xref: /openbmc/u-boot/README (revision 36dd5f1b)
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  /sandbox		Files generic to HW-independent "sandbox"
147  /sh			Files generic to SH architecture
148  /x86			Files generic to x86 architecture
149/api			Machine/arch independent API for external apps
150/board			Board dependent files
151/cmd			U-Boot commands functions
152/common			Misc architecture independent functions
153/configs		Board default configuration files
154/disk			Code for disk drive partition handling
155/doc			Documentation (don't expect too much)
156/drivers		Commonly used device drivers
157/dts			Contains Makefile for building internal U-Boot fdt.
158/examples		Example code for standalone applications, etc.
159/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
160/include		Header Files
161/lib			Library routines generic to all architectures
162/Licenses		Various license files
163/net			Networking code
164/post			Power On Self Test
165/scripts		Various build scripts and Makefiles
166/test			Various unit test files
167/tools			Tools to build S-Record or U-Boot images, etc.
168
169Software Configuration:
170=======================
171
172Configuration is usually done using C preprocessor defines; the
173rationale behind that is to avoid dead code whenever possible.
174
175There are two classes of configuration variables:
176
177* Configuration _OPTIONS_:
178  These are selectable by the user and have names beginning with
179  "CONFIG_".
180
181* Configuration _SETTINGS_:
182  These depend on the hardware etc. and should not be meddled with if
183  you don't know what you're doing; they have names beginning with
184  "CONFIG_SYS_".
185
186Previously, all configuration was done by hand, which involved creating
187symbolic links and editing configuration files manually. More recently,
188U-Boot has added the Kbuild infrastructure used by the Linux kernel,
189allowing you to use the "make menuconfig" command to configure your
190build.
191
192
193Selection of Processor Architecture and Board Type:
194---------------------------------------------------
195
196For all supported boards there are ready-to-use default
197configurations available; just type "make <board_name>_defconfig".
198
199Example: For a TQM823L module type:
200
201	cd u-boot
202	make TQM823L_defconfig
203
204Note: If you're looking for the default configuration file for a board
205you're sure used to be there but is now missing, check the file
206doc/README.scrapyard for a list of no longer supported boards.
207
208Sandbox Environment:
209--------------------
210
211U-Boot can be built natively to run on a Linux host using the 'sandbox'
212board. This allows feature development which is not board- or architecture-
213specific to be undertaken on a native platform. The sandbox is also used to
214run some of U-Boot's tests.
215
216See board/sandbox/README.sandbox for more details.
217
218
219Board Initialisation Flow:
220--------------------------
221
222This is the intended start-up flow for boards. This should apply for both
223SPL and U-Boot proper (i.e. they both follow the same rules).
224
225Note: "SPL" stands for "Secondary Program Loader," which is explained in
226more detail later in this file.
227
228At present, SPL mostly uses a separate code path, but the function names
229and roles of each function are the same. Some boards or architectures
230may not conform to this.  At least most ARM boards which use
231CONFIG_SPL_FRAMEWORK conform to this.
232
233Execution typically starts with an architecture-specific (and possibly
234CPU-specific) start.S file, such as:
235
236	- arch/arm/cpu/armv7/start.S
237	- arch/powerpc/cpu/mpc83xx/start.S
238	- arch/mips/cpu/start.S
239
240and so on. From there, three functions are called; the purpose and
241limitations of each of these functions are described below.
242
243lowlevel_init():
244	- purpose: essential init to permit execution to reach board_init_f()
245	- no global_data or BSS
246	- there is no stack (ARMv7 may have one but it will soon be removed)
247	- must not set up SDRAM or use console
248	- must only do the bare minimum to allow execution to continue to
249		board_init_f()
250	- this is almost never needed
251	- return normally from this function
252
253board_init_f():
254	- purpose: set up the machine ready for running board_init_r():
255		i.e. SDRAM and serial UART
256	- global_data is available
257	- stack is in SRAM
258	- BSS is not available, so you cannot use global/static variables,
259		only stack variables and global_data
260
261	Non-SPL-specific notes:
262	- dram_init() is called to set up DRAM. If already done in SPL this
263		can do nothing
264
265	SPL-specific notes:
266	- you can override the entire board_init_f() function with your own
267		version as needed.
268	- preloader_console_init() can be called here in extremis
269	- should set up SDRAM, and anything needed to make the UART work
270	- these is no need to clear BSS, it will be done by crt0.S
271	- must return normally from this function (don't call board_init_r()
272		directly)
273
274Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
275this point the stack and global_data are relocated to below
276CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
277memory.
278
279board_init_r():
280	- purpose: main execution, common code
281	- global_data is available
282	- SDRAM is available
283	- BSS is available, all static/global variables can be used
284	- execution eventually continues to main_loop()
285
286	Non-SPL-specific notes:
287	- U-Boot is relocated to the top of memory and is now running from
288		there.
289
290	SPL-specific notes:
291	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
292		CONFIG_SPL_STACK_R_ADDR points into SDRAM
293	- preloader_console_init() can be called here - typically this is
294		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
295		spl_board_init() function containing this call
296	- loads U-Boot or (in falcon mode) Linux
297
298
299
300Configuration Options:
301----------------------
302
303Configuration depends on the combination of board and CPU type; all
304such information is kept in a configuration file
305"include/configs/<board_name>.h".
306
307Example: For a TQM823L module, all configuration settings are in
308"include/configs/TQM823L.h".
309
310
311Many of the options are named exactly as the corresponding Linux
312kernel configuration options. The intention is to make it easier to
313build a config tool - later.
314
315- ARM Platform Bus Type(CCI):
316		CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
317		provides full cache coherency between two clusters of multi-core
318		CPUs and I/O coherency for devices and I/O masters
319
320		CONFIG_SYS_FSL_HAS_CCI400
321
322		Defined For SoC that has cache coherent interconnect
323		CCN-400
324
325		CONFIG_SYS_FSL_HAS_CCN504
326
327		Defined for SoC that has cache coherent interconnect CCN-504
328
329The following options need to be configured:
330
331- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
332
333- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
334
335- Marvell Family Member
336		CONFIG_SYS_MVFS		- define it if you want to enable
337					  multiple fs option at one time
338					  for marvell soc family
339
340- 85xx CPU Options:
341		CONFIG_SYS_PPC64
342
343		Specifies that the core is a 64-bit PowerPC implementation (implements
344		the "64" category of the Power ISA). This is necessary for ePAPR
345		compliance, among other possible reasons.
346
347		CONFIG_SYS_FSL_TBCLK_DIV
348
349		Defines the core time base clock divider ratio compared to the
350		system clock.  On most PQ3 devices this is 8, on newer QorIQ
351		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
352
353		CONFIG_SYS_FSL_PCIE_COMPAT
354
355		Defines the string to utilize when trying to match PCIe device
356		tree nodes for the given platform.
357
358		CONFIG_SYS_FSL_ERRATUM_A004510
359
360		Enables a workaround for erratum A004510.  If set,
361		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
362		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
363
364		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
365		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
366
367		Defines one or two SoC revisions (low 8 bits of SVR)
368		for which the A004510 workaround should be applied.
369
370		The rest of SVR is either not relevant to the decision
371		of whether the erratum is present (e.g. p2040 versus
372		p2041) or is implied by the build target, which controls
373		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
374
375		See Freescale App Note 4493 for more information about
376		this erratum.
377
378		CONFIG_A003399_NOR_WORKAROUND
379		Enables a workaround for IFC erratum A003399. It is only
380		required during NOR boot.
381
382		CONFIG_A008044_WORKAROUND
383		Enables a workaround for T1040/T1042 erratum A008044. It is only
384		required during NAND boot and valid for Rev 1.0 SoC revision
385
386		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
387
388		This is the value to write into CCSR offset 0x18600
389		according to the A004510 workaround.
390
391		CONFIG_SYS_FSL_DSP_DDR_ADDR
392		This value denotes start offset of DDR memory which is
393		connected exclusively to the DSP cores.
394
395		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
396		This value denotes start offset of M2 memory
397		which is directly connected to the DSP core.
398
399		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
400		This value denotes start offset of M3 memory which is directly
401		connected to the DSP core.
402
403		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
404		This value denotes start offset of DSP CCSR space.
405
406		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
407		Single Source Clock is clocking mode present in some of FSL SoC's.
408		In this mode, a single differential clock is used to supply
409		clocks to the sysclock, ddrclock and usbclock.
410
411		CONFIG_SYS_CPC_REINIT_F
412		This CONFIG is defined when the CPC is configured as SRAM at the
413		time of U-Boot entry and is required to be re-initialized.
414
415		CONFIG_DEEP_SLEEP
416		Indicates this SoC supports deep sleep feature. If deep sleep is
417		supported, core will start to execute uboot when wakes up.
418
419- Generic CPU options:
420		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
421
422		Defines the endianess of the CPU. Implementation of those
423		values is arch specific.
424
425		CONFIG_SYS_FSL_DDR
426		Freescale DDR driver in use. This type of DDR controller is
427		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
428		SoCs.
429
430		CONFIG_SYS_FSL_DDR_ADDR
431		Freescale DDR memory-mapped register base.
432
433		CONFIG_SYS_FSL_DDR_EMU
434		Specify emulator support for DDR. Some DDR features such as
435		deskew training are not available.
436
437		CONFIG_SYS_FSL_DDRC_GEN1
438		Freescale DDR1 controller.
439
440		CONFIG_SYS_FSL_DDRC_GEN2
441		Freescale DDR2 controller.
442
443		CONFIG_SYS_FSL_DDRC_GEN3
444		Freescale DDR3 controller.
445
446		CONFIG_SYS_FSL_DDRC_GEN4
447		Freescale DDR4 controller.
448
449		CONFIG_SYS_FSL_DDRC_ARM_GEN3
450		Freescale DDR3 controller for ARM-based SoCs.
451
452		CONFIG_SYS_FSL_DDR1
453		Board config to use DDR1. It can be enabled for SoCs with
454		Freescale DDR1 or DDR2 controllers, depending on the board
455		implemetation.
456
457		CONFIG_SYS_FSL_DDR2
458		Board config to use DDR2. It can be enabled for SoCs with
459		Freescale DDR2 or DDR3 controllers, depending on the board
460		implementation.
461
462		CONFIG_SYS_FSL_DDR3
463		Board config to use DDR3. It can be enabled for SoCs with
464		Freescale DDR3 or DDR3L controllers.
465
466		CONFIG_SYS_FSL_DDR3L
467		Board config to use DDR3L. It can be enabled for SoCs with
468		DDR3L controllers.
469
470		CONFIG_SYS_FSL_DDR4
471		Board config to use DDR4. It can be enabled for SoCs with
472		DDR4 controllers.
473
474		CONFIG_SYS_FSL_IFC_BE
475		Defines the IFC controller register space as Big Endian
476
477		CONFIG_SYS_FSL_IFC_LE
478		Defines the IFC controller register space as Little Endian
479
480		CONFIG_SYS_FSL_IFC_CLK_DIV
481		Defines divider of platform clock(clock input to IFC controller).
482
483		CONFIG_SYS_FSL_LBC_CLK_DIV
484		Defines divider of platform clock(clock input to eLBC controller).
485
486		CONFIG_SYS_FSL_PBL_PBI
487		It enables addition of RCW (Power on reset configuration) in built image.
488		Please refer doc/README.pblimage for more details
489
490		CONFIG_SYS_FSL_PBL_RCW
491		It adds PBI(pre-boot instructions) commands in u-boot build image.
492		PBI commands can be used to configure SoC before it starts the execution.
493		Please refer doc/README.pblimage for more details
494
495		CONFIG_SPL_FSL_PBL
496		It adds a target to create boot binary having SPL binary in PBI format
497		concatenated with u-boot binary.
498
499		CONFIG_SYS_FSL_DDR_BE
500		Defines the DDR controller register space as Big Endian
501
502		CONFIG_SYS_FSL_DDR_LE
503		Defines the DDR controller register space as Little Endian
504
505		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
506		Physical address from the view of DDR controllers. It is the
507		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
508		it could be different for ARM SoCs.
509
510		CONFIG_SYS_FSL_DDR_INTLV_256B
511		DDR controller interleaving on 256-byte. This is a special
512		interleaving mode, handled by Dickens for Freescale layerscape
513		SoCs with ARM core.
514
515		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
516		Number of controllers used as main memory.
517
518		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
519		Number of controllers used for other than main memory.
520
521		CONFIG_SYS_FSL_HAS_DP_DDR
522		Defines the SoC has DP-DDR used for DPAA.
523
524		CONFIG_SYS_FSL_SEC_BE
525		Defines the SEC controller register space as Big Endian
526
527		CONFIG_SYS_FSL_SEC_LE
528		Defines the SEC controller register space as Little Endian
529
530- MIPS CPU options:
531		CONFIG_SYS_INIT_SP_OFFSET
532
533		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
534		pointer. This is needed for the temporary stack before
535		relocation.
536
537		CONFIG_SYS_MIPS_CACHE_MODE
538
539		Cache operation mode for the MIPS CPU.
540		See also arch/mips/include/asm/mipsregs.h.
541		Possible values are:
542			CONF_CM_CACHABLE_NO_WA
543			CONF_CM_CACHABLE_WA
544			CONF_CM_UNCACHED
545			CONF_CM_CACHABLE_NONCOHERENT
546			CONF_CM_CACHABLE_CE
547			CONF_CM_CACHABLE_COW
548			CONF_CM_CACHABLE_CUW
549			CONF_CM_CACHABLE_ACCELERATED
550
551		CONFIG_SYS_XWAY_EBU_BOOTCFG
552
553		Special option for Lantiq XWAY SoCs for booting from NOR flash.
554		See also arch/mips/cpu/mips32/start.S.
555
556		CONFIG_XWAY_SWAP_BYTES
557
558		Enable compilation of tools/xway-swap-bytes needed for Lantiq
559		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
560		be swapped if a flash programmer is used.
561
562- ARM options:
563		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
564
565		Select high exception vectors of the ARM core, e.g., do not
566		clear the V bit of the c1 register of CP15.
567
568		COUNTER_FREQUENCY
569		Generic timer clock source frequency.
570
571		COUNTER_FREQUENCY_REAL
572		Generic timer clock source frequency if the real clock is
573		different from COUNTER_FREQUENCY, and can only be determined
574		at run time.
575
576- Tegra SoC options:
577		CONFIG_TEGRA_SUPPORT_NON_SECURE
578
579		Support executing U-Boot in non-secure (NS) mode. Certain
580		impossible actions will be skipped if the CPU is in NS mode,
581		such as ARM architectural timer initialization.
582
583- Linux Kernel Interface:
584		CONFIG_CLOCKS_IN_MHZ
585
586		U-Boot stores all clock information in Hz
587		internally. For binary compatibility with older Linux
588		kernels (which expect the clocks passed in the
589		bd_info data to be in MHz) the environment variable
590		"clocks_in_mhz" can be defined so that U-Boot
591		converts clock data to MHZ before passing it to the
592		Linux kernel.
593		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
594		"clocks_in_mhz=1" is automatically included in the
595		default environment.
596
597		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
598
599		When transferring memsize parameter to Linux, some versions
600		expect it to be in bytes, others in MB.
601		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
602
603		CONFIG_OF_LIBFDT
604
605		New kernel versions are expecting firmware settings to be
606		passed using flattened device trees (based on open firmware
607		concepts).
608
609		CONFIG_OF_LIBFDT
610		 * New libfdt-based support
611		 * Adds the "fdt" command
612		 * The bootm command automatically updates the fdt
613
614		OF_TBCLK - The timebase frequency.
615		OF_STDOUT_PATH - The path to the console device
616
617		boards with QUICC Engines require OF_QE to set UCC MAC
618		addresses
619
620		CONFIG_OF_BOARD_SETUP
621
622		Board code has addition modification that it wants to make
623		to the flat device tree before handing it off to the kernel
624
625		CONFIG_OF_SYSTEM_SETUP
626
627		Other code has addition modification that it wants to make
628		to the flat device tree before handing it off to the kernel.
629		This causes ft_system_setup() to be called before booting
630		the kernel.
631
632		CONFIG_OF_IDE_FIXUP
633
634		U-Boot can detect if an IDE device is present or not.
635		If not, and this new config option is activated, U-Boot
636		removes the ATA node from the DTS before booting Linux,
637		so the Linux IDE driver does not probe the device and
638		crash. This is needed for buggy hardware (uc101) where
639		no pull down resistor is connected to the signal IDE5V_DD7.
640
641		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
642
643		This setting is mandatory for all boards that have only one
644		machine type and must be used to specify the machine type
645		number as it appears in the ARM machine registry
646		(see http://www.arm.linux.org.uk/developer/machines/).
647		Only boards that have multiple machine types supported
648		in a single configuration file and the machine type is
649		runtime discoverable, do not have to use this setting.
650
651- vxWorks boot parameters:
652
653		bootvx constructs a valid bootline using the following
654		environments variables: bootdev, bootfile, ipaddr, netmask,
655		serverip, gatewayip, hostname, othbootargs.
656		It loads the vxWorks image pointed bootfile.
657
658		Note: If a "bootargs" environment is defined, it will overwride
659		the defaults discussed just above.
660
661- Cache Configuration:
662		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
663		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
664		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
665
666- Cache Configuration for ARM:
667		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
668				      controller
669		CONFIG_SYS_PL310_BASE - Physical base address of PL310
670					controller register space
671
672- Serial Ports:
673		CONFIG_PL010_SERIAL
674
675		Define this if you want support for Amba PrimeCell PL010 UARTs.
676
677		CONFIG_PL011_SERIAL
678
679		Define this if you want support for Amba PrimeCell PL011 UARTs.
680
681		CONFIG_PL011_CLOCK
682
683		If you have Amba PrimeCell PL011 UARTs, set this variable to
684		the clock speed of the UARTs.
685
686		CONFIG_PL01x_PORTS
687
688		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
689		define this to a list of base addresses for each (supported)
690		port. See e.g. include/configs/versatile.h
691
692		CONFIG_SERIAL_HW_FLOW_CONTROL
693
694		Define this variable to enable hw flow control in serial driver.
695		Current user of this option is drivers/serial/nsl16550.c driver
696
697- Console Baudrate:
698		CONFIG_BAUDRATE - in bps
699		Select one of the baudrates listed in
700		CONFIG_SYS_BAUDRATE_TABLE, see below.
701
702- Autoboot Command:
703		CONFIG_BOOTCOMMAND
704		Only needed when CONFIG_BOOTDELAY is enabled;
705		define a command string that is automatically executed
706		when no character is read on the console interface
707		within "Boot Delay" after reset.
708
709		CONFIG_RAMBOOT and CONFIG_NFSBOOT
710		The value of these goes into the environment as
711		"ramboot" and "nfsboot" respectively, and can be used
712		as a convenience, when switching between booting from
713		RAM and NFS.
714
715- Bootcount:
716		CONFIG_BOOTCOUNT_LIMIT
717		Implements a mechanism for detecting a repeating reboot
718		cycle, see:
719		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
720
721		CONFIG_BOOTCOUNT_ENV
722		If no softreset save registers are found on the hardware
723		"bootcount" is stored in the environment. To prevent a
724		saveenv on all reboots, the environment variable
725		"upgrade_available" is used. If "upgrade_available" is
726		0, "bootcount" is always 0, if "upgrade_available" is
727		1 "bootcount" is incremented in the environment.
728		So the Userspace Applikation must set the "upgrade_available"
729		and "bootcount" variable to 0, if a boot was successfully.
730
731- Pre-Boot Commands:
732		CONFIG_PREBOOT
733
734		When this option is #defined, the existence of the
735		environment variable "preboot" will be checked
736		immediately before starting the CONFIG_BOOTDELAY
737		countdown and/or running the auto-boot command resp.
738		entering interactive mode.
739
740		This feature is especially useful when "preboot" is
741		automatically generated or modified. For an example
742		see the LWMON board specific code: here "preboot" is
743		modified when the user holds down a certain
744		combination of keys on the (special) keyboard when
745		booting the systems
746
747- Serial Download Echo Mode:
748		CONFIG_LOADS_ECHO
749		If defined to 1, all characters received during a
750		serial download (using the "loads" command) are
751		echoed back. This might be needed by some terminal
752		emulations (like "cu"), but may as well just take
753		time on others. This setting #define's the initial
754		value of the "loads_echo" environment variable.
755
756- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
757		CONFIG_KGDB_BAUDRATE
758		Select one of the baudrates listed in
759		CONFIG_SYS_BAUDRATE_TABLE, see below.
760
761- Removal of commands
762		If no commands are needed to boot, you can disable
763		CONFIG_CMDLINE to remove them. In this case, the command line
764		will not be available, and when U-Boot wants to execute the
765		boot command (on start-up) it will call board_run_command()
766		instead. This can reduce image size significantly for very
767		simple boot procedures.
768
769- Regular expression support:
770		CONFIG_REGEX
771		If this variable is defined, U-Boot is linked against
772		the SLRE (Super Light Regular Expression) library,
773		which adds regex support to some commands, as for
774		example "env grep" and "setexpr".
775
776- Device tree:
777		CONFIG_OF_CONTROL
778		If this variable is defined, U-Boot will use a device tree
779		to configure its devices, instead of relying on statically
780		compiled #defines in the board file. This option is
781		experimental and only available on a few boards. The device
782		tree is available in the global data as gd->fdt_blob.
783
784		U-Boot needs to get its device tree from somewhere. This can
785		be done using one of the three options below:
786
787		CONFIG_OF_EMBED
788		If this variable is defined, U-Boot will embed a device tree
789		binary in its image. This device tree file should be in the
790		board directory and called <soc>-<board>.dts. The binary file
791		is then picked up in board_init_f() and made available through
792		the global data structure as gd->fdt_blob.
793
794		CONFIG_OF_SEPARATE
795		If this variable is defined, U-Boot will build a device tree
796		binary. It will be called u-boot.dtb. Architecture-specific
797		code will locate it at run-time. Generally this works by:
798
799			cat u-boot.bin u-boot.dtb >image.bin
800
801		and in fact, U-Boot does this for you, creating a file called
802		u-boot-dtb.bin which is useful in the common case. You can
803		still use the individual files if you need something more
804		exotic.
