw
932		CONFIG_CMD_MEMTEST	* mtest
933		CONFIG_CMD_MISC		  Misc functions like sleep etc
934		CONFIG_CMD_MMC		* MMC memory mapped support
935		CONFIG_CMD_MII		* MII utility commands
936		CONFIG_CMD_MTDPARTS	* MTD partition support
937		CONFIG_CMD_NAND		* NAND support
938		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
939		CONFIG_CMD_NFS		  NFS support
940		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
941		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
942		CONFIG_CMD_PCI		* pciinfo
943		CONFIG_CMD_PCMCIA		* PCMCIA support
944		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
945					  host
946		CONFIG_CMD_PORTIO	* Port I/O
947		CONFIG_CMD_READ		* Read raw data from partition
948		CONFIG_CMD_REGINFO	* Register dump
949		CONFIG_CMD_RUN		  run command in env variable
950		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
951		CONFIG_CMD_SAVES	* save S record dump
952		CONFIG_SCSI		* SCSI Support
953		CONFIG_CMD_SDRAM	* print SDRAM configuration information
954					  (requires CONFIG_CMD_I2C)
955		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
956					  (4xx only)
957		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
958		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
959					  (requires CONFIG_CMD_MEMORY)
960		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
961		CONFIG_CMD_SOURCE	  "source" command Support
962		CONFIG_CMD_SPI		* SPI serial bus support
963		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
964		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
965		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
966		CONFIG_CMD_TIMER	* access to the system tick timer
967		CONFIG_CMD_USB		* USB support
968		CONFIG_CMD_CDP		* Cisco Discover Protocol support
969		CONFIG_CMD_MFSL		* Microblaze FSL support
970		CONFIG_CMD_XIMG		  Load part of Multi Image
971		CONFIG_CMD_UUID		* Generate random UUID or GUID string
972
973		EXAMPLE: If you want all functions except of network
974		support you can write:
975
976		#include "config_cmd_all.h"
977		#undef CONFIG_CMD_NET
978
979	Other Commands:
980		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
981
982	Note:	Don't enable the "icache" and "dcache" commands
983		(configuration option CONFIG_CMD_CACHE) unless you know
984		what you (and your U-Boot users) are doing. Data
985		cache cannot be enabled on systems like the 8xx or
986		8260 (where accesses to the IMMR region must be
987		uncached), and it cannot be disabled on all other
988		systems where we (mis-) use the data cache to hold an
989		initial stack and some data.
990
991
992		XXX - this list needs to get updated!
993
994- Removal of commands
995		If no commands are needed to boot, you can disable
996		CONFIG_CMDLINE to remove them. In this case, the command line
997		will not be available, and when U-Boot wants to execute the
998		boot command (on start-up) it will call board_run_command()
999		instead. This can reduce image size significantly for very
1000		simple boot procedures.
1001
1002- Regular expression support:
1003		CONFIG_REGEX
1004		If this variable is defined, U-Boot is linked against
1005		the SLRE (Super Light Regular Expression) library,
1006		which adds regex support to some commands, as for
1007		example "env grep" and "setexpr".
1008
1009- Device tree:
1010		CONFIG_OF_CONTROL
1011		If this variable is defined, U-Boot will use a device tree
1012		to configure its devices, instead of relying on statically
1013		compiled #defines in the board file. This option is
1014		experimental and only available on a few boards. The device
1015		tree is available in the global data as gd->fdt_blob.
1016
1017		U-Boot needs to get its device tree from somewhere. This can
1018		be done using one of the two options below:
1019
1020		CONFIG_OF_EMBED
1021		If this variable is defined, U-Boot will embed a device tree
1022		binary in its image. This device tree file should be in the
1023		board directory and called <soc>-<board>.dts. The binary file
1024		is then picked up in board_init_f() and made available through
1025		the global data structure as gd->blob.
1026
1027		CONFIG_OF_SEPARATE
1028		If this variable is defined, U-Boot will build a device tree
1029		binary. It will be called u-boot.dtb. Architecture-specific
1030		code will locate it at run-time. Generally this works by:
1031
1032			cat u-boot.bin u-boot.dtb >image.bin
1033
1034		and in fact, U-Boot does this for you, creating a file called
1035		u-boot-dtb.bin which is useful in the common case. You can
1036		still use the individual files if you need something more
1037		exotic.
1038
1039- Watchdog:
1040		CONFIG_WATCHDOG
1041		If this variable is defined, it enables watchdog
1042		support for the SoC. There must be support in the SoC
1043		specific code for a watchdog. For the 8xx and 8260
1044		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1045		register.  When supported for a specific SoC is
1046		available, then no further board specific code should
1047		be needed to use it.
1048
1049		CONFIG_HW_WATCHDOG
1050		When using a watchdog circuitry external to the used
1051		SoC, then define this variable and provide board
1052		specific code for the "hw_watchdog_reset" function.
1053
1054		CONFIG_AT91_HW_WDT_TIMEOUT
1055		specify the timeout in seconds. default 2 seconds.
1056
1057- U-Boot Version:
1058		CONFIG_VERSION_VARIABLE
1059		If this variable is defined, an environment variable
1060		named "ver" is created by U-Boot showing the U-Boot
1061		version as printed by the "version" command.
1062		Any change to this variable will be reverted at the
1063		next reset.
1064
1065- Real-Time Clock:
1066
1067		When CONFIG_CMD_DATE is selected, the type of the RTC
1068		has to be selected, too. Define exactly one of the
1069		following options:
1070
1071		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1072		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1073		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1074		CONFIG_RTC_MC146818	- use MC146818 RTC
1075		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1076		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1077		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1078		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1079		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1080		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1081		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1082		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1083		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1084					  RV3029 RTC.
1085
1086		Note that if the RTC uses I2C, then the I2C interface
1087		must also be configured. See I2C Support, below.
1088
1089- GPIO Support:
1090		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1091
1092		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1093		chip-ngpio pairs that tell the PCA953X driver the number of
1094		pins supported by a particular chip.
1095
1096		Note that if the GPIO device uses I2C, then the I2C interface
1097		must also be configured. See I2C Support, below.
1098
1099- I/O tracing:
1100		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1101		accesses and can checksum them or write a list of them out
1102		to memory. See the 'iotrace' command for details. This is
1103		useful for testing device drivers since it can confirm that
1104		the driver behaves the same way before and after a code
1105		change. Currently this is supported on sandbox and arm. To
1106		add support for your architecture, add '#include <iotrace.h>'
1107		to the bottom of arch/<arch>/include/asm/io.h and test.
1108
1109		Example output from the 'iotrace stats' command is below.
1110		Note that if the trace buffer is exhausted, the checksum will
1111		still continue to operate.
1112
1113			iotrace is enabled
1114			Start:  10000000	(buffer start address)
1115			Size:   00010000	(buffer size)
1116			Offset: 00000120	(current buffer offset)
1117			Output: 10000120	(start + offset)
1118			Count:  00000018	(number of trace records)
1119			CRC32:  9526fb66	(CRC32 of all trace records)
1120
1121- Timestamp Support:
1122
1123		When CONFIG_TIMESTAMP is selected, the timestamp
1124		(date and time) of an image is printed by image
1125		commands like bootm or iminfo. This option is
1126		automatically enabled when you select CONFIG_CMD_DATE .
1127
1128- Partition Labels (disklabels) Supported:
1129		Zero or more of the following:
1130		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1131		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1132				       Intel architecture, USB sticks, etc.
1133		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1134		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1135				       bootloader.  Note 2TB partition limit; see
1136				       disk/part_efi.c
1137		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1138
1139		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1140		CONFIG_SCSI) you must configure support for at
1141		least one non-MTD partition type as well.
1142
1143- IDE Reset method:
1144		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1145		board configurations files but used nowhere!
1146
1147		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1148		be performed by calling the function
1149			ide_set_reset(int reset)
1150		which has to be defined in a board specific file
1151
1152- ATAPI Support:
1153		CONFIG_ATAPI
1154
1155		Set this to enable ATAPI support.
1156
1157- LBA48 Support
1158		CONFIG_LBA48
1159
1160		Set this to enable support for disks larger than 137GB
1161		Also look at CONFIG_SYS_64BIT_LBA.
1162		Whithout these , LBA48 support uses 32bit variables and will 'only'
1163		support disks up to 2.1TB.
1164
1165		CONFIG_SYS_64BIT_LBA:
1166			When enabled, makes the IDE subsystem use 64bit sector addresses.
1167			Default is 32bit.
1168
1169- SCSI Support:
1170		At the moment only there is only support for the
1171		SYM53C8XX SCSI controller; define
1172		CONFIG_SCSI_SYM53C8XX to enable it.
1173
1174		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1175		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1176		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1177		maximum numbers of LUNs, SCSI ID's and target
1178		devices.
1179		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1180
1181		The environment variable 'scsidevs' is set to the number of
1182		SCSI devices found during the last scan.
1183
1184- NETWORK Support (PCI):
1185		CONFIG_E1000
1186		Support for Intel 8254x/8257x gigabit chips.
1187
1188		CONFIG_E1000_SPI
1189		Utility code for direct access to the SPI bus on Intel 8257x.
1190		This does not do anything useful unless you set at least one
1191		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1192
1193		CONFIG_E1000_SPI_GENERIC
1194		Allow generic access to the SPI bus on the Intel 8257x, for
1195		example with the "sspi" command.
1196
1197		CONFIG_CMD_E1000
1198		Management command for E1000 devices.  When used on devices
1199		with SPI support you can reprogram the EEPROM from U-Boot.
1200
1201		CONFIG_EEPRO100
1202		Support for Intel 82557/82559/82559ER chips.
1203		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1204		write routine for first time initialisation.
1205
1206		CONFIG_TULIP
1207		Support for Digital 2114x chips.
1208		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1209		modem chip initialisation (KS8761/QS6611).
1210
1211		CONFIG_NATSEMI
1212		Support for National dp83815 chips.
1213
1214		CONFIG_NS8382X
1215		Support for National dp8382[01] gigabit chips.
1216
1217- NETWORK Support (other):
1218
1219		CONFIG_DRIVER_AT91EMAC
1220		Support for AT91RM9200 EMAC.
1221
1222			CONFIG_RMII
1223			Define this to use reduced MII inteface
1224
1225			CONFIG_DRIVER_AT91EMAC_QUIET
1226			If this defined, the driver is quiet.
1227			The driver doen't show link status messages.
1228
1229		CONFIG_CALXEDA_XGMAC
1230		Support for the Calxeda XGMAC device
1231
1232		CONFIG_LAN91C96
1233		Support for SMSC's LAN91C96 chips.
1234
1235			CONFIG_LAN91C96_USE_32_BIT
1236			Define this to enable 32 bit addressing
1237
1238		CONFIG_SMC91111
1239		Support for SMSC's LAN91C111 chip
1240
1241			CONFIG_SMC91111_BASE
1242			Define this to hold the physical address
1243			of the device (I/O space)
1244
1245			CONFIG_SMC_USE_32_BIT
1246			Define this if data bus is 32 bits
1247
1248			CONFIG_SMC_USE_IOFUNCS
1249			Define this to use i/o functions instead of macros
1250			(some hardware wont work with macros)
1251
1252		CONFIG_DRIVER_TI_EMAC
1253		Support for davinci emac
1254
1255			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1256			Define this if you have more then 3 PHYs.
1257
1258		CONFIG_FTGMAC100
1259		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1260
1261			CONFIG_FTGMAC100_EGIGA
1262			Define this to use GE link update with gigabit PHY.
1263			Define this if FTGMAC100 is connected to gigabit PHY.
1264			If your system has 10/100 PHY only, it might not occur
1265			wrong behavior. Because PHY usually return timeout or
1266			useless data when polling gigabit status and gigabit
1267			control registers. This behavior won't affect the
1268			correctnessof 10/100 link speed update.
1269
1270		CONFIG_SMC911X
1271		Support for SMSC's LAN911x and LAN921x chips
1272
1273			CONFIG_SMC911X_BASE
1274			Define this to hold the physical address
1275			of the device (I/O space)
1276
1277			CONFIG_SMC911X_32_BIT
1278			Define this if data bus is 32 bits
1279
1280			CONFIG_SMC911X_16_BIT
1281			Define this if data bus is 16 bits. If your processor
1282			automatically converts one 32 bit word to two 16 bit
1283			words you may also try CONFIG_SMC911X_32_BIT.
1284
1285		CONFIG_SH_ETHER
1286		Support for Renesas on-chip Ethernet controller
1287
1288			CONFIG_SH_ETHER_USE_PORT
1289			Define the number of ports to be used
1290
1291			CONFIG_SH_ETHER_PHY_ADDR
1292			Define the ETH PHY's address
1293
1294			CONFIG_SH_ETHER_CACHE_WRITEBACK
1295			If this option is set, the driver enables cache flush.
1296
1297- PWM Support:
1298		CONFIG_PWM_IMX
1299		Support for PWM module on the imx6.
1300
1301- TPM Support:
1302		CONFIG_TPM
1303		Support TPM devices.
1304
1305		CONFIG_TPM_TIS_INFINEON
1306		Support for Infineon i2c bus TPM devices. Only one device
1307		per system is supported at this time.
1308
1309			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1310			Define the burst count bytes upper limit
1311
1312		CONFIG_TPM_ST33ZP24
1313		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1314
1315			CONFIG_TPM_ST33ZP24_I2C
1316			Support for STMicroelectronics ST33ZP24 I2C devices.
1317			Requires TPM_ST33ZP24 and I2C.
1318
1319			CONFIG_TPM_ST33ZP24_SPI
1320			Support for STMicroelectronics ST33ZP24 SPI devices.
1321			Requires TPM_ST33ZP24 and SPI.
1322
1323		CONFIG_TPM_ATMEL_TWI
1324		Support for Atmel TWI TPM device. Requires I2C support.
1325
1326		CONFIG_TPM_TIS_LPC
1327		Support for generic parallel port TPM devices. Only one device
1328		per system is supported at this time.
1329
1330			CONFIG_TPM_TIS_BASE_ADDRESS
1331			Base address where the generic TPM device is mapped
1332			to. Contemporary x86 systems usually map it at
1333			0xfed40000.
1334
1335		CONFIG_CMD_TPM
1336		Add tpm monitor functions.
1337		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1338		provides monitor access to authorized functions.
1339
1340		CONFIG_TPM
1341		Define this to enable the TPM support library which provides
1342		functional interfaces to some TPM commands.
1343		Requires support for a TPM device.
1344
1345		CONFIG_TPM_AUTH_SESSIONS
1346		Define this to enable authorized functions in the TPM library.
1347		Requires CONFIG_TPM and CONFIG_SHA1.
1348
1349- USB Support:
1350		At the moment only the UHCI host controller is
1351		supported (PIP405, MIP405, MPC5200); define
1352		CONFIG_USB_UHCI to enable it.
1353		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1354		and define CONFIG_USB_STORAGE to enable the USB
1355		storage devices.
1356		Note:
1357		Supported are USB Keyboards and USB Floppy drives
1358		(TEAC FD-05PUB).
1359		MPC5200 USB requires additional defines:
1360			CONFIG_USB_CLOCK
1361				for 528 MHz Clock: 0x0001bbbb
1362			CONFIG_PSC3_USB
1363				for USB on PSC3
1364			CONFIG_USB_CONFIG
1365				for differential drivers: 0x00001000
1366				for single ended drivers: 0x00005000
1367				for differential drivers on PSC3: 0x00000100
1368				for single ended drivers on PSC3: 0x00004100
1369			CONFIG_SYS_USB_EVENT_POLL
1370				May be defined to allow interrupt polling
1371				instead of using asynchronous interrupts
1372
1373		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1374		txfilltuning field in the EHCI controller on reset.
1375
1376		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1377		HW module registers.
1378
1379- USB Device:
1380		Define the below if you wish to use the USB console.
1381		Once firmware is rebuilt from a serial console issue the
1382		command "setenv stdin usbtty; setenv stdout usbtty" and
1383		attach your USB cable. The Unix command "dmesg" should print
1384		it has found a new device. The environment variable usbtty
1385		can be set to gserial or cdc_acm to enable your device to
1386		appear to a USB host as a Linux gserial device or a
1387		Common Device Class Abstract Control Model serial device.
1388		If you select usbtty = gserial you should be able to enumerate
1389		a Linux host by
1390		# modprobe usbserial vendor=0xVendorID product=0xProductID
1391		else if using cdc_acm, simply setting the environment
1392		variable usbtty to be cdc_acm should suffice. The following
1393		might be defined in YourBoardName.h
1394
1395			CONFIG_USB_DEVICE
1396			Define this to build a UDC device
1397
1398			CONFIG_USB_TTY
1399			Define this to have a tty type of device available to
1400			talk to the UDC device
1401
1402			CONFIG_USBD_HS
1403			Define this to enable the high speed support for usb
1404			device and usbtty. If this feature is enabled, a routine
1405			int is_usbd_high_speed(void)
1406			also needs to be defined by the driver to dynamically poll
1407			whether the enumeration has succeded at high speed or full
1408			speed.
1409
1410			CONFIG_SYS_CONSOLE_IS_IN_ENV
1411			Define this if you want stdin, stdout &/or stderr to
1412			be set to usbtty.
1413
1414			mpc8xx:
1415				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1416				Derive USB clock from external clock "blah"
1417				- CONFIG_SYS_USB_EXTC_CLK 0x02
1418
1419		If you have a USB-IF assigned VendorID then you may wish to
1420		define your own vendor specific values either in BoardName.h
1421		or directly in usbd_vendor_info.h. If you don't define
1422		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1423		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1424		should pretend to be a Linux device to it's target host.
1425
1426			CONFIG_USBD_MANUFACTURER
1427			Define this string as the name of your company for
1428			- CONFIG_USBD_MANUFACTURER "my company"
1429
1430			CONFIG_USBD_PRODUCT_NAME
1431			Define this string as the name of your product
1432			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1433
1434			CONFIG_USBD_VENDORID
1435			Define this as your assigned Vendor ID from the USB
1436			Implementors Forum. This *must* be a genuine Vendor ID
1437			to avoid polluting the USB namespace.
1438			- CONFIG_USBD_VENDORID 0xFFFF
1439
1440			CONFIG_USBD_PRODUCTID
1441			Define this as the unique Product ID
1442			for your device
1443			- CONFIG_USBD_PRODUCTID 0xFFFF
1444
1445- ULPI Layer Support:
1446		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1447		the generic ULPI layer. The generic layer accesses the ULPI PHY
1448		via the platform viewport, so you need both the genric layer and
1449		the viewport enabled. Currently only Chipidea/ARC based
1450		viewport is supported.
1451		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1452		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1453		If your ULPI phy needs a different reference clock than the
1454		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1455		the appropriate value in Hz.
1456
1457- MMC Support:
1458		The MMC controller on the Intel PXA is supported. To
1459		enable this define CONFIG_MMC. The MMC can be
1460		accessed from the boot prompt by mapping the device
1461		to physical memory similar to flash. Command line is
1462		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1463		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1464
1465		CONFIG_SH_MMCIF
1466		Support for Renesas on-chip MMCIF controller
1467
1468			CONFIG_SH_MMCIF_ADDR
1469			Define the base address of MMCIF registers
1470
1471			CONFIG_SH_MMCIF_CLK
1472			Define the clock frequency for MMCIF
1473
1474		CONFIG_GENERIC_MMC
1475		Enable the generic MMC driver
1476
1477		CONFIG_SUPPORT_EMMC_BOOT
1478		Enable some additional features of the eMMC boot partitions.
1479
1480		CONFIG_SUPPORT_EMMC_RPMB
1481		Enable the commands for reading, writing and programming the
1482		key for the Replay Protection Memory Block partition in eMMC.
1483
1484- USB Device Firmware Update (DFU) class support:
1485		CONFIG_USB_FUNCTION_DFU
1486		This enables the USB portion of the DFU USB class
1487
1488		CONFIG_CMD_DFU
1489		This enables the command "dfu" which is used to have
1490		U-Boot create a DFU class device via USB.  This command
1491		requires that the "dfu_alt_info" environment variable be
1492		set and define the alt settings to expose to the host.
1493
1494		CONFIG_DFU_MMC
1495		This enables support for exposing (e)MMC devices via DFU.
1496
1497		CONFIG_DFU_NAND
1498		This enables support for exposing NAND devices via DFU.
1499
1500		CONFIG_DFU_RAM
1501		This enables support for exposing RAM via DFU.
1502		Note: DFU spec refer to non-volatile memory usage, but
1503		allow usages beyond the scope of spec - here RAM usage,
1504		one that would help mostly the developer.
1505
1506		CONFIG_SYS_DFU_DATA_BUF_SIZE
1507		Dfu transfer uses a buffer before writing data to the
1508		raw storage device. Make the size (in bytes) of this buffer
1509		configurable. The size of this buffer is also configurable
1510		through the "dfu_bufsiz" environment variable.
1511
1512		CONFIG_SYS_DFU_MAX_FILE_SIZE
1513		When updating files rather than the raw storage device,
1514		we use a static buffer to copy the file into and then write
1515		the buffer once we've been given the whole file.  Define
1516		this to the maximum filesize (in bytes) for the buffer.
1517		Default is 4 MiB if undefined.
1518
1519		DFU_DEFAULT_POLL_TIMEOUT
1520		Poll timeout [ms], is the timeout a device can send to the
1521		host. The host must wait for this timeout before sending
1522		a subsequent DFU_GET_STATUS request to the device.
1523
1524		DFU_MANIFEST_POLL_TIMEOUT
1525		Poll timeout [ms], which the device sends to the host when
1526		entering dfuMANIFEST state. Host waits this timeout, before
1527		sending again an USB request to the device.
1528
1529- USB Device Android Fastboot support:
1530		CONFIG_USB_FUNCTION_FASTBOOT
1531		This enables the USB part of the fastboot gadget
1532
1533		CONFIG_CMD_FASTBOOT
1534		This enables the command "fastboot" which enables the Android
1535		fastboot mode for the platform's USB device. Fastboot is a USB
1536		protocol for downloading images, flashing and device control
1537		used on Android devices.
1538		See doc/README.android-fastboot for more information.
1539
1540		CONFIG_ANDROID_BOOT_IMAGE
1541		This enables support for booting images which use the Android
1542		image format header.
1543
1544		CONFIG_FASTBOOT_BUF_ADDR
1545		The fastboot protocol requires a large memory buffer for
1546		downloads. Define this to the starting RAM address to use for
1547		downloaded images.
1548
1549		CONFIG_FASTBOOT_BUF_SIZE
1550		The fastboot protocol requires a large memory buffer for
1551		downloads. This buffer should be as large as possible for a
1552		platform. Define this to the size available RAM for fastboot.
1553
1554		CONFIG_FASTBOOT_FLASH
1555		The fastboot protocol includes a "flash" command for writing
1556		the downloaded image to a non-volatile storage device. Define
1557		this to enable the "fastboot flash" command.
1558
1559		CONFIG_FASTBOOT_FLASH_MMC_DEV
1560		The fastboot "flash" command requires additional information
1561		regarding the non-volatile storage device. Define this to
1562		the eMMC device that fastboot should use to store the image.
1563
1564		CONFIG_FASTBOOT_GPT_NAME
1565		The fastboot "flash" command supports writing the downloaded
1566		image to the Protective MBR and the Primary GUID Partition
1567		Table. (Additionally, this downloaded image is post-processed
1568		to generate and write the Backup GUID Partition Table.)
1569		This occurs when the specified "partition name" on the
1570		"fastboot flash" command line matches this value.
1571		The default is "gpt" if undefined.
1572
1573		CONFIG_FASTBOOT_MBR_NAME
1574		The fastboot "flash" command supports writing the downloaded
1575		image to DOS MBR.
