xref: /openbmc/u-boot/README (revision a55d29d2)
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  /avr32		Files generic to AVR32 architecture
140  /m68k			Files generic to m68k architecture
141  /microblaze		Files generic to microblaze architecture
142  /mips			Files generic to MIPS architecture
143  /nds32		Files generic to NDS32 architecture
144  /nios2		Files generic to Altera NIOS2 architecture
145  /openrisc		Files generic to OpenRISC architecture
146  /powerpc		Files generic to PowerPC architecture
147  /sandbox		Files generic to HW-independent "sandbox"
148  /sh			Files generic to SH architecture
149  /x86			Files generic to x86 architecture
150/api			Machine/arch independent API for external apps
151/board			Board dependent files
152/cmd			U-Boot commands functions
153/common			Misc architecture independent functions
154/configs		Board default configuration files
155/disk			Code for disk drive partition handling
156/doc			Documentation (don't expect too much)
157/drivers		Commonly used device drivers
158/dts			Contains Makefile for building internal U-Boot fdt.
159/examples		Example code for standalone applications, etc.
160/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
161/include		Header Files
162/lib			Library routines generic to all architectures
163/Licenses		Various license files
164/net			Networking code
165/post			Power On Self Test
166/scripts		Various build scripts and Makefiles
167/test			Various unit test files
168/tools			Tools to build S-Record or U-Boot images, etc.
169
170Software Configuration:
171=======================
172
173Configuration is usually done using C preprocessor defines; the
174rationale behind that is to avoid dead code whenever possible.
175
176There are two classes of configuration variables:
177
178* Configuration _OPTIONS_:
179  These are selectable by the user and have names beginning with
180  "CONFIG_".
181
182* Configuration _SETTINGS_:
183  These depend on the hardware etc. and should not be meddled with if
184  you don't know what you're doing; they have names beginning with
185  "CONFIG_SYS_".
186
187Previously, all configuration was done by hand, which involved creating
188symbolic links and editing configuration files manually. More recently,
189U-Boot has added the Kbuild infrastructure used by the Linux kernel,
190allowing you to use the "make menuconfig" command to configure your
191build.
192
193
194Selection of Processor Architecture and Board Type:
195---------------------------------------------------
196
197For all supported boards there are ready-to-use default
198configurations available; just type "make <board_name>_defconfig".
199
200Example: For a TQM823L module type:
201
202	cd u-boot
203	make TQM823L_defconfig
204
205Note: If you're looking for the default configuration file for a board
206you're sure used to be there but is now missing, check the file
207doc/README.scrapyard for a list of no longer supported boards.
208
209Sandbox Environment:
210--------------------
211
212U-Boot can be built natively to run on a Linux host using the 'sandbox'
213board. This allows feature development which is not board- or architecture-
214specific to be undertaken on a native platform. The sandbox is also used to
215run some of U-Boot's tests.
216
217See board/sandbox/README.sandbox for more details.
218
219
220Board Initialisation Flow:
221--------------------------
222
223This is the intended start-up flow for boards. This should apply for both
224SPL and U-Boot proper (i.e. they both follow the same rules).
225
226Note: "SPL" stands for "Secondary Program Loader," which is explained in
227more detail later in this file.
228
229At present, SPL mostly uses a separate code path, but the function names
230and roles of each function are the same. Some boards or architectures
231may not conform to this.  At least most ARM boards which use
232CONFIG_SPL_FRAMEWORK conform to this.
233
234Execution typically starts with an architecture-specific (and possibly
235CPU-specific) start.S file, such as:
236
237	- arch/arm/cpu/armv7/start.S
238	- arch/powerpc/cpu/mpc83xx/start.S
239	- arch/mips/cpu/start.S
240
241and so on. From there, three functions are called; the purpose and
242limitations of each of these functions are described below.
243
244lowlevel_init():
245	- purpose: essential init to permit execution to reach board_init_f()
246	- no global_data or BSS
247	- there is no stack (ARMv7 may have one but it will soon be removed)
248	- must not set up SDRAM or use console
249	- must only do the bare minimum to allow execution to continue to
250		board_init_f()
251	- this is almost never needed
252	- return normally from this function
253
254board_init_f():
255	- purpose: set up the machine ready for running board_init_r():
256		i.e. SDRAM and serial UART
257	- global_data is available
258	- stack is in SRAM
259	- BSS is not available, so you cannot use global/static variables,
260		only stack variables and global_data
261
262	Non-SPL-specific notes:
263	- dram_init() is called to set up DRAM. If already done in SPL this
264		can do nothing
265
266	SPL-specific notes:
267	- you can override the entire board_init_f() function with your own
268		version as needed.
269	- preloader_console_init() can be called here in extremis
270	- should set up SDRAM, and anything needed to make the UART work
271	- these is no need to clear BSS, it will be done by crt0.S
272	- must return normally from this function (don't call board_init_r()
273		directly)
274
275Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
276this point the stack and global_data are relocated to below
277CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
278memory.
279
280board_init_r():
281	- purpose: main execution, common code
282	- global_data is available
283	- SDRAM is available
284	- BSS is available, all static/global variables can be used
285	- execution eventually continues to main_loop()
286
287	Non-SPL-specific notes:
288	- U-Boot is relocated to the top of memory and is now running from
289		there.
290
291	SPL-specific notes:
292	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
293		CONFIG_SPL_STACK_R_ADDR points into SDRAM
294	- preloader_console_init() can be called here - typically this is
295		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
296		spl_board_init() function containing this call
297	- loads U-Boot or (in falcon mode) Linux
298
299
300
301Configuration Options:
302----------------------
303
304Configuration depends on the combination of board and CPU type; all
305such information is kept in a configuration file
306"include/configs/<board_name>.h".
307
308Example: For a TQM823L module, all configuration settings are in
309"include/configs/TQM823L.h".
310
311
312Many of the options are named exactly as the corresponding Linux
313kernel configuration options. The intention is to make it easier to
314build a config tool - later.
315
316
317The following options need to be configured:
318
319- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
320
321- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
322
323- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
324		Define exactly one, e.g. CONFIG_ATSTK1002
325
326- Marvell Family Member
327		CONFIG_SYS_MVFS		- define it if you want to enable
328					  multiple fs option at one time
329					  for marvell soc family
330
331- 8xx CPU Options: (if using an MPC8xx CPU)
332		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
333					  get_gclk_freq() cannot work
334					  e.g. if there is no 32KHz
335					  reference PIT/RTC clock
336		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
337					  or XTAL/EXTAL)
338
339- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
340		CONFIG_SYS_8xx_CPUCLK_MIN
341		CONFIG_SYS_8xx_CPUCLK_MAX
342		CONFIG_8xx_CPUCLK_DEFAULT
343			See doc/README.MPC866
344
345		CONFIG_SYS_MEASURE_CPUCLK
346
347		Define this to measure the actual CPU clock instead
348		of relying on the correctness of the configured
349		values. Mostly useful for board bringup to make sure
350		the PLL is locked at the intended frequency. Note
351		that this requires a (stable) reference clock (32 kHz
352		RTC clock or CONFIG_SYS_8XX_XIN)
353
354		CONFIG_SYS_DELAYED_ICACHE
355
356		Define this option if you want to enable the
357		ICache only when Code runs from RAM.
358
359- 85xx CPU Options:
360		CONFIG_SYS_PPC64
361
362		Specifies that the core is a 64-bit PowerPC implementation (implements
363		the "64" category of the Power ISA). This is necessary for ePAPR
364		compliance, among other possible reasons.
365
366		CONFIG_SYS_FSL_TBCLK_DIV
367
368		Defines the core time base clock divider ratio compared to the
369		system clock.  On most PQ3 devices this is 8, on newer QorIQ
370		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
371
372		CONFIG_SYS_FSL_PCIE_COMPAT
373
374		Defines the string to utilize when trying to match PCIe device
375		tree nodes for the given platform.
376
377		CONFIG_SYS_FSL_ERRATUM_A004510
378
379		Enables a workaround for erratum A004510.  If set,
380		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
381		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
382
383		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
384		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
385
386		Defines one or two SoC revisions (low 8 bits of SVR)
387		for which the A004510 workaround should be applied.
388
389		The rest of SVR is either not relevant to the decision
390		of whether the erratum is present (e.g. p2040 versus
391		p2041) or is implied by the build target, which controls
392		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
393
394		See Freescale App Note 4493 for more information about
395		this erratum.
396
397		CONFIG_A003399_NOR_WORKAROUND
398		Enables a workaround for IFC erratum A003399. It is only
399		required during NOR boot.
400
401		CONFIG_A008044_WORKAROUND
402		Enables a workaround for T1040/T1042 erratum A008044. It is only
403		required during NAND boot and valid for Rev 1.0 SoC revision
404
405		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
406
407		This is the value to write into CCSR offset 0x18600
408		according to the A004510 workaround.
409
410		CONFIG_SYS_FSL_DSP_DDR_ADDR
411		This value denotes start offset of DDR memory which is
412		connected exclusively to the DSP cores.
413
414		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
415		This value denotes start offset of M2 memory
416		which is directly connected to the DSP core.
417
418		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
419		This value denotes start offset of M3 memory which is directly
420		connected to the DSP core.
421
422		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
423		This value denotes start offset of DSP CCSR space.
424
425		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
426		Single Source Clock is clocking mode present in some of FSL SoC's.
427		In this mode, a single differential clock is used to supply
428		clocks to the sysclock, ddrclock and usbclock.
429
430		CONFIG_SYS_CPC_REINIT_F
431		This CONFIG is defined when the CPC is configured as SRAM at the
432		time of U-Boot entry and is required to be re-initialized.
433
434		CONFIG_DEEP_SLEEP
435		Indicates this SoC supports deep sleep feature. If deep sleep is
436		supported, core will start to execute uboot when wakes up.
437
438- Generic CPU options:
439		CONFIG_SYS_GENERIC_GLOBAL_DATA
440		Defines global data is initialized in generic board board_init_f().
441		If this macro is defined, global data is created and cleared in
442		generic board board_init_f(). Without this macro, architecture/board
443		should initialize global data before calling board_init_f().
444
445		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
446
447		Defines the endianess of the CPU. Implementation of those
448		values is arch specific.
449
450		CONFIG_SYS_FSL_DDR
451		Freescale DDR driver in use. This type of DDR controller is
452		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
453		SoCs.
454
455		CONFIG_SYS_FSL_DDR_ADDR
456		Freescale DDR memory-mapped register base.
457
458		CONFIG_SYS_FSL_DDR_EMU
459		Specify emulator support for DDR. Some DDR features such as
460		deskew training are not available.
461
462		CONFIG_SYS_FSL_DDRC_GEN1
463		Freescale DDR1 controller.
464
465		CONFIG_SYS_FSL_DDRC_GEN2
466		Freescale DDR2 controller.
467
468		CONFIG_SYS_FSL_DDRC_GEN3
469		Freescale DDR3 controller.
470
471		CONFIG_SYS_FSL_DDRC_GEN4
472		Freescale DDR4 controller.
473
474		CONFIG_SYS_FSL_DDRC_ARM_GEN3
475		Freescale DDR3 controller for ARM-based SoCs.
476
477		CONFIG_SYS_FSL_DDR1
478		Board config to use DDR1. It can be enabled for SoCs with
479		Freescale DDR1 or DDR2 controllers, depending on the board
480		implemetation.
481
482		CONFIG_SYS_FSL_DDR2
483		Board config to use DDR2. It can be enabled for SoCs with
484		Freescale DDR2 or DDR3 controllers, depending on the board
485		implementation.
486
487		CONFIG_SYS_FSL_DDR3
488		Board config to use DDR3. It can be enabled for SoCs with
489		Freescale DDR3 or DDR3L controllers.
490
491		CONFIG_SYS_FSL_DDR3L
492		Board config to use DDR3L. It can be enabled for SoCs with
493		DDR3L controllers.
494
495		CONFIG_SYS_FSL_DDR4
496		Board config to use DDR4. It can be enabled for SoCs with
497		DDR4 controllers.
498
499		CONFIG_SYS_FSL_IFC_BE
500		Defines the IFC controller register space as Big Endian
501
502		CONFIG_SYS_FSL_IFC_LE
503		Defines the IFC controller register space as Little Endian
504
505		CONFIG_SYS_FSL_IFC_CLK_DIV
506		Defines divider of platform clock(clock input to IFC controller).
507
508		CONFIG_SYS_FSL_LBC_CLK_DIV
509		Defines divider of platform clock(clock input to eLBC controller).
510
511		CONFIG_SYS_FSL_PBL_PBI
512		It enables addition of RCW (Power on reset configuration) in built image.
513		Please refer doc/README.pblimage for more details
514
515		CONFIG_SYS_FSL_PBL_RCW
516		It adds PBI(pre-boot instructions) commands in u-boot build image.
517		PBI commands can be used to configure SoC before it starts the execution.
518		Please refer doc/README.pblimage for more details
519
520		CONFIG_SPL_FSL_PBL
521		It adds a target to create boot binary having SPL binary in PBI format
522		concatenated with u-boot binary.
523
524		CONFIG_SYS_FSL_DDR_BE
525		Defines the DDR controller register space as Big Endian
526
527		CONFIG_SYS_FSL_DDR_LE
528		Defines the DDR controller register space as Little Endian
529
530		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
531		Physical address from the view of DDR controllers. It is the
532		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
533		it could be different for ARM SoCs.
534
535		CONFIG_SYS_FSL_DDR_INTLV_256B
536		DDR controller interleaving on 256-byte. This is a special
537		interleaving mode, handled by Dickens for Freescale layerscape
538		SoCs with ARM core.
539
540		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
541		Number of controllers used as main memory.
542
543		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
544		Number of controllers used for other than main memory.
545
546		CONFIG_SYS_FSL_HAS_DP_DDR
547		Defines the SoC has DP-DDR used for DPAA.
548
549		CONFIG_SYS_FSL_SEC_BE
550		Defines the SEC controller register space as Big Endian
551
552		CONFIG_SYS_FSL_SEC_LE
553		Defines the SEC controller register space as Little Endian
554
555- MIPS CPU options:
556		CONFIG_SYS_INIT_SP_OFFSET
557
558		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
559		pointer. This is needed for the temporary stack before
560		relocation.
561
562		CONFIG_SYS_MIPS_CACHE_MODE
563
564		Cache operation mode for the MIPS CPU.
565		See also arch/mips/include/asm/mipsregs.h.
566		Possible values are:
567			CONF_CM_CACHABLE_NO_WA
568			CONF_CM_CACHABLE_WA
569			CONF_CM_UNCACHED
570			CONF_CM_CACHABLE_NONCOHERENT
571			CONF_CM_CACHABLE_CE
572			CONF_CM_CACHABLE_COW
573			CONF_CM_CACHABLE_CUW
574			CONF_CM_CACHABLE_ACCELERATED
575
576		CONFIG_SYS_XWAY_EBU_BOOTCFG
577
578		Special option for Lantiq XWAY SoCs for booting from NOR flash.
579		See also arch/mips/cpu/mips32/start.S.
580
581		CONFIG_XWAY_SWAP_BYTES
582
583		Enable compilation of tools/xway-swap-bytes needed for Lantiq
584		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
585		be swapped if a flash programmer is used.
586
587- ARM options:
588		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
589
590		Select high exception vectors of the ARM core, e.g., do not
591		clear the V bit of the c1 register of CP15.
592
593		COUNTER_FREQUENCY
594		Generic timer clock source frequency.
595
596		COUNTER_FREQUENCY_REAL
597		Generic timer clock source frequency if the real clock is
598		different from COUNTER_FREQUENCY, and can only be determined
599		at run time.
600
601- Tegra SoC options:
602		CONFIG_TEGRA_SUPPORT_NON_SECURE
603
604		Support executing U-Boot in non-secure (NS) mode. Certain
605		impossible actions will be skipped if the CPU is in NS mode,
606		such as ARM architectural timer initialization.
607
608- Linux Kernel Interface:
609		CONFIG_CLOCKS_IN_MHZ
610
611		U-Boot stores all clock information in Hz
612		internally. For binary compatibility with older Linux
613		kernels (which expect the clocks passed in the
614		bd_info data to be in MHz) the environment variable
615		"clocks_in_mhz" can be defined so that U-Boot
616		converts clock data to MHZ before passing it to the
617		Linux kernel.
618		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
619		"clocks_in_mhz=1" is automatically included in the
620		default environment.
621
622		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
623
624		When transferring memsize parameter to Linux, some versions
625		expect it to be in bytes, others in MB.
626		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
627
628		CONFIG_OF_LIBFDT
629
630		New kernel versions are expecting firmware settings to be
631		passed using flattened device trees (based on open firmware
632		concepts).
633
634		CONFIG_OF_LIBFDT
635		 * New libfdt-based support
636		 * Adds the "fdt" command
637		 * The bootm command automatically updates the fdt
638
639		OF_CPU - The proper name of the cpus node (only required for
640			MPC512X and MPC5xxx based boards).
641		OF_SOC - The proper name of the soc node (only required for
642			MPC512X and MPC5xxx based boards).
643		OF_TBCLK - The timebase frequency.
644		OF_STDOUT_PATH - The path to the console device
645
646		boards with QUICC Engines require OF_QE to set UCC MAC
647		addresses
648
649		CONFIG_OF_BOARD_SETUP
650
651		Board code has addition modification that it wants to make
652		to the flat device tree before handing it off to the kernel
653
654		CONFIG_OF_SYSTEM_SETUP
655
656		Other code has addition modification that it wants to make
657		to the flat device tree before handing it off to the kernel.
658		This causes ft_system_setup() to be called before booting
659		the kernel.
660
661		CONFIG_OF_IDE_FIXUP
662
663		U-Boot can detect if an IDE device is present or not.
664		If not, and this new config option is activated, U-Boot
665		removes the ATA node from the DTS before booting Linux,
666		so the Linux IDE driver does not probe the device and
667		crash. This is needed for buggy hardware (uc101) where
668		no pull down resistor is connected to the signal IDE5V_DD7.
669
670		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
671
672		This setting is mandatory for all boards that have only one
673		machine type and must be used to specify the machine type
674		number as it appears in the ARM machine registry
675		(see http://www.arm.linux.org.uk/developer/machines/).
676		Only boards that have multiple machine types supported
677		in a single configuration file and the machine type is
678		runtime discoverable, do not have to use this setting.
679
680- vxWorks boot parameters:
681
682		bootvx constructs a valid bootline using the following
683		environments variables: bootdev, bootfile, ipaddr, netmask,
684		serverip, gatewayip, hostname, othbootargs.
685		It loads the vxWorks image pointed bootfile.
686
687		Note: If a "bootargs" environment is defined, it will overwride
688		the defaults discussed just above.
689
690- Cache Configuration:
691		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
692		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
693		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
694
695- Cache Configuration for ARM:
696		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
697				      controller
698		CONFIG_SYS_PL310_BASE - Physical base address of PL310
699					controller register space
700
701- Serial Ports:
702		CONFIG_PL010_SERIAL
703
704		Define this if you want support for Amba PrimeCell PL010 UARTs.
705
706		CONFIG_PL011_SERIAL
707
708		Define this if you want support for Amba PrimeCell PL011 UARTs.
709
710		CONFIG_PL011_CLOCK
711
712		If you have Amba PrimeCell PL011 UARTs, set this variable to
713		the clock speed of the UARTs.
714
715		CONFIG_PL01x_PORTS
716
717		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
718		define this to a list of base addresses for each (supported)
719		port. See e.g. include/configs/versatile.h
720
721		CONFIG_SERIAL_HW_FLOW_CONTROL
722
723		Define this variable to enable hw flow control in serial driver.
724		Current user of this option is drivers/serial/nsl16550.c driver
725
726- Console Interface:
727		Depending on board, define exactly one serial port
728		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
729		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
730		console by defining CONFIG_8xx_CONS_NONE
731
732		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
733		port routines must be defined elsewhere
734		(i.e. serial_init(), serial_getc(), ...)
735
736- Console Baudrate:
737		CONFIG_BAUDRATE - in bps
738		Select one of the baudrates listed in
739		CONFIG_SYS_BAUDRATE_TABLE, see below.
740		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
741
742- Console Rx buffer length
743		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
744		the maximum receive buffer length for the SMC.
745		This option is actual only for 82xx and 8xx possible.
746		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
747		must be defined, to setup the maximum idle timeout for
748		the SMC.
749
750- Autoboot Command:
751		CONFIG_BOOTCOMMAND
752		Only needed when CONFIG_BOOTDELAY is enabled;
753		define a command string that is automatically executed
754		when no character is read on the console interface
755		within "Boot Delay" after reset.
756
757		CONFIG_BOOTARGS
758		This can be used to pass arguments to the bootm
759		command. The value of CONFIG_BOOTARGS goes into the
760		environment value "bootargs".
761
762		CONFIG_RAMBOOT and CONFIG_NFSBOOT
763		The value of these goes into the environment as
764		"ramboot" and "nfsboot" respectively, and can be used
765		as a convenience, when switching between booting from
766		RAM and NFS.
767
768- Bootcount:
769		CONFIG_BOOTCOUNT_LIMIT
770		Implements a mechanism for detecting a repeating reboot
771		cycle, see:
772		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
773
774		CONFIG_BOOTCOUNT_ENV
775		If no softreset save registers are found on the hardware
776		"bootcount" is stored in the environment. To prevent a
777		saveenv on all reboots, the environment variable
778		"upgrade_available" is used. If "upgrade_available" is
779		0, "bootcount" is always 0, if "upgrade_available" is
780		1 "bootcount" is incremented in the environment.
781		So the Userspace Applikation must set the "upgrade_available"
782		and "bootcount" variable to 0, if a boot was successfully.
783
784- Pre-Boot Commands:
785		CONFIG_PREBOOT
786
787		When this option is #defined, the existence of the
788		environment variable "preboot" will be checked
789		immediately before starting the CONFIG_BOOTDELAY
790		countdown and/or running the auto-boot command resp.
791		entering interactive mode.
792
793		This feature is especially useful when "preboot" is
794		automatically generated or modified. For an example
795		see the LWMON board specific code: here "preboot" is
796		modified when the user holds down a certain
797		combination of keys on the (special) keyboard when
798		booting the systems
799
800- Serial Download Echo Mode:
801		CONFIG_LOADS_ECHO
802		If defined to 1, all characters received during a
803		serial download (using the "loads" command) are
804		echoed back. This might be needed by some terminal
805		emulations (like "cu"), but may as well just take
806		time on others. This setting #define's the initial
807		value of the "loads_echo" environment variable.
808
809- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
810		CONFIG_KGDB_BAUDRATE
811		Select one of the baudrates listed in
812		CONFIG_SYS_BAUDRATE_TABLE, see below.
813
814- Monitor Functions:
815		Monitor commands can be included or excluded
816		from the build by using the #include files
817		<config_cmd_all.h> and #undef'ing unwanted
818		commands, or adding #define's for wanted commands.
819
820		The default command configuration includes all commands
821		except those marked below with a "*".
822
823		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
824		CONFIG_CMD_ASKENV	* ask for env variable
825		CONFIG_CMD_BDI		  bdinfo
826		CONFIG_CMD_BOOTD	  bootd
827		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
828		CONFIG_CMD_CACHE	* icache, dcache
829		CONFIG_CMD_CONSOLE	  coninfo
830		CONFIG_CMD_CRC32	* crc32
831		CONFIG_CMD_DHCP		* DHCP support
832		CONFIG_CMD_DIAG		* Diagnostics
833		CONFIG_CMD_ECHO		  echo arguments
834		CONFIG_CMD_EDITENV	  edit env variable
835		CONFIG_CMD_ELF		* bootelf, bootvx
836		CONFIG_CMD_ENV_FLAGS	* display details about env flags
837		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
838		CONFIG_CMD_EXPORTENV	* export the environment
839		CONFIG_CMD_EXT2		* ext2 command support
840		CONFIG_CMD_EXT4		* ext4 command support
841		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
842					  that work for multiple fs types
843		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
844		CONFIG_CMD_SAVEENV	  saveenv
845		CONFIG_CMD_FDC		* Floppy Disk Support
846		CONFIG_CMD_FAT		* FAT command support
847		CONFIG_CMD_FLASH	  flinfo, erase, protect
848		CONFIG_CMD_FPGA		  FPGA device initialization support
849		CONFIG_CMD_FUSE		* Device fuse support
850		CONFIG_CMD_GETTIME	* Get time since boot
851		CONFIG_CMD_GO		* the 'go' command (exec code)
852		CONFIG_CMD_GREPENV	* search environment
853		CONFIG_CMD_HASH		* calculate hash / digest
854		CONFIG_CMD_I2C		* I2C serial bus support
855		CONFIG_CMD_IDE		* IDE harddisk support
856		CONFIG_CMD_IMI		  iminfo
857		CONFIG_CMD_IMLS		  List all images found in NOR flash
858		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
859		CONFIG_CMD_IMMAP	* IMMR dump support
860		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
861		CONFIG_CMD_IMPORTENV	* import an environment
862		CONFIG_CMD_INI		* import data from an ini file into the env
863		CONFIG_CMD_IRQ		* irqinfo
864		CONFIG_CMD_ITEST	  Integer/string test of 2 values
865		CONFIG_CMD_JFFS2	* JFFS2 Support
866		CONFIG_CMD_KGDB		* kgdb
867		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
868		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
869					  (169.254.*.*)
870		CONFIG_CMD_LOADB	  loadb
871		CONFIG_CMD_LOADS	  loads
872		CONFIG_CMD_MD5SUM	* print md5 message digest
873					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
874		CONFIG_CMD_MEMINFO	* Display detailed memory information
875		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
876					  loop, loopw
877		CONFIG_CMD_MEMTEST	* mtest
878		CONFIG_CMD_MISC		  Misc functions like sleep etc
879		CONFIG_CMD_MMC		* MMC memory mapped support
880		CONFIG_CMD_MII		* MII utility commands
881		CONFIG_CMD_MTDPARTS	* MTD partition support
882		CONFIG_CMD_NAND		* NAND support
883		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
884		CONFIG_CMD_NFS		  NFS support
885		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
886		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
887		CONFIG_CMD_PCI		* pciinfo
888		CONFIG_CMD_PCMCIA		* PCMCIA support
889		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
890					  host
891		CONFIG_CMD_PORTIO	* Port I/O
892		CONFIG_CMD_READ		* Read raw data from partition
893		CONFIG_CMD_REGINFO	* Register dump
894		CONFIG_CMD_RUN		  run command in env variable
895		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
896		CONFIG_CMD_SAVES	* save S record dump
897		CONFIG_SCSI		* SCSI Support
898		CONFIG_CMD_SDRAM	* print SDRAM configuration information
899					  (requires CONFIG_CMD_I2C)
900		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
901					  (4xx only)
902		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
903		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
904					  (requires CONFIG_CMD_MEMORY)
905		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
906		CONFIG_CMD_SOURCE	  "source" command Support
907		CONFIG_CMD_SPI		* SPI serial bus support
908		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
909		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
910		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
911		CONFIG_CMD_TIMER	* access to the system tick timer
912		CONFIG_CMD_USB		* USB support
913		CONFIG_CMD_CDP		* Cisco Discover Protocol support
914		CONFIG_CMD_MFSL		* Microblaze FSL support
915		CONFIG_CMD_XIMG		  Load part of Multi Image
916		CONFIG_CMD_UUID		* Generate random UUID or GUID string
917
918		EXAMPLE: If you want all functions except of network
919		support you can write:
920
921		#include "config_cmd_all.h"
922		#undef CONFIG_CMD_NET
923
924	Other Commands:
925		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
926
927	Note:	Don't enable the "icache" and "dcache" commands
928		(configuration option CONFIG_CMD_CACHE) unless you know
929		what you (and your U-Boot users) are doing. Data
930		cache cannot be enabled on systems like the 8xx or
931		8260 (where accesses to the IMMR region must be
932		uncached), and it cannot be disabled on all other
933		systems where we (mis-) use the data cache to hold an
934		initial stack and some data.
