xref: /openbmc/u-boot/README (revision 7f666555)
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
316The following options need to be configured:
317
318- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
319
320- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
321
322- Marvell Family Member
323		CONFIG_SYS_MVFS		- define it if you want to enable
324					  multiple fs option at one time
325					  for marvell soc family
326
327- 85xx CPU Options:
328		CONFIG_SYS_PPC64
329
330		Specifies that the core is a 64-bit PowerPC implementation (implements
331		the "64" category of the Power ISA). This is necessary for ePAPR
332		compliance, among other possible reasons.
333
334		CONFIG_SYS_FSL_TBCLK_DIV
335
336		Defines the core time base clock divider ratio compared to the
337		system clock.  On most PQ3 devices this is 8, on newer QorIQ
338		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
339
340		CONFIG_SYS_FSL_PCIE_COMPAT
341
342		Defines the string to utilize when trying to match PCIe device
343		tree nodes for the given platform.
344
345		CONFIG_SYS_FSL_ERRATUM_A004510
346
347		Enables a workaround for erratum A004510.  If set,
348		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
349		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
350
351		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
352		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
353
354		Defines one or two SoC revisions (low 8 bits of SVR)
355		for which the A004510 workaround should be applied.
356
357		The rest of SVR is either not relevant to the decision
358		of whether the erratum is present (e.g. p2040 versus
359		p2041) or is implied by the build target, which controls
360		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
361
362		See Freescale App Note 4493 for more information about
363		this erratum.
364
365		CONFIG_A003399_NOR_WORKAROUND
366		Enables a workaround for IFC erratum A003399. It is only
367		required during NOR boot.
368
369		CONFIG_A008044_WORKAROUND
370		Enables a workaround for T1040/T1042 erratum A008044. It is only
371		required during NAND boot and valid for Rev 1.0 SoC revision
372
373		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
374
375		This is the value to write into CCSR offset 0x18600
376		according to the A004510 workaround.
377
378		CONFIG_SYS_FSL_DSP_DDR_ADDR
379		This value denotes start offset of DDR memory which is
380		connected exclusively to the DSP cores.
381
382		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
383		This value denotes start offset of M2 memory
384		which is directly connected to the DSP core.
385
386		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
387		This value denotes start offset of M3 memory which is directly
388		connected to the DSP core.
389
390		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
391		This value denotes start offset of DSP CCSR space.
392
393		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
394		Single Source Clock is clocking mode present in some of FSL SoC's.
395		In this mode, a single differential clock is used to supply
396		clocks to the sysclock, ddrclock and usbclock.
397
398		CONFIG_SYS_CPC_REINIT_F
399		This CONFIG is defined when the CPC is configured as SRAM at the
400		time of U-Boot entry and is required to be re-initialized.
401
402		CONFIG_DEEP_SLEEP
403		Indicates this SoC supports deep sleep feature. If deep sleep is
404		supported, core will start to execute uboot when wakes up.
405
406- Generic CPU options:
407		CONFIG_SYS_GENERIC_GLOBAL_DATA
408		Defines global data is initialized in generic board board_init_f().
409		If this macro is defined, global data is created and cleared in
410		generic board board_init_f(). Without this macro, architecture/board
411		should initialize global data before calling board_init_f().
412
413		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
414
415		Defines the endianess of the CPU. Implementation of those
416		values is arch specific.
417
418		CONFIG_SYS_FSL_DDR
419		Freescale DDR driver in use. This type of DDR controller is
420		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
421		SoCs.
422
423		CONFIG_SYS_FSL_DDR_ADDR
424		Freescale DDR memory-mapped register base.
425
426		CONFIG_SYS_FSL_DDR_EMU
427		Specify emulator support for DDR. Some DDR features such as
428		deskew training are not available.
429
430		CONFIG_SYS_FSL_DDRC_GEN1
431		Freescale DDR1 controller.
432
433		CONFIG_SYS_FSL_DDRC_GEN2
434		Freescale DDR2 controller.
435
436		CONFIG_SYS_FSL_DDRC_GEN3
437		Freescale DDR3 controller.
438
439		CONFIG_SYS_FSL_DDRC_GEN4
440		Freescale DDR4 controller.
441
442		CONFIG_SYS_FSL_DDRC_ARM_GEN3
443		Freescale DDR3 controller for ARM-based SoCs.
444
445		CONFIG_SYS_FSL_DDR1
446		Board config to use DDR1. It can be enabled for SoCs with
447		Freescale DDR1 or DDR2 controllers, depending on the board
448		implemetation.
449
450		CONFIG_SYS_FSL_DDR2
451		Board config to use DDR2. It can be enabled for SoCs with
452		Freescale DDR2 or DDR3 controllers, depending on the board
453		implementation.
454
455		CONFIG_SYS_FSL_DDR3
456		Board config to use DDR3. It can be enabled for SoCs with
457		Freescale DDR3 or DDR3L controllers.
458
459		CONFIG_SYS_FSL_DDR3L
460		Board config to use DDR3L. It can be enabled for SoCs with
461		DDR3L controllers.
462
463		CONFIG_SYS_FSL_DDR4
464		Board config to use DDR4. It can be enabled for SoCs with
465		DDR4 controllers.
466
467		CONFIG_SYS_FSL_IFC_BE
468		Defines the IFC controller register space as Big Endian
469
470		CONFIG_SYS_FSL_IFC_LE
471		Defines the IFC controller register space as Little Endian
472
473		CONFIG_SYS_FSL_IFC_CLK_DIV
474		Defines divider of platform clock(clock input to IFC controller).
475
476		CONFIG_SYS_FSL_LBC_CLK_DIV
477		Defines divider of platform clock(clock input to eLBC controller).
478
479		CONFIG_SYS_FSL_PBL_PBI
480		It enables addition of RCW (Power on reset configuration) in built image.
481		Please refer doc/README.pblimage for more details
482
483		CONFIG_SYS_FSL_PBL_RCW
484		It adds PBI(pre-boot instructions) commands in u-boot build image.
485		PBI commands can be used to configure SoC before it starts the execution.
486		Please refer doc/README.pblimage for more details
487
488		CONFIG_SPL_FSL_PBL
489		It adds a target to create boot binary having SPL binary in PBI format
490		concatenated with u-boot binary.
491
492		CONFIG_SYS_FSL_DDR_BE
493		Defines the DDR controller register space as Big Endian
494
495		CONFIG_SYS_FSL_DDR_LE
496		Defines the DDR controller register space as Little Endian
497
498		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
499		Physical address from the view of DDR controllers. It is the
500		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
501		it could be different for ARM SoCs.
502
503		CONFIG_SYS_FSL_DDR_INTLV_256B
504		DDR controller interleaving on 256-byte. This is a special
505		interleaving mode, handled by Dickens for Freescale layerscape
506		SoCs with ARM core.
507
508		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
509		Number of controllers used as main memory.
510
511		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
512		Number of controllers used for other than main memory.
513
514		CONFIG_SYS_FSL_HAS_DP_DDR
515		Defines the SoC has DP-DDR used for DPAA.
516
517		CONFIG_SYS_FSL_SEC_BE
518		Defines the SEC controller register space as Big Endian
519
520		CONFIG_SYS_FSL_SEC_LE
521		Defines the SEC controller register space as Little Endian
522
523- MIPS CPU options:
524		CONFIG_SYS_INIT_SP_OFFSET
525
526		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
527		pointer. This is needed for the temporary stack before
528		relocation.
529
530		CONFIG_SYS_MIPS_CACHE_MODE
531
532		Cache operation mode for the MIPS CPU.
533		See also arch/mips/include/asm/mipsregs.h.
534		Possible values are:
535			CONF_CM_CACHABLE_NO_WA
536			CONF_CM_CACHABLE_WA
537			CONF_CM_UNCACHED
538			CONF_CM_CACHABLE_NONCOHERENT
539			CONF_CM_CACHABLE_CE
540			CONF_CM_CACHABLE_COW
541			CONF_CM_CACHABLE_CUW
542			CONF_CM_CACHABLE_ACCELERATED
543
544		CONFIG_SYS_XWAY_EBU_BOOTCFG
545
546		Special option for Lantiq XWAY SoCs for booting from NOR flash.
547		See also arch/mips/cpu/mips32/start.S.
548
549		CONFIG_XWAY_SWAP_BYTES
550
551		Enable compilation of tools/xway-swap-bytes needed for Lantiq
552		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
553		be swapped if a flash programmer is used.
554
555- ARM options:
556		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
557
558		Select high exception vectors of the ARM core, e.g., do not
559		clear the V bit of the c1 register of CP15.
560
561		COUNTER_FREQUENCY
562		Generic timer clock source frequency.
563
564		COUNTER_FREQUENCY_REAL
565		Generic timer clock source frequency if the real clock is
566		different from COUNTER_FREQUENCY, and can only be determined
567		at run time.
568
569- Tegra SoC options:
570		CONFIG_TEGRA_SUPPORT_NON_SECURE
571
572		Support executing U-Boot in non-secure (NS) mode. Certain
573		impossible actions will be skipped if the CPU is in NS mode,
574		such as ARM architectural timer initialization.
575
576- Linux Kernel Interface:
577		CONFIG_CLOCKS_IN_MHZ
578
579		U-Boot stores all clock information in Hz
580		internally. For binary compatibility with older Linux
581		kernels (which expect the clocks passed in the
582		bd_info data to be in MHz) the environment variable
583		"clocks_in_mhz" can be defined so that U-Boot
584		converts clock data to MHZ before passing it to the
585		Linux kernel.
586		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
587		"clocks_in_mhz=1" is automatically included in the
588		default environment.
589
590		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
591
592		When transferring memsize parameter to Linux, some versions
593		expect it to be in bytes, others in MB.
594		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
595
596		CONFIG_OF_LIBFDT
597
598		New kernel versions are expecting firmware settings to be
599		passed using flattened device trees (based on open firmware
600		concepts).
601
602		CONFIG_OF_LIBFDT
603		 * New libfdt-based support
604		 * Adds the "fdt" command
605		 * The bootm command automatically updates the fdt
606
607		OF_TBCLK - The timebase frequency.
608		OF_STDOUT_PATH - The path to the console device
609
610		boards with QUICC Engines require OF_QE to set UCC MAC
611		addresses
612
613		CONFIG_OF_BOARD_SETUP
614
615		Board code has addition modification that it wants to make
616		to the flat device tree before handing it off to the kernel
617
618		CONFIG_OF_SYSTEM_SETUP
619
620		Other code has addition modification that it wants to make
621		to the flat device tree before handing it off to the kernel.
622		This causes ft_system_setup() to be called before booting
623		the kernel.
624
625		CONFIG_OF_IDE_FIXUP
626
627		U-Boot can detect if an IDE device is present or not.
628		If not, and this new config option is activated, U-Boot
629		removes the ATA node from the DTS before booting Linux,
630		so the Linux IDE driver does not probe the device and
631		crash. This is needed for buggy hardware (uc101) where
632		no pull down resistor is connected to the signal IDE5V_DD7.
633
634		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
635
636		This setting is mandatory for all boards that have only one
637		machine type and must be used to specify the machine type
638		number as it appears in the ARM machine registry
639		(see http://www.arm.linux.org.uk/developer/machines/).
640		Only boards that have multiple machine types supported
641		in a single configuration file and the machine type is
642		runtime discoverable, do not have to use this setting.
643
644- vxWorks boot parameters:
645
646		bootvx constructs a valid bootline using the following
647		environments variables: bootdev, bootfile, ipaddr, netmask,
648		serverip, gatewayip, hostname, othbootargs.
649		It loads the vxWorks image pointed bootfile.
650
651		Note: If a "bootargs" environment is defined, it will overwride
652		the defaults discussed just above.
653
654- Cache Configuration:
655		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
656		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
657		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
658
659- Cache Configuration for ARM:
660		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
661				      controller
662		CONFIG_SYS_PL310_BASE - Physical base address of PL310
663					controller register space
664
665- Serial Ports:
666		CONFIG_PL010_SERIAL
667
668		Define this if you want support for Amba PrimeCell PL010 UARTs.
669
670		CONFIG_PL011_SERIAL
671
672		Define this if you want support for Amba PrimeCell PL011 UARTs.
673
674		CONFIG_PL011_CLOCK
675
676		If you have Amba PrimeCell PL011 UARTs, set this variable to
677		the clock speed of the UARTs.
678
679		CONFIG_PL01x_PORTS
680
681		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
682		define this to a list of base addresses for each (supported)
683		port. See e.g. include/configs/versatile.h
684
685		CONFIG_SERIAL_HW_FLOW_CONTROL
686
687		Define this variable to enable hw flow control in serial driver.
688		Current user of this option is drivers/serial/nsl16550.c driver
689
690- Console Baudrate:
691		CONFIG_BAUDRATE - in bps
692		Select one of the baudrates listed in
693		CONFIG_SYS_BAUDRATE_TABLE, see below.
694
695- Autoboot Command:
696		CONFIG_BOOTCOMMAND
697		Only needed when CONFIG_BOOTDELAY is enabled;
698		define a command string that is automatically executed
699		when no character is read on the console interface
700		within "Boot Delay" after reset.
701
702		CONFIG_BOOTARGS
703		This can be used to pass arguments to the bootm
704		command. The value of CONFIG_BOOTARGS goes into the
705		environment value "bootargs".
706
707		CONFIG_RAMBOOT and CONFIG_NFSBOOT
708		The value of these goes into the environment as
709		"ramboot" and "nfsboot" respectively, and can be used
710		as a convenience, when switching between booting from
711		RAM and NFS.
712
713- Bootcount:
714		CONFIG_BOOTCOUNT_LIMIT
715		Implements a mechanism for detecting a repeating reboot
716		cycle, see:
717		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
718
719		CONFIG_BOOTCOUNT_ENV
720		If no softreset save registers are found on the hardware
721		"bootcount" is stored in the environment. To prevent a
722		saveenv on all reboots, the environment variable
723		"upgrade_available" is used. If "upgrade_available" is
724		0, "bootcount" is always 0, if "upgrade_available" is
725		1 "bootcount" is incremented in the environment.
726		So the Userspace Applikation must set the "upgrade_available"
727		and "bootcount" variable to 0, if a boot was successfully.
728
729- Pre-Boot Commands:
730		CONFIG_PREBOOT
731
732		When this option is #defined, the existence of the
733		environment variable "preboot" will be checked
734		immediately before starting the CONFIG_BOOTDELAY
735		countdown and/or running the auto-boot command resp.
736		entering interactive mode.
737
738		This feature is especially useful when "preboot" is
739		automatically generated or modified. For an example
740		see the LWMON board specific code: here "preboot" is
741		modified when the user holds down a certain
742		combination of keys on the (special) keyboard when
743		booting the systems
744
745- Serial Download Echo Mode:
746		CONFIG_LOADS_ECHO
747		If defined to 1, all characters received during a
748		serial download (using the "loads" command) are
749		echoed back. This might be needed by some terminal
750		emulations (like "cu"), but may as well just take
751		time on others. This setting #define's the initial
752		value of the "loads_echo" environment variable.
753
754- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
755		CONFIG_KGDB_BAUDRATE
756		Select one of the baudrates listed in
757		CONFIG_SYS_BAUDRATE_TABLE, see below.
758
759- Monitor Functions:
760		Monitor commands can be included or excluded
761		from the build by using the #include files
762		<config_cmd_all.h> and #undef'ing unwanted
763		commands, or adding #define's for wanted commands.
764
765		The default command configuration includes all commands
766		except those marked below with a "*".
767
768		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
769		CONFIG_CMD_ASKENV	* ask for env variable
770		CONFIG_CMD_BDI		  bdinfo
771		CONFIG_CMD_BOOTD	  bootd
772		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
773		CONFIG_CMD_CACHE	* icache, dcache
774		CONFIG_CMD_CONSOLE	  coninfo
775		CONFIG_CMD_DHCP		* DHCP support
776		CONFIG_CMD_DIAG		* Diagnostics
777		CONFIG_CMD_ECHO		  echo arguments
778		CONFIG_CMD_EDITENV	  edit env variable
779		CONFIG_CMD_ELF		* bootelf, bootvx
780		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
781		CONFIG_CMD_EXPORTENV	* export the environment
782		CONFIG_CMD_EXT2		* ext2 command support
783		CONFIG_CMD_EXT4		* ext4 command support
784		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
785					  that work for multiple fs types
786		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
787		CONFIG_CMD_SAVEENV	  saveenv
788		CONFIG_CMD_FLASH	  flinfo, erase, protect
789		CONFIG_CMD_FPGA		  FPGA device initialization support
790		CONFIG_CMD_GO		* the 'go' command (exec code)
791		CONFIG_CMD_GREPENV	* search environment
792		CONFIG_CMD_I2C		* I2C serial bus support
793		CONFIG_CMD_IMI		  iminfo
794		CONFIG_CMD_IMLS		  List all images found in NOR flash
795		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
796		CONFIG_CMD_IMPORTENV	* import an environment
797		CONFIG_CMD_INI		* import data from an ini file into the env
798		CONFIG_CMD_ITEST	  Integer/string test of 2 values
799		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
800		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
801					  (169.254.*.*)
802		CONFIG_CMD_LOADB	  loadb
803		CONFIG_CMD_LOADS	  loads
804		CONFIG_CMD_MD5SUM	* print md5 message digest
805					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
806		CONFIG_CMD_MEMINFO	* Display detailed memory information
807		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
808					  loop, loopw
809		CONFIG_CMD_MEMTEST	* mtest
810		CONFIG_CMD_MISC		  Misc functions like sleep etc
811		CONFIG_CMD_MMC		* MMC memory mapped support
812		CONFIG_CMD_MII		* MII utility commands
813		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
814		CONFIG_CMD_NFS		  NFS support
815		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
816					  host
817		CONFIG_CMD_PORTIO	* Port I/O
818		CONFIG_CMD_READ		* Read raw data from partition
819		CONFIG_CMD_REGINFO	* Register dump
820		CONFIG_CMD_RUN		  run command in env variable
821		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
822		CONFIG_CMD_SAVES	* save S record dump
823		CONFIG_CMD_SDRAM	* print SDRAM configuration information
824					  (requires CONFIG_CMD_I2C)
825		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
826		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
827		CONFIG_CMD_SOURCE	  "source" command Support
828		CONFIG_CMD_SPI		* SPI serial bus support
829		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
830		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
831		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
832		CONFIG_CMD_TIMER	* access to the system tick timer
833		CONFIG_CMD_USB		* USB support
834		CONFIG_CMD_CDP		* Cisco Discover Protocol support
835		CONFIG_CMD_XIMG		  Load part of Multi Image
836		CONFIG_CMD_UUID		* Generate random UUID or GUID string
837
838		EXAMPLE: If you want all functions except of network
839		support you can write:
840
841		#include "config_cmd_all.h"
842		#undef CONFIG_CMD_NET
843
844	Other Commands:
845		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
846
847	Note:	Don't enable the "icache" and "dcache" commands
848		(configuration option CONFIG_CMD_CACHE) unless you know
849		what you (and your U-Boot users) are doing. Data
850		cache cannot be enabled on systems like the
851		8xx (where accesses to the IMMR region must be
852		uncached), and it cannot be disabled on all other
853		systems where we (mis-) use the data cache to hold an
854		initial stack and some data.
855
856
857		XXX - this list needs to get updated!
858
859- Removal of commands
860		If no commands are needed to boot, you can disable
861		CONFIG_CMDLINE to remove them. In this case, the command line
862		will not be available, and when U-Boot wants to execute the
863		boot command (on start-up) it will call board_run_command()
864		instead. This can reduce image size significantly for very
865		simple boot procedures.
866
867- Regular expression support:
868		CONFIG_REGEX
869		If this variable is defined, U-Boot is linked against
870		the SLRE (Super Light Regular Expression) library,
871		which adds regex support to some commands, as for
872		example "env grep" and "setexpr".
873
874- Device tree:
875		CONFIG_OF_CONTROL
876		If this variable is defined, U-Boot will use a device tree
877		to configure its devices, instead of relying on statically
878		compiled #defines in the board file. This option is
879		experimental and only available on a few boards. The device
880		tree is available in the global data as gd->fdt_blob.
881
882		U-Boot needs to get its device tree from somewhere. This can
883		be done using one of the three options below:
884
885		CONFIG_OF_EMBED
886		If this variable is defined, U-Boot will embed a device tree
887		binary in its image. This device tree file should be in the
888		board directory and called <soc>-<board>.dts. The binary file
889		is then picked up in board_init_f() and made available through
890		the global data structure as gd->blob.
891
892		CONFIG_OF_SEPARATE
893		If this variable is defined, U-Boot will build a device tree
894		binary. It will be called u-boot.dtb. Architecture-specific
895		code will locate it at run-time. Generally this works by:
896
897			cat u-boot.bin u-boot.dtb >image.bin
898
899		and in fact, U-Boot does this for you, creating a file called
900		u-boot-dtb.bin which is useful in the common case. You can
901		still use the individual files if you need something more
902		exotic.
903
904		CONFIG_OF_BOARD
905		If this variable is defined, U-Boot will use the device tree
906		provided by the board at runtime instead of embedding one with
907		the image. Only boards defining board_fdt_blob_setup() support
908		this option (see include/fdtdec.h file).
909
910- Watchdog:
911		CONFIG_WATCHDOG
912		If this variable is defined, it enables watchdog
913		support for the SoC. There must be support in the SoC
914		specific code for a watchdog. For the 8xx
915		CPUs, the SIU Watchdog feature is enabled in the SYPCR
916		register.  When supported for a specific SoC is
917		available, then no further board specific code should
918		be needed to use it.
919
920		CONFIG_HW_WATCHDOG
921		When using a watchdog circuitry external to the used
922		SoC, then define this variable and provide board
923		specific code for the "hw_watchdog_reset" function.
924
925		CONFIG_AT91_HW_WDT_TIMEOUT
926		specify the timeout in seconds. default 2 seconds.
927
928- U-Boot Version:
929		CONFIG_VERSION_VARIABLE
930		If this variable is defined, an environment variable
931		named "ver" is created by U-Boot showing the U-Boot
932		version as printed by the "version" command.
933		Any change to this variable will be reverted at the
934		next reset.