805
806		CONFIG_OF_BOARD
807		If this variable is defined, U-Boot will use the device tree
808		provided by the board at runtime instead of embedding one with
809		the image. Only boards defining board_fdt_blob_setup() support
810		this option (see include/fdtdec.h file).
811
812- Watchdog:
813		CONFIG_WATCHDOG
814		If this variable is defined, it enables watchdog
815		support for the SoC. There must be support in the SoC
816		specific code for a watchdog. For the 8xx
817		CPUs, the SIU Watchdog feature is enabled in the SYPCR
818		register.  When supported for a specific SoC is
819		available, then no further board specific code should
820		be needed to use it.
821
822		CONFIG_HW_WATCHDOG
823		When using a watchdog circuitry external to the used
824		SoC, then define this variable and provide board
825		specific code for the "hw_watchdog_reset" function.
826
827		CONFIG_AT91_HW_WDT_TIMEOUT
828		specify the timeout in seconds. default 2 seconds.
829
830- U-Boot Version:
831		CONFIG_VERSION_VARIABLE
832		If this variable is defined, an environment variable
833		named "ver" is created by U-Boot showing the U-Boot
834		version as printed by the "version" command.
835		Any change to this variable will be reverted at the
836		next reset.
837
838- Real-Time Clock:
839
840		When CONFIG_CMD_DATE is selected, the type of the RTC
841		has to be selected, too. Define exactly one of the
842		following options:
843
844		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
845		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
846		CONFIG_RTC_MC146818	- use MC146818 RTC
847		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
848		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
849		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
850		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
851		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
852		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
853		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
854		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
855		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
856					  RV3029 RTC.
857
858		Note that if the RTC uses I2C, then the I2C interface
859		must also be configured. See I2C Support, below.
860
861- GPIO Support:
862		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
863
864		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
865		chip-ngpio pairs that tell the PCA953X driver the number of
866		pins supported by a particular chip.
867
868		Note that if the GPIO device uses I2C, then the I2C interface
869		must also be configured. See I2C Support, below.
870
871- I/O tracing:
872		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
873		accesses and can checksum them or write a list of them out
874		to memory. See the 'iotrace' command for details. This is
875		useful for testing device drivers since it can confirm that
876		the driver behaves the same way before and after a code
877		change. Currently this is supported on sandbox and arm. To
878		add support for your architecture, add '#include <iotrace.h>'
879		to the bottom of arch/<arch>/include/asm/io.h and test.
880
881		Example output from the 'iotrace stats' command is below.
882		Note that if the trace buffer is exhausted, the checksum will
883		still continue to operate.
884
885			iotrace is enabled
886			Start:  10000000	(buffer start address)
887			Size:   00010000	(buffer size)
888			Offset: 00000120	(current buffer offset)
889			Output: 10000120	(start + offset)
890			Count:  00000018	(number of trace records)
891			CRC32:  9526fb66	(CRC32 of all trace records)
892
893- Timestamp Support:
894
895		When CONFIG_TIMESTAMP is selected, the timestamp
896		(date and time) of an image is printed by image
897		commands like bootm or iminfo. This option is
898		automatically enabled when you select CONFIG_CMD_DATE .
899
900- Partition Labels (disklabels) Supported:
901		Zero or more of the following:
902		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
903		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
904		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
905				       bootloader.  Note 2TB partition limit; see
906				       disk/part_efi.c
907		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
908
909		If IDE or SCSI support is enabled (CONFIG_IDE or
910		CONFIG_SCSI) you must configure support for at
911		least one non-MTD partition type as well.
912
913- IDE Reset method:
914		CONFIG_IDE_RESET_ROUTINE - this is defined in several
915		board configurations files but used nowhere!
916
917		CONFIG_IDE_RESET - is this is defined, IDE Reset will
918		be performed by calling the function
919			ide_set_reset(int reset)
920		which has to be defined in a board specific file
921
922- ATAPI Support:
923		CONFIG_ATAPI
924
925		Set this to enable ATAPI support.
926
927- LBA48 Support
928		CONFIG_LBA48
929
930		Set this to enable support for disks larger than 137GB
931		Also look at CONFIG_SYS_64BIT_LBA.
932		Whithout these , LBA48 support uses 32bit variables and will 'only'
933		support disks up to 2.1TB.
934
935		CONFIG_SYS_64BIT_LBA:
936			When enabled, makes the IDE subsystem use 64bit sector addresses.
937			Default is 32bit.
938
939- SCSI Support:
940		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
941		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
942		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
943		maximum numbers of LUNs, SCSI ID's and target
944		devices.
945
946		The environment variable 'scsidevs' is set to the number of
947		SCSI devices found during the last scan.
948
949- NETWORK Support (PCI):
950		CONFIG_E1000
951		Support for Intel 8254x/8257x gigabit chips.
952
953		CONFIG_E1000_SPI
954		Utility code for direct access to the SPI bus on Intel 8257x.
955		This does not do anything useful unless you set at least one
956		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
957
958		CONFIG_E1000_SPI_GENERIC
959		Allow generic access to the SPI bus on the Intel 8257x, for
960		example with the "sspi" command.
961
962		CONFIG_EEPRO100
963		Support for Intel 82557/82559/82559ER chips.
964		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
965		write routine for first time initialisation.
966
967		CONFIG_TULIP
968		Support for Digital 2114x chips.
969		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
970		modem chip initialisation (KS8761/QS6611).
971
972		CONFIG_NATSEMI
973		Support for National dp83815 chips.
974
975		CONFIG_NS8382X
976		Support for National dp8382[01] gigabit chips.
977
978- NETWORK Support (other):
979
980		CONFIG_DRIVER_AT91EMAC
981		Support for AT91RM9200 EMAC.
982
983			CONFIG_RMII
984			Define this to use reduced MII inteface
985
986			CONFIG_DRIVER_AT91EMAC_QUIET
987			If this defined, the driver is quiet.
988			The driver doen't show link status messages.
989
990		CONFIG_CALXEDA_XGMAC
991		Support for the Calxeda XGMAC device
992
993		CONFIG_LAN91C96
994		Support for SMSC's LAN91C96 chips.
995
996			CONFIG_LAN91C96_USE_32_BIT
997			Define this to enable 32 bit addressing
998
999		CONFIG_SMC91111
1000		Support for SMSC's LAN91C111 chip
1001
1002			CONFIG_SMC91111_BASE
1003			Define this to hold the physical address
1004			of the device (I/O space)
1005
1006			CONFIG_SMC_USE_32_BIT
1007			Define this if data bus is 32 bits
1008
1009			CONFIG_SMC_USE_IOFUNCS
1010			Define this to use i/o functions instead of macros
1011			(some hardware wont work with macros)
1012
1013		CONFIG_DRIVER_TI_EMAC
1014		Support for davinci emac
1015
1016			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1017			Define this if you have more then 3 PHYs.
1018
1019		CONFIG_FTGMAC100
1020		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1021
1022			CONFIG_FTGMAC100_EGIGA
1023			Define this to use GE link update with gigabit PHY.
1024			Define this if FTGMAC100 is connected to gigabit PHY.
1025			If your system has 10/100 PHY only, it might not occur
1026			wrong behavior. Because PHY usually return timeout or
1027			useless data when polling gigabit status and gigabit
1028			control registers. This behavior won't affect the
1029			correctnessof 10/100 link speed update.
1030
1031		CONFIG_SMC911X
1032		Support for SMSC's LAN911x and LAN921x chips
1033
1034			CONFIG_SMC911X_BASE
1035			Define this to hold the physical address
1036			of the device (I/O space)
1037
1038			CONFIG_SMC911X_32_BIT
1039			Define this if data bus is 32 bits
1040
1041			CONFIG_SMC911X_16_BIT
1042			Define this if data bus is 16 bits. If your processor
1043			automatically converts one 32 bit word to two 16 bit
1044			words you may also try CONFIG_SMC911X_32_BIT.
1045
1046		CONFIG_SH_ETHER
1047		Support for Renesas on-chip Ethernet controller
1048
1049			CONFIG_SH_ETHER_USE_PORT
1050			Define the number of ports to be used
1051
1052			CONFIG_SH_ETHER_PHY_ADDR
1053			Define the ETH PHY's address
1054
1055			CONFIG_SH_ETHER_CACHE_WRITEBACK
1056			If this option is set, the driver enables cache flush.
1057
1058- PWM Support:
1059		CONFIG_PWM_IMX
1060		Support for PWM module on the imx6.
1061
1062- TPM Support:
1063		CONFIG_TPM
1064		Support TPM devices.
1065
1066		CONFIG_TPM_TIS_INFINEON
1067		Support for Infineon i2c bus TPM devices. Only one device
1068		per system is supported at this time.
1069
1070			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1071			Define the burst count bytes upper limit
1072
1073		CONFIG_TPM_ST33ZP24
1074		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1075
1076			CONFIG_TPM_ST33ZP24_I2C
1077			Support for STMicroelectronics ST33ZP24 I2C devices.
1078			Requires TPM_ST33ZP24 and I2C.
1079
1080			CONFIG_TPM_ST33ZP24_SPI
1081			Support for STMicroelectronics ST33ZP24 SPI devices.
1082			Requires TPM_ST33ZP24 and SPI.
1083
1084		CONFIG_TPM_ATMEL_TWI
1085		Support for Atmel TWI TPM device. Requires I2C support.
1086
1087		CONFIG_TPM_TIS_LPC
1088		Support for generic parallel port TPM devices. Only one device
1089		per system is supported at this time.
1090
1091			CONFIG_TPM_TIS_BASE_ADDRESS
1092			Base address where the generic TPM device is mapped
1093			to. Contemporary x86 systems usually map it at
1094			0xfed40000.
1095
1096		CONFIG_TPM
1097		Define this to enable the TPM support library which provides
1098		functional interfaces to some TPM commands.
1099		Requires support for a TPM device.
1100
1101		CONFIG_TPM_AUTH_SESSIONS
1102		Define this to enable authorized functions in the TPM library.
1103		Requires CONFIG_TPM and CONFIG_SHA1.
1104
1105- USB Support:
1106		At the moment only the UHCI host controller is
1107		supported (PIP405, MIP405); define
1108		CONFIG_USB_UHCI to enable it.
1109		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1110		and define CONFIG_USB_STORAGE to enable the USB
1111		storage devices.
1112		Note:
1113		Supported are USB Keyboards and USB Floppy drives
1114		(TEAC FD-05PUB).
1115
1116		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1117		txfilltuning field in the EHCI controller on reset.
1118
1119		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1120		HW module registers.
1121
1122- USB Device:
1123		Define the below if you wish to use the USB console.
1124		Once firmware is rebuilt from a serial console issue the
1125		command "setenv stdin usbtty; setenv stdout usbtty" and
1126		attach your USB cable. The Unix command "dmesg" should print
1127		it has found a new device. The environment variable usbtty
1128		can be set to gserial or cdc_acm to enable your device to
1129		appear to a USB host as a Linux gserial device or a
1130		Common Device Class Abstract Control Model serial device.
1131		If you select usbtty = gserial you should be able to enumerate
1132		a Linux host by
1133		# modprobe usbserial vendor=0xVendorID product=0xProductID
1134		else if using cdc_acm, simply setting the environment
1135		variable usbtty to be cdc_acm should suffice. The following
1136		might be defined in YourBoardName.h
1137
1138			CONFIG_USB_DEVICE
1139			Define this to build a UDC device
1140
1141			CONFIG_USB_TTY
1142			Define this to have a tty type of device available to
1143			talk to the UDC device
1144
1145			CONFIG_USBD_HS
1146			Define this to enable the high speed support for usb
1147			device and usbtty. If this feature is enabled, a routine
1148			int is_usbd_high_speed(void)
1149			also needs to be defined by the driver to dynamically poll
1150			whether the enumeration has succeded at high speed or full
1151			speed.
1152
1153			CONFIG_SYS_CONSOLE_IS_IN_ENV
1154			Define this if you want stdin, stdout &/or stderr to
1155			be set to usbtty.
1156
1157		If you have a USB-IF assigned VendorID then you may wish to
1158		define your own vendor specific values either in BoardName.h
1159		or directly in usbd_vendor_info.h. If you don't define
1160		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1161		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1162		should pretend to be a Linux device to it's target host.
1163
1164			CONFIG_USBD_MANUFACTURER
1165			Define this string as the name of your company for
1166			- CONFIG_USBD_MANUFACTURER "my company"
1167
1168			CONFIG_USBD_PRODUCT_NAME
1169			Define this string as the name of your product
1170			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1171
1172			CONFIG_USBD_VENDORID
1173			Define this as your assigned Vendor ID from the USB
1174			Implementors Forum. This *must* be a genuine Vendor ID
1175			to avoid polluting the USB namespace.
1176			- CONFIG_USBD_VENDORID 0xFFFF
1177
1178			CONFIG_USBD_PRODUCTID
1179			Define this as the unique Product ID
1180			for your device
1181			- CONFIG_USBD_PRODUCTID 0xFFFF
1182
1183- ULPI Layer Support:
1184		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1185		the generic ULPI layer. The generic layer accesses the ULPI PHY
1186		via the platform viewport, so you need both the genric layer and
1187		the viewport enabled. Currently only Chipidea/ARC based
1188		viewport is supported.
1189		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1190		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1191		If your ULPI phy needs a different reference clock than the
1192		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1193		the appropriate value in Hz.
1194
1195- MMC Support:
1196		The MMC controller on the Intel PXA is supported. To
1197		enable this define CONFIG_MMC. The MMC can be
1198		accessed from the boot prompt by mapping the device
1199		to physical memory similar to flash. Command line is
1200		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1201		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1202
1203		CONFIG_SH_MMCIF
1204		Support for Renesas on-chip MMCIF controller
1205
1206			CONFIG_SH_MMCIF_ADDR
1207			Define the base address of MMCIF registers
1208
1209			CONFIG_SH_MMCIF_CLK
1210			Define the clock frequency for MMCIF
1211
1212		CONFIG_SUPPORT_EMMC_BOOT
1213		Enable some additional features of the eMMC boot partitions.
1214
1215		CONFIG_SUPPORT_EMMC_RPMB
1216		Enable the commands for reading, writing and programming the
1217		key for the Replay Protection Memory Block partition in eMMC.
1218
1219- USB Device Firmware Update (DFU) class support:
1220		CONFIG_USB_FUNCTION_DFU
1221		This enables the USB portion of the DFU USB class
1222
1223		CONFIG_DFU_MMC
1224		This enables support for exposing (e)MMC devices via DFU.
1225
1226		CONFIG_DFU_NAND
1227		This enables support for exposing NAND devices via DFU.
1228
1229		CONFIG_DFU_RAM
1230		This enables support for exposing RAM via DFU.
1231		Note: DFU spec refer to non-volatile memory usage, but
1232		allow usages beyond the scope of spec - here RAM usage,
1233		one that would help mostly the developer.
1234
1235		CONFIG_SYS_DFU_DATA_BUF_SIZE
1236		Dfu transfer uses a buffer before writing data to the
1237		raw storage device. Make the size (in bytes) of this buffer
1238		configurable. The size of this buffer is also configurable
1239		through the "dfu_bufsiz" environment variable.
1240
1241		CONFIG_SYS_DFU_MAX_FILE_SIZE
1242		When updating files rather than the raw storage device,
1243		we use a static buffer to copy the file into and then write
1244		the buffer once we've been given the whole file.  Define
1245		this to the maximum filesize (in bytes) for the buffer.
1246		Default is 4 MiB if undefined.
1247
1248		DFU_DEFAULT_POLL_TIMEOUT
1249		Poll timeout [ms], is the timeout a device can send to the
1250		host. The host must wait for this timeout before sending
1251		a subsequent DFU_GET_STATUS request to the device.
1252
1253		DFU_MANIFEST_POLL_TIMEOUT
1254		Poll timeout [ms], which the device sends to the host when
1255		entering dfuMANIFEST state. Host waits this timeout, before
1256		sending again an USB request to the device.
1257
1258- Journaling Flash filesystem support:
1259		CONFIG_JFFS2_NAND
1260		Define these for a default partition on a NAND device
1261
1262		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1263		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1264		Define these for a default partition on a NOR device
1265
1266- Keyboard Support:
1267		See Kconfig help for available keyboard drivers.
1268
1269		CONFIG_KEYBOARD
1270
1271		Define this to enable a custom keyboard support.
1272		This simply calls drv_keyboard_init() which must be
1273		defined in your board-specific files. This option is deprecated
1274		and is only used by novena. For new boards, use driver model
1275		instead.
1276
1277- Video support:
1278		CONFIG_FSL_DIU_FB
1279		Enable the Freescale DIU video driver.	Reference boards for
1280		SOCs that have a DIU should define this macro to enable DIU
1281		support, and should also define these other macros:
1282
1283			CONFIG_SYS_DIU_ADDR
1284			CONFIG_VIDEO
1285			CONFIG_CFB_CONSOLE
1286			CONFIG_VIDEO_SW_CURSOR
1287			CONFIG_VGA_AS_SINGLE_DEVICE
1288			CONFIG_VIDEO_LOGO
1289			CONFIG_VIDEO_BMP_LOGO
1290
1291		The DIU driver will look for the 'video-mode' environment
1292		variable, and if defined, enable the DIU as a console during
1293		boot.  See the documentation file doc/README.video for a
1294		description of this variable.
1295
1296- LCD Support:	CONFIG_LCD
1297
1298		Define this to enable LCD support (for output to LCD
1299		display); also select one of the supported displays
1300		by defining one of these:
1301
1302		CONFIG_ATMEL_LCD:
1303
1304			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1305
1306		CONFIG_NEC_NL6448AC33:
1307
1308			NEC NL6448AC33-18. Active, color, single scan.
1309
1310		CONFIG_NEC_NL6448BC20
1311
1312			NEC NL6448BC20-08. 6.5", 640x480.
1313			Active, color, single scan.
1314
1315		CONFIG_NEC_NL6448BC33_54
1316
1317			NEC NL6448BC33-54. 10.4", 640x480.
1318			Active, color, single scan.
1319
1320		CONFIG_SHARP_16x9
1321
1322			Sharp 320x240. Active, color, single scan.
1323			It isn't 16x9, and I am not sure what it is.
1324
1325		CONFIG_SHARP_LQ64D341
1326
1327			Sharp LQ64D341 display, 640x480.
1328			Active, color, single scan.
1329
1330		CONFIG_HLD1045
1331
1332			HLD1045 display, 640x480.
1333			Active, color, single scan.
1334
1335		CONFIG_OPTREX_BW
1336
1337			Optrex	 CBL50840-2 NF-FW 99 22 M5
1338			or
1339			Hitachi	 LMG6912RPFC-00T
1340			or
1341			Hitachi	 SP14Q002
1342
1343			320x240. Black & white.
1344
1345		CONFIG_LCD_ALIGNMENT
1346
1347		Normally the LCD is page-aligned (typically 4KB). If this is
1348		defined then the LCD will be aligned to this value instead.
1349		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1350		here, since it is cheaper to change data cache settings on
1351		a per-section basis.
1352
1353
1354		CONFIG_LCD_ROTATION
1355
1356		Sometimes, for example if the display is mounted in portrait
1357		mode or even if it's mounted landscape but rotated by 180degree,
1358		we need to rotate our content of the display relative to the
1359		framebuffer, so that user can read the messages which are
1360		printed out.
1361		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1362		initialized with a given rotation from "vl_rot" out of
1363		"vidinfo_t" which is provided by the board specific code.
1364		The value for vl_rot is coded as following (matching to
1365		fbcon=rotate:<n> linux-kernel commandline):
1366		0 = no rotation respectively 0 degree
1367		1 = 90 degree rotation
1368		2 = 180 degree rotation
1369		3 = 270 degree rotation
1370
1371		If CONFIG_LCD_ROTATION is not defined, the console will be
1372		initialized with 0degree rotation.
1373
1374		CONFIG_LCD_BMP_RLE8
1375
1376		Support drawing of RLE8-compressed bitmaps on the LCD.
1377
1378		CONFIG_I2C_EDID
1379
1380		Enables an 'i2c edid' command which can read EDID
1381		information over I2C from an attached LCD display.
1382
1383- Splash Screen Support: CONFIG_SPLASH_SCREEN
1384
1385		If this option is set, the environment is checked for
1386		a variable "splashimage". If found, the usual display
1387		of logo, copyright and system information on the LCD
1388		is suppressed and the BMP image at the address
1389		specified in "splashimage" is loaded instead. The
1390		console is redirected to the "nulldev", too. This
1391		allows for a "silent" boot where a splash screen is
1392		loaded very quickly after power-on.
1393
1394		CONFIG_SPLASHIMAGE_GUARD
1395
1396		If this option is set, then U-Boot will prevent the environment
1397		variable "splashimage" from being set to a problematic address
1398		(see doc/README.displaying-bmps).
1399		This option is useful for targets where, due to alignment
1400		restrictions, an improperly aligned BMP image will cause a data
1401		abort. If you think you will not have problems with unaligned
1402		accesses (for example because your toolchain prevents them)
1403		there is no need to set this option.
1404
1405		CONFIG_SPLASH_SCREEN_ALIGN
1406
1407		If this option is set the splash image can be freely positioned
1408		on the screen. Environment variable "splashpos" specifies the
1409		position as "x,y". If a positive number is given it is used as
1410		number of pixel from left/top. If a negative number is given it
1411		is used as number of pixel from right/bottom. You can also
1412		specify 'm' for centering the image.
1413
1414		Example:
1415		setenv splashpos m,m
1416			=> image at center of screen
1417
1418		setenv splashpos 30,20
1419			=> image at x = 30 and y = 20
1420
1421		setenv splashpos -10,m
1422			=> vertically centered image
1423			   at x = dspWidth - bmpWidth - 9
1424
1425- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1426
1427		If this option is set, additionally to standard BMP
1428		images, gzipped BMP images can be displayed via the
1429		splashscreen support or the bmp command.