935
936
937		XXX - this list needs to get updated!
938
939- Removal of commands
940		If no commands are needed to boot, you can disable
941		CONFIG_CMDLINE to remove them. In this case, the command line
942		will not be available, and when U-Boot wants to execute the
943		boot command (on start-up) it will call board_run_command()
944		instead. This can reduce image size significantly for very
945		simple boot procedures.
946
947- Regular expression support:
948		CONFIG_REGEX
949		If this variable is defined, U-Boot is linked against
950		the SLRE (Super Light Regular Expression) library,
951		which adds regex support to some commands, as for
952		example "env grep" and "setexpr".
953
954- Device tree:
955		CONFIG_OF_CONTROL
956		If this variable is defined, U-Boot will use a device tree
957		to configure its devices, instead of relying on statically
958		compiled #defines in the board file. This option is
959		experimental and only available on a few boards. The device
960		tree is available in the global data as gd->fdt_blob.
961
962		U-Boot needs to get its device tree from somewhere. This can
963		be done using one of the three options below:
964
965		CONFIG_OF_EMBED
966		If this variable is defined, U-Boot will embed a device tree
967		binary in its image. This device tree file should be in the
968		board directory and called <soc>-<board>.dts. The binary file
969		is then picked up in board_init_f() and made available through
970		the global data structure as gd->blob.
971
972		CONFIG_OF_SEPARATE
973		If this variable is defined, U-Boot will build a device tree
974		binary. It will be called u-boot.dtb. Architecture-specific
975		code will locate it at run-time. Generally this works by:
976
977			cat u-boot.bin u-boot.dtb >image.bin
978
979		and in fact, U-Boot does this for you, creating a file called
980		u-boot-dtb.bin which is useful in the common case. You can
981		still use the individual files if you need something more
982		exotic.
983
984		CONFIG_OF_BOARD
985		If this variable is defined, U-Boot will use the device tree
986		provided by the board at runtime instead of embedding one with
987		the image. Only boards defining board_fdt_blob_setup() support
988		this option (see include/fdtdec.h file).
989
990- Watchdog:
991		CONFIG_WATCHDOG
992		If this variable is defined, it enables watchdog
993		support for the SoC. There must be support in the SoC
994		specific code for a watchdog. For the 8xx and 8260
995		CPUs, the SIU Watchdog feature is enabled in the SYPCR
996		register.  When supported for a specific SoC is
997		available, then no further board specific code should
998		be needed to use it.
999
1000		CONFIG_HW_WATCHDOG
1001		When using a watchdog circuitry external to the used
1002		SoC, then define this variable and provide board
1003		specific code for the "hw_watchdog_reset" function.
1004
1005		CONFIG_AT91_HW_WDT_TIMEOUT
1006		specify the timeout in seconds. default 2 seconds.
1007
1008- U-Boot Version:
1009		CONFIG_VERSION_VARIABLE
1010		If this variable is defined, an environment variable
1011		named "ver" is created by U-Boot showing the U-Boot
1012		version as printed by the "version" command.
1013		Any change to this variable will be reverted at the
1014		next reset.
1015
1016- Real-Time Clock:
1017
1018		When CONFIG_CMD_DATE is selected, the type of the RTC
1019		has to be selected, too. Define exactly one of the
1020		following options:
1021
1022		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1023		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1024		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1025		CONFIG_RTC_MC146818	- use MC146818 RTC
1026		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1027		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1028		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1029		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1030		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1031		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1032		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1033		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1034		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1035					  RV3029 RTC.
1036
1037		Note that if the RTC uses I2C, then the I2C interface
1038		must also be configured. See I2C Support, below.
1039
1040- GPIO Support:
1041		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1042
1043		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1044		chip-ngpio pairs that tell the PCA953X driver the number of
1045		pins supported by a particular chip.
1046
1047		Note that if the GPIO device uses I2C, then the I2C interface
1048		must also be configured. See I2C Support, below.
1049
1050- I/O tracing:
1051		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1052		accesses and can checksum them or write a list of them out
1053		to memory. See the 'iotrace' command for details. This is
1054		useful for testing device drivers since it can confirm that
1055		the driver behaves the same way before and after a code
1056		change. Currently this is supported on sandbox and arm. To
1057		add support for your architecture, add '#include <iotrace.h>'
1058		to the bottom of arch/<arch>/include/asm/io.h and test.
1059
1060		Example output from the 'iotrace stats' command is below.
1061		Note that if the trace buffer is exhausted, the checksum will
1062		still continue to operate.
1063
1064			iotrace is enabled
1065			Start:  10000000	(buffer start address)
1066			Size:   00010000	(buffer size)
1067			Offset: 00000120	(current buffer offset)
1068			Output: 10000120	(start + offset)
1069			Count:  00000018	(number of trace records)
1070			CRC32:  9526fb66	(CRC32 of all trace records)
1071
1072- Timestamp Support:
1073
1074		When CONFIG_TIMESTAMP is selected, the timestamp
1075		(date and time) of an image is printed by image
1076		commands like bootm or iminfo. This option is
1077		automatically enabled when you select CONFIG_CMD_DATE .
1078
1079- Partition Labels (disklabels) Supported:
1080		Zero or more of the following:
1081		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1082		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1083				       Intel architecture, USB sticks, etc.
1084		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1085		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1086				       bootloader.  Note 2TB partition limit; see
1087				       disk/part_efi.c
1088		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1089
1090		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1091		CONFIG_SCSI) you must configure support for at
1092		least one non-MTD partition type as well.
1093
1094- IDE Reset method:
1095		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1096		board configurations files but used nowhere!
1097
1098		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1099		be performed by calling the function
1100			ide_set_reset(int reset)
1101		which has to be defined in a board specific file
1102
1103- ATAPI Support:
1104		CONFIG_ATAPI
1105
1106		Set this to enable ATAPI support.
1107
1108- LBA48 Support
1109		CONFIG_LBA48
1110
1111		Set this to enable support for disks larger than 137GB
1112		Also look at CONFIG_SYS_64BIT_LBA.
1113		Whithout these , LBA48 support uses 32bit variables and will 'only'
1114		support disks up to 2.1TB.
1115
1116		CONFIG_SYS_64BIT_LBA:
1117			When enabled, makes the IDE subsystem use 64bit sector addresses.
1118			Default is 32bit.
1119
1120- SCSI Support:
1121		At the moment only there is only support for the
1122		SYM53C8XX SCSI controller; define
1123		CONFIG_SCSI_SYM53C8XX to enable it.
1124
1125		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1126		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1127		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1128		maximum numbers of LUNs, SCSI ID's and target
1129		devices.
1130		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1131
1132		The environment variable 'scsidevs' is set to the number of
1133		SCSI devices found during the last scan.
1134
1135- NETWORK Support (PCI):
1136		CONFIG_E1000
1137		Support for Intel 8254x/8257x gigabit chips.
1138
1139		CONFIG_E1000_SPI
1140		Utility code for direct access to the SPI bus on Intel 8257x.
1141		This does not do anything useful unless you set at least one
1142		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1143
1144		CONFIG_E1000_SPI_GENERIC
1145		Allow generic access to the SPI bus on the Intel 8257x, for
1146		example with the "sspi" command.
1147
1148		CONFIG_CMD_E1000
1149		Management command for E1000 devices.  When used on devices
1150		with SPI support you can reprogram the EEPROM from U-Boot.
1151
1152		CONFIG_EEPRO100
1153		Support for Intel 82557/82559/82559ER chips.
1154		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1155		write routine for first time initialisation.
1156
1157		CONFIG_TULIP
1158		Support for Digital 2114x chips.
1159		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1160		modem chip initialisation (KS8761/QS6611).
1161
1162		CONFIG_NATSEMI
1163		Support for National dp83815 chips.
1164
1165		CONFIG_NS8382X
1166		Support for National dp8382[01] gigabit chips.
1167
1168- NETWORK Support (other):
1169
1170		CONFIG_DRIVER_AT91EMAC
1171		Support for AT91RM9200 EMAC.
1172
1173			CONFIG_RMII
1174			Define this to use reduced MII inteface
1175
1176			CONFIG_DRIVER_AT91EMAC_QUIET
1177			If this defined, the driver is quiet.
1178			The driver doen't show link status messages.
1179
1180		CONFIG_CALXEDA_XGMAC
1181		Support for the Calxeda XGMAC device
1182
1183		CONFIG_LAN91C96
1184		Support for SMSC's LAN91C96 chips.
1185
1186			CONFIG_LAN91C96_USE_32_BIT
1187			Define this to enable 32 bit addressing
1188
1189		CONFIG_SMC91111
1190		Support for SMSC's LAN91C111 chip
1191
1192			CONFIG_SMC91111_BASE
1193			Define this to hold the physical address
1194			of the device (I/O space)
1195
1196			CONFIG_SMC_USE_32_BIT
1197			Define this if data bus is 32 bits
1198
1199			CONFIG_SMC_USE_IOFUNCS
1200			Define this to use i/o functions instead of macros
1201			(some hardware wont work with macros)
1202
1203		CONFIG_DRIVER_TI_EMAC
1204		Support for davinci emac
1205
1206			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1207			Define this if you have more then 3 PHYs.
1208
1209		CONFIG_FTGMAC100
1210		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1211
1212			CONFIG_FTGMAC100_EGIGA
1213			Define this to use GE link update with gigabit PHY.
1214			Define this if FTGMAC100 is connected to gigabit PHY.
1215			If your system has 10/100 PHY only, it might not occur
1216			wrong behavior. Because PHY usually return timeout or
1217			useless data when polling gigabit status and gigabit
1218			control registers. This behavior won't affect the
1219			correctnessof 10/100 link speed update.
1220
1221		CONFIG_SMC911X
1222		Support for SMSC's LAN911x and LAN921x chips
1223
1224			CONFIG_SMC911X_BASE
1225			Define this to hold the physical address
1226			of the device (I/O space)
1227
1228			CONFIG_SMC911X_32_BIT
1229			Define this if data bus is 32 bits
1230
1231			CONFIG_SMC911X_16_BIT
1232			Define this if data bus is 16 bits. If your processor
1233			automatically converts one 32 bit word to two 16 bit
1234			words you may also try CONFIG_SMC911X_32_BIT.
1235
1236		CONFIG_SH_ETHER
1237		Support for Renesas on-chip Ethernet controller
1238
1239			CONFIG_SH_ETHER_USE_PORT
1240			Define the number of ports to be used
1241
1242			CONFIG_SH_ETHER_PHY_ADDR
1243			Define the ETH PHY's address
1244
1245			CONFIG_SH_ETHER_CACHE_WRITEBACK
1246			If this option is set, the driver enables cache flush.
1247
1248- PWM Support:
1249		CONFIG_PWM_IMX
1250		Support for PWM module on the imx6.
1251
1252- TPM Support:
1253		CONFIG_TPM
1254		Support TPM devices.
1255
1256		CONFIG_TPM_TIS_INFINEON
1257		Support for Infineon i2c bus TPM devices. Only one device
1258		per system is supported at this time.
1259
1260			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1261			Define the burst count bytes upper limit
1262
1263		CONFIG_TPM_ST33ZP24
1264		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1265
1266			CONFIG_TPM_ST33ZP24_I2C
1267			Support for STMicroelectronics ST33ZP24 I2C devices.
1268			Requires TPM_ST33ZP24 and I2C.
1269
1270			CONFIG_TPM_ST33ZP24_SPI
1271			Support for STMicroelectronics ST33ZP24 SPI devices.
1272			Requires TPM_ST33ZP24 and SPI.
1273
1274		CONFIG_TPM_ATMEL_TWI
1275		Support for Atmel TWI TPM device. Requires I2C support.
1276
1277		CONFIG_TPM_TIS_LPC
1278		Support for generic parallel port TPM devices. Only one device
1279		per system is supported at this time.
1280
1281			CONFIG_TPM_TIS_BASE_ADDRESS
1282			Base address where the generic TPM device is mapped
1283			to. Contemporary x86 systems usually map it at
1284			0xfed40000.
1285
1286		CONFIG_CMD_TPM
1287		Add tpm monitor functions.
1288		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1289		provides monitor access to authorized functions.
1290
1291		CONFIG_TPM
1292		Define this to enable the TPM support library which provides
1293		functional interfaces to some TPM commands.
1294		Requires support for a TPM device.
1295
1296		CONFIG_TPM_AUTH_SESSIONS
1297		Define this to enable authorized functions in the TPM library.
1298		Requires CONFIG_TPM and CONFIG_SHA1.
1299
1300- USB Support:
1301		At the moment only the UHCI host controller is
1302		supported (PIP405, MIP405, MPC5200); define
1303		CONFIG_USB_UHCI to enable it.
1304		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1305		and define CONFIG_USB_STORAGE to enable the USB
1306		storage devices.
1307		Note:
1308		Supported are USB Keyboards and USB Floppy drives
1309		(TEAC FD-05PUB).
1310		MPC5200 USB requires additional defines:
1311			CONFIG_USB_CLOCK
1312				for 528 MHz Clock: 0x0001bbbb
1313			CONFIG_PSC3_USB
1314				for USB on PSC3
1315			CONFIG_USB_CONFIG
1316				for differential drivers: 0x00001000
1317				for single ended drivers: 0x00005000
1318				for differential drivers on PSC3: 0x00000100
1319				for single ended drivers on PSC3: 0x00004100
1320			CONFIG_SYS_USB_EVENT_POLL
1321				May be defined to allow interrupt polling
1322				instead of using asynchronous interrupts
1323
1324		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1325		txfilltuning field in the EHCI controller on reset.
1326
1327		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1328		HW module registers.
1329
1330- USB Device:
1331		Define the below if you wish to use the USB console.
1332		Once firmware is rebuilt from a serial console issue the
1333		command "setenv stdin usbtty; setenv stdout usbtty" and
1334		attach your USB cable. The Unix command "dmesg" should print
1335		it has found a new device. The environment variable usbtty
1336		can be set to gserial or cdc_acm to enable your device to
1337		appear to a USB host as a Linux gserial device or a
1338		Common Device Class Abstract Control Model serial device.
1339		If you select usbtty = gserial you should be able to enumerate
1340		a Linux host by
1341		# modprobe usbserial vendor=0xVendorID product=0xProductID
1342		else if using cdc_acm, simply setting the environment
1343		variable usbtty to be cdc_acm should suffice. The following
1344		might be defined in YourBoardName.h
1345
1346			CONFIG_USB_DEVICE
1347			Define this to build a UDC device
1348
1349			CONFIG_USB_TTY
1350			Define this to have a tty type of device available to
1351			talk to the UDC device
1352
1353			CONFIG_USBD_HS
1354			Define this to enable the high speed support for usb
1355			device and usbtty. If this feature is enabled, a routine
1356			int is_usbd_high_speed(void)
1357			also needs to be defined by the driver to dynamically poll
1358			whether the enumeration has succeded at high speed or full
1359			speed.
1360
1361			CONFIG_SYS_CONSOLE_IS_IN_ENV
1362			Define this if you want stdin, stdout &/or stderr to
1363			be set to usbtty.
1364
1365			mpc8xx:
1366				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1367				Derive USB clock from external clock "blah"
1368				- CONFIG_SYS_USB_EXTC_CLK 0x02
1369
1370		If you have a USB-IF assigned VendorID then you may wish to
1371		define your own vendor specific values either in BoardName.h
1372		or directly in usbd_vendor_info.h. If you don't define
1373		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1374		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1375		should pretend to be a Linux device to it's target host.
1376
1377			CONFIG_USBD_MANUFACTURER
1378			Define this string as the name of your company for
1379			- CONFIG_USBD_MANUFACTURER "my company"
1380
1381			CONFIG_USBD_PRODUCT_NAME
1382			Define this string as the name of your product
1383			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1384
1385			CONFIG_USBD_VENDORID
1386			Define this as your assigned Vendor ID from the USB
1387			Implementors Forum. This *must* be a genuine Vendor ID
1388			to avoid polluting the USB namespace.
1389			- CONFIG_USBD_VENDORID 0xFFFF
1390
1391			CONFIG_USBD_PRODUCTID
1392			Define this as the unique Product ID
1393			for your device
1394			- CONFIG_USBD_PRODUCTID 0xFFFF
1395
1396- ULPI Layer Support:
1397		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1398		the generic ULPI layer. The generic layer accesses the ULPI PHY
1399		via the platform viewport, so you need both the genric layer and
1400		the viewport enabled. Currently only Chipidea/ARC based
1401		viewport is supported.
1402		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1403		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1404		If your ULPI phy needs a different reference clock than the
1405		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1406		the appropriate value in Hz.
1407
1408- MMC Support:
1409		The MMC controller on the Intel PXA is supported. To
1410		enable this define CONFIG_MMC. The MMC can be
1411		accessed from the boot prompt by mapping the device
1412		to physical memory similar to flash. Command line is
1413		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1414		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1415
1416		CONFIG_SH_MMCIF
1417		Support for Renesas on-chip MMCIF controller
1418
1419			CONFIG_SH_MMCIF_ADDR
1420			Define the base address of MMCIF registers
1421
1422			CONFIG_SH_MMCIF_CLK
1423			Define the clock frequency for MMCIF
1424
1425		CONFIG_SUPPORT_EMMC_BOOT
1426		Enable some additional features of the eMMC boot partitions.
1427
1428		CONFIG_SUPPORT_EMMC_RPMB
1429		Enable the commands for reading, writing and programming the
1430		key for the Replay Protection Memory Block partition in eMMC.
1431
1432- USB Device Firmware Update (DFU) class support:
1433		CONFIG_USB_FUNCTION_DFU
1434		This enables the USB portion of the DFU USB class
1435
1436		CONFIG_CMD_DFU
1437		This enables the command "dfu" which is used to have
1438		U-Boot create a DFU class device via USB.  This command
1439		requires that the "dfu_alt_info" environment variable be
1440		set and define the alt settings to expose to the host.
1441
1442		CONFIG_DFU_MMC
1443		This enables support for exposing (e)MMC devices via DFU.
1444
1445		CONFIG_DFU_NAND
1446		This enables support for exposing NAND devices via DFU.
1447
1448		CONFIG_DFU_RAM
1449		This enables support for exposing RAM via DFU.
1450		Note: DFU spec refer to non-volatile memory usage, but
1451		allow usages beyond the scope of spec - here RAM usage,
1452		one that would help mostly the developer.
1453
1454		CONFIG_SYS_DFU_DATA_BUF_SIZE
1455		Dfu transfer uses a buffer before writing data to the
1456		raw storage device. Make the size (in bytes) of this buffer
1457		configurable. The size of this buffer is also configurable
1458		through the "dfu_bufsiz" environment variable.
1459
1460		CONFIG_SYS_DFU_MAX_FILE_SIZE
1461		When updating files rather than the raw storage device,
1462		we use a static buffer to copy the file into and then write
1463		the buffer once we've been given the whole file.  Define
1464		this to the maximum filesize (in bytes) for the buffer.
1465		Default is 4 MiB if undefined.
1466
1467		DFU_DEFAULT_POLL_TIMEOUT
1468		Poll timeout [ms], is the timeout a device can send to the
1469		host. The host must wait for this timeout before sending
1470		a subsequent DFU_GET_STATUS request to the device.
1471
1472		DFU_MANIFEST_POLL_TIMEOUT
1473		Poll timeout [ms], which the device sends to the host when
1474		entering dfuMANIFEST state. Host waits this timeout, before
1475		sending again an USB request to the device.
1476
1477- USB Device Android Fastboot support:
1478		CONFIG_USB_FUNCTION_FASTBOOT
1479		This enables the USB part of the fastboot gadget
1480
1481		CONFIG_CMD_FASTBOOT
1482		This enables the command "fastboot" which enables the Android
1483		fastboot mode for the platform's USB device. Fastboot is a USB
1484		protocol for downloading images, flashing and device control
1485		used on Android devices.
1486		See doc/README.android-fastboot for more information.
1487
1488		CONFIG_ANDROID_BOOT_IMAGE
1489		This enables support for booting images which use the Android
1490		image format header.
1491
1492		CONFIG_FASTBOOT_BUF_ADDR
1493		The fastboot protocol requires a large memory buffer for
1494		downloads. Define this to the starting RAM address to use for
1495		downloaded images.
1496
1497		CONFIG_FASTBOOT_BUF_SIZE
1498		The fastboot protocol requires a large memory buffer for
1499		downloads. This buffer should be as large as possible for a
1500		platform. Define this to the size available RAM for fastboot.
1501
1502		CONFIG_FASTBOOT_FLASH
1503		The fastboot protocol includes a "flash" command for writing
1504		the downloaded image to a non-volatile storage device. Define
1505		this to enable the "fastboot flash" command.
1506
1507		CONFIG_FASTBOOT_FLASH_MMC_DEV
1508		The fastboot "flash" command requires additional information
1509		regarding the non-volatile storage device. Define this to
1510		the eMMC device that fastboot should use to store the image.
1511
1512		CONFIG_FASTBOOT_GPT_NAME
1513		The fastboot "flash" command supports writing the downloaded
1514		image to the Protective MBR and the Primary GUID Partition
1515		Table. (Additionally, this downloaded image is post-processed
1516		to generate and write the Backup GUID Partition Table.)
1517		This occurs when the specified "partition name" on the
1518		"fastboot flash" command line matches this value.
1519		The default is "gpt" if undefined.
1520
1521		CONFIG_FASTBOOT_MBR_NAME
1522		The fastboot "flash" command supports writing the downloaded
1523		image to DOS MBR.
1524		This occurs when the "partition name" specified on the
1525		"fastboot flash" command line matches this value.
1526		If not defined the default value "mbr" is used.
1527
1528- Journaling Flash filesystem support:
1529		CONFIG_JFFS2_NAND
1530		Define these for a default partition on a NAND device
1531
1532		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1533		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1534		Define these for a default partition on a NOR device
1535
1536- FAT(File Allocation Table) filesystem write function support:
1537		CONFIG_FAT_WRITE
1538
1539		Define this to enable support for saving memory data as a
1540		file in FAT formatted partition.
1541
1542		This will also enable the command "fatwrite" enabling the
1543		user to write files to FAT.
1544
1545- FAT(File Allocation Table) filesystem cluster size:
1546		CONFIG_FS_FAT_MAX_CLUSTSIZE
1547
1548		Define the max cluster size for fat operations else
1549		a default value of 65536 will be defined.
1550
1551- Keyboard Support:
1552		See Kconfig help for available keyboard drivers.
1553
1554		CONFIG_KEYBOARD
1555
1556		Define this to enable a custom keyboard support.
1557		This simply calls drv_keyboard_init() which must be
1558		defined in your board-specific files. This option is deprecated
1559		and is only used by novena. For new boards, use driver model
1560		instead.
1561
1562- Video support:
1563		CONFIG_FSL_DIU_FB
1564		Enable the Freescale DIU video driver.	Reference boards for
1565		SOCs that have a DIU should define this macro to enable DIU
1566		support, and should also define these other macros:
1567
1568			CONFIG_SYS_DIU_ADDR
1569			CONFIG_VIDEO
1570			CONFIG_CFB_CONSOLE
1571			CONFIG_VIDEO_SW_CURSOR
1572			CONFIG_VGA_AS_SINGLE_DEVICE
1573			CONFIG_VIDEO_LOGO
1574			CONFIG_VIDEO_BMP_LOGO
1575
1576		The DIU driver will look for the 'video-mode' environment
1577		variable, and if defined, enable the DIU as a console during
1578		boot.  See the documentation file doc/README.video for a
1579		description of this variable.
