xref: /openbmc/u-boot/README (revision 173f023f)
1#
2# (C) Copyright 2000 - 2013
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# SPDX-License-Identifier:	GPL-2.0+
6#
7
8Summary:
9========
10
11This directory contains the source code for U-Boot, a boot loader for
12Embedded boards based on PowerPC, ARM, MIPS and several other
13processors, which can be installed in a boot ROM and used to
14initialize and test the hardware or to download and run application
15code.
16
17The development of U-Boot is closely related to Linux: some parts of
18the source code originate in the Linux source tree, we have some
19header files in common, and special provision has been made to
20support booting of Linux images.
21
22Some attention has been paid to make this software easily
23configurable and extendable. For instance, all monitor commands are
24implemented with the same call interface, so that it's very easy to
25add new commands. Also, instead of permanently adding rarely used
26code (for instance hardware test utilities) to the monitor, you can
27load and run it dynamically.
28
29
30Status:
31=======
32
33In general, all boards for which a configuration option exists in the
34Makefile have been tested to some extent and can be considered
35"working". In fact, many of them are used in production systems.
36
37In case of problems see the CHANGELOG file to find out who contributed
38the specific port. In addition, there are various MAINTAINERS files
39scattered throughout the U-Boot source identifying the people or
40companies responsible for various boards and subsystems.
41
42Note: As of August, 2010, there is no longer a CHANGELOG file in the
43actual U-Boot source tree; however, it can be created dynamically
44from the Git log using:
45
46	make CHANGELOG
47
48
49Where to get help:
50==================
51
52In case you have questions about, problems with or contributions for
53U-Boot, you should send a message to the U-Boot mailing list at
54<u-boot@lists.denx.de>. There is also an archive of previous traffic
55on the mailing list - please search the archive before asking FAQ's.
56Please see http://lists.denx.de/pipermail/u-boot and
57http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
58
59
60Where to get source code:
61=========================
62
63The U-Boot source code is maintained in the Git repository at
64git://www.denx.de/git/u-boot.git ; you can browse it online at
65http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
66
67The "snapshot" links on this page allow you to download tarballs of
68any version you might be interested in. Official releases are also
69available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
70directory.
71
72Pre-built (and tested) images are available from
73ftp://ftp.denx.de/pub/u-boot/images/
74
75
76Where we come from:
77===================
78
79- start from 8xxrom sources
80- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
81- clean up code
82- make it easier to add custom boards
83- make it possible to add other [PowerPC] CPUs
84- extend functions, especially:
85  * Provide extended interface to Linux boot loader
86  * S-Record download
87  * network boot
88  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
89- create ARMBoot project (http://sourceforge.net/projects/armboot)
90- add other CPU families (starting with ARM)
91- create U-Boot project (http://sourceforge.net/projects/u-boot)
92- current project page: see http://www.denx.de/wiki/U-Boot
93
94
95Names and Spelling:
96===================
97
98The "official" name of this project is "Das U-Boot". The spelling
99"U-Boot" shall be used in all written text (documentation, comments
100in source files etc.). Example:
101
102	This is the README file for the U-Boot project.
103
104File names etc. shall be based on the string "u-boot". Examples:
105
106	include/asm-ppc/u-boot.h
107
108	#include <asm/u-boot.h>
109
110Variable names, preprocessor constants etc. shall be either based on
111the string "u_boot" or on "U_BOOT". Example:
112
113	U_BOOT_VERSION		u_boot_logo
114	IH_OS_U_BOOT		u_boot_hush_start
115
116
117Versioning:
118===========
119
120Starting with the release in October 2008, the names of the releases
121were changed from numerical release numbers without deeper meaning
122into a time stamp based numbering. Regular releases are identified by
123names consisting of the calendar year and month of the release date.
124Additional fields (if present) indicate release candidates or bug fix
125releases in "stable" maintenance trees.
126
127Examples:
128	U-Boot v2009.11	    - Release November 2009
129	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
130	U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
131
132
133Directory Hierarchy:
134====================
135
136/arch			Architecture specific files
137  /arc			Files generic to ARC architecture
138  /arm			Files generic to ARM architecture
139  /m68k			Files generic to m68k architecture
140  /microblaze		Files generic to microblaze architecture
141  /mips			Files generic to MIPS architecture
142  /nds32		Files generic to NDS32 architecture
143  /nios2		Files generic to Altera NIOS2 architecture
144  /openrisc		Files generic to OpenRISC architecture
145  /powerpc		Files generic to PowerPC architecture
146  /riscv		Files generic to RISC-V architecture
147  /sandbox		Files generic to HW-independent "sandbox"
148  /sh			Files generic to SH architecture
149  /x86			Files generic to x86 architecture
150/api			Machine/arch independent API for external apps
151/board			Board dependent files
152/cmd			U-Boot commands functions
153/common			Misc architecture independent functions
154/configs		Board default configuration files
155/disk			Code for disk drive partition handling
156/doc			Documentation (don't expect too much)
157/drivers		Commonly used device drivers
158/dts			Contains Makefile for building internal U-Boot fdt.
159/examples		Example code for standalone applications, etc.
160/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
161/include		Header Files
162/lib			Library routines generic to all architectures
163/Licenses		Various license files
164/net			Networking code
165/post			Power On Self Test
166/scripts		Various build scripts and Makefiles
167/test			Various unit test files
168/tools			Tools to build S-Record or U-Boot images, etc.
169
170Software Configuration:
171=======================
172
173Configuration is usually done using C preprocessor defines; the
174rationale behind that is to avoid dead code whenever possible.
175
176There are two classes of configuration variables:
177
178* Configuration _OPTIONS_:
179  These are selectable by the user and have names beginning with
180  "CONFIG_".
181
182* Configuration _SETTINGS_:
183  These depend on the hardware etc. and should not be meddled with if
184  you don't know what you're doing; they have names beginning with
185  "CONFIG_SYS_".
186
187Previously, all configuration was done by hand, which involved creating
188symbolic links and editing configuration files manually. More recently,
189U-Boot has added the Kbuild infrastructure used by the Linux kernel,
190allowing you to use the "make menuconfig" command to configure your
191build.
192
193
194Selection of Processor Architecture and Board Type:
195---------------------------------------------------
196
197For all supported boards there are ready-to-use default
198configurations available; just type "make <board_name>_defconfig".
199
200Example: For a TQM823L module type:
201
202	cd u-boot
203	make TQM823L_defconfig
204
205Note: If you're looking for the default configuration file for a board
206you're sure used to be there but is now missing, check the file
207doc/README.scrapyard for a list of no longer supported boards.
208
209Sandbox Environment:
210--------------------
211
212U-Boot can be built natively to run on a Linux host using the 'sandbox'
213board. This allows feature development which is not board- or architecture-
214specific to be undertaken on a native platform. The sandbox is also used to
215run some of U-Boot's tests.
216
217See board/sandbox/README.sandbox for more details.
218
219
220Board Initialisation Flow:
221--------------------------
222
223This is the intended start-up flow for boards. This should apply for both
224SPL and U-Boot proper (i.e. they both follow the same rules).
225
226Note: "SPL" stands for "Secondary Program Loader," which is explained in
227more detail later in this file.
228
229At present, SPL mostly uses a separate code path, but the function names
230and roles of each function are the same. Some boards or architectures
231may not conform to this.  At least most ARM boards which use
232CONFIG_SPL_FRAMEWORK conform to this.
233
234Execution typically starts with an architecture-specific (and possibly
235CPU-specific) start.S file, such as:
236
237	- arch/arm/cpu/armv7/start.S
238	- arch/powerpc/cpu/mpc83xx/start.S
239	- arch/mips/cpu/start.S
240
241and so on. From there, three functions are called; the purpose and
242limitations of each of these functions are described below.
243
244lowlevel_init():
245	- purpose: essential init to permit execution to reach board_init_f()
246	- no global_data or BSS
247	- there is no stack (ARMv7 may have one but it will soon be removed)
248	- must not set up SDRAM or use console
249	- must only do the bare minimum to allow execution to continue to
250		board_init_f()
251	- this is almost never needed
252	- return normally from this function
253
254board_init_f():
255	- purpose: set up the machine ready for running board_init_r():
256		i.e. SDRAM and serial UART
257	- global_data is available
258	- stack is in SRAM
259	- BSS is not available, so you cannot use global/static variables,
260		only stack variables and global_data
261
262	Non-SPL-specific notes:
263	- dram_init() is called to set up DRAM. If already done in SPL this
264		can do nothing
265
266	SPL-specific notes:
267	- you can override the entire board_init_f() function with your own
268		version as needed.
269	- preloader_console_init() can be called here in extremis
270	- should set up SDRAM, and anything needed to make the UART work
271	- these is no need to clear BSS, it will be done by crt0.S
272	- must return normally from this function (don't call board_init_r()
273		directly)
274
275Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
276this point the stack and global_data are relocated to below
277CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
278memory.
279
280board_init_r():
281	- purpose: main execution, common code
282	- global_data is available
283	- SDRAM is available
284	- BSS is available, all static/global variables can be used
285	- execution eventually continues to main_loop()
286
287	Non-SPL-specific notes:
288	- U-Boot is relocated to the top of memory and is now running from
289		there.
290
291	SPL-specific notes:
292	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
293		CONFIG_SPL_STACK_R_ADDR points into SDRAM
294	- preloader_console_init() can be called here - typically this is
295		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
296		spl_board_init() function containing this call
297	- loads U-Boot or (in falcon mode) Linux
298
299
300
301Configuration Options:
302----------------------
303
304Configuration depends on the combination of board and CPU type; all
305such information is kept in a configuration file
306"include/configs/<board_name>.h".
307
308Example: For a TQM823L module, all configuration settings are in
309"include/configs/TQM823L.h".
310
311
312Many of the options are named exactly as the corresponding Linux
313kernel configuration options. The intention is to make it easier to
314build a config tool - later.
315
316- ARM Platform Bus Type(CCI):
317		CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
318		provides full cache coherency between two clusters of multi-core
319		CPUs and I/O coherency for devices and I/O masters
320
321		CONFIG_SYS_FSL_HAS_CCI400
322
323		Defined For SoC that has cache coherent interconnect
324		CCN-400
325
326		CONFIG_SYS_FSL_HAS_CCN504
327
328		Defined for SoC that has cache coherent interconnect CCN-504
329
330The following options need to be configured:
331
332- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
333
334- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
335
336- Marvell Family Member
337		CONFIG_SYS_MVFS		- define it if you want to enable
338					  multiple fs option at one time
339					  for marvell soc family
340
341- 85xx CPU Options:
342		CONFIG_SYS_PPC64
343
344		Specifies that the core is a 64-bit PowerPC implementation (implements
345		the "64" category of the Power ISA). This is necessary for ePAPR
346		compliance, among other possible reasons.
347
348		CONFIG_SYS_FSL_TBCLK_DIV
349
350		Defines the core time base clock divider ratio compared to the
351		system clock.  On most PQ3 devices this is 8, on newer QorIQ
352		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
353
354		CONFIG_SYS_FSL_PCIE_COMPAT
355
356		Defines the string to utilize when trying to match PCIe device
357		tree nodes for the given platform.
358
359		CONFIG_SYS_FSL_ERRATUM_A004510
360
361		Enables a workaround for erratum A004510.  If set,
362		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
363		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
364
365		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
366		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
367
368		Defines one or two SoC revisions (low 8 bits of SVR)
369		for which the A004510 workaround should be applied.
370
371		The rest of SVR is either not relevant to the decision
372		of whether the erratum is present (e.g. p2040 versus
373		p2041) or is implied by the build target, which controls
374		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
375
376		See Freescale App Note 4493 for more information about
377		this erratum.
378
379		CONFIG_A003399_NOR_WORKAROUND
380		Enables a workaround for IFC erratum A003399. It is only
381		required during NOR boot.
382
383		CONFIG_A008044_WORKAROUND
384		Enables a workaround for T1040/T1042 erratum A008044. It is only
385		required during NAND boot and valid for Rev 1.0 SoC revision
386
387		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
388
389		This is the value to write into CCSR offset 0x18600
390		according to the A004510 workaround.
391
392		CONFIG_SYS_FSL_DSP_DDR_ADDR
393		This value denotes start offset of DDR memory which is
394		connected exclusively to the DSP cores.
395
396		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
397		This value denotes start offset of M2 memory
398		which is directly connected to the DSP core.
399
400		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
401		This value denotes start offset of M3 memory which is directly
402		connected to the DSP core.
403
404		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
405		This value denotes start offset of DSP CCSR space.
406
407		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
408		Single Source Clock is clocking mode present in some of FSL SoC's.
409		In this mode, a single differential clock is used to supply
410		clocks to the sysclock, ddrclock and usbclock.
411
412		CONFIG_SYS_CPC_REINIT_F
413		This CONFIG is defined when the CPC is configured as SRAM at the
414		time of U-Boot entry and is required to be re-initialized.
415
416		CONFIG_DEEP_SLEEP
417		Indicates this SoC supports deep sleep feature. If deep sleep is
418		supported, core will start to execute uboot when wakes up.
419
420- Generic CPU options:
421		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
422
423		Defines the endianess of the CPU. Implementation of those
424		values is arch specific.
425
426		CONFIG_SYS_FSL_DDR
427		Freescale DDR driver in use. This type of DDR controller is
428		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
429		SoCs.
430
431		CONFIG_SYS_FSL_DDR_ADDR
432		Freescale DDR memory-mapped register base.
433
434		CONFIG_SYS_FSL_DDR_EMU
435		Specify emulator support for DDR. Some DDR features such as
436		deskew training are not available.
437
438		CONFIG_SYS_FSL_DDRC_GEN1
439		Freescale DDR1 controller.
440
441		CONFIG_SYS_FSL_DDRC_GEN2
442		Freescale DDR2 controller.
443
444		CONFIG_SYS_FSL_DDRC_GEN3
445		Freescale DDR3 controller.
446
447		CONFIG_SYS_FSL_DDRC_GEN4
448		Freescale DDR4 controller.
449
450		CONFIG_SYS_FSL_DDRC_ARM_GEN3
451		Freescale DDR3 controller for ARM-based SoCs.
452
453		CONFIG_SYS_FSL_DDR1
454		Board config to use DDR1. It can be enabled for SoCs with
455		Freescale DDR1 or DDR2 controllers, depending on the board
456		implemetation.
457
458		CONFIG_SYS_FSL_DDR2
459		Board config to use DDR2. It can be enabled for SoCs with
460		Freescale DDR2 or DDR3 controllers, depending on the board
461		implementation.
462
463		CONFIG_SYS_FSL_DDR3
464		Board config to use DDR3. It can be enabled for SoCs with
465		Freescale DDR3 or DDR3L controllers.
466
467		CONFIG_SYS_FSL_DDR3L
468		Board config to use DDR3L. It can be enabled for SoCs with
469		DDR3L controllers.
470
471		CONFIG_SYS_FSL_DDR4
472		Board config to use DDR4. It can be enabled for SoCs with
473		DDR4 controllers.
474
475		CONFIG_SYS_FSL_IFC_BE
476		Defines the IFC controller register space as Big Endian
477
478		CONFIG_SYS_FSL_IFC_LE
479		Defines the IFC controller register space as Little Endian
480
481		CONFIG_SYS_FSL_IFC_CLK_DIV
482		Defines divider of platform clock(clock input to IFC controller).
483
484		CONFIG_SYS_FSL_LBC_CLK_DIV
485		Defines divider of platform clock(clock input to eLBC controller).
486
487		CONFIG_SYS_FSL_PBL_PBI
488		It enables addition of RCW (Power on reset configuration) in built image.
489		Please refer doc/README.pblimage for more details
490
491		CONFIG_SYS_FSL_PBL_RCW
492		It adds PBI(pre-boot instructions) commands in u-boot build image.
493		PBI commands can be used to configure SoC before it starts the execution.
494		Please refer doc/README.pblimage for more details
495
496		CONFIG_SPL_FSL_PBL
497		It adds a target to create boot binary having SPL binary in PBI format
498		concatenated with u-boot binary.
499
500		CONFIG_SYS_FSL_DDR_BE
501		Defines the DDR controller register space as Big Endian
502
503		CONFIG_SYS_FSL_DDR_LE
504		Defines the DDR controller register space as Little Endian
505
506		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
507		Physical address from the view of DDR controllers. It is the
508		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
509		it could be different for ARM SoCs.
510
511		CONFIG_SYS_FSL_DDR_INTLV_256B
512		DDR controller interleaving on 256-byte. This is a special
513		interleaving mode, handled by Dickens for Freescale layerscape
514		SoCs with ARM core.
515
516		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
517		Number of controllers used as main memory.
518
519		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
520		Number of controllers used for other than main memory.
521
522		CONFIG_SYS_FSL_HAS_DP_DDR
523		Defines the SoC has DP-DDR used for DPAA.
524
525		CONFIG_SYS_FSL_SEC_BE
526		Defines the SEC controller register space as Big Endian
527
528		CONFIG_SYS_FSL_SEC_LE
529		Defines the SEC controller register space as Little Endian
530
531- MIPS CPU options:
532		CONFIG_SYS_INIT_SP_OFFSET
533
534		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
535		pointer. This is needed for the temporary stack before
536		relocation.
537
538		CONFIG_SYS_MIPS_CACHE_MODE
539
540		Cache operation mode for the MIPS CPU.
541		See also arch/mips/include/asm/mipsregs.h.
542		Possible values are:
543			CONF_CM_CACHABLE_NO_WA
544			CONF_CM_CACHABLE_WA
545			CONF_CM_UNCACHED
546			CONF_CM_CACHABLE_NONCOHERENT
547			CONF_CM_CACHABLE_CE
548			CONF_CM_CACHABLE_COW
549			CONF_CM_CACHABLE_CUW
550			CONF_CM_CACHABLE_ACCELERATED
551
552		CONFIG_SYS_XWAY_EBU_BOOTCFG
553
554		Special option for Lantiq XWAY SoCs for booting from NOR flash.
555		See also arch/mips/cpu/mips32/start.S.
556
557		CONFIG_XWAY_SWAP_BYTES
558
559		Enable compilation of tools/xway-swap-bytes needed for Lantiq
560		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
561		be swapped if a flash programmer is used.
562
563- ARM options:
564		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
565
566		Select high exception vectors of the ARM core, e.g., do not
567		clear the V bit of the c1 register of CP15.
568
569		COUNTER_FREQUENCY
570		Generic timer clock source frequency.
571
572		COUNTER_FREQUENCY_REAL
573		Generic timer clock source frequency if the real clock is
574		different from COUNTER_FREQUENCY, and can only be determined
575		at run time.
576
577- Tegra SoC options:
578		CONFIG_TEGRA_SUPPORT_NON_SECURE
579
580		Support executing U-Boot in non-secure (NS) mode. Certain
581		impossible actions will be skipped if the CPU is in NS mode,
582		such as ARM architectural timer initialization.
583
584- Linux Kernel Interface:
585		CONFIG_CLOCKS_IN_MHZ
586
587		U-Boot stores all clock information in Hz
588		internally. For binary compatibility with older Linux
589		kernels (which expect the clocks passed in the
590		bd_info data to be in MHz) the environment variable
591		"clocks_in_mhz" can be defined so that U-Boot
592		converts clock data to MHZ before passing it to the
593		Linux kernel.
594		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
595		"clocks_in_mhz=1" is automatically included in the
596		default environment.
597
598		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
599
600		When transferring memsize parameter to Linux, some versions
601		expect it to be in bytes, others in MB.
602		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
603
604		CONFIG_OF_LIBFDT
605
606		New kernel versions are expecting firmware settings to be
607		passed using flattened device trees (based on open firmware
608		concepts).
609
610		CONFIG_OF_LIBFDT
611		 * New libfdt-based support
612		 * Adds the "fdt" command
613		 * The bootm command automatically updates the fdt
614
615		OF_TBCLK - The timebase frequency.
616		OF_STDOUT_PATH - The path to the console device
617
618		boards with QUICC Engines require OF_QE to set UCC MAC
619		addresses
620
621		CONFIG_OF_BOARD_SETUP
622
623		Board code has addition modification that it wants to make
624		to the flat device tree before handing it off to the kernel
625
626		CONFIG_OF_SYSTEM_SETUP
627
628		Other code has addition modification that it wants to make
629		to the flat device tree before handing it off to the kernel.
630		This causes ft_system_setup() to be called before booting
631		the kernel.
632
633		CONFIG_OF_IDE_FIXUP
634
635		U-Boot can detect if an IDE device is present or not.
636		If not, and this new config option is activated, U-Boot
637		removes the ATA node from the DTS before booting Linux,
638		so the Linux IDE driver does not probe the device and
639		crash. This is needed for buggy hardware (uc101) where
640		no pull down resistor is connected to the signal IDE5V_DD7.
641
642		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
643
644		This setting is mandatory for all boards that have only one
645		machine type and must be used to specify the machine type
646		number as it appears in the ARM machine registry
647		(see http://www.arm.linux.org.uk/developer/machines/).
648		Only boards that have multiple machine types supported
649		in a single configuration file and the machine type is
650		runtime discoverable, do not have to use this setting.
651
652- vxWorks boot parameters:
653
654		bootvx constructs a valid bootline using the following
655		environments variables: bootdev, bootfile, ipaddr, netmask,
656		serverip, gatewayip, hostname, othbootargs.
657		It loads the vxWorks image pointed bootfile.
658
659		Note: If a "bootargs" environment is defined, it will overwride
660		the defaults discussed just above.
661
662- Cache Configuration:
663		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
664		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
665		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
666
667- Cache Configuration for ARM:
668		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
669				      controller
670		CONFIG_SYS_PL310_BASE - Physical base address of PL310
671					controller register space
672
673- Serial Ports:
674		CONFIG_PL010_SERIAL
675
676		Define this if you want support for Amba PrimeCell PL010 UARTs.
677
678		CONFIG_PL011_SERIAL
679
680		Define this if you want support for Amba PrimeCell PL011 UARTs.
681
682		CONFIG_PL011_CLOCK
683
684		If you have Amba PrimeCell PL011 UARTs, set this variable to
685		the clock speed of the UARTs.
686
687		CONFIG_PL01x_PORTS
688
689		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
690		define this to a list of base addresses for each (supported)
691		port. See e.g. include/configs/versatile.h
692
693		CONFIG_SERIAL_HW_FLOW_CONTROL
694
695		Define this variable to enable hw flow control in serial driver.
696		Current user of this option is drivers/serial/nsl16550.c driver
697
698- Console Baudrate:
699		CONFIG_BAUDRATE - in bps
700		Select one of the baudrates listed in
701		CONFIG_SYS_BAUDRATE_TABLE, see below.
702
703- Autoboot Command:
704		CONFIG_BOOTCOMMAND
705		Only needed when CONFIG_BOOTDELAY is enabled;
706		define a command string that is automatically executed
707		when no character is read on the console interface
708		within "Boot Delay" after reset.
