xref: /openbmc/u-boot/README (revision 6500ec7a)
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_PCMCIA		* PCMCIA support
816		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
817					  host
818		CONFIG_CMD_PORTIO	* Port I/O
819		CONFIG_CMD_READ		* Read raw data from partition
820		CONFIG_CMD_REGINFO	* Register dump
821		CONFIG_CMD_RUN		  run command in env variable
822		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
823		CONFIG_CMD_SAVES	* save S record dump
824		CONFIG_CMD_SDRAM	* print SDRAM configuration information
825					  (requires CONFIG_CMD_I2C)
826		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
827		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
828		CONFIG_CMD_SOURCE	  "source" command Support
829		CONFIG_CMD_SPI		* SPI serial bus support
830		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
831		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
832		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
833		CONFIG_CMD_TIMER	* access to the system tick timer
834		CONFIG_CMD_USB		* USB support
835		CONFIG_CMD_CDP		* Cisco Discover Protocol support
836		CONFIG_CMD_XIMG		  Load part of Multi Image
837		CONFIG_CMD_UUID		* Generate random UUID or GUID string
838
839		EXAMPLE: If you want all functions except of network
840		support you can write:
841
842		#include "config_cmd_all.h"
843		#undef CONFIG_CMD_NET
844
845	Other Commands:
846		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
847
848	Note:	Don't enable the "icache" and "dcache" commands
849		(configuration option CONFIG_CMD_CACHE) unless you know
850		what you (and your U-Boot users) are doing. Data
851		cache cannot be enabled on systems like the
852		8xx (where accesses to the IMMR region must be
853		uncached), and it cannot be disabled on all other
854		systems where we (mis-) use the data cache to hold an
855		initial stack and some data.
856
857
858		XXX - this list needs to get updated!
859
860- Removal of commands
861		If no commands are needed to boot, you can disable
862		CONFIG_CMDLINE to remove them. In this case, the command line
863		will not be available, and when U-Boot wants to execute the
864		boot command (on start-up) it will call board_run_command()
865		instead. This can reduce image size significantly for very
866		simple boot procedures.
867
868- Regular expression support:
869		CONFIG_REGEX
870		If this variable is defined, U-Boot is linked against
871		the SLRE (Super Light Regular Expression) library,
872		which adds regex support to some commands, as for
873		example "env grep" and "setexpr".
874
875- Device tree:
876		CONFIG_OF_CONTROL
877		If this variable is defined, U-Boot will use a device tree
878		to configure its devices, instead of relying on statically
879		compiled #defines in the board file. This option is
880		experimental and only available on a few boards. The device
881		tree is available in the global data as gd->fdt_blob.
882
883		U-Boot needs to get its device tree from somewhere. This can
884		be done using one of the three options below:
885
886		CONFIG_OF_EMBED
887		If this variable is defined, U-Boot will embed a device tree
888		binary in its image. This device tree file should be in the
889		board directory and called <soc>-<board>.dts. The binary file
890		is then picked up in board_init_f() and made available through
891		the global data structure as gd->blob.
892
893		CONFIG_OF_SEPARATE
894		If this variable is defined, U-Boot will build a device tree
895		binary. It will be called u-boot.dtb. Architecture-specific
896		code will locate it at run-time. Generally this works by:
897
898			cat u-boot.bin u-boot.dtb >image.bin
899
900		and in fact, U-Boot does this for you, creating a file called
901		u-boot-dtb.bin which is useful in the common case. You can
902		still use the individual files if you need something more
903		exotic.
904
905		CONFIG_OF_BOARD
906		If this variable is defined, U-Boot will use the device tree
907		provided by the board at runtime instead of embedding one with
908		the image. Only boards defining board_fdt_blob_setup() support
909		this option (see include/fdtdec.h file).
910
911- Watchdog:
912		CONFIG_WATCHDOG
913		If this variable is defined, it enables watchdog
914		support for the SoC. There must be support in the SoC
915		specific code for a watchdog. For the 8xx
916		CPUs, the SIU Watchdog feature is enabled in the SYPCR
917		register.  When supported for a specific SoC is
918		available, then no further board specific code should
919		be needed to use it.
920
921		CONFIG_HW_WATCHDOG
922		When using a watchdog circuitry external to the used
923		SoC, then define this variable and provide board
924		specific code for the "hw_watchdog_reset" function.
925
926		CONFIG_AT91_HW_WDT_TIMEOUT
927		specify the timeout in seconds. default 2 seconds.
928
929- U-Boot Version:
930		CONFIG_VERSION_VARIABLE
931		If this variable is defined, an environment variable
932		named "ver" is created by U-Boot showing the U-Boot
933		version as printed by the "version" command.
934		Any change to this variable will be reverted at the
935		next reset.
936
937- Real-Time Clock:
938
939		When CONFIG_CMD_DATE is selected, the type of the RTC
940		has to be selected, too. Define exactly one of the
941		following options:
942
943		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
944		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
945		CONFIG_RTC_MC146818	- use MC146818 RTC
946		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
947		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
948		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
949		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
950		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
951		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
952		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
953		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
954		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
955					  RV3029 RTC.
956
957		Note that if the RTC uses I2C, then the I2C interface
958		must also be configured. See I2C Support, below.
959
960- GPIO Support:
961		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
962
963		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
964		chip-ngpio pairs that tell the PCA953X driver the number of
965		pins supported by a particular chip.
966
967		Note that if the GPIO device uses I2C, then the I2C interface
968		must also be configured. See I2C Support, below.
969
970- I/O tracing:
971		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
972		accesses and can checksum them or write a list of them out
973		to memory. See the 'iotrace' command for details. This is
974		useful for testing device drivers since it can confirm that
975		the driver behaves the same way before and after a code
976		change. Currently this is supported on sandbox and arm. To
977		add support for your architecture, add '#include <iotrace.h>'
978		to the bottom of arch/<arch>/include/asm/io.h and test.
979
980		Example output from the 'iotrace stats' command is below.
981		Note that if the trace buffer is exhausted, the checksum will
982		still continue to operate.
983
984			iotrace is enabled
985			Start:  10000000	(buffer start address)
986			Size:   00010000	(buffer size)
987			Offset: 00000120	(current buffer offset)
988			Output: 10000120	(start + offset)
989			Count:  00000018	(number of trace records)
990			CRC32:  9526fb66	(CRC32 of all trace records)
991
992- Timestamp Support:
993
994		When CONFIG_TIMESTAMP is selected, the timestamp
995		(date and time) of an image is printed by image
996		commands like bootm or iminfo. This option is
997		automatically enabled when you select CONFIG_CMD_DATE .
998
999- Partition Labels (disklabels) Supported:
1000		Zero or more of the following:
1001		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1002		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1003		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1004				       bootloader.  Note 2TB partition limit; see
1005				       disk/part_efi.c
1006		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1007
1008		If IDE or SCSI support is enabled (CONFIG_IDE or
1009		CONFIG_SCSI) you must configure support for at
1010		least one non-MTD partition type as well.
1011
1012- IDE Reset method:
1013		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1014		board configurations files but used nowhere!
1015
1016		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1017		be performed by calling the function
1018			ide_set_reset(int reset)
1019		which has to be defined in a board specific file
1020
1021- ATAPI Support:
1022		CONFIG_ATAPI
1023
1024		Set this to enable ATAPI support.
1025
1026- LBA48 Support
1027		CONFIG_LBA48
1028
1029		Set this to enable support for disks larger than 137GB
1030		Also look at CONFIG_SYS_64BIT_LBA.
1031		Whithout these , LBA48 support uses 32bit variables and will 'only'
1032		support disks up to 2.1TB.
1033
1034		CONFIG_SYS_64BIT_LBA:
1035			When enabled, makes the IDE subsystem use 64bit sector addresses.
1036			Default is 32bit.
1037
1038- SCSI Support:
1039		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1040		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1041		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1042		maximum numbers of LUNs, SCSI ID's and target
1043		devices.
1044
1045		The environment variable 'scsidevs' is set to the number of
1046		SCSI devices found during the last scan.
1047
1048- NETWORK Support (PCI):
1049		CONFIG_E1000
1050		Support for Intel 8254x/8257x gigabit chips.
1051
1052		CONFIG_E1000_SPI
1053		Utility code for direct access to the SPI bus on Intel 8257x.
1054		This does not do anything useful unless you set at least one
1055		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1056
1057		CONFIG_E1000_SPI_GENERIC
1058		Allow generic access to the SPI bus on the Intel 8257x, for
1059		example with the "sspi" command.
1060
1061		CONFIG_CMD_E1000
1062		Management command for E1000 devices.  When used on devices
1063		with SPI support you can reprogram the EEPROM from U-Boot.
1064
1065		CONFIG_EEPRO100
1066		Support for Intel 82557/82559/82559ER chips.
1067		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1068		write routine for first time initialisation.
1069
1070		CONFIG_TULIP
1071		Support for Digital 2114x chips.
1072		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1073		modem chip initialisation (KS8761/QS6611).
1074
1075		CONFIG_NATSEMI
1076		Support for National dp83815 chips.
1077
1078		CONFIG_NS8382X
1079		Support for National dp8382[01] gigabit chips.
1080
1081- NETWORK Support (other):
1082
1083		CONFIG_DRIVER_AT91EMAC
1084		Support for AT91RM9200 EMAC.
1085
1086			CONFIG_RMII
1087			Define this to use reduced MII inteface
1088
1089			CONFIG_DRIVER_AT91EMAC_QUIET
1090			If this defined, the driver is quiet.
1091			The driver doen't show link status messages.
1092
1093		CONFIG_CALXEDA_XGMAC
1094		Support for the Calxeda XGMAC device
1095
1096		CONFIG_LAN91C96
1097		Support for SMSC's LAN91C96 chips.
1098
1099			CONFIG_LAN91C96_USE_32_BIT
1100			Define this to enable 32 bit addressing
1101
1102		CONFIG_SMC91111
1103		Support for SMSC's LAN91C111 chip
1104
1105			CONFIG_SMC91111_BASE
1106			Define this to hold the physical address
1107			of the device (I/O space)
1108
1109			CONFIG_SMC_USE_32_BIT
1110			Define this if data bus is 32 bits
1111
1112			CONFIG_SMC_USE_IOFUNCS
1113			Define this to use i/o functions instead of macros
1114			(some hardware wont work with macros)
1115
1116		CONFIG_DRIVER_TI_EMAC
1117		Support for davinci emac
1118
1119			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1120			Define this if you have more then 3 PHYs.
1121
1122		CONFIG_FTGMAC100
1123		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1124
1125			CONFIG_FTGMAC100_EGIGA
1126			Define this to use GE link update with gigabit PHY.
1127			Define this if FTGMAC100 is connected to gigabit PHY.
1128			If your system has 10/100 PHY only, it might not occur
1129			wrong behavior. Because PHY usually return timeout or
1130			useless data when polling gigabit status and gigabit
1131			control registers. This behavior won't affect the
1132			correctnessof 10/100 link speed update.
1133
1134		CONFIG_SMC911X
1135		Support for SMSC's LAN911x and LAN921x chips
1136
1137			CONFIG_SMC911X_BASE
1138			Define this to hold the physical address
1139			of the device (I/O space)
1140
1141			CONFIG_SMC911X_32_BIT
1142			Define this if data bus is 32 bits
1143
1144			CONFIG_SMC911X_16_BIT
1145			Define this if data bus is 16 bits. If your processor
1146			automatically converts one 32 bit word to two 16 bit
1147			words you may also try CONFIG_SMC911X_32_BIT.
1148
1149		CONFIG_SH_ETHER
1150		Support for Renesas on-chip Ethernet controller
1151
1152			CONFIG_SH_ETHER_USE_PORT
1153			Define the number of ports to be used
1154
1155			CONFIG_SH_ETHER_PHY_ADDR
1156			Define the ETH PHY's address
1157
1158			CONFIG_SH_ETHER_CACHE_WRITEBACK
1159			If this option is set, the driver enables cache flush.
1160
1161- PWM Support:
1162		CONFIG_PWM_IMX
1163		Support for PWM module on the imx6.
1164
1165- TPM Support:
1166		CONFIG_TPM
1167		Support TPM devices.
1168
1169		CONFIG_TPM_TIS_INFINEON
1170		Support for Infineon i2c bus TPM devices. Only one device
1171		per system is supported at this time.
1172
1173			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1174			Define the burst count bytes upper limit
1175
1176		CONFIG_TPM_ST33ZP24
1177		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1178
1179			CONFIG_TPM_ST33ZP24_I2C
1180			Support for STMicroelectronics ST33ZP24 I2C devices.
1181			Requires TPM_ST33ZP24 and I2C.
1182
1183			CONFIG_TPM_ST33ZP24_SPI
1184			Support for STMicroelectronics ST33ZP24 SPI devices.
1185			Requires TPM_ST33ZP24 and SPI.
1186
1187		CONFIG_TPM_ATMEL_TWI
1188		Support for Atmel TWI TPM device. Requires I2C support.
1189
1190		CONFIG_TPM_TIS_LPC
1191		Support for generic parallel port TPM devices. Only one device
1192		per system is supported at this time.
1193
1194			CONFIG_TPM_TIS_BASE_ADDRESS
1195			Base address where the generic TPM device is mapped
1196			to. Contemporary x86 systems usually map it at
1197			0xfed40000.
1198
1199		CONFIG_CMD_TPM
1200		Add tpm monitor functions.
1201		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1202		provides monitor access to authorized functions.
1203
1204		CONFIG_TPM
1205		Define this to enable the TPM support library which provides
1206		functional interfaces to some TPM commands.
1207		Requires support for a TPM device.
1208
1209		CONFIG_TPM_AUTH_SESSIONS
1210		Define this to enable authorized functions in the TPM library.
1211		Requires CONFIG_TPM and CONFIG_SHA1.
1212
1213- USB Support:
1214		At the moment only the UHCI host controller is
1215		supported (PIP405, MIP405); define
1216		CONFIG_USB_UHCI to enable it.
1217		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1218		and define CONFIG_USB_STORAGE to enable the USB
1219		storage devices.
1220		Note:
1221		Supported are USB Keyboards and USB Floppy drives
1222		(TEAC FD-05PUB).
1223
1224		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1225		txfilltuning field in the EHCI controller on reset.
1226
1227		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1228		HW module registers.
1229
1230- USB Device:
1231		Define the below if you wish to use the USB console.
1232		Once firmware is rebuilt from a serial console issue the
1233		command "setenv stdin usbtty; setenv stdout usbtty" and
1234		attach your USB cable. The Unix command "dmesg" should print
1235		it has found a new device. The environment variable usbtty
1236		can be set to gserial or cdc_acm to enable your device to
1237		appear to a USB host as a Linux gserial device or a
1238		Common Device Class Abstract Control Model serial device.
1239		If you select usbtty = gserial you should be able to enumerate
1240		a Linux host by
1241		# modprobe usbserial vendor=0xVendorID product=0xProductID
1242		else if using cdc_acm, simply setting the environment
1243		variable usbtty to be cdc_acm should suffice. The following
1244		might be defined in YourBoardName.h
1245
1246			CONFIG_USB_DEVICE
1247			Define this to build a UDC device
1248
1249			CONFIG_USB_TTY
1250			Define this to have a tty type of device available to
1251			talk to the UDC device
1252
1253			CONFIG_USBD_HS
1254			Define this to enable the high speed support for usb
1255			device and usbtty. If this feature is enabled, a routine
1256			int is_usbd_high_speed(void)
1257			also needs to be defined by the driver to dynamically poll
1258			whether the enumeration has succeded at high speed or full
1259			speed.
1260
1261			CONFIG_SYS_CONSOLE_IS_IN_ENV
1262			Define this if you want stdin, stdout &/or stderr to
1263			be set to usbtty.
1264
1265		If you have a USB-IF assigned VendorID then you may wish to
1266		define your own vendor specific values either in BoardName.h
1267		or directly in usbd_vendor_info.h. If you don't define
1268		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1269		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1270		should pretend to be a Linux device to it's target host.
1271
1272			CONFIG_USBD_MANUFACTURER
1273			Define this string as the name of your company for
1274			- CONFIG_USBD_MANUFACTURER "my company"
1275
1276			CONFIG_USBD_PRODUCT_NAME
1277			Define this string as the name of your product
1278			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1279
1280			CONFIG_USBD_VENDORID
1281			Define this as your assigned Vendor ID from the USB
1282			Implementors Forum. This *must* be a genuine Vendor ID
1283			to avoid polluting the USB namespace.
1284			- CONFIG_USBD_VENDORID 0xFFFF
1285
1286			CONFIG_USBD_PRODUCTID
1287			Define this as the unique Product ID
1288			for your device
1289			- CONFIG_USBD_PRODUCTID 0xFFFF
1290
1291- ULPI Layer Support:
1292		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1293		the generic ULPI layer. The generic layer accesses the ULPI PHY
1294		via the platform viewport, so you need both the genric layer and
1295		the viewport enabled. Currently only Chipidea/ARC based
1296		viewport is supported.
1297		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1298		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1299		If your ULPI phy needs a different reference clock than the
1300		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1301		the appropriate value in Hz.
1302
1303- MMC Support:
1304		The MMC controller on the Intel PXA is supported. To
1305		enable this define CONFIG_MMC. The MMC can be
1306		accessed from the boot prompt by mapping the device
1307		to physical memory similar to flash. Command line is
1308		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1309		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1310
1311		CONFIG_SH_MMCIF
1312		Support for Renesas on-chip MMCIF controller
1313
1314			CONFIG_SH_MMCIF_ADDR
1315			Define the base address of MMCIF registers
1316
1317			CONFIG_SH_MMCIF_CLK
1318			Define the clock frequency for MMCIF
1319
1320		CONFIG_SUPPORT_EMMC_BOOT
1321		Enable some additional features of the eMMC boot partitions.
1322
1323		CONFIG_SUPPORT_EMMC_RPMB
1324		Enable the commands for reading, writing and programming the
1325		key for the Replay Protection Memory Block partition in eMMC.
1326
1327- USB Device Firmware Update (DFU) class support:
1328		CONFIG_USB_FUNCTION_DFU
1329		This enables the USB portion of the DFU USB class
1330
1331		CONFIG_CMD_DFU
1332		This enables the command "dfu" which is used to have
1333		U-Boot create a DFU class device via USB.  This command
1334		requires that the "dfu_alt_info" environment variable be
1335		set and define the alt settings to expose to the host.
1336
1337		CONFIG_DFU_MMC
1338		This enables support for exposing (e)MMC devices via DFU.
1339
1340		CONFIG_DFU_NAND
1341		This enables support for exposing NAND devices via DFU.
1342
1343		CONFIG_DFU_RAM
1344		This enables support for exposing RAM via DFU.
1345		Note: DFU spec refer to non-volatile memory usage, but
1346		allow usages beyond the scope of spec - here RAM usage,
1347		one that would help mostly the developer.
1348
1349		CONFIG_SYS_DFU_DATA_BUF_SIZE
1350		Dfu transfer uses a buffer before writing data to the
1351		raw storage device. Make the size (in bytes) of this buffer
1352		configurable. The size of this buffer is also configurable
1353		through the "dfu_bufsiz" environment variable.
1354
1355		CONFIG_SYS_DFU_MAX_FILE_SIZE
1356		When updating files rather than the raw storage device,
1357		we use a static buffer to copy the file into and then write
1358		the buffer once we've been given the whole file.  Define
1359		this to the maximum filesize (in bytes) for the buffer.
1360		Default is 4 MiB if undefined.
1361
1362		DFU_DEFAULT_POLL_TIMEOUT
1363		Poll timeout [ms], is the timeout a device can send to the
1364		host. The host must wait for this timeout before sending
1365		a subsequent DFU_GET_STATUS request to the device.
1366
1367		DFU_MANIFEST_POLL_TIMEOUT
1368		Poll timeout [ms], which the device sends to the host when
1369		entering dfuMANIFEST state. Host waits this timeout, before
1370		sending again an USB request to the device.
1371
1372- USB Device Android Fastboot support:
1373		CONFIG_USB_FUNCTION_FASTBOOT
1374		This enables the USB part of the fastboot gadget
1375
1376		CONFIG_CMD_FASTBOOT
1377		This enables the command "fastboot" which enables the Android
1378		fastboot mode for the platform's USB device. Fastboot is a USB
1379		protocol for downloading images, flashing and device control
1380		used on Android devices.