1580
1581- LCD Support:	CONFIG_LCD
1582
1583		Define this to enable LCD support (for output to LCD
1584		display); also select one of the supported displays
1585		by defining one of these:
1586
1587		CONFIG_ATMEL_LCD:
1588
1589			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1590
1591		CONFIG_NEC_NL6448AC33:
1592
1593			NEC NL6448AC33-18. Active, color, single scan.
1594
1595		CONFIG_NEC_NL6448BC20
1596
1597			NEC NL6448BC20-08. 6.5", 640x480.
1598			Active, color, single scan.
1599
1600		CONFIG_NEC_NL6448BC33_54
1601
1602			NEC NL6448BC33-54. 10.4", 640x480.
1603			Active, color, single scan.
1604
1605		CONFIG_SHARP_16x9
1606
1607			Sharp 320x240. Active, color, single scan.
1608			It isn't 16x9, and I am not sure what it is.
1609
1610		CONFIG_SHARP_LQ64D341
1611
1612			Sharp LQ64D341 display, 640x480.
1613			Active, color, single scan.
1614
1615		CONFIG_HLD1045
1616
1617			HLD1045 display, 640x480.
1618			Active, color, single scan.
1619
1620		CONFIG_OPTREX_BW
1621
1622			Optrex	 CBL50840-2 NF-FW 99 22 M5
1623			or
1624			Hitachi	 LMG6912RPFC-00T
1625			or
1626			Hitachi	 SP14Q002
1627
1628			320x240. Black & white.
1629
1630		CONFIG_LCD_ALIGNMENT
1631
1632		Normally the LCD is page-aligned (typically 4KB). If this is
1633		defined then the LCD will be aligned to this value instead.
1634		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1635		here, since it is cheaper to change data cache settings on
1636		a per-section basis.
1637
1638
1639		CONFIG_LCD_ROTATION
1640
1641		Sometimes, for example if the display is mounted in portrait
1642		mode or even if it's mounted landscape but rotated by 180degree,
1643		we need to rotate our content of the display relative to the
1644		framebuffer, so that user can read the messages which are
1645		printed out.
1646		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1647		initialized with a given rotation from "vl_rot" out of
1648		"vidinfo_t" which is provided by the board specific code.
1649		The value for vl_rot is coded as following (matching to
1650		fbcon=rotate:<n> linux-kernel commandline):
1651		0 = no rotation respectively 0 degree
1652		1 = 90 degree rotation
1653		2 = 180 degree rotation
1654		3 = 270 degree rotation
1655
1656		If CONFIG_LCD_ROTATION is not defined, the console will be
1657		initialized with 0degree rotation.
1658
1659		CONFIG_LCD_BMP_RLE8
1660
1661		Support drawing of RLE8-compressed bitmaps on the LCD.
1662
1663		CONFIG_I2C_EDID
1664
1665		Enables an 'i2c edid' command which can read EDID
1666		information over I2C from an attached LCD display.
1667
1668- Splash Screen Support: CONFIG_SPLASH_SCREEN
1669
1670		If this option is set, the environment is checked for
1671		a variable "splashimage". If found, the usual display
1672		of logo, copyright and system information on the LCD
1673		is suppressed and the BMP image at the address
1674		specified in "splashimage" is loaded instead. The
1675		console is redirected to the "nulldev", too. This
1676		allows for a "silent" boot where a splash screen is
1677		loaded very quickly after power-on.
1678
1679		CONFIG_SPLASHIMAGE_GUARD
1680
1681		If this option is set, then U-Boot will prevent the environment
1682		variable "splashimage" from being set to a problematic address
1683		(see doc/README.displaying-bmps).
1684		This option is useful for targets where, due to alignment
1685		restrictions, an improperly aligned BMP image will cause a data
1686		abort. If you think you will not have problems with unaligned
1687		accesses (for example because your toolchain prevents them)
1688		there is no need to set this option.
1689
1690		CONFIG_SPLASH_SCREEN_ALIGN
1691
1692		If this option is set the splash image can be freely positioned
1693		on the screen. Environment variable "splashpos" specifies the
1694		position as "x,y". If a positive number is given it is used as
1695		number of pixel from left/top. If a negative number is given it
1696		is used as number of pixel from right/bottom. You can also
1697		specify 'm' for centering the image.
1698
1699		Example:
1700		setenv splashpos m,m
1701			=> image at center of screen
1702
1703		setenv splashpos 30,20
1704			=> image at x = 30 and y = 20
1705
1706		setenv splashpos -10,m
1707			=> vertically centered image
1708			   at x = dspWidth - bmpWidth - 9
1709
1710- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1711
1712		If this option is set, additionally to standard BMP
1713		images, gzipped BMP images can be displayed via the
1714		splashscreen support or the bmp command.
1715
1716- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1717
1718		If this option is set, 8-bit RLE compressed BMP images
1719		can be displayed via the splashscreen support or the
1720		bmp command.
1721
1722- Compression support:
1723		CONFIG_GZIP
1724
1725		Enabled by default to support gzip compressed images.
1726
1727		CONFIG_BZIP2
1728
1729		If this option is set, support for bzip2 compressed
1730		images is included. If not, only uncompressed and gzip
1731		compressed images are supported.
1732
1733		NOTE: the bzip2 algorithm requires a lot of RAM, so
1734		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1735		be at least 4MB.
1736
1737		CONFIG_LZMA
1738
1739		If this option is set, support for lzma compressed
1740		images is included.
1741
1742		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1743		requires an amount of dynamic memory that is given by the
1744		formula:
1745
1746			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1747
1748		Where lc and lp stand for, respectively, Literal context bits
1749		and Literal pos bits.
1750
1751		This value is upper-bounded by 14MB in the worst case. Anyway,
1752		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1753		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1754		a very small buffer.
1755
1756		Use the lzmainfo tool to determinate the lc and lp values and
1757		then calculate the amount of needed dynamic memory (ensuring
1758		the appropriate CONFIG_SYS_MALLOC_LEN value).
1759
1760		CONFIG_LZO
1761
1762		If this option is set, support for LZO compressed images
1763		is included.
1764
1765- MII/PHY support:
1766		CONFIG_PHY_ADDR
1767
1768		The address of PHY on MII bus.
1769
1770		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1771
1772		The clock frequency of the MII bus
1773
1774		CONFIG_PHY_GIGE
1775
1776		If this option is set, support for speed/duplex
1777		detection of gigabit PHY is included.
1778
1779		CONFIG_PHY_RESET_DELAY
1780
1781		Some PHY like Intel LXT971A need extra delay after
1782		reset before any MII register access is possible.
1783		For such PHY, set this option to the usec delay
1784		required. (minimum 300usec for LXT971A)
1785
1786		CONFIG_PHY_CMD_DELAY (ppc4xx)
1787
1788		Some PHY like Intel LXT971A need extra delay after
1789		command issued before MII status register can be read
1790
1791- IP address:
1792		CONFIG_IPADDR
1793
1794		Define a default value for the IP address to use for
1795		the default Ethernet interface, in case this is not
1796		determined through e.g. bootp.
1797		(Environment variable "ipaddr")
1798
1799- Server IP address:
1800		CONFIG_SERVERIP
1801
1802		Defines a default value for the IP address of a TFTP
1803		server to contact when using the "tftboot" command.
1804		(Environment variable "serverip")
1805
1806		CONFIG_KEEP_SERVERADDR
1807
1808		Keeps the server's MAC address, in the env 'serveraddr'
1809		for passing to bootargs (like Linux's netconsole option)
1810
1811- Gateway IP address:
1812		CONFIG_GATEWAYIP
1813
1814		Defines a default value for the IP address of the
1815		default router where packets to other networks are
1816		sent to.
1817		(Environment variable "gatewayip")
1818
1819- Subnet mask:
1820		CONFIG_NETMASK
1821
1822		Defines a default value for the subnet mask (or
1823		routing prefix) which is used to determine if an IP
1824		address belongs to the local subnet or needs to be
1825		forwarded through a router.
1826		(Environment variable "netmask")
1827
1828- Multicast TFTP Mode:
1829		CONFIG_MCAST_TFTP
1830
1831		Defines whether you want to support multicast TFTP as per
1832		rfc-2090; for example to work with atftp.  Lets lots of targets
1833		tftp down the same boot image concurrently.  Note: the Ethernet
1834		driver in use must provide a function: mcast() to join/leave a
1835		multicast group.
1836
1837- BOOTP Recovery Mode:
1838		CONFIG_BOOTP_RANDOM_DELAY
1839
1840		If you have many targets in a network that try to
1841		boot using BOOTP, you may want to avoid that all
1842		systems send out BOOTP requests at precisely the same
1843		moment (which would happen for instance at recovery
1844		from a power failure, when all systems will try to
1845		boot, thus flooding the BOOTP server. Defining
1846		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1847		inserted before sending out BOOTP requests. The
1848		following delays are inserted then:
1849
1850		1st BOOTP request:	delay 0 ... 1 sec
1851		2nd BOOTP request:	delay 0 ... 2 sec
1852		3rd BOOTP request:	delay 0 ... 4 sec
1853		4th and following
1854		BOOTP requests:		delay 0 ... 8 sec
1855
1856		CONFIG_BOOTP_ID_CACHE_SIZE
1857
1858		BOOTP packets are uniquely identified using a 32-bit ID. The
1859		server will copy the ID from client requests to responses and
1860		U-Boot will use this to determine if it is the destination of
1861		an incoming response. Some servers will check that addresses
1862		aren't in use before handing them out (usually using an ARP
1863		ping) and therefore take up to a few hundred milliseconds to
1864		respond. Network congestion may also influence the time it
1865		takes for a response to make it back to the client. If that
1866		time is too long, U-Boot will retransmit requests. In order
1867		to allow earlier responses to still be accepted after these
1868		retransmissions, U-Boot's BOOTP client keeps a small cache of
1869		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1870		cache. The default is to keep IDs for up to four outstanding
1871		requests. Increasing this will allow U-Boot to accept offers
1872		from a BOOTP client in networks with unusually high latency.
1873
1874- DHCP Advanced Options:
1875		You can fine tune the DHCP functionality by defining
1876		CONFIG_BOOTP_* symbols:
1877
1878		CONFIG_BOOTP_SUBNETMASK
1879		CONFIG_BOOTP_GATEWAY
1880		CONFIG_BOOTP_HOSTNAME
1881		CONFIG_BOOTP_NISDOMAIN
1882		CONFIG_BOOTP_BOOTPATH
1883		CONFIG_BOOTP_BOOTFILESIZE
1884		CONFIG_BOOTP_DNS
1885		CONFIG_BOOTP_DNS2
1886		CONFIG_BOOTP_SEND_HOSTNAME
1887		CONFIG_BOOTP_NTPSERVER
1888		CONFIG_BOOTP_TIMEOFFSET
1889		CONFIG_BOOTP_VENDOREX
1890		CONFIG_BOOTP_MAY_FAIL
1891
1892		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1893		environment variable, not the BOOTP server.
1894
1895		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1896		after the configured retry count, the call will fail
1897		instead of starting over.  This can be used to fail over
1898		to Link-local IP address configuration if the DHCP server
1899		is not available.
1900
1901		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1902		serverip from a DHCP server, it is possible that more
1903		than one DNS serverip is offered to the client.
1904		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1905		serverip will be stored in the additional environment
1906		variable "dnsip2". The first DNS serverip is always
1907		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1908		is defined.
1909
1910		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1911		to do a dynamic update of a DNS server. To do this, they
1912		need the hostname of the DHCP requester.
1913		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1914		of the "hostname" environment variable is passed as
1915		option 12 to the DHCP server.
1916
1917		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1918
1919		A 32bit value in microseconds for a delay between
1920		receiving a "DHCP Offer" and sending the "DHCP Request".
1921		This fixes a problem with certain DHCP servers that don't
1922		respond 100% of the time to a "DHCP request". E.g. On an
1923		AT91RM9200 processor running at 180MHz, this delay needed
1924		to be *at least* 15,000 usec before a Windows Server 2003
1925		DHCP server would reply 100% of the time. I recommend at
1926		least 50,000 usec to be safe. The alternative is to hope
1927		that one of the retries will be successful but note that
1928		the DHCP timeout and retry process takes a longer than
1929		this delay.
1930
1931 - Link-local IP address negotiation:
1932		Negotiate with other link-local clients on the local network
1933		for an address that doesn't require explicit configuration.
1934		This is especially useful if a DHCP server cannot be guaranteed
1935		to exist in all environments that the device must operate.
1936
1937		See doc/README.link-local for more information.
1938
1939 - CDP Options:
1940		CONFIG_CDP_DEVICE_ID
1941
1942		The device id used in CDP trigger frames.
1943
1944		CONFIG_CDP_DEVICE_ID_PREFIX
1945
1946		A two character string which is prefixed to the MAC address
1947		of the device.
1948
1949		CONFIG_CDP_PORT_ID
1950
1951		A printf format string which contains the ascii name of
1952		the port. Normally is set to "eth%d" which sets
1953		eth0 for the first Ethernet, eth1 for the second etc.
1954
1955		CONFIG_CDP_CAPABILITIES
1956
1957		A 32bit integer which indicates the device capabilities;
1958		0x00000010 for a normal host which does not forwards.
1959
1960		CONFIG_CDP_VERSION
1961
1962		An ascii string containing the version of the software.
1963
1964		CONFIG_CDP_PLATFORM
1965
1966		An ascii string containing the name of the platform.
1967
1968		CONFIG_CDP_TRIGGER
1969
1970		A 32bit integer sent on the trigger.
1971
1972		CONFIG_CDP_POWER_CONSUMPTION
1973
1974		A 16bit integer containing the power consumption of the
1975		device in .1 of milliwatts.
1976
1977		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1978
1979		A byte containing the id of the VLAN.
1980
1981- Status LED:	CONFIG_LED_STATUS
1982
1983		Several configurations allow to display the current
1984		status using a LED. For instance, the LED will blink
1985		fast while running U-Boot code, stop blinking as
1986		soon as a reply to a BOOTP request was received, and
1987		start blinking slow once the Linux kernel is running
1988		(supported by a status LED driver in the Linux
1989		kernel). Defining CONFIG_LED_STATUS enables this
1990		feature in U-Boot.
1991
1992		Additional options:
1993
1994		CONFIG_LED_STATUS_GPIO
1995		The status LED can be connected to a GPIO pin.
1996		In such cases, the gpio_led driver can be used as a
1997		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1998		to include the gpio_led driver in the U-Boot binary.
1999
2000		CONFIG_GPIO_LED_INVERTED_TABLE
2001		Some GPIO connected LEDs may have inverted polarity in which
2002		case the GPIO high value corresponds to LED off state and
2003		GPIO low value corresponds to LED on state.
2004		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2005		with a list of GPIO LEDs that have inverted polarity.
2006
2007- CAN Support:	CONFIG_CAN_DRIVER
2008
2009		Defining CONFIG_CAN_DRIVER enables CAN driver support
2010		on those systems that support this (optional)
2011		feature, like the TQM8xxL modules.
2012
2013- I2C Support:	CONFIG_SYS_I2C
2014
2015		This enable the NEW i2c subsystem, and will allow you to use
2016		i2c commands at the u-boot command line (as long as you set
2017		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2018		based realtime clock chips or other i2c devices. See
2019		common/cmd_i2c.c for a description of the command line
2020		interface.
2021
2022		ported i2c driver to the new framework:
2023		- drivers/i2c/soft_i2c.c:
2024		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2025		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2026		    for defining speed and slave address
2027		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2028		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2029		    for defining speed and slave address
2030		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2031		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2032		    for defining speed and slave address
2033		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2034		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2035		    for defining speed and slave address
2036
2037		- drivers/i2c/fsl_i2c.c:
2038		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2039		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2040		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2041		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2042		    bus.
2043		  - If your board supports a second fsl i2c bus, define
2044		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2045		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2046		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2047		    second bus.
2048
2049		- drivers/i2c/tegra_i2c.c:
2050		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2051		  - This driver adds 4 i2c buses with a fix speed from
2052		    100000 and the slave addr 0!
2053
2054		- drivers/i2c/ppc4xx_i2c.c
2055		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2056		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2057		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2058
2059		- drivers/i2c/i2c_mxc.c
2060		  - activate this driver with CONFIG_SYS_I2C_MXC
2061		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
2062		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
2063		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
2064		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
2065		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2066		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2067		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2068		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2069		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2070		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2071		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
2072		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
2073		If those defines are not set, default value is 100000
2074		for speed, and 0 for slave.
2075
2076		- drivers/i2c/rcar_i2c.c:
2077		  - activate this driver with CONFIG_SYS_I2C_RCAR
2078		  - This driver adds 4 i2c buses
2079
2080		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2081		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2082		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2083		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2084		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2085		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2086		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2087		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2088		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2089
2090		- drivers/i2c/sh_i2c.c:
2091		  - activate this driver with CONFIG_SYS_I2C_SH
2092		  - This driver adds from 2 to 5 i2c buses
2093
2094		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2095		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2096		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2097		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2098		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2099		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2100		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2101		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2102		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2103		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2104		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2105
2106		- drivers/i2c/omap24xx_i2c.c
2107		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2108		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2109		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2110		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2111		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2112		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2113		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2114		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2115		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2116		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2117		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2118
2119		- drivers/i2c/zynq_i2c.c
2120		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2121		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2122		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2123
2124		- drivers/i2c/s3c24x0_i2c.c:
2125		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2126		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2127		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2128		    with a fix speed from 100000 and the slave addr 0!
2129
2130		- drivers/i2c/ihs_i2c.c
2131		  - activate this driver with CONFIG_SYS_I2C_IHS
2132		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2133		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2134		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2135		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2136		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2137		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2138		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2139		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2140		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2141		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2142		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2143		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2144		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
2145		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
2146		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
2147		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
2148		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
2149		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
2150		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
2151		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
2152		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
2153
2154		additional defines:
2155
2156		CONFIG_SYS_NUM_I2C_BUSES
2157		Hold the number of i2c buses you want to use.
2158
2159		CONFIG_SYS_I2C_DIRECT_BUS
2160		define this, if you don't use i2c muxes on your hardware.
2161		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2162		omit this define.
2163
2164		CONFIG_SYS_I2C_MAX_HOPS
2165		define how many muxes are maximal consecutively connected
2166		on one i2c bus. If you not use i2c muxes, omit this
2167		define.
2168
2169		CONFIG_SYS_I2C_BUSES
2170		hold a list of buses you want to use, only used if
2171		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2172		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2173		CONFIG_SYS_NUM_I2C_BUSES = 9:
2174
2175		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2176					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2177					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2178					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2179					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2180					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2181					{1, {I2C_NULL_HOP}}, \
2182					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2183					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2184					}
2185
2186		which defines
2187			bus 0 on adapter 0 without a mux
2188			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2189			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2190			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2191			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2192			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2193			bus 6 on adapter 1 without a mux
2194			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2195			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2196
2197		If you do not have i2c muxes on your board, omit this define.
2198
2199- Legacy I2C Support:
2200		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2201		then the following macros need to be defined (examples are
2202		from include/configs/lwmon.h):
2203
2204		I2C_INIT
2205
2206		(Optional). Any commands necessary to enable the I2C
2207		controller or configure ports.
2208
2209		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2210
2211		I2C_PORT
2212
2213		(Only for MPC8260 CPU). The I/O port to use (the code
2214		assumes both bits are on the same port). Valid values
2215		are 0..3 for ports A..D.
2216
2217		I2C_ACTIVE
2218
2219		The code necessary to make the I2C data line active
2220		(driven).  If the data line is open collector, this
2221		define can be null.
2222
2223		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2224
2225		I2C_TRISTATE
2226
2227		The code necessary to make the I2C data line tri-stated
2228		(inactive).  If the data line is open collector, this
2229		define can be null.
2230
2231		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2232
2233		I2C_READ
2234
2235		Code that returns true if the I2C data line is high,
2236		false if it is low.
2237
2238		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2239
2240		I2C_SDA(bit)
2241
2242		If <bit> is true, sets the I2C data line high. If it
2243		is false, it clears it (low).
2244
2245		eg: #define I2C_SDA(bit) \
2246			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2247			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2248
2249		I2C_SCL(bit)
2250
2251		If <bit> is true, sets the I2C clock line high. If it
2252		is false, it clears it (low).
2253
2254		eg: #define I2C_SCL(bit) \
2255			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2256			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2257
2258		I2C_DELAY
2259
2260		This delay is invoked four times per clock cycle so this
2261		controls the rate of data transfer.  The data rate thus
2262		is 1 / (I2C_DELAY * 4). Often defined to be something
2263		like:
2264
2265		#define I2C_DELAY  udelay(2)
2266
2267		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2268
2269		If your arch supports the generic GPIO framework (asm/gpio.h),
2270		then you may alternatively define the two GPIOs that are to be
2271		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2272		have GPIO-based defaults assigned to them as appropriate.
2273
2274		You should define these to the GPIO value as given directly to
2275		the generic GPIO functions.
2276
2277		CONFIG_SYS_I2C_INIT_BOARD
2278
2279		When a board is reset during an i2c bus transfer
2280		chips might think that the current transfer is still
2281		in progress. On some boards it is possible to access
2282		the i2c SCLK line directly, either by using the
2283		processor pin as a GPIO or by having a second pin
2284		connected to the bus. If this option is defined a
2285		custom i2c_init_board() routine in boards/xxx/board.c
2286		is run early in the boot sequence.
2287
2288		CONFIG_I2C_MULTI_BUS
2289
2290		This option allows the use of multiple I2C buses, each of which
2291		must have a controller.	 At any point in time, only one bus is
2292		active.	 To switch to a different bus, use the 'i2c dev' command.
2293		Note that bus numbering is zero-based.
2294
2295		CONFIG_SYS_I2C_NOPROBES
2296
2297		This option specifies a list of I2C devices that will be skipped
2298		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2299		is set, specify a list of bus-device pairs.  Otherwise, specify
2300		a 1D array of device addresses
2301
2302		e.g.
2303			#undef	CONFIG_I2C_MULTI_BUS
2304			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2305
2306		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2307
2308			#define CONFIG_I2C_MULTI_BUS
2309			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2310
2311		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2312
2313		CONFIG_SYS_SPD_BUS_NUM
2314
2315		If defined, then this indicates the I2C bus number for DDR SPD.
2316		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2317
2318		CONFIG_SYS_RTC_BUS_NUM
2319
2320		If defined, then this indicates the I2C bus number for the RTC.
2321		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2322
2323		CONFIG_SOFT_I2C_READ_REPEATED_START
2324
2325		defining this will force the i2c_read() function in
2326		the soft_i2c driver to perform an I2C repeated start
2327		between writing the address pointer and reading the
2328		data.  If this define is omitted the default behaviour
2329		of doing a stop-start sequence will be used.  Most I2C
2330		devices can use either method, but some require one or
2331		the other.
2332
2333- SPI Support:	CONFIG_SPI
2334
2335		Enables SPI driver (so far only tested with
2336		SPI EEPROM, also an instance works with Crystal A/D and
2337		D/As on the SACSng board)
2338
2339		CONFIG_SH_SPI
2340
2341		Enables the driver for SPI controller on SuperH. Currently
2342		only SH7757 is supported.
2343
2344		CONFIG_SOFT_SPI
2345
2346		Enables a software (bit-bang) SPI driver rather than
2347		using hardware support. This is a general purpose
2348		driver that only requires three general I/O port pins
2349		(two outputs, one input) to function. If this is
2350		defined, the board configuration must define several
2351		SPI configuration items (port pins to use, etc). For
2352		an example, see include/configs/sacsng.h.
2353
2354		CONFIG_HARD_SPI
2355
2356		Enables a hardware SPI driver for general-purpose reads
2357		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2358		must define a list of chip-select function pointers.
2359		Currently supported on some MPC8xxx processors.	 For an
2360		example, see include/configs/mpc8349emds.h.
2361
2362		CONFIG_MXC_SPI
2363
2364		Enables the driver for the SPI controllers on i.MX and MXC
2365		SoCs. Currently i.MX31/35/51 are supported.
2366
2367		CONFIG_SYS_SPI_MXC_WAIT
2368		Timeout for waiting until spi transfer completed.
2369		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2370
2371- FPGA Support: CONFIG_FPGA
2372
2373		Enables FPGA subsystem.
2374
2375		CONFIG_FPGA_<vendor>
2376
2377		Enables support for specific chip vendors.
2378		(ALTERA, XILINX)
2379
2380		CONFIG_FPGA_<family>
2381
2382		Enables support for FPGA family.
2383		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2384
2385		CONFIG_FPGA_COUNT
2386
2387		Specify the number of FPGA devices to support.
2388
2389		CONFIG_CMD_FPGA_LOADMK
2390
2391		Enable support for fpga loadmk command
2392
2393		CONFIG_CMD_FPGA_LOADP
2394
2395		Enable support for fpga loadp command - load partial bitstream
2396
2397		CONFIG_CMD_FPGA_LOADBP
2398
2399		Enable support for fpga loadbp command - load partial bitstream
2400		(Xilinx only)
2401
2402		CONFIG_SYS_FPGA_PROG_FEEDBACK
2403
2404		Enable printing of hash marks during FPGA configuration.
2405
2406		CONFIG_SYS_FPGA_CHECK_BUSY
2407
2408		Enable checks on FPGA configuration interface busy
2409		status by the configuration function. This option
2410		will require a board or device specific function to
2411		be written.
2412
2413		CONFIG_FPGA_DELAY
2414
2415		If defined, a function that provides delays in the FPGA
2416		configuration driver.
2417
2418		CONFIG_SYS_FPGA_CHECK_CTRLC
2419		Allow Control-C to interrupt FPGA configuration
2420
2421		CONFIG_SYS_FPGA_CHECK_ERROR
2422
2423		Check for configuration errors during FPGA bitfile
2424		loading. For example, abort during Virtex II
2425		configuration if the INIT_B line goes low (which
2426		indicated a CRC error).
2427
2428		CONFIG_SYS_FPGA_WAIT_INIT
2429
2430		Maximum time to wait for the INIT_B line to de-assert
2431		after PROB_B has been de-asserted during a Virtex II
2432		FPGA configuration sequence. The default time is 500
2433		ms.