709
710		CONFIG_RAMBOOT and CONFIG_NFSBOOT
711		The value of these goes into the environment as
712		"ramboot" and "nfsboot" respectively, and can be used
713		as a convenience, when switching between booting from
714		RAM and NFS.
715
716- Bootcount:
717		CONFIG_BOOTCOUNT_LIMIT
718		Implements a mechanism for detecting a repeating reboot
719		cycle, see:
720		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
721
722		CONFIG_BOOTCOUNT_ENV
723		If no softreset save registers are found on the hardware
724		"bootcount" is stored in the environment. To prevent a
725		saveenv on all reboots, the environment variable
726		"upgrade_available" is used. If "upgrade_available" is
727		0, "bootcount" is always 0, if "upgrade_available" is
728		1 "bootcount" is incremented in the environment.
729		So the Userspace Applikation must set the "upgrade_available"
730		and "bootcount" variable to 0, if a boot was successfully.
731
732- Pre-Boot Commands:
733		CONFIG_PREBOOT
734
735		When this option is #defined, the existence of the
736		environment variable "preboot" will be checked
737		immediately before starting the CONFIG_BOOTDELAY
738		countdown and/or running the auto-boot command resp.
739		entering interactive mode.
740
741		This feature is especially useful when "preboot" is
742		automatically generated or modified. For an example
743		see the LWMON board specific code: here "preboot" is
744		modified when the user holds down a certain
745		combination of keys on the (special) keyboard when
746		booting the systems
747
748- Serial Download Echo Mode:
749		CONFIG_LOADS_ECHO
750		If defined to 1, all characters received during a
751		serial download (using the "loads" command) are
752		echoed back. This might be needed by some terminal
753		emulations (like "cu"), but may as well just take
754		time on others. This setting #define's the initial
755		value of the "loads_echo" environment variable.
756
757- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
758		CONFIG_KGDB_BAUDRATE
759		Select one of the baudrates listed in
760		CONFIG_SYS_BAUDRATE_TABLE, see below.
761
762- Removal of commands
763		If no commands are needed to boot, you can disable
764		CONFIG_CMDLINE to remove them. In this case, the command line
765		will not be available, and when U-Boot wants to execute the
766		boot command (on start-up) it will call board_run_command()
767		instead. This can reduce image size significantly for very
768		simple boot procedures.
769
770- Regular expression support:
771		CONFIG_REGEX
772		If this variable is defined, U-Boot is linked against
773		the SLRE (Super Light Regular Expression) library,
774		which adds regex support to some commands, as for
775		example "env grep" and "setexpr".
776
777- Device tree:
778		CONFIG_OF_CONTROL
779		If this variable is defined, U-Boot will use a device tree
780		to configure its devices, instead of relying on statically
781		compiled #defines in the board file. This option is
782		experimental and only available on a few boards. The device
783		tree is available in the global data as gd->fdt_blob.
784
785		U-Boot needs to get its device tree from somewhere. This can
786		be done using one of the three options below:
787
788		CONFIG_OF_EMBED
789		If this variable is defined, U-Boot will embed a device tree
790		binary in its image. This device tree file should be in the
791		board directory and called <soc>-<board>.dts. The binary file
792		is then picked up in board_init_f() and made available through
793		the global data structure as gd->fdt_blob.
794
795		CONFIG_OF_SEPARATE
796		If this variable is defined, U-Boot will build a device tree
797		binary. It will be called u-boot.dtb. Architecture-specific
798		code will locate it at run-time. Generally this works by:
799
800			cat u-boot.bin u-boot.dtb >image.bin
801
802		and in fact, U-Boot does this for you, creating a file called
803		u-boot-dtb.bin which is useful in the common case. You can
804		still use the individual files if you need something more
805		exotic.
806
807		CONFIG_OF_BOARD
808		If this variable is defined, U-Boot will use the device tree
809		provided by the board at runtime instead of embedding one with
810		the image. Only boards defining board_fdt_blob_setup() support
811		this option (see include/fdtdec.h file).
812
813- Watchdog:
814		CONFIG_WATCHDOG
815		If this variable is defined, it enables watchdog
816		support for the SoC. There must be support in the SoC
817		specific code for a watchdog. For the 8xx
818		CPUs, the SIU Watchdog feature is enabled in the SYPCR
819		register.  When supported for a specific SoC is
820		available, then no further board specific code should
821		be needed to use it.
822
823		CONFIG_HW_WATCHDOG
824		When using a watchdog circuitry external to the used
825		SoC, then define this variable and provide board
826		specific code for the "hw_watchdog_reset" function.
827
828		CONFIG_AT91_HW_WDT_TIMEOUT
829		specify the timeout in seconds. default 2 seconds.
830
831- U-Boot Version:
832		CONFIG_VERSION_VARIABLE
833		If this variable is defined, an environment variable
834		named "ver" is created by U-Boot showing the U-Boot
835		version as printed by the "version" command.
836		Any change to this variable will be reverted at the
837		next reset.
838
839- Real-Time Clock:
840
841		When CONFIG_CMD_DATE is selected, the type of the RTC
842		has to be selected, too. Define exactly one of the
843		following options:
844
845		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
846		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
847		CONFIG_RTC_MC146818	- use MC146818 RTC
848		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
849		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
850		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
851		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
852		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
853		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
854		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
855		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
856		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
857					  RV3029 RTC.
858
859		Note that if the RTC uses I2C, then the I2C interface
860		must also be configured. See I2C Support, below.
861
862- GPIO Support:
863		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
864
865		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
866		chip-ngpio pairs that tell the PCA953X driver the number of
867		pins supported by a particular chip.
868
869		Note that if the GPIO device uses I2C, then the I2C interface
870		must also be configured. See I2C Support, below.
871
872- I/O tracing:
873		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
874		accesses and can checksum them or write a list of them out
875		to memory. See the 'iotrace' command for details. This is
876		useful for testing device drivers since it can confirm that
877		the driver behaves the same way before and after a code
878		change. Currently this is supported on sandbox and arm. To
879		add support for your architecture, add '#include <iotrace.h>'
880		to the bottom of arch/<arch>/include/asm/io.h and test.
881
882		Example output from the 'iotrace stats' command is below.
883		Note that if the trace buffer is exhausted, the checksum will
884		still continue to operate.
885
886			iotrace is enabled
887			Start:  10000000	(buffer start address)
888			Size:   00010000	(buffer size)
889			Offset: 00000120	(current buffer offset)
890			Output: 10000120	(start + offset)
891			Count:  00000018	(number of trace records)
892			CRC32:  9526fb66	(CRC32 of all trace records)
893
894- Timestamp Support:
895
896		When CONFIG_TIMESTAMP is selected, the timestamp
897		(date and time) of an image is printed by image
898		commands like bootm or iminfo. This option is
899		automatically enabled when you select CONFIG_CMD_DATE .
900
901- Partition Labels (disklabels) Supported:
902		Zero or more of the following:
903		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
904		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
905		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
906				       bootloader.  Note 2TB partition limit; see
907				       disk/part_efi.c
908		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
909
910		If IDE or SCSI support is enabled (CONFIG_IDE or
911		CONFIG_SCSI) you must configure support for at
912		least one non-MTD partition type as well.
913
914- IDE Reset method:
915		CONFIG_IDE_RESET_ROUTINE - this is defined in several
916		board configurations files but used nowhere!
917
918		CONFIG_IDE_RESET - is this is defined, IDE Reset will
919		be performed by calling the function
920			ide_set_reset(int reset)
921		which has to be defined in a board specific file
922
923- ATAPI Support:
924		CONFIG_ATAPI
925
926		Set this to enable ATAPI support.
927
928- LBA48 Support
929		CONFIG_LBA48
930
931		Set this to enable support for disks larger than 137GB
932		Also look at CONFIG_SYS_64BIT_LBA.
933		Whithout these , LBA48 support uses 32bit variables and will 'only'
934		support disks up to 2.1TB.
935
936		CONFIG_SYS_64BIT_LBA:
937			When enabled, makes the IDE subsystem use 64bit sector addresses.
938			Default is 32bit.
939
940- SCSI Support:
941		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
942		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
943		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
944		maximum numbers of LUNs, SCSI ID's and target
945		devices.
946
947		The environment variable 'scsidevs' is set to the number of
948		SCSI devices found during the last scan.
949
950- NETWORK Support (PCI):
951		CONFIG_E1000
952		Support for Intel 8254x/8257x gigabit chips.
953
954		CONFIG_E1000_SPI
955		Utility code for direct access to the SPI bus on Intel 8257x.
956		This does not do anything useful unless you set at least one
957		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
958
959		CONFIG_E1000_SPI_GENERIC
960		Allow generic access to the SPI bus on the Intel 8257x, for
961		example with the "sspi" command.
962
963		CONFIG_EEPRO100
964		Support for Intel 82557/82559/82559ER chips.
965		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
966		write routine for first time initialisation.
967
968		CONFIG_TULIP
969		Support for Digital 2114x chips.
970		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
971		modem chip initialisation (KS8761/QS6611).
972
973		CONFIG_NATSEMI
974		Support for National dp83815 chips.
975
976		CONFIG_NS8382X
977		Support for National dp8382[01] gigabit chips.
978
979- NETWORK Support (other):
980
981		CONFIG_DRIVER_AT91EMAC
982		Support for AT91RM9200 EMAC.
983
984			CONFIG_RMII
985			Define this to use reduced MII inteface
986
987			CONFIG_DRIVER_AT91EMAC_QUIET
988			If this defined, the driver is quiet.
989			The driver doen't show link status messages.
990
991		CONFIG_CALXEDA_XGMAC
992		Support for the Calxeda XGMAC device
993
994		CONFIG_LAN91C96
995		Support for SMSC's LAN91C96 chips.
996
997			CONFIG_LAN91C96_USE_32_BIT
998			Define this to enable 32 bit addressing
999
1000		CONFIG_SMC91111
1001		Support for SMSC's LAN91C111 chip
1002
1003			CONFIG_SMC91111_BASE
1004			Define this to hold the physical address
1005			of the device (I/O space)
1006
1007			CONFIG_SMC_USE_32_BIT
1008			Define this if data bus is 32 bits
1009
1010			CONFIG_SMC_USE_IOFUNCS
1011			Define this to use i/o functions instead of macros
1012			(some hardware wont work with macros)
1013
1014		CONFIG_DRIVER_TI_EMAC
1015		Support for davinci emac
1016
1017			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1018			Define this if you have more then 3 PHYs.
1019
1020		CONFIG_FTGMAC100
1021		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1022
1023			CONFIG_FTGMAC100_EGIGA
1024			Define this to use GE link update with gigabit PHY.
1025			Define this if FTGMAC100 is connected to gigabit PHY.
1026			If your system has 10/100 PHY only, it might not occur
1027			wrong behavior. Because PHY usually return timeout or
1028			useless data when polling gigabit status and gigabit
1029			control registers. This behavior won't affect the
1030			correctnessof 10/100 link speed update.
1031
1032		CONFIG_SH_ETHER
1033		Support for Renesas on-chip Ethernet controller
1034
1035			CONFIG_SH_ETHER_USE_PORT
1036			Define the number of ports to be used
1037
1038			CONFIG_SH_ETHER_PHY_ADDR
1039			Define the ETH PHY's address
1040
1041			CONFIG_SH_ETHER_CACHE_WRITEBACK
1042			If this option is set, the driver enables cache flush.
1043
1044- PWM Support:
1045		CONFIG_PWM_IMX
1046		Support for PWM module on the imx6.
1047
1048- TPM Support:
1049		CONFIG_TPM
1050		Support TPM devices.
1051
1052		CONFIG_TPM_TIS_INFINEON
1053		Support for Infineon i2c bus TPM devices. Only one device
1054		per system is supported at this time.
1055
1056			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1057			Define the burst count bytes upper limit
1058
1059		CONFIG_TPM_ST33ZP24
1060		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1061
1062			CONFIG_TPM_ST33ZP24_I2C
1063			Support for STMicroelectronics ST33ZP24 I2C devices.
1064			Requires TPM_ST33ZP24 and I2C.
1065
1066			CONFIG_TPM_ST33ZP24_SPI
1067			Support for STMicroelectronics ST33ZP24 SPI devices.
1068			Requires TPM_ST33ZP24 and SPI.
1069
1070		CONFIG_TPM_ATMEL_TWI
1071		Support for Atmel TWI TPM device. Requires I2C support.
1072
1073		CONFIG_TPM_TIS_LPC
1074		Support for generic parallel port TPM devices. Only one device
1075		per system is supported at this time.
1076
1077			CONFIG_TPM_TIS_BASE_ADDRESS
1078			Base address where the generic TPM device is mapped
1079			to. Contemporary x86 systems usually map it at
1080			0xfed40000.
1081
1082		CONFIG_TPM
1083		Define this to enable the TPM support library which provides
1084		functional interfaces to some TPM commands.
1085		Requires support for a TPM device.
1086
1087		CONFIG_TPM_AUTH_SESSIONS
1088		Define this to enable authorized functions in the TPM library.
1089		Requires CONFIG_TPM and CONFIG_SHA1.
1090
1091- USB Support:
1092		At the moment only the UHCI host controller is
1093		supported (PIP405, MIP405); define
1094		CONFIG_USB_UHCI to enable it.
1095		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1096		and define CONFIG_USB_STORAGE to enable the USB
1097		storage devices.
1098		Note:
1099		Supported are USB Keyboards and USB Floppy drives
1100		(TEAC FD-05PUB).
1101
1102		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1103		txfilltuning field in the EHCI controller on reset.
1104
1105		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1106		HW module registers.
1107
1108- USB Device:
1109		Define the below if you wish to use the USB console.
1110		Once firmware is rebuilt from a serial console issue the
1111		command "setenv stdin usbtty; setenv stdout usbtty" and
1112		attach your USB cable. The Unix command "dmesg" should print
1113		it has found a new device. The environment variable usbtty
1114		can be set to gserial or cdc_acm to enable your device to
1115		appear to a USB host as a Linux gserial device or a
1116		Common Device Class Abstract Control Model serial device.
1117		If you select usbtty = gserial you should be able to enumerate
1118		a Linux host by
1119		# modprobe usbserial vendor=0xVendorID product=0xProductID
1120		else if using cdc_acm, simply setting the environment
1121		variable usbtty to be cdc_acm should suffice. The following
1122		might be defined in YourBoardName.h
1123
1124			CONFIG_USB_DEVICE
1125			Define this to build a UDC device
1126
1127			CONFIG_USB_TTY
1128			Define this to have a tty type of device available to
1129			talk to the UDC device
1130
1131			CONFIG_USBD_HS
1132			Define this to enable the high speed support for usb
1133			device and usbtty. If this feature is enabled, a routine
1134			int is_usbd_high_speed(void)
1135			also needs to be defined by the driver to dynamically poll
1136			whether the enumeration has succeded at high speed or full
1137			speed.
1138
1139			CONFIG_SYS_CONSOLE_IS_IN_ENV
1140			Define this if you want stdin, stdout &/or stderr to
1141			be set to usbtty.
1142
1143		If you have a USB-IF assigned VendorID then you may wish to
1144		define your own vendor specific values either in BoardName.h
1145		or directly in usbd_vendor_info.h. If you don't define
1146		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1147		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1148		should pretend to be a Linux device to it's target host.
1149
1150			CONFIG_USBD_MANUFACTURER
1151			Define this string as the name of your company for
1152			- CONFIG_USBD_MANUFACTURER "my company"
1153
1154			CONFIG_USBD_PRODUCT_NAME
1155			Define this string as the name of your product
1156			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1157
1158			CONFIG_USBD_VENDORID
1159			Define this as your assigned Vendor ID from the USB
1160			Implementors Forum. This *must* be a genuine Vendor ID
1161			to avoid polluting the USB namespace.
1162			- CONFIG_USBD_VENDORID 0xFFFF
1163
1164			CONFIG_USBD_PRODUCTID
1165			Define this as the unique Product ID
1166			for your device
1167			- CONFIG_USBD_PRODUCTID 0xFFFF
1168
1169- ULPI Layer Support:
1170		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1171		the generic ULPI layer. The generic layer accesses the ULPI PHY
1172		via the platform viewport, so you need both the genric layer and
1173		the viewport enabled. Currently only Chipidea/ARC based
1174		viewport is supported.
1175		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1176		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1177		If your ULPI phy needs a different reference clock than the
1178		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1179		the appropriate value in Hz.
1180
1181- MMC Support:
1182		The MMC controller on the Intel PXA is supported. To
1183		enable this define CONFIG_MMC. The MMC can be
1184		accessed from the boot prompt by mapping the device
1185		to physical memory similar to flash. Command line is
1186		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1187		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1188
1189		CONFIG_SH_MMCIF
1190		Support for Renesas on-chip MMCIF controller
1191
1192			CONFIG_SH_MMCIF_ADDR
1193			Define the base address of MMCIF registers
1194
1195			CONFIG_SH_MMCIF_CLK
1196			Define the clock frequency for MMCIF
1197
1198		CONFIG_SUPPORT_EMMC_BOOT
1199		Enable some additional features of the eMMC boot partitions.
1200
1201		CONFIG_SUPPORT_EMMC_RPMB
1202		Enable the commands for reading, writing and programming the
1203		key for the Replay Protection Memory Block partition in eMMC.
1204
1205- USB Device Firmware Update (DFU) class support:
1206		CONFIG_USB_FUNCTION_DFU
1207		This enables the USB portion of the DFU USB class
1208
1209		CONFIG_DFU_MMC
1210		This enables support for exposing (e)MMC devices via DFU.
1211
1212		CONFIG_DFU_NAND
1213		This enables support for exposing NAND devices via DFU.
1214
1215		CONFIG_DFU_RAM
1216		This enables support for exposing RAM via DFU.
1217		Note: DFU spec refer to non-volatile memory usage, but
1218		allow usages beyond the scope of spec - here RAM usage,
1219		one that would help mostly the developer.
1220
1221		CONFIG_SYS_DFU_DATA_BUF_SIZE
1222		Dfu transfer uses a buffer before writing data to the
1223		raw storage device. Make the size (in bytes) of this buffer
1224		configurable. The size of this buffer is also configurable
1225		through the "dfu_bufsiz" environment variable.
1226
1227		CONFIG_SYS_DFU_MAX_FILE_SIZE
1228		When updating files rather than the raw storage device,
1229		we use a static buffer to copy the file into and then write
1230		the buffer once we've been given the whole file.  Define
1231		this to the maximum filesize (in bytes) for the buffer.
1232		Default is 4 MiB if undefined.
1233
1234		DFU_DEFAULT_POLL_TIMEOUT
1235		Poll timeout [ms], is the timeout a device can send to the
1236		host. The host must wait for this timeout before sending
1237		a subsequent DFU_GET_STATUS request to the device.
1238
1239		DFU_MANIFEST_POLL_TIMEOUT
1240		Poll timeout [ms], which the device sends to the host when
1241		entering dfuMANIFEST state. Host waits this timeout, before
1242		sending again an USB request to the device.
1243
1244- Journaling Flash filesystem support:
1245		CONFIG_JFFS2_NAND
1246		Define these for a default partition on a NAND device
1247
1248		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1249		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1250		Define these for a default partition on a NOR device
1251
1252- Keyboard Support:
1253		See Kconfig help for available keyboard drivers.
1254
1255		CONFIG_KEYBOARD
1256
1257		Define this to enable a custom keyboard support.
1258		This simply calls drv_keyboard_init() which must be
1259		defined in your board-specific files. This option is deprecated
1260		and is only used by novena. For new boards, use driver model
1261		instead.
1262
1263- Video support:
1264		CONFIG_FSL_DIU_FB
1265		Enable the Freescale DIU video driver.	Reference boards for
1266		SOCs that have a DIU should define this macro to enable DIU
1267		support, and should also define these other macros:
1268
1269			CONFIG_SYS_DIU_ADDR
1270			CONFIG_VIDEO
1271			CONFIG_CFB_CONSOLE
1272			CONFIG_VIDEO_SW_CURSOR
1273			CONFIG_VGA_AS_SINGLE_DEVICE
1274			CONFIG_VIDEO_LOGO
1275			CONFIG_VIDEO_BMP_LOGO
1276
1277		The DIU driver will look for the 'video-mode' environment
1278		variable, and if defined, enable the DIU as a console during
1279		boot.  See the documentation file doc/README.video for a
1280		description of this variable.
1281
1282- LCD Support:	CONFIG_LCD
1283
1284		Define this to enable LCD support (for output to LCD
1285		display); also select one of the supported displays
1286		by defining one of these:
1287
1288		CONFIG_ATMEL_LCD:
1289
1290			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1291
1292		CONFIG_NEC_NL6448AC33:
1293
1294			NEC NL6448AC33-18. Active, color, single scan.
1295
1296		CONFIG_NEC_NL6448BC20
1297
1298			NEC NL6448BC20-08. 6.5", 640x480.
1299			Active, color, single scan.
1300
1301		CONFIG_NEC_NL6448BC33_54
1302
1303			NEC NL6448BC33-54. 10.4", 640x480.
1304			Active, color, single scan.
1305
1306		CONFIG_SHARP_16x9
1307
1308			Sharp 320x240. Active, color, single scan.
1309			It isn't 16x9, and I am not sure what it is.
1310
1311		CONFIG_SHARP_LQ64D341
1312
1313			Sharp LQ64D341 display, 640x480.
1314			Active, color, single scan.
1315
1316		CONFIG_HLD1045
1317
1318			HLD1045 display, 640x480.
1319			Active, color, single scan.
1320
1321		CONFIG_OPTREX_BW
1322
1323			Optrex	 CBL50840-2 NF-FW 99 22 M5
1324			or
1325			Hitachi	 LMG6912RPFC-00T
1326			or
1327			Hitachi	 SP14Q002
1328
1329			320x240. Black & white.
1330
1331		CONFIG_LCD_ALIGNMENT
1332
1333		Normally the LCD is page-aligned (typically 4KB). If this is
1334		defined then the LCD will be aligned to this value instead.
1335		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1336		here, since it is cheaper to change data cache settings on
1337		a per-section basis.
1338
1339
1340		CONFIG_LCD_ROTATION
1341
1342		Sometimes, for example if the display is mounted in portrait
1343		mode or even if it's mounted landscape but rotated by 180degree,
1344		we need to rotate our content of the display relative to the
1345		framebuffer, so that user can read the messages which are
1346		printed out.
