xref: /openbmc/u-boot/README (revision 853f7f50)
1# SPDX-License-Identifier: GPL-2.0+
2#
3# (C) Copyright 2000 - 2013
4# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
5
6Summary:
7========
8
9This directory contains the source code for U-Boot, a boot loader for
10Embedded boards based on PowerPC, ARM, MIPS and several other
11processors, which can be installed in a boot ROM and used to
12initialize and test the hardware or to download and run application
13code.
14
15The development of U-Boot is closely related to Linux: some parts of
16the source code originate in the Linux source tree, we have some
17header files in common, and special provision has been made to
18support booting of Linux images.
19
20Some attention has been paid to make this software easily
21configurable and extendable. For instance, all monitor commands are
22implemented with the same call interface, so that it's very easy to
23add new commands. Also, instead of permanently adding rarely used
24code (for instance hardware test utilities) to the monitor, you can
25load and run it dynamically.
26
27
28Status:
29=======
30
31In general, all boards for which a configuration option exists in the
32Makefile have been tested to some extent and can be considered
33"working". In fact, many of them are used in production systems.
34
35In case of problems see the CHANGELOG file to find out who contributed
36the specific port. In addition, there are various MAINTAINERS files
37scattered throughout the U-Boot source identifying the people or
38companies responsible for various boards and subsystems.
39
40Note: As of August, 2010, there is no longer a CHANGELOG file in the
41actual U-Boot source tree; however, it can be created dynamically
42from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot, you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see http://lists.denx.de/pipermail/u-boot and
55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
56
57
58Where to get source code:
59=========================
60
61The U-Boot source code is maintained in the Git repository at
62git://www.denx.de/git/u-boot.git ; you can browse it online at
63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
64
65The "snapshot" links on this page allow you to download tarballs of
66any version you might be interested in. Official releases are also
67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
68directory.
69
70Pre-built (and tested) images are available from
71ftp://ftp.denx.de/pub/u-boot/images/
72
73
74Where we come from:
75===================
76
77- start from 8xxrom sources
78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
79- clean up code
80- make it easier to add custom boards
81- make it possible to add other [PowerPC] CPUs
82- extend functions, especially:
83  * Provide extended interface to Linux boot loader
84  * S-Record download
85  * network boot
86  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
87- create ARMBoot project (http://sourceforge.net/projects/armboot)
88- add other CPU families (starting with ARM)
89- create U-Boot project (http://sourceforge.net/projects/u-boot)
90- current project page: see http://www.denx.de/wiki/U-Boot
91
92
93Names and Spelling:
94===================
95
96The "official" name of this project is "Das U-Boot". The spelling
97"U-Boot" shall be used in all written text (documentation, comments
98in source files etc.). Example:
99
100	This is the README file for the U-Boot project.
101
102File names etc. shall be based on the string "u-boot". Examples:
103
104	include/asm-ppc/u-boot.h
105
106	#include <asm/u-boot.h>
107
108Variable names, preprocessor constants etc. shall be either based on
109the string "u_boot" or on "U_BOOT". Example:
110
111	U_BOOT_VERSION		u_boot_logo
112	IH_OS_U_BOOT		u_boot_hush_start
113
114
115Versioning:
116===========
117
118Starting with the release in October 2008, the names of the releases
119were changed from numerical release numbers without deeper meaning
120into a time stamp based numbering. Regular releases are identified by
121names consisting of the calendar year and month of the release date.
122Additional fields (if present) indicate release candidates or bug fix
123releases in "stable" maintenance trees.
124
125Examples:
126	U-Boot v2009.11	    - Release November 2009
127	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
128	U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
129
130
131Directory Hierarchy:
132====================
133
134/arch			Architecture specific files
135  /arc			Files generic to ARC architecture
136  /arm			Files generic to ARM architecture
137  /m68k			Files generic to m68k architecture
138  /microblaze		Files generic to microblaze architecture
139  /mips			Files generic to MIPS architecture
140  /nds32		Files generic to NDS32 architecture
141  /nios2		Files generic to Altera NIOS2 architecture
142  /openrisc		Files generic to OpenRISC architecture
143  /powerpc		Files generic to PowerPC architecture
144  /riscv		Files generic to RISC-V architecture
145  /sandbox		Files generic to HW-independent "sandbox"
146  /sh			Files generic to SH architecture
147  /x86			Files generic to x86 architecture
148/api			Machine/arch independent API for external apps
149/board			Board dependent files
150/cmd			U-Boot commands functions
151/common			Misc architecture independent functions
152/configs		Board default configuration files
153/disk			Code for disk drive partition handling
154/doc			Documentation (don't expect too much)
155/drivers		Commonly used device drivers
156/dts			Contains Makefile for building internal U-Boot fdt.
157/examples		Example code for standalone applications, etc.
158/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
159/include		Header Files
160/lib			Library routines generic to all architectures
161/Licenses		Various license files
162/net			Networking code
163/post			Power On Self Test
164/scripts		Various build scripts and Makefiles
165/test			Various unit test files
166/tools			Tools to build S-Record or U-Boot images, etc.
167
168Software Configuration:
169=======================
170
171Configuration is usually done using C preprocessor defines; the
172rationale behind that is to avoid dead code whenever possible.
173
174There are two classes of configuration variables:
175
176* Configuration _OPTIONS_:
177  These are selectable by the user and have names beginning with
178  "CONFIG_".
179
180* Configuration _SETTINGS_:
181  These depend on the hardware etc. and should not be meddled with if
182  you don't know what you're doing; they have names beginning with
183  "CONFIG_SYS_".
184
185Previously, all configuration was done by hand, which involved creating
186symbolic links and editing configuration files manually. More recently,
187U-Boot has added the Kbuild infrastructure used by the Linux kernel,
188allowing you to use the "make menuconfig" command to configure your
189build.
190
191
192Selection of Processor Architecture and Board Type:
193---------------------------------------------------
194
195For all supported boards there are ready-to-use default
196configurations available; just type "make <board_name>_defconfig".
197
198Example: For a TQM823L module type:
199
200	cd u-boot
201	make TQM823L_defconfig
202
203Note: If you're looking for the default configuration file for a board
204you're sure used to be there but is now missing, check the file
205doc/README.scrapyard for a list of no longer supported boards.
206
207Sandbox Environment:
208--------------------
209
210U-Boot can be built natively to run on a Linux host using the 'sandbox'
211board. This allows feature development which is not board- or architecture-
212specific to be undertaken on a native platform. The sandbox is also used to
213run some of U-Boot's tests.
214
215See board/sandbox/README.sandbox for more details.
216
217
218Board Initialisation Flow:
219--------------------------
220
221This is the intended start-up flow for boards. This should apply for both
222SPL and U-Boot proper (i.e. they both follow the same rules).
223
224Note: "SPL" stands for "Secondary Program Loader," which is explained in
225more detail later in this file.
226
227At present, SPL mostly uses a separate code path, but the function names
228and roles of each function are the same. Some boards or architectures
229may not conform to this.  At least most ARM boards which use
230CONFIG_SPL_FRAMEWORK conform to this.
231
232Execution typically starts with an architecture-specific (and possibly
233CPU-specific) start.S file, such as:
234
235	- arch/arm/cpu/armv7/start.S
236	- arch/powerpc/cpu/mpc83xx/start.S
237	- arch/mips/cpu/start.S
238
239and so on. From there, three functions are called; the purpose and
240limitations of each of these functions are described below.
241
242lowlevel_init():
243	- purpose: essential init to permit execution to reach board_init_f()
244	- no global_data or BSS
245	- there is no stack (ARMv7 may have one but it will soon be removed)
246	- must not set up SDRAM or use console
247	- must only do the bare minimum to allow execution to continue to
248		board_init_f()
249	- this is almost never needed
250	- return normally from this function
251
252board_init_f():
253	- purpose: set up the machine ready for running board_init_r():
254		i.e. SDRAM and serial UART
255	- global_data is available
256	- stack is in SRAM
257	- BSS is not available, so you cannot use global/static variables,
258		only stack variables and global_data
259
260	Non-SPL-specific notes:
261	- dram_init() is called to set up DRAM. If already done in SPL this
262		can do nothing
263
264	SPL-specific notes:
265	- you can override the entire board_init_f() function with your own
266		version as needed.
267	- preloader_console_init() can be called here in extremis
268	- should set up SDRAM, and anything needed to make the UART work
269	- these is no need to clear BSS, it will be done by crt0.S
270	- must return normally from this function (don't call board_init_r()
271		directly)
272
273Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
274this point the stack and global_data are relocated to below
275CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
276memory.
277
278board_init_r():
279	- purpose: main execution, common code
280	- global_data is available
281	- SDRAM is available
282	- BSS is available, all static/global variables can be used
283	- execution eventually continues to main_loop()
284
285	Non-SPL-specific notes:
286	- U-Boot is relocated to the top of memory and is now running from
287		there.
288
289	SPL-specific notes:
290	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
291		CONFIG_SPL_STACK_R_ADDR points into SDRAM
292	- preloader_console_init() can be called here - typically this is
293		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
294		spl_board_init() function containing this call
295	- loads U-Boot or (in falcon mode) Linux
296
297
298
299Configuration Options:
300----------------------
301
302Configuration depends on the combination of board and CPU type; all
303such information is kept in a configuration file
304"include/configs/<board_name>.h".
305
306Example: For a TQM823L module, all configuration settings are in
307"include/configs/TQM823L.h".
308
309
310Many of the options are named exactly as the corresponding Linux
311kernel configuration options. The intention is to make it easier to
312build a config tool - later.
313
314- ARM Platform Bus Type(CCI):
315		CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
316		provides full cache coherency between two clusters of multi-core
317		CPUs and I/O coherency for devices and I/O masters
318
319		CONFIG_SYS_FSL_HAS_CCI400
320
321		Defined For SoC that has cache coherent interconnect
322		CCN-400
323
324		CONFIG_SYS_FSL_HAS_CCN504
325
326		Defined for SoC that has cache coherent interconnect CCN-504
327
328The following options need to be configured:
329
330- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
331
332- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
333
334- 85xx CPU Options:
335		CONFIG_SYS_PPC64
336
337		Specifies that the core is a 64-bit PowerPC implementation (implements
338		the "64" category of the Power ISA). This is necessary for ePAPR
339		compliance, among other possible reasons.
340
341		CONFIG_SYS_FSL_TBCLK_DIV
342
343		Defines the core time base clock divider ratio compared to the
344		system clock.  On most PQ3 devices this is 8, on newer QorIQ
345		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
346
347		CONFIG_SYS_FSL_PCIE_COMPAT
348
349		Defines the string to utilize when trying to match PCIe device
350		tree nodes for the given platform.
351
352		CONFIG_SYS_FSL_ERRATUM_A004510
353
354		Enables a workaround for erratum A004510.  If set,
355		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
356		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
357
358		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
359		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
360
361		Defines one or two SoC revisions (low 8 bits of SVR)
362		for which the A004510 workaround should be applied.
363
364		The rest of SVR is either not relevant to the decision
365		of whether the erratum is present (e.g. p2040 versus
366		p2041) or is implied by the build target, which controls
367		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
368
369		See Freescale App Note 4493 for more information about
370		this erratum.
371
372		CONFIG_A003399_NOR_WORKAROUND
373		Enables a workaround for IFC erratum A003399. It is only
374		required during NOR boot.
375
376		CONFIG_A008044_WORKAROUND
377		Enables a workaround for T1040/T1042 erratum A008044. It is only
378		required during NAND boot and valid for Rev 1.0 SoC revision
379
380		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
381
382		This is the value to write into CCSR offset 0x18600
383		according to the A004510 workaround.
384
385		CONFIG_SYS_FSL_DSP_DDR_ADDR
386		This value denotes start offset of DDR memory which is
387		connected exclusively to the DSP cores.
388
389		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
390		This value denotes start offset of M2 memory
391		which is directly connected to the DSP core.
392
393		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
394		This value denotes start offset of M3 memory which is directly
395		connected to the DSP core.
396
397		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
398		This value denotes start offset of DSP CCSR space.
399
400		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
401		Single Source Clock is clocking mode present in some of FSL SoC's.
402		In this mode, a single differential clock is used to supply
403		clocks to the sysclock, ddrclock and usbclock.
404
405		CONFIG_SYS_CPC_REINIT_F
406		This CONFIG is defined when the CPC is configured as SRAM at the
407		time of U-Boot entry and is required to be re-initialized.
408
409		CONFIG_DEEP_SLEEP
410		Indicates this SoC supports deep sleep feature. If deep sleep is
411		supported, core will start to execute uboot when wakes up.
412
413- Generic CPU options:
414		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
415
416		Defines the endianess of the CPU. Implementation of those
417		values is arch specific.
418
419		CONFIG_SYS_FSL_DDR
420		Freescale DDR driver in use. This type of DDR controller is
421		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
422		SoCs.
423
424		CONFIG_SYS_FSL_DDR_ADDR
425		Freescale DDR memory-mapped register base.
426
427		CONFIG_SYS_FSL_DDR_EMU
428		Specify emulator support for DDR. Some DDR features such as
429		deskew training are not available.
430
431		CONFIG_SYS_FSL_DDRC_GEN1
432		Freescale DDR1 controller.
433
434		CONFIG_SYS_FSL_DDRC_GEN2
435		Freescale DDR2 controller.
436
437		CONFIG_SYS_FSL_DDRC_GEN3
438		Freescale DDR3 controller.
439
440		CONFIG_SYS_FSL_DDRC_GEN4
441		Freescale DDR4 controller.
442
443		CONFIG_SYS_FSL_DDRC_ARM_GEN3
444		Freescale DDR3 controller for ARM-based SoCs.
445
446		CONFIG_SYS_FSL_DDR1
447		Board config to use DDR1. It can be enabled for SoCs with
448		Freescale DDR1 or DDR2 controllers, depending on the board
449		implemetation.
450
451		CONFIG_SYS_FSL_DDR2
452		Board config to use DDR2. It can be enabled for SoCs with
453		Freescale DDR2 or DDR3 controllers, depending on the board
454		implementation.
455
456		CONFIG_SYS_FSL_DDR3
457		Board config to use DDR3. It can be enabled for SoCs with
458		Freescale DDR3 or DDR3L controllers.
459
460		CONFIG_SYS_FSL_DDR3L
461		Board config to use DDR3L. It can be enabled for SoCs with
462		DDR3L controllers.
463
464		CONFIG_SYS_FSL_DDR4
465		Board config to use DDR4. It can be enabled for SoCs with
466		DDR4 controllers.
467
468		CONFIG_SYS_FSL_IFC_BE
469		Defines the IFC controller register space as Big Endian
470
471		CONFIG_SYS_FSL_IFC_LE
472		Defines the IFC controller register space as Little Endian
473
474		CONFIG_SYS_FSL_IFC_CLK_DIV
475		Defines divider of platform clock(clock input to IFC controller).
476
477		CONFIG_SYS_FSL_LBC_CLK_DIV
478		Defines divider of platform clock(clock input to eLBC controller).
479
480		CONFIG_SYS_FSL_PBL_PBI
481		It enables addition of RCW (Power on reset configuration) in built image.
482		Please refer doc/README.pblimage for more details
483
484		CONFIG_SYS_FSL_PBL_RCW
485		It adds PBI(pre-boot instructions) commands in u-boot build image.
486		PBI commands can be used to configure SoC before it starts the execution.
487		Please refer doc/README.pblimage for more details
488
489		CONFIG_SPL_FSL_PBL
490		It adds a target to create boot binary having SPL binary in PBI format
491		concatenated with u-boot binary.
492
493		CONFIG_SYS_FSL_DDR_BE
494		Defines the DDR controller register space as Big Endian
495
496		CONFIG_SYS_FSL_DDR_LE
497		Defines the DDR controller register space as Little Endian
498
499		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
500		Physical address from the view of DDR controllers. It is the
501		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
502		it could be different for ARM SoCs.
503
504		CONFIG_SYS_FSL_DDR_INTLV_256B
505		DDR controller interleaving on 256-byte. This is a special
506		interleaving mode, handled by Dickens for Freescale layerscape
507		SoCs with ARM core.
508
509		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
510		Number of controllers used as main memory.
511
512		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
513		Number of controllers used for other than main memory.
514
515		CONFIG_SYS_FSL_HAS_DP_DDR
516		Defines the SoC has DP-DDR used for DPAA.
517
518		CONFIG_SYS_FSL_SEC_BE
519		Defines the SEC controller register space as Big Endian
520
521		CONFIG_SYS_FSL_SEC_LE
522		Defines the SEC controller register space as Little Endian
523
524- MIPS CPU options:
525		CONFIG_SYS_INIT_SP_OFFSET
526
527		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
528		pointer. This is needed for the temporary stack before
529		relocation.
530
531		CONFIG_SYS_MIPS_CACHE_MODE
532
533		Cache operation mode for the MIPS CPU.
534		See also arch/mips/include/asm/mipsregs.h.
535		Possible values are:
536			CONF_CM_CACHABLE_NO_WA
537			CONF_CM_CACHABLE_WA
538			CONF_CM_UNCACHED
539			CONF_CM_CACHABLE_NONCOHERENT
540			CONF_CM_CACHABLE_CE
541			CONF_CM_CACHABLE_COW
542			CONF_CM_CACHABLE_CUW
543			CONF_CM_CACHABLE_ACCELERATED
544
545		CONFIG_SYS_XWAY_EBU_BOOTCFG
546
547		Special option for Lantiq XWAY SoCs for booting from NOR flash.
548		See also arch/mips/cpu/mips32/start.S.
549
550		CONFIG_XWAY_SWAP_BYTES
551
552		Enable compilation of tools/xway-swap-bytes needed for Lantiq
553		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
554		be swapped if a flash programmer is used.
555
556- ARM options:
557		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
558
559		Select high exception vectors of the ARM core, e.g., do not
560		clear the V bit of the c1 register of CP15.
561
562		COUNTER_FREQUENCY
563		Generic timer clock source frequency.
564
565		COUNTER_FREQUENCY_REAL
566		Generic timer clock source frequency if the real clock is
567		different from COUNTER_FREQUENCY, and can only be determined
568		at run time.
569
570- Tegra SoC options:
571		CONFIG_TEGRA_SUPPORT_NON_SECURE
572
573		Support executing U-Boot in non-secure (NS) mode. Certain
574		impossible actions will be skipped if the CPU is in NS mode,
575		such as ARM architectural timer initialization.
576
577- Linux Kernel Interface:
578		CONFIG_CLOCKS_IN_MHZ
579
580		U-Boot stores all clock information in Hz
581		internally. For binary compatibility with older Linux
582		kernels (which expect the clocks passed in the
583		bd_info data to be in MHz) the environment variable
584		"clocks_in_mhz" can be defined so that U-Boot
585		converts clock data to MHZ before passing it to the
586		Linux kernel.
587		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
588		"clocks_in_mhz=1" is automatically included in the
589		default environment.
590
591		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
592
593		When transferring memsize parameter to Linux, some versions
594		expect it to be in bytes, others in MB.
595		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
596
597		CONFIG_OF_LIBFDT
598
599		New kernel versions are expecting firmware settings to be
600		passed using flattened device trees (based on open firmware
601		concepts).
602
603		CONFIG_OF_LIBFDT
604		 * New libfdt-based support
605		 * Adds the "fdt" command
606		 * The bootm command automatically updates the fdt
607
608		OF_TBCLK - The timebase frequency.
609		OF_STDOUT_PATH - The path to the console device
610
611		boards with QUICC Engines require OF_QE to set UCC MAC
612		addresses
613
614		CONFIG_OF_BOARD_SETUP
615
616		Board code has addition modification that it wants to make
617		to the flat device tree before handing it off to the kernel
618
619		CONFIG_OF_SYSTEM_SETUP
620
621		Other code has addition modification that it wants to make
622		to the flat device tree before handing it off to the kernel.
623		This causes ft_system_setup() to be called before booting
624		the kernel.
625
626		CONFIG_OF_IDE_FIXUP
627
628		U-Boot can detect if an IDE device is present or not.
629		If not, and this new config option is activated, U-Boot
630		removes the ATA node from the DTS before booting Linux,
631		so the Linux IDE driver does not probe the device and
632		crash. This is needed for buggy hardware (uc101) where
633		no pull down resistor is connected to the signal IDE5V_DD7.
634
635		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
636
637		This setting is mandatory for all boards that have only one
638		machine type and must be used to specify the machine type
639		number as it appears in the ARM machine registry
640		(see http://www.arm.linux.org.uk/developer/machines/).
641		Only boards that have multiple machine types supported
642		in a single configuration file and the machine type is
643		runtime discoverable, do not have to use this setting.
644
645- vxWorks boot parameters:
646
647		bootvx constructs a valid bootline using the following
648		environments variables: bootdev, bootfile, ipaddr, netmask,
649		serverip, gatewayip, hostname, othbootargs.
650		It loads the vxWorks image pointed bootfile.
651
652		Note: If a "bootargs" environment is defined, it will overwride
653		the defaults discussed just above.
654
655- Cache Configuration:
656		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
657		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
658		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
659
660- Cache Configuration for ARM:
661		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
662				      controller
663		CONFIG_SYS_PL310_BASE - Physical base address of PL310
664					controller register space
665
666- Serial Ports:
667		CONFIG_PL010_SERIAL
668
669		Define this if you want support for Amba PrimeCell PL010 UARTs.
670
671		CONFIG_PL011_SERIAL
672
673		Define this if you want support for Amba PrimeCell PL011 UARTs.
674
675		CONFIG_PL011_CLOCK
676
677		If you have Amba PrimeCell PL011 UARTs, set this variable to
678		the clock speed of the UARTs.