2434
2435		CONFIG_SYS_FPGA_WAIT_BUSY
2436
2437		Maximum time to wait for BUSY to de-assert during
2438		Virtex II FPGA configuration. The default is 5 ms.
2439
2440		CONFIG_SYS_FPGA_WAIT_CONFIG
2441
2442		Time to wait after FPGA configuration. The default is
2443		200 ms.
2444
2445- Configuration Management:
2446		CONFIG_BUILD_TARGET
2447
2448		Some SoCs need special image types (e.g. U-Boot binary
2449		with a special header) as build targets. By defining
2450		CONFIG_BUILD_TARGET in the SoC / board header, this
2451		special image will be automatically built upon calling
2452		make / buildman.
2453
2454		CONFIG_IDENT_STRING
2455
2456		If defined, this string will be added to the U-Boot
2457		version information (U_BOOT_VERSION)
2458
2459- Vendor Parameter Protection:
2460
2461		U-Boot considers the values of the environment
2462		variables "serial#" (Board Serial Number) and
2463		"ethaddr" (Ethernet Address) to be parameters that
2464		are set once by the board vendor / manufacturer, and
2465		protects these variables from casual modification by
2466		the user. Once set, these variables are read-only,
2467		and write or delete attempts are rejected. You can
2468		change this behaviour:
2469
2470		If CONFIG_ENV_OVERWRITE is #defined in your config
2471		file, the write protection for vendor parameters is
2472		completely disabled. Anybody can change or delete
2473		these parameters.
2474
2475		Alternatively, if you define _both_ an ethaddr in the
2476		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2477		Ethernet address is installed in the environment,
2478		which can be changed exactly ONCE by the user. [The
2479		serial# is unaffected by this, i. e. it remains
2480		read-only.]
2481
2482		The same can be accomplished in a more flexible way
2483		for any variable by configuring the type of access
2484		to allow for those variables in the ".flags" variable
2485		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2486
2487- Protected RAM:
2488		CONFIG_PRAM
2489
2490		Define this variable to enable the reservation of
2491		"protected RAM", i. e. RAM which is not overwritten
2492		by U-Boot. Define CONFIG_PRAM to hold the number of
2493		kB you want to reserve for pRAM. You can overwrite
2494		this default value by defining an environment
2495		variable "pram" to the number of kB you want to
2496		reserve. Note that the board info structure will
2497		still show the full amount of RAM. If pRAM is
2498		reserved, a new environment variable "mem" will
2499		automatically be defined to hold the amount of
2500		remaining RAM in a form that can be passed as boot
2501		argument to Linux, for instance like that:
2502
2503			setenv bootargs ... mem=\${mem}
2504			saveenv
2505
2506		This way you can tell Linux not to use this memory,
2507		either, which results in a memory region that will
2508		not be affected by reboots.
2509
2510		*WARNING* If your board configuration uses automatic
2511		detection of the RAM size, you must make sure that
2512		this memory test is non-destructive. So far, the
2513		following board configurations are known to be
2514		"pRAM-clean":
2515
2516			IVMS8, IVML24, SPD8xx, TQM8xxL,
2517			HERMES, IP860, RPXlite, LWMON,
2518			FLAGADM, TQM8260
2519
2520- Access to physical memory region (> 4GB)
2521		Some basic support is provided for operations on memory not
2522		normally accessible to U-Boot - e.g. some architectures
2523		support access to more than 4GB of memory on 32-bit
2524		machines using physical address extension or similar.
2525		Define CONFIG_PHYSMEM to access this basic support, which
2526		currently only supports clearing the memory.
2527
2528- Error Recovery:
2529		CONFIG_PANIC_HANG
2530
2531		Define this variable to stop the system in case of a
2532		fatal error, so that you have to reset it manually.
2533		This is probably NOT a good idea for an embedded
2534		system where you want the system to reboot
2535		automatically as fast as possible, but it may be
2536		useful during development since you can try to debug
2537		the conditions that lead to the situation.
2538
2539		CONFIG_NET_RETRY_COUNT
2540
2541		This variable defines the number of retries for
2542		network operations like ARP, RARP, TFTP, or BOOTP
2543		before giving up the operation. If not defined, a
2544		default value of 5 is used.
2545
2546		CONFIG_ARP_TIMEOUT
2547
2548		Timeout waiting for an ARP reply in milliseconds.
2549
2550		CONFIG_NFS_TIMEOUT
2551
2552		Timeout in milliseconds used in NFS protocol.
2553		If you encounter "ERROR: Cannot umount" in nfs command,
2554		try longer timeout such as
2555		#define CONFIG_NFS_TIMEOUT 10000UL
2556
2557- Command Interpreter:
2558		CONFIG_AUTO_COMPLETE
2559
2560		Enable auto completion of commands using TAB.
2561
2562		CONFIG_SYS_PROMPT_HUSH_PS2
2563
2564		This defines the secondary prompt string, which is
2565		printed when the command interpreter needs more input
2566		to complete a command. Usually "> ".
2567
2568	Note:
2569
2570		In the current implementation, the local variables
2571		space and global environment variables space are
2572		separated. Local variables are those you define by
2573		simply typing `name=value'. To access a local
2574		variable later on, you have write `$name' or
2575		`${name}'; to execute the contents of a variable
2576		directly type `$name' at the command prompt.
2577
2578		Global environment variables are those you use
2579		setenv/printenv to work with. To run a command stored
2580		in such a variable, you need to use the run command,
2581		and you must not use the '$' sign to access them.
2582
2583		To store commands and special characters in a
2584		variable, please use double quotation marks
2585		surrounding the whole text of the variable, instead
2586		of the backslashes before semicolons and special
2587		symbols.
2588
2589- Command Line Editing and History:
2590		CONFIG_CMDLINE_EDITING
2591
2592		Enable editing and History functions for interactive
2593		command line input operations
2594
2595- Command Line PS1/PS2 support:
2596		CONFIG_CMDLINE_PS_SUPPORT
2597
2598		Enable support for changing the command prompt string
2599		at run-time. Only static string is supported so far.
2600		The string is obtained from environment variables PS1
2601		and PS2.
2602
2603- Default Environment:
2604		CONFIG_EXTRA_ENV_SETTINGS
2605
2606		Define this to contain any number of null terminated
2607		strings (variable = value pairs) that will be part of
2608		the default environment compiled into the boot image.
2609
2610		For example, place something like this in your
2611		board's config file:
2612
2613		#define CONFIG_EXTRA_ENV_SETTINGS \
2614			"myvar1=value1\0" \
2615			"myvar2=value2\0"
2616
2617		Warning: This method is based on knowledge about the
2618		internal format how the environment is stored by the
2619		U-Boot code. This is NOT an official, exported
2620		interface! Although it is unlikely that this format
2621		will change soon, there is no guarantee either.
2622		You better know what you are doing here.
2623
2624		Note: overly (ab)use of the default environment is
2625		discouraged. Make sure to check other ways to preset
2626		the environment like the "source" command or the
2627		boot command first.
2628
2629		CONFIG_ENV_VARS_UBOOT_CONFIG
2630
2631		Define this in order to add variables describing the
2632		U-Boot build configuration to the default environment.
2633		These will be named arch, cpu, board, vendor, and soc.
2634
2635		Enabling this option will cause the following to be defined:
2636
2637		- CONFIG_SYS_ARCH
2638		- CONFIG_SYS_CPU
2639		- CONFIG_SYS_BOARD
2640		- CONFIG_SYS_VENDOR
2641		- CONFIG_SYS_SOC
2642
2643		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2644
2645		Define this in order to add variables describing certain
2646		run-time determined information about the hardware to the
2647		environment.  These will be named board_name, board_rev.
2648
2649		CONFIG_DELAY_ENVIRONMENT
2650
2651		Normally the environment is loaded when the board is
2652		initialised so that it is available to U-Boot. This inhibits
2653		that so that the environment is not available until
2654		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2655		this is instead controlled by the value of
2656		/config/load-environment.
2657
2658- DataFlash Support:
2659		CONFIG_HAS_DATAFLASH
2660
2661		Defining this option enables DataFlash features and
2662		allows to read/write in Dataflash via the standard
2663		commands cp, md...
2664
2665- Serial Flash support
2666		CONFIG_CMD_SF
2667
2668		Defining this option enables SPI flash commands
2669		'sf probe/read/write/erase/update'.
2670
2671		Usage requires an initial 'probe' to define the serial
2672		flash parameters, followed by read/write/erase/update
2673		commands.
2674
2675		The following defaults may be provided by the platform
2676		to handle the common case when only a single serial
2677		flash is present on the system.
2678
2679		CONFIG_SF_DEFAULT_BUS		Bus identifier
2680		CONFIG_SF_DEFAULT_CS		Chip-select
2681		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2682		CONFIG_SF_DEFAULT_SPEED		in Hz
2683
2684		CONFIG_CMD_SF_TEST
2685
2686		Define this option to include a destructive SPI flash
2687		test ('sf test').
2688
2689		CONFIG_SF_DUAL_FLASH		Dual flash memories
2690
2691		Define this option to use dual flash support where two flash
2692		memories can be connected with a given cs line.
2693		Currently Xilinx Zynq qspi supports these type of connections.
2694
2695- SystemACE Support:
2696		CONFIG_SYSTEMACE
2697
2698		Adding this option adds support for Xilinx SystemACE
2699		chips attached via some sort of local bus. The address
2700		of the chip must also be defined in the
2701		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2702
2703		#define CONFIG_SYSTEMACE
2704		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2705
2706		When SystemACE support is added, the "ace" device type
2707		becomes available to the fat commands, i.e. fatls.
2708
2709- TFTP Fixed UDP Port:
2710		CONFIG_TFTP_PORT
2711
2712		If this is defined, the environment variable tftpsrcp
2713		is used to supply the TFTP UDP source port value.
2714		If tftpsrcp isn't defined, the normal pseudo-random port
2715		number generator is used.
2716
2717		Also, the environment variable tftpdstp is used to supply
2718		the TFTP UDP destination port value.  If tftpdstp isn't
2719		defined, the normal port 69 is used.
2720
2721		The purpose for tftpsrcp is to allow a TFTP server to
2722		blindly start the TFTP transfer using the pre-configured
2723		target IP address and UDP port. This has the effect of
2724		"punching through" the (Windows XP) firewall, allowing
2725		the remainder of the TFTP transfer to proceed normally.
2726		A better solution is to properly configure the firewall,
2727		but sometimes that is not allowed.
2728
2729- Hashing support:
2730		CONFIG_CMD_HASH
2731
2732		This enables a generic 'hash' command which can produce
2733		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2734
2735		CONFIG_HASH_VERIFY
2736
2737		Enable the hash verify command (hash -v). This adds to code
2738		size a little.
2739
2740		Note: There is also a sha1sum command, which should perhaps
2741		be deprecated in favour of 'hash sha1'.
2742
2743- Freescale i.MX specific commands:
2744		CONFIG_CMD_HDMIDETECT
2745		This enables 'hdmidet' command which returns true if an
2746		HDMI monitor is detected.  This command is i.MX 6 specific.
2747
2748- bootcount support:
2749		CONFIG_BOOTCOUNT_LIMIT
2750
2751		This enables the bootcounter support, see:
2752		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2753
2754		CONFIG_AT91SAM9XE
2755		enable special bootcounter support on at91sam9xe based boards.
2756		CONFIG_SOC_DA8XX
2757		enable special bootcounter support on da850 based boards.
2758		CONFIG_BOOTCOUNT_RAM
2759		enable support for the bootcounter in RAM
2760		CONFIG_BOOTCOUNT_I2C
2761		enable support for the bootcounter on an i2c (like RTC) device.
2762			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2763			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2764						    the bootcounter.
2765			CONFIG_BOOTCOUNT_ALEN = address len
2766
2767- Show boot progress:
2768		CONFIG_SHOW_BOOT_PROGRESS
2769
2770		Defining this option allows to add some board-
2771		specific code (calling a user-provided function
2772		"show_boot_progress(int)") that enables you to show
2773		the system's boot progress on some display (for
2774		example, some LED's) on your board. At the moment,
2775		the following checkpoints are implemented:
2776
2777
2778Legacy uImage format:
2779
2780  Arg	Where			When
2781    1	common/cmd_bootm.c	before attempting to boot an image
2782   -1	common/cmd_bootm.c	Image header has bad	 magic number
2783    2	common/cmd_bootm.c	Image header has correct magic number
2784   -2	common/cmd_bootm.c	Image header has bad	 checksum
2785    3	common/cmd_bootm.c	Image header has correct checksum
2786   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2787    4	common/cmd_bootm.c	Image data   has correct checksum
2788   -4	common/cmd_bootm.c	Image is for unsupported architecture
2789    5	common/cmd_bootm.c	Architecture check OK
2790   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2791    6	common/cmd_bootm.c	Image Type check OK
2792   -6	common/cmd_bootm.c	gunzip uncompression error
2793   -7	common/cmd_bootm.c	Unimplemented compression type
2794    7	common/cmd_bootm.c	Uncompression OK
2795    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2796   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2797
2798    9	common/image.c		Start initial ramdisk verification
2799  -10	common/image.c		Ramdisk header has bad	   magic number
2800  -11	common/image.c		Ramdisk header has bad	   checksum
2801   10	common/image.c		Ramdisk header is OK
2802  -12	common/image.c		Ramdisk data   has bad	   checksum
2803   11	common/image.c		Ramdisk data   has correct checksum
2804   12	common/image.c		Ramdisk verification complete, start loading
2805  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2806   13	common/image.c		Start multifile image verification
2807   14	common/image.c		No initial ramdisk, no multifile, continue.
2808
2809   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2810
2811  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2812  -31	post/post.c		POST test failed, detected by post_output_backlog()
2813  -32	post/post.c		POST test failed, detected by post_run_single()
2814
2815   34	common/cmd_doc.c	before loading a Image from a DOC device
2816  -35	common/cmd_doc.c	Bad usage of "doc" command
2817   35	common/cmd_doc.c	correct usage of "doc" command
2818  -36	common/cmd_doc.c	No boot device
2819   36	common/cmd_doc.c	correct boot device
2820  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2821   37	common/cmd_doc.c	correct chip ID found, device available
2822  -38	common/cmd_doc.c	Read Error on boot device
2823   38	common/cmd_doc.c	reading Image header from DOC device OK
2824  -39	common/cmd_doc.c	Image header has bad magic number
2825   39	common/cmd_doc.c	Image header has correct magic number
2826  -40	common/cmd_doc.c	Error reading Image from DOC device
2827   40	common/cmd_doc.c	Image header has correct magic number
2828   41	common/cmd_ide.c	before loading a Image from a IDE device
2829  -42	common/cmd_ide.c	Bad usage of "ide" command
2830   42	common/cmd_ide.c	correct usage of "ide" command
2831  -43	common/cmd_ide.c	No boot device
2832   43	common/cmd_ide.c	boot device found
2833  -44	common/cmd_ide.c	Device not available
2834   44	common/cmd_ide.c	Device available
2835  -45	common/cmd_ide.c	wrong partition selected
2836   45	common/cmd_ide.c	partition selected
2837  -46	common/cmd_ide.c	Unknown partition table
2838   46	common/cmd_ide.c	valid partition table found
2839  -47	common/cmd_ide.c	Invalid partition type
2840   47	common/cmd_ide.c	correct partition type
2841  -48	common/cmd_ide.c	Error reading Image Header on boot device
2842   48	common/cmd_ide.c	reading Image Header from IDE device OK
2843  -49	common/cmd_ide.c	Image header has bad magic number
2844   49	common/cmd_ide.c	Image header has correct magic number
2845  -50	common/cmd_ide.c	Image header has bad	 checksum
2846   50	common/cmd_ide.c	Image header has correct checksum
2847  -51	common/cmd_ide.c	Error reading Image from IDE device
2848   51	common/cmd_ide.c	reading Image from IDE device OK
2849   52	common/cmd_nand.c	before loading a Image from a NAND device
2850  -53	common/cmd_nand.c	Bad usage of "nand" command
2851   53	common/cmd_nand.c	correct usage of "nand" command
2852  -54	common/cmd_nand.c	No boot device
2853   54	common/cmd_nand.c	boot device found
2854  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2855   55	common/cmd_nand.c	correct chip ID found, device available
2856  -56	common/cmd_nand.c	Error reading Image Header on boot device
2857   56	common/cmd_nand.c	reading Image Header from NAND device OK
2858  -57	common/cmd_nand.c	Image header has bad magic number
2859   57	common/cmd_nand.c	Image header has correct magic number
2860  -58	common/cmd_nand.c	Error reading Image from NAND device
2861   58	common/cmd_nand.c	reading Image from NAND device OK
2862
2863  -60	common/env_common.c	Environment has a bad CRC, using default
2864
2865   64	net/eth.c		starting with Ethernet configuration.
2866  -64	net/eth.c		no Ethernet found.
2867   65	net/eth.c		Ethernet found.
2868
2869  -80	common/cmd_net.c	usage wrong
2870   80	common/cmd_net.c	before calling net_loop()
2871  -81	common/cmd_net.c	some error in net_loop() occurred
2872   81	common/cmd_net.c	net_loop() back without error
2873  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2874   82	common/cmd_net.c	trying automatic boot
2875   83	common/cmd_net.c	running "source" command
2876  -83	common/cmd_net.c	some error in automatic boot or "source" command
2877   84	common/cmd_net.c	end without errors
2878
2879FIT uImage format:
2880
2881  Arg	Where			When
2882  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2883 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2884  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2885 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2886  102	common/cmd_bootm.c	Kernel unit name specified
2887 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2888  103	common/cmd_bootm.c	Found configuration node
2889  104	common/cmd_bootm.c	Got kernel subimage node offset
2890 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2891  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2892 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2893  106	common/cmd_bootm.c	Architecture check OK
2894 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2895  107	common/cmd_bootm.c	Kernel subimage type OK
2896 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2897  108	common/cmd_bootm.c	Got kernel subimage data/size
2898 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2899 -109	common/cmd_bootm.c	Can't get kernel subimage type
2900 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2901 -111	common/cmd_bootm.c	Can't get kernel subimage os
2902 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2903 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2904
2905  120	common/image.c		Start initial ramdisk verification
2906 -120	common/image.c		Ramdisk FIT image has incorrect format
2907  121	common/image.c		Ramdisk FIT image has correct format
2908  122	common/image.c		No ramdisk subimage unit name, using configuration
2909 -122	common/image.c		Can't get configuration for ramdisk subimage
2910  123	common/image.c		Ramdisk unit name specified
2911 -124	common/image.c		Can't get ramdisk subimage node offset
2912  125	common/image.c		Got ramdisk subimage node offset
2913 -125	common/image.c		Ramdisk subimage hash verification failed
2914  126	common/image.c		Ramdisk subimage hash verification OK
2915 -126	common/image.c		Ramdisk subimage for unsupported architecture
2916  127	common/image.c		Architecture check OK
2917 -127	common/image.c		Can't get ramdisk subimage data/size
2918  128	common/image.c		Got ramdisk subimage data/size
2919  129	common/image.c		Can't get ramdisk load address
2920 -129	common/image.c		Got ramdisk load address
2921
2922 -130	common/cmd_doc.c	Incorrect FIT image format
2923  131	common/cmd_doc.c	FIT image format OK
2924
2925 -140	common/cmd_ide.c	Incorrect FIT image format
2926  141	common/cmd_ide.c	FIT image format OK
2927
2928 -150	common/cmd_nand.c	Incorrect FIT image format
2929  151	common/cmd_nand.c	FIT image format OK
2930
2931- legacy image format:
2932		CONFIG_IMAGE_FORMAT_LEGACY
2933		enables the legacy image format support in U-Boot.
2934
2935		Default:
2936		enabled if CONFIG_FIT_SIGNATURE is not defined.
2937
2938		CONFIG_DISABLE_IMAGE_LEGACY
2939		disable the legacy image format
2940
2941		This define is introduced, as the legacy image format is
2942		enabled per default for backward compatibility.
2943
2944- Standalone program support:
2945		CONFIG_STANDALONE_LOAD_ADDR
2946
2947		This option defines a board specific value for the
2948		address where standalone program gets loaded, thus
2949		overwriting the architecture dependent default
2950		settings.
2951
2952- Frame Buffer Address:
2953		CONFIG_FB_ADDR
2954
2955		Define CONFIG_FB_ADDR if you want to use specific
2956		address for frame buffer.  This is typically the case
2957		when using a graphics controller has separate video
2958		memory.  U-Boot will then place the frame buffer at
2959		the given address instead of dynamically reserving it
2960		in system RAM by calling lcd_setmem(), which grabs
2961		the memory for the frame buffer depending on the
2962		configured panel size.
2963
2964		Please see board_init_f function.
2965
2966- Automatic software updates via TFTP server
2967		CONFIG_UPDATE_TFTP
2968		CONFIG_UPDATE_TFTP_CNT_MAX
2969		CONFIG_UPDATE_TFTP_MSEC_MAX
2970
2971		These options enable and control the auto-update feature;
2972		for a more detailed description refer to doc/README.update.
2973
2974- MTD Support (mtdparts command, UBI support)
2975		CONFIG_MTD_DEVICE
2976
2977		Adds the MTD device infrastructure from the Linux kernel.
2978		Needed for mtdparts command support.
2979
2980		CONFIG_MTD_PARTITIONS
2981
2982		Adds the MTD partitioning infrastructure from the Linux
2983		kernel. Needed for UBI support.
2984
2985- UBI support
2986		CONFIG_CMD_UBI
2987
2988		Adds commands for interacting with MTD partitions formatted
2989		with the UBI flash translation layer
2990
2991		Requires also defining CONFIG_RBTREE
2992
2993		CONFIG_UBI_SILENCE_MSG
2994
2995		Make the verbose messages from UBI stop printing.  This leaves
2996		warnings and errors enabled.
2997
2998
2999		CONFIG_MTD_UBI_WL_THRESHOLD
3000		This parameter defines the maximum difference between the highest
3001		erase counter value and the lowest erase counter value of eraseblocks
3002		of UBI devices. When this threshold is exceeded, UBI starts performing
3003		wear leveling by means of moving data from eraseblock with low erase
3004		counter to eraseblocks with high erase counter.
3005
3006		The default value should be OK for SLC NAND flashes, NOR flashes and
3007		other flashes which have eraseblock life-cycle 100000 or more.
3008		However, in case of MLC NAND flashes which typically have eraseblock
3009		life-cycle less than 10000, the threshold should be lessened (e.g.,
3010		to 128 or 256, although it does not have to be power of 2).
3011
3012		default: 4096
3013
3014		CONFIG_MTD_UBI_BEB_LIMIT
3015		This option specifies the maximum bad physical eraseblocks UBI
3016		expects on the MTD device (per 1024 eraseblocks). If the
3017		underlying flash does not admit of bad eraseblocks (e.g. NOR
3018		flash), this value is ignored.
3019
3020		NAND datasheets often specify the minimum and maximum NVM
3021		(Number of Valid Blocks) for the flashes' endurance lifetime.
3022		The maximum expected bad eraseblocks per 1024 eraseblocks
3023		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3024		which gives 20 for most NANDs (MaxNVB is basically the total
3025		count of eraseblocks on the chip).
3026
3027		To put it differently, if this value is 20, UBI will try to
3028		reserve about 1.9% of physical eraseblocks for bad blocks
3029		handling. And that will be 1.9% of eraseblocks on the entire
3030		NAND chip, not just the MTD partition UBI attaches. This means
3031		that if you have, say, a NAND flash chip admits maximum 40 bad
3032		eraseblocks, and it is split on two MTD partitions of the same
3033		size, UBI will reserve 40 eraseblocks when attaching a
3034		partition.
3035
3036		default: 20
3037
3038		CONFIG_MTD_UBI_FASTMAP
3039		Fastmap is a mechanism which allows attaching an UBI device
3040		in nearly constant time. Instead of scanning the whole MTD device it
3041		only has to locate a checkpoint (called fastmap) on the device.
3042		The on-flash fastmap contains all information needed to attach
3043		the device. Using fastmap makes only sense on large devices where
3044		attaching by scanning takes long. UBI will not automatically install
3045		a fastmap on old images, but you can set the UBI parameter
3046		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3047		that fastmap-enabled images are still usable with UBI implementations
3048		without	fastmap support. On typical flash devices the whole fastmap
3049		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3050
3051		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3052		Set this parameter to enable fastmap automatically on images
3053		without a fastmap.
3054		default: 0
3055
3056		CONFIG_MTD_UBI_FM_DEBUG
3057		Enable UBI fastmap debug
3058		default: 0
3059
3060- UBIFS support
3061		CONFIG_CMD_UBIFS
3062
3063		Adds commands for interacting with UBI volumes formatted as
3064		UBIFS.  UBIFS is read-only in u-boot.
3065
3066		Requires UBI support as well as CONFIG_LZO
3067
3068		CONFIG_UBIFS_SILENCE_MSG
3069
3070		Make the verbose messages from UBIFS stop printing.  This leaves
3071		warnings and errors enabled.
3072
3073- SPL framework
3074		CONFIG_SPL
3075		Enable building of SPL globally.
3076
3077		CONFIG_SPL_LDSCRIPT
3078		LDSCRIPT for linking the SPL binary.
3079
3080		CONFIG_SPL_MAX_FOOTPRINT
3081		Maximum size in memory allocated to the SPL, BSS included.
3082		When defined, the linker checks that the actual memory
3083		used by SPL from _start to __bss_end does not exceed it.
3084		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3085		must not be both defined at the same time.
3086
3087		CONFIG_SPL_MAX_SIZE
3088		Maximum size of the SPL image (text, data, rodata, and
3089		linker lists sections), BSS excluded.
3090		When defined, the linker checks that the actual size does
3091		not exceed it.