1347		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1348		initialized with a given rotation from "vl_rot" out of
1349		"vidinfo_t" which is provided by the board specific code.
1350		The value for vl_rot is coded as following (matching to
1351		fbcon=rotate:<n> linux-kernel commandline):
1352		0 = no rotation respectively 0 degree
1353		1 = 90 degree rotation
1354		2 = 180 degree rotation
1355		3 = 270 degree rotation
1356
1357		If CONFIG_LCD_ROTATION is not defined, the console will be
1358		initialized with 0degree rotation.
1359
1360		CONFIG_LCD_BMP_RLE8
1361
1362		Support drawing of RLE8-compressed bitmaps on the LCD.
1363
1364		CONFIG_I2C_EDID
1365
1366		Enables an 'i2c edid' command which can read EDID
1367		information over I2C from an attached LCD display.
1368
1369- Splash Screen Support: CONFIG_SPLASH_SCREEN
1370
1371		If this option is set, the environment is checked for
1372		a variable "splashimage". If found, the usual display
1373		of logo, copyright and system information on the LCD
1374		is suppressed and the BMP image at the address
1375		specified in "splashimage" is loaded instead. The
1376		console is redirected to the "nulldev", too. This
1377		allows for a "silent" boot where a splash screen is
1378		loaded very quickly after power-on.
1379
1380		CONFIG_SPLASHIMAGE_GUARD
1381
1382		If this option is set, then U-Boot will prevent the environment
1383		variable "splashimage" from being set to a problematic address
1384		(see doc/README.displaying-bmps).
1385		This option is useful for targets where, due to alignment
1386		restrictions, an improperly aligned BMP image will cause a data
1387		abort. If you think you will not have problems with unaligned
1388		accesses (for example because your toolchain prevents them)
1389		there is no need to set this option.
1390
1391		CONFIG_SPLASH_SCREEN_ALIGN
1392
1393		If this option is set the splash image can be freely positioned
1394		on the screen. Environment variable "splashpos" specifies the
1395		position as "x,y". If a positive number is given it is used as
1396		number of pixel from left/top. If a negative number is given it
1397		is used as number of pixel from right/bottom. You can also
1398		specify 'm' for centering the image.
1399
1400		Example:
1401		setenv splashpos m,m
1402			=> image at center of screen
1403
1404		setenv splashpos 30,20
1405			=> image at x = 30 and y = 20
1406
1407		setenv splashpos -10,m
1408			=> vertically centered image
1409			   at x = dspWidth - bmpWidth - 9
1410
1411- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1412
1413		If this option is set, additionally to standard BMP
1414		images, gzipped BMP images can be displayed via the
1415		splashscreen support or the bmp command.
1416
1417- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1418
1419		If this option is set, 8-bit RLE compressed BMP images
1420		can be displayed via the splashscreen support or the
1421		bmp command.
1422
1423- Compression support:
1424		CONFIG_GZIP
1425
1426		Enabled by default to support gzip compressed images.
1427
1428		CONFIG_BZIP2
1429
1430		If this option is set, support for bzip2 compressed
1431		images is included. If not, only uncompressed and gzip
1432		compressed images are supported.
1433
1434		NOTE: the bzip2 algorithm requires a lot of RAM, so
1435		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1436		be at least 4MB.
1437
1438- MII/PHY support:
1439		CONFIG_PHY_ADDR
1440
1441		The address of PHY on MII bus.
1442
1443		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1444
1445		The clock frequency of the MII bus
1446
1447		CONFIG_PHY_RESET_DELAY
1448
1449		Some PHY like Intel LXT971A need extra delay after
1450		reset before any MII register access is possible.
1451		For such PHY, set this option to the usec delay
1452		required. (minimum 300usec for LXT971A)
1453
1454		CONFIG_PHY_CMD_DELAY (ppc4xx)
1455
1456		Some PHY like Intel LXT971A need extra delay after
1457		command issued before MII status register can be read
1458
1459- IP address:
1460		CONFIG_IPADDR
1461
1462		Define a default value for the IP address to use for
1463		the default Ethernet interface, in case this is not
1464		determined through e.g. bootp.
1465		(Environment variable "ipaddr")
1466
1467- Server IP address:
1468		CONFIG_SERVERIP
1469
1470		Defines a default value for the IP address of a TFTP
1471		server to contact when using the "tftboot" command.
1472		(Environment variable "serverip")
1473
1474		CONFIG_KEEP_SERVERADDR
1475
1476		Keeps the server's MAC address, in the env 'serveraddr'
1477		for passing to bootargs (like Linux's netconsole option)
1478
1479- Gateway IP address:
1480		CONFIG_GATEWAYIP
1481
1482		Defines a default value for the IP address of the
1483		default router where packets to other networks are
1484		sent to.
1485		(Environment variable "gatewayip")
1486
1487- Subnet mask:
1488		CONFIG_NETMASK
1489
1490		Defines a default value for the subnet mask (or
1491		routing prefix) which is used to determine if an IP
1492		address belongs to the local subnet or needs to be
1493		forwarded through a router.
1494		(Environment variable "netmask")
1495
1496- Multicast TFTP Mode:
1497		CONFIG_MCAST_TFTP
1498
1499		Defines whether you want to support multicast TFTP as per
1500		rfc-2090; for example to work with atftp.  Lets lots of targets
1501		tftp down the same boot image concurrently.  Note: the Ethernet
1502		driver in use must provide a function: mcast() to join/leave a
1503		multicast group.
1504
1505- BOOTP Recovery Mode:
1506		CONFIG_BOOTP_RANDOM_DELAY
1507
1508		If you have many targets in a network that try to
1509		boot using BOOTP, you may want to avoid that all
1510		systems send out BOOTP requests at precisely the same
1511		moment (which would happen for instance at recovery
1512		from a power failure, when all systems will try to
1513		boot, thus flooding the BOOTP server. Defining
1514		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1515		inserted before sending out BOOTP requests. The
1516		following delays are inserted then:
1517
1518		1st BOOTP request:	delay 0 ... 1 sec
1519		2nd BOOTP request:	delay 0 ... 2 sec
1520		3rd BOOTP request:	delay 0 ... 4 sec
1521		4th and following
1522		BOOTP requests:		delay 0 ... 8 sec
1523
1524		CONFIG_BOOTP_ID_CACHE_SIZE
1525
1526		BOOTP packets are uniquely identified using a 32-bit ID. The
1527		server will copy the ID from client requests to responses and
1528		U-Boot will use this to determine if it is the destination of
1529		an incoming response. Some servers will check that addresses
1530		aren't in use before handing them out (usually using an ARP
1531		ping) and therefore take up to a few hundred milliseconds to
1532		respond. Network congestion may also influence the time it
1533		takes for a response to make it back to the client. If that
1534		time is too long, U-Boot will retransmit requests. In order
1535		to allow earlier responses to still be accepted after these
1536		retransmissions, U-Boot's BOOTP client keeps a small cache of
1537		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1538		cache. The default is to keep IDs for up to four outstanding
1539		requests. Increasing this will allow U-Boot to accept offers
1540		from a BOOTP client in networks with unusually high latency.
1541
1542- DHCP Advanced Options:
1543		You can fine tune the DHCP functionality by defining
1544		CONFIG_BOOTP_* symbols:
1545
1546		CONFIG_BOOTP_SUBNETMASK
1547		CONFIG_BOOTP_GATEWAY
1548		CONFIG_BOOTP_HOSTNAME
1549		CONFIG_BOOTP_NISDOMAIN
1550		CONFIG_BOOTP_BOOTPATH
1551		CONFIG_BOOTP_BOOTFILESIZE
1552		CONFIG_BOOTP_DNS
1553		CONFIG_BOOTP_DNS2
1554		CONFIG_BOOTP_SEND_HOSTNAME
1555		CONFIG_BOOTP_NTPSERVER
1556		CONFIG_BOOTP_TIMEOFFSET
1557		CONFIG_BOOTP_VENDOREX
1558		CONFIG_BOOTP_MAY_FAIL
1559
1560		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1561		environment variable, not the BOOTP server.
1562
1563		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1564		after the configured retry count, the call will fail
1565		instead of starting over.  This can be used to fail over
1566		to Link-local IP address configuration if the DHCP server
1567		is not available.
1568
1569		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1570		serverip from a DHCP server, it is possible that more
1571		than one DNS serverip is offered to the client.
1572		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1573		serverip will be stored in the additional environment
1574		variable "dnsip2". The first DNS serverip is always
1575		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1576		is defined.
1577
1578		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1579		to do a dynamic update of a DNS server. To do this, they
1580		need the hostname of the DHCP requester.
1581		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1582		of the "hostname" environment variable is passed as
1583		option 12 to the DHCP server.
1584
1585		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1586
1587		A 32bit value in microseconds for a delay between
1588		receiving a "DHCP Offer" and sending the "DHCP Request".
1589		This fixes a problem with certain DHCP servers that don't
1590		respond 100% of the time to a "DHCP request". E.g. On an
1591		AT91RM9200 processor running at 180MHz, this delay needed
1592		to be *at least* 15,000 usec before a Windows Server 2003
1593		DHCP server would reply 100% of the time. I recommend at
1594		least 50,000 usec to be safe. The alternative is to hope
1595		that one of the retries will be successful but note that
1596		the DHCP timeout and retry process takes a longer than
1597		this delay.
1598
1599 - Link-local IP address negotiation:
1600		Negotiate with other link-local clients on the local network
1601		for an address that doesn't require explicit configuration.
1602		This is especially useful if a DHCP server cannot be guaranteed
1603		to exist in all environments that the device must operate.
1604
1605		See doc/README.link-local for more information.
1606
1607 - MAC address from environment variables
1608
1609		FDT_SEQ_MACADDR_FROM_ENV
1610
1611		Fix-up device tree with MAC addresses fetched sequentially from
1612		environment variables. This config work on assumption that
1613		non-usable ethernet node of device-tree are either not present
1614		or their status has been marked as "disabled".
1615
1616 - CDP Options:
1617		CONFIG_CDP_DEVICE_ID
1618
1619		The device id used in CDP trigger frames.
1620
1621		CONFIG_CDP_DEVICE_ID_PREFIX
1622
1623		A two character string which is prefixed to the MAC address
1624		of the device.
1625
1626		CONFIG_CDP_PORT_ID
1627
1628		A printf format string which contains the ascii name of
1629		the port. Normally is set to "eth%d" which sets
1630		eth0 for the first Ethernet, eth1 for the second etc.
1631
1632		CONFIG_CDP_CAPABILITIES
1633
1634		A 32bit integer which indicates the device capabilities;
1635		0x00000010 for a normal host which does not forwards.
1636
1637		CONFIG_CDP_VERSION
1638
1639		An ascii string containing the version of the software.
1640
1641		CONFIG_CDP_PLATFORM
1642
1643		An ascii string containing the name of the platform.
1644
1645		CONFIG_CDP_TRIGGER
1646
1647		A 32bit integer sent on the trigger.
1648
1649		CONFIG_CDP_POWER_CONSUMPTION
1650
1651		A 16bit integer containing the power consumption of the
1652		device in .1 of milliwatts.
1653
1654		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1655
1656		A byte containing the id of the VLAN.
1657
1658- Status LED:	CONFIG_LED_STATUS
1659
1660		Several configurations allow to display the current
1661		status using a LED. For instance, the LED will blink
1662		fast while running U-Boot code, stop blinking as
1663		soon as a reply to a BOOTP request was received, and
1664		start blinking slow once the Linux kernel is running
1665		(supported by a status LED driver in the Linux
1666		kernel). Defining CONFIG_LED_STATUS enables this
1667		feature in U-Boot.
1668
1669		Additional options:
1670
1671		CONFIG_LED_STATUS_GPIO
1672		The status LED can be connected to a GPIO pin.
1673		In such cases, the gpio_led driver can be used as a
1674		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1675		to include the gpio_led driver in the U-Boot binary.
1676
1677		CONFIG_GPIO_LED_INVERTED_TABLE
1678		Some GPIO connected LEDs may have inverted polarity in which
1679		case the GPIO high value corresponds to LED off state and
1680		GPIO low value corresponds to LED on state.
1681		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1682		with a list of GPIO LEDs that have inverted polarity.
1683
1684- I2C Support:	CONFIG_SYS_I2C
1685
1686		This enable the NEW i2c subsystem, and will allow you to use
1687		i2c commands at the u-boot command line (as long as you set
1688		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1689		based realtime clock chips or other i2c devices. See
1690		common/cmd_i2c.c for a description of the command line
1691		interface.
1692
1693		ported i2c driver to the new framework:
1694		- drivers/i2c/soft_i2c.c:
1695		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1696		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1697		    for defining speed and slave address
1698		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1699		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1700		    for defining speed and slave address
1701		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1702		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1703		    for defining speed and slave address
1704		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1705		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1706		    for defining speed and slave address
1707
1708		- drivers/i2c/fsl_i2c.c:
1709		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1710		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1711		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1712		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1713		    bus.
1714		  - If your board supports a second fsl i2c bus, define
1715		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1716		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1717		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1718		    second bus.
1719
1720		- drivers/i2c/tegra_i2c.c:
1721		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1722		  - This driver adds 4 i2c buses with a fix speed from
1723		    100000 and the slave addr 0!
1724
1725		- drivers/i2c/ppc4xx_i2c.c
1726		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1727		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1728		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1729
1730		- drivers/i2c/i2c_mxc.c
1731		  - activate this driver with CONFIG_SYS_I2C_MXC
1732		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1733		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1734		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1735		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1736		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1737		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1738		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1739		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1740		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1741		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1742		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1743		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1744		If those defines are not set, default value is 100000
1745		for speed, and 0 for slave.
1746
1747		- drivers/i2c/rcar_i2c.c:
1748		  - activate this driver with CONFIG_SYS_I2C_RCAR
1749		  - This driver adds 4 i2c buses
1750
1751		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1752		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1753		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1754		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1755		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1756		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1757		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1758		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1759		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1760
1761		- drivers/i2c/sh_i2c.c:
1762		  - activate this driver with CONFIG_SYS_I2C_SH
1763		  - This driver adds from 2 to 5 i2c buses
1764
1765		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1766		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1767		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1768		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1769		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1770		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1771		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1772		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1773		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1774		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1775		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1776
1777		- drivers/i2c/omap24xx_i2c.c
1778		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1779		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1780		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1781		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1782		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1783		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1784		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1785		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1786		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1787		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1788		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1789
1790		- drivers/i2c/zynq_i2c.c
1791		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1792		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1793		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1794
1795		- drivers/i2c/s3c24x0_i2c.c:
1796		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1797		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1798		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1799		    with a fix speed from 100000 and the slave addr 0!
1800
1801		- drivers/i2c/ihs_i2c.c
1802		  - activate this driver with CONFIG_SYS_I2C_IHS
1803		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1804		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1805		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1806		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1807		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1808		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1809		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1810		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1811		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1812		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1813		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1814		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1815		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1816		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1817		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1818		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1819		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1820		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1821		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1822		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1823		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1824
1825		additional defines:
1826
1827		CONFIG_SYS_NUM_I2C_BUSES
1828		Hold the number of i2c buses you want to use.
1829
1830		CONFIG_SYS_I2C_DIRECT_BUS
1831		define this, if you don't use i2c muxes on your hardware.
1832		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1833		omit this define.
1834
1835		CONFIG_SYS_I2C_MAX_HOPS
1836		define how many muxes are maximal consecutively connected
1837		on one i2c bus. If you not use i2c muxes, omit this
1838		define.
1839
1840		CONFIG_SYS_I2C_BUSES
1841		hold a list of buses you want to use, only used if
1842		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1843		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1844		CONFIG_SYS_NUM_I2C_BUSES = 9:
1845
1846		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1847					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1848					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1849					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1850					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1851					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1852					{1, {I2C_NULL_HOP}}, \
1853					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1854					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1855					}
1856
1857		which defines
1858			bus 0 on adapter 0 without a mux
1859			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1860			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1861			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1862			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1863			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1864			bus 6 on adapter 1 without a mux
1865			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1866			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1867
1868		If you do not have i2c muxes on your board, omit this define.
1869
1870- Legacy I2C Support:
1871		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1872		then the following macros need to be defined (examples are
1873		from include/configs/lwmon.h):
1874
1875		I2C_INIT
1876
1877		(Optional). Any commands necessary to enable the I2C
1878		controller or configure ports.
1879
1880		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1881
1882		I2C_ACTIVE
1883
1884		The code necessary to make the I2C data line active
1885		(driven).  If the data line is open collector, this
1886		define can be null.
1887
1888		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1889
1890		I2C_TRISTATE
1891
1892		The code necessary to make the I2C data line tri-stated
1893		(inactive).  If the data line is open collector, this
1894		define can be null.
1895
1896		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1897
1898		I2C_READ
1899
1900		Code that returns true if the I2C data line is high,
1901		false if it is low.
1902
1903		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1904
1905		I2C_SDA(bit)
1906
1907		If <bit> is true, sets the I2C data line high. If it
1908		is false, it clears it (low).
1909
1910		eg: #define I2C_SDA(bit) \
1911			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1912			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1913
1914		I2C_SCL(bit)
1915
1916		If <bit> is true, sets the I2C clock line high. If it
1917		is false, it clears it (low).
1918
1919		eg: #define I2C_SCL(bit) \
1920			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1921			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1922
1923		I2C_DELAY
1924
1925		This delay is invoked four times per clock cycle so this
1926		controls the rate of data transfer.  The data rate thus
1927		is 1 / (I2C_DELAY * 4). Often defined to be something
1928		like:
1929
1930		#define I2C_DELAY  udelay(2)
1931
1932		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1933
1934		If your arch supports the generic GPIO framework (asm/gpio.h),
1935		then you may alternatively define the two GPIOs that are to be
1936		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1937		have GPIO-based defaults assigned to them as appropriate.
1938
1939		You should define these to the GPIO value as given directly to
1940		the generic GPIO functions.
1941
1942		CONFIG_SYS_I2C_INIT_BOARD
1943
1944		When a board is reset during an i2c bus transfer
1945		chips might think that the current transfer is still
1946		in progress. On some boards it is possible to access
1947		the i2c SCLK line directly, either by using the
1948		processor pin as a GPIO or by having a second pin
1949		connected to the bus. If this option is defined a
1950		custom i2c_init_board() routine in boards/xxx/board.c
1951		is run early in the boot sequence.
1952
1953		CONFIG_I2C_MULTI_BUS
1954
1955		This option allows the use of multiple I2C buses, each of which
1956		must have a controller.	 At any point in time, only one bus is
1957		active.	 To switch to a different bus, use the 'i2c dev' command.
1958		Note that bus numbering is zero-based.
1959
1960		CONFIG_SYS_I2C_NOPROBES
1961
1962		This option specifies a list of I2C devices that will be skipped
1963		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1964		is set, specify a list of bus-device pairs.  Otherwise, specify
1965		a 1D array of device addresses
1966
1967		e.g.
1968			#undef	CONFIG_I2C_MULTI_BUS
1969			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1970
1971		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1972
1973			#define CONFIG_I2C_MULTI_BUS
1974			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1975
1976		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1977
1978		CONFIG_SYS_SPD_BUS_NUM
1979
1980		If defined, then this indicates the I2C bus number for DDR SPD.
1981		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1982
1983		CONFIG_SYS_RTC_BUS_NUM
1984
1985		If defined, then this indicates the I2C bus number for the RTC.
1986		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1987
1988		CONFIG_SOFT_I2C_READ_REPEATED_START
1989
1990		defining this will force the i2c_read() function in
1991		the soft_i2c driver to perform an I2C repeated start
1992		between writing the address pointer and reading the
1993		data.  If this define is omitted the default behaviour
1994		of doing a stop-start sequence will be used.  Most I2C
1995		devices can use either method, but some require one or
1996		the other.
1997
1998- SPI Support:	CONFIG_SPI
1999
2000		Enables SPI driver (so far only tested with
2001		SPI EEPROM, also an instance works with Crystal A/D and
2002		D/As on the SACSng board)
2003
2004		CONFIG_SH_SPI
2005
2006		Enables the driver for SPI controller on SuperH. Currently
2007		only SH7757 is supported.
2008
2009		CONFIG_SOFT_SPI
2010
2011		Enables a software (bit-bang) SPI driver rather than
2012		using hardware support. This is a general purpose
2013		driver that only requires three general I/O port pins
2014		(two outputs, one input) to function. If this is
2015		defined, the board configuration must define several
2016		SPI configuration items (port pins to use, etc). For
2017		an example, see include/configs/sacsng.h.
2018
2019		CONFIG_HARD_SPI
2020
2021		Enables a hardware SPI driver for general-purpose reads
2022		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2023		must define a list of chip-select function pointers.
2024		Currently supported on some MPC8xxx processors.	 For an
2025		example, see include/configs/mpc8349emds.h.
2026
2027		CONFIG_MXC_SPI
2028
2029		Enables the driver for the SPI controllers on i.MX and MXC
2030		SoCs. Currently i.MX31/35/51 are supported.
2031
2032		CONFIG_SYS_SPI_MXC_WAIT
2033		Timeout for waiting until spi transfer completed.
2034		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2035
2036- FPGA Support: CONFIG_FPGA
2037
2038		Enables FPGA subsystem.
2039
2040		CONFIG_FPGA_<vendor>
2041
2042		Enables support for specific chip vendors.
2043		(ALTERA, XILINX)
2044
2045		CONFIG_FPGA_<family>
2046
2047		Enables support for FPGA family.
2048		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2049
2050		CONFIG_FPGA_COUNT
2051
2052		Specify the number of FPGA devices to support.
2053
2054		CONFIG_SYS_FPGA_PROG_FEEDBACK
2055
2056		Enable printing of hash marks during FPGA configuration.
2057
2058		CONFIG_SYS_FPGA_CHECK_BUSY
2059
2060		Enable checks on FPGA configuration interface busy
2061		status by the configuration function. This option
2062		will require a board or device specific function to
2063		be written.
2064
2065		CONFIG_FPGA_DELAY
2066
2067		If defined, a function that provides delays in the FPGA
2068		configuration driver.
2069
2070		CONFIG_SYS_FPGA_CHECK_CTRLC
2071		Allow Control-C to interrupt FPGA configuration
2072
2073		CONFIG_SYS_FPGA_CHECK_ERROR
2074
2075		Check for configuration errors during FPGA bitfile
2076		loading. For example, abort during Virtex II
2077		configuration if the INIT_B line goes low (which
2078		indicated a CRC error).
2079
2080		CONFIG_SYS_FPGA_WAIT_INIT
2081
2082		Maximum time to wait for the INIT_B line to de-assert
2083		after PROB_B has been de-asserted during a Virtex II
2084		FPGA configuration sequence. The default time is 500
2085		ms.