1381		See doc/README.android-fastboot for more information.
1382
1383		CONFIG_ANDROID_BOOT_IMAGE
1384		This enables support for booting images which use the Android
1385		image format header.
1386
1387		CONFIG_FASTBOOT_BUF_ADDR
1388		The fastboot protocol requires a large memory buffer for
1389		downloads. Define this to the starting RAM address to use for
1390		downloaded images.
1391
1392		CONFIG_FASTBOOT_BUF_SIZE
1393		The fastboot protocol requires a large memory buffer for
1394		downloads. This buffer should be as large as possible for a
1395		platform. Define this to the size available RAM for fastboot.
1396
1397		CONFIG_FASTBOOT_FLASH
1398		The fastboot protocol includes a "flash" command for writing
1399		the downloaded image to a non-volatile storage device. Define
1400		this to enable the "fastboot flash" command.
1401
1402		CONFIG_FASTBOOT_FLASH_MMC_DEV
1403		The fastboot "flash" command requires additional information
1404		regarding the non-volatile storage device. Define this to
1405		the eMMC device that fastboot should use to store the image.
1406
1407		CONFIG_FASTBOOT_GPT_NAME
1408		The fastboot "flash" command supports writing the downloaded
1409		image to the Protective MBR and the Primary GUID Partition
1410		Table. (Additionally, this downloaded image is post-processed
1411		to generate and write the Backup GUID Partition Table.)
1412		This occurs when the specified "partition name" on the
1413		"fastboot flash" command line matches this value.
1414		The default is "gpt" if undefined.
1415
1416		CONFIG_FASTBOOT_MBR_NAME
1417		The fastboot "flash" command supports writing the downloaded
1418		image to DOS MBR.
1419		This occurs when the "partition name" specified on the
1420		"fastboot flash" command line matches this value.
1421		If not defined the default value "mbr" is used.
1422
1423- Journaling Flash filesystem support:
1424		CONFIG_JFFS2_NAND
1425		Define these for a default partition on a NAND device
1426
1427		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1428		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1429		Define these for a default partition on a NOR device
1430
1431- Keyboard Support:
1432		See Kconfig help for available keyboard drivers.
1433
1434		CONFIG_KEYBOARD
1435
1436		Define this to enable a custom keyboard support.
1437		This simply calls drv_keyboard_init() which must be
1438		defined in your board-specific files. This option is deprecated
1439		and is only used by novena. For new boards, use driver model
1440		instead.
1441
1442- Video support:
1443		CONFIG_FSL_DIU_FB
1444		Enable the Freescale DIU video driver.	Reference boards for
1445		SOCs that have a DIU should define this macro to enable DIU
1446		support, and should also define these other macros:
1447
1448			CONFIG_SYS_DIU_ADDR
1449			CONFIG_VIDEO
1450			CONFIG_CFB_CONSOLE
1451			CONFIG_VIDEO_SW_CURSOR
1452			CONFIG_VGA_AS_SINGLE_DEVICE
1453			CONFIG_VIDEO_LOGO
1454			CONFIG_VIDEO_BMP_LOGO
1455
1456		The DIU driver will look for the 'video-mode' environment
1457		variable, and if defined, enable the DIU as a console during
1458		boot.  See the documentation file doc/README.video for a
1459		description of this variable.
1460
1461- LCD Support:	CONFIG_LCD
1462
1463		Define this to enable LCD support (for output to LCD
1464		display); also select one of the supported displays
1465		by defining one of these:
1466
1467		CONFIG_ATMEL_LCD:
1468
1469			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1470
1471		CONFIG_NEC_NL6448AC33:
1472
1473			NEC NL6448AC33-18. Active, color, single scan.
1474
1475		CONFIG_NEC_NL6448BC20
1476
1477			NEC NL6448BC20-08. 6.5", 640x480.
1478			Active, color, single scan.
1479
1480		CONFIG_NEC_NL6448BC33_54
1481
1482			NEC NL6448BC33-54. 10.4", 640x480.
1483			Active, color, single scan.
1484
1485		CONFIG_SHARP_16x9
1486
1487			Sharp 320x240. Active, color, single scan.
1488			It isn't 16x9, and I am not sure what it is.
1489
1490		CONFIG_SHARP_LQ64D341
1491
1492			Sharp LQ64D341 display, 640x480.
1493			Active, color, single scan.
1494
1495		CONFIG_HLD1045
1496
1497			HLD1045 display, 640x480.
1498			Active, color, single scan.
1499
1500		CONFIG_OPTREX_BW
1501
1502			Optrex	 CBL50840-2 NF-FW 99 22 M5
1503			or
1504			Hitachi	 LMG6912RPFC-00T
1505			or
1506			Hitachi	 SP14Q002
1507
1508			320x240. Black & white.
1509
1510		CONFIG_LCD_ALIGNMENT
1511
1512		Normally the LCD is page-aligned (typically 4KB). If this is
1513		defined then the LCD will be aligned to this value instead.
1514		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1515		here, since it is cheaper to change data cache settings on
1516		a per-section basis.
1517
1518
1519		CONFIG_LCD_ROTATION
1520
1521		Sometimes, for example if the display is mounted in portrait
1522		mode or even if it's mounted landscape but rotated by 180degree,
1523		we need to rotate our content of the display relative to the
1524		framebuffer, so that user can read the messages which are
1525		printed out.
1526		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1527		initialized with a given rotation from "vl_rot" out of
1528		"vidinfo_t" which is provided by the board specific code.
1529		The value for vl_rot is coded as following (matching to
1530		fbcon=rotate:<n> linux-kernel commandline):
1531		0 = no rotation respectively 0 degree
1532		1 = 90 degree rotation
1533		2 = 180 degree rotation
1534		3 = 270 degree rotation
1535
1536		If CONFIG_LCD_ROTATION is not defined, the console will be
1537		initialized with 0degree rotation.
1538
1539		CONFIG_LCD_BMP_RLE8
1540
1541		Support drawing of RLE8-compressed bitmaps on the LCD.
1542
1543		CONFIG_I2C_EDID
1544
1545		Enables an 'i2c edid' command which can read EDID
1546		information over I2C from an attached LCD display.
1547
1548- Splash Screen Support: CONFIG_SPLASH_SCREEN
1549
1550		If this option is set, the environment is checked for
1551		a variable "splashimage". If found, the usual display
1552		of logo, copyright and system information on the LCD
1553		is suppressed and the BMP image at the address
1554		specified in "splashimage" is loaded instead. The
1555		console is redirected to the "nulldev", too. This
1556		allows for a "silent" boot where a splash screen is
1557		loaded very quickly after power-on.
1558
1559		CONFIG_SPLASHIMAGE_GUARD
1560
1561		If this option is set, then U-Boot will prevent the environment
1562		variable "splashimage" from being set to a problematic address
1563		(see doc/README.displaying-bmps).
1564		This option is useful for targets where, due to alignment
1565		restrictions, an improperly aligned BMP image will cause a data
1566		abort. If you think you will not have problems with unaligned
1567		accesses (for example because your toolchain prevents them)
1568		there is no need to set this option.
1569
1570		CONFIG_SPLASH_SCREEN_ALIGN
1571
1572		If this option is set the splash image can be freely positioned
1573		on the screen. Environment variable "splashpos" specifies the
1574		position as "x,y". If a positive number is given it is used as
1575		number of pixel from left/top. If a negative number is given it
1576		is used as number of pixel from right/bottom. You can also
1577		specify 'm' for centering the image.
1578
1579		Example:
1580		setenv splashpos m,m
1581			=> image at center of screen
1582
1583		setenv splashpos 30,20
1584			=> image at x = 30 and y = 20
1585
1586		setenv splashpos -10,m
1587			=> vertically centered image
1588			   at x = dspWidth - bmpWidth - 9
1589
1590- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1591
1592		If this option is set, additionally to standard BMP
1593		images, gzipped BMP images can be displayed via the
1594		splashscreen support or the bmp command.
1595
1596- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1597
1598		If this option is set, 8-bit RLE compressed BMP images
1599		can be displayed via the splashscreen support or the
1600		bmp command.
1601
1602- Compression support:
1603		CONFIG_GZIP
1604
1605		Enabled by default to support gzip compressed images.
1606
1607		CONFIG_BZIP2
1608
1609		If this option is set, support for bzip2 compressed
1610		images is included. If not, only uncompressed and gzip
1611		compressed images are supported.
1612
1613		NOTE: the bzip2 algorithm requires a lot of RAM, so
1614		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1615		be at least 4MB.
1616
1617- MII/PHY support:
1618		CONFIG_PHY_ADDR
1619
1620		The address of PHY on MII bus.
1621
1622		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1623
1624		The clock frequency of the MII bus
1625
1626		CONFIG_PHY_RESET_DELAY
1627
1628		Some PHY like Intel LXT971A need extra delay after
1629		reset before any MII register access is possible.
1630		For such PHY, set this option to the usec delay
1631		required. (minimum 300usec for LXT971A)
1632
1633		CONFIG_PHY_CMD_DELAY (ppc4xx)
1634
1635		Some PHY like Intel LXT971A need extra delay after
1636		command issued before MII status register can be read
1637
1638- IP address:
1639		CONFIG_IPADDR
1640
1641		Define a default value for the IP address to use for
1642		the default Ethernet interface, in case this is not
1643		determined through e.g. bootp.
1644		(Environment variable "ipaddr")
1645
1646- Server IP address:
1647		CONFIG_SERVERIP
1648
1649		Defines a default value for the IP address of a TFTP
1650		server to contact when using the "tftboot" command.
1651		(Environment variable "serverip")
1652
1653		CONFIG_KEEP_SERVERADDR
1654
1655		Keeps the server's MAC address, in the env 'serveraddr'
1656		for passing to bootargs (like Linux's netconsole option)
1657
1658- Gateway IP address:
1659		CONFIG_GATEWAYIP
1660
1661		Defines a default value for the IP address of the
1662		default router where packets to other networks are
1663		sent to.
1664		(Environment variable "gatewayip")
1665
1666- Subnet mask:
1667		CONFIG_NETMASK
1668
1669		Defines a default value for the subnet mask (or
1670		routing prefix) which is used to determine if an IP
1671		address belongs to the local subnet or needs to be
1672		forwarded through a router.
1673		(Environment variable "netmask")
1674
1675- Multicast TFTP Mode:
1676		CONFIG_MCAST_TFTP
1677
1678		Defines whether you want to support multicast TFTP as per
1679		rfc-2090; for example to work with atftp.  Lets lots of targets
1680		tftp down the same boot image concurrently.  Note: the Ethernet
1681		driver in use must provide a function: mcast() to join/leave a
1682		multicast group.
1683
1684- BOOTP Recovery Mode:
1685		CONFIG_BOOTP_RANDOM_DELAY
1686
1687		If you have many targets in a network that try to
1688		boot using BOOTP, you may want to avoid that all
1689		systems send out BOOTP requests at precisely the same
1690		moment (which would happen for instance at recovery
1691		from a power failure, when all systems will try to
1692		boot, thus flooding the BOOTP server. Defining
1693		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1694		inserted before sending out BOOTP requests. The
1695		following delays are inserted then:
1696
1697		1st BOOTP request:	delay 0 ... 1 sec
1698		2nd BOOTP request:	delay 0 ... 2 sec
1699		3rd BOOTP request:	delay 0 ... 4 sec
1700		4th and following
1701		BOOTP requests:		delay 0 ... 8 sec
1702
1703		CONFIG_BOOTP_ID_CACHE_SIZE
1704
1705		BOOTP packets are uniquely identified using a 32-bit ID. The
1706		server will copy the ID from client requests to responses and
1707		U-Boot will use this to determine if it is the destination of
1708		an incoming response. Some servers will check that addresses
1709		aren't in use before handing them out (usually using an ARP
1710		ping) and therefore take up to a few hundred milliseconds to
1711		respond. Network congestion may also influence the time it
1712		takes for a response to make it back to the client. If that
1713		time is too long, U-Boot will retransmit requests. In order
1714		to allow earlier responses to still be accepted after these
1715		retransmissions, U-Boot's BOOTP client keeps a small cache of
1716		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1717		cache. The default is to keep IDs for up to four outstanding
1718		requests. Increasing this will allow U-Boot to accept offers
1719		from a BOOTP client in networks with unusually high latency.
1720
1721- DHCP Advanced Options:
1722		You can fine tune the DHCP functionality by defining
1723		CONFIG_BOOTP_* symbols:
1724
1725		CONFIG_BOOTP_SUBNETMASK
1726		CONFIG_BOOTP_GATEWAY
1727		CONFIG_BOOTP_HOSTNAME
1728		CONFIG_BOOTP_NISDOMAIN
1729		CONFIG_BOOTP_BOOTPATH
1730		CONFIG_BOOTP_BOOTFILESIZE
1731		CONFIG_BOOTP_DNS
1732		CONFIG_BOOTP_DNS2
1733		CONFIG_BOOTP_SEND_HOSTNAME
1734		CONFIG_BOOTP_NTPSERVER
1735		CONFIG_BOOTP_TIMEOFFSET
1736		CONFIG_BOOTP_VENDOREX
1737		CONFIG_BOOTP_MAY_FAIL
1738
1739		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1740		environment variable, not the BOOTP server.
1741
1742		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1743		after the configured retry count, the call will fail
1744		instead of starting over.  This can be used to fail over
1745		to Link-local IP address configuration if the DHCP server
1746		is not available.
1747
1748		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1749		serverip from a DHCP server, it is possible that more
1750		than one DNS serverip is offered to the client.
1751		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1752		serverip will be stored in the additional environment
1753		variable "dnsip2". The first DNS serverip is always
1754		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1755		is defined.
1756
1757		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1758		to do a dynamic update of a DNS server. To do this, they
1759		need the hostname of the DHCP requester.
1760		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1761		of the "hostname" environment variable is passed as
1762		option 12 to the DHCP server.
1763
1764		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1765
1766		A 32bit value in microseconds for a delay between
1767		receiving a "DHCP Offer" and sending the "DHCP Request".
1768		This fixes a problem with certain DHCP servers that don't
1769		respond 100% of the time to a "DHCP request". E.g. On an
1770		AT91RM9200 processor running at 180MHz, this delay needed
1771		to be *at least* 15,000 usec before a Windows Server 2003
1772		DHCP server would reply 100% of the time. I recommend at
1773		least 50,000 usec to be safe. The alternative is to hope
1774		that one of the retries will be successful but note that
1775		the DHCP timeout and retry process takes a longer than
1776		this delay.
1777
1778 - Link-local IP address negotiation:
1779		Negotiate with other link-local clients on the local network
1780		for an address that doesn't require explicit configuration.
1781		This is especially useful if a DHCP server cannot be guaranteed
1782		to exist in all environments that the device must operate.
1783
1784		See doc/README.link-local for more information.
1785
1786 - CDP Options:
1787		CONFIG_CDP_DEVICE_ID
1788
1789		The device id used in CDP trigger frames.
1790
1791		CONFIG_CDP_DEVICE_ID_PREFIX
1792
1793		A two character string which is prefixed to the MAC address
1794		of the device.
1795
1796		CONFIG_CDP_PORT_ID
1797
1798		A printf format string which contains the ascii name of
1799		the port. Normally is set to "eth%d" which sets
1800		eth0 for the first Ethernet, eth1 for the second etc.
1801
1802		CONFIG_CDP_CAPABILITIES
1803
1804		A 32bit integer which indicates the device capabilities;
1805		0x00000010 for a normal host which does not forwards.
1806
1807		CONFIG_CDP_VERSION
1808
1809		An ascii string containing the version of the software.
1810
1811		CONFIG_CDP_PLATFORM
1812
1813		An ascii string containing the name of the platform.
1814
1815		CONFIG_CDP_TRIGGER
1816
1817		A 32bit integer sent on the trigger.
1818
1819		CONFIG_CDP_POWER_CONSUMPTION
1820
1821		A 16bit integer containing the power consumption of the
1822		device in .1 of milliwatts.
1823
1824		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1825
1826		A byte containing the id of the VLAN.
1827
1828- Status LED:	CONFIG_LED_STATUS
1829
1830		Several configurations allow to display the current
1831		status using a LED. For instance, the LED will blink
1832		fast while running U-Boot code, stop blinking as
1833		soon as a reply to a BOOTP request was received, and
1834		start blinking slow once the Linux kernel is running
1835		(supported by a status LED driver in the Linux
1836		kernel). Defining CONFIG_LED_STATUS enables this
1837		feature in U-Boot.
1838
1839		Additional options:
1840
1841		CONFIG_LED_STATUS_GPIO
1842		The status LED can be connected to a GPIO pin.
1843		In such cases, the gpio_led driver can be used as a
1844		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1845		to include the gpio_led driver in the U-Boot binary.
1846
1847		CONFIG_GPIO_LED_INVERTED_TABLE
1848		Some GPIO connected LEDs may have inverted polarity in which
1849		case the GPIO high value corresponds to LED off state and
1850		GPIO low value corresponds to LED on state.
1851		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1852		with a list of GPIO LEDs that have inverted polarity.
1853
1854- I2C Support:	CONFIG_SYS_I2C
1855
1856		This enable the NEW i2c subsystem, and will allow you to use
1857		i2c commands at the u-boot command line (as long as you set
1858		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1859		based realtime clock chips or other i2c devices. See
1860		common/cmd_i2c.c for a description of the command line
1861		interface.
1862
1863		ported i2c driver to the new framework:
1864		- drivers/i2c/soft_i2c.c:
1865		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1866		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1867		    for defining speed and slave address
1868		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1869		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1870		    for defining speed and slave address
1871		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1872		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1873		    for defining speed and slave address
1874		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1875		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1876		    for defining speed and slave address
1877
1878		- drivers/i2c/fsl_i2c.c:
1879		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1880		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1881		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1882		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1883		    bus.
1884		  - If your board supports a second fsl i2c bus, define
1885		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1886		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1887		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1888		    second bus.
1889
1890		- drivers/i2c/tegra_i2c.c:
1891		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1892		  - This driver adds 4 i2c buses with a fix speed from
1893		    100000 and the slave addr 0!
1894
1895		- drivers/i2c/ppc4xx_i2c.c
1896		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1897		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1898		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1899
1900		- drivers/i2c/i2c_mxc.c
1901		  - activate this driver with CONFIG_SYS_I2C_MXC
1902		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1903		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1904		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1905		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1906		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1907		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1908		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1909		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1910		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1911		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1912		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1913		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1914		If those defines are not set, default value is 100000
1915		for speed, and 0 for slave.
1916
1917		- drivers/i2c/rcar_i2c.c:
1918		  - activate this driver with CONFIG_SYS_I2C_RCAR
1919		  - This driver adds 4 i2c buses
1920
1921		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1922		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1923		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1924		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1925		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1926		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1927		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1928		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1929		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1930
1931		- drivers/i2c/sh_i2c.c:
1932		  - activate this driver with CONFIG_SYS_I2C_SH
1933		  - This driver adds from 2 to 5 i2c buses
1934
1935		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1936		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1937		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1938		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1939		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1940		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1941		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1942		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1943		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1944		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1945		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1946
1947		- drivers/i2c/omap24xx_i2c.c
1948		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1949		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1950		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1951		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1952		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1953		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1954		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1955		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1956		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1957		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1958		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1959
1960		- drivers/i2c/zynq_i2c.c
1961		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1962		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1963		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1964
1965		- drivers/i2c/s3c24x0_i2c.c:
1966		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1967		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1968		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1969		    with a fix speed from 100000 and the slave addr 0!
1970
1971		- drivers/i2c/ihs_i2c.c
1972		  - activate this driver with CONFIG_SYS_I2C_IHS
1973		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1974		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1975		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1976		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1977		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1978		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1979		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1980		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1981		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1982		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1983		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1984		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1985		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1986		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1987		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1988		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1989		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1990		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1991		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1992		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1993		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1994
1995		additional defines:
1996
1997		CONFIG_SYS_NUM_I2C_BUSES
1998		Hold the number of i2c buses you want to use.
1999
2000		CONFIG_SYS_I2C_DIRECT_BUS
2001		define this, if you don't use i2c muxes on your hardware.