3092
3093		CONFIG_SPL_TEXT_BASE
3094		TEXT_BASE for linking the SPL binary.
3095
3096		CONFIG_SPL_RELOC_TEXT_BASE
3097		Address to relocate to.  If unspecified, this is equal to
3098		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3099
3100		CONFIG_SPL_BSS_START_ADDR
3101		Link address for the BSS within the SPL binary.
3102
3103		CONFIG_SPL_BSS_MAX_SIZE
3104		Maximum size in memory allocated to the SPL BSS.
3105		When defined, the linker checks that the actual memory used
3106		by SPL from __bss_start to __bss_end does not exceed it.
3107		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3108		must not be both defined at the same time.
3109
3110		CONFIG_SPL_STACK
3111		Adress of the start of the stack SPL will use
3112
3113		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3114		When defined, SPL will panic() if the image it has
3115		loaded does not have a signature.
3116		Defining this is useful when code which loads images
3117		in SPL cannot guarantee that absolutely all read errors
3118		will be caught.
3119		An example is the LPC32XX MLC NAND driver, which will
3120		consider that a completely unreadable NAND block is bad,
3121		and thus should be skipped silently.
3122
3123		CONFIG_SPL_RELOC_STACK
3124		Adress of the start of the stack SPL will use after
3125		relocation.  If unspecified, this is equal to
3126		CONFIG_SPL_STACK.
3127
3128		CONFIG_SYS_SPL_MALLOC_START
3129		Starting address of the malloc pool used in SPL.
3130		When this option is set the full malloc is used in SPL and
3131		it is set up by spl_init() and before that, the simple malloc()
3132		can be used if CONFIG_SYS_MALLOC_F is defined.
3133
3134		CONFIG_SYS_SPL_MALLOC_SIZE
3135		The size of the malloc pool used in SPL.
3136
3137		CONFIG_SPL_FRAMEWORK
3138		Enable the SPL framework under common/.  This framework
3139		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3140		NAND loading of the Linux Kernel.
3141
3142		CONFIG_SPL_OS_BOOT
3143		Enable booting directly to an OS from SPL.
3144		See also: doc/README.falcon
3145
3146		CONFIG_SPL_DISPLAY_PRINT
3147		For ARM, enable an optional function to print more information
3148		about the running system.
3149
3150		CONFIG_SPL_INIT_MINIMAL
3151		Arch init code should be built for a very small image
3152
3153		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3154		Partition on the MMC to load U-Boot from when the MMC is being
3155		used in raw mode
3156
3157		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3158		Sector to load kernel uImage from when MMC is being
3159		used in raw mode (for Falcon mode)
3160
3161		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3162		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3163		Sector and number of sectors to load kernel argument
3164		parameters from when MMC is being used in raw mode
3165		(for falcon mode)
3166
3167		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3168		Partition on the MMC to load U-Boot from when the MMC is being
3169		used in fs mode
3170
3171		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3172		Filename to read to load U-Boot when reading from filesystem
3173
3174		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3175		Filename to read to load kernel uImage when reading
3176		from filesystem (for Falcon mode)
3177
3178		CONFIG_SPL_FS_LOAD_ARGS_NAME
3179		Filename to read to load kernel argument parameters
3180		when reading from filesystem (for Falcon mode)
3181
3182		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3183		Set this for NAND SPL on PPC mpc83xx targets, so that
3184		start.S waits for the rest of the SPL to load before
3185		continuing (the hardware starts execution after just
3186		loading the first page rather than the full 4K).
3187
3188		CONFIG_SPL_SKIP_RELOCATE
3189		Avoid SPL relocation
3190
3191		CONFIG_SPL_NAND_BASE
3192		Include nand_base.c in the SPL.  Requires
3193		CONFIG_SPL_NAND_DRIVERS.
3194
3195		CONFIG_SPL_NAND_DRIVERS
3196		SPL uses normal NAND drivers, not minimal drivers.
3197
3198		CONFIG_SPL_NAND_ECC
3199		Include standard software ECC in the SPL
3200
3201		CONFIG_SPL_NAND_SIMPLE
3202		Support for NAND boot using simple NAND drivers that
3203		expose the cmd_ctrl() interface.
3204
3205		CONFIG_SPL_UBI
3206		Support for a lightweight UBI (fastmap) scanner and
3207		loader
3208
3209		CONFIG_SPL_NAND_RAW_ONLY
3210		Support to boot only raw u-boot.bin images. Use this only
3211		if you need to save space.
3212
3213		CONFIG_SPL_COMMON_INIT_DDR
3214		Set for common ddr init with serial presence detect in
3215		SPL binary.
3216
3217		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3218		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3219		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3220		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3221		CONFIG_SYS_NAND_ECCBYTES
3222		Defines the size and behavior of the NAND that SPL uses
3223		to read U-Boot
3224
3225		CONFIG_SPL_NAND_BOOT
3226		Add support NAND boot
3227
3228		CONFIG_SYS_NAND_U_BOOT_OFFS
3229		Location in NAND to read U-Boot from
3230
3231		CONFIG_SYS_NAND_U_BOOT_DST
3232		Location in memory to load U-Boot to
3233
3234		CONFIG_SYS_NAND_U_BOOT_SIZE
3235		Size of image to load
3236
3237		CONFIG_SYS_NAND_U_BOOT_START
3238		Entry point in loaded image to jump to
3239
3240		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3241		Define this if you need to first read the OOB and then the
3242		data. This is used, for example, on davinci platforms.
3243
3244		CONFIG_SPL_OMAP3_ID_NAND
3245		Support for an OMAP3-specific set of functions to return the
3246		ID and MFR of the first attached NAND chip, if present.
3247
3248		CONFIG_SPL_RAM_DEVICE
3249		Support for running image already present in ram, in SPL binary
3250
3251		CONFIG_SPL_PAD_TO
3252		Image offset to which the SPL should be padded before appending
3253		the SPL payload. By default, this is defined as
3254		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3255		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3256		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3257
3258		CONFIG_SPL_TARGET
3259		Final target image containing SPL and payload.  Some SPLs
3260		use an arch-specific makefile fragment instead, for
3261		example if more than one image needs to be produced.
3262
3263		CONFIG_FIT_SPL_PRINT
3264		Printing information about a FIT image adds quite a bit of
3265		code to SPL. So this is normally disabled in SPL. Use this
3266		option to re-enable it. This will affect the output of the
3267		bootm command when booting a FIT image.
3268
3269- TPL framework
3270		CONFIG_TPL
3271		Enable building of TPL globally.
3272
3273		CONFIG_TPL_PAD_TO
3274		Image offset to which the TPL should be padded before appending
3275		the TPL payload. By default, this is defined as
3276		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3277		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3278		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3279
3280- Interrupt support (PPC):
3281
3282		There are common interrupt_init() and timer_interrupt()
3283		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3284		for CPU specific initialization. interrupt_init_cpu()
3285		should set decrementer_count to appropriate value. If
3286		CPU resets decrementer automatically after interrupt
3287		(ppc4xx) it should set decrementer_count to zero.
3288		timer_interrupt() calls timer_interrupt_cpu() for CPU
3289		specific handling. If board has watchdog / status_led
3290		/ other_activity_monitor it works automatically from
3291		general timer_interrupt().
3292
3293
3294Board initialization settings:
3295------------------------------
3296
3297During Initialization u-boot calls a number of board specific functions
3298to allow the preparation of board specific prerequisites, e.g. pin setup
3299before drivers are initialized. To enable these callbacks the
3300following configuration macros have to be defined. Currently this is
3301architecture specific, so please check arch/your_architecture/lib/board.c
3302typically in board_init_f() and board_init_r().
3303
3304- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3305- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3306- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3307- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3308
3309Configuration Settings:
3310-----------------------
3311
3312- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3313		Optionally it can be defined to support 64-bit memory commands.
3314
3315- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3316		undefine this when you're short of memory.
3317
3318- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3319		width of the commands listed in the 'help' command output.
3320
3321- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3322		prompt for user input.
3323
3324- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3325
3326- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3327
3328- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3329
3330- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3331		the application (usually a Linux kernel) when it is
3332		booted
3333
3334- CONFIG_SYS_BAUDRATE_TABLE:
3335		List of legal baudrate settings for this board.
3336
3337- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3338		Begin and End addresses of the area used by the
3339		simple memory test.
3340
3341- CONFIG_SYS_ALT_MEMTEST:
3342		Enable an alternate, more extensive memory test.
3343
3344- CONFIG_SYS_MEMTEST_SCRATCH:
3345		Scratch address used by the alternate memory test
3346		You only need to set this if address zero isn't writeable
3347
3348- CONFIG_SYS_MEM_RESERVE_SECURE
3349		Only implemented for ARMv8 for now.
3350		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
3351		is substracted from total RAM and won't be reported to OS.
3352		This memory can be used as secure memory. A variable
3353		gd->arch.secure_ram is used to track the location. In systems
3354		the RAM base is not zero, or RAM is divided into banks,
3355		this variable needs to be recalcuated to get the address.
3356
3357- CONFIG_SYS_MEM_TOP_HIDE:
3358		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3359		this specified memory area will get subtracted from the top
3360		(end) of RAM and won't get "touched" at all by U-Boot. By
3361		fixing up gd->ram_size the Linux kernel should gets passed
3362		the now "corrected" memory size and won't touch it either.
3363		This should work for arch/ppc and arch/powerpc. Only Linux
3364		board ports in arch/powerpc with bootwrapper support that
3365		recalculate the memory size from the SDRAM controller setup
3366		will have to get fixed in Linux additionally.
3367
3368		This option can be used as a workaround for the 440EPx/GRx
3369		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3370		be touched.
3371
3372		WARNING: Please make sure that this value is a multiple of
3373		the Linux page size (normally 4k). If this is not the case,
3374		then the end address of the Linux memory will be located at a
3375		non page size aligned address and this could cause major
3376		problems.
3377
3378- CONFIG_SYS_LOADS_BAUD_CHANGE:
3379		Enable temporary baudrate change while serial download
3380
3381- CONFIG_SYS_SDRAM_BASE:
3382		Physical start address of SDRAM. _Must_ be 0 here.
3383
3384- CONFIG_SYS_FLASH_BASE:
3385		Physical start address of Flash memory.
3386
3387- CONFIG_SYS_MONITOR_BASE:
3388		Physical start address of boot monitor code (set by
3389		make config files to be same as the text base address
3390		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3391		CONFIG_SYS_FLASH_BASE when booting from flash.
3392
3393- CONFIG_SYS_MONITOR_LEN:
3394		Size of memory reserved for monitor code, used to
3395		determine _at_compile_time_ (!) if the environment is
3396		embedded within the U-Boot image, or in a separate
3397		flash sector.
3398
3399- CONFIG_SYS_MALLOC_LEN:
3400		Size of DRAM reserved for malloc() use.
3401
3402- CONFIG_SYS_MALLOC_F_LEN
3403		Size of the malloc() pool for use before relocation. If
3404		this is defined, then a very simple malloc() implementation
3405		will become available before relocation. The address is just
3406		below the global data, and the stack is moved down to make
3407		space.
3408
3409		This feature allocates regions with increasing addresses
3410		within the region. calloc() is supported, but realloc()
3411		is not available. free() is supported but does nothing.
3412		The memory will be freed (or in fact just forgotten) when
3413		U-Boot relocates itself.
3414
3415- CONFIG_SYS_MALLOC_SIMPLE
3416		Provides a simple and small malloc() and calloc() for those
3417		boards which do not use the full malloc in SPL (which is
3418		enabled with CONFIG_SYS_SPL_MALLOC_START).
3419
3420- CONFIG_SYS_NONCACHED_MEMORY:
3421		Size of non-cached memory area. This area of memory will be
3422		typically located right below the malloc() area and mapped
3423		uncached in the MMU. This is useful for drivers that would
3424		otherwise require a lot of explicit cache maintenance. For
3425		some drivers it's also impossible to properly maintain the
3426		cache. For example if the regions that need to be flushed
3427		are not a multiple of the cache-line size, *and* padding
3428		cannot be allocated between the regions to align them (i.e.
3429		if the HW requires a contiguous array of regions, and the
3430		size of each region is not cache-aligned), then a flush of
3431		one region may result in overwriting data that hardware has
3432		written to another region in the same cache-line. This can
3433		happen for example in network drivers where descriptors for
3434		buffers are typically smaller than the CPU cache-line (e.g.
3435		16 bytes vs. 32 or 64 bytes).
3436
3437		Non-cached memory is only supported on 32-bit ARM at present.
3438
3439- CONFIG_SYS_BOOTM_LEN:
3440		Normally compressed uImages are limited to an
3441		uncompressed size of 8 MBytes. If this is not enough,
3442		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3443		to adjust this setting to your needs.
3444
3445- CONFIG_SYS_BOOTMAPSZ:
3446		Maximum size of memory mapped by the startup code of
3447		the Linux kernel; all data that must be processed by
3448		the Linux kernel (bd_info, boot arguments, FDT blob if
3449		used) must be put below this limit, unless "bootm_low"
3450		environment variable is defined and non-zero. In such case
3451		all data for the Linux kernel must be between "bootm_low"
3452		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3453		variable "bootm_mapsize" will override the value of
3454		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3455		then the value in "bootm_size" will be used instead.
3456
3457- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3458		Enable initrd_high functionality.  If defined then the
3459		initrd_high feature is enabled and the bootm ramdisk subcommand
3460		is enabled.
3461
3462- CONFIG_SYS_BOOT_GET_CMDLINE:
3463		Enables allocating and saving kernel cmdline in space between
3464		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3465
3466- CONFIG_SYS_BOOT_GET_KBD:
3467		Enables allocating and saving a kernel copy of the bd_info in
3468		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3469
3470- CONFIG_SYS_MAX_FLASH_BANKS:
3471		Max number of Flash memory banks
3472
3473- CONFIG_SYS_MAX_FLASH_SECT:
3474		Max number of sectors on a Flash chip
3475
3476- CONFIG_SYS_FLASH_ERASE_TOUT:
3477		Timeout for Flash erase operations (in ms)
3478
3479- CONFIG_SYS_FLASH_WRITE_TOUT:
3480		Timeout for Flash write operations (in ms)
3481
3482- CONFIG_SYS_FLASH_LOCK_TOUT
3483		Timeout for Flash set sector lock bit operation (in ms)
3484
3485- CONFIG_SYS_FLASH_UNLOCK_TOUT
3486		Timeout for Flash clear lock bits operation (in ms)
3487
3488- CONFIG_SYS_FLASH_PROTECTION
3489		If defined, hardware flash sectors protection is used
3490		instead of U-Boot software protection.
3491
3492- CONFIG_SYS_DIRECT_FLASH_TFTP:
3493
3494		Enable TFTP transfers directly to flash memory;
3495		without this option such a download has to be
3496		performed in two steps: (1) download to RAM, and (2)
3497		copy from RAM to flash.
3498
3499		The two-step approach is usually more reliable, since
3500		you can check if the download worked before you erase
3501		the flash, but in some situations (when system RAM is
3502		too limited to allow for a temporary copy of the
3503		downloaded image) this option may be very useful.
3504
3505- CONFIG_SYS_FLASH_CFI:
3506		Define if the flash driver uses extra elements in the
3507		common flash structure for storing flash geometry.
3508
3509- CONFIG_FLASH_CFI_DRIVER
3510		This option also enables the building of the cfi_flash driver
3511		in the drivers directory
3512
3513- CONFIG_FLASH_CFI_MTD
3514		This option enables the building of the cfi_mtd driver
3515		in the drivers directory. The driver exports CFI flash
3516		to the MTD layer.
3517
3518- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3519		Use buffered writes to flash.
3520
3521- CONFIG_FLASH_SPANSION_S29WS_N
3522		s29ws-n MirrorBit flash has non-standard addresses for buffered
3523		write commands.
3524
3525- CONFIG_SYS_FLASH_QUIET_TEST
3526		If this option is defined, the common CFI flash doesn't
3527		print it's warning upon not recognized FLASH banks. This
3528		is useful, if some of the configured banks are only
3529		optionally available.
3530
3531- CONFIG_FLASH_SHOW_PROGRESS
3532		If defined (must be an integer), print out countdown
3533		digits and dots.  Recommended value: 45 (9..1) for 80
3534		column displays, 15 (3..1) for 40 column displays.
3535
3536- CONFIG_FLASH_VERIFY
3537		If defined, the content of the flash (destination) is compared
3538		against the source after the write operation. An error message
3539		will be printed when the contents are not identical.
3540		Please note that this option is useless in nearly all cases,
3541		since such flash programming errors usually are detected earlier
3542		while unprotecting/erasing/programming. Please only enable
3543		this option if you really know what you are doing.
3544
3545- CONFIG_SYS_RX_ETH_BUFFER:
3546		Defines the number of Ethernet receive buffers. On some
3547		Ethernet controllers it is recommended to set this value
3548		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3549		buffers can be full shortly after enabling the interface
3550		on high Ethernet traffic.
3551		Defaults to 4 if not defined.
3552
3553- CONFIG_ENV_MAX_ENTRIES
3554
3555	Maximum number of entries in the hash table that is used
3556	internally to store the environment settings. The default
3557	setting is supposed to be generous and should work in most
3558	cases. This setting can be used to tune behaviour; see
3559	lib/hashtable.c for details.
3560
3561- CONFIG_ENV_FLAGS_LIST_DEFAULT
3562- CONFIG_ENV_FLAGS_LIST_STATIC
3563	Enable validation of the values given to environment variables when
3564	calling env set.  Variables can be restricted to only decimal,
3565	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3566	the variables can also be restricted to IP address or MAC address.
3567
3568	The format of the list is:
3569		type_attribute = [s|d|x|b|i|m]
3570		access_attribute = [a|r|o|c]
3571		attributes = type_attribute[access_attribute]
3572		entry = variable_name[:attributes]
3573		list = entry[,list]
3574
3575	The type attributes are:
3576		s - String (default)
3577		d - Decimal
3578		x - Hexadecimal
3579		b - Boolean ([1yYtT|0nNfF])
3580		i - IP address
3581		m - MAC address
3582
3583	The access attributes are:
3584		a - Any (default)
3585		r - Read-only
3586		o - Write-once
3587		c - Change-default
3588
3589	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3590		Define this to a list (string) to define the ".flags"
3591		environment variable in the default or embedded environment.
3592
3593	- CONFIG_ENV_FLAGS_LIST_STATIC
3594		Define this to a list (string) to define validation that
3595		should be done if an entry is not found in the ".flags"
3596		environment variable.  To override a setting in the static
3597		list, simply add an entry for the same variable name to the
3598		".flags" variable.
3599
3600	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3601	regular expression. This allows multiple variables to define the same
3602	flags without explicitly listing them for each variable.
3603
3604- CONFIG_ENV_ACCESS_IGNORE_FORCE
3605	If defined, don't allow the -f switch to env set override variable
3606	access flags.
3607
3608- CONFIG_USE_STDINT
3609	If stdint.h is available with your toolchain you can define this
3610	option to enable it. You can provide option 'USE_STDINT=1' when
3611	building U-Boot to enable this.
3612
3613The following definitions that deal with the placement and management
3614of environment data (variable area); in general, we support the
3615following configurations:
3616
3617- CONFIG_BUILD_ENVCRC:
3618
3619	Builds up envcrc with the target environment so that external utils
3620	may easily extract it and embed it in final U-Boot images.
3621
3622- CONFIG_ENV_IS_IN_FLASH:
3623
3624	Define this if the environment is in flash memory.
3625
3626	a) The environment occupies one whole flash sector, which is
3627	   "embedded" in the text segment with the U-Boot code. This
3628	   happens usually with "bottom boot sector" or "top boot
3629	   sector" type flash chips, which have several smaller
3630	   sectors at the start or the end. For instance, such a
3631	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3632	   such a case you would place the environment in one of the
3633	   4 kB sectors - with U-Boot code before and after it. With
3634	   "top boot sector" type flash chips, you would put the
3635	   environment in one of the last sectors, leaving a gap
3636	   between U-Boot and the environment.
3637
3638	- CONFIG_ENV_OFFSET:
3639
3640	   Offset of environment data (variable area) to the
3641	   beginning of flash memory; for instance, with bottom boot
3642	   type flash chips the second sector can be used: the offset
3643	   for this sector is given here.
3644
3645	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3646
3647	- CONFIG_ENV_ADDR:
3648
3649	   This is just another way to specify the start address of
3650	   the flash sector containing the environment (instead of
3651	   CONFIG_ENV_OFFSET).
3652
3653	- CONFIG_ENV_SECT_SIZE:
3654
3655	   Size of the sector containing the environment.
3656
3657
3658	b) Sometimes flash chips have few, equal sized, BIG sectors.
3659	   In such a case you don't want to spend a whole sector for
3660	   the environment.
3661
3662	- CONFIG_ENV_SIZE:
3663
3664	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3665	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3666	   of this flash sector for the environment. This saves
3667	   memory for the RAM copy of the environment.
3668
3669	   It may also save flash memory if you decide to use this
3670	   when your environment is "embedded" within U-Boot code,
3671	   since then the remainder of the flash sector could be used
3672	   for U-Boot code. It should be pointed out that this is
3673	   STRONGLY DISCOURAGED from a robustness point of view:
3674	   updating the environment in flash makes it always
3675	   necessary to erase the WHOLE sector. If something goes
3676	   wrong before the contents has been restored from a copy in
3677	   RAM, your target system will be dead.
3678
3679	- CONFIG_ENV_ADDR_REDUND
3680	  CONFIG_ENV_SIZE_REDUND
3681
3682	   These settings describe a second storage area used to hold
3683	   a redundant copy of the environment data, so that there is
3684	   a valid backup copy in case there is a power failure during
3685	   a "saveenv" operation.
3686
3687BE CAREFUL! Any changes to the flash layout, and some changes to the
3688source code will make it necessary to adapt <board>/u-boot.lds*
3689accordingly!
3690
3691
3692- CONFIG_ENV_IS_IN_NVRAM:
3693
3694	Define this if you have some non-volatile memory device
3695	(NVRAM, battery buffered SRAM) which you want to use for the
3696	environment.
3697
3698	- CONFIG_ENV_ADDR:
3699	- CONFIG_ENV_SIZE:
3700
3701	  These two #defines are used to determine the memory area you
3702	  want to use for environment. It is assumed that this memory
3703	  can just be read and written to, without any special
3704	  provision.
3705
3706BE CAREFUL! The first access to the environment happens quite early
3707in U-Boot initialization (when we try to get the setting of for the
3708console baudrate). You *MUST* have mapped your NVRAM area then, or
3709U-Boot will hang.
3710
3711Please note that even with NVRAM we still use a copy of the
3712environment in RAM: we could work on NVRAM directly, but we want to
3713keep settings there always unmodified except somebody uses "saveenv"
3714to save the current settings.
3715
3716
3717- CONFIG_ENV_IS_IN_EEPROM:
3718
3719	Use this if you have an EEPROM or similar serial access
3720	device and a driver for it.
3721
3722	- CONFIG_ENV_OFFSET:
3723	- CONFIG_ENV_SIZE:
3724
3725	  These two #defines specify the offset and size of the
3726	  environment area within the total memory of your EEPROM.
3727
3728	- CONFIG_SYS_I2C_EEPROM_ADDR:
3729	  If defined, specified the chip address of the EEPROM device.
3730	  The default address is zero.
3731
3732	- CONFIG_SYS_I2C_EEPROM_BUS:
3733	  If defined, specified the i2c bus of the EEPROM device.
3734
3735	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3736	  If defined, the number of bits used to address bytes in a
3737	  single page in the EEPROM device.  A 64 byte page, for example
3738	  would require six bits.
3739
3740	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3741	  If defined, the number of milliseconds to delay between
3742	  page writes.	The default is zero milliseconds.
3743
3744	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3745	  The length in bytes of the EEPROM memory array address.  Note
3746	  that this is NOT the chip address length!
3747
3748	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3749	  EEPROM chips that implement "address overflow" are ones
3750	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3751	  address and the extra bits end up in the "chip address" bit
3752	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3753	  byte chips.
3754
3755	  Note that we consider the length of the address field to
3756	  still be one byte because the extra address bits are hidden
3757	  in the chip address.
3758
3759	- CONFIG_SYS_EEPROM_SIZE:
3760	  The size in bytes of the EEPROM device.
3761
3762	- CONFIG_ENV_EEPROM_IS_ON_I2C
3763	  define this, if you have I2C and SPI activated, and your
3764	  EEPROM, which holds the environment, is on the I2C bus.
3765
3766	- CONFIG_I2C_ENV_EEPROM_BUS
3767	  if you have an Environment on an EEPROM reached over
3768	  I2C muxes, you can define here, how to reach this
3769	  EEPROM. For example:
3770
3771	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3772
3773	  EEPROM which holds the environment, is reached over
3774	  a pca9547 i2c mux with address 0x70, channel 3.
3775
3776- CONFIG_ENV_IS_IN_DATAFLASH:
3777
3778	Define this if you have a DataFlash memory device which you
3779	want to use for the environment.
3780
3781	- CONFIG_ENV_OFFSET:
3782	- CONFIG_ENV_ADDR:
3783	- CONFIG_ENV_SIZE:
3784
3785	  These three #defines specify the offset and size of the
3786	  environment area within the total memory of your DataFlash placed
3787	  at the specified address.
3788
3789- CONFIG_ENV_IS_IN_SPI_FLASH:
3790
3791	Define this if you have a SPI Flash memory device which you
3792	want to use for the environment.
3793
3794	- CONFIG_ENV_OFFSET:
3795	- CONFIG_ENV_SIZE:
3796
3797	  These two #defines specify the offset and size of the
3798	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
3799	  aligned to an erase sector boundary.
3800
3801	- CONFIG_ENV_SECT_SIZE:
3802
3803	  Define the SPI flash's sector size.
3804
3805	- CONFIG_ENV_OFFSET_REDUND (optional):
3806
3807	  This setting describes a second storage area of CONFIG_ENV_SIZE
3808	  size used to hold a redundant copy of the environment data, so
3809	  that there is a valid backup copy in case there is a power failure
3810	  during a "saveenv" operation. CONFIG_ENV_OFFSET_REDUND must be
3811	  aligned to an erase sector boundary.