935
936- Real-Time Clock:
937
938		When CONFIG_CMD_DATE is selected, the type of the RTC
939		has to be selected, too. Define exactly one of the
940		following options:
941
942		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
943		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
944		CONFIG_RTC_MC146818	- use MC146818 RTC
945		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
946		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
947		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
948		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
949		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
950		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
951		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
952		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
953		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
954					  RV3029 RTC.
955
956		Note that if the RTC uses I2C, then the I2C interface
957		must also be configured. See I2C Support, below.
958
959- GPIO Support:
960		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
961
962		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
963		chip-ngpio pairs that tell the PCA953X driver the number of
964		pins supported by a particular chip.
965
966		Note that if the GPIO device uses I2C, then the I2C interface
967		must also be configured. See I2C Support, below.
968
969- I/O tracing:
970		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
971		accesses and can checksum them or write a list of them out
972		to memory. See the 'iotrace' command for details. This is
973		useful for testing device drivers since it can confirm that
974		the driver behaves the same way before and after a code
975		change. Currently this is supported on sandbox and arm. To
976		add support for your architecture, add '#include <iotrace.h>'
977		to the bottom of arch/<arch>/include/asm/io.h and test.
978
979		Example output from the 'iotrace stats' command is below.
980		Note that if the trace buffer is exhausted, the checksum will
981		still continue to operate.
982
983			iotrace is enabled
984			Start:  10000000	(buffer start address)
985			Size:   00010000	(buffer size)
986			Offset: 00000120	(current buffer offset)
987			Output: 10000120	(start + offset)
988			Count:  00000018	(number of trace records)
989			CRC32:  9526fb66	(CRC32 of all trace records)
990
991- Timestamp Support:
992
993		When CONFIG_TIMESTAMP is selected, the timestamp
994		(date and time) of an image is printed by image
995		commands like bootm or iminfo. This option is
996		automatically enabled when you select CONFIG_CMD_DATE .
997
998- Partition Labels (disklabels) Supported:
999		Zero or more of the following:
1000		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1001		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1002		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1003				       bootloader.  Note 2TB partition limit; see
1004				       disk/part_efi.c
1005		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1006
1007		If IDE or SCSI support is enabled (CONFIG_IDE or
1008		CONFIG_SCSI) you must configure support for at
1009		least one non-MTD partition type as well.
1010
1011- IDE Reset method:
1012		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1013		board configurations files but used nowhere!
1014
1015		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1016		be performed by calling the function
1017			ide_set_reset(int reset)
1018		which has to be defined in a board specific file
1019
1020- ATAPI Support:
1021		CONFIG_ATAPI
1022
1023		Set this to enable ATAPI support.
1024
1025- LBA48 Support
1026		CONFIG_LBA48
1027
1028		Set this to enable support for disks larger than 137GB
1029		Also look at CONFIG_SYS_64BIT_LBA.
1030		Whithout these , LBA48 support uses 32bit variables and will 'only'
1031		support disks up to 2.1TB.
1032
1033		CONFIG_SYS_64BIT_LBA:
1034			When enabled, makes the IDE subsystem use 64bit sector addresses.
1035			Default is 32bit.
1036
1037- SCSI Support:
1038		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1039		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1040		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1041		maximum numbers of LUNs, SCSI ID's and target
1042		devices.
1043
1044		The environment variable 'scsidevs' is set to the number of
1045		SCSI devices found during the last scan.
1046
1047- NETWORK Support (PCI):
1048		CONFIG_E1000
1049		Support for Intel 8254x/8257x gigabit chips.
1050
1051		CONFIG_E1000_SPI
1052		Utility code for direct access to the SPI bus on Intel 8257x.
1053		This does not do anything useful unless you set at least one
1054		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1055
1056		CONFIG_E1000_SPI_GENERIC
1057		Allow generic access to the SPI bus on the Intel 8257x, for
1058		example with the "sspi" command.
1059
1060		CONFIG_CMD_E1000
1061		Management command for E1000 devices.  When used on devices
1062		with SPI support you can reprogram the EEPROM from U-Boot.
1063
1064		CONFIG_EEPRO100
1065		Support for Intel 82557/82559/82559ER chips.
1066		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1067		write routine for first time initialisation.
1068
1069		CONFIG_TULIP
1070		Support for Digital 2114x chips.
1071		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1072		modem chip initialisation (KS8761/QS6611).
1073
1074		CONFIG_NATSEMI
1075		Support for National dp83815 chips.
1076
1077		CONFIG_NS8382X
1078		Support for National dp8382[01] gigabit chips.
1079
1080- NETWORK Support (other):
1081
1082		CONFIG_DRIVER_AT91EMAC
1083		Support for AT91RM9200 EMAC.
1084
1085			CONFIG_RMII
1086			Define this to use reduced MII inteface
1087
1088			CONFIG_DRIVER_AT91EMAC_QUIET
1089			If this defined, the driver is quiet.
1090			The driver doen't show link status messages.
1091
1092		CONFIG_CALXEDA_XGMAC
1093		Support for the Calxeda XGMAC device
1094
1095		CONFIG_LAN91C96
1096		Support for SMSC's LAN91C96 chips.
1097
1098			CONFIG_LAN91C96_USE_32_BIT
1099			Define this to enable 32 bit addressing
1100
1101		CONFIG_SMC91111
1102		Support for SMSC's LAN91C111 chip
1103
1104			CONFIG_SMC91111_BASE
1105			Define this to hold the physical address
1106			of the device (I/O space)
1107
1108			CONFIG_SMC_USE_32_BIT
1109			Define this if data bus is 32 bits
1110
1111			CONFIG_SMC_USE_IOFUNCS
1112			Define this to use i/o functions instead of macros
1113			(some hardware wont work with macros)
1114
1115		CONFIG_DRIVER_TI_EMAC
1116		Support for davinci emac
1117
1118			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1119			Define this if you have more then 3 PHYs.
1120
1121		CONFIG_FTGMAC100
1122		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1123
1124			CONFIG_FTGMAC100_EGIGA
1125			Define this to use GE link update with gigabit PHY.
1126			Define this if FTGMAC100 is connected to gigabit PHY.
1127			If your system has 10/100 PHY only, it might not occur
1128			wrong behavior. Because PHY usually return timeout or
1129			useless data when polling gigabit status and gigabit
1130			control registers. This behavior won't affect the
1131			correctnessof 10/100 link speed update.
1132
1133		CONFIG_SMC911X
1134		Support for SMSC's LAN911x and LAN921x chips
1135
1136			CONFIG_SMC911X_BASE
1137			Define this to hold the physical address
1138			of the device (I/O space)
1139
1140			CONFIG_SMC911X_32_BIT
1141			Define this if data bus is 32 bits
1142
1143			CONFIG_SMC911X_16_BIT
1144			Define this if data bus is 16 bits. If your processor
1145			automatically converts one 32 bit word to two 16 bit
1146			words you may also try CONFIG_SMC911X_32_BIT.
1147
1148		CONFIG_SH_ETHER
1149		Support for Renesas on-chip Ethernet controller
1150
1151			CONFIG_SH_ETHER_USE_PORT
1152			Define the number of ports to be used
1153
1154			CONFIG_SH_ETHER_PHY_ADDR
1155			Define the ETH PHY's address
1156
1157			CONFIG_SH_ETHER_CACHE_WRITEBACK
1158			If this option is set, the driver enables cache flush.
1159
1160- PWM Support:
1161		CONFIG_PWM_IMX
1162		Support for PWM module on the imx6.
1163
1164- TPM Support:
1165		CONFIG_TPM
1166		Support TPM devices.
1167
1168		CONFIG_TPM_TIS_INFINEON
1169		Support for Infineon i2c bus TPM devices. Only one device
1170		per system is supported at this time.
1171
1172			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1173			Define the burst count bytes upper limit
1174
1175		CONFIG_TPM_ST33ZP24
1176		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1177
1178			CONFIG_TPM_ST33ZP24_I2C
1179			Support for STMicroelectronics ST33ZP24 I2C devices.
1180			Requires TPM_ST33ZP24 and I2C.
1181
1182			CONFIG_TPM_ST33ZP24_SPI
1183			Support for STMicroelectronics ST33ZP24 SPI devices.
1184			Requires TPM_ST33ZP24 and SPI.
1185
1186		CONFIG_TPM_ATMEL_TWI
1187		Support for Atmel TWI TPM device. Requires I2C support.
1188
1189		CONFIG_TPM_TIS_LPC
1190		Support for generic parallel port TPM devices. Only one device
1191		per system is supported at this time.
1192
1193			CONFIG_TPM_TIS_BASE_ADDRESS
1194			Base address where the generic TPM device is mapped
1195			to. Contemporary x86 systems usually map it at
1196			0xfed40000.
1197
1198		CONFIG_CMD_TPM
1199		Add tpm monitor functions.
1200		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1201		provides monitor access to authorized functions.
1202
1203		CONFIG_TPM
1204		Define this to enable the TPM support library which provides
1205		functional interfaces to some TPM commands.
1206		Requires support for a TPM device.
1207
1208		CONFIG_TPM_AUTH_SESSIONS
1209		Define this to enable authorized functions in the TPM library.
1210		Requires CONFIG_TPM and CONFIG_SHA1.
1211
1212- USB Support:
1213		At the moment only the UHCI host controller is
1214		supported (PIP405, MIP405); define
1215		CONFIG_USB_UHCI to enable it.
1216		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1217		and define CONFIG_USB_STORAGE to enable the USB
1218		storage devices.
1219		Note:
1220		Supported are USB Keyboards and USB Floppy drives
1221		(TEAC FD-05PUB).
1222
1223		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1224		txfilltuning field in the EHCI controller on reset.
1225
1226		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1227		HW module registers.
1228
1229- USB Device:
1230		Define the below if you wish to use the USB console.
1231		Once firmware is rebuilt from a serial console issue the
1232		command "setenv stdin usbtty; setenv stdout usbtty" and
1233		attach your USB cable. The Unix command "dmesg" should print
1234		it has found a new device. The environment variable usbtty
1235		can be set to gserial or cdc_acm to enable your device to
1236		appear to a USB host as a Linux gserial device or a
1237		Common Device Class Abstract Control Model serial device.
1238		If you select usbtty = gserial you should be able to enumerate
1239		a Linux host by
1240		# modprobe usbserial vendor=0xVendorID product=0xProductID
1241		else if using cdc_acm, simply setting the environment
1242		variable usbtty to be cdc_acm should suffice. The following
1243		might be defined in YourBoardName.h
1244
1245			CONFIG_USB_DEVICE
1246			Define this to build a UDC device
1247
1248			CONFIG_USB_TTY
1249			Define this to have a tty type of device available to
1250			talk to the UDC device
1251
1252			CONFIG_USBD_HS
1253			Define this to enable the high speed support for usb
1254			device and usbtty. If this feature is enabled, a routine
1255			int is_usbd_high_speed(void)
1256			also needs to be defined by the driver to dynamically poll
1257			whether the enumeration has succeded at high speed or full
1258			speed.
1259
1260			CONFIG_SYS_CONSOLE_IS_IN_ENV
1261			Define this if you want stdin, stdout &/or stderr to
1262			be set to usbtty.
1263
1264		If you have a USB-IF assigned VendorID then you may wish to
1265		define your own vendor specific values either in BoardName.h
1266		or directly in usbd_vendor_info.h. If you don't define
1267		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1268		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1269		should pretend to be a Linux device to it's target host.
1270
1271			CONFIG_USBD_MANUFACTURER
1272			Define this string as the name of your company for
1273			- CONFIG_USBD_MANUFACTURER "my company"
1274
1275			CONFIG_USBD_PRODUCT_NAME
1276			Define this string as the name of your product
1277			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1278
1279			CONFIG_USBD_VENDORID
1280			Define this as your assigned Vendor ID from the USB
1281			Implementors Forum. This *must* be a genuine Vendor ID
1282			to avoid polluting the USB namespace.
1283			- CONFIG_USBD_VENDORID 0xFFFF
1284
1285			CONFIG_USBD_PRODUCTID
1286			Define this as the unique Product ID
1287			for your device
1288			- CONFIG_USBD_PRODUCTID 0xFFFF
1289
1290- ULPI Layer Support:
1291		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1292		the generic ULPI layer. The generic layer accesses the ULPI PHY
1293		via the platform viewport, so you need both the genric layer and
1294		the viewport enabled. Currently only Chipidea/ARC based
1295		viewport is supported.
1296		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1297		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1298		If your ULPI phy needs a different reference clock than the
1299		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1300		the appropriate value in Hz.
1301
1302- MMC Support:
1303		The MMC controller on the Intel PXA is supported. To
1304		enable this define CONFIG_MMC. The MMC can be
1305		accessed from the boot prompt by mapping the device
1306		to physical memory similar to flash. Command line is
1307		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1308		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1309
1310		CONFIG_SH_MMCIF
1311		Support for Renesas on-chip MMCIF controller
1312
1313			CONFIG_SH_MMCIF_ADDR
1314			Define the base address of MMCIF registers
1315
1316			CONFIG_SH_MMCIF_CLK
1317			Define the clock frequency for MMCIF
1318
1319		CONFIG_SUPPORT_EMMC_BOOT
1320		Enable some additional features of the eMMC boot partitions.
1321
1322		CONFIG_SUPPORT_EMMC_RPMB
1323		Enable the commands for reading, writing and programming the
1324		key for the Replay Protection Memory Block partition in eMMC.
1325
1326- USB Device Firmware Update (DFU) class support:
1327		CONFIG_USB_FUNCTION_DFU
1328		This enables the USB portion of the DFU USB class
1329
1330		CONFIG_CMD_DFU
1331		This enables the command "dfu" which is used to have
1332		U-Boot create a DFU class device via USB.  This command
1333		requires that the "dfu_alt_info" environment variable be
1334		set and define the alt settings to expose to the host.
1335
1336		CONFIG_DFU_MMC
1337		This enables support for exposing (e)MMC devices via DFU.
1338
1339		CONFIG_DFU_NAND
1340		This enables support for exposing NAND devices via DFU.
1341
1342		CONFIG_DFU_RAM
1343		This enables support for exposing RAM via DFU.
1344		Note: DFU spec refer to non-volatile memory usage, but
1345		allow usages beyond the scope of spec - here RAM usage,
1346		one that would help mostly the developer.
1347
1348		CONFIG_SYS_DFU_DATA_BUF_SIZE
1349		Dfu transfer uses a buffer before writing data to the
1350		raw storage device. Make the size (in bytes) of this buffer
1351		configurable. The size of this buffer is also configurable
1352		through the "dfu_bufsiz" environment variable.
1353
1354		CONFIG_SYS_DFU_MAX_FILE_SIZE
1355		When updating files rather than the raw storage device,
1356		we use a static buffer to copy the file into and then write
1357		the buffer once we've been given the whole file.  Define
1358		this to the maximum filesize (in bytes) for the buffer.
1359		Default is 4 MiB if undefined.
1360
1361		DFU_DEFAULT_POLL_TIMEOUT
1362		Poll timeout [ms], is the timeout a device can send to the
1363		host. The host must wait for this timeout before sending
1364		a subsequent DFU_GET_STATUS request to the device.
1365
1366		DFU_MANIFEST_POLL_TIMEOUT
1367		Poll timeout [ms], which the device sends to the host when
1368		entering dfuMANIFEST state. Host waits this timeout, before
1369		sending again an USB request to the device.
1370
1371- USB Device Android Fastboot support:
1372		CONFIG_USB_FUNCTION_FASTBOOT
1373		This enables the USB part of the fastboot gadget
1374
1375		CONFIG_CMD_FASTBOOT
1376		This enables the command "fastboot" which enables the Android
1377		fastboot mode for the platform's USB device. Fastboot is a USB
1378		protocol for downloading images, flashing and device control
1379		used on Android devices.
1380		See doc/README.android-fastboot for more information.
1381
1382		CONFIG_ANDROID_BOOT_IMAGE
1383		This enables support for booting images which use the Android
1384		image format header.
1385
1386		CONFIG_FASTBOOT_BUF_ADDR
1387		The fastboot protocol requires a large memory buffer for
1388		downloads. Define this to the starting RAM address to use for
1389		downloaded images.
1390
1391		CONFIG_FASTBOOT_BUF_SIZE
1392		The fastboot protocol requires a large memory buffer for
1393		downloads. This buffer should be as large as possible for a
1394		platform. Define this to the size available RAM for fastboot.
1395
1396		CONFIG_FASTBOOT_FLASH
1397		The fastboot protocol includes a "flash" command for writing
1398		the downloaded image to a non-volatile storage device. Define
1399		this to enable the "fastboot flash" command.
1400
1401		CONFIG_FASTBOOT_FLASH_MMC_DEV
1402		The fastboot "flash" command requires additional information
1403		regarding the non-volatile storage device. Define this to
1404		the eMMC device that fastboot should use to store the image.
1405
1406		CONFIG_FASTBOOT_GPT_NAME
1407		The fastboot "flash" command supports writing the downloaded
1408		image to the Protective MBR and the Primary GUID Partition
1409		Table. (Additionally, this downloaded image is post-processed
1410		to generate and write the Backup GUID Partition Table.)
1411		This occurs when the specified "partition name" on the
1412		"fastboot flash" command line matches this value.
1413		The default is "gpt" if undefined.
1414
1415		CONFIG_FASTBOOT_MBR_NAME
1416		The fastboot "flash" command supports writing the downloaded
1417		image to DOS MBR.
1418		This occurs when the "partition name" specified on the
1419		"fastboot flash" command line matches this value.
1420		If not defined the default value "mbr" is used.
1421
1422- Journaling Flash filesystem support:
1423		CONFIG_JFFS2_NAND
1424		Define these for a default partition on a NAND device
1425
1426		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1427		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1428		Define these for a default partition on a NOR device
1429
1430- Keyboard Support:
1431		See Kconfig help for available keyboard drivers.
1432
1433		CONFIG_KEYBOARD
1434
1435		Define this to enable a custom keyboard support.
1436		This simply calls drv_keyboard_init() which must be
1437		defined in your board-specific files. This option is deprecated
1438		and is only used by novena. For new boards, use driver model
1439		instead.
1440
1441- Video support:
1442		CONFIG_FSL_DIU_FB
1443		Enable the Freescale DIU video driver.	Reference boards for
1444		SOCs that have a DIU should define this macro to enable DIU
1445		support, and should also define these other macros:
1446
1447			CONFIG_SYS_DIU_ADDR
1448			CONFIG_VIDEO
1449			CONFIG_CFB_CONSOLE
1450			CONFIG_VIDEO_SW_CURSOR
1451			CONFIG_VGA_AS_SINGLE_DEVICE
1452			CONFIG_VIDEO_LOGO
1453			CONFIG_VIDEO_BMP_LOGO
1454
1455		The DIU driver will look for the 'video-mode' environment
1456		variable, and if defined, enable the DIU as a console during
1457		boot.  See the documentation file doc/README.video for a
1458		description of this variable.
1459
1460- LCD Support:	CONFIG_LCD
1461
1462		Define this to enable LCD support (for output to LCD
1463		display); also select one of the supported displays
1464		by defining one of these:
1465
1466		CONFIG_ATMEL_LCD:
1467
1468			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1469
1470		CONFIG_NEC_NL6448AC33:
1471
1472			NEC NL6448AC33-18. Active, color, single scan.
1473
1474		CONFIG_NEC_NL6448BC20
1475
1476			NEC NL6448BC20-08. 6.5", 640x480.
1477			Active, color, single scan.
1478
1479		CONFIG_NEC_NL6448BC33_54
1480
1481			NEC NL6448BC33-54. 10.4", 640x480.
1482			Active, color, single scan.
1483
1484		CONFIG_SHARP_16x9
1485
1486			Sharp 320x240. Active, color, single scan.
1487			It isn't 16x9, and I am not sure what it is.
1488
1489		CONFIG_SHARP_LQ64D341
1490
1491			Sharp LQ64D341 display, 640x480.
1492			Active, color, single scan.
1493
1494		CONFIG_HLD1045
1495
1496			HLD1045 display, 640x480.
1497			Active, color, single scan.
1498
1499		CONFIG_OPTREX_BW
1500
1501			Optrex	 CBL50840-2 NF-FW 99 22 M5
1502			or
1503			Hitachi	 LMG6912RPFC-00T
1504			or
1505			Hitachi	 SP14Q002
1506
1507			320x240. Black & white.
1508
1509		CONFIG_LCD_ALIGNMENT
1510
1511		Normally the LCD is page-aligned (typically 4KB). If this is
1512		defined then the LCD will be aligned to this value instead.
1513		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1514		here, since it is cheaper to change data cache settings on
1515		a per-section basis.
1516
1517
1518		CONFIG_LCD_ROTATION
1519
1520		Sometimes, for example if the display is mounted in portrait
1521		mode or even if it's mounted landscape but rotated by 180degree,
1522		we need to rotate our content of the display relative to the
1523		framebuffer, so that user can read the messages which are
1524		printed out.
1525		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1526		initialized with a given rotation from "vl_rot" out of
1527		"vidinfo_t" which is provided by the board specific code.
1528		The value for vl_rot is coded as following (matching to
1529		fbcon=rotate:<n> linux-kernel commandline):
1530		0 = no rotation respectively 0 degree
1531		1 = 90 degree rotation
1532		2 = 180 degree rotation
1533		3 = 270 degree rotation
1534
1535		If CONFIG_LCD_ROTATION is not defined, the console will be
1536		initialized with 0degree rotation.
1537
1538		CONFIG_LCD_BMP_RLE8
1539
1540		Support drawing of RLE8-compressed bitmaps on the LCD.
1541
1542		CONFIG_I2C_EDID
1543
1544		Enables an 'i2c edid' command which can read EDID
1545		information over I2C from an attached LCD display.
1546
1547- Splash Screen Support: CONFIG_SPLASH_SCREEN
1548
1549		If this option is set, the environment is checked for
1550		a variable "splashimage". If found, the usual display
1551		of logo, copyright and system information on the LCD
1552		is suppressed and the BMP image at the address
1553		specified in "splashimage" is loaded instead. The
1554		console is redirected to the "nulldev", too. This
1555		allows for a "silent" boot where a splash screen is
1556		loaded very quickly after power-on.
1557
1558		CONFIG_SPLASHIMAGE_GUARD
1559
1560		If this option is set, then U-Boot will prevent the environment
1561		variable "splashimage" from being set to a problematic address
1562		(see doc/README.displaying-bmps).