1576		This occurs when the "partition name" specified on the
1577		"fastboot flash" command line matches this value.
1578		If not defined the default value "mbr" is used.
1579
1580- Journaling Flash filesystem support:
1581		CONFIG_JFFS2_NAND
1582		Define these for a default partition on a NAND device
1583
1584		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1585		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1586		Define these for a default partition on a NOR device
1587
1588- FAT(File Allocation Table) filesystem write function support:
1589		CONFIG_FAT_WRITE
1590
1591		Define this to enable support for saving memory data as a
1592		file in FAT formatted partition.
1593
1594		This will also enable the command "fatwrite" enabling the
1595		user to write files to FAT.
1596
1597CBFS (Coreboot Filesystem) support
1598		CONFIG_CMD_CBFS
1599
1600		Define this to enable support for reading from a Coreboot
1601		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1602		and cbfsload.
1603
1604- FAT(File Allocation Table) filesystem cluster size:
1605		CONFIG_FS_FAT_MAX_CLUSTSIZE
1606
1607		Define the max cluster size for fat operations else
1608		a default value of 65536 will be defined.
1609
1610- Keyboard Support:
1611		See Kconfig help for available keyboard drivers.
1612
1613		CONFIG_KEYBOARD
1614
1615		Define this to enable a custom keyboard support.
1616		This simply calls drv_keyboard_init() which must be
1617		defined in your board-specific files. This option is deprecated
1618		and is only used by novena. For new boards, use driver model
1619		instead.
1620
1621- Video support:
1622		CONFIG_VIDEO_CT69000
1623
1624		Enable Chips & Technologies 69000 Video chip
1625
1626		CONFIG_VIDEO_SMI_LYNXEM
1627		Enable Silicon Motion SMI 712/710/810 Video chip. The
1628		video output is selected via environment 'videoout'
1629		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1630		assumed.
1631
1632		For the CT69000 and SMI_LYNXEM drivers, videomode is
1633		selected via environment 'videomode'. Two different ways
1634		are possible:
1635		- "videomode=num"   'num' is a standard LiLo mode numbers.
1636		Following standard modes are supported	(* is default):
1637
1638		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1639		-------------+---------------------------------------------
1640		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1641		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1642		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1643		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1644		-------------+---------------------------------------------
1645		(i.e. setenv videomode 317; saveenv; reset;)
1646
1647		- "videomode=bootargs" all the video parameters are parsed
1648		from the bootargs. (See drivers/video/videomodes.c)
1649
1650
1651		CONFIG_VIDEO_SED13806
1652		Enable Epson SED13806 driver. This driver supports 8bpp
1653		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1654		or CONFIG_VIDEO_SED13806_16BPP
1655
1656		CONFIG_FSL_DIU_FB
1657		Enable the Freescale DIU video driver.	Reference boards for
1658		SOCs that have a DIU should define this macro to enable DIU
1659		support, and should also define these other macros:
1660
1661			CONFIG_SYS_DIU_ADDR
1662			CONFIG_VIDEO
1663			CONFIG_CMD_BMP
1664			CONFIG_CFB_CONSOLE
1665			CONFIG_VIDEO_SW_CURSOR
1666			CONFIG_VGA_AS_SINGLE_DEVICE
1667			CONFIG_VIDEO_LOGO
1668			CONFIG_VIDEO_BMP_LOGO
1669
1670		The DIU driver will look for the 'video-mode' environment
1671		variable, and if defined, enable the DIU as a console during
1672		boot.  See the documentation file doc/README.video for a
1673		description of this variable.
1674
1675- LCD Support:	CONFIG_LCD
1676
1677		Define this to enable LCD support (for output to LCD
1678		display); also select one of the supported displays
1679		by defining one of these:
1680
1681		CONFIG_ATMEL_LCD:
1682
1683			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1684
1685		CONFIG_NEC_NL6448AC33:
1686
1687			NEC NL6448AC33-18. Active, color, single scan.
1688
1689		CONFIG_NEC_NL6448BC20
1690
1691			NEC NL6448BC20-08. 6.5", 640x480.
1692			Active, color, single scan.
1693
1694		CONFIG_NEC_NL6448BC33_54
1695
1696			NEC NL6448BC33-54. 10.4", 640x480.
1697			Active, color, single scan.
1698
1699		CONFIG_SHARP_16x9
1700
1701			Sharp 320x240. Active, color, single scan.
1702			It isn't 16x9, and I am not sure what it is.
1703
1704		CONFIG_SHARP_LQ64D341
1705
1706			Sharp LQ64D341 display, 640x480.
1707			Active, color, single scan.
1708
1709		CONFIG_HLD1045
1710
1711			HLD1045 display, 640x480.
1712			Active, color, single scan.
1713
1714		CONFIG_OPTREX_BW
1715
1716			Optrex	 CBL50840-2 NF-FW 99 22 M5
1717			or
1718			Hitachi	 LMG6912RPFC-00T
1719			or
1720			Hitachi	 SP14Q002
1721
1722			320x240. Black & white.
1723
1724		Normally display is black on white background; define
1725		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1726
1727		CONFIG_LCD_ALIGNMENT
1728
1729		Normally the LCD is page-aligned (typically 4KB). If this is
1730		defined then the LCD will be aligned to this value instead.
1731		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1732		here, since it is cheaper to change data cache settings on
1733		a per-section basis.
1734
1735		CONFIG_CONSOLE_SCROLL_LINES
1736
1737		When the console need to be scrolled, this is the number of
1738		lines to scroll by. It defaults to 1. Increasing this makes
1739		the console jump but can help speed up operation when scrolling
1740		is slow.
1741
1742		CONFIG_LCD_ROTATION
1743
1744		Sometimes, for example if the display is mounted in portrait
1745		mode or even if it's mounted landscape but rotated by 180degree,
1746		we need to rotate our content of the display relative to the
1747		framebuffer, so that user can read the messages which are
1748		printed out.
1749		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1750		initialized with a given rotation from "vl_rot" out of
1751		"vidinfo_t" which is provided by the board specific code.
1752		The value for vl_rot is coded as following (matching to
1753		fbcon=rotate:<n> linux-kernel commandline):
1754		0 = no rotation respectively 0 degree
1755		1 = 90 degree rotation
1756		2 = 180 degree rotation
1757		3 = 270 degree rotation
1758
1759		If CONFIG_LCD_ROTATION is not defined, the console will be
1760		initialized with 0degree rotation.
1761
1762		CONFIG_LCD_BMP_RLE8
1763
1764		Support drawing of RLE8-compressed bitmaps on the LCD.
1765
1766		CONFIG_I2C_EDID
1767
1768		Enables an 'i2c edid' command which can read EDID
1769		information over I2C from an attached LCD display.
1770
1771- Splash Screen Support: CONFIG_SPLASH_SCREEN
1772
1773		If this option is set, the environment is checked for
1774		a variable "splashimage". If found, the usual display
1775		of logo, copyright and system information on the LCD
1776		is suppressed and the BMP image at the address
1777		specified in "splashimage" is loaded instead. The
1778		console is redirected to the "nulldev", too. This
1779		allows for a "silent" boot where a splash screen is
1780		loaded very quickly after power-on.
1781
1782		CONFIG_SPLASHIMAGE_GUARD
1783
1784		If this option is set, then U-Boot will prevent the environment
1785		variable "splashimage" from being set to a problematic address
1786		(see doc/README.displaying-bmps).
1787		This option is useful for targets where, due to alignment
1788		restrictions, an improperly aligned BMP image will cause a data
1789		abort. If you think you will not have problems with unaligned
1790		accesses (for example because your toolchain prevents them)
1791		there is no need to set this option.
1792
1793		CONFIG_SPLASH_SCREEN_ALIGN
1794
1795		If this option is set the splash image can be freely positioned
1796		on the screen. Environment variable "splashpos" specifies the
1797		position as "x,y". If a positive number is given it is used as
1798		number of pixel from left/top. If a negative number is given it
1799		is used as number of pixel from right/bottom. You can also
1800		specify 'm' for centering the image.
1801
1802		Example:
1803		setenv splashpos m,m
1804			=> image at center of screen
1805
1806		setenv splashpos 30,20
1807			=> image at x = 30 and y = 20
1808
1809		setenv splashpos -10,m
1810			=> vertically centered image
1811			   at x = dspWidth - bmpWidth - 9
1812
1813- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1814
1815		If this option is set, additionally to standard BMP
1816		images, gzipped BMP images can be displayed via the
1817		splashscreen support or the bmp command.
1818
1819- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1820
1821		If this option is set, 8-bit RLE compressed BMP images
1822		can be displayed via the splashscreen support or the
1823		bmp command.
1824
1825- Do compressing for memory range:
1826		CONFIG_CMD_ZIP
1827
1828		If this option is set, it would use zlib deflate method
1829		to compress the specified memory at its best effort.
1830
1831- Compression support:
1832		CONFIG_GZIP
1833
1834		Enabled by default to support gzip compressed images.
1835
1836		CONFIG_BZIP2
1837
1838		If this option is set, support for bzip2 compressed
1839		images is included. If not, only uncompressed and gzip
1840		compressed images are supported.
1841
1842		NOTE: the bzip2 algorithm requires a lot of RAM, so
1843		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1844		be at least 4MB.
1845
1846		CONFIG_LZMA
1847
1848		If this option is set, support for lzma compressed
1849		images is included.
1850
1851		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1852		requires an amount of dynamic memory that is given by the
1853		formula:
1854
1855			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1856
1857		Where lc and lp stand for, respectively, Literal context bits
1858		and Literal pos bits.
1859
1860		This value is upper-bounded by 14MB in the worst case. Anyway,
1861		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1862		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1863		a very small buffer.
1864
1865		Use the lzmainfo tool to determinate the lc and lp values and
1866		then calculate the amount of needed dynamic memory (ensuring
1867		the appropriate CONFIG_SYS_MALLOC_LEN value).
1868
1869		CONFIG_LZO
1870
1871		If this option is set, support for LZO compressed images
1872		is included.
1873
1874- MII/PHY support:
1875		CONFIG_PHY_ADDR
1876
1877		The address of PHY on MII bus.
1878
1879		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1880
1881		The clock frequency of the MII bus
1882
1883		CONFIG_PHY_GIGE
1884
1885		If this option is set, support for speed/duplex
1886		detection of gigabit PHY is included.
1887
1888		CONFIG_PHY_RESET_DELAY
1889
1890		Some PHY like Intel LXT971A need extra delay after
1891		reset before any MII register access is possible.
1892		For such PHY, set this option to the usec delay
1893		required. (minimum 300usec for LXT971A)
1894
1895		CONFIG_PHY_CMD_DELAY (ppc4xx)
1896
1897		Some PHY like Intel LXT971A need extra delay after
1898		command issued before MII status register can be read
1899
1900- IP address:
1901		CONFIG_IPADDR
1902
1903		Define a default value for the IP address to use for
1904		the default Ethernet interface, in case this is not
1905		determined through e.g. bootp.
1906		(Environment variable "ipaddr")
1907
1908- Server IP address:
1909		CONFIG_SERVERIP
1910
1911		Defines a default value for the IP address of a TFTP
1912		server to contact when using the "tftboot" command.
1913		(Environment variable "serverip")
1914
1915		CONFIG_KEEP_SERVERADDR
1916
1917		Keeps the server's MAC address, in the env 'serveraddr'
1918		for passing to bootargs (like Linux's netconsole option)
1919
1920- Gateway IP address:
1921		CONFIG_GATEWAYIP
1922
1923		Defines a default value for the IP address of the
1924		default router where packets to other networks are
1925		sent to.
1926		(Environment variable "gatewayip")
1927
1928- Subnet mask:
1929		CONFIG_NETMASK
1930
1931		Defines a default value for the subnet mask (or
1932		routing prefix) which is used to determine if an IP
1933		address belongs to the local subnet or needs to be
1934		forwarded through a router.
1935		(Environment variable "netmask")
1936
1937- Multicast TFTP Mode:
1938		CONFIG_MCAST_TFTP
1939
1940		Defines whether you want to support multicast TFTP as per
1941		rfc-2090; for example to work with atftp.  Lets lots of targets
1942		tftp down the same boot image concurrently.  Note: the Ethernet
1943		driver in use must provide a function: mcast() to join/leave a
1944		multicast group.
1945
1946- BOOTP Recovery Mode:
1947		CONFIG_BOOTP_RANDOM_DELAY
1948
1949		If you have many targets in a network that try to
1950		boot using BOOTP, you may want to avoid that all
1951		systems send out BOOTP requests at precisely the same
1952		moment (which would happen for instance at recovery
1953		from a power failure, when all systems will try to
1954		boot, thus flooding the BOOTP server. Defining
1955		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1956		inserted before sending out BOOTP requests. The
1957		following delays are inserted then:
1958
1959		1st BOOTP request:	delay 0 ... 1 sec
1960		2nd BOOTP request:	delay 0 ... 2 sec
1961		3rd BOOTP request:	delay 0 ... 4 sec
1962		4th and following
1963		BOOTP requests:		delay 0 ... 8 sec
1964
1965		CONFIG_BOOTP_ID_CACHE_SIZE
1966
1967		BOOTP packets are uniquely identified using a 32-bit ID. The
1968		server will copy the ID from client requests to responses and
1969		U-Boot will use this to determine if it is the destination of
1970		an incoming response. Some servers will check that addresses
1971		aren't in use before handing them out (usually using an ARP
1972		ping) and therefore take up to a few hundred milliseconds to
1973		respond. Network congestion may also influence the time it
1974		takes for a response to make it back to the client. If that
1975		time is too long, U-Boot will retransmit requests. In order
1976		to allow earlier responses to still be accepted after these
1977		retransmissions, U-Boot's BOOTP client keeps a small cache of
1978		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1979		cache. The default is to keep IDs for up to four outstanding
1980		requests. Increasing this will allow U-Boot to accept offers
1981		from a BOOTP client in networks with unusually high latency.
1982
1983- DHCP Advanced Options:
1984		You can fine tune the DHCP functionality by defining
1985		CONFIG_BOOTP_* symbols:
1986
1987		CONFIG_BOOTP_SUBNETMASK
1988		CONFIG_BOOTP_GATEWAY
1989		CONFIG_BOOTP_HOSTNAME
1990		CONFIG_BOOTP_NISDOMAIN
1991		CONFIG_BOOTP_BOOTPATH
1992		CONFIG_BOOTP_BOOTFILESIZE
1993		CONFIG_BOOTP_DNS
1994		CONFIG_BOOTP_DNS2
1995		CONFIG_BOOTP_SEND_HOSTNAME
1996		CONFIG_BOOTP_NTPSERVER
1997		CONFIG_BOOTP_TIMEOFFSET
1998		CONFIG_BOOTP_VENDOREX
1999		CONFIG_BOOTP_MAY_FAIL
2000
2001		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
2002		environment variable, not the BOOTP server.
2003
2004		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
2005		after the configured retry count, the call will fail
2006		instead of starting over.  This can be used to fail over
2007		to Link-local IP address configuration if the DHCP server
2008		is not available.
2009
2010		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
2011		serverip from a DHCP server, it is possible that more
2012		than one DNS serverip is offered to the client.
2013		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
2014		serverip will be stored in the additional environment
2015		variable "dnsip2". The first DNS serverip is always
2016		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2017		is defined.
2018
2019		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2020		to do a dynamic update of a DNS server. To do this, they
2021		need the hostname of the DHCP requester.
2022		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2023		of the "hostname" environment variable is passed as
2024		option 12 to the DHCP server.
2025
2026		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2027
2028		A 32bit value in microseconds for a delay between
2029		receiving a "DHCP Offer" and sending the "DHCP Request".
2030		This fixes a problem with certain DHCP servers that don't
2031		respond 100% of the time to a "DHCP request". E.g. On an
2032		AT91RM9200 processor running at 180MHz, this delay needed
2033		to be *at least* 15,000 usec before a Windows Server 2003
2034		DHCP server would reply 100% of the time. I recommend at
2035		least 50,000 usec to be safe. The alternative is to hope
2036		that one of the retries will be successful but note that
2037		the DHCP timeout and retry process takes a longer than
2038		this delay.
2039
2040 - Link-local IP address negotiation:
2041		Negotiate with other link-local clients on the local network
2042		for an address that doesn't require explicit configuration.
2043		This is especially useful if a DHCP server cannot be guaranteed
2044		to exist in all environments that the device must operate.
2045
2046		See doc/README.link-local for more information.
2047
2048 - CDP Options:
2049		CONFIG_CDP_DEVICE_ID
2050
2051		The device id used in CDP trigger frames.
2052
2053		CONFIG_CDP_DEVICE_ID_PREFIX
2054
2055		A two character string which is prefixed to the MAC address
2056		of the device.
2057
2058		CONFIG_CDP_PORT_ID
2059
2060		A printf format string which contains the ascii name of
2061		the port. Normally is set to "eth%d" which sets
2062		eth0 for the first Ethernet, eth1 for the second etc.
2063
2064		CONFIG_CDP_CAPABILITIES
2065
2066		A 32bit integer which indicates the device capabilities;
2067		0x00000010 for a normal host which does not forwards.
2068
2069		CONFIG_CDP_VERSION
2070
2071		An ascii string containing the version of the software.
2072
2073		CONFIG_CDP_PLATFORM
2074
2075		An ascii string containing the name of the platform.
2076
2077		CONFIG_CDP_TRIGGER
2078
2079		A 32bit integer sent on the trigger.
2080
2081		CONFIG_CDP_POWER_CONSUMPTION
2082
2083		A 16bit integer containing the power consumption of the
2084		device in .1 of milliwatts.
2085
2086		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2087
2088		A byte containing the id of the VLAN.
2089
2090- Status LED:	CONFIG_STATUS_LED
2091
2092		Several configurations allow to display the current
2093		status using a LED. For instance, the LED will blink
2094		fast while running U-Boot code, stop blinking as
2095		soon as a reply to a BOOTP request was received, and
2096		start blinking slow once the Linux kernel is running
2097		(supported by a status LED driver in the Linux
2098		kernel). Defining CONFIG_STATUS_LED enables this
2099		feature in U-Boot.
2100
2101		Additional options:
2102
2103		CONFIG_GPIO_LED
2104		The status LED can be connected to a GPIO pin.
2105		In such cases, the gpio_led driver can be used as a
2106		status LED backend implementation. Define CONFIG_GPIO_LED
2107		to include the gpio_led driver in the U-Boot binary.
2108
2109		CONFIG_GPIO_LED_INVERTED_TABLE
2110		Some GPIO connected LEDs may have inverted polarity in which
2111		case the GPIO high value corresponds to LED off state and
2112		GPIO low value corresponds to LED on state.
2113		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2114		with a list of GPIO LEDs that have inverted polarity.
2115
2116- CAN Support:	CONFIG_CAN_DRIVER
2117
2118		Defining CONFIG_CAN_DRIVER enables CAN driver support
2119		on those systems that support this (optional)
2120		feature, like the TQM8xxL modules.
2121
2122- I2C Support:	CONFIG_SYS_I2C
2123
2124		This enable the NEW i2c subsystem, and will allow you to use
2125		i2c commands at the u-boot command line (as long as you set
2126		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2127		based realtime clock chips or other i2c devices. See
2128		common/cmd_i2c.c for a description of the command line
2129		interface.
2130
2131		ported i2c driver to the new framework:
2132		- drivers/i2c/soft_i2c.c:
2133		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2134		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2135		    for defining speed and slave address
2136		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2137		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2138		    for defining speed and slave address
2139		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2140		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2141		    for defining speed and slave address
2142		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2143		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2144		    for defining speed and slave address
2145
2146		- drivers/i2c/fsl_i2c.c:
2147		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2148		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2149		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2150		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2151		    bus.
2152		  - If your board supports a second fsl i2c bus, define
2153		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2154		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2155		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2156		    second bus.
2157
2158		- drivers/i2c/tegra_i2c.c:
2159		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2160		  - This driver adds 4 i2c buses with a fix speed from
2161		    100000 and the slave addr 0!
2162
2163		- drivers/i2c/ppc4xx_i2c.c
2164		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2165		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2166		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2167
2168		- drivers/i2c/i2c_mxc.c
2169		  - activate this driver with CONFIG_SYS_I2C_MXC
2170		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
2171		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
2172		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
2173		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
2174		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2175		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2176		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2177		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2178		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2179		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2180		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
2181		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
2182		If those defines are not set, default value is 100000
2183		for speed, and 0 for slave.
2184
2185		- drivers/i2c/rcar_i2c.c:
2186		  - activate this driver with CONFIG_SYS_I2C_RCAR
2187		  - This driver adds 4 i2c buses
2188
2189		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2190		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2191		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2192		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2193		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2194		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2195		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2196		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2197		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2198
2199		- drivers/i2c/sh_i2c.c:
2200		  - activate this driver with CONFIG_SYS_I2C_SH
2201		  - This driver adds from 2 to 5 i2c buses
2202
2203		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2204		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2205		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2206		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2207		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2208		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2209		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2210		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2211		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2212		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2213		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2214
2215		- drivers/i2c/omap24xx_i2c.c
2216		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2217		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2218		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2219		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2220		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2221		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2222		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2223		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2224		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2225		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2226		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2227
2228		- drivers/i2c/zynq_i2c.c
2229		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2230		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2231		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2232
2233		- drivers/i2c/s3c24x0_i2c.c:
2234		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2235		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2236		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2237		    with a fix speed from 100000 and the slave addr 0!
2238
2239		- drivers/i2c/ihs_i2c.c
2240		  - activate this driver with CONFIG_SYS_I2C_IHS
2241		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2242		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2243		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2244		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2245		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2246		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2247		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2248		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2249		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2250		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2251		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2252		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2253		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
2254		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
2255		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
2256		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
2257		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
2258		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
2259		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
2260		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
2261		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
2262
2263		additional defines:
2264
2265		CONFIG_SYS_NUM_I2C_BUSES
2266		Hold the number of i2c buses you want to use.
2267
2268		CONFIG_SYS_I2C_DIRECT_BUS
2269		define this, if you don't use i2c muxes on your hardware.
2270		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2271		omit this define.
2272
2273		CONFIG_SYS_I2C_MAX_HOPS
2274		define how many muxes are maximal consecutively connected
2275		on one i2c bus. If you not use i2c muxes, omit this
2276		define.
2277
2278		CONFIG_SYS_I2C_BUSES
2279		hold a list of buses you want to use, only used if
2280		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2281		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2282		CONFIG_SYS_NUM_I2C_BUSES = 9:
2283
2284		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2285					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2286					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2287					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2288					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2289					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2290					{1, {I2C_NULL_HOP}}, \
2291					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2292					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2293					}
2294
2295		which defines
2296			bus 0 on adapter 0 without a mux
2297			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2298			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2299			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2300			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2301			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2302			bus 6 on adapter 1 without a mux
2303			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2304			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2305
2306		If you do not have i2c muxes on your board, omit this define.
2307
2308- Legacy I2C Support:	CONFIG_HARD_I2C
2309
2310		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2311		provides the following compelling advantages:
2312
2313		- more than one i2c adapter is usable
2314		- approved multibus support
2315		- better i2c mux support
2316
2317		** Please consider updating your I2C driver now. **
2318
2319		These enable legacy I2C serial bus commands. Defining
2320		CONFIG_HARD_I2C will include the appropriate I2C driver
2321		for the selected CPU.
2322
2323		This will allow you to use i2c commands at the u-boot
2324		command line (as long as you set CONFIG_CMD_I2C in
2325		CONFIG_COMMANDS) and communicate with i2c based realtime
2326		clock chips. See common/cmd_i2c.c for a description of the
2327		command line interface.
2328
2329		CONFIG_HARD_I2C selects a hardware I2C controller.
2330
2331		There are several other quantities that must also be
2332		defined when you define CONFIG_HARD_I2C.