3812
3813	- CONFIG_ENV_SPI_BUS (optional):
3814	- CONFIG_ENV_SPI_CS (optional):
3815
3816	  Define the SPI bus and chip select. If not defined they will be 0.
3817
3818	- CONFIG_ENV_SPI_MAX_HZ (optional):
3819
3820	  Define the SPI max work clock. If not defined then use 1MHz.
3821
3822	- CONFIG_ENV_SPI_MODE (optional):
3823
3824	  Define the SPI work mode. If not defined then use SPI_MODE_3.
3825
3826- CONFIG_ENV_IS_IN_REMOTE:
3827
3828	Define this if you have a remote memory space which you
3829	want to use for the local device's environment.
3830
3831	- CONFIG_ENV_ADDR:
3832	- CONFIG_ENV_SIZE:
3833
3834	  These two #defines specify the address and size of the
3835	  environment area within the remote memory space. The
3836	  local device can get the environment from remote memory
3837	  space by SRIO or PCIE links.
3838
3839BE CAREFUL! For some special cases, the local device can not use
3840"saveenv" command. For example, the local device will get the
3841environment stored in a remote NOR flash by SRIO or PCIE link,
3842but it can not erase, write this NOR flash by SRIO or PCIE interface.
3843
3844- CONFIG_ENV_IS_IN_NAND:
3845
3846	Define this if you have a NAND device which you want to use
3847	for the environment.
3848
3849	- CONFIG_ENV_OFFSET:
3850	- CONFIG_ENV_SIZE:
3851
3852	  These two #defines specify the offset and size of the environment
3853	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3854	  aligned to an erase block boundary.
3855
3856	- CONFIG_ENV_OFFSET_REDUND (optional):
3857
3858	  This setting describes a second storage area of CONFIG_ENV_SIZE
3859	  size used to hold a redundant copy of the environment data, so
3860	  that there is a valid backup copy in case there is a power failure
3861	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_REDUND must be
3862	  aligned to an erase block boundary.
3863
3864	- CONFIG_ENV_RANGE (optional):
3865
3866	  Specifies the length of the region in which the environment
3867	  can be written.  This should be a multiple of the NAND device's
3868	  block size.  Specifying a range with more erase blocks than
3869	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3870	  the range to be avoided.
3871
3872	- CONFIG_ENV_OFFSET_OOB (optional):
3873
3874	  Enables support for dynamically retrieving the offset of the
3875	  environment from block zero's out-of-band data.  The
3876	  "nand env.oob" command can be used to record this offset.
3877	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3878	  using CONFIG_ENV_OFFSET_OOB.
3879
3880- CONFIG_NAND_ENV_DST
3881
3882	Defines address in RAM to which the nand_spl code should copy the
3883	environment. If redundant environment is used, it will be copied to
3884	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3885
3886- CONFIG_ENV_IS_IN_UBI:
3887
3888	Define this if you have an UBI volume that you want to use for the
3889	environment.  This has the benefit of wear-leveling the environment
3890	accesses, which is important on NAND.
3891
3892	- CONFIG_ENV_UBI_PART:
3893
3894	  Define this to a string that is the mtd partition containing the UBI.
3895
3896	- CONFIG_ENV_UBI_VOLUME:
3897
3898	  Define this to the name of the volume that you want to store the
3899	  environment in.
3900
3901	- CONFIG_ENV_UBI_VOLUME_REDUND:
3902
3903	  Define this to the name of another volume to store a second copy of
3904	  the environment in.  This will enable redundant environments in UBI.
3905	  It is assumed that both volumes are in the same MTD partition.
3906
3907	- CONFIG_UBI_SILENCE_MSG
3908	- CONFIG_UBIFS_SILENCE_MSG
3909
3910	  You will probably want to define these to avoid a really noisy system
3911	  when storing the env in UBI.
3912
3913- CONFIG_ENV_IS_IN_FAT:
3914       Define this if you want to use the FAT file system for the environment.
3915
3916       - FAT_ENV_INTERFACE:
3917
3918         Define this to a string that is the name of the block device.
3919
3920       - FAT_ENV_DEVICE_AND_PART:
3921
3922         Define this to a string to specify the partition of the device. It can
3923         be as following:
3924
3925           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
3926               - "D:P": device D partition P. Error occurs if device D has no
3927                        partition table.
3928               - "D:0": device D.
3929               - "D" or "D:": device D partition 1 if device D has partition
3930                              table, or the whole device D if has no partition
3931                              table.
3932               - "D:auto": first partition in device D with bootable flag set.
3933                           If none, first valid partition in device D. If no
3934                           partition table then means device D.
3935
3936       - FAT_ENV_FILE:
3937
3938         It's a string of the FAT file name. This file use to store the
3939         environment.
3940
3941       - CONFIG_FAT_WRITE:
3942         This should be defined. Otherwise it cannot save the environment file.
3943
3944- CONFIG_ENV_IS_IN_MMC:
3945
3946	Define this if you have an MMC device which you want to use for the
3947	environment.
3948
3949	- CONFIG_SYS_MMC_ENV_DEV:
3950
3951	  Specifies which MMC device the environment is stored in.
3952
3953	- CONFIG_SYS_MMC_ENV_PART (optional):
3954
3955	  Specifies which MMC partition the environment is stored in. If not
3956	  set, defaults to partition 0, the user area. Common values might be
3957	  1 (first MMC boot partition), 2 (second MMC boot partition).
3958
3959	- CONFIG_ENV_OFFSET:
3960	- CONFIG_ENV_SIZE:
3961
3962	  These two #defines specify the offset and size of the environment
3963	  area within the specified MMC device.
3964
3965	  If offset is positive (the usual case), it is treated as relative to
3966	  the start of the MMC partition. If offset is negative, it is treated
3967	  as relative to the end of the MMC partition. This can be useful if
3968	  your board may be fitted with different MMC devices, which have
3969	  different sizes for the MMC partitions, and you always want the
3970	  environment placed at the very end of the partition, to leave the
3971	  maximum possible space before it, to store other data.
3972
3973	  These two values are in units of bytes, but must be aligned to an
3974	  MMC sector boundary.
3975
3976	- CONFIG_ENV_OFFSET_REDUND (optional):
3977
3978	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
3979	  hold a redundant copy of the environment data. This provides a
3980	  valid backup copy in case the other copy is corrupted, e.g. due
3981	  to a power failure during a "saveenv" operation.
3982
3983	  This value may also be positive or negative; this is handled in the
3984	  same way as CONFIG_ENV_OFFSET.
3985
3986	  This value is also in units of bytes, but must also be aligned to
3987	  an MMC sector boundary.
3988
3989	- CONFIG_ENV_SIZE_REDUND (optional):
3990
3991	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
3992	  set. If this value is set, it must be set to the same value as
3993	  CONFIG_ENV_SIZE.
3994
3995- CONFIG_SYS_SPI_INIT_OFFSET
3996
3997	Defines offset to the initial SPI buffer area in DPRAM. The
3998	area is used at an early stage (ROM part) if the environment
3999	is configured to reside in the SPI EEPROM: We need a 520 byte
4000	scratch DPRAM area. It is used between the two initialization
4001	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4002	to be a good choice since it makes it far enough from the
4003	start of the data area as well as from the stack pointer.
4004
4005Please note that the environment is read-only until the monitor
4006has been relocated to RAM and a RAM copy of the environment has been
4007created; also, when using EEPROM you will have to use getenv_f()
4008until then to read environment variables.
4009
4010The environment is protected by a CRC32 checksum. Before the monitor
4011is relocated into RAM, as a result of a bad CRC you will be working
4012with the compiled-in default environment - *silently*!!! [This is
4013necessary, because the first environment variable we need is the
4014"baudrate" setting for the console - if we have a bad CRC, we don't
4015have any device yet where we could complain.]
4016
4017Note: once the monitor has been relocated, then it will complain if
4018the default environment is used; a new CRC is computed as soon as you
4019use the "saveenv" command to store a valid environment.
4020
4021- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4022		Echo the inverted Ethernet link state to the fault LED.
4023
4024		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4025		      also needs to be defined.
4026
4027- CONFIG_SYS_FAULT_MII_ADDR:
4028		MII address of the PHY to check for the Ethernet link state.
4029
4030- CONFIG_NS16550_MIN_FUNCTIONS:
4031		Define this if you desire to only have use of the NS16550_init
4032		and NS16550_putc functions for the serial driver located at
4033		drivers/serial/ns16550.c.  This option is useful for saving
4034		space for already greatly restricted images, including but not
4035		limited to NAND_SPL configurations.
4036
4037- CONFIG_DISPLAY_BOARDINFO
4038		Display information about the board that U-Boot is running on
4039		when U-Boot starts up. The board function checkboard() is called
4040		to do this.
4041
4042- CONFIG_DISPLAY_BOARDINFO_LATE
4043		Similar to the previous option, but display this information
4044		later, once stdio is running and output goes to the LCD, if
4045		present.
4046
4047- CONFIG_BOARD_SIZE_LIMIT:
4048		Maximum size of the U-Boot image. When defined, the
4049		build system checks that the actual size does not
4050		exceed it.
4051
4052Low Level (hardware related) configuration options:
4053---------------------------------------------------
4054
4055- CONFIG_SYS_CACHELINE_SIZE:
4056		Cache Line Size of the CPU.
4057
4058- CONFIG_SYS_DEFAULT_IMMR:
4059		Default address of the IMMR after system reset.
4060
4061		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4062		and RPXsuper) to be able to adjust the position of
4063		the IMMR register after a reset.
4064
4065- CONFIG_SYS_CCSRBAR_DEFAULT:
4066		Default (power-on reset) physical address of CCSR on Freescale
4067		PowerPC SOCs.
4068
4069- CONFIG_SYS_CCSRBAR:
4070		Virtual address of CCSR.  On a 32-bit build, this is typically
4071		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4072
4073		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4074		for cross-platform code that uses that macro instead.
4075
4076- CONFIG_SYS_CCSRBAR_PHYS:
4077		Physical address of CCSR.  CCSR can be relocated to a new
4078		physical address, if desired.  In this case, this macro should
4079		be set to that address.	 Otherwise, it should be set to the
4080		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4081		is typically relocated on 36-bit builds.  It is recommended
4082		that this macro be defined via the _HIGH and _LOW macros:
4083
4084		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4085			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4086
4087- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4088		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4089		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4090		used in assembly code, so it must not contain typecasts or
4091		integer size suffixes (e.g. "ULL").
4092
4093- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4094		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4095		used in assembly code, so it must not contain typecasts or
4096		integer size suffixes (e.g. "ULL").
4097
4098- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4099		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4100		forced to a value that ensures that CCSR is not relocated.
4101
4102- Floppy Disk Support:
4103		CONFIG_SYS_FDC_DRIVE_NUMBER
4104
4105		the default drive number (default value 0)
4106
4107		CONFIG_SYS_ISA_IO_STRIDE
4108
4109		defines the spacing between FDC chipset registers
4110		(default value 1)
4111
4112		CONFIG_SYS_ISA_IO_OFFSET
4113
4114		defines the offset of register from address. It
4115		depends on which part of the data bus is connected to
4116		the FDC chipset. (default value 0)
4117
4118		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4119		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4120		default value.
4121
4122		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4123		fdc_hw_init() is called at the beginning of the FDC
4124		setup. fdc_hw_init() must be provided by the board
4125		source code. It is used to make hardware-dependent
4126		initializations.
4127
4128- CONFIG_IDE_AHB:
4129		Most IDE controllers were designed to be connected with PCI
4130		interface. Only few of them were designed for AHB interface.
4131		When software is doing ATA command and data transfer to
4132		IDE devices through IDE-AHB controller, some additional
4133		registers accessing to these kind of IDE-AHB controller
4134		is required.
4135
4136- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4137		DO NOT CHANGE unless you know exactly what you're
4138		doing! (11-4) [MPC8xx/82xx systems only]
4139
4140- CONFIG_SYS_INIT_RAM_ADDR:
4141
4142		Start address of memory area that can be used for
4143		initial data and stack; please note that this must be
4144		writable memory that is working WITHOUT special
4145		initialization, i. e. you CANNOT use normal RAM which
4146		will become available only after programming the
4147		memory controller and running certain initialization
4148		sequences.
4149
4150		U-Boot uses the following memory types:
4151		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4152		- MPC824X: data cache
4153		- PPC4xx:  data cache
4154
4155- CONFIG_SYS_GBL_DATA_OFFSET:
4156
4157		Offset of the initial data structure in the memory
4158		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4159		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4160		data is located at the end of the available space
4161		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4162		GENERATED_GBL_DATA_SIZE), and the initial stack is just
4163		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4164		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4165
4166	Note:
4167		On the MPC824X (or other systems that use the data
4168		cache for initial memory) the address chosen for
4169		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4170		point to an otherwise UNUSED address space between
4171		the top of RAM and the start of the PCI space.
4172
4173- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4174
4175- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4176
4177- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4178
4179- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4180
4181- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4182
4183- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4184
4185- CONFIG_SYS_OR_TIMING_SDRAM:
4186		SDRAM timing
4187
4188- CONFIG_SYS_MAMR_PTA:
4189		periodic timer for refresh
4190
4191- CONFIG_SYS_DER:	Debug Event Register (37-47)
4192
4193- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4194  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4195  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4196  CONFIG_SYS_BR1_PRELIM:
4197		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4198
4199- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4200  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4201  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4202		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4203
4204- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4205  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4206		Machine Mode Register and Memory Periodic Timer
4207		Prescaler definitions (SDRAM timing)
4208
4209- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4210		enable I2C microcode relocation patch (MPC8xx);
4211		define relocation offset in DPRAM [DSP2]
4212
4213- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4214		enable SMC microcode relocation patch (MPC8xx);
4215		define relocation offset in DPRAM [SMC1]
4216
4217- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4218		enable SPI microcode relocation patch (MPC8xx);
4219		define relocation offset in DPRAM [SCC4]
4220
4221- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4222		Offset of the bootmode word in DPRAM used by post
4223		(Power On Self Tests). This definition overrides
4224		#define'd default value in commproc.h resp.
4225		cpm_8260.h.
4226
4227- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4228  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4229  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4230  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4231  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4232  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4233  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4234  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4235		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4236
4237- CONFIG_PCI_DISABLE_PCIE:
4238		Disable PCI-Express on systems where it is supported but not
4239		required.
4240
4241- CONFIG_PCI_ENUM_ONLY
4242		Only scan through and get the devices on the buses.
4243		Don't do any setup work, presumably because someone or
4244		something has already done it, and we don't need to do it
4245		a second time.	Useful for platforms that are pre-booted
4246		by coreboot or similar.
4247
4248- CONFIG_PCI_INDIRECT_BRIDGE:
4249		Enable support for indirect PCI bridges.
4250
4251- CONFIG_SYS_SRIO:
4252		Chip has SRIO or not
4253
4254- CONFIG_SRIO1:
4255		Board has SRIO 1 port available
4256
4257- CONFIG_SRIO2:
4258		Board has SRIO 2 port available
4259
4260- CONFIG_SRIO_PCIE_BOOT_MASTER
4261		Board can support master function for Boot from SRIO and PCIE
4262
4263- CONFIG_SYS_SRIOn_MEM_VIRT:
4264		Virtual Address of SRIO port 'n' memory region
4265
4266- CONFIG_SYS_SRIOn_MEM_PHYS:
4267		Physical Address of SRIO port 'n' memory region
4268
4269- CONFIG_SYS_SRIOn_MEM_SIZE:
4270		Size of SRIO port 'n' memory region
4271
4272- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4273		Defined to tell the NAND controller that the NAND chip is using
4274		a 16 bit bus.
4275		Not all NAND drivers use this symbol.
4276		Example of drivers that use it:
4277		- drivers/mtd/nand/ndfc.c
4278		- drivers/mtd/nand/mxc_nand.c
4279
4280- CONFIG_SYS_NDFC_EBC0_CFG
4281		Sets the EBC0_CFG register for the NDFC. If not defined
4282		a default value will be used.
4283
4284- CONFIG_SPD_EEPROM
4285		Get DDR timing information from an I2C EEPROM. Common
4286		with pluggable memory modules such as SODIMMs
4287
4288  SPD_EEPROM_ADDRESS
4289		I2C address of the SPD EEPROM
4290
4291- CONFIG_SYS_SPD_BUS_NUM
4292		If SPD EEPROM is on an I2C bus other than the first
4293		one, specify here. Note that the value must resolve
4294		to something your driver can deal with.
4295
4296- CONFIG_SYS_DDR_RAW_TIMING
4297		Get DDR timing information from other than SPD. Common with
4298		soldered DDR chips onboard without SPD. DDR raw timing
4299		parameters are extracted from datasheet and hard-coded into
4300		header files or board specific files.
4301
4302- CONFIG_FSL_DDR_INTERACTIVE
4303		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4304
4305- CONFIG_FSL_DDR_SYNC_REFRESH
4306		Enable sync of refresh for multiple controllers.
4307
4308- CONFIG_FSL_DDR_BIST
4309		Enable built-in memory test for Freescale DDR controllers.
4310
4311- CONFIG_SYS_83XX_DDR_USES_CS0
4312		Only for 83xx systems. If specified, then DDR should
4313		be configured using CS0 and CS1 instead of CS2 and CS3.
4314
4315- CONFIG_ETHER_ON_FEC[12]
4316		Define to enable FEC[12] on a 8xx series processor.
4317
4318- CONFIG_FEC[12]_PHY
4319		Define to the hardcoded PHY address which corresponds
4320		to the given FEC; i. e.
4321			#define CONFIG_FEC1_PHY 4
4322		means that the PHY with address 4 is connected to FEC1
4323
4324		When set to -1, means to probe for first available.
4325
4326- CONFIG_FEC[12]_PHY_NORXERR
4327		The PHY does not have a RXERR line (RMII only).
4328		(so program the FEC to ignore it).
4329
4330- CONFIG_RMII
4331		Enable RMII mode for all FECs.
4332		Note that this is a global option, we can't
4333		have one FEC in standard MII mode and another in RMII mode.
4334
4335- CONFIG_CRC32_VERIFY
4336		Add a verify option to the crc32 command.
4337		The syntax is:
4338
4339		=> crc32 -v <address> <count> <crc32>
4340
4341		Where address/count indicate a memory area
4342		and crc32 is the correct crc32 which the
4343		area should have.
4344
4345- CONFIG_LOOPW
4346		Add the "loopw" memory command. This only takes effect if
4347		the memory commands are activated globally (CONFIG_CMD_MEM).
4348
4349- CONFIG_MX_CYCLIC
4350		Add the "mdc" and "mwc" memory commands. These are cyclic
4351		"md/mw" commands.
4352		Examples:
4353
4354		=> mdc.b 10 4 500
4355		This command will print 4 bytes (10,11,12,13) each 500 ms.
4356
4357		=> mwc.l 100 12345678 10
4358		This command will write 12345678 to address 100 all 10 ms.
4359
4360		This only takes effect if the memory commands are activated
4361		globally (CONFIG_CMD_MEM).
4362
4363- CONFIG_SKIP_LOWLEVEL_INIT
4364		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4365		low level initializations (like setting up the memory
4366		controller) are omitted and/or U-Boot does not
4367		relocate itself into RAM.
4368
4369		Normally this variable MUST NOT be defined. The only
4370		exception is when U-Boot is loaded (to RAM) by some
4371		other boot loader or by a debugger which performs
4372		these initializations itself.
4373
4374- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
4375		[ARM926EJ-S only] This allows just the call to lowlevel_init()
4376		to be skipped. The normal CP15 init (such as enabling the
4377		instruction cache) is still performed.
4378
4379- CONFIG_SPL_BUILD
4380		Modifies the behaviour of start.S when compiling a loader
4381		that is executed before the actual U-Boot. E.g. when
4382		compiling a NAND SPL.
4383
4384- CONFIG_TPL_BUILD
4385		Modifies the behaviour of start.S  when compiling a loader
4386		that is executed after the SPL and before the actual U-Boot.
4387		It is loaded by the SPL.
4388
4389- CONFIG_SYS_MPC85XX_NO_RESETVEC
4390		Only for 85xx systems. If this variable is specified, the section
4391		.resetvec is not kept and the section .bootpg is placed in the
4392		previous 4k of the .text section.
4393
4394- CONFIG_ARCH_MAP_SYSMEM
4395		Generally U-Boot (and in particular the md command) uses
4396		effective address. It is therefore not necessary to regard
4397		U-Boot address as virtual addresses that need to be translated
4398		to physical addresses. However, sandbox requires this, since
4399		it maintains its own little RAM buffer which contains all
4400		addressable memory. This option causes some memory accesses
4401		to be mapped through map_sysmem() / unmap_sysmem().
4402
4403- CONFIG_X86_RESET_VECTOR
4404		If defined, the x86 reset vector code is included. This is not
4405		needed when U-Boot is running from Coreboot.
4406
4407- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4408		Enables the RTC32K OSC on AM33xx based plattforms
4409
4410- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4411		Option to disable subpage write in NAND driver
4412		driver that uses this:
4413		drivers/mtd/nand/davinci_nand.c
4414
4415Freescale QE/FMAN Firmware Support:
4416-----------------------------------
4417
4418The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4419loading of "firmware", which is encoded in the QE firmware binary format.
4420This firmware often needs to be loaded during U-Boot booting, so macros
4421are used to identify the storage device (NOR flash, SPI, etc) and the address
4422within that device.
4423
4424- CONFIG_SYS_FMAN_FW_ADDR
4425	The address in the storage device where the FMAN microcode is located.  The
4426	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4427	is also specified.
4428
4429- CONFIG_SYS_QE_FW_ADDR
4430	The address in the storage device where the QE microcode is located.  The
4431	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4432	is also specified.
4433
4434- CONFIG_SYS_QE_FMAN_FW_LENGTH
4435	The maximum possible size of the firmware.  The firmware binary format
4436	has a field that specifies the actual size of the firmware, but it
4437	might not be possible to read any part of the firmware unless some
4438	local storage is allocated to hold the entire firmware first.
4439
4440- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4441	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4442	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4443	virtual address in NOR flash.
4444
4445- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4446	Specifies that QE/FMAN firmware is located in NAND flash.
4447	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4448
4449- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4450	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4451	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4452
4453- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4454	Specifies that QE/FMAN firmware is located in the remote (master)
4455	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4456	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4457	window->master inbound window->master LAW->the ucode address in
4458	master's memory space.
4459
4460Freescale Layerscape Management Complex Firmware Support:
4461---------------------------------------------------------
4462The Freescale Layerscape Management Complex (MC) supports the loading of
4463"firmware".
4464This firmware often needs to be loaded during U-Boot booting, so macros
4465are used to identify the storage device (NOR flash, SPI, etc) and the address
4466within that device.
4467
4468- CONFIG_FSL_MC_ENET
4469	Enable the MC driver for Layerscape SoCs.
4470
4471Freescale Layerscape Debug Server Support:
4472-------------------------------------------
4473The Freescale Layerscape Debug Server Support supports the loading of
4474"Debug Server firmware" and triggering SP boot-rom.
4475This firmware often needs to be loaded during U-Boot booting.
4476
4477- CONFIG_SYS_MC_RSV_MEM_ALIGN
4478	Define alignment of reserved memory MC requires
4479
4480Reproducible builds
4481-------------------
4482
4483In order to achieve reproducible builds, timestamps used in the U-Boot build
4484process have to be set to a fixed value.
4485
4486This is done using the SOURCE_DATE_EPOCH environment variable.
4487SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
4488option for U-Boot or an environment variable in U-Boot.
4489
4490SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
4491
4492Building the Software:
4493======================
4494
4495Building U-Boot has been tested in several native build environments
4496and in many different cross environments. Of course we cannot support
4497all possibly existing versions of cross development tools in all
4498(potentially obsolete) versions. In case of tool chain problems we
4499recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4500which is extensively used to build and test U-Boot.
4501
4502If you are not using a native environment, it is assumed that you
4503have GNU cross compiling tools available in your path. In this case,
4504you must set the environment variable CROSS_COMPILE in your shell.
4505Note that no changes to the Makefile or any other source files are
4506necessary. For example using the ELDK on a 4xx CPU, please enter:
4507
4508	$ CROSS_COMPILE=ppc_4xx-
4509	$ export CROSS_COMPILE
4510
4511Note: If you wish to generate Windows versions of the utilities in
4512      the tools directory you can use the MinGW toolchain
4513      (http://www.mingw.org).  Set your HOST tools to the MinGW
4514      toolchain and execute 'make tools'.  For example:
4515
4516       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4517
4518      Binaries such as tools/mkimage.exe will be created which can
4519      be executed on computers running Windows.
4520
4521U-Boot is intended to be simple to build. After installing the
4522sources you must configure U-Boot for one specific board type. This
4523is done by typing:
4524
4525	make NAME_defconfig
4526
4527where "NAME_defconfig" is the name of one of the existing configu-
4528rations; see boards.cfg for supported names.
4529
4530Note: for some board special configuration names may exist; check if
4531      additional information is available from the board vendor; for
4532      instance, the TQM823L systems are available without (standard)
4533      or with LCD support. You can select such additional "features"
4534      when choosing the configuration, i. e.
4535
4536      make TQM823L_defconfig
4537	- will configure for a plain TQM823L, i. e. no LCD support
4538
4539      make TQM823L_LCD_defconfig
4540	- will configure for a TQM823L with U-Boot console on LCD
4541
4542      etc.
4543
4544
4545Finally, type "make all", and you should get some working U-Boot
4546images ready for download to / installation on your system:
4547
4548- "u-boot.bin" is a raw binary image
4549- "u-boot" is an image in ELF binary format
4550- "u-boot.srec" is in Motorola S-Record format
4551
4552By default the build is performed locally and the objects are saved
4553in the source directory. One of the two methods can be used to change
4554this behavior and build U-Boot to some external directory:
4555
45561. Add O= to the make command line invocations:
4557
4558	make O=/tmp/build distclean
4559	make O=/tmp/build NAME_defconfig
4560	make O=/tmp/build all
4561
45622. Set environment variable KBUILD_OUTPUT to point to the desired location:
4563
4564	export KBUILD_OUTPUT=/tmp/build
4565	make distclean
4566	make NAME_defconfig
4567	make all
4568
4569Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
4570variable.