1430
1431- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1432
1433		If this option is set, 8-bit RLE compressed BMP images
1434		can be displayed via the splashscreen support or the
1435		bmp command.
1436
1437- Compression support:
1438		CONFIG_GZIP
1439
1440		Enabled by default to support gzip compressed images.
1441
1442		CONFIG_BZIP2
1443
1444		If this option is set, support for bzip2 compressed
1445		images is included. If not, only uncompressed and gzip
1446		compressed images are supported.
1447
1448		NOTE: the bzip2 algorithm requires a lot of RAM, so
1449		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1450		be at least 4MB.
1451
1452- MII/PHY support:
1453		CONFIG_PHY_ADDR
1454
1455		The address of PHY on MII bus.
1456
1457		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1458
1459		The clock frequency of the MII bus
1460
1461		CONFIG_PHY_RESET_DELAY
1462
1463		Some PHY like Intel LXT971A need extra delay after
1464		reset before any MII register access is possible.
1465		For such PHY, set this option to the usec delay
1466		required. (minimum 300usec for LXT971A)
1467
1468		CONFIG_PHY_CMD_DELAY (ppc4xx)
1469
1470		Some PHY like Intel LXT971A need extra delay after
1471		command issued before MII status register can be read
1472
1473- IP address:
1474		CONFIG_IPADDR
1475
1476		Define a default value for the IP address to use for
1477		the default Ethernet interface, in case this is not
1478		determined through e.g. bootp.
1479		(Environment variable "ipaddr")
1480
1481- Server IP address:
1482		CONFIG_SERVERIP
1483
1484		Defines a default value for the IP address of a TFTP
1485		server to contact when using the "tftboot" command.
1486		(Environment variable "serverip")
1487
1488		CONFIG_KEEP_SERVERADDR
1489
1490		Keeps the server's MAC address, in the env 'serveraddr'
1491		for passing to bootargs (like Linux's netconsole option)
1492
1493- Gateway IP address:
1494		CONFIG_GATEWAYIP
1495
1496		Defines a default value for the IP address of the
1497		default router where packets to other networks are
1498		sent to.
1499		(Environment variable "gatewayip")
1500
1501- Subnet mask:
1502		CONFIG_NETMASK
1503
1504		Defines a default value for the subnet mask (or
1505		routing prefix) which is used to determine if an IP
1506		address belongs to the local subnet or needs to be
1507		forwarded through a router.
1508		(Environment variable "netmask")
1509
1510- Multicast TFTP Mode:
1511		CONFIG_MCAST_TFTP
1512
1513		Defines whether you want to support multicast TFTP as per
1514		rfc-2090; for example to work with atftp.  Lets lots of targets
1515		tftp down the same boot image concurrently.  Note: the Ethernet
1516		driver in use must provide a function: mcast() to join/leave a
1517		multicast group.
1518
1519- BOOTP Recovery Mode:
1520		CONFIG_BOOTP_RANDOM_DELAY
1521
1522		If you have many targets in a network that try to
1523		boot using BOOTP, you may want to avoid that all
1524		systems send out BOOTP requests at precisely the same
1525		moment (which would happen for instance at recovery
1526		from a power failure, when all systems will try to
1527		boot, thus flooding the BOOTP server. Defining
1528		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1529		inserted before sending out BOOTP requests. The
1530		following delays are inserted then:
1531
1532		1st BOOTP request:	delay 0 ... 1 sec
1533		2nd BOOTP request:	delay 0 ... 2 sec
1534		3rd BOOTP request:	delay 0 ... 4 sec
1535		4th and following
1536		BOOTP requests:		delay 0 ... 8 sec
1537
1538		CONFIG_BOOTP_ID_CACHE_SIZE
1539
1540		BOOTP packets are uniquely identified using a 32-bit ID. The
1541		server will copy the ID from client requests to responses and
1542		U-Boot will use this to determine if it is the destination of
1543		an incoming response. Some servers will check that addresses
1544		aren't in use before handing them out (usually using an ARP
1545		ping) and therefore take up to a few hundred milliseconds to
1546		respond. Network congestion may also influence the time it
1547		takes for a response to make it back to the client. If that
1548		time is too long, U-Boot will retransmit requests. In order
1549		to allow earlier responses to still be accepted after these
1550		retransmissions, U-Boot's BOOTP client keeps a small cache of
1551		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1552		cache. The default is to keep IDs for up to four outstanding
1553		requests. Increasing this will allow U-Boot to accept offers
1554		from a BOOTP client in networks with unusually high latency.
1555
1556- DHCP Advanced Options:
1557		You can fine tune the DHCP functionality by defining
1558		CONFIG_BOOTP_* symbols:
1559
1560		CONFIG_BOOTP_SUBNETMASK
1561		CONFIG_BOOTP_GATEWAY
1562		CONFIG_BOOTP_HOSTNAME
1563		CONFIG_BOOTP_NISDOMAIN
1564		CONFIG_BOOTP_BOOTPATH
1565		CONFIG_BOOTP_BOOTFILESIZE
1566		CONFIG_BOOTP_DNS
1567		CONFIG_BOOTP_DNS2
1568		CONFIG_BOOTP_SEND_HOSTNAME
1569		CONFIG_BOOTP_NTPSERVER
1570		CONFIG_BOOTP_TIMEOFFSET
1571		CONFIG_BOOTP_VENDOREX
1572		CONFIG_BOOTP_MAY_FAIL
1573
1574		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1575		environment variable, not the BOOTP server.
1576
1577		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1578		after the configured retry count, the call will fail
1579		instead of starting over.  This can be used to fail over
1580		to Link-local IP address configuration if the DHCP server
1581		is not available.
1582
1583		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1584		serverip from a DHCP server, it is possible that more
1585		than one DNS serverip is offered to the client.
1586		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1587		serverip will be stored in the additional environment
1588		variable "dnsip2". The first DNS serverip is always
1589		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1590		is defined.
1591
1592		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1593		to do a dynamic update of a DNS server. To do this, they
1594		need the hostname of the DHCP requester.
1595		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1596		of the "hostname" environment variable is passed as
1597		option 12 to the DHCP server.
1598
1599		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1600
1601		A 32bit value in microseconds for a delay between
1602		receiving a "DHCP Offer" and sending the "DHCP Request".
1603		This fixes a problem with certain DHCP servers that don't
1604		respond 100% of the time to a "DHCP request". E.g. On an
1605		AT91RM9200 processor running at 180MHz, this delay needed
1606		to be *at least* 15,000 usec before a Windows Server 2003
1607		DHCP server would reply 100% of the time. I recommend at
1608		least 50,000 usec to be safe. The alternative is to hope
1609		that one of the retries will be successful but note that
1610		the DHCP timeout and retry process takes a longer than
1611		this delay.
1612
1613 - Link-local IP address negotiation:
1614		Negotiate with other link-local clients on the local network
1615		for an address that doesn't require explicit configuration.
1616		This is especially useful if a DHCP server cannot be guaranteed
1617		to exist in all environments that the device must operate.
1618
1619		See doc/README.link-local for more information.
1620
1621 - CDP Options:
1622		CONFIG_CDP_DEVICE_ID
1623
1624		The device id used in CDP trigger frames.
1625
1626		CONFIG_CDP_DEVICE_ID_PREFIX
1627
1628		A two character string which is prefixed to the MAC address
1629		of the device.
1630
1631		CONFIG_CDP_PORT_ID
1632
1633		A printf format string which contains the ascii name of
1634		the port. Normally is set to "eth%d" which sets
1635		eth0 for the first Ethernet, eth1 for the second etc.
1636
1637		CONFIG_CDP_CAPABILITIES
1638
1639		A 32bit integer which indicates the device capabilities;
1640		0x00000010 for a normal host which does not forwards.
1641
1642		CONFIG_CDP_VERSION
1643
1644		An ascii string containing the version of the software.
1645
1646		CONFIG_CDP_PLATFORM
1647
1648		An ascii string containing the name of the platform.
1649
1650		CONFIG_CDP_TRIGGER
1651
1652		A 32bit integer sent on the trigger.
1653
1654		CONFIG_CDP_POWER_CONSUMPTION
1655
1656		A 16bit integer containing the power consumption of the
1657		device in .1 of milliwatts.
1658
1659		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1660
1661		A byte containing the id of the VLAN.
1662
1663- Status LED:	CONFIG_LED_STATUS
1664
1665		Several configurations allow to display the current
1666		status using a LED. For instance, the LED will blink
1667		fast while running U-Boot code, stop blinking as
1668		soon as a reply to a BOOTP request was received, and
1669		start blinking slow once the Linux kernel is running
1670		(supported by a status LED driver in the Linux
1671		kernel). Defining CONFIG_LED_STATUS enables this
1672		feature in U-Boot.
1673
1674		Additional options:
1675
1676		CONFIG_LED_STATUS_GPIO
1677		The status LED can be connected to a GPIO pin.
1678		In such cases, the gpio_led driver can be used as a
1679		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1680		to include the gpio_led driver in the U-Boot binary.
1681
1682		CONFIG_GPIO_LED_INVERTED_TABLE
1683		Some GPIO connected LEDs may have inverted polarity in which
1684		case the GPIO high value corresponds to LED off state and
1685		GPIO low value corresponds to LED on state.
1686		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1687		with a list of GPIO LEDs that have inverted polarity.
1688
1689- I2C Support:	CONFIG_SYS_I2C
1690
1691		This enable the NEW i2c subsystem, and will allow you to use
1692		i2c commands at the u-boot command line (as long as you set
1693		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1694		based realtime clock chips or other i2c devices. See
1695		common/cmd_i2c.c for a description of the command line
1696		interface.
1697
1698		ported i2c driver to the new framework:
1699		- drivers/i2c/soft_i2c.c:
1700		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1701		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1702		    for defining speed and slave address
1703		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1704		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1705		    for defining speed and slave address
1706		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1707		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1708		    for defining speed and slave address
1709		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1710		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1711		    for defining speed and slave address
1712
1713		- drivers/i2c/fsl_i2c.c:
1714		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1715		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1716		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1717		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1718		    bus.
1719		  - If your board supports a second fsl i2c bus, define
1720		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1721		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1722		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1723		    second bus.
1724
1725		- drivers/i2c/tegra_i2c.c:
1726		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1727		  - This driver adds 4 i2c buses with a fix speed from
1728		    100000 and the slave addr 0!
1729
1730		- drivers/i2c/ppc4xx_i2c.c
1731		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1732		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1733		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1734
1735		- drivers/i2c/i2c_mxc.c
1736		  - activate this driver with CONFIG_SYS_I2C_MXC
1737		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1738		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1739		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1740		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1741		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1742		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1743		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1744		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1745		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1746		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1747		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1748		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1749		If those defines are not set, default value is 100000
1750		for speed, and 0 for slave.
1751
1752		- drivers/i2c/rcar_i2c.c:
1753		  - activate this driver with CONFIG_SYS_I2C_RCAR
1754		  - This driver adds 4 i2c buses
1755
1756		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1757		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1758		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1759		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1760		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1761		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1762		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1763		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1764		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1765
1766		- drivers/i2c/sh_i2c.c:
1767		  - activate this driver with CONFIG_SYS_I2C_SH
1768		  - This driver adds from 2 to 5 i2c buses
1769
1770		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1771		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1772		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1773		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1774		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1775		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1776		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1777		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1778		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1779		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1780		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1781
1782		- drivers/i2c/omap24xx_i2c.c
1783		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1784		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1785		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1786		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1787		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1788		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1789		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1790		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1791		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1792		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1793		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1794
1795		- drivers/i2c/zynq_i2c.c
1796		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1797		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1798		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1799
1800		- drivers/i2c/s3c24x0_i2c.c:
1801		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1802		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1803		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1804		    with a fix speed from 100000 and the slave addr 0!
1805
1806		- drivers/i2c/ihs_i2c.c
1807		  - activate this driver with CONFIG_SYS_I2C_IHS
1808		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1809		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1810		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1811		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1812		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1813		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1814		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1815		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1816		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1817		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1818		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1819		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1820		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1821		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1822		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1823		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1824		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1825		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1826		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1827		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1828		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1829
1830		additional defines:
1831
1832		CONFIG_SYS_NUM_I2C_BUSES
1833		Hold the number of i2c buses you want to use.
1834
1835		CONFIG_SYS_I2C_DIRECT_BUS
1836		define this, if you don't use i2c muxes on your hardware.
1837		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1838		omit this define.
1839
1840		CONFIG_SYS_I2C_MAX_HOPS
1841		define how many muxes are maximal consecutively connected
1842		on one i2c bus. If you not use i2c muxes, omit this
1843		define.
1844
1845		CONFIG_SYS_I2C_BUSES
1846		hold a list of buses you want to use, only used if
1847		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1848		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1849		CONFIG_SYS_NUM_I2C_BUSES = 9:
1850
1851		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1852					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1853					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1854					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1855					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1856					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1857					{1, {I2C_NULL_HOP}}, \
1858					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1859					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1860					}
1861
1862		which defines
1863			bus 0 on adapter 0 without a mux
1864			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1865			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1866			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1867			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1868			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1869			bus 6 on adapter 1 without a mux
1870			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1871			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1872
1873		If you do not have i2c muxes on your board, omit this define.
1874
1875- Legacy I2C Support:
1876		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1877		then the following macros need to be defined (examples are
1878		from include/configs/lwmon.h):
1879
1880		I2C_INIT
1881
1882		(Optional). Any commands necessary to enable the I2C
1883		controller or configure ports.
1884
1885		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1886
1887		I2C_ACTIVE
1888
1889		The code necessary to make the I2C data line active
1890		(driven).  If the data line is open collector, this
1891		define can be null.
1892
1893		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1894
1895		I2C_TRISTATE
1896
1897		The code necessary to make the I2C data line tri-stated
1898		(inactive).  If the data line is open collector, this
1899		define can be null.
1900
1901		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1902
1903		I2C_READ
1904
1905		Code that returns true if the I2C data line is high,
1906		false if it is low.
1907
1908		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1909
1910		I2C_SDA(bit)
1911
1912		If <bit> is true, sets the I2C data line high. If it
1913		is false, it clears it (low).
1914
1915		eg: #define I2C_SDA(bit) \
1916			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1917			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1918
1919		I2C_SCL(bit)
1920
1921		If <bit> is true, sets the I2C clock line high. If it
1922		is false, it clears it (low).
1923
1924		eg: #define I2C_SCL(bit) \
1925			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1926			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1927
1928		I2C_DELAY
1929
1930		This delay is invoked four times per clock cycle so this
1931		controls the rate of data transfer.  The data rate thus
1932		is 1 / (I2C_DELAY * 4). Often defined to be something
1933		like:
1934
1935		#define I2C_DELAY  udelay(2)
1936
1937		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1938
1939		If your arch supports the generic GPIO framework (asm/gpio.h),
1940		then you may alternatively define the two GPIOs that are to be
1941		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1942		have GPIO-based defaults assigned to them as appropriate.
1943
1944		You should define these to the GPIO value as given directly to
1945		the generic GPIO functions.
1946
1947		CONFIG_SYS_I2C_INIT_BOARD
1948
1949		When a board is reset during an i2c bus transfer
1950		chips might think that the current transfer is still
1951		in progress. On some boards it is possible to access
1952		the i2c SCLK line directly, either by using the
1953		processor pin as a GPIO or by having a second pin
1954		connected to the bus. If this option is defined a
1955		custom i2c_init_board() routine in boards/xxx/board.c
1956		is run early in the boot sequence.
1957
1958		CONFIG_I2C_MULTI_BUS
1959
1960		This option allows the use of multiple I2C buses, each of which
1961		must have a controller.	 At any point in time, only one bus is
1962		active.	 To switch to a different bus, use the 'i2c dev' command.
1963		Note that bus numbering is zero-based.
1964
1965		CONFIG_SYS_I2C_NOPROBES
1966
1967		This option specifies a list of I2C devices that will be skipped
1968		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1969		is set, specify a list of bus-device pairs.  Otherwise, specify
1970		a 1D array of device addresses
1971
1972		e.g.
1973			#undef	CONFIG_I2C_MULTI_BUS
1974			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1975
1976		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1977
1978			#define CONFIG_I2C_MULTI_BUS
1979			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1980
1981		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1982
1983		CONFIG_SYS_SPD_BUS_NUM
1984
1985		If defined, then this indicates the I2C bus number for DDR SPD.
1986		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1987
1988		CONFIG_SYS_RTC_BUS_NUM
1989
1990		If defined, then this indicates the I2C bus number for the RTC.
1991		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1992
1993		CONFIG_SOFT_I2C_READ_REPEATED_START
1994
1995		defining this will force the i2c_read() function in
1996		the soft_i2c driver to perform an I2C repeated start
1997		between writing the address pointer and reading the
1998		data.  If this define is omitted the default behaviour
1999		of doing a stop-start sequence will be used.  Most I2C
2000		devices can use either method, but some require one or
2001		the other.
2002
2003- SPI Support:	CONFIG_SPI
2004
2005		Enables SPI driver (so far only tested with
2006		SPI EEPROM, also an instance works with Crystal A/D and
2007		D/As on the SACSng board)
2008
2009		CONFIG_SH_SPI
2010
2011		Enables the driver for SPI controller on SuperH. Currently
2012		only SH7757 is supported.
2013
2014		CONFIG_SOFT_SPI
2015
2016		Enables a software (bit-bang) SPI driver rather than
2017		using hardware support. This is a general purpose
2018		driver that only requires three general I/O port pins
2019		(two outputs, one input) to function. If this is
2020		defined, the board configuration must define several
2021		SPI configuration items (port pins to use, etc). For
2022		an example, see include/configs/sacsng.h.
2023
2024		CONFIG_HARD_SPI
2025
2026		Enables a hardware SPI driver for general-purpose reads
2027		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2028		must define a list of chip-select function pointers.
2029		Currently supported on some MPC8xxx processors.	 For an
2030		example, see include/configs/mpc8349emds.h.
2031
2032		CONFIG_MXC_SPI
2033
2034		Enables the driver for the SPI controllers on i.MX and MXC
2035		SoCs. Currently i.MX31/35/51 are supported.
2036
2037		CONFIG_SYS_SPI_MXC_WAIT
2038		Timeout for waiting until spi transfer completed.
2039		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2040
2041- FPGA Support: CONFIG_FPGA
2042
2043		Enables FPGA subsystem.
2044
2045		CONFIG_FPGA_<vendor>
2046
2047		Enables support for specific chip vendors.
2048		(ALTERA, XILINX)
2049
2050		CONFIG_FPGA_<family>
2051
2052		Enables support for FPGA family.
2053		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2054
2055		CONFIG_FPGA_COUNT
2056
2057		Specify the number of FPGA devices to support.
2058
2059		CONFIG_SYS_FPGA_PROG_FEEDBACK
2060
2061		Enable printing of hash marks during FPGA configuration.
2062
2063		CONFIG_SYS_FPGA_CHECK_BUSY
2064
2065		Enable checks on FPGA configuration interface busy
2066		status by the configuration function. This option
2067		will require a board or device specific function to
2068		be written.
2069
2070		CONFIG_FPGA_DELAY
2071
2072		If defined, a function that provides delays in the FPGA
2073		configuration driver.
2074
2075		CONFIG_SYS_FPGA_CHECK_CTRLC
2076		Allow Control-C to interrupt FPGA configuration
2077
2078		CONFIG_SYS_FPGA_CHECK_ERROR
2079
2080		Check for configuration errors during FPGA bitfile
2081		loading. For example, abort during Virtex II
2082		configuration if the INIT_B line goes low (which
2083		indicated a CRC error).
2084
2085		CONFIG_SYS_FPGA_WAIT_INIT
2086
2087		Maximum time to wait for the INIT_B line to de-assert
2088		after PROB_B has been de-asserted during a Virtex II
2089		FPGA configuration sequence. The default time is 500
2090		ms.
2091
2092		CONFIG_SYS_FPGA_WAIT_BUSY
2093
2094		Maximum time to wait for BUSY to de-assert during
2095		Virtex II FPGA configuration. The default is 5 ms.
2096
2097		CONFIG_SYS_FPGA_WAIT_CONFIG
2098
2099		Time to wait after FPGA configuration. The default is
2100		200 ms.
2101
2102- Configuration Management:
2103		CONFIG_BUILD_TARGET
2104
2105		Some SoCs need special image types (e.g. U-Boot binary
2106		with a special header) as build targets. By defining
2107		CONFIG_BUILD_TARGET in the SoC / board header, this
2108		special image will be automatically built upon calling
2109		make / buildman.
2110
2111		CONFIG_IDENT_STRING
2112
2113		If defined, this string will be added to the U-Boot
2114		version information (U_BOOT_VERSION)
2115
2116- Vendor Parameter Protection:
2117
2118		U-Boot considers the values of the environment
2119		variables "serial#" (Board Serial Number) and
2120		"ethaddr" (Ethernet Address) to be parameters that
2121		are set once by the board vendor / manufacturer, and
2122		protects these variables from casual modification by
2123		the user. Once set, these variables are read-only,
2124		and write or delete attempts are rejected. You can
2125		change this behaviour:
2126
2127		If CONFIG_ENV_OVERWRITE is #defined in your config
2128		file, the write protection for vendor parameters is
2129		completely disabled. Anybody can change or delete
2130		these parameters.
2131
2132		Alternatively, if you define _both_ an ethaddr in the
2133		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2134		Ethernet address is installed in the environment,
2135		which can be changed exactly ONCE by the user. [The
2136		serial# is unaffected by this, i. e. it remains
2137		read-only.]
2138
2139		The same can be accomplished in a more flexible way
2140		for any variable by configuring the type of access
2141		to allow for those variables in the ".flags" variable
2142		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2143
2144- Protected RAM:
2145		CONFIG_PRAM
2146
2147		Define this variable to enable the reservation of
2148		"protected RAM", i. e. RAM which is not overwritten
2149		by U-Boot. Define CONFIG_PRAM to hold the number of
2150		kB you want to reserve for pRAM. You can overwrite
2151		this default value by defining an environment
2152		variable "pram" to the number of kB you want to
2153		reserve. Note that the board info structure will
2154		still show the full amount of RAM. If pRAM is
2155		reserved, a new environment variable "mem" will
2156		automatically be defined to hold the amount of
2157		remaining RAM in a form that can be passed as boot
2158		argument to Linux, for instance like that:
2159
2160			setenv bootargs ... mem=\${mem}
2161			saveenv
2162
2163		This way you can tell Linux not to use this memory,
2164		either, which results in a memory region that will
2165		not be affected by reboots.