2333
2334		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2335		to be the frequency (in Hz) at which you wish your i2c bus
2336		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2337		the CPU's i2c node address).
2338
2339		Now, the u-boot i2c code for the mpc8xx
2340		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2341		and so its address should therefore be cleared to 0 (See,
2342		eg, MPC823e User's Manual p.16-473). So, set
2343		CONFIG_SYS_I2C_SLAVE to 0.
2344
2345		CONFIG_SYS_I2C_INIT_MPC5XXX
2346
2347		When a board is reset during an i2c bus transfer
2348		chips might think that the current transfer is still
2349		in progress.  Reset the slave devices by sending start
2350		commands until the slave device responds.
2351
2352		That's all that's required for CONFIG_HARD_I2C.
2353
2354		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2355		then the following macros need to be defined (examples are
2356		from include/configs/lwmon.h):
2357
2358		I2C_INIT
2359
2360		(Optional). Any commands necessary to enable the I2C
2361		controller or configure ports.
2362
2363		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2364
2365		I2C_PORT
2366
2367		(Only for MPC8260 CPU). The I/O port to use (the code
2368		assumes both bits are on the same port). Valid values
2369		are 0..3 for ports A..D.
2370
2371		I2C_ACTIVE
2372
2373		The code necessary to make the I2C data line active
2374		(driven).  If the data line is open collector, this
2375		define can be null.
2376
2377		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2378
2379		I2C_TRISTATE
2380
2381		The code necessary to make the I2C data line tri-stated
2382		(inactive).  If the data line is open collector, this
2383		define can be null.
2384
2385		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2386
2387		I2C_READ
2388
2389		Code that returns true if the I2C data line is high,
2390		false if it is low.
2391
2392		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2393
2394		I2C_SDA(bit)
2395
2396		If <bit> is true, sets the I2C data line high. If it
2397		is false, it clears it (low).
2398
2399		eg: #define I2C_SDA(bit) \
2400			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2401			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2402
2403		I2C_SCL(bit)
2404
2405		If <bit> is true, sets the I2C clock line high. If it
2406		is false, it clears it (low).
2407
2408		eg: #define I2C_SCL(bit) \
2409			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2410			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2411
2412		I2C_DELAY
2413
2414		This delay is invoked four times per clock cycle so this
2415		controls the rate of data transfer.  The data rate thus
2416		is 1 / (I2C_DELAY * 4). Often defined to be something
2417		like:
2418
2419		#define I2C_DELAY  udelay(2)
2420
2421		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2422
2423		If your arch supports the generic GPIO framework (asm/gpio.h),
2424		then you may alternatively define the two GPIOs that are to be
2425		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2426		have GPIO-based defaults assigned to them as appropriate.
2427
2428		You should define these to the GPIO value as given directly to
2429		the generic GPIO functions.
2430
2431		CONFIG_SYS_I2C_INIT_BOARD
2432
2433		When a board is reset during an i2c bus transfer
2434		chips might think that the current transfer is still
2435		in progress. On some boards it is possible to access
2436		the i2c SCLK line directly, either by using the
2437		processor pin as a GPIO or by having a second pin
2438		connected to the bus. If this option is defined a
2439		custom i2c_init_board() routine in boards/xxx/board.c
2440		is run early in the boot sequence.
2441
2442		CONFIG_SYS_I2C_BOARD_LATE_INIT
2443
2444		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2445		defined a custom i2c_board_late_init() routine in
2446		boards/xxx/board.c is run AFTER the operations in i2c_init()
2447		is completed. This callpoint can be used to unreset i2c bus
2448		using CPU i2c controller register accesses for CPUs whose i2c
2449		controller provide such a method. It is called at the end of
2450		i2c_init() to allow i2c_init operations to setup the i2c bus
2451		controller on the CPU (e.g. setting bus speed & slave address).
2452
2453		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2454
2455		This option enables configuration of bi_iic_fast[] flags
2456		in u-boot bd_info structure based on u-boot environment
2457		variable "i2cfast". (see also i2cfast)
2458
2459		CONFIG_I2C_MULTI_BUS
2460
2461		This option allows the use of multiple I2C buses, each of which
2462		must have a controller.	 At any point in time, only one bus is
2463		active.	 To switch to a different bus, use the 'i2c dev' command.
2464		Note that bus numbering is zero-based.
2465
2466		CONFIG_SYS_I2C_NOPROBES
2467
2468		This option specifies a list of I2C devices that will be skipped
2469		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2470		is set, specify a list of bus-device pairs.  Otherwise, specify
2471		a 1D array of device addresses
2472
2473		e.g.
2474			#undef	CONFIG_I2C_MULTI_BUS
2475			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2476
2477		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2478
2479			#define CONFIG_I2C_MULTI_BUS
2480			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2481
2482		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2483
2484		CONFIG_SYS_SPD_BUS_NUM
2485
2486		If defined, then this indicates the I2C bus number for DDR SPD.
2487		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2488
2489		CONFIG_SYS_RTC_BUS_NUM
2490
2491		If defined, then this indicates the I2C bus number for the RTC.
2492		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2493
2494		CONFIG_SYS_DTT_BUS_NUM
2495
2496		If defined, then this indicates the I2C bus number for the DTT.
2497		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2498
2499		CONFIG_SYS_I2C_DTT_ADDR:
2500
2501		If defined, specifies the I2C address of the DTT device.
2502		If not defined, then U-Boot uses predefined value for
2503		specified DTT device.
2504
2505		CONFIG_SOFT_I2C_READ_REPEATED_START
2506
2507		defining this will force the i2c_read() function in
2508		the soft_i2c driver to perform an I2C repeated start
2509		between writing the address pointer and reading the
2510		data.  If this define is omitted the default behaviour
2511		of doing a stop-start sequence will be used.  Most I2C
2512		devices can use either method, but some require one or
2513		the other.
2514
2515- SPI Support:	CONFIG_SPI
2516
2517		Enables SPI driver (so far only tested with
2518		SPI EEPROM, also an instance works with Crystal A/D and
2519		D/As on the SACSng board)
2520
2521		CONFIG_SH_SPI
2522
2523		Enables the driver for SPI controller on SuperH. Currently
2524		only SH7757 is supported.
2525
2526		CONFIG_SOFT_SPI
2527
2528		Enables a software (bit-bang) SPI driver rather than
2529		using hardware support. This is a general purpose
2530		driver that only requires three general I/O port pins
2531		(two outputs, one input) to function. If this is
2532		defined, the board configuration must define several
2533		SPI configuration items (port pins to use, etc). For
2534		an example, see include/configs/sacsng.h.
2535
2536		CONFIG_HARD_SPI
2537
2538		Enables a hardware SPI driver for general-purpose reads
2539		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2540		must define a list of chip-select function pointers.
2541		Currently supported on some MPC8xxx processors.	 For an
2542		example, see include/configs/mpc8349emds.h.
2543
2544		CONFIG_MXC_SPI
2545
2546		Enables the driver for the SPI controllers on i.MX and MXC
2547		SoCs. Currently i.MX31/35/51 are supported.
2548
2549		CONFIG_SYS_SPI_MXC_WAIT
2550		Timeout for waiting until spi transfer completed.
2551		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2552
2553- FPGA Support: CONFIG_FPGA
2554
2555		Enables FPGA subsystem.
2556
2557		CONFIG_FPGA_<vendor>
2558
2559		Enables support for specific chip vendors.
2560		(ALTERA, XILINX)
2561
2562		CONFIG_FPGA_<family>
2563
2564		Enables support for FPGA family.
2565		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2566
2567		CONFIG_FPGA_COUNT
2568
2569		Specify the number of FPGA devices to support.
2570
2571		CONFIG_CMD_FPGA_LOADMK
2572
2573		Enable support for fpga loadmk command
2574
2575		CONFIG_CMD_FPGA_LOADP
2576
2577		Enable support for fpga loadp command - load partial bitstream
2578
2579		CONFIG_CMD_FPGA_LOADBP
2580
2581		Enable support for fpga loadbp command - load partial bitstream
2582		(Xilinx only)
2583
2584		CONFIG_SYS_FPGA_PROG_FEEDBACK
2585
2586		Enable printing of hash marks during FPGA configuration.
2587
2588		CONFIG_SYS_FPGA_CHECK_BUSY
2589
2590		Enable checks on FPGA configuration interface busy
2591		status by the configuration function. This option
2592		will require a board or device specific function to
2593		be written.
2594
2595		CONFIG_FPGA_DELAY
2596
2597		If defined, a function that provides delays in the FPGA
2598		configuration driver.
2599
2600		CONFIG_SYS_FPGA_CHECK_CTRLC
2601		Allow Control-C to interrupt FPGA configuration
2602
2603		CONFIG_SYS_FPGA_CHECK_ERROR
2604
2605		Check for configuration errors during FPGA bitfile
2606		loading. For example, abort during Virtex II
2607		configuration if the INIT_B line goes low (which
2608		indicated a CRC error).
2609
2610		CONFIG_SYS_FPGA_WAIT_INIT
2611
2612		Maximum time to wait for the INIT_B line to de-assert
2613		after PROB_B has been de-asserted during a Virtex II
2614		FPGA configuration sequence. The default time is 500
2615		ms.
2616
2617		CONFIG_SYS_FPGA_WAIT_BUSY
2618
2619		Maximum time to wait for BUSY to de-assert during
2620		Virtex II FPGA configuration. The default is 5 ms.
2621
2622		CONFIG_SYS_FPGA_WAIT_CONFIG
2623
2624		Time to wait after FPGA configuration. The default is
2625		200 ms.
2626
2627- Configuration Management:
2628		CONFIG_BUILD_TARGET
2629
2630		Some SoCs need special image types (e.g. U-Boot binary
2631		with a special header) as build targets. By defining
2632		CONFIG_BUILD_TARGET in the SoC / board header, this
2633		special image will be automatically built upon calling
2634		make / buildman.
2635
2636		CONFIG_IDENT_STRING
2637
2638		If defined, this string will be added to the U-Boot
2639		version information (U_BOOT_VERSION)
2640
2641- Vendor Parameter Protection:
2642
2643		U-Boot considers the values of the environment
2644		variables "serial#" (Board Serial Number) and
2645		"ethaddr" (Ethernet Address) to be parameters that
2646		are set once by the board vendor / manufacturer, and
2647		protects these variables from casual modification by
2648		the user. Once set, these variables are read-only,
2649		and write or delete attempts are rejected. You can
2650		change this behaviour:
2651
2652		If CONFIG_ENV_OVERWRITE is #defined in your config
2653		file, the write protection for vendor parameters is
2654		completely disabled. Anybody can change or delete
2655		these parameters.
2656
2657		Alternatively, if you define _both_ an ethaddr in the
2658		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2659		Ethernet address is installed in the environment,
2660		which can be changed exactly ONCE by the user. [The
2661		serial# is unaffected by this, i. e. it remains
2662		read-only.]
2663
2664		The same can be accomplished in a more flexible way
2665		for any variable by configuring the type of access
2666		to allow for those variables in the ".flags" variable
2667		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2668
2669- Protected RAM:
2670		CONFIG_PRAM
2671
2672		Define this variable to enable the reservation of
2673		"protected RAM", i. e. RAM which is not overwritten
2674		by U-Boot. Define CONFIG_PRAM to hold the number of
2675		kB you want to reserve for pRAM. You can overwrite
2676		this default value by defining an environment
2677		variable "pram" to the number of kB you want to
2678		reserve. Note that the board info structure will
2679		still show the full amount of RAM. If pRAM is
2680		reserved, a new environment variable "mem" will
2681		automatically be defined to hold the amount of
2682		remaining RAM in a form that can be passed as boot
2683		argument to Linux, for instance like that:
2684
2685			setenv bootargs ... mem=\${mem}
2686			saveenv
2687
2688		This way you can tell Linux not to use this memory,
2689		either, which results in a memory region that will
2690		not be affected by reboots.
2691
2692		*WARNING* If your board configuration uses automatic
2693		detection of the RAM size, you must make sure that
2694		this memory test is non-destructive. So far, the
2695		following board configurations are known to be
2696		"pRAM-clean":
2697
2698			IVMS8, IVML24, SPD8xx, TQM8xxL,
2699			HERMES, IP860, RPXlite, LWMON,
2700			FLAGADM, TQM8260
2701
2702- Access to physical memory region (> 4GB)
2703		Some basic support is provided for operations on memory not
2704		normally accessible to U-Boot - e.g. some architectures
2705		support access to more than 4GB of memory on 32-bit
2706		machines using physical address extension or similar.
2707		Define CONFIG_PHYSMEM to access this basic support, which
2708		currently only supports clearing the memory.
2709
2710- Error Recovery:
2711		CONFIG_PANIC_HANG
2712
2713		Define this variable to stop the system in case of a
2714		fatal error, so that you have to reset it manually.
2715		This is probably NOT a good idea for an embedded
2716		system where you want the system to reboot
2717		automatically as fast as possible, but it may be
2718		useful during development since you can try to debug
2719		the conditions that lead to the situation.
2720
2721		CONFIG_NET_RETRY_COUNT
2722
2723		This variable defines the number of retries for
2724		network operations like ARP, RARP, TFTP, or BOOTP
2725		before giving up the operation. If not defined, a
2726		default value of 5 is used.
2727
2728		CONFIG_ARP_TIMEOUT
2729
2730		Timeout waiting for an ARP reply in milliseconds.
2731
2732		CONFIG_NFS_TIMEOUT
2733
2734		Timeout in milliseconds used in NFS protocol.
2735		If you encounter "ERROR: Cannot umount" in nfs command,
2736		try longer timeout such as
2737		#define CONFIG_NFS_TIMEOUT 10000UL
2738
2739- Command Interpreter:
2740		CONFIG_AUTO_COMPLETE
2741
2742		Enable auto completion of commands using TAB.
2743
2744		CONFIG_SYS_PROMPT_HUSH_PS2
2745
2746		This defines the secondary prompt string, which is
2747		printed when the command interpreter needs more input
2748		to complete a command. Usually "> ".
2749
2750	Note:
2751
2752		In the current implementation, the local variables
2753		space and global environment variables space are
2754		separated. Local variables are those you define by
2755		simply typing `name=value'. To access a local
2756		variable later on, you have write `$name' or
2757		`${name}'; to execute the contents of a variable
2758		directly type `$name' at the command prompt.
2759
2760		Global environment variables are those you use
2761		setenv/printenv to work with. To run a command stored
2762		in such a variable, you need to use the run command,
2763		and you must not use the '$' sign to access them.
2764
2765		To store commands and special characters in a
2766		variable, please use double quotation marks
2767		surrounding the whole text of the variable, instead
2768		of the backslashes before semicolons and special
2769		symbols.
2770
2771- Command Line Editing and History:
2772		CONFIG_CMDLINE_EDITING
2773
2774		Enable editing and History functions for interactive
2775		command line input operations
2776
2777- Command Line PS1/PS2 support:
2778		CONFIG_CMDLINE_PS_SUPPORT
2779
2780		Enable support for changing the command prompt string
2781		at run-time. Only static string is supported so far.
2782		The string is obtained from environment variables PS1
2783		and PS2.
2784
2785- Default Environment:
2786		CONFIG_EXTRA_ENV_SETTINGS
2787
2788		Define this to contain any number of null terminated
2789		strings (variable = value pairs) that will be part of
2790		the default environment compiled into the boot image.
2791
2792		For example, place something like this in your
2793		board's config file:
2794
2795		#define CONFIG_EXTRA_ENV_SETTINGS \
2796			"myvar1=value1\0" \
2797			"myvar2=value2\0"
2798
2799		Warning: This method is based on knowledge about the
2800		internal format how the environment is stored by the
2801		U-Boot code. This is NOT an official, exported
2802		interface! Although it is unlikely that this format
2803		will change soon, there is no guarantee either.
2804		You better know what you are doing here.
2805
2806		Note: overly (ab)use of the default environment is
2807		discouraged. Make sure to check other ways to preset
2808		the environment like the "source" command or the
2809		boot command first.
2810
2811		CONFIG_ENV_VARS_UBOOT_CONFIG
2812
2813		Define this in order to add variables describing the
2814		U-Boot build configuration to the default environment.
2815		These will be named arch, cpu, board, vendor, and soc.
2816
2817		Enabling this option will cause the following to be defined:
2818
2819		- CONFIG_SYS_ARCH
2820		- CONFIG_SYS_CPU
2821		- CONFIG_SYS_BOARD
2822		- CONFIG_SYS_VENDOR
2823		- CONFIG_SYS_SOC
2824
2825		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2826
2827		Define this in order to add variables describing certain
2828		run-time determined information about the hardware to the
2829		environment.  These will be named board_name, board_rev.
2830
2831		CONFIG_DELAY_ENVIRONMENT
2832
2833		Normally the environment is loaded when the board is
2834		initialised so that it is available to U-Boot. This inhibits
2835		that so that the environment is not available until
2836		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2837		this is instead controlled by the value of
2838		/config/load-environment.
2839
2840- Parallel Flash support:
2841		CONFIG_SYS_NO_FLASH
2842
2843		Traditionally U-Boot was run on systems with parallel NOR
2844		flash. This option is used to disable support for parallel NOR
2845		flash. This option should be defined if the board does not have
2846		parallel flash.
2847
2848		If this option is not defined one of the generic flash drivers
2849		(e.g.  CONFIG_FLASH_CFI_DRIVER or CONFIG_ST_SMI) must be
2850		selected or the board must provide an implementation of the
2851		flash API (see include/flash.h).
2852
2853- DataFlash Support:
2854		CONFIG_HAS_DATAFLASH
2855
2856		Defining this option enables DataFlash features and
2857		allows to read/write in Dataflash via the standard
2858		commands cp, md...
2859
2860- Serial Flash support
2861		CONFIG_CMD_SF
2862
2863		Defining this option enables SPI flash commands
2864		'sf probe/read/write/erase/update'.
2865
2866		Usage requires an initial 'probe' to define the serial
2867		flash parameters, followed by read/write/erase/update
2868		commands.
2869
2870		The following defaults may be provided by the platform
2871		to handle the common case when only a single serial
2872		flash is present on the system.
2873
2874		CONFIG_SF_DEFAULT_BUS		Bus identifier
2875		CONFIG_SF_DEFAULT_CS		Chip-select
2876		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2877		CONFIG_SF_DEFAULT_SPEED		in Hz
2878
2879		CONFIG_CMD_SF_TEST
2880
2881		Define this option to include a destructive SPI flash
2882		test ('sf test').
2883
2884		CONFIG_SF_DUAL_FLASH		Dual flash memories
2885
2886		Define this option to use dual flash support where two flash
2887		memories can be connected with a given cs line.
2888		Currently Xilinx Zynq qspi supports these type of connections.
2889
2890- SystemACE Support:
2891		CONFIG_SYSTEMACE
2892
2893		Adding this option adds support for Xilinx SystemACE
2894		chips attached via some sort of local bus. The address
2895		of the chip must also be defined in the
2896		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2897
2898		#define CONFIG_SYSTEMACE
2899		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2900
2901		When SystemACE support is added, the "ace" device type
2902		becomes available to the fat commands, i.e. fatls.
2903
2904- TFTP Fixed UDP Port:
2905		CONFIG_TFTP_PORT
2906
2907		If this is defined, the environment variable tftpsrcp
2908		is used to supply the TFTP UDP source port value.
2909		If tftpsrcp isn't defined, the normal pseudo-random port
2910		number generator is used.
2911
2912		Also, the environment variable tftpdstp is used to supply
2913		the TFTP UDP destination port value.  If tftpdstp isn't
2914		defined, the normal port 69 is used.
2915
2916		The purpose for tftpsrcp is to allow a TFTP server to
2917		blindly start the TFTP transfer using the pre-configured
2918		target IP address and UDP port. This has the effect of
2919		"punching through" the (Windows XP) firewall, allowing
2920		the remainder of the TFTP transfer to proceed normally.
2921		A better solution is to properly configure the firewall,
2922		but sometimes that is not allowed.
2923
2924- Hashing support:
2925		CONFIG_CMD_HASH
2926
2927		This enables a generic 'hash' command which can produce
2928		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2929
2930		CONFIG_HASH_VERIFY
2931
2932		Enable the hash verify command (hash -v). This adds to code
2933		size a little.
2934
2935		CONFIG_SHA1 - This option enables support of hashing using SHA1
2936		algorithm. The hash is calculated in software.
2937		CONFIG_SHA256 - This option enables support of hashing using
2938		SHA256 algorithm. The hash is calculated in software.
2939		CONFIG_SHA_HW_ACCEL - This option enables hardware acceleration
2940		for SHA1/SHA256 hashing.
2941		This affects the 'hash' command and also the
2942		hash_lookup_algo() function.
2943		CONFIG_SHA_PROG_HW_ACCEL - This option enables
2944		hardware-acceleration for SHA1/SHA256 progressive hashing.
2945		Data can be streamed in a block at a time and the hashing
2946		is performed in hardware.
2947
2948		Note: There is also a sha1sum command, which should perhaps
2949		be deprecated in favour of 'hash sha1'.
2950
2951- Freescale i.MX specific commands:
2952		CONFIG_CMD_HDMIDETECT
2953		This enables 'hdmidet' command which returns true if an
2954		HDMI monitor is detected.  This command is i.MX 6 specific.
2955
2956		CONFIG_CMD_BMODE
2957		This enables the 'bmode' (bootmode) command for forcing
2958		a boot from specific media.
2959
2960		This is useful for forcing the ROM's usb downloader to
2961		activate upon a watchdog reset which is nice when iterating
2962		on U-Boot.  Using the reset button or running bmode normal
2963		will set it back to normal.  This command currently
2964		supports i.MX53 and i.MX6.
2965
2966- bootcount support:
2967		CONFIG_BOOTCOUNT_LIMIT
2968
2969		This enables the bootcounter support, see:
2970		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2971
2972		CONFIG_AT91SAM9XE
2973		enable special bootcounter support on at91sam9xe based boards.
2974		CONFIG_BLACKFIN
2975		enable special bootcounter support on blackfin based boards.
2976		CONFIG_SOC_DA8XX
2977		enable special bootcounter support on da850 based boards.
2978		CONFIG_BOOTCOUNT_RAM
2979		enable support for the bootcounter in RAM
2980		CONFIG_BOOTCOUNT_I2C
2981		enable support for the bootcounter on an i2c (like RTC) device.
2982			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2983			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2984						    the bootcounter.
2985			CONFIG_BOOTCOUNT_ALEN = address len
2986
2987- Show boot progress:
2988		CONFIG_SHOW_BOOT_PROGRESS
2989
2990		Defining this option allows to add some board-
2991		specific code (calling a user-provided function
2992		"show_boot_progress(int)") that enables you to show
2993		the system's boot progress on some display (for
2994		example, some LED's) on your board. At the moment,
2995		the following checkpoints are implemented:
2996
2997
2998Legacy uImage format:
2999
3000  Arg	Where			When
3001    1	common/cmd_bootm.c	before attempting to boot an image
3002   -1	common/cmd_bootm.c	Image header has bad	 magic number
3003    2	common/cmd_bootm.c	Image header has correct magic number
3004   -2	common/cmd_bootm.c	Image header has bad	 checksum
3005    3	common/cmd_bootm.c	Image header has correct checksum
3006   -3	common/cmd_bootm.c	Image data   has bad	 checksum
3007    4	common/cmd_bootm.c	Image data   has correct checksum
3008   -4	common/cmd_bootm.c	Image is for unsupported architecture
3009    5	common/cmd_bootm.c	Architecture check OK
3010   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
3011    6	common/cmd_bootm.c	Image Type check OK
3012   -6	common/cmd_bootm.c	gunzip uncompression error
3013   -7	common/cmd_bootm.c	Unimplemented compression type
3014    7	common/cmd_bootm.c	Uncompression OK
3015    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3016   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3017
3018    9	common/image.c		Start initial ramdisk verification
3019  -10	common/image.c		Ramdisk header has bad	   magic number
3020  -11	common/image.c		Ramdisk header has bad	   checksum
3021   10	common/image.c		Ramdisk header is OK
3022  -12	common/image.c		Ramdisk data   has bad	   checksum
3023   11	common/image.c		Ramdisk data   has correct checksum
3024   12	common/image.c		Ramdisk verification complete, start loading
3025  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3026   13	common/image.c		Start multifile image verification
3027   14	common/image.c		No initial ramdisk, no multifile, continue.