4571
4572
4573Please be aware that the Makefiles assume you are using GNU make, so
4574for instance on NetBSD you might need to use "gmake" instead of
4575native "make".
4576
4577
4578If the system board that you have is not listed, then you will need
4579to port U-Boot to your hardware platform. To do this, follow these
4580steps:
4581
45821.  Create a new directory to hold your board specific code. Add any
4583    files you need. In your board directory, you will need at least
4584    the "Makefile" and a "<board>.c".
45852.  Create a new configuration file "include/configs/<board>.h" for
4586    your board.
45873.  If you're porting U-Boot to a new CPU, then also create a new
4588    directory to hold your CPU specific code. Add any files you need.
45894.  Run "make <board>_defconfig" with your new name.
45905.  Type "make", and you should get a working "u-boot.srec" file
4591    to be installed on your target system.
45926.  Debug and solve any problems that might arise.
4593    [Of course, this last step is much harder than it sounds.]
4594
4595
4596Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4597==============================================================
4598
4599If you have modified U-Boot sources (for instance added a new board
4600or support for new devices, a new CPU, etc.) you are expected to
4601provide feedback to the other developers. The feedback normally takes
4602the form of a "patch", i. e. a context diff against a certain (latest
4603official or latest in the git repository) version of U-Boot sources.
4604
4605But before you submit such a patch, please verify that your modifi-
4606cation did not break existing code. At least make sure that *ALL* of
4607the supported boards compile WITHOUT ANY compiler warnings. To do so,
4608just run the buildman script (tools/buildman/buildman), which will
4609configure and build U-Boot for ALL supported system. Be warned, this
4610will take a while. Please see the buildman README, or run 'buildman -H'
4611for documentation.
4612
4613
4614See also "U-Boot Porting Guide" below.
4615
4616
4617Monitor Commands - Overview:
4618============================
4619
4620go	- start application at address 'addr'
4621run	- run commands in an environment variable
4622bootm	- boot application image from memory
4623bootp	- boot image via network using BootP/TFTP protocol
4624bootz   - boot zImage from memory
4625tftpboot- boot image via network using TFTP protocol
4626	       and env variables "ipaddr" and "serverip"
4627	       (and eventually "gatewayip")
4628tftpput - upload a file via network using TFTP protocol
4629rarpboot- boot image via network using RARP/TFTP protocol
4630diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4631loads	- load S-Record file over serial line
4632loadb	- load binary file over serial line (kermit mode)
4633md	- memory display
4634mm	- memory modify (auto-incrementing)
4635nm	- memory modify (constant address)
4636mw	- memory write (fill)
4637cp	- memory copy
4638cmp	- memory compare
4639crc32	- checksum calculation
4640i2c	- I2C sub-system
4641sspi	- SPI utility commands
4642base	- print or set address offset
4643printenv- print environment variables
4644setenv	- set environment variables
4645saveenv - save environment variables to persistent storage
4646protect - enable or disable FLASH write protection
4647erase	- erase FLASH memory
4648flinfo	- print FLASH memory information
4649nand	- NAND memory operations (see doc/README.nand)
4650bdinfo	- print Board Info structure
4651iminfo	- print header information for application image
4652coninfo - print console devices and informations
4653ide	- IDE sub-system
4654loop	- infinite loop on address range
4655loopw	- infinite write loop on address range
4656mtest	- simple RAM test
4657icache	- enable or disable instruction cache
4658dcache	- enable or disable data cache
4659reset	- Perform RESET of the CPU
4660echo	- echo args to console
4661version - print monitor version
4662help	- print online help
4663?	- alias for 'help'
4664
4665
4666Monitor Commands - Detailed Description:
4667========================================
4668
4669TODO.
4670
4671For now: just type "help <command>".
4672
4673
4674Environment Variables:
4675======================
4676
4677U-Boot supports user configuration using Environment Variables which
4678can be made persistent by saving to Flash memory.
4679
4680Environment Variables are set using "setenv", printed using
4681"printenv", and saved to Flash using "saveenv". Using "setenv"
4682without a value can be used to delete a variable from the
4683environment. As long as you don't save the environment you are
4684working with an in-memory copy. In case the Flash area containing the
4685environment is erased by accident, a default environment is provided.
4686
4687Some configuration options can be set using Environment Variables.
4688
4689List of environment variables (most likely not complete):
4690
4691  baudrate	- see CONFIG_BAUDRATE
4692
4693  bootdelay	- see CONFIG_BOOTDELAY
4694
4695  bootcmd	- see CONFIG_BOOTCOMMAND
4696
4697  bootargs	- Boot arguments when booting an RTOS image
4698
4699  bootfile	- Name of the image to load with TFTP
4700
4701  bootm_low	- Memory range available for image processing in the bootm
4702		  command can be restricted. This variable is given as
4703		  a hexadecimal number and defines lowest address allowed
4704		  for use by the bootm command. See also "bootm_size"
4705		  environment variable. Address defined by "bootm_low" is
4706		  also the base of the initial memory mapping for the Linux
4707		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4708		  bootm_mapsize.
4709
4710  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4711		  This variable is given as a hexadecimal number and it
4712		  defines the size of the memory region starting at base
4713		  address bootm_low that is accessible by the Linux kernel
4714		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4715		  as the default value if it is defined, and bootm_size is
4716		  used otherwise.
4717
4718  bootm_size	- Memory range available for image processing in the bootm
4719		  command can be restricted. This variable is given as
4720		  a hexadecimal number and defines the size of the region
4721		  allowed for use by the bootm command. See also "bootm_low"
4722		  environment variable.
4723
4724  updatefile	- Location of the software update file on a TFTP server, used
4725		  by the automatic software update feature. Please refer to
4726		  documentation in doc/README.update for more details.
4727
4728  autoload	- if set to "no" (any string beginning with 'n'),
4729		  "bootp" will just load perform a lookup of the
4730		  configuration from the BOOTP server, but not try to
4731		  load any image using TFTP
4732
4733  autostart	- if set to "yes", an image loaded using the "bootp",
4734		  "rarpboot", "tftpboot" or "diskboot" commands will
4735		  be automatically started (by internally calling
4736		  "bootm")
4737
4738		  If set to "no", a standalone image passed to the
4739		  "bootm" command will be copied to the load address
4740		  (and eventually uncompressed), but NOT be started.
4741		  This can be used to load and uncompress arbitrary
4742		  data.
4743
4744  fdt_high	- if set this restricts the maximum address that the
4745		  flattened device tree will be copied into upon boot.
4746		  For example, if you have a system with 1 GB memory
4747		  at physical address 0x10000000, while Linux kernel
4748		  only recognizes the first 704 MB as low memory, you
4749		  may need to set fdt_high as 0x3C000000 to have the
4750		  device tree blob be copied to the maximum address
4751		  of the 704 MB low memory, so that Linux kernel can
4752		  access it during the boot procedure.
4753
4754		  If this is set to the special value 0xFFFFFFFF then
4755		  the fdt will not be copied at all on boot.  For this
4756		  to work it must reside in writable memory, have
4757		  sufficient padding on the end of it for u-boot to
4758		  add the information it needs into it, and the memory
4759		  must be accessible by the kernel.
4760
4761  fdtcontroladdr- if set this is the address of the control flattened
4762		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4763		  defined.
4764
4765  i2cfast	- (PPC405GP|PPC405EP only)
4766		  if set to 'y' configures Linux I2C driver for fast
4767		  mode (400kHZ). This environment variable is used in
4768		  initialization code. So, for changes to be effective
4769		  it must be saved and board must be reset.
4770
4771  initrd_high	- restrict positioning of initrd images:
4772		  If this variable is not set, initrd images will be
4773		  copied to the highest possible address in RAM; this
4774		  is usually what you want since it allows for
4775		  maximum initrd size. If for some reason you want to
4776		  make sure that the initrd image is loaded below the
4777		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4778		  variable to a value of "no" or "off" or "0".
4779		  Alternatively, you can set it to a maximum upper
4780		  address to use (U-Boot will still check that it
4781		  does not overwrite the U-Boot stack and data).
4782
4783		  For instance, when you have a system with 16 MB
4784		  RAM, and want to reserve 4 MB from use by Linux,
4785		  you can do this by adding "mem=12M" to the value of
4786		  the "bootargs" variable. However, now you must make
4787		  sure that the initrd image is placed in the first
4788		  12 MB as well - this can be done with
4789
4790		  setenv initrd_high 00c00000
4791
4792		  If you set initrd_high to 0xFFFFFFFF, this is an
4793		  indication to U-Boot that all addresses are legal
4794		  for the Linux kernel, including addresses in flash
4795		  memory. In this case U-Boot will NOT COPY the
4796		  ramdisk at all. This may be useful to reduce the
4797		  boot time on your system, but requires that this
4798		  feature is supported by your Linux kernel.
4799
4800  ipaddr	- IP address; needed for tftpboot command
4801
4802  loadaddr	- Default load address for commands like "bootp",
4803		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4804
4805  loads_echo	- see CONFIG_LOADS_ECHO
4806
4807  serverip	- TFTP server IP address; needed for tftpboot command
4808
4809  bootretry	- see CONFIG_BOOT_RETRY_TIME
4810
4811  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4812
4813  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4814
4815  ethprime	- controls which interface is used first.
4816
4817  ethact	- controls which interface is currently active.
4818		  For example you can do the following
4819
4820		  => setenv ethact FEC
4821		  => ping 192.168.0.1 # traffic sent on FEC
4822		  => setenv ethact SCC
4823		  => ping 10.0.0.1 # traffic sent on SCC
4824
4825  ethrotate	- When set to "no" U-Boot does not go through all
4826		  available network interfaces.
4827		  It just stays at the currently selected interface.
4828
4829  netretry	- When set to "no" each network operation will
4830		  either succeed or fail without retrying.
4831		  When set to "once" the network operation will
4832		  fail when all the available network interfaces
4833		  are tried once without success.
4834		  Useful on scripts which control the retry operation
4835		  themselves.
4836
4837  npe_ucode	- set load address for the NPE microcode
4838
4839  silent_linux  - If set then Linux will be told to boot silently, by
4840		  changing the console to be empty. If "yes" it will be
4841		  made silent. If "no" it will not be made silent. If
4842		  unset, then it will be made silent if the U-Boot console
4843		  is silent.
4844
4845  tftpsrcp	- If this is set, the value is used for TFTP's
4846		  UDP source port.
4847
4848  tftpdstp	- If this is set, the value is used for TFTP's UDP
4849		  destination port instead of the Well Know Port 69.
4850
4851  tftpblocksize - Block size to use for TFTP transfers; if not set,
4852		  we use the TFTP server's default block size
4853
4854  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4855		  seconds, minimum value is 1000 = 1 second). Defines
4856		  when a packet is considered to be lost so it has to
4857		  be retransmitted. The default is 5000 = 5 seconds.
4858		  Lowering this value may make downloads succeed
4859		  faster in networks with high packet loss rates or
4860		  with unreliable TFTP servers.
4861
4862  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
4863		  unit, minimum value = 0). Defines how many timeouts
4864		  can happen during a single file transfer before that
4865		  transfer is aborted. The default is 10, and 0 means
4866		  'no timeouts allowed'. Increasing this value may help
4867		  downloads succeed with high packet loss rates, or with
4868		  unreliable TFTP servers or client hardware.
4869
4870  vlan		- When set to a value < 4095 the traffic over
4871		  Ethernet is encapsulated/received over 802.1q
4872		  VLAN tagged frames.
4873
4874  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
4875		  Unsigned value, in milliseconds. If not set, the period will
4876		  be either the default (28000), or a value based on
4877		  CONFIG_NET_RETRY_COUNT, if defined. This value has
4878		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
4879
4880The following image location variables contain the location of images
4881used in booting. The "Image" column gives the role of the image and is
4882not an environment variable name. The other columns are environment
4883variable names. "File Name" gives the name of the file on a TFTP
4884server, "RAM Address" gives the location in RAM the image will be
4885loaded to, and "Flash Location" gives the image's address in NOR
4886flash or offset in NAND flash.
4887
4888*Note* - these variables don't have to be defined for all boards, some
4889boards currently use other variables for these purposes, and some
4890boards use these variables for other purposes.
4891
4892Image		    File Name	     RAM Address       Flash Location
4893-----		    ---------	     -----------       --------------
4894u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4895Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4896device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4897ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4898
4899The following environment variables may be used and automatically
4900updated by the network boot commands ("bootp" and "rarpboot"),
4901depending the information provided by your boot server:
4902
4903  bootfile	- see above
4904  dnsip		- IP address of your Domain Name Server
4905  dnsip2	- IP address of your secondary Domain Name Server
4906  gatewayip	- IP address of the Gateway (Router) to use
4907  hostname	- Target hostname
4908  ipaddr	- see above
4909  netmask	- Subnet Mask
4910  rootpath	- Pathname of the root filesystem on the NFS server
4911  serverip	- see above
4912
4913
4914There are two special Environment Variables:
4915
4916  serial#	- contains hardware identification information such
4917		  as type string and/or serial number
4918  ethaddr	- Ethernet address
4919
4920These variables can be set only once (usually during manufacturing of
4921the board). U-Boot refuses to delete or overwrite these variables
4922once they have been set once.
4923
4924
4925Further special Environment Variables:
4926
4927  ver		- Contains the U-Boot version string as printed
4928		  with the "version" command. This variable is
4929		  readonly (see CONFIG_VERSION_VARIABLE).
4930
4931
4932Please note that changes to some configuration parameters may take
4933only effect after the next boot (yes, that's just like Windoze :-).
4934
4935
4936Callback functions for environment variables:
4937---------------------------------------------
4938
4939For some environment variables, the behavior of u-boot needs to change
4940when their values are changed.  This functionality allows functions to
4941be associated with arbitrary variables.  On creation, overwrite, or
4942deletion, the callback will provide the opportunity for some side
4943effect to happen or for the change to be rejected.
4944
4945The callbacks are named and associated with a function using the
4946U_BOOT_ENV_CALLBACK macro in your board or driver code.
4947
4948These callbacks are associated with variables in one of two ways.  The
4949static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4950in the board configuration to a string that defines a list of
4951associations.  The list must be in the following format:
4952
4953	entry = variable_name[:callback_name]
4954	list = entry[,list]
4955
4956If the callback name is not specified, then the callback is deleted.
4957Spaces are also allowed anywhere in the list.
4958
4959Callbacks can also be associated by defining the ".callbacks" variable
4960with the same list format above.  Any association in ".callbacks" will
4961override any association in the static list. You can define
4962CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4963".callbacks" environment variable in the default or embedded environment.
4964
4965If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4966regular expression. This allows multiple variables to be connected to
4967the same callback without explicitly listing them all out.
4968
4969
4970Command Line Parsing:
4971=====================
4972
4973There are two different command line parsers available with U-Boot:
4974the old "simple" one, and the much more powerful "hush" shell:
4975
4976Old, simple command line parser:
4977--------------------------------
4978
4979- supports environment variables (through setenv / saveenv commands)
4980- several commands on one line, separated by ';'
4981- variable substitution using "... ${name} ..." syntax
4982- special characters ('$', ';') can be escaped by prefixing with '\',
4983  for example:
4984	setenv bootcmd bootm \${address}
4985- You can also escape text by enclosing in single apostrophes, for example:
4986	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4987
4988Hush shell:
4989-----------
4990
4991- similar to Bourne shell, with control structures like
4992  if...then...else...fi, for...do...done; while...do...done,
4993  until...do...done, ...
4994- supports environment ("global") variables (through setenv / saveenv
4995  commands) and local shell variables (through standard shell syntax
4996  "name=value"); only environment variables can be used with "run"
4997  command
4998
4999General rules:
5000--------------
5001
5002(1) If a command line (or an environment variable executed by a "run"
5003    command) contains several commands separated by semicolon, and
5004    one of these commands fails, then the remaining commands will be
5005    executed anyway.
5006
5007(2) If you execute several variables with one call to run (i. e.
5008    calling run with a list of variables as arguments), any failing
5009    command will cause "run" to terminate, i. e. the remaining
5010    variables are not executed.
5011
5012Note for Redundant Ethernet Interfaces:
5013=======================================
5014
5015Some boards come with redundant Ethernet interfaces; U-Boot supports
5016such configurations and is capable of automatic selection of a
5017"working" interface when needed. MAC assignment works as follows:
5018
5019Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5020MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5021"eth1addr" (=>eth1), "eth2addr", ...
5022
5023If the network interface stores some valid MAC address (for instance
5024in SROM), this is used as default address if there is NO correspon-
5025ding setting in the environment; if the corresponding environment
5026variable is set, this overrides the settings in the card; that means:
5027
5028o If the SROM has a valid MAC address, and there is no address in the
5029  environment, the SROM's address is used.
5030
5031o If there is no valid address in the SROM, and a definition in the
5032  environment exists, then the value from the environment variable is
5033  used.
5034
5035o If both the SROM and the environment contain a MAC address, and
5036  both addresses are the same, this MAC address is used.
5037
5038o If both the SROM and the environment contain a MAC address, and the
5039  addresses differ, the value from the environment is used and a
5040  warning is printed.
5041
5042o If neither SROM nor the environment contain a MAC address, an error
5043  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
5044  a random, locally-assigned MAC is used.
5045
5046If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5047will be programmed into hardware as part of the initialization process.	 This
5048may be skipped by setting the appropriate 'ethmacskip' environment variable.
5049The naming convention is as follows:
5050"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5051
5052Image Formats:
5053==============
5054
5055U-Boot is capable of booting (and performing other auxiliary operations on)
5056images in two formats:
5057
5058New uImage format (FIT)
5059-----------------------
5060
5061Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5062to Flattened Device Tree). It allows the use of images with multiple
5063components (several kernels, ramdisks, etc.), with contents protected by
5064SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5065
5066
5067Old uImage format
5068-----------------
5069
5070Old image format is based on binary files which can be basically anything,
5071preceded by a special header; see the definitions in include/image.h for
5072details; basically, the header defines the following image properties:
5073
5074* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5075  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5076  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5077  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5078  INTEGRITY).
5079* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5080  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5081  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5082* Compression Type (uncompressed, gzip, bzip2)
5083* Load Address
5084* Entry Point
5085* Image Name
5086* Image Timestamp
5087
5088The header is marked by a special Magic Number, and both the header
5089and the data portions of the image are secured against corruption by
5090CRC32 checksums.
5091
5092
5093Linux Support:
5094==============
5095
5096Although U-Boot should support any OS or standalone application
5097easily, the main focus has always been on Linux during the design of
5098U-Boot.
5099
5100U-Boot includes many features that so far have been part of some
5101special "boot loader" code within the Linux kernel. Also, any
5102"initrd" images to be used are no longer part of one big Linux image;
5103instead, kernel and "initrd" are separate images. This implementation
5104serves several purposes:
5105
5106- the same features can be used for other OS or standalone
5107  applications (for instance: using compressed images to reduce the
5108  Flash memory footprint)
5109
5110- it becomes much easier to port new Linux kernel versions because
5111  lots of low-level, hardware dependent stuff are done by U-Boot
5112
5113- the same Linux kernel image can now be used with different "initrd"
5114  images; of course this also means that different kernel images can
5115  be run with the same "initrd". This makes testing easier (you don't
5116  have to build a new "zImage.initrd" Linux image when you just
5117  change a file in your "initrd"). Also, a field-upgrade of the
5118  software is easier now.
5119
5120
5121Linux HOWTO:
5122============
5123
5124Porting Linux to U-Boot based systems:
5125---------------------------------------
5126
5127U-Boot cannot save you from doing all the necessary modifications to
5128configure the Linux device drivers for use with your target hardware
5129(no, we don't intend to provide a full virtual machine interface to
5130Linux :-).
5131
5132But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5133
5134Just make sure your machine specific header file (for instance
5135include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5136Information structure as we define in include/asm-<arch>/u-boot.h,
5137and make sure that your definition of IMAP_ADDR uses the same value
5138as your U-Boot configuration in CONFIG_SYS_IMMR.
5139
5140Note that U-Boot now has a driver model, a unified model for drivers.
5141If you are adding a new driver, plumb it into driver model. If there
5142is no uclass available, you are encouraged to create one. See
5143doc/driver-model.
5144
5145
5146Configuring the Linux kernel:
5147-----------------------------
5148
5149No specific requirements for U-Boot. Make sure you have some root
5150device (initial ramdisk, NFS) for your target system.
5151
5152
5153Building a Linux Image:
5154-----------------------
5155
5156With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5157not used. If you use recent kernel source, a new build target
5158"uImage" will exist which automatically builds an image usable by
5159U-Boot. Most older kernels also have support for a "pImage" target,
5160which was introduced for our predecessor project PPCBoot and uses a
5161100% compatible format.
5162
5163Example:
5164
5165	make TQM850L_defconfig
5166	make oldconfig
5167	make dep
5168	make uImage
5169
5170The "uImage" build target uses a special tool (in 'tools/mkimage') to
5171encapsulate a compressed Linux kernel image with header	 information,
5172CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5173
5174* build a standard "vmlinux" kernel image (in ELF binary format):
5175
5176* convert the kernel into a raw binary image:
5177
5178	${CROSS_COMPILE}-objcopy -O binary \
5179				 -R .note -R .comment \
5180				 -S vmlinux linux.bin
5181
5182* compress the binary image:
5183
5184	gzip -9 linux.bin
5185
5186* package compressed binary image for U-Boot:
5187
5188	mkimage -A ppc -O linux -T kernel -C gzip \
5189		-a 0 -e 0 -n "Linux Kernel Image" \
5190		-d linux.bin.gz uImage
5191
5192
5193The "mkimage" tool can also be used to create ramdisk images for use
5194with U-Boot, either separated from the Linux kernel image, or
5195combined into one file. "mkimage" encapsulates the images with a 64
5196byte header containing information about target architecture,
5197operating system, image type, compression method, entry points, time
5198stamp, CRC32 checksums, etc.
5199
5200"mkimage" can be called in two ways: to verify existing images and
5201print the header information, or to build new images.
5202
5203In the first form (with "-l" option) mkimage lists the information
5204contained in the header of an existing U-Boot image; this includes
5205checksum verification:
5206
5207	tools/mkimage -l image
5208	  -l ==> list image header information
5209
5210The second form (with "-d" option) is used to build a U-Boot image
5211from a "data file" which is used as image payload:
5212
5213	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5214		      -n name -d data_file image
5215	  -A ==> set architecture to 'arch'
5216	  -O ==> set operating system to 'os'
5217	  -T ==> set image type to 'type'
5218	  -C ==> set compression type 'comp'
5219	  -a ==> set load address to 'addr' (hex)
5220	  -e ==> set entry point to 'ep' (hex)
5221	  -n ==> set image name to 'name'
5222	  -d ==> use image data from 'datafile'
5223
5224Right now, all Linux kernels for PowerPC systems use the same load
5225address (0x00000000), but the entry point address depends on the
5226kernel version:
5227
5228- 2.2.x kernels have the entry point at 0x0000000C,
5229- 2.3.x and later kernels have the entry point at 0x00000000.
5230
5231So a typical call to build a U-Boot image would read:
5232
5233	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5234	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5235	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5236	> examples/uImage.TQM850L
5237	Image Name:   2.4.4 kernel for TQM850L
5238	Created:      Wed Jul 19 02:34:59 2000
5239	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5240	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5241	Load Address: 0x00000000
5242	Entry Point:  0x00000000
5243
5244To verify the contents of the image (or check for corruption):
5245
5246	-> tools/mkimage -l examples/uImage.TQM850L
5247	Image Name:   2.4.4 kernel for TQM850L
5248	Created:      Wed Jul 19 02:34:59 2000
5249	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5250	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5251	Load Address: 0x00000000
5252	Entry Point:  0x00000000
5253
5254NOTE: for embedded systems where boot time is critical you can trade
5255speed for memory and install an UNCOMPRESSED image instead: this
5256needs more space in Flash, but boots much faster since it does not
5257need to be uncompressed:
5258
5259	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5260	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5261	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5262	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5263	> examples/uImage.TQM850L-uncompressed
5264	Image Name:   2.4.4 kernel for TQM850L
5265	Created:      Wed Jul 19 02:34:59 2000
5266	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5267	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5268	Load Address: 0x00000000
5269	Entry Point:  0x00000000
5270
5271
5272Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5273when your kernel is intended to use an initial ramdisk:
5274
5275	-> tools/mkimage -n 'Simple Ramdisk Image' \
5276	> -A ppc -O linux -T ramdisk -C gzip \
5277	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5278	Image Name:   Simple Ramdisk Image
5279	Created:      Wed Jan 12 14:01:50 2000
5280	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5281	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5282	Load Address: 0x00000000
5283	Entry Point:  0x00000000
5284
5285The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5286option performs the converse operation of the mkimage's second form (the "-d"
5287option). Given an image built by mkimage, the dumpimage extracts a "data file"
5288from the image:
5289
5290	tools/dumpimage -i image -T type -p position data_file
5291	  -i ==> extract from the 'image' a specific 'data_file'
5292	  -T ==> set image type to 'type'
5293	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5294
5295
5296Installing a Linux Image:
5297-------------------------
5298
5299To downloading a U-Boot image over the serial (console) interface,
5300you must convert the image to S-Record format:
5301
5302	objcopy -I binary -O srec examples/image examples/image.srec
5303
5304The 'objcopy' does not understand the information in the U-Boot
5305image header, so the resulting S-Record file will be relative to
5306address 0x00000000. To load it to a given address, you need to
5307specify the target address as 'offset' parameter with the 'loads'
5308command.