2166
2167		*WARNING* If your board configuration uses automatic
2168		detection of the RAM size, you must make sure that
2169		this memory test is non-destructive. So far, the
2170		following board configurations are known to be
2171		"pRAM-clean":
2172
2173			IVMS8, IVML24, SPD8xx,
2174			HERMES, IP860, RPXlite, LWMON,
2175			FLAGADM
2176
2177- Access to physical memory region (> 4GB)
2178		Some basic support is provided for operations on memory not
2179		normally accessible to U-Boot - e.g. some architectures
2180		support access to more than 4GB of memory on 32-bit
2181		machines using physical address extension or similar.
2182		Define CONFIG_PHYSMEM to access this basic support, which
2183		currently only supports clearing the memory.
2184
2185- Error Recovery:
2186		CONFIG_PANIC_HANG
2187
2188		Define this variable to stop the system in case of a
2189		fatal error, so that you have to reset it manually.
2190		This is probably NOT a good idea for an embedded
2191		system where you want the system to reboot
2192		automatically as fast as possible, but it may be
2193		useful during development since you can try to debug
2194		the conditions that lead to the situation.
2195
2196		CONFIG_NET_RETRY_COUNT
2197
2198		This variable defines the number of retries for
2199		network operations like ARP, RARP, TFTP, or BOOTP
2200		before giving up the operation. If not defined, a
2201		default value of 5 is used.
2202
2203		CONFIG_ARP_TIMEOUT
2204
2205		Timeout waiting for an ARP reply in milliseconds.
2206
2207		CONFIG_NFS_TIMEOUT
2208
2209		Timeout in milliseconds used in NFS protocol.
2210		If you encounter "ERROR: Cannot umount" in nfs command,
2211		try longer timeout such as
2212		#define CONFIG_NFS_TIMEOUT 10000UL
2213
2214- Command Interpreter:
2215		CONFIG_AUTO_COMPLETE
2216
2217		Enable auto completion of commands using TAB.
2218
2219		CONFIG_SYS_PROMPT_HUSH_PS2
2220
2221		This defines the secondary prompt string, which is
2222		printed when the command interpreter needs more input
2223		to complete a command. Usually "> ".
2224
2225	Note:
2226
2227		In the current implementation, the local variables
2228		space and global environment variables space are
2229		separated. Local variables are those you define by
2230		simply typing `name=value'. To access a local
2231		variable later on, you have write `$name' or
2232		`${name}'; to execute the contents of a variable
2233		directly type `$name' at the command prompt.
2234
2235		Global environment variables are those you use
2236		setenv/printenv to work with. To run a command stored
2237		in such a variable, you need to use the run command,
2238		and you must not use the '$' sign to access them.
2239
2240		To store commands and special characters in a
2241		variable, please use double quotation marks
2242		surrounding the whole text of the variable, instead
2243		of the backslashes before semicolons and special
2244		symbols.
2245
2246- Command Line Editing and History:
2247		CONFIG_CMDLINE_EDITING
2248
2249		Enable editing and History functions for interactive
2250		command line input operations
2251
2252- Command Line PS1/PS2 support:
2253		CONFIG_CMDLINE_PS_SUPPORT
2254
2255		Enable support for changing the command prompt string
2256		at run-time. Only static string is supported so far.
2257		The string is obtained from environment variables PS1
2258		and PS2.
2259
2260- Default Environment:
2261		CONFIG_EXTRA_ENV_SETTINGS
2262
2263		Define this to contain any number of null terminated
2264		strings (variable = value pairs) that will be part of
2265		the default environment compiled into the boot image.
2266
2267		For example, place something like this in your
2268		board's config file:
2269
2270		#define CONFIG_EXTRA_ENV_SETTINGS \
2271			"myvar1=value1\0" \
2272			"myvar2=value2\0"
2273
2274		Warning: This method is based on knowledge about the
2275		internal format how the environment is stored by the
2276		U-Boot code. This is NOT an official, exported
2277		interface! Although it is unlikely that this format
2278		will change soon, there is no guarantee either.
2279		You better know what you are doing here.
2280
2281		Note: overly (ab)use of the default environment is
2282		discouraged. Make sure to check other ways to preset
2283		the environment like the "source" command or the
2284		boot command first.
2285
2286		CONFIG_ENV_VARS_UBOOT_CONFIG
2287
2288		Define this in order to add variables describing the
2289		U-Boot build configuration to the default environment.
2290		These will be named arch, cpu, board, vendor, and soc.
2291
2292		Enabling this option will cause the following to be defined:
2293
2294		- CONFIG_SYS_ARCH
2295		- CONFIG_SYS_CPU
2296		- CONFIG_SYS_BOARD
2297		- CONFIG_SYS_VENDOR
2298		- CONFIG_SYS_SOC
2299
2300		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2301
2302		Define this in order to add variables describing certain
2303		run-time determined information about the hardware to the
2304		environment.  These will be named board_name, board_rev.
2305
2306		CONFIG_DELAY_ENVIRONMENT
2307
2308		Normally the environment is loaded when the board is
2309		initialised so that it is available to U-Boot. This inhibits
2310		that so that the environment is not available until
2311		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2312		this is instead controlled by the value of
2313		/config/load-environment.
2314
2315- DataFlash Support:
2316		CONFIG_HAS_DATAFLASH
2317
2318		Defining this option enables DataFlash features and
2319		allows to read/write in Dataflash via the standard
2320		commands cp, md...
2321
2322- Serial Flash support
2323		Usage requires an initial 'sf probe' to define the serial
2324		flash parameters, followed by read/write/erase/update
2325		commands.
2326
2327		The following defaults may be provided by the platform
2328		to handle the common case when only a single serial
2329		flash is present on the system.
2330
2331		CONFIG_SF_DEFAULT_BUS		Bus identifier
2332		CONFIG_SF_DEFAULT_CS		Chip-select
2333		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2334		CONFIG_SF_DEFAULT_SPEED		in Hz
2335
2336		CONFIG_SYSTEMACE
2337
2338		Adding this option adds support for Xilinx SystemACE
2339		chips attached via some sort of local bus. The address
2340		of the chip must also be defined in the
2341		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2342
2343		#define CONFIG_SYSTEMACE
2344		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2345
2346		When SystemACE support is added, the "ace" device type
2347		becomes available to the fat commands, i.e. fatls.
2348
2349- TFTP Fixed UDP Port:
2350		CONFIG_TFTP_PORT
2351
2352		If this is defined, the environment variable tftpsrcp
2353		is used to supply the TFTP UDP source port value.
2354		If tftpsrcp isn't defined, the normal pseudo-random port
2355		number generator is used.
2356
2357		Also, the environment variable tftpdstp is used to supply
2358		the TFTP UDP destination port value.  If tftpdstp isn't
2359		defined, the normal port 69 is used.
2360
2361		The purpose for tftpsrcp is to allow a TFTP server to
2362		blindly start the TFTP transfer using the pre-configured
2363		target IP address and UDP port. This has the effect of
2364		"punching through" the (Windows XP) firewall, allowing
2365		the remainder of the TFTP transfer to proceed normally.
2366		A better solution is to properly configure the firewall,
2367		but sometimes that is not allowed.
2368
2369- bootcount support:
2370		CONFIG_BOOTCOUNT_LIMIT
2371
2372		This enables the bootcounter support, see:
2373		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2374
2375		CONFIG_AT91SAM9XE
2376		enable special bootcounter support on at91sam9xe based boards.
2377		CONFIG_SOC_DA8XX
2378		enable special bootcounter support on da850 based boards.
2379		CONFIG_BOOTCOUNT_RAM
2380		enable support for the bootcounter in RAM
2381		CONFIG_BOOTCOUNT_I2C
2382		enable support for the bootcounter on an i2c (like RTC) device.
2383			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2384			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2385						    the bootcounter.
2386			CONFIG_BOOTCOUNT_ALEN = address len
2387
2388- Show boot progress:
2389		CONFIG_SHOW_BOOT_PROGRESS
2390
2391		Defining this option allows to add some board-
2392		specific code (calling a user-provided function
2393		"show_boot_progress(int)") that enables you to show
2394		the system's boot progress on some display (for
2395		example, some LED's) on your board. At the moment,
2396		the following checkpoints are implemented:
2397
2398
2399Legacy uImage format:
2400
2401  Arg	Where			When
2402    1	common/cmd_bootm.c	before attempting to boot an image
2403   -1	common/cmd_bootm.c	Image header has bad	 magic number
2404    2	common/cmd_bootm.c	Image header has correct magic number
2405   -2	common/cmd_bootm.c	Image header has bad	 checksum
2406    3	common/cmd_bootm.c	Image header has correct checksum
2407   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2408    4	common/cmd_bootm.c	Image data   has correct checksum
2409   -4	common/cmd_bootm.c	Image is for unsupported architecture
2410    5	common/cmd_bootm.c	Architecture check OK
2411   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2412    6	common/cmd_bootm.c	Image Type check OK
2413   -6	common/cmd_bootm.c	gunzip uncompression error
2414   -7	common/cmd_bootm.c	Unimplemented compression type
2415    7	common/cmd_bootm.c	Uncompression OK
2416    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2417   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2418
2419    9	common/image.c		Start initial ramdisk verification
2420  -10	common/image.c		Ramdisk header has bad	   magic number
2421  -11	common/image.c		Ramdisk header has bad	   checksum
2422   10	common/image.c		Ramdisk header is OK
2423  -12	common/image.c		Ramdisk data   has bad	   checksum
2424   11	common/image.c		Ramdisk data   has correct checksum
2425   12	common/image.c		Ramdisk verification complete, start loading
2426  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2427   13	common/image.c		Start multifile image verification
2428   14	common/image.c		No initial ramdisk, no multifile, continue.
2429
2430   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2431
2432  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2433  -31	post/post.c		POST test failed, detected by post_output_backlog()
2434  -32	post/post.c		POST test failed, detected by post_run_single()
2435
2436   34	common/cmd_doc.c	before loading a Image from a DOC device
2437  -35	common/cmd_doc.c	Bad usage of "doc" command
2438   35	common/cmd_doc.c	correct usage of "doc" command
2439  -36	common/cmd_doc.c	No boot device
2440   36	common/cmd_doc.c	correct boot device
2441  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2442   37	common/cmd_doc.c	correct chip ID found, device available
2443  -38	common/cmd_doc.c	Read Error on boot device
2444   38	common/cmd_doc.c	reading Image header from DOC device OK
2445  -39	common/cmd_doc.c	Image header has bad magic number
2446   39	common/cmd_doc.c	Image header has correct magic number
2447  -40	common/cmd_doc.c	Error reading Image from DOC device
2448   40	common/cmd_doc.c	Image header has correct magic number
2449   41	common/cmd_ide.c	before loading a Image from a IDE device
2450  -42	common/cmd_ide.c	Bad usage of "ide" command
2451   42	common/cmd_ide.c	correct usage of "ide" command
2452  -43	common/cmd_ide.c	No boot device
2453   43	common/cmd_ide.c	boot device found
2454  -44	common/cmd_ide.c	Device not available
2455   44	common/cmd_ide.c	Device available
2456  -45	common/cmd_ide.c	wrong partition selected
2457   45	common/cmd_ide.c	partition selected
2458  -46	common/cmd_ide.c	Unknown partition table
2459   46	common/cmd_ide.c	valid partition table found
2460  -47	common/cmd_ide.c	Invalid partition type
2461   47	common/cmd_ide.c	correct partition type
2462  -48	common/cmd_ide.c	Error reading Image Header on boot device
2463   48	common/cmd_ide.c	reading Image Header from IDE device OK
2464  -49	common/cmd_ide.c	Image header has bad magic number
2465   49	common/cmd_ide.c	Image header has correct magic number
2466  -50	common/cmd_ide.c	Image header has bad	 checksum
2467   50	common/cmd_ide.c	Image header has correct checksum
2468  -51	common/cmd_ide.c	Error reading Image from IDE device
2469   51	common/cmd_ide.c	reading Image from IDE device OK
2470   52	common/cmd_nand.c	before loading a Image from a NAND device
2471  -53	common/cmd_nand.c	Bad usage of "nand" command
2472   53	common/cmd_nand.c	correct usage of "nand" command
2473  -54	common/cmd_nand.c	No boot device
2474   54	common/cmd_nand.c	boot device found
2475  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2476   55	common/cmd_nand.c	correct chip ID found, device available
2477  -56	common/cmd_nand.c	Error reading Image Header on boot device
2478   56	common/cmd_nand.c	reading Image Header from NAND device OK
2479  -57	common/cmd_nand.c	Image header has bad magic number
2480   57	common/cmd_nand.c	Image header has correct magic number
2481  -58	common/cmd_nand.c	Error reading Image from NAND device
2482   58	common/cmd_nand.c	reading Image from NAND device OK
2483
2484  -60	common/env_common.c	Environment has a bad CRC, using default
2485
2486   64	net/eth.c		starting with Ethernet configuration.
2487  -64	net/eth.c		no Ethernet found.
2488   65	net/eth.c		Ethernet found.
2489
2490  -80	common/cmd_net.c	usage wrong
2491   80	common/cmd_net.c	before calling net_loop()
2492  -81	common/cmd_net.c	some error in net_loop() occurred
2493   81	common/cmd_net.c	net_loop() back without error
2494  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2495   82	common/cmd_net.c	trying automatic boot
2496   83	common/cmd_net.c	running "source" command
2497  -83	common/cmd_net.c	some error in automatic boot or "source" command
2498   84	common/cmd_net.c	end without errors
2499
2500FIT uImage format:
2501
2502  Arg	Where			When
2503  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2504 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2505  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2506 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2507  102	common/cmd_bootm.c	Kernel unit name specified
2508 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2509  103	common/cmd_bootm.c	Found configuration node
2510  104	common/cmd_bootm.c	Got kernel subimage node offset
2511 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2512  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2513 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2514  106	common/cmd_bootm.c	Architecture check OK
2515 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2516  107	common/cmd_bootm.c	Kernel subimage type OK
2517 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2518  108	common/cmd_bootm.c	Got kernel subimage data/size
2519 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2520 -109	common/cmd_bootm.c	Can't get kernel subimage type
2521 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2522 -111	common/cmd_bootm.c	Can't get kernel subimage os
2523 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2524 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2525
2526  120	common/image.c		Start initial ramdisk verification
2527 -120	common/image.c		Ramdisk FIT image has incorrect format
2528  121	common/image.c		Ramdisk FIT image has correct format
2529  122	common/image.c		No ramdisk subimage unit name, using configuration
2530 -122	common/image.c		Can't get configuration for ramdisk subimage
2531  123	common/image.c		Ramdisk unit name specified
2532 -124	common/image.c		Can't get ramdisk subimage node offset
2533  125	common/image.c		Got ramdisk subimage node offset
2534 -125	common/image.c		Ramdisk subimage hash verification failed
2535  126	common/image.c		Ramdisk subimage hash verification OK
2536 -126	common/image.c		Ramdisk subimage for unsupported architecture
2537  127	common/image.c		Architecture check OK
2538 -127	common/image.c		Can't get ramdisk subimage data/size
2539  128	common/image.c		Got ramdisk subimage data/size
2540  129	common/image.c		Can't get ramdisk load address
2541 -129	common/image.c		Got ramdisk load address
2542
2543 -130	common/cmd_doc.c	Incorrect FIT image format
2544  131	common/cmd_doc.c	FIT image format OK
2545
2546 -140	common/cmd_ide.c	Incorrect FIT image format
2547  141	common/cmd_ide.c	FIT image format OK
2548
2549 -150	common/cmd_nand.c	Incorrect FIT image format
2550  151	common/cmd_nand.c	FIT image format OK
2551
2552- legacy image format:
2553		CONFIG_IMAGE_FORMAT_LEGACY
2554		enables the legacy image format support in U-Boot.
2555
2556		Default:
2557		enabled if CONFIG_FIT_SIGNATURE is not defined.
2558
2559		CONFIG_DISABLE_IMAGE_LEGACY
2560		disable the legacy image format
2561
2562		This define is introduced, as the legacy image format is
2563		enabled per default for backward compatibility.
2564
2565- Standalone program support:
2566		CONFIG_STANDALONE_LOAD_ADDR
2567
2568		This option defines a board specific value for the
2569		address where standalone program gets loaded, thus
2570		overwriting the architecture dependent default
2571		settings.
2572
2573- Frame Buffer Address:
2574		CONFIG_FB_ADDR
2575
2576		Define CONFIG_FB_ADDR if you want to use specific
2577		address for frame buffer.  This is typically the case
2578		when using a graphics controller has separate video
2579		memory.  U-Boot will then place the frame buffer at
2580		the given address instead of dynamically reserving it
2581		in system RAM by calling lcd_setmem(), which grabs
2582		the memory for the frame buffer depending on the
2583		configured panel size.
2584
2585		Please see board_init_f function.
2586
2587- Automatic software updates via TFTP server
2588		CONFIG_UPDATE_TFTP
2589		CONFIG_UPDATE_TFTP_CNT_MAX
2590		CONFIG_UPDATE_TFTP_MSEC_MAX
2591
2592		These options enable and control the auto-update feature;
2593		for a more detailed description refer to doc/README.update.
2594
2595- MTD Support (mtdparts command, UBI support)
2596		CONFIG_MTD_DEVICE
2597
2598		Adds the MTD device infrastructure from the Linux kernel.
2599		Needed for mtdparts command support.
2600
2601		CONFIG_MTD_PARTITIONS
2602
2603		Adds the MTD partitioning infrastructure from the Linux
2604		kernel. Needed for UBI support.
2605
2606- UBI support
2607		CONFIG_UBI_SILENCE_MSG
2608
2609		Make the verbose messages from UBI stop printing.  This leaves
2610		warnings and errors enabled.
2611
2612
2613		CONFIG_MTD_UBI_WL_THRESHOLD
2614		This parameter defines the maximum difference between the highest
2615		erase counter value and the lowest erase counter value of eraseblocks
2616		of UBI devices. When this threshold is exceeded, UBI starts performing
2617		wear leveling by means of moving data from eraseblock with low erase
2618		counter to eraseblocks with high erase counter.
2619
2620		The default value should be OK for SLC NAND flashes, NOR flashes and
2621		other flashes which have eraseblock life-cycle 100000 or more.
2622		However, in case of MLC NAND flashes which typically have eraseblock
2623		life-cycle less than 10000, the threshold should be lessened (e.g.,
2624		to 128 or 256, although it does not have to be power of 2).
2625
2626		default: 4096
2627
2628		CONFIG_MTD_UBI_BEB_LIMIT
2629		This option specifies the maximum bad physical eraseblocks UBI
2630		expects on the MTD device (per 1024 eraseblocks). If the
2631		underlying flash does not admit of bad eraseblocks (e.g. NOR
2632		flash), this value is ignored.
2633
2634		NAND datasheets often specify the minimum and maximum NVM
2635		(Number of Valid Blocks) for the flashes' endurance lifetime.
2636		The maximum expected bad eraseblocks per 1024 eraseblocks
2637		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2638		which gives 20 for most NANDs (MaxNVB is basically the total
2639		count of eraseblocks on the chip).
2640
2641		To put it differently, if this value is 20, UBI will try to
2642		reserve about 1.9% of physical eraseblocks for bad blocks
2643		handling. And that will be 1.9% of eraseblocks on the entire
2644		NAND chip, not just the MTD partition UBI attaches. This means
2645		that if you have, say, a NAND flash chip admits maximum 40 bad
2646		eraseblocks, and it is split on two MTD partitions of the same
2647		size, UBI will reserve 40 eraseblocks when attaching a
2648		partition.
2649
2650		default: 20
2651
2652		CONFIG_MTD_UBI_FASTMAP
2653		Fastmap is a mechanism which allows attaching an UBI device
2654		in nearly constant time. Instead of scanning the whole MTD device it
2655		only has to locate a checkpoint (called fastmap) on the device.
2656		The on-flash fastmap contains all information needed to attach
2657		the device. Using fastmap makes only sense on large devices where
2658		attaching by scanning takes long. UBI will not automatically install
2659		a fastmap on old images, but you can set the UBI parameter
2660		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2661		that fastmap-enabled images are still usable with UBI implementations
2662		without	fastmap support. On typical flash devices the whole fastmap
2663		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2664
2665		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2666		Set this parameter to enable fastmap automatically on images
2667		without a fastmap.
2668		default: 0
2669
2670		CONFIG_MTD_UBI_FM_DEBUG
2671		Enable UBI fastmap debug
2672		default: 0
2673
2674- UBIFS support
2675		CONFIG_UBIFS_SILENCE_MSG
2676
2677		Make the verbose messages from UBIFS stop printing.  This leaves
2678		warnings and errors enabled.
2679
2680- SPL framework
2681		CONFIG_SPL
2682		Enable building of SPL globally.
2683
2684		CONFIG_SPL_LDSCRIPT
2685		LDSCRIPT for linking the SPL binary.
2686
2687		CONFIG_SPL_MAX_FOOTPRINT
2688		Maximum size in memory allocated to the SPL, BSS included.
2689		When defined, the linker checks that the actual memory
2690		used by SPL from _start to __bss_end does not exceed it.
2691		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2692		must not be both defined at the same time.
2693
2694		CONFIG_SPL_MAX_SIZE
2695		Maximum size of the SPL image (text, data, rodata, and
2696		linker lists sections), BSS excluded.
2697		When defined, the linker checks that the actual size does
2698		not exceed it.