3028
3029   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3030
3031  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3032  -31	post/post.c		POST test failed, detected by post_output_backlog()
3033  -32	post/post.c		POST test failed, detected by post_run_single()
3034
3035   34	common/cmd_doc.c	before loading a Image from a DOC device
3036  -35	common/cmd_doc.c	Bad usage of "doc" command
3037   35	common/cmd_doc.c	correct usage of "doc" command
3038  -36	common/cmd_doc.c	No boot device
3039   36	common/cmd_doc.c	correct boot device
3040  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3041   37	common/cmd_doc.c	correct chip ID found, device available
3042  -38	common/cmd_doc.c	Read Error on boot device
3043   38	common/cmd_doc.c	reading Image header from DOC device OK
3044  -39	common/cmd_doc.c	Image header has bad magic number
3045   39	common/cmd_doc.c	Image header has correct magic number
3046  -40	common/cmd_doc.c	Error reading Image from DOC device
3047   40	common/cmd_doc.c	Image header has correct magic number
3048   41	common/cmd_ide.c	before loading a Image from a IDE device
3049  -42	common/cmd_ide.c	Bad usage of "ide" command
3050   42	common/cmd_ide.c	correct usage of "ide" command
3051  -43	common/cmd_ide.c	No boot device
3052   43	common/cmd_ide.c	boot device found
3053  -44	common/cmd_ide.c	Device not available
3054   44	common/cmd_ide.c	Device available
3055  -45	common/cmd_ide.c	wrong partition selected
3056   45	common/cmd_ide.c	partition selected
3057  -46	common/cmd_ide.c	Unknown partition table
3058   46	common/cmd_ide.c	valid partition table found
3059  -47	common/cmd_ide.c	Invalid partition type
3060   47	common/cmd_ide.c	correct partition type
3061  -48	common/cmd_ide.c	Error reading Image Header on boot device
3062   48	common/cmd_ide.c	reading Image Header from IDE device OK
3063  -49	common/cmd_ide.c	Image header has bad magic number
3064   49	common/cmd_ide.c	Image header has correct magic number
3065  -50	common/cmd_ide.c	Image header has bad	 checksum
3066   50	common/cmd_ide.c	Image header has correct checksum
3067  -51	common/cmd_ide.c	Error reading Image from IDE device
3068   51	common/cmd_ide.c	reading Image from IDE device OK
3069   52	common/cmd_nand.c	before loading a Image from a NAND device
3070  -53	common/cmd_nand.c	Bad usage of "nand" command
3071   53	common/cmd_nand.c	correct usage of "nand" command
3072  -54	common/cmd_nand.c	No boot device
3073   54	common/cmd_nand.c	boot device found
3074  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3075   55	common/cmd_nand.c	correct chip ID found, device available
3076  -56	common/cmd_nand.c	Error reading Image Header on boot device
3077   56	common/cmd_nand.c	reading Image Header from NAND device OK
3078  -57	common/cmd_nand.c	Image header has bad magic number
3079   57	common/cmd_nand.c	Image header has correct magic number
3080  -58	common/cmd_nand.c	Error reading Image from NAND device
3081   58	common/cmd_nand.c	reading Image from NAND device OK
3082
3083  -60	common/env_common.c	Environment has a bad CRC, using default
3084
3085   64	net/eth.c		starting with Ethernet configuration.
3086  -64	net/eth.c		no Ethernet found.
3087   65	net/eth.c		Ethernet found.
3088
3089  -80	common/cmd_net.c	usage wrong
3090   80	common/cmd_net.c	before calling net_loop()
3091  -81	common/cmd_net.c	some error in net_loop() occurred
3092   81	common/cmd_net.c	net_loop() back without error
3093  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3094   82	common/cmd_net.c	trying automatic boot
3095   83	common/cmd_net.c	running "source" command
3096  -83	common/cmd_net.c	some error in automatic boot or "source" command
3097   84	common/cmd_net.c	end without errors
3098
3099FIT uImage format:
3100
3101  Arg	Where			When
3102  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3103 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3104  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3105 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3106  102	common/cmd_bootm.c	Kernel unit name specified
3107 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3108  103	common/cmd_bootm.c	Found configuration node
3109  104	common/cmd_bootm.c	Got kernel subimage node offset
3110 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3111  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3112 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3113  106	common/cmd_bootm.c	Architecture check OK
3114 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3115  107	common/cmd_bootm.c	Kernel subimage type OK
3116 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3117  108	common/cmd_bootm.c	Got kernel subimage data/size
3118 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3119 -109	common/cmd_bootm.c	Can't get kernel subimage type
3120 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3121 -111	common/cmd_bootm.c	Can't get kernel subimage os
3122 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3123 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3124
3125  120	common/image.c		Start initial ramdisk verification
3126 -120	common/image.c		Ramdisk FIT image has incorrect format
3127  121	common/image.c		Ramdisk FIT image has correct format
3128  122	common/image.c		No ramdisk subimage unit name, using configuration
3129 -122	common/image.c		Can't get configuration for ramdisk subimage
3130  123	common/image.c		Ramdisk unit name specified
3131 -124	common/image.c		Can't get ramdisk subimage node offset
3132  125	common/image.c		Got ramdisk subimage node offset
3133 -125	common/image.c		Ramdisk subimage hash verification failed
3134  126	common/image.c		Ramdisk subimage hash verification OK
3135 -126	common/image.c		Ramdisk subimage for unsupported architecture
3136  127	common/image.c		Architecture check OK
3137 -127	common/image.c		Can't get ramdisk subimage data/size
3138  128	common/image.c		Got ramdisk subimage data/size
3139  129	common/image.c		Can't get ramdisk load address
3140 -129	common/image.c		Got ramdisk load address
3141
3142 -130	common/cmd_doc.c	Incorrect FIT image format
3143  131	common/cmd_doc.c	FIT image format OK
3144
3145 -140	common/cmd_ide.c	Incorrect FIT image format
3146  141	common/cmd_ide.c	FIT image format OK
3147
3148 -150	common/cmd_nand.c	Incorrect FIT image format
3149  151	common/cmd_nand.c	FIT image format OK
3150
3151- legacy image format:
3152		CONFIG_IMAGE_FORMAT_LEGACY
3153		enables the legacy image format support in U-Boot.
3154
3155		Default:
3156		enabled if CONFIG_FIT_SIGNATURE is not defined.
3157
3158		CONFIG_DISABLE_IMAGE_LEGACY
3159		disable the legacy image format
3160
3161		This define is introduced, as the legacy image format is
3162		enabled per default for backward compatibility.
3163
3164- FIT image support:
3165		CONFIG_FIT_DISABLE_SHA256
3166		Supporting SHA256 hashes has quite an impact on binary size.
3167		For constrained systems sha256 hash support can be disabled
3168		with this option.
3169
3170		TODO(sjg@chromium.org): Adjust this option to be positive,
3171		and move it to Kconfig
3172
3173- Standalone program support:
3174		CONFIG_STANDALONE_LOAD_ADDR
3175
3176		This option defines a board specific value for the
3177		address where standalone program gets loaded, thus
3178		overwriting the architecture dependent default
3179		settings.
3180
3181- Frame Buffer Address:
3182		CONFIG_FB_ADDR
3183
3184		Define CONFIG_FB_ADDR if you want to use specific
3185		address for frame buffer.  This is typically the case
3186		when using a graphics controller has separate video
3187		memory.  U-Boot will then place the frame buffer at
3188		the given address instead of dynamically reserving it
3189		in system RAM by calling lcd_setmem(), which grabs
3190		the memory for the frame buffer depending on the
3191		configured panel size.
3192
3193		Please see board_init_f function.
3194
3195- Automatic software updates via TFTP server
3196		CONFIG_UPDATE_TFTP
3197		CONFIG_UPDATE_TFTP_CNT_MAX
3198		CONFIG_UPDATE_TFTP_MSEC_MAX
3199
3200		These options enable and control the auto-update feature;
3201		for a more detailed description refer to doc/README.update.
3202
3203- MTD Support (mtdparts command, UBI support)
3204		CONFIG_MTD_DEVICE
3205
3206		Adds the MTD device infrastructure from the Linux kernel.
3207		Needed for mtdparts command support.
3208
3209		CONFIG_MTD_PARTITIONS
3210
3211		Adds the MTD partitioning infrastructure from the Linux
3212		kernel. Needed for UBI support.
3213
3214- UBI support
3215		CONFIG_CMD_UBI
3216
3217		Adds commands for interacting with MTD partitions formatted
3218		with the UBI flash translation layer
3219
3220		Requires also defining CONFIG_RBTREE
3221
3222		CONFIG_UBI_SILENCE_MSG
3223
3224		Make the verbose messages from UBI stop printing.  This leaves
3225		warnings and errors enabled.
3226
3227
3228		CONFIG_MTD_UBI_WL_THRESHOLD
3229		This parameter defines the maximum difference between the highest
3230		erase counter value and the lowest erase counter value of eraseblocks
3231		of UBI devices. When this threshold is exceeded, UBI starts performing
3232		wear leveling by means of moving data from eraseblock with low erase
3233		counter to eraseblocks with high erase counter.
3234
3235		The default value should be OK for SLC NAND flashes, NOR flashes and
3236		other flashes which have eraseblock life-cycle 100000 or more.
3237		However, in case of MLC NAND flashes which typically have eraseblock
3238		life-cycle less than 10000, the threshold should be lessened (e.g.,
3239		to 128 or 256, although it does not have to be power of 2).
3240
3241		default: 4096
3242
3243		CONFIG_MTD_UBI_BEB_LIMIT
3244		This option specifies the maximum bad physical eraseblocks UBI
3245		expects on the MTD device (per 1024 eraseblocks). If the
3246		underlying flash does not admit of bad eraseblocks (e.g. NOR
3247		flash), this value is ignored.
3248
3249		NAND datasheets often specify the minimum and maximum NVM
3250		(Number of Valid Blocks) for the flashes' endurance lifetime.
3251		The maximum expected bad eraseblocks per 1024 eraseblocks
3252		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3253		which gives 20 for most NANDs (MaxNVB is basically the total
3254		count of eraseblocks on the chip).
3255
3256		To put it differently, if this value is 20, UBI will try to
3257		reserve about 1.9% of physical eraseblocks for bad blocks
3258		handling. And that will be 1.9% of eraseblocks on the entire
3259		NAND chip, not just the MTD partition UBI attaches. This means
3260		that if you have, say, a NAND flash chip admits maximum 40 bad
3261		eraseblocks, and it is split on two MTD partitions of the same
3262		size, UBI will reserve 40 eraseblocks when attaching a
3263		partition.
3264
3265		default: 20
3266
3267		CONFIG_MTD_UBI_FASTMAP
3268		Fastmap is a mechanism which allows attaching an UBI device
3269		in nearly constant time. Instead of scanning the whole MTD device it
3270		only has to locate a checkpoint (called fastmap) on the device.
3271		The on-flash fastmap contains all information needed to attach
3272		the device. Using fastmap makes only sense on large devices where
3273		attaching by scanning takes long. UBI will not automatically install
3274		a fastmap on old images, but you can set the UBI parameter
3275		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3276		that fastmap-enabled images are still usable with UBI implementations
3277		without	fastmap support. On typical flash devices the whole fastmap
3278		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3279
3280		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3281		Set this parameter to enable fastmap automatically on images
3282		without a fastmap.
3283		default: 0
3284
3285		CONFIG_MTD_UBI_FM_DEBUG
3286		Enable UBI fastmap debug
3287		default: 0
3288
3289- UBIFS support
3290		CONFIG_CMD_UBIFS
3291
3292		Adds commands for interacting with UBI volumes formatted as
3293		UBIFS.  UBIFS is read-only in u-boot.
3294
3295		Requires UBI support as well as CONFIG_LZO
3296
3297		CONFIG_UBIFS_SILENCE_MSG
3298
3299		Make the verbose messages from UBIFS stop printing.  This leaves
3300		warnings and errors enabled.
3301
3302- SPL framework
3303		CONFIG_SPL
3304		Enable building of SPL globally.
3305
3306		CONFIG_SPL_LDSCRIPT
3307		LDSCRIPT for linking the SPL binary.
3308
3309		CONFIG_SPL_MAX_FOOTPRINT
3310		Maximum size in memory allocated to the SPL, BSS included.
3311		When defined, the linker checks that the actual memory
3312		used by SPL from _start to __bss_end does not exceed it.
3313		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3314		must not be both defined at the same time.
3315
3316		CONFIG_SPL_MAX_SIZE
3317		Maximum size of the SPL image (text, data, rodata, and
3318		linker lists sections), BSS excluded.
3319		When defined, the linker checks that the actual size does
3320		not exceed it.
3321
3322		CONFIG_SPL_TEXT_BASE
3323		TEXT_BASE for linking the SPL binary.
3324
3325		CONFIG_SPL_RELOC_TEXT_BASE
3326		Address to relocate to.  If unspecified, this is equal to
3327		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3328
3329		CONFIG_SPL_BSS_START_ADDR
3330		Link address for the BSS within the SPL binary.
3331
3332		CONFIG_SPL_BSS_MAX_SIZE
3333		Maximum size in memory allocated to the SPL BSS.
3334		When defined, the linker checks that the actual memory used
3335		by SPL from __bss_start to __bss_end does not exceed it.
3336		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3337		must not be both defined at the same time.
3338
3339		CONFIG_SPL_STACK
3340		Adress of the start of the stack SPL will use
3341
3342		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3343		When defined, SPL will panic() if the image it has
3344		loaded does not have a signature.
3345		Defining this is useful when code which loads images
3346		in SPL cannot guarantee that absolutely all read errors
3347		will be caught.
3348		An example is the LPC32XX MLC NAND driver, which will
3349		consider that a completely unreadable NAND block is bad,
3350		and thus should be skipped silently.
3351
3352		CONFIG_SPL_ABORT_ON_RAW_IMAGE
3353		When defined, SPL will proceed to another boot method
3354		if the image it has loaded does not have a signature.
3355
3356		CONFIG_SPL_RELOC_STACK
3357		Adress of the start of the stack SPL will use after
3358		relocation.  If unspecified, this is equal to
3359		CONFIG_SPL_STACK.
3360
3361		CONFIG_SYS_SPL_MALLOC_START
3362		Starting address of the malloc pool used in SPL.
3363		When this option is set the full malloc is used in SPL and
3364		it is set up by spl_init() and before that, the simple malloc()
3365		can be used if CONFIG_SYS_MALLOC_F is defined.
3366
3367		CONFIG_SYS_SPL_MALLOC_SIZE
3368		The size of the malloc pool used in SPL.
3369
3370		CONFIG_SPL_FRAMEWORK
3371		Enable the SPL framework under common/.  This framework
3372		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3373		NAND loading of the Linux Kernel.
3374
3375		CONFIG_SPL_OS_BOOT
3376		Enable booting directly to an OS from SPL.
3377		See also: doc/README.falcon
3378
3379		CONFIG_SPL_DISPLAY_PRINT
3380		For ARM, enable an optional function to print more information
3381		about the running system.
3382
3383		CONFIG_SPL_INIT_MINIMAL
3384		Arch init code should be built for a very small image
3385
3386		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3387		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3388		Address and partition on the MMC to load U-Boot from
3389		when the MMC is being used in raw mode.
3390
3391		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3392		Partition on the MMC to load U-Boot from when the MMC is being
3393		used in raw mode
3394
3395		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3396		Sector to load kernel uImage from when MMC is being
3397		used in raw mode (for Falcon mode)
3398
3399		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3400		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3401		Sector and number of sectors to load kernel argument
3402		parameters from when MMC is being used in raw mode
3403		(for falcon mode)
3404
3405		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3406		Partition on the MMC to load U-Boot from when the MMC is being
3407		used in fs mode
3408
3409		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3410		Filename to read to load U-Boot when reading from filesystem
3411
3412		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3413		Filename to read to load kernel uImage when reading
3414		from filesystem (for Falcon mode)
3415
3416		CONFIG_SPL_FS_LOAD_ARGS_NAME
3417		Filename to read to load kernel argument parameters
3418		when reading from filesystem (for Falcon mode)
3419
3420		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3421		Set this for NAND SPL on PPC mpc83xx targets, so that
3422		start.S waits for the rest of the SPL to load before
3423		continuing (the hardware starts execution after just
3424		loading the first page rather than the full 4K).
3425
3426		CONFIG_SPL_SKIP_RELOCATE
3427		Avoid SPL relocation
3428
3429		CONFIG_SPL_NAND_BASE
3430		Include nand_base.c in the SPL.  Requires
3431		CONFIG_SPL_NAND_DRIVERS.
3432
3433		CONFIG_SPL_NAND_DRIVERS
3434		SPL uses normal NAND drivers, not minimal drivers.
3435
3436		CONFIG_SPL_NAND_ECC
3437		Include standard software ECC in the SPL
3438
3439		CONFIG_SPL_NAND_SIMPLE
3440		Support for NAND boot using simple NAND drivers that
3441		expose the cmd_ctrl() interface.
3442
3443		CONFIG_SPL_UBI
3444		Support for a lightweight UBI (fastmap) scanner and
3445		loader
3446
3447		CONFIG_SPL_NAND_RAW_ONLY
3448		Support to boot only raw u-boot.bin images. Use this only
3449		if you need to save space.
3450
3451		CONFIG_SPL_COMMON_INIT_DDR
3452		Set for common ddr init with serial presence detect in
3453		SPL binary.
3454
3455		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3456		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3457		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3458		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3459		CONFIG_SYS_NAND_ECCBYTES
3460		Defines the size and behavior of the NAND that SPL uses
3461		to read U-Boot
3462
3463		CONFIG_SPL_NAND_BOOT
3464		Add support NAND boot
3465
3466		CONFIG_SYS_NAND_U_BOOT_OFFS
3467		Location in NAND to read U-Boot from
3468
3469		CONFIG_SYS_NAND_U_BOOT_DST
3470		Location in memory to load U-Boot to
3471
3472		CONFIG_SYS_NAND_U_BOOT_SIZE
3473		Size of image to load
3474
3475		CONFIG_SYS_NAND_U_BOOT_START
3476		Entry point in loaded image to jump to
3477
3478		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3479		Define this if you need to first read the OOB and then the
3480		data. This is used, for example, on davinci platforms.
3481
3482		CONFIG_SPL_OMAP3_ID_NAND
3483		Support for an OMAP3-specific set of functions to return the
3484		ID and MFR of the first attached NAND chip, if present.
3485
3486		CONFIG_SPL_RAM_DEVICE
3487		Support for running image already present in ram, in SPL binary
3488
3489		CONFIG_SPL_PAD_TO
3490		Image offset to which the SPL should be padded before appending
3491		the SPL payload. By default, this is defined as
3492		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3493		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3494		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3495
3496		CONFIG_SPL_TARGET
3497		Final target image containing SPL and payload.  Some SPLs
3498		use an arch-specific makefile fragment instead, for
3499		example if more than one image needs to be produced.
3500
3501		CONFIG_FIT_SPL_PRINT
3502		Printing information about a FIT image adds quite a bit of
3503		code to SPL. So this is normally disabled in SPL. Use this
3504		option to re-enable it. This will affect the output of the
3505		bootm command when booting a FIT image.
3506
3507- TPL framework
3508		CONFIG_TPL
3509		Enable building of TPL globally.
3510
3511		CONFIG_TPL_PAD_TO
3512		Image offset to which the TPL should be padded before appending
3513		the TPL payload. By default, this is defined as
3514		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3515		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3516		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3517
3518- Interrupt support (PPC):
3519
3520		There are common interrupt_init() and timer_interrupt()
3521		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3522		for CPU specific initialization. interrupt_init_cpu()
3523		should set decrementer_count to appropriate value. If
3524		CPU resets decrementer automatically after interrupt
3525		(ppc4xx) it should set decrementer_count to zero.
3526		timer_interrupt() calls timer_interrupt_cpu() for CPU
3527		specific handling. If board has watchdog / status_led
3528		/ other_activity_monitor it works automatically from
3529		general timer_interrupt().
3530
3531
3532Board initialization settings:
3533------------------------------
3534
3535During Initialization u-boot calls a number of board specific functions
3536to allow the preparation of board specific prerequisites, e.g. pin setup
3537before drivers are initialized. To enable these callbacks the
3538following configuration macros have to be defined. Currently this is
3539architecture specific, so please check arch/your_architecture/lib/board.c
3540typically in board_init_f() and board_init_r().
3541
3542- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3543- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3544- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3545- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3546
3547Configuration Settings:
3548-----------------------
3549
3550- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3551		Optionally it can be defined to support 64-bit memory commands.
3552
3553- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3554		undefine this when you're short of memory.
3555
3556- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3557		width of the commands listed in the 'help' command output.
3558
3559- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3560		prompt for user input.
3561
3562- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3563
3564- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3565
3566- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3567
3568- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3569		the application (usually a Linux kernel) when it is
3570		booted
3571
3572- CONFIG_SYS_BAUDRATE_TABLE:
3573		List of legal baudrate settings for this board.
3574
3575- CONFIG_SYS_CONSOLE_INFO_QUIET
3576		Suppress display of console information at boot.
3577
3578- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3579		Enable the call to overwrite_console().
3580
3581- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3582		Enable overwrite of previous console environment settings.
3583
3584- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3585		Begin and End addresses of the area used by the
3586		simple memory test.
3587
3588- CONFIG_SYS_ALT_MEMTEST:
3589		Enable an alternate, more extensive memory test.
3590
3591- CONFIG_SYS_MEMTEST_SCRATCH:
3592		Scratch address used by the alternate memory test
3593		You only need to set this if address zero isn't writeable
3594
3595- CONFIG_SYS_MEM_RESERVE_SECURE
3596		Only implemented for ARMv8 for now.
3597		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
3598		is substracted from total RAM and won't be reported to OS.
3599		This memory can be used as secure memory. A variable
3600		gd->arch.secure_ram is used to track the location. In systems
3601		the RAM base is not zero, or RAM is divided into banks,
3602		this variable needs to be recalcuated to get the address.
3603
3604- CONFIG_SYS_MEM_TOP_HIDE:
3605		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3606		this specified memory area will get subtracted from the top
3607		(end) of RAM and won't get "touched" at all by U-Boot. By
3608		fixing up gd->ram_size the Linux kernel should gets passed
3609		the now "corrected" memory size and won't touch it either.
3610		This should work for arch/ppc and arch/powerpc. Only Linux
3611		board ports in arch/powerpc with bootwrapper support that
3612		recalculate the memory size from the SDRAM controller setup
3613		will have to get fixed in Linux additionally.
3614
3615		This option can be used as a workaround for the 440EPx/GRx
3616		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3617		be touched.
3618
3619		WARNING: Please make sure that this value is a multiple of
3620		the Linux page size (normally 4k). If this is not the case,
3621		then the end address of the Linux memory will be located at a
3622		non page size aligned address and this could cause major
3623		problems.