1563		This option is useful for targets where, due to alignment
1564		restrictions, an improperly aligned BMP image will cause a data
1565		abort. If you think you will not have problems with unaligned
1566		accesses (for example because your toolchain prevents them)
1567		there is no need to set this option.
1568
1569		CONFIG_SPLASH_SCREEN_ALIGN
1570
1571		If this option is set the splash image can be freely positioned
1572		on the screen. Environment variable "splashpos" specifies the
1573		position as "x,y". If a positive number is given it is used as
1574		number of pixel from left/top. If a negative number is given it
1575		is used as number of pixel from right/bottom. You can also
1576		specify 'm' for centering the image.
1577
1578		Example:
1579		setenv splashpos m,m
1580			=> image at center of screen
1581
1582		setenv splashpos 30,20
1583			=> image at x = 30 and y = 20
1584
1585		setenv splashpos -10,m
1586			=> vertically centered image
1587			   at x = dspWidth - bmpWidth - 9
1588
1589- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1590
1591		If this option is set, additionally to standard BMP
1592		images, gzipped BMP images can be displayed via the
1593		splashscreen support or the bmp command.
1594
1595- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1596
1597		If this option is set, 8-bit RLE compressed BMP images
1598		can be displayed via the splashscreen support or the
1599		bmp command.
1600
1601- Compression support:
1602		CONFIG_GZIP
1603
1604		Enabled by default to support gzip compressed images.
1605
1606		CONFIG_BZIP2
1607
1608		If this option is set, support for bzip2 compressed
1609		images is included. If not, only uncompressed and gzip
1610		compressed images are supported.
1611
1612		NOTE: the bzip2 algorithm requires a lot of RAM, so
1613		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1614		be at least 4MB.
1615
1616- MII/PHY support:
1617		CONFIG_PHY_ADDR
1618
1619		The address of PHY on MII bus.
1620
1621		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1622
1623		The clock frequency of the MII bus
1624
1625		CONFIG_PHY_RESET_DELAY
1626
1627		Some PHY like Intel LXT971A need extra delay after
1628		reset before any MII register access is possible.
1629		For such PHY, set this option to the usec delay
1630		required. (minimum 300usec for LXT971A)
1631
1632		CONFIG_PHY_CMD_DELAY (ppc4xx)
1633
1634		Some PHY like Intel LXT971A need extra delay after
1635		command issued before MII status register can be read
1636
1637- IP address:
1638		CONFIG_IPADDR
1639
1640		Define a default value for the IP address to use for
1641		the default Ethernet interface, in case this is not
1642		determined through e.g. bootp.
1643		(Environment variable "ipaddr")
1644
1645- Server IP address:
1646		CONFIG_SERVERIP
1647
1648		Defines a default value for the IP address of a TFTP
1649		server to contact when using the "tftboot" command.
1650		(Environment variable "serverip")
1651
1652		CONFIG_KEEP_SERVERADDR
1653
1654		Keeps the server's MAC address, in the env 'serveraddr'
1655		for passing to bootargs (like Linux's netconsole option)
1656
1657- Gateway IP address:
1658		CONFIG_GATEWAYIP
1659
1660		Defines a default value for the IP address of the
1661		default router where packets to other networks are
1662		sent to.
1663		(Environment variable "gatewayip")
1664
1665- Subnet mask:
1666		CONFIG_NETMASK
1667
1668		Defines a default value for the subnet mask (or
1669		routing prefix) which is used to determine if an IP
1670		address belongs to the local subnet or needs to be
1671		forwarded through a router.
1672		(Environment variable "netmask")
1673
1674- Multicast TFTP Mode:
1675		CONFIG_MCAST_TFTP
1676
1677		Defines whether you want to support multicast TFTP as per
1678		rfc-2090; for example to work with atftp.  Lets lots of targets
1679		tftp down the same boot image concurrently.  Note: the Ethernet
1680		driver in use must provide a function: mcast() to join/leave a
1681		multicast group.
1682
1683- BOOTP Recovery Mode:
1684		CONFIG_BOOTP_RANDOM_DELAY
1685
1686		If you have many targets in a network that try to
1687		boot using BOOTP, you may want to avoid that all
1688		systems send out BOOTP requests at precisely the same
1689		moment (which would happen for instance at recovery
1690		from a power failure, when all systems will try to
1691		boot, thus flooding the BOOTP server. Defining
1692		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1693		inserted before sending out BOOTP requests. The
1694		following delays are inserted then:
1695
1696		1st BOOTP request:	delay 0 ... 1 sec
1697		2nd BOOTP request:	delay 0 ... 2 sec
1698		3rd BOOTP request:	delay 0 ... 4 sec
1699		4th and following
1700		BOOTP requests:		delay 0 ... 8 sec
1701
1702		CONFIG_BOOTP_ID_CACHE_SIZE
1703
1704		BOOTP packets are uniquely identified using a 32-bit ID. The
1705		server will copy the ID from client requests to responses and
1706		U-Boot will use this to determine if it is the destination of
1707		an incoming response. Some servers will check that addresses
1708		aren't in use before handing them out (usually using an ARP
1709		ping) and therefore take up to a few hundred milliseconds to
1710		respond. Network congestion may also influence the time it
1711		takes for a response to make it back to the client. If that
1712		time is too long, U-Boot will retransmit requests. In order
1713		to allow earlier responses to still be accepted after these
1714		retransmissions, U-Boot's BOOTP client keeps a small cache of
1715		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1716		cache. The default is to keep IDs for up to four outstanding
1717		requests. Increasing this will allow U-Boot to accept offers
1718		from a BOOTP client in networks with unusually high latency.
1719
1720- DHCP Advanced Options:
1721		You can fine tune the DHCP functionality by defining
1722		CONFIG_BOOTP_* symbols:
1723
1724		CONFIG_BOOTP_SUBNETMASK
1725		CONFIG_BOOTP_GATEWAY
1726		CONFIG_BOOTP_HOSTNAME
1727		CONFIG_BOOTP_NISDOMAIN
1728		CONFIG_BOOTP_BOOTPATH
1729		CONFIG_BOOTP_BOOTFILESIZE
1730		CONFIG_BOOTP_DNS
1731		CONFIG_BOOTP_DNS2
1732		CONFIG_BOOTP_SEND_HOSTNAME
1733		CONFIG_BOOTP_NTPSERVER
1734		CONFIG_BOOTP_TIMEOFFSET
1735		CONFIG_BOOTP_VENDOREX
1736		CONFIG_BOOTP_MAY_FAIL
1737
1738		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1739		environment variable, not the BOOTP server.
1740
1741		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1742		after the configured retry count, the call will fail
1743		instead of starting over.  This can be used to fail over
1744		to Link-local IP address configuration if the DHCP server
1745		is not available.
1746
1747		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1748		serverip from a DHCP server, it is possible that more
1749		than one DNS serverip is offered to the client.
1750		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1751		serverip will be stored in the additional environment
1752		variable "dnsip2". The first DNS serverip is always
1753		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1754		is defined.
1755
1756		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1757		to do a dynamic update of a DNS server. To do this, they
1758		need the hostname of the DHCP requester.
1759		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1760		of the "hostname" environment variable is passed as
1761		option 12 to the DHCP server.
1762
1763		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1764
1765		A 32bit value in microseconds for a delay between
1766		receiving a "DHCP Offer" and sending the "DHCP Request".
1767		This fixes a problem with certain DHCP servers that don't
1768		respond 100% of the time to a "DHCP request". E.g. On an
1769		AT91RM9200 processor running at 180MHz, this delay needed
1770		to be *at least* 15,000 usec before a Windows Server 2003
1771		DHCP server would reply 100% of the time. I recommend at
1772		least 50,000 usec to be safe. The alternative is to hope
1773		that one of the retries will be successful but note that
1774		the DHCP timeout and retry process takes a longer than
1775		this delay.
1776
1777 - Link-local IP address negotiation:
1778		Negotiate with other link-local clients on the local network
1779		for an address that doesn't require explicit configuration.
1780		This is especially useful if a DHCP server cannot be guaranteed
1781		to exist in all environments that the device must operate.
1782
1783		See doc/README.link-local for more information.
1784
1785 - CDP Options:
1786		CONFIG_CDP_DEVICE_ID
1787
1788		The device id used in CDP trigger frames.
1789
1790		CONFIG_CDP_DEVICE_ID_PREFIX
1791
1792		A two character string which is prefixed to the MAC address
1793		of the device.
1794
1795		CONFIG_CDP_PORT_ID
1796
1797		A printf format string which contains the ascii name of
1798		the port. Normally is set to "eth%d" which sets
1799		eth0 for the first Ethernet, eth1 for the second etc.
1800
1801		CONFIG_CDP_CAPABILITIES
1802
1803		A 32bit integer which indicates the device capabilities;
1804		0x00000010 for a normal host which does not forwards.
1805
1806		CONFIG_CDP_VERSION
1807
1808		An ascii string containing the version of the software.
1809
1810		CONFIG_CDP_PLATFORM
1811
1812		An ascii string containing the name of the platform.
1813
1814		CONFIG_CDP_TRIGGER
1815
1816		A 32bit integer sent on the trigger.
1817
1818		CONFIG_CDP_POWER_CONSUMPTION
1819
1820		A 16bit integer containing the power consumption of the
1821		device in .1 of milliwatts.
1822
1823		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1824
1825		A byte containing the id of the VLAN.
1826
1827- Status LED:	CONFIG_LED_STATUS
1828
1829		Several configurations allow to display the current
1830		status using a LED. For instance, the LED will blink
1831		fast while running U-Boot code, stop blinking as
1832		soon as a reply to a BOOTP request was received, and
1833		start blinking slow once the Linux kernel is running
1834		(supported by a status LED driver in the Linux
1835		kernel). Defining CONFIG_LED_STATUS enables this
1836		feature in U-Boot.
1837
1838		Additional options:
1839
1840		CONFIG_LED_STATUS_GPIO
1841		The status LED can be connected to a GPIO pin.
1842		In such cases, the gpio_led driver can be used as a
1843		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1844		to include the gpio_led driver in the U-Boot binary.
1845
1846		CONFIG_GPIO_LED_INVERTED_TABLE
1847		Some GPIO connected LEDs may have inverted polarity in which
1848		case the GPIO high value corresponds to LED off state and
1849		GPIO low value corresponds to LED on state.
1850		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1851		with a list of GPIO LEDs that have inverted polarity.
1852
1853- I2C Support:	CONFIG_SYS_I2C
1854
1855		This enable the NEW i2c subsystem, and will allow you to use
1856		i2c commands at the u-boot command line (as long as you set
1857		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1858		based realtime clock chips or other i2c devices. See
1859		common/cmd_i2c.c for a description of the command line
1860		interface.
1861
1862		ported i2c driver to the new framework:
1863		- drivers/i2c/soft_i2c.c:
1864		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1865		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1866		    for defining speed and slave address
1867		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1868		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1869		    for defining speed and slave address
1870		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1871		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1872		    for defining speed and slave address
1873		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1874		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1875		    for defining speed and slave address
1876
1877		- drivers/i2c/fsl_i2c.c:
1878		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1879		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1880		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1881		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1882		    bus.
1883		  - If your board supports a second fsl i2c bus, define
1884		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1885		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1886		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1887		    second bus.
1888
1889		- drivers/i2c/tegra_i2c.c:
1890		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1891		  - This driver adds 4 i2c buses with a fix speed from
1892		    100000 and the slave addr 0!
1893
1894		- drivers/i2c/ppc4xx_i2c.c
1895		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1896		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1897		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1898
1899		- drivers/i2c/i2c_mxc.c
1900		  - activate this driver with CONFIG_SYS_I2C_MXC
1901		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1902		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1903		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1904		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1905		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1906		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1907		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1908		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1909		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1910		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1911		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1912		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1913		If those defines are not set, default value is 100000
1914		for speed, and 0 for slave.
1915
1916		- drivers/i2c/rcar_i2c.c:
1917		  - activate this driver with CONFIG_SYS_I2C_RCAR
1918		  - This driver adds 4 i2c buses
1919
1920		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1921		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1922		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1923		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1924		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1925		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1926		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1927		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1928		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1929
1930		- drivers/i2c/sh_i2c.c:
1931		  - activate this driver with CONFIG_SYS_I2C_SH
1932		  - This driver adds from 2 to 5 i2c buses
1933
1934		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1935		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1936		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1937		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1938		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1939		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1940		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1941		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1942		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1943		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1944		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1945
1946		- drivers/i2c/omap24xx_i2c.c
1947		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1948		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1949		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1950		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1951		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1952		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1953		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1954		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1955		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1956		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1957		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1958
1959		- drivers/i2c/zynq_i2c.c
1960		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1961		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1962		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1963
1964		- drivers/i2c/s3c24x0_i2c.c:
1965		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1966		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1967		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1968		    with a fix speed from 100000 and the slave addr 0!
1969
1970		- drivers/i2c/ihs_i2c.c
1971		  - activate this driver with CONFIG_SYS_I2C_IHS
1972		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1973		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1974		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1975		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1976		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1977		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1978		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1979		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1980		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1981		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1982		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1983		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1984		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1985		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1986		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1987		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1988		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1989		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1990		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1991		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1992		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1993
1994		additional defines:
1995
1996		CONFIG_SYS_NUM_I2C_BUSES
1997		Hold the number of i2c buses you want to use.
1998
1999		CONFIG_SYS_I2C_DIRECT_BUS
2000		define this, if you don't use i2c muxes on your hardware.
2001		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2002		omit this define.
2003
2004		CONFIG_SYS_I2C_MAX_HOPS
2005		define how many muxes are maximal consecutively connected
2006		on one i2c bus. If you not use i2c muxes, omit this
2007		define.
2008
2009		CONFIG_SYS_I2C_BUSES
2010		hold a list of buses you want to use, only used if
2011		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2012		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2013		CONFIG_SYS_NUM_I2C_BUSES = 9:
2014
2015		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2016					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2017					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2018					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2019					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2020					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2021					{1, {I2C_NULL_HOP}}, \
2022					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2023					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2024					}
2025
2026		which defines
2027			bus 0 on adapter 0 without a mux
2028			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2029			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2030			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2031			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2032			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2033			bus 6 on adapter 1 without a mux
2034			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2035			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2036
2037		If you do not have i2c muxes on your board, omit this define.
2038
2039- Legacy I2C Support:
2040		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2041		then the following macros need to be defined (examples are
2042		from include/configs/lwmon.h):
2043
2044		I2C_INIT
2045
2046		(Optional). Any commands necessary to enable the I2C
2047		controller or configure ports.
2048
2049		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2050
2051		I2C_ACTIVE
2052
2053		The code necessary to make the I2C data line active
2054		(driven).  If the data line is open collector, this
2055		define can be null.
2056
2057		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2058
2059		I2C_TRISTATE
2060
2061		The code necessary to make the I2C data line tri-stated
2062		(inactive).  If the data line is open collector, this
2063		define can be null.
2064
2065		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2066
2067		I2C_READ
2068
2069		Code that returns true if the I2C data line is high,
2070		false if it is low.
2071
2072		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2073
2074		I2C_SDA(bit)
2075
2076		If <bit> is true, sets the I2C data line high. If it
2077		is false, it clears it (low).
2078
2079		eg: #define I2C_SDA(bit) \
2080			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2081			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2082
2083		I2C_SCL(bit)
2084
2085		If <bit> is true, sets the I2C clock line high. If it
2086		is false, it clears it (low).
2087
2088		eg: #define I2C_SCL(bit) \
2089			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2090			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2091
2092		I2C_DELAY
2093
2094		This delay is invoked four times per clock cycle so this
2095		controls the rate of data transfer.  The data rate thus
2096		is 1 / (I2C_DELAY * 4). Often defined to be something
2097		like:
2098
2099		#define I2C_DELAY  udelay(2)
2100
2101		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2102
2103		If your arch supports the generic GPIO framework (asm/gpio.h),
2104		then you may alternatively define the two GPIOs that are to be
2105		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2106		have GPIO-based defaults assigned to them as appropriate.
2107
2108		You should define these to the GPIO value as given directly to
2109		the generic GPIO functions.
2110
2111		CONFIG_SYS_I2C_INIT_BOARD
2112
2113		When a board is reset during an i2c bus transfer
2114		chips might think that the current transfer is still
2115		in progress. On some boards it is possible to access
2116		the i2c SCLK line directly, either by using the
2117		processor pin as a GPIO or by having a second pin
2118		connected to the bus. If this option is defined a
2119		custom i2c_init_board() routine in boards/xxx/board.c
2120		is run early in the boot sequence.
2121
2122		CONFIG_I2C_MULTI_BUS
2123
2124		This option allows the use of multiple I2C buses, each of which
2125		must have a controller.	 At any point in time, only one bus is
2126		active.	 To switch to a different bus, use the 'i2c dev' command.
2127		Note that bus numbering is zero-based.
2128
2129		CONFIG_SYS_I2C_NOPROBES
2130
2131		This option specifies a list of I2C devices that will be skipped
2132		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2133		is set, specify a list of bus-device pairs.  Otherwise, specify
2134		a 1D array of device addresses
2135
2136		e.g.
2137			#undef	CONFIG_I2C_MULTI_BUS
2138			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2139
2140		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2141
2142			#define CONFIG_I2C_MULTI_BUS
2143			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2144
2145		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2146
2147		CONFIG_SYS_SPD_BUS_NUM
2148
2149		If defined, then this indicates the I2C bus number for DDR SPD.
2150		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2151
2152		CONFIG_SYS_RTC_BUS_NUM
2153
2154		If defined, then this indicates the I2C bus number for the RTC.
2155		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2156
2157		CONFIG_SOFT_I2C_READ_REPEATED_START
2158
2159		defining this will force the i2c_read() function in
2160		the soft_i2c driver to perform an I2C repeated start
2161		between writing the address pointer and reading the
2162		data.  If this define is omitted the default behaviour
2163		of doing a stop-start sequence will be used.  Most I2C
2164		devices can use either method, but some require one or
2165		the other.
2166
2167- SPI Support:	CONFIG_SPI
2168
2169		Enables SPI driver (so far only tested with
2170		SPI EEPROM, also an instance works with Crystal A/D and
2171		D/As on the SACSng board)
2172
2173		CONFIG_SH_SPI
2174
2175		Enables the driver for SPI controller on SuperH. Currently
2176		only SH7757 is supported.
2177
2178		CONFIG_SOFT_SPI
2179
2180		Enables a software (bit-bang) SPI driver rather than
2181		using hardware support. This is a general purpose
2182		driver that only requires three general I/O port pins
2183		(two outputs, one input) to function. If this is
2184		defined, the board configuration must define several
2185		SPI configuration items (port pins to use, etc). For
2186		an example, see include/configs/sacsng.h.
2187
2188		CONFIG_HARD_SPI
2189
2190		Enables a hardware SPI driver for general-purpose reads
2191		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2192		must define a list of chip-select function pointers.
2193		Currently supported on some MPC8xxx processors.	 For an
2194		example, see include/configs/mpc8349emds.h.
2195
2196		CONFIG_MXC_SPI
2197
2198		Enables the driver for the SPI controllers on i.MX and MXC
2199		SoCs. Currently i.MX31/35/51 are supported.
2200
2201		CONFIG_SYS_SPI_MXC_WAIT
2202		Timeout for waiting until spi transfer completed.
2203		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2204
2205- FPGA Support: CONFIG_FPGA
2206
2207		Enables FPGA subsystem.
2208
2209		CONFIG_FPGA_<vendor>
2210
2211		Enables support for specific chip vendors.
2212		(ALTERA, XILINX)
2213
2214		CONFIG_FPGA_<family>
2215
2216		Enables support for FPGA family.
2217		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2218
2219		CONFIG_FPGA_COUNT
2220
2221		Specify the number of FPGA devices to support.
2222
2223		CONFIG_SYS_FPGA_PROG_FEEDBACK
2224
2225		Enable printing of hash marks during FPGA configuration.
2226
2227		CONFIG_SYS_FPGA_CHECK_BUSY
2228
2229		Enable checks on FPGA configuration interface busy
2230		status by the configuration function. This option
2231		will require a board or device specific function to
2232		be written.
2233
2234		CONFIG_FPGA_DELAY
2235
2236		If defined, a function that provides delays in the FPGA
2237		configuration driver.
2238
2239		CONFIG_SYS_FPGA_CHECK_CTRLC
2240		Allow Control-C to interrupt FPGA configuration
2241
2242		CONFIG_SYS_FPGA_CHECK_ERROR
2243
2244		Check for configuration errors during FPGA bitfile
2245		loading. For example, abort during Virtex II
2246		configuration if the INIT_B line goes low (which
2247		indicated a CRC error).
2248
2249		CONFIG_SYS_FPGA_WAIT_INIT
2250
2251		Maximum time to wait for the INIT_B line to de-assert
2252		after PROB_B has been de-asserted during a Virtex II
2253		FPGA configuration sequence. The default time is 500
2254		ms.
2255
2256		CONFIG_SYS_FPGA_WAIT_BUSY
2257
2258		Maximum time to wait for BUSY to de-assert during
2259		Virtex II FPGA configuration. The default is 5 ms.
2260
2261		CONFIG_SYS_FPGA_WAIT_CONFIG
2262
2263		Time to wait after FPGA configuration. The default is
2264		200 ms.
2265
2266- Configuration Management:
2267		CONFIG_BUILD_TARGET
2268
2269		Some SoCs need special image types (e.g. U-Boot binary
2270		with a special header) as build targets. By defining
2271		CONFIG_BUILD_TARGET in the SoC / board header, this
2272		special image will be automatically built upon calling
2273		make / buildman.
2274
2275		CONFIG_IDENT_STRING
2276
2277		If defined, this string will be added to the U-Boot
2278		version information (U_BOOT_VERSION)
2279
2280- Vendor Parameter Protection:
2281
2282		U-Boot considers the values of the environment
2283		variables "serial#" (Board Serial Number) and
2284		"ethaddr" (Ethernet Address) to be parameters that
2285		are set once by the board vendor / manufacturer, and
2286		protects these variables from casual modification by
2287		the user. Once set, these variables are read-only,
2288		and write or delete attempts are rejected. You can
2289		change this behaviour:
2290
2291		If CONFIG_ENV_OVERWRITE is #defined in your config
2292		file, the write protection for vendor parameters is
2293		completely disabled. Anybody can change or delete
2294		these parameters.