2002		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2003		omit this define.
2004
2005		CONFIG_SYS_I2C_MAX_HOPS
2006		define how many muxes are maximal consecutively connected
2007		on one i2c bus. If you not use i2c muxes, omit this
2008		define.
2009
2010		CONFIG_SYS_I2C_BUSES
2011		hold a list of buses you want to use, only used if
2012		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2013		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2014		CONFIG_SYS_NUM_I2C_BUSES = 9:
2015
2016		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2017					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2018					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2019					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2020					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2021					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2022					{1, {I2C_NULL_HOP}}, \
2023					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2024					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2025					}
2026
2027		which defines
2028			bus 0 on adapter 0 without a mux
2029			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2030			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2031			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2032			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2033			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2034			bus 6 on adapter 1 without a mux
2035			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2036			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2037
2038		If you do not have i2c muxes on your board, omit this define.
2039
2040- Legacy I2C Support:
2041		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2042		then the following macros need to be defined (examples are
2043		from include/configs/lwmon.h):
2044
2045		I2C_INIT
2046
2047		(Optional). Any commands necessary to enable the I2C
2048		controller or configure ports.
2049
2050		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2051
2052		I2C_ACTIVE
2053
2054		The code necessary to make the I2C data line active
2055		(driven).  If the data line is open collector, this
2056		define can be null.
2057
2058		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2059
2060		I2C_TRISTATE
2061
2062		The code necessary to make the I2C data line tri-stated
2063		(inactive).  If the data line is open collector, this
2064		define can be null.
2065
2066		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2067
2068		I2C_READ
2069
2070		Code that returns true if the I2C data line is high,
2071		false if it is low.
2072
2073		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2074
2075		I2C_SDA(bit)
2076
2077		If <bit> is true, sets the I2C data line high. If it
2078		is false, it clears it (low).
2079
2080		eg: #define I2C_SDA(bit) \
2081			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2082			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2083
2084		I2C_SCL(bit)
2085
2086		If <bit> is true, sets the I2C clock line high. If it
2087		is false, it clears it (low).
2088
2089		eg: #define I2C_SCL(bit) \
2090			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2091			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2092
2093		I2C_DELAY
2094
2095		This delay is invoked four times per clock cycle so this
2096		controls the rate of data transfer.  The data rate thus
2097		is 1 / (I2C_DELAY * 4). Often defined to be something
2098		like:
2099
2100		#define I2C_DELAY  udelay(2)
2101
2102		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2103
2104		If your arch supports the generic GPIO framework (asm/gpio.h),
2105		then you may alternatively define the two GPIOs that are to be
2106		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2107		have GPIO-based defaults assigned to them as appropriate.
2108
2109		You should define these to the GPIO value as given directly to
2110		the generic GPIO functions.
2111
2112		CONFIG_SYS_I2C_INIT_BOARD
2113
2114		When a board is reset during an i2c bus transfer
2115		chips might think that the current transfer is still
2116		in progress. On some boards it is possible to access
2117		the i2c SCLK line directly, either by using the
2118		processor pin as a GPIO or by having a second pin
2119		connected to the bus. If this option is defined a
2120		custom i2c_init_board() routine in boards/xxx/board.c
2121		is run early in the boot sequence.
2122
2123		CONFIG_I2C_MULTI_BUS
2124
2125		This option allows the use of multiple I2C buses, each of which
2126		must have a controller.	 At any point in time, only one bus is
2127		active.	 To switch to a different bus, use the 'i2c dev' command.
2128		Note that bus numbering is zero-based.
2129
2130		CONFIG_SYS_I2C_NOPROBES
2131
2132		This option specifies a list of I2C devices that will be skipped
2133		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2134		is set, specify a list of bus-device pairs.  Otherwise, specify
2135		a 1D array of device addresses
2136
2137		e.g.
2138			#undef	CONFIG_I2C_MULTI_BUS
2139			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2140
2141		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2142
2143			#define CONFIG_I2C_MULTI_BUS
2144			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2145
2146		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2147
2148		CONFIG_SYS_SPD_BUS_NUM
2149
2150		If defined, then this indicates the I2C bus number for DDR SPD.
2151		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2152
2153		CONFIG_SYS_RTC_BUS_NUM
2154
2155		If defined, then this indicates the I2C bus number for the RTC.
2156		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2157
2158		CONFIG_SOFT_I2C_READ_REPEATED_START
2159
2160		defining this will force the i2c_read() function in
2161		the soft_i2c driver to perform an I2C repeated start
2162		between writing the address pointer and reading the
2163		data.  If this define is omitted the default behaviour
2164		of doing a stop-start sequence will be used.  Most I2C
2165		devices can use either method, but some require one or
2166		the other.
2167
2168- SPI Support:	CONFIG_SPI
2169
2170		Enables SPI driver (so far only tested with
2171		SPI EEPROM, also an instance works with Crystal A/D and
2172		D/As on the SACSng board)
2173
2174		CONFIG_SH_SPI
2175
2176		Enables the driver for SPI controller on SuperH. Currently
2177		only SH7757 is supported.
2178
2179		CONFIG_SOFT_SPI
2180
2181		Enables a software (bit-bang) SPI driver rather than
2182		using hardware support. This is a general purpose
2183		driver that only requires three general I/O port pins
2184		(two outputs, one input) to function. If this is
2185		defined, the board configuration must define several
2186		SPI configuration items (port pins to use, etc). For
2187		an example, see include/configs/sacsng.h.
2188
2189		CONFIG_HARD_SPI
2190
2191		Enables a hardware SPI driver for general-purpose reads
2192		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2193		must define a list of chip-select function pointers.
2194		Currently supported on some MPC8xxx processors.	 For an
2195		example, see include/configs/mpc8349emds.h.
2196
2197		CONFIG_MXC_SPI
2198
2199		Enables the driver for the SPI controllers on i.MX and MXC
2200		SoCs. Currently i.MX31/35/51 are supported.
2201
2202		CONFIG_SYS_SPI_MXC_WAIT
2203		Timeout for waiting until spi transfer completed.
2204		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2205
2206- FPGA Support: CONFIG_FPGA
2207
2208		Enables FPGA subsystem.
2209
2210		CONFIG_FPGA_<vendor>
2211
2212		Enables support for specific chip vendors.
2213		(ALTERA, XILINX)
2214
2215		CONFIG_FPGA_<family>
2216
2217		Enables support for FPGA family.
2218		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2219
2220		CONFIG_FPGA_COUNT
2221
2222		Specify the number of FPGA devices to support.
2223
2224		CONFIG_SYS_FPGA_PROG_FEEDBACK
2225
2226		Enable printing of hash marks during FPGA configuration.
2227
2228		CONFIG_SYS_FPGA_CHECK_BUSY
2229
2230		Enable checks on FPGA configuration interface busy
2231		status by the configuration function. This option
2232		will require a board or device specific function to
2233		be written.
2234
2235		CONFIG_FPGA_DELAY
2236
2237		If defined, a function that provides delays in the FPGA
2238		configuration driver.
2239
2240		CONFIG_SYS_FPGA_CHECK_CTRLC
2241		Allow Control-C to interrupt FPGA configuration
2242
2243		CONFIG_SYS_FPGA_CHECK_ERROR
2244
2245		Check for configuration errors during FPGA bitfile
2246		loading. For example, abort during Virtex II
2247		configuration if the INIT_B line goes low (which
2248		indicated a CRC error).
2249
2250		CONFIG_SYS_FPGA_WAIT_INIT
2251
2252		Maximum time to wait for the INIT_B line to de-assert
2253		after PROB_B has been de-asserted during a Virtex II
2254		FPGA configuration sequence. The default time is 500
2255		ms.
2256
2257		CONFIG_SYS_FPGA_WAIT_BUSY
2258
2259		Maximum time to wait for BUSY to de-assert during
2260		Virtex II FPGA configuration. The default is 5 ms.
2261
2262		CONFIG_SYS_FPGA_WAIT_CONFIG
2263
2264		Time to wait after FPGA configuration. The default is
2265		200 ms.
2266
2267- Configuration Management:
2268		CONFIG_BUILD_TARGET
2269
2270		Some SoCs need special image types (e.g. U-Boot binary
2271		with a special header) as build targets. By defining
2272		CONFIG_BUILD_TARGET in the SoC / board header, this
2273		special image will be automatically built upon calling
2274		make / buildman.
2275
2276		CONFIG_IDENT_STRING
2277
2278		If defined, this string will be added to the U-Boot
2279		version information (U_BOOT_VERSION)
2280
2281- Vendor Parameter Protection:
2282
2283		U-Boot considers the values of the environment
2284		variables "serial#" (Board Serial Number) and
2285		"ethaddr" (Ethernet Address) to be parameters that
2286		are set once by the board vendor / manufacturer, and
2287		protects these variables from casual modification by
2288		the user. Once set, these variables are read-only,
2289		and write or delete attempts are rejected. You can
2290		change this behaviour:
2291
2292		If CONFIG_ENV_OVERWRITE is #defined in your config
2293		file, the write protection for vendor parameters is
2294		completely disabled. Anybody can change or delete
2295		these parameters.
2296
2297		Alternatively, if you define _both_ an ethaddr in the
2298		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2299		Ethernet address is installed in the environment,
2300		which can be changed exactly ONCE by the user. [The
2301		serial# is unaffected by this, i. e. it remains
2302		read-only.]
2303
2304		The same can be accomplished in a more flexible way
2305		for any variable by configuring the type of access
2306		to allow for those variables in the ".flags" variable
2307		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2308
2309- Protected RAM:
2310		CONFIG_PRAM
2311
2312		Define this variable to enable the reservation of
2313		"protected RAM", i. e. RAM which is not overwritten
2314		by U-Boot. Define CONFIG_PRAM to hold the number of
2315		kB you want to reserve for pRAM. You can overwrite
2316		this default value by defining an environment
2317		variable "pram" to the number of kB you want to
2318		reserve. Note that the board info structure will
2319		still show the full amount of RAM. If pRAM is
2320		reserved, a new environment variable "mem" will
2321		automatically be defined to hold the amount of
2322		remaining RAM in a form that can be passed as boot
2323		argument to Linux, for instance like that:
2324
2325			setenv bootargs ... mem=\${mem}
2326			saveenv
2327
2328		This way you can tell Linux not to use this memory,
2329		either, which results in a memory region that will
2330		not be affected by reboots.
2331
2332		*WARNING* If your board configuration uses automatic
2333		detection of the RAM size, you must make sure that
2334		this memory test is non-destructive. So far, the
2335		following board configurations are known to be
2336		"pRAM-clean":
2337
2338			IVMS8, IVML24, SPD8xx,
2339			HERMES, IP860, RPXlite, LWMON,
2340			FLAGADM
2341
2342- Access to physical memory region (> 4GB)
2343		Some basic support is provided for operations on memory not
2344		normally accessible to U-Boot - e.g. some architectures
2345		support access to more than 4GB of memory on 32-bit
2346		machines using physical address extension or similar.
2347		Define CONFIG_PHYSMEM to access this basic support, which
2348		currently only supports clearing the memory.
2349
2350- Error Recovery:
2351		CONFIG_PANIC_HANG
2352
2353		Define this variable to stop the system in case of a
2354		fatal error, so that you have to reset it manually.
2355		This is probably NOT a good idea for an embedded
2356		system where you want the system to reboot
2357		automatically as fast as possible, but it may be
2358		useful during development since you can try to debug
2359		the conditions that lead to the situation.
2360
2361		CONFIG_NET_RETRY_COUNT
2362
2363		This variable defines the number of retries for
2364		network operations like ARP, RARP, TFTP, or BOOTP
2365		before giving up the operation. If not defined, a
2366		default value of 5 is used.
2367
2368		CONFIG_ARP_TIMEOUT
2369
2370		Timeout waiting for an ARP reply in milliseconds.
2371
2372		CONFIG_NFS_TIMEOUT
2373
2374		Timeout in milliseconds used in NFS protocol.
2375		If you encounter "ERROR: Cannot umount" in nfs command,
2376		try longer timeout such as
2377		#define CONFIG_NFS_TIMEOUT 10000UL
2378
2379- Command Interpreter:
2380		CONFIG_AUTO_COMPLETE
2381
2382		Enable auto completion of commands using TAB.
2383
2384		CONFIG_SYS_PROMPT_HUSH_PS2
2385
2386		This defines the secondary prompt string, which is
2387		printed when the command interpreter needs more input
2388		to complete a command. Usually "> ".
2389
2390	Note:
2391
2392		In the current implementation, the local variables
2393		space and global environment variables space are
2394		separated. Local variables are those you define by
2395		simply typing `name=value'. To access a local
2396		variable later on, you have write `$name' or
2397		`${name}'; to execute the contents of a variable
2398		directly type `$name' at the command prompt.
2399
2400		Global environment variables are those you use
2401		setenv/printenv to work with. To run a command stored
2402		in such a variable, you need to use the run command,
2403		and you must not use the '$' sign to access them.
2404
2405		To store commands and special characters in a
2406		variable, please use double quotation marks
2407		surrounding the whole text of the variable, instead
2408		of the backslashes before semicolons and special
2409		symbols.
2410
2411- Command Line Editing and History:
2412		CONFIG_CMDLINE_EDITING
2413
2414		Enable editing and History functions for interactive
2415		command line input operations
2416
2417- Command Line PS1/PS2 support:
2418		CONFIG_CMDLINE_PS_SUPPORT
2419
2420		Enable support for changing the command prompt string
2421		at run-time. Only static string is supported so far.
2422		The string is obtained from environment variables PS1
2423		and PS2.
2424
2425- Default Environment:
2426		CONFIG_EXTRA_ENV_SETTINGS
2427
2428		Define this to contain any number of null terminated
2429		strings (variable = value pairs) that will be part of
2430		the default environment compiled into the boot image.
2431
2432		For example, place something like this in your
2433		board's config file:
2434
2435		#define CONFIG_EXTRA_ENV_SETTINGS \
2436			"myvar1=value1\0" \
2437			"myvar2=value2\0"
2438
2439		Warning: This method is based on knowledge about the
2440		internal format how the environment is stored by the
2441		U-Boot code. This is NOT an official, exported
2442		interface! Although it is unlikely that this format
2443		will change soon, there is no guarantee either.
2444		You better know what you are doing here.
2445
2446		Note: overly (ab)use of the default environment is
2447		discouraged. Make sure to check other ways to preset
2448		the environment like the "source" command or the
2449		boot command first.
2450
2451		CONFIG_ENV_VARS_UBOOT_CONFIG
2452
2453		Define this in order to add variables describing the
2454		U-Boot build configuration to the default environment.
2455		These will be named arch, cpu, board, vendor, and soc.
2456
2457		Enabling this option will cause the following to be defined:
2458
2459		- CONFIG_SYS_ARCH
2460		- CONFIG_SYS_CPU
2461		- CONFIG_SYS_BOARD
2462		- CONFIG_SYS_VENDOR
2463		- CONFIG_SYS_SOC
2464
2465		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2466
2467		Define this in order to add variables describing certain
2468		run-time determined information about the hardware to the
2469		environment.  These will be named board_name, board_rev.
2470
2471		CONFIG_DELAY_ENVIRONMENT
2472
2473		Normally the environment is loaded when the board is
2474		initialised so that it is available to U-Boot. This inhibits
2475		that so that the environment is not available until
2476		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2477		this is instead controlled by the value of
2478		/config/load-environment.
2479
2480- DataFlash Support:
2481		CONFIG_HAS_DATAFLASH
2482
2483		Defining this option enables DataFlash features and
2484		allows to read/write in Dataflash via the standard
2485		commands cp, md...
2486
2487- Serial Flash support
2488		CONFIG_CMD_SF
2489
2490		Defining this option enables SPI flash commands
2491		'sf probe/read/write/erase/update'.
2492
2493		Usage requires an initial 'probe' to define the serial
2494		flash parameters, followed by read/write/erase/update
2495		commands.
2496
2497		The following defaults may be provided by the platform
2498		to handle the common case when only a single serial
2499		flash is present on the system.
2500
2501		CONFIG_SF_DEFAULT_BUS		Bus identifier
2502		CONFIG_SF_DEFAULT_CS		Chip-select
2503		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2504		CONFIG_SF_DEFAULT_SPEED		in Hz
2505
2506		CONFIG_CMD_SF_TEST
2507
2508		Define this option to include a destructive SPI flash
2509		test ('sf test').
2510
2511- SystemACE Support:
2512		CONFIG_SYSTEMACE
2513
2514		Adding this option adds support for Xilinx SystemACE
2515		chips attached via some sort of local bus. The address
2516		of the chip must also be defined in the
2517		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2518
2519		#define CONFIG_SYSTEMACE
2520		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2521
2522		When SystemACE support is added, the "ace" device type
2523		becomes available to the fat commands, i.e. fatls.
2524
2525- TFTP Fixed UDP Port:
2526		CONFIG_TFTP_PORT
2527
2528		If this is defined, the environment variable tftpsrcp
2529		is used to supply the TFTP UDP source port value.
2530		If tftpsrcp isn't defined, the normal pseudo-random port
2531		number generator is used.
2532
2533		Also, the environment variable tftpdstp is used to supply
2534		the TFTP UDP destination port value.  If tftpdstp isn't
2535		defined, the normal port 69 is used.
2536
2537		The purpose for tftpsrcp is to allow a TFTP server to
2538		blindly start the TFTP transfer using the pre-configured
2539		target IP address and UDP port. This has the effect of
2540		"punching through" the (Windows XP) firewall, allowing
2541		the remainder of the TFTP transfer to proceed normally.
2542		A better solution is to properly configure the firewall,
2543		but sometimes that is not allowed.
2544
2545- bootcount support:
2546		CONFIG_BOOTCOUNT_LIMIT
2547
2548		This enables the bootcounter support, see:
2549		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2550
2551		CONFIG_AT91SAM9XE
2552		enable special bootcounter support on at91sam9xe based boards.
2553		CONFIG_SOC_DA8XX
2554		enable special bootcounter support on da850 based boards.
2555		CONFIG_BOOTCOUNT_RAM
2556		enable support for the bootcounter in RAM
2557		CONFIG_BOOTCOUNT_I2C
2558		enable support for the bootcounter on an i2c (like RTC) device.
2559			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2560			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2561						    the bootcounter.
2562			CONFIG_BOOTCOUNT_ALEN = address len
2563
2564- Show boot progress:
2565		CONFIG_SHOW_BOOT_PROGRESS
2566
2567		Defining this option allows to add some board-
2568		specific code (calling a user-provided function
2569		"show_boot_progress(int)") that enables you to show
2570		the system's boot progress on some display (for
2571		example, some LED's) on your board. At the moment,
2572		the following checkpoints are implemented:
2573
2574
2575Legacy uImage format:
2576
2577  Arg	Where			When
2578    1	common/cmd_bootm.c	before attempting to boot an image
2579   -1	common/cmd_bootm.c	Image header has bad	 magic number
2580    2	common/cmd_bootm.c	Image header has correct magic number
2581   -2	common/cmd_bootm.c	Image header has bad	 checksum
2582    3	common/cmd_bootm.c	Image header has correct checksum
2583   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2584    4	common/cmd_bootm.c	Image data   has correct checksum
2585   -4	common/cmd_bootm.c	Image is for unsupported architecture
2586    5	common/cmd_bootm.c	Architecture check OK
2587   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2588    6	common/cmd_bootm.c	Image Type check OK
2589   -6	common/cmd_bootm.c	gunzip uncompression error
2590   -7	common/cmd_bootm.c	Unimplemented compression type
2591    7	common/cmd_bootm.c	Uncompression OK
2592    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2593   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2594
2595    9	common/image.c		Start initial ramdisk verification
2596  -10	common/image.c		Ramdisk header has bad	   magic number
2597  -11	common/image.c		Ramdisk header has bad	   checksum
2598   10	common/image.c		Ramdisk header is OK
2599  -12	common/image.c		Ramdisk data   has bad	   checksum
2600   11	common/image.c		Ramdisk data   has correct checksum
2601   12	common/image.c		Ramdisk verification complete, start loading
2602  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2603   13	common/image.c		Start multifile image verification
2604   14	common/image.c		No initial ramdisk, no multifile, continue.