2086
2087		CONFIG_SYS_FPGA_WAIT_BUSY
2088
2089		Maximum time to wait for BUSY to de-assert during
2090		Virtex II FPGA configuration. The default is 5 ms.
2091
2092		CONFIG_SYS_FPGA_WAIT_CONFIG
2093
2094		Time to wait after FPGA configuration. The default is
2095		200 ms.
2096
2097- Configuration Management:
2098		CONFIG_BUILD_TARGET
2099
2100		Some SoCs need special image types (e.g. U-Boot binary
2101		with a special header) as build targets. By defining
2102		CONFIG_BUILD_TARGET in the SoC / board header, this
2103		special image will be automatically built upon calling
2104		make / buildman.
2105
2106		CONFIG_IDENT_STRING
2107
2108		If defined, this string will be added to the U-Boot
2109		version information (U_BOOT_VERSION)
2110
2111- Vendor Parameter Protection:
2112
2113		U-Boot considers the values of the environment
2114		variables "serial#" (Board Serial Number) and
2115		"ethaddr" (Ethernet Address) to be parameters that
2116		are set once by the board vendor / manufacturer, and
2117		protects these variables from casual modification by
2118		the user. Once set, these variables are read-only,
2119		and write or delete attempts are rejected. You can
2120		change this behaviour:
2121
2122		If CONFIG_ENV_OVERWRITE is #defined in your config
2123		file, the write protection for vendor parameters is
2124		completely disabled. Anybody can change or delete
2125		these parameters.
2126
2127		Alternatively, if you define _both_ an ethaddr in the
2128		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2129		Ethernet address is installed in the environment,
2130		which can be changed exactly ONCE by the user. [The
2131		serial# is unaffected by this, i. e. it remains
2132		read-only.]
2133
2134		The same can be accomplished in a more flexible way
2135		for any variable by configuring the type of access
2136		to allow for those variables in the ".flags" variable
2137		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2138
2139- Protected RAM:
2140		CONFIG_PRAM
2141
2142		Define this variable to enable the reservation of
2143		"protected RAM", i. e. RAM which is not overwritten
2144		by U-Boot. Define CONFIG_PRAM to hold the number of
2145		kB you want to reserve for pRAM. You can overwrite
2146		this default value by defining an environment
2147		variable "pram" to the number of kB you want to
2148		reserve. Note that the board info structure will
2149		still show the full amount of RAM. If pRAM is
2150		reserved, a new environment variable "mem" will
2151		automatically be defined to hold the amount of
2152		remaining RAM in a form that can be passed as boot
2153		argument to Linux, for instance like that:
2154
2155			setenv bootargs ... mem=\${mem}
2156			saveenv
2157
2158		This way you can tell Linux not to use this memory,
2159		either, which results in a memory region that will
2160		not be affected by reboots.
2161
2162		*WARNING* If your board configuration uses automatic
2163		detection of the RAM size, you must make sure that
2164		this memory test is non-destructive. So far, the
2165		following board configurations are known to be
2166		"pRAM-clean":
2167
2168			IVMS8, IVML24, SPD8xx,
2169			HERMES, IP860, RPXlite, LWMON,
2170			FLAGADM
2171
2172- Access to physical memory region (> 4GB)
2173		Some basic support is provided for operations on memory not
2174		normally accessible to U-Boot - e.g. some architectures
2175		support access to more than 4GB of memory on 32-bit
2176		machines using physical address extension or similar.
2177		Define CONFIG_PHYSMEM to access this basic support, which
2178		currently only supports clearing the memory.
2179
2180- Error Recovery:
2181		CONFIG_NET_RETRY_COUNT
2182
2183		This variable defines the number of retries for
2184		network operations like ARP, RARP, TFTP, or BOOTP
2185		before giving up the operation. If not defined, a
2186		default value of 5 is used.
2187
2188		CONFIG_ARP_TIMEOUT
2189
2190		Timeout waiting for an ARP reply in milliseconds.
2191
2192		CONFIG_NFS_TIMEOUT
2193
2194		Timeout in milliseconds used in NFS protocol.
2195		If you encounter "ERROR: Cannot umount" in nfs command,
2196		try longer timeout such as
2197		#define CONFIG_NFS_TIMEOUT 10000UL
2198
2199- Command Interpreter:
2200		CONFIG_AUTO_COMPLETE
2201
2202		Enable auto completion of commands using TAB.
2203
2204		CONFIG_SYS_PROMPT_HUSH_PS2
2205
2206		This defines the secondary prompt string, which is
2207		printed when the command interpreter needs more input
2208		to complete a command. Usually "> ".
2209
2210	Note:
2211
2212		In the current implementation, the local variables
2213		space and global environment variables space are
2214		separated. Local variables are those you define by
2215		simply typing `name=value'. To access a local
2216		variable later on, you have write `$name' or
2217		`${name}'; to execute the contents of a variable
2218		directly type `$name' at the command prompt.
2219
2220		Global environment variables are those you use
2221		setenv/printenv to work with. To run a command stored
2222		in such a variable, you need to use the run command,
2223		and you must not use the '$' sign to access them.
2224
2225		To store commands and special characters in a
2226		variable, please use double quotation marks
2227		surrounding the whole text of the variable, instead
2228		of the backslashes before semicolons and special
2229		symbols.
2230
2231- Command Line Editing and History:
2232		CONFIG_CMDLINE_EDITING
2233
2234		Enable editing and History functions for interactive
2235		command line input operations
2236
2237- Command Line PS1/PS2 support:
2238		CONFIG_CMDLINE_PS_SUPPORT
2239
2240		Enable support for changing the command prompt string
2241		at run-time. Only static string is supported so far.
2242		The string is obtained from environment variables PS1
2243		and PS2.
2244
2245- Default Environment:
2246		CONFIG_EXTRA_ENV_SETTINGS
2247
2248		Define this to contain any number of null terminated
2249		strings (variable = value pairs) that will be part of
2250		the default environment compiled into the boot image.
2251
2252		For example, place something like this in your
2253		board's config file:
2254
2255		#define CONFIG_EXTRA_ENV_SETTINGS \
2256			"myvar1=value1\0" \
2257			"myvar2=value2\0"
2258
2259		Warning: This method is based on knowledge about the
2260		internal format how the environment is stored by the
2261		U-Boot code. This is NOT an official, exported
2262		interface! Although it is unlikely that this format
2263		will change soon, there is no guarantee either.
2264		You better know what you are doing here.
2265
2266		Note: overly (ab)use of the default environment is
2267		discouraged. Make sure to check other ways to preset
2268		the environment like the "source" command or the
2269		boot command first.
2270
2271		CONFIG_ENV_VARS_UBOOT_CONFIG
2272
2273		Define this in order to add variables describing the
2274		U-Boot build configuration to the default environment.
2275		These will be named arch, cpu, board, vendor, and soc.
2276
2277		Enabling this option will cause the following to be defined:
2278
2279		- CONFIG_SYS_ARCH
2280		- CONFIG_SYS_CPU
2281		- CONFIG_SYS_BOARD
2282		- CONFIG_SYS_VENDOR
2283		- CONFIG_SYS_SOC
2284
2285		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2286
2287		Define this in order to add variables describing certain
2288		run-time determined information about the hardware to the
2289		environment.  These will be named board_name, board_rev.
2290
2291		CONFIG_DELAY_ENVIRONMENT
2292
2293		Normally the environment is loaded when the board is
2294		initialised so that it is available to U-Boot. This inhibits
2295		that so that the environment is not available until
2296		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2297		this is instead controlled by the value of
2298		/config/load-environment.
2299
2300- Serial Flash support
2301		Usage requires an initial 'sf probe' to define the serial
2302		flash parameters, followed by read/write/erase/update
2303		commands.
2304
2305		The following defaults may be provided by the platform
2306		to handle the common case when only a single serial
2307		flash is present on the system.
2308
2309		CONFIG_SF_DEFAULT_BUS		Bus identifier
2310		CONFIG_SF_DEFAULT_CS		Chip-select
2311		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2312		CONFIG_SF_DEFAULT_SPEED		in Hz
2313
2314		CONFIG_SYSTEMACE
2315
2316		Adding this option adds support for Xilinx SystemACE
2317		chips attached via some sort of local bus. The address
2318		of the chip must also be defined in the
2319		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2320
2321		#define CONFIG_SYSTEMACE
2322		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2323
2324		When SystemACE support is added, the "ace" device type
2325		becomes available to the fat commands, i.e. fatls.
2326
2327- TFTP Fixed UDP Port:
2328		CONFIG_TFTP_PORT
2329
2330		If this is defined, the environment variable tftpsrcp
2331		is used to supply the TFTP UDP source port value.
2332		If tftpsrcp isn't defined, the normal pseudo-random port
2333		number generator is used.
2334
2335		Also, the environment variable tftpdstp is used to supply
2336		the TFTP UDP destination port value.  If tftpdstp isn't
2337		defined, the normal port 69 is used.
2338
2339		The purpose for tftpsrcp is to allow a TFTP server to
2340		blindly start the TFTP transfer using the pre-configured
2341		target IP address and UDP port. This has the effect of
2342		"punching through" the (Windows XP) firewall, allowing
2343		the remainder of the TFTP transfer to proceed normally.
2344		A better solution is to properly configure the firewall,
2345		but sometimes that is not allowed.
2346
2347- bootcount support:
2348		CONFIG_BOOTCOUNT_LIMIT
2349
2350		This enables the bootcounter support, see:
2351		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2352
2353		CONFIG_AT91SAM9XE
2354		enable special bootcounter support on at91sam9xe based boards.
2355		CONFIG_SOC_DA8XX
2356		enable special bootcounter support on da850 based boards.
2357		CONFIG_BOOTCOUNT_RAM
2358		enable support for the bootcounter in RAM
2359		CONFIG_BOOTCOUNT_I2C
2360		enable support for the bootcounter on an i2c (like RTC) device.
2361			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2362			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2363						    the bootcounter.
2364			CONFIG_BOOTCOUNT_ALEN = address len
2365		CONFIG_BOOTCOUNT_EXT
2366		enable support for the bootcounter in EXT filesystem
2367			CONFIG_SYS_BOOTCOUNT_ADDR = RAM address used for read
2368                                                    and write.
2369			CONFIG_SYS_BOOTCOUNT_EXT_INTERFACE = interface
2370			CONFIG_SYS_BOOTCOUNT_EXT_DEVPART = device and part
2371			CONFIG_SYS_BOOTCOUNT_EXT_NAME = filename
2372
2373- Show boot progress:
2374		CONFIG_SHOW_BOOT_PROGRESS
2375
2376		Defining this option allows to add some board-
2377		specific code (calling a user-provided function
2378		"show_boot_progress(int)") that enables you to show
2379		the system's boot progress on some display (for
2380		example, some LED's) on your board. At the moment,
2381		the following checkpoints are implemented:
2382
2383
2384Legacy uImage format:
2385
2386  Arg	Where			When
2387    1	common/cmd_bootm.c	before attempting to boot an image
2388   -1	common/cmd_bootm.c	Image header has bad	 magic number
2389    2	common/cmd_bootm.c	Image header has correct magic number
2390   -2	common/cmd_bootm.c	Image header has bad	 checksum
2391    3	common/cmd_bootm.c	Image header has correct checksum
2392   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2393    4	common/cmd_bootm.c	Image data   has correct checksum
2394   -4	common/cmd_bootm.c	Image is for unsupported architecture
2395    5	common/cmd_bootm.c	Architecture check OK
2396   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2397    6	common/cmd_bootm.c	Image Type check OK
2398   -6	common/cmd_bootm.c	gunzip uncompression error
2399   -7	common/cmd_bootm.c	Unimplemented compression type
2400    7	common/cmd_bootm.c	Uncompression OK
2401    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2402   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2403
2404    9	common/image.c		Start initial ramdisk verification
2405  -10	common/image.c		Ramdisk header has bad	   magic number
2406  -11	common/image.c		Ramdisk header has bad	   checksum
2407   10	common/image.c		Ramdisk header is OK
2408  -12	common/image.c		Ramdisk data   has bad	   checksum
2409   11	common/image.c		Ramdisk data   has correct checksum
2410   12	common/image.c		Ramdisk verification complete, start loading
2411  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2412   13	common/image.c		Start multifile image verification
2413   14	common/image.c		No initial ramdisk, no multifile, continue.
2414
2415   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2416
2417  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2418  -31	post/post.c		POST test failed, detected by post_output_backlog()
2419  -32	post/post.c		POST test failed, detected by post_run_single()
2420
2421   34	common/cmd_doc.c	before loading a Image from a DOC device
2422  -35	common/cmd_doc.c	Bad usage of "doc" command
2423   35	common/cmd_doc.c	correct usage of "doc" command
2424  -36	common/cmd_doc.c	No boot device
2425   36	common/cmd_doc.c	correct boot device
2426  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2427   37	common/cmd_doc.c	correct chip ID found, device available
2428  -38	common/cmd_doc.c	Read Error on boot device
2429   38	common/cmd_doc.c	reading Image header from DOC device OK
2430  -39	common/cmd_doc.c	Image header has bad magic number
2431   39	common/cmd_doc.c	Image header has correct magic number
2432  -40	common/cmd_doc.c	Error reading Image from DOC device
2433   40	common/cmd_doc.c	Image header has correct magic number
2434   41	common/cmd_ide.c	before loading a Image from a IDE device
2435  -42	common/cmd_ide.c	Bad usage of "ide" command
2436   42	common/cmd_ide.c	correct usage of "ide" command
2437  -43	common/cmd_ide.c	No boot device
2438   43	common/cmd_ide.c	boot device found
2439  -44	common/cmd_ide.c	Device not available
2440   44	common/cmd_ide.c	Device available
2441  -45	common/cmd_ide.c	wrong partition selected
2442   45	common/cmd_ide.c	partition selected
2443  -46	common/cmd_ide.c	Unknown partition table
2444   46	common/cmd_ide.c	valid partition table found
2445  -47	common/cmd_ide.c	Invalid partition type
2446   47	common/cmd_ide.c	correct partition type
2447  -48	common/cmd_ide.c	Error reading Image Header on boot device
2448   48	common/cmd_ide.c	reading Image Header from IDE device OK
2449  -49	common/cmd_ide.c	Image header has bad magic number
2450   49	common/cmd_ide.c	Image header has correct magic number
2451  -50	common/cmd_ide.c	Image header has bad	 checksum
2452   50	common/cmd_ide.c	Image header has correct checksum
2453  -51	common/cmd_ide.c	Error reading Image from IDE device
2454   51	common/cmd_ide.c	reading Image from IDE device OK
2455   52	common/cmd_nand.c	before loading a Image from a NAND device
2456  -53	common/cmd_nand.c	Bad usage of "nand" command
2457   53	common/cmd_nand.c	correct usage of "nand" command
2458  -54	common/cmd_nand.c	No boot device
2459   54	common/cmd_nand.c	boot device found
2460  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2461   55	common/cmd_nand.c	correct chip ID found, device available
2462  -56	common/cmd_nand.c	Error reading Image Header on boot device
2463   56	common/cmd_nand.c	reading Image Header from NAND device OK
2464  -57	common/cmd_nand.c	Image header has bad magic number
2465   57	common/cmd_nand.c	Image header has correct magic number
2466  -58	common/cmd_nand.c	Error reading Image from NAND device
2467   58	common/cmd_nand.c	reading Image from NAND device OK
2468
2469  -60	common/env_common.c	Environment has a bad CRC, using default
2470
2471   64	net/eth.c		starting with Ethernet configuration.
2472  -64	net/eth.c		no Ethernet found.
2473   65	net/eth.c		Ethernet found.
2474
2475  -80	common/cmd_net.c	usage wrong
2476   80	common/cmd_net.c	before calling net_loop()
2477  -81	common/cmd_net.c	some error in net_loop() occurred
2478   81	common/cmd_net.c	net_loop() back without error
2479  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2480   82	common/cmd_net.c	trying automatic boot
2481   83	common/cmd_net.c	running "source" command
2482  -83	common/cmd_net.c	some error in automatic boot or "source" command
2483   84	common/cmd_net.c	end without errors
2484
2485FIT uImage format:
2486
2487  Arg	Where			When
2488  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2489 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2490  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2491 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2492  102	common/cmd_bootm.c	Kernel unit name specified
2493 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2494  103	common/cmd_bootm.c	Found configuration node
2495  104	common/cmd_bootm.c	Got kernel subimage node offset
2496 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2497  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2498 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2499  106	common/cmd_bootm.c	Architecture check OK
2500 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2501  107	common/cmd_bootm.c	Kernel subimage type OK
2502 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2503  108	common/cmd_bootm.c	Got kernel subimage data/size
2504 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2505 -109	common/cmd_bootm.c	Can't get kernel subimage type
2506 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2507 -111	common/cmd_bootm.c	Can't get kernel subimage os
2508 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2509 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2510
2511  120	common/image.c		Start initial ramdisk verification
2512 -120	common/image.c		Ramdisk FIT image has incorrect format
2513  121	common/image.c		Ramdisk FIT image has correct format
2514  122	common/image.c		No ramdisk subimage unit name, using configuration
2515 -122	common/image.c		Can't get configuration for ramdisk subimage
2516  123	common/image.c		Ramdisk unit name specified
2517 -124	common/image.c		Can't get ramdisk subimage node offset
2518  125	common/image.c		Got ramdisk subimage node offset
2519 -125	common/image.c		Ramdisk subimage hash verification failed
2520  126	common/image.c		Ramdisk subimage hash verification OK
2521 -126	common/image.c		Ramdisk subimage for unsupported architecture
2522  127	common/image.c		Architecture check OK
2523 -127	common/image.c		Can't get ramdisk subimage data/size
2524  128	common/image.c		Got ramdisk subimage data/size
2525  129	common/image.c		Can't get ramdisk load address
2526 -129	common/image.c		Got ramdisk load address
2527
2528 -130	common/cmd_doc.c	Incorrect FIT image format
2529  131	common/cmd_doc.c	FIT image format OK
2530
2531 -140	common/cmd_ide.c	Incorrect FIT image format
2532  141	common/cmd_ide.c	FIT image format OK
2533
2534 -150	common/cmd_nand.c	Incorrect FIT image format
2535  151	common/cmd_nand.c	FIT image format OK
2536
2537- legacy image format:
2538		CONFIG_IMAGE_FORMAT_LEGACY
2539		enables the legacy image format support in U-Boot.
2540
2541		Default:
2542		enabled if CONFIG_FIT_SIGNATURE is not defined.
2543
2544		CONFIG_DISABLE_IMAGE_LEGACY
2545		disable the legacy image format
2546
2547		This define is introduced, as the legacy image format is
2548		enabled per default for backward compatibility.
2549
2550- Standalone program support:
2551		CONFIG_STANDALONE_LOAD_ADDR
2552
2553		This option defines a board specific value for the
2554		address where standalone program gets loaded, thus
2555		overwriting the architecture dependent default
2556		settings.
2557
2558- Frame Buffer Address:
2559		CONFIG_FB_ADDR
2560
2561		Define CONFIG_FB_ADDR if you want to use specific
2562		address for frame buffer.  This is typically the case
2563		when using a graphics controller has separate video
2564		memory.  U-Boot will then place the frame buffer at
2565		the given address instead of dynamically reserving it
2566		in system RAM by calling lcd_setmem(), which grabs
2567		the memory for the frame buffer depending on the
2568		configured panel size.
2569
2570		Please see board_init_f function.
2571
2572- Automatic software updates via TFTP server
2573		CONFIG_UPDATE_TFTP
2574		CONFIG_UPDATE_TFTP_CNT_MAX
2575		CONFIG_UPDATE_TFTP_MSEC_MAX
2576
2577		These options enable and control the auto-update feature;
2578		for a more detailed description refer to doc/README.update.
2579
2580- MTD Support (mtdparts command, UBI support)
2581		CONFIG_MTD_DEVICE
2582
2583		Adds the MTD device infrastructure from the Linux kernel.
2584		Needed for mtdparts command support.
2585
2586		CONFIG_MTD_PARTITIONS
2587
2588		Adds the MTD partitioning infrastructure from the Linux
2589		kernel. Needed for UBI support.
2590
2591- UBI support
2592		CONFIG_UBI_SILENCE_MSG
2593
2594		Make the verbose messages from UBI stop printing.  This leaves
2595		warnings and errors enabled.
2596
2597
2598		CONFIG_MTD_UBI_WL_THRESHOLD
2599		This parameter defines the maximum difference between the highest
2600		erase counter value and the lowest erase counter value of eraseblocks
2601		of UBI devices. When this threshold is exceeded, UBI starts performing
2602		wear leveling by means of moving data from eraseblock with low erase
2603		counter to eraseblocks with high erase counter.
2604
2605		The default value should be OK for SLC NAND flashes, NOR flashes and
2606		other flashes which have eraseblock life-cycle 100000 or more.
2607		However, in case of MLC NAND flashes which typically have eraseblock
2608		life-cycle less than 10000, the threshold should be lessened (e.g.,
2609		to 128 or 256, although it does not have to be power of 2).
2610
2611		default: 4096
2612
2613		CONFIG_MTD_UBI_BEB_LIMIT
2614		This option specifies the maximum bad physical eraseblocks UBI
2615		expects on the MTD device (per 1024 eraseblocks). If the
2616		underlying flash does not admit of bad eraseblocks (e.g. NOR
2617		flash), this value is ignored.
2618
2619		NAND datasheets often specify the minimum and maximum NVM
2620		(Number of Valid Blocks) for the flashes' endurance lifetime.
2621		The maximum expected bad eraseblocks per 1024 eraseblocks
2622		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2623		which gives 20 for most NANDs (MaxNVB is basically the total
2624		count of eraseblocks on the chip).
2625
2626		To put it differently, if this value is 20, UBI will try to
2627		reserve about 1.9% of physical eraseblocks for bad blocks
2628		handling. And that will be 1.9% of eraseblocks on the entire
2629		NAND chip, not just the MTD partition UBI attaches. This means
2630		that if you have, say, a NAND flash chip admits maximum 40 bad
2631		eraseblocks, and it is split on two MTD partitions of the same
2632		size, UBI will reserve 40 eraseblocks when attaching a
2633		partition.
2634
2635		default: 20
2636
2637		CONFIG_MTD_UBI_FASTMAP
2638		Fastmap is a mechanism which allows attaching an UBI device
2639		in nearly constant time. Instead of scanning the whole MTD device it
2640		only has to locate a checkpoint (called fastmap) on the device.