5309
5310Example: install the image to address 0x40100000 (which on the
5311TQM8xxL is in the first Flash bank):
5312
5313	=> erase 40100000 401FFFFF
5314
5315	.......... done
5316	Erased 8 sectors
5317
5318	=> loads 40100000
5319	## Ready for S-Record download ...
5320	~>examples/image.srec
5321	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5322	...
5323	15989 15990 15991 15992
5324	[file transfer complete]
5325	[connected]
5326	## Start Addr = 0x00000000
5327
5328
5329You can check the success of the download using the 'iminfo' command;
5330this includes a checksum verification so you can be sure no data
5331corruption happened:
5332
5333	=> imi 40100000
5334
5335	## Checking Image at 40100000 ...
5336	   Image Name:	 2.2.13 for initrd on TQM850L
5337	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5338	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5339	   Load Address: 00000000
5340	   Entry Point:	 0000000c
5341	   Verifying Checksum ... OK
5342
5343
5344Boot Linux:
5345-----------
5346
5347The "bootm" command is used to boot an application that is stored in
5348memory (RAM or Flash). In case of a Linux kernel image, the contents
5349of the "bootargs" environment variable is passed to the kernel as
5350parameters. You can check and modify this variable using the
5351"printenv" and "setenv" commands:
5352
5353
5354	=> printenv bootargs
5355	bootargs=root=/dev/ram
5356
5357	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5358
5359	=> printenv bootargs
5360	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5361
5362	=> bootm 40020000
5363	## Booting Linux kernel at 40020000 ...
5364	   Image Name:	 2.2.13 for NFS on TQM850L
5365	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5366	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5367	   Load Address: 00000000
5368	   Entry Point:	 0000000c
5369	   Verifying Checksum ... OK
5370	   Uncompressing Kernel Image ... OK
5371	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
5372	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5373	time_init: decrementer frequency = 187500000/60
5374	Calibrating delay loop... 49.77 BogoMIPS
5375	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5376	...
5377
5378If you want to boot a Linux kernel with initial RAM disk, you pass
5379the memory addresses of both the kernel and the initrd image (PPBCOOT
5380format!) to the "bootm" command:
5381
5382	=> imi 40100000 40200000
5383
5384	## Checking Image at 40100000 ...
5385	   Image Name:	 2.2.13 for initrd on TQM850L
5386	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5387	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5388	   Load Address: 00000000
5389	   Entry Point:	 0000000c
5390	   Verifying Checksum ... OK
5391
5392	## Checking Image at 40200000 ...
5393	   Image Name:	 Simple Ramdisk Image
5394	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5395	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5396	   Load Address: 00000000
5397	   Entry Point:	 00000000
5398	   Verifying Checksum ... OK
5399
5400	=> bootm 40100000 40200000
5401	## Booting Linux kernel at 40100000 ...
5402	   Image Name:	 2.2.13 for initrd on TQM850L
5403	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5404	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5405	   Load Address: 00000000
5406	   Entry Point:	 0000000c
5407	   Verifying Checksum ... OK
5408	   Uncompressing Kernel Image ... OK
5409	## Loading RAMDisk Image at 40200000 ...
5410	   Image Name:	 Simple Ramdisk Image
5411	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5412	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5413	   Load Address: 00000000
5414	   Entry Point:	 00000000
5415	   Verifying Checksum ... OK
5416	   Loading Ramdisk ... OK
5417	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
5418	Boot arguments: root=/dev/ram
5419	time_init: decrementer frequency = 187500000/60
5420	Calibrating delay loop... 49.77 BogoMIPS
5421	...
5422	RAMDISK: Compressed image found at block 0
5423	VFS: Mounted root (ext2 filesystem).
5424
5425	bash#
5426
5427Boot Linux and pass a flat device tree:
5428-----------
5429
5430First, U-Boot must be compiled with the appropriate defines. See the section
5431titled "Linux Kernel Interface" above for a more in depth explanation. The
5432following is an example of how to start a kernel and pass an updated
5433flat device tree:
5434
5435=> print oftaddr
5436oftaddr=0x300000
5437=> print oft
5438oft=oftrees/mpc8540ads.dtb
5439=> tftp $oftaddr $oft
5440Speed: 1000, full duplex
5441Using TSEC0 device
5442TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5443Filename 'oftrees/mpc8540ads.dtb'.
5444Load address: 0x300000
5445Loading: #
5446done
5447Bytes transferred = 4106 (100a hex)
5448=> tftp $loadaddr $bootfile
5449Speed: 1000, full duplex
5450Using TSEC0 device
5451TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5452Filename 'uImage'.
5453Load address: 0x200000
5454Loading:############
5455done
5456Bytes transferred = 1029407 (fb51f hex)
5457=> print loadaddr
5458loadaddr=200000
5459=> print oftaddr
5460oftaddr=0x300000
5461=> bootm $loadaddr - $oftaddr
5462## Booting image at 00200000 ...
5463   Image Name:	 Linux-2.6.17-dirty
5464   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5465   Data Size:	 1029343 Bytes = 1005.2 kB
5466   Load Address: 00000000
5467   Entry Point:	 00000000
5468   Verifying Checksum ... OK
5469   Uncompressing Kernel Image ... OK
5470Booting using flat device tree at 0x300000
5471Using MPC85xx ADS machine description
5472Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5473[snip]
5474
5475
5476More About U-Boot Image Types:
5477------------------------------
5478
5479U-Boot supports the following image types:
5480
5481   "Standalone Programs" are directly runnable in the environment
5482	provided by U-Boot; it is expected that (if they behave
5483	well) you can continue to work in U-Boot after return from
5484	the Standalone Program.
5485   "OS Kernel Images" are usually images of some Embedded OS which
5486	will take over control completely. Usually these programs
5487	will install their own set of exception handlers, device
5488	drivers, set up the MMU, etc. - this means, that you cannot
5489	expect to re-enter U-Boot except by resetting the CPU.
5490   "RAMDisk Images" are more or less just data blocks, and their
5491	parameters (address, size) are passed to an OS kernel that is
5492	being started.
5493   "Multi-File Images" contain several images, typically an OS
5494	(Linux) kernel image and one or more data images like
5495	RAMDisks. This construct is useful for instance when you want
5496	to boot over the network using BOOTP etc., where the boot
5497	server provides just a single image file, but you want to get
5498	for instance an OS kernel and a RAMDisk image.
5499
5500	"Multi-File Images" start with a list of image sizes, each
5501	image size (in bytes) specified by an "uint32_t" in network
5502	byte order. This list is terminated by an "(uint32_t)0".
5503	Immediately after the terminating 0 follow the images, one by
5504	one, all aligned on "uint32_t" boundaries (size rounded up to
5505	a multiple of 4 bytes).
5506
5507   "Firmware Images" are binary images containing firmware (like
5508	U-Boot or FPGA images) which usually will be programmed to
5509	flash memory.
5510
5511   "Script files" are command sequences that will be executed by
5512	U-Boot's command interpreter; this feature is especially
5513	useful when you configure U-Boot to use a real shell (hush)
5514	as command interpreter.
5515
5516Booting the Linux zImage:
5517-------------------------
5518
5519On some platforms, it's possible to boot Linux zImage. This is done
5520using the "bootz" command. The syntax of "bootz" command is the same
5521as the syntax of "bootm" command.
5522
5523Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5524kernel with raw initrd images. The syntax is slightly different, the
5525address of the initrd must be augmented by it's size, in the following
5526format: "<initrd addres>:<initrd size>".
5527
5528
5529Standalone HOWTO:
5530=================
5531
5532One of the features of U-Boot is that you can dynamically load and
5533run "standalone" applications, which can use some resources of
5534U-Boot like console I/O functions or interrupt services.
5535
5536Two simple examples are included with the sources:
5537
5538"Hello World" Demo:
5539-------------------
5540
5541'examples/hello_world.c' contains a small "Hello World" Demo
5542application; it is automatically compiled when you build U-Boot.
5543It's configured to run at address 0x00040004, so you can play with it
5544like that:
5545
5546	=> loads
5547	## Ready for S-Record download ...
5548	~>examples/hello_world.srec
5549	1 2 3 4 5 6 7 8 9 10 11 ...
5550	[file transfer complete]
5551	[connected]
5552	## Start Addr = 0x00040004
5553
5554	=> go 40004 Hello World! This is a test.
5555	## Starting application at 0x00040004 ...
5556	Hello World
5557	argc = 7
5558	argv[0] = "40004"
5559	argv[1] = "Hello"
5560	argv[2] = "World!"
5561	argv[3] = "This"
5562	argv[4] = "is"
5563	argv[5] = "a"
5564	argv[6] = "test."
5565	argv[7] = "<NULL>"
5566	Hit any key to exit ...
5567
5568	## Application terminated, rc = 0x0
5569
5570Another example, which demonstrates how to register a CPM interrupt
5571handler with the U-Boot code, can be found in 'examples/timer.c'.
5572Here, a CPM timer is set up to generate an interrupt every second.
5573The interrupt service routine is trivial, just printing a '.'
5574character, but this is just a demo program. The application can be
5575controlled by the following keys:
5576
5577	? - print current values og the CPM Timer registers
5578	b - enable interrupts and start timer
5579	e - stop timer and disable interrupts
5580	q - quit application
5581
5582	=> loads
5583	## Ready for S-Record download ...
5584	~>examples/timer.srec
5585	1 2 3 4 5 6 7 8 9 10 11 ...
5586	[file transfer complete]
5587	[connected]
5588	## Start Addr = 0x00040004
5589
5590	=> go 40004
5591	## Starting application at 0x00040004 ...
5592	TIMERS=0xfff00980
5593	Using timer 1
5594	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5595
5596Hit 'b':
5597	[q, b, e, ?] Set interval 1000000 us
5598	Enabling timer
5599Hit '?':
5600	[q, b, e, ?] ........
5601	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5602Hit '?':
5603	[q, b, e, ?] .
5604	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5605Hit '?':
5606	[q, b, e, ?] .
5607	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5608Hit '?':
5609	[q, b, e, ?] .
5610	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5611Hit 'e':
5612	[q, b, e, ?] ...Stopping timer
5613Hit 'q':
5614	[q, b, e, ?] ## Application terminated, rc = 0x0
5615
5616
5617Minicom warning:
5618================
5619
5620Over time, many people have reported problems when trying to use the
5621"minicom" terminal emulation program for serial download. I (wd)
5622consider minicom to be broken, and recommend not to use it. Under
5623Unix, I recommend to use C-Kermit for general purpose use (and
5624especially for kermit binary protocol download ("loadb" command), and
5625use "cu" for S-Record download ("loads" command).  See
5626http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5627for help with kermit.
5628
5629
5630Nevertheless, if you absolutely want to use it try adding this
5631configuration to your "File transfer protocols" section:
5632
5633	   Name	   Program			Name U/D FullScr IO-Red. Multi
5634	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5635	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5636
5637
5638NetBSD Notes:
5639=============
5640
5641Starting at version 0.9.2, U-Boot supports NetBSD both as host
5642(build U-Boot) and target system (boots NetBSD/mpc8xx).
5643
5644Building requires a cross environment; it is known to work on
5645NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5646need gmake since the Makefiles are not compatible with BSD make).
5647Note that the cross-powerpc package does not install include files;
5648attempting to build U-Boot will fail because <machine/ansi.h> is
5649missing.  This file has to be installed and patched manually:
5650
5651	# cd /usr/pkg/cross/powerpc-netbsd/include
5652	# mkdir powerpc
5653	# ln -s powerpc machine
5654	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5655	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5656
5657Native builds *don't* work due to incompatibilities between native
5658and U-Boot include files.
5659
5660Booting assumes that (the first part of) the image booted is a
5661stage-2 loader which in turn loads and then invokes the kernel
5662proper. Loader sources will eventually appear in the NetBSD source
5663tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5664meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5665
5666
5667Implementation Internals:
5668=========================
5669
5670The following is not intended to be a complete description of every
5671implementation detail. However, it should help to understand the
5672inner workings of U-Boot and make it easier to port it to custom
5673hardware.
5674
5675
5676Initial Stack, Global Data:
5677---------------------------
5678
5679The implementation of U-Boot is complicated by the fact that U-Boot
5680starts running out of ROM (flash memory), usually without access to
5681system RAM (because the memory controller is not initialized yet).
5682This means that we don't have writable Data or BSS segments, and BSS
5683is not initialized as zero. To be able to get a C environment working
5684at all, we have to allocate at least a minimal stack. Implementation
5685options for this are defined and restricted by the CPU used: Some CPU
5686models provide on-chip memory (like the IMMR area on MPC8xx and
5687MPC826x processors), on others (parts of) the data cache can be
5688locked as (mis-) used as memory, etc.
5689
5690	Chris Hallinan posted a good summary of these issues to the
5691	U-Boot mailing list:
5692
5693	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5694	From: "Chris Hallinan" <clh@net1plus.com>
5695	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5696	...
5697
5698	Correct me if I'm wrong, folks, but the way I understand it
5699	is this: Using DCACHE as initial RAM for Stack, etc, does not
5700	require any physical RAM backing up the cache. The cleverness
5701	is that the cache is being used as a temporary supply of
5702	necessary storage before the SDRAM controller is setup. It's
5703	beyond the scope of this list to explain the details, but you
5704	can see how this works by studying the cache architecture and
5705	operation in the architecture and processor-specific manuals.
5706
5707	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5708	is another option for the system designer to use as an
5709	initial stack/RAM area prior to SDRAM being available. Either
5710	option should work for you. Using CS 4 should be fine if your
5711	board designers haven't used it for something that would
5712	cause you grief during the initial boot! It is frequently not
5713	used.
5714
5715	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5716	with your processor/board/system design. The default value
5717	you will find in any recent u-boot distribution in
5718	walnut.h should work for you. I'd set it to a value larger
5719	than your SDRAM module. If you have a 64MB SDRAM module, set
5720	it above 400_0000. Just make sure your board has no resources
5721	that are supposed to respond to that address! That code in
5722	start.S has been around a while and should work as is when
5723	you get the config right.
5724
5725	-Chris Hallinan
5726	DS4.COM, Inc.
5727
5728It is essential to remember this, since it has some impact on the C
5729code for the initialization procedures:
5730
5731* Initialized global data (data segment) is read-only. Do not attempt
5732  to write it.
5733
5734* Do not use any uninitialized global data (or implicitly initialized
5735  as zero data - BSS segment) at all - this is undefined, initiali-
5736  zation is performed later (when relocating to RAM).
5737
5738* Stack space is very limited. Avoid big data buffers or things like
5739  that.
5740
5741Having only the stack as writable memory limits means we cannot use
5742normal global data to share information between the code. But it
5743turned out that the implementation of U-Boot can be greatly
5744simplified by making a global data structure (gd_t) available to all
5745functions. We could pass a pointer to this data as argument to _all_
5746functions, but this would bloat the code. Instead we use a feature of
5747the GCC compiler (Global Register Variables) to share the data: we
5748place a pointer (gd) to the global data into a register which we
5749reserve for this purpose.
5750
5751When choosing a register for such a purpose we are restricted by the
5752relevant  (E)ABI  specifications for the current architecture, and by
5753GCC's implementation.
5754
5755For PowerPC, the following registers have specific use:
5756	R1:	stack pointer
5757	R2:	reserved for system use
5758	R3-R4:	parameter passing and return values
5759	R5-R10: parameter passing
5760	R13:	small data area pointer
5761	R30:	GOT pointer
5762	R31:	frame pointer
5763
5764	(U-Boot also uses R12 as internal GOT pointer. r12
5765	is a volatile register so r12 needs to be reset when
5766	going back and forth between asm and C)
5767
5768    ==> U-Boot will use R2 to hold a pointer to the global data
5769
5770    Note: on PPC, we could use a static initializer (since the
5771    address of the global data structure is known at compile time),
5772    but it turned out that reserving a register results in somewhat
5773    smaller code - although the code savings are not that big (on
5774    average for all boards 752 bytes for the whole U-Boot image,
5775    624 text + 127 data).
5776
5777On ARM, the following registers are used:
5778
5779	R0:	function argument word/integer result
5780	R1-R3:	function argument word
5781	R9:	platform specific
5782	R10:	stack limit (used only if stack checking is enabled)
5783	R11:	argument (frame) pointer
5784	R12:	temporary workspace
5785	R13:	stack pointer
5786	R14:	link register
5787	R15:	program counter
5788
5789    ==> U-Boot will use R9 to hold a pointer to the global data
5790
5791    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5792
5793On Nios II, the ABI is documented here:
5794	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5795
5796    ==> U-Boot will use gp to hold a pointer to the global data
5797
5798    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5799    to access small data sections, so gp is free.
5800
5801On NDS32, the following registers are used:
5802
5803	R0-R1:	argument/return
5804	R2-R5:	argument
5805	R15:	temporary register for assembler
5806	R16:	trampoline register
5807	R28:	frame pointer (FP)
5808	R29:	global pointer (GP)
5809	R30:	link register (LP)
5810	R31:	stack pointer (SP)
5811	PC:	program counter (PC)
5812
5813    ==> U-Boot will use R10 to hold a pointer to the global data
5814
5815NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5816or current versions of GCC may "optimize" the code too much.
5817
5818Memory Management:
5819------------------
5820
5821U-Boot runs in system state and uses physical addresses, i.e. the
5822MMU is not used either for address mapping nor for memory protection.
5823
5824The available memory is mapped to fixed addresses using the memory
5825controller. In this process, a contiguous block is formed for each
5826memory type (Flash, SDRAM, SRAM), even when it consists of several
5827physical memory banks.
5828
5829U-Boot is installed in the first 128 kB of the first Flash bank (on
5830TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5831booting and sizing and initializing DRAM, the code relocates itself
5832to the upper end of DRAM. Immediately below the U-Boot code some
5833memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5834configuration setting]. Below that, a structure with global Board
5835Info data is placed, followed by the stack (growing downward).
5836
5837Additionally, some exception handler code is copied to the low 8 kB
5838of DRAM (0x00000000 ... 0x00001FFF).
5839
5840So a typical memory configuration with 16 MB of DRAM could look like
5841this:
5842
5843	0x0000 0000	Exception Vector code
5844	      :
5845	0x0000 1FFF
5846	0x0000 2000	Free for Application Use
5847	      :
5848	      :
5849
5850	      :
5851	      :
5852	0x00FB FF20	Monitor Stack (Growing downward)
5853	0x00FB FFAC	Board Info Data and permanent copy of global data
5854	0x00FC 0000	Malloc Arena
5855	      :
5856	0x00FD FFFF
5857	0x00FE 0000	RAM Copy of Monitor Code
5858	...		eventually: LCD or video framebuffer
5859	...		eventually: pRAM (Protected RAM - unchanged by reset)
5860	0x00FF FFFF	[End of RAM]
5861
5862
5863System Initialization:
5864----------------------
5865
5866In the reset configuration, U-Boot starts at the reset entry point
5867(on most PowerPC systems at address 0x00000100). Because of the reset
5868configuration for CS0# this is a mirror of the on board Flash memory.
5869To be able to re-map memory U-Boot then jumps to its link address.
5870To be able to implement the initialization code in C, a (small!)
5871initial stack is set up in the internal Dual Ported RAM (in case CPUs
5872which provide such a feature like MPC8xx or MPC8260), or in a locked
5873part of the data cache. After that, U-Boot initializes the CPU core,
5874the caches and the SIU.
5875
5876Next, all (potentially) available memory banks are mapped using a
5877preliminary mapping. For example, we put them on 512 MB boundaries
5878(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5879on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5880programmed for SDRAM access. Using the temporary configuration, a
5881simple memory test is run that determines the size of the SDRAM
5882banks.
5883
5884When there is more than one SDRAM bank, and the banks are of
5885different size, the largest is mapped first. For equal size, the first
5886bank (CS2#) is mapped first. The first mapping is always for address
58870x00000000, with any additional banks following immediately to create
5888contiguous memory starting from 0.
5889
5890Then, the monitor installs itself at the upper end of the SDRAM area
5891and allocates memory for use by malloc() and for the global Board
5892Info data; also, the exception vector code is copied to the low RAM
5893pages, and the final stack is set up.
5894
5895Only after this relocation will you have a "normal" C environment;
5896until that you are restricted in several ways, mostly because you are
5897running from ROM, and because the code will have to be relocated to a
5898new address in RAM.
5899
5900
5901U-Boot Porting Guide:
5902----------------------
5903
5904[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5905list, October 2002]
5906
5907
5908int main(int argc, char *argv[])
5909{
5910	sighandler_t no_more_time;
5911
5912	signal(SIGALRM, no_more_time);
5913	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5914
5915	if (available_money > available_manpower) {
5916		Pay consultant to port U-Boot;
5917		return 0;
5918	}
5919
5920	Download latest U-Boot source;
5921
5922	Subscribe to u-boot mailing list;
5923
5924	if (clueless)
5925		email("Hi, I am new to U-Boot, how do I get started?");
5926
5927	while (learning) {
5928		Read the README file in the top level directory;
5929		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5930		Read applicable doc/*.README;
5931		Read the source, Luke;
5932		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5933	}
5934
5935	if (available_money > toLocalCurrency ($2500))
5936		Buy a BDI3000;
5937	else
5938		Add a lot of aggravation and time;
5939
5940	if (a similar board exists) {	/* hopefully... */
5941		cp -a board/<similar> board/<myboard>
5942		cp include/configs/<similar>.h include/configs/<myboard>.h
5943	} else {
5944		Create your own board support subdirectory;
5945		Create your own board include/configs/<myboard>.h file;
5946	}
5947	Edit new board/<myboard> files
5948	Edit new include/configs/<myboard>.h
5949
5950	while (!accepted) {
5951		while (!running) {
5952			do {
5953				Add / modify source code;
5954			} until (compiles);
5955			Debug;
5956			if (clueless)
5957				email("Hi, I am having problems...");
5958		}
5959		Send patch file to the U-Boot email list;
5960		if (reasonable critiques)
5961			Incorporate improvements from email list code review;
5962		else
5963			Defend code as written;
5964	}
5965
5966	return 0;
5967}
5968
5969void no_more_time (int sig)
5970{
5971      hire_a_guru();
5972}
5973
5974
5975Coding Standards:
5976-----------------
5977
5978All contributions to U-Boot should conform to the Linux kernel
5979coding style; see the file "Documentation/CodingStyle" and the script
5980"scripts/Lindent" in your Linux kernel source directory.
5981
5982Source files originating from a different project (for example the
5983MTD subsystem) are generally exempt from these guidelines and are not
5984reformatted to ease subsequent migration to newer versions of those
5985sources.
5986
5987Please note that U-Boot is implemented in C (and to some small parts in
5988Assembler); no C++ is used, so please do not use C++ style comments (//)
5989in your code.
5990
5991Please also stick to the following formatting rules:
5992- remove any trailing white space
5993- use TAB characters for indentation and vertical alignment, not spaces
5994- make sure NOT to use DOS '\r\n' line feeds
5995- do not add more than 2 consecutive empty lines to source files
5996- do not add trailing empty lines to source files
5997
5998Submissions which do not conform to the standards may be returned
5999with a request to reformat the changes.
6000
6001
6002Submitting Patches:
6003-------------------
6004
6005Since the number of patches for U-Boot is growing, we need to
6006establish some rules. Submissions which do not conform to these rules
6007may be rejected, even when they contain important and valuable stuff.
6008
6009Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6010
6011Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6012see http://lists.denx.de/mailman/listinfo/u-boot
6013
6014When you send a patch, please include the following information with
6015it:
6016
6017* For bug fixes: a description of the bug and how your patch fixes
6018  this bug. Please try to include a way of demonstrating that the
6019  patch actually fixes something.
6020
6021* For new features: a description of the feature and your
6022  implementation.
6023
6024* A CHANGELOG entry as plaintext (separate from the patch)
6025
6026* For major contributions, add a MAINTAINERS file with your
6027  information and associated file and directory references.
6028
6029* When you add support for a new board, don't forget to add a
6030  maintainer e-mail address to the boards.cfg file, too.
6031
6032* If your patch adds new configuration options, don't forget to
6033  document these in the README file.
6034
6035* The patch itself. If you are using git (which is *strongly*
6036  recommended) you can easily generate the patch using the
6037  "git format-patch". If you then use "git send-email" to send it to
6038  the U-Boot mailing list, you will avoid most of the common problems
6039  with some other mail clients.
6040
6041  If you cannot use git, use "diff -purN OLD NEW". If your version of
6042  diff does not support these options, then get the latest version of
6043  GNU diff.
6044
6045  The current directory when running this command shall be the parent
6046  directory of the U-Boot source tree (i. e. please make sure that
6047  your patch includes sufficient directory information for the
6048  affected files).
6049
6050  We prefer patches as plain text. MIME attachments are discouraged,
6051  and compressed attachments must not be used.
6052
6053* If one logical set of modifications affects or creates several
6054  files, all these changes shall be submitted in a SINGLE patch file.
6055
6056* Changesets that contain different, unrelated modifications shall be
6057  submitted as SEPARATE patches, one patch per changeset.
6058
6059
6060Notes:
6061
6062* Before sending the patch, run the buildman script on your patched
6063  source tree and make sure that no errors or warnings are reported
6064  for any of the boards.
6065
6066* Keep your modifications to the necessary minimum: A patch
6067  containing several unrelated changes or arbitrary reformats will be
6068  returned with a request to re-formatting / split it.
6069
6070* If you modify existing code, make sure that your new code does not
6071  add to the memory footprint of the code ;-) Small is beautiful!
6072  When adding new features, these should compile conditionally only
6073  (using #ifdef), and the resulting code with the new feature
6074  disabled must not need more memory than the old code without your
6075  modification.
6076
6077* Remember that there is a size limit of 100 kB per message on the
6078  u-boot mailing list. Bigger patches will be moderated. If they are
6079  reasonable and not too big, they will be acknowledged. But patches
6080  bigger than the size limit should be avoided.
6081