2605
2606   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2607
2608  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2609  -31	post/post.c		POST test failed, detected by post_output_backlog()
2610  -32	post/post.c		POST test failed, detected by post_run_single()
2611
2612   34	common/cmd_doc.c	before loading a Image from a DOC device
2613  -35	common/cmd_doc.c	Bad usage of "doc" command
2614   35	common/cmd_doc.c	correct usage of "doc" command
2615  -36	common/cmd_doc.c	No boot device
2616   36	common/cmd_doc.c	correct boot device
2617  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2618   37	common/cmd_doc.c	correct chip ID found, device available
2619  -38	common/cmd_doc.c	Read Error on boot device
2620   38	common/cmd_doc.c	reading Image header from DOC device OK
2621  -39	common/cmd_doc.c	Image header has bad magic number
2622   39	common/cmd_doc.c	Image header has correct magic number
2623  -40	common/cmd_doc.c	Error reading Image from DOC device
2624   40	common/cmd_doc.c	Image header has correct magic number
2625   41	common/cmd_ide.c	before loading a Image from a IDE device
2626  -42	common/cmd_ide.c	Bad usage of "ide" command
2627   42	common/cmd_ide.c	correct usage of "ide" command
2628  -43	common/cmd_ide.c	No boot device
2629   43	common/cmd_ide.c	boot device found
2630  -44	common/cmd_ide.c	Device not available
2631   44	common/cmd_ide.c	Device available
2632  -45	common/cmd_ide.c	wrong partition selected
2633   45	common/cmd_ide.c	partition selected
2634  -46	common/cmd_ide.c	Unknown partition table
2635   46	common/cmd_ide.c	valid partition table found
2636  -47	common/cmd_ide.c	Invalid partition type
2637   47	common/cmd_ide.c	correct partition type
2638  -48	common/cmd_ide.c	Error reading Image Header on boot device
2639   48	common/cmd_ide.c	reading Image Header from IDE device OK
2640  -49	common/cmd_ide.c	Image header has bad magic number
2641   49	common/cmd_ide.c	Image header has correct magic number
2642  -50	common/cmd_ide.c	Image header has bad	 checksum
2643   50	common/cmd_ide.c	Image header has correct checksum
2644  -51	common/cmd_ide.c	Error reading Image from IDE device
2645   51	common/cmd_ide.c	reading Image from IDE device OK
2646   52	common/cmd_nand.c	before loading a Image from a NAND device
2647  -53	common/cmd_nand.c	Bad usage of "nand" command
2648   53	common/cmd_nand.c	correct usage of "nand" command
2649  -54	common/cmd_nand.c	No boot device
2650   54	common/cmd_nand.c	boot device found
2651  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2652   55	common/cmd_nand.c	correct chip ID found, device available
2653  -56	common/cmd_nand.c	Error reading Image Header on boot device
2654   56	common/cmd_nand.c	reading Image Header from NAND device OK
2655  -57	common/cmd_nand.c	Image header has bad magic number
2656   57	common/cmd_nand.c	Image header has correct magic number
2657  -58	common/cmd_nand.c	Error reading Image from NAND device
2658   58	common/cmd_nand.c	reading Image from NAND device OK
2659
2660  -60	common/env_common.c	Environment has a bad CRC, using default
2661
2662   64	net/eth.c		starting with Ethernet configuration.
2663  -64	net/eth.c		no Ethernet found.
2664   65	net/eth.c		Ethernet found.
2665
2666  -80	common/cmd_net.c	usage wrong
2667   80	common/cmd_net.c	before calling net_loop()
2668  -81	common/cmd_net.c	some error in net_loop() occurred
2669   81	common/cmd_net.c	net_loop() back without error
2670  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2671   82	common/cmd_net.c	trying automatic boot
2672   83	common/cmd_net.c	running "source" command
2673  -83	common/cmd_net.c	some error in automatic boot or "source" command
2674   84	common/cmd_net.c	end without errors
2675
2676FIT uImage format:
2677
2678  Arg	Where			When
2679  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2680 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2681  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2682 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2683  102	common/cmd_bootm.c	Kernel unit name specified
2684 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2685  103	common/cmd_bootm.c	Found configuration node
2686  104	common/cmd_bootm.c	Got kernel subimage node offset
2687 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2688  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2689 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2690  106	common/cmd_bootm.c	Architecture check OK
2691 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2692  107	common/cmd_bootm.c	Kernel subimage type OK
2693 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2694  108	common/cmd_bootm.c	Got kernel subimage data/size
2695 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2696 -109	common/cmd_bootm.c	Can't get kernel subimage type
2697 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2698 -111	common/cmd_bootm.c	Can't get kernel subimage os
2699 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2700 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2701
2702  120	common/image.c		Start initial ramdisk verification
2703 -120	common/image.c		Ramdisk FIT image has incorrect format
2704  121	common/image.c		Ramdisk FIT image has correct format
2705  122	common/image.c		No ramdisk subimage unit name, using configuration
2706 -122	common/image.c		Can't get configuration for ramdisk subimage
2707  123	common/image.c		Ramdisk unit name specified
2708 -124	common/image.c		Can't get ramdisk subimage node offset
2709  125	common/image.c		Got ramdisk subimage node offset
2710 -125	common/image.c		Ramdisk subimage hash verification failed
2711  126	common/image.c		Ramdisk subimage hash verification OK
2712 -126	common/image.c		Ramdisk subimage for unsupported architecture
2713  127	common/image.c		Architecture check OK
2714 -127	common/image.c		Can't get ramdisk subimage data/size
2715  128	common/image.c		Got ramdisk subimage data/size
2716  129	common/image.c		Can't get ramdisk load address
2717 -129	common/image.c		Got ramdisk load address
2718
2719 -130	common/cmd_doc.c	Incorrect FIT image format
2720  131	common/cmd_doc.c	FIT image format OK
2721
2722 -140	common/cmd_ide.c	Incorrect FIT image format
2723  141	common/cmd_ide.c	FIT image format OK
2724
2725 -150	common/cmd_nand.c	Incorrect FIT image format
2726  151	common/cmd_nand.c	FIT image format OK
2727
2728- legacy image format:
2729		CONFIG_IMAGE_FORMAT_LEGACY
2730		enables the legacy image format support in U-Boot.
2731
2732		Default:
2733		enabled if CONFIG_FIT_SIGNATURE is not defined.
2734
2735		CONFIG_DISABLE_IMAGE_LEGACY
2736		disable the legacy image format
2737
2738		This define is introduced, as the legacy image format is
2739		enabled per default for backward compatibility.
2740
2741- Standalone program support:
2742		CONFIG_STANDALONE_LOAD_ADDR
2743
2744		This option defines a board specific value for the
2745		address where standalone program gets loaded, thus
2746		overwriting the architecture dependent default
2747		settings.
2748
2749- Frame Buffer Address:
2750		CONFIG_FB_ADDR
2751
2752		Define CONFIG_FB_ADDR if you want to use specific
2753		address for frame buffer.  This is typically the case
2754		when using a graphics controller has separate video
2755		memory.  U-Boot will then place the frame buffer at
2756		the given address instead of dynamically reserving it
2757		in system RAM by calling lcd_setmem(), which grabs
2758		the memory for the frame buffer depending on the
2759		configured panel size.
2760
2761		Please see board_init_f function.
2762
2763- Automatic software updates via TFTP server
2764		CONFIG_UPDATE_TFTP
2765		CONFIG_UPDATE_TFTP_CNT_MAX
2766		CONFIG_UPDATE_TFTP_MSEC_MAX
2767
2768		These options enable and control the auto-update feature;
2769		for a more detailed description refer to doc/README.update.
2770
2771- MTD Support (mtdparts command, UBI support)
2772		CONFIG_MTD_DEVICE
2773
2774		Adds the MTD device infrastructure from the Linux kernel.
2775		Needed for mtdparts command support.
2776
2777		CONFIG_MTD_PARTITIONS
2778
2779		Adds the MTD partitioning infrastructure from the Linux
2780		kernel. Needed for UBI support.
2781
2782- UBI support
2783		CONFIG_UBI_SILENCE_MSG
2784
2785		Make the verbose messages from UBI stop printing.  This leaves
2786		warnings and errors enabled.
2787
2788
2789		CONFIG_MTD_UBI_WL_THRESHOLD
2790		This parameter defines the maximum difference between the highest
2791		erase counter value and the lowest erase counter value of eraseblocks
2792		of UBI devices. When this threshold is exceeded, UBI starts performing
2793		wear leveling by means of moving data from eraseblock with low erase
2794		counter to eraseblocks with high erase counter.
2795
2796		The default value should be OK for SLC NAND flashes, NOR flashes and
2797		other flashes which have eraseblock life-cycle 100000 or more.
2798		However, in case of MLC NAND flashes which typically have eraseblock
2799		life-cycle less than 10000, the threshold should be lessened (e.g.,
2800		to 128 or 256, although it does not have to be power of 2).
2801
2802		default: 4096
2803
2804		CONFIG_MTD_UBI_BEB_LIMIT
2805		This option specifies the maximum bad physical eraseblocks UBI
2806		expects on the MTD device (per 1024 eraseblocks). If the
2807		underlying flash does not admit of bad eraseblocks (e.g. NOR
2808		flash), this value is ignored.
2809
2810		NAND datasheets often specify the minimum and maximum NVM
2811		(Number of Valid Blocks) for the flashes' endurance lifetime.
2812		The maximum expected bad eraseblocks per 1024 eraseblocks
2813		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2814		which gives 20 for most NANDs (MaxNVB is basically the total
2815		count of eraseblocks on the chip).
2816
2817		To put it differently, if this value is 20, UBI will try to
2818		reserve about 1.9% of physical eraseblocks for bad blocks
2819		handling. And that will be 1.9% of eraseblocks on the entire
2820		NAND chip, not just the MTD partition UBI attaches. This means
2821		that if you have, say, a NAND flash chip admits maximum 40 bad
2822		eraseblocks, and it is split on two MTD partitions of the same
2823		size, UBI will reserve 40 eraseblocks when attaching a
2824		partition.
2825
2826		default: 20
2827
2828		CONFIG_MTD_UBI_FASTMAP
2829		Fastmap is a mechanism which allows attaching an UBI device
2830		in nearly constant time. Instead of scanning the whole MTD device it
2831		only has to locate a checkpoint (called fastmap) on the device.
2832		The on-flash fastmap contains all information needed to attach
2833		the device. Using fastmap makes only sense on large devices where
2834		attaching by scanning takes long. UBI will not automatically install
2835		a fastmap on old images, but you can set the UBI parameter
2836		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2837		that fastmap-enabled images are still usable with UBI implementations
2838		without	fastmap support. On typical flash devices the whole fastmap
2839		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2840
2841		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2842		Set this parameter to enable fastmap automatically on images
2843		without a fastmap.
2844		default: 0
2845
2846		CONFIG_MTD_UBI_FM_DEBUG
2847		Enable UBI fastmap debug
2848		default: 0
2849
2850- UBIFS support
2851		CONFIG_UBIFS_SILENCE_MSG
2852
2853		Make the verbose messages from UBIFS stop printing.  This leaves
2854		warnings and errors enabled.
2855
2856- SPL framework
2857		CONFIG_SPL
2858		Enable building of SPL globally.
2859
2860		CONFIG_SPL_LDSCRIPT
2861		LDSCRIPT for linking the SPL binary.
2862
2863		CONFIG_SPL_MAX_FOOTPRINT
2864		Maximum size in memory allocated to the SPL, BSS included.
2865		When defined, the linker checks that the actual memory
2866		used by SPL from _start to __bss_end does not exceed it.
2867		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2868		must not be both defined at the same time.
2869
2870		CONFIG_SPL_MAX_SIZE
2871		Maximum size of the SPL image (text, data, rodata, and
2872		linker lists sections), BSS excluded.
2873		When defined, the linker checks that the actual size does
2874		not exceed it.
2875
2876		CONFIG_SPL_TEXT_BASE
2877		TEXT_BASE for linking the SPL binary.
2878
2879		CONFIG_SPL_RELOC_TEXT_BASE
2880		Address to relocate to.  If unspecified, this is equal to
2881		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2882
2883		CONFIG_SPL_BSS_START_ADDR
2884		Link address for the BSS within the SPL binary.
2885
2886		CONFIG_SPL_BSS_MAX_SIZE
2887		Maximum size in memory allocated to the SPL BSS.
2888		When defined, the linker checks that the actual memory used
2889		by SPL from __bss_start to __bss_end does not exceed it.
2890		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2891		must not be both defined at the same time.
2892
2893		CONFIG_SPL_STACK
2894		Adress of the start of the stack SPL will use
2895
2896		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2897		When defined, SPL will panic() if the image it has
2898		loaded does not have a signature.
2899		Defining this is useful when code which loads images
2900		in SPL cannot guarantee that absolutely all read errors
2901		will be caught.
2902		An example is the LPC32XX MLC NAND driver, which will
2903		consider that a completely unreadable NAND block is bad,
2904		and thus should be skipped silently.
2905
2906		CONFIG_SPL_RELOC_STACK
2907		Adress of the start of the stack SPL will use after
2908		relocation.  If unspecified, this is equal to
2909		CONFIG_SPL_STACK.
2910
2911		CONFIG_SYS_SPL_MALLOC_START
2912		Starting address of the malloc pool used in SPL.
2913		When this option is set the full malloc is used in SPL and
2914		it is set up by spl_init() and before that, the simple malloc()
2915		can be used if CONFIG_SYS_MALLOC_F is defined.
2916
2917		CONFIG_SYS_SPL_MALLOC_SIZE
2918		The size of the malloc pool used in SPL.
2919
2920		CONFIG_SPL_FRAMEWORK
2921		Enable the SPL framework under common/.  This framework
2922		supports MMC, NAND and YMODEM loading of U-Boot and NAND
2923		NAND loading of the Linux Kernel.
2924
2925		CONFIG_SPL_OS_BOOT
2926		Enable booting directly to an OS from SPL.
2927		See also: doc/README.falcon
2928
2929		CONFIG_SPL_DISPLAY_PRINT
2930		For ARM, enable an optional function to print more information
2931		about the running system.
2932
2933		CONFIG_SPL_INIT_MINIMAL
2934		Arch init code should be built for a very small image
2935
2936		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2937		Partition on the MMC to load U-Boot from when the MMC is being
2938		used in raw mode
2939
2940		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2941		Sector to load kernel uImage from when MMC is being
2942		used in raw mode (for Falcon mode)
2943
2944		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2945		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2946		Sector and number of sectors to load kernel argument
2947		parameters from when MMC is being used in raw mode
2948		(for falcon mode)
2949
2950		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2951		Partition on the MMC to load U-Boot from when the MMC is being
2952		used in fs mode
2953
2954		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2955		Filename to read to load U-Boot when reading from filesystem
2956
2957		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2958		Filename to read to load kernel uImage when reading
2959		from filesystem (for Falcon mode)
2960
2961		CONFIG_SPL_FS_LOAD_ARGS_NAME
2962		Filename to read to load kernel argument parameters
2963		when reading from filesystem (for Falcon mode)
2964
2965		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2966		Set this for NAND SPL on PPC mpc83xx targets, so that
2967		start.S waits for the rest of the SPL to load before
2968		continuing (the hardware starts execution after just
2969		loading the first page rather than the full 4K).
2970
2971		CONFIG_SPL_SKIP_RELOCATE
2972		Avoid SPL relocation
2973
2974		CONFIG_SPL_NAND_BASE
2975		Include nand_base.c in the SPL.  Requires
2976		CONFIG_SPL_NAND_DRIVERS.
2977
2978		CONFIG_SPL_NAND_DRIVERS
2979		SPL uses normal NAND drivers, not minimal drivers.
2980
2981		CONFIG_SPL_NAND_ECC
2982		Include standard software ECC in the SPL
2983
2984		CONFIG_SPL_NAND_SIMPLE
2985		Support for NAND boot using simple NAND drivers that
2986		expose the cmd_ctrl() interface.
2987
2988		CONFIG_SPL_UBI
2989		Support for a lightweight UBI (fastmap) scanner and
2990		loader
2991
2992		CONFIG_SPL_NAND_RAW_ONLY
2993		Support to boot only raw u-boot.bin images. Use this only
2994		if you need to save space.
2995
2996		CONFIG_SPL_COMMON_INIT_DDR
2997		Set for common ddr init with serial presence detect in
2998		SPL binary.
2999
3000		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3001		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3002		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3003		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3004		CONFIG_SYS_NAND_ECCBYTES
3005		Defines the size and behavior of the NAND that SPL uses
3006		to read U-Boot
3007
3008		CONFIG_SPL_NAND_BOOT
3009		Add support NAND boot
3010
3011		CONFIG_SYS_NAND_U_BOOT_OFFS
3012		Location in NAND to read U-Boot from
3013
3014		CONFIG_SYS_NAND_U_BOOT_DST
3015		Location in memory to load U-Boot to
3016
3017		CONFIG_SYS_NAND_U_BOOT_SIZE
3018		Size of image to load
3019
3020		CONFIG_SYS_NAND_U_BOOT_START
3021		Entry point in loaded image to jump to
3022
3023		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3024		Define this if you need to first read the OOB and then the
3025		data. This is used, for example, on davinci platforms.
3026
3027		CONFIG_SPL_OMAP3_ID_NAND
3028		Support for an OMAP3-specific set of functions to return the
3029		ID and MFR of the first attached NAND chip, if present.
3030
3031		CONFIG_SPL_RAM_DEVICE
3032		Support for running image already present in ram, in SPL binary
3033
3034		CONFIG_SPL_PAD_TO
3035		Image offset to which the SPL should be padded before appending
3036		the SPL payload. By default, this is defined as
3037		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3038		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3039		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3040
3041		CONFIG_SPL_TARGET
3042		Final target image containing SPL and payload.  Some SPLs
3043		use an arch-specific makefile fragment instead, for
3044		example if more than one image needs to be produced.
3045
3046		CONFIG_FIT_SPL_PRINT
3047		Printing information about a FIT image adds quite a bit of
3048		code to SPL. So this is normally disabled in SPL. Use this
3049		option to re-enable it. This will affect the output of the
3050		bootm command when booting a FIT image.
3051
3052- TPL framework
3053		CONFIG_TPL
3054		Enable building of TPL globally.
3055
3056		CONFIG_TPL_PAD_TO
3057		Image offset to which the TPL should be padded before appending
3058		the TPL payload. By default, this is defined as
3059		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3060		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3061		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3062
3063- Interrupt support (PPC):
3064
3065		There are common interrupt_init() and timer_interrupt()
3066		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3067		for CPU specific initialization. interrupt_init_cpu()
3068		should set decrementer_count to appropriate value. If
3069		CPU resets decrementer automatically after interrupt
3070		(ppc4xx) it should set decrementer_count to zero.
3071		timer_interrupt() calls timer_interrupt_cpu() for CPU
3072		specific handling. If board has watchdog / status_led
3073		/ other_activity_monitor it works automatically from
3074		general timer_interrupt().
3075
3076
3077Board initialization settings:
3078------------------------------
3079
3080During Initialization u-boot calls a number of board specific functions
3081to allow the preparation of board specific prerequisites, e.g. pin setup
3082before drivers are initialized. To enable these callbacks the
3083following configuration macros have to be defined. Currently this is
3084architecture specific, so please check arch/your_architecture/lib/board.c
3085typically in board_init_f() and board_init_r().
3086
3087- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3088- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3089- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3090- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3091
3092Configuration Settings:
3093-----------------------
3094
3095- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3096		Optionally it can be defined to support 64-bit memory commands.
3097
3098- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3099		undefine this when you're short of memory.
3100
3101- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3102		width of the commands listed in the 'help' command output.
3103
3104- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3105		prompt for user input.
3106
3107- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3108
3109- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3110
3111- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3112
3113- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3114		the application (usually a Linux kernel) when it is
3115		booted
3116
3117- CONFIG_SYS_BAUDRATE_TABLE:
3118		List of legal baudrate settings for this board.
3119
3120- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3121		Begin and End addresses of the area used by the
3122		simple memory test.