2295
2296		Alternatively, if you define _both_ an ethaddr in the
2297		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2298		Ethernet address is installed in the environment,
2299		which can be changed exactly ONCE by the user. [The
2300		serial# is unaffected by this, i. e. it remains
2301		read-only.]
2302
2303		The same can be accomplished in a more flexible way
2304		for any variable by configuring the type of access
2305		to allow for those variables in the ".flags" variable
2306		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2307
2308- Protected RAM:
2309		CONFIG_PRAM
2310
2311		Define this variable to enable the reservation of
2312		"protected RAM", i. e. RAM which is not overwritten
2313		by U-Boot. Define CONFIG_PRAM to hold the number of
2314		kB you want to reserve for pRAM. You can overwrite
2315		this default value by defining an environment
2316		variable "pram" to the number of kB you want to
2317		reserve. Note that the board info structure will
2318		still show the full amount of RAM. If pRAM is
2319		reserved, a new environment variable "mem" will
2320		automatically be defined to hold the amount of
2321		remaining RAM in a form that can be passed as boot
2322		argument to Linux, for instance like that:
2323
2324			setenv bootargs ... mem=\${mem}
2325			saveenv
2326
2327		This way you can tell Linux not to use this memory,
2328		either, which results in a memory region that will
2329		not be affected by reboots.
2330
2331		*WARNING* If your board configuration uses automatic
2332		detection of the RAM size, you must make sure that
2333		this memory test is non-destructive. So far, the
2334		following board configurations are known to be
2335		"pRAM-clean":
2336
2337			IVMS8, IVML24, SPD8xx,
2338			HERMES, IP860, RPXlite, LWMON,
2339			FLAGADM
2340
2341- Access to physical memory region (> 4GB)
2342		Some basic support is provided for operations on memory not
2343		normally accessible to U-Boot - e.g. some architectures
2344		support access to more than 4GB of memory on 32-bit
2345		machines using physical address extension or similar.
2346		Define CONFIG_PHYSMEM to access this basic support, which
2347		currently only supports clearing the memory.
2348
2349- Error Recovery:
2350		CONFIG_PANIC_HANG
2351
2352		Define this variable to stop the system in case of a
2353		fatal error, so that you have to reset it manually.
2354		This is probably NOT a good idea for an embedded
2355		system where you want the system to reboot
2356		automatically as fast as possible, but it may be
2357		useful during development since you can try to debug
2358		the conditions that lead to the situation.
2359
2360		CONFIG_NET_RETRY_COUNT
2361
2362		This variable defines the number of retries for
2363		network operations like ARP, RARP, TFTP, or BOOTP
2364		before giving up the operation. If not defined, a
2365		default value of 5 is used.
2366
2367		CONFIG_ARP_TIMEOUT
2368
2369		Timeout waiting for an ARP reply in milliseconds.
2370
2371		CONFIG_NFS_TIMEOUT
2372
2373		Timeout in milliseconds used in NFS protocol.
2374		If you encounter "ERROR: Cannot umount" in nfs command,
2375		try longer timeout such as
2376		#define CONFIG_NFS_TIMEOUT 10000UL
2377
2378- Command Interpreter:
2379		CONFIG_AUTO_COMPLETE
2380
2381		Enable auto completion of commands using TAB.
2382
2383		CONFIG_SYS_PROMPT_HUSH_PS2
2384
2385		This defines the secondary prompt string, which is
2386		printed when the command interpreter needs more input
2387		to complete a command. Usually "> ".
2388
2389	Note:
2390
2391		In the current implementation, the local variables
2392		space and global environment variables space are
2393		separated. Local variables are those you define by
2394		simply typing `name=value'. To access a local
2395		variable later on, you have write `$name' or
2396		`${name}'; to execute the contents of a variable
2397		directly type `$name' at the command prompt.
2398
2399		Global environment variables are those you use
2400		setenv/printenv to work with. To run a command stored
2401		in such a variable, you need to use the run command,
2402		and you must not use the '$' sign to access them.
2403
2404		To store commands and special characters in a
2405		variable, please use double quotation marks
2406		surrounding the whole text of the variable, instead
2407		of the backslashes before semicolons and special
2408		symbols.
2409
2410- Command Line Editing and History:
2411		CONFIG_CMDLINE_EDITING
2412
2413		Enable editing and History functions for interactive
2414		command line input operations
2415
2416- Command Line PS1/PS2 support:
2417		CONFIG_CMDLINE_PS_SUPPORT
2418
2419		Enable support for changing the command prompt string
2420		at run-time. Only static string is supported so far.
2421		The string is obtained from environment variables PS1
2422		and PS2.
2423
2424- Default Environment:
2425		CONFIG_EXTRA_ENV_SETTINGS
2426
2427		Define this to contain any number of null terminated
2428		strings (variable = value pairs) that will be part of
2429		the default environment compiled into the boot image.
2430
2431		For example, place something like this in your
2432		board's config file:
2433
2434		#define CONFIG_EXTRA_ENV_SETTINGS \
2435			"myvar1=value1\0" \
2436			"myvar2=value2\0"
2437
2438		Warning: This method is based on knowledge about the
2439		internal format how the environment is stored by the
2440		U-Boot code. This is NOT an official, exported
2441		interface! Although it is unlikely that this format
2442		will change soon, there is no guarantee either.
2443		You better know what you are doing here.
2444
2445		Note: overly (ab)use of the default environment is
2446		discouraged. Make sure to check other ways to preset
2447		the environment like the "source" command or the
2448		boot command first.
2449
2450		CONFIG_ENV_VARS_UBOOT_CONFIG
2451
2452		Define this in order to add variables describing the
2453		U-Boot build configuration to the default environment.
2454		These will be named arch, cpu, board, vendor, and soc.
2455
2456		Enabling this option will cause the following to be defined:
2457
2458		- CONFIG_SYS_ARCH
2459		- CONFIG_SYS_CPU
2460		- CONFIG_SYS_BOARD
2461		- CONFIG_SYS_VENDOR
2462		- CONFIG_SYS_SOC
2463
2464		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2465
2466		Define this in order to add variables describing certain
2467		run-time determined information about the hardware to the
2468		environment.  These will be named board_name, board_rev.
2469
2470		CONFIG_DELAY_ENVIRONMENT
2471
2472		Normally the environment is loaded when the board is
2473		initialised so that it is available to U-Boot. This inhibits
2474		that so that the environment is not available until
2475		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2476		this is instead controlled by the value of
2477		/config/load-environment.
2478
2479- DataFlash Support:
2480		CONFIG_HAS_DATAFLASH
2481
2482		Defining this option enables DataFlash features and
2483		allows to read/write in Dataflash via the standard
2484		commands cp, md...
2485
2486- Serial Flash support
2487		CONFIG_CMD_SF
2488
2489		Defining this option enables SPI flash commands
2490		'sf probe/read/write/erase/update'.
2491
2492		Usage requires an initial 'probe' to define the serial
2493		flash parameters, followed by read/write/erase/update
2494		commands.
2495
2496		The following defaults may be provided by the platform
2497		to handle the common case when only a single serial
2498		flash is present on the system.
2499
2500		CONFIG_SF_DEFAULT_BUS		Bus identifier
2501		CONFIG_SF_DEFAULT_CS		Chip-select
2502		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2503		CONFIG_SF_DEFAULT_SPEED		in Hz
2504
2505		CONFIG_CMD_SF_TEST
2506
2507		Define this option to include a destructive SPI flash
2508		test ('sf test').
2509
2510- SystemACE Support:
2511		CONFIG_SYSTEMACE
2512
2513		Adding this option adds support for Xilinx SystemACE
2514		chips attached via some sort of local bus. The address
2515		of the chip must also be defined in the
2516		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2517
2518		#define CONFIG_SYSTEMACE
2519		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2520
2521		When SystemACE support is added, the "ace" device type
2522		becomes available to the fat commands, i.e. fatls.
2523
2524- TFTP Fixed UDP Port:
2525		CONFIG_TFTP_PORT
2526
2527		If this is defined, the environment variable tftpsrcp
2528		is used to supply the TFTP UDP source port value.
2529		If tftpsrcp isn't defined, the normal pseudo-random port
2530		number generator is used.
2531
2532		Also, the environment variable tftpdstp is used to supply
2533		the TFTP UDP destination port value.  If tftpdstp isn't
2534		defined, the normal port 69 is used.
2535
2536		The purpose for tftpsrcp is to allow a TFTP server to
2537		blindly start the TFTP transfer using the pre-configured
2538		target IP address and UDP port. This has the effect of
2539		"punching through" the (Windows XP) firewall, allowing
2540		the remainder of the TFTP transfer to proceed normally.
2541		A better solution is to properly configure the firewall,
2542		but sometimes that is not allowed.
2543
2544- bootcount support:
2545		CONFIG_BOOTCOUNT_LIMIT
2546
2547		This enables the bootcounter support, see:
2548		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2549
2550		CONFIG_AT91SAM9XE
2551		enable special bootcounter support on at91sam9xe based boards.
2552		CONFIG_SOC_DA8XX
2553		enable special bootcounter support on da850 based boards.
2554		CONFIG_BOOTCOUNT_RAM
2555		enable support for the bootcounter in RAM
2556		CONFIG_BOOTCOUNT_I2C
2557		enable support for the bootcounter on an i2c (like RTC) device.
2558			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2559			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2560						    the bootcounter.
2561			CONFIG_BOOTCOUNT_ALEN = address len
2562
2563- Show boot progress:
2564		CONFIG_SHOW_BOOT_PROGRESS
2565
2566		Defining this option allows to add some board-
2567		specific code (calling a user-provided function
2568		"show_boot_progress(int)") that enables you to show
2569		the system's boot progress on some display (for
2570		example, some LED's) on your board. At the moment,
2571		the following checkpoints are implemented:
2572
2573
2574Legacy uImage format:
2575
2576  Arg	Where			When
2577    1	common/cmd_bootm.c	before attempting to boot an image
2578   -1	common/cmd_bootm.c	Image header has bad	 magic number
2579    2	common/cmd_bootm.c	Image header has correct magic number
2580   -2	common/cmd_bootm.c	Image header has bad	 checksum
2581    3	common/cmd_bootm.c	Image header has correct checksum
2582   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2583    4	common/cmd_bootm.c	Image data   has correct checksum
2584   -4	common/cmd_bootm.c	Image is for unsupported architecture
2585    5	common/cmd_bootm.c	Architecture check OK
2586   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2587    6	common/cmd_bootm.c	Image Type check OK
2588   -6	common/cmd_bootm.c	gunzip uncompression error
2589   -7	common/cmd_bootm.c	Unimplemented compression type
2590    7	common/cmd_bootm.c	Uncompression OK
2591    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2592   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2593
2594    9	common/image.c		Start initial ramdisk verification
2595  -10	common/image.c		Ramdisk header has bad	   magic number
2596  -11	common/image.c		Ramdisk header has bad	   checksum
2597   10	common/image.c		Ramdisk header is OK
2598  -12	common/image.c		Ramdisk data   has bad	   checksum
2599   11	common/image.c		Ramdisk data   has correct checksum
2600   12	common/image.c		Ramdisk verification complete, start loading
2601  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2602   13	common/image.c		Start multifile image verification
2603   14	common/image.c		No initial ramdisk, no multifile, continue.
2604
2605   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2606
2607  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2608  -31	post/post.c		POST test failed, detected by post_output_backlog()
2609  -32	post/post.c		POST test failed, detected by post_run_single()
2610
2611   34	common/cmd_doc.c	before loading a Image from a DOC device
2612  -35	common/cmd_doc.c	Bad usage of "doc" command
2613   35	common/cmd_doc.c	correct usage of "doc" command
2614  -36	common/cmd_doc.c	No boot device
2615   36	common/cmd_doc.c	correct boot device
2616  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2617   37	common/cmd_doc.c	correct chip ID found, device available
2618  -38	common/cmd_doc.c	Read Error on boot device
2619   38	common/cmd_doc.c	reading Image header from DOC device OK
2620  -39	common/cmd_doc.c	Image header has bad magic number
2621   39	common/cmd_doc.c	Image header has correct magic number
2622  -40	common/cmd_doc.c	Error reading Image from DOC device
2623   40	common/cmd_doc.c	Image header has correct magic number
2624   41	common/cmd_ide.c	before loading a Image from a IDE device
2625  -42	common/cmd_ide.c	Bad usage of "ide" command
2626   42	common/cmd_ide.c	correct usage of "ide" command
2627  -43	common/cmd_ide.c	No boot device
2628   43	common/cmd_ide.c	boot device found
2629  -44	common/cmd_ide.c	Device not available
2630   44	common/cmd_ide.c	Device available
2631  -45	common/cmd_ide.c	wrong partition selected
2632   45	common/cmd_ide.c	partition selected
2633  -46	common/cmd_ide.c	Unknown partition table
2634   46	common/cmd_ide.c	valid partition table found
2635  -47	common/cmd_ide.c	Invalid partition type
2636   47	common/cmd_ide.c	correct partition type
2637  -48	common/cmd_ide.c	Error reading Image Header on boot device
2638   48	common/cmd_ide.c	reading Image Header from IDE device OK
2639  -49	common/cmd_ide.c	Image header has bad magic number
2640   49	common/cmd_ide.c	Image header has correct magic number
2641  -50	common/cmd_ide.c	Image header has bad	 checksum
2642   50	common/cmd_ide.c	Image header has correct checksum
2643  -51	common/cmd_ide.c	Error reading Image from IDE device
2644   51	common/cmd_ide.c	reading Image from IDE device OK
2645   52	common/cmd_nand.c	before loading a Image from a NAND device
2646  -53	common/cmd_nand.c	Bad usage of "nand" command
2647   53	common/cmd_nand.c	correct usage of "nand" command
2648  -54	common/cmd_nand.c	No boot device
2649   54	common/cmd_nand.c	boot device found
2650  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2651   55	common/cmd_nand.c	correct chip ID found, device available
2652  -56	common/cmd_nand.c	Error reading Image Header on boot device
2653   56	common/cmd_nand.c	reading Image Header from NAND device OK
2654  -57	common/cmd_nand.c	Image header has bad magic number
2655   57	common/cmd_nand.c	Image header has correct magic number
2656  -58	common/cmd_nand.c	Error reading Image from NAND device
2657   58	common/cmd_nand.c	reading Image from NAND device OK
2658
2659  -60	common/env_common.c	Environment has a bad CRC, using default
2660
2661   64	net/eth.c		starting with Ethernet configuration.
2662  -64	net/eth.c		no Ethernet found.
2663   65	net/eth.c		Ethernet found.
2664
2665  -80	common/cmd_net.c	usage wrong
2666   80	common/cmd_net.c	before calling net_loop()
2667  -81	common/cmd_net.c	some error in net_loop() occurred
2668   81	common/cmd_net.c	net_loop() back without error
2669  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2670   82	common/cmd_net.c	trying automatic boot
2671   83	common/cmd_net.c	running "source" command
2672  -83	common/cmd_net.c	some error in automatic boot or "source" command
2673   84	common/cmd_net.c	end without errors
2674
2675FIT uImage format:
2676
2677  Arg	Where			When
2678  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2679 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2680  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2681 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2682  102	common/cmd_bootm.c	Kernel unit name specified
2683 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2684  103	common/cmd_bootm.c	Found configuration node
2685  104	common/cmd_bootm.c	Got kernel subimage node offset
2686 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2687  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2688 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2689  106	common/cmd_bootm.c	Architecture check OK
2690 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2691  107	common/cmd_bootm.c	Kernel subimage type OK
2692 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2693  108	common/cmd_bootm.c	Got kernel subimage data/size
2694 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2695 -109	common/cmd_bootm.c	Can't get kernel subimage type
2696 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2697 -111	common/cmd_bootm.c	Can't get kernel subimage os
2698 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2699 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2700
2701  120	common/image.c		Start initial ramdisk verification
2702 -120	common/image.c		Ramdisk FIT image has incorrect format
2703  121	common/image.c		Ramdisk FIT image has correct format
2704  122	common/image.c		No ramdisk subimage unit name, using configuration
2705 -122	common/image.c		Can't get configuration for ramdisk subimage
2706  123	common/image.c		Ramdisk unit name specified
2707 -124	common/image.c		Can't get ramdisk subimage node offset
2708  125	common/image.c		Got ramdisk subimage node offset
2709 -125	common/image.c		Ramdisk subimage hash verification failed
2710  126	common/image.c		Ramdisk subimage hash verification OK
2711 -126	common/image.c		Ramdisk subimage for unsupported architecture
2712  127	common/image.c		Architecture check OK
2713 -127	common/image.c		Can't get ramdisk subimage data/size
2714  128	common/image.c		Got ramdisk subimage data/size
2715  129	common/image.c		Can't get ramdisk load address
2716 -129	common/image.c		Got ramdisk load address
2717
2718 -130	common/cmd_doc.c	Incorrect FIT image format
2719  131	common/cmd_doc.c	FIT image format OK
2720
2721 -140	common/cmd_ide.c	Incorrect FIT image format
2722  141	common/cmd_ide.c	FIT image format OK
2723
2724 -150	common/cmd_nand.c	Incorrect FIT image format
2725  151	common/cmd_nand.c	FIT image format OK
2726
2727- legacy image format:
2728		CONFIG_IMAGE_FORMAT_LEGACY
2729		enables the legacy image format support in U-Boot.
2730
2731		Default:
2732		enabled if CONFIG_FIT_SIGNATURE is not defined.
2733
2734		CONFIG_DISABLE_IMAGE_LEGACY
2735		disable the legacy image format
2736
2737		This define is introduced, as the legacy image format is
2738		enabled per default for backward compatibility.
2739
2740- Standalone program support:
2741		CONFIG_STANDALONE_LOAD_ADDR
2742
2743		This option defines a board specific value for the
2744		address where standalone program gets loaded, thus
2745		overwriting the architecture dependent default
2746		settings.
2747
2748- Frame Buffer Address:
2749		CONFIG_FB_ADDR
2750
2751		Define CONFIG_FB_ADDR if you want to use specific
2752		address for frame buffer.  This is typically the case
2753		when using a graphics controller has separate video
2754		memory.  U-Boot will then place the frame buffer at
2755		the given address instead of dynamically reserving it
2756		in system RAM by calling lcd_setmem(), which grabs
2757		the memory for the frame buffer depending on the
2758		configured panel size.
2759
2760		Please see board_init_f function.
2761
2762- Automatic software updates via TFTP server
2763		CONFIG_UPDATE_TFTP
2764		CONFIG_UPDATE_TFTP_CNT_MAX
2765		CONFIG_UPDATE_TFTP_MSEC_MAX
2766
2767		These options enable and control the auto-update feature;
2768		for a more detailed description refer to doc/README.update.
2769
2770- MTD Support (mtdparts command, UBI support)
2771		CONFIG_MTD_DEVICE
2772
2773		Adds the MTD device infrastructure from the Linux kernel.
2774		Needed for mtdparts command support.
2775
2776		CONFIG_MTD_PARTITIONS
2777
2778		Adds the MTD partitioning infrastructure from the Linux
2779		kernel. Needed for UBI support.
2780
2781- UBI support
2782		CONFIG_UBI_SILENCE_MSG
2783
2784		Make the verbose messages from UBI stop printing.  This leaves
2785		warnings and errors enabled.
2786
2787
2788		CONFIG_MTD_UBI_WL_THRESHOLD
2789		This parameter defines the maximum difference between the highest
2790		erase counter value and the lowest erase counter value of eraseblocks
2791		of UBI devices. When this threshold is exceeded, UBI starts performing
2792		wear leveling by means of moving data from eraseblock with low erase
2793		counter to eraseblocks with high erase counter.
2794
2795		The default value should be OK for SLC NAND flashes, NOR flashes and
2796		other flashes which have eraseblock life-cycle 100000 or more.
2797		However, in case of MLC NAND flashes which typically have eraseblock
2798		life-cycle less than 10000, the threshold should be lessened (e.g.,
2799		to 128 or 256, although it does not have to be power of 2).
2800
2801		default: 4096
2802
2803		CONFIG_MTD_UBI_BEB_LIMIT
2804		This option specifies the maximum bad physical eraseblocks UBI
2805		expects on the MTD device (per 1024 eraseblocks). If the
2806		underlying flash does not admit of bad eraseblocks (e.g. NOR
2807		flash), this value is ignored.
2808
2809		NAND datasheets often specify the minimum and maximum NVM
2810		(Number of Valid Blocks) for the flashes' endurance lifetime.
2811		The maximum expected bad eraseblocks per 1024 eraseblocks
2812		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2813		which gives 20 for most NANDs (MaxNVB is basically the total
2814		count of eraseblocks on the chip).
2815
2816		To put it differently, if this value is 20, UBI will try to
2817		reserve about 1.9% of physical eraseblocks for bad blocks
2818		handling. And that will be 1.9% of eraseblocks on the entire
2819		NAND chip, not just the MTD partition UBI attaches. This means
2820		that if you have, say, a NAND flash chip admits maximum 40 bad
2821		eraseblocks, and it is split on two MTD partitions of the same
2822		size, UBI will reserve 40 eraseblocks when attaching a
2823		partition.
2824
2825		default: 20
2826
2827		CONFIG_MTD_UBI_FASTMAP
2828		Fastmap is a mechanism which allows attaching an UBI device
2829		in nearly constant time. Instead of scanning the whole MTD device it
2830		only has to locate a checkpoint (called fastmap) on the device.
2831		The on-flash fastmap contains all information needed to attach
2832		the device. Using fastmap makes only sense on large devices where
2833		attaching by scanning takes long. UBI will not automatically install
2834		a fastmap on old images, but you can set the UBI parameter
2835		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2836		that fastmap-enabled images are still usable with UBI implementations
2837		without	fastmap support. On typical flash devices the whole fastmap
2838		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2839
2840		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2841		Set this parameter to enable fastmap automatically on images
2842		without a fastmap.
2843		default: 0
2844
2845		CONFIG_MTD_UBI_FM_DEBUG
2846		Enable UBI fastmap debug
2847		default: 0
2848
2849- UBIFS support
2850		CONFIG_UBIFS_SILENCE_MSG
2851
2852		Make the verbose messages from UBIFS stop printing.  This leaves
2853		warnings and errors enabled.