3624
3625- CONFIG_SYS_LOADS_BAUD_CHANGE:
3626		Enable temporary baudrate change while serial download
3627
3628- CONFIG_SYS_SDRAM_BASE:
3629		Physical start address of SDRAM. _Must_ be 0 here.
3630
3631- CONFIG_SYS_FLASH_BASE:
3632		Physical start address of Flash memory.
3633
3634- CONFIG_SYS_MONITOR_BASE:
3635		Physical start address of boot monitor code (set by
3636		make config files to be same as the text base address
3637		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3638		CONFIG_SYS_FLASH_BASE when booting from flash.
3639
3640- CONFIG_SYS_MONITOR_LEN:
3641		Size of memory reserved for monitor code, used to
3642		determine _at_compile_time_ (!) if the environment is
3643		embedded within the U-Boot image, or in a separate
3644		flash sector.
3645
3646- CONFIG_SYS_MALLOC_LEN:
3647		Size of DRAM reserved for malloc() use.
3648
3649- CONFIG_SYS_MALLOC_F_LEN
3650		Size of the malloc() pool for use before relocation. If
3651		this is defined, then a very simple malloc() implementation
3652		will become available before relocation. The address is just
3653		below the global data, and the stack is moved down to make
3654		space.
3655
3656		This feature allocates regions with increasing addresses
3657		within the region. calloc() is supported, but realloc()
3658		is not available. free() is supported but does nothing.
3659		The memory will be freed (or in fact just forgotten) when
3660		U-Boot relocates itself.
3661
3662- CONFIG_SYS_MALLOC_SIMPLE
3663		Provides a simple and small malloc() and calloc() for those
3664		boards which do not use the full malloc in SPL (which is
3665		enabled with CONFIG_SYS_SPL_MALLOC_START).
3666
3667- CONFIG_SYS_NONCACHED_MEMORY:
3668		Size of non-cached memory area. This area of memory will be
3669		typically located right below the malloc() area and mapped
3670		uncached in the MMU. This is useful for drivers that would
3671		otherwise require a lot of explicit cache maintenance. For
3672		some drivers it's also impossible to properly maintain the
3673		cache. For example if the regions that need to be flushed
3674		are not a multiple of the cache-line size, *and* padding
3675		cannot be allocated between the regions to align them (i.e.
3676		if the HW requires a contiguous array of regions, and the
3677		size of each region is not cache-aligned), then a flush of
3678		one region may result in overwriting data that hardware has
3679		written to another region in the same cache-line. This can
3680		happen for example in network drivers where descriptors for
3681		buffers are typically smaller than the CPU cache-line (e.g.
3682		16 bytes vs. 32 or 64 bytes).
3683
3684		Non-cached memory is only supported on 32-bit ARM at present.
3685
3686- CONFIG_SYS_BOOTM_LEN:
3687		Normally compressed uImages are limited to an
3688		uncompressed size of 8 MBytes. If this is not enough,
3689		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3690		to adjust this setting to your needs.
3691
3692- CONFIG_SYS_BOOTMAPSZ:
3693		Maximum size of memory mapped by the startup code of
3694		the Linux kernel; all data that must be processed by
3695		the Linux kernel (bd_info, boot arguments, FDT blob if
3696		used) must be put below this limit, unless "bootm_low"
3697		environment variable is defined and non-zero. In such case
3698		all data for the Linux kernel must be between "bootm_low"
3699		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3700		variable "bootm_mapsize" will override the value of
3701		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3702		then the value in "bootm_size" will be used instead.
3703
3704- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3705		Enable initrd_high functionality.  If defined then the
3706		initrd_high feature is enabled and the bootm ramdisk subcommand
3707		is enabled.
3708
3709- CONFIG_SYS_BOOT_GET_CMDLINE:
3710		Enables allocating and saving kernel cmdline in space between
3711		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3712
3713- CONFIG_SYS_BOOT_GET_KBD:
3714		Enables allocating and saving a kernel copy of the bd_info in
3715		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3716
3717- CONFIG_SYS_MAX_FLASH_BANKS:
3718		Max number of Flash memory banks
3719
3720- CONFIG_SYS_MAX_FLASH_SECT:
3721		Max number of sectors on a Flash chip
3722
3723- CONFIG_SYS_FLASH_ERASE_TOUT:
3724		Timeout for Flash erase operations (in ms)
3725
3726- CONFIG_SYS_FLASH_WRITE_TOUT:
3727		Timeout for Flash write operations (in ms)
3728
3729- CONFIG_SYS_FLASH_LOCK_TOUT
3730		Timeout for Flash set sector lock bit operation (in ms)
3731
3732- CONFIG_SYS_FLASH_UNLOCK_TOUT
3733		Timeout for Flash clear lock bits operation (in ms)
3734
3735- CONFIG_SYS_FLASH_PROTECTION
3736		If defined, hardware flash sectors protection is used
3737		instead of U-Boot software protection.
3738
3739- CONFIG_SYS_DIRECT_FLASH_TFTP:
3740
3741		Enable TFTP transfers directly to flash memory;
3742		without this option such a download has to be
3743		performed in two steps: (1) download to RAM, and (2)
3744		copy from RAM to flash.
3745
3746		The two-step approach is usually more reliable, since
3747		you can check if the download worked before you erase
3748		the flash, but in some situations (when system RAM is
3749		too limited to allow for a temporary copy of the
3750		downloaded image) this option may be very useful.
3751
3752- CONFIG_SYS_FLASH_CFI:
3753		Define if the flash driver uses extra elements in the
3754		common flash structure for storing flash geometry.
3755
3756- CONFIG_FLASH_CFI_DRIVER
3757		This option also enables the building of the cfi_flash driver
3758		in the drivers directory
3759
3760- CONFIG_FLASH_CFI_MTD
3761		This option enables the building of the cfi_mtd driver
3762		in the drivers directory. The driver exports CFI flash
3763		to the MTD layer.
3764
3765- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3766		Use buffered writes to flash.
3767
3768- CONFIG_FLASH_SPANSION_S29WS_N
3769		s29ws-n MirrorBit flash has non-standard addresses for buffered
3770		write commands.
3771
3772- CONFIG_SYS_FLASH_QUIET_TEST
3773		If this option is defined, the common CFI flash doesn't
3774		print it's warning upon not recognized FLASH banks. This
3775		is useful, if some of the configured banks are only
3776		optionally available.
3777
3778- CONFIG_FLASH_SHOW_PROGRESS
3779		If defined (must be an integer), print out countdown
3780		digits and dots.  Recommended value: 45 (9..1) for 80
3781		column displays, 15 (3..1) for 40 column displays.
3782
3783- CONFIG_FLASH_VERIFY
3784		If defined, the content of the flash (destination) is compared
3785		against the source after the write operation. An error message
3786		will be printed when the contents are not identical.
3787		Please note that this option is useless in nearly all cases,
3788		since such flash programming errors usually are detected earlier
3789		while unprotecting/erasing/programming. Please only enable
3790		this option if you really know what you are doing.
3791
3792- CONFIG_SYS_RX_ETH_BUFFER:
3793		Defines the number of Ethernet receive buffers. On some
3794		Ethernet controllers it is recommended to set this value
3795		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3796		buffers can be full shortly after enabling the interface
3797		on high Ethernet traffic.
3798		Defaults to 4 if not defined.
3799
3800- CONFIG_ENV_MAX_ENTRIES
3801
3802	Maximum number of entries in the hash table that is used
3803	internally to store the environment settings. The default
3804	setting is supposed to be generous and should work in most
3805	cases. This setting can be used to tune behaviour; see
3806	lib/hashtable.c for details.
3807
3808- CONFIG_ENV_FLAGS_LIST_DEFAULT
3809- CONFIG_ENV_FLAGS_LIST_STATIC
3810	Enable validation of the values given to environment variables when
3811	calling env set.  Variables can be restricted to only decimal,
3812	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3813	the variables can also be restricted to IP address or MAC address.
3814
3815	The format of the list is:
3816		type_attribute = [s|d|x|b|i|m]
3817		access_attribute = [a|r|o|c]
3818		attributes = type_attribute[access_attribute]
3819		entry = variable_name[:attributes]
3820		list = entry[,list]
3821
3822	The type attributes are:
3823		s - String (default)
3824		d - Decimal
3825		x - Hexadecimal
3826		b - Boolean ([1yYtT|0nNfF])
3827		i - IP address
3828		m - MAC address
3829
3830	The access attributes are:
3831		a - Any (default)
3832		r - Read-only
3833		o - Write-once
3834		c - Change-default
3835
3836	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3837		Define this to a list (string) to define the ".flags"
3838		environment variable in the default or embedded environment.
3839
3840	- CONFIG_ENV_FLAGS_LIST_STATIC
3841		Define this to a list (string) to define validation that
3842		should be done if an entry is not found in the ".flags"
3843		environment variable.  To override a setting in the static
3844		list, simply add an entry for the same variable name to the
3845		".flags" variable.
3846
3847	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3848	regular expression. This allows multiple variables to define the same
3849	flags without explicitly listing them for each variable.
3850
3851- CONFIG_ENV_ACCESS_IGNORE_FORCE
3852	If defined, don't allow the -f switch to env set override variable
3853	access flags.
3854
3855- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3856	This is set by OMAP boards for the max time that reset should
3857	be asserted. See doc/README.omap-reset-time for details on how
3858	the value can be calculated on a given board.
3859
3860- CONFIG_USE_STDINT
3861	If stdint.h is available with your toolchain you can define this
3862	option to enable it. You can provide option 'USE_STDINT=1' when
3863	building U-Boot to enable this.
3864
3865The following definitions that deal with the placement and management
3866of environment data (variable area); in general, we support the
3867following configurations:
3868
3869- CONFIG_BUILD_ENVCRC:
3870
3871	Builds up envcrc with the target environment so that external utils
3872	may easily extract it and embed it in final U-Boot images.
3873
3874- CONFIG_ENV_IS_IN_FLASH:
3875
3876	Define this if the environment is in flash memory.
3877
3878	a) The environment occupies one whole flash sector, which is
3879	   "embedded" in the text segment with the U-Boot code. This
3880	   happens usually with "bottom boot sector" or "top boot
3881	   sector" type flash chips, which have several smaller
3882	   sectors at the start or the end. For instance, such a
3883	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3884	   such a case you would place the environment in one of the
3885	   4 kB sectors - with U-Boot code before and after it. With
3886	   "top boot sector" type flash chips, you would put the
3887	   environment in one of the last sectors, leaving a gap
3888	   between U-Boot and the environment.
3889
3890	- CONFIG_ENV_OFFSET:
3891
3892	   Offset of environment data (variable area) to the
3893	   beginning of flash memory; for instance, with bottom boot
3894	   type flash chips the second sector can be used: the offset
3895	   for this sector is given here.
3896
3897	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3898
3899	- CONFIG_ENV_ADDR:
3900
3901	   This is just another way to specify the start address of
3902	   the flash sector containing the environment (instead of
3903	   CONFIG_ENV_OFFSET).
3904
3905	- CONFIG_ENV_SECT_SIZE:
3906
3907	   Size of the sector containing the environment.
3908
3909
3910	b) Sometimes flash chips have few, equal sized, BIG sectors.
3911	   In such a case you don't want to spend a whole sector for
3912	   the environment.
3913
3914	- CONFIG_ENV_SIZE:
3915
3916	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3917	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3918	   of this flash sector for the environment. This saves
3919	   memory for the RAM copy of the environment.
3920
3921	   It may also save flash memory if you decide to use this
3922	   when your environment is "embedded" within U-Boot code,
3923	   since then the remainder of the flash sector could be used
3924	   for U-Boot code. It should be pointed out that this is
3925	   STRONGLY DISCOURAGED from a robustness point of view:
3926	   updating the environment in flash makes it always
3927	   necessary to erase the WHOLE sector. If something goes
3928	   wrong before the contents has been restored from a copy in
3929	   RAM, your target system will be dead.
3930
3931	- CONFIG_ENV_ADDR_REDUND
3932	  CONFIG_ENV_SIZE_REDUND
3933
3934	   These settings describe a second storage area used to hold
3935	   a redundant copy of the environment data, so that there is
3936	   a valid backup copy in case there is a power failure during
3937	   a "saveenv" operation.
3938
3939BE CAREFUL! Any changes to the flash layout, and some changes to the
3940source code will make it necessary to adapt <board>/u-boot.lds*
3941accordingly!
3942
3943
3944- CONFIG_ENV_IS_IN_NVRAM:
3945
3946	Define this if you have some non-volatile memory device
3947	(NVRAM, battery buffered SRAM) which you want to use for the
3948	environment.
3949
3950	- CONFIG_ENV_ADDR:
3951	- CONFIG_ENV_SIZE:
3952
3953	  These two #defines are used to determine the memory area you
3954	  want to use for environment. It is assumed that this memory
3955	  can just be read and written to, without any special
3956	  provision.
3957
3958BE CAREFUL! The first access to the environment happens quite early
3959in U-Boot initialization (when we try to get the setting of for the
3960console baudrate). You *MUST* have mapped your NVRAM area then, or
3961U-Boot will hang.
3962
3963Please note that even with NVRAM we still use a copy of the
3964environment in RAM: we could work on NVRAM directly, but we want to
3965keep settings there always unmodified except somebody uses "saveenv"
3966to save the current settings.
3967
3968
3969- CONFIG_ENV_IS_IN_EEPROM:
3970
3971	Use this if you have an EEPROM or similar serial access
3972	device and a driver for it.
3973
3974	- CONFIG_ENV_OFFSET:
3975	- CONFIG_ENV_SIZE:
3976
3977	  These two #defines specify the offset and size of the
3978	  environment area within the total memory of your EEPROM.
3979
3980	- CONFIG_SYS_I2C_EEPROM_ADDR:
3981	  If defined, specified the chip address of the EEPROM device.
3982	  The default address is zero.
3983
3984	- CONFIG_SYS_I2C_EEPROM_BUS:
3985	  If defined, specified the i2c bus of the EEPROM device.
3986
3987	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3988	  If defined, the number of bits used to address bytes in a
3989	  single page in the EEPROM device.  A 64 byte page, for example
3990	  would require six bits.
3991
3992	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3993	  If defined, the number of milliseconds to delay between
3994	  page writes.	The default is zero milliseconds.
3995
3996	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3997	  The length in bytes of the EEPROM memory array address.  Note
3998	  that this is NOT the chip address length!
3999
4000	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
4001	  EEPROM chips that implement "address overflow" are ones
4002	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
4003	  address and the extra bits end up in the "chip address" bit
4004	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
4005	  byte chips.
4006
4007	  Note that we consider the length of the address field to
4008	  still be one byte because the extra address bits are hidden
4009	  in the chip address.
4010
4011	- CONFIG_SYS_EEPROM_SIZE:
4012	  The size in bytes of the EEPROM device.
4013
4014	- CONFIG_ENV_EEPROM_IS_ON_I2C
4015	  define this, if you have I2C and SPI activated, and your
4016	  EEPROM, which holds the environment, is on the I2C bus.
4017
4018	- CONFIG_I2C_ENV_EEPROM_BUS
4019	  if you have an Environment on an EEPROM reached over
4020	  I2C muxes, you can define here, how to reach this
4021	  EEPROM. For example:
4022
4023	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
4024
4025	  EEPROM which holds the environment, is reached over
4026	  a pca9547 i2c mux with address 0x70, channel 3.
4027
4028- CONFIG_ENV_IS_IN_DATAFLASH:
4029
4030	Define this if you have a DataFlash memory device which you
4031	want to use for the environment.
4032
4033	- CONFIG_ENV_OFFSET:
4034	- CONFIG_ENV_ADDR:
4035	- CONFIG_ENV_SIZE:
4036
4037	  These three #defines specify the offset and size of the
4038	  environment area within the total memory of your DataFlash placed
4039	  at the specified address.
4040
4041- CONFIG_ENV_IS_IN_SPI_FLASH:
4042
4043	Define this if you have a SPI Flash memory device which you
4044	want to use for the environment.
4045
4046	- CONFIG_ENV_OFFSET:
4047	- CONFIG_ENV_SIZE:
4048
4049	  These two #defines specify the offset and size of the
4050	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
4051	  aligned to an erase sector boundary.
4052
4053	- CONFIG_ENV_SECT_SIZE:
4054
4055	  Define the SPI flash's sector size.
4056
4057	- CONFIG_ENV_OFFSET_REDUND (optional):
4058
4059	  This setting describes a second storage area of CONFIG_ENV_SIZE
4060	  size used to hold a redundant copy of the environment data, so
4061	  that there is a valid backup copy in case there is a power failure
4062	  during a "saveenv" operation. CONFIG_ENV_OFFSET_REDUND must be
4063	  aligned to an erase sector boundary.
4064
4065	- CONFIG_ENV_SPI_BUS (optional):
4066	- CONFIG_ENV_SPI_CS (optional):
4067
4068	  Define the SPI bus and chip select. If not defined they will be 0.
4069
4070	- CONFIG_ENV_SPI_MAX_HZ (optional):
4071
4072	  Define the SPI max work clock. If not defined then use 1MHz.
4073
4074	- CONFIG_ENV_SPI_MODE (optional):
4075
4076	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4077
4078- CONFIG_ENV_IS_IN_REMOTE:
4079
4080	Define this if you have a remote memory space which you
4081	want to use for the local device's environment.
4082
4083	- CONFIG_ENV_ADDR:
4084	- CONFIG_ENV_SIZE:
4085
4086	  These two #defines specify the address and size of the
4087	  environment area within the remote memory space. The
4088	  local device can get the environment from remote memory
4089	  space by SRIO or PCIE links.
4090
4091BE CAREFUL! For some special cases, the local device can not use
4092"saveenv" command. For example, the local device will get the
4093environment stored in a remote NOR flash by SRIO or PCIE link,
4094but it can not erase, write this NOR flash by SRIO or PCIE interface.
4095
4096- CONFIG_ENV_IS_IN_NAND:
4097
4098	Define this if you have a NAND device which you want to use
4099	for the environment.
4100
4101	- CONFIG_ENV_OFFSET:
4102	- CONFIG_ENV_SIZE:
4103
4104	  These two #defines specify the offset and size of the environment
4105	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4106	  aligned to an erase block boundary.
4107
4108	- CONFIG_ENV_OFFSET_REDUND (optional):
4109
4110	  This setting describes a second storage area of CONFIG_ENV_SIZE
4111	  size used to hold a redundant copy of the environment data, so
4112	  that there is a valid backup copy in case there is a power failure
4113	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_REDUND must be
4114	  aligned to an erase block boundary.
4115
4116	- CONFIG_ENV_RANGE (optional):
4117
4118	  Specifies the length of the region in which the environment
4119	  can be written.  This should be a multiple of the NAND device's
4120	  block size.  Specifying a range with more erase blocks than
4121	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4122	  the range to be avoided.
4123
4124	- CONFIG_ENV_OFFSET_OOB (optional):
4125
4126	  Enables support for dynamically retrieving the offset of the
4127	  environment from block zero's out-of-band data.  The
4128	  "nand env.oob" command can be used to record this offset.
4129	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4130	  using CONFIG_ENV_OFFSET_OOB.
4131
4132- CONFIG_NAND_ENV_DST
4133
4134	Defines address in RAM to which the nand_spl code should copy the
4135	environment. If redundant environment is used, it will be copied to
4136	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4137
4138- CONFIG_ENV_IS_IN_UBI:
4139
4140	Define this if you have an UBI volume that you want to use for the
4141	environment.  This has the benefit of wear-leveling the environment
4142	accesses, which is important on NAND.
4143
4144	- CONFIG_ENV_UBI_PART:
4145
4146	  Define this to a string that is the mtd partition containing the UBI.
4147
4148	- CONFIG_ENV_UBI_VOLUME:
4149
4150	  Define this to the name of the volume that you want to store the
4151	  environment in.
4152
4153	- CONFIG_ENV_UBI_VOLUME_REDUND:
4154
4155	  Define this to the name of another volume to store a second copy of
4156	  the environment in.  This will enable redundant environments in UBI.
4157	  It is assumed that both volumes are in the same MTD partition.
4158
4159	- CONFIG_UBI_SILENCE_MSG
4160	- CONFIG_UBIFS_SILENCE_MSG
4161
4162	  You will probably want to define these to avoid a really noisy system
4163	  when storing the env in UBI.
4164
4165- CONFIG_ENV_IS_IN_FAT:
4166       Define this if you want to use the FAT file system for the environment.
4167
4168       - FAT_ENV_INTERFACE:
4169
4170         Define this to a string that is the name of the block device.
4171
4172       - FAT_ENV_DEV_AND_PART:
4173
4174         Define this to a string to specify the partition of the device. It can
4175         be as following:
4176
4177           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4178               - "D:P": device D partition P. Error occurs if device D has no
4179                        partition table.
4180               - "D:0": device D.
4181               - "D" or "D:": device D partition 1 if device D has partition
4182                              table, or the whole device D if has no partition
4183                              table.
4184               - "D:auto": first partition in device D with bootable flag set.
4185                           If none, first valid partition in device D. If no
4186                           partition table then means device D.
4187
4188       - FAT_ENV_FILE:
4189
4190         It's a string of the FAT file name. This file use to store the
4191         environment.
4192
4193       - CONFIG_FAT_WRITE:
4194         This should be defined. Otherwise it cannot save the environment file.
4195
4196- CONFIG_ENV_IS_IN_MMC:
4197
4198	Define this if you have an MMC device which you want to use for the
4199	environment.
4200
4201	- CONFIG_SYS_MMC_ENV_DEV:
4202
4203	  Specifies which MMC device the environment is stored in.
4204
4205	- CONFIG_SYS_MMC_ENV_PART (optional):
4206
4207	  Specifies which MMC partition the environment is stored in. If not
4208	  set, defaults to partition 0, the user area. Common values might be
4209	  1 (first MMC boot partition), 2 (second MMC boot partition).
4210
4211	- CONFIG_ENV_OFFSET:
4212	- CONFIG_ENV_SIZE:
4213
4214	  These two #defines specify the offset and size of the environment
4215	  area within the specified MMC device.
4216
4217	  If offset is positive (the usual case), it is treated as relative to
4218	  the start of the MMC partition. If offset is negative, it is treated
4219	  as relative to the end of the MMC partition. This can be useful if
4220	  your board may be fitted with different MMC devices, which have
4221	  different sizes for the MMC partitions, and you always want the
4222	  environment placed at the very end of the partition, to leave the
4223	  maximum possible space before it, to store other data.
4224
4225	  These two values are in units of bytes, but must be aligned to an
4226	  MMC sector boundary.
4227
4228	- CONFIG_ENV_OFFSET_REDUND (optional):
4229
4230	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4231	  hold a redundant copy of the environment data. This provides a
4232	  valid backup copy in case the other copy is corrupted, e.g. due
4233	  to a power failure during a "saveenv" operation.
4234
4235	  This value may also be positive or negative; this is handled in the
4236	  same way as CONFIG_ENV_OFFSET.
4237
4238	  This value is also in units of bytes, but must also be aligned to
4239	  an MMC sector boundary.
4240
4241	- CONFIG_ENV_SIZE_REDUND (optional):
4242
4243	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4244	  set. If this value is set, it must be set to the same value as
4245	  CONFIG_ENV_SIZE.
4246
4247- CONFIG_SYS_SPI_INIT_OFFSET
4248
4249	Defines offset to the initial SPI buffer area in DPRAM. The
4250	area is used at an early stage (ROM part) if the environment
4251	is configured to reside in the SPI EEPROM: We need a 520 byte
4252	scratch DPRAM area. It is used between the two initialization
4253	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4254	to be a good choice since it makes it far enough from the
4255	start of the data area as well as from the stack pointer.
4256
4257Please note that the environment is read-only until the monitor
4258has been relocated to RAM and a RAM copy of the environment has been
4259created; also, when using EEPROM you will have to use getenv_f()
4260until then to read environment variables.