679
680		CONFIG_PL01x_PORTS
681
682		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
683		define this to a list of base addresses for each (supported)
684		port. See e.g. include/configs/versatile.h
685
686		CONFIG_SERIAL_HW_FLOW_CONTROL
687
688		Define this variable to enable hw flow control in serial driver.
689		Current user of this option is drivers/serial/nsl16550.c driver
690
691- Console Baudrate:
692		CONFIG_BAUDRATE - in bps
693		Select one of the baudrates listed in
694		CONFIG_SYS_BAUDRATE_TABLE, see below.
695
696- Autoboot Command:
697		CONFIG_BOOTCOMMAND
698		Only needed when CONFIG_BOOTDELAY is enabled;
699		define a command string that is automatically executed
700		when no character is read on the console interface
701		within "Boot Delay" after reset.
702
703		CONFIG_RAMBOOT and CONFIG_NFSBOOT
704		The value of these goes into the environment as
705		"ramboot" and "nfsboot" respectively, and can be used
706		as a convenience, when switching between booting from
707		RAM and NFS.
708
709- Pre-Boot Commands:
710		CONFIG_PREBOOT
711
712		When this option is #defined, the existence of the
713		environment variable "preboot" will be checked
714		immediately before starting the CONFIG_BOOTDELAY
715		countdown and/or running the auto-boot command resp.
716		entering interactive mode.
717
718		This feature is especially useful when "preboot" is
719		automatically generated or modified. For an example
720		see the LWMON board specific code: here "preboot" is
721		modified when the user holds down a certain
722		combination of keys on the (special) keyboard when
723		booting the systems
724
725- Serial Download Echo Mode:
726		CONFIG_LOADS_ECHO
727		If defined to 1, all characters received during a
728		serial download (using the "loads" command) are
729		echoed back. This might be needed by some terminal
730		emulations (like "cu"), but may as well just take
731		time on others. This setting #define's the initial
732		value of the "loads_echo" environment variable.
733
734- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
735		CONFIG_KGDB_BAUDRATE
736		Select one of the baudrates listed in
737		CONFIG_SYS_BAUDRATE_TABLE, see below.
738
739- Removal of commands
740		If no commands are needed to boot, you can disable
741		CONFIG_CMDLINE to remove them. In this case, the command line
742		will not be available, and when U-Boot wants to execute the
743		boot command (on start-up) it will call board_run_command()
744		instead. This can reduce image size significantly for very
745		simple boot procedures.
746
747- Regular expression support:
748		CONFIG_REGEX
749		If this variable is defined, U-Boot is linked against
750		the SLRE (Super Light Regular Expression) library,
751		which adds regex support to some commands, as for
752		example "env grep" and "setexpr".
753
754- Device tree:
755		CONFIG_OF_CONTROL
756		If this variable is defined, U-Boot will use a device tree
757		to configure its devices, instead of relying on statically
758		compiled #defines in the board file. This option is
759		experimental and only available on a few boards. The device
760		tree is available in the global data as gd->fdt_blob.
761
762		U-Boot needs to get its device tree from somewhere. This can
763		be done using one of the three options below:
764
765		CONFIG_OF_EMBED
766		If this variable is defined, U-Boot will embed a device tree
767		binary in its image. This device tree file should be in the
768		board directory and called <soc>-<board>.dts. The binary file
769		is then picked up in board_init_f() and made available through
770		the global data structure as gd->fdt_blob.
771
772		CONFIG_OF_SEPARATE
773		If this variable is defined, U-Boot will build a device tree
774		binary. It will be called u-boot.dtb. Architecture-specific
775		code will locate it at run-time. Generally this works by:
776
777			cat u-boot.bin u-boot.dtb >image.bin
778
779		and in fact, U-Boot does this for you, creating a file called
780		u-boot-dtb.bin which is useful in the common case. You can
781		still use the individual files if you need something more
782		exotic.
783
784		CONFIG_OF_BOARD
785		If this variable is defined, U-Boot will use the device tree
786		provided by the board at runtime instead of embedding one with
787		the image. Only boards defining board_fdt_blob_setup() support
788		this option (see include/fdtdec.h file).
789
790- Watchdog:
791		CONFIG_WATCHDOG
792		If this variable is defined, it enables watchdog
793		support for the SoC. There must be support in the SoC
794		specific code for a watchdog. For the 8xx
795		CPUs, the SIU Watchdog feature is enabled in the SYPCR
796		register.  When supported for a specific SoC is
797		available, then no further board specific code should
798		be needed to use it.
799
800		CONFIG_HW_WATCHDOG
801		When using a watchdog circuitry external to the used
802		SoC, then define this variable and provide board
803		specific code for the "hw_watchdog_reset" function.
804
805		CONFIG_AT91_HW_WDT_TIMEOUT
806		specify the timeout in seconds. default 2 seconds.
807
808- Real-Time Clock:
809
810		When CONFIG_CMD_DATE is selected, the type of the RTC
811		has to be selected, too. Define exactly one of the
812		following options:
813
814		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
815		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
816		CONFIG_RTC_MC146818	- use MC146818 RTC
817		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
818		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
819		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
820		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
821		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
822		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
823		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
824		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
825		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
826					  RV3029 RTC.
827
828		Note that if the RTC uses I2C, then the I2C interface
829		must also be configured. See I2C Support, below.
830
831- GPIO Support:
832		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
833
834		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
835		chip-ngpio pairs that tell the PCA953X driver the number of
836		pins supported by a particular chip.
837
838		Note that if the GPIO device uses I2C, then the I2C interface
839		must also be configured. See I2C Support, below.
840
841- I/O tracing:
842		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
843		accesses and can checksum them or write a list of them out
844		to memory. See the 'iotrace' command for details. This is
845		useful for testing device drivers since it can confirm that
846		the driver behaves the same way before and after a code
847		change. Currently this is supported on sandbox and arm. To
848		add support for your architecture, add '#include <iotrace.h>'
849		to the bottom of arch/<arch>/include/asm/io.h and test.
850
851		Example output from the 'iotrace stats' command is below.
852		Note that if the trace buffer is exhausted, the checksum will
853		still continue to operate.
854
855			iotrace is enabled
856			Start:  10000000	(buffer start address)
857			Size:   00010000	(buffer size)
858			Offset: 00000120	(current buffer offset)
859			Output: 10000120	(start + offset)
860			Count:  00000018	(number of trace records)
861			CRC32:  9526fb66	(CRC32 of all trace records)
862
863- Timestamp Support:
864
865		When CONFIG_TIMESTAMP is selected, the timestamp
866		(date and time) of an image is printed by image
867		commands like bootm or iminfo. This option is
868		automatically enabled when you select CONFIG_CMD_DATE .
869
870- Partition Labels (disklabels) Supported:
871		Zero or more of the following:
872		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
873		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
874		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
875				       bootloader.  Note 2TB partition limit; see
876				       disk/part_efi.c
877		CONFIG_SCSI) you must configure support for at
878		least one non-MTD partition type as well.
879
880- IDE Reset method:
881		CONFIG_IDE_RESET_ROUTINE - this is defined in several
882		board configurations files but used nowhere!
883
884		CONFIG_IDE_RESET - is this is defined, IDE Reset will
885		be performed by calling the function
886			ide_set_reset(int reset)
887		which has to be defined in a board specific file
888
889- ATAPI Support:
890		CONFIG_ATAPI
891
892		Set this to enable ATAPI support.
893
894- LBA48 Support
895		CONFIG_LBA48
896
897		Set this to enable support for disks larger than 137GB
898		Also look at CONFIG_SYS_64BIT_LBA.
899		Whithout these , LBA48 support uses 32bit variables and will 'only'
900		support disks up to 2.1TB.
901
902		CONFIG_SYS_64BIT_LBA:
903			When enabled, makes the IDE subsystem use 64bit sector addresses.
904			Default is 32bit.
905
906- SCSI Support:
907		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
908		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
909		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
910		maximum numbers of LUNs, SCSI ID's and target
911		devices.
912
913		The environment variable 'scsidevs' is set to the number of
914		SCSI devices found during the last scan.
915
916- NETWORK Support (PCI):
917		CONFIG_E1000
918		Support for Intel 8254x/8257x gigabit chips.
919
920		CONFIG_E1000_SPI
921		Utility code for direct access to the SPI bus on Intel 8257x.
922		This does not do anything useful unless you set at least one
923		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
924
925		CONFIG_E1000_SPI_GENERIC
926		Allow generic access to the SPI bus on the Intel 8257x, for
927		example with the "sspi" command.
928
929		CONFIG_EEPRO100
930		Support for Intel 82557/82559/82559ER chips.
931		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
932		write routine for first time initialisation.
933
934		CONFIG_TULIP
935		Support for Digital 2114x chips.
936		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
937		modem chip initialisation (KS8761/QS6611).
938
939		CONFIG_NATSEMI
940		Support for National dp83815 chips.
941
942		CONFIG_NS8382X
943		Support for National dp8382[01] gigabit chips.
944
945- NETWORK Support (other):
946
947		CONFIG_DRIVER_AT91EMAC
948		Support for AT91RM9200 EMAC.
949
950			CONFIG_RMII
951			Define this to use reduced MII inteface
952
953			CONFIG_DRIVER_AT91EMAC_QUIET
954			If this defined, the driver is quiet.
955			The driver doen't show link status messages.
956
957		CONFIG_CALXEDA_XGMAC
958		Support for the Calxeda XGMAC device
959
960		CONFIG_LAN91C96
961		Support for SMSC's LAN91C96 chips.
962
963			CONFIG_LAN91C96_USE_32_BIT
964			Define this to enable 32 bit addressing
965
966		CONFIG_SMC91111
967		Support for SMSC's LAN91C111 chip
968
969			CONFIG_SMC91111_BASE
970			Define this to hold the physical address
971			of the device (I/O space)
972
973			CONFIG_SMC_USE_32_BIT
974			Define this if data bus is 32 bits
975
976			CONFIG_SMC_USE_IOFUNCS
977			Define this to use i/o functions instead of macros
978			(some hardware wont work with macros)
979
980			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
981			Define this if you have more then 3 PHYs.
982
983		CONFIG_FTGMAC100
984		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
985
986			CONFIG_FTGMAC100_EGIGA
987			Define this to use GE link update with gigabit PHY.
988			Define this if FTGMAC100 is connected to gigabit PHY.
989			If your system has 10/100 PHY only, it might not occur
990			wrong behavior. Because PHY usually return timeout or
991			useless data when polling gigabit status and gigabit
992			control registers. This behavior won't affect the
993			correctnessof 10/100 link speed update.
994
995		CONFIG_SH_ETHER
996		Support for Renesas on-chip Ethernet controller
997
998			CONFIG_SH_ETHER_USE_PORT
999			Define the number of ports to be used
1000
1001			CONFIG_SH_ETHER_PHY_ADDR
1002			Define the ETH PHY's address
1003
1004			CONFIG_SH_ETHER_CACHE_WRITEBACK
1005			If this option is set, the driver enables cache flush.
1006
1007- PWM Support:
1008		CONFIG_PWM_IMX
1009		Support for PWM module on the imx6.
1010
1011- TPM Support:
1012		CONFIG_TPM
1013		Support TPM devices.
1014
1015		CONFIG_TPM_TIS_INFINEON
1016		Support for Infineon i2c bus TPM devices. Only one device
1017		per system is supported at this time.
1018
1019			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1020			Define the burst count bytes upper limit
1021
1022		CONFIG_TPM_ST33ZP24
1023		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1024
1025			CONFIG_TPM_ST33ZP24_I2C
1026			Support for STMicroelectronics ST33ZP24 I2C devices.
1027			Requires TPM_ST33ZP24 and I2C.
1028
1029			CONFIG_TPM_ST33ZP24_SPI
1030			Support for STMicroelectronics ST33ZP24 SPI devices.
1031			Requires TPM_ST33ZP24 and SPI.
1032
1033		CONFIG_TPM_ATMEL_TWI
1034		Support for Atmel TWI TPM device. Requires I2C support.
1035
1036		CONFIG_TPM_TIS_LPC
1037		Support for generic parallel port TPM devices. Only one device
1038		per system is supported at this time.
1039
1040			CONFIG_TPM_TIS_BASE_ADDRESS
1041			Base address where the generic TPM device is mapped
1042			to. Contemporary x86 systems usually map it at
1043			0xfed40000.
1044
1045		CONFIG_TPM
1046		Define this to enable the TPM support library which provides
1047		functional interfaces to some TPM commands.
1048		Requires support for a TPM device.
1049
1050		CONFIG_TPM_AUTH_SESSIONS
1051		Define this to enable authorized functions in the TPM library.
1052		Requires CONFIG_TPM and CONFIG_SHA1.
1053
1054- USB Support:
1055		At the moment only the UHCI host controller is
1056		supported (PIP405, MIP405); define
1057		CONFIG_USB_UHCI to enable it.
1058		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1059		and define CONFIG_USB_STORAGE to enable the USB
1060		storage devices.
1061		Note:
1062		Supported are USB Keyboards and USB Floppy drives
1063		(TEAC FD-05PUB).
1064
1065		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1066		txfilltuning field in the EHCI controller on reset.
1067
1068		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1069		HW module registers.
1070
1071- USB Device:
1072		Define the below if you wish to use the USB console.
1073		Once firmware is rebuilt from a serial console issue the
1074		command "setenv stdin usbtty; setenv stdout usbtty" and
1075		attach your USB cable. The Unix command "dmesg" should print
1076		it has found a new device. The environment variable usbtty
1077		can be set to gserial or cdc_acm to enable your device to
1078		appear to a USB host as a Linux gserial device or a
1079		Common Device Class Abstract Control Model serial device.
1080		If you select usbtty = gserial you should be able to enumerate
1081		a Linux host by
1082		# modprobe usbserial vendor=0xVendorID product=0xProductID
1083		else if using cdc_acm, simply setting the environment
1084		variable usbtty to be cdc_acm should suffice. The following
1085		might be defined in YourBoardName.h
1086
1087			CONFIG_USB_DEVICE
1088			Define this to build a UDC device
1089
1090			CONFIG_USB_TTY
1091			Define this to have a tty type of device available to
1092			talk to the UDC device
1093
1094			CONFIG_USBD_HS
1095			Define this to enable the high speed support for usb
1096			device and usbtty. If this feature is enabled, a routine
1097			int is_usbd_high_speed(void)
1098			also needs to be defined by the driver to dynamically poll
1099			whether the enumeration has succeded at high speed or full
1100			speed.
1101
1102			CONFIG_SYS_CONSOLE_IS_IN_ENV
1103			Define this if you want stdin, stdout &/or stderr to
1104			be set to usbtty.
1105
1106		If you have a USB-IF assigned VendorID then you may wish to
1107		define your own vendor specific values either in BoardName.h
1108		or directly in usbd_vendor_info.h. If you don't define
1109		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1110		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1111		should pretend to be a Linux device to it's target host.
1112
1113			CONFIG_USBD_MANUFACTURER
1114			Define this string as the name of your company for
1115			- CONFIG_USBD_MANUFACTURER "my company"
1116
1117			CONFIG_USBD_PRODUCT_NAME
1118			Define this string as the name of your product
1119			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1120
1121			CONFIG_USBD_VENDORID
1122			Define this as your assigned Vendor ID from the USB
1123			Implementors Forum. This *must* be a genuine Vendor ID
1124			to avoid polluting the USB namespace.
1125			- CONFIG_USBD_VENDORID 0xFFFF
1126
1127			CONFIG_USBD_PRODUCTID
1128			Define this as the unique Product ID
1129			for your device
1130			- CONFIG_USBD_PRODUCTID 0xFFFF
1131
1132- ULPI Layer Support:
1133		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1134		the generic ULPI layer. The generic layer accesses the ULPI PHY
1135		via the platform viewport, so you need both the genric layer and
1136		the viewport enabled. Currently only Chipidea/ARC based
1137		viewport is supported.
1138		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1139		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1140		If your ULPI phy needs a different reference clock than the
1141		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1142		the appropriate value in Hz.
1143
1144- MMC Support:
1145		The MMC controller on the Intel PXA is supported. To
1146		enable this define CONFIG_MMC. The MMC can be
1147		accessed from the boot prompt by mapping the device
1148		to physical memory similar to flash. Command line is
1149		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1150		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1151
1152		CONFIG_SH_MMCIF
1153		Support for Renesas on-chip MMCIF controller
1154
1155			CONFIG_SH_MMCIF_ADDR
1156			Define the base address of MMCIF registers
1157
1158			CONFIG_SH_MMCIF_CLK
1159			Define the clock frequency for MMCIF
1160
1161		CONFIG_SUPPORT_EMMC_BOOT
1162		Enable some additional features of the eMMC boot partitions.
1163
1164- USB Device Firmware Update (DFU) class support:
1165		CONFIG_DFU_OVER_USB
1166		This enables the USB portion of the DFU USB class
1167
1168		CONFIG_DFU_MMC
1169		This enables support for exposing (e)MMC devices via DFU.
1170
1171		CONFIG_DFU_NAND
1172		This enables support for exposing NAND devices via DFU.
1173
1174		CONFIG_DFU_RAM
1175		This enables support for exposing RAM via DFU.
1176		Note: DFU spec refer to non-volatile memory usage, but
1177		allow usages beyond the scope of spec - here RAM usage,
1178		one that would help mostly the developer.
1179
1180		CONFIG_SYS_DFU_DATA_BUF_SIZE
1181		Dfu transfer uses a buffer before writing data to the
1182		raw storage device. Make the size (in bytes) of this buffer
1183		configurable. The size of this buffer is also configurable
1184		through the "dfu_bufsiz" environment variable.
1185
1186		CONFIG_SYS_DFU_MAX_FILE_SIZE
1187		When updating files rather than the raw storage device,
1188		we use a static buffer to copy the file into and then write
1189		the buffer once we've been given the whole file.  Define
1190		this to the maximum filesize (in bytes) for the buffer.
1191		Default is 4 MiB if undefined.
1192
1193		DFU_DEFAULT_POLL_TIMEOUT
1194		Poll timeout [ms], is the timeout a device can send to the
1195		host. The host must wait for this timeout before sending
1196		a subsequent DFU_GET_STATUS request to the device.
1197
1198		DFU_MANIFEST_POLL_TIMEOUT
1199		Poll timeout [ms], which the device sends to the host when
1200		entering dfuMANIFEST state. Host waits this timeout, before
1201		sending again an USB request to the device.
1202
1203- Journaling Flash filesystem support:
1204		CONFIG_JFFS2_NAND
1205		Define these for a default partition on a NAND device
1206
1207		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1208		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1209		Define these for a default partition on a NOR device
1210
1211- Keyboard Support:
1212		See Kconfig help for available keyboard drivers.
1213
1214		CONFIG_KEYBOARD
1215
1216		Define this to enable a custom keyboard support.
1217		This simply calls drv_keyboard_init() which must be
1218		defined in your board-specific files. This option is deprecated
1219		and is only used by novena. For new boards, use driver model
1220		instead.
1221
1222- Video support:
1223		CONFIG_FSL_DIU_FB
1224		Enable the Freescale DIU video driver.	Reference boards for
1225		SOCs that have a DIU should define this macro to enable DIU
1226		support, and should also define these other macros:
1227
1228			CONFIG_SYS_DIU_ADDR
1229			CONFIG_VIDEO
1230			CONFIG_CFB_CONSOLE
1231			CONFIG_VIDEO_SW_CURSOR
1232			CONFIG_VGA_AS_SINGLE_DEVICE
1233			CONFIG_VIDEO_LOGO
1234			CONFIG_VIDEO_BMP_LOGO
1235
1236		The DIU driver will look for the 'video-mode' environment
1237		variable, and if defined, enable the DIU as a console during
1238		boot.  See the documentation file doc/README.video for a
1239		description of this variable.
1240
1241- LCD Support:	CONFIG_LCD
1242
1243		Define this to enable LCD support (for output to LCD
1244		display); also select one of the supported displays
1245		by defining one of these:
1246
1247		CONFIG_ATMEL_LCD:
1248
1249			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1250
1251		CONFIG_NEC_NL6448AC33:
1252
1253			NEC NL6448AC33-18. Active, color, single scan.
1254
1255		CONFIG_NEC_NL6448BC20
1256
1257			NEC NL6448BC20-08. 6.5", 640x480.
1258			Active, color, single scan.
1259
1260		CONFIG_NEC_NL6448BC33_54
1261
1262			NEC NL6448BC33-54. 10.4", 640x480.
1263			Active, color, single scan.
1264
1265		CONFIG_SHARP_16x9
1266
1267			Sharp 320x240. Active, color, single scan.
1268			It isn't 16x9, and I am not sure what it is.
1269
1270		CONFIG_SHARP_LQ64D341
1271
1272			Sharp LQ64D341 display, 640x480.
1273			Active, color, single scan.
1274
1275		CONFIG_HLD1045
1276
1277			HLD1045 display, 640x480.
1278			Active, color, single scan.
1279
1280		CONFIG_OPTREX_BW
1281
1282			Optrex	 CBL50840-2 NF-FW 99 22 M5
1283			or
1284			Hitachi	 LMG6912RPFC-00T
1285			or
1286			Hitachi	 SP14Q002
1287
1288			320x240. Black & white.
1289
1290		CONFIG_LCD_ALIGNMENT
1291
1292		Normally the LCD is page-aligned (typically 4KB). If this is
1293		defined then the LCD will be aligned to this value instead.
1294		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1295		here, since it is cheaper to change data cache settings on
1296		a per-section basis.
1297
1298
1299		CONFIG_LCD_ROTATION
1300
1301		Sometimes, for example if the display is mounted in portrait
1302		mode or even if it's mounted landscape but rotated by 180degree,
1303		we need to rotate our content of the display relative to the
1304		framebuffer, so that user can read the messages which are
1305		printed out.
1306		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1307		initialized with a given rotation from "vl_rot" out of
1308		"vidinfo_t" which is provided by the board specific code.
