xref: /openbmc/u-boot/README (revision 2cfcee82)
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_XWAY_SWAP_BYTES
532
533		Enable compilation of tools/xway-swap-bytes needed for Lantiq
534		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
535		be swapped if a flash programmer is used.
536
537- ARM options:
538		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
539
540		Select high exception vectors of the ARM core, e.g., do not
541		clear the V bit of the c1 register of CP15.
542
543		COUNTER_FREQUENCY
544		Generic timer clock source frequency.
545
546		COUNTER_FREQUENCY_REAL
547		Generic timer clock source frequency if the real clock is
548		different from COUNTER_FREQUENCY, and can only be determined
549		at run time.
550
551- Tegra SoC options:
552		CONFIG_TEGRA_SUPPORT_NON_SECURE
553
554		Support executing U-Boot in non-secure (NS) mode. Certain
555		impossible actions will be skipped if the CPU is in NS mode,
556		such as ARM architectural timer initialization.
557
558- Linux Kernel Interface:
559		CONFIG_CLOCKS_IN_MHZ
560
561		U-Boot stores all clock information in Hz
562		internally. For binary compatibility with older Linux
563		kernels (which expect the clocks passed in the
564		bd_info data to be in MHz) the environment variable
565		"clocks_in_mhz" can be defined so that U-Boot
566		converts clock data to MHZ before passing it to the
567		Linux kernel.
568		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
569		"clocks_in_mhz=1" is automatically included in the
570		default environment.
571
572		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
573
574		When transferring memsize parameter to Linux, some versions
575		expect it to be in bytes, others in MB.
576		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
577
578		CONFIG_OF_LIBFDT
579
580		New kernel versions are expecting firmware settings to be
581		passed using flattened device trees (based on open firmware
582		concepts).
583
584		CONFIG_OF_LIBFDT
585		 * New libfdt-based support
586		 * Adds the "fdt" command
587		 * The bootm command automatically updates the fdt
588
589		OF_TBCLK - The timebase frequency.
590		OF_STDOUT_PATH - The path to the console device
591
592		boards with QUICC Engines require OF_QE to set UCC MAC
593		addresses
594
595		CONFIG_OF_BOARD_SETUP
596
597		Board code has addition modification that it wants to make
598		to the flat device tree before handing it off to the kernel
599
600		CONFIG_OF_SYSTEM_SETUP
601
602		Other code has addition modification that it wants to make
603		to the flat device tree before handing it off to the kernel.
604		This causes ft_system_setup() to be called before booting
605		the kernel.
606
607		CONFIG_OF_IDE_FIXUP
608
609		U-Boot can detect if an IDE device is present or not.
610		If not, and this new config option is activated, U-Boot
611		removes the ATA node from the DTS before booting Linux,
612		so the Linux IDE driver does not probe the device and
613		crash. This is needed for buggy hardware (uc101) where
614		no pull down resistor is connected to the signal IDE5V_DD7.
615
616		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
617
618		This setting is mandatory for all boards that have only one
619		machine type and must be used to specify the machine type
620		number as it appears in the ARM machine registry
621		(see http://www.arm.linux.org.uk/developer/machines/).
622		Only boards that have multiple machine types supported
623		in a single configuration file and the machine type is
624		runtime discoverable, do not have to use this setting.
625
626- vxWorks boot parameters:
627
628		bootvx constructs a valid bootline using the following
629		environments variables: bootdev, bootfile, ipaddr, netmask,
630		serverip, gatewayip, hostname, othbootargs.
631		It loads the vxWorks image pointed bootfile.
632
633		Note: If a "bootargs" environment is defined, it will overwride
634		the defaults discussed just above.
635
636- Cache Configuration:
637		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
638		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
639		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
640
641- Cache Configuration for ARM:
642		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
643				      controller
644		CONFIG_SYS_PL310_BASE - Physical base address of PL310
645					controller register space
646
647- Serial Ports:
648		CONFIG_PL010_SERIAL
649
650		Define this if you want support for Amba PrimeCell PL010 UARTs.
651
652		CONFIG_PL011_SERIAL
653
654		Define this if you want support for Amba PrimeCell PL011 UARTs.
655
656		CONFIG_PL011_CLOCK
657
658		If you have Amba PrimeCell PL011 UARTs, set this variable to
659		the clock speed of the UARTs.