2854
2855- SPL framework
2856		CONFIG_SPL
2857		Enable building of SPL globally.
2858
2859		CONFIG_SPL_LDSCRIPT
2860		LDSCRIPT for linking the SPL binary.
2861
2862		CONFIG_SPL_MAX_FOOTPRINT
2863		Maximum size in memory allocated to the SPL, BSS included.
2864		When defined, the linker checks that the actual memory
2865		used by SPL from _start to __bss_end does not exceed it.
2866		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2867		must not be both defined at the same time.
2868
2869		CONFIG_SPL_MAX_SIZE
2870		Maximum size of the SPL image (text, data, rodata, and
2871		linker lists sections), BSS excluded.
2872		When defined, the linker checks that the actual size does
2873		not exceed it.
2874
2875		CONFIG_SPL_TEXT_BASE
2876		TEXT_BASE for linking the SPL binary.
2877
2878		CONFIG_SPL_RELOC_TEXT_BASE
2879		Address to relocate to.  If unspecified, this is equal to
2880		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2881
2882		CONFIG_SPL_BSS_START_ADDR
2883		Link address for the BSS within the SPL binary.
2884
2885		CONFIG_SPL_BSS_MAX_SIZE
2886		Maximum size in memory allocated to the SPL BSS.
2887		When defined, the linker checks that the actual memory used
2888		by SPL from __bss_start to __bss_end does not exceed it.
2889		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2890		must not be both defined at the same time.
2891
2892		CONFIG_SPL_STACK
2893		Adress of the start of the stack SPL will use
2894
2895		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2896		When defined, SPL will panic() if the image it has
2897		loaded does not have a signature.
2898		Defining this is useful when code which loads images
2899		in SPL cannot guarantee that absolutely all read errors
2900		will be caught.
2901		An example is the LPC32XX MLC NAND driver, which will
2902		consider that a completely unreadable NAND block is bad,
2903		and thus should be skipped silently.
2904
2905		CONFIG_SPL_RELOC_STACK
2906		Adress of the start of the stack SPL will use after
2907		relocation.  If unspecified, this is equal to
2908		CONFIG_SPL_STACK.
2909
2910		CONFIG_SYS_SPL_MALLOC_START
2911		Starting address of the malloc pool used in SPL.
2912		When this option is set the full malloc is used in SPL and
2913		it is set up by spl_init() and before that, the simple malloc()
2914		can be used if CONFIG_SYS_MALLOC_F is defined.
2915
2916		CONFIG_SYS_SPL_MALLOC_SIZE
2917		The size of the malloc pool used in SPL.
2918
2919		CONFIG_SPL_FRAMEWORK
2920		Enable the SPL framework under common/.  This framework
2921		supports MMC, NAND and YMODEM loading of U-Boot and NAND
2922		NAND loading of the Linux Kernel.
2923
2924		CONFIG_SPL_OS_BOOT
2925		Enable booting directly to an OS from SPL.
2926		See also: doc/README.falcon
2927
2928		CONFIG_SPL_DISPLAY_PRINT
2929		For ARM, enable an optional function to print more information
2930		about the running system.
2931
2932		CONFIG_SPL_INIT_MINIMAL
2933		Arch init code should be built for a very small image
2934
2935		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2936		Partition on the MMC to load U-Boot from when the MMC is being
2937		used in raw mode
2938
2939		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2940		Sector to load kernel uImage from when MMC is being
2941		used in raw mode (for Falcon mode)
2942
2943		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2944		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2945		Sector and number of sectors to load kernel argument
2946		parameters from when MMC is being used in raw mode
2947		(for falcon mode)
2948
2949		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2950		Partition on the MMC to load U-Boot from when the MMC is being
2951		used in fs mode
2952
2953		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2954		Filename to read to load U-Boot when reading from filesystem
2955
2956		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2957		Filename to read to load kernel uImage when reading
2958		from filesystem (for Falcon mode)
2959
2960		CONFIG_SPL_FS_LOAD_ARGS_NAME
2961		Filename to read to load kernel argument parameters
2962		when reading from filesystem (for Falcon mode)
2963
2964		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2965		Set this for NAND SPL on PPC mpc83xx targets, so that
2966		start.S waits for the rest of the SPL to load before
2967		continuing (the hardware starts execution after just
2968		loading the first page rather than the full 4K).
2969
2970		CONFIG_SPL_SKIP_RELOCATE
2971		Avoid SPL relocation
2972
2973		CONFIG_SPL_NAND_BASE
2974		Include nand_base.c in the SPL.  Requires
2975		CONFIG_SPL_NAND_DRIVERS.
2976
2977		CONFIG_SPL_NAND_DRIVERS
2978		SPL uses normal NAND drivers, not minimal drivers.
2979
2980		CONFIG_SPL_NAND_ECC
2981		Include standard software ECC in the SPL
2982
2983		CONFIG_SPL_NAND_SIMPLE
2984		Support for NAND boot using simple NAND drivers that
2985		expose the cmd_ctrl() interface.
2986
2987		CONFIG_SPL_UBI
2988		Support for a lightweight UBI (fastmap) scanner and
2989		loader
2990
2991		CONFIG_SPL_NAND_RAW_ONLY
2992		Support to boot only raw u-boot.bin images. Use this only
2993		if you need to save space.
2994
2995		CONFIG_SPL_COMMON_INIT_DDR
2996		Set for common ddr init with serial presence detect in
2997		SPL binary.
2998
2999		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3000		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3001		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3002		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3003		CONFIG_SYS_NAND_ECCBYTES
3004		Defines the size and behavior of the NAND that SPL uses
3005		to read U-Boot
3006
3007		CONFIG_SPL_NAND_BOOT
3008		Add support NAND boot
3009
3010		CONFIG_SYS_NAND_U_BOOT_OFFS
3011		Location in NAND to read U-Boot from
3012
3013		CONFIG_SYS_NAND_U_BOOT_DST
3014		Location in memory to load U-Boot to
3015
3016		CONFIG_SYS_NAND_U_BOOT_SIZE
3017		Size of image to load
3018
3019		CONFIG_SYS_NAND_U_BOOT_START
3020		Entry point in loaded image to jump to
3021
3022		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3023		Define this if you need to first read the OOB and then the
3024		data. This is used, for example, on davinci platforms.
3025
3026		CONFIG_SPL_OMAP3_ID_NAND
3027		Support for an OMAP3-specific set of functions to return the
3028		ID and MFR of the first attached NAND chip, if present.
3029
3030		CONFIG_SPL_RAM_DEVICE
3031		Support for running image already present in ram, in SPL binary
3032
3033		CONFIG_SPL_PAD_TO
3034		Image offset to which the SPL should be padded before appending
3035		the SPL payload. By default, this is defined as
3036		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3037		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3038		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3039
3040		CONFIG_SPL_TARGET
3041		Final target image containing SPL and payload.  Some SPLs
3042		use an arch-specific makefile fragment instead, for
3043		example if more than one image needs to be produced.
3044
3045		CONFIG_FIT_SPL_PRINT
3046		Printing information about a FIT image adds quite a bit of
3047		code to SPL. So this is normally disabled in SPL. Use this
3048		option to re-enable it. This will affect the output of the
3049		bootm command when booting a FIT image.
3050
3051- TPL framework
3052		CONFIG_TPL
3053		Enable building of TPL globally.
3054
3055		CONFIG_TPL_PAD_TO
3056		Image offset to which the TPL should be padded before appending
3057		the TPL payload. By default, this is defined as
3058		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3059		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3060		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3061
3062- Interrupt support (PPC):
3063
3064		There are common interrupt_init() and timer_interrupt()
3065		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3066		for CPU specific initialization. interrupt_init_cpu()
3067		should set decrementer_count to appropriate value. If
3068		CPU resets decrementer automatically after interrupt
3069		(ppc4xx) it should set decrementer_count to zero.
3070		timer_interrupt() calls timer_interrupt_cpu() for CPU
3071		specific handling. If board has watchdog / status_led
3072		/ other_activity_monitor it works automatically from
3073		general timer_interrupt().
3074
3075
3076Board initialization settings:
3077------------------------------
3078
3079During Initialization u-boot calls a number of board specific functions
3080to allow the preparation of board specific prerequisites, e.g. pin setup
3081before drivers are initialized. To enable these callbacks the
3082following configuration macros have to be defined. Currently this is
3083architecture specific, so please check arch/your_architecture/lib/board.c
3084typically in board_init_f() and board_init_r().
3085
3086- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3087- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3088- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3089- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3090
3091Configuration Settings:
3092-----------------------
3093
3094- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3095		Optionally it can be defined to support 64-bit memory commands.
3096
3097- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3098		undefine this when you're short of memory.
3099
3100- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3101		width of the commands listed in the 'help' command output.
3102
3103- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3104		prompt for user input.
3105
3106- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3107
3108- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3109
3110- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3111
3112- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3113		the application (usually a Linux kernel) when it is
3114		booted
3115
3116- CONFIG_SYS_BAUDRATE_TABLE:
3117		List of legal baudrate settings for this board.
3118
3119- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3120		Begin and End addresses of the area used by the
3121		simple memory test.
3122
3123- CONFIG_SYS_ALT_MEMTEST:
3124		Enable an alternate, more extensive memory test.
3125
3126- CONFIG_SYS_MEMTEST_SCRATCH:
3127		Scratch address used by the alternate memory test
3128		You only need to set this if address zero isn't writeable
3129
3130- CONFIG_SYS_MEM_RESERVE_SECURE
3131		Only implemented for ARMv8 for now.
3132		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
3133		is substracted from total RAM and won't be reported to OS.
3134		This memory can be used as secure memory. A variable
3135		gd->arch.secure_ram is used to track the location. In systems
3136		the RAM base is not zero, or RAM is divided into banks,
3137		this variable needs to be recalcuated to get the address.
3138
3139- CONFIG_SYS_MEM_TOP_HIDE:
3140		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3141		this specified memory area will get subtracted from the top
3142		(end) of RAM and won't get "touched" at all by U-Boot. By
3143		fixing up gd->ram_size the Linux kernel should gets passed
3144		the now "corrected" memory size and won't touch it either.
3145		This should work for arch/ppc and arch/powerpc. Only Linux
3146		board ports in arch/powerpc with bootwrapper support that
3147		recalculate the memory size from the SDRAM controller setup
3148		will have to get fixed in Linux additionally.
3149
3150		This option can be used as a workaround for the 440EPx/GRx
3151		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3152		be touched.
3153
3154		WARNING: Please make sure that this value is a multiple of
3155		the Linux page size (normally 4k). If this is not the case,
3156		then the end address of the Linux memory will be located at a
3157		non page size aligned address and this could cause major
3158		problems.
3159
3160- CONFIG_SYS_LOADS_BAUD_CHANGE:
3161		Enable temporary baudrate change while serial download
3162
3163- CONFIG_SYS_SDRAM_BASE:
3164		Physical start address of SDRAM. _Must_ be 0 here.
3165
3166- CONFIG_SYS_FLASH_BASE:
3167		Physical start address of Flash memory.
3168
3169- CONFIG_SYS_MONITOR_BASE:
3170		Physical start address of boot monitor code (set by
3171		make config files to be same as the text base address
3172		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3173		CONFIG_SYS_FLASH_BASE when booting from flash.
3174
3175- CONFIG_SYS_MONITOR_LEN:
3176		Size of memory reserved for monitor code, used to
3177		determine _at_compile_time_ (!) if the environment is
3178		embedded within the U-Boot image, or in a separate
3179		flash sector.
3180
3181- CONFIG_SYS_MALLOC_LEN:
3182		Size of DRAM reserved for malloc() use.
3183
3184- CONFIG_SYS_MALLOC_F_LEN
3185		Size of the malloc() pool for use before relocation. If
3186		this is defined, then a very simple malloc() implementation
3187		will become available before relocation. The address is just
3188		below the global data, and the stack is moved down to make
3189		space.
3190
3191		This feature allocates regions with increasing addresses
3192		within the region. calloc() is supported, but realloc()
3193		is not available. free() is supported but does nothing.
3194		The memory will be freed (or in fact just forgotten) when
3195		U-Boot relocates itself.
3196
3197- CONFIG_SYS_MALLOC_SIMPLE
3198		Provides a simple and small malloc() and calloc() for those
3199		boards which do not use the full malloc in SPL (which is
3200		enabled with CONFIG_SYS_SPL_MALLOC_START).
3201
3202- CONFIG_SYS_NONCACHED_MEMORY:
3203		Size of non-cached memory area. This area of memory will be
3204		typically located right below the malloc() area and mapped
3205		uncached in the MMU. This is useful for drivers that would
3206		otherwise require a lot of explicit cache maintenance. For
3207		some drivers it's also impossible to properly maintain the
3208		cache. For example if the regions that need to be flushed
3209		are not a multiple of the cache-line size, *and* padding
3210		cannot be allocated between the regions to align them (i.e.
3211		if the HW requires a contiguous array of regions, and the
3212		size of each region is not cache-aligned), then a flush of
3213		one region may result in overwriting data that hardware has
3214		written to another region in the same cache-line. This can
3215		happen for example in network drivers where descriptors for
3216		buffers are typically smaller than the CPU cache-line (e.g.
3217		16 bytes vs. 32 or 64 bytes).
3218
3219		Non-cached memory is only supported on 32-bit ARM at present.
3220
3221- CONFIG_SYS_BOOTM_LEN:
3222		Normally compressed uImages are limited to an
3223		uncompressed size of 8 MBytes. If this is not enough,
3224		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3225		to adjust this setting to your needs.
3226
3227- CONFIG_SYS_BOOTMAPSZ:
3228		Maximum size of memory mapped by the startup code of
3229		the Linux kernel; all data that must be processed by
3230		the Linux kernel (bd_info, boot arguments, FDT blob if
3231		used) must be put below this limit, unless "bootm_low"
3232		environment variable is defined and non-zero. In such case
3233		all data for the Linux kernel must be between "bootm_low"
3234		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3235		variable "bootm_mapsize" will override the value of
3236		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3237		then the value in "bootm_size" will be used instead.
3238
3239- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3240		Enable initrd_high functionality.  If defined then the
3241		initrd_high feature is enabled and the bootm ramdisk subcommand
3242		is enabled.
3243
3244- CONFIG_SYS_BOOT_GET_CMDLINE:
3245		Enables allocating and saving kernel cmdline in space between
3246		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3247
3248- CONFIG_SYS_BOOT_GET_KBD:
3249		Enables allocating and saving a kernel copy of the bd_info in
3250		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3251
3252- CONFIG_SYS_MAX_FLASH_BANKS:
3253		Max number of Flash memory banks
3254
3255- CONFIG_SYS_MAX_FLASH_SECT:
3256		Max number of sectors on a Flash chip
3257
3258- CONFIG_SYS_FLASH_ERASE_TOUT:
3259		Timeout for Flash erase operations (in ms)
3260
3261- CONFIG_SYS_FLASH_WRITE_TOUT:
3262		Timeout for Flash write operations (in ms)
3263
3264- CONFIG_SYS_FLASH_LOCK_TOUT
3265		Timeout for Flash set sector lock bit operation (in ms)
3266
3267- CONFIG_SYS_FLASH_UNLOCK_TOUT
3268		Timeout for Flash clear lock bits operation (in ms)
3269
3270- CONFIG_SYS_FLASH_PROTECTION
3271		If defined, hardware flash sectors protection is used
3272		instead of U-Boot software protection.
3273
3274- CONFIG_SYS_DIRECT_FLASH_TFTP:
3275
3276		Enable TFTP transfers directly to flash memory;
3277		without this option such a download has to be
3278		performed in two steps: (1) download to RAM, and (2)
3279		copy from RAM to flash.
3280
3281		The two-step approach is usually more reliable, since
3282		you can check if the download worked before you erase
3283		the flash, but in some situations (when system RAM is
3284		too limited to allow for a temporary copy of the
3285		downloaded image) this option may be very useful.
3286
3287- CONFIG_SYS_FLASH_CFI:
3288		Define if the flash driver uses extra elements in the
3289		common flash structure for storing flash geometry.
3290
3291- CONFIG_FLASH_CFI_DRIVER
3292		This option also enables the building of the cfi_flash driver
3293		in the drivers directory
3294
3295- CONFIG_FLASH_CFI_MTD
3296		This option enables the building of the cfi_mtd driver
3297		in the drivers directory. The driver exports CFI flash
3298		to the MTD layer.
3299
3300- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3301		Use buffered writes to flash.
3302
3303- CONFIG_FLASH_SPANSION_S29WS_N
3304		s29ws-n MirrorBit flash has non-standard addresses for buffered
3305		write commands.
3306
3307- CONFIG_SYS_FLASH_QUIET_TEST
3308		If this option is defined, the common CFI flash doesn't
3309		print it's warning upon not recognized FLASH banks. This
3310		is useful, if some of the configured banks are only
3311		optionally available.
3312
3313- CONFIG_FLASH_SHOW_PROGRESS
3314		If defined (must be an integer), print out countdown
3315		digits and dots.  Recommended value: 45 (9..1) for 80
3316		column displays, 15 (3..1) for 40 column displays.
3317
3318- CONFIG_FLASH_VERIFY
3319		If defined, the content of the flash (destination) is compared
3320		against the source after the write operation. An error message
3321		will be printed when the contents are not identical.
3322		Please note that this option is useless in nearly all cases,
3323		since such flash programming errors usually are detected earlier
3324		while unprotecting/erasing/programming. Please only enable
3325		this option if you really know what you are doing.
3326
3327- CONFIG_SYS_RX_ETH_BUFFER:
3328		Defines the number of Ethernet receive buffers. On some
3329		Ethernet controllers it is recommended to set this value
3330		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3331		buffers can be full shortly after enabling the interface
3332		on high Ethernet traffic.
3333		Defaults to 4 if not defined.
3334
3335- CONFIG_ENV_MAX_ENTRIES
3336
3337	Maximum number of entries in the hash table that is used
3338	internally to store the environment settings. The default
3339	setting is supposed to be generous and should work in most
3340	cases. This setting can be used to tune behaviour; see
3341	lib/hashtable.c for details.
3342
3343- CONFIG_ENV_FLAGS_LIST_DEFAULT
3344- CONFIG_ENV_FLAGS_LIST_STATIC
3345	Enable validation of the values given to environment variables when
3346	calling env set.  Variables can be restricted to only decimal,
3347	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3348	the variables can also be restricted to IP address or MAC address.
3349
3350	The format of the list is:
3351		type_attribute = [s|d|x|b|i|m]
3352		access_attribute = [a|r|o|c]
3353		attributes = type_attribute[access_attribute]
3354		entry = variable_name[:attributes]
3355		list = entry[,list]
3356
3357	The type attributes are:
3358		s - String (default)
3359		d - Decimal
3360		x - Hexadecimal
3361		b - Boolean ([1yYtT|0nNfF])
3362		i - IP address
3363		m - MAC address
3364
3365	The access attributes are:
3366		a - Any (default)
3367		r - Read-only
3368		o - Write-once
3369		c - Change-default
3370
3371	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3372		Define this to a list (string) to define the ".flags"
3373		environment variable in the default or embedded environment.
3374
3375	- CONFIG_ENV_FLAGS_LIST_STATIC
3376		Define this to a list (string) to define validation that
3377		should be done if an entry is not found in the ".flags"
3378		environment variable.  To override a setting in the static
3379		list, simply add an entry for the same variable name to the
3380		".flags" variable.
3381
3382	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3383	regular expression. This allows multiple variables to define the same
3384	flags without explicitly listing them for each variable.
3385
3386- CONFIG_ENV_ACCESS_IGNORE_FORCE
3387	If defined, don't allow the -f switch to env set override variable
3388	access flags.
3389
3390- CONFIG_USE_STDINT
3391	If stdint.h is available with your toolchain you can define this
3392	option to enable it. You can provide option 'USE_STDINT=1' when
3393	building U-Boot to enable this.
3394
3395The following definitions that deal with the placement and management
3396of environment data (variable area); in general, we support the
3397following configurations:
3398
3399- CONFIG_BUILD_ENVCRC:
3400
3401	Builds up envcrc with the target environment so that external utils
3402	may easily extract it and embed it in final U-Boot images.
3403
3404BE CAREFUL! The first access to the environment happens quite early
3405in U-Boot initialization (when we try to get the setting of for the
3406console baudrate). You *MUST* have mapped your NVRAM area then, or
3407U-Boot will hang.
3408
3409Please note that even with NVRAM we still use a copy of the
3410environment in RAM: we could work on NVRAM directly, but we want to
3411keep settings there always unmodified except somebody uses "saveenv"
3412to save the current settings.
3413
3414BE CAREFUL! For some special cases, the local device can not use
3415"saveenv" command. For example, the local device will get the
3416environment stored in a remote NOR flash by SRIO or PCIE link,
3417but it can not erase, write this NOR flash by SRIO or PCIE interface.
3418
3419- CONFIG_NAND_ENV_DST
3420
3421	Defines address in RAM to which the nand_spl code should copy the
3422	environment. If redundant environment is used, it will be copied to
3423	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3424
3425Please note that the environment is read-only until the monitor
3426has been relocated to RAM and a RAM copy of the environment has been
3427created; also, when using EEPROM you will have to use getenv_f()
3428until then to read environment variables.
3429
3430The environment is protected by a CRC32 checksum. Before the monitor
3431is relocated into RAM, as a result of a bad CRC you will be working
3432with the compiled-in default environment - *silently*!!! [This is
3433necessary, because the first environment variable we need is the
3434"baudrate" setting for the console - if we have a bad CRC, we don't
3435have any device yet where we could complain.]
3436
3437Note: once the monitor has been relocated, then it will complain if
3438the default environment is used; a new CRC is computed as soon as you
3439use the "saveenv" command to store a valid environment.
3440
3441- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3442		Echo the inverted Ethernet link state to the fault LED.
3443
3444		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3445		      also needs to be defined.
3446
3447- CONFIG_SYS_FAULT_MII_ADDR:
3448		MII address of the PHY to check for the Ethernet link state.
3449
3450- CONFIG_NS16550_MIN_FUNCTIONS:
3451		Define this if you desire to only have use of the NS16550_init
3452		and NS16550_putc functions for the serial driver located at
3453		drivers/serial/ns16550.c.  This option is useful for saving
3454		space for already greatly restricted images, including but not
3455		limited to NAND_SPL configurations.
3456
3457- CONFIG_DISPLAY_BOARDINFO
3458		Display information about the board that U-Boot is running on
3459		when U-Boot starts up. The board function checkboard() is called
3460		to do this.