1309		The value for vl_rot is coded as following (matching to
1310		fbcon=rotate:<n> linux-kernel commandline):
1311		0 = no rotation respectively 0 degree
1312		1 = 90 degree rotation
1313		2 = 180 degree rotation
1314		3 = 270 degree rotation
1315
1316		If CONFIG_LCD_ROTATION is not defined, the console will be
1317		initialized with 0degree rotation.
1318
1319		CONFIG_LCD_BMP_RLE8
1320
1321		Support drawing of RLE8-compressed bitmaps on the LCD.
1322
1323		CONFIG_I2C_EDID
1324
1325		Enables an 'i2c edid' command which can read EDID
1326		information over I2C from an attached LCD display.
1327
1328- Splash Screen Support: CONFIG_SPLASH_SCREEN
1329
1330		If this option is set, the environment is checked for
1331		a variable "splashimage". If found, the usual display
1332		of logo, copyright and system information on the LCD
1333		is suppressed and the BMP image at the address
1334		specified in "splashimage" is loaded instead. The
1335		console is redirected to the "nulldev", too. This
1336		allows for a "silent" boot where a splash screen is
1337		loaded very quickly after power-on.
1338
1339		CONFIG_SPLASHIMAGE_GUARD
1340
1341		If this option is set, then U-Boot will prevent the environment
1342		variable "splashimage" from being set to a problematic address
1343		(see doc/README.displaying-bmps).
1344		This option is useful for targets where, due to alignment
1345		restrictions, an improperly aligned BMP image will cause a data
1346		abort. If you think you will not have problems with unaligned
1347		accesses (for example because your toolchain prevents them)
1348		there is no need to set this option.
1349
1350		CONFIG_SPLASH_SCREEN_ALIGN
1351
1352		If this option is set the splash image can be freely positioned
1353		on the screen. Environment variable "splashpos" specifies the
1354		position as "x,y". If a positive number is given it is used as
1355		number of pixel from left/top. If a negative number is given it
1356		is used as number of pixel from right/bottom. You can also
1357		specify 'm' for centering the image.
1358
1359		Example:
1360		setenv splashpos m,m
1361			=> image at center of screen
1362
1363		setenv splashpos 30,20
1364			=> image at x = 30 and y = 20
1365
1366		setenv splashpos -10,m
1367			=> vertically centered image
1368			   at x = dspWidth - bmpWidth - 9
1369
1370- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1371
1372		If this option is set, additionally to standard BMP
1373		images, gzipped BMP images can be displayed via the
1374		splashscreen support or the bmp command.
1375
1376- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1377
1378		If this option is set, 8-bit RLE compressed BMP images
1379		can be displayed via the splashscreen support or the
1380		bmp command.
1381
1382- Compression support:
1383		CONFIG_GZIP
1384
1385		Enabled by default to support gzip compressed images.
1386
1387		CONFIG_BZIP2
1388
1389		If this option is set, support for bzip2 compressed
1390		images is included. If not, only uncompressed and gzip
1391		compressed images are supported.
1392
1393		NOTE: the bzip2 algorithm requires a lot of RAM, so
1394		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1395		be at least 4MB.
1396
1397- MII/PHY support:
1398		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1399
1400		The clock frequency of the MII bus
1401
1402		CONFIG_PHY_RESET_DELAY
1403
1404		Some PHY like Intel LXT971A need extra delay after
1405		reset before any MII register access is possible.
1406		For such PHY, set this option to the usec delay
1407		required. (minimum 300usec for LXT971A)
1408
1409		CONFIG_PHY_CMD_DELAY (ppc4xx)
1410
1411		Some PHY like Intel LXT971A need extra delay after
1412		command issued before MII status register can be read
1413
1414- IP address:
1415		CONFIG_IPADDR
1416
1417		Define a default value for the IP address to use for
1418		the default Ethernet interface, in case this is not
1419		determined through e.g. bootp.
1420		(Environment variable "ipaddr")
1421
1422- Server IP address:
1423		CONFIG_SERVERIP
1424
1425		Defines a default value for the IP address of a TFTP
1426		server to contact when using the "tftboot" command.
1427		(Environment variable "serverip")
1428
1429		CONFIG_KEEP_SERVERADDR
1430
1431		Keeps the server's MAC address, in the env 'serveraddr'
1432		for passing to bootargs (like Linux's netconsole option)
1433
1434- Gateway IP address:
1435		CONFIG_GATEWAYIP
1436
1437		Defines a default value for the IP address of the
1438		default router where packets to other networks are
1439		sent to.
1440		(Environment variable "gatewayip")
1441
1442- Subnet mask:
1443		CONFIG_NETMASK
1444
1445		Defines a default value for the subnet mask (or
1446		routing prefix) which is used to determine if an IP
1447		address belongs to the local subnet or needs to be
1448		forwarded through a router.
1449		(Environment variable "netmask")
1450
1451- Multicast TFTP Mode:
1452		CONFIG_MCAST_TFTP
1453
1454		Defines whether you want to support multicast TFTP as per
1455		rfc-2090; for example to work with atftp.  Lets lots of targets
1456		tftp down the same boot image concurrently.  Note: the Ethernet
1457		driver in use must provide a function: mcast() to join/leave a
1458		multicast group.
1459
1460- BOOTP Recovery Mode:
1461		CONFIG_BOOTP_RANDOM_DELAY
1462
1463		If you have many targets in a network that try to
1464		boot using BOOTP, you may want to avoid that all
1465		systems send out BOOTP requests at precisely the same
1466		moment (which would happen for instance at recovery
1467		from a power failure, when all systems will try to
1468		boot, thus flooding the BOOTP server. Defining
1469		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1470		inserted before sending out BOOTP requests. The
1471		following delays are inserted then:
1472
1473		1st BOOTP request:	delay 0 ... 1 sec
1474		2nd BOOTP request:	delay 0 ... 2 sec
1475		3rd BOOTP request:	delay 0 ... 4 sec
1476		4th and following
1477		BOOTP requests:		delay 0 ... 8 sec
1478
1479		CONFIG_BOOTP_ID_CACHE_SIZE
1480
1481		BOOTP packets are uniquely identified using a 32-bit ID. The
1482		server will copy the ID from client requests to responses and
1483		U-Boot will use this to determine if it is the destination of
1484		an incoming response. Some servers will check that addresses
1485		aren't in use before handing them out (usually using an ARP
1486		ping) and therefore take up to a few hundred milliseconds to
1487		respond. Network congestion may also influence the time it
1488		takes for a response to make it back to the client. If that
1489		time is too long, U-Boot will retransmit requests. In order
1490		to allow earlier responses to still be accepted after these
1491		retransmissions, U-Boot's BOOTP client keeps a small cache of
1492		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1493		cache. The default is to keep IDs for up to four outstanding
1494		requests. Increasing this will allow U-Boot to accept offers
1495		from a BOOTP client in networks with unusually high latency.
1496
1497- DHCP Advanced Options:
1498		You can fine tune the DHCP functionality by defining
1499		CONFIG_BOOTP_* symbols:
1500
1501		CONFIG_BOOTP_NISDOMAIN
1502		CONFIG_BOOTP_BOOTFILESIZE
1503		CONFIG_BOOTP_SEND_HOSTNAME
1504		CONFIG_BOOTP_NTPSERVER
1505		CONFIG_BOOTP_TIMEOFFSET
1506		CONFIG_BOOTP_VENDOREX
1507		CONFIG_BOOTP_MAY_FAIL
1508
1509		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1510		environment variable, not the BOOTP server.
1511
1512		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1513		after the configured retry count, the call will fail
1514		instead of starting over.  This can be used to fail over
1515		to Link-local IP address configuration if the DHCP server
1516		is not available.
1517
1518		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1519		to do a dynamic update of a DNS server. To do this, they
1520		need the hostname of the DHCP requester.
1521		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1522		of the "hostname" environment variable is passed as
1523		option 12 to the DHCP server.
1524
1525		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1526
1527		A 32bit value in microseconds for a delay between
1528		receiving a "DHCP Offer" and sending the "DHCP Request".
1529		This fixes a problem with certain DHCP servers that don't
1530		respond 100% of the time to a "DHCP request". E.g. On an
1531		AT91RM9200 processor running at 180MHz, this delay needed
1532		to be *at least* 15,000 usec before a Windows Server 2003
1533		DHCP server would reply 100% of the time. I recommend at
1534		least 50,000 usec to be safe. The alternative is to hope
1535		that one of the retries will be successful but note that
1536		the DHCP timeout and retry process takes a longer than
1537		this delay.
1538
1539 - Link-local IP address negotiation:
1540		Negotiate with other link-local clients on the local network
1541		for an address that doesn't require explicit configuration.
1542		This is especially useful if a DHCP server cannot be guaranteed
1543		to exist in all environments that the device must operate.
1544
1545		See doc/README.link-local for more information.
1546
1547 - MAC address from environment variables
1548
1549		FDT_SEQ_MACADDR_FROM_ENV
1550
1551		Fix-up device tree with MAC addresses fetched sequentially from
1552		environment variables. This config work on assumption that
1553		non-usable ethernet node of device-tree are either not present
1554		or their status has been marked as "disabled".
1555
1556 - CDP Options:
1557		CONFIG_CDP_DEVICE_ID
1558
1559		The device id used in CDP trigger frames.
1560
1561		CONFIG_CDP_DEVICE_ID_PREFIX
1562
1563		A two character string which is prefixed to the MAC address
1564		of the device.
1565
1566		CONFIG_CDP_PORT_ID
1567
1568		A printf format string which contains the ascii name of
1569		the port. Normally is set to "eth%d" which sets
1570		eth0 for the first Ethernet, eth1 for the second etc.
1571
1572		CONFIG_CDP_CAPABILITIES
1573
1574		A 32bit integer which indicates the device capabilities;
1575		0x00000010 for a normal host which does not forwards.
1576
1577		CONFIG_CDP_VERSION
1578
1579		An ascii string containing the version of the software.
1580
1581		CONFIG_CDP_PLATFORM
1582
1583		An ascii string containing the name of the platform.
1584
1585		CONFIG_CDP_TRIGGER
1586
1587		A 32bit integer sent on the trigger.
1588
1589		CONFIG_CDP_POWER_CONSUMPTION
1590
1591		A 16bit integer containing the power consumption of the
1592		device in .1 of milliwatts.
1593
1594		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1595
1596		A byte containing the id of the VLAN.
1597
1598- Status LED:	CONFIG_LED_STATUS
1599
1600		Several configurations allow to display the current
1601		status using a LED. For instance, the LED will blink
1602		fast while running U-Boot code, stop blinking as
1603		soon as a reply to a BOOTP request was received, and
1604		start blinking slow once the Linux kernel is running
1605		(supported by a status LED driver in the Linux
1606		kernel). Defining CONFIG_LED_STATUS enables this
1607		feature in U-Boot.
1608
1609		Additional options:
1610
1611		CONFIG_LED_STATUS_GPIO
1612		The status LED can be connected to a GPIO pin.
1613		In such cases, the gpio_led driver can be used as a
1614		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1615		to include the gpio_led driver in the U-Boot binary.
1616
1617		CONFIG_GPIO_LED_INVERTED_TABLE
1618		Some GPIO connected LEDs may have inverted polarity in which
1619		case the GPIO high value corresponds to LED off state and
1620		GPIO low value corresponds to LED on state.
1621		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1622		with a list of GPIO LEDs that have inverted polarity.
1623
1624- I2C Support:	CONFIG_SYS_I2C
1625
1626		This enable the NEW i2c subsystem, and will allow you to use
1627		i2c commands at the u-boot command line (as long as you set
1628		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1629		based realtime clock chips or other i2c devices. See
1630		common/cmd_i2c.c for a description of the command line
1631		interface.
1632
1633		ported i2c driver to the new framework:
1634		- drivers/i2c/soft_i2c.c:
1635		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1636		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1637		    for defining speed and slave address
1638		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1639		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1640		    for defining speed and slave address
1641		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1642		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1643		    for defining speed and slave address
1644		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1645		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1646		    for defining speed and slave address
1647
1648		- drivers/i2c/fsl_i2c.c:
1649		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1650		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1651		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1652		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1653		    bus.
1654		  - If your board supports a second fsl i2c bus, define
1655		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1656		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1657		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1658		    second bus.
1659
1660		- drivers/i2c/tegra_i2c.c:
1661		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1662		  - This driver adds 4 i2c buses with a fix speed from
1663		    100000 and the slave addr 0!
1664
1665		- drivers/i2c/ppc4xx_i2c.c
1666		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1667		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1668		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1669
1670		- drivers/i2c/i2c_mxc.c
1671		  - activate this driver with CONFIG_SYS_I2C_MXC
1672		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1673		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1674		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1675		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1676		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1677		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1678		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1679		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1680		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1681		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1682		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1683		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1684		If those defines are not set, default value is 100000
1685		for speed, and 0 for slave.
1686
1687		- drivers/i2c/rcar_i2c.c:
1688		  - activate this driver with CONFIG_SYS_I2C_RCAR
1689		  - This driver adds 4 i2c buses
1690
1691		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1692		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1693		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1694		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1695		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1696		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1697		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1698		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1699		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1700
1701		- drivers/i2c/sh_i2c.c:
1702		  - activate this driver with CONFIG_SYS_I2C_SH
1703		  - This driver adds from 2 to 5 i2c buses
1704
1705		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1706		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1707		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1708		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1709		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1710		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1711		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1712		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1713		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1714		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1715		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1716
1717		- drivers/i2c/omap24xx_i2c.c
1718		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1719		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1720		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1721		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1722		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1723		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1724		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1725		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1726		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1727		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1728		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1729
1730		- drivers/i2c/zynq_i2c.c
1731		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1732		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1733		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1734
1735		- drivers/i2c/s3c24x0_i2c.c:
1736		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1737		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1738		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1739		    with a fix speed from 100000 and the slave addr 0!
1740
1741		- drivers/i2c/ihs_i2c.c
1742		  - activate this driver with CONFIG_SYS_I2C_IHS
1743		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1744		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1745		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1746		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1747		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1748		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1749		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1750		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1751		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1752		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1753		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1754		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1755		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1756		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1757		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1758		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1759		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1760		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1761		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1762		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1763		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1764
1765		additional defines:
1766
1767		CONFIG_SYS_NUM_I2C_BUSES
1768		Hold the number of i2c buses you want to use.
1769
1770		CONFIG_SYS_I2C_DIRECT_BUS
1771		define this, if you don't use i2c muxes on your hardware.
1772		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1773		omit this define.
1774
1775		CONFIG_SYS_I2C_MAX_HOPS
1776		define how many muxes are maximal consecutively connected
1777		on one i2c bus. If you not use i2c muxes, omit this
1778		define.
1779
1780		CONFIG_SYS_I2C_BUSES
1781		hold a list of buses you want to use, only used if
1782		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1783		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1784		CONFIG_SYS_NUM_I2C_BUSES = 9:
1785
1786		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1787					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1788					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1789					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1790					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1791					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1792					{1, {I2C_NULL_HOP}}, \
1793					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1794					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1795					}
1796
1797		which defines
1798			bus 0 on adapter 0 without a mux
1799			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1800			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1801			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1802			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1803			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1804			bus 6 on adapter 1 without a mux
1805			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1806			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1807
1808		If you do not have i2c muxes on your board, omit this define.
1809
1810- Legacy I2C Support:
1811		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1812		then the following macros need to be defined (examples are
1813		from include/configs/lwmon.h):
1814
1815		I2C_INIT
1816
1817		(Optional). Any commands necessary to enable the I2C
1818		controller or configure ports.
1819
1820		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1821
1822		I2C_ACTIVE
1823
1824		The code necessary to make the I2C data line active
1825		(driven).  If the data line is open collector, this
1826		define can be null.
1827
1828		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1829
1830		I2C_TRISTATE
1831
1832		The code necessary to make the I2C data line tri-stated
1833		(inactive).  If the data line is open collector, this
1834		define can be null.
1835
1836		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1837
1838		I2C_READ
1839
1840		Code that returns true if the I2C data line is high,
1841		false if it is low.
1842
1843		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1844
1845		I2C_SDA(bit)
1846
1847		If <bit> is true, sets the I2C data line high. If it
1848		is false, it clears it (low).
1849
1850		eg: #define I2C_SDA(bit) \
1851			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1852			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1853
1854		I2C_SCL(bit)
1855
1856		If <bit> is true, sets the I2C clock line high. If it
1857		is false, it clears it (low).
1858
1859		eg: #define I2C_SCL(bit) \
1860			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1861			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1862
1863		I2C_DELAY
1864
1865		This delay is invoked four times per clock cycle so this
1866		controls the rate of data transfer.  The data rate thus
1867		is 1 / (I2C_DELAY * 4). Often defined to be something
1868		like:
1869
1870		#define I2C_DELAY  udelay(2)
1871
1872		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1873
1874		If your arch supports the generic GPIO framework (asm/gpio.h),
1875		then you may alternatively define the two GPIOs that are to be
1876		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1877		have GPIO-based defaults assigned to them as appropriate.
1878
1879		You should define these to the GPIO value as given directly to
1880		the generic GPIO functions.
1881
1882		CONFIG_SYS_I2C_INIT_BOARD
1883
1884		When a board is reset during an i2c bus transfer
1885		chips might think that the current transfer is still
1886		in progress. On some boards it is possible to access
1887		the i2c SCLK line directly, either by using the
1888		processor pin as a GPIO or by having a second pin
1889		connected to the bus. If this option is defined a
1890		custom i2c_init_board() routine in boards/xxx/board.c
1891		is run early in the boot sequence.
1892
1893		CONFIG_I2C_MULTI_BUS
1894
1895		This option allows the use of multiple I2C buses, each of which
1896		must have a controller.	 At any point in time, only one bus is
1897		active.	 To switch to a different bus, use the 'i2c dev' command.
1898		Note that bus numbering is zero-based.
1899
1900		CONFIG_SYS_I2C_NOPROBES
1901
1902		This option specifies a list of I2C devices that will be skipped
1903		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1904		is set, specify a list of bus-device pairs.  Otherwise, specify
1905		a 1D array of device addresses
1906
1907		e.g.
1908			#undef	CONFIG_I2C_MULTI_BUS
1909			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1910
1911		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1912
1913			#define CONFIG_I2C_MULTI_BUS
1914			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1915
1916		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1917
1918		CONFIG_SYS_SPD_BUS_NUM
1919
1920		If defined, then this indicates the I2C bus number for DDR SPD.
1921		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1922
1923		CONFIG_SYS_RTC_BUS_NUM
1924
1925		If defined, then this indicates the I2C bus number for the RTC.
1926		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1927
1928		CONFIG_SOFT_I2C_READ_REPEATED_START
1929
1930		defining this will force the i2c_read() function in
1931		the soft_i2c driver to perform an I2C repeated start
1932		between writing the address pointer and reading the
1933		data.  If this define is omitted the default behaviour
1934		of doing a stop-start sequence will be used.  Most I2C
1935		devices can use either method, but some require one or
1936		the other.
1937
1938- SPI Support:	CONFIG_SPI
1939
1940		Enables SPI driver (so far only tested with
1941		SPI EEPROM, also an instance works with Crystal A/D and
1942		D/As on the SACSng board)
1943
1944		CONFIG_SOFT_SPI
1945
1946		Enables a software (bit-bang) SPI driver rather than
1947		using hardware support. This is a general purpose
1948		driver that only requires three general I/O port pins
1949		(two outputs, one input) to function. If this is
1950		defined, the board configuration must define several
1951		SPI configuration items (port pins to use, etc). For
1952		an example, see include/configs/sacsng.h.
1953
1954		CONFIG_HARD_SPI
1955
1956		Enables a hardware SPI driver for general-purpose reads
1957		and writes.  As with CONFIG_SOFT_SPI, the board configuration
1958		must define a list of chip-select function pointers.
1959		Currently supported on some MPC8xxx processors.	 For an
1960		example, see include/configs/mpc8349emds.h.
1961
1962		CONFIG_SYS_SPI_MXC_WAIT
1963		Timeout for waiting until spi transfer completed.
1964		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1965
1966- FPGA Support: CONFIG_FPGA
1967
1968		Enables FPGA subsystem.
1969
1970		CONFIG_FPGA_<vendor>
1971
1972		Enables support for specific chip vendors.
1973		(ALTERA, XILINX)
1974
1975		CONFIG_FPGA_<family>
1976
1977		Enables support for FPGA family.
1978		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1979
1980		CONFIG_FPGA_COUNT
1981
1982		Specify the number of FPGA devices to support.
1983
1984		CONFIG_SYS_FPGA_PROG_FEEDBACK
1985
1986		Enable printing of hash marks during FPGA configuration.
1987
1988		CONFIG_SYS_FPGA_CHECK_BUSY
1989
1990		Enable checks on FPGA configuration interface busy
1991		status by the configuration function. This option
1992		will require a board or device specific function to
1993		be written.
1994
1995		CONFIG_FPGA_DELAY
1996
1997		If defined, a function that provides delays in the FPGA
1998		configuration driver.
1999
2000		CONFIG_SYS_FPGA_CHECK_CTRLC
2001		Allow Control-C to interrupt FPGA configuration
2002
2003		CONFIG_SYS_FPGA_CHECK_ERROR
2004
2005		Check for configuration errors during FPGA bitfile
2006		loading. For example, abort during Virtex II
2007		configuration if the INIT_B line goes low (which
2008		indicated a CRC error).
2009
2010		CONFIG_SYS_FPGA_WAIT_INIT
2011
2012		Maximum time to wait for the INIT_B line to de-assert
2013		after PROB_B has been de-asserted during a Virtex II
2014		FPGA configuration sequence. The default time is 500
2015		ms.
2016
2017		CONFIG_SYS_FPGA_WAIT_BUSY
2018
2019		Maximum time to wait for BUSY to de-assert during
2020		Virtex II FPGA configuration. The default is 5 ms.
2021
2022		CONFIG_SYS_FPGA_WAIT_CONFIG
2023
2024		Time to wait after FPGA configuration. The default is
2025		200 ms.