2641		The on-flash fastmap contains all information needed to attach
2642		the device. Using fastmap makes only sense on large devices where
2643		attaching by scanning takes long. UBI will not automatically install
2644		a fastmap on old images, but you can set the UBI parameter
2645		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2646		that fastmap-enabled images are still usable with UBI implementations
2647		without	fastmap support. On typical flash devices the whole fastmap
2648		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2649
2650		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2651		Set this parameter to enable fastmap automatically on images
2652		without a fastmap.
2653		default: 0
2654
2655		CONFIG_MTD_UBI_FM_DEBUG
2656		Enable UBI fastmap debug
2657		default: 0
2658
2659- UBIFS support
2660		CONFIG_UBIFS_SILENCE_MSG
2661
2662		Make the verbose messages from UBIFS stop printing.  This leaves
2663		warnings and errors enabled.
2664
2665- SPL framework
2666		CONFIG_SPL
2667		Enable building of SPL globally.
2668
2669		CONFIG_SPL_LDSCRIPT
2670		LDSCRIPT for linking the SPL binary.
2671
2672		CONFIG_SPL_MAX_FOOTPRINT
2673		Maximum size in memory allocated to the SPL, BSS included.
2674		When defined, the linker checks that the actual memory
2675		used by SPL from _start to __bss_end does not exceed it.
2676		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2677		must not be both defined at the same time.
2678
2679		CONFIG_SPL_MAX_SIZE
2680		Maximum size of the SPL image (text, data, rodata, and
2681		linker lists sections), BSS excluded.
2682		When defined, the linker checks that the actual size does
2683		not exceed it.
2684
2685		CONFIG_SPL_TEXT_BASE
2686		TEXT_BASE for linking the SPL binary.
2687
2688		CONFIG_SPL_RELOC_TEXT_BASE
2689		Address to relocate to.  If unspecified, this is equal to
2690		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2691
2692		CONFIG_SPL_BSS_START_ADDR
2693		Link address for the BSS within the SPL binary.
2694
2695		CONFIG_SPL_BSS_MAX_SIZE
2696		Maximum size in memory allocated to the SPL BSS.
2697		When defined, the linker checks that the actual memory used
2698		by SPL from __bss_start to __bss_end does not exceed it.
2699		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2700		must not be both defined at the same time.
2701
2702		CONFIG_SPL_STACK
2703		Adress of the start of the stack SPL will use
2704
2705		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2706		When defined, SPL will panic() if the image it has
2707		loaded does not have a signature.
2708		Defining this is useful when code which loads images
2709		in SPL cannot guarantee that absolutely all read errors
2710		will be caught.
2711		An example is the LPC32XX MLC NAND driver, which will
2712		consider that a completely unreadable NAND block is bad,
2713		and thus should be skipped silently.
2714
2715		CONFIG_SPL_RELOC_STACK
2716		Adress of the start of the stack SPL will use after
2717		relocation.  If unspecified, this is equal to
2718		CONFIG_SPL_STACK.
2719
2720		CONFIG_SYS_SPL_MALLOC_START
2721		Starting address of the malloc pool used in SPL.
2722		When this option is set the full malloc is used in SPL and
2723		it is set up by spl_init() and before that, the simple malloc()
2724		can be used if CONFIG_SYS_MALLOC_F is defined.
2725
2726		CONFIG_SYS_SPL_MALLOC_SIZE
2727		The size of the malloc pool used in SPL.
2728
2729		CONFIG_SPL_FRAMEWORK
2730		Enable the SPL framework under common/.  This framework
2731		supports MMC, NAND and YMODEM loading of U-Boot and NAND
2732		NAND loading of the Linux Kernel.
2733
2734		CONFIG_SPL_OS_BOOT
2735		Enable booting directly to an OS from SPL.
2736		See also: doc/README.falcon
2737
2738		CONFIG_SPL_DISPLAY_PRINT
2739		For ARM, enable an optional function to print more information
2740		about the running system.
2741
2742		CONFIG_SPL_INIT_MINIMAL
2743		Arch init code should be built for a very small image
2744
2745		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2746		Partition on the MMC to load U-Boot from when the MMC is being
2747		used in raw mode
2748
2749		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2750		Sector to load kernel uImage from when MMC is being
2751		used in raw mode (for Falcon mode)
2752
2753		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2754		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2755		Sector and number of sectors to load kernel argument
2756		parameters from when MMC is being used in raw mode
2757		(for falcon mode)
2758
2759		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2760		Partition on the MMC to load U-Boot from when the MMC is being
2761		used in fs mode
2762
2763		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2764		Filename to read to load U-Boot when reading from filesystem
2765
2766		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2767		Filename to read to load kernel uImage when reading
2768		from filesystem (for Falcon mode)
2769
2770		CONFIG_SPL_FS_LOAD_ARGS_NAME
2771		Filename to read to load kernel argument parameters
2772		when reading from filesystem (for Falcon mode)
2773
2774		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2775		Set this for NAND SPL on PPC mpc83xx targets, so that
2776		start.S waits for the rest of the SPL to load before
2777		continuing (the hardware starts execution after just
2778		loading the first page rather than the full 4K).
2779
2780		CONFIG_SPL_SKIP_RELOCATE
2781		Avoid SPL relocation
2782
2783		CONFIG_SPL_NAND_BASE
2784		Include nand_base.c in the SPL.  Requires
2785		CONFIG_SPL_NAND_DRIVERS.
2786
2787		CONFIG_SPL_NAND_DRIVERS
2788		SPL uses normal NAND drivers, not minimal drivers.
2789
2790		CONFIG_SPL_NAND_ECC
2791		Include standard software ECC in the SPL
2792
2793		CONFIG_SPL_NAND_SIMPLE
2794		Support for NAND boot using simple NAND drivers that
2795		expose the cmd_ctrl() interface.
2796
2797		CONFIG_SPL_UBI
2798		Support for a lightweight UBI (fastmap) scanner and
2799		loader
2800
2801		CONFIG_SPL_NAND_RAW_ONLY
2802		Support to boot only raw u-boot.bin images. Use this only
2803		if you need to save space.
2804
2805		CONFIG_SPL_COMMON_INIT_DDR
2806		Set for common ddr init with serial presence detect in
2807		SPL binary.
2808
2809		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2810		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2811		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2812		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2813		CONFIG_SYS_NAND_ECCBYTES
2814		Defines the size and behavior of the NAND that SPL uses
2815		to read U-Boot
2816
2817		CONFIG_SPL_NAND_BOOT
2818		Add support NAND boot
2819
2820		CONFIG_SYS_NAND_U_BOOT_OFFS
2821		Location in NAND to read U-Boot from
2822
2823		CONFIG_SYS_NAND_U_BOOT_DST
2824		Location in memory to load U-Boot to
2825
2826		CONFIG_SYS_NAND_U_BOOT_SIZE
2827		Size of image to load
2828
2829		CONFIG_SYS_NAND_U_BOOT_START
2830		Entry point in loaded image to jump to
2831
2832		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2833		Define this if you need to first read the OOB and then the
2834		data. This is used, for example, on davinci platforms.
2835
2836		CONFIG_SPL_RAM_DEVICE
2837		Support for running image already present in ram, in SPL binary
2838
2839		CONFIG_SPL_PAD_TO
2840		Image offset to which the SPL should be padded before appending
2841		the SPL payload. By default, this is defined as
2842		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2843		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2844		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2845
2846		CONFIG_SPL_TARGET
2847		Final target image containing SPL and payload.  Some SPLs
2848		use an arch-specific makefile fragment instead, for
2849		example if more than one image needs to be produced.
2850
2851		CONFIG_FIT_SPL_PRINT
2852		Printing information about a FIT image adds quite a bit of
2853		code to SPL. So this is normally disabled in SPL. Use this
2854		option to re-enable it. This will affect the output of the
2855		bootm command when booting a FIT image.
2856
2857- TPL framework
2858		CONFIG_TPL
2859		Enable building of TPL globally.
2860
2861		CONFIG_TPL_PAD_TO
2862		Image offset to which the TPL should be padded before appending
2863		the TPL payload. By default, this is defined as
2864		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2865		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2866		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2867
2868- Interrupt support (PPC):
2869
2870		There are common interrupt_init() and timer_interrupt()
2871		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2872		for CPU specific initialization. interrupt_init_cpu()
2873		should set decrementer_count to appropriate value. If
2874		CPU resets decrementer automatically after interrupt
2875		(ppc4xx) it should set decrementer_count to zero.
2876		timer_interrupt() calls timer_interrupt_cpu() for CPU
2877		specific handling. If board has watchdog / status_led
2878		/ other_activity_monitor it works automatically from
2879		general timer_interrupt().
2880
2881
2882Board initialization settings:
2883------------------------------
2884
2885During Initialization u-boot calls a number of board specific functions
2886to allow the preparation of board specific prerequisites, e.g. pin setup
2887before drivers are initialized. To enable these callbacks the
2888following configuration macros have to be defined. Currently this is
2889architecture specific, so please check arch/your_architecture/lib/board.c
2890typically in board_init_f() and board_init_r().
2891
2892- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2893- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2894- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2895- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2896
2897Configuration Settings:
2898-----------------------
2899
2900- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2901		Optionally it can be defined to support 64-bit memory commands.
2902
2903- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2904		undefine this when you're short of memory.
2905
2906- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2907		width of the commands listed in the 'help' command output.
2908
2909- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2910		prompt for user input.
2911
2912- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2913
2914- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2915
2916- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2917
2918- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2919		the application (usually a Linux kernel) when it is
2920		booted
2921
2922- CONFIG_SYS_BAUDRATE_TABLE:
2923		List of legal baudrate settings for this board.
2924
2925- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2926		Begin and End addresses of the area used by the
2927		simple memory test.
2928
2929- CONFIG_SYS_ALT_MEMTEST:
2930		Enable an alternate, more extensive memory test.
2931
2932- CONFIG_SYS_MEMTEST_SCRATCH:
2933		Scratch address used by the alternate memory test
2934		You only need to set this if address zero isn't writeable
2935
2936- CONFIG_SYS_MEM_RESERVE_SECURE
2937		Only implemented for ARMv8 for now.
2938		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2939		is substracted from total RAM and won't be reported to OS.
2940		This memory can be used as secure memory. A variable
2941		gd->arch.secure_ram is used to track the location. In systems
2942		the RAM base is not zero, or RAM is divided into banks,
2943		this variable needs to be recalcuated to get the address.
2944
2945- CONFIG_SYS_MEM_TOP_HIDE:
2946		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2947		this specified memory area will get subtracted from the top
2948		(end) of RAM and won't get "touched" at all by U-Boot. By
2949		fixing up gd->ram_size the Linux kernel should gets passed
2950		the now "corrected" memory size and won't touch it either.
2951		This should work for arch/ppc and arch/powerpc. Only Linux
2952		board ports in arch/powerpc with bootwrapper support that
2953		recalculate the memory size from the SDRAM controller setup
2954		will have to get fixed in Linux additionally.
2955
2956		This option can be used as a workaround for the 440EPx/GRx
2957		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2958		be touched.
2959
2960		WARNING: Please make sure that this value is a multiple of
2961		the Linux page size (normally 4k). If this is not the case,
2962		then the end address of the Linux memory will be located at a
2963		non page size aligned address and this could cause major
2964		problems.
2965
2966- CONFIG_SYS_LOADS_BAUD_CHANGE:
2967		Enable temporary baudrate change while serial download
2968
2969- CONFIG_SYS_SDRAM_BASE:
2970		Physical start address of SDRAM. _Must_ be 0 here.
2971
2972- CONFIG_SYS_FLASH_BASE:
2973		Physical start address of Flash memory.
2974
2975- CONFIG_SYS_MONITOR_BASE:
2976		Physical start address of boot monitor code (set by
2977		make config files to be same as the text base address
2978		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2979		CONFIG_SYS_FLASH_BASE when booting from flash.
2980
2981- CONFIG_SYS_MONITOR_LEN:
2982		Size of memory reserved for monitor code, used to
2983		determine _at_compile_time_ (!) if the environment is
2984		embedded within the U-Boot image, or in a separate
2985		flash sector.
2986
2987- CONFIG_SYS_MALLOC_LEN:
2988		Size of DRAM reserved for malloc() use.
2989
2990- CONFIG_SYS_MALLOC_F_LEN
2991		Size of the malloc() pool for use before relocation. If
2992		this is defined, then a very simple malloc() implementation
2993		will become available before relocation. The address is just
2994		below the global data, and the stack is moved down to make
2995		space.
2996
2997		This feature allocates regions with increasing addresses
2998		within the region. calloc() is supported, but realloc()
2999		is not available. free() is supported but does nothing.
3000		The memory will be freed (or in fact just forgotten) when
3001		U-Boot relocates itself.
3002
3003- CONFIG_SYS_MALLOC_SIMPLE
3004		Provides a simple and small malloc() and calloc() for those
3005		boards which do not use the full malloc in SPL (which is
3006		enabled with CONFIG_SYS_SPL_MALLOC_START).
3007
3008- CONFIG_SYS_NONCACHED_MEMORY:
3009		Size of non-cached memory area. This area of memory will be
3010		typically located right below the malloc() area and mapped
3011		uncached in the MMU. This is useful for drivers that would
3012		otherwise require a lot of explicit cache maintenance. For
3013		some drivers it's also impossible to properly maintain the
3014		cache. For example if the regions that need to be flushed
3015		are not a multiple of the cache-line size, *and* padding
3016		cannot be allocated between the regions to align them (i.e.
3017		if the HW requires a contiguous array of regions, and the
3018		size of each region is not cache-aligned), then a flush of
3019		one region may result in overwriting data that hardware has
3020		written to another region in the same cache-line. This can
3021		happen for example in network drivers where descriptors for
3022		buffers are typically smaller than the CPU cache-line (e.g.
3023		16 bytes vs. 32 or 64 bytes).
3024
3025		Non-cached memory is only supported on 32-bit ARM at present.
3026
3027- CONFIG_SYS_BOOTM_LEN:
3028		Normally compressed uImages are limited to an
3029		uncompressed size of 8 MBytes. If this is not enough,
3030		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3031		to adjust this setting to your needs.
3032
3033- CONFIG_SYS_BOOTMAPSZ:
3034		Maximum size of memory mapped by the startup code of
3035		the Linux kernel; all data that must be processed by
3036		the Linux kernel (bd_info, boot arguments, FDT blob if
3037		used) must be put below this limit, unless "bootm_low"
3038		environment variable is defined and non-zero. In such case
3039		all data for the Linux kernel must be between "bootm_low"
3040		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3041		variable "bootm_mapsize" will override the value of
3042		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3043		then the value in "bootm_size" will be used instead.
3044
3045- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3046		Enable initrd_high functionality.  If defined then the
3047		initrd_high feature is enabled and the bootm ramdisk subcommand
3048		is enabled.
3049
3050- CONFIG_SYS_BOOT_GET_CMDLINE:
3051		Enables allocating and saving kernel cmdline in space between
3052		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3053
3054- CONFIG_SYS_BOOT_GET_KBD:
3055		Enables allocating and saving a kernel copy of the bd_info in
3056		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3057
3058- CONFIG_SYS_MAX_FLASH_BANKS:
3059		Max number of Flash memory banks
3060
3061- CONFIG_SYS_MAX_FLASH_SECT:
3062		Max number of sectors on a Flash chip
3063
3064- CONFIG_SYS_FLASH_ERASE_TOUT:
3065		Timeout for Flash erase operations (in ms)
3066
3067- CONFIG_SYS_FLASH_WRITE_TOUT:
3068		Timeout for Flash write operations (in ms)
3069
3070- CONFIG_SYS_FLASH_LOCK_TOUT
3071		Timeout for Flash set sector lock bit operation (in ms)
3072
3073- CONFIG_SYS_FLASH_UNLOCK_TOUT
3074		Timeout for Flash clear lock bits operation (in ms)
3075
3076- CONFIG_SYS_FLASH_PROTECTION
3077		If defined, hardware flash sectors protection is used
3078		instead of U-Boot software protection.
3079
3080- CONFIG_SYS_DIRECT_FLASH_TFTP:
3081
3082		Enable TFTP transfers directly to flash memory;
3083		without this option such a download has to be
3084		performed in two steps: (1) download to RAM, and (2)
3085		copy from RAM to flash.
3086
3087		The two-step approach is usually more reliable, since
3088		you can check if the download worked before you erase
3089		the flash, but in some situations (when system RAM is
3090		too limited to allow for a temporary copy of the
3091		downloaded image) this option may be very useful.
3092
3093- CONFIG_SYS_FLASH_CFI:
3094		Define if the flash driver uses extra elements in the
3095		common flash structure for storing flash geometry.
3096
3097- CONFIG_FLASH_CFI_DRIVER
3098		This option also enables the building of the cfi_flash driver
3099		in the drivers directory
3100
3101- CONFIG_FLASH_CFI_MTD
3102		This option enables the building of the cfi_mtd driver
3103		in the drivers directory. The driver exports CFI flash
3104		to the MTD layer.
3105
3106- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3107		Use buffered writes to flash.
3108
3109- CONFIG_FLASH_SPANSION_S29WS_N
3110		s29ws-n MirrorBit flash has non-standard addresses for buffered
3111		write commands.
3112
3113- CONFIG_SYS_FLASH_QUIET_TEST
3114		If this option is defined, the common CFI flash doesn't
3115		print it's warning upon not recognized FLASH banks. This
3116		is useful, if some of the configured banks are only
3117		optionally available.
3118
3119- CONFIG_FLASH_SHOW_PROGRESS
3120		If defined (must be an integer), print out countdown
3121		digits and dots.  Recommended value: 45 (9..1) for 80
3122		column displays, 15 (3..1) for 40 column displays.
3123
3124- CONFIG_FLASH_VERIFY
3125		If defined, the content of the flash (destination) is compared
3126		against the source after the write operation. An error message
3127		will be printed when the contents are not identical.
3128		Please note that this option is useless in nearly all cases,
3129		since such flash programming errors usually are detected earlier
3130		while unprotecting/erasing/programming. Please only enable
3131		this option if you really know what you are doing.
3132
3133- CONFIG_SYS_RX_ETH_BUFFER:
3134		Defines the number of Ethernet receive buffers. On some
3135		Ethernet controllers it is recommended to set this value
3136		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3137		buffers can be full shortly after enabling the interface
3138		on high Ethernet traffic.
3139		Defaults to 4 if not defined.
3140
3141- CONFIG_ENV_MAX_ENTRIES
3142
3143	Maximum number of entries in the hash table that is used
3144	internally to store the environment settings. The default
3145	setting is supposed to be generous and should work in most
3146	cases. This setting can be used to tune behaviour; see
3147	lib/hashtable.c for details.
3148
3149- CONFIG_ENV_FLAGS_LIST_DEFAULT
3150- CONFIG_ENV_FLAGS_LIST_STATIC
3151	Enable validation of the values given to environment variables when
3152	calling env set.  Variables can be restricted to only decimal,
3153	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3154	the variables can also be restricted to IP address or MAC address.
3155
3156	The format of the list is:
3157		type_attribute = [s|d|x|b|i|m]
3158		access_attribute = [a|r|o|c]
3159		attributes = type_attribute[access_attribute]
3160		entry = variable_name[:attributes]
3161		list = entry[,list]
3162
3163	The type attributes are:
3164		s - String (default)
3165		d - Decimal
3166		x - Hexadecimal
3167		b - Boolean ([1yYtT|0nNfF])
3168		i - IP address
3169		m - MAC address
3170
3171	The access attributes are:
3172		a - Any (default)
3173		r - Read-only
3174		o - Write-once
3175		c - Change-default
3176
3177	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3178		Define this to a list (string) to define the ".flags"
3179		environment variable in the default or embedded environment.
3180
3181	- CONFIG_ENV_FLAGS_LIST_STATIC
3182		Define this to a list (string) to define validation that
3183		should be done if an entry is not found in the ".flags"
3184		environment variable.  To override a setting in the static
3185		list, simply add an entry for the same variable name to the
3186		".flags" variable.
3187
3188	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3189	regular expression. This allows multiple variables to define the same
3190	flags without explicitly listing them for each variable.
3191
3192- CONFIG_ENV_ACCESS_IGNORE_FORCE
3193	If defined, don't allow the -f switch to env set override variable
3194	access flags.
3195
3196- CONFIG_USE_STDINT
3197	If stdint.h is available with your toolchain you can define this
3198	option to enable it. You can provide option 'USE_STDINT=1' when
3199	building U-Boot to enable this.
3200
3201The following definitions that deal with the placement and management
3202of environment data (variable area); in general, we support the
3203following configurations:
3204
3205- CONFIG_BUILD_ENVCRC:
3206
3207	Builds up envcrc with the target environment so that external utils
3208	may easily extract it and embed it in final U-Boot images.
3209
3210BE CAREFUL! The first access to the environment happens quite early
3211in U-Boot initialization (when we try to get the setting of for the
3212console baudrate). You *MUST* have mapped your NVRAM area then, or
3213U-Boot will hang.
3214
3215Please note that even with NVRAM we still use a copy of the
3216environment in RAM: we could work on NVRAM directly, but we want to
3217keep settings there always unmodified except somebody uses "saveenv"
3218to save the current settings.
3219
3220BE CAREFUL! For some special cases, the local device can not use
3221"saveenv" command. For example, the local device will get the
3222environment stored in a remote NOR flash by SRIO or PCIE link,
3223but it can not erase, write this NOR flash by SRIO or PCIE interface.
3224
3225- CONFIG_NAND_ENV_DST
3226
3227	Defines address in RAM to which the nand_spl code should copy the
3228	environment. If redundant environment is used, it will be copied to
3229	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3230
3231Please note that the environment is read-only until the monitor
3232has been relocated to RAM and a RAM copy of the environment has been
3233created; also, when using EEPROM you will have to use env_get_f()
3234until then to read environment variables.
3235
3236The environment is protected by a CRC32 checksum. Before the monitor
3237is relocated into RAM, as a result of a bad CRC you will be working
3238with the compiled-in default environment - *silently*!!! [This is
3239necessary, because the first environment variable we need is the
3240"baudrate" setting for the console - if we have a bad CRC, we don't
3241have any device yet where we could complain.]
3242
3243Note: once the monitor has been relocated, then it will complain if
3244the default environment is used; a new CRC is computed as soon as you
3245use the "saveenv" command to store a valid environment.
3246
3247- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3248		Echo the inverted Ethernet link state to the fault LED.
3249
3250		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3251		      also needs to be defined.