3123
3124- CONFIG_SYS_ALT_MEMTEST:
3125		Enable an alternate, more extensive memory test.
3126
3127- CONFIG_SYS_MEMTEST_SCRATCH:
3128		Scratch address used by the alternate memory test
3129		You only need to set this if address zero isn't writeable
3130
3131- CONFIG_SYS_MEM_RESERVE_SECURE
3132		Only implemented for ARMv8 for now.
3133		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
3134		is substracted from total RAM and won't be reported to OS.
3135		This memory can be used as secure memory. A variable
3136		gd->arch.secure_ram is used to track the location. In systems
3137		the RAM base is not zero, or RAM is divided into banks,
3138		this variable needs to be recalcuated to get the address.
3139
3140- CONFIG_SYS_MEM_TOP_HIDE:
3141		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3142		this specified memory area will get subtracted from the top
3143		(end) of RAM and won't get "touched" at all by U-Boot. By
3144		fixing up gd->ram_size the Linux kernel should gets passed
3145		the now "corrected" memory size and won't touch it either.
3146		This should work for arch/ppc and arch/powerpc. Only Linux
3147		board ports in arch/powerpc with bootwrapper support that
3148		recalculate the memory size from the SDRAM controller setup
3149		will have to get fixed in Linux additionally.
3150
3151		This option can be used as a workaround for the 440EPx/GRx
3152		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3153		be touched.
3154
3155		WARNING: Please make sure that this value is a multiple of
3156		the Linux page size (normally 4k). If this is not the case,
3157		then the end address of the Linux memory will be located at a
3158		non page size aligned address and this could cause major
3159		problems.
3160
3161- CONFIG_SYS_LOADS_BAUD_CHANGE:
3162		Enable temporary baudrate change while serial download
3163
3164- CONFIG_SYS_SDRAM_BASE:
3165		Physical start address of SDRAM. _Must_ be 0 here.
3166
3167- CONFIG_SYS_FLASH_BASE:
3168		Physical start address of Flash memory.
3169
3170- CONFIG_SYS_MONITOR_BASE:
3171		Physical start address of boot monitor code (set by
3172		make config files to be same as the text base address
3173		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3174		CONFIG_SYS_FLASH_BASE when booting from flash.
3175
3176- CONFIG_SYS_MONITOR_LEN:
3177		Size of memory reserved for monitor code, used to
3178		determine _at_compile_time_ (!) if the environment is
3179		embedded within the U-Boot image, or in a separate
3180		flash sector.
3181
3182- CONFIG_SYS_MALLOC_LEN:
3183		Size of DRAM reserved for malloc() use.
3184
3185- CONFIG_SYS_MALLOC_F_LEN
3186		Size of the malloc() pool for use before relocation. If
3187		this is defined, then a very simple malloc() implementation
3188		will become available before relocation. The address is just
3189		below the global data, and the stack is moved down to make
3190		space.
3191
3192		This feature allocates regions with increasing addresses
3193		within the region. calloc() is supported, but realloc()
3194		is not available. free() is supported but does nothing.
3195		The memory will be freed (or in fact just forgotten) when
3196		U-Boot relocates itself.
3197
3198- CONFIG_SYS_MALLOC_SIMPLE
3199		Provides a simple and small malloc() and calloc() for those
3200		boards which do not use the full malloc in SPL (which is
3201		enabled with CONFIG_SYS_SPL_MALLOC_START).
3202
3203- CONFIG_SYS_NONCACHED_MEMORY:
3204		Size of non-cached memory area. This area of memory will be
3205		typically located right below the malloc() area and mapped
3206		uncached in the MMU. This is useful for drivers that would
3207		otherwise require a lot of explicit cache maintenance. For
3208		some drivers it's also impossible to properly maintain the
3209		cache. For example if the regions that need to be flushed
3210		are not a multiple of the cache-line size, *and* padding
3211		cannot be allocated between the regions to align them (i.e.
3212		if the HW requires a contiguous array of regions, and the
3213		size of each region is not cache-aligned), then a flush of
3214		one region may result in overwriting data that hardware has
3215		written to another region in the same cache-line. This can
3216		happen for example in network drivers where descriptors for
3217		buffers are typically smaller than the CPU cache-line (e.g.
3218		16 bytes vs. 32 or 64 bytes).
3219
3220		Non-cached memory is only supported on 32-bit ARM at present.
3221
3222- CONFIG_SYS_BOOTM_LEN:
3223		Normally compressed uImages are limited to an
3224		uncompressed size of 8 MBytes. If this is not enough,
3225		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3226		to adjust this setting to your needs.
3227
3228- CONFIG_SYS_BOOTMAPSZ:
3229		Maximum size of memory mapped by the startup code of
3230		the Linux kernel; all data that must be processed by
3231		the Linux kernel (bd_info, boot arguments, FDT blob if
3232		used) must be put below this limit, unless "bootm_low"
3233		environment variable is defined and non-zero. In such case
3234		all data for the Linux kernel must be between "bootm_low"
3235		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3236		variable "bootm_mapsize" will override the value of
3237		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3238		then the value in "bootm_size" will be used instead.
3239
3240- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3241		Enable initrd_high functionality.  If defined then the
3242		initrd_high feature is enabled and the bootm ramdisk subcommand
3243		is enabled.
3244
3245- CONFIG_SYS_BOOT_GET_CMDLINE:
3246		Enables allocating and saving kernel cmdline in space between
3247		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3248
3249- CONFIG_SYS_BOOT_GET_KBD:
3250		Enables allocating and saving a kernel copy of the bd_info in
3251		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3252
3253- CONFIG_SYS_MAX_FLASH_BANKS:
3254		Max number of Flash memory banks
3255
3256- CONFIG_SYS_MAX_FLASH_SECT:
3257		Max number of sectors on a Flash chip
3258
3259- CONFIG_SYS_FLASH_ERASE_TOUT:
3260		Timeout for Flash erase operations (in ms)
3261
3262- CONFIG_SYS_FLASH_WRITE_TOUT:
3263		Timeout for Flash write operations (in ms)
3264
3265- CONFIG_SYS_FLASH_LOCK_TOUT
3266		Timeout for Flash set sector lock bit operation (in ms)
3267
3268- CONFIG_SYS_FLASH_UNLOCK_TOUT
3269		Timeout for Flash clear lock bits operation (in ms)
3270
3271- CONFIG_SYS_FLASH_PROTECTION
3272		If defined, hardware flash sectors protection is used
3273		instead of U-Boot software protection.
3274
3275- CONFIG_SYS_DIRECT_FLASH_TFTP:
3276
3277		Enable TFTP transfers directly to flash memory;
3278		without this option such a download has to be
3279		performed in two steps: (1) download to RAM, and (2)
3280		copy from RAM to flash.
3281
3282		The two-step approach is usually more reliable, since
3283		you can check if the download worked before you erase
3284		the flash, but in some situations (when system RAM is
3285		too limited to allow for a temporary copy of the
3286		downloaded image) this option may be very useful.
3287
3288- CONFIG_SYS_FLASH_CFI:
3289		Define if the flash driver uses extra elements in the
3290		common flash structure for storing flash geometry.
3291
3292- CONFIG_FLASH_CFI_DRIVER
3293		This option also enables the building of the cfi_flash driver
3294		in the drivers directory
3295
3296- CONFIG_FLASH_CFI_MTD
3297		This option enables the building of the cfi_mtd driver
3298		in the drivers directory. The driver exports CFI flash
3299		to the MTD layer.
3300
3301- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3302		Use buffered writes to flash.
3303
3304- CONFIG_FLASH_SPANSION_S29WS_N
3305		s29ws-n MirrorBit flash has non-standard addresses for buffered
3306		write commands.
3307
3308- CONFIG_SYS_FLASH_QUIET_TEST
3309		If this option is defined, the common CFI flash doesn't
3310		print it's warning upon not recognized FLASH banks. This
3311		is useful, if some of the configured banks are only
3312		optionally available.
3313
3314- CONFIG_FLASH_SHOW_PROGRESS
3315		If defined (must be an integer), print out countdown
3316		digits and dots.  Recommended value: 45 (9..1) for 80
3317		column displays, 15 (3..1) for 40 column displays.
3318
3319- CONFIG_FLASH_VERIFY
3320		If defined, the content of the flash (destination) is compared
3321		against the source after the write operation. An error message
3322		will be printed when the contents are not identical.
3323		Please note that this option is useless in nearly all cases,
3324		since such flash programming errors usually are detected earlier
3325		while unprotecting/erasing/programming. Please only enable
3326		this option if you really know what you are doing.
3327
3328- CONFIG_SYS_RX_ETH_BUFFER:
3329		Defines the number of Ethernet receive buffers. On some
3330		Ethernet controllers it is recommended to set this value
3331		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3332		buffers can be full shortly after enabling the interface
3333		on high Ethernet traffic.
3334		Defaults to 4 if not defined.
3335
3336- CONFIG_ENV_MAX_ENTRIES
3337
3338	Maximum number of entries in the hash table that is used
3339	internally to store the environment settings. The default
3340	setting is supposed to be generous and should work in most
3341	cases. This setting can be used to tune behaviour; see
3342	lib/hashtable.c for details.
3343
3344- CONFIG_ENV_FLAGS_LIST_DEFAULT
3345- CONFIG_ENV_FLAGS_LIST_STATIC
3346	Enable validation of the values given to environment variables when
3347	calling env set.  Variables can be restricted to only decimal,
3348	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3349	the variables can also be restricted to IP address or MAC address.
3350
3351	The format of the list is:
3352		type_attribute = [s|d|x|b|i|m]
3353		access_attribute = [a|r|o|c]
3354		attributes = type_attribute[access_attribute]
3355		entry = variable_name[:attributes]
3356		list = entry[,list]
3357
3358	The type attributes are:
3359		s - String (default)
3360		d - Decimal
3361		x - Hexadecimal
3362		b - Boolean ([1yYtT|0nNfF])
3363		i - IP address
3364		m - MAC address
3365
3366	The access attributes are:
3367		a - Any (default)
3368		r - Read-only
3369		o - Write-once
3370		c - Change-default
3371
3372	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3373		Define this to a list (string) to define the ".flags"
3374		environment variable in the default or embedded environment.
3375
3376	- CONFIG_ENV_FLAGS_LIST_STATIC
3377		Define this to a list (string) to define validation that
3378		should be done if an entry is not found in the ".flags"
3379		environment variable.  To override a setting in the static
3380		list, simply add an entry for the same variable name to the
3381		".flags" variable.
3382
3383	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3384	regular expression. This allows multiple variables to define the same
3385	flags without explicitly listing them for each variable.
3386
3387- CONFIG_ENV_ACCESS_IGNORE_FORCE
3388	If defined, don't allow the -f switch to env set override variable
3389	access flags.
3390
3391- CONFIG_USE_STDINT
3392	If stdint.h is available with your toolchain you can define this
3393	option to enable it. You can provide option 'USE_STDINT=1' when
3394	building U-Boot to enable this.
3395
3396The following definitions that deal with the placement and management
3397of environment data (variable area); in general, we support the
3398following configurations:
3399
3400- CONFIG_BUILD_ENVCRC:
3401
3402	Builds up envcrc with the target environment so that external utils
3403	may easily extract it and embed it in final U-Boot images.
3404
3405BE CAREFUL! The first access to the environment happens quite early
3406in U-Boot initialization (when we try to get the setting of for the
3407console baudrate). You *MUST* have mapped your NVRAM area then, or
3408U-Boot will hang.
3409
3410Please note that even with NVRAM we still use a copy of the
3411environment in RAM: we could work on NVRAM directly, but we want to
3412keep settings there always unmodified except somebody uses "saveenv"
3413to save the current settings.
3414
3415BE CAREFUL! For some special cases, the local device can not use
3416"saveenv" command. For example, the local device will get the
3417environment stored in a remote NOR flash by SRIO or PCIE link,
3418but it can not erase, write this NOR flash by SRIO or PCIE interface.
3419
3420- CONFIG_NAND_ENV_DST
3421
3422	Defines address in RAM to which the nand_spl code should copy the
3423	environment. If redundant environment is used, it will be copied to
3424	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3425
3426Please note that the environment is read-only until the monitor
3427has been relocated to RAM and a RAM copy of the environment has been
3428created; also, when using EEPROM you will have to use getenv_f()
3429until then to read environment variables.
3430
3431The environment is protected by a CRC32 checksum. Before the monitor
3432is relocated into RAM, as a result of a bad CRC you will be working
3433with the compiled-in default environment - *silently*!!! [This is
3434necessary, because the first environment variable we need is the
3435"baudrate" setting for the console - if we have a bad CRC, we don't
3436have any device yet where we could complain.]
3437
3438Note: once the monitor has been relocated, then it will complain if
3439the default environment is used; a new CRC is computed as soon as you
3440use the "saveenv" command to store a valid environment.
3441
3442- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3443		Echo the inverted Ethernet link state to the fault LED.
3444
3445		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3446		      also needs to be defined.
3447
3448- CONFIG_SYS_FAULT_MII_ADDR:
3449		MII address of the PHY to check for the Ethernet link state.
3450
3451- CONFIG_NS16550_MIN_FUNCTIONS:
3452		Define this if you desire to only have use of the NS16550_init
3453		and NS16550_putc functions for the serial driver located at
3454		drivers/serial/ns16550.c.  This option is useful for saving
3455		space for already greatly restricted images, including but not
3456		limited to NAND_SPL configurations.
3457
3458- CONFIG_DISPLAY_BOARDINFO
3459		Display information about the board that U-Boot is running on
3460		when U-Boot starts up. The board function checkboard() is called
3461		to do this.
3462
3463- CONFIG_DISPLAY_BOARDINFO_LATE
3464		Similar to the previous option, but display this information
3465		later, once stdio is running and output goes to the LCD, if
3466		present.
3467
3468- CONFIG_BOARD_SIZE_LIMIT:
3469		Maximum size of the U-Boot image. When defined, the
3470		build system checks that the actual size does not
3471		exceed it.
3472
3473Low Level (hardware related) configuration options:
3474---------------------------------------------------
3475
3476- CONFIG_SYS_CACHELINE_SIZE:
3477		Cache Line Size of the CPU.
3478
3479- CONFIG_SYS_CCSRBAR_DEFAULT:
3480		Default (power-on reset) physical address of CCSR on Freescale
3481		PowerPC SOCs.
3482
3483- CONFIG_SYS_CCSRBAR:
3484		Virtual address of CCSR.  On a 32-bit build, this is typically
3485		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3486
3487- CONFIG_SYS_CCSRBAR_PHYS:
3488		Physical address of CCSR.  CCSR can be relocated to a new
3489		physical address, if desired.  In this case, this macro should
3490		be set to that address.	 Otherwise, it should be set to the
3491		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3492		is typically relocated on 36-bit builds.  It is recommended
3493		that this macro be defined via the _HIGH and _LOW macros:
3494
3495		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3496			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3497
3498- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3499		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3500		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3501		used in assembly code, so it must not contain typecasts or
3502		integer size suffixes (e.g. "ULL").
3503
3504- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3505		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3506		used in assembly code, so it must not contain typecasts or
3507		integer size suffixes (e.g. "ULL").
3508
3509- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3510		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3511		forced to a value that ensures that CCSR is not relocated.
3512
3513- Floppy Disk Support:
3514		CONFIG_SYS_FDC_DRIVE_NUMBER
3515
3516		the default drive number (default value 0)
3517
3518		CONFIG_SYS_ISA_IO_STRIDE
3519
3520		defines the spacing between FDC chipset registers
3521		(default value 1)
3522
3523		CONFIG_SYS_ISA_IO_OFFSET
3524
3525		defines the offset of register from address. It
3526		depends on which part of the data bus is connected to
3527		the FDC chipset. (default value 0)
3528
3529		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3530		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3531		default value.
3532
3533		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3534		fdc_hw_init() is called at the beginning of the FDC
3535		setup. fdc_hw_init() must be provided by the board
3536		source code. It is used to make hardware-dependent
3537		initializations.
3538
3539- CONFIG_IDE_AHB:
3540		Most IDE controllers were designed to be connected with PCI
3541		interface. Only few of them were designed for AHB interface.
3542		When software is doing ATA command and data transfer to
3543		IDE devices through IDE-AHB controller, some additional
3544		registers accessing to these kind of IDE-AHB controller
3545		is required.
3546
3547- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3548		DO NOT CHANGE unless you know exactly what you're
3549		doing! (11-4) [MPC8xx systems only]
3550
3551- CONFIG_SYS_INIT_RAM_ADDR:
3552
3553		Start address of memory area that can be used for
3554		initial data and stack; please note that this must be
3555		writable memory that is working WITHOUT special
3556		initialization, i. e. you CANNOT use normal RAM which
3557		will become available only after programming the
3558		memory controller and running certain initialization
3559		sequences.
3560
3561		U-Boot uses the following memory types:
3562		- MPC8xx: IMMR (internal memory of the CPU)
3563
3564- CONFIG_SYS_GBL_DATA_OFFSET:
3565
3566		Offset of the initial data structure in the memory
3567		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3568		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3569		data is located at the end of the available space
3570		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3571		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3572		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3573		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3574
3575	Note:
3576		On the MPC824X (or other systems that use the data
3577		cache for initial memory) the address chosen for
3578		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3579		point to an otherwise UNUSED address space between
3580		the top of RAM and the start of the PCI space.
3581
3582- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3583
3584- CONFIG_SYS_OR_TIMING_SDRAM:
3585		SDRAM timing
3586
3587- CONFIG_SYS_MAMR_PTA:
3588		periodic timer for refresh
3589
3590- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3591  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3592  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3593  CONFIG_SYS_BR1_PRELIM:
3594		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3595
3596- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3597  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3598  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3599		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3600
3601- CONFIG_PCI_ENUM_ONLY
3602		Only scan through and get the devices on the buses.
3603		Don't do any setup work, presumably because someone or
3604		something has already done it, and we don't need to do it
3605		a second time.	Useful for platforms that are pre-booted
3606		by coreboot or similar.
3607
3608- CONFIG_PCI_INDIRECT_BRIDGE:
3609		Enable support for indirect PCI bridges.
3610
3611- CONFIG_SYS_SRIO:
3612		Chip has SRIO or not
3613
3614- CONFIG_SRIO1:
3615		Board has SRIO 1 port available
3616
3617- CONFIG_SRIO2:
3618		Board has SRIO 2 port available
3619
3620- CONFIG_SRIO_PCIE_BOOT_MASTER
3621		Board can support master function for Boot from SRIO and PCIE
3622
3623- CONFIG_SYS_SRIOn_MEM_VIRT:
3624		Virtual Address of SRIO port 'n' memory region
3625
3626- CONFIG_SYS_SRIOn_MEM_PHYS:
3627		Physical Address of SRIO port 'n' memory region
3628
3629- CONFIG_SYS_SRIOn_MEM_SIZE:
3630		Size of SRIO port 'n' memory region
3631
3632- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3633		Defined to tell the NAND controller that the NAND chip is using
3634		a 16 bit bus.
3635		Not all NAND drivers use this symbol.
3636		Example of drivers that use it:
3637		- drivers/mtd/nand/ndfc.c
3638		- drivers/mtd/nand/mxc_nand.c
3639
3640- CONFIG_SYS_NDFC_EBC0_CFG
3641		Sets the EBC0_CFG register for the NDFC. If not defined
3642		a default value will be used.
3643
3644- CONFIG_SPD_EEPROM
3645		Get DDR timing information from an I2C EEPROM. Common
3646		with pluggable memory modules such as SODIMMs
3647
3648  SPD_EEPROM_ADDRESS
3649		I2C address of the SPD EEPROM
3650
3651- CONFIG_SYS_SPD_BUS_NUM
3652		If SPD EEPROM is on an I2C bus other than the first
3653		one, specify here. Note that the value must resolve
3654		to something your driver can deal with.
3655
3656- CONFIG_SYS_DDR_RAW_TIMING
3657		Get DDR timing information from other than SPD. Common with
3658		soldered DDR chips onboard without SPD. DDR raw timing
3659		parameters are extracted from datasheet and hard-coded into
3660		header files or board specific files.