3461
3462- CONFIG_DISPLAY_BOARDINFO_LATE
3463		Similar to the previous option, but display this information
3464		later, once stdio is running and output goes to the LCD, if
3465		present.
3466
3467- CONFIG_BOARD_SIZE_LIMIT:
3468		Maximum size of the U-Boot image. When defined, the
3469		build system checks that the actual size does not
3470		exceed it.
3471
3472Low Level (hardware related) configuration options:
3473---------------------------------------------------
3474
3475- CONFIG_SYS_CACHELINE_SIZE:
3476		Cache Line Size of the CPU.
3477
3478- CONFIG_SYS_CCSRBAR_DEFAULT:
3479		Default (power-on reset) physical address of CCSR on Freescale
3480		PowerPC SOCs.
3481
3482- CONFIG_SYS_CCSRBAR:
3483		Virtual address of CCSR.  On a 32-bit build, this is typically
3484		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3485
3486- CONFIG_SYS_CCSRBAR_PHYS:
3487		Physical address of CCSR.  CCSR can be relocated to a new
3488		physical address, if desired.  In this case, this macro should
3489		be set to that address.	 Otherwise, it should be set to the
3490		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3491		is typically relocated on 36-bit builds.  It is recommended
3492		that this macro be defined via the _HIGH and _LOW macros:
3493
3494		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3495			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3496
3497- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3498		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3499		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3500		used in assembly code, so it must not contain typecasts or
3501		integer size suffixes (e.g. "ULL").
3502
3503- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3504		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3505		used in assembly code, so it must not contain typecasts or
3506		integer size suffixes (e.g. "ULL").
3507
3508- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3509		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3510		forced to a value that ensures that CCSR is not relocated.
3511
3512- Floppy Disk Support:
3513		CONFIG_SYS_FDC_DRIVE_NUMBER
3514
3515		the default drive number (default value 0)
3516
3517		CONFIG_SYS_ISA_IO_STRIDE
3518
3519		defines the spacing between FDC chipset registers
3520		(default value 1)
3521
3522		CONFIG_SYS_ISA_IO_OFFSET
3523
3524		defines the offset of register from address. It
3525		depends on which part of the data bus is connected to
3526		the FDC chipset. (default value 0)
3527
3528		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3529		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3530		default value.
3531
3532		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3533		fdc_hw_init() is called at the beginning of the FDC
3534		setup. fdc_hw_init() must be provided by the board
3535		source code. It is used to make hardware-dependent
3536		initializations.
3537
3538- CONFIG_IDE_AHB:
3539		Most IDE controllers were designed to be connected with PCI
3540		interface. Only few of them were designed for AHB interface.
3541		When software is doing ATA command and data transfer to
3542		IDE devices through IDE-AHB controller, some additional
3543		registers accessing to these kind of IDE-AHB controller
3544		is required.
3545
3546- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3547		DO NOT CHANGE unless you know exactly what you're
3548		doing! (11-4) [MPC8xx systems only]
3549
3550- CONFIG_SYS_INIT_RAM_ADDR:
3551
3552		Start address of memory area that can be used for
3553		initial data and stack; please note that this must be
3554		writable memory that is working WITHOUT special
3555		initialization, i. e. you CANNOT use normal RAM which
3556		will become available only after programming the
3557		memory controller and running certain initialization
3558		sequences.
3559
3560		U-Boot uses the following memory types:
3561		- MPC8xx: IMMR (internal memory of the CPU)
3562
3563- CONFIG_SYS_GBL_DATA_OFFSET:
3564
3565		Offset of the initial data structure in the memory
3566		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3567		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3568		data is located at the end of the available space
3569		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3570		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3571		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3572		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3573
3574	Note:
3575		On the MPC824X (or other systems that use the data
3576		cache for initial memory) the address chosen for
3577		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3578		point to an otherwise UNUSED address space between
3579		the top of RAM and the start of the PCI space.
3580
3581- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3582
3583- CONFIG_SYS_OR_TIMING_SDRAM:
3584		SDRAM timing
3585
3586- CONFIG_SYS_MAMR_PTA:
3587		periodic timer for refresh
3588
3589- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3590  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3591  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3592  CONFIG_SYS_BR1_PRELIM:
3593		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3594
3595- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3596  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3597  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3598		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3599
3600- CONFIG_PCI_ENUM_ONLY
3601		Only scan through and get the devices on the buses.
3602		Don't do any setup work, presumably because someone or
3603		something has already done it, and we don't need to do it
3604		a second time.	Useful for platforms that are pre-booted
3605		by coreboot or similar.
3606
3607- CONFIG_PCI_INDIRECT_BRIDGE:
3608		Enable support for indirect PCI bridges.
3609
3610- CONFIG_SYS_SRIO:
3611		Chip has SRIO or not
3612
3613- CONFIG_SRIO1:
3614		Board has SRIO 1 port available
3615
3616- CONFIG_SRIO2:
3617		Board has SRIO 2 port available
3618
3619- CONFIG_SRIO_PCIE_BOOT_MASTER
3620		Board can support master function for Boot from SRIO and PCIE
3621
3622- CONFIG_SYS_SRIOn_MEM_VIRT:
3623		Virtual Address of SRIO port 'n' memory region
3624
3625- CONFIG_SYS_SRIOn_MEM_PHYS:
3626		Physical Address of SRIO port 'n' memory region
3627
3628- CONFIG_SYS_SRIOn_MEM_SIZE:
3629		Size of SRIO port 'n' memory region
3630
3631- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3632		Defined to tell the NAND controller that the NAND chip is using
3633		a 16 bit bus.
3634		Not all NAND drivers use this symbol.
3635		Example of drivers that use it:
3636		- drivers/mtd/nand/ndfc.c
3637		- drivers/mtd/nand/mxc_nand.c
3638
3639- CONFIG_SYS_NDFC_EBC0_CFG
3640		Sets the EBC0_CFG register for the NDFC. If not defined
3641		a default value will be used.
3642
3643- CONFIG_SPD_EEPROM
3644		Get DDR timing information from an I2C EEPROM. Common
3645		with pluggable memory modules such as SODIMMs
3646
3647  SPD_EEPROM_ADDRESS
3648		I2C address of the SPD EEPROM
3649
3650- CONFIG_SYS_SPD_BUS_NUM
3651		If SPD EEPROM is on an I2C bus other than the first
3652		one, specify here. Note that the value must resolve
3653		to something your driver can deal with.
3654
3655- CONFIG_SYS_DDR_RAW_TIMING
3656		Get DDR timing information from other than SPD. Common with
3657		soldered DDR chips onboard without SPD. DDR raw timing
3658		parameters are extracted from datasheet and hard-coded into
3659		header files or board specific files.
3660
3661- CONFIG_FSL_DDR_INTERACTIVE
3662		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3663
3664- CONFIG_FSL_DDR_SYNC_REFRESH
3665		Enable sync of refresh for multiple controllers.
3666
3667- CONFIG_FSL_DDR_BIST
3668		Enable built-in memory test for Freescale DDR controllers.
3669
3670- CONFIG_SYS_83XX_DDR_USES_CS0
3671		Only for 83xx systems. If specified, then DDR should
3672		be configured using CS0 and CS1 instead of CS2 and CS3.
3673
3674- CONFIG_RMII
3675		Enable RMII mode for all FECs.
3676		Note that this is a global option, we can't
3677		have one FEC in standard MII mode and another in RMII mode.
3678
3679- CONFIG_CRC32_VERIFY
3680		Add a verify option to the crc32 command.
3681		The syntax is:
3682
3683		=> crc32 -v <address> <count> <crc32>
3684
3685		Where address/count indicate a memory area
3686		and crc32 is the correct crc32 which the
3687		area should have.
3688
3689- CONFIG_LOOPW
3690		Add the "loopw" memory command. This only takes effect if
3691		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3692
3693- CONFIG_MX_CYCLIC
3694		Add the "mdc" and "mwc" memory commands. These are cyclic
3695		"md/mw" commands.
3696		Examples:
3697
3698		=> mdc.b 10 4 500
3699		This command will print 4 bytes (10,11,12,13) each 500 ms.
3700
3701		=> mwc.l 100 12345678 10
3702		This command will write 12345678 to address 100 all 10 ms.
3703
3704		This only takes effect if the memory commands are activated
3705		globally (CONFIG_CMD_MEMORY).
3706
3707- CONFIG_SKIP_LOWLEVEL_INIT
3708		[ARM, NDS32, MIPS only] If this variable is defined, then certain
3709		low level initializations (like setting up the memory
3710		controller) are omitted and/or U-Boot does not
3711		relocate itself into RAM.
3712
3713		Normally this variable MUST NOT be defined. The only
3714		exception is when U-Boot is loaded (to RAM) by some
3715		other boot loader or by a debugger which performs
3716		these initializations itself.
3717
3718- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3719		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3720		to be skipped. The normal CP15 init (such as enabling the
3721		instruction cache) is still performed.
3722
3723- CONFIG_SPL_BUILD
3724		Modifies the behaviour of start.S when compiling a loader
3725		that is executed before the actual U-Boot. E.g. when
3726		compiling a NAND SPL.
3727
3728- CONFIG_TPL_BUILD
3729		Modifies the behaviour of start.S  when compiling a loader
3730		that is executed after the SPL and before the actual U-Boot.
3731		It is loaded by the SPL.
3732
3733- CONFIG_SYS_MPC85XX_NO_RESETVEC
3734		Only for 85xx systems. If this variable is specified, the section
3735		.resetvec is not kept and the section .bootpg is placed in the
3736		previous 4k of the .text section.
3737
3738- CONFIG_ARCH_MAP_SYSMEM
3739		Generally U-Boot (and in particular the md command) uses
3740		effective address. It is therefore not necessary to regard
3741		U-Boot address as virtual addresses that need to be translated
3742		to physical addresses. However, sandbox requires this, since
3743		it maintains its own little RAM buffer which contains all
3744		addressable memory. This option causes some memory accesses
3745		to be mapped through map_sysmem() / unmap_sysmem().
3746
3747- CONFIG_X86_RESET_VECTOR
3748		If defined, the x86 reset vector code is included. This is not
3749		needed when U-Boot is running from Coreboot.
3750
3751- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
3752		Enables the RTC32K OSC on AM33xx based plattforms
3753
3754- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3755		Option to disable subpage write in NAND driver
3756		driver that uses this:
3757		drivers/mtd/nand/davinci_nand.c
3758
3759Freescale QE/FMAN Firmware Support:
3760-----------------------------------
3761
3762The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3763loading of "firmware", which is encoded in the QE firmware binary format.
3764This firmware often needs to be loaded during U-Boot booting, so macros
3765are used to identify the storage device (NOR flash, SPI, etc) and the address
3766within that device.
3767
3768- CONFIG_SYS_FMAN_FW_ADDR
3769	The address in the storage device where the FMAN microcode is located.  The
3770	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3771	is also specified.
3772
3773- CONFIG_SYS_QE_FW_ADDR
3774	The address in the storage device where the QE microcode is located.  The
3775	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3776	is also specified.
3777
3778- CONFIG_SYS_QE_FMAN_FW_LENGTH
3779	The maximum possible size of the firmware.  The firmware binary format
3780	has a field that specifies the actual size of the firmware, but it
3781	might not be possible to read any part of the firmware unless some
3782	local storage is allocated to hold the entire firmware first.
3783
3784- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3785	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3786	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3787	virtual address in NOR flash.
3788
3789- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3790	Specifies that QE/FMAN firmware is located in NAND flash.
3791	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3792
3793- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3794	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3795	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3796
3797- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3798	Specifies that QE/FMAN firmware is located in the remote (master)
3799	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3800	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3801	window->master inbound window->master LAW->the ucode address in
3802	master's memory space.
3803
3804Freescale Layerscape Management Complex Firmware Support:
3805---------------------------------------------------------
3806The Freescale Layerscape Management Complex (MC) supports the loading of
3807"firmware".
3808This firmware often needs to be loaded during U-Boot booting, so macros
3809are used to identify the storage device (NOR flash, SPI, etc) and the address
3810within that device.
3811
3812- CONFIG_FSL_MC_ENET
3813	Enable the MC driver for Layerscape SoCs.
3814
3815Freescale Layerscape Debug Server Support:
3816-------------------------------------------
3817The Freescale Layerscape Debug Server Support supports the loading of
3818"Debug Server firmware" and triggering SP boot-rom.
3819This firmware often needs to be loaded during U-Boot booting.
3820
3821- CONFIG_SYS_MC_RSV_MEM_ALIGN
3822	Define alignment of reserved memory MC requires
3823
3824Reproducible builds
3825-------------------
3826
3827In order to achieve reproducible builds, timestamps used in the U-Boot build
3828process have to be set to a fixed value.
3829
3830This is done using the SOURCE_DATE_EPOCH environment variable.
3831SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3832option for U-Boot or an environment variable in U-Boot.
3833
3834SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3835
3836Building the Software:
3837======================
3838
3839Building U-Boot has been tested in several native build environments
3840and in many different cross environments. Of course we cannot support
3841all possibly existing versions of cross development tools in all
3842(potentially obsolete) versions. In case of tool chain problems we
3843recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3844which is extensively used to build and test U-Boot.
3845
3846If you are not using a native environment, it is assumed that you
3847have GNU cross compiling tools available in your path. In this case,
3848you must set the environment variable CROSS_COMPILE in your shell.
3849Note that no changes to the Makefile or any other source files are
3850necessary. For example using the ELDK on a 4xx CPU, please enter:
3851
3852	$ CROSS_COMPILE=ppc_4xx-
3853	$ export CROSS_COMPILE
3854
3855Note: If you wish to generate Windows versions of the utilities in
3856      the tools directory you can use the MinGW toolchain
3857      (http://www.mingw.org).  Set your HOST tools to the MinGW
3858      toolchain and execute 'make tools'.  For example:
3859
3860       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3861
3862      Binaries such as tools/mkimage.exe will be created which can
3863      be executed on computers running Windows.
3864
3865U-Boot is intended to be simple to build. After installing the
3866sources you must configure U-Boot for one specific board type. This
3867is done by typing:
3868
3869	make NAME_defconfig
3870
3871where "NAME_defconfig" is the name of one of the existing configu-
3872rations; see boards.cfg for supported names.
3873
3874Note: for some board special configuration names may exist; check if
3875      additional information is available from the board vendor; for
3876      instance, the TQM823L systems are available without (standard)
3877      or with LCD support. You can select such additional "features"
3878      when choosing the configuration, i. e.
3879
3880      make TQM823L_defconfig
3881	- will configure for a plain TQM823L, i. e. no LCD support
3882
3883      make TQM823L_LCD_defconfig
3884	- will configure for a TQM823L with U-Boot console on LCD
3885
3886      etc.
3887
3888
3889Finally, type "make all", and you should get some working U-Boot
3890images ready for download to / installation on your system:
3891
3892- "u-boot.bin" is a raw binary image
3893- "u-boot" is an image in ELF binary format
3894- "u-boot.srec" is in Motorola S-Record format
3895
3896By default the build is performed locally and the objects are saved
3897in the source directory. One of the two methods can be used to change
3898this behavior and build U-Boot to some external directory:
3899
39001. Add O= to the make command line invocations:
3901
3902	make O=/tmp/build distclean
3903	make O=/tmp/build NAME_defconfig
3904	make O=/tmp/build all
3905
39062. Set environment variable KBUILD_OUTPUT to point to the desired location:
3907
3908	export KBUILD_OUTPUT=/tmp/build
3909	make distclean
3910	make NAME_defconfig
3911	make all
3912
3913Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3914variable.
3915
3916
3917Please be aware that the Makefiles assume you are using GNU make, so
3918for instance on NetBSD you might need to use "gmake" instead of
3919native "make".
3920
3921
3922If the system board that you have is not listed, then you will need
3923to port U-Boot to your hardware platform. To do this, follow these
3924steps:
3925
39261.  Create a new directory to hold your board specific code. Add any
3927    files you need. In your board directory, you will need at least
3928    the "Makefile" and a "<board>.c".
39292.  Create a new configuration file "include/configs/<board>.h" for
3930    your board.
39313.  If you're porting U-Boot to a new CPU, then also create a new
3932    directory to hold your CPU specific code. Add any files you need.
39334.  Run "make <board>_defconfig" with your new name.
39345.  Type "make", and you should get a working "u-boot.srec" file
3935    to be installed on your target system.
39366.  Debug and solve any problems that might arise.
3937    [Of course, this last step is much harder than it sounds.]
3938
3939
3940Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3941==============================================================
3942
3943If you have modified U-Boot sources (for instance added a new board
3944or support for new devices, a new CPU, etc.) you are expected to
3945provide feedback to the other developers. The feedback normally takes
3946the form of a "patch", i. e. a context diff against a certain (latest
3947official or latest in the git repository) version of U-Boot sources.
3948
3949But before you submit such a patch, please verify that your modifi-
3950cation did not break existing code. At least make sure that *ALL* of
3951the supported boards compile WITHOUT ANY compiler warnings. To do so,
3952just run the buildman script (tools/buildman/buildman), which will
3953configure and build U-Boot for ALL supported system. Be warned, this
3954will take a while. Please see the buildman README, or run 'buildman -H'
3955for documentation.
3956
3957
3958See also "U-Boot Porting Guide" below.
3959
3960
3961Monitor Commands - Overview:
3962============================
3963
3964go	- start application at address 'addr'
3965run	- run commands in an environment variable
3966bootm	- boot application image from memory
3967bootp	- boot image via network using BootP/TFTP protocol
3968bootz   - boot zImage from memory
3969tftpboot- boot image via network using TFTP protocol
3970	       and env variables "ipaddr" and "serverip"
3971	       (and eventually "gatewayip")
3972tftpput - upload a file via network using TFTP protocol
3973rarpboot- boot image via network using RARP/TFTP protocol
3974diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3975loads	- load S-Record file over serial line
3976loadb	- load binary file over serial line (kermit mode)
3977md	- memory display
3978mm	- memory modify (auto-incrementing)
3979nm	- memory modify (constant address)
3980mw	- memory write (fill)
3981cp	- memory copy
3982cmp	- memory compare
3983crc32	- checksum calculation
3984i2c	- I2C sub-system
3985sspi	- SPI utility commands
3986base	- print or set address offset
3987printenv- print environment variables
3988setenv	- set environment variables
3989saveenv - save environment variables to persistent storage
3990protect - enable or disable FLASH write protection
3991erase	- erase FLASH memory
3992flinfo	- print FLASH memory information
3993nand	- NAND memory operations (see doc/README.nand)
3994bdinfo	- print Board Info structure
3995iminfo	- print header information for application image
3996coninfo - print console devices and informations
3997ide	- IDE sub-system
3998loop	- infinite loop on address range
3999loopw	- infinite write loop on address range
4000mtest	- simple RAM test
4001icache	- enable or disable instruction cache
4002dcache	- enable or disable data cache
4003reset	- Perform RESET of the CPU
4004echo	- echo args to console
4005version - print monitor version
4006help	- print online help
4007?	- alias for 'help'
4008
4009
4010Monitor Commands - Detailed Description:
4011========================================
4012
4013TODO.
4014
4015For now: just type "help <command>".
4016
4017
4018Environment Variables:
4019======================
4020
4021U-Boot supports user configuration using Environment Variables which
4022can be made persistent by saving to Flash memory.
4023
4024Environment Variables are set using "setenv", printed using
4025"printenv", and saved to Flash using "saveenv". Using "setenv"
4026without a value can be used to delete a variable from the
4027environment. As long as you don't save the environment you are
4028working with an in-memory copy. In case the Flash area containing the
4029environment is erased by accident, a default environment is provided.
4030
4031Some configuration options can be set using Environment Variables.
4032
4033List of environment variables (most likely not complete):
4034
4035  baudrate	- see CONFIG_BAUDRATE
4036
4037  bootdelay	- see CONFIG_BOOTDELAY
4038
4039  bootcmd	- see CONFIG_BOOTCOMMAND
4040
4041  bootargs	- Boot arguments when booting an RTOS image
4042
4043  bootfile	- Name of the image to load with TFTP
4044
4045  bootm_low	- Memory range available for image processing in the bootm
4046		  command can be restricted. This variable is given as
4047		  a hexadecimal number and defines lowest address allowed
4048		  for use by the bootm command. See also "bootm_size"
4049		  environment variable. Address defined by "bootm_low" is
4050		  also the base of the initial memory mapping for the Linux
4051		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4052		  bootm_mapsize.
4053
4054  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4055		  This variable is given as a hexadecimal number and it
4056		  defines the size of the memory region starting at base
4057		  address bootm_low that is accessible by the Linux kernel
4058		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4059		  as the default value if it is defined, and bootm_size is
4060		  used otherwise.
4061
4062  bootm_size	- Memory range available for image processing in the bootm
4063		  command can be restricted. This variable is given as
4064		  a hexadecimal number and defines the size of the region
4065		  allowed for use by the bootm command. See also "bootm_low"
4066		  environment variable.
4067
4068  updatefile	- Location of the software update file on a TFTP server, used
4069		  by the automatic software update feature. Please refer to
4070		  documentation in doc/README.update for more details.
4071
4072  autoload	- if set to "no" (any string beginning with 'n'),
4073		  "bootp" will just load perform a lookup of the
4074		  configuration from the BOOTP server, but not try to
4075		  load any image using TFTP
4076
4077  autostart	- if set to "yes", an image loaded using the "bootp",
4078		  "rarpboot", "tftpboot" or "diskboot" commands will
4079		  be automatically started (by internally calling
4080		  "bootm")
4081
4082		  If set to "no", a standalone image passed to the
4083		  "bootm" command will be copied to the load address
4084		  (and eventually uncompressed), but NOT be started.
4085		  This can be used to load and uncompress arbitrary
4086		  data.
4087
4088  fdt_high	- if set this restricts the maximum address that the
4089		  flattened device tree will be copied into upon boot.
4090		  For example, if you have a system with 1 GB memory
4091		  at physical address 0x10000000, while Linux kernel
4092		  only recognizes the first 704 MB as low memory, you
4093		  may need to set fdt_high as 0x3C000000 to have the
4094		  device tree blob be copied to the maximum address
4095		  of the 704 MB low memory, so that Linux kernel can
4096		  access it during the boot procedure.