2026
2027- Configuration Management:
2028		CONFIG_BUILD_TARGET
2029
2030		Some SoCs need special image types (e.g. U-Boot binary
2031		with a special header) as build targets. By defining
2032		CONFIG_BUILD_TARGET in the SoC / board header, this
2033		special image will be automatically built upon calling
2034		make / buildman.
2035
2036		CONFIG_IDENT_STRING
2037
2038		If defined, this string will be added to the U-Boot
2039		version information (U_BOOT_VERSION)
2040
2041- Vendor Parameter Protection:
2042
2043		U-Boot considers the values of the environment
2044		variables "serial#" (Board Serial Number) and
2045		"ethaddr" (Ethernet Address) to be parameters that
2046		are set once by the board vendor / manufacturer, and
2047		protects these variables from casual modification by
2048		the user. Once set, these variables are read-only,
2049		and write or delete attempts are rejected. You can
2050		change this behaviour:
2051
2052		If CONFIG_ENV_OVERWRITE is #defined in your config
2053		file, the write protection for vendor parameters is
2054		completely disabled. Anybody can change or delete
2055		these parameters.
2056
2057		Alternatively, if you define _both_ an ethaddr in the
2058		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2059		Ethernet address is installed in the environment,
2060		which can be changed exactly ONCE by the user. [The
2061		serial# is unaffected by this, i. e. it remains
2062		read-only.]
2063
2064		The same can be accomplished in a more flexible way
2065		for any variable by configuring the type of access
2066		to allow for those variables in the ".flags" variable
2067		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2068
2069- Protected RAM:
2070		CONFIG_PRAM
2071
2072		Define this variable to enable the reservation of
2073		"protected RAM", i. e. RAM which is not overwritten
2074		by U-Boot. Define CONFIG_PRAM to hold the number of
2075		kB you want to reserve for pRAM. You can overwrite
2076		this default value by defining an environment
2077		variable "pram" to the number of kB you want to
2078		reserve. Note that the board info structure will
2079		still show the full amount of RAM. If pRAM is
2080		reserved, a new environment variable "mem" will
2081		automatically be defined to hold the amount of
2082		remaining RAM in a form that can be passed as boot
2083		argument to Linux, for instance like that:
2084
2085			setenv bootargs ... mem=\${mem}
2086			saveenv
2087
2088		This way you can tell Linux not to use this memory,
2089		either, which results in a memory region that will
2090		not be affected by reboots.
2091
2092		*WARNING* If your board configuration uses automatic
2093		detection of the RAM size, you must make sure that
2094		this memory test is non-destructive. So far, the
2095		following board configurations are known to be
2096		"pRAM-clean":
2097
2098			IVMS8, IVML24, SPD8xx,
2099			HERMES, IP860, RPXlite, LWMON,
2100			FLAGADM
2101
2102- Access to physical memory region (> 4GB)
2103		Some basic support is provided for operations on memory not
2104		normally accessible to U-Boot - e.g. some architectures
2105		support access to more than 4GB of memory on 32-bit
2106		machines using physical address extension or similar.
2107		Define CONFIG_PHYSMEM to access this basic support, which
2108		currently only supports clearing the memory.
2109
2110- Error Recovery:
2111		CONFIG_NET_RETRY_COUNT
2112
2113		This variable defines the number of retries for
2114		network operations like ARP, RARP, TFTP, or BOOTP
2115		before giving up the operation. If not defined, a
2116		default value of 5 is used.
2117
2118		CONFIG_ARP_TIMEOUT
2119
2120		Timeout waiting for an ARP reply in milliseconds.
2121
2122		CONFIG_NFS_TIMEOUT
2123
2124		Timeout in milliseconds used in NFS protocol.
2125		If you encounter "ERROR: Cannot umount" in nfs command,
2126		try longer timeout such as
2127		#define CONFIG_NFS_TIMEOUT 10000UL
2128
2129- Command Interpreter:
2130		CONFIG_SYS_PROMPT_HUSH_PS2
2131
2132		This defines the secondary prompt string, which is
2133		printed when the command interpreter needs more input
2134		to complete a command. Usually "> ".
2135
2136	Note:
2137
2138		In the current implementation, the local variables
2139		space and global environment variables space are
2140		separated. Local variables are those you define by
2141		simply typing `name=value'. To access a local
2142		variable later on, you have write `$name' or
2143		`${name}'; to execute the contents of a variable
2144		directly type `$name' at the command prompt.
2145
2146		Global environment variables are those you use
2147		setenv/printenv to work with. To run a command stored
2148		in such a variable, you need to use the run command,
2149		and you must not use the '$' sign to access them.
2150
2151		To store commands and special characters in a
2152		variable, please use double quotation marks
2153		surrounding the whole text of the variable, instead
2154		of the backslashes before semicolons and special
2155		symbols.
2156
2157- Command Line Editing and History:
2158		CONFIG_CMDLINE_PS_SUPPORT
2159
2160		Enable support for changing the command prompt string
2161		at run-time. Only static string is supported so far.
2162		The string is obtained from environment variables PS1
2163		and PS2.
2164
2165- Default Environment:
2166		CONFIG_EXTRA_ENV_SETTINGS
2167
2168		Define this to contain any number of null terminated
2169		strings (variable = value pairs) that will be part of
2170		the default environment compiled into the boot image.
2171
2172		For example, place something like this in your
2173		board's config file:
2174
2175		#define CONFIG_EXTRA_ENV_SETTINGS \
2176			"myvar1=value1\0" \
2177			"myvar2=value2\0"
2178
2179		Warning: This method is based on knowledge about the
2180		internal format how the environment is stored by the
2181		U-Boot code. This is NOT an official, exported
2182		interface! Although it is unlikely that this format
2183		will change soon, there is no guarantee either.
2184		You better know what you are doing here.
2185
2186		Note: overly (ab)use of the default environment is
2187		discouraged. Make sure to check other ways to preset
2188		the environment like the "source" command or the
2189		boot command first.
2190
2191		CONFIG_DELAY_ENVIRONMENT
2192
2193		Normally the environment is loaded when the board is
2194		initialised so that it is available to U-Boot. This inhibits
2195		that so that the environment is not available until
2196		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2197		this is instead controlled by the value of
2198		/config/load-environment.
2199
2200- Serial Flash support
2201		Usage requires an initial 'sf probe' to define the serial
2202		flash parameters, followed by read/write/erase/update
2203		commands.
2204
2205		The following defaults may be provided by the platform
2206		to handle the common case when only a single serial
2207		flash is present on the system.
2208
2209		CONFIG_SF_DEFAULT_BUS		Bus identifier
2210		CONFIG_SF_DEFAULT_CS		Chip-select
2211		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2212		CONFIG_SF_DEFAULT_SPEED		in Hz
2213
2214
2215- TFTP Fixed UDP Port:
2216		CONFIG_TFTP_PORT
2217
2218		If this is defined, the environment variable tftpsrcp
2219		is used to supply the TFTP UDP source port value.
2220		If tftpsrcp isn't defined, the normal pseudo-random port
2221		number generator is used.
2222
2223		Also, the environment variable tftpdstp is used to supply
2224		the TFTP UDP destination port value.  If tftpdstp isn't
2225		defined, the normal port 69 is used.
2226
2227		The purpose for tftpsrcp is to allow a TFTP server to
2228		blindly start the TFTP transfer using the pre-configured
2229		target IP address and UDP port. This has the effect of
2230		"punching through" the (Windows XP) firewall, allowing
2231		the remainder of the TFTP transfer to proceed normally.
2232		A better solution is to properly configure the firewall,
2233		but sometimes that is not allowed.
2234
2235- Show boot progress:
2236		CONFIG_SHOW_BOOT_PROGRESS
2237
2238		Defining this option allows to add some board-
2239		specific code (calling a user-provided function
2240		"show_boot_progress(int)") that enables you to show
2241		the system's boot progress on some display (for
2242		example, some LED's) on your board. At the moment,
2243		the following checkpoints are implemented:
2244
2245
2246Legacy uImage format:
2247
2248  Arg	Where			When
2249    1	common/cmd_bootm.c	before attempting to boot an image
2250   -1	common/cmd_bootm.c	Image header has bad	 magic number
2251    2	common/cmd_bootm.c	Image header has correct magic number
2252   -2	common/cmd_bootm.c	Image header has bad	 checksum
2253    3	common/cmd_bootm.c	Image header has correct checksum
2254   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2255    4	common/cmd_bootm.c	Image data   has correct checksum
2256   -4	common/cmd_bootm.c	Image is for unsupported architecture
2257    5	common/cmd_bootm.c	Architecture check OK
2258   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2259    6	common/cmd_bootm.c	Image Type check OK
2260   -6	common/cmd_bootm.c	gunzip uncompression error
2261   -7	common/cmd_bootm.c	Unimplemented compression type
2262    7	common/cmd_bootm.c	Uncompression OK
2263    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2264   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2265
2266    9	common/image.c		Start initial ramdisk verification
2267  -10	common/image.c		Ramdisk header has bad	   magic number
2268  -11	common/image.c		Ramdisk header has bad	   checksum
2269   10	common/image.c		Ramdisk header is OK
2270  -12	common/image.c		Ramdisk data   has bad	   checksum
2271   11	common/image.c		Ramdisk data   has correct checksum
2272   12	common/image.c		Ramdisk verification complete, start loading
2273  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2274   13	common/image.c		Start multifile image verification
2275   14	common/image.c		No initial ramdisk, no multifile, continue.
2276
2277   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2278
2279  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2280  -31	post/post.c		POST test failed, detected by post_output_backlog()
2281  -32	post/post.c		POST test failed, detected by post_run_single()
2282
2283   34	common/cmd_doc.c	before loading a Image from a DOC device
2284  -35	common/cmd_doc.c	Bad usage of "doc" command
2285   35	common/cmd_doc.c	correct usage of "doc" command
2286  -36	common/cmd_doc.c	No boot device
2287   36	common/cmd_doc.c	correct boot device
2288  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2289   37	common/cmd_doc.c	correct chip ID found, device available
2290  -38	common/cmd_doc.c	Read Error on boot device
2291   38	common/cmd_doc.c	reading Image header from DOC device OK
2292  -39	common/cmd_doc.c	Image header has bad magic number
2293   39	common/cmd_doc.c	Image header has correct magic number
2294  -40	common/cmd_doc.c	Error reading Image from DOC device
2295   40	common/cmd_doc.c	Image header has correct magic number
2296   41	common/cmd_ide.c	before loading a Image from a IDE device
2297  -42	common/cmd_ide.c	Bad usage of "ide" command
2298   42	common/cmd_ide.c	correct usage of "ide" command
2299  -43	common/cmd_ide.c	No boot device
2300   43	common/cmd_ide.c	boot device found
2301  -44	common/cmd_ide.c	Device not available
2302   44	common/cmd_ide.c	Device available
2303  -45	common/cmd_ide.c	wrong partition selected
2304   45	common/cmd_ide.c	partition selected
2305  -46	common/cmd_ide.c	Unknown partition table
2306   46	common/cmd_ide.c	valid partition table found
2307  -47	common/cmd_ide.c	Invalid partition type
2308   47	common/cmd_ide.c	correct partition type
2309  -48	common/cmd_ide.c	Error reading Image Header on boot device
2310   48	common/cmd_ide.c	reading Image Header from IDE device OK
2311  -49	common/cmd_ide.c	Image header has bad magic number
2312   49	common/cmd_ide.c	Image header has correct magic number
2313  -50	common/cmd_ide.c	Image header has bad	 checksum
2314   50	common/cmd_ide.c	Image header has correct checksum
2315  -51	common/cmd_ide.c	Error reading Image from IDE device
2316   51	common/cmd_ide.c	reading Image from IDE device OK
2317   52	common/cmd_nand.c	before loading a Image from a NAND device
2318  -53	common/cmd_nand.c	Bad usage of "nand" command
2319   53	common/cmd_nand.c	correct usage of "nand" command
2320  -54	common/cmd_nand.c	No boot device
2321   54	common/cmd_nand.c	boot device found
2322  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2323   55	common/cmd_nand.c	correct chip ID found, device available
2324  -56	common/cmd_nand.c	Error reading Image Header on boot device
2325   56	common/cmd_nand.c	reading Image Header from NAND device OK
2326  -57	common/cmd_nand.c	Image header has bad magic number
2327   57	common/cmd_nand.c	Image header has correct magic number
2328  -58	common/cmd_nand.c	Error reading Image from NAND device
2329   58	common/cmd_nand.c	reading Image from NAND device OK
2330
2331  -60	common/env_common.c	Environment has a bad CRC, using default
2332
2333   64	net/eth.c		starting with Ethernet configuration.
2334  -64	net/eth.c		no Ethernet found.
2335   65	net/eth.c		Ethernet found.
2336
2337  -80	common/cmd_net.c	usage wrong
2338   80	common/cmd_net.c	before calling net_loop()
2339  -81	common/cmd_net.c	some error in net_loop() occurred
2340   81	common/cmd_net.c	net_loop() back without error
2341  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2342   82	common/cmd_net.c	trying automatic boot
2343   83	common/cmd_net.c	running "source" command
2344  -83	common/cmd_net.c	some error in automatic boot or "source" command
2345   84	common/cmd_net.c	end without errors
2346
2347FIT uImage format:
2348
2349  Arg	Where			When
2350  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2351 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2352  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2353 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2354  102	common/cmd_bootm.c	Kernel unit name specified
2355 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2356  103	common/cmd_bootm.c	Found configuration node
2357  104	common/cmd_bootm.c	Got kernel subimage node offset
2358 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2359  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2360 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2361  106	common/cmd_bootm.c	Architecture check OK
2362 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2363  107	common/cmd_bootm.c	Kernel subimage type OK
2364 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2365  108	common/cmd_bootm.c	Got kernel subimage data/size
2366 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2367 -109	common/cmd_bootm.c	Can't get kernel subimage type
2368 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2369 -111	common/cmd_bootm.c	Can't get kernel subimage os
2370 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2371 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2372
2373  120	common/image.c		Start initial ramdisk verification
2374 -120	common/image.c		Ramdisk FIT image has incorrect format
2375  121	common/image.c		Ramdisk FIT image has correct format
2376  122	common/image.c		No ramdisk subimage unit name, using configuration
2377 -122	common/image.c		Can't get configuration for ramdisk subimage
2378  123	common/image.c		Ramdisk unit name specified
2379 -124	common/image.c		Can't get ramdisk subimage node offset
2380  125	common/image.c		Got ramdisk subimage node offset
2381 -125	common/image.c		Ramdisk subimage hash verification failed
2382  126	common/image.c		Ramdisk subimage hash verification OK
2383 -126	common/image.c		Ramdisk subimage for unsupported architecture
2384  127	common/image.c		Architecture check OK
2385 -127	common/image.c		Can't get ramdisk subimage data/size
2386  128	common/image.c		Got ramdisk subimage data/size
2387  129	common/image.c		Can't get ramdisk load address
2388 -129	common/image.c		Got ramdisk load address
2389
2390 -130	common/cmd_doc.c	Incorrect FIT image format
2391  131	common/cmd_doc.c	FIT image format OK
2392
2393 -140	common/cmd_ide.c	Incorrect FIT image format
2394  141	common/cmd_ide.c	FIT image format OK
2395
2396 -150	common/cmd_nand.c	Incorrect FIT image format
2397  151	common/cmd_nand.c	FIT image format OK
2398
2399- Standalone program support:
2400		CONFIG_STANDALONE_LOAD_ADDR
2401
2402		This option defines a board specific value for the
2403		address where standalone program gets loaded, thus
2404		overwriting the architecture dependent default
2405		settings.
2406
2407- Frame Buffer Address:
2408		CONFIG_FB_ADDR
2409
2410		Define CONFIG_FB_ADDR if you want to use specific
2411		address for frame buffer.  This is typically the case
2412		when using a graphics controller has separate video
2413		memory.  U-Boot will then place the frame buffer at
2414		the given address instead of dynamically reserving it
2415		in system RAM by calling lcd_setmem(), which grabs
2416		the memory for the frame buffer depending on the
2417		configured panel size.
2418
2419		Please see board_init_f function.
2420
2421- Automatic software updates via TFTP server
2422		CONFIG_UPDATE_TFTP
2423		CONFIG_UPDATE_TFTP_CNT_MAX
2424		CONFIG_UPDATE_TFTP_MSEC_MAX
2425
2426		These options enable and control the auto-update feature;
2427		for a more detailed description refer to doc/README.update.
2428
2429- MTD Support (mtdparts command, UBI support)
2430		CONFIG_MTD_UBI_WL_THRESHOLD
2431		This parameter defines the maximum difference between the highest
2432		erase counter value and the lowest erase counter value of eraseblocks
2433		of UBI devices. When this threshold is exceeded, UBI starts performing
2434		wear leveling by means of moving data from eraseblock with low erase
2435		counter to eraseblocks with high erase counter.
2436
2437		The default value should be OK for SLC NAND flashes, NOR flashes and
2438		other flashes which have eraseblock life-cycle 100000 or more.
2439		However, in case of MLC NAND flashes which typically have eraseblock
2440		life-cycle less than 10000, the threshold should be lessened (e.g.,
2441		to 128 or 256, although it does not have to be power of 2).
2442
2443		default: 4096
2444
2445		CONFIG_MTD_UBI_BEB_LIMIT
2446		This option specifies the maximum bad physical eraseblocks UBI
2447		expects on the MTD device (per 1024 eraseblocks). If the
2448		underlying flash does not admit of bad eraseblocks (e.g. NOR
2449		flash), this value is ignored.
2450
2451		NAND datasheets often specify the minimum and maximum NVM
2452		(Number of Valid Blocks) for the flashes' endurance lifetime.
2453		The maximum expected bad eraseblocks per 1024 eraseblocks
2454		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2455		which gives 20 for most NANDs (MaxNVB is basically the total
2456		count of eraseblocks on the chip).
2457
2458		To put it differently, if this value is 20, UBI will try to
2459		reserve about 1.9% of physical eraseblocks for bad blocks
2460		handling. And that will be 1.9% of eraseblocks on the entire
2461		NAND chip, not just the MTD partition UBI attaches. This means
2462		that if you have, say, a NAND flash chip admits maximum 40 bad
2463		eraseblocks, and it is split on two MTD partitions of the same
2464		size, UBI will reserve 40 eraseblocks when attaching a
2465		partition.
2466
2467		default: 20
2468
2469		CONFIG_MTD_UBI_FASTMAP
2470		Fastmap is a mechanism which allows attaching an UBI device
2471		in nearly constant time. Instead of scanning the whole MTD device it
2472		only has to locate a checkpoint (called fastmap) on the device.
2473		The on-flash fastmap contains all information needed to attach
2474		the device. Using fastmap makes only sense on large devices where
2475		attaching by scanning takes long. UBI will not automatically install
2476		a fastmap on old images, but you can set the UBI parameter
2477		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2478		that fastmap-enabled images are still usable with UBI implementations
2479		without	fastmap support. On typical flash devices the whole fastmap
2480		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2481
2482		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2483		Set this parameter to enable fastmap automatically on images
2484		without a fastmap.
2485		default: 0
2486
2487		CONFIG_MTD_UBI_FM_DEBUG
2488		Enable UBI fastmap debug
2489		default: 0
2490
2491- SPL framework
2492		CONFIG_SPL
2493		Enable building of SPL globally.
2494
2495		CONFIG_SPL_LDSCRIPT
2496		LDSCRIPT for linking the SPL binary.
2497
2498		CONFIG_SPL_MAX_FOOTPRINT
2499		Maximum size in memory allocated to the SPL, BSS included.
2500		When defined, the linker checks that the actual memory
2501		used by SPL from _start to __bss_end does not exceed it.
2502		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2503		must not be both defined at the same time.
2504
2505		CONFIG_SPL_MAX_SIZE
2506		Maximum size of the SPL image (text, data, rodata, and
2507		linker lists sections), BSS excluded.
2508		When defined, the linker checks that the actual size does
2509		not exceed it.
2510
2511		CONFIG_SPL_TEXT_BASE
2512		TEXT_BASE for linking the SPL binary.
2513
2514		CONFIG_SPL_RELOC_TEXT_BASE
2515		Address to relocate to.  If unspecified, this is equal to
2516		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2517
2518		CONFIG_SPL_BSS_START_ADDR
2519		Link address for the BSS within the SPL binary.
2520
2521		CONFIG_SPL_BSS_MAX_SIZE
2522		Maximum size in memory allocated to the SPL BSS.
2523		When defined, the linker checks that the actual memory used
2524		by SPL from __bss_start to __bss_end does not exceed it.
2525		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2526		must not be both defined at the same time.
2527
2528		CONFIG_SPL_STACK
2529		Adress of the start of the stack SPL will use
2530
2531		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2532		When defined, SPL will panic() if the image it has
2533		loaded does not have a signature.
2534		Defining this is useful when code which loads images
2535		in SPL cannot guarantee that absolutely all read errors
2536		will be caught.
2537		An example is the LPC32XX MLC NAND driver, which will
2538		consider that a completely unreadable NAND block is bad,
2539		and thus should be skipped silently.
2540
2541		CONFIG_SPL_RELOC_STACK
2542		Adress of the start of the stack SPL will use after
2543		relocation.  If unspecified, this is equal to
2544		CONFIG_SPL_STACK.
2545
2546		CONFIG_SYS_SPL_MALLOC_START
2547		Starting address of the malloc pool used in SPL.
2548		When this option is set the full malloc is used in SPL and
2549		it is set up by spl_init() and before that, the simple malloc()
2550		can be used if CONFIG_SYS_MALLOC_F is defined.