3661
3662- CONFIG_FSL_DDR_INTERACTIVE
3663		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3664
3665- CONFIG_FSL_DDR_SYNC_REFRESH
3666		Enable sync of refresh for multiple controllers.
3667
3668- CONFIG_FSL_DDR_BIST
3669		Enable built-in memory test for Freescale DDR controllers.
3670
3671- CONFIG_SYS_83XX_DDR_USES_CS0
3672		Only for 83xx systems. If specified, then DDR should
3673		be configured using CS0 and CS1 instead of CS2 and CS3.
3674
3675- CONFIG_RMII
3676		Enable RMII mode for all FECs.
3677		Note that this is a global option, we can't
3678		have one FEC in standard MII mode and another in RMII mode.
3679
3680- CONFIG_CRC32_VERIFY
3681		Add a verify option to the crc32 command.
3682		The syntax is:
3683
3684		=> crc32 -v <address> <count> <crc32>
3685
3686		Where address/count indicate a memory area
3687		and crc32 is the correct crc32 which the
3688		area should have.
3689
3690- CONFIG_LOOPW
3691		Add the "loopw" memory command. This only takes effect if
3692		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3693
3694- CONFIG_MX_CYCLIC
3695		Add the "mdc" and "mwc" memory commands. These are cyclic
3696		"md/mw" commands.
3697		Examples:
3698
3699		=> mdc.b 10 4 500
3700		This command will print 4 bytes (10,11,12,13) each 500 ms.
3701
3702		=> mwc.l 100 12345678 10
3703		This command will write 12345678 to address 100 all 10 ms.
3704
3705		This only takes effect if the memory commands are activated
3706		globally (CONFIG_CMD_MEMORY).
3707
3708- CONFIG_SKIP_LOWLEVEL_INIT
3709		[ARM, NDS32, MIPS only] If this variable is defined, then certain
3710		low level initializations (like setting up the memory
3711		controller) are omitted and/or U-Boot does not
3712		relocate itself into RAM.
3713
3714		Normally this variable MUST NOT be defined. The only
3715		exception is when U-Boot is loaded (to RAM) by some
3716		other boot loader or by a debugger which performs
3717		these initializations itself.
3718
3719- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3720		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3721		to be skipped. The normal CP15 init (such as enabling the
3722		instruction cache) is still performed.
3723
3724- CONFIG_SPL_BUILD
3725		Modifies the behaviour of start.S when compiling a loader
3726		that is executed before the actual U-Boot. E.g. when
3727		compiling a NAND SPL.
3728
3729- CONFIG_TPL_BUILD
3730		Modifies the behaviour of start.S  when compiling a loader
3731		that is executed after the SPL and before the actual U-Boot.
3732		It is loaded by the SPL.
3733
3734- CONFIG_SYS_MPC85XX_NO_RESETVEC
3735		Only for 85xx systems. If this variable is specified, the section
3736		.resetvec is not kept and the section .bootpg is placed in the
3737		previous 4k of the .text section.
3738
3739- CONFIG_ARCH_MAP_SYSMEM
3740		Generally U-Boot (and in particular the md command) uses
3741		effective address. It is therefore not necessary to regard
3742		U-Boot address as virtual addresses that need to be translated
3743		to physical addresses. However, sandbox requires this, since
3744		it maintains its own little RAM buffer which contains all
3745		addressable memory. This option causes some memory accesses
3746		to be mapped through map_sysmem() / unmap_sysmem().
3747
3748- CONFIG_X86_RESET_VECTOR
3749		If defined, the x86 reset vector code is included. This is not
3750		needed when U-Boot is running from Coreboot.
3751
3752- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
3753		Enables the RTC32K OSC on AM33xx based plattforms
3754
3755- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3756		Option to disable subpage write in NAND driver
3757		driver that uses this:
3758		drivers/mtd/nand/davinci_nand.c
3759
3760Freescale QE/FMAN Firmware Support:
3761-----------------------------------
3762
3763The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3764loading of "firmware", which is encoded in the QE firmware binary format.
3765This firmware often needs to be loaded during U-Boot booting, so macros
3766are used to identify the storage device (NOR flash, SPI, etc) and the address
3767within that device.
3768
3769- CONFIG_SYS_FMAN_FW_ADDR
3770	The address in the storage device where the FMAN microcode is located.  The
3771	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3772	is also specified.
3773
3774- CONFIG_SYS_QE_FW_ADDR
3775	The address in the storage device where the QE microcode is located.  The
3776	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3777	is also specified.
3778
3779- CONFIG_SYS_QE_FMAN_FW_LENGTH
3780	The maximum possible size of the firmware.  The firmware binary format
3781	has a field that specifies the actual size of the firmware, but it
3782	might not be possible to read any part of the firmware unless some
3783	local storage is allocated to hold the entire firmware first.
3784
3785- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3786	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3787	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3788	virtual address in NOR flash.
3789
3790- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3791	Specifies that QE/FMAN firmware is located in NAND flash.
3792	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3793
3794- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3795	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3796	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3797
3798- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3799	Specifies that QE/FMAN firmware is located in the remote (master)
3800	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3801	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3802	window->master inbound window->master LAW->the ucode address in
3803	master's memory space.
3804
3805Freescale Layerscape Management Complex Firmware Support:
3806---------------------------------------------------------
3807The Freescale Layerscape Management Complex (MC) supports the loading of
3808"firmware".
3809This firmware often needs to be loaded during U-Boot booting, so macros
3810are used to identify the storage device (NOR flash, SPI, etc) and the address
3811within that device.
3812
3813- CONFIG_FSL_MC_ENET
3814	Enable the MC driver for Layerscape SoCs.
3815
3816Freescale Layerscape Debug Server Support:
3817-------------------------------------------
3818The Freescale Layerscape Debug Server Support supports the loading of
3819"Debug Server firmware" and triggering SP boot-rom.
3820This firmware often needs to be loaded during U-Boot booting.
3821
3822- CONFIG_SYS_MC_RSV_MEM_ALIGN
3823	Define alignment of reserved memory MC requires
3824
3825Reproducible builds
3826-------------------
3827
3828In order to achieve reproducible builds, timestamps used in the U-Boot build
3829process have to be set to a fixed value.
3830
3831This is done using the SOURCE_DATE_EPOCH environment variable.
3832SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3833option for U-Boot or an environment variable in U-Boot.
3834
3835SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3836
3837Building the Software:
3838======================
3839
3840Building U-Boot has been tested in several native build environments
3841and in many different cross environments. Of course we cannot support
3842all possibly existing versions of cross development tools in all
3843(potentially obsolete) versions. In case of tool chain problems we
3844recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3845which is extensively used to build and test U-Boot.
3846
3847If you are not using a native environment, it is assumed that you
3848have GNU cross compiling tools available in your path. In this case,
3849you must set the environment variable CROSS_COMPILE in your shell.
3850Note that no changes to the Makefile or any other source files are
3851necessary. For example using the ELDK on a 4xx CPU, please enter:
3852
3853	$ CROSS_COMPILE=ppc_4xx-
3854	$ export CROSS_COMPILE
3855
3856Note: If you wish to generate Windows versions of the utilities in
3857      the tools directory you can use the MinGW toolchain
3858      (http://www.mingw.org).  Set your HOST tools to the MinGW
3859      toolchain and execute 'make tools'.  For example:
3860
3861       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3862
3863      Binaries such as tools/mkimage.exe will be created which can
3864      be executed on computers running Windows.
3865
3866U-Boot is intended to be simple to build. After installing the
3867sources you must configure U-Boot for one specific board type. This
3868is done by typing:
3869
3870	make NAME_defconfig
3871
3872where "NAME_defconfig" is the name of one of the existing configu-
3873rations; see boards.cfg for supported names.
3874
3875Note: for some board special configuration names may exist; check if
3876      additional information is available from the board vendor; for
3877      instance, the TQM823L systems are available without (standard)
3878      or with LCD support. You can select such additional "features"
3879      when choosing the configuration, i. e.
3880
3881      make TQM823L_defconfig
3882	- will configure for a plain TQM823L, i. e. no LCD support
3883
3884      make TQM823L_LCD_defconfig
3885	- will configure for a TQM823L with U-Boot console on LCD
3886
3887      etc.
3888
3889
3890Finally, type "make all", and you should get some working U-Boot
3891images ready for download to / installation on your system:
3892
3893- "u-boot.bin" is a raw binary image
3894- "u-boot" is an image in ELF binary format
3895- "u-boot.srec" is in Motorola S-Record format
3896
3897By default the build is performed locally and the objects are saved
3898in the source directory. One of the two methods can be used to change
3899this behavior and build U-Boot to some external directory:
3900
39011. Add O= to the make command line invocations:
3902
3903	make O=/tmp/build distclean
3904	make O=/tmp/build NAME_defconfig
3905	make O=/tmp/build all
3906
39072. Set environment variable KBUILD_OUTPUT to point to the desired location:
3908
3909	export KBUILD_OUTPUT=/tmp/build
3910	make distclean
3911	make NAME_defconfig
3912	make all
3913
3914Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3915variable.
3916
3917
3918Please be aware that the Makefiles assume you are using GNU make, so
3919for instance on NetBSD you might need to use "gmake" instead of
3920native "make".
3921
3922
3923If the system board that you have is not listed, then you will need
3924to port U-Boot to your hardware platform. To do this, follow these
3925steps:
3926
39271.  Create a new directory to hold your board specific code. Add any
3928    files you need. In your board directory, you will need at least
3929    the "Makefile" and a "<board>.c".
39302.  Create a new configuration file "include/configs/<board>.h" for
3931    your board.
39323.  If you're porting U-Boot to a new CPU, then also create a new
3933    directory to hold your CPU specific code. Add any files you need.
39344.  Run "make <board>_defconfig" with your new name.
39355.  Type "make", and you should get a working "u-boot.srec" file
3936    to be installed on your target system.
39376.  Debug and solve any problems that might arise.
3938    [Of course, this last step is much harder than it sounds.]
3939
3940
3941Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3942==============================================================
3943
3944If you have modified U-Boot sources (for instance added a new board
3945or support for new devices, a new CPU, etc.) you are expected to
3946provide feedback to the other developers. The feedback normally takes
3947the form of a "patch", i. e. a context diff against a certain (latest
3948official or latest in the git repository) version of U-Boot sources.
3949
3950But before you submit such a patch, please verify that your modifi-
3951cation did not break existing code. At least make sure that *ALL* of
3952the supported boards compile WITHOUT ANY compiler warnings. To do so,
3953just run the buildman script (tools/buildman/buildman), which will
3954configure and build U-Boot for ALL supported system. Be warned, this
3955will take a while. Please see the buildman README, or run 'buildman -H'
3956for documentation.
3957
3958
3959See also "U-Boot Porting Guide" below.
3960
3961
3962Monitor Commands - Overview:
3963============================
3964
3965go	- start application at address 'addr'
3966run	- run commands in an environment variable
3967bootm	- boot application image from memory
3968bootp	- boot image via network using BootP/TFTP protocol
3969bootz   - boot zImage from memory
3970tftpboot- boot image via network using TFTP protocol
3971	       and env variables "ipaddr" and "serverip"
3972	       (and eventually "gatewayip")
3973tftpput - upload a file via network using TFTP protocol
3974rarpboot- boot image via network using RARP/TFTP protocol
3975diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3976loads	- load S-Record file over serial line
3977loadb	- load binary file over serial line (kermit mode)
3978md	- memory display
3979mm	- memory modify (auto-incrementing)
3980nm	- memory modify (constant address)
3981mw	- memory write (fill)
3982cp	- memory copy
3983cmp	- memory compare
3984crc32	- checksum calculation
3985i2c	- I2C sub-system
3986sspi	- SPI utility commands
3987base	- print or set address offset
3988printenv- print environment variables
3989setenv	- set environment variables
3990saveenv - save environment variables to persistent storage
3991protect - enable or disable FLASH write protection
3992erase	- erase FLASH memory
3993flinfo	- print FLASH memory information
3994nand	- NAND memory operations (see doc/README.nand)
3995bdinfo	- print Board Info structure
3996iminfo	- print header information for application image
3997coninfo - print console devices and informations
3998ide	- IDE sub-system
3999loop	- infinite loop on address range
4000loopw	- infinite write loop on address range
4001mtest	- simple RAM test
4002icache	- enable or disable instruction cache
4003dcache	- enable or disable data cache
4004reset	- Perform RESET of the CPU
4005echo	- echo args to console
4006version - print monitor version
4007help	- print online help
4008?	- alias for 'help'
4009
4010
4011Monitor Commands - Detailed Description:
4012========================================
4013
4014TODO.
4015
4016For now: just type "help <command>".
4017
4018
4019Environment Variables:
4020======================
4021
4022U-Boot supports user configuration using Environment Variables which
4023can be made persistent by saving to Flash memory.
4024
4025Environment Variables are set using "setenv", printed using
4026"printenv", and saved to Flash using "saveenv". Using "setenv"
4027without a value can be used to delete a variable from the
4028environment. As long as you don't save the environment you are
4029working with an in-memory copy. In case the Flash area containing the
4030environment is erased by accident, a default environment is provided.
4031
4032Some configuration options can be set using Environment Variables.
4033
4034List of environment variables (most likely not complete):
4035
4036  baudrate	- see CONFIG_BAUDRATE
4037
4038  bootdelay	- see CONFIG_BOOTDELAY
4039
4040  bootcmd	- see CONFIG_BOOTCOMMAND
4041
4042  bootargs	- Boot arguments when booting an RTOS image
4043
4044  bootfile	- Name of the image to load with TFTP
4045
4046  bootm_low	- Memory range available for image processing in the bootm
4047		  command can be restricted. This variable is given as
4048		  a hexadecimal number and defines lowest address allowed
4049		  for use by the bootm command. See also "bootm_size"
4050		  environment variable. Address defined by "bootm_low" is
4051		  also the base of the initial memory mapping for the Linux
4052		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4053		  bootm_mapsize.
4054
4055  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4056		  This variable is given as a hexadecimal number and it
4057		  defines the size of the memory region starting at base
4058		  address bootm_low that is accessible by the Linux kernel
4059		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4060		  as the default value if it is defined, and bootm_size is
4061		  used otherwise.
4062
4063  bootm_size	- Memory range available for image processing in the bootm
4064		  command can be restricted. This variable is given as
4065		  a hexadecimal number and defines the size of the region
4066		  allowed for use by the bootm command. See also "bootm_low"
4067		  environment variable.
4068
4069  updatefile	- Location of the software update file on a TFTP server, used
4070		  by the automatic software update feature. Please refer to
4071		  documentation in doc/README.update for more details.
4072
4073  autoload	- if set to "no" (any string beginning with 'n'),
4074		  "bootp" will just load perform a lookup of the
4075		  configuration from the BOOTP server, but not try to
4076		  load any image using TFTP
4077
4078  autostart	- if set to "yes", an image loaded using the "bootp",
4079		  "rarpboot", "tftpboot" or "diskboot" commands will
4080		  be automatically started (by internally calling
4081		  "bootm")
4082
4083		  If set to "no", a standalone image passed to the
4084		  "bootm" command will be copied to the load address
4085		  (and eventually uncompressed), but NOT be started.
4086		  This can be used to load and uncompress arbitrary
4087		  data.
4088
4089  fdt_high	- if set this restricts the maximum address that the
4090		  flattened device tree will be copied into upon boot.
4091		  For example, if you have a system with 1 GB memory
4092		  at physical address 0x10000000, while Linux kernel
4093		  only recognizes the first 704 MB as low memory, you
4094		  may need to set fdt_high as 0x3C000000 to have the
4095		  device tree blob be copied to the maximum address
4096		  of the 704 MB low memory, so that Linux kernel can
4097		  access it during the boot procedure.
4098
4099		  If this is set to the special value 0xFFFFFFFF then
4100		  the fdt will not be copied at all on boot.  For this
4101		  to work it must reside in writable memory, have
4102		  sufficient padding on the end of it for u-boot to
4103		  add the information it needs into it, and the memory
4104		  must be accessible by the kernel.
4105
4106  fdtcontroladdr- if set this is the address of the control flattened
4107		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4108		  defined.
4109
4110  i2cfast	- (PPC405GP|PPC405EP only)
4111		  if set to 'y' configures Linux I2C driver for fast
4112		  mode (400kHZ). This environment variable is used in
4113		  initialization code. So, for changes to be effective
4114		  it must be saved and board must be reset.
4115
4116  initrd_high	- restrict positioning of initrd images:
4117		  If this variable is not set, initrd images will be
4118		  copied to the highest possible address in RAM; this
4119		  is usually what you want since it allows for
4120		  maximum initrd size. If for some reason you want to
4121		  make sure that the initrd image is loaded below the
4122		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4123		  variable to a value of "no" or "off" or "0".
4124		  Alternatively, you can set it to a maximum upper
4125		  address to use (U-Boot will still check that it
4126		  does not overwrite the U-Boot stack and data).
4127
4128		  For instance, when you have a system with 16 MB
4129		  RAM, and want to reserve 4 MB from use by Linux,
4130		  you can do this by adding "mem=12M" to the value of
4131		  the "bootargs" variable. However, now you must make
4132		  sure that the initrd image is placed in the first
4133		  12 MB as well - this can be done with
4134
4135		  setenv initrd_high 00c00000
4136
4137		  If you set initrd_high to 0xFFFFFFFF, this is an
4138		  indication to U-Boot that all addresses are legal
4139		  for the Linux kernel, including addresses in flash
4140		  memory. In this case U-Boot will NOT COPY the
4141		  ramdisk at all. This may be useful to reduce the
4142		  boot time on your system, but requires that this
4143		  feature is supported by your Linux kernel.
4144
4145  ipaddr	- IP address; needed for tftpboot command
4146
4147  loadaddr	- Default load address for commands like "bootp",
4148		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4149
4150  loads_echo	- see CONFIG_LOADS_ECHO
4151
4152  serverip	- TFTP server IP address; needed for tftpboot command
4153
4154  bootretry	- see CONFIG_BOOT_RETRY_TIME
4155
4156  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4157
4158  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4159
4160  ethprime	- controls which interface is used first.
4161
4162  ethact	- controls which interface is currently active.
4163		  For example you can do the following
4164
4165		  => setenv ethact FEC
4166		  => ping 192.168.0.1 # traffic sent on FEC
4167		  => setenv ethact SCC
4168		  => ping 10.0.0.1 # traffic sent on SCC
4169
4170  ethrotate	- When set to "no" U-Boot does not go through all
4171		  available network interfaces.
4172		  It just stays at the currently selected interface.
4173
4174  netretry	- When set to "no" each network operation will
4175		  either succeed or fail without retrying.
4176		  When set to "once" the network operation will
4177		  fail when all the available network interfaces
4178		  are tried once without success.
4179		  Useful on scripts which control the retry operation
4180		  themselves.
4181
4182  npe_ucode	- set load address for the NPE microcode
4183
4184  silent_linux  - If set then Linux will be told to boot silently, by
4185		  changing the console to be empty. If "yes" it will be
4186		  made silent. If "no" it will not be made silent. If
4187		  unset, then it will be made silent if the U-Boot console
4188		  is silent.
4189
4190  tftpsrcp	- If this is set, the value is used for TFTP's
4191		  UDP source port.
4192
4193  tftpdstp	- If this is set, the value is used for TFTP's UDP
4194		  destination port instead of the Well Know Port 69.
4195
4196  tftpblocksize - Block size to use for TFTP transfers; if not set,
4197		  we use the TFTP server's default block size
4198
4199  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4200		  seconds, minimum value is 1000 = 1 second). Defines
4201		  when a packet is considered to be lost so it has to
4202		  be retransmitted. The default is 5000 = 5 seconds.
4203		  Lowering this value may make downloads succeed
4204		  faster in networks with high packet loss rates or
4205		  with unreliable TFTP servers.
4206
4207  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
4208		  unit, minimum value = 0). Defines how many timeouts
4209		  can happen during a single file transfer before that
4210		  transfer is aborted. The default is 10, and 0 means
4211		  'no timeouts allowed'. Increasing this value may help
4212		  downloads succeed with high packet loss rates, or with
4213		  unreliable TFTP servers or client hardware.