2699
2700		CONFIG_SPL_TEXT_BASE
2701		TEXT_BASE for linking the SPL binary.
2702
2703		CONFIG_SPL_RELOC_TEXT_BASE
2704		Address to relocate to.  If unspecified, this is equal to
2705		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2706
2707		CONFIG_SPL_BSS_START_ADDR
2708		Link address for the BSS within the SPL binary.
2709
2710		CONFIG_SPL_BSS_MAX_SIZE
2711		Maximum size in memory allocated to the SPL BSS.
2712		When defined, the linker checks that the actual memory used
2713		by SPL from __bss_start to __bss_end does not exceed it.
2714		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2715		must not be both defined at the same time.
2716
2717		CONFIG_SPL_STACK
2718		Adress of the start of the stack SPL will use
2719
2720		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2721		When defined, SPL will panic() if the image it has
2722		loaded does not have a signature.
2723		Defining this is useful when code which loads images
2724		in SPL cannot guarantee that absolutely all read errors
2725		will be caught.
2726		An example is the LPC32XX MLC NAND driver, which will
2727		consider that a completely unreadable NAND block is bad,
2728		and thus should be skipped silently.
2729
2730		CONFIG_SPL_RELOC_STACK
2731		Adress of the start of the stack SPL will use after
2732		relocation.  If unspecified, this is equal to
2733		CONFIG_SPL_STACK.
2734
2735		CONFIG_SYS_SPL_MALLOC_START
2736		Starting address of the malloc pool used in SPL.
2737		When this option is set the full malloc is used in SPL and
2738		it is set up by spl_init() and before that, the simple malloc()
2739		can be used if CONFIG_SYS_MALLOC_F is defined.
2740
2741		CONFIG_SYS_SPL_MALLOC_SIZE
2742		The size of the malloc pool used in SPL.
2743
2744		CONFIG_SPL_FRAMEWORK
2745		Enable the SPL framework under common/.  This framework
2746		supports MMC, NAND and YMODEM loading of U-Boot and NAND
2747		NAND loading of the Linux Kernel.
2748
2749		CONFIG_SPL_OS_BOOT
2750		Enable booting directly to an OS from SPL.
2751		See also: doc/README.falcon
2752
2753		CONFIG_SPL_DISPLAY_PRINT
2754		For ARM, enable an optional function to print more information
2755		about the running system.
2756
2757		CONFIG_SPL_INIT_MINIMAL
2758		Arch init code should be built for a very small image
2759
2760		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2761		Partition on the MMC to load U-Boot from when the MMC is being
2762		used in raw mode
2763
2764		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2765		Sector to load kernel uImage from when MMC is being
2766		used in raw mode (for Falcon mode)
2767
2768		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2769		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2770		Sector and number of sectors to load kernel argument
2771		parameters from when MMC is being used in raw mode
2772		(for falcon mode)
2773
2774		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2775		Partition on the MMC to load U-Boot from when the MMC is being
2776		used in fs mode
2777
2778		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2779		Filename to read to load U-Boot when reading from filesystem
2780
2781		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2782		Filename to read to load kernel uImage when reading
2783		from filesystem (for Falcon mode)
2784
2785		CONFIG_SPL_FS_LOAD_ARGS_NAME
2786		Filename to read to load kernel argument parameters
2787		when reading from filesystem (for Falcon mode)
2788
2789		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2790		Set this for NAND SPL on PPC mpc83xx targets, so that
2791		start.S waits for the rest of the SPL to load before
2792		continuing (the hardware starts execution after just
2793		loading the first page rather than the full 4K).
2794
2795		CONFIG_SPL_SKIP_RELOCATE
2796		Avoid SPL relocation
2797
2798		CONFIG_SPL_NAND_BASE
2799		Include nand_base.c in the SPL.  Requires
2800		CONFIG_SPL_NAND_DRIVERS.
2801
2802		CONFIG_SPL_NAND_DRIVERS
2803		SPL uses normal NAND drivers, not minimal drivers.
2804
2805		CONFIG_SPL_NAND_ECC
2806		Include standard software ECC in the SPL
2807
2808		CONFIG_SPL_NAND_SIMPLE
2809		Support for NAND boot using simple NAND drivers that
2810		expose the cmd_ctrl() interface.
2811
2812		CONFIG_SPL_UBI
2813		Support for a lightweight UBI (fastmap) scanner and
2814		loader
2815
2816		CONFIG_SPL_NAND_RAW_ONLY
2817		Support to boot only raw u-boot.bin images. Use this only
2818		if you need to save space.
2819
2820		CONFIG_SPL_COMMON_INIT_DDR
2821		Set for common ddr init with serial presence detect in
2822		SPL binary.
2823
2824		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2825		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2826		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2827		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2828		CONFIG_SYS_NAND_ECCBYTES
2829		Defines the size and behavior of the NAND that SPL uses
2830		to read U-Boot
2831
2832		CONFIG_SPL_NAND_BOOT
2833		Add support NAND boot
2834
2835		CONFIG_SYS_NAND_U_BOOT_OFFS
2836		Location in NAND to read U-Boot from
2837
2838		CONFIG_SYS_NAND_U_BOOT_DST
2839		Location in memory to load U-Boot to
2840
2841		CONFIG_SYS_NAND_U_BOOT_SIZE
2842		Size of image to load
2843
2844		CONFIG_SYS_NAND_U_BOOT_START
2845		Entry point in loaded image to jump to
2846
2847		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2848		Define this if you need to first read the OOB and then the
2849		data. This is used, for example, on davinci platforms.
2850
2851		CONFIG_SPL_RAM_DEVICE
2852		Support for running image already present in ram, in SPL binary
2853
2854		CONFIG_SPL_PAD_TO
2855		Image offset to which the SPL should be padded before appending
2856		the SPL payload. By default, this is defined as
2857		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2858		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2859		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2860
2861		CONFIG_SPL_TARGET
2862		Final target image containing SPL and payload.  Some SPLs
2863		use an arch-specific makefile fragment instead, for
2864		example if more than one image needs to be produced.
2865
2866		CONFIG_FIT_SPL_PRINT
2867		Printing information about a FIT image adds quite a bit of
2868		code to SPL. So this is normally disabled in SPL. Use this
2869		option to re-enable it. This will affect the output of the
2870		bootm command when booting a FIT image.
2871
2872- TPL framework
2873		CONFIG_TPL
2874		Enable building of TPL globally.
2875
2876		CONFIG_TPL_PAD_TO
2877		Image offset to which the TPL should be padded before appending
2878		the TPL payload. By default, this is defined as
2879		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2880		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2881		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2882
2883- Interrupt support (PPC):
2884
2885		There are common interrupt_init() and timer_interrupt()
2886		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2887		for CPU specific initialization. interrupt_init_cpu()
2888		should set decrementer_count to appropriate value. If
2889		CPU resets decrementer automatically after interrupt
2890		(ppc4xx) it should set decrementer_count to zero.
2891		timer_interrupt() calls timer_interrupt_cpu() for CPU
2892		specific handling. If board has watchdog / status_led
2893		/ other_activity_monitor it works automatically from
2894		general timer_interrupt().
2895
2896
2897Board initialization settings:
2898------------------------------
2899
2900During Initialization u-boot calls a number of board specific functions
2901to allow the preparation of board specific prerequisites, e.g. pin setup
2902before drivers are initialized. To enable these callbacks the
2903following configuration macros have to be defined. Currently this is
2904architecture specific, so please check arch/your_architecture/lib/board.c
2905typically in board_init_f() and board_init_r().
2906
2907- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2908- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2909- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2910- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2911
2912Configuration Settings:
2913-----------------------
2914
2915- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2916		Optionally it can be defined to support 64-bit memory commands.
2917
2918- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2919		undefine this when you're short of memory.
2920
2921- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2922		width of the commands listed in the 'help' command output.
2923
2924- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2925		prompt for user input.
2926
2927- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2928
2929- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2930
2931- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2932
2933- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2934		the application (usually a Linux kernel) when it is
2935		booted
2936
2937- CONFIG_SYS_BAUDRATE_TABLE:
2938		List of legal baudrate settings for this board.
2939
2940- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2941		Begin and End addresses of the area used by the
2942		simple memory test.
2943
2944- CONFIG_SYS_ALT_MEMTEST:
2945		Enable an alternate, more extensive memory test.
2946
2947- CONFIG_SYS_MEMTEST_SCRATCH:
2948		Scratch address used by the alternate memory test
2949		You only need to set this if address zero isn't writeable
2950
2951- CONFIG_SYS_MEM_RESERVE_SECURE
2952		Only implemented for ARMv8 for now.
2953		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2954		is substracted from total RAM and won't be reported to OS.
2955		This memory can be used as secure memory. A variable
2956		gd->arch.secure_ram is used to track the location. In systems
2957		the RAM base is not zero, or RAM is divided into banks,
2958		this variable needs to be recalcuated to get the address.
2959
2960- CONFIG_SYS_MEM_TOP_HIDE:
2961		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2962		this specified memory area will get subtracted from the top
2963		(end) of RAM and won't get "touched" at all by U-Boot. By
2964		fixing up gd->ram_size the Linux kernel should gets passed
2965		the now "corrected" memory size and won't touch it either.
2966		This should work for arch/ppc and arch/powerpc. Only Linux
2967		board ports in arch/powerpc with bootwrapper support that
2968		recalculate the memory size from the SDRAM controller setup
2969		will have to get fixed in Linux additionally.
2970
2971		This option can be used as a workaround for the 440EPx/GRx
2972		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2973		be touched.
2974
2975		WARNING: Please make sure that this value is a multiple of
2976		the Linux page size (normally 4k). If this is not the case,
2977		then the end address of the Linux memory will be located at a
2978		non page size aligned address and this could cause major
2979		problems.
2980
2981- CONFIG_SYS_LOADS_BAUD_CHANGE:
2982		Enable temporary baudrate change while serial download
2983
2984- CONFIG_SYS_SDRAM_BASE:
2985		Physical start address of SDRAM. _Must_ be 0 here.
2986
2987- CONFIG_SYS_FLASH_BASE:
2988		Physical start address of Flash memory.
2989
2990- CONFIG_SYS_MONITOR_BASE:
2991		Physical start address of boot monitor code (set by
2992		make config files to be same as the text base address
2993		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2994		CONFIG_SYS_FLASH_BASE when booting from flash.
2995
2996- CONFIG_SYS_MONITOR_LEN:
2997		Size of memory reserved for monitor code, used to
2998		determine _at_compile_time_ (!) if the environment is
2999		embedded within the U-Boot image, or in a separate
3000		flash sector.
3001
3002- CONFIG_SYS_MALLOC_LEN:
3003		Size of DRAM reserved for malloc() use.
3004
3005- CONFIG_SYS_MALLOC_F_LEN
3006		Size of the malloc() pool for use before relocation. If
3007		this is defined, then a very simple malloc() implementation
3008		will become available before relocation. The address is just
3009		below the global data, and the stack is moved down to make
3010		space.
3011
3012		This feature allocates regions with increasing addresses
3013		within the region. calloc() is supported, but realloc()
3014		is not available. free() is supported but does nothing.
3015		The memory will be freed (or in fact just forgotten) when
3016		U-Boot relocates itself.
3017
3018- CONFIG_SYS_MALLOC_SIMPLE
3019		Provides a simple and small malloc() and calloc() for those
3020		boards which do not use the full malloc in SPL (which is
3021		enabled with CONFIG_SYS_SPL_MALLOC_START).
3022
3023- CONFIG_SYS_NONCACHED_MEMORY:
3024		Size of non-cached memory area. This area of memory will be
3025		typically located right below the malloc() area and mapped
3026		uncached in the MMU. This is useful for drivers that would
3027		otherwise require a lot of explicit cache maintenance. For
3028		some drivers it's also impossible to properly maintain the
3029		cache. For example if the regions that need to be flushed
3030		are not a multiple of the cache-line size, *and* padding
3031		cannot be allocated between the regions to align them (i.e.
3032		if the HW requires a contiguous array of regions, and the
3033		size of each region is not cache-aligned), then a flush of
3034		one region may result in overwriting data that hardware has
3035		written to another region in the same cache-line. This can
3036		happen for example in network drivers where descriptors for
3037		buffers are typically smaller than the CPU cache-line (e.g.
3038		16 bytes vs. 32 or 64 bytes).
3039
3040		Non-cached memory is only supported on 32-bit ARM at present.
3041
3042- CONFIG_SYS_BOOTM_LEN:
3043		Normally compressed uImages are limited to an
3044		uncompressed size of 8 MBytes. If this is not enough,
3045		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3046		to adjust this setting to your needs.
3047
3048- CONFIG_SYS_BOOTMAPSZ:
3049		Maximum size of memory mapped by the startup code of
3050		the Linux kernel; all data that must be processed by
3051		the Linux kernel (bd_info, boot arguments, FDT blob if
3052		used) must be put below this limit, unless "bootm_low"
3053		environment variable is defined and non-zero. In such case
3054		all data for the Linux kernel must be between "bootm_low"
3055		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3056		variable "bootm_mapsize" will override the value of
3057		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3058		then the value in "bootm_size" will be used instead.
3059
3060- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3061		Enable initrd_high functionality.  If defined then the
3062		initrd_high feature is enabled and the bootm ramdisk subcommand
3063		is enabled.
3064
3065- CONFIG_SYS_BOOT_GET_CMDLINE:
3066		Enables allocating and saving kernel cmdline in space between
3067		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3068
3069- CONFIG_SYS_BOOT_GET_KBD:
3070		Enables allocating and saving a kernel copy of the bd_info in
3071		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3072
3073- CONFIG_SYS_MAX_FLASH_BANKS:
3074		Max number of Flash memory banks
3075
3076- CONFIG_SYS_MAX_FLASH_SECT:
3077		Max number of sectors on a Flash chip
3078
3079- CONFIG_SYS_FLASH_ERASE_TOUT:
3080		Timeout for Flash erase operations (in ms)
3081
3082- CONFIG_SYS_FLASH_WRITE_TOUT:
3083		Timeout for Flash write operations (in ms)
3084
3085- CONFIG_SYS_FLASH_LOCK_TOUT
3086		Timeout for Flash set sector lock bit operation (in ms)
3087
3088- CONFIG_SYS_FLASH_UNLOCK_TOUT
3089		Timeout for Flash clear lock bits operation (in ms)
3090
3091- CONFIG_SYS_FLASH_PROTECTION
3092		If defined, hardware flash sectors protection is used
3093		instead of U-Boot software protection.
3094
3095- CONFIG_SYS_DIRECT_FLASH_TFTP:
3096
3097		Enable TFTP transfers directly to flash memory;
3098		without this option such a download has to be
3099		performed in two steps: (1) download to RAM, and (2)
3100		copy from RAM to flash.
3101
3102		The two-step approach is usually more reliable, since
3103		you can check if the download worked before you erase
3104		the flash, but in some situations (when system RAM is
3105		too limited to allow for a temporary copy of the
3106		downloaded image) this option may be very useful.
3107
3108- CONFIG_SYS_FLASH_CFI:
3109		Define if the flash driver uses extra elements in the
3110		common flash structure for storing flash geometry.
3111
3112- CONFIG_FLASH_CFI_DRIVER
3113		This option also enables the building of the cfi_flash driver
3114		in the drivers directory
3115
3116- CONFIG_FLASH_CFI_MTD
3117		This option enables the building of the cfi_mtd driver
3118		in the drivers directory. The driver exports CFI flash
3119		to the MTD layer.
3120
3121- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3122		Use buffered writes to flash.
3123
3124- CONFIG_FLASH_SPANSION_S29WS_N
3125		s29ws-n MirrorBit flash has non-standard addresses for buffered
3126		write commands.
3127
3128- CONFIG_SYS_FLASH_QUIET_TEST
3129		If this option is defined, the common CFI flash doesn't
3130		print it's warning upon not recognized FLASH banks. This
3131		is useful, if some of the configured banks are only
3132		optionally available.
3133
3134- CONFIG_FLASH_SHOW_PROGRESS
3135		If defined (must be an integer), print out countdown
3136		digits and dots.  Recommended value: 45 (9..1) for 80
3137		column displays, 15 (3..1) for 40 column displays.
3138
3139- CONFIG_FLASH_VERIFY
3140		If defined, the content of the flash (destination) is compared
3141		against the source after the write operation. An error message
3142		will be printed when the contents are not identical.
3143		Please note that this option is useless in nearly all cases,
3144		since such flash programming errors usually are detected earlier
3145		while unprotecting/erasing/programming. Please only enable
3146		this option if you really know what you are doing.
3147
3148- CONFIG_SYS_RX_ETH_BUFFER:
3149		Defines the number of Ethernet receive buffers. On some
3150		Ethernet controllers it is recommended to set this value
3151		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3152		buffers can be full shortly after enabling the interface
3153		on high Ethernet traffic.
3154		Defaults to 4 if not defined.
3155
3156- CONFIG_ENV_MAX_ENTRIES
3157
3158	Maximum number of entries in the hash table that is used
3159	internally to store the environment settings. The default
3160	setting is supposed to be generous and should work in most
3161	cases. This setting can be used to tune behaviour; see
3162	lib/hashtable.c for details.
3163
3164- CONFIG_ENV_FLAGS_LIST_DEFAULT
3165- CONFIG_ENV_FLAGS_LIST_STATIC
3166	Enable validation of the values given to environment variables when
3167	calling env set.  Variables can be restricted to only decimal,
3168	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3169	the variables can also be restricted to IP address or MAC address.
3170
3171	The format of the list is:
3172		type_attribute = [s|d|x|b|i|m]
3173		access_attribute = [a|r|o|c]
3174		attributes = type_attribute[access_attribute]
3175		entry = variable_name[:attributes]
3176		list = entry[,list]
3177
3178	The type attributes are:
3179		s - String (default)
3180		d - Decimal
3181		x - Hexadecimal
3182		b - Boolean ([1yYtT|0nNfF])
3183		i - IP address
3184		m - MAC address
3185
3186	The access attributes are:
3187		a - Any (default)
3188		r - Read-only
3189		o - Write-once
3190		c - Change-default
3191
3192	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3193		Define this to a list (string) to define the ".flags"
3194		environment variable in the default or embedded environment.
3195
3196	- CONFIG_ENV_FLAGS_LIST_STATIC
3197		Define this to a list (string) to define validation that
3198		should be done if an entry is not found in the ".flags"
3199		environment variable.  To override a setting in the static
3200		list, simply add an entry for the same variable name to the
3201		".flags" variable.
3202
3203	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3204	regular expression. This allows multiple variables to define the same
3205	flags without explicitly listing them for each variable.
3206
3207- CONFIG_ENV_ACCESS_IGNORE_FORCE
3208	If defined, don't allow the -f switch to env set override variable
3209	access flags.
3210
3211- CONFIG_USE_STDINT
3212	If stdint.h is available with your toolchain you can define this
3213	option to enable it. You can provide option 'USE_STDINT=1' when
3214	building U-Boot to enable this.
3215
3216The following definitions that deal with the placement and management
3217of environment data (variable area); in general, we support the
3218following configurations:
3219
3220- CONFIG_BUILD_ENVCRC:
3221
3222	Builds up envcrc with the target environment so that external utils
3223	may easily extract it and embed it in final U-Boot images.
3224
3225BE CAREFUL! The first access to the environment happens quite early
3226in U-Boot initialization (when we try to get the setting of for the
3227console baudrate). You *MUST* have mapped your NVRAM area then, or
3228U-Boot will hang.
3229
3230Please note that even with NVRAM we still use a copy of the
3231environment in RAM: we could work on NVRAM directly, but we want to
3232keep settings there always unmodified except somebody uses "saveenv"
3233to save the current settings.
3234
3235BE CAREFUL! For some special cases, the local device can not use
3236"saveenv" command. For example, the local device will get the
3237environment stored in a remote NOR flash by SRIO or PCIE link,
3238but it can not erase, write this NOR flash by SRIO or PCIE interface.
3239
3240- CONFIG_NAND_ENV_DST
3241
3242	Defines address in RAM to which the nand_spl code should copy the
3243	environment. If redundant environment is used, it will be copied to
3244	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3245
3246Please note that the environment is read-only until the monitor
3247has been relocated to RAM and a RAM copy of the environment has been
3248created; also, when using EEPROM you will have to use env_get_f()
3249until then to read environment variables.
3250
3251The environment is protected by a CRC32 checksum. Before the monitor
3252is relocated into RAM, as a result of a bad CRC you will be working
3253with the compiled-in default environment - *silently*!!! [This is
3254necessary, because the first environment variable we need is the
3255"baudrate" setting for the console - if we have a bad CRC, we don't
3256have any device yet where we could complain.]
3257
3258Note: once the monitor has been relocated, then it will complain if
3259the default environment is used; a new CRC is computed as soon as you
3260use the "saveenv" command to store a valid environment.
3261
3262- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3263		Echo the inverted Ethernet link state to the fault LED.
3264
3265		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3266		      also needs to be defined.
3267
3268- CONFIG_SYS_FAULT_MII_ADDR:
3269		MII address of the PHY to check for the Ethernet link state.
3270
3271- CONFIG_NS16550_MIN_FUNCTIONS:
3272		Define this if you desire to only have use of the NS16550_init
3273		and NS16550_putc functions for the serial driver located at
3274		drivers/serial/ns16550.c.  This option is useful for saving
3275		space for already greatly restricted images, including but not
3276		limited to NAND_SPL configurations.
3277
3278- CONFIG_DISPLAY_BOARDINFO
3279		Display information about the board that U-Boot is running on
3280		when U-Boot starts up. The board function checkboard() is called
3281		to do this.
3282
3283- CONFIG_DISPLAY_BOARDINFO_LATE
3284		Similar to the previous option, but display this information
3285		later, once stdio is running and output goes to the LCD, if
3286		present.
3287
3288- CONFIG_BOARD_SIZE_LIMIT:
3289		Maximum size of the U-Boot image. When defined, the
3290		build system checks that the actual size does not
3291		exceed it.