3252
3253- CONFIG_SYS_FAULT_MII_ADDR:
3254		MII address of the PHY to check for the Ethernet link state.
3255
3256- CONFIG_NS16550_MIN_FUNCTIONS:
3257		Define this if you desire to only have use of the NS16550_init
3258		and NS16550_putc functions for the serial driver located at
3259		drivers/serial/ns16550.c.  This option is useful for saving
3260		space for already greatly restricted images, including but not
3261		limited to NAND_SPL configurations.
3262
3263- CONFIG_DISPLAY_BOARDINFO
3264		Display information about the board that U-Boot is running on
3265		when U-Boot starts up. The board function checkboard() is called
3266		to do this.
3267
3268- CONFIG_DISPLAY_BOARDINFO_LATE
3269		Similar to the previous option, but display this information
3270		later, once stdio is running and output goes to the LCD, if
3271		present.
3272
3273- CONFIG_BOARD_SIZE_LIMIT:
3274		Maximum size of the U-Boot image. When defined, the
3275		build system checks that the actual size does not
3276		exceed it.
3277
3278Low Level (hardware related) configuration options:
3279---------------------------------------------------
3280
3281- CONFIG_SYS_CACHELINE_SIZE:
3282		Cache Line Size of the CPU.
3283
3284- CONFIG_SYS_CCSRBAR_DEFAULT:
3285		Default (power-on reset) physical address of CCSR on Freescale
3286		PowerPC SOCs.
3287
3288- CONFIG_SYS_CCSRBAR:
3289		Virtual address of CCSR.  On a 32-bit build, this is typically
3290		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3291
3292- CONFIG_SYS_CCSRBAR_PHYS:
3293		Physical address of CCSR.  CCSR can be relocated to a new
3294		physical address, if desired.  In this case, this macro should
3295		be set to that address.	 Otherwise, it should be set to the
3296		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3297		is typically relocated on 36-bit builds.  It is recommended
3298		that this macro be defined via the _HIGH and _LOW macros:
3299
3300		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3301			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3302
3303- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3304		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3305		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3306		used in assembly code, so it must not contain typecasts or
3307		integer size suffixes (e.g. "ULL").
3308
3309- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3310		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3311		used in assembly code, so it must not contain typecasts or
3312		integer size suffixes (e.g. "ULL").
3313
3314- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3315		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3316		forced to a value that ensures that CCSR is not relocated.
3317
3318- Floppy Disk Support:
3319		CONFIG_SYS_FDC_DRIVE_NUMBER
3320
3321		the default drive number (default value 0)
3322
3323		CONFIG_SYS_ISA_IO_STRIDE
3324
3325		defines the spacing between FDC chipset registers
3326		(default value 1)
3327
3328		CONFIG_SYS_ISA_IO_OFFSET
3329
3330		defines the offset of register from address. It
3331		depends on which part of the data bus is connected to
3332		the FDC chipset. (default value 0)
3333
3334		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3335		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3336		default value.
3337
3338		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3339		fdc_hw_init() is called at the beginning of the FDC
3340		setup. fdc_hw_init() must be provided by the board
3341		source code. It is used to make hardware-dependent
3342		initializations.
3343
3344- CONFIG_IDE_AHB:
3345		Most IDE controllers were designed to be connected with PCI
3346		interface. Only few of them were designed for AHB interface.
3347		When software is doing ATA command and data transfer to
3348		IDE devices through IDE-AHB controller, some additional
3349		registers accessing to these kind of IDE-AHB controller
3350		is required.
3351
3352- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3353		DO NOT CHANGE unless you know exactly what you're
3354		doing! (11-4) [MPC8xx systems only]
3355
3356- CONFIG_SYS_INIT_RAM_ADDR:
3357
3358		Start address of memory area that can be used for
3359		initial data and stack; please note that this must be
3360		writable memory that is working WITHOUT special
3361		initialization, i. e. you CANNOT use normal RAM which
3362		will become available only after programming the
3363		memory controller and running certain initialization
3364		sequences.
3365
3366		U-Boot uses the following memory types:
3367		- MPC8xx: IMMR (internal memory of the CPU)
3368
3369- CONFIG_SYS_GBL_DATA_OFFSET:
3370
3371		Offset of the initial data structure in the memory
3372		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3373		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3374		data is located at the end of the available space
3375		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3376		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3377		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3378		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3379
3380	Note:
3381		On the MPC824X (or other systems that use the data
3382		cache for initial memory) the address chosen for
3383		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3384		point to an otherwise UNUSED address space between
3385		the top of RAM and the start of the PCI space.
3386
3387- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3388
3389- CONFIG_SYS_OR_TIMING_SDRAM:
3390		SDRAM timing
3391
3392- CONFIG_SYS_MAMR_PTA:
3393		periodic timer for refresh
3394
3395- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3396  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3397  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3398  CONFIG_SYS_BR1_PRELIM:
3399		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3400
3401- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3402  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3403  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3404		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3405
3406- CONFIG_PCI_ENUM_ONLY
3407		Only scan through and get the devices on the buses.
3408		Don't do any setup work, presumably because someone or
3409		something has already done it, and we don't need to do it
3410		a second time.	Useful for platforms that are pre-booted
3411		by coreboot or similar.
3412
3413- CONFIG_PCI_INDIRECT_BRIDGE:
3414		Enable support for indirect PCI bridges.
3415
3416- CONFIG_SYS_SRIO:
3417		Chip has SRIO or not
3418
3419- CONFIG_SRIO1:
3420		Board has SRIO 1 port available
3421
3422- CONFIG_SRIO2:
3423		Board has SRIO 2 port available
3424
3425- CONFIG_SRIO_PCIE_BOOT_MASTER
3426		Board can support master function for Boot from SRIO and PCIE
3427
3428- CONFIG_SYS_SRIOn_MEM_VIRT:
3429		Virtual Address of SRIO port 'n' memory region
3430
3431- CONFIG_SYS_SRIOn_MEM_PHYS:
3432		Physical Address of SRIO port 'n' memory region
3433
3434- CONFIG_SYS_SRIOn_MEM_SIZE:
3435		Size of SRIO port 'n' memory region
3436
3437- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3438		Defined to tell the NAND controller that the NAND chip is using
3439		a 16 bit bus.
3440		Not all NAND drivers use this symbol.
3441		Example of drivers that use it:
3442		- drivers/mtd/nand/ndfc.c
3443		- drivers/mtd/nand/mxc_nand.c
3444
3445- CONFIG_SYS_NDFC_EBC0_CFG
3446		Sets the EBC0_CFG register for the NDFC. If not defined
3447		a default value will be used.
3448
3449- CONFIG_SPD_EEPROM
3450		Get DDR timing information from an I2C EEPROM. Common
3451		with pluggable memory modules such as SODIMMs
3452
3453  SPD_EEPROM_ADDRESS
3454		I2C address of the SPD EEPROM
3455
3456- CONFIG_SYS_SPD_BUS_NUM
3457		If SPD EEPROM is on an I2C bus other than the first
3458		one, specify here. Note that the value must resolve
3459		to something your driver can deal with.
3460
3461- CONFIG_SYS_DDR_RAW_TIMING
3462		Get DDR timing information from other than SPD. Common with
3463		soldered DDR chips onboard without SPD. DDR raw timing
3464		parameters are extracted from datasheet and hard-coded into
3465		header files or board specific files.
3466
3467- CONFIG_FSL_DDR_INTERACTIVE
3468		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3469
3470- CONFIG_FSL_DDR_SYNC_REFRESH
3471		Enable sync of refresh for multiple controllers.
3472
3473- CONFIG_FSL_DDR_BIST
3474		Enable built-in memory test for Freescale DDR controllers.
3475
3476- CONFIG_SYS_83XX_DDR_USES_CS0
3477		Only for 83xx systems. If specified, then DDR should
3478		be configured using CS0 and CS1 instead of CS2 and CS3.
3479
3480- CONFIG_RMII
3481		Enable RMII mode for all FECs.
3482		Note that this is a global option, we can't
3483		have one FEC in standard MII mode and another in RMII mode.
3484
3485- CONFIG_CRC32_VERIFY
3486		Add a verify option to the crc32 command.
3487		The syntax is:
3488
3489		=> crc32 -v <address> <count> <crc32>
3490
3491		Where address/count indicate a memory area
3492		and crc32 is the correct crc32 which the
3493		area should have.
3494
3495- CONFIG_LOOPW
3496		Add the "loopw" memory command. This only takes effect if
3497		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3498
3499- CONFIG_MX_CYCLIC
3500		Add the "mdc" and "mwc" memory commands. These are cyclic
3501		"md/mw" commands.
3502		Examples:
3503
3504		=> mdc.b 10 4 500
3505		This command will print 4 bytes (10,11,12,13) each 500 ms.
3506
3507		=> mwc.l 100 12345678 10
3508		This command will write 12345678 to address 100 all 10 ms.
3509
3510		This only takes effect if the memory commands are activated
3511		globally (CONFIG_CMD_MEMORY).
3512
3513- CONFIG_SKIP_LOWLEVEL_INIT
3514		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3515		low level initializations (like setting up the memory
3516		controller) are omitted and/or U-Boot does not
3517		relocate itself into RAM.
3518
3519		Normally this variable MUST NOT be defined. The only
3520		exception is when U-Boot is loaded (to RAM) by some
3521		other boot loader or by a debugger which performs
3522		these initializations itself.
3523
3524- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3525		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3526		to be skipped. The normal CP15 init (such as enabling the
3527		instruction cache) is still performed.
3528
3529- CONFIG_SPL_BUILD
3530		Modifies the behaviour of start.S when compiling a loader
3531		that is executed before the actual U-Boot. E.g. when
3532		compiling a NAND SPL.
3533
3534- CONFIG_TPL_BUILD
3535		Modifies the behaviour of start.S  when compiling a loader
3536		that is executed after the SPL and before the actual U-Boot.
3537		It is loaded by the SPL.
3538
3539- CONFIG_SYS_MPC85XX_NO_RESETVEC
3540		Only for 85xx systems. If this variable is specified, the section
3541		.resetvec is not kept and the section .bootpg is placed in the
3542		previous 4k of the .text section.
3543
3544- CONFIG_ARCH_MAP_SYSMEM
3545		Generally U-Boot (and in particular the md command) uses
3546		effective address. It is therefore not necessary to regard
3547		U-Boot address as virtual addresses that need to be translated
3548		to physical addresses. However, sandbox requires this, since
3549		it maintains its own little RAM buffer which contains all
3550		addressable memory. This option causes some memory accesses
3551		to be mapped through map_sysmem() / unmap_sysmem().
3552
3553- CONFIG_X86_RESET_VECTOR
3554		If defined, the x86 reset vector code is included. This is not
3555		needed when U-Boot is running from Coreboot.
3556
3557- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
3558		Enables the RTC32K OSC on AM33xx based plattforms
3559
3560- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3561		Option to disable subpage write in NAND driver
3562		driver that uses this:
3563		drivers/mtd/nand/davinci_nand.c
3564
3565Freescale QE/FMAN Firmware Support:
3566-----------------------------------
3567
3568The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3569loading of "firmware", which is encoded in the QE firmware binary format.
3570This firmware often needs to be loaded during U-Boot booting, so macros
3571are used to identify the storage device (NOR flash, SPI, etc) and the address
3572within that device.
3573
3574- CONFIG_SYS_FMAN_FW_ADDR
3575	The address in the storage device where the FMAN microcode is located.  The
3576	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3577	is also specified.
3578
3579- CONFIG_SYS_QE_FW_ADDR
3580	The address in the storage device where the QE microcode is located.  The
3581	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3582	is also specified.
3583
3584- CONFIG_SYS_QE_FMAN_FW_LENGTH
3585	The maximum possible size of the firmware.  The firmware binary format
3586	has a field that specifies the actual size of the firmware, but it
3587	might not be possible to read any part of the firmware unless some
3588	local storage is allocated to hold the entire firmware first.
3589
3590- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3591	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3592	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3593	virtual address in NOR flash.
3594
3595- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3596	Specifies that QE/FMAN firmware is located in NAND flash.
3597	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3598
3599- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3600	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3601	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3602
3603- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3604	Specifies that QE/FMAN firmware is located in the remote (master)
3605	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3606	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3607	window->master inbound window->master LAW->the ucode address in
3608	master's memory space.
3609
3610Freescale Layerscape Management Complex Firmware Support:
3611---------------------------------------------------------
3612The Freescale Layerscape Management Complex (MC) supports the loading of
3613"firmware".
3614This firmware often needs to be loaded during U-Boot booting, so macros
3615are used to identify the storage device (NOR flash, SPI, etc) and the address
3616within that device.
3617
3618- CONFIG_FSL_MC_ENET
3619	Enable the MC driver for Layerscape SoCs.
3620
3621Freescale Layerscape Debug Server Support:
3622-------------------------------------------
3623The Freescale Layerscape Debug Server Support supports the loading of
3624"Debug Server firmware" and triggering SP boot-rom.
3625This firmware often needs to be loaded during U-Boot booting.
3626
3627- CONFIG_SYS_MC_RSV_MEM_ALIGN
3628	Define alignment of reserved memory MC requires
3629
3630Reproducible builds
3631-------------------
3632
3633In order to achieve reproducible builds, timestamps used in the U-Boot build
3634process have to be set to a fixed value.
3635
3636This is done using the SOURCE_DATE_EPOCH environment variable.
3637SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3638option for U-Boot or an environment variable in U-Boot.
3639
3640SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3641
3642Building the Software:
3643======================
3644
3645Building U-Boot has been tested in several native build environments
3646and in many different cross environments. Of course we cannot support
3647all possibly existing versions of cross development tools in all
3648(potentially obsolete) versions. In case of tool chain problems we
3649recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3650which is extensively used to build and test U-Boot.
3651
3652If you are not using a native environment, it is assumed that you
3653have GNU cross compiling tools available in your path. In this case,
3654you must set the environment variable CROSS_COMPILE in your shell.
3655Note that no changes to the Makefile or any other source files are
3656necessary. For example using the ELDK on a 4xx CPU, please enter:
3657
3658	$ CROSS_COMPILE=ppc_4xx-
3659	$ export CROSS_COMPILE
3660
3661Note: If you wish to generate Windows versions of the utilities in
3662      the tools directory you can use the MinGW toolchain
3663      (http://www.mingw.org).  Set your HOST tools to the MinGW
3664      toolchain and execute 'make tools'.  For example:
3665
3666       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3667
3668      Binaries such as tools/mkimage.exe will be created which can
3669      be executed on computers running Windows.
3670
3671U-Boot is intended to be simple to build. After installing the
3672sources you must configure U-Boot for one specific board type. This
3673is done by typing:
3674
3675	make NAME_defconfig
3676
3677where "NAME_defconfig" is the name of one of the existing configu-
3678rations; see boards.cfg for supported names.
3679
3680Note: for some board special configuration names may exist; check if
3681      additional information is available from the board vendor; for
3682      instance, the TQM823L systems are available without (standard)
3683      or with LCD support. You can select such additional "features"
3684      when choosing the configuration, i. e.
3685
3686      make TQM823L_defconfig
3687	- will configure for a plain TQM823L, i. e. no LCD support
3688
3689      make TQM823L_LCD_defconfig
3690	- will configure for a TQM823L with U-Boot console on LCD
3691
3692      etc.
3693
3694
3695Finally, type "make all", and you should get some working U-Boot
3696images ready for download to / installation on your system:
3697
3698- "u-boot.bin" is a raw binary image
3699- "u-boot" is an image in ELF binary format
3700- "u-boot.srec" is in Motorola S-Record format
3701
3702By default the build is performed locally and the objects are saved
3703in the source directory. One of the two methods can be used to change
3704this behavior and build U-Boot to some external directory:
3705
37061. Add O= to the make command line invocations:
3707
3708	make O=/tmp/build distclean
3709	make O=/tmp/build NAME_defconfig
3710	make O=/tmp/build all
3711
37122. Set environment variable KBUILD_OUTPUT to point to the desired location:
3713
3714	export KBUILD_OUTPUT=/tmp/build
3715	make distclean
3716	make NAME_defconfig
3717	make all
3718
3719Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3720variable.
3721
3722
3723Please be aware that the Makefiles assume you are using GNU make, so
3724for instance on NetBSD you might need to use "gmake" instead of
3725native "make".
3726
3727
3728If the system board that you have is not listed, then you will need
3729to port U-Boot to your hardware platform. To do this, follow these
3730steps:
3731
37321.  Create a new directory to hold your board specific code. Add any
3733    files you need. In your board directory, you will need at least
3734    the "Makefile" and a "<board>.c".
37352.  Create a new configuration file "include/configs/<board>.h" for
3736    your board.
37373.  If you're porting U-Boot to a new CPU, then also create a new
3738    directory to hold your CPU specific code. Add any files you need.
37394.  Run "make <board>_defconfig" with your new name.
37405.  Type "make", and you should get a working "u-boot.srec" file
3741    to be installed on your target system.
37426.  Debug and solve any problems that might arise.
3743    [Of course, this last step is much harder than it sounds.]
3744
3745
3746Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3747==============================================================
3748
3749If you have modified U-Boot sources (for instance added a new board
3750or support for new devices, a new CPU, etc.) you are expected to
3751provide feedback to the other developers. The feedback normally takes
3752the form of a "patch", i. e. a context diff against a certain (latest
3753official or latest in the git repository) version of U-Boot sources.
3754
3755But before you submit such a patch, please verify that your modifi-
3756cation did not break existing code. At least make sure that *ALL* of
3757the supported boards compile WITHOUT ANY compiler warnings. To do so,
3758just run the buildman script (tools/buildman/buildman), which will
3759configure and build U-Boot for ALL supported system. Be warned, this
3760will take a while. Please see the buildman README, or run 'buildman -H'
3761for documentation.
3762
3763
3764See also "U-Boot Porting Guide" below.
3765
3766
3767Monitor Commands - Overview:
3768============================
3769
3770go	- start application at address 'addr'
3771run	- run commands in an environment variable
3772bootm	- boot application image from memory
3773bootp	- boot image via network using BootP/TFTP protocol
3774bootz   - boot zImage from memory
3775tftpboot- boot image via network using TFTP protocol
3776	       and env variables "ipaddr" and "serverip"
3777	       (and eventually "gatewayip")
3778tftpput - upload a file via network using TFTP protocol
3779rarpboot- boot image via network using RARP/TFTP protocol
3780diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3781loads	- load S-Record file over serial line
3782loadb	- load binary file over serial line (kermit mode)
3783md	- memory display
3784mm	- memory modify (auto-incrementing)
3785nm	- memory modify (constant address)
3786mw	- memory write (fill)
3787cp	- memory copy
3788cmp	- memory compare
3789crc32	- checksum calculation
3790i2c	- I2C sub-system
3791sspi	- SPI utility commands
3792base	- print or set address offset
3793printenv- print environment variables
3794setenv	- set environment variables
3795saveenv - save environment variables to persistent storage
3796protect - enable or disable FLASH write protection
3797erase	- erase FLASH memory
3798flinfo	- print FLASH memory information
3799nand	- NAND memory operations (see doc/README.nand)
3800bdinfo	- print Board Info structure
3801iminfo	- print header information for application image
3802coninfo - print console devices and informations
3803ide	- IDE sub-system
3804loop	- infinite loop on address range
3805loopw	- infinite write loop on address range
3806mtest	- simple RAM test
3807icache	- enable or disable instruction cache
3808dcache	- enable or disable data cache
3809reset	- Perform RESET of the CPU
3810echo	- echo args to console
3811version - print monitor version
3812help	- print online help
3813?	- alias for 'help'
3814
3815
3816Monitor Commands - Detailed Description:
3817========================================
3818
3819TODO.
3820
3821For now: just type "help <command>".
3822
3823
3824Environment Variables:
3825======================
3826
3827U-Boot supports user configuration using Environment Variables which
3828can be made persistent by saving to Flash memory.
3829
3830Environment Variables are set using "setenv", printed using
3831"printenv", and saved to Flash using "saveenv". Using "setenv"
3832without a value can be used to delete a variable from the
3833environment. As long as you don't save the environment you are
3834working with an in-memory copy. In case the Flash area containing the
3835environment is erased by accident, a default environment is provided.
3836
3837Some configuration options can be set using Environment Variables.
3838
3839List of environment variables (most likely not complete):
3840
3841  baudrate	- see CONFIG_BAUDRATE
3842
3843  bootdelay	- see CONFIG_BOOTDELAY
3844
3845  bootcmd	- see CONFIG_BOOTCOMMAND
3846
3847  bootargs	- Boot arguments when booting an RTOS image
3848
3849  bootfile	- Name of the image to load with TFTP
3850
3851  bootm_low	- Memory range available for image processing in the bootm
3852		  command can be restricted. This variable is given as
3853		  a hexadecimal number and defines lowest address allowed
3854		  for use by the bootm command. See also "bootm_size"
3855		  environment variable. Address defined by "bootm_low" is
3856		  also the base of the initial memory mapping for the Linux
3857		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3858		  bootm_mapsize.
3859
3860  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3861		  This variable is given as a hexadecimal number and it
3862		  defines the size of the memory region starting at base
3863		  address bootm_low that is accessible by the Linux kernel
3864		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3865		  as the default value if it is defined, and bootm_size is
3866		  used otherwise.
3867
3868  bootm_size	- Memory range available for image processing in the bootm
3869		  command can be restricted. This variable is given as
3870		  a hexadecimal number and defines the size of the region
3871		  allowed for use by the bootm command. See also "bootm_low"
3872		  environment variable.
3873
3874  updatefile	- Location of the software update file on a TFTP server, used
3875		  by the automatic software update feature. Please refer to
3876		  documentation in doc/README.update for more details.
3877
3878  autoload	- if set to "no" (any string beginning with 'n'),
3879		  "bootp" will just load perform a lookup of the
3880		  configuration from the BOOTP server, but not try to
3881		  load any image using TFTP
3882
3883  autostart	- if set to "yes", an image loaded using the "bootp",
3884		  "rarpboot", "tftpboot" or "diskboot" commands will
3885		  be automatically started (by internally calling
3886		  "bootm")
3887
3888		  If set to "no", a standalone image passed to the
3889		  "bootm" command will be copied to the load address
3890		  (and eventually uncompressed), but NOT be started.
3891		  This can be used to load and uncompress arbitrary
3892		  data.
3893
3894  fdt_high	- if set this restricts the maximum address that the
3895		  flattened device tree will be copied into upon boot.
3896		  For example, if you have a system with 1 GB memory
3897		  at physical address 0x10000000, while Linux kernel
3898		  only recognizes the first 704 MB as low memory, you
3899		  may need to set fdt_high as 0x3C000000 to have the
3900		  device tree blob be copied to the maximum address
3901		  of the 704 MB low memory, so that Linux kernel can
3902		  access it during the boot procedure.