4214
4215  vlan		- When set to a value < 4095 the traffic over
4216		  Ethernet is encapsulated/received over 802.1q
4217		  VLAN tagged frames.
4218
4219  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
4220		  Unsigned value, in milliseconds. If not set, the period will
4221		  be either the default (28000), or a value based on
4222		  CONFIG_NET_RETRY_COUNT, if defined. This value has
4223		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
4224
4225The following image location variables contain the location of images
4226used in booting. The "Image" column gives the role of the image and is
4227not an environment variable name. The other columns are environment
4228variable names. "File Name" gives the name of the file on a TFTP
4229server, "RAM Address" gives the location in RAM the image will be
4230loaded to, and "Flash Location" gives the image's address in NOR
4231flash or offset in NAND flash.
4232
4233*Note* - these variables don't have to be defined for all boards, some
4234boards currently use other variables for these purposes, and some
4235boards use these variables for other purposes.
4236
4237Image		    File Name	     RAM Address       Flash Location
4238-----		    ---------	     -----------       --------------
4239u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4240Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4241device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4242ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4243
4244The following environment variables may be used and automatically
4245updated by the network boot commands ("bootp" and "rarpboot"),
4246depending the information provided by your boot server:
4247
4248  bootfile	- see above
4249  dnsip		- IP address of your Domain Name Server
4250  dnsip2	- IP address of your secondary Domain Name Server
4251  gatewayip	- IP address of the Gateway (Router) to use
4252  hostname	- Target hostname
4253  ipaddr	- see above
4254  netmask	- Subnet Mask
4255  rootpath	- Pathname of the root filesystem on the NFS server
4256  serverip	- see above
4257
4258
4259There are two special Environment Variables:
4260
4261  serial#	- contains hardware identification information such
4262		  as type string and/or serial number
4263  ethaddr	- Ethernet address
4264
4265These variables can be set only once (usually during manufacturing of
4266the board). U-Boot refuses to delete or overwrite these variables
4267once they have been set once.
4268
4269
4270Further special Environment Variables:
4271
4272  ver		- Contains the U-Boot version string as printed
4273		  with the "version" command. This variable is
4274		  readonly (see CONFIG_VERSION_VARIABLE).
4275
4276
4277Please note that changes to some configuration parameters may take
4278only effect after the next boot (yes, that's just like Windoze :-).
4279
4280
4281Callback functions for environment variables:
4282---------------------------------------------
4283
4284For some environment variables, the behavior of u-boot needs to change
4285when their values are changed.  This functionality allows functions to
4286be associated with arbitrary variables.  On creation, overwrite, or
4287deletion, the callback will provide the opportunity for some side
4288effect to happen or for the change to be rejected.
4289
4290The callbacks are named and associated with a function using the
4291U_BOOT_ENV_CALLBACK macro in your board or driver code.
4292
4293These callbacks are associated with variables in one of two ways.  The
4294static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4295in the board configuration to a string that defines a list of
4296associations.  The list must be in the following format:
4297
4298	entry = variable_name[:callback_name]
4299	list = entry[,list]
4300
4301If the callback name is not specified, then the callback is deleted.
4302Spaces are also allowed anywhere in the list.
4303
4304Callbacks can also be associated by defining the ".callbacks" variable
4305with the same list format above.  Any association in ".callbacks" will
4306override any association in the static list. You can define
4307CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4308".callbacks" environment variable in the default or embedded environment.
4309
4310If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4311regular expression. This allows multiple variables to be connected to
4312the same callback without explicitly listing them all out.
4313
4314
4315Command Line Parsing:
4316=====================
4317
4318There are two different command line parsers available with U-Boot:
4319the old "simple" one, and the much more powerful "hush" shell:
4320
4321Old, simple command line parser:
4322--------------------------------
4323
4324- supports environment variables (through setenv / saveenv commands)
4325- several commands on one line, separated by ';'
4326- variable substitution using "... ${name} ..." syntax
4327- special characters ('$', ';') can be escaped by prefixing with '\',
4328  for example:
4329	setenv bootcmd bootm \${address}
4330- You can also escape text by enclosing in single apostrophes, for example:
4331	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4332
4333Hush shell:
4334-----------
4335
4336- similar to Bourne shell, with control structures like
4337  if...then...else...fi, for...do...done; while...do...done,
4338  until...do...done, ...
4339- supports environment ("global") variables (through setenv / saveenv
4340  commands) and local shell variables (through standard shell syntax
4341  "name=value"); only environment variables can be used with "run"
4342  command
4343
4344General rules:
4345--------------
4346
4347(1) If a command line (or an environment variable executed by a "run"
4348    command) contains several commands separated by semicolon, and
4349    one of these commands fails, then the remaining commands will be
4350    executed anyway.
4351
4352(2) If you execute several variables with one call to run (i. e.
4353    calling run with a list of variables as arguments), any failing
4354    command will cause "run" to terminate, i. e. the remaining
4355    variables are not executed.
4356
4357Note for Redundant Ethernet Interfaces:
4358=======================================
4359
4360Some boards come with redundant Ethernet interfaces; U-Boot supports
4361such configurations and is capable of automatic selection of a
4362"working" interface when needed. MAC assignment works as follows:
4363
4364Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4365MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4366"eth1addr" (=>eth1), "eth2addr", ...
4367
4368If the network interface stores some valid MAC address (for instance
4369in SROM), this is used as default address if there is NO correspon-
4370ding setting in the environment; if the corresponding environment
4371variable is set, this overrides the settings in the card; that means:
4372
4373o If the SROM has a valid MAC address, and there is no address in the
4374  environment, the SROM's address is used.
4375
4376o If there is no valid address in the SROM, and a definition in the
4377  environment exists, then the value from the environment variable is
4378  used.
4379
4380o If both the SROM and the environment contain a MAC address, and
4381  both addresses are the same, this MAC address is used.
4382
4383o If both the SROM and the environment contain a MAC address, and the
4384  addresses differ, the value from the environment is used and a
4385  warning is printed.
4386
4387o If neither SROM nor the environment contain a MAC address, an error
4388  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4389  a random, locally-assigned MAC is used.
4390
4391If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4392will be programmed into hardware as part of the initialization process.	 This
4393may be skipped by setting the appropriate 'ethmacskip' environment variable.
4394The naming convention is as follows:
4395"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4396
4397Image Formats:
4398==============
4399
4400U-Boot is capable of booting (and performing other auxiliary operations on)
4401images in two formats:
4402
4403New uImage format (FIT)
4404-----------------------
4405
4406Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4407to Flattened Device Tree). It allows the use of images with multiple
4408components (several kernels, ramdisks, etc.), with contents protected by
4409SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4410
4411
4412Old uImage format
4413-----------------
4414
4415Old image format is based on binary files which can be basically anything,
4416preceded by a special header; see the definitions in include/image.h for
4417details; basically, the header defines the following image properties:
4418
4419* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4420  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4421  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4422  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4423  INTEGRITY).
4424* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4425  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4426  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4427* Compression Type (uncompressed, gzip, bzip2)
4428* Load Address
4429* Entry Point
4430* Image Name
4431* Image Timestamp
4432
4433The header is marked by a special Magic Number, and both the header
4434and the data portions of the image are secured against corruption by
4435CRC32 checksums.
4436
4437
4438Linux Support:
4439==============
4440
4441Although U-Boot should support any OS or standalone application
4442easily, the main focus has always been on Linux during the design of
4443U-Boot.
4444
4445U-Boot includes many features that so far have been part of some
4446special "boot loader" code within the Linux kernel. Also, any
4447"initrd" images to be used are no longer part of one big Linux image;
4448instead, kernel and "initrd" are separate images. This implementation
4449serves several purposes:
4450
4451- the same features can be used for other OS or standalone
4452  applications (for instance: using compressed images to reduce the
4453  Flash memory footprint)
4454
4455- it becomes much easier to port new Linux kernel versions because
4456  lots of low-level, hardware dependent stuff are done by U-Boot
4457
4458- the same Linux kernel image can now be used with different "initrd"
4459  images; of course this also means that different kernel images can
4460  be run with the same "initrd". This makes testing easier (you don't
4461  have to build a new "zImage.initrd" Linux image when you just
4462  change a file in your "initrd"). Also, a field-upgrade of the
4463  software is easier now.
4464
4465
4466Linux HOWTO:
4467============
4468
4469Porting Linux to U-Boot based systems:
4470---------------------------------------
4471
4472U-Boot cannot save you from doing all the necessary modifications to
4473configure the Linux device drivers for use with your target hardware
4474(no, we don't intend to provide a full virtual machine interface to
4475Linux :-).
4476
4477But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4478
4479Just make sure your machine specific header file (for instance
4480include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4481Information structure as we define in include/asm-<arch>/u-boot.h,
4482and make sure that your definition of IMAP_ADDR uses the same value
4483as your U-Boot configuration in CONFIG_SYS_IMMR.
4484
4485Note that U-Boot now has a driver model, a unified model for drivers.
4486If you are adding a new driver, plumb it into driver model. If there
4487is no uclass available, you are encouraged to create one. See
4488doc/driver-model.
4489
4490
4491Configuring the Linux kernel:
4492-----------------------------
4493
4494No specific requirements for U-Boot. Make sure you have some root
4495device (initial ramdisk, NFS) for your target system.
4496
4497
4498Building a Linux Image:
4499-----------------------
4500
4501With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4502not used. If you use recent kernel source, a new build target
4503"uImage" will exist which automatically builds an image usable by
4504U-Boot. Most older kernels also have support for a "pImage" target,
4505which was introduced for our predecessor project PPCBoot and uses a
4506100% compatible format.
4507
4508Example:
4509
4510	make TQM850L_defconfig
4511	make oldconfig
4512	make dep
4513	make uImage
4514
4515The "uImage" build target uses a special tool (in 'tools/mkimage') to
4516encapsulate a compressed Linux kernel image with header	 information,
4517CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4518
4519* build a standard "vmlinux" kernel image (in ELF binary format):
4520
4521* convert the kernel into a raw binary image:
4522
4523	${CROSS_COMPILE}-objcopy -O binary \
4524				 -R .note -R .comment \
4525				 -S vmlinux linux.bin
4526
4527* compress the binary image:
4528
4529	gzip -9 linux.bin
4530
4531* package compressed binary image for U-Boot:
4532
4533	mkimage -A ppc -O linux -T kernel -C gzip \
4534		-a 0 -e 0 -n "Linux Kernel Image" \
4535		-d linux.bin.gz uImage
4536
4537
4538The "mkimage" tool can also be used to create ramdisk images for use
4539with U-Boot, either separated from the Linux kernel image, or
4540combined into one file. "mkimage" encapsulates the images with a 64
4541byte header containing information about target architecture,
4542operating system, image type, compression method, entry points, time
4543stamp, CRC32 checksums, etc.
4544
4545"mkimage" can be called in two ways: to verify existing images and
4546print the header information, or to build new images.
4547
4548In the first form (with "-l" option) mkimage lists the information
4549contained in the header of an existing U-Boot image; this includes
4550checksum verification:
4551
4552	tools/mkimage -l image
4553	  -l ==> list image header information
4554
4555The second form (with "-d" option) is used to build a U-Boot image
4556from a "data file" which is used as image payload:
4557
4558	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4559		      -n name -d data_file image
4560	  -A ==> set architecture to 'arch'
4561	  -O ==> set operating system to 'os'
4562	  -T ==> set image type to 'type'
4563	  -C ==> set compression type 'comp'
4564	  -a ==> set load address to 'addr' (hex)
4565	  -e ==> set entry point to 'ep' (hex)
4566	  -n ==> set image name to 'name'
4567	  -d ==> use image data from 'datafile'
4568
4569Right now, all Linux kernels for PowerPC systems use the same load
4570address (0x00000000), but the entry point address depends on the
4571kernel version:
4572
4573- 2.2.x kernels have the entry point at 0x0000000C,
4574- 2.3.x and later kernels have the entry point at 0x00000000.
4575
4576So a typical call to build a U-Boot image would read:
4577
4578	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4579	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4580	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4581	> examples/uImage.TQM850L
4582	Image Name:   2.4.4 kernel for TQM850L
4583	Created:      Wed Jul 19 02:34:59 2000
4584	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4585	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4586	Load Address: 0x00000000
4587	Entry Point:  0x00000000
4588
4589To verify the contents of the image (or check for corruption):
4590
4591	-> tools/mkimage -l examples/uImage.TQM850L
4592	Image Name:   2.4.4 kernel for TQM850L
4593	Created:      Wed Jul 19 02:34:59 2000
4594	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4595	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4596	Load Address: 0x00000000
4597	Entry Point:  0x00000000
4598
4599NOTE: for embedded systems where boot time is critical you can trade
4600speed for memory and install an UNCOMPRESSED image instead: this
4601needs more space in Flash, but boots much faster since it does not
4602need to be uncompressed:
4603
4604	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4605	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4606	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4607	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4608	> examples/uImage.TQM850L-uncompressed
4609	Image Name:   2.4.4 kernel for TQM850L
4610	Created:      Wed Jul 19 02:34:59 2000
4611	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4612	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4613	Load Address: 0x00000000
4614	Entry Point:  0x00000000
4615
4616
4617Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4618when your kernel is intended to use an initial ramdisk:
4619
4620	-> tools/mkimage -n 'Simple Ramdisk Image' \
4621	> -A ppc -O linux -T ramdisk -C gzip \
4622	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4623	Image Name:   Simple Ramdisk Image
4624	Created:      Wed Jan 12 14:01:50 2000
4625	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4626	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4627	Load Address: 0x00000000
4628	Entry Point:  0x00000000
4629
4630The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4631option performs the converse operation of the mkimage's second form (the "-d"
4632option). Given an image built by mkimage, the dumpimage extracts a "data file"
4633from the image:
4634
4635	tools/dumpimage -i image -T type -p position data_file
4636	  -i ==> extract from the 'image' a specific 'data_file'
4637	  -T ==> set image type to 'type'
4638	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4639
4640
4641Installing a Linux Image:
4642-------------------------
4643
4644To downloading a U-Boot image over the serial (console) interface,
4645you must convert the image to S-Record format:
4646
4647	objcopy -I binary -O srec examples/image examples/image.srec
4648
4649The 'objcopy' does not understand the information in the U-Boot
4650image header, so the resulting S-Record file will be relative to
4651address 0x00000000. To load it to a given address, you need to
4652specify the target address as 'offset' parameter with the 'loads'
4653command.
4654
4655Example: install the image to address 0x40100000 (which on the
4656TQM8xxL is in the first Flash bank):
4657
4658	=> erase 40100000 401FFFFF
4659
4660	.......... done
4661	Erased 8 sectors
4662
4663	=> loads 40100000
4664	## Ready for S-Record download ...
4665	~>examples/image.srec
4666	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4667	...
4668	15989 15990 15991 15992
4669	[file transfer complete]
4670	[connected]
4671	## Start Addr = 0x00000000
4672
4673
4674You can check the success of the download using the 'iminfo' command;
4675this includes a checksum verification so you can be sure no data
4676corruption happened:
4677
4678	=> imi 40100000
4679
4680	## Checking Image at 40100000 ...
4681	   Image Name:	 2.2.13 for initrd on TQM850L
4682	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4683	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4684	   Load Address: 00000000
4685	   Entry Point:	 0000000c
4686	   Verifying Checksum ... OK
4687
4688
4689Boot Linux:
4690-----------
4691
4692The "bootm" command is used to boot an application that is stored in
4693memory (RAM or Flash). In case of a Linux kernel image, the contents
4694of the "bootargs" environment variable is passed to the kernel as
4695parameters. You can check and modify this variable using the
4696"printenv" and "setenv" commands:
4697
4698
4699	=> printenv bootargs
4700	bootargs=root=/dev/ram
4701
4702	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4703
4704	=> printenv bootargs
4705	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4706
4707	=> bootm 40020000
4708	## Booting Linux kernel at 40020000 ...
4709	   Image Name:	 2.2.13 for NFS on TQM850L
4710	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4711	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4712	   Load Address: 00000000
4713	   Entry Point:	 0000000c
4714	   Verifying Checksum ... OK
4715	   Uncompressing Kernel Image ... OK
4716	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
4717	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4718	time_init: decrementer frequency = 187500000/60
4719	Calibrating delay loop... 49.77 BogoMIPS
4720	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4721	...
4722
4723If you want to boot a Linux kernel with initial RAM disk, you pass
4724the memory addresses of both the kernel and the initrd image (PPBCOOT
4725format!) to the "bootm" command:
4726
4727	=> imi 40100000 40200000
4728
4729	## Checking Image at 40100000 ...
4730	   Image Name:	 2.2.13 for initrd on TQM850L
4731	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4732	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4733	   Load Address: 00000000
4734	   Entry Point:	 0000000c
4735	   Verifying Checksum ... OK
4736
4737	## Checking Image at 40200000 ...
4738	   Image Name:	 Simple Ramdisk Image
4739	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4740	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4741	   Load Address: 00000000
4742	   Entry Point:	 00000000
4743	   Verifying Checksum ... OK
4744
4745	=> bootm 40100000 40200000
4746	## Booting Linux kernel at 40100000 ...
4747	   Image Name:	 2.2.13 for initrd on TQM850L
4748	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4749	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4750	   Load Address: 00000000
4751	   Entry Point:	 0000000c
4752	   Verifying Checksum ... OK
4753	   Uncompressing Kernel Image ... OK
4754	## Loading RAMDisk Image at 40200000 ...
4755	   Image Name:	 Simple Ramdisk Image
4756	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4757	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4758	   Load Address: 00000000
4759	   Entry Point:	 00000000
4760	   Verifying Checksum ... OK
4761	   Loading Ramdisk ... OK
4762	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
4763	Boot arguments: root=/dev/ram
4764	time_init: decrementer frequency = 187500000/60
4765	Calibrating delay loop... 49.77 BogoMIPS
4766	...
4767	RAMDISK: Compressed image found at block 0
4768	VFS: Mounted root (ext2 filesystem).
4769
4770	bash#
4771
4772Boot Linux and pass a flat device tree:
4773-----------
4774
4775First, U-Boot must be compiled with the appropriate defines. See the section
4776titled "Linux Kernel Interface" above for a more in depth explanation. The
4777following is an example of how to start a kernel and pass an updated
4778flat device tree:
4779
4780=> print oftaddr
4781oftaddr=0x300000
4782=> print oft
4783oft=oftrees/mpc8540ads.dtb
4784=> tftp $oftaddr $oft
4785Speed: 1000, full duplex
4786Using TSEC0 device
4787TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4788Filename 'oftrees/mpc8540ads.dtb'.
4789Load address: 0x300000
4790Loading: #
4791done
4792Bytes transferred = 4106 (100a hex)
4793=> tftp $loadaddr $bootfile
4794Speed: 1000, full duplex
4795Using TSEC0 device
4796TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4797Filename 'uImage'.
4798Load address: 0x200000
4799Loading:############
4800done
4801Bytes transferred = 1029407 (fb51f hex)
4802=> print loadaddr
4803loadaddr=200000
4804=> print oftaddr
4805oftaddr=0x300000
4806=> bootm $loadaddr - $oftaddr
4807## Booting image at 00200000 ...
4808   Image Name:	 Linux-2.6.17-dirty
4809   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4810   Data Size:	 1029343 Bytes = 1005.2 kB
4811   Load Address: 00000000
4812   Entry Point:	 00000000
4813   Verifying Checksum ... OK
4814   Uncompressing Kernel Image ... OK
4815Booting using flat device tree at 0x300000
4816Using MPC85xx ADS machine description
4817Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4818[snip]
4819
4820
4821More About U-Boot Image Types:
4822------------------------------
4823
4824U-Boot supports the following image types:
4825
4826   "Standalone Programs" are directly runnable in the environment
4827	provided by U-Boot; it is expected that (if they behave
4828	well) you can continue to work in U-Boot after return from
4829	the Standalone Program.
4830   "OS Kernel Images" are usually images of some Embedded OS which
4831	will take over control completely. Usually these programs
4832	will install their own set of exception handlers, device
4833	drivers, set up the MMU, etc. - this means, that you cannot
4834	expect to re-enter U-Boot except by resetting the CPU.