4261
4262The environment is protected by a CRC32 checksum. Before the monitor
4263is relocated into RAM, as a result of a bad CRC you will be working
4264with the compiled-in default environment - *silently*!!! [This is
4265necessary, because the first environment variable we need is the
4266"baudrate" setting for the console - if we have a bad CRC, we don't
4267have any device yet where we could complain.]
4268
4269Note: once the monitor has been relocated, then it will complain if
4270the default environment is used; a new CRC is computed as soon as you
4271use the "saveenv" command to store a valid environment.
4272
4273- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4274		Echo the inverted Ethernet link state to the fault LED.
4275
4276		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4277		      also needs to be defined.
4278
4279- CONFIG_SYS_FAULT_MII_ADDR:
4280		MII address of the PHY to check for the Ethernet link state.
4281
4282- CONFIG_NS16550_MIN_FUNCTIONS:
4283		Define this if you desire to only have use of the NS16550_init
4284		and NS16550_putc functions for the serial driver located at
4285		drivers/serial/ns16550.c.  This option is useful for saving
4286		space for already greatly restricted images, including but not
4287		limited to NAND_SPL configurations.
4288
4289- CONFIG_DISPLAY_BOARDINFO
4290		Display information about the board that U-Boot is running on
4291		when U-Boot starts up. The board function checkboard() is called
4292		to do this.
4293
4294- CONFIG_DISPLAY_BOARDINFO_LATE
4295		Similar to the previous option, but display this information
4296		later, once stdio is running and output goes to the LCD, if
4297		present.
4298
4299- CONFIG_BOARD_SIZE_LIMIT:
4300		Maximum size of the U-Boot image. When defined, the
4301		build system checks that the actual size does not
4302		exceed it.
4303
4304Low Level (hardware related) configuration options:
4305---------------------------------------------------
4306
4307- CONFIG_SYS_CACHELINE_SIZE:
4308		Cache Line Size of the CPU.
4309
4310- CONFIG_SYS_DEFAULT_IMMR:
4311		Default address of the IMMR after system reset.
4312
4313		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4314		and RPXsuper) to be able to adjust the position of
4315		the IMMR register after a reset.
4316
4317- CONFIG_SYS_CCSRBAR_DEFAULT:
4318		Default (power-on reset) physical address of CCSR on Freescale
4319		PowerPC SOCs.
4320
4321- CONFIG_SYS_CCSRBAR:
4322		Virtual address of CCSR.  On a 32-bit build, this is typically
4323		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4324
4325		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4326		for cross-platform code that uses that macro instead.
4327
4328- CONFIG_SYS_CCSRBAR_PHYS:
4329		Physical address of CCSR.  CCSR can be relocated to a new
4330		physical address, if desired.  In this case, this macro should
4331		be set to that address.	 Otherwise, it should be set to the
4332		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4333		is typically relocated on 36-bit builds.  It is recommended
4334		that this macro be defined via the _HIGH and _LOW macros:
4335
4336		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4337			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4338
4339- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4340		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4341		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4342		used in assembly code, so it must not contain typecasts or
4343		integer size suffixes (e.g. "ULL").
4344
4345- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4346		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4347		used in assembly code, so it must not contain typecasts or
4348		integer size suffixes (e.g. "ULL").
4349
4350- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4351		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4352		forced to a value that ensures that CCSR is not relocated.
4353
4354- Floppy Disk Support:
4355		CONFIG_SYS_FDC_DRIVE_NUMBER
4356
4357		the default drive number (default value 0)
4358
4359		CONFIG_SYS_ISA_IO_STRIDE
4360
4361		defines the spacing between FDC chipset registers
4362		(default value 1)
4363
4364		CONFIG_SYS_ISA_IO_OFFSET
4365
4366		defines the offset of register from address. It
4367		depends on which part of the data bus is connected to
4368		the FDC chipset. (default value 0)
4369
4370		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4371		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4372		default value.
4373
4374		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4375		fdc_hw_init() is called at the beginning of the FDC
4376		setup. fdc_hw_init() must be provided by the board
4377		source code. It is used to make hardware-dependent
4378		initializations.
4379
4380- CONFIG_IDE_AHB:
4381		Most IDE controllers were designed to be connected with PCI
4382		interface. Only few of them were designed for AHB interface.
4383		When software is doing ATA command and data transfer to
4384		IDE devices through IDE-AHB controller, some additional
4385		registers accessing to these kind of IDE-AHB controller
4386		is required.
4387
4388- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4389		DO NOT CHANGE unless you know exactly what you're
4390		doing! (11-4) [MPC8xx/82xx systems only]
4391
4392- CONFIG_SYS_INIT_RAM_ADDR:
4393
4394		Start address of memory area that can be used for
4395		initial data and stack; please note that this must be
4396		writable memory that is working WITHOUT special
4397		initialization, i. e. you CANNOT use normal RAM which
4398		will become available only after programming the
4399		memory controller and running certain initialization
4400		sequences.
4401
4402		U-Boot uses the following memory types:
4403		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4404		- MPC824X: data cache
4405		- PPC4xx:  data cache
4406
4407- CONFIG_SYS_GBL_DATA_OFFSET:
4408
4409		Offset of the initial data structure in the memory
4410		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4411		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4412		data is located at the end of the available space
4413		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4414		GENERATED_GBL_DATA_SIZE), and the initial stack is just
4415		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4416		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4417
4418	Note:
4419		On the MPC824X (or other systems that use the data
4420		cache for initial memory) the address chosen for
4421		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4422		point to an otherwise UNUSED address space between
4423		the top of RAM and the start of the PCI space.
4424
4425- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4426
4427- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4428
4429- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4430
4431- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4432
4433- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4434
4435- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4436
4437- CONFIG_SYS_OR_TIMING_SDRAM:
4438		SDRAM timing
4439
4440- CONFIG_SYS_MAMR_PTA:
4441		periodic timer for refresh
4442
4443- CONFIG_SYS_DER:	Debug Event Register (37-47)
4444
4445- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4446  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4447  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4448  CONFIG_SYS_BR1_PRELIM:
4449		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4450
4451- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4452  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4453  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4454		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4455
4456- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4457  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4458		Machine Mode Register and Memory Periodic Timer
4459		Prescaler definitions (SDRAM timing)
4460
4461- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4462		enable I2C microcode relocation patch (MPC8xx);
4463		define relocation offset in DPRAM [DSP2]
4464
4465- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4466		enable SMC microcode relocation patch (MPC8xx);
4467		define relocation offset in DPRAM [SMC1]
4468
4469- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4470		enable SPI microcode relocation patch (MPC8xx);
4471		define relocation offset in DPRAM [SCC4]
4472
4473- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4474		Offset of the bootmode word in DPRAM used by post
4475		(Power On Self Tests). This definition overrides
4476		#define'd default value in commproc.h resp.
4477		cpm_8260.h.
4478
4479- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4480  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4481  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4482  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4483  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4484  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4485  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4486  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4487		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4488
4489- CONFIG_PCI_DISABLE_PCIE:
4490		Disable PCI-Express on systems where it is supported but not
4491		required.
4492
4493- CONFIG_PCI_ENUM_ONLY
4494		Only scan through and get the devices on the buses.
4495		Don't do any setup work, presumably because someone or
4496		something has already done it, and we don't need to do it
4497		a second time.	Useful for platforms that are pre-booted
4498		by coreboot or similar.
4499
4500- CONFIG_PCI_INDIRECT_BRIDGE:
4501		Enable support for indirect PCI bridges.
4502
4503- CONFIG_SYS_SRIO:
4504		Chip has SRIO or not
4505
4506- CONFIG_SRIO1:
4507		Board has SRIO 1 port available
4508
4509- CONFIG_SRIO2:
4510		Board has SRIO 2 port available
4511
4512- CONFIG_SRIO_PCIE_BOOT_MASTER
4513		Board can support master function for Boot from SRIO and PCIE
4514
4515- CONFIG_SYS_SRIOn_MEM_VIRT:
4516		Virtual Address of SRIO port 'n' memory region
4517
4518- CONFIG_SYS_SRIOn_MEM_PHYS:
4519		Physical Address of SRIO port 'n' memory region
4520
4521- CONFIG_SYS_SRIOn_MEM_SIZE:
4522		Size of SRIO port 'n' memory region
4523
4524- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4525		Defined to tell the NAND controller that the NAND chip is using
4526		a 16 bit bus.
4527		Not all NAND drivers use this symbol.
4528		Example of drivers that use it:
4529		- drivers/mtd/nand/ndfc.c
4530		- drivers/mtd/nand/mxc_nand.c
4531
4532- CONFIG_SYS_NDFC_EBC0_CFG
4533		Sets the EBC0_CFG register for the NDFC. If not defined
4534		a default value will be used.
4535
4536- CONFIG_SPD_EEPROM
4537		Get DDR timing information from an I2C EEPROM. Common
4538		with pluggable memory modules such as SODIMMs
4539
4540  SPD_EEPROM_ADDRESS
4541		I2C address of the SPD EEPROM
4542
4543- CONFIG_SYS_SPD_BUS_NUM
4544		If SPD EEPROM is on an I2C bus other than the first
4545		one, specify here. Note that the value must resolve
4546		to something your driver can deal with.
4547
4548- CONFIG_SYS_DDR_RAW_TIMING
4549		Get DDR timing information from other than SPD. Common with
4550		soldered DDR chips onboard without SPD. DDR raw timing
4551		parameters are extracted from datasheet and hard-coded into
4552		header files or board specific files.
4553
4554- CONFIG_FSL_DDR_INTERACTIVE
4555		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4556
4557- CONFIG_FSL_DDR_SYNC_REFRESH
4558		Enable sync of refresh for multiple controllers.
4559
4560- CONFIG_FSL_DDR_BIST
4561		Enable built-in memory test for Freescale DDR controllers.
4562
4563- CONFIG_SYS_83XX_DDR_USES_CS0
4564		Only for 83xx systems. If specified, then DDR should
4565		be configured using CS0 and CS1 instead of CS2 and CS3.
4566
4567- CONFIG_ETHER_ON_FEC[12]
4568		Define to enable FEC[12] on a 8xx series processor.
4569
4570- CONFIG_FEC[12]_PHY
4571		Define to the hardcoded PHY address which corresponds
4572		to the given FEC; i. e.
4573			#define CONFIG_FEC1_PHY 4
4574		means that the PHY with address 4 is connected to FEC1
4575
4576		When set to -1, means to probe for first available.
4577
4578- CONFIG_FEC[12]_PHY_NORXERR
4579		The PHY does not have a RXERR line (RMII only).
4580		(so program the FEC to ignore it).
4581
4582- CONFIG_RMII
4583		Enable RMII mode for all FECs.
4584		Note that this is a global option, we can't
4585		have one FEC in standard MII mode and another in RMII mode.
4586
4587- CONFIG_CRC32_VERIFY
4588		Add a verify option to the crc32 command.
4589		The syntax is:
4590
4591		=> crc32 -v <address> <count> <crc32>
4592
4593		Where address/count indicate a memory area
4594		and crc32 is the correct crc32 which the
4595		area should have.
4596
4597- CONFIG_LOOPW
4598		Add the "loopw" memory command. This only takes effect if
4599		the memory commands are activated globally (CONFIG_CMD_MEM).
4600
4601- CONFIG_MX_CYCLIC
4602		Add the "mdc" and "mwc" memory commands. These are cyclic
4603		"md/mw" commands.
4604		Examples:
4605
4606		=> mdc.b 10 4 500
4607		This command will print 4 bytes (10,11,12,13) each 500 ms.
4608
4609		=> mwc.l 100 12345678 10
4610		This command will write 12345678 to address 100 all 10 ms.
4611
4612		This only takes effect if the memory commands are activated
4613		globally (CONFIG_CMD_MEM).
4614
4615- CONFIG_SKIP_LOWLEVEL_INIT
4616		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4617		low level initializations (like setting up the memory
4618		controller) are omitted and/or U-Boot does not
4619		relocate itself into RAM.
4620
4621		Normally this variable MUST NOT be defined. The only
4622		exception is when U-Boot is loaded (to RAM) by some
4623		other boot loader or by a debugger which performs
4624		these initializations itself.
4625
4626- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
4627		[ARM926EJ-S only] This allows just the call to lowlevel_init()
4628		to be skipped. The normal CP15 init (such as enabling the
4629		instruction cache) is still performed.
4630
4631- CONFIG_SPL_BUILD
4632		Modifies the behaviour of start.S when compiling a loader
4633		that is executed before the actual U-Boot. E.g. when
4634		compiling a NAND SPL.
4635
4636- CONFIG_TPL_BUILD
4637		Modifies the behaviour of start.S  when compiling a loader
4638		that is executed after the SPL and before the actual U-Boot.
4639		It is loaded by the SPL.
4640
4641- CONFIG_SYS_MPC85XX_NO_RESETVEC
4642		Only for 85xx systems. If this variable is specified, the section
4643		.resetvec is not kept and the section .bootpg is placed in the
4644		previous 4k of the .text section.
4645
4646- CONFIG_ARCH_MAP_SYSMEM
4647		Generally U-Boot (and in particular the md command) uses
4648		effective address. It is therefore not necessary to regard
4649		U-Boot address as virtual addresses that need to be translated
4650		to physical addresses. However, sandbox requires this, since
4651		it maintains its own little RAM buffer which contains all
4652		addressable memory. This option causes some memory accesses
4653		to be mapped through map_sysmem() / unmap_sysmem().
4654
4655- CONFIG_USE_ARCH_MEMCPY
4656  CONFIG_USE_ARCH_MEMSET
4657		If these options are used a optimized version of memcpy/memset will
4658		be used if available. These functions may be faster under some
4659		conditions but may increase the binary size.
4660
4661- CONFIG_X86_RESET_VECTOR
4662		If defined, the x86 reset vector code is included. This is not
4663		needed when U-Boot is running from Coreboot.
4664
4665- CONFIG_SYS_MPUCLK
4666		Defines the MPU clock speed (in MHz).
4667
4668		NOTE : currently only supported on AM335x platforms.
4669
4670- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4671		Enables the RTC32K OSC on AM33xx based plattforms
4672
4673- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4674		Option to disable subpage write in NAND driver
4675		driver that uses this:
4676		drivers/mtd/nand/davinci_nand.c
4677
4678Freescale QE/FMAN Firmware Support:
4679-----------------------------------
4680
4681The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4682loading of "firmware", which is encoded in the QE firmware binary format.
4683This firmware often needs to be loaded during U-Boot booting, so macros
4684are used to identify the storage device (NOR flash, SPI, etc) and the address
4685within that device.
4686
4687- CONFIG_SYS_FMAN_FW_ADDR
4688	The address in the storage device where the FMAN microcode is located.  The
4689	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4690	is also specified.
4691
4692- CONFIG_SYS_QE_FW_ADDR
4693	The address in the storage device where the QE microcode is located.  The
4694	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4695	is also specified.
4696
4697- CONFIG_SYS_QE_FMAN_FW_LENGTH
4698	The maximum possible size of the firmware.  The firmware binary format
4699	has a field that specifies the actual size of the firmware, but it
4700	might not be possible to read any part of the firmware unless some
4701	local storage is allocated to hold the entire firmware first.
4702
4703- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4704	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4705	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4706	virtual address in NOR flash.
4707
4708- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4709	Specifies that QE/FMAN firmware is located in NAND flash.
4710	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4711
4712- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4713	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4714	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4715
4716- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4717	Specifies that QE/FMAN firmware is located in the remote (master)
4718	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4719	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4720	window->master inbound window->master LAW->the ucode address in
4721	master's memory space.
4722
4723Freescale Layerscape Management Complex Firmware Support:
4724---------------------------------------------------------
4725The Freescale Layerscape Management Complex (MC) supports the loading of
4726"firmware".
4727This firmware often needs to be loaded during U-Boot booting, so macros
4728are used to identify the storage device (NOR flash, SPI, etc) and the address
4729within that device.
4730
4731- CONFIG_FSL_MC_ENET
4732	Enable the MC driver for Layerscape SoCs.
4733
4734Freescale Layerscape Debug Server Support:
4735-------------------------------------------
4736The Freescale Layerscape Debug Server Support supports the loading of
4737"Debug Server firmware" and triggering SP boot-rom.
4738This firmware often needs to be loaded during U-Boot booting.
4739
4740- CONFIG_SYS_MC_RSV_MEM_ALIGN
4741	Define alignment of reserved memory MC requires
4742
4743Reproducible builds
4744-------------------
4745
4746In order to achieve reproducible builds, timestamps used in the U-Boot build
4747process have to be set to a fixed value.
4748
4749This is done using the SOURCE_DATE_EPOCH environment variable.
4750SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
4751option for U-Boot or an environment variable in U-Boot.
4752
4753SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
4754
4755Building the Software:
4756======================
4757
4758Building U-Boot has been tested in several native build environments
4759and in many different cross environments. Of course we cannot support
4760all possibly existing versions of cross development tools in all
4761(potentially obsolete) versions. In case of tool chain problems we
4762recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4763which is extensively used to build and test U-Boot.
4764
4765If you are not using a native environment, it is assumed that you
4766have GNU cross compiling tools available in your path. In this case,
4767you must set the environment variable CROSS_COMPILE in your shell.
4768Note that no changes to the Makefile or any other source files are
4769necessary. For example using the ELDK on a 4xx CPU, please enter:
4770
4771	$ CROSS_COMPILE=ppc_4xx-
4772	$ export CROSS_COMPILE
4773
4774Note: If you wish to generate Windows versions of the utilities in
4775      the tools directory you can use the MinGW toolchain
4776      (http://www.mingw.org).  Set your HOST tools to the MinGW
4777      toolchain and execute 'make tools'.  For example:
4778
4779       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4780
4781      Binaries such as tools/mkimage.exe will be created which can
4782      be executed on computers running Windows.
4783
4784U-Boot is intended to be simple to build. After installing the
4785sources you must configure U-Boot for one specific board type. This
4786is done by typing:
4787
4788	make NAME_defconfig
4789
4790where "NAME_defconfig" is the name of one of the existing configu-
4791rations; see boards.cfg for supported names.
4792
4793Note: for some board special configuration names may exist; check if
4794      additional information is available from the board vendor; for
4795      instance, the TQM823L systems are available without (standard)
4796      or with LCD support. You can select such additional "features"
4797      when choosing the configuration, i. e.
4798
4799      make TQM823L_defconfig
4800	- will configure for a plain TQM823L, i. e. no LCD support
4801
4802      make TQM823L_LCD_defconfig
4803	- will configure for a TQM823L with U-Boot console on LCD
4804
4805      etc.
4806
4807
4808Finally, type "make all", and you should get some working U-Boot
4809images ready for download to / installation on your system:
4810
4811- "u-boot.bin" is a raw binary image
4812- "u-boot" is an image in ELF binary format
4813- "u-boot.srec" is in Motorola S-Record format
4814
4815By default the build is performed locally and the objects are saved
4816in the source directory. One of the two methods can be used to change
4817this behavior and build U-Boot to some external directory:
4818
48191. Add O= to the make command line invocations:
4820
4821	make O=/tmp/build distclean
4822	make O=/tmp/build NAME_defconfig
4823	make O=/tmp/build all
4824
48252. Set environment variable KBUILD_OUTPUT to point to the desired location:
4826
4827	export KBUILD_OUTPUT=/tmp/build
4828	make distclean
4829	make NAME_defconfig
4830	make all
4831
4832Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
4833variable.
4834
4835
4836Please be aware that the Makefiles assume you are using GNU make, so
4837for instance on NetBSD you might need to use "gmake" instead of
4838native "make".
4839
4840
4841If the system board that you have is not listed, then you will need
4842to port U-Boot to your hardware platform. To do this, follow these
4843steps:
4844
48451.  Create a new directory to hold your board specific code. Add any
4846    files you need. In your board directory, you will need at least
4847    the "Makefile" and a "<board>.c".
48482.  Create a new configuration file "include/configs/<board>.h" for
4849    your board.
48503.  If you're porting U-Boot to a new CPU, then also create a new
4851    directory to hold your CPU specific code. Add any files you need.
48524.  Run "make <board>_defconfig" with your new name.
48535.  Type "make", and you should get a working "u-boot.srec" file
4854    to be installed on your target system.
48556.  Debug and solve any problems that might arise.
4856    [Of course, this last step is much harder than it sounds.]
4857
4858
4859Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4860==============================================================
4861
4862If you have modified U-Boot sources (for instance added a new board
4863or support for new devices, a new CPU, etc.) you are expected to
4864provide feedback to the other developers. The feedback normally takes
4865the form of a "patch", i. e. a context diff against a certain (latest
4866official or latest in the git repository) version of U-Boot sources.
4867
4868But before you submit such a patch, please verify that your modifi-
4869cation did not break existing code. At least make sure that *ALL* of
4870the supported boards compile WITHOUT ANY compiler warnings. To do so,
4871just run the buildman script (tools/buildman/buildman), which will
4872configure and build U-Boot for ALL supported system. Be warned, this
4873will take a while. Please see the buildman README, or run 'buildman -H'
4874for documentation.
4875
4876
4877See also "U-Boot Porting Guide" below.
4878
4879
4880Monitor Commands - Overview:
4881============================
4882
4883go	- start application at address 'addr'
4884run	- run commands in an environment variable
4885bootm	- boot application image from memory
4886bootp	- boot image via network using BootP/TFTP protocol
4887bootz   - boot zImage from memory
4888tftpboot- boot image via network using TFTP protocol
4889	       and env variables "ipaddr" and "serverip"
4890	       (and eventually "gatewayip")
4891tftpput - upload a file via network using TFTP protocol
4892rarpboot- boot image via network using RARP/TFTP protocol
4893diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4894loads	- load S-Record file over serial line
4895loadb	- load binary file over serial line (kermit mode)
4896md	- memory display
4897mm	- memory modify (auto-incrementing)
4898nm	- memory modify (constant address)
4899mw	- memory write (fill)
4900cp	- memory copy
4901cmp	- memory compare
4902crc32	- checksum calculation
4903i2c	- I2C sub-system
4904sspi	- SPI utility commands
4905base	- print or set address offset
4906printenv- print environment variables
4907setenv	- set environment variables
4908saveenv - save environment variables to persistent storage
4909protect - enable or disable FLASH write protection
4910erase	- erase FLASH memory
4911flinfo	- print FLASH memory information
4912nand	- NAND memory operations (see doc/README.nand)
4913bdinfo	- print Board Info structure
4914iminfo	- print header information for application image
4915coninfo - print console devices and informations
4916ide	- IDE sub-system
4917loop	- infinite loop on address range
4918loopw	- infinite write loop on address range
4919mtest	- simple RAM test
4920icache	- enable or disable instruction cache
4921dcache	- enable or disable data cache
4922reset	- Perform RESET of the CPU
4923echo	- echo args to console
4924version - print monitor version
4925help	- print online help
4926?	- alias for 'help'
4927
4928
4929Monitor Commands - Detailed Description:
4930========================================
4931
4932TODO.
4933
4934For now: just type "help <command>".
4935
4936
4937Environment Variables:
4938======================
4939
4940U-Boot supports user configuration using Environment Variables which
4941can be made persistent by saving to Flash memory.
4942
4943Environment Variables are set using "setenv", printed using
4944"printenv", and saved to Flash using "saveenv". Using "setenv"
4945without a value can be used to delete a variable from the
4946environment. As long as you don't save the environment you are
4947working with an in-memory copy. In case the Flash area containing the
4948environment is erased by accident, a default environment is provided.
4949
4950Some configuration options can be set using Environment Variables.