2551
2552		CONFIG_SYS_SPL_MALLOC_SIZE
2553		The size of the malloc pool used in SPL.
2554
2555		CONFIG_SPL_OS_BOOT
2556		Enable booting directly to an OS from SPL.
2557		See also: doc/README.falcon
2558
2559		CONFIG_SPL_DISPLAY_PRINT
2560		For ARM, enable an optional function to print more information
2561		about the running system.
2562
2563		CONFIG_SPL_INIT_MINIMAL
2564		Arch init code should be built for a very small image
2565
2566		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2567		Partition on the MMC to load U-Boot from when the MMC is being
2568		used in raw mode
2569
2570		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2571		Sector to load kernel uImage from when MMC is being
2572		used in raw mode (for Falcon mode)
2573
2574		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2575		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2576		Sector and number of sectors to load kernel argument
2577		parameters from when MMC is being used in raw mode
2578		(for falcon mode)
2579
2580		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2581		Partition on the MMC to load U-Boot from when the MMC is being
2582		used in fs mode
2583
2584		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2585		Filename to read to load U-Boot when reading from filesystem
2586
2587		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2588		Filename to read to load kernel uImage when reading
2589		from filesystem (for Falcon mode)
2590
2591		CONFIG_SPL_FS_LOAD_ARGS_NAME
2592		Filename to read to load kernel argument parameters
2593		when reading from filesystem (for Falcon mode)
2594
2595		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2596		Set this for NAND SPL on PPC mpc83xx targets, so that
2597		start.S waits for the rest of the SPL to load before
2598		continuing (the hardware starts execution after just
2599		loading the first page rather than the full 4K).
2600
2601		CONFIG_SPL_SKIP_RELOCATE
2602		Avoid SPL relocation
2603
2604		CONFIG_SPL_NAND_BASE
2605		Include nand_base.c in the SPL.  Requires
2606		CONFIG_SPL_NAND_DRIVERS.
2607
2608		CONFIG_SPL_NAND_DRIVERS
2609		SPL uses normal NAND drivers, not minimal drivers.
2610
2611		CONFIG_SPL_NAND_IDENT
2612		SPL uses the chip ID list to identify the NAND flash.
2613		Requires CONFIG_SPL_NAND_BASE.
2614
2615		CONFIG_SPL_NAND_ECC
2616		Include standard software ECC in the SPL
2617
2618		CONFIG_SPL_NAND_SIMPLE
2619		Support for NAND boot using simple NAND drivers that
2620		expose the cmd_ctrl() interface.
2621
2622		CONFIG_SPL_UBI
2623		Support for a lightweight UBI (fastmap) scanner and
2624		loader
2625
2626		CONFIG_SPL_NAND_RAW_ONLY
2627		Support to boot only raw u-boot.bin images. Use this only
2628		if you need to save space.
2629
2630		CONFIG_SPL_COMMON_INIT_DDR
2631		Set for common ddr init with serial presence detect in
2632		SPL binary.
2633
2634		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2635		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2636		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2637		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2638		CONFIG_SYS_NAND_ECCBYTES
2639		Defines the size and behavior of the NAND that SPL uses
2640		to read U-Boot
2641
2642		CONFIG_SPL_NAND_BOOT
2643		Add support NAND boot
2644
2645		CONFIG_SYS_NAND_U_BOOT_OFFS
2646		Location in NAND to read U-Boot from
2647
2648		CONFIG_SYS_NAND_U_BOOT_DST
2649		Location in memory to load U-Boot to
2650
2651		CONFIG_SYS_NAND_U_BOOT_SIZE
2652		Size of image to load
2653
2654		CONFIG_SYS_NAND_U_BOOT_START
2655		Entry point in loaded image to jump to
2656
2657		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2658		Define this if you need to first read the OOB and then the
2659		data. This is used, for example, on davinci platforms.
2660
2661		CONFIG_SPL_RAM_DEVICE
2662		Support for running image already present in ram, in SPL binary
2663
2664		CONFIG_SPL_PAD_TO
2665		Image offset to which the SPL should be padded before appending
2666		the SPL payload. By default, this is defined as
2667		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2668		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2669		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2670
2671		CONFIG_SPL_TARGET
2672		Final target image containing SPL and payload.  Some SPLs
2673		use an arch-specific makefile fragment instead, for
2674		example if more than one image needs to be produced.
2675
2676		CONFIG_SPL_FIT_PRINT
2677		Printing information about a FIT image adds quite a bit of
2678		code to SPL. So this is normally disabled in SPL. Use this
2679		option to re-enable it. This will affect the output of the
2680		bootm command when booting a FIT image.
2681
2682- TPL framework
2683		CONFIG_TPL
2684		Enable building of TPL globally.
2685
2686		CONFIG_TPL_PAD_TO
2687		Image offset to which the TPL should be padded before appending
2688		the TPL payload. By default, this is defined as
2689		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2690		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2691		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2692
2693- Interrupt support (PPC):
2694
2695		There are common interrupt_init() and timer_interrupt()
2696		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2697		for CPU specific initialization. interrupt_init_cpu()
2698		should set decrementer_count to appropriate value. If
2699		CPU resets decrementer automatically after interrupt
2700		(ppc4xx) it should set decrementer_count to zero.
2701		timer_interrupt() calls timer_interrupt_cpu() for CPU
2702		specific handling. If board has watchdog / status_led
2703		/ other_activity_monitor it works automatically from
2704		general timer_interrupt().
2705
2706
2707Board initialization settings:
2708------------------------------
2709
2710During Initialization u-boot calls a number of board specific functions
2711to allow the preparation of board specific prerequisites, e.g. pin setup
2712before drivers are initialized. To enable these callbacks the
2713following configuration macros have to be defined. Currently this is
2714architecture specific, so please check arch/your_architecture/lib/board.c
2715typically in board_init_f() and board_init_r().
2716
2717- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2718- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2719- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2720- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2721
2722Configuration Settings:
2723-----------------------
2724
2725- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2726		Optionally it can be defined to support 64-bit memory commands.
2727
2728- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2729		undefine this when you're short of memory.
2730
2731- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2732		width of the commands listed in the 'help' command output.
2733
2734- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2735		prompt for user input.
2736
2737- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2738
2739- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2740
2741- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2742
2743- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2744		the application (usually a Linux kernel) when it is
2745		booted
2746
2747- CONFIG_SYS_BAUDRATE_TABLE:
2748		List of legal baudrate settings for this board.
2749
2750- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2751		Begin and End addresses of the area used by the
2752		simple memory test.
2753
2754- CONFIG_SYS_MEMTEST_SCRATCH:
2755		Scratch address used by the alternate memory test
2756		You only need to set this if address zero isn't writeable
2757
2758- CONFIG_SYS_MEM_RESERVE_SECURE
2759		Only implemented for ARMv8 for now.
2760		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2761		is substracted from total RAM and won't be reported to OS.
2762		This memory can be used as secure memory. A variable
2763		gd->arch.secure_ram is used to track the location. In systems
2764		the RAM base is not zero, or RAM is divided into banks,
2765		this variable needs to be recalcuated to get the address.
2766
2767- CONFIG_SYS_MEM_TOP_HIDE:
2768		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2769		this specified memory area will get subtracted from the top
2770		(end) of RAM and won't get "touched" at all by U-Boot. By
2771		fixing up gd->ram_size the Linux kernel should gets passed
2772		the now "corrected" memory size and won't touch it either.
2773		This should work for arch/ppc and arch/powerpc. Only Linux
2774		board ports in arch/powerpc with bootwrapper support that
2775		recalculate the memory size from the SDRAM controller setup
2776		will have to get fixed in Linux additionally.
2777
2778		This option can be used as a workaround for the 440EPx/GRx
2779		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2780		be touched.
2781
2782		WARNING: Please make sure that this value is a multiple of
2783		the Linux page size (normally 4k). If this is not the case,
2784		then the end address of the Linux memory will be located at a
2785		non page size aligned address and this could cause major
2786		problems.
2787
2788- CONFIG_SYS_LOADS_BAUD_CHANGE:
2789		Enable temporary baudrate change while serial download
2790
2791- CONFIG_SYS_SDRAM_BASE:
2792		Physical start address of SDRAM. _Must_ be 0 here.
2793
2794- CONFIG_SYS_FLASH_BASE:
2795		Physical start address of Flash memory.
2796
2797- CONFIG_SYS_MONITOR_BASE:
2798		Physical start address of boot monitor code (set by
2799		make config files to be same as the text base address
2800		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2801		CONFIG_SYS_FLASH_BASE when booting from flash.
2802
2803- CONFIG_SYS_MONITOR_LEN:
2804		Size of memory reserved for monitor code, used to
2805		determine _at_compile_time_ (!) if the environment is
2806		embedded within the U-Boot image, or in a separate
2807		flash sector.
2808
2809- CONFIG_SYS_MALLOC_LEN:
2810		Size of DRAM reserved for malloc() use.
2811
2812- CONFIG_SYS_MALLOC_F_LEN
2813		Size of the malloc() pool for use before relocation. If
2814		this is defined, then a very simple malloc() implementation
2815		will become available before relocation. The address is just
2816		below the global data, and the stack is moved down to make
2817		space.
2818
2819		This feature allocates regions with increasing addresses
2820		within the region. calloc() is supported, but realloc()
2821		is not available. free() is supported but does nothing.
2822		The memory will be freed (or in fact just forgotten) when
2823		U-Boot relocates itself.
2824
2825- CONFIG_SYS_MALLOC_SIMPLE
2826		Provides a simple and small malloc() and calloc() for those
2827		boards which do not use the full malloc in SPL (which is
2828		enabled with CONFIG_SYS_SPL_MALLOC_START).
2829
2830- CONFIG_SYS_NONCACHED_MEMORY:
2831		Size of non-cached memory area. This area of memory will be
2832		typically located right below the malloc() area and mapped
2833		uncached in the MMU. This is useful for drivers that would
2834		otherwise require a lot of explicit cache maintenance. For
2835		some drivers it's also impossible to properly maintain the
2836		cache. For example if the regions that need to be flushed
2837		are not a multiple of the cache-line size, *and* padding
2838		cannot be allocated between the regions to align them (i.e.
2839		if the HW requires a contiguous array of regions, and the
2840		size of each region is not cache-aligned), then a flush of
2841		one region may result in overwriting data that hardware has
2842		written to another region in the same cache-line. This can
2843		happen for example in network drivers where descriptors for
2844		buffers are typically smaller than the CPU cache-line (e.g.
2845		16 bytes vs. 32 or 64 bytes).
2846
2847		Non-cached memory is only supported on 32-bit ARM at present.
2848
2849- CONFIG_SYS_BOOTM_LEN:
2850		Normally compressed uImages are limited to an
2851		uncompressed size of 8 MBytes. If this is not enough,
2852		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2853		to adjust this setting to your needs.
2854
2855- CONFIG_SYS_BOOTMAPSZ:
2856		Maximum size of memory mapped by the startup code of
2857		the Linux kernel; all data that must be processed by
2858		the Linux kernel (bd_info, boot arguments, FDT blob if
2859		used) must be put below this limit, unless "bootm_low"
2860		environment variable is defined and non-zero. In such case
2861		all data for the Linux kernel must be between "bootm_low"
2862		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2863		variable "bootm_mapsize" will override the value of
2864		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2865		then the value in "bootm_size" will be used instead.
2866
2867- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2868		Enable initrd_high functionality.  If defined then the
2869		initrd_high feature is enabled and the bootm ramdisk subcommand
2870		is enabled.
2871
2872- CONFIG_SYS_BOOT_GET_CMDLINE:
2873		Enables allocating and saving kernel cmdline in space between
2874		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2875
2876- CONFIG_SYS_BOOT_GET_KBD:
2877		Enables allocating and saving a kernel copy of the bd_info in
2878		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2879
2880- CONFIG_SYS_MAX_FLASH_BANKS:
2881		Max number of Flash memory banks
2882
2883- CONFIG_SYS_MAX_FLASH_SECT:
2884		Max number of sectors on a Flash chip
2885
2886- CONFIG_SYS_FLASH_ERASE_TOUT:
2887		Timeout for Flash erase operations (in ms)
2888
2889- CONFIG_SYS_FLASH_WRITE_TOUT:
2890		Timeout for Flash write operations (in ms)
2891
2892- CONFIG_SYS_FLASH_LOCK_TOUT
2893		Timeout for Flash set sector lock bit operation (in ms)
2894
2895- CONFIG_SYS_FLASH_UNLOCK_TOUT
2896		Timeout for Flash clear lock bits operation (in ms)
2897
2898- CONFIG_SYS_FLASH_PROTECTION
2899		If defined, hardware flash sectors protection is used
2900		instead of U-Boot software protection.
2901
2902- CONFIG_SYS_DIRECT_FLASH_TFTP:
2903
2904		Enable TFTP transfers directly to flash memory;
2905		without this option such a download has to be
2906		performed in two steps: (1) download to RAM, and (2)
2907		copy from RAM to flash.
2908
2909		The two-step approach is usually more reliable, since
2910		you can check if the download worked before you erase
2911		the flash, but in some situations (when system RAM is
2912		too limited to allow for a temporary copy of the
2913		downloaded image) this option may be very useful.
2914
2915- CONFIG_SYS_FLASH_CFI:
2916		Define if the flash driver uses extra elements in the
2917		common flash structure for storing flash geometry.
2918
2919- CONFIG_FLASH_CFI_DRIVER
2920		This option also enables the building of the cfi_flash driver
2921		in the drivers directory
2922
2923- CONFIG_FLASH_CFI_MTD
2924		This option enables the building of the cfi_mtd driver
2925		in the drivers directory. The driver exports CFI flash
2926		to the MTD layer.
2927
2928- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2929		Use buffered writes to flash.
2930
2931- CONFIG_FLASH_SPANSION_S29WS_N
2932		s29ws-n MirrorBit flash has non-standard addresses for buffered
2933		write commands.
2934
2935- CONFIG_SYS_FLASH_QUIET_TEST
2936		If this option is defined, the common CFI flash doesn't
2937		print it's warning upon not recognized FLASH banks. This
2938		is useful, if some of the configured banks are only
2939		optionally available.
2940
2941- CONFIG_FLASH_SHOW_PROGRESS
2942		If defined (must be an integer), print out countdown
2943		digits and dots.  Recommended value: 45 (9..1) for 80
2944		column displays, 15 (3..1) for 40 column displays.
2945
2946- CONFIG_FLASH_VERIFY
2947		If defined, the content of the flash (destination) is compared
2948		against the source after the write operation. An error message
2949		will be printed when the contents are not identical.
2950		Please note that this option is useless in nearly all cases,
2951		since such flash programming errors usually are detected earlier
2952		while unprotecting/erasing/programming. Please only enable
2953		this option if you really know what you are doing.
2954
2955- CONFIG_SYS_RX_ETH_BUFFER:
2956		Defines the number of Ethernet receive buffers. On some
2957		Ethernet controllers it is recommended to set this value
2958		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2959		buffers can be full shortly after enabling the interface
2960		on high Ethernet traffic.
2961		Defaults to 4 if not defined.
2962
2963- CONFIG_ENV_MAX_ENTRIES
2964
2965	Maximum number of entries in the hash table that is used
2966	internally to store the environment settings. The default
2967	setting is supposed to be generous and should work in most
2968	cases. This setting can be used to tune behaviour; see
2969	lib/hashtable.c for details.
2970
2971- CONFIG_ENV_FLAGS_LIST_DEFAULT
2972- CONFIG_ENV_FLAGS_LIST_STATIC
2973	Enable validation of the values given to environment variables when
2974	calling env set.  Variables can be restricted to only decimal,
2975	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2976	the variables can also be restricted to IP address or MAC address.
2977
2978	The format of the list is:
2979		type_attribute = [s|d|x|b|i|m]
2980		access_attribute = [a|r|o|c]
2981		attributes = type_attribute[access_attribute]
2982		entry = variable_name[:attributes]
2983		list = entry[,list]
2984
2985	The type attributes are:
2986		s - String (default)
2987		d - Decimal
2988		x - Hexadecimal
2989		b - Boolean ([1yYtT|0nNfF])
2990		i - IP address
2991		m - MAC address
2992
2993	The access attributes are:
2994		a - Any (default)
2995		r - Read-only
2996		o - Write-once
2997		c - Change-default
2998
2999	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3000		Define this to a list (string) to define the ".flags"
3001		environment variable in the default or embedded environment.
3002
3003	- CONFIG_ENV_FLAGS_LIST_STATIC
3004		Define this to a list (string) to define validation that
3005		should be done if an entry is not found in the ".flags"
3006		environment variable.  To override a setting in the static
3007		list, simply add an entry for the same variable name to the
3008		".flags" variable.
3009
3010	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3011	regular expression. This allows multiple variables to define the same
3012	flags without explicitly listing them for each variable.
3013
3014- CONFIG_ENV_ACCESS_IGNORE_FORCE
3015	If defined, don't allow the -f switch to env set override variable
3016	access flags.
3017
3018The following definitions that deal with the placement and management
3019of environment data (variable area); in general, we support the
3020following configurations:
3021
3022- CONFIG_BUILD_ENVCRC:
3023
3024	Builds up envcrc with the target environment so that external utils
3025	may easily extract it and embed it in final U-Boot images.
3026
3027BE CAREFUL! The first access to the environment happens quite early
3028in U-Boot initialization (when we try to get the setting of for the
3029console baudrate). You *MUST* have mapped your NVRAM area then, or
3030U-Boot will hang.
3031
3032Please note that even with NVRAM we still use a copy of the
3033environment in RAM: we could work on NVRAM directly, but we want to
3034keep settings there always unmodified except somebody uses "saveenv"
3035to save the current settings.
3036
3037BE CAREFUL! For some special cases, the local device can not use
3038"saveenv" command. For example, the local device will get the
3039environment stored in a remote NOR flash by SRIO or PCIE link,
3040but it can not erase, write this NOR flash by SRIO or PCIE interface.
3041
3042- CONFIG_NAND_ENV_DST
3043
3044	Defines address in RAM to which the nand_spl code should copy the
3045	environment. If redundant environment is used, it will be copied to
3046	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3047
3048Please note that the environment is read-only until the monitor
3049has been relocated to RAM and a RAM copy of the environment has been
3050created; also, when using EEPROM you will have to use env_get_f()
3051until then to read environment variables.
3052
3053The environment is protected by a CRC32 checksum. Before the monitor
3054is relocated into RAM, as a result of a bad CRC you will be working
3055with the compiled-in default environment - *silently*!!! [This is
3056necessary, because the first environment variable we need is the
3057"baudrate" setting for the console - if we have a bad CRC, we don't
3058have any device yet where we could complain.]
3059
3060Note: once the monitor has been relocated, then it will complain if
3061the default environment is used; a new CRC is computed as soon as you
3062use the "saveenv" command to store a valid environment.
3063
3064- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3065		Echo the inverted Ethernet link state to the fault LED.
3066
3067		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3068		      also needs to be defined.
3069
3070- CONFIG_SYS_FAULT_MII_ADDR:
3071		MII address of the PHY to check for the Ethernet link state.
3072
3073- CONFIG_NS16550_MIN_FUNCTIONS:
3074		Define this if you desire to only have use of the NS16550_init
3075		and NS16550_putc functions for the serial driver located at
3076		drivers/serial/ns16550.c.  This option is useful for saving
3077		space for already greatly restricted images, including but not
3078		limited to NAND_SPL configurations.
3079
3080- CONFIG_DISPLAY_BOARDINFO
3081		Display information about the board that U-Boot is running on
3082		when U-Boot starts up. The board function checkboard() is called
3083		to do this.
3084
3085- CONFIG_DISPLAY_BOARDINFO_LATE
3086		Similar to the previous option, but display this information
3087		later, once stdio is running and output goes to the LCD, if
3088		present.
3089
3090- CONFIG_BOARD_SIZE_LIMIT:
3091		Maximum size of the U-Boot image. When defined, the
3092		build system checks that the actual size does not
3093		exceed it.
3094
3095Low Level (hardware related) configuration options:
3096---------------------------------------------------
3097
3098- CONFIG_SYS_CACHELINE_SIZE:
3099		Cache Line Size of the CPU.
3100
3101- CONFIG_SYS_CCSRBAR_DEFAULT:
3102		Default (power-on reset) physical address of CCSR on Freescale
3103		PowerPC SOCs.
3104
3105- CONFIG_SYS_CCSRBAR:
3106		Virtual address of CCSR.  On a 32-bit build, this is typically
3107		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3108
3109- CONFIG_SYS_CCSRBAR_PHYS:
3110		Physical address of CCSR.  CCSR can be relocated to a new
3111		physical address, if desired.  In this case, this macro should
3112		be set to that address.	 Otherwise, it should be set to the
3113		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3114		is typically relocated on 36-bit builds.  It is recommended
3115		that this macro be defined via the _HIGH and _LOW macros:
3116
3117		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3118			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3119
3120- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3121		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3122		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3123		used in assembly code, so it must not contain typecasts or
3124		integer size suffixes (e.g. "ULL").
3125
3126- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3127		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3128		used in assembly code, so it must not contain typecasts or
3129		integer size suffixes (e.g. "ULL").
3130
3131- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3132		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3133		forced to a value that ensures that CCSR is not relocated.
3134
3135- Floppy Disk Support:
3136		CONFIG_SYS_FDC_DRIVE_NUMBER
3137
3138		the default drive number (default value 0)
3139
3140		CONFIG_SYS_ISA_IO_STRIDE
3141
3142		defines the spacing between FDC chipset registers
3143		(default value 1)
3144
3145		CONFIG_SYS_ISA_IO_OFFSET
3146
3147		defines the offset of register from address. It
3148		depends on which part of the data bus is connected to
3149		the FDC chipset. (default value 0)
3150
3151		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3152		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3153		default value.
3154
3155		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3156		fdc_hw_init() is called at the beginning of the FDC
3157		setup. fdc_hw_init() must be provided by the board
3158		source code. It is used to make hardware-dependent
3159		initializations.