4835   "RAMDisk Images" are more or less just data blocks, and their
4836	parameters (address, size) are passed to an OS kernel that is
4837	being started.
4838   "Multi-File Images" contain several images, typically an OS
4839	(Linux) kernel image and one or more data images like
4840	RAMDisks. This construct is useful for instance when you want
4841	to boot over the network using BOOTP etc., where the boot
4842	server provides just a single image file, but you want to get
4843	for instance an OS kernel and a RAMDisk image.
4844
4845	"Multi-File Images" start with a list of image sizes, each
4846	image size (in bytes) specified by an "uint32_t" in network
4847	byte order. This list is terminated by an "(uint32_t)0".
4848	Immediately after the terminating 0 follow the images, one by
4849	one, all aligned on "uint32_t" boundaries (size rounded up to
4850	a multiple of 4 bytes).
4851
4852   "Firmware Images" are binary images containing firmware (like
4853	U-Boot or FPGA images) which usually will be programmed to
4854	flash memory.
4855
4856   "Script files" are command sequences that will be executed by
4857	U-Boot's command interpreter; this feature is especially
4858	useful when you configure U-Boot to use a real shell (hush)
4859	as command interpreter.
4860
4861Booting the Linux zImage:
4862-------------------------
4863
4864On some platforms, it's possible to boot Linux zImage. This is done
4865using the "bootz" command. The syntax of "bootz" command is the same
4866as the syntax of "bootm" command.
4867
4868Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4869kernel with raw initrd images. The syntax is slightly different, the
4870address of the initrd must be augmented by it's size, in the following
4871format: "<initrd addres>:<initrd size>".
4872
4873
4874Standalone HOWTO:
4875=================
4876
4877One of the features of U-Boot is that you can dynamically load and
4878run "standalone" applications, which can use some resources of
4879U-Boot like console I/O functions or interrupt services.
4880
4881Two simple examples are included with the sources:
4882
4883"Hello World" Demo:
4884-------------------
4885
4886'examples/hello_world.c' contains a small "Hello World" Demo
4887application; it is automatically compiled when you build U-Boot.
4888It's configured to run at address 0x00040004, so you can play with it
4889like that:
4890
4891	=> loads
4892	## Ready for S-Record download ...
4893	~>examples/hello_world.srec
4894	1 2 3 4 5 6 7 8 9 10 11 ...
4895	[file transfer complete]
4896	[connected]
4897	## Start Addr = 0x00040004
4898
4899	=> go 40004 Hello World! This is a test.
4900	## Starting application at 0x00040004 ...
4901	Hello World
4902	argc = 7
4903	argv[0] = "40004"
4904	argv[1] = "Hello"
4905	argv[2] = "World!"
4906	argv[3] = "This"
4907	argv[4] = "is"
4908	argv[5] = "a"
4909	argv[6] = "test."
4910	argv[7] = "<NULL>"
4911	Hit any key to exit ...
4912
4913	## Application terminated, rc = 0x0
4914
4915Another example, which demonstrates how to register a CPM interrupt
4916handler with the U-Boot code, can be found in 'examples/timer.c'.
4917Here, a CPM timer is set up to generate an interrupt every second.
4918The interrupt service routine is trivial, just printing a '.'
4919character, but this is just a demo program. The application can be
4920controlled by the following keys:
4921
4922	? - print current values og the CPM Timer registers
4923	b - enable interrupts and start timer
4924	e - stop timer and disable interrupts
4925	q - quit application
4926
4927	=> loads
4928	## Ready for S-Record download ...
4929	~>examples/timer.srec
4930	1 2 3 4 5 6 7 8 9 10 11 ...
4931	[file transfer complete]
4932	[connected]
4933	## Start Addr = 0x00040004
4934
4935	=> go 40004
4936	## Starting application at 0x00040004 ...
4937	TIMERS=0xfff00980
4938	Using timer 1
4939	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4940
4941Hit 'b':
4942	[q, b, e, ?] Set interval 1000000 us
4943	Enabling timer
4944Hit '?':
4945	[q, b, e, ?] ........
4946	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4947Hit '?':
4948	[q, b, e, ?] .
4949	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4950Hit '?':
4951	[q, b, e, ?] .
4952	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4953Hit '?':
4954	[q, b, e, ?] .
4955	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4956Hit 'e':
4957	[q, b, e, ?] ...Stopping timer
4958Hit 'q':
4959	[q, b, e, ?] ## Application terminated, rc = 0x0
4960
4961
4962Minicom warning:
4963================
4964
4965Over time, many people have reported problems when trying to use the
4966"minicom" terminal emulation program for serial download. I (wd)
4967consider minicom to be broken, and recommend not to use it. Under
4968Unix, I recommend to use C-Kermit for general purpose use (and
4969especially for kermit binary protocol download ("loadb" command), and
4970use "cu" for S-Record download ("loads" command).  See
4971http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4972for help with kermit.
4973
4974
4975Nevertheless, if you absolutely want to use it try adding this
4976configuration to your "File transfer protocols" section:
4977
4978	   Name	   Program			Name U/D FullScr IO-Red. Multi
4979	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4980	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4981
4982
4983NetBSD Notes:
4984=============
4985
4986Starting at version 0.9.2, U-Boot supports NetBSD both as host
4987(build U-Boot) and target system (boots NetBSD/mpc8xx).
4988
4989Building requires a cross environment; it is known to work on
4990NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4991need gmake since the Makefiles are not compatible with BSD make).
4992Note that the cross-powerpc package does not install include files;
4993attempting to build U-Boot will fail because <machine/ansi.h> is
4994missing.  This file has to be installed and patched manually:
4995
4996	# cd /usr/pkg/cross/powerpc-netbsd/include
4997	# mkdir powerpc
4998	# ln -s powerpc machine
4999	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5000	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5001
5002Native builds *don't* work due to incompatibilities between native
5003and U-Boot include files.
5004
5005Booting assumes that (the first part of) the image booted is a
5006stage-2 loader which in turn loads and then invokes the kernel
5007proper. Loader sources will eventually appear in the NetBSD source
5008tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5009meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5010
5011
5012Implementation Internals:
5013=========================
5014
5015The following is not intended to be a complete description of every
5016implementation detail. However, it should help to understand the
5017inner workings of U-Boot and make it easier to port it to custom
5018hardware.
5019
5020
5021Initial Stack, Global Data:
5022---------------------------
5023
5024The implementation of U-Boot is complicated by the fact that U-Boot
5025starts running out of ROM (flash memory), usually without access to
5026system RAM (because the memory controller is not initialized yet).
5027This means that we don't have writable Data or BSS segments, and BSS
5028is not initialized as zero. To be able to get a C environment working
5029at all, we have to allocate at least a minimal stack. Implementation
5030options for this are defined and restricted by the CPU used: Some CPU
5031models provide on-chip memory (like the IMMR area on MPC8xx and
5032MPC826x processors), on others (parts of) the data cache can be
5033locked as (mis-) used as memory, etc.
5034
5035	Chris Hallinan posted a good summary of these issues to the
5036	U-Boot mailing list:
5037
5038	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5039	From: "Chris Hallinan" <clh@net1plus.com>
5040	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5041	...
5042
5043	Correct me if I'm wrong, folks, but the way I understand it
5044	is this: Using DCACHE as initial RAM for Stack, etc, does not
5045	require any physical RAM backing up the cache. The cleverness
5046	is that the cache is being used as a temporary supply of
5047	necessary storage before the SDRAM controller is setup. It's
5048	beyond the scope of this list to explain the details, but you
5049	can see how this works by studying the cache architecture and
5050	operation in the architecture and processor-specific manuals.
5051
5052	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5053	is another option for the system designer to use as an
5054	initial stack/RAM area prior to SDRAM being available. Either
5055	option should work for you. Using CS 4 should be fine if your
5056	board designers haven't used it for something that would
5057	cause you grief during the initial boot! It is frequently not
5058	used.
5059
5060	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5061	with your processor/board/system design. The default value
5062	you will find in any recent u-boot distribution in
5063	walnut.h should work for you. I'd set it to a value larger
5064	than your SDRAM module. If you have a 64MB SDRAM module, set
5065	it above 400_0000. Just make sure your board has no resources
5066	that are supposed to respond to that address! That code in
5067	start.S has been around a while and should work as is when
5068	you get the config right.
5069
5070	-Chris Hallinan
5071	DS4.COM, Inc.
5072
5073It is essential to remember this, since it has some impact on the C
5074code for the initialization procedures:
5075
5076* Initialized global data (data segment) is read-only. Do not attempt
5077  to write it.
5078
5079* Do not use any uninitialized global data (or implicitly initialized
5080  as zero data - BSS segment) at all - this is undefined, initiali-
5081  zation is performed later (when relocating to RAM).
5082
5083* Stack space is very limited. Avoid big data buffers or things like
5084  that.
5085
5086Having only the stack as writable memory limits means we cannot use
5087normal global data to share information between the code. But it
5088turned out that the implementation of U-Boot can be greatly
5089simplified by making a global data structure (gd_t) available to all
5090functions. We could pass a pointer to this data as argument to _all_
5091functions, but this would bloat the code. Instead we use a feature of
5092the GCC compiler (Global Register Variables) to share the data: we
5093place a pointer (gd) to the global data into a register which we
5094reserve for this purpose.
5095
5096When choosing a register for such a purpose we are restricted by the
5097relevant  (E)ABI  specifications for the current architecture, and by
5098GCC's implementation.
5099
5100For PowerPC, the following registers have specific use:
5101	R1:	stack pointer
5102	R2:	reserved for system use
5103	R3-R4:	parameter passing and return values
5104	R5-R10: parameter passing
5105	R13:	small data area pointer
5106	R30:	GOT pointer
5107	R31:	frame pointer
5108
5109	(U-Boot also uses R12 as internal GOT pointer. r12
5110	is a volatile register so r12 needs to be reset when
5111	going back and forth between asm and C)
5112
5113    ==> U-Boot will use R2 to hold a pointer to the global data
5114
5115    Note: on PPC, we could use a static initializer (since the
5116    address of the global data structure is known at compile time),
5117    but it turned out that reserving a register results in somewhat
5118    smaller code - although the code savings are not that big (on
5119    average for all boards 752 bytes for the whole U-Boot image,
5120    624 text + 127 data).
5121
5122On ARM, the following registers are used:
5123
5124	R0:	function argument word/integer result
5125	R1-R3:	function argument word
5126	R9:	platform specific
5127	R10:	stack limit (used only if stack checking is enabled)
5128	R11:	argument (frame) pointer
5129	R12:	temporary workspace
5130	R13:	stack pointer
5131	R14:	link register
5132	R15:	program counter
5133
5134    ==> U-Boot will use R9 to hold a pointer to the global data
5135
5136    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5137
5138On Nios II, the ABI is documented here:
5139	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5140
5141    ==> U-Boot will use gp to hold a pointer to the global data
5142
5143    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5144    to access small data sections, so gp is free.
5145
5146On NDS32, the following registers are used:
5147
5148	R0-R1:	argument/return
5149	R2-R5:	argument
5150	R15:	temporary register for assembler
5151	R16:	trampoline register
5152	R28:	frame pointer (FP)
5153	R29:	global pointer (GP)
5154	R30:	link register (LP)
5155	R31:	stack pointer (SP)
5156	PC:	program counter (PC)
5157
5158    ==> U-Boot will use R10 to hold a pointer to the global data
5159
5160NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5161or current versions of GCC may "optimize" the code too much.
5162
5163Memory Management:
5164------------------
5165
5166U-Boot runs in system state and uses physical addresses, i.e. the
5167MMU is not used either for address mapping nor for memory protection.
5168
5169The available memory is mapped to fixed addresses using the memory
5170controller. In this process, a contiguous block is formed for each
5171memory type (Flash, SDRAM, SRAM), even when it consists of several
5172physical memory banks.
5173
5174U-Boot is installed in the first 128 kB of the first Flash bank (on
5175TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5176booting and sizing and initializing DRAM, the code relocates itself
5177to the upper end of DRAM. Immediately below the U-Boot code some
5178memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5179configuration setting]. Below that, a structure with global Board
5180Info data is placed, followed by the stack (growing downward).
5181
5182Additionally, some exception handler code is copied to the low 8 kB
5183of DRAM (0x00000000 ... 0x00001FFF).
5184
5185So a typical memory configuration with 16 MB of DRAM could look like
5186this:
5187
5188	0x0000 0000	Exception Vector code
5189	      :
5190	0x0000 1FFF
5191	0x0000 2000	Free for Application Use
5192	      :
5193	      :
5194
5195	      :
5196	      :
5197	0x00FB FF20	Monitor Stack (Growing downward)
5198	0x00FB FFAC	Board Info Data and permanent copy of global data
5199	0x00FC 0000	Malloc Arena
5200	      :
5201	0x00FD FFFF
5202	0x00FE 0000	RAM Copy of Monitor Code
5203	...		eventually: LCD or video framebuffer
5204	...		eventually: pRAM (Protected RAM - unchanged by reset)
5205	0x00FF FFFF	[End of RAM]
5206
5207
5208System Initialization:
5209----------------------
5210
5211In the reset configuration, U-Boot starts at the reset entry point
5212(on most PowerPC systems at address 0x00000100). Because of the reset
5213configuration for CS0# this is a mirror of the on board Flash memory.
5214To be able to re-map memory U-Boot then jumps to its link address.
5215To be able to implement the initialization code in C, a (small!)
5216initial stack is set up in the internal Dual Ported RAM (in case CPUs
5217which provide such a feature like), or in a locked part of the data
5218cache. After that, U-Boot initializes the CPU core, the caches and
5219the SIU.
5220
5221Next, all (potentially) available memory banks are mapped using a
5222preliminary mapping. For example, we put them on 512 MB boundaries
5223(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5224on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5225programmed for SDRAM access. Using the temporary configuration, a
5226simple memory test is run that determines the size of the SDRAM
5227banks.
5228
5229When there is more than one SDRAM bank, and the banks are of
5230different size, the largest is mapped first. For equal size, the first
5231bank (CS2#) is mapped first. The first mapping is always for address
52320x00000000, with any additional banks following immediately to create
5233contiguous memory starting from 0.
5234
5235Then, the monitor installs itself at the upper end of the SDRAM area
5236and allocates memory for use by malloc() and for the global Board
5237Info data; also, the exception vector code is copied to the low RAM
5238pages, and the final stack is set up.
5239
5240Only after this relocation will you have a "normal" C environment;
5241until that you are restricted in several ways, mostly because you are
5242running from ROM, and because the code will have to be relocated to a
5243new address in RAM.
5244
5245
5246U-Boot Porting Guide:
5247----------------------
5248
5249[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5250list, October 2002]
5251
5252
5253int main(int argc, char *argv[])
5254{
5255	sighandler_t no_more_time;
5256
5257	signal(SIGALRM, no_more_time);
5258	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5259
5260	if (available_money > available_manpower) {
5261		Pay consultant to port U-Boot;
5262		return 0;
5263	}
5264
5265	Download latest U-Boot source;
5266
5267	Subscribe to u-boot mailing list;
5268
5269	if (clueless)
5270		email("Hi, I am new to U-Boot, how do I get started?");
5271
5272	while (learning) {
5273		Read the README file in the top level directory;
5274		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5275		Read applicable doc/*.README;
5276		Read the source, Luke;
5277		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5278	}
5279
5280	if (available_money > toLocalCurrency ($2500))
5281		Buy a BDI3000;
5282	else
5283		Add a lot of aggravation and time;
5284
5285	if (a similar board exists) {	/* hopefully... */
5286		cp -a board/<similar> board/<myboard>
5287		cp include/configs/<similar>.h include/configs/<myboard>.h
5288	} else {
5289		Create your own board support subdirectory;
5290		Create your own board include/configs/<myboard>.h file;
5291	}
5292	Edit new board/<myboard> files
5293	Edit new include/configs/<myboard>.h
5294
5295	while (!accepted) {
5296		while (!running) {
5297			do {
5298				Add / modify source code;
5299			} until (compiles);
5300			Debug;
5301			if (clueless)
5302				email("Hi, I am having problems...");
5303		}
5304		Send patch file to the U-Boot email list;
5305		if (reasonable critiques)
5306			Incorporate improvements from email list code review;
5307		else
5308			Defend code as written;
5309	}
5310
5311	return 0;
5312}
5313
5314void no_more_time (int sig)
5315{
5316      hire_a_guru();
5317}
5318
5319
5320Coding Standards:
5321-----------------
5322
5323All contributions to U-Boot should conform to the Linux kernel
5324coding style; see the file "Documentation/CodingStyle" and the script
5325"scripts/Lindent" in your Linux kernel source directory.
5326
5327Source files originating from a different project (for example the
5328MTD subsystem) are generally exempt from these guidelines and are not
5329reformatted to ease subsequent migration to newer versions of those
5330sources.
5331
5332Please note that U-Boot is implemented in C (and to some small parts in
5333Assembler); no C++ is used, so please do not use C++ style comments (//)
5334in your code.
5335
5336Please also stick to the following formatting rules:
5337- remove any trailing white space
5338- use TAB characters for indentation and vertical alignment, not spaces
5339- make sure NOT to use DOS '\r\n' line feeds
5340- do not add more than 2 consecutive empty lines to source files
5341- do not add trailing empty lines to source files
5342
5343Submissions which do not conform to the standards may be returned
5344with a request to reformat the changes.
5345
5346
5347Submitting Patches:
5348-------------------
5349
5350Since the number of patches for U-Boot is growing, we need to
5351establish some rules. Submissions which do not conform to these rules
5352may be rejected, even when they contain important and valuable stuff.
5353
5354Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5355
5356Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5357see http://lists.denx.de/mailman/listinfo/u-boot
5358
5359When you send a patch, please include the following information with
5360it:
5361
5362* For bug fixes: a description of the bug and how your patch fixes
5363  this bug. Please try to include a way of demonstrating that the
5364  patch actually fixes something.
5365
5366* For new features: a description of the feature and your
5367  implementation.
5368
5369* A CHANGELOG entry as plaintext (separate from the patch)
5370
5371* For major contributions, add a MAINTAINERS file with your
5372  information and associated file and directory references.
5373
5374* When you add support for a new board, don't forget to add a
5375  maintainer e-mail address to the boards.cfg file, too.
5376
5377* If your patch adds new configuration options, don't forget to
5378  document these in the README file.
5379
5380* The patch itself. If you are using git (which is *strongly*
5381  recommended) you can easily generate the patch using the
5382  "git format-patch". If you then use "git send-email" to send it to
5383  the U-Boot mailing list, you will avoid most of the common problems
5384  with some other mail clients.
5385
5386  If you cannot use git, use "diff -purN OLD NEW". If your version of
5387  diff does not support these options, then get the latest version of
5388  GNU diff.
5389
5390  The current directory when running this command shall be the parent
5391  directory of the U-Boot source tree (i. e. please make sure that
5392  your patch includes sufficient directory information for the
5393  affected files).
5394
5395  We prefer patches as plain text. MIME attachments are discouraged,
5396  and compressed attachments must not be used.
5397
5398* If one logical set of modifications affects or creates several
5399  files, all these changes shall be submitted in a SINGLE patch file.
5400
5401* Changesets that contain different, unrelated modifications shall be
5402  submitted as SEPARATE patches, one patch per changeset.
5403
5404
5405Notes:
5406
5407* Before sending the patch, run the buildman script on your patched
5408  source tree and make sure that no errors or warnings are reported
5409  for any of the boards.
5410
5411* Keep your modifications to the necessary minimum: A patch
5412  containing several unrelated changes or arbitrary reformats will be
5413  returned with a request to re-formatting / split it.
5414
5415* If you modify existing code, make sure that your new code does not
5416  add to the memory footprint of the code ;-) Small is beautiful!
5417  When adding new features, these should compile conditionally only
5418  (using #ifdef), and the resulting code with the new feature
5419  disabled must not need more memory than the old code without your
5420  modification.
5421
5422* Remember that there is a size limit of 100 kB per message on the
5423  u-boot mailing list. Bigger patches will be moderated. If they are
5424  reasonable and not too big, they will be acknowledged. But patches
5425  bigger than the size limit should be avoided.
5426