3292
3293Low Level (hardware related) configuration options:
3294---------------------------------------------------
3295
3296- CONFIG_SYS_CACHELINE_SIZE:
3297		Cache Line Size of the CPU.
3298
3299- CONFIG_SYS_CCSRBAR_DEFAULT:
3300		Default (power-on reset) physical address of CCSR on Freescale
3301		PowerPC SOCs.
3302
3303- CONFIG_SYS_CCSRBAR:
3304		Virtual address of CCSR.  On a 32-bit build, this is typically
3305		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3306
3307- CONFIG_SYS_CCSRBAR_PHYS:
3308		Physical address of CCSR.  CCSR can be relocated to a new
3309		physical address, if desired.  In this case, this macro should
3310		be set to that address.	 Otherwise, it should be set to the
3311		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3312		is typically relocated on 36-bit builds.  It is recommended
3313		that this macro be defined via the _HIGH and _LOW macros:
3314
3315		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3316			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3317
3318- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3319		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3320		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3321		used in assembly code, so it must not contain typecasts or
3322		integer size suffixes (e.g. "ULL").
3323
3324- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3325		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3326		used in assembly code, so it must not contain typecasts or
3327		integer size suffixes (e.g. "ULL").
3328
3329- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3330		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3331		forced to a value that ensures that CCSR is not relocated.
3332
3333- Floppy Disk Support:
3334		CONFIG_SYS_FDC_DRIVE_NUMBER
3335
3336		the default drive number (default value 0)
3337
3338		CONFIG_SYS_ISA_IO_STRIDE
3339
3340		defines the spacing between FDC chipset registers
3341		(default value 1)
3342
3343		CONFIG_SYS_ISA_IO_OFFSET
3344
3345		defines the offset of register from address. It
3346		depends on which part of the data bus is connected to
3347		the FDC chipset. (default value 0)
3348
3349		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3350		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3351		default value.
3352
3353		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3354		fdc_hw_init() is called at the beginning of the FDC
3355		setup. fdc_hw_init() must be provided by the board
3356		source code. It is used to make hardware-dependent
3357		initializations.
3358
3359- CONFIG_IDE_AHB:
3360		Most IDE controllers were designed to be connected with PCI
3361		interface. Only few of them were designed for AHB interface.
3362		When software is doing ATA command and data transfer to
3363		IDE devices through IDE-AHB controller, some additional
3364		registers accessing to these kind of IDE-AHB controller
3365		is required.
3366
3367- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3368		DO NOT CHANGE unless you know exactly what you're
3369		doing! (11-4) [MPC8xx systems only]
3370
3371- CONFIG_SYS_INIT_RAM_ADDR:
3372
3373		Start address of memory area that can be used for
3374		initial data and stack; please note that this must be
3375		writable memory that is working WITHOUT special
3376		initialization, i. e. you CANNOT use normal RAM which
3377		will become available only after programming the
3378		memory controller and running certain initialization
3379		sequences.
3380
3381		U-Boot uses the following memory types:
3382		- MPC8xx: IMMR (internal memory of the CPU)
3383
3384- CONFIG_SYS_GBL_DATA_OFFSET:
3385
3386		Offset of the initial data structure in the memory
3387		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3388		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3389		data is located at the end of the available space
3390		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3391		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3392		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3393		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3394
3395	Note:
3396		On the MPC824X (or other systems that use the data
3397		cache for initial memory) the address chosen for
3398		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3399		point to an otherwise UNUSED address space between
3400		the top of RAM and the start of the PCI space.
3401
3402- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3403
3404- CONFIG_SYS_OR_TIMING_SDRAM:
3405		SDRAM timing
3406
3407- CONFIG_SYS_MAMR_PTA:
3408		periodic timer for refresh
3409
3410- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3411  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3412  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3413  CONFIG_SYS_BR1_PRELIM:
3414		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3415
3416- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3417  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3418  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3419		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3420
3421- CONFIG_PCI_ENUM_ONLY
3422		Only scan through and get the devices on the buses.
3423		Don't do any setup work, presumably because someone or
3424		something has already done it, and we don't need to do it
3425		a second time.	Useful for platforms that are pre-booted
3426		by coreboot or similar.
3427
3428- CONFIG_PCI_INDIRECT_BRIDGE:
3429		Enable support for indirect PCI bridges.
3430
3431- CONFIG_SYS_SRIO:
3432		Chip has SRIO or not
3433
3434- CONFIG_SRIO1:
3435		Board has SRIO 1 port available
3436
3437- CONFIG_SRIO2:
3438		Board has SRIO 2 port available
3439
3440- CONFIG_SRIO_PCIE_BOOT_MASTER
3441		Board can support master function for Boot from SRIO and PCIE
3442
3443- CONFIG_SYS_SRIOn_MEM_VIRT:
3444		Virtual Address of SRIO port 'n' memory region
3445
3446- CONFIG_SYS_SRIOn_MEM_PHYS:
3447		Physical Address of SRIO port 'n' memory region
3448
3449- CONFIG_SYS_SRIOn_MEM_SIZE:
3450		Size of SRIO port 'n' memory region
3451
3452- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3453		Defined to tell the NAND controller that the NAND chip is using
3454		a 16 bit bus.
3455		Not all NAND drivers use this symbol.
3456		Example of drivers that use it:
3457		- drivers/mtd/nand/ndfc.c
3458		- drivers/mtd/nand/mxc_nand.c
3459
3460- CONFIG_SYS_NDFC_EBC0_CFG
3461		Sets the EBC0_CFG register for the NDFC. If not defined
3462		a default value will be used.
3463
3464- CONFIG_SPD_EEPROM
3465		Get DDR timing information from an I2C EEPROM. Common
3466		with pluggable memory modules such as SODIMMs
3467
3468  SPD_EEPROM_ADDRESS
3469		I2C address of the SPD EEPROM
3470
3471- CONFIG_SYS_SPD_BUS_NUM
3472		If SPD EEPROM is on an I2C bus other than the first
3473		one, specify here. Note that the value must resolve
3474		to something your driver can deal with.
3475
3476- CONFIG_SYS_DDR_RAW_TIMING
3477		Get DDR timing information from other than SPD. Common with
3478		soldered DDR chips onboard without SPD. DDR raw timing
3479		parameters are extracted from datasheet and hard-coded into
3480		header files or board specific files.
3481
3482- CONFIG_FSL_DDR_INTERACTIVE
3483		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3484
3485- CONFIG_FSL_DDR_SYNC_REFRESH
3486		Enable sync of refresh for multiple controllers.
3487
3488- CONFIG_FSL_DDR_BIST
3489		Enable built-in memory test for Freescale DDR controllers.
3490
3491- CONFIG_SYS_83XX_DDR_USES_CS0
3492		Only for 83xx systems. If specified, then DDR should
3493		be configured using CS0 and CS1 instead of CS2 and CS3.
3494
3495- CONFIG_RMII
3496		Enable RMII mode for all FECs.
3497		Note that this is a global option, we can't
3498		have one FEC in standard MII mode and another in RMII mode.
3499
3500- CONFIG_CRC32_VERIFY
3501		Add a verify option to the crc32 command.
3502		The syntax is:
3503
3504		=> crc32 -v <address> <count> <crc32>
3505
3506		Where address/count indicate a memory area
3507		and crc32 is the correct crc32 which the
3508		area should have.
3509
3510- CONFIG_LOOPW
3511		Add the "loopw" memory command. This only takes effect if
3512		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3513
3514- CONFIG_MX_CYCLIC
3515		Add the "mdc" and "mwc" memory commands. These are cyclic
3516		"md/mw" commands.
3517		Examples:
3518
3519		=> mdc.b 10 4 500
3520		This command will print 4 bytes (10,11,12,13) each 500 ms.
3521
3522		=> mwc.l 100 12345678 10
3523		This command will write 12345678 to address 100 all 10 ms.
3524
3525		This only takes effect if the memory commands are activated
3526		globally (CONFIG_CMD_MEMORY).
3527
3528- CONFIG_SKIP_LOWLEVEL_INIT
3529		[ARM, NDS32, MIPS only] If this variable is defined, then certain
3530		low level initializations (like setting up the memory
3531		controller) are omitted and/or U-Boot does not
3532		relocate itself into RAM.
3533
3534		Normally this variable MUST NOT be defined. The only
3535		exception is when U-Boot is loaded (to RAM) by some
3536		other boot loader or by a debugger which performs
3537		these initializations itself.
3538
3539- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3540		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3541		to be skipped. The normal CP15 init (such as enabling the
3542		instruction cache) is still performed.
3543
3544- CONFIG_SPL_BUILD
3545		Modifies the behaviour of start.S when compiling a loader
3546		that is executed before the actual U-Boot. E.g. when
3547		compiling a NAND SPL.
3548
3549- CONFIG_TPL_BUILD
3550		Modifies the behaviour of start.S  when compiling a loader
3551		that is executed after the SPL and before the actual U-Boot.
3552		It is loaded by the SPL.
3553
3554- CONFIG_SYS_MPC85XX_NO_RESETVEC
3555		Only for 85xx systems. If this variable is specified, the section
3556		.resetvec is not kept and the section .bootpg is placed in the
3557		previous 4k of the .text section.
3558
3559- CONFIG_ARCH_MAP_SYSMEM
3560		Generally U-Boot (and in particular the md command) uses
3561		effective address. It is therefore not necessary to regard
3562		U-Boot address as virtual addresses that need to be translated
3563		to physical addresses. However, sandbox requires this, since
3564		it maintains its own little RAM buffer which contains all
3565		addressable memory. This option causes some memory accesses
3566		to be mapped through map_sysmem() / unmap_sysmem().
3567
3568- CONFIG_X86_RESET_VECTOR
3569		If defined, the x86 reset vector code is included. This is not
3570		needed when U-Boot is running from Coreboot.
3571
3572- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
3573		Enables the RTC32K OSC on AM33xx based plattforms
3574
3575- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3576		Option to disable subpage write in NAND driver
3577		driver that uses this:
3578		drivers/mtd/nand/davinci_nand.c
3579
3580Freescale QE/FMAN Firmware Support:
3581-----------------------------------
3582
3583The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3584loading of "firmware", which is encoded in the QE firmware binary format.
3585This firmware often needs to be loaded during U-Boot booting, so macros
3586are used to identify the storage device (NOR flash, SPI, etc) and the address
3587within that device.
3588
3589- CONFIG_SYS_FMAN_FW_ADDR
3590	The address in the storage device where the FMAN microcode is located.  The
3591	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3592	is also specified.
3593
3594- CONFIG_SYS_QE_FW_ADDR
3595	The address in the storage device where the QE microcode is located.  The
3596	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3597	is also specified.
3598
3599- CONFIG_SYS_QE_FMAN_FW_LENGTH
3600	The maximum possible size of the firmware.  The firmware binary format
3601	has a field that specifies the actual size of the firmware, but it
3602	might not be possible to read any part of the firmware unless some
3603	local storage is allocated to hold the entire firmware first.
3604
3605- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3606	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3607	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3608	virtual address in NOR flash.
3609
3610- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3611	Specifies that QE/FMAN firmware is located in NAND flash.
3612	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3613
3614- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3615	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3616	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3617
3618- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3619	Specifies that QE/FMAN firmware is located in the remote (master)
3620	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3621	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3622	window->master inbound window->master LAW->the ucode address in
3623	master's memory space.
3624
3625Freescale Layerscape Management Complex Firmware Support:
3626---------------------------------------------------------
3627The Freescale Layerscape Management Complex (MC) supports the loading of
3628"firmware".
3629This firmware often needs to be loaded during U-Boot booting, so macros
3630are used to identify the storage device (NOR flash, SPI, etc) and the address
3631within that device.
3632
3633- CONFIG_FSL_MC_ENET
3634	Enable the MC driver for Layerscape SoCs.
3635
3636Freescale Layerscape Debug Server Support:
3637-------------------------------------------
3638The Freescale Layerscape Debug Server Support supports the loading of
3639"Debug Server firmware" and triggering SP boot-rom.
3640This firmware often needs to be loaded during U-Boot booting.
3641
3642- CONFIG_SYS_MC_RSV_MEM_ALIGN
3643	Define alignment of reserved memory MC requires
3644
3645Reproducible builds
3646-------------------
3647
3648In order to achieve reproducible builds, timestamps used in the U-Boot build
3649process have to be set to a fixed value.
3650
3651This is done using the SOURCE_DATE_EPOCH environment variable.
3652SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3653option for U-Boot or an environment variable in U-Boot.
3654
3655SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3656
3657Building the Software:
3658======================
3659
3660Building U-Boot has been tested in several native build environments
3661and in many different cross environments. Of course we cannot support
3662all possibly existing versions of cross development tools in all
3663(potentially obsolete) versions. In case of tool chain problems we
3664recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3665which is extensively used to build and test U-Boot.
3666
3667If you are not using a native environment, it is assumed that you
3668have GNU cross compiling tools available in your path. In this case,
3669you must set the environment variable CROSS_COMPILE in your shell.
3670Note that no changes to the Makefile or any other source files are
3671necessary. For example using the ELDK on a 4xx CPU, please enter:
3672
3673	$ CROSS_COMPILE=ppc_4xx-
3674	$ export CROSS_COMPILE
3675
3676Note: If you wish to generate Windows versions of the utilities in
3677      the tools directory you can use the MinGW toolchain
3678      (http://www.mingw.org).  Set your HOST tools to the MinGW
3679      toolchain and execute 'make tools'.  For example:
3680
3681       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3682
3683      Binaries such as tools/mkimage.exe will be created which can
3684      be executed on computers running Windows.
3685
3686U-Boot is intended to be simple to build. After installing the
3687sources you must configure U-Boot for one specific board type. This
3688is done by typing:
3689
3690	make NAME_defconfig
3691
3692where "NAME_defconfig" is the name of one of the existing configu-
3693rations; see boards.cfg for supported names.
3694
3695Note: for some board special configuration names may exist; check if
3696      additional information is available from the board vendor; for
3697      instance, the TQM823L systems are available without (standard)
3698      or with LCD support. You can select such additional "features"
3699      when choosing the configuration, i. e.
3700
3701      make TQM823L_defconfig
3702	- will configure for a plain TQM823L, i. e. no LCD support
3703
3704      make TQM823L_LCD_defconfig
3705	- will configure for a TQM823L with U-Boot console on LCD
3706
3707      etc.
3708
3709
3710Finally, type "make all", and you should get some working U-Boot
3711images ready for download to / installation on your system:
3712
3713- "u-boot.bin" is a raw binary image
3714- "u-boot" is an image in ELF binary format
3715- "u-boot.srec" is in Motorola S-Record format
3716
3717By default the build is performed locally and the objects are saved
3718in the source directory. One of the two methods can be used to change
3719this behavior and build U-Boot to some external directory:
3720
37211. Add O= to the make command line invocations:
3722
3723	make O=/tmp/build distclean
3724	make O=/tmp/build NAME_defconfig
3725	make O=/tmp/build all
3726
37272. Set environment variable KBUILD_OUTPUT to point to the desired location:
3728
3729	export KBUILD_OUTPUT=/tmp/build
3730	make distclean
3731	make NAME_defconfig
3732	make all
3733
3734Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3735variable.
3736
3737
3738Please be aware that the Makefiles assume you are using GNU make, so
3739for instance on NetBSD you might need to use "gmake" instead of
3740native "make".
3741
3742
3743If the system board that you have is not listed, then you will need
3744to port U-Boot to your hardware platform. To do this, follow these
3745steps:
3746
37471.  Create a new directory to hold your board specific code. Add any
3748    files you need. In your board directory, you will need at least
3749    the "Makefile" and a "<board>.c".
37502.  Create a new configuration file "include/configs/<board>.h" for
3751    your board.
37523.  If you're porting U-Boot to a new CPU, then also create a new
3753    directory to hold your CPU specific code. Add any files you need.
37544.  Run "make <board>_defconfig" with your new name.
37555.  Type "make", and you should get a working "u-boot.srec" file
3756    to be installed on your target system.
37576.  Debug and solve any problems that might arise.
3758    [Of course, this last step is much harder than it sounds.]
3759
3760
3761Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3762==============================================================
3763
3764If you have modified U-Boot sources (for instance added a new board
3765or support for new devices, a new CPU, etc.) you are expected to
3766provide feedback to the other developers. The feedback normally takes
3767the form of a "patch", i. e. a context diff against a certain (latest
3768official or latest in the git repository) version of U-Boot sources.
3769
3770But before you submit such a patch, please verify that your modifi-
3771cation did not break existing code. At least make sure that *ALL* of
3772the supported boards compile WITHOUT ANY compiler warnings. To do so,
3773just run the buildman script (tools/buildman/buildman), which will
3774configure and build U-Boot for ALL supported system. Be warned, this
3775will take a while. Please see the buildman README, or run 'buildman -H'
3776for documentation.
3777
3778
3779See also "U-Boot Porting Guide" below.
3780
3781
3782Monitor Commands - Overview:
3783============================
3784
3785go	- start application at address 'addr'
3786run	- run commands in an environment variable
3787bootm	- boot application image from memory
3788bootp	- boot image via network using BootP/TFTP protocol
3789bootz   - boot zImage from memory
3790tftpboot- boot image via network using TFTP protocol
3791	       and env variables "ipaddr" and "serverip"
3792	       (and eventually "gatewayip")
3793tftpput - upload a file via network using TFTP protocol
3794rarpboot- boot image via network using RARP/TFTP protocol
3795diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3796loads	- load S-Record file over serial line
3797loadb	- load binary file over serial line (kermit mode)
3798md	- memory display
3799mm	- memory modify (auto-incrementing)
3800nm	- memory modify (constant address)
3801mw	- memory write (fill)
3802cp	- memory copy
3803cmp	- memory compare
3804crc32	- checksum calculation
3805i2c	- I2C sub-system
3806sspi	- SPI utility commands
3807base	- print or set address offset
3808printenv- print environment variables
3809setenv	- set environment variables
3810saveenv - save environment variables to persistent storage
3811protect - enable or disable FLASH write protection
3812erase	- erase FLASH memory
3813flinfo	- print FLASH memory information
3814nand	- NAND memory operations (see doc/README.nand)
3815bdinfo	- print Board Info structure
3816iminfo	- print header information for application image
3817coninfo - print console devices and informations
3818ide	- IDE sub-system
3819loop	- infinite loop on address range
3820loopw	- infinite write loop on address range
3821mtest	- simple RAM test
3822icache	- enable or disable instruction cache
3823dcache	- enable or disable data cache
3824reset	- Perform RESET of the CPU
3825echo	- echo args to console
3826version - print monitor version
3827help	- print online help
3828?	- alias for 'help'
3829
3830
3831Monitor Commands - Detailed Description:
3832========================================
3833
3834TODO.
3835
3836For now: just type "help <command>".
3837
3838
3839Environment Variables:
3840======================
3841
3842U-Boot supports user configuration using Environment Variables which
3843can be made persistent by saving to Flash memory.
3844
3845Environment Variables are set using "setenv", printed using
3846"printenv", and saved to Flash using "saveenv". Using "setenv"
3847without a value can be used to delete a variable from the
3848environment. As long as you don't save the environment you are
3849working with an in-memory copy. In case the Flash area containing the
3850environment is erased by accident, a default environment is provided.
3851
3852Some configuration options can be set using Environment Variables.
3853
3854List of environment variables (most likely not complete):
3855
3856  baudrate	- see CONFIG_BAUDRATE
3857
3858  bootdelay	- see CONFIG_BOOTDELAY
3859
3860  bootcmd	- see CONFIG_BOOTCOMMAND
3861
3862  bootargs	- Boot arguments when booting an RTOS image
3863
3864  bootfile	- Name of the image to load with TFTP
3865
3866  bootm_low	- Memory range available for image processing in the bootm
3867		  command can be restricted. This variable is given as
3868		  a hexadecimal number and defines lowest address allowed
3869		  for use by the bootm command. See also "bootm_size"
3870		  environment variable. Address defined by "bootm_low" is
3871		  also the base of the initial memory mapping for the Linux
3872		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3873		  bootm_mapsize.
3874
3875  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3876		  This variable is given as a hexadecimal number and it
3877		  defines the size of the memory region starting at base
3878		  address bootm_low that is accessible by the Linux kernel
3879		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3880		  as the default value if it is defined, and bootm_size is
3881		  used otherwise.
3882
3883  bootm_size	- Memory range available for image processing in the bootm
3884		  command can be restricted. This variable is given as
3885		  a hexadecimal number and defines the size of the region
3886		  allowed for use by the bootm command. See also "bootm_low"
3887		  environment variable.
3888
3889  updatefile	- Location of the software update file on a TFTP server, used
3890		  by the automatic software update feature. Please refer to
3891		  documentation in doc/README.update for more details.
3892
3893  autoload	- if set to "no" (any string beginning with 'n'),
3894		  "bootp" will just load perform a lookup of the
3895		  configuration from the BOOTP server, but not try to
3896		  load any image using TFTP
3897
3898  autostart	- if set to "yes", an image loaded using the "bootp",
3899		  "rarpboot", "tftpboot" or "diskboot" commands will
3900		  be automatically started (by internally calling
3901		  "bootm")
3902
3903		  If set to "no", a standalone image passed to the
3904		  "bootm" command will be copied to the load address
3905		  (and eventually uncompressed), but NOT be started.
3906		  This can be used to load and uncompress arbitrary
3907		  data.
3908
3909  fdt_high	- if set this restricts the maximum address that the
3910		  flattened device tree will be copied into upon boot.
3911		  For example, if you have a system with 1 GB memory
3912		  at physical address 0x10000000, while Linux kernel
3913		  only recognizes the first 704 MB as low memory, you
3914		  may need to set fdt_high as 0x3C000000 to have the
3915		  device tree blob be copied to the maximum address
3916		  of the 704 MB low memory, so that Linux kernel can
3917		  access it during the boot procedure.
3918
3919		  If this is set to the special value 0xFFFFFFFF then
3920		  the fdt will not be copied at all on boot.  For this
3921		  to work it must reside in writable memory, have
3922		  sufficient padding on the end of it for u-boot to
3923		  add the information it needs into it, and the memory
3924		  must be accessible by the kernel.
3925
3926  fdtcontroladdr- if set this is the address of the control flattened
3927		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3928		  defined.
3929
3930  i2cfast	- (PPC405GP|PPC405EP only)
3931		  if set to 'y' configures Linux I2C driver for fast
3932		  mode (400kHZ). This environment variable is used in
3933		  initialization code. So, for changes to be effective
3934		  it must be saved and board must be reset.