3160
3161- CONFIG_IDE_AHB:
3162		Most IDE controllers were designed to be connected with PCI
3163		interface. Only few of them were designed for AHB interface.
3164		When software is doing ATA command and data transfer to
3165		IDE devices through IDE-AHB controller, some additional
3166		registers accessing to these kind of IDE-AHB controller
3167		is required.
3168
3169- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3170		DO NOT CHANGE unless you know exactly what you're
3171		doing! (11-4) [MPC8xx systems only]
3172
3173- CONFIG_SYS_INIT_RAM_ADDR:
3174
3175		Start address of memory area that can be used for
3176		initial data and stack; please note that this must be
3177		writable memory that is working WITHOUT special
3178		initialization, i. e. you CANNOT use normal RAM which
3179		will become available only after programming the
3180		memory controller and running certain initialization
3181		sequences.
3182
3183		U-Boot uses the following memory types:
3184		- MPC8xx: IMMR (internal memory of the CPU)
3185
3186- CONFIG_SYS_GBL_DATA_OFFSET:
3187
3188		Offset of the initial data structure in the memory
3189		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3190		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3191		data is located at the end of the available space
3192		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3193		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3194		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3195		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3196
3197	Note:
3198		On the MPC824X (or other systems that use the data
3199		cache for initial memory) the address chosen for
3200		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3201		point to an otherwise UNUSED address space between
3202		the top of RAM and the start of the PCI space.
3203
3204- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3205
3206- CONFIG_SYS_OR_TIMING_SDRAM:
3207		SDRAM timing
3208
3209- CONFIG_SYS_MAMR_PTA:
3210		periodic timer for refresh
3211
3212- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3213  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3214  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3215  CONFIG_SYS_BR1_PRELIM:
3216		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3217
3218- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3219  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3220  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3221		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3222
3223- CONFIG_PCI_ENUM_ONLY
3224		Only scan through and get the devices on the buses.
3225		Don't do any setup work, presumably because someone or
3226		something has already done it, and we don't need to do it
3227		a second time.	Useful for platforms that are pre-booted
3228		by coreboot or similar.
3229
3230- CONFIG_PCI_INDIRECT_BRIDGE:
3231		Enable support for indirect PCI bridges.
3232
3233- CONFIG_SYS_SRIO:
3234		Chip has SRIO or not
3235
3236- CONFIG_SRIO1:
3237		Board has SRIO 1 port available
3238
3239- CONFIG_SRIO2:
3240		Board has SRIO 2 port available
3241
3242- CONFIG_SRIO_PCIE_BOOT_MASTER
3243		Board can support master function for Boot from SRIO and PCIE
3244
3245- CONFIG_SYS_SRIOn_MEM_VIRT:
3246		Virtual Address of SRIO port 'n' memory region
3247
3248- CONFIG_SYS_SRIOn_MEM_PHYS:
3249		Physical Address of SRIO port 'n' memory region
3250
3251- CONFIG_SYS_SRIOn_MEM_SIZE:
3252		Size of SRIO port 'n' memory region
3253
3254- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3255		Defined to tell the NAND controller that the NAND chip is using
3256		a 16 bit bus.
3257		Not all NAND drivers use this symbol.
3258		Example of drivers that use it:
3259		- drivers/mtd/nand/ndfc.c
3260		- drivers/mtd/nand/mxc_nand.c
3261
3262- CONFIG_SYS_NDFC_EBC0_CFG
3263		Sets the EBC0_CFG register for the NDFC. If not defined
3264		a default value will be used.
3265
3266- CONFIG_SPD_EEPROM
3267		Get DDR timing information from an I2C EEPROM. Common
3268		with pluggable memory modules such as SODIMMs
3269
3270  SPD_EEPROM_ADDRESS
3271		I2C address of the SPD EEPROM
3272
3273- CONFIG_SYS_SPD_BUS_NUM
3274		If SPD EEPROM is on an I2C bus other than the first
3275		one, specify here. Note that the value must resolve
3276		to something your driver can deal with.
3277
3278- CONFIG_SYS_DDR_RAW_TIMING
3279		Get DDR timing information from other than SPD. Common with
3280		soldered DDR chips onboard without SPD. DDR raw timing
3281		parameters are extracted from datasheet and hard-coded into
3282		header files or board specific files.
3283
3284- CONFIG_FSL_DDR_INTERACTIVE
3285		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3286
3287- CONFIG_FSL_DDR_SYNC_REFRESH
3288		Enable sync of refresh for multiple controllers.
3289
3290- CONFIG_FSL_DDR_BIST
3291		Enable built-in memory test for Freescale DDR controllers.
3292
3293- CONFIG_SYS_83XX_DDR_USES_CS0
3294		Only for 83xx systems. If specified, then DDR should
3295		be configured using CS0 and CS1 instead of CS2 and CS3.
3296
3297- CONFIG_RMII
3298		Enable RMII mode for all FECs.
3299		Note that this is a global option, we can't
3300		have one FEC in standard MII mode and another in RMII mode.
3301
3302- CONFIG_CRC32_VERIFY
3303		Add a verify option to the crc32 command.
3304		The syntax is:
3305
3306		=> crc32 -v <address> <count> <crc32>
3307
3308		Where address/count indicate a memory area
3309		and crc32 is the correct crc32 which the
3310		area should have.
3311
3312- CONFIG_LOOPW
3313		Add the "loopw" memory command. This only takes effect if
3314		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3315
3316- CONFIG_MX_CYCLIC
3317		Add the "mdc" and "mwc" memory commands. These are cyclic
3318		"md/mw" commands.
3319		Examples:
3320
3321		=> mdc.b 10 4 500
3322		This command will print 4 bytes (10,11,12,13) each 500 ms.
3323
3324		=> mwc.l 100 12345678 10
3325		This command will write 12345678 to address 100 all 10 ms.
3326
3327		This only takes effect if the memory commands are activated
3328		globally (CONFIG_CMD_MEMORY).
3329
3330- CONFIG_SKIP_LOWLEVEL_INIT
3331		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3332		low level initializations (like setting up the memory
3333		controller) are omitted and/or U-Boot does not
3334		relocate itself into RAM.
3335
3336		Normally this variable MUST NOT be defined. The only
3337		exception is when U-Boot is loaded (to RAM) by some
3338		other boot loader or by a debugger which performs
3339		these initializations itself.
3340
3341- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3342		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3343		to be skipped. The normal CP15 init (such as enabling the
3344		instruction cache) is still performed.
3345
3346- CONFIG_SPL_BUILD
3347		Modifies the behaviour of start.S when compiling a loader
3348		that is executed before the actual U-Boot. E.g. when
3349		compiling a NAND SPL.
3350
3351- CONFIG_TPL_BUILD
3352		Modifies the behaviour of start.S  when compiling a loader
3353		that is executed after the SPL and before the actual U-Boot.
3354		It is loaded by the SPL.
3355
3356- CONFIG_SYS_MPC85XX_NO_RESETVEC
3357		Only for 85xx systems. If this variable is specified, the section
3358		.resetvec is not kept and the section .bootpg is placed in the
3359		previous 4k of the .text section.
3360
3361- CONFIG_ARCH_MAP_SYSMEM
3362		Generally U-Boot (and in particular the md command) uses
3363		effective address. It is therefore not necessary to regard
3364		U-Boot address as virtual addresses that need to be translated
3365		to physical addresses. However, sandbox requires this, since
3366		it maintains its own little RAM buffer which contains all
3367		addressable memory. This option causes some memory accesses
3368		to be mapped through map_sysmem() / unmap_sysmem().
3369
3370- CONFIG_X86_RESET_VECTOR
3371		If defined, the x86 reset vector code is included. This is not
3372		needed when U-Boot is running from Coreboot.
3373
3374- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3375		Option to disable subpage write in NAND driver
3376		driver that uses this:
3377		drivers/mtd/nand/davinci_nand.c
3378
3379Freescale QE/FMAN Firmware Support:
3380-----------------------------------
3381
3382The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3383loading of "firmware", which is encoded in the QE firmware binary format.
3384This firmware often needs to be loaded during U-Boot booting, so macros
3385are used to identify the storage device (NOR flash, SPI, etc) and the address
3386within that device.
3387
3388- CONFIG_SYS_FMAN_FW_ADDR
3389	The address in the storage device where the FMAN microcode is located.  The
3390	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3391	is also specified.
3392
3393- CONFIG_SYS_QE_FW_ADDR
3394	The address in the storage device where the QE microcode is located.  The
3395	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3396	is also specified.
3397
3398- CONFIG_SYS_QE_FMAN_FW_LENGTH
3399	The maximum possible size of the firmware.  The firmware binary format
3400	has a field that specifies the actual size of the firmware, but it
3401	might not be possible to read any part of the firmware unless some
3402	local storage is allocated to hold the entire firmware first.
3403
3404- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3405	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3406	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3407	virtual address in NOR flash.
3408
3409- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3410	Specifies that QE/FMAN firmware is located in NAND flash.
3411	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3412
3413- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3414	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3415	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3416
3417- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3418	Specifies that QE/FMAN firmware is located in the remote (master)
3419	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3420	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3421	window->master inbound window->master LAW->the ucode address in
3422	master's memory space.
3423
3424Freescale Layerscape Management Complex Firmware Support:
3425---------------------------------------------------------
3426The Freescale Layerscape Management Complex (MC) supports the loading of
3427"firmware".
3428This firmware often needs to be loaded during U-Boot booting, so macros
3429are used to identify the storage device (NOR flash, SPI, etc) and the address
3430within that device.
3431
3432- CONFIG_FSL_MC_ENET
3433	Enable the MC driver for Layerscape SoCs.
3434
3435Freescale Layerscape Debug Server Support:
3436-------------------------------------------
3437The Freescale Layerscape Debug Server Support supports the loading of
3438"Debug Server firmware" and triggering SP boot-rom.
3439This firmware often needs to be loaded during U-Boot booting.
3440
3441- CONFIG_SYS_MC_RSV_MEM_ALIGN
3442	Define alignment of reserved memory MC requires
3443
3444Reproducible builds
3445-------------------
3446
3447In order to achieve reproducible builds, timestamps used in the U-Boot build
3448process have to be set to a fixed value.
3449
3450This is done using the SOURCE_DATE_EPOCH environment variable.
3451SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3452option for U-Boot or an environment variable in U-Boot.
3453
3454SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3455
3456Building the Software:
3457======================
3458
3459Building U-Boot has been tested in several native build environments
3460and in many different cross environments. Of course we cannot support
3461all possibly existing versions of cross development tools in all
3462(potentially obsolete) versions. In case of tool chain problems we
3463recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3464which is extensively used to build and test U-Boot.
3465
3466If you are not using a native environment, it is assumed that you
3467have GNU cross compiling tools available in your path. In this case,
3468you must set the environment variable CROSS_COMPILE in your shell.
3469Note that no changes to the Makefile or any other source files are
3470necessary. For example using the ELDK on a 4xx CPU, please enter:
3471
3472	$ CROSS_COMPILE=ppc_4xx-
3473	$ export CROSS_COMPILE
3474
3475Note: If you wish to generate Windows versions of the utilities in
3476      the tools directory you can use the MinGW toolchain
3477      (http://www.mingw.org).  Set your HOST tools to the MinGW
3478      toolchain and execute 'make tools'.  For example:
3479
3480       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3481
3482      Binaries such as tools/mkimage.exe will be created which can
3483      be executed on computers running Windows.
3484
3485U-Boot is intended to be simple to build. After installing the
3486sources you must configure U-Boot for one specific board type. This
3487is done by typing:
3488
3489	make NAME_defconfig
3490
3491where "NAME_defconfig" is the name of one of the existing configu-
3492rations; see boards.cfg for supported names.
3493
3494Note: for some board special configuration names may exist; check if
3495      additional information is available from the board vendor; for
3496      instance, the TQM823L systems are available without (standard)
3497      or with LCD support. You can select such additional "features"
3498      when choosing the configuration, i. e.
3499
3500      make TQM823L_defconfig
3501	- will configure for a plain TQM823L, i. e. no LCD support
3502
3503      make TQM823L_LCD_defconfig
3504	- will configure for a TQM823L with U-Boot console on LCD
3505
3506      etc.
3507
3508
3509Finally, type "make all", and you should get some working U-Boot
3510images ready for download to / installation on your system:
3511
3512- "u-boot.bin" is a raw binary image
3513- "u-boot" is an image in ELF binary format
3514- "u-boot.srec" is in Motorola S-Record format
3515
3516By default the build is performed locally and the objects are saved
3517in the source directory. One of the two methods can be used to change
3518this behavior and build U-Boot to some external directory:
3519
35201. Add O= to the make command line invocations:
3521
3522	make O=/tmp/build distclean
3523	make O=/tmp/build NAME_defconfig
3524	make O=/tmp/build all
3525
35262. Set environment variable KBUILD_OUTPUT to point to the desired location:
3527
3528	export KBUILD_OUTPUT=/tmp/build
3529	make distclean
3530	make NAME_defconfig
3531	make all
3532
3533Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3534variable.
3535
3536User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3537setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3538For example to treat all compiler warnings as errors:
3539
3540	make KCFLAGS=-Werror
3541
3542Please be aware that the Makefiles assume you are using GNU make, so
3543for instance on NetBSD you might need to use "gmake" instead of
3544native "make".
3545
3546
3547If the system board that you have is not listed, then you will need
3548to port U-Boot to your hardware platform. To do this, follow these
3549steps:
3550
35511.  Create a new directory to hold your board specific code. Add any
3552    files you need. In your board directory, you will need at least
3553    the "Makefile" and a "<board>.c".
35542.  Create a new configuration file "include/configs/<board>.h" for
3555    your board.
35563.  If you're porting U-Boot to a new CPU, then also create a new
3557    directory to hold your CPU specific code. Add any files you need.
35584.  Run "make <board>_defconfig" with your new name.
35595.  Type "make", and you should get a working "u-boot.srec" file
3560    to be installed on your target system.
35616.  Debug and solve any problems that might arise.
3562    [Of course, this last step is much harder than it sounds.]
3563
3564
3565Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3566==============================================================
3567
3568If you have modified U-Boot sources (for instance added a new board
3569or support for new devices, a new CPU, etc.) you are expected to
3570provide feedback to the other developers. The feedback normally takes
3571the form of a "patch", i. e. a context diff against a certain (latest
3572official or latest in the git repository) version of U-Boot sources.
3573
3574But before you submit such a patch, please verify that your modifi-
3575cation did not break existing code. At least make sure that *ALL* of
3576the supported boards compile WITHOUT ANY compiler warnings. To do so,
3577just run the buildman script (tools/buildman/buildman), which will
3578configure and build U-Boot for ALL supported system. Be warned, this
3579will take a while. Please see the buildman README, or run 'buildman -H'
3580for documentation.
3581
3582
3583See also "U-Boot Porting Guide" below.
3584
3585
3586Monitor Commands - Overview:
3587============================
3588
3589go	- start application at address 'addr'
3590run	- run commands in an environment variable
3591bootm	- boot application image from memory
3592bootp	- boot image via network using BootP/TFTP protocol
3593bootz   - boot zImage from memory
3594tftpboot- boot image via network using TFTP protocol
3595	       and env variables "ipaddr" and "serverip"
3596	       (and eventually "gatewayip")
3597tftpput - upload a file via network using TFTP protocol
3598rarpboot- boot image via network using RARP/TFTP protocol
3599diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3600loads	- load S-Record file over serial line
3601loadb	- load binary file over serial line (kermit mode)
3602md	- memory display
3603mm	- memory modify (auto-incrementing)
3604nm	- memory modify (constant address)
3605mw	- memory write (fill)
3606cp	- memory copy
3607cmp	- memory compare
3608crc32	- checksum calculation
3609i2c	- I2C sub-system
3610sspi	- SPI utility commands
3611base	- print or set address offset
3612printenv- print environment variables
3613setenv	- set environment variables
3614saveenv - save environment variables to persistent storage
3615protect - enable or disable FLASH write protection
3616erase	- erase FLASH memory
3617flinfo	- print FLASH memory information
3618nand	- NAND memory operations (see doc/README.nand)
3619bdinfo	- print Board Info structure
3620iminfo	- print header information for application image
3621coninfo - print console devices and informations
3622ide	- IDE sub-system
3623loop	- infinite loop on address range
3624loopw	- infinite write loop on address range
3625mtest	- simple RAM test
3626icache	- enable or disable instruction cache
3627dcache	- enable or disable data cache
3628reset	- Perform RESET of the CPU
3629echo	- echo args to console
3630version - print monitor version
3631help	- print online help
3632?	- alias for 'help'
3633
3634
3635Monitor Commands - Detailed Description:
3636========================================
3637
3638TODO.
3639
3640For now: just type "help <command>".
3641
3642
3643Environment Variables:
3644======================
3645
3646U-Boot supports user configuration using Environment Variables which
3647can be made persistent by saving to Flash memory.
3648
3649Environment Variables are set using "setenv", printed using
3650"printenv", and saved to Flash using "saveenv". Using "setenv"
3651without a value can be used to delete a variable from the
3652environment. As long as you don't save the environment you are
3653working with an in-memory copy. In case the Flash area containing the
3654environment is erased by accident, a default environment is provided.
3655
3656Some configuration options can be set using Environment Variables.
3657
3658List of environment variables (most likely not complete):
3659
3660  baudrate	- see CONFIG_BAUDRATE
3661
3662  bootdelay	- see CONFIG_BOOTDELAY
3663
3664  bootcmd	- see CONFIG_BOOTCOMMAND
3665
3666  bootargs	- Boot arguments when booting an RTOS image
3667
3668  bootfile	- Name of the image to load with TFTP
3669
3670  bootm_low	- Memory range available for image processing in the bootm
3671		  command can be restricted. This variable is given as
3672		  a hexadecimal number and defines lowest address allowed
3673		  for use by the bootm command. See also "bootm_size"
3674		  environment variable. Address defined by "bootm_low" is
3675		  also the base of the initial memory mapping for the Linux
3676		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3677		  bootm_mapsize.
3678
3679  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3680		  This variable is given as a hexadecimal number and it
3681		  defines the size of the memory region starting at base
3682		  address bootm_low that is accessible by the Linux kernel
3683		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3684		  as the default value if it is defined, and bootm_size is
3685		  used otherwise.
3686
3687  bootm_size	- Memory range available for image processing in the bootm
3688		  command can be restricted. This variable is given as
3689		  a hexadecimal number and defines the size of the region
3690		  allowed for use by the bootm command. See also "bootm_low"
3691		  environment variable.
3692
3693  updatefile	- Location of the software update file on a TFTP server, used
3694		  by the automatic software update feature. Please refer to
3695		  documentation in doc/README.update for more details.
3696
3697  autoload	- if set to "no" (any string beginning with 'n'),
3698		  "bootp" will just load perform a lookup of the
3699		  configuration from the BOOTP server, but not try to
3700		  load any image using TFTP
3701
3702  autostart	- if set to "yes", an image loaded using the "bootp",
3703		  "rarpboot", "tftpboot" or "diskboot" commands will
3704		  be automatically started (by internally calling
3705		  "bootm")
3706
3707		  If set to "no", a standalone image passed to the
3708		  "bootm" command will be copied to the load address
3709		  (and eventually uncompressed), but NOT be started.
3710		  This can be used to load and uncompress arbitrary
3711		  data.
3712
3713  fdt_high	- if set this restricts the maximum address that the
3714		  flattened device tree will be copied into upon boot.
3715		  For example, if you have a system with 1 GB memory
3716		  at physical address 0x10000000, while Linux kernel
3717		  only recognizes the first 704 MB as low memory, you
3718		  may need to set fdt_high as 0x3C000000 to have the
3719		  device tree blob be copied to the maximum address
3720		  of the 704 MB low memory, so that Linux kernel can
3721		  access it during the boot procedure.
3722
3723		  If this is set to the special value 0xFFFFFFFF then
3724		  the fdt will not be copied at all on boot.  For this
3725		  to work it must reside in writable memory, have
3726		  sufficient padding on the end of it for u-boot to
3727		  add the information it needs into it, and the memory
3728		  must be accessible by the kernel.
3729
3730  fdtcontroladdr- if set this is the address of the control flattened
3731		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3732		  defined.
3733
3734  i2cfast	- (PPC405GP|PPC405EP only)
3735		  if set to 'y' configures Linux I2C driver for fast
3736		  mode (400kHZ). This environment variable is used in
3737		  initialization code. So, for changes to be effective
3738		  it must be saved and board must be reset.
3739
3740  initrd_high	- restrict positioning of initrd images:
3741		  If this variable is not set, initrd images will be
3742		  copied to the highest possible address in RAM; this
3743		  is usually what you want since it allows for
3744		  maximum initrd size. If for some reason you want to
3745		  make sure that the initrd image is loaded below the
3746		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3747		  variable to a value of "no" or "off" or "0".
3748		  Alternatively, you can set it to a maximum upper
3749		  address to use (U-Boot will still check that it
3750		  does not overwrite the U-Boot stack and data).
3751
3752		  For instance, when you have a system with 16 MB
3753		  RAM, and want to reserve 4 MB from use by Linux,
3754		  you can do this by adding "mem=12M" to the value of
3755		  the "bootargs" variable. However, now you must make
3756		  sure that the initrd image is placed in the first
3757		  12 MB as well - this can be done with
3758
3759		  setenv initrd_high 00c00000
3760
3761		  If you set initrd_high to 0xFFFFFFFF, this is an
3762		  indication to U-Boot that all addresses are legal
3763		  for the Linux kernel, including addresses in flash
3764		  memory. In this case U-Boot will NOT COPY the
3765		  ramdisk at all. This may be useful to reduce the
3766		  boot time on your system, but requires that this
3767		  feature is supported by your Linux kernel.