4951
4952List of environment variables (most likely not complete):
4953
4954  baudrate	- see CONFIG_BAUDRATE
4955
4956  bootdelay	- see CONFIG_BOOTDELAY
4957
4958  bootcmd	- see CONFIG_BOOTCOMMAND
4959
4960  bootargs	- Boot arguments when booting an RTOS image
4961
4962  bootfile	- Name of the image to load with TFTP
4963
4964  bootm_low	- Memory range available for image processing in the bootm
4965		  command can be restricted. This variable is given as
4966		  a hexadecimal number and defines lowest address allowed
4967		  for use by the bootm command. See also "bootm_size"
4968		  environment variable. Address defined by "bootm_low" is
4969		  also the base of the initial memory mapping for the Linux
4970		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4971		  bootm_mapsize.
4972
4973  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4974		  This variable is given as a hexadecimal number and it
4975		  defines the size of the memory region starting at base
4976		  address bootm_low that is accessible by the Linux kernel
4977		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4978		  as the default value if it is defined, and bootm_size is
4979		  used otherwise.
4980
4981  bootm_size	- Memory range available for image processing in the bootm
4982		  command can be restricted. This variable is given as
4983		  a hexadecimal number and defines the size of the region
4984		  allowed for use by the bootm command. See also "bootm_low"
4985		  environment variable.
4986
4987  updatefile	- Location of the software update file on a TFTP server, used
4988		  by the automatic software update feature. Please refer to
4989		  documentation in doc/README.update for more details.
4990
4991  autoload	- if set to "no" (any string beginning with 'n'),
4992		  "bootp" will just load perform a lookup of the
4993		  configuration from the BOOTP server, but not try to
4994		  load any image using TFTP
4995
4996  autostart	- if set to "yes", an image loaded using the "bootp",
4997		  "rarpboot", "tftpboot" or "diskboot" commands will
4998		  be automatically started (by internally calling
4999		  "bootm")
5000
5001		  If set to "no", a standalone image passed to the
5002		  "bootm" command will be copied to the load address
5003		  (and eventually uncompressed), but NOT be started.
5004		  This can be used to load and uncompress arbitrary
5005		  data.
5006
5007  fdt_high	- if set this restricts the maximum address that the
5008		  flattened device tree will be copied into upon boot.
5009		  For example, if you have a system with 1 GB memory
5010		  at physical address 0x10000000, while Linux kernel
5011		  only recognizes the first 704 MB as low memory, you
5012		  may need to set fdt_high as 0x3C000000 to have the
5013		  device tree blob be copied to the maximum address
5014		  of the 704 MB low memory, so that Linux kernel can
5015		  access it during the boot procedure.
5016
5017		  If this is set to the special value 0xFFFFFFFF then
5018		  the fdt will not be copied at all on boot.  For this
5019		  to work it must reside in writable memory, have
5020		  sufficient padding on the end of it for u-boot to
5021		  add the information it needs into it, and the memory
5022		  must be accessible by the kernel.
5023
5024  fdtcontroladdr- if set this is the address of the control flattened
5025		  device tree used by U-Boot when CONFIG_OF_CONTROL is
5026		  defined.
5027
5028  i2cfast	- (PPC405GP|PPC405EP only)
5029		  if set to 'y' configures Linux I2C driver for fast
5030		  mode (400kHZ). This environment variable is used in
5031		  initialization code. So, for changes to be effective
5032		  it must be saved and board must be reset.
5033
5034  initrd_high	- restrict positioning of initrd images:
5035		  If this variable is not set, initrd images will be
5036		  copied to the highest possible address in RAM; this
5037		  is usually what you want since it allows for
5038		  maximum initrd size. If for some reason you want to
5039		  make sure that the initrd image is loaded below the
5040		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
5041		  variable to a value of "no" or "off" or "0".
5042		  Alternatively, you can set it to a maximum upper
5043		  address to use (U-Boot will still check that it
5044		  does not overwrite the U-Boot stack and data).
5045
5046		  For instance, when you have a system with 16 MB
5047		  RAM, and want to reserve 4 MB from use by Linux,
5048		  you can do this by adding "mem=12M" to the value of
5049		  the "bootargs" variable. However, now you must make
5050		  sure that the initrd image is placed in the first
5051		  12 MB as well - this can be done with
5052
5053		  setenv initrd_high 00c00000
5054
5055		  If you set initrd_high to 0xFFFFFFFF, this is an
5056		  indication to U-Boot that all addresses are legal
5057		  for the Linux kernel, including addresses in flash
5058		  memory. In this case U-Boot will NOT COPY the
5059		  ramdisk at all. This may be useful to reduce the
5060		  boot time on your system, but requires that this
5061		  feature is supported by your Linux kernel.
5062
5063  ipaddr	- IP address; needed for tftpboot command
5064
5065  loadaddr	- Default load address for commands like "bootp",
5066		  "rarpboot", "tftpboot", "loadb" or "diskboot"
5067
5068  loads_echo	- see CONFIG_LOADS_ECHO
5069
5070  serverip	- TFTP server IP address; needed for tftpboot command
5071
5072  bootretry	- see CONFIG_BOOT_RETRY_TIME
5073
5074  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5075
5076  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5077
5078  ethprime	- controls which interface is used first.
5079
5080  ethact	- controls which interface is currently active.
5081		  For example you can do the following
5082
5083		  => setenv ethact FEC
5084		  => ping 192.168.0.1 # traffic sent on FEC
5085		  => setenv ethact SCC
5086		  => ping 10.0.0.1 # traffic sent on SCC
5087
5088  ethrotate	- When set to "no" U-Boot does not go through all
5089		  available network interfaces.
5090		  It just stays at the currently selected interface.
5091
5092  netretry	- When set to "no" each network operation will
5093		  either succeed or fail without retrying.
5094		  When set to "once" the network operation will
5095		  fail when all the available network interfaces
5096		  are tried once without success.
5097		  Useful on scripts which control the retry operation
5098		  themselves.
5099
5100  npe_ucode	- set load address for the NPE microcode
5101
5102  silent_linux  - If set then Linux will be told to boot silently, by
5103		  changing the console to be empty. If "yes" it will be
5104		  made silent. If "no" it will not be made silent. If
5105		  unset, then it will be made silent if the U-Boot console
5106		  is silent.
5107
5108  tftpsrcp	- If this is set, the value is used for TFTP's
5109		  UDP source port.
5110
5111  tftpdstp	- If this is set, the value is used for TFTP's UDP
5112		  destination port instead of the Well Know Port 69.
5113
5114  tftpblocksize - Block size to use for TFTP transfers; if not set,
5115		  we use the TFTP server's default block size
5116
5117  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5118		  seconds, minimum value is 1000 = 1 second). Defines
5119		  when a packet is considered to be lost so it has to
5120		  be retransmitted. The default is 5000 = 5 seconds.
5121		  Lowering this value may make downloads succeed
5122		  faster in networks with high packet loss rates or
5123		  with unreliable TFTP servers.
5124
5125  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
5126		  unit, minimum value = 0). Defines how many timeouts
5127		  can happen during a single file transfer before that
5128		  transfer is aborted. The default is 10, and 0 means
5129		  'no timeouts allowed'. Increasing this value may help
5130		  downloads succeed with high packet loss rates, or with
5131		  unreliable TFTP servers or client hardware.
5132
5133  vlan		- When set to a value < 4095 the traffic over
5134		  Ethernet is encapsulated/received over 802.1q
5135		  VLAN tagged frames.
5136
5137  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
5138		  Unsigned value, in milliseconds. If not set, the period will
5139		  be either the default (28000), or a value based on
5140		  CONFIG_NET_RETRY_COUNT, if defined. This value has
5141		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
5142
5143The following image location variables contain the location of images
5144used in booting. The "Image" column gives the role of the image and is
5145not an environment variable name. The other columns are environment
5146variable names. "File Name" gives the name of the file on a TFTP
5147server, "RAM Address" gives the location in RAM the image will be
5148loaded to, and "Flash Location" gives the image's address in NOR
5149flash or offset in NAND flash.
5150
5151*Note* - these variables don't have to be defined for all boards, some
5152boards currently use other variables for these purposes, and some
5153boards use these variables for other purposes.
5154
5155Image		    File Name	     RAM Address       Flash Location
5156-----		    ---------	     -----------       --------------
5157u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5158Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5159device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5160ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5161
5162The following environment variables may be used and automatically
5163updated by the network boot commands ("bootp" and "rarpboot"),
5164depending the information provided by your boot server:
5165
5166  bootfile	- see above
5167  dnsip		- IP address of your Domain Name Server
5168  dnsip2	- IP address of your secondary Domain Name Server
5169  gatewayip	- IP address of the Gateway (Router) to use
5170  hostname	- Target hostname
5171  ipaddr	- see above
5172  netmask	- Subnet Mask
5173  rootpath	- Pathname of the root filesystem on the NFS server
5174  serverip	- see above
5175
5176
5177There are two special Environment Variables:
5178
5179  serial#	- contains hardware identification information such
5180		  as type string and/or serial number
5181  ethaddr	- Ethernet address
5182
5183These variables can be set only once (usually during manufacturing of
5184the board). U-Boot refuses to delete or overwrite these variables
5185once they have been set once.
5186
5187
5188Further special Environment Variables:
5189
5190  ver		- Contains the U-Boot version string as printed
5191		  with the "version" command. This variable is
5192		  readonly (see CONFIG_VERSION_VARIABLE).
5193
5194
5195Please note that changes to some configuration parameters may take
5196only effect after the next boot (yes, that's just like Windoze :-).
5197
5198
5199Callback functions for environment variables:
5200---------------------------------------------
5201
5202For some environment variables, the behavior of u-boot needs to change
5203when their values are changed.  This functionality allows functions to
5204be associated with arbitrary variables.  On creation, overwrite, or
5205deletion, the callback will provide the opportunity for some side
5206effect to happen or for the change to be rejected.
5207
5208The callbacks are named and associated with a function using the
5209U_BOOT_ENV_CALLBACK macro in your board or driver code.
5210
5211These callbacks are associated with variables in one of two ways.  The
5212static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5213in the board configuration to a string that defines a list of
5214associations.  The list must be in the following format:
5215
5216	entry = variable_name[:callback_name]
5217	list = entry[,list]
5218
5219If the callback name is not specified, then the callback is deleted.
5220Spaces are also allowed anywhere in the list.
5221
5222Callbacks can also be associated by defining the ".callbacks" variable
5223with the same list format above.  Any association in ".callbacks" will
5224override any association in the static list. You can define
5225CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5226".callbacks" environment variable in the default or embedded environment.
5227
5228If CONFIG_REGEX is defined, the variable_name above is evaluated as a
5229regular expression. This allows multiple variables to be connected to
5230the same callback without explicitly listing them all out.
5231
5232
5233Command Line Parsing:
5234=====================
5235
5236There are two different command line parsers available with U-Boot:
5237the old "simple" one, and the much more powerful "hush" shell:
5238
5239Old, simple command line parser:
5240--------------------------------
5241
5242- supports environment variables (through setenv / saveenv commands)
5243- several commands on one line, separated by ';'
5244- variable substitution using "... ${name} ..." syntax
5245- special characters ('$', ';') can be escaped by prefixing with '\',
5246  for example:
5247	setenv bootcmd bootm \${address}
5248- You can also escape text by enclosing in single apostrophes, for example:
5249	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5250
5251Hush shell:
5252-----------
5253
5254- similar to Bourne shell, with control structures like
5255  if...then...else...fi, for...do...done; while...do...done,
5256  until...do...done, ...
5257- supports environment ("global") variables (through setenv / saveenv
5258  commands) and local shell variables (through standard shell syntax
5259  "name=value"); only environment variables can be used with "run"
5260  command
5261
5262General rules:
5263--------------
5264
5265(1) If a command line (or an environment variable executed by a "run"
5266    command) contains several commands separated by semicolon, and
5267    one of these commands fails, then the remaining commands will be
5268    executed anyway.
5269
5270(2) If you execute several variables with one call to run (i. e.
5271    calling run with a list of variables as arguments), any failing
5272    command will cause "run" to terminate, i. e. the remaining
5273    variables are not executed.
5274
5275Note for Redundant Ethernet Interfaces:
5276=======================================
5277
5278Some boards come with redundant Ethernet interfaces; U-Boot supports
5279such configurations and is capable of automatic selection of a
5280"working" interface when needed. MAC assignment works as follows:
5281
5282Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5283MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5284"eth1addr" (=>eth1), "eth2addr", ...
5285
5286If the network interface stores some valid MAC address (for instance
5287in SROM), this is used as default address if there is NO correspon-
5288ding setting in the environment; if the corresponding environment
5289variable is set, this overrides the settings in the card; that means:
5290
5291o If the SROM has a valid MAC address, and there is no address in the
5292  environment, the SROM's address is used.
5293
5294o If there is no valid address in the SROM, and a definition in the
5295  environment exists, then the value from the environment variable is
5296  used.
5297
5298o If both the SROM and the environment contain a MAC address, and
5299  both addresses are the same, this MAC address is used.
5300
5301o If both the SROM and the environment contain a MAC address, and the
5302  addresses differ, the value from the environment is used and a
5303  warning is printed.
5304
5305o If neither SROM nor the environment contain a MAC address, an error
5306  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
5307  a random, locally-assigned MAC is used.
5308
5309If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5310will be programmed into hardware as part of the initialization process.	 This
5311may be skipped by setting the appropriate 'ethmacskip' environment variable.
5312The naming convention is as follows:
5313"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5314
5315Image Formats:
5316==============
5317
5318U-Boot is capable of booting (and performing other auxiliary operations on)
5319images in two formats:
5320
5321New uImage format (FIT)
5322-----------------------
5323
5324Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5325to Flattened Device Tree). It allows the use of images with multiple
5326components (several kernels, ramdisks, etc.), with contents protected by
5327SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5328
5329
5330Old uImage format
5331-----------------
5332
5333Old image format is based on binary files which can be basically anything,
5334preceded by a special header; see the definitions in include/image.h for
5335details; basically, the header defines the following image properties:
5336
5337* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5338  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5339  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5340  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5341  INTEGRITY).
5342* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5343  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5344  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5345* Compression Type (uncompressed, gzip, bzip2)
5346* Load Address
5347* Entry Point
5348* Image Name
5349* Image Timestamp
5350
5351The header is marked by a special Magic Number, and both the header
5352and the data portions of the image are secured against corruption by
5353CRC32 checksums.
5354
5355
5356Linux Support:
5357==============
5358
5359Although U-Boot should support any OS or standalone application
5360easily, the main focus has always been on Linux during the design of
5361U-Boot.
5362
5363U-Boot includes many features that so far have been part of some
5364special "boot loader" code within the Linux kernel. Also, any
5365"initrd" images to be used are no longer part of one big Linux image;
5366instead, kernel and "initrd" are separate images. This implementation
5367serves several purposes:
5368
5369- the same features can be used for other OS or standalone
5370  applications (for instance: using compressed images to reduce the
5371  Flash memory footprint)
5372
5373- it becomes much easier to port new Linux kernel versions because
5374  lots of low-level, hardware dependent stuff are done by U-Boot
5375
5376- the same Linux kernel image can now be used with different "initrd"
5377  images; of course this also means that different kernel images can
5378  be run with the same "initrd". This makes testing easier (you don't
5379  have to build a new "zImage.initrd" Linux image when you just
5380  change a file in your "initrd"). Also, a field-upgrade of the
5381  software is easier now.
5382
5383
5384Linux HOWTO:
5385============
5386
5387Porting Linux to U-Boot based systems:
5388---------------------------------------
5389
5390U-Boot cannot save you from doing all the necessary modifications to
5391configure the Linux device drivers for use with your target hardware
5392(no, we don't intend to provide a full virtual machine interface to
5393Linux :-).
5394
5395But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5396
5397Just make sure your machine specific header file (for instance
5398include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5399Information structure as we define in include/asm-<arch>/u-boot.h,
5400and make sure that your definition of IMAP_ADDR uses the same value
5401as your U-Boot configuration in CONFIG_SYS_IMMR.
5402
5403Note that U-Boot now has a driver model, a unified model for drivers.
5404If you are adding a new driver, plumb it into driver model. If there
5405is no uclass available, you are encouraged to create one. See
5406doc/driver-model.
5407
5408
5409Configuring the Linux kernel:
5410-----------------------------
5411
5412No specific requirements for U-Boot. Make sure you have some root
5413device (initial ramdisk, NFS) for your target system.
5414
5415
5416Building a Linux Image:
5417-----------------------
5418
5419With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5420not used. If you use recent kernel source, a new build target
5421"uImage" will exist which automatically builds an image usable by
5422U-Boot. Most older kernels also have support for a "pImage" target,
5423which was introduced for our predecessor project PPCBoot and uses a
5424100% compatible format.
5425
5426Example:
5427
5428	make TQM850L_defconfig
5429	make oldconfig
5430	make dep
5431	make uImage
5432
5433The "uImage" build target uses a special tool (in 'tools/mkimage') to
5434encapsulate a compressed Linux kernel image with header	 information,
5435CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5436
5437* build a standard "vmlinux" kernel image (in ELF binary format):
5438
5439* convert the kernel into a raw binary image:
5440
5441	${CROSS_COMPILE}-objcopy -O binary \
5442				 -R .note -R .comment \
5443				 -S vmlinux linux.bin
5444
5445* compress the binary image:
5446
5447	gzip -9 linux.bin
5448
5449* package compressed binary image for U-Boot:
5450
5451	mkimage -A ppc -O linux -T kernel -C gzip \
5452		-a 0 -e 0 -n "Linux Kernel Image" \
5453		-d linux.bin.gz uImage
5454
5455
5456The "mkimage" tool can also be used to create ramdisk images for use
5457with U-Boot, either separated from the Linux kernel image, or
5458combined into one file. "mkimage" encapsulates the images with a 64
5459byte header containing information about target architecture,
5460operating system, image type, compression method, entry points, time
5461stamp, CRC32 checksums, etc.
5462
5463"mkimage" can be called in two ways: to verify existing images and
5464print the header information, or to build new images.
5465
5466In the first form (with "-l" option) mkimage lists the information
5467contained in the header of an existing U-Boot image; this includes
5468checksum verification:
5469
5470	tools/mkimage -l image
5471	  -l ==> list image header information
5472
5473The second form (with "-d" option) is used to build a U-Boot image
5474from a "data file" which is used as image payload:
5475
5476	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5477		      -n name -d data_file image
5478	  -A ==> set architecture to 'arch'
5479	  -O ==> set operating system to 'os'
5480	  -T ==> set image type to 'type'
5481	  -C ==> set compression type 'comp'
5482	  -a ==> set load address to 'addr' (hex)
5483	  -e ==> set entry point to 'ep' (hex)
5484	  -n ==> set image name to 'name'
5485	  -d ==> use image data from 'datafile'
5486
5487Right now, all Linux kernels for PowerPC systems use the same load
5488address (0x00000000), but the entry point address depends on the
5489kernel version:
5490
5491- 2.2.x kernels have the entry point at 0x0000000C,
5492- 2.3.x and later kernels have the entry point at 0x00000000.
5493
5494So a typical call to build a U-Boot image would read:
5495
5496	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5497	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5498	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5499	> examples/uImage.TQM850L
5500	Image Name:   2.4.4 kernel for TQM850L
5501	Created:      Wed Jul 19 02:34:59 2000
5502	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5503	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5504	Load Address: 0x00000000
5505	Entry Point:  0x00000000
5506
5507To verify the contents of the image (or check for corruption):
5508
5509	-> tools/mkimage -l examples/uImage.TQM850L
5510	Image Name:   2.4.4 kernel for TQM850L
5511	Created:      Wed Jul 19 02:34:59 2000
5512	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5513	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5514	Load Address: 0x00000000
5515	Entry Point:  0x00000000
5516
5517NOTE: for embedded systems where boot time is critical you can trade
5518speed for memory and install an UNCOMPRESSED image instead: this
5519needs more space in Flash, but boots much faster since it does not
5520need to be uncompressed:
5521
5522	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5523	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5524	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5525	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5526	> examples/uImage.TQM850L-uncompressed
5527	Image Name:   2.4.4 kernel for TQM850L
5528	Created:      Wed Jul 19 02:34:59 2000
5529	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5530	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5531	Load Address: 0x00000000
5532	Entry Point:  0x00000000
5533
5534
5535Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5536when your kernel is intended to use an initial ramdisk:
5537
5538	-> tools/mkimage -n 'Simple Ramdisk Image' \
5539	> -A ppc -O linux -T ramdisk -C gzip \
5540	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5541	Image Name:   Simple Ramdisk Image
5542	Created:      Wed Jan 12 14:01:50 2000
5543	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5544	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5545	Load Address: 0x00000000
5546	Entry Point:  0x00000000
5547
5548The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5549option performs the converse operation of the mkimage's second form (the "-d"
5550option). Given an image built by mkimage, the dumpimage extracts a "data file"
5551from the image:
5552
5553	tools/dumpimage -i image -T type -p position data_file
5554	  -i ==> extract from the 'image' a specific 'data_file'
5555	  -T ==> set image type to 'type'
5556	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5557
5558
5559Installing a Linux Image:
5560-------------------------
5561
5562To downloading a U-Boot image over the serial (console) interface,
5563you must convert the image to S-Record format:
5564
5565	objcopy -I binary -O srec examples/image examples/image.srec
5566
5567The 'objcopy' does not understand the information in the U-Boot
5568image header, so the resulting S-Record file will be relative to
5569address 0x00000000. To load it to a given address, you need to
5570specify the target address as 'offset' parameter with the 'loads'
5571command.
5572
5573Example: install the image to address 0x40100000 (which on the
5574TQM8xxL is in the first Flash bank):
5575
5576	=> erase 40100000 401FFFFF
5577
5578	.......... done
5579	Erased 8 sectors
5580
5581	=> loads 40100000
5582	## Ready for S-Record download ...
5583	~>examples/image.srec
5584	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5585	...
5586	15989 15990 15991 15992
5587	[file transfer complete]
5588	[connected]
5589	## Start Addr = 0x00000000
5590
5591
5592You can check the success of the download using the 'iminfo' command;
5593this includes a checksum verification so you can be sure no data
5594corruption happened:
5595
5596	=> imi 40100000
5597
5598	## Checking Image at 40100000 ...
5599	   Image Name:	 2.2.13 for initrd on TQM850L
5600	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5601	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5602	   Load Address: 00000000
5603	   Entry Point:	 0000000c
5604	   Verifying Checksum ... OK
5605
5606
5607Boot Linux:
5608-----------
5609
5610The "bootm" command is used to boot an application that is stored in
5611memory (RAM or Flash). In case of a Linux kernel image, the contents
5612of the "bootargs" environment variable is passed to the kernel as
5613parameters. You can check and modify this variable using the
5614"printenv" and "setenv" commands:
5615
5616
5617	=> printenv bootargs
5618	bootargs=root=/dev/ram
5619
5620	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5621
5622	=> printenv bootargs
5623	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5624
5625	=> bootm 40020000
5626	## Booting Linux kernel at 40020000 ...
5627	   Image Name:	 2.2.13 for NFS on TQM850L
5628	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5629	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5630	   Load Address: 00000000
5631	   Entry Point:	 0000000c
5632	   Verifying Checksum ... OK
5633	   Uncompressing Kernel Image ... OK
5634	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
5635	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5636	time_init: decrementer frequency = 187500000/60
5637	Calibrating delay loop... 49.77 BogoMIPS
5638	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5639	...
5640
5641If you want to boot a Linux kernel with initial RAM disk, you pass
5642the memory addresses of both the kernel and the initrd image (PPBCOOT
5643format!) to the "bootm" command:
5644
5645	=> imi 40100000 40200000
5646
5647	## Checking Image at 40100000 ...
5648	   Image Name:	 2.2.13 for initrd on TQM850L
5649	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5650	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5651	   Load Address: 00000000
5652	   Entry Point:	 0000000c
5653	   Verifying Checksum ... OK
5654
5655	## Checking Image at 40200000 ...