3935
3936  initrd_high	- restrict positioning of initrd images:
3937		  If this variable is not set, initrd images will be
3938		  copied to the highest possible address in RAM; this
3939		  is usually what you want since it allows for
3940		  maximum initrd size. If for some reason you want to
3941		  make sure that the initrd image is loaded below the
3942		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3943		  variable to a value of "no" or "off" or "0".
3944		  Alternatively, you can set it to a maximum upper
3945		  address to use (U-Boot will still check that it
3946		  does not overwrite the U-Boot stack and data).
3947
3948		  For instance, when you have a system with 16 MB
3949		  RAM, and want to reserve 4 MB from use by Linux,
3950		  you can do this by adding "mem=12M" to the value of
3951		  the "bootargs" variable. However, now you must make
3952		  sure that the initrd image is placed in the first
3953		  12 MB as well - this can be done with
3954
3955		  setenv initrd_high 00c00000
3956
3957		  If you set initrd_high to 0xFFFFFFFF, this is an
3958		  indication to U-Boot that all addresses are legal
3959		  for the Linux kernel, including addresses in flash
3960		  memory. In this case U-Boot will NOT COPY the
3961		  ramdisk at all. This may be useful to reduce the
3962		  boot time on your system, but requires that this
3963		  feature is supported by your Linux kernel.
3964
3965  ipaddr	- IP address; needed for tftpboot command
3966
3967  loadaddr	- Default load address for commands like "bootp",
3968		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3969
3970  loads_echo	- see CONFIG_LOADS_ECHO
3971
3972  serverip	- TFTP server IP address; needed for tftpboot command
3973
3974  bootretry	- see CONFIG_BOOT_RETRY_TIME
3975
3976  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3977
3978  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3979
3980  ethprime	- controls which interface is used first.
3981
3982  ethact	- controls which interface is currently active.
3983		  For example you can do the following
3984
3985		  => setenv ethact FEC
3986		  => ping 192.168.0.1 # traffic sent on FEC
3987		  => setenv ethact SCC
3988		  => ping 10.0.0.1 # traffic sent on SCC
3989
3990  ethrotate	- When set to "no" U-Boot does not go through all
3991		  available network interfaces.
3992		  It just stays at the currently selected interface.
3993
3994  netretry	- When set to "no" each network operation will
3995		  either succeed or fail without retrying.
3996		  When set to "once" the network operation will
3997		  fail when all the available network interfaces
3998		  are tried once without success.
3999		  Useful on scripts which control the retry operation
4000		  themselves.
4001
4002  npe_ucode	- set load address for the NPE microcode
4003
4004  silent_linux  - If set then Linux will be told to boot silently, by
4005		  changing the console to be empty. If "yes" it will be
4006		  made silent. If "no" it will not be made silent. If
4007		  unset, then it will be made silent if the U-Boot console
4008		  is silent.
4009
4010  tftpsrcp	- If this is set, the value is used for TFTP's
4011		  UDP source port.
4012
4013  tftpdstp	- If this is set, the value is used for TFTP's UDP
4014		  destination port instead of the Well Know Port 69.
4015
4016  tftpblocksize - Block size to use for TFTP transfers; if not set,
4017		  we use the TFTP server's default block size
4018
4019  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4020		  seconds, minimum value is 1000 = 1 second). Defines
4021		  when a packet is considered to be lost so it has to
4022		  be retransmitted. The default is 5000 = 5 seconds.
4023		  Lowering this value may make downloads succeed
4024		  faster in networks with high packet loss rates or
4025		  with unreliable TFTP servers.
4026
4027  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
4028		  unit, minimum value = 0). Defines how many timeouts
4029		  can happen during a single file transfer before that
4030		  transfer is aborted. The default is 10, and 0 means
4031		  'no timeouts allowed'. Increasing this value may help
4032		  downloads succeed with high packet loss rates, or with
4033		  unreliable TFTP servers or client hardware.
4034
4035  vlan		- When set to a value < 4095 the traffic over
4036		  Ethernet is encapsulated/received over 802.1q
4037		  VLAN tagged frames.
4038
4039  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
4040		  Unsigned value, in milliseconds. If not set, the period will
4041		  be either the default (28000), or a value based on
4042		  CONFIG_NET_RETRY_COUNT, if defined. This value has
4043		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
4044
4045The following image location variables contain the location of images
4046used in booting. The "Image" column gives the role of the image and is
4047not an environment variable name. The other columns are environment
4048variable names. "File Name" gives the name of the file on a TFTP
4049server, "RAM Address" gives the location in RAM the image will be
4050loaded to, and "Flash Location" gives the image's address in NOR
4051flash or offset in NAND flash.
4052
4053*Note* - these variables don't have to be defined for all boards, some
4054boards currently use other variables for these purposes, and some
4055boards use these variables for other purposes.
4056
4057Image		    File Name	     RAM Address       Flash Location
4058-----		    ---------	     -----------       --------------
4059u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4060Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4061device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4062ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4063
4064The following environment variables may be used and automatically
4065updated by the network boot commands ("bootp" and "rarpboot"),
4066depending the information provided by your boot server:
4067
4068  bootfile	- see above
4069  dnsip		- IP address of your Domain Name Server
4070  dnsip2	- IP address of your secondary Domain Name Server
4071  gatewayip	- IP address of the Gateway (Router) to use
4072  hostname	- Target hostname
4073  ipaddr	- see above
4074  netmask	- Subnet Mask
4075  rootpath	- Pathname of the root filesystem on the NFS server
4076  serverip	- see above
4077
4078
4079There are two special Environment Variables:
4080
4081  serial#	- contains hardware identification information such
4082		  as type string and/or serial number
4083  ethaddr	- Ethernet address
4084
4085These variables can be set only once (usually during manufacturing of
4086the board). U-Boot refuses to delete or overwrite these variables
4087once they have been set once.
4088
4089
4090Further special Environment Variables:
4091
4092  ver		- Contains the U-Boot version string as printed
4093		  with the "version" command. This variable is
4094		  readonly (see CONFIG_VERSION_VARIABLE).
4095
4096
4097Please note that changes to some configuration parameters may take
4098only effect after the next boot (yes, that's just like Windoze :-).
4099
4100
4101Callback functions for environment variables:
4102---------------------------------------------
4103
4104For some environment variables, the behavior of u-boot needs to change
4105when their values are changed.  This functionality allows functions to
4106be associated with arbitrary variables.  On creation, overwrite, or
4107deletion, the callback will provide the opportunity for some side
4108effect to happen or for the change to be rejected.
4109
4110The callbacks are named and associated with a function using the
4111U_BOOT_ENV_CALLBACK macro in your board or driver code.
4112
4113These callbacks are associated with variables in one of two ways.  The
4114static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4115in the board configuration to a string that defines a list of
4116associations.  The list must be in the following format:
4117
4118	entry = variable_name[:callback_name]
4119	list = entry[,list]
4120
4121If the callback name is not specified, then the callback is deleted.
4122Spaces are also allowed anywhere in the list.
4123
4124Callbacks can also be associated by defining the ".callbacks" variable
4125with the same list format above.  Any association in ".callbacks" will
4126override any association in the static list. You can define
4127CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4128".callbacks" environment variable in the default or embedded environment.
4129
4130If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4131regular expression. This allows multiple variables to be connected to
4132the same callback without explicitly listing them all out.
4133
4134
4135Command Line Parsing:
4136=====================
4137
4138There are two different command line parsers available with U-Boot:
4139the old "simple" one, and the much more powerful "hush" shell:
4140
4141Old, simple command line parser:
4142--------------------------------
4143
4144- supports environment variables (through setenv / saveenv commands)
4145- several commands on one line, separated by ';'
4146- variable substitution using "... ${name} ..." syntax
4147- special characters ('$', ';') can be escaped by prefixing with '\',
4148  for example:
4149	setenv bootcmd bootm \${address}
4150- You can also escape text by enclosing in single apostrophes, for example:
4151	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4152
4153Hush shell:
4154-----------
4155
4156- similar to Bourne shell, with control structures like
4157  if...then...else...fi, for...do...done; while...do...done,
4158  until...do...done, ...
4159- supports environment ("global") variables (through setenv / saveenv
4160  commands) and local shell variables (through standard shell syntax
4161  "name=value"); only environment variables can be used with "run"
4162  command
4163
4164General rules:
4165--------------
4166
4167(1) If a command line (or an environment variable executed by a "run"
4168    command) contains several commands separated by semicolon, and
4169    one of these commands fails, then the remaining commands will be
4170    executed anyway.
4171
4172(2) If you execute several variables with one call to run (i. e.
4173    calling run with a list of variables as arguments), any failing
4174    command will cause "run" to terminate, i. e. the remaining
4175    variables are not executed.
4176
4177Note for Redundant Ethernet Interfaces:
4178=======================================
4179
4180Some boards come with redundant Ethernet interfaces; U-Boot supports
4181such configurations and is capable of automatic selection of a
4182"working" interface when needed. MAC assignment works as follows:
4183
4184Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4185MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4186"eth1addr" (=>eth1), "eth2addr", ...
4187
4188If the network interface stores some valid MAC address (for instance
4189in SROM), this is used as default address if there is NO correspon-
4190ding setting in the environment; if the corresponding environment
4191variable is set, this overrides the settings in the card; that means:
4192
4193o If the SROM has a valid MAC address, and there is no address in the
4194  environment, the SROM's address is used.
4195
4196o If there is no valid address in the SROM, and a definition in the
4197  environment exists, then the value from the environment variable is
4198  used.
4199
4200o If both the SROM and the environment contain a MAC address, and
4201  both addresses are the same, this MAC address is used.
4202
4203o If both the SROM and the environment contain a MAC address, and the
4204  addresses differ, the value from the environment is used and a
4205  warning is printed.
4206
4207o If neither SROM nor the environment contain a MAC address, an error
4208  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4209  a random, locally-assigned MAC is used.
4210
4211If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4212will be programmed into hardware as part of the initialization process.	 This
4213may be skipped by setting the appropriate 'ethmacskip' environment variable.
4214The naming convention is as follows:
4215"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4216
4217Image Formats:
4218==============
4219
4220U-Boot is capable of booting (and performing other auxiliary operations on)
4221images in two formats:
4222
4223New uImage format (FIT)
4224-----------------------
4225
4226Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4227to Flattened Device Tree). It allows the use of images with multiple
4228components (several kernels, ramdisks, etc.), with contents protected by
4229SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4230
4231
4232Old uImage format
4233-----------------
4234
4235Old image format is based on binary files which can be basically anything,
4236preceded by a special header; see the definitions in include/image.h for
4237details; basically, the header defines the following image properties:
4238
4239* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4240  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4241  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4242  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4243  INTEGRITY).
4244* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4245  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4246  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4247* Compression Type (uncompressed, gzip, bzip2)
4248* Load Address
4249* Entry Point
4250* Image Name
4251* Image Timestamp
4252
4253The header is marked by a special Magic Number, and both the header
4254and the data portions of the image are secured against corruption by
4255CRC32 checksums.
4256
4257
4258Linux Support:
4259==============
4260
4261Although U-Boot should support any OS or standalone application
4262easily, the main focus has always been on Linux during the design of
4263U-Boot.
4264
4265U-Boot includes many features that so far have been part of some
4266special "boot loader" code within the Linux kernel. Also, any
4267"initrd" images to be used are no longer part of one big Linux image;
4268instead, kernel and "initrd" are separate images. This implementation
4269serves several purposes:
4270
4271- the same features can be used for other OS or standalone
4272  applications (for instance: using compressed images to reduce the
4273  Flash memory footprint)
4274
4275- it becomes much easier to port new Linux kernel versions because
4276  lots of low-level, hardware dependent stuff are done by U-Boot
4277
4278- the same Linux kernel image can now be used with different "initrd"
4279  images; of course this also means that different kernel images can
4280  be run with the same "initrd". This makes testing easier (you don't
4281  have to build a new "zImage.initrd" Linux image when you just
4282  change a file in your "initrd"). Also, a field-upgrade of the
4283  software is easier now.
4284
4285
4286Linux HOWTO:
4287============
4288
4289Porting Linux to U-Boot based systems:
4290---------------------------------------
4291
4292U-Boot cannot save you from doing all the necessary modifications to
4293configure the Linux device drivers for use with your target hardware
4294(no, we don't intend to provide a full virtual machine interface to
4295Linux :-).
4296
4297But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4298
4299Just make sure your machine specific header file (for instance
4300include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4301Information structure as we define in include/asm-<arch>/u-boot.h,
4302and make sure that your definition of IMAP_ADDR uses the same value
4303as your U-Boot configuration in CONFIG_SYS_IMMR.
4304
4305Note that U-Boot now has a driver model, a unified model for drivers.
4306If you are adding a new driver, plumb it into driver model. If there
4307is no uclass available, you are encouraged to create one. See
4308doc/driver-model.
4309
4310
4311Configuring the Linux kernel:
4312-----------------------------
4313
4314No specific requirements for U-Boot. Make sure you have some root
4315device (initial ramdisk, NFS) for your target system.
4316
4317
4318Building a Linux Image:
4319-----------------------
4320
4321With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4322not used. If you use recent kernel source, a new build target
4323"uImage" will exist which automatically builds an image usable by
4324U-Boot. Most older kernels also have support for a "pImage" target,
4325which was introduced for our predecessor project PPCBoot and uses a
4326100% compatible format.
4327
4328Example:
4329
4330	make TQM850L_defconfig
4331	make oldconfig
4332	make dep
4333	make uImage
4334
4335The "uImage" build target uses a special tool (in 'tools/mkimage') to
4336encapsulate a compressed Linux kernel image with header	 information,
4337CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4338
4339* build a standard "vmlinux" kernel image (in ELF binary format):
4340
4341* convert the kernel into a raw binary image:
4342
4343	${CROSS_COMPILE}-objcopy -O binary \
4344				 -R .note -R .comment \
4345				 -S vmlinux linux.bin
4346
4347* compress the binary image:
4348
4349	gzip -9 linux.bin
4350
4351* package compressed binary image for U-Boot:
4352
4353	mkimage -A ppc -O linux -T kernel -C gzip \
4354		-a 0 -e 0 -n "Linux Kernel Image" \
4355		-d linux.bin.gz uImage
4356
4357
4358The "mkimage" tool can also be used to create ramdisk images for use
4359with U-Boot, either separated from the Linux kernel image, or
4360combined into one file. "mkimage" encapsulates the images with a 64
4361byte header containing information about target architecture,
4362operating system, image type, compression method, entry points, time
4363stamp, CRC32 checksums, etc.
4364
4365"mkimage" can be called in two ways: to verify existing images and
4366print the header information, or to build new images.
4367
4368In the first form (with "-l" option) mkimage lists the information
4369contained in the header of an existing U-Boot image; this includes
4370checksum verification:
4371
4372	tools/mkimage -l image
4373	  -l ==> list image header information
4374
4375The second form (with "-d" option) is used to build a U-Boot image
4376from a "data file" which is used as image payload:
4377
4378	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4379		      -n name -d data_file image
4380	  -A ==> set architecture to 'arch'
4381	  -O ==> set operating system to 'os'
4382	  -T ==> set image type to 'type'
4383	  -C ==> set compression type 'comp'
4384	  -a ==> set load address to 'addr' (hex)
4385	  -e ==> set entry point to 'ep' (hex)
4386	  -n ==> set image name to 'name'
4387	  -d ==> use image data from 'datafile'
4388
4389Right now, all Linux kernels for PowerPC systems use the same load
4390address (0x00000000), but the entry point address depends on the
4391kernel version:
4392
4393- 2.2.x kernels have the entry point at 0x0000000C,
4394- 2.3.x and later kernels have the entry point at 0x00000000.
4395
4396So a typical call to build a U-Boot image would read:
4397
4398	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4399	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4400	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4401	> examples/uImage.TQM850L
4402	Image Name:   2.4.4 kernel for TQM850L
4403	Created:      Wed Jul 19 02:34:59 2000
4404	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4405	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4406	Load Address: 0x00000000
4407	Entry Point:  0x00000000
4408
4409To verify the contents of the image (or check for corruption):
4410
4411	-> tools/mkimage -l examples/uImage.TQM850L
4412	Image Name:   2.4.4 kernel for TQM850L
4413	Created:      Wed Jul 19 02:34:59 2000
4414	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4415	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4416	Load Address: 0x00000000
4417	Entry Point:  0x00000000
4418
4419NOTE: for embedded systems where boot time is critical you can trade
4420speed for memory and install an UNCOMPRESSED image instead: this
4421needs more space in Flash, but boots much faster since it does not
4422need to be uncompressed:
4423
4424	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4425	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4426	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4427	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4428	> examples/uImage.TQM850L-uncompressed
4429	Image Name:   2.4.4 kernel for TQM850L
4430	Created:      Wed Jul 19 02:34:59 2000
4431	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4432	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4433	Load Address: 0x00000000
4434	Entry Point:  0x00000000
4435
4436
4437Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4438when your kernel is intended to use an initial ramdisk:
4439
4440	-> tools/mkimage -n 'Simple Ramdisk Image' \
4441	> -A ppc -O linux -T ramdisk -C gzip \
4442	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4443	Image Name:   Simple Ramdisk Image
4444	Created:      Wed Jan 12 14:01:50 2000
4445	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4446	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4447	Load Address: 0x00000000
4448	Entry Point:  0x00000000
4449
4450The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4451option performs the converse operation of the mkimage's second form (the "-d"
4452option). Given an image built by mkimage, the dumpimage extracts a "data file"
4453from the image:
4454
4455	tools/dumpimage -i image -T type -p position data_file
4456	  -i ==> extract from the 'image' a specific 'data_file'
4457	  -T ==> set image type to 'type'
4458	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4459
4460
4461Installing a Linux Image:
4462-------------------------
4463
4464To downloading a U-Boot image over the serial (console) interface,
4465you must convert the image to S-Record format:
4466
4467	objcopy -I binary -O srec examples/image examples/image.srec
4468
4469The 'objcopy' does not understand the information in the U-Boot
4470image header, so the resulting S-Record file will be relative to
4471address 0x00000000. To load it to a given address, you need to
4472specify the target address as 'offset' parameter with the 'loads'
4473command.
4474
4475Example: install the image to address 0x40100000 (which on the
4476TQM8xxL is in the first Flash bank):
4477
4478	=> erase 40100000 401FFFFF
4479
4480	.......... done
4481	Erased 8 sectors
4482
4483	=> loads 40100000
4484	## Ready for S-Record download ...
4485	~>examples/image.srec
4486	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4487	...
4488	15989 15990 15991 15992
4489	[file transfer complete]
4490	[connected]
4491	## Start Addr = 0x00000000
4492
4493
4494You can check the success of the download using the 'iminfo' command;
4495this includes a checksum verification so you can be sure no data
4496corruption happened:
4497
4498	=> imi 40100000
4499
4500	## Checking Image at 40100000 ...
4501	   Image Name:	 2.2.13 for initrd on TQM850L
4502	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4503	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4504	   Load Address: 00000000
4505	   Entry Point:	 0000000c
4506	   Verifying Checksum ... OK
4507
4508
4509Boot Linux:
4510-----------
4511
4512The "bootm" command is used to boot an application that is stored in
4513memory (RAM or Flash). In case of a Linux kernel image, the contents
4514of the "bootargs" environment variable is passed to the kernel as
4515parameters. You can check and modify this variable using the
4516"printenv" and "setenv" commands:
4517
4518
4519	=> printenv bootargs
4520	bootargs=root=/dev/ram
4521
4522	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4523
4524	=> printenv bootargs
4525	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4526
4527	=> bootm 40020000
4528	## Booting Linux kernel at 40020000 ...
4529	   Image Name:	 2.2.13 for NFS on TQM850L
4530	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4531	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4532	   Load Address: 00000000
4533	   Entry Point:	 0000000c
4534	   Verifying Checksum ... OK
4535	   Uncompressing Kernel Image ... OK
4536	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
4537	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4538	time_init: decrementer frequency = 187500000/60
4539	Calibrating delay loop... 49.77 BogoMIPS
4540	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4541	...
4542
4543If you want to boot a Linux kernel with initial RAM disk, you pass
4544the memory addresses of both the kernel and the initrd image (PPBCOOT
4545format!) to the "bootm" command:
4546
4547	=> imi 40100000 40200000
4548
4549	## Checking Image at 40100000 ...
4550	   Image Name:	 2.2.13 for initrd on TQM850L
4551	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4552	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4553	   Load Address: 00000000
4554	   Entry Point:	 0000000c
4555	   Verifying Checksum ... OK
4556
4557	## Checking Image at 40200000 ...
4558	   Image Name:	 Simple Ramdisk Image
4559	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4560	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4561	   Load Address: 00000000
4562	   Entry Point:	 00000000
4563	   Verifying Checksum ... OK
4564
4565	=> bootm 40100000 40200000
4566	## Booting Linux kernel at 40100000 ...
4567	   Image Name:	 2.2.13 for initrd on TQM850L
4568	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4569	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4570	   Load Address: 00000000
4571	   Entry Point:	 0000000c
4572	   Verifying Checksum ... OK
4573	   Uncompressing Kernel Image ... OK
4574	## Loading RAMDisk Image at 40200000 ...
4575	   Image Name:	 Simple Ramdisk Image
4576	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4577	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4578	   Load Address: 00000000
4579	   Entry Point:	 00000000
4580	   Verifying Checksum ... OK
4581	   Loading Ramdisk ... OK
4582	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
4583	Boot arguments: root=/dev/ram
4584	time_init: decrementer frequency = 187500000/60
4585	Calibrating delay loop... 49.77 BogoMIPS
4586	...