3768
3769  ipaddr	- IP address; needed for tftpboot command
3770
3771  loadaddr	- Default load address for commands like "bootp",
3772		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3773
3774  loads_echo	- see CONFIG_LOADS_ECHO
3775
3776  serverip	- TFTP server IP address; needed for tftpboot command
3777
3778  bootretry	- see CONFIG_BOOT_RETRY_TIME
3779
3780  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3781
3782  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3783
3784  ethprime	- controls which interface is used first.
3785
3786  ethact	- controls which interface is currently active.
3787		  For example you can do the following
3788
3789		  => setenv ethact FEC
3790		  => ping 192.168.0.1 # traffic sent on FEC
3791		  => setenv ethact SCC
3792		  => ping 10.0.0.1 # traffic sent on SCC
3793
3794  ethrotate	- When set to "no" U-Boot does not go through all
3795		  available network interfaces.
3796		  It just stays at the currently selected interface.
3797
3798  netretry	- When set to "no" each network operation will
3799		  either succeed or fail without retrying.
3800		  When set to "once" the network operation will
3801		  fail when all the available network interfaces
3802		  are tried once without success.
3803		  Useful on scripts which control the retry operation
3804		  themselves.
3805
3806  npe_ucode	- set load address for the NPE microcode
3807
3808  silent_linux  - If set then Linux will be told to boot silently, by
3809		  changing the console to be empty. If "yes" it will be
3810		  made silent. If "no" it will not be made silent. If
3811		  unset, then it will be made silent if the U-Boot console
3812		  is silent.
3813
3814  tftpsrcp	- If this is set, the value is used for TFTP's
3815		  UDP source port.
3816
3817  tftpdstp	- If this is set, the value is used for TFTP's UDP
3818		  destination port instead of the Well Know Port 69.
3819
3820  tftpblocksize - Block size to use for TFTP transfers; if not set,
3821		  we use the TFTP server's default block size
3822
3823  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3824		  seconds, minimum value is 1000 = 1 second). Defines
3825		  when a packet is considered to be lost so it has to
3826		  be retransmitted. The default is 5000 = 5 seconds.
3827		  Lowering this value may make downloads succeed
3828		  faster in networks with high packet loss rates or
3829		  with unreliable TFTP servers.
3830
3831  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3832		  unit, minimum value = 0). Defines how many timeouts
3833		  can happen during a single file transfer before that
3834		  transfer is aborted. The default is 10, and 0 means
3835		  'no timeouts allowed'. Increasing this value may help
3836		  downloads succeed with high packet loss rates, or with
3837		  unreliable TFTP servers or client hardware.
3838
3839  vlan		- When set to a value < 4095 the traffic over
3840		  Ethernet is encapsulated/received over 802.1q
3841		  VLAN tagged frames.
3842
3843  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3844		  Unsigned value, in milliseconds. If not set, the period will
3845		  be either the default (28000), or a value based on
3846		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3847		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3848
3849The following image location variables contain the location of images
3850used in booting. The "Image" column gives the role of the image and is
3851not an environment variable name. The other columns are environment
3852variable names. "File Name" gives the name of the file on a TFTP
3853server, "RAM Address" gives the location in RAM the image will be
3854loaded to, and "Flash Location" gives the image's address in NOR
3855flash or offset in NAND flash.
3856
3857*Note* - these variables don't have to be defined for all boards, some
3858boards currently use other variables for these purposes, and some
3859boards use these variables for other purposes.
3860
3861Image		    File Name	     RAM Address       Flash Location
3862-----		    ---------	     -----------       --------------
3863u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3864Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3865device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3866ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3867
3868The following environment variables may be used and automatically
3869updated by the network boot commands ("bootp" and "rarpboot"),
3870depending the information provided by your boot server:
3871
3872  bootfile	- see above
3873  dnsip		- IP address of your Domain Name Server
3874  dnsip2	- IP address of your secondary Domain Name Server
3875  gatewayip	- IP address of the Gateway (Router) to use
3876  hostname	- Target hostname
3877  ipaddr	- see above
3878  netmask	- Subnet Mask
3879  rootpath	- Pathname of the root filesystem on the NFS server
3880  serverip	- see above
3881
3882
3883There are two special Environment Variables:
3884
3885  serial#	- contains hardware identification information such
3886		  as type string and/or serial number
3887  ethaddr	- Ethernet address
3888
3889These variables can be set only once (usually during manufacturing of
3890the board). U-Boot refuses to delete or overwrite these variables
3891once they have been set once.
3892
3893
3894Further special Environment Variables:
3895
3896  ver		- Contains the U-Boot version string as printed
3897		  with the "version" command. This variable is
3898		  readonly (see CONFIG_VERSION_VARIABLE).
3899
3900
3901Please note that changes to some configuration parameters may take
3902only effect after the next boot (yes, that's just like Windoze :-).
3903
3904
3905Callback functions for environment variables:
3906---------------------------------------------
3907
3908For some environment variables, the behavior of u-boot needs to change
3909when their values are changed.  This functionality allows functions to
3910be associated with arbitrary variables.  On creation, overwrite, or
3911deletion, the callback will provide the opportunity for some side
3912effect to happen or for the change to be rejected.
3913
3914The callbacks are named and associated with a function using the
3915U_BOOT_ENV_CALLBACK macro in your board or driver code.
3916
3917These callbacks are associated with variables in one of two ways.  The
3918static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3919in the board configuration to a string that defines a list of
3920associations.  The list must be in the following format:
3921
3922	entry = variable_name[:callback_name]
3923	list = entry[,list]
3924
3925If the callback name is not specified, then the callback is deleted.
3926Spaces are also allowed anywhere in the list.
3927
3928Callbacks can also be associated by defining the ".callbacks" variable
3929with the same list format above.  Any association in ".callbacks" will
3930override any association in the static list. You can define
3931CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3932".callbacks" environment variable in the default or embedded environment.
3933
3934If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3935regular expression. This allows multiple variables to be connected to
3936the same callback without explicitly listing them all out.
3937
3938The signature of the callback functions is:
3939
3940    int callback(const char *name, const char *value, enum env_op op, int flags)
3941
3942* name - changed environment variable
3943* value - new value of the environment variable
3944* op - operation (create, overwrite, or delete)
3945* flags - attributes of the environment variable change, see flags H_* in
3946  include/search.h
3947
3948The return value is 0 if the variable change is accepted and 1 otherwise.
3949
3950Command Line Parsing:
3951=====================
3952
3953There are two different command line parsers available with U-Boot:
3954the old "simple" one, and the much more powerful "hush" shell:
3955
3956Old, simple command line parser:
3957--------------------------------
3958
3959- supports environment variables (through setenv / saveenv commands)
3960- several commands on one line, separated by ';'
3961- variable substitution using "... ${name} ..." syntax
3962- special characters ('$', ';') can be escaped by prefixing with '\',
3963  for example:
3964	setenv bootcmd bootm \${address}
3965- You can also escape text by enclosing in single apostrophes, for example:
3966	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3967
3968Hush shell:
3969-----------
3970
3971- similar to Bourne shell, with control structures like
3972  if...then...else...fi, for...do...done; while...do...done,
3973  until...do...done, ...
3974- supports environment ("global") variables (through setenv / saveenv
3975  commands) and local shell variables (through standard shell syntax
3976  "name=value"); only environment variables can be used with "run"
3977  command
3978
3979General rules:
3980--------------
3981
3982(1) If a command line (or an environment variable executed by a "run"
3983    command) contains several commands separated by semicolon, and
3984    one of these commands fails, then the remaining commands will be
3985    executed anyway.
3986
3987(2) If you execute several variables with one call to run (i. e.
3988    calling run with a list of variables as arguments), any failing
3989    command will cause "run" to terminate, i. e. the remaining
3990    variables are not executed.
3991
3992Note for Redundant Ethernet Interfaces:
3993=======================================
3994
3995Some boards come with redundant Ethernet interfaces; U-Boot supports
3996such configurations and is capable of automatic selection of a
3997"working" interface when needed. MAC assignment works as follows:
3998
3999Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4000MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4001"eth1addr" (=>eth1), "eth2addr", ...
4002
4003If the network interface stores some valid MAC address (for instance
4004in SROM), this is used as default address if there is NO correspon-
4005ding setting in the environment; if the corresponding environment
4006variable is set, this overrides the settings in the card; that means:
4007
4008o If the SROM has a valid MAC address, and there is no address in the
4009  environment, the SROM's address is used.
4010
4011o If there is no valid address in the SROM, and a definition in the
4012  environment exists, then the value from the environment variable is
4013  used.
4014
4015o If both the SROM and the environment contain a MAC address, and
4016  both addresses are the same, this MAC address is used.
4017
4018o If both the SROM and the environment contain a MAC address, and the
4019  addresses differ, the value from the environment is used and a
4020  warning is printed.
4021
4022o If neither SROM nor the environment contain a MAC address, an error
4023  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4024  a random, locally-assigned MAC is used.
4025
4026If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4027will be programmed into hardware as part of the initialization process.	 This
4028may be skipped by setting the appropriate 'ethmacskip' environment variable.
4029The naming convention is as follows:
4030"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4031
4032Image Formats:
4033==============
4034
4035U-Boot is capable of booting (and performing other auxiliary operations on)
4036images in two formats:
4037
4038New uImage format (FIT)
4039-----------------------
4040
4041Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4042to Flattened Device Tree). It allows the use of images with multiple
4043components (several kernels, ramdisks, etc.), with contents protected by
4044SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4045
4046
4047Old uImage format
4048-----------------
4049
4050Old image format is based on binary files which can be basically anything,
4051preceded by a special header; see the definitions in include/image.h for
4052details; basically, the header defines the following image properties:
4053
4054* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4055  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4056  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4057  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4058  INTEGRITY).
4059* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4060  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4061  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4062* Compression Type (uncompressed, gzip, bzip2)
4063* Load Address
4064* Entry Point
4065* Image Name
4066* Image Timestamp
4067
4068The header is marked by a special Magic Number, and both the header
4069and the data portions of the image are secured against corruption by
4070CRC32 checksums.
4071
4072
4073Linux Support:
4074==============
4075
4076Although U-Boot should support any OS or standalone application
4077easily, the main focus has always been on Linux during the design of
4078U-Boot.
4079
4080U-Boot includes many features that so far have been part of some
4081special "boot loader" code within the Linux kernel. Also, any
4082"initrd" images to be used are no longer part of one big Linux image;
4083instead, kernel and "initrd" are separate images. This implementation
4084serves several purposes:
4085
4086- the same features can be used for other OS or standalone
4087  applications (for instance: using compressed images to reduce the
4088  Flash memory footprint)
4089
4090- it becomes much easier to port new Linux kernel versions because
4091  lots of low-level, hardware dependent stuff are done by U-Boot
4092
4093- the same Linux kernel image can now be used with different "initrd"
4094  images; of course this also means that different kernel images can
4095  be run with the same "initrd". This makes testing easier (you don't
4096  have to build a new "zImage.initrd" Linux image when you just
4097  change a file in your "initrd"). Also, a field-upgrade of the
4098  software is easier now.
4099
4100
4101Linux HOWTO:
4102============
4103
4104Porting Linux to U-Boot based systems:
4105---------------------------------------
4106
4107U-Boot cannot save you from doing all the necessary modifications to
4108configure the Linux device drivers for use with your target hardware
4109(no, we don't intend to provide a full virtual machine interface to
4110Linux :-).
4111
4112But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4113
4114Just make sure your machine specific header file (for instance
4115include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4116Information structure as we define in include/asm-<arch>/u-boot.h,
4117and make sure that your definition of IMAP_ADDR uses the same value
4118as your U-Boot configuration in CONFIG_SYS_IMMR.
4119
4120Note that U-Boot now has a driver model, a unified model for drivers.
4121If you are adding a new driver, plumb it into driver model. If there
4122is no uclass available, you are encouraged to create one. See
4123doc/driver-model.
4124
4125
4126Configuring the Linux kernel:
4127-----------------------------
4128
4129No specific requirements for U-Boot. Make sure you have some root
4130device (initial ramdisk, NFS) for your target system.
4131
4132
4133Building a Linux Image:
4134-----------------------
4135
4136With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4137not used. If you use recent kernel source, a new build target
4138"uImage" will exist which automatically builds an image usable by
4139U-Boot. Most older kernels also have support for a "pImage" target,
4140which was introduced for our predecessor project PPCBoot and uses a
4141100% compatible format.
4142
4143Example:
4144
4145	make TQM850L_defconfig
4146	make oldconfig
4147	make dep
4148	make uImage
4149
4150The "uImage" build target uses a special tool (in 'tools/mkimage') to
4151encapsulate a compressed Linux kernel image with header	 information,
4152CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4153
4154* build a standard "vmlinux" kernel image (in ELF binary format):
4155
4156* convert the kernel into a raw binary image:
4157
4158	${CROSS_COMPILE}-objcopy -O binary \
4159				 -R .note -R .comment \
4160				 -S vmlinux linux.bin
4161
4162* compress the binary image:
4163
4164	gzip -9 linux.bin
4165
4166* package compressed binary image for U-Boot:
4167
4168	mkimage -A ppc -O linux -T kernel -C gzip \
4169		-a 0 -e 0 -n "Linux Kernel Image" \
4170		-d linux.bin.gz uImage
4171
4172
4173The "mkimage" tool can also be used to create ramdisk images for use
4174with U-Boot, either separated from the Linux kernel image, or
4175combined into one file. "mkimage" encapsulates the images with a 64
4176byte header containing information about target architecture,
4177operating system, image type, compression method, entry points, time
4178stamp, CRC32 checksums, etc.
4179
4180"mkimage" can be called in two ways: to verify existing images and
4181print the header information, or to build new images.
4182
4183In the first form (with "-l" option) mkimage lists the information
4184contained in the header of an existing U-Boot image; this includes
4185checksum verification:
4186
4187	tools/mkimage -l image
4188	  -l ==> list image header information
4189
4190The second form (with "-d" option) is used to build a U-Boot image
4191from a "data file" which is used as image payload:
4192
4193	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4194		      -n name -d data_file image
4195	  -A ==> set architecture to 'arch'
4196	  -O ==> set operating system to 'os'
4197	  -T ==> set image type to 'type'
4198	  -C ==> set compression type 'comp'
4199	  -a ==> set load address to 'addr' (hex)
4200	  -e ==> set entry point to 'ep' (hex)
4201	  -n ==> set image name to 'name'
4202	  -d ==> use image data from 'datafile'
4203
4204Right now, all Linux kernels for PowerPC systems use the same load
4205address (0x00000000), but the entry point address depends on the
4206kernel version:
4207
4208- 2.2.x kernels have the entry point at 0x0000000C,
4209- 2.3.x and later kernels have the entry point at 0x00000000.
4210
4211So a typical call to build a U-Boot image would read:
4212
4213	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4214	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4215	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4216	> examples/uImage.TQM850L
4217	Image Name:   2.4.4 kernel for TQM850L
4218	Created:      Wed Jul 19 02:34:59 2000
4219	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4220	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4221	Load Address: 0x00000000
4222	Entry Point:  0x00000000
4223
4224To verify the contents of the image (or check for corruption):
4225
4226	-> tools/mkimage -l examples/uImage.TQM850L
4227	Image Name:   2.4.4 kernel for TQM850L
4228	Created:      Wed Jul 19 02:34:59 2000
4229	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4230	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4231	Load Address: 0x00000000
4232	Entry Point:  0x00000000
4233
4234NOTE: for embedded systems where boot time is critical you can trade
4235speed for memory and install an UNCOMPRESSED image instead: this
4236needs more space in Flash, but boots much faster since it does not
4237need to be uncompressed:
4238
4239	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4240	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4241	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4242	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4243	> examples/uImage.TQM850L-uncompressed
4244	Image Name:   2.4.4 kernel for TQM850L
4245	Created:      Wed Jul 19 02:34:59 2000
4246	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4247	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4248	Load Address: 0x00000000
4249	Entry Point:  0x00000000
4250
4251
4252Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4253when your kernel is intended to use an initial ramdisk:
4254
4255	-> tools/mkimage -n 'Simple Ramdisk Image' \
4256	> -A ppc -O linux -T ramdisk -C gzip \
4257	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4258	Image Name:   Simple Ramdisk Image
4259	Created:      Wed Jan 12 14:01:50 2000
4260	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4261	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4262	Load Address: 0x00000000
4263	Entry Point:  0x00000000
4264
4265The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4266option performs the converse operation of the mkimage's second form (the "-d"
4267option). Given an image built by mkimage, the dumpimage extracts a "data file"
4268from the image:
4269
4270	tools/dumpimage -i image -T type -p position data_file
4271	  -i ==> extract from the 'image' a specific 'data_file'
4272	  -T ==> set image type to 'type'
4273	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4274
4275
4276Installing a Linux Image:
4277-------------------------
4278
4279To downloading a U-Boot image over the serial (console) interface,
4280you must convert the image to S-Record format:
4281
4282	objcopy -I binary -O srec examples/image examples/image.srec
4283
4284The 'objcopy' does not understand the information in the U-Boot
4285image header, so the resulting S-Record file will be relative to
4286address 0x00000000. To load it to a given address, you need to
4287specify the target address as 'offset' parameter with the 'loads'
4288command.
4289
4290Example: install the image to address 0x40100000 (which on the
4291TQM8xxL is in the first Flash bank):
4292
4293	=> erase 40100000 401FFFFF
4294
4295	.......... done
4296	Erased 8 sectors
4297
4298	=> loads 40100000
4299	## Ready for S-Record download ...
4300	~>examples/image.srec
4301	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4302	...
4303	15989 15990 15991 15992
4304	[file transfer complete]
4305	[connected]
4306	## Start Addr = 0x00000000
4307
4308
4309You can check the success of the download using the 'iminfo' command;
4310this includes a checksum verification so you can be sure no data
4311corruption happened:
4312
4313	=> imi 40100000
4314
4315	## Checking Image at 40100000 ...
4316	   Image Name:	 2.2.13 for initrd on TQM850L
4317	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4318	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4319	   Load Address: 00000000
4320	   Entry Point:	 0000000c
4321	   Verifying Checksum ... OK
4322
4323
4324Boot Linux:
4325-----------
4326
4327The "bootm" command is used to boot an application that is stored in
4328memory (RAM or Flash). In case of a Linux kernel image, the contents
4329of the "bootargs" environment variable is passed to the kernel as
4330parameters. You can check and modify this variable using the
4331"printenv" and "setenv" commands:
4332
4333
4334	=> printenv bootargs
4335	bootargs=root=/dev/ram
4336
4337	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4338
4339	=> printenv bootargs
4340	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4341
4342	=> bootm 40020000
4343	## Booting Linux kernel at 40020000 ...
4344	   Image Name:	 2.2.13 for NFS on TQM850L
4345	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4346	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4347	   Load Address: 00000000
4348	   Entry Point:	 0000000c
4349	   Verifying Checksum ... OK
4350	   Uncompressing Kernel Image ... OK
4351	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
4352	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4353	time_init: decrementer frequency = 187500000/60
4354	Calibrating delay loop... 49.77 BogoMIPS
4355	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4356	...
4357
4358If you want to boot a Linux kernel with initial RAM disk, you pass
4359the memory addresses of both the kernel and the initrd image (PPBCOOT
4360format!) to the "bootm" command:
4361
4362	=> imi 40100000 40200000
4363
4364	## Checking Image at 40100000 ...
4365	   Image Name:	 2.2.13 for initrd on TQM850L
4366	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4367	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4368	   Load Address: 00000000
4369	   Entry Point:	 0000000c
4370	   Verifying Checksum ... OK
4371
4372	## Checking Image at 40200000 ...
4373	   Image Name:	 Simple Ramdisk Image
4374	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4375	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4376	   Load Address: 00000000
4377	   Entry Point:	 00000000
4378	   Verifying Checksum ... OK
4379
4380	=> bootm 40100000 40200000
4381	## Booting Linux kernel at 40100000 ...
4382	   Image Name:	 2.2.13 for initrd on TQM850L
4383	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4384	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4385	   Load Address: 00000000
4386	   Entry Point:	 0000000c
4387	   Verifying Checksum ... OK
4388	   Uncompressing Kernel Image ... OK
4389	## Loading RAMDisk Image at 40200000 ...
4390	   Image Name:	 Simple Ramdisk Image
4391	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4392	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4393	   Load Address: 00000000
4394	   Entry Point:	 00000000
4395	   Verifying Checksum ... OK
4396	   Loading Ramdisk ... OK
4397	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
4398	Boot arguments: root=/dev/ram
4399	time_init: decrementer frequency = 187500000/60
4400	Calibrating delay loop... 49.77 BogoMIPS
4401	...
4402	RAMDISK: Compressed image found at block 0
4403	VFS: Mounted root (ext2 filesystem).
4404
4405	bash#
4406
4407Boot Linux and pass a flat device tree:
4408-----------
4409
4410First, U-Boot must be compiled with the appropriate defines. See the section
4411titled "Linux Kernel Interface" above for a more in depth explanation. The
4412following is an example of how to start a kernel and pass an updated
4413flat device tree:
4414
4415=> print oftaddr
4416oftaddr=0x300000
4417=> print oft
4418oft=oftrees/mpc8540ads.dtb
4419=> tftp $oftaddr $oft
4420Speed: 1000, full duplex
4421Using TSEC0 device
4422TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4423Filename 'oftrees/mpc8540ads.dtb'.
4424Load address: 0x300000
4425Loading: #
4426done
4427Bytes transferred = 4106 (100a hex)
4428=> tftp $loadaddr $bootfile
4429Speed: 1000, full duplex
4430Using TSEC0 device
4431TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4432Filename 'uImage'.
4433Load address: 0x200000
4434Loading:############
4435done
4436Bytes transferred = 1029407 (fb51f hex)
4437=> print loadaddr
4438loadaddr=200000
4439=> print oftaddr
4440oftaddr=0x300000
4441=> bootm $loadaddr - $oftaddr
4442## Booting image at 00200000 ...