5656	   Image Name:	 Simple Ramdisk Image
5657	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5658	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5659	   Load Address: 00000000
5660	   Entry Point:	 00000000
5661	   Verifying Checksum ... OK
5662
5663	=> bootm 40100000 40200000
5664	## Booting Linux kernel at 40100000 ...
5665	   Image Name:	 2.2.13 for initrd on TQM850L
5666	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5667	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5668	   Load Address: 00000000
5669	   Entry Point:	 0000000c
5670	   Verifying Checksum ... OK
5671	   Uncompressing Kernel Image ... OK
5672	## Loading RAMDisk Image at 40200000 ...
5673	   Image Name:	 Simple Ramdisk Image
5674	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5675	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5676	   Load Address: 00000000
5677	   Entry Point:	 00000000
5678	   Verifying Checksum ... OK
5679	   Loading Ramdisk ... OK
5680	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
5681	Boot arguments: root=/dev/ram
5682	time_init: decrementer frequency = 187500000/60
5683	Calibrating delay loop... 49.77 BogoMIPS
5684	...
5685	RAMDISK: Compressed image found at block 0
5686	VFS: Mounted root (ext2 filesystem).
5687
5688	bash#
5689
5690Boot Linux and pass a flat device tree:
5691-----------
5692
5693First, U-Boot must be compiled with the appropriate defines. See the section
5694titled "Linux Kernel Interface" above for a more in depth explanation. The
5695following is an example of how to start a kernel and pass an updated
5696flat device tree:
5697
5698=> print oftaddr
5699oftaddr=0x300000
5700=> print oft
5701oft=oftrees/mpc8540ads.dtb
5702=> tftp $oftaddr $oft
5703Speed: 1000, full duplex
5704Using TSEC0 device
5705TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5706Filename 'oftrees/mpc8540ads.dtb'.
5707Load address: 0x300000
5708Loading: #
5709done
5710Bytes transferred = 4106 (100a hex)
5711=> tftp $loadaddr $bootfile
5712Speed: 1000, full duplex
5713Using TSEC0 device
5714TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5715Filename 'uImage'.
5716Load address: 0x200000
5717Loading:############
5718done
5719Bytes transferred = 1029407 (fb51f hex)
5720=> print loadaddr
5721loadaddr=200000
5722=> print oftaddr
5723oftaddr=0x300000
5724=> bootm $loadaddr - $oftaddr
5725## Booting image at 00200000 ...
5726   Image Name:	 Linux-2.6.17-dirty
5727   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5728   Data Size:	 1029343 Bytes = 1005.2 kB
5729   Load Address: 00000000
5730   Entry Point:	 00000000
5731   Verifying Checksum ... OK
5732   Uncompressing Kernel Image ... OK
5733Booting using flat device tree at 0x300000
5734Using MPC85xx ADS machine description
5735Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5736[snip]
5737
5738
5739More About U-Boot Image Types:
5740------------------------------
5741
5742U-Boot supports the following image types:
5743
5744   "Standalone Programs" are directly runnable in the environment
5745	provided by U-Boot; it is expected that (if they behave
5746	well) you can continue to work in U-Boot after return from
5747	the Standalone Program.
5748   "OS Kernel Images" are usually images of some Embedded OS which
5749	will take over control completely. Usually these programs
5750	will install their own set of exception handlers, device
5751	drivers, set up the MMU, etc. - this means, that you cannot
5752	expect to re-enter U-Boot except by resetting the CPU.
5753   "RAMDisk Images" are more or less just data blocks, and their
5754	parameters (address, size) are passed to an OS kernel that is
5755	being started.
5756   "Multi-File Images" contain several images, typically an OS
5757	(Linux) kernel image and one or more data images like
5758	RAMDisks. This construct is useful for instance when you want
5759	to boot over the network using BOOTP etc., where the boot
5760	server provides just a single image file, but you want to get
5761	for instance an OS kernel and a RAMDisk image.
5762
5763	"Multi-File Images" start with a list of image sizes, each
5764	image size (in bytes) specified by an "uint32_t" in network
5765	byte order. This list is terminated by an "(uint32_t)0".
5766	Immediately after the terminating 0 follow the images, one by
5767	one, all aligned on "uint32_t" boundaries (size rounded up to
5768	a multiple of 4 bytes).
5769
5770   "Firmware Images" are binary images containing firmware (like
5771	U-Boot or FPGA images) which usually will be programmed to
5772	flash memory.
5773
5774   "Script files" are command sequences that will be executed by
5775	U-Boot's command interpreter; this feature is especially
5776	useful when you configure U-Boot to use a real shell (hush)
5777	as command interpreter.
5778
5779Booting the Linux zImage:
5780-------------------------
5781
5782On some platforms, it's possible to boot Linux zImage. This is done
5783using the "bootz" command. The syntax of "bootz" command is the same
5784as the syntax of "bootm" command.
5785
5786Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5787kernel with raw initrd images. The syntax is slightly different, the
5788address of the initrd must be augmented by it's size, in the following
5789format: "<initrd addres>:<initrd size>".
5790
5791
5792Standalone HOWTO:
5793=================
5794
5795One of the features of U-Boot is that you can dynamically load and
5796run "standalone" applications, which can use some resources of
5797U-Boot like console I/O functions or interrupt services.
5798
5799Two simple examples are included with the sources:
5800
5801"Hello World" Demo:
5802-------------------
5803
5804'examples/hello_world.c' contains a small "Hello World" Demo
5805application; it is automatically compiled when you build U-Boot.
5806It's configured to run at address 0x00040004, so you can play with it
5807like that:
5808
5809	=> loads
5810	## Ready for S-Record download ...
5811	~>examples/hello_world.srec
5812	1 2 3 4 5 6 7 8 9 10 11 ...
5813	[file transfer complete]
5814	[connected]
5815	## Start Addr = 0x00040004
5816
5817	=> go 40004 Hello World! This is a test.
5818	## Starting application at 0x00040004 ...
5819	Hello World
5820	argc = 7
5821	argv[0] = "40004"
5822	argv[1] = "Hello"
5823	argv[2] = "World!"
5824	argv[3] = "This"
5825	argv[4] = "is"
5826	argv[5] = "a"
5827	argv[6] = "test."
5828	argv[7] = "<NULL>"
5829	Hit any key to exit ...
5830
5831	## Application terminated, rc = 0x0
5832
5833Another example, which demonstrates how to register a CPM interrupt
5834handler with the U-Boot code, can be found in 'examples/timer.c'.
5835Here, a CPM timer is set up to generate an interrupt every second.
5836The interrupt service routine is trivial, just printing a '.'
5837character, but this is just a demo program. The application can be
5838controlled by the following keys:
5839
5840	? - print current values og the CPM Timer registers
5841	b - enable interrupts and start timer
5842	e - stop timer and disable interrupts
5843	q - quit application
5844
5845	=> loads
5846	## Ready for S-Record download ...
5847	~>examples/timer.srec
5848	1 2 3 4 5 6 7 8 9 10 11 ...
5849	[file transfer complete]
5850	[connected]
5851	## Start Addr = 0x00040004
5852
5853	=> go 40004
5854	## Starting application at 0x00040004 ...
5855	TIMERS=0xfff00980
5856	Using timer 1
5857	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5858
5859Hit 'b':
5860	[q, b, e, ?] Set interval 1000000 us
5861	Enabling timer
5862Hit '?':
5863	[q, b, e, ?] ........
5864	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5865Hit '?':
5866	[q, b, e, ?] .
5867	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5868Hit '?':
5869	[q, b, e, ?] .
5870	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5871Hit '?':
5872	[q, b, e, ?] .
5873	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5874Hit 'e':
5875	[q, b, e, ?] ...Stopping timer
5876Hit 'q':
5877	[q, b, e, ?] ## Application terminated, rc = 0x0
5878
5879
5880Minicom warning:
5881================
5882
5883Over time, many people have reported problems when trying to use the
5884"minicom" terminal emulation program for serial download. I (wd)
5885consider minicom to be broken, and recommend not to use it. Under
5886Unix, I recommend to use C-Kermit for general purpose use (and
5887especially for kermit binary protocol download ("loadb" command), and
5888use "cu" for S-Record download ("loads" command).  See
5889http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5890for help with kermit.
5891
5892
5893Nevertheless, if you absolutely want to use it try adding this
5894configuration to your "File transfer protocols" section:
5895
5896	   Name	   Program			Name U/D FullScr IO-Red. Multi
5897	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5898	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5899
5900
5901NetBSD Notes:
5902=============
5903
5904Starting at version 0.9.2, U-Boot supports NetBSD both as host
5905(build U-Boot) and target system (boots NetBSD/mpc8xx).
5906
5907Building requires a cross environment; it is known to work on
5908NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5909need gmake since the Makefiles are not compatible with BSD make).
5910Note that the cross-powerpc package does not install include files;
5911attempting to build U-Boot will fail because <machine/ansi.h> is
5912missing.  This file has to be installed and patched manually:
5913
5914	# cd /usr/pkg/cross/powerpc-netbsd/include
5915	# mkdir powerpc
5916	# ln -s powerpc machine
5917	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5918	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5919
5920Native builds *don't* work due to incompatibilities between native
5921and U-Boot include files.
5922
5923Booting assumes that (the first part of) the image booted is a
5924stage-2 loader which in turn loads and then invokes the kernel
5925proper. Loader sources will eventually appear in the NetBSD source
5926tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5927meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5928
5929
5930Implementation Internals:
5931=========================
5932
5933The following is not intended to be a complete description of every
5934implementation detail. However, it should help to understand the
5935inner workings of U-Boot and make it easier to port it to custom
5936hardware.
5937
5938
5939Initial Stack, Global Data:
5940---------------------------
5941
5942The implementation of U-Boot is complicated by the fact that U-Boot
5943starts running out of ROM (flash memory), usually without access to
5944system RAM (because the memory controller is not initialized yet).
5945This means that we don't have writable Data or BSS segments, and BSS
5946is not initialized as zero. To be able to get a C environment working
5947at all, we have to allocate at least a minimal stack. Implementation
5948options for this are defined and restricted by the CPU used: Some CPU
5949models provide on-chip memory (like the IMMR area on MPC8xx and
5950MPC826x processors), on others (parts of) the data cache can be
5951locked as (mis-) used as memory, etc.
5952
5953	Chris Hallinan posted a good summary of these issues to the
5954	U-Boot mailing list:
5955
5956	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5957	From: "Chris Hallinan" <clh@net1plus.com>
5958	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5959	...
5960
5961	Correct me if I'm wrong, folks, but the way I understand it
5962	is this: Using DCACHE as initial RAM for Stack, etc, does not
5963	require any physical RAM backing up the cache. The cleverness
5964	is that the cache is being used as a temporary supply of
5965	necessary storage before the SDRAM controller is setup. It's
5966	beyond the scope of this list to explain the details, but you
5967	can see how this works by studying the cache architecture and
5968	operation in the architecture and processor-specific manuals.
5969
5970	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5971	is another option for the system designer to use as an
5972	initial stack/RAM area prior to SDRAM being available. Either
5973	option should work for you. Using CS 4 should be fine if your
5974	board designers haven't used it for something that would
5975	cause you grief during the initial boot! It is frequently not
5976	used.
5977
5978	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5979	with your processor/board/system design. The default value
5980	you will find in any recent u-boot distribution in
5981	walnut.h should work for you. I'd set it to a value larger
5982	than your SDRAM module. If you have a 64MB SDRAM module, set
5983	it above 400_0000. Just make sure your board has no resources
5984	that are supposed to respond to that address! That code in
5985	start.S has been around a while and should work as is when
5986	you get the config right.
5987
5988	-Chris Hallinan
5989	DS4.COM, Inc.
5990
5991It is essential to remember this, since it has some impact on the C
5992code for the initialization procedures:
5993
5994* Initialized global data (data segment) is read-only. Do not attempt
5995  to write it.
5996
5997* Do not use any uninitialized global data (or implicitly initialized
5998  as zero data - BSS segment) at all - this is undefined, initiali-
5999  zation is performed later (when relocating to RAM).
6000
6001* Stack space is very limited. Avoid big data buffers or things like
6002  that.
6003
6004Having only the stack as writable memory limits means we cannot use
6005normal global data to share information between the code. But it
6006turned out that the implementation of U-Boot can be greatly
6007simplified by making a global data structure (gd_t) available to all
6008functions. We could pass a pointer to this data as argument to _all_
6009functions, but this would bloat the code. Instead we use a feature of
6010the GCC compiler (Global Register Variables) to share the data: we
6011place a pointer (gd) to the global data into a register which we
6012reserve for this purpose.
6013
6014When choosing a register for such a purpose we are restricted by the
6015relevant  (E)ABI  specifications for the current architecture, and by
6016GCC's implementation.
6017
6018For PowerPC, the following registers have specific use:
6019	R1:	stack pointer
6020	R2:	reserved for system use
6021	R3-R4:	parameter passing and return values
6022	R5-R10: parameter passing
6023	R13:	small data area pointer
6024	R30:	GOT pointer
6025	R31:	frame pointer
6026
6027	(U-Boot also uses R12 as internal GOT pointer. r12
6028	is a volatile register so r12 needs to be reset when
6029	going back and forth between asm and C)
6030
6031    ==> U-Boot will use R2 to hold a pointer to the global data
6032
6033    Note: on PPC, we could use a static initializer (since the
6034    address of the global data structure is known at compile time),
6035    but it turned out that reserving a register results in somewhat
6036    smaller code - although the code savings are not that big (on
6037    average for all boards 752 bytes for the whole U-Boot image,
6038    624 text + 127 data).
6039
6040On Blackfin, the normal C ABI (except for P3) is followed as documented here:
6041	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
6042
6043    ==> U-Boot will use P3 to hold a pointer to the global data
6044
6045On ARM, the following registers are used:
6046
6047	R0:	function argument word/integer result
6048	R1-R3:	function argument word
6049	R9:	platform specific
6050	R10:	stack limit (used only if stack checking is enabled)
6051	R11:	argument (frame) pointer
6052	R12:	temporary workspace
6053	R13:	stack pointer
6054	R14:	link register
6055	R15:	program counter
6056
6057    ==> U-Boot will use R9 to hold a pointer to the global data
6058
6059    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
6060
6061On Nios II, the ABI is documented here:
6062	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
6063
6064    ==> U-Boot will use gp to hold a pointer to the global data
6065
6066    Note: on Nios II, we give "-G0" option to gcc and don't use gp
6067    to access small data sections, so gp is free.
6068
6069On NDS32, the following registers are used:
6070
6071	R0-R1:	argument/return
6072	R2-R5:	argument
6073	R15:	temporary register for assembler
6074	R16:	trampoline register
6075	R28:	frame pointer (FP)
6076	R29:	global pointer (GP)
6077	R30:	link register (LP)
6078	R31:	stack pointer (SP)
6079	PC:	program counter (PC)
6080
6081    ==> U-Boot will use R10 to hold a pointer to the global data
6082
6083NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6084or current versions of GCC may "optimize" the code too much.
6085
6086Memory Management:
6087------------------
6088
6089U-Boot runs in system state and uses physical addresses, i.e. the
6090MMU is not used either for address mapping nor for memory protection.
6091
6092The available memory is mapped to fixed addresses using the memory
6093controller. In this process, a contiguous block is formed for each
6094memory type (Flash, SDRAM, SRAM), even when it consists of several
6095physical memory banks.
6096
6097U-Boot is installed in the first 128 kB of the first Flash bank (on
6098TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6099booting and sizing and initializing DRAM, the code relocates itself
6100to the upper end of DRAM. Immediately below the U-Boot code some
6101memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6102configuration setting]. Below that, a structure with global Board
6103Info data is placed, followed by the stack (growing downward).
6104
6105Additionally, some exception handler code is copied to the low 8 kB
6106of DRAM (0x00000000 ... 0x00001FFF).
6107
6108So a typical memory configuration with 16 MB of DRAM could look like
6109this:
6110
6111	0x0000 0000	Exception Vector code
6112	      :
6113	0x0000 1FFF
6114	0x0000 2000	Free for Application Use
6115	      :
6116	      :
6117
6118	      :
6119	      :
6120	0x00FB FF20	Monitor Stack (Growing downward)
6121	0x00FB FFAC	Board Info Data and permanent copy of global data
6122	0x00FC 0000	Malloc Arena
6123	      :
6124	0x00FD FFFF
6125	0x00FE 0000	RAM Copy of Monitor Code
6126	...		eventually: LCD or video framebuffer
6127	...		eventually: pRAM (Protected RAM - unchanged by reset)
6128	0x00FF FFFF	[End of RAM]
6129
6130
6131System Initialization:
6132----------------------
6133
6134In the reset configuration, U-Boot starts at the reset entry point
6135(on most PowerPC systems at address 0x00000100). Because of the reset
6136configuration for CS0# this is a mirror of the on board Flash memory.
6137To be able to re-map memory U-Boot then jumps to its link address.
6138To be able to implement the initialization code in C, a (small!)
6139initial stack is set up in the internal Dual Ported RAM (in case CPUs
6140which provide such a feature like MPC8xx or MPC8260), or in a locked
6141part of the data cache. After that, U-Boot initializes the CPU core,
6142the caches and the SIU.
6143
6144Next, all (potentially) available memory banks are mapped using a
6145preliminary mapping. For example, we put them on 512 MB boundaries
6146(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6147on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6148programmed for SDRAM access. Using the temporary configuration, a
6149simple memory test is run that determines the size of the SDRAM
6150banks.
6151
6152When there is more than one SDRAM bank, and the banks are of
6153different size, the largest is mapped first. For equal size, the first
6154bank (CS2#) is mapped first. The first mapping is always for address
61550x00000000, with any additional banks following immediately to create
6156contiguous memory starting from 0.
6157
6158Then, the monitor installs itself at the upper end of the SDRAM area
6159and allocates memory for use by malloc() and for the global Board
6160Info data; also, the exception vector code is copied to the low RAM
6161pages, and the final stack is set up.
6162
6163Only after this relocation will you have a "normal" C environment;
6164until that you are restricted in several ways, mostly because you are
6165running from ROM, and because the code will have to be relocated to a
6166new address in RAM.
6167
6168
6169U-Boot Porting Guide:
6170----------------------
6171
6172[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6173list, October 2002]
6174
6175
6176int main(int argc, char *argv[])
6177{
6178	sighandler_t no_more_time;
6179
6180	signal(SIGALRM, no_more_time);
6181	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6182
6183	if (available_money > available_manpower) {
6184		Pay consultant to port U-Boot;
6185		return 0;
6186	}
6187
6188	Download latest U-Boot source;
6189
6190	Subscribe to u-boot mailing list;
6191
6192	if (clueless)
6193		email("Hi, I am new to U-Boot, how do I get started?");
6194
6195	while (learning) {
6196		Read the README file in the top level directory;
6197		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6198		Read applicable doc/*.README;
6199		Read the source, Luke;
6200		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6201	}
6202
6203	if (available_money > toLocalCurrency ($2500))
6204		Buy a BDI3000;
6205	else
6206		Add a lot of aggravation and time;
6207
6208	if (a similar board exists) {	/* hopefully... */
6209		cp -a board/<similar> board/<myboard>
6210		cp include/configs/<similar>.h include/configs/<myboard>.h
6211	} else {
6212		Create your own board support subdirectory;
6213		Create your own board include/configs/<myboard>.h file;
6214	}
6215	Edit new board/<myboard> files
6216	Edit new include/configs/<myboard>.h
6217
6218	while (!accepted) {
6219		while (!running) {
6220			do {
6221				Add / modify source code;
6222			} until (compiles);
6223			Debug;
6224			if (clueless)
6225				email("Hi, I am having problems...");
6226		}
6227		Send patch file to the U-Boot email list;
6228		if (reasonable critiques)
6229			Incorporate improvements from email list code review;
6230		else
6231			Defend code as written;
6232	}
6233
6234	return 0;
6235}
6236
6237void no_more_time (int sig)
6238{
6239      hire_a_guru();
6240}
6241
6242
6243Coding Standards:
6244-----------------
6245
6246All contributions to U-Boot should conform to the Linux kernel
6247coding style; see the file "Documentation/CodingStyle" and the script
6248"scripts/Lindent" in your Linux kernel source directory.
6249
6250Source files originating from a different project (for example the
6251MTD subsystem) are generally exempt from these guidelines and are not
6252reformatted to ease subsequent migration to newer versions of those
6253sources.
6254
6255Please note that U-Boot is implemented in C (and to some small parts in
6256Assembler); no C++ is used, so please do not use C++ style comments (//)
6257in your code.
6258
6259Please also stick to the following formatting rules:
6260- remove any trailing white space
6261- use TAB characters for indentation and vertical alignment, not spaces
6262- make sure NOT to use DOS '\r\n' line feeds
6263- do not add more than 2 consecutive empty lines to source files
6264- do not add trailing empty lines to source files
6265
6266Submissions which do not conform to the standards may be returned
6267with a request to reformat the changes.
6268
6269
6270Submitting Patches:
6271-------------------
6272
6273Since the number of patches for U-Boot is growing, we need to
6274establish some rules. Submissions which do not conform to these rules
6275may be rejected, even when they contain important and valuable stuff.
6276
6277Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6278
6279Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6280see http://lists.denx.de/mailman/listinfo/u-boot
6281
6282When you send a patch, please include the following information with
6283it:
6284
6285* For bug fixes: a description of the bug and how your patch fixes
6286  this bug. Please try to include a way of demonstrating that the
6287  patch actually fixes something.
6288
6289* For new features: a description of the feature and your
6290  implementation.
6291
6292* A CHANGELOG entry as plaintext (separate from the patch)
6293
6294* For major contributions, add a MAINTAINERS file with your
6295  information and associated file and directory references.
6296
6297* When you add support for a new board, don't forget to add a
6298  maintainer e-mail address to the boards.cfg file, too.
6299
6300* If your patch adds new configuration options, don't forget to
6301  document these in the README file.
6302
6303* The patch itself. If you are using git (which is *strongly*
6304  recommended) you can easily generate the patch using the
6305  "git format-patch". If you then use "git send-email" to send it to
6306  the U-Boot mailing list, you will avoid most of the common problems
6307  with some other mail clients.
6308
6309  If you cannot use git, use "diff -purN OLD NEW". If your version of
6310  diff does not support these options, then get the latest version of
6311  GNU diff.
6312
6313  The current directory when running this command shall be the parent
6314  directory of the U-Boot source tree (i. e. please make sure that
6315  your patch includes sufficient directory information for the
6316  affected files).
6317
6318  We prefer patches as plain text. MIME attachments are discouraged,
6319  and compressed attachments must not be used.
6320
6321* If one logical set of modifications affects or creates several
6322  files, all these changes shall be submitted in a SINGLE patch file.
6323
6324* Changesets that contain different, unrelated modifications shall be
6325  submitted as SEPARATE patches, one patch per changeset.
6326
6327
6328Notes:
6329
6330* Before sending the patch, run the buildman script on your patched
6331  source tree and make sure that no errors or warnings are reported
6332  for any of the boards.
6333
6334* Keep your modifications to the necessary minimum: A patch
6335  containing several unrelated changes or arbitrary reformats will be
6336  returned with a request to re-formatting / split it.
6337
6338* If you modify existing code, make sure that your new code does not
6339  add to the memory footprint of the code ;-) Small is beautiful!
6340  When adding new features, these should compile conditionally only
6341  (using #ifdef), and the resulting code with the new feature
6342  disabled must not need more memory than the old code without your
6343  modification.
6344
6345* Remember that there is a size limit of 100 kB per message on the
6346  u-boot mailing list. Bigger patches will be moderated. If they are
6347  reasonable and not too big, they will be acknowledged. But patches
6348  bigger than the size limit should be avoided.
6349