4587	RAMDISK: Compressed image found at block 0
4588	VFS: Mounted root (ext2 filesystem).
4589
4590	bash#
4591
4592Boot Linux and pass a flat device tree:
4593-----------
4594
4595First, U-Boot must be compiled with the appropriate defines. See the section
4596titled "Linux Kernel Interface" above for a more in depth explanation. The
4597following is an example of how to start a kernel and pass an updated
4598flat device tree:
4599
4600=> print oftaddr
4601oftaddr=0x300000
4602=> print oft
4603oft=oftrees/mpc8540ads.dtb
4604=> tftp $oftaddr $oft
4605Speed: 1000, full duplex
4606Using TSEC0 device
4607TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4608Filename 'oftrees/mpc8540ads.dtb'.
4609Load address: 0x300000
4610Loading: #
4611done
4612Bytes transferred = 4106 (100a hex)
4613=> tftp $loadaddr $bootfile
4614Speed: 1000, full duplex
4615Using TSEC0 device
4616TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4617Filename 'uImage'.
4618Load address: 0x200000
4619Loading:############
4620done
4621Bytes transferred = 1029407 (fb51f hex)
4622=> print loadaddr
4623loadaddr=200000
4624=> print oftaddr
4625oftaddr=0x300000
4626=> bootm $loadaddr - $oftaddr
4627## Booting image at 00200000 ...
4628   Image Name:	 Linux-2.6.17-dirty
4629   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4630   Data Size:	 1029343 Bytes = 1005.2 kB
4631   Load Address: 00000000
4632   Entry Point:	 00000000
4633   Verifying Checksum ... OK
4634   Uncompressing Kernel Image ... OK
4635Booting using flat device tree at 0x300000
4636Using MPC85xx ADS machine description
4637Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4638[snip]
4639
4640
4641More About U-Boot Image Types:
4642------------------------------
4643
4644U-Boot supports the following image types:
4645
4646   "Standalone Programs" are directly runnable in the environment
4647	provided by U-Boot; it is expected that (if they behave
4648	well) you can continue to work in U-Boot after return from
4649	the Standalone Program.
4650   "OS Kernel Images" are usually images of some Embedded OS which
4651	will take over control completely. Usually these programs
4652	will install their own set of exception handlers, device
4653	drivers, set up the MMU, etc. - this means, that you cannot
4654	expect to re-enter U-Boot except by resetting the CPU.
4655   "RAMDisk Images" are more or less just data blocks, and their
4656	parameters (address, size) are passed to an OS kernel that is
4657	being started.
4658   "Multi-File Images" contain several images, typically an OS
4659	(Linux) kernel image and one or more data images like
4660	RAMDisks. This construct is useful for instance when you want
4661	to boot over the network using BOOTP etc., where the boot
4662	server provides just a single image file, but you want to get
4663	for instance an OS kernel and a RAMDisk image.
4664
4665	"Multi-File Images" start with a list of image sizes, each
4666	image size (in bytes) specified by an "uint32_t" in network
4667	byte order. This list is terminated by an "(uint32_t)0".
4668	Immediately after the terminating 0 follow the images, one by
4669	one, all aligned on "uint32_t" boundaries (size rounded up to
4670	a multiple of 4 bytes).
4671
4672   "Firmware Images" are binary images containing firmware (like
4673	U-Boot or FPGA images) which usually will be programmed to
4674	flash memory.
4675
4676   "Script files" are command sequences that will be executed by
4677	U-Boot's command interpreter; this feature is especially
4678	useful when you configure U-Boot to use a real shell (hush)
4679	as command interpreter.
4680
4681Booting the Linux zImage:
4682-------------------------
4683
4684On some platforms, it's possible to boot Linux zImage. This is done
4685using the "bootz" command. The syntax of "bootz" command is the same
4686as the syntax of "bootm" command.
4687
4688Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4689kernel with raw initrd images. The syntax is slightly different, the
4690address of the initrd must be augmented by it's size, in the following
4691format: "<initrd addres>:<initrd size>".
4692
4693
4694Standalone HOWTO:
4695=================
4696
4697One of the features of U-Boot is that you can dynamically load and
4698run "standalone" applications, which can use some resources of
4699U-Boot like console I/O functions or interrupt services.
4700
4701Two simple examples are included with the sources:
4702
4703"Hello World" Demo:
4704-------------------
4705
4706'examples/hello_world.c' contains a small "Hello World" Demo
4707application; it is automatically compiled when you build U-Boot.
4708It's configured to run at address 0x00040004, so you can play with it
4709like that:
4710
4711	=> loads
4712	## Ready for S-Record download ...
4713	~>examples/hello_world.srec
4714	1 2 3 4 5 6 7 8 9 10 11 ...
4715	[file transfer complete]
4716	[connected]
4717	## Start Addr = 0x00040004
4718
4719	=> go 40004 Hello World! This is a test.
4720	## Starting application at 0x00040004 ...
4721	Hello World
4722	argc = 7
4723	argv[0] = "40004"
4724	argv[1] = "Hello"
4725	argv[2] = "World!"
4726	argv[3] = "This"
4727	argv[4] = "is"
4728	argv[5] = "a"
4729	argv[6] = "test."
4730	argv[7] = "<NULL>"
4731	Hit any key to exit ...
4732
4733	## Application terminated, rc = 0x0
4734
4735Another example, which demonstrates how to register a CPM interrupt
4736handler with the U-Boot code, can be found in 'examples/timer.c'.
4737Here, a CPM timer is set up to generate an interrupt every second.
4738The interrupt service routine is trivial, just printing a '.'
4739character, but this is just a demo program. The application can be
4740controlled by the following keys:
4741
4742	? - print current values og the CPM Timer registers
4743	b - enable interrupts and start timer
4744	e - stop timer and disable interrupts
4745	q - quit application
4746
4747	=> loads
4748	## Ready for S-Record download ...
4749	~>examples/timer.srec
4750	1 2 3 4 5 6 7 8 9 10 11 ...
4751	[file transfer complete]
4752	[connected]
4753	## Start Addr = 0x00040004
4754
4755	=> go 40004
4756	## Starting application at 0x00040004 ...
4757	TIMERS=0xfff00980
4758	Using timer 1
4759	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4760
4761Hit 'b':
4762	[q, b, e, ?] Set interval 1000000 us
4763	Enabling timer
4764Hit '?':
4765	[q, b, e, ?] ........
4766	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4767Hit '?':
4768	[q, b, e, ?] .
4769	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4770Hit '?':
4771	[q, b, e, ?] .
4772	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4773Hit '?':
4774	[q, b, e, ?] .
4775	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4776Hit 'e':
4777	[q, b, e, ?] ...Stopping timer
4778Hit 'q':
4779	[q, b, e, ?] ## Application terminated, rc = 0x0
4780
4781
4782Minicom warning:
4783================
4784
4785Over time, many people have reported problems when trying to use the
4786"minicom" terminal emulation program for serial download. I (wd)
4787consider minicom to be broken, and recommend not to use it. Under
4788Unix, I recommend to use C-Kermit for general purpose use (and
4789especially for kermit binary protocol download ("loadb" command), and
4790use "cu" for S-Record download ("loads" command).  See
4791http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4792for help with kermit.
4793
4794
4795Nevertheless, if you absolutely want to use it try adding this
4796configuration to your "File transfer protocols" section:
4797
4798	   Name	   Program			Name U/D FullScr IO-Red. Multi
4799	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4800	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4801
4802
4803NetBSD Notes:
4804=============
4805
4806Starting at version 0.9.2, U-Boot supports NetBSD both as host
4807(build U-Boot) and target system (boots NetBSD/mpc8xx).
4808
4809Building requires a cross environment; it is known to work on
4810NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4811need gmake since the Makefiles are not compatible with BSD make).
4812Note that the cross-powerpc package does not install include files;
4813attempting to build U-Boot will fail because <machine/ansi.h> is
4814missing.  This file has to be installed and patched manually:
4815
4816	# cd /usr/pkg/cross/powerpc-netbsd/include
4817	# mkdir powerpc
4818	# ln -s powerpc machine
4819	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4820	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4821
4822Native builds *don't* work due to incompatibilities between native
4823and U-Boot include files.
4824
4825Booting assumes that (the first part of) the image booted is a
4826stage-2 loader which in turn loads and then invokes the kernel
4827proper. Loader sources will eventually appear in the NetBSD source
4828tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4829meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4830
4831
4832Implementation Internals:
4833=========================
4834
4835The following is not intended to be a complete description of every
4836implementation detail. However, it should help to understand the
4837inner workings of U-Boot and make it easier to port it to custom
4838hardware.
4839
4840
4841Initial Stack, Global Data:
4842---------------------------
4843
4844The implementation of U-Boot is complicated by the fact that U-Boot
4845starts running out of ROM (flash memory), usually without access to
4846system RAM (because the memory controller is not initialized yet).
4847This means that we don't have writable Data or BSS segments, and BSS
4848is not initialized as zero. To be able to get a C environment working
4849at all, we have to allocate at least a minimal stack. Implementation
4850options for this are defined and restricted by the CPU used: Some CPU
4851models provide on-chip memory (like the IMMR area on MPC8xx and
4852MPC826x processors), on others (parts of) the data cache can be
4853locked as (mis-) used as memory, etc.
4854
4855	Chris Hallinan posted a good summary of these issues to the
4856	U-Boot mailing list:
4857
4858	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4859	From: "Chris Hallinan" <clh@net1plus.com>
4860	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4861	...
4862
4863	Correct me if I'm wrong, folks, but the way I understand it
4864	is this: Using DCACHE as initial RAM for Stack, etc, does not
4865	require any physical RAM backing up the cache. The cleverness
4866	is that the cache is being used as a temporary supply of
4867	necessary storage before the SDRAM controller is setup. It's
4868	beyond the scope of this list to explain the details, but you
4869	can see how this works by studying the cache architecture and
4870	operation in the architecture and processor-specific manuals.
4871
4872	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4873	is another option for the system designer to use as an
4874	initial stack/RAM area prior to SDRAM being available. Either
4875	option should work for you. Using CS 4 should be fine if your
4876	board designers haven't used it for something that would
4877	cause you grief during the initial boot! It is frequently not
4878	used.
4879
4880	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4881	with your processor/board/system design. The default value
4882	you will find in any recent u-boot distribution in
4883	walnut.h should work for you. I'd set it to a value larger
4884	than your SDRAM module. If you have a 64MB SDRAM module, set
4885	it above 400_0000. Just make sure your board has no resources
4886	that are supposed to respond to that address! That code in
4887	start.S has been around a while and should work as is when
4888	you get the config right.
4889
4890	-Chris Hallinan
4891	DS4.COM, Inc.
4892
4893It is essential to remember this, since it has some impact on the C
4894code for the initialization procedures:
4895
4896* Initialized global data (data segment) is read-only. Do not attempt
4897  to write it.
4898
4899* Do not use any uninitialized global data (or implicitly initialized
4900  as zero data - BSS segment) at all - this is undefined, initiali-
4901  zation is performed later (when relocating to RAM).
4902
4903* Stack space is very limited. Avoid big data buffers or things like
4904  that.
4905
4906Having only the stack as writable memory limits means we cannot use
4907normal global data to share information between the code. But it
4908turned out that the implementation of U-Boot can be greatly
4909simplified by making a global data structure (gd_t) available to all
4910functions. We could pass a pointer to this data as argument to _all_
4911functions, but this would bloat the code. Instead we use a feature of
4912the GCC compiler (Global Register Variables) to share the data: we
4913place a pointer (gd) to the global data into a register which we
4914reserve for this purpose.
4915
4916When choosing a register for such a purpose we are restricted by the
4917relevant  (E)ABI  specifications for the current architecture, and by
4918GCC's implementation.
4919
4920For PowerPC, the following registers have specific use:
4921	R1:	stack pointer
4922	R2:	reserved for system use
4923	R3-R4:	parameter passing and return values
4924	R5-R10: parameter passing
4925	R13:	small data area pointer
4926	R30:	GOT pointer
4927	R31:	frame pointer
4928
4929	(U-Boot also uses R12 as internal GOT pointer. r12
4930	is a volatile register so r12 needs to be reset when
4931	going back and forth between asm and C)
4932
4933    ==> U-Boot will use R2 to hold a pointer to the global data
4934
4935    Note: on PPC, we could use a static initializer (since the
4936    address of the global data structure is known at compile time),
4937    but it turned out that reserving a register results in somewhat
4938    smaller code - although the code savings are not that big (on
4939    average for all boards 752 bytes for the whole U-Boot image,
4940    624 text + 127 data).
4941
4942On ARM, the following registers are used:
4943
4944	R0:	function argument word/integer result
4945	R1-R3:	function argument word
4946	R9:	platform specific
4947	R10:	stack limit (used only if stack checking is enabled)
4948	R11:	argument (frame) pointer
4949	R12:	temporary workspace
4950	R13:	stack pointer
4951	R14:	link register
4952	R15:	program counter
4953
4954    ==> U-Boot will use R9 to hold a pointer to the global data
4955
4956    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4957
4958On Nios II, the ABI is documented here:
4959	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4960
4961    ==> U-Boot will use gp to hold a pointer to the global data
4962
4963    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4964    to access small data sections, so gp is free.
4965
4966On NDS32, the following registers are used:
4967
4968	R0-R1:	argument/return
4969	R2-R5:	argument
4970	R15:	temporary register for assembler
4971	R16:	trampoline register
4972	R28:	frame pointer (FP)
4973	R29:	global pointer (GP)
4974	R30:	link register (LP)
4975	R31:	stack pointer (SP)
4976	PC:	program counter (PC)
4977
4978    ==> U-Boot will use R10 to hold a pointer to the global data
4979
4980NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4981or current versions of GCC may "optimize" the code too much.
4982
4983Memory Management:
4984------------------
4985
4986U-Boot runs in system state and uses physical addresses, i.e. the
4987MMU is not used either for address mapping nor for memory protection.
4988
4989The available memory is mapped to fixed addresses using the memory
4990controller. In this process, a contiguous block is formed for each
4991memory type (Flash, SDRAM, SRAM), even when it consists of several
4992physical memory banks.
4993
4994U-Boot is installed in the first 128 kB of the first Flash bank (on
4995TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4996booting and sizing and initializing DRAM, the code relocates itself
4997to the upper end of DRAM. Immediately below the U-Boot code some
4998memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4999configuration setting]. Below that, a structure with global Board
5000Info data is placed, followed by the stack (growing downward).
5001
5002Additionally, some exception handler code is copied to the low 8 kB
5003of DRAM (0x00000000 ... 0x00001FFF).
5004
5005So a typical memory configuration with 16 MB of DRAM could look like
5006this:
5007
5008	0x0000 0000	Exception Vector code
5009	      :
5010	0x0000 1FFF
5011	0x0000 2000	Free for Application Use
5012	      :
5013	      :
5014
5015	      :
5016	      :
5017	0x00FB FF20	Monitor Stack (Growing downward)
5018	0x00FB FFAC	Board Info Data and permanent copy of global data
5019	0x00FC 0000	Malloc Arena
5020	      :
5021	0x00FD FFFF
5022	0x00FE 0000	RAM Copy of Monitor Code
5023	...		eventually: LCD or video framebuffer
5024	...		eventually: pRAM (Protected RAM - unchanged by reset)
5025	0x00FF FFFF	[End of RAM]
5026
5027
5028System Initialization:
5029----------------------
5030
5031In the reset configuration, U-Boot starts at the reset entry point
5032(on most PowerPC systems at address 0x00000100). Because of the reset
5033configuration for CS0# this is a mirror of the on board Flash memory.
5034To be able to re-map memory U-Boot then jumps to its link address.
5035To be able to implement the initialization code in C, a (small!)
5036initial stack is set up in the internal Dual Ported RAM (in case CPUs
5037which provide such a feature like), or in a locked part of the data
5038cache. After that, U-Boot initializes the CPU core, the caches and
5039the SIU.
5040
5041Next, all (potentially) available memory banks are mapped using a
5042preliminary mapping. For example, we put them on 512 MB boundaries
5043(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5044on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5045programmed for SDRAM access. Using the temporary configuration, a
5046simple memory test is run that determines the size of the SDRAM
5047banks.
5048
5049When there is more than one SDRAM bank, and the banks are of
5050different size, the largest is mapped first. For equal size, the first
5051bank (CS2#) is mapped first. The first mapping is always for address
50520x00000000, with any additional banks following immediately to create
5053contiguous memory starting from 0.
5054
5055Then, the monitor installs itself at the upper end of the SDRAM area
5056and allocates memory for use by malloc() and for the global Board
5057Info data; also, the exception vector code is copied to the low RAM
5058pages, and the final stack is set up.
5059
5060Only after this relocation will you have a "normal" C environment;
5061until that you are restricted in several ways, mostly because you are
5062running from ROM, and because the code will have to be relocated to a
5063new address in RAM.
5064
5065
5066U-Boot Porting Guide:
5067----------------------
5068
5069[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5070list, October 2002]
5071
5072
5073int main(int argc, char *argv[])
5074{
5075	sighandler_t no_more_time;
5076
5077	signal(SIGALRM, no_more_time);
5078	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5079
5080	if (available_money > available_manpower) {
5081		Pay consultant to port U-Boot;
5082		return 0;
5083	}
5084
5085	Download latest U-Boot source;
5086
5087	Subscribe to u-boot mailing list;
5088
5089	if (clueless)
5090		email("Hi, I am new to U-Boot, how do I get started?");
5091
5092	while (learning) {
5093		Read the README file in the top level directory;
5094		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5095		Read applicable doc/*.README;
5096		Read the source, Luke;
5097		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5098	}
5099
5100	if (available_money > toLocalCurrency ($2500))
5101		Buy a BDI3000;
5102	else
5103		Add a lot of aggravation and time;
5104
5105	if (a similar board exists) {	/* hopefully... */
5106		cp -a board/<similar> board/<myboard>
5107		cp include/configs/<similar>.h include/configs/<myboard>.h
5108	} else {
5109		Create your own board support subdirectory;
5110		Create your own board include/configs/<myboard>.h file;
5111	}
5112	Edit new board/<myboard> files
5113	Edit new include/configs/<myboard>.h
5114
5115	while (!accepted) {
5116		while (!running) {
5117			do {
5118				Add / modify source code;
5119			} until (compiles);
5120			Debug;
5121			if (clueless)
5122				email("Hi, I am having problems...");
5123		}
5124		Send patch file to the U-Boot email list;
5125		if (reasonable critiques)
5126			Incorporate improvements from email list code review;
5127		else
5128			Defend code as written;
5129	}
5130
5131	return 0;
5132}
5133
5134void no_more_time (int sig)
5135{
5136      hire_a_guru();
5137}
5138
5139
5140Coding Standards:
5141-----------------
5142
5143All contributions to U-Boot should conform to the Linux kernel
5144coding style; see the file "Documentation/CodingStyle" and the script
5145"scripts/Lindent" in your Linux kernel source directory.
5146
5147Source files originating from a different project (for example the
5148MTD subsystem) are generally exempt from these guidelines and are not
5149reformatted to ease subsequent migration to newer versions of those
5150sources.
5151
5152Please note that U-Boot is implemented in C (and to some small parts in
5153Assembler); no C++ is used, so please do not use C++ style comments (//)
5154in your code.
5155
5156Please also stick to the following formatting rules:
5157- remove any trailing white space
5158- use TAB characters for indentation and vertical alignment, not spaces
5159- make sure NOT to use DOS '\r\n' line feeds
5160- do not add more than 2 consecutive empty lines to source files
5161- do not add trailing empty lines to source files
5162
5163Submissions which do not conform to the standards may be returned
5164with a request to reformat the changes.
5165
5166
5167Submitting Patches:
5168-------------------
5169
5170Since the number of patches for U-Boot is growing, we need to
5171establish some rules. Submissions which do not conform to these rules
5172may be rejected, even when they contain important and valuable stuff.
5173
5174Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5175
5176Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5177see http://lists.denx.de/mailman/listinfo/u-boot
5178
5179When you send a patch, please include the following information with
5180it:
5181
5182* For bug fixes: a description of the bug and how your patch fixes
5183  this bug. Please try to include a way of demonstrating that the
5184  patch actually fixes something.
5185
5186* For new features: a description of the feature and your
5187  implementation.
5188
5189* A CHANGELOG entry as plaintext (separate from the patch)
5190
5191* For major contributions, add a MAINTAINERS file with your
5192  information and associated file and directory references.
5193
5194* When you add support for a new board, don't forget to add a
5195  maintainer e-mail address to the boards.cfg file, too.
5196
5197* If your patch adds new configuration options, don't forget to
5198  document these in the README file.
5199
5200* The patch itself. If you are using git (which is *strongly*
5201  recommended) you can easily generate the patch using the
5202  "git format-patch". If you then use "git send-email" to send it to
5203  the U-Boot mailing list, you will avoid most of the common problems
5204  with some other mail clients.
5205
5206  If you cannot use git, use "diff -purN OLD NEW". If your version of
5207  diff does not support these options, then get the latest version of
5208  GNU diff.
5209
5210  The current directory when running this command shall be the parent
5211  directory of the U-Boot source tree (i. e. please make sure that
5212  your patch includes sufficient directory information for the
5213  affected files).
5214
5215  We prefer patches as plain text. MIME attachments are discouraged,
5216  and compressed attachments must not be used.
5217
5218* If one logical set of modifications affects or creates several
5219  files, all these changes shall be submitted in a SINGLE patch file.
5220
5221* Changesets that contain different, unrelated modifications shall be
5222  submitted as SEPARATE patches, one patch per changeset.
5223
5224
5225Notes:
5226
5227* Before sending the patch, run the buildman script on your patched
5228  source tree and make sure that no errors or warnings are reported
5229  for any of the boards.
5230
5231* Keep your modifications to the necessary minimum: A patch
5232  containing several unrelated changes or arbitrary reformats will be
5233  returned with a request to re-formatting / split it.
5234
5235* If you modify existing code, make sure that your new code does not
5236  add to the memory footprint of the code ;-) Small is beautiful!
5237  When adding new features, these should compile conditionally only
5238  (using #ifdef), and the resulting code with the new feature
5239  disabled must not need more memory than the old code without your
5240  modification.
5241
5242* Remember that there is a size limit of 100 kB per message on the
5243  u-boot mailing list. Bigger patches will be moderated. If they are
5244  reasonable and not too big, they will be acknowledged. But patches
5245  bigger than the size limit should be avoided.
5246