3903
3904		  If this is set to the special value 0xFFFFFFFF then
3905		  the fdt will not be copied at all on boot.  For this
3906		  to work it must reside in writable memory, have
3907		  sufficient padding on the end of it for u-boot to
3908		  add the information it needs into it, and the memory
3909		  must be accessible by the kernel.
3910
3911  fdtcontroladdr- if set this is the address of the control flattened
3912		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3913		  defined.
3914
3915  i2cfast	- (PPC405GP|PPC405EP only)
3916		  if set to 'y' configures Linux I2C driver for fast
3917		  mode (400kHZ). This environment variable is used in
3918		  initialization code. So, for changes to be effective
3919		  it must be saved and board must be reset.
3920
3921  initrd_high	- restrict positioning of initrd images:
3922		  If this variable is not set, initrd images will be
3923		  copied to the highest possible address in RAM; this
3924		  is usually what you want since it allows for
3925		  maximum initrd size. If for some reason you want to
3926		  make sure that the initrd image is loaded below the
3927		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3928		  variable to a value of "no" or "off" or "0".
3929		  Alternatively, you can set it to a maximum upper
3930		  address to use (U-Boot will still check that it
3931		  does not overwrite the U-Boot stack and data).
3932
3933		  For instance, when you have a system with 16 MB
3934		  RAM, and want to reserve 4 MB from use by Linux,
3935		  you can do this by adding "mem=12M" to the value of
3936		  the "bootargs" variable. However, now you must make
3937		  sure that the initrd image is placed in the first
3938		  12 MB as well - this can be done with
3939
3940		  setenv initrd_high 00c00000
3941
3942		  If you set initrd_high to 0xFFFFFFFF, this is an
3943		  indication to U-Boot that all addresses are legal
3944		  for the Linux kernel, including addresses in flash
3945		  memory. In this case U-Boot will NOT COPY the
3946		  ramdisk at all. This may be useful to reduce the
3947		  boot time on your system, but requires that this
3948		  feature is supported by your Linux kernel.
3949
3950  ipaddr	- IP address; needed for tftpboot command
3951
3952  loadaddr	- Default load address for commands like "bootp",
3953		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3954
3955  loads_echo	- see CONFIG_LOADS_ECHO
3956
3957  serverip	- TFTP server IP address; needed for tftpboot command
3958
3959  bootretry	- see CONFIG_BOOT_RETRY_TIME
3960
3961  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3962
3963  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3964
3965  ethprime	- controls which interface is used first.
3966
3967  ethact	- controls which interface is currently active.
3968		  For example you can do the following
3969
3970		  => setenv ethact FEC
3971		  => ping 192.168.0.1 # traffic sent on FEC
3972		  => setenv ethact SCC
3973		  => ping 10.0.0.1 # traffic sent on SCC
3974
3975  ethrotate	- When set to "no" U-Boot does not go through all
3976		  available network interfaces.
3977		  It just stays at the currently selected interface.
3978
3979  netretry	- When set to "no" each network operation will
3980		  either succeed or fail without retrying.
3981		  When set to "once" the network operation will
3982		  fail when all the available network interfaces
3983		  are tried once without success.
3984		  Useful on scripts which control the retry operation
3985		  themselves.
3986
3987  npe_ucode	- set load address for the NPE microcode
3988
3989  silent_linux  - If set then Linux will be told to boot silently, by
3990		  changing the console to be empty. If "yes" it will be
3991		  made silent. If "no" it will not be made silent. If
3992		  unset, then it will be made silent if the U-Boot console
3993		  is silent.
3994
3995  tftpsrcp	- If this is set, the value is used for TFTP's
3996		  UDP source port.
3997
3998  tftpdstp	- If this is set, the value is used for TFTP's UDP
3999		  destination port instead of the Well Know Port 69.
4000
4001  tftpblocksize - Block size to use for TFTP transfers; if not set,
4002		  we use the TFTP server's default block size
4003
4004  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4005		  seconds, minimum value is 1000 = 1 second). Defines
4006		  when a packet is considered to be lost so it has to
4007		  be retransmitted. The default is 5000 = 5 seconds.
4008		  Lowering this value may make downloads succeed
4009		  faster in networks with high packet loss rates or
4010		  with unreliable TFTP servers.
4011
4012  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
4013		  unit, minimum value = 0). Defines how many timeouts
4014		  can happen during a single file transfer before that
4015		  transfer is aborted. The default is 10, and 0 means
4016		  'no timeouts allowed'. Increasing this value may help
4017		  downloads succeed with high packet loss rates, or with
4018		  unreliable TFTP servers or client hardware.
4019
4020  vlan		- When set to a value < 4095 the traffic over
4021		  Ethernet is encapsulated/received over 802.1q
4022		  VLAN tagged frames.
4023
4024  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
4025		  Unsigned value, in milliseconds. If not set, the period will
4026		  be either the default (28000), or a value based on
4027		  CONFIG_NET_RETRY_COUNT, if defined. This value has
4028		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
4029
4030The following image location variables contain the location of images
4031used in booting. The "Image" column gives the role of the image and is
4032not an environment variable name. The other columns are environment
4033variable names. "File Name" gives the name of the file on a TFTP
4034server, "RAM Address" gives the location in RAM the image will be
4035loaded to, and "Flash Location" gives the image's address in NOR
4036flash or offset in NAND flash.
4037
4038*Note* - these variables don't have to be defined for all boards, some
4039boards currently use other variables for these purposes, and some
4040boards use these variables for other purposes.
4041
4042Image		    File Name	     RAM Address       Flash Location
4043-----		    ---------	     -----------       --------------
4044u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4045Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4046device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4047ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4048
4049The following environment variables may be used and automatically
4050updated by the network boot commands ("bootp" and "rarpboot"),
4051depending the information provided by your boot server:
4052
4053  bootfile	- see above
4054  dnsip		- IP address of your Domain Name Server
4055  dnsip2	- IP address of your secondary Domain Name Server
4056  gatewayip	- IP address of the Gateway (Router) to use
4057  hostname	- Target hostname
4058  ipaddr	- see above
4059  netmask	- Subnet Mask
4060  rootpath	- Pathname of the root filesystem on the NFS server
4061  serverip	- see above
4062
4063
4064There are two special Environment Variables:
4065
4066  serial#	- contains hardware identification information such
4067		  as type string and/or serial number
4068  ethaddr	- Ethernet address
4069
4070These variables can be set only once (usually during manufacturing of
4071the board). U-Boot refuses to delete or overwrite these variables
4072once they have been set once.
4073
4074
4075Further special Environment Variables:
4076
4077  ver		- Contains the U-Boot version string as printed
4078		  with the "version" command. This variable is
4079		  readonly (see CONFIG_VERSION_VARIABLE).
4080
4081
4082Please note that changes to some configuration parameters may take
4083only effect after the next boot (yes, that's just like Windoze :-).
4084
4085
4086Callback functions for environment variables:
4087---------------------------------------------
4088
4089For some environment variables, the behavior of u-boot needs to change
4090when their values are changed.  This functionality allows functions to
4091be associated with arbitrary variables.  On creation, overwrite, or
4092deletion, the callback will provide the opportunity for some side
4093effect to happen or for the change to be rejected.
4094
4095The callbacks are named and associated with a function using the
4096U_BOOT_ENV_CALLBACK macro in your board or driver code.
4097
4098These callbacks are associated with variables in one of two ways.  The
4099static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4100in the board configuration to a string that defines a list of
4101associations.  The list must be in the following format:
4102
4103	entry = variable_name[:callback_name]
4104	list = entry[,list]
4105
4106If the callback name is not specified, then the callback is deleted.
4107Spaces are also allowed anywhere in the list.
4108
4109Callbacks can also be associated by defining the ".callbacks" variable
4110with the same list format above.  Any association in ".callbacks" will
4111override any association in the static list. You can define
4112CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4113".callbacks" environment variable in the default or embedded environment.
4114
4115If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4116regular expression. This allows multiple variables to be connected to
4117the same callback without explicitly listing them all out.
4118
4119
4120Command Line Parsing:
4121=====================
4122
4123There are two different command line parsers available with U-Boot:
4124the old "simple" one, and the much more powerful "hush" shell:
4125
4126Old, simple command line parser:
4127--------------------------------
4128
4129- supports environment variables (through setenv / saveenv commands)
4130- several commands on one line, separated by ';'
4131- variable substitution using "... ${name} ..." syntax
4132- special characters ('$', ';') can be escaped by prefixing with '\',
4133  for example:
4134	setenv bootcmd bootm \${address}
4135- You can also escape text by enclosing in single apostrophes, for example:
4136	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4137
4138Hush shell:
4139-----------
4140
4141- similar to Bourne shell, with control structures like
4142  if...then...else...fi, for...do...done; while...do...done,
4143  until...do...done, ...
4144- supports environment ("global") variables (through setenv / saveenv
4145  commands) and local shell variables (through standard shell syntax
4146  "name=value"); only environment variables can be used with "run"
4147  command
4148
4149General rules:
4150--------------
4151
4152(1) If a command line (or an environment variable executed by a "run"
4153    command) contains several commands separated by semicolon, and
4154    one of these commands fails, then the remaining commands will be
4155    executed anyway.
4156
4157(2) If you execute several variables with one call to run (i. e.
4158    calling run with a list of variables as arguments), any failing
4159    command will cause "run" to terminate, i. e. the remaining
4160    variables are not executed.
4161
4162Note for Redundant Ethernet Interfaces:
4163=======================================
4164
4165Some boards come with redundant Ethernet interfaces; U-Boot supports
4166such configurations and is capable of automatic selection of a
4167"working" interface when needed. MAC assignment works as follows:
4168
4169Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4170MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4171"eth1addr" (=>eth1), "eth2addr", ...
4172
4173If the network interface stores some valid MAC address (for instance
4174in SROM), this is used as default address if there is NO correspon-
4175ding setting in the environment; if the corresponding environment
4176variable is set, this overrides the settings in the card; that means:
4177
4178o If the SROM has a valid MAC address, and there is no address in the
4179  environment, the SROM's address is used.
4180
4181o If there is no valid address in the SROM, and a definition in the
4182  environment exists, then the value from the environment variable is
4183  used.
4184
4185o If both the SROM and the environment contain a MAC address, and
4186  both addresses are the same, this MAC address is used.
4187
4188o If both the SROM and the environment contain a MAC address, and the
4189  addresses differ, the value from the environment is used and a
4190  warning is printed.
4191
4192o If neither SROM nor the environment contain a MAC address, an error
4193  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4194  a random, locally-assigned MAC is used.
4195
4196If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4197will be programmed into hardware as part of the initialization process.	 This
4198may be skipped by setting the appropriate 'ethmacskip' environment variable.
4199The naming convention is as follows:
4200"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4201
4202Image Formats:
4203==============
4204
4205U-Boot is capable of booting (and performing other auxiliary operations on)
4206images in two formats:
4207
4208New uImage format (FIT)
4209-----------------------
4210
4211Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4212to Flattened Device Tree). It allows the use of images with multiple
4213components (several kernels, ramdisks, etc.), with contents protected by
4214SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4215
4216
4217Old uImage format
4218-----------------
4219
4220Old image format is based on binary files which can be basically anything,
4221preceded by a special header; see the definitions in include/image.h for
4222details; basically, the header defines the following image properties:
4223
4224* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4225  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4226  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4227  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4228  INTEGRITY).
4229* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4230  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4231  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4232* Compression Type (uncompressed, gzip, bzip2)
4233* Load Address
4234* Entry Point
4235* Image Name
4236* Image Timestamp
4237
4238The header is marked by a special Magic Number, and both the header
4239and the data portions of the image are secured against corruption by
4240CRC32 checksums.
4241
4242
4243Linux Support:
4244==============
4245
4246Although U-Boot should support any OS or standalone application
4247easily, the main focus has always been on Linux during the design of
4248U-Boot.
4249
4250U-Boot includes many features that so far have been part of some
4251special "boot loader" code within the Linux kernel. Also, any
4252"initrd" images to be used are no longer part of one big Linux image;
4253instead, kernel and "initrd" are separate images. This implementation
4254serves several purposes:
4255
4256- the same features can be used for other OS or standalone
4257  applications (for instance: using compressed images to reduce the
4258  Flash memory footprint)
4259
4260- it becomes much easier to port new Linux kernel versions because
4261  lots of low-level, hardware dependent stuff are done by U-Boot
4262
4263- the same Linux kernel image can now be used with different "initrd"
4264  images; of course this also means that different kernel images can
4265  be run with the same "initrd". This makes testing easier (you don't
4266  have to build a new "zImage.initrd" Linux image when you just
4267  change a file in your "initrd"). Also, a field-upgrade of the
4268  software is easier now.
4269
4270
4271Linux HOWTO:
4272============
4273
4274Porting Linux to U-Boot based systems:
4275---------------------------------------
4276
4277U-Boot cannot save you from doing all the necessary modifications to
4278configure the Linux device drivers for use with your target hardware
4279(no, we don't intend to provide a full virtual machine interface to
4280Linux :-).
4281
4282But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4283
4284Just make sure your machine specific header file (for instance
4285include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4286Information structure as we define in include/asm-<arch>/u-boot.h,
4287and make sure that your definition of IMAP_ADDR uses the same value
4288as your U-Boot configuration in CONFIG_SYS_IMMR.
4289
4290Note that U-Boot now has a driver model, a unified model for drivers.
4291If you are adding a new driver, plumb it into driver model. If there
4292is no uclass available, you are encouraged to create one. See
4293doc/driver-model.
4294
4295
4296Configuring the Linux kernel:
4297-----------------------------
4298
4299No specific requirements for U-Boot. Make sure you have some root
4300device (initial ramdisk, NFS) for your target system.
4301
4302
4303Building a Linux Image:
4304-----------------------
4305
4306With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4307not used. If you use recent kernel source, a new build target
4308"uImage" will exist which automatically builds an image usable by
4309U-Boot. Most older kernels also have support for a "pImage" target,
4310which was introduced for our predecessor project PPCBoot and uses a
4311100% compatible format.
4312
4313Example:
4314
4315	make TQM850L_defconfig
4316	make oldconfig
4317	make dep
4318	make uImage
4319
4320The "uImage" build target uses a special tool (in 'tools/mkimage') to
4321encapsulate a compressed Linux kernel image with header	 information,
4322CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4323
4324* build a standard "vmlinux" kernel image (in ELF binary format):
4325
4326* convert the kernel into a raw binary image:
4327
4328	${CROSS_COMPILE}-objcopy -O binary \
4329				 -R .note -R .comment \
4330				 -S vmlinux linux.bin
4331
4332* compress the binary image:
4333
4334	gzip -9 linux.bin
4335
4336* package compressed binary image for U-Boot:
4337
4338	mkimage -A ppc -O linux -T kernel -C gzip \
4339		-a 0 -e 0 -n "Linux Kernel Image" \
4340		-d linux.bin.gz uImage
4341
4342
4343The "mkimage" tool can also be used to create ramdisk images for use
4344with U-Boot, either separated from the Linux kernel image, or
4345combined into one file. "mkimage" encapsulates the images with a 64
4346byte header containing information about target architecture,
4347operating system, image type, compression method, entry points, time
4348stamp, CRC32 checksums, etc.
4349
4350"mkimage" can be called in two ways: to verify existing images and
4351print the header information, or to build new images.
4352
4353In the first form (with "-l" option) mkimage lists the information
4354contained in the header of an existing U-Boot image; this includes
4355checksum verification:
4356
4357	tools/mkimage -l image
4358	  -l ==> list image header information
4359
4360The second form (with "-d" option) is used to build a U-Boot image
4361from a "data file" which is used as image payload:
4362
4363	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4364		      -n name -d data_file image
4365	  -A ==> set architecture to 'arch'
4366	  -O ==> set operating system to 'os'
4367	  -T ==> set image type to 'type'
4368	  -C ==> set compression type 'comp'
4369	  -a ==> set load address to 'addr' (hex)
4370	  -e ==> set entry point to 'ep' (hex)
4371	  -n ==> set image name to 'name'
4372	  -d ==> use image data from 'datafile'
4373
4374Right now, all Linux kernels for PowerPC systems use the same load
4375address (0x00000000), but the entry point address depends on the
4376kernel version:
4377
4378- 2.2.x kernels have the entry point at 0x0000000C,
4379- 2.3.x and later kernels have the entry point at 0x00000000.
4380
4381So a typical call to build a U-Boot image would read:
4382
4383	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4384	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4385	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4386	> examples/uImage.TQM850L
4387	Image Name:   2.4.4 kernel for TQM850L
4388	Created:      Wed Jul 19 02:34:59 2000
4389	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4390	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4391	Load Address: 0x00000000
4392	Entry Point:  0x00000000
4393
4394To verify the contents of the image (or check for corruption):
4395
4396	-> tools/mkimage -l examples/uImage.TQM850L
4397	Image Name:   2.4.4 kernel for TQM850L
4398	Created:      Wed Jul 19 02:34:59 2000
4399	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4400	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4401	Load Address: 0x00000000
4402	Entry Point:  0x00000000
4403
4404NOTE: for embedded systems where boot time is critical you can trade
4405speed for memory and install an UNCOMPRESSED image instead: this
4406needs more space in Flash, but boots much faster since it does not
4407need to be uncompressed:
4408
4409	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4410	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4411	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4412	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4413	> examples/uImage.TQM850L-uncompressed
4414	Image Name:   2.4.4 kernel for TQM850L
4415	Created:      Wed Jul 19 02:34:59 2000
4416	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4417	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4418	Load Address: 0x00000000
4419	Entry Point:  0x00000000
4420
4421
4422Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4423when your kernel is intended to use an initial ramdisk:
4424
4425	-> tools/mkimage -n 'Simple Ramdisk Image' \
4426	> -A ppc -O linux -T ramdisk -C gzip \
4427	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4428	Image Name:   Simple Ramdisk Image
4429	Created:      Wed Jan 12 14:01:50 2000
4430	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4431	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4432	Load Address: 0x00000000
4433	Entry Point:  0x00000000
4434
4435The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4436option performs the converse operation of the mkimage's second form (the "-d"
4437option). Given an image built by mkimage, the dumpimage extracts a "data file"
4438from the image:
4439
4440	tools/dumpimage -i image -T type -p position data_file
4441	  -i ==> extract from the 'image' a specific 'data_file'
4442	  -T ==> set image type to 'type'
4443	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4444
4445
4446Installing a Linux Image:
4447-------------------------
4448
4449To downloading a U-Boot image over the serial (console) interface,
4450you must convert the image to S-Record format:
4451
4452	objcopy -I binary -O srec examples/image examples/image.srec
4453
4454The 'objcopy' does not understand the information in the U-Boot
4455image header, so the resulting S-Record file will be relative to
4456address 0x00000000. To load it to a given address, you need to
4457specify the target address as 'offset' parameter with the 'loads'
4458command.
4459
4460Example: install the image to address 0x40100000 (which on the
4461TQM8xxL is in the first Flash bank):
4462
4463	=> erase 40100000 401FFFFF
4464
4465	.......... done
4466	Erased 8 sectors
4467
4468	=> loads 40100000
4469	## Ready for S-Record download ...
4470	~>examples/image.srec
4471	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4472	...
4473	15989 15990 15991 15992
4474	[file transfer complete]
4475	[connected]
4476	## Start Addr = 0x00000000
4477
4478
4479You can check the success of the download using the 'iminfo' command;
4480this includes a checksum verification so you can be sure no data
4481corruption happened:
4482
4483	=> imi 40100000
4484
4485	## Checking Image at 40100000 ...
4486	   Image Name:	 2.2.13 for initrd on TQM850L
4487	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4488	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4489	   Load Address: 00000000
4490	   Entry Point:	 0000000c
4491	   Verifying Checksum ... OK
4492
4493
4494Boot Linux:
4495-----------
4496
4497The "bootm" command is used to boot an application that is stored in
4498memory (RAM or Flash). In case of a Linux kernel image, the contents
4499of the "bootargs" environment variable is passed to the kernel as
4500parameters. You can check and modify this variable using the
4501"printenv" and "setenv" commands:
4502
4503
4504	=> printenv bootargs
4505	bootargs=root=/dev/ram
4506
4507	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4508
4509	=> printenv bootargs
4510	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4511
4512	=> bootm 40020000
4513	## Booting Linux kernel at 40020000 ...
4514	   Image Name:	 2.2.13 for NFS on TQM850L
4515	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4516	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4517	   Load Address: 00000000
4518	   Entry Point:	 0000000c
4519	   Verifying Checksum ... OK
4520	   Uncompressing Kernel Image ... OK
4521	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
4522	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4523	time_init: decrementer frequency = 187500000/60
4524	Calibrating delay loop... 49.77 BogoMIPS
4525	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4526	...
4527
4528If you want to boot a Linux kernel with initial RAM disk, you pass
4529the memory addresses of both the kernel and the initrd image (PPBCOOT
4530format!) to the "bootm" command:
4531
4532	=> imi 40100000 40200000
4533
4534	## Checking Image at 40100000 ...
4535	   Image Name:	 2.2.13 for initrd on TQM850L
4536	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4537	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4538	   Load Address: 00000000
4539	   Entry Point:	 0000000c
4540	   Verifying Checksum ... OK
4541
4542	## Checking Image at 40200000 ...
4543	   Image Name:	 Simple Ramdisk Image
4544	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4545	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4546	   Load Address: 00000000
4547	   Entry Point:	 00000000
4548	   Verifying Checksum ... OK
4549
4550	=> bootm 40100000 40200000
4551	## Booting Linux kernel at 40100000 ...
4552	   Image Name:	 2.2.13 for initrd on TQM850L
4553	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4554	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4555	   Load Address: 00000000
4556	   Entry Point:	 0000000c
4557	   Verifying Checksum ... OK
4558	   Uncompressing Kernel Image ... OK
4559	## Loading RAMDisk Image at 40200000 ...
4560	   Image Name:	 Simple Ramdisk Image
4561	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4562	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4563	   Load Address: 00000000
4564	   Entry Point:	 00000000
4565	   Verifying Checksum ... OK
4566	   Loading Ramdisk ... OK
4567	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
4568	Boot arguments: root=/dev/ram
4569	time_init: decrementer frequency = 187500000/60
4570	Calibrating delay loop... 49.77 BogoMIPS
4571	...
4572	RAMDISK: Compressed image found at block 0
4573	VFS: Mounted root (ext2 filesystem).
4574
4575	bash#
4576
4577Boot Linux and pass a flat device tree:
4578-----------
4579
4580First, U-Boot must be compiled with the appropriate defines. See the section
4581titled "Linux Kernel Interface" above for a more in depth explanation. The
4582following is an example of how to start a kernel and pass an updated
4583flat device tree:
4584
4585=> print oftaddr
4586oftaddr=0x300000
4587=> print oft
4588oft=oftrees/mpc8540ads.dtb
4589=> tftp $oftaddr $oft
4590Speed: 1000, full duplex
4591Using TSEC0 device
4592TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4593Filename 'oftrees/mpc8540ads.dtb'.