4443   Image Name:	 Linux-2.6.17-dirty
4444   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4445   Data Size:	 1029343 Bytes = 1005.2 kB
4446   Load Address: 00000000
4447   Entry Point:	 00000000
4448   Verifying Checksum ... OK
4449   Uncompressing Kernel Image ... OK
4450Booting using flat device tree at 0x300000
4451Using MPC85xx ADS machine description
4452Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4453[snip]
4454
4455
4456More About U-Boot Image Types:
4457------------------------------
4458
4459U-Boot supports the following image types:
4460
4461   "Standalone Programs" are directly runnable in the environment
4462	provided by U-Boot; it is expected that (if they behave
4463	well) you can continue to work in U-Boot after return from
4464	the Standalone Program.
4465   "OS Kernel Images" are usually images of some Embedded OS which
4466	will take over control completely. Usually these programs
4467	will install their own set of exception handlers, device
4468	drivers, set up the MMU, etc. - this means, that you cannot
4469	expect to re-enter U-Boot except by resetting the CPU.
4470   "RAMDisk Images" are more or less just data blocks, and their
4471	parameters (address, size) are passed to an OS kernel that is
4472	being started.
4473   "Multi-File Images" contain several images, typically an OS
4474	(Linux) kernel image and one or more data images like
4475	RAMDisks. This construct is useful for instance when you want
4476	to boot over the network using BOOTP etc., where the boot
4477	server provides just a single image file, but you want to get
4478	for instance an OS kernel and a RAMDisk image.
4479
4480	"Multi-File Images" start with a list of image sizes, each
4481	image size (in bytes) specified by an "uint32_t" in network
4482	byte order. This list is terminated by an "(uint32_t)0".
4483	Immediately after the terminating 0 follow the images, one by
4484	one, all aligned on "uint32_t" boundaries (size rounded up to
4485	a multiple of 4 bytes).
4486
4487   "Firmware Images" are binary images containing firmware (like
4488	U-Boot or FPGA images) which usually will be programmed to
4489	flash memory.
4490
4491   "Script files" are command sequences that will be executed by
4492	U-Boot's command interpreter; this feature is especially
4493	useful when you configure U-Boot to use a real shell (hush)
4494	as command interpreter.
4495
4496Booting the Linux zImage:
4497-------------------------
4498
4499On some platforms, it's possible to boot Linux zImage. This is done
4500using the "bootz" command. The syntax of "bootz" command is the same
4501as the syntax of "bootm" command.
4502
4503Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4504kernel with raw initrd images. The syntax is slightly different, the
4505address of the initrd must be augmented by it's size, in the following
4506format: "<initrd addres>:<initrd size>".
4507
4508
4509Standalone HOWTO:
4510=================
4511
4512One of the features of U-Boot is that you can dynamically load and
4513run "standalone" applications, which can use some resources of
4514U-Boot like console I/O functions or interrupt services.
4515
4516Two simple examples are included with the sources:
4517
4518"Hello World" Demo:
4519-------------------
4520
4521'examples/hello_world.c' contains a small "Hello World" Demo
4522application; it is automatically compiled when you build U-Boot.
4523It's configured to run at address 0x00040004, so you can play with it
4524like that:
4525
4526	=> loads
4527	## Ready for S-Record download ...
4528	~>examples/hello_world.srec
4529	1 2 3 4 5 6 7 8 9 10 11 ...
4530	[file transfer complete]
4531	[connected]
4532	## Start Addr = 0x00040004
4533
4534	=> go 40004 Hello World! This is a test.
4535	## Starting application at 0x00040004 ...
4536	Hello World
4537	argc = 7
4538	argv[0] = "40004"
4539	argv[1] = "Hello"
4540	argv[2] = "World!"
4541	argv[3] = "This"
4542	argv[4] = "is"
4543	argv[5] = "a"
4544	argv[6] = "test."
4545	argv[7] = "<NULL>"
4546	Hit any key to exit ...
4547
4548	## Application terminated, rc = 0x0
4549
4550Another example, which demonstrates how to register a CPM interrupt
4551handler with the U-Boot code, can be found in 'examples/timer.c'.
4552Here, a CPM timer is set up to generate an interrupt every second.
4553The interrupt service routine is trivial, just printing a '.'
4554character, but this is just a demo program. The application can be
4555controlled by the following keys:
4556
4557	? - print current values og the CPM Timer registers
4558	b - enable interrupts and start timer
4559	e - stop timer and disable interrupts
4560	q - quit application
4561
4562	=> loads
4563	## Ready for S-Record download ...
4564	~>examples/timer.srec
4565	1 2 3 4 5 6 7 8 9 10 11 ...
4566	[file transfer complete]
4567	[connected]
4568	## Start Addr = 0x00040004
4569
4570	=> go 40004
4571	## Starting application at 0x00040004 ...
4572	TIMERS=0xfff00980
4573	Using timer 1
4574	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4575
4576Hit 'b':
4577	[q, b, e, ?] Set interval 1000000 us
4578	Enabling timer
4579Hit '?':
4580	[q, b, e, ?] ........
4581	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4582Hit '?':
4583	[q, b, e, ?] .
4584	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4585Hit '?':
4586	[q, b, e, ?] .
4587	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4588Hit '?':
4589	[q, b, e, ?] .
4590	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4591Hit 'e':
4592	[q, b, e, ?] ...Stopping timer
4593Hit 'q':
4594	[q, b, e, ?] ## Application terminated, rc = 0x0
4595
4596
4597Minicom warning:
4598================
4599
4600Over time, many people have reported problems when trying to use the
4601"minicom" terminal emulation program for serial download. I (wd)
4602consider minicom to be broken, and recommend not to use it. Under
4603Unix, I recommend to use C-Kermit for general purpose use (and
4604especially for kermit binary protocol download ("loadb" command), and
4605use "cu" for S-Record download ("loads" command).  See
4606http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4607for help with kermit.
4608
4609
4610Nevertheless, if you absolutely want to use it try adding this
4611configuration to your "File transfer protocols" section:
4612
4613	   Name	   Program			Name U/D FullScr IO-Red. Multi
4614	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4615	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4616
4617
4618NetBSD Notes:
4619=============
4620
4621Starting at version 0.9.2, U-Boot supports NetBSD both as host
4622(build U-Boot) and target system (boots NetBSD/mpc8xx).
4623
4624Building requires a cross environment; it is known to work on
4625NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4626need gmake since the Makefiles are not compatible with BSD make).
4627Note that the cross-powerpc package does not install include files;
4628attempting to build U-Boot will fail because <machine/ansi.h> is
4629missing.  This file has to be installed and patched manually:
4630
4631	# cd /usr/pkg/cross/powerpc-netbsd/include
4632	# mkdir powerpc
4633	# ln -s powerpc machine
4634	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4635	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4636
4637Native builds *don't* work due to incompatibilities between native
4638and U-Boot include files.
4639
4640Booting assumes that (the first part of) the image booted is a
4641stage-2 loader which in turn loads and then invokes the kernel
4642proper. Loader sources will eventually appear in the NetBSD source
4643tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4644meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4645
4646
4647Implementation Internals:
4648=========================
4649
4650The following is not intended to be a complete description of every
4651implementation detail. However, it should help to understand the
4652inner workings of U-Boot and make it easier to port it to custom
4653hardware.
4654
4655
4656Initial Stack, Global Data:
4657---------------------------
4658
4659The implementation of U-Boot is complicated by the fact that U-Boot
4660starts running out of ROM (flash memory), usually without access to
4661system RAM (because the memory controller is not initialized yet).
4662This means that we don't have writable Data or BSS segments, and BSS
4663is not initialized as zero. To be able to get a C environment working
4664at all, we have to allocate at least a minimal stack. Implementation
4665options for this are defined and restricted by the CPU used: Some CPU
4666models provide on-chip memory (like the IMMR area on MPC8xx and
4667MPC826x processors), on others (parts of) the data cache can be
4668locked as (mis-) used as memory, etc.
4669
4670	Chris Hallinan posted a good summary of these issues to the
4671	U-Boot mailing list:
4672
4673	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4674	From: "Chris Hallinan" <clh@net1plus.com>
4675	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4676	...
4677
4678	Correct me if I'm wrong, folks, but the way I understand it
4679	is this: Using DCACHE as initial RAM for Stack, etc, does not
4680	require any physical RAM backing up the cache. The cleverness
4681	is that the cache is being used as a temporary supply of
4682	necessary storage before the SDRAM controller is setup. It's
4683	beyond the scope of this list to explain the details, but you
4684	can see how this works by studying the cache architecture and
4685	operation in the architecture and processor-specific manuals.
4686
4687	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4688	is another option for the system designer to use as an
4689	initial stack/RAM area prior to SDRAM being available. Either
4690	option should work for you. Using CS 4 should be fine if your
4691	board designers haven't used it for something that would
4692	cause you grief during the initial boot! It is frequently not
4693	used.
4694
4695	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4696	with your processor/board/system design. The default value
4697	you will find in any recent u-boot distribution in
4698	walnut.h should work for you. I'd set it to a value larger
4699	than your SDRAM module. If you have a 64MB SDRAM module, set
4700	it above 400_0000. Just make sure your board has no resources
4701	that are supposed to respond to that address! That code in
4702	start.S has been around a while and should work as is when
4703	you get the config right.
4704
4705	-Chris Hallinan
4706	DS4.COM, Inc.
4707
4708It is essential to remember this, since it has some impact on the C
4709code for the initialization procedures:
4710
4711* Initialized global data (data segment) is read-only. Do not attempt
4712  to write it.
4713
4714* Do not use any uninitialized global data (or implicitly initialized
4715  as zero data - BSS segment) at all - this is undefined, initiali-
4716  zation is performed later (when relocating to RAM).
4717
4718* Stack space is very limited. Avoid big data buffers or things like
4719  that.
4720
4721Having only the stack as writable memory limits means we cannot use
4722normal global data to share information between the code. But it
4723turned out that the implementation of U-Boot can be greatly
4724simplified by making a global data structure (gd_t) available to all
4725functions. We could pass a pointer to this data as argument to _all_
4726functions, but this would bloat the code. Instead we use a feature of
4727the GCC compiler (Global Register Variables) to share the data: we
4728place a pointer (gd) to the global data into a register which we
4729reserve for this purpose.
4730
4731When choosing a register for such a purpose we are restricted by the
4732relevant  (E)ABI  specifications for the current architecture, and by
4733GCC's implementation.
4734
4735For PowerPC, the following registers have specific use:
4736	R1:	stack pointer
4737	R2:	reserved for system use
4738	R3-R4:	parameter passing and return values
4739	R5-R10: parameter passing
4740	R13:	small data area pointer
4741	R30:	GOT pointer
4742	R31:	frame pointer
4743
4744	(U-Boot also uses R12 as internal GOT pointer. r12
4745	is a volatile register so r12 needs to be reset when
4746	going back and forth between asm and C)
4747
4748    ==> U-Boot will use R2 to hold a pointer to the global data
4749
4750    Note: on PPC, we could use a static initializer (since the
4751    address of the global data structure is known at compile time),
4752    but it turned out that reserving a register results in somewhat
4753    smaller code - although the code savings are not that big (on
4754    average for all boards 752 bytes for the whole U-Boot image,
4755    624 text + 127 data).
4756
4757On ARM, the following registers are used:
4758
4759	R0:	function argument word/integer result
4760	R1-R3:	function argument word
4761	R9:	platform specific
4762	R10:	stack limit (used only if stack checking is enabled)
4763	R11:	argument (frame) pointer
4764	R12:	temporary workspace
4765	R13:	stack pointer
4766	R14:	link register
4767	R15:	program counter
4768
4769    ==> U-Boot will use R9 to hold a pointer to the global data
4770
4771    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4772
4773On Nios II, the ABI is documented here:
4774	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4775
4776    ==> U-Boot will use gp to hold a pointer to the global data
4777
4778    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4779    to access small data sections, so gp is free.
4780
4781On NDS32, the following registers are used:
4782
4783	R0-R1:	argument/return
4784	R2-R5:	argument
4785	R15:	temporary register for assembler
4786	R16:	trampoline register
4787	R28:	frame pointer (FP)
4788	R29:	global pointer (GP)
4789	R30:	link register (LP)
4790	R31:	stack pointer (SP)
4791	PC:	program counter (PC)
4792
4793    ==> U-Boot will use R10 to hold a pointer to the global data
4794
4795NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4796or current versions of GCC may "optimize" the code too much.
4797
4798On RISC-V, the following registers are used:
4799
4800	x0: hard-wired zero (zero)
4801	x1: return address (ra)
4802	x2:	stack pointer (sp)
4803	x3:	global pointer (gp)
4804	x4:	thread pointer (tp)
4805	x5:	link register (t0)
4806	x8:	frame pointer (fp)
4807	x10-x11:	arguments/return values (a0-1)
4808	x12-x17:	arguments (a2-7)
4809	x28-31:	 temporaries (t3-6)
4810	pc:	program counter (pc)
4811
4812    ==> U-Boot will use gp to hold a pointer to the global data
4813
4814Memory Management:
4815------------------
4816
4817U-Boot runs in system state and uses physical addresses, i.e. the
4818MMU is not used either for address mapping nor for memory protection.
4819
4820The available memory is mapped to fixed addresses using the memory
4821controller. In this process, a contiguous block is formed for each
4822memory type (Flash, SDRAM, SRAM), even when it consists of several
4823physical memory banks.
4824
4825U-Boot is installed in the first 128 kB of the first Flash bank (on
4826TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4827booting and sizing and initializing DRAM, the code relocates itself
4828to the upper end of DRAM. Immediately below the U-Boot code some
4829memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4830configuration setting]. Below that, a structure with global Board
4831Info data is placed, followed by the stack (growing downward).
4832
4833Additionally, some exception handler code is copied to the low 8 kB
4834of DRAM (0x00000000 ... 0x00001FFF).
4835
4836So a typical memory configuration with 16 MB of DRAM could look like
4837this:
4838
4839	0x0000 0000	Exception Vector code
4840	      :
4841	0x0000 1FFF
4842	0x0000 2000	Free for Application Use
4843	      :
4844	      :
4845
4846	      :
4847	      :
4848	0x00FB FF20	Monitor Stack (Growing downward)
4849	0x00FB FFAC	Board Info Data and permanent copy of global data
4850	0x00FC 0000	Malloc Arena
4851	      :
4852	0x00FD FFFF
4853	0x00FE 0000	RAM Copy of Monitor Code
4854	...		eventually: LCD or video framebuffer
4855	...		eventually: pRAM (Protected RAM - unchanged by reset)
4856	0x00FF FFFF	[End of RAM]
4857
4858
4859System Initialization:
4860----------------------
4861
4862In the reset configuration, U-Boot starts at the reset entry point
4863(on most PowerPC systems at address 0x00000100). Because of the reset
4864configuration for CS0# this is a mirror of the on board Flash memory.
4865To be able to re-map memory U-Boot then jumps to its link address.
4866To be able to implement the initialization code in C, a (small!)
4867initial stack is set up in the internal Dual Ported RAM (in case CPUs
4868which provide such a feature like), or in a locked part of the data
4869cache. After that, U-Boot initializes the CPU core, the caches and
4870the SIU.
4871
4872Next, all (potentially) available memory banks are mapped using a
4873preliminary mapping. For example, we put them on 512 MB boundaries
4874(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4875on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4876programmed for SDRAM access. Using the temporary configuration, a
4877simple memory test is run that determines the size of the SDRAM
4878banks.
4879
4880When there is more than one SDRAM bank, and the banks are of
4881different size, the largest is mapped first. For equal size, the first
4882bank (CS2#) is mapped first. The first mapping is always for address
48830x00000000, with any additional banks following immediately to create
4884contiguous memory starting from 0.
4885
4886Then, the monitor installs itself at the upper end of the SDRAM area
4887and allocates memory for use by malloc() and for the global Board
4888Info data; also, the exception vector code is copied to the low RAM
4889pages, and the final stack is set up.
4890
4891Only after this relocation will you have a "normal" C environment;
4892until that you are restricted in several ways, mostly because you are
4893running from ROM, and because the code will have to be relocated to a
4894new address in RAM.
4895
4896
4897U-Boot Porting Guide:
4898----------------------
4899
4900[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4901list, October 2002]
4902
4903
4904int main(int argc, char *argv[])
4905{
4906	sighandler_t no_more_time;
4907
4908	signal(SIGALRM, no_more_time);
4909	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4910
4911	if (available_money > available_manpower) {
4912		Pay consultant to port U-Boot;
4913		return 0;
4914	}
4915
4916	Download latest U-Boot source;
4917
4918	Subscribe to u-boot mailing list;
4919
4920	if (clueless)
4921		email("Hi, I am new to U-Boot, how do I get started?");
4922
4923	while (learning) {
4924		Read the README file in the top level directory;
4925		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4926		Read applicable doc/*.README;
4927		Read the source, Luke;
4928		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4929	}
4930
4931	if (available_money > toLocalCurrency ($2500))
4932		Buy a BDI3000;
4933	else
4934		Add a lot of aggravation and time;
4935
4936	if (a similar board exists) {	/* hopefully... */
4937		cp -a board/<similar> board/<myboard>
4938		cp include/configs/<similar>.h include/configs/<myboard>.h
4939	} else {
4940		Create your own board support subdirectory;
4941		Create your own board include/configs/<myboard>.h file;
4942	}
4943	Edit new board/<myboard> files
4944	Edit new include/configs/<myboard>.h
4945
4946	while (!accepted) {
4947		while (!running) {
4948			do {
4949				Add / modify source code;
4950			} until (compiles);
4951			Debug;
4952			if (clueless)
4953				email("Hi, I am having problems...");
4954		}
4955		Send patch file to the U-Boot email list;
4956		if (reasonable critiques)
4957			Incorporate improvements from email list code review;
4958		else
4959			Defend code as written;
4960	}
4961
4962	return 0;
4963}
4964
4965void no_more_time (int sig)
4966{
4967      hire_a_guru();
4968}
4969
4970
4971Coding Standards:
4972-----------------
4973
4974All contributions to U-Boot should conform to the Linux kernel
4975coding style; see the kernel coding style guide at
4976https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4977script "scripts/Lindent" in your Linux kernel source directory.
4978
4979Source files originating from a different project (for example the
4980MTD subsystem) are generally exempt from these guidelines and are not
4981reformatted to ease subsequent migration to newer versions of those
4982sources.
4983
4984Please note that U-Boot is implemented in C (and to some small parts in
4985Assembler); no C++ is used, so please do not use C++ style comments (//)
4986in your code.
4987
4988Please also stick to the following formatting rules:
4989- remove any trailing white space
4990- use TAB characters for indentation and vertical alignment, not spaces
4991- make sure NOT to use DOS '\r\n' line feeds
4992- do not add more than 2 consecutive empty lines to source files
4993- do not add trailing empty lines to source files
4994
4995Submissions which do not conform to the standards may be returned
4996with a request to reformat the changes.
4997
4998
4999Submitting Patches:
5000-------------------
5001
5002Since the number of patches for U-Boot is growing, we need to
5003establish some rules. Submissions which do not conform to these rules
5004may be rejected, even when they contain important and valuable stuff.
5005
5006Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5007
5008Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5009see https://lists.denx.de/listinfo/u-boot
5010
5011When you send a patch, please include the following information with
5012it:
5013
5014* For bug fixes: a description of the bug and how your patch fixes
5015  this bug. Please try to include a way of demonstrating that the
5016  patch actually fixes something.
5017
5018* For new features: a description of the feature and your
5019  implementation.
5020
5021* A CHANGELOG entry as plaintext (separate from the patch)
5022
5023* For major contributions, add a MAINTAINERS file with your
5024  information and associated file and directory references.
5025
5026* When you add support for a new board, don't forget to add a
5027  maintainer e-mail address to the boards.cfg file, too.
5028
5029* If your patch adds new configuration options, don't forget to
5030  document these in the README file.
5031
5032* The patch itself. If you are using git (which is *strongly*
5033  recommended) you can easily generate the patch using the
5034  "git format-patch". If you then use "git send-email" to send it to
5035  the U-Boot mailing list, you will avoid most of the common problems
5036  with some other mail clients.
5037
5038  If you cannot use git, use "diff -purN OLD NEW". If your version of
5039  diff does not support these options, then get the latest version of
5040  GNU diff.
5041
5042  The current directory when running this command shall be the parent
5043  directory of the U-Boot source tree (i. e. please make sure that
5044  your patch includes sufficient directory information for the
5045  affected files).
5046
5047  We prefer patches as plain text. MIME attachments are discouraged,
5048  and compressed attachments must not be used.
5049
5050* If one logical set of modifications affects or creates several
5051  files, all these changes shall be submitted in a SINGLE patch file.
5052
5053* Changesets that contain different, unrelated modifications shall be
5054  submitted as SEPARATE patches, one patch per changeset.
5055
5056
5057Notes:
5058
5059* Before sending the patch, run the buildman script on your patched
5060  source tree and make sure that no errors or warnings are reported
5061  for any of the boards.
5062
5063* Keep your modifications to the necessary minimum: A patch
5064  containing several unrelated changes or arbitrary reformats will be
5065  returned with a request to re-formatting / split it.
5066
5067* If you modify existing code, make sure that your new code does not
5068  add to the memory footprint of the code ;-) Small is beautiful!
5069  When adding new features, these should compile conditionally only
5070  (using #ifdef), and the resulting code with the new feature
5071  disabled must not need more memory than the old code without your
5072  modification.
5073
5074* Remember that there is a size limit of 100 kB per message on the
5075  u-boot mailing list. Bigger patches will be moderated. If they are
5076  reasonable and not too big, they will be acknowledged. But patches
5077  bigger than the size limit should be avoided.
5078