4097
4098		  If this is set to the special value 0xFFFFFFFF then
4099		  the fdt will not be copied at all on boot.  For this
4100		  to work it must reside in writable memory, have
4101		  sufficient padding on the end of it for u-boot to
4102		  add the information it needs into it, and the memory
4103		  must be accessible by the kernel.
4104
4105  fdtcontroladdr- if set this is the address of the control flattened
4106		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4107		  defined.
4108
4109  i2cfast	- (PPC405GP|PPC405EP only)
4110		  if set to 'y' configures Linux I2C driver for fast
4111		  mode (400kHZ). This environment variable is used in
4112		  initialization code. So, for changes to be effective
4113		  it must be saved and board must be reset.
4114
4115  initrd_high	- restrict positioning of initrd images:
4116		  If this variable is not set, initrd images will be
4117		  copied to the highest possible address in RAM; this
4118		  is usually what you want since it allows for
4119		  maximum initrd size. If for some reason you want to
4120		  make sure that the initrd image is loaded below the
4121		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4122		  variable to a value of "no" or "off" or "0".
4123		  Alternatively, you can set it to a maximum upper
4124		  address to use (U-Boot will still check that it
4125		  does not overwrite the U-Boot stack and data).
4126
4127		  For instance, when you have a system with 16 MB
4128		  RAM, and want to reserve 4 MB from use by Linux,
4129		  you can do this by adding "mem=12M" to the value of
4130		  the "bootargs" variable. However, now you must make
4131		  sure that the initrd image is placed in the first
4132		  12 MB as well - this can be done with
4133
4134		  setenv initrd_high 00c00000
4135
4136		  If you set initrd_high to 0xFFFFFFFF, this is an
4137		  indication to U-Boot that all addresses are legal
4138		  for the Linux kernel, including addresses in flash
4139		  memory. In this case U-Boot will NOT COPY the
4140		  ramdisk at all. This may be useful to reduce the
4141		  boot time on your system, but requires that this
4142		  feature is supported by your Linux kernel.
4143
4144  ipaddr	- IP address; needed for tftpboot command
4145
4146  loadaddr	- Default load address for commands like "bootp",
4147		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4148
4149  loads_echo	- see CONFIG_LOADS_ECHO
4150
4151  serverip	- TFTP server IP address; needed for tftpboot command
4152
4153  bootretry	- see CONFIG_BOOT_RETRY_TIME
4154
4155  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4156
4157  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4158
4159  ethprime	- controls which interface is used first.
4160
4161  ethact	- controls which interface is currently active.
4162		  For example you can do the following
4163
4164		  => setenv ethact FEC
4165		  => ping 192.168.0.1 # traffic sent on FEC
4166		  => setenv ethact SCC
4167		  => ping 10.0.0.1 # traffic sent on SCC
4168
4169  ethrotate	- When set to "no" U-Boot does not go through all
4170		  available network interfaces.
4171		  It just stays at the currently selected interface.
4172
4173  netretry	- When set to "no" each network operation will
4174		  either succeed or fail without retrying.
4175		  When set to "once" the network operation will
4176		  fail when all the available network interfaces
4177		  are tried once without success.
4178		  Useful on scripts which control the retry operation
4179		  themselves.
4180
4181  npe_ucode	- set load address for the NPE microcode
4182
4183  silent_linux  - If set then Linux will be told to boot silently, by
4184		  changing the console to be empty. If "yes" it will be
4185		  made silent. If "no" it will not be made silent. If
4186		  unset, then it will be made silent if the U-Boot console
4187		  is silent.
4188
4189  tftpsrcp	- If this is set, the value is used for TFTP's
4190		  UDP source port.
4191
4192  tftpdstp	- If this is set, the value is used for TFTP's UDP
4193		  destination port instead of the Well Know Port 69.
4194
4195  tftpblocksize - Block size to use for TFTP transfers; if not set,
4196		  we use the TFTP server's default block size
4197
4198  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4199		  seconds, minimum value is 1000 = 1 second). Defines
4200		  when a packet is considered to be lost so it has to
4201		  be retransmitted. The default is 5000 = 5 seconds.
4202		  Lowering this value may make downloads succeed
4203		  faster in networks with high packet loss rates or
4204		  with unreliable TFTP servers.
4205
4206  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
4207		  unit, minimum value = 0). Defines how many timeouts
4208		  can happen during a single file transfer before that
4209		  transfer is aborted. The default is 10, and 0 means
4210		  'no timeouts allowed'. Increasing this value may help
4211		  downloads succeed with high packet loss rates, or with
4212		  unreliable TFTP servers or client hardware.
4213
4214  vlan		- When set to a value < 4095 the traffic over
4215		  Ethernet is encapsulated/received over 802.1q
4216		  VLAN tagged frames.
4217
4218  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
4219		  Unsigned value, in milliseconds. If not set, the period will
4220		  be either the default (28000), or a value based on
4221		  CONFIG_NET_RETRY_COUNT, if defined. This value has
4222		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
4223
4224The following image location variables contain the location of images
4225used in booting. The "Image" column gives the role of the image and is
4226not an environment variable name. The other columns are environment
4227variable names. "File Name" gives the name of the file on a TFTP
4228server, "RAM Address" gives the location in RAM the image will be
4229loaded to, and "Flash Location" gives the image's address in NOR
4230flash or offset in NAND flash.
4231
4232*Note* - these variables don't have to be defined for all boards, some
4233boards currently use other variables for these purposes, and some
4234boards use these variables for other purposes.
4235
4236Image		    File Name	     RAM Address       Flash Location
4237-----		    ---------	     -----------       --------------
4238u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4239Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4240device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4241ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4242
4243The following environment variables may be used and automatically
4244updated by the network boot commands ("bootp" and "rarpboot"),
4245depending the information provided by your boot server:
4246
4247  bootfile	- see above
4248  dnsip		- IP address of your Domain Name Server
4249  dnsip2	- IP address of your secondary Domain Name Server
4250  gatewayip	- IP address of the Gateway (Router) to use
4251  hostname	- Target hostname
4252  ipaddr	- see above
4253  netmask	- Subnet Mask
4254  rootpath	- Pathname of the root filesystem on the NFS server
4255  serverip	- see above
4256
4257
4258There are two special Environment Variables:
4259
4260  serial#	- contains hardware identification information such
4261		  as type string and/or serial number
4262  ethaddr	- Ethernet address
4263
4264These variables can be set only once (usually during manufacturing of
4265the board). U-Boot refuses to delete or overwrite these variables
4266once they have been set once.
4267
4268
4269Further special Environment Variables:
4270
4271  ver		- Contains the U-Boot version string as printed
4272		  with the "version" command. This variable is
4273		  readonly (see CONFIG_VERSION_VARIABLE).
4274
4275
4276Please note that changes to some configuration parameters may take
4277only effect after the next boot (yes, that's just like Windoze :-).
4278
4279
4280Callback functions for environment variables:
4281---------------------------------------------
4282
4283For some environment variables, the behavior of u-boot needs to change
4284when their values are changed.  This functionality allows functions to
4285be associated with arbitrary variables.  On creation, overwrite, or
4286deletion, the callback will provide the opportunity for some side
4287effect to happen or for the change to be rejected.
4288
4289The callbacks are named and associated with a function using the
4290U_BOOT_ENV_CALLBACK macro in your board or driver code.
4291
4292These callbacks are associated with variables in one of two ways.  The
4293static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4294in the board configuration to a string that defines a list of
4295associations.  The list must be in the following format:
4296
4297	entry = variable_name[:callback_name]
4298	list = entry[,list]
4299
4300If the callback name is not specified, then the callback is deleted.
4301Spaces are also allowed anywhere in the list.
4302
4303Callbacks can also be associated by defining the ".callbacks" variable
4304with the same list format above.  Any association in ".callbacks" will
4305override any association in the static list. You can define
4306CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4307".callbacks" environment variable in the default or embedded environment.
4308
4309If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4310regular expression. This allows multiple variables to be connected to
4311the same callback without explicitly listing them all out.
4312
4313
4314Command Line Parsing:
4315=====================
4316
4317There are two different command line parsers available with U-Boot:
4318the old "simple" one, and the much more powerful "hush" shell:
4319
4320Old, simple command line parser:
4321--------------------------------
4322
4323- supports environment variables (through setenv / saveenv commands)
4324- several commands on one line, separated by ';'
4325- variable substitution using "... ${name} ..." syntax
4326- special characters ('$', ';') can be escaped by prefixing with '\',
4327  for example:
4328	setenv bootcmd bootm \${address}
4329- You can also escape text by enclosing in single apostrophes, for example:
4330	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4331
4332Hush shell:
4333-----------
4334
4335- similar to Bourne shell, with control structures like
4336  if...then...else...fi, for...do...done; while...do...done,
4337  until...do...done, ...
4338- supports environment ("global") variables (through setenv / saveenv
4339  commands) and local shell variables (through standard shell syntax
4340  "name=value"); only environment variables can be used with "run"
4341  command
4342
4343General rules:
4344--------------
4345
4346(1) If a command line (or an environment variable executed by a "run"
4347    command) contains several commands separated by semicolon, and
4348    one of these commands fails, then the remaining commands will be
4349    executed anyway.
4350
4351(2) If you execute several variables with one call to run (i. e.
4352    calling run with a list of variables as arguments), any failing
4353    command will cause "run" to terminate, i. e. the remaining
4354    variables are not executed.
4355
4356Note for Redundant Ethernet Interfaces:
4357=======================================
4358
4359Some boards come with redundant Ethernet interfaces; U-Boot supports
4360such configurations and is capable of automatic selection of a
4361"working" interface when needed. MAC assignment works as follows:
4362
4363Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4364MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4365"eth1addr" (=>eth1), "eth2addr", ...
4366
4367If the network interface stores some valid MAC address (for instance
4368in SROM), this is used as default address if there is NO correspon-
4369ding setting in the environment; if the corresponding environment
4370variable is set, this overrides the settings in the card; that means:
4371
4372o If the SROM has a valid MAC address, and there is no address in the
4373  environment, the SROM's address is used.
4374
4375o If there is no valid address in the SROM, and a definition in the
4376  environment exists, then the value from the environment variable is
4377  used.
4378
4379o If both the SROM and the environment contain a MAC address, and
4380  both addresses are the same, this MAC address is used.
4381
4382o If both the SROM and the environment contain a MAC address, and the
4383  addresses differ, the value from the environment is used and a
4384  warning is printed.
4385
4386o If neither SROM nor the environment contain a MAC address, an error
4387  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4388  a random, locally-assigned MAC is used.
4389
4390If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4391will be programmed into hardware as part of the initialization process.	 This
4392may be skipped by setting the appropriate 'ethmacskip' environment variable.
4393The naming convention is as follows:
4394"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4395
4396Image Formats:
4397==============
4398
4399U-Boot is capable of booting (and performing other auxiliary operations on)
4400images in two formats:
4401
4402New uImage format (FIT)
4403-----------------------
4404
4405Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4406to Flattened Device Tree). It allows the use of images with multiple
4407components (several kernels, ramdisks, etc.), with contents protected by
4408SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4409
4410
4411Old uImage format
4412-----------------
4413
4414Old image format is based on binary files which can be basically anything,
4415preceded by a special header; see the definitions in include/image.h for
4416details; basically, the header defines the following image properties:
4417
4418* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4419  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4420  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4421  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4422  INTEGRITY).
4423* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4424  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4425  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4426* Compression Type (uncompressed, gzip, bzip2)
4427* Load Address
4428* Entry Point
4429* Image Name
4430* Image Timestamp
4431
4432The header is marked by a special Magic Number, and both the header
4433and the data portions of the image are secured against corruption by
4434CRC32 checksums.
4435
4436
4437Linux Support:
4438==============
4439
4440Although U-Boot should support any OS or standalone application
4441easily, the main focus has always been on Linux during the design of
4442U-Boot.
4443
4444U-Boot includes many features that so far have been part of some
4445special "boot loader" code within the Linux kernel. Also, any
4446"initrd" images to be used are no longer part of one big Linux image;
4447instead, kernel and "initrd" are separate images. This implementation
4448serves several purposes:
4449
4450- the same features can be used for other OS or standalone
4451  applications (for instance: using compressed images to reduce the
4452  Flash memory footprint)
4453
4454- it becomes much easier to port new Linux kernel versions because
4455  lots of low-level, hardware dependent stuff are done by U-Boot
4456
4457- the same Linux kernel image can now be used with different "initrd"
4458  images; of course this also means that different kernel images can
4459  be run with the same "initrd". This makes testing easier (you don't
4460  have to build a new "zImage.initrd" Linux image when you just
4461  change a file in your "initrd"). Also, a field-upgrade of the
4462  software is easier now.
4463
4464
4465Linux HOWTO:
4466============
4467
4468Porting Linux to U-Boot based systems:
4469---------------------------------------
4470
4471U-Boot cannot save you from doing all the necessary modifications to
4472configure the Linux device drivers for use with your target hardware
4473(no, we don't intend to provide a full virtual machine interface to
4474Linux :-).
4475
4476But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4477
4478Just make sure your machine specific header file (for instance
4479include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4480Information structure as we define in include/asm-<arch>/u-boot.h,
4481and make sure that your definition of IMAP_ADDR uses the same value
4482as your U-Boot configuration in CONFIG_SYS_IMMR.
4483
4484Note that U-Boot now has a driver model, a unified model for drivers.
4485If you are adding a new driver, plumb it into driver model. If there
4486is no uclass available, you are encouraged to create one. See
4487doc/driver-model.
4488
4489
4490Configuring the Linux kernel:
4491-----------------------------
4492
4493No specific requirements for U-Boot. Make sure you have some root
4494device (initial ramdisk, NFS) for your target system.
4495
4496
4497Building a Linux Image:
4498-----------------------
4499
4500With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4501not used. If you use recent kernel source, a new build target
4502"uImage" will exist which automatically builds an image usable by
4503U-Boot. Most older kernels also have support for a "pImage" target,
4504which was introduced for our predecessor project PPCBoot and uses a
4505100% compatible format.
4506
4507Example:
4508
4509	make TQM850L_defconfig
4510	make oldconfig
4511	make dep
4512	make uImage
4513
4514The "uImage" build target uses a special tool (in 'tools/mkimage') to
4515encapsulate a compressed Linux kernel image with header	 information,
4516CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4517
4518* build a standard "vmlinux" kernel image (in ELF binary format):
4519
4520* convert the kernel into a raw binary image:
4521
4522	${CROSS_COMPILE}-objcopy -O binary \
4523				 -R .note -R .comment \
4524				 -S vmlinux linux.bin
4525
4526* compress the binary image:
4527
4528	gzip -9 linux.bin
4529
4530* package compressed binary image for U-Boot:
4531
4532	mkimage -A ppc -O linux -T kernel -C gzip \
4533		-a 0 -e 0 -n "Linux Kernel Image" \
4534		-d linux.bin.gz uImage
4535
4536
4537The "mkimage" tool can also be used to create ramdisk images for use
4538with U-Boot, either separated from the Linux kernel image, or
4539combined into one file. "mkimage" encapsulates the images with a 64
4540byte header containing information about target architecture,
4541operating system, image type, compression method, entry points, time
4542stamp, CRC32 checksums, etc.
4543
4544"mkimage" can be called in two ways: to verify existing images and
4545print the header information, or to build new images.
4546
4547In the first form (with "-l" option) mkimage lists the information
4548contained in the header of an existing U-Boot image; this includes
4549checksum verification:
4550
4551	tools/mkimage -l image
4552	  -l ==> list image header information
4553
4554The second form (with "-d" option) is used to build a U-Boot image
4555from a "data file" which is used as image payload:
4556
4557	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4558		      -n name -d data_file image
4559	  -A ==> set architecture to 'arch'
4560	  -O ==> set operating system to 'os'
4561	  -T ==> set image type to 'type'
4562	  -C ==> set compression type 'comp'
4563	  -a ==> set load address to 'addr' (hex)
4564	  -e ==> set entry point to 'ep' (hex)
4565	  -n ==> set image name to 'name'
4566	  -d ==> use image data from 'datafile'
4567
4568Right now, all Linux kernels for PowerPC systems use the same load
4569address (0x00000000), but the entry point address depends on the
4570kernel version:
4571
4572- 2.2.x kernels have the entry point at 0x0000000C,
4573- 2.3.x and later kernels have the entry point at 0x00000000.
4574
4575So a typical call to build a U-Boot image would read:
4576
4577	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4578	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4579	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4580	> examples/uImage.TQM850L
4581	Image Name:   2.4.4 kernel for TQM850L
4582	Created:      Wed Jul 19 02:34:59 2000
4583	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4584	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4585	Load Address: 0x00000000
4586	Entry Point:  0x00000000
4587
4588To verify the contents of the image (or check for corruption):
4589
4590	-> tools/mkimage -l examples/uImage.TQM850L
4591	Image Name:   2.4.4 kernel for TQM850L
4592	Created:      Wed Jul 19 02:34:59 2000
4593	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4594	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4595	Load Address: 0x00000000
4596	Entry Point:  0x00000000
4597
4598NOTE: for embedded systems where boot time is critical you can trade
4599speed for memory and install an UNCOMPRESSED image instead: this
4600needs more space in Flash, but boots much faster since it does not
4601need to be uncompressed:
4602
4603	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4604	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4605	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4606	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4607	> examples/uImage.TQM850L-uncompressed
4608	Image Name:   2.4.4 kernel for TQM850L
4609	Created:      Wed Jul 19 02:34:59 2000
4610	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4611	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4612	Load Address: 0x00000000
4613	Entry Point:  0x00000000
4614
4615
4616Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4617when your kernel is intended to use an initial ramdisk:
4618
4619	-> tools/mkimage -n 'Simple Ramdisk Image' \
4620	> -A ppc -O linux -T ramdisk -C gzip \
4621	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4622	Image Name:   Simple Ramdisk Image
4623	Created:      Wed Jan 12 14:01:50 2000
4624	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4625	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4626	Load Address: 0x00000000
4627	Entry Point:  0x00000000
4628
4629The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4630option performs the converse operation of the mkimage's second form (the "-d"
4631option). Given an image built by mkimage, the dumpimage extracts a "data file"
4632from the image:
4633
4634	tools/dumpimage -i image -T type -p position data_file
4635	  -i ==> extract from the 'image' a specific 'data_file'
4636	  -T ==> set image type to 'type'
4637	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4638
4639
4640Installing a Linux Image:
4641-------------------------
4642
4643To downloading a U-Boot image over the serial (console) interface,
4644you must convert the image to S-Record format:
4645
4646	objcopy -I binary -O srec examples/image examples/image.srec
4647
4648The 'objcopy' does not understand the information in the U-Boot
4649image header, so the resulting S-Record file will be relative to
4650address 0x00000000. To load it to a given address, you need to
4651specify the target address as 'offset' parameter with the 'loads'
4652command.
4653
4654Example: install the image to address 0x40100000 (which on the
4655TQM8xxL is in the first Flash bank):
4656
4657	=> erase 40100000 401FFFFF
4658
4659	.......... done
4660	Erased 8 sectors
4661
4662	=> loads 40100000
4663	## Ready for S-Record download ...
4664	~>examples/image.srec
4665	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4666	...
4667	15989 15990 15991 15992
4668	[file transfer complete]
4669	[connected]
4670	## Start Addr = 0x00000000
4671
4672
4673You can check the success of the download using the 'iminfo' command;
4674this includes a checksum verification so you can be sure no data
4675corruption happened:
4676
4677	=> imi 40100000
4678
4679	## Checking Image at 40100000 ...
4680	   Image Name:	 2.2.13 for initrd on TQM850L
4681	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4682	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4683	   Load Address: 00000000
4684	   Entry Point:	 0000000c
4685	   Verifying Checksum ... OK
4686
4687
4688Boot Linux:
4689-----------
4690
4691The "bootm" command is used to boot an application that is stored in
4692memory (RAM or Flash). In case of a Linux kernel image, the contents
4693of the "bootargs" environment variable is passed to the kernel as
4694parameters. You can check and modify this variable using the
4695"printenv" and "setenv" commands:
4696
4697
4698	=> printenv bootargs
4699	bootargs=root=/dev/ram
4700
4701	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4702
4703	=> printenv bootargs
4704	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4705
4706	=> bootm 40020000
4707	## Booting Linux kernel at 40020000 ...
4708	   Image Name:	 2.2.13 for NFS on TQM850L
4709	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4710	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4711	   Load Address: 00000000
4712	   Entry Point:	 0000000c
4713	   Verifying Checksum ... OK
4714	   Uncompressing Kernel Image ... OK
4715	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
4716	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4717	time_init: decrementer frequency = 187500000/60
4718	Calibrating delay loop... 49.77 BogoMIPS
4719	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4720	...
4721
4722If you want to boot a Linux kernel with initial RAM disk, you pass
4723the memory addresses of both the kernel and the initrd image (PPBCOOT
4724format!) to the "bootm" command:
4725
4726	=> imi 40100000 40200000
4727
4728	## Checking Image at 40100000 ...
4729	   Image Name:	 2.2.13 for initrd on TQM850L
4730	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4731	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4732	   Load Address: 00000000
4733	   Entry Point:	 0000000c
4734	   Verifying Checksum ... OK
4735
4736	## Checking Image at 40200000 ...
4737	   Image Name:	 Simple Ramdisk Image
4738	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4739	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4740	   Load Address: 00000000
4741	   Entry Point:	 00000000
4742	   Verifying Checksum ... OK
4743
4744	=> bootm 40100000 40200000
4745	## Booting Linux kernel at 40100000 ...
4746	   Image Name:	 2.2.13 for initrd on TQM850L
4747	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4748	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4749	   Load Address: 00000000
4750	   Entry Point:	 0000000c
4751	   Verifying Checksum ... OK
4752	   Uncompressing Kernel Image ... OK
4753	## Loading RAMDisk Image at 40200000 ...
4754	   Image Name:	 Simple Ramdisk Image
4755	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4756	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4757	   Load Address: 00000000
4758	   Entry Point:	 00000000
4759	   Verifying Checksum ... OK
4760	   Loading Ramdisk ... OK
4761	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
4762	Boot arguments: root=/dev/ram
4763	time_init: decrementer frequency = 187500000/60
4764	Calibrating delay loop... 49.77 BogoMIPS
4765	...