4594Load address: 0x300000
4595Loading: #
4596done
4597Bytes transferred = 4106 (100a hex)
4598=> tftp $loadaddr $bootfile
4599Speed: 1000, full duplex
4600Using TSEC0 device
4601TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4602Filename 'uImage'.
4603Load address: 0x200000
4604Loading:############
4605done
4606Bytes transferred = 1029407 (fb51f hex)
4607=> print loadaddr
4608loadaddr=200000
4609=> print oftaddr
4610oftaddr=0x300000
4611=> bootm $loadaddr - $oftaddr
4612## Booting image at 00200000 ...
4613   Image Name:	 Linux-2.6.17-dirty
4614   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4615   Data Size:	 1029343 Bytes = 1005.2 kB
4616   Load Address: 00000000
4617   Entry Point:	 00000000
4618   Verifying Checksum ... OK
4619   Uncompressing Kernel Image ... OK
4620Booting using flat device tree at 0x300000
4621Using MPC85xx ADS machine description
4622Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4623[snip]
4624
4625
4626More About U-Boot Image Types:
4627------------------------------
4628
4629U-Boot supports the following image types:
4630
4631   "Standalone Programs" are directly runnable in the environment
4632	provided by U-Boot; it is expected that (if they behave
4633	well) you can continue to work in U-Boot after return from
4634	the Standalone Program.
4635   "OS Kernel Images" are usually images of some Embedded OS which
4636	will take over control completely. Usually these programs
4637	will install their own set of exception handlers, device
4638	drivers, set up the MMU, etc. - this means, that you cannot
4639	expect to re-enter U-Boot except by resetting the CPU.
4640   "RAMDisk Images" are more or less just data blocks, and their
4641	parameters (address, size) are passed to an OS kernel that is
4642	being started.
4643   "Multi-File Images" contain several images, typically an OS
4644	(Linux) kernel image and one or more data images like
4645	RAMDisks. This construct is useful for instance when you want
4646	to boot over the network using BOOTP etc., where the boot
4647	server provides just a single image file, but you want to get
4648	for instance an OS kernel and a RAMDisk image.
4649
4650	"Multi-File Images" start with a list of image sizes, each
4651	image size (in bytes) specified by an "uint32_t" in network
4652	byte order. This list is terminated by an "(uint32_t)0".
4653	Immediately after the terminating 0 follow the images, one by
4654	one, all aligned on "uint32_t" boundaries (size rounded up to
4655	a multiple of 4 bytes).
4656
4657   "Firmware Images" are binary images containing firmware (like
4658	U-Boot or FPGA images) which usually will be programmed to
4659	flash memory.
4660
4661   "Script files" are command sequences that will be executed by
4662	U-Boot's command interpreter; this feature is especially
4663	useful when you configure U-Boot to use a real shell (hush)
4664	as command interpreter.
4665
4666Booting the Linux zImage:
4667-------------------------
4668
4669On some platforms, it's possible to boot Linux zImage. This is done
4670using the "bootz" command. The syntax of "bootz" command is the same
4671as the syntax of "bootm" command.
4672
4673Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4674kernel with raw initrd images. The syntax is slightly different, the
4675address of the initrd must be augmented by it's size, in the following
4676format: "<initrd addres>:<initrd size>".
4677
4678
4679Standalone HOWTO:
4680=================
4681
4682One of the features of U-Boot is that you can dynamically load and
4683run "standalone" applications, which can use some resources of
4684U-Boot like console I/O functions or interrupt services.
4685
4686Two simple examples are included with the sources:
4687
4688"Hello World" Demo:
4689-------------------
4690
4691'examples/hello_world.c' contains a small "Hello World" Demo
4692application; it is automatically compiled when you build U-Boot.
4693It's configured to run at address 0x00040004, so you can play with it
4694like that:
4695
4696	=> loads
4697	## Ready for S-Record download ...
4698	~>examples/hello_world.srec
4699	1 2 3 4 5 6 7 8 9 10 11 ...
4700	[file transfer complete]
4701	[connected]
4702	## Start Addr = 0x00040004
4703
4704	=> go 40004 Hello World! This is a test.
4705	## Starting application at 0x00040004 ...
4706	Hello World
4707	argc = 7
4708	argv[0] = "40004"
4709	argv[1] = "Hello"
4710	argv[2] = "World!"
4711	argv[3] = "This"
4712	argv[4] = "is"
4713	argv[5] = "a"
4714	argv[6] = "test."
4715	argv[7] = "<NULL>"
4716	Hit any key to exit ...
4717
4718	## Application terminated, rc = 0x0
4719
4720Another example, which demonstrates how to register a CPM interrupt
4721handler with the U-Boot code, can be found in 'examples/timer.c'.
4722Here, a CPM timer is set up to generate an interrupt every second.
4723The interrupt service routine is trivial, just printing a '.'
4724character, but this is just a demo program. The application can be
4725controlled by the following keys:
4726
4727	? - print current values og the CPM Timer registers
4728	b - enable interrupts and start timer
4729	e - stop timer and disable interrupts
4730	q - quit application
4731
4732	=> loads
4733	## Ready for S-Record download ...
4734	~>examples/timer.srec
4735	1 2 3 4 5 6 7 8 9 10 11 ...
4736	[file transfer complete]
4737	[connected]
4738	## Start Addr = 0x00040004
4739
4740	=> go 40004
4741	## Starting application at 0x00040004 ...
4742	TIMERS=0xfff00980
4743	Using timer 1
4744	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4745
4746Hit 'b':
4747	[q, b, e, ?] Set interval 1000000 us
4748	Enabling timer
4749Hit '?':
4750	[q, b, e, ?] ........
4751	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4752Hit '?':
4753	[q, b, e, ?] .
4754	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4755Hit '?':
4756	[q, b, e, ?] .
4757	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4758Hit '?':
4759	[q, b, e, ?] .
4760	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4761Hit 'e':
4762	[q, b, e, ?] ...Stopping timer
4763Hit 'q':
4764	[q, b, e, ?] ## Application terminated, rc = 0x0
4765
4766
4767Minicom warning:
4768================
4769
4770Over time, many people have reported problems when trying to use the
4771"minicom" terminal emulation program for serial download. I (wd)
4772consider minicom to be broken, and recommend not to use it. Under
4773Unix, I recommend to use C-Kermit for general purpose use (and
4774especially for kermit binary protocol download ("loadb" command), and
4775use "cu" for S-Record download ("loads" command).  See
4776http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4777for help with kermit.
4778
4779
4780Nevertheless, if you absolutely want to use it try adding this
4781configuration to your "File transfer protocols" section:
4782
4783	   Name	   Program			Name U/D FullScr IO-Red. Multi
4784	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4785	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4786
4787
4788NetBSD Notes:
4789=============
4790
4791Starting at version 0.9.2, U-Boot supports NetBSD both as host
4792(build U-Boot) and target system (boots NetBSD/mpc8xx).
4793
4794Building requires a cross environment; it is known to work on
4795NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4796need gmake since the Makefiles are not compatible with BSD make).
4797Note that the cross-powerpc package does not install include files;
4798attempting to build U-Boot will fail because <machine/ansi.h> is
4799missing.  This file has to be installed and patched manually:
4800
4801	# cd /usr/pkg/cross/powerpc-netbsd/include
4802	# mkdir powerpc
4803	# ln -s powerpc machine
4804	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4805	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4806
4807Native builds *don't* work due to incompatibilities between native
4808and U-Boot include files.
4809
4810Booting assumes that (the first part of) the image booted is a
4811stage-2 loader which in turn loads and then invokes the kernel
4812proper. Loader sources will eventually appear in the NetBSD source
4813tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4814meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4815
4816
4817Implementation Internals:
4818=========================
4819
4820The following is not intended to be a complete description of every
4821implementation detail. However, it should help to understand the
4822inner workings of U-Boot and make it easier to port it to custom
4823hardware.
4824
4825
4826Initial Stack, Global Data:
4827---------------------------
4828
4829The implementation of U-Boot is complicated by the fact that U-Boot
4830starts running out of ROM (flash memory), usually without access to
4831system RAM (because the memory controller is not initialized yet).
4832This means that we don't have writable Data or BSS segments, and BSS
4833is not initialized as zero. To be able to get a C environment working
4834at all, we have to allocate at least a minimal stack. Implementation
4835options for this are defined and restricted by the CPU used: Some CPU
4836models provide on-chip memory (like the IMMR area on MPC8xx and
4837MPC826x processors), on others (parts of) the data cache can be
4838locked as (mis-) used as memory, etc.
4839
4840	Chris Hallinan posted a good summary of these issues to the
4841	U-Boot mailing list:
4842
4843	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4844	From: "Chris Hallinan" <clh@net1plus.com>
4845	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4846	...
4847
4848	Correct me if I'm wrong, folks, but the way I understand it
4849	is this: Using DCACHE as initial RAM for Stack, etc, does not
4850	require any physical RAM backing up the cache. The cleverness
4851	is that the cache is being used as a temporary supply of
4852	necessary storage before the SDRAM controller is setup. It's
4853	beyond the scope of this list to explain the details, but you
4854	can see how this works by studying the cache architecture and
4855	operation in the architecture and processor-specific manuals.
4856
4857	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4858	is another option for the system designer to use as an
4859	initial stack/RAM area prior to SDRAM being available. Either
4860	option should work for you. Using CS 4 should be fine if your
4861	board designers haven't used it for something that would
4862	cause you grief during the initial boot! It is frequently not
4863	used.
4864
4865	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4866	with your processor/board/system design. The default value
4867	you will find in any recent u-boot distribution in
4868	walnut.h should work for you. I'd set it to a value larger
4869	than your SDRAM module. If you have a 64MB SDRAM module, set
4870	it above 400_0000. Just make sure your board has no resources
4871	that are supposed to respond to that address! That code in
4872	start.S has been around a while and should work as is when
4873	you get the config right.
4874
4875	-Chris Hallinan
4876	DS4.COM, Inc.
4877
4878It is essential to remember this, since it has some impact on the C
4879code for the initialization procedures:
4880
4881* Initialized global data (data segment) is read-only. Do not attempt
4882  to write it.
4883
4884* Do not use any uninitialized global data (or implicitly initialized
4885  as zero data - BSS segment) at all - this is undefined, initiali-
4886  zation is performed later (when relocating to RAM).
4887
4888* Stack space is very limited. Avoid big data buffers or things like
4889  that.
4890
4891Having only the stack as writable memory limits means we cannot use
4892normal global data to share information between the code. But it
4893turned out that the implementation of U-Boot can be greatly
4894simplified by making a global data structure (gd_t) available to all
4895functions. We could pass a pointer to this data as argument to _all_
4896functions, but this would bloat the code. Instead we use a feature of
4897the GCC compiler (Global Register Variables) to share the data: we
4898place a pointer (gd) to the global data into a register which we
4899reserve for this purpose.
4900
4901When choosing a register for such a purpose we are restricted by the
4902relevant  (E)ABI  specifications for the current architecture, and by
4903GCC's implementation.
4904
4905For PowerPC, the following registers have specific use:
4906	R1:	stack pointer
4907	R2:	reserved for system use
4908	R3-R4:	parameter passing and return values
4909	R5-R10: parameter passing
4910	R13:	small data area pointer
4911	R30:	GOT pointer
4912	R31:	frame pointer
4913
4914	(U-Boot also uses R12 as internal GOT pointer. r12
4915	is a volatile register so r12 needs to be reset when
4916	going back and forth between asm and C)
4917
4918    ==> U-Boot will use R2 to hold a pointer to the global data
4919
4920    Note: on PPC, we could use a static initializer (since the
4921    address of the global data structure is known at compile time),
4922    but it turned out that reserving a register results in somewhat
4923    smaller code - although the code savings are not that big (on
4924    average for all boards 752 bytes for the whole U-Boot image,
4925    624 text + 127 data).
4926
4927On ARM, the following registers are used:
4928
4929	R0:	function argument word/integer result
4930	R1-R3:	function argument word
4931	R9:	platform specific
4932	R10:	stack limit (used only if stack checking is enabled)
4933	R11:	argument (frame) pointer
4934	R12:	temporary workspace
4935	R13:	stack pointer
4936	R14:	link register
4937	R15:	program counter
4938
4939    ==> U-Boot will use R9 to hold a pointer to the global data
4940
4941    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4942
4943On Nios II, the ABI is documented here:
4944	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4945
4946    ==> U-Boot will use gp to hold a pointer to the global data
4947
4948    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4949    to access small data sections, so gp is free.
4950
4951On NDS32, the following registers are used:
4952
4953	R0-R1:	argument/return
4954	R2-R5:	argument
4955	R15:	temporary register for assembler
4956	R16:	trampoline register
4957	R28:	frame pointer (FP)
4958	R29:	global pointer (GP)
4959	R30:	link register (LP)
4960	R31:	stack pointer (SP)
4961	PC:	program counter (PC)
4962
4963    ==> U-Boot will use R10 to hold a pointer to the global data
4964
4965NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4966or current versions of GCC may "optimize" the code too much.
4967
4968On RISC-V, the following registers are used:
4969
4970	x0: hard-wired zero (zero)
4971	x1: return address (ra)
4972	x2:	stack pointer (sp)
4973	x3:	global pointer (gp)
4974	x4:	thread pointer (tp)
4975	x5:	link register (t0)
4976	x8:	frame pointer (fp)
4977	x10-x11:	arguments/return values (a0-1)
4978	x12-x17:	arguments (a2-7)
4979	x28-31:	 temporaries (t3-6)
4980	pc:	program counter (pc)
4981
4982    ==> U-Boot will use gp to hold a pointer to the global data
4983
4984Memory Management:
4985------------------
4986
4987U-Boot runs in system state and uses physical addresses, i.e. the
4988MMU is not used either for address mapping nor for memory protection.
4989
4990The available memory is mapped to fixed addresses using the memory
4991controller. In this process, a contiguous block is formed for each
4992memory type (Flash, SDRAM, SRAM), even when it consists of several
4993physical memory banks.
4994
4995U-Boot is installed in the first 128 kB of the first Flash bank (on
4996TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4997booting and sizing and initializing DRAM, the code relocates itself
4998to the upper end of DRAM. Immediately below the U-Boot code some
4999memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5000configuration setting]. Below that, a structure with global Board
5001Info data is placed, followed by the stack (growing downward).
5002
5003Additionally, some exception handler code is copied to the low 8 kB
5004of DRAM (0x00000000 ... 0x00001FFF).
5005
5006So a typical memory configuration with 16 MB of DRAM could look like
5007this:
5008
5009	0x0000 0000	Exception Vector code
5010	      :
5011	0x0000 1FFF
5012	0x0000 2000	Free for Application Use
5013	      :
5014	      :
5015
5016	      :
5017	      :
5018	0x00FB FF20	Monitor Stack (Growing downward)
5019	0x00FB FFAC	Board Info Data and permanent copy of global data
5020	0x00FC 0000	Malloc Arena
5021	      :
5022	0x00FD FFFF
5023	0x00FE 0000	RAM Copy of Monitor Code
5024	...		eventually: LCD or video framebuffer
5025	...		eventually: pRAM (Protected RAM - unchanged by reset)
5026	0x00FF FFFF	[End of RAM]
5027
5028
5029System Initialization:
5030----------------------
5031
5032In the reset configuration, U-Boot starts at the reset entry point
5033(on most PowerPC systems at address 0x00000100). Because of the reset
5034configuration for CS0# this is a mirror of the on board Flash memory.
5035To be able to re-map memory U-Boot then jumps to its link address.
5036To be able to implement the initialization code in C, a (small!)
5037initial stack is set up in the internal Dual Ported RAM (in case CPUs
5038which provide such a feature like), or in a locked part of the data
5039cache. After that, U-Boot initializes the CPU core, the caches and
5040the SIU.
5041
5042Next, all (potentially) available memory banks are mapped using a
5043preliminary mapping. For example, we put them on 512 MB boundaries
5044(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5045on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5046programmed for SDRAM access. Using the temporary configuration, a
5047simple memory test is run that determines the size of the SDRAM
5048banks.
5049
5050When there is more than one SDRAM bank, and the banks are of
5051different size, the largest is mapped first. For equal size, the first
5052bank (CS2#) is mapped first. The first mapping is always for address
50530x00000000, with any additional banks following immediately to create
5054contiguous memory starting from 0.
5055
5056Then, the monitor installs itself at the upper end of the SDRAM area
5057and allocates memory for use by malloc() and for the global Board
5058Info data; also, the exception vector code is copied to the low RAM
5059pages, and the final stack is set up.
5060
5061Only after this relocation will you have a "normal" C environment;
5062until that you are restricted in several ways, mostly because you are
5063running from ROM, and because the code will have to be relocated to a
5064new address in RAM.
5065
5066
5067U-Boot Porting Guide:
5068----------------------
5069
5070[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5071list, October 2002]
5072
5073
5074int main(int argc, char *argv[])
5075{
5076	sighandler_t no_more_time;
5077
5078	signal(SIGALRM, no_more_time);
5079	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5080
5081	if (available_money > available_manpower) {
5082		Pay consultant to port U-Boot;
5083		return 0;
5084	}
5085
5086	Download latest U-Boot source;
5087
5088	Subscribe to u-boot mailing list;
5089
5090	if (clueless)
5091		email("Hi, I am new to U-Boot, how do I get started?");
5092
5093	while (learning) {
5094		Read the README file in the top level directory;
5095		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5096		Read applicable doc/*.README;
5097		Read the source, Luke;
5098		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5099	}
5100
5101	if (available_money > toLocalCurrency ($2500))
5102		Buy a BDI3000;
5103	else
5104		Add a lot of aggravation and time;
5105
5106	if (a similar board exists) {	/* hopefully... */
5107		cp -a board/<similar> board/<myboard>
5108		cp include/configs/<similar>.h include/configs/<myboard>.h
5109	} else {
5110		Create your own board support subdirectory;
5111		Create your own board include/configs/<myboard>.h file;
5112	}
5113	Edit new board/<myboard> files
5114	Edit new include/configs/<myboard>.h
5115
5116	while (!accepted) {
5117		while (!running) {
5118			do {
5119				Add / modify source code;
5120			} until (compiles);
5121			Debug;
5122			if (clueless)
5123				email("Hi, I am having problems...");
5124		}
5125		Send patch file to the U-Boot email list;
5126		if (reasonable critiques)
5127			Incorporate improvements from email list code review;
5128		else
5129			Defend code as written;
5130	}
5131
5132	return 0;
5133}
5134
5135void no_more_time (int sig)
5136{
5137      hire_a_guru();
5138}
5139
5140
5141Coding Standards:
5142-----------------
5143
5144All contributions to U-Boot should conform to the Linux kernel
5145coding style; see the kernel coding style guide at
5146https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
5147script "scripts/Lindent" in your Linux kernel source directory.
5148
5149Source files originating from a different project (for example the
5150MTD subsystem) are generally exempt from these guidelines and are not
5151reformatted to ease subsequent migration to newer versions of those
5152sources.
5153
5154Please note that U-Boot is implemented in C (and to some small parts in
5155Assembler); no C++ is used, so please do not use C++ style comments (//)
5156in your code.
5157
5158Please also stick to the following formatting rules:
5159- remove any trailing white space
5160- use TAB characters for indentation and vertical alignment, not spaces
5161- make sure NOT to use DOS '\r\n' line feeds
5162- do not add more than 2 consecutive empty lines to source files
5163- do not add trailing empty lines to source files
5164
5165Submissions which do not conform to the standards may be returned
5166with a request to reformat the changes.
5167
5168
5169Submitting Patches:
5170-------------------
5171
5172Since the number of patches for U-Boot is growing, we need to
5173establish some rules. Submissions which do not conform to these rules
5174may be rejected, even when they contain important and valuable stuff.
5175
5176Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5177
5178Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5179see https://lists.denx.de/listinfo/u-boot
5180
5181When you send a patch, please include the following information with
5182it:
5183
5184* For bug fixes: a description of the bug and how your patch fixes
5185  this bug. Please try to include a way of demonstrating that the
5186  patch actually fixes something.
5187
5188* For new features: a description of the feature and your
5189  implementation.
5190
5191* A CHANGELOG entry as plaintext (separate from the patch)
5192
5193* For major contributions, add a MAINTAINERS file with your
5194  information and associated file and directory references.
5195
5196* When you add support for a new board, don't forget to add a
5197  maintainer e-mail address to the boards.cfg file, too.
5198
5199* If your patch adds new configuration options, don't forget to
5200  document these in the README file.
5201
5202* The patch itself. If you are using git (which is *strongly*
5203  recommended) you can easily generate the patch using the
5204  "git format-patch". If you then use "git send-email" to send it to
5205  the U-Boot mailing list, you will avoid most of the common problems
5206  with some other mail clients.
5207
5208  If you cannot use git, use "diff -purN OLD NEW". If your version of
5209  diff does not support these options, then get the latest version of
5210  GNU diff.
5211
5212  The current directory when running this command shall be the parent
5213  directory of the U-Boot source tree (i. e. please make sure that
5214  your patch includes sufficient directory information for the
5215  affected files).
5216
5217  We prefer patches as plain text. MIME attachments are discouraged,
5218  and compressed attachments must not be used.
5219
5220* If one logical set of modifications affects or creates several
5221  files, all these changes shall be submitted in a SINGLE patch file.
5222
5223* Changesets that contain different, unrelated modifications shall be
5224  submitted as SEPARATE patches, one patch per changeset.
5225
5226
5227Notes:
5228
5229* Before sending the patch, run the buildman script on your patched
5230  source tree and make sure that no errors or warnings are reported
5231  for any of the boards.
5232
5233* Keep your modifications to the necessary minimum: A patch
5234  containing several unrelated changes or arbitrary reformats will be
5235  returned with a request to re-formatting / split it.
5236
5237* If you modify existing code, make sure that your new code does not
5238  add to the memory footprint of the code ;-) Small is beautiful!
5239  When adding new features, these should compile conditionally only
5240  (using #ifdef), and the resulting code with the new feature
5241  disabled must not need more memory than the old code without your
5242  modification.
5243
5244* Remember that there is a size limit of 100 kB per message on the
5245  u-boot mailing list. Bigger patches will be moderated. If they are
5246  reasonable and not too big, they will be acknowledged. But patches
5247  bigger than the size limit should be avoided.
5248