4766	RAMDISK: Compressed image found at block 0
4767	VFS: Mounted root (ext2 filesystem).
4768
4769	bash#
4770
4771Boot Linux and pass a flat device tree:
4772-----------
4773
4774First, U-Boot must be compiled with the appropriate defines. See the section
4775titled "Linux Kernel Interface" above for a more in depth explanation. The
4776following is an example of how to start a kernel and pass an updated
4777flat device tree:
4778
4779=> print oftaddr
4780oftaddr=0x300000
4781=> print oft
4782oft=oftrees/mpc8540ads.dtb
4783=> tftp $oftaddr $oft
4784Speed: 1000, full duplex
4785Using TSEC0 device
4786TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4787Filename 'oftrees/mpc8540ads.dtb'.
4788Load address: 0x300000
4789Loading: #
4790done
4791Bytes transferred = 4106 (100a hex)
4792=> tftp $loadaddr $bootfile
4793Speed: 1000, full duplex
4794Using TSEC0 device
4795TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4796Filename 'uImage'.
4797Load address: 0x200000
4798Loading:############
4799done
4800Bytes transferred = 1029407 (fb51f hex)
4801=> print loadaddr
4802loadaddr=200000
4803=> print oftaddr
4804oftaddr=0x300000
4805=> bootm $loadaddr - $oftaddr
4806## Booting image at 00200000 ...
4807   Image Name:	 Linux-2.6.17-dirty
4808   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4809   Data Size:	 1029343 Bytes = 1005.2 kB
4810   Load Address: 00000000
4811   Entry Point:	 00000000
4812   Verifying Checksum ... OK
4813   Uncompressing Kernel Image ... OK
4814Booting using flat device tree at 0x300000
4815Using MPC85xx ADS machine description
4816Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4817[snip]
4818
4819
4820More About U-Boot Image Types:
4821------------------------------
4822
4823U-Boot supports the following image types:
4824
4825   "Standalone Programs" are directly runnable in the environment
4826	provided by U-Boot; it is expected that (if they behave
4827	well) you can continue to work in U-Boot after return from
4828	the Standalone Program.
4829   "OS Kernel Images" are usually images of some Embedded OS which
4830	will take over control completely. Usually these programs
4831	will install their own set of exception handlers, device
4832	drivers, set up the MMU, etc. - this means, that you cannot
4833	expect to re-enter U-Boot except by resetting the CPU.
4834   "RAMDisk Images" are more or less just data blocks, and their
4835	parameters (address, size) are passed to an OS kernel that is
4836	being started.
4837   "Multi-File Images" contain several images, typically an OS
4838	(Linux) kernel image and one or more data images like
4839	RAMDisks. This construct is useful for instance when you want
4840	to boot over the network using BOOTP etc., where the boot
4841	server provides just a single image file, but you want to get
4842	for instance an OS kernel and a RAMDisk image.
4843
4844	"Multi-File Images" start with a list of image sizes, each
4845	image size (in bytes) specified by an "uint32_t" in network
4846	byte order. This list is terminated by an "(uint32_t)0".
4847	Immediately after the terminating 0 follow the images, one by
4848	one, all aligned on "uint32_t" boundaries (size rounded up to
4849	a multiple of 4 bytes).
4850
4851   "Firmware Images" are binary images containing firmware (like
4852	U-Boot or FPGA images) which usually will be programmed to
4853	flash memory.
4854
4855   "Script files" are command sequences that will be executed by
4856	U-Boot's command interpreter; this feature is especially
4857	useful when you configure U-Boot to use a real shell (hush)
4858	as command interpreter.
4859
4860Booting the Linux zImage:
4861-------------------------
4862
4863On some platforms, it's possible to boot Linux zImage. This is done
4864using the "bootz" command. The syntax of "bootz" command is the same
4865as the syntax of "bootm" command.
4866
4867Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4868kernel with raw initrd images. The syntax is slightly different, the
4869address of the initrd must be augmented by it's size, in the following
4870format: "<initrd addres>:<initrd size>".
4871
4872
4873Standalone HOWTO:
4874=================
4875
4876One of the features of U-Boot is that you can dynamically load and
4877run "standalone" applications, which can use some resources of
4878U-Boot like console I/O functions or interrupt services.
4879
4880Two simple examples are included with the sources:
4881
4882"Hello World" Demo:
4883-------------------
4884
4885'examples/hello_world.c' contains a small "Hello World" Demo
4886application; it is automatically compiled when you build U-Boot.
4887It's configured to run at address 0x00040004, so you can play with it
4888like that:
4889
4890	=> loads
4891	## Ready for S-Record download ...
4892	~>examples/hello_world.srec
4893	1 2 3 4 5 6 7 8 9 10 11 ...
4894	[file transfer complete]
4895	[connected]
4896	## Start Addr = 0x00040004
4897
4898	=> go 40004 Hello World! This is a test.
4899	## Starting application at 0x00040004 ...
4900	Hello World
4901	argc = 7
4902	argv[0] = "40004"
4903	argv[1] = "Hello"
4904	argv[2] = "World!"
4905	argv[3] = "This"
4906	argv[4] = "is"
4907	argv[5] = "a"
4908	argv[6] = "test."
4909	argv[7] = "<NULL>"
4910	Hit any key to exit ...
4911
4912	## Application terminated, rc = 0x0
4913
4914Another example, which demonstrates how to register a CPM interrupt
4915handler with the U-Boot code, can be found in 'examples/timer.c'.
4916Here, a CPM timer is set up to generate an interrupt every second.
4917The interrupt service routine is trivial, just printing a '.'
4918character, but this is just a demo program. The application can be
4919controlled by the following keys:
4920
4921	? - print current values og the CPM Timer registers
4922	b - enable interrupts and start timer
4923	e - stop timer and disable interrupts
4924	q - quit application
4925
4926	=> loads
4927	## Ready for S-Record download ...
4928	~>examples/timer.srec
4929	1 2 3 4 5 6 7 8 9 10 11 ...
4930	[file transfer complete]
4931	[connected]
4932	## Start Addr = 0x00040004
4933
4934	=> go 40004
4935	## Starting application at 0x00040004 ...
4936	TIMERS=0xfff00980
4937	Using timer 1
4938	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4939
4940Hit 'b':
4941	[q, b, e, ?] Set interval 1000000 us
4942	Enabling timer
4943Hit '?':
4944	[q, b, e, ?] ........
4945	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4946Hit '?':
4947	[q, b, e, ?] .
4948	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4949Hit '?':
4950	[q, b, e, ?] .
4951	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4952Hit '?':
4953	[q, b, e, ?] .
4954	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4955Hit 'e':
4956	[q, b, e, ?] ...Stopping timer
4957Hit 'q':
4958	[q, b, e, ?] ## Application terminated, rc = 0x0
4959
4960
4961Minicom warning:
4962================
4963
4964Over time, many people have reported problems when trying to use the
4965"minicom" terminal emulation program for serial download. I (wd)
4966consider minicom to be broken, and recommend not to use it. Under
4967Unix, I recommend to use C-Kermit for general purpose use (and
4968especially for kermit binary protocol download ("loadb" command), and
4969use "cu" for S-Record download ("loads" command).  See
4970http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4971for help with kermit.
4972
4973
4974Nevertheless, if you absolutely want to use it try adding this
4975configuration to your "File transfer protocols" section:
4976
4977	   Name	   Program			Name U/D FullScr IO-Red. Multi
4978	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4979	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4980
4981
4982NetBSD Notes:
4983=============
4984
4985Starting at version 0.9.2, U-Boot supports NetBSD both as host
4986(build U-Boot) and target system (boots NetBSD/mpc8xx).
4987
4988Building requires a cross environment; it is known to work on
4989NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4990need gmake since the Makefiles are not compatible with BSD make).
4991Note that the cross-powerpc package does not install include files;
4992attempting to build U-Boot will fail because <machine/ansi.h> is
4993missing.  This file has to be installed and patched manually:
4994
4995	# cd /usr/pkg/cross/powerpc-netbsd/include
4996	# mkdir powerpc
4997	# ln -s powerpc machine
4998	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4999	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5000
5001Native builds *don't* work due to incompatibilities between native
5002and U-Boot include files.
5003
5004Booting assumes that (the first part of) the image booted is a
5005stage-2 loader which in turn loads and then invokes the kernel
5006proper. Loader sources will eventually appear in the NetBSD source
5007tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5008meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5009
5010
5011Implementation Internals:
5012=========================
5013
5014The following is not intended to be a complete description of every
5015implementation detail. However, it should help to understand the
5016inner workings of U-Boot and make it easier to port it to custom
5017hardware.
5018
5019
5020Initial Stack, Global Data:
5021---------------------------
5022
5023The implementation of U-Boot is complicated by the fact that U-Boot
5024starts running out of ROM (flash memory), usually without access to
5025system RAM (because the memory controller is not initialized yet).
5026This means that we don't have writable Data or BSS segments, and BSS
5027is not initialized as zero. To be able to get a C environment working
5028at all, we have to allocate at least a minimal stack. Implementation
5029options for this are defined and restricted by the CPU used: Some CPU
5030models provide on-chip memory (like the IMMR area on MPC8xx and
5031MPC826x processors), on others (parts of) the data cache can be
5032locked as (mis-) used as memory, etc.
5033
5034	Chris Hallinan posted a good summary of these issues to the
5035	U-Boot mailing list:
5036
5037	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5038	From: "Chris Hallinan" <clh@net1plus.com>
5039	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5040	...
5041
5042	Correct me if I'm wrong, folks, but the way I understand it
5043	is this: Using DCACHE as initial RAM for Stack, etc, does not
5044	require any physical RAM backing up the cache. The cleverness
5045	is that the cache is being used as a temporary supply of
5046	necessary storage before the SDRAM controller is setup. It's
5047	beyond the scope of this list to explain the details, but you
5048	can see how this works by studying the cache architecture and
5049	operation in the architecture and processor-specific manuals.
5050
5051	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5052	is another option for the system designer to use as an
5053	initial stack/RAM area prior to SDRAM being available. Either
5054	option should work for you. Using CS 4 should be fine if your
5055	board designers haven't used it for something that would
5056	cause you grief during the initial boot! It is frequently not
5057	used.
5058
5059	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5060	with your processor/board/system design. The default value
5061	you will find in any recent u-boot distribution in
5062	walnut.h should work for you. I'd set it to a value larger
5063	than your SDRAM module. If you have a 64MB SDRAM module, set
5064	it above 400_0000. Just make sure your board has no resources
5065	that are supposed to respond to that address! That code in
5066	start.S has been around a while and should work as is when
5067	you get the config right.
5068
5069	-Chris Hallinan
5070	DS4.COM, Inc.
5071
5072It is essential to remember this, since it has some impact on the C
5073code for the initialization procedures:
5074
5075* Initialized global data (data segment) is read-only. Do not attempt
5076  to write it.
5077
5078* Do not use any uninitialized global data (or implicitly initialized
5079  as zero data - BSS segment) at all - this is undefined, initiali-
5080  zation is performed later (when relocating to RAM).
5081
5082* Stack space is very limited. Avoid big data buffers or things like
5083  that.
5084
5085Having only the stack as writable memory limits means we cannot use
5086normal global data to share information between the code. But it
5087turned out that the implementation of U-Boot can be greatly
5088simplified by making a global data structure (gd_t) available to all
5089functions. We could pass a pointer to this data as argument to _all_
5090functions, but this would bloat the code. Instead we use a feature of
5091the GCC compiler (Global Register Variables) to share the data: we
5092place a pointer (gd) to the global data into a register which we
5093reserve for this purpose.
5094
5095When choosing a register for such a purpose we are restricted by the
5096relevant  (E)ABI  specifications for the current architecture, and by
5097GCC's implementation.
5098
5099For PowerPC, the following registers have specific use:
5100	R1:	stack pointer
5101	R2:	reserved for system use
5102	R3-R4:	parameter passing and return values
5103	R5-R10: parameter passing
5104	R13:	small data area pointer
5105	R30:	GOT pointer
5106	R31:	frame pointer
5107
5108	(U-Boot also uses R12 as internal GOT pointer. r12
5109	is a volatile register so r12 needs to be reset when
5110	going back and forth between asm and C)
5111
5112    ==> U-Boot will use R2 to hold a pointer to the global data
5113
5114    Note: on PPC, we could use a static initializer (since the
5115    address of the global data structure is known at compile time),
5116    but it turned out that reserving a register results in somewhat
5117    smaller code - although the code savings are not that big (on
5118    average for all boards 752 bytes for the whole U-Boot image,
5119    624 text + 127 data).
5120
5121On ARM, the following registers are used:
5122
5123	R0:	function argument word/integer result
5124	R1-R3:	function argument word
5125	R9:	platform specific
5126	R10:	stack limit (used only if stack checking is enabled)
5127	R11:	argument (frame) pointer
5128	R12:	temporary workspace
5129	R13:	stack pointer
5130	R14:	link register
5131	R15:	program counter
5132
5133    ==> U-Boot will use R9 to hold a pointer to the global data
5134
5135    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5136
5137On Nios II, the ABI is documented here:
5138	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5139
5140    ==> U-Boot will use gp to hold a pointer to the global data
5141
5142    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5143    to access small data sections, so gp is free.
5144
5145On NDS32, the following registers are used:
5146
5147	R0-R1:	argument/return
5148	R2-R5:	argument
5149	R15:	temporary register for assembler
5150	R16:	trampoline register
5151	R28:	frame pointer (FP)
5152	R29:	global pointer (GP)
5153	R30:	link register (LP)
5154	R31:	stack pointer (SP)
5155	PC:	program counter (PC)
5156
5157    ==> U-Boot will use R10 to hold a pointer to the global data
5158
5159NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5160or current versions of GCC may "optimize" the code too much.
5161
5162Memory Management:
5163------------------
5164
5165U-Boot runs in system state and uses physical addresses, i.e. the
5166MMU is not used either for address mapping nor for memory protection.
5167
5168The available memory is mapped to fixed addresses using the memory
5169controller. In this process, a contiguous block is formed for each
5170memory type (Flash, SDRAM, SRAM), even when it consists of several
5171physical memory banks.
5172
5173U-Boot is installed in the first 128 kB of the first Flash bank (on
5174TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5175booting and sizing and initializing DRAM, the code relocates itself
5176to the upper end of DRAM. Immediately below the U-Boot code some
5177memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5178configuration setting]. Below that, a structure with global Board
5179Info data is placed, followed by the stack (growing downward).
5180
5181Additionally, some exception handler code is copied to the low 8 kB
5182of DRAM (0x00000000 ... 0x00001FFF).
5183
5184So a typical memory configuration with 16 MB of DRAM could look like
5185this:
5186
5187	0x0000 0000	Exception Vector code
5188	      :
5189	0x0000 1FFF
5190	0x0000 2000	Free for Application Use
5191	      :
5192	      :
5193
5194	      :
5195	      :
5196	0x00FB FF20	Monitor Stack (Growing downward)
5197	0x00FB FFAC	Board Info Data and permanent copy of global data
5198	0x00FC 0000	Malloc Arena
5199	      :
5200	0x00FD FFFF
5201	0x00FE 0000	RAM Copy of Monitor Code
5202	...		eventually: LCD or video framebuffer
5203	...		eventually: pRAM (Protected RAM - unchanged by reset)
5204	0x00FF FFFF	[End of RAM]
5205
5206
5207System Initialization:
5208----------------------
5209
5210In the reset configuration, U-Boot starts at the reset entry point
5211(on most PowerPC systems at address 0x00000100). Because of the reset
5212configuration for CS0# this is a mirror of the on board Flash memory.
5213To be able to re-map memory U-Boot then jumps to its link address.
5214To be able to implement the initialization code in C, a (small!)
5215initial stack is set up in the internal Dual Ported RAM (in case CPUs
5216which provide such a feature like), or in a locked part of the data
5217cache. After that, U-Boot initializes the CPU core, the caches and
5218the SIU.
5219
5220Next, all (potentially) available memory banks are mapped using a
5221preliminary mapping. For example, we put them on 512 MB boundaries
5222(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5223on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5224programmed for SDRAM access. Using the temporary configuration, a
5225simple memory test is run that determines the size of the SDRAM
5226banks.
5227
5228When there is more than one SDRAM bank, and the banks are of
5229different size, the largest is mapped first. For equal size, the first
5230bank (CS2#) is mapped first. The first mapping is always for address
52310x00000000, with any additional banks following immediately to create
5232contiguous memory starting from 0.
5233
5234Then, the monitor installs itself at the upper end of the SDRAM area
5235and allocates memory for use by malloc() and for the global Board
5236Info data; also, the exception vector code is copied to the low RAM
5237pages, and the final stack is set up.
5238
5239Only after this relocation will you have a "normal" C environment;
5240until that you are restricted in several ways, mostly because you are
5241running from ROM, and because the code will have to be relocated to a
5242new address in RAM.
5243
5244
5245U-Boot Porting Guide:
5246----------------------
5247
5248[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5249list, October 2002]
5250
5251
5252int main(int argc, char *argv[])
5253{
5254	sighandler_t no_more_time;
5255
5256	signal(SIGALRM, no_more_time);
5257	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5258
5259	if (available_money > available_manpower) {
5260		Pay consultant to port U-Boot;
5261		return 0;
5262	}
5263
5264	Download latest U-Boot source;
5265
5266	Subscribe to u-boot mailing list;
5267
5268	if (clueless)
5269		email("Hi, I am new to U-Boot, how do I get started?");
5270
5271	while (learning) {
5272		Read the README file in the top level directory;
5273		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5274		Read applicable doc/*.README;
5275		Read the source, Luke;
5276		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5277	}
5278
5279	if (available_money > toLocalCurrency ($2500))
5280		Buy a BDI3000;
5281	else
5282		Add a lot of aggravation and time;
5283
5284	if (a similar board exists) {	/* hopefully... */
5285		cp -a board/<similar> board/<myboard>
5286		cp include/configs/<similar>.h include/configs/<myboard>.h
5287	} else {
5288		Create your own board support subdirectory;
5289		Create your own board include/configs/<myboard>.h file;
5290	}
5291	Edit new board/<myboard> files
5292	Edit new include/configs/<myboard>.h
5293
5294	while (!accepted) {
5295		while (!running) {
5296			do {
5297				Add / modify source code;
5298			} until (compiles);
5299			Debug;
5300			if (clueless)
5301				email("Hi, I am having problems...");
5302		}
5303		Send patch file to the U-Boot email list;
5304		if (reasonable critiques)
5305			Incorporate improvements from email list code review;
5306		else
5307			Defend code as written;
5308	}
5309
5310	return 0;
5311}
5312
5313void no_more_time (int sig)
5314{
5315      hire_a_guru();
5316}
5317
5318
5319Coding Standards:
5320-----------------
5321
5322All contributions to U-Boot should conform to the Linux kernel
5323coding style; see the file "Documentation/CodingStyle" and the script
5324"scripts/Lindent" in your Linux kernel source directory.
5325
5326Source files originating from a different project (for example the
5327MTD subsystem) are generally exempt from these guidelines and are not
5328reformatted to ease subsequent migration to newer versions of those
5329sources.
5330
5331Please note that U-Boot is implemented in C (and to some small parts in
5332Assembler); no C++ is used, so please do not use C++ style comments (//)
5333in your code.
5334
5335Please also stick to the following formatting rules:
5336- remove any trailing white space
5337- use TAB characters for indentation and vertical alignment, not spaces
5338- make sure NOT to use DOS '\r\n' line feeds
5339- do not add more than 2 consecutive empty lines to source files
5340- do not add trailing empty lines to source files
5341
5342Submissions which do not conform to the standards may be returned
5343with a request to reformat the changes.
5344
5345
5346Submitting Patches:
5347-------------------
5348
5349Since the number of patches for U-Boot is growing, we need to
5350establish some rules. Submissions which do not conform to these rules
5351may be rejected, even when they contain important and valuable stuff.
5352
5353Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5354
5355Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5356see http://lists.denx.de/mailman/listinfo/u-boot
5357
5358When you send a patch, please include the following information with
5359it:
5360
5361* For bug fixes: a description of the bug and how your patch fixes
5362  this bug. Please try to include a way of demonstrating that the
5363  patch actually fixes something.
5364
5365* For new features: a description of the feature and your
5366  implementation.
5367
5368* A CHANGELOG entry as plaintext (separate from the patch)
5369
5370* For major contributions, add a MAINTAINERS file with your
5371  information and associated file and directory references.
5372
5373* When you add support for a new board, don't forget to add a
5374  maintainer e-mail address to the boards.cfg file, too.
5375
5376* If your patch adds new configuration options, don't forget to
5377  document these in the README file.
5378
5379* The patch itself. If you are using git (which is *strongly*
5380  recommended) you can easily generate the patch using the
5381  "git format-patch". If you then use "git send-email" to send it to
5382  the U-Boot mailing list, you will avoid most of the common problems
5383  with some other mail clients.
5384
5385  If you cannot use git, use "diff -purN OLD NEW". If your version of
5386  diff does not support these options, then get the latest version of
5387  GNU diff.
5388
5389  The current directory when running this command shall be the parent
5390  directory of the U-Boot source tree (i. e. please make sure that
5391  your patch includes sufficient directory information for the
5392  affected files).
5393
5394  We prefer patches as plain text. MIME attachments are discouraged,
5395  and compressed attachments must not be used.
5396
5397* If one logical set of modifications affects or creates several
5398  files, all these changes shall be submitted in a SINGLE patch file.
5399
5400* Changesets that contain different, unrelated modifications shall be
5401  submitted as SEPARATE patches, one patch per changeset.
5402
5403
5404Notes:
5405
5406* Before sending the patch, run the buildman script on your patched
5407  source tree and make sure that no errors or warnings are reported
5408  for any of the boards.
5409
5410* Keep your modifications to the necessary minimum: A patch
5411  containing several unrelated changes or arbitrary reformats will be
5412  returned with a request to re-formatting / split it.
5413
5414* If you modify existing code, make sure that your new code does not
5415  add to the memory footprint of the code ;-) Small is beautiful!
5416  When adding new features, these should compile conditionally only
5417  (using #ifdef), and the resulting code with the new feature
5418  disabled must not need more memory than the old code without your
5419  modification.
5420
5421* Remember that there is a size limit of 100 kB per message on the
5422  u-boot mailing list. Bigger patches will be moderated. If they are
5423  reasonable and not too big, they will be acknowledged. But patches
5424  bigger than the size limit should be avoided.
5425