660
661		CONFIG_PL01x_PORTS
662
663		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
664		define this to a list of base addresses for each (supported)
665		port. See e.g. include/configs/versatile.h
666
667		CONFIG_SERIAL_HW_FLOW_CONTROL
668
669		Define this variable to enable hw flow control in serial driver.
670		Current user of this option is drivers/serial/nsl16550.c driver
671
672- Console Baudrate:
673		CONFIG_BAUDRATE - in bps
674		Select one of the baudrates listed in
675		CONFIG_SYS_BAUDRATE_TABLE, see below.
676
677- Autoboot Command:
678		CONFIG_BOOTCOMMAND
679		Only needed when CONFIG_BOOTDELAY is enabled;
680		define a command string that is automatically executed
681		when no character is read on the console interface
682		within "Boot Delay" after reset.
683
684		CONFIG_RAMBOOT and CONFIG_NFSBOOT
685		The value of these goes into the environment as
686		"ramboot" and "nfsboot" respectively, and can be used
687		as a convenience, when switching between booting from
688		RAM and NFS.
689
690- Pre-Boot Commands:
691		CONFIG_PREBOOT
692
693		When this option is #defined, the existence of the
694		environment variable "preboot" will be checked
695		immediately before starting the CONFIG_BOOTDELAY
696		countdown and/or running the auto-boot command resp.
697		entering interactive mode.
698
699		This feature is especially useful when "preboot" is
700		automatically generated or modified. For an example
701		see the LWMON board specific code: here "preboot" is
702		modified when the user holds down a certain
703		combination of keys on the (special) keyboard when
704		booting the systems
705
706- Serial Download Echo Mode:
707		CONFIG_LOADS_ECHO
708		If defined to 1, all characters received during a
709		serial download (using the "loads" command) are
710		echoed back. This might be needed by some terminal
711		emulations (like "cu"), but may as well just take
712		time on others. This setting #define's the initial
713		value of the "loads_echo" environment variable.
714
715- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
716		CONFIG_KGDB_BAUDRATE
717		Select one of the baudrates listed in
718		CONFIG_SYS_BAUDRATE_TABLE, see below.
719
720- Removal of commands
721		If no commands are needed to boot, you can disable
722		CONFIG_CMDLINE to remove them. In this case, the command line
723		will not be available, and when U-Boot wants to execute the
724		boot command (on start-up) it will call board_run_command()
725		instead. This can reduce image size significantly for very
726		simple boot procedures.
727
728- Regular expression support:
729		CONFIG_REGEX
730		If this variable is defined, U-Boot is linked against
731		the SLRE (Super Light Regular Expression) library,
732		which adds regex support to some commands, as for
733		example "env grep" and "setexpr".
734
735- Device tree:
736		CONFIG_OF_CONTROL
737		If this variable is defined, U-Boot will use a device tree
738		to configure its devices, instead of relying on statically
739		compiled #defines in the board file. This option is
740		experimental and only available on a few boards. The device
741		tree is available in the global data as gd->fdt_blob.
742
743		U-Boot needs to get its device tree from somewhere. This can
744		be done using one of the three options below:
745
746		CONFIG_OF_EMBED
747		If this variable is defined, U-Boot will embed a device tree
748		binary in its image. This device tree file should be in the
749		board directory and called <soc>-<board>.dts. The binary file
750		is then picked up in board_init_f() and made available through
751		the global data structure as gd->fdt_blob.
752
753		CONFIG_OF_SEPARATE
754		If this variable is defined, U-Boot will build a device tree
755		binary. It will be called u-boot.dtb. Architecture-specific
756		code will locate it at run-time. Generally this works by:
757
758			cat u-boot.bin u-boot.dtb >image.bin
759
760		and in fact, U-Boot does this for you, creating a file called
761		u-boot-dtb.bin which is useful in the common case. You can
762		still use the individual files if you need something more
763		exotic.
764
765		CONFIG_OF_BOARD
766		If this variable is defined, U-Boot will use the device tree
767		provided by the board at runtime instead of embedding one with
768		the image. Only boards defining board_fdt_blob_setup() support
769		this option (see include/fdtdec.h file).
770
771- Watchdog:
772		CONFIG_WATCHDOG
773		If this variable is defined, it enables watchdog
774		support for the SoC. There must be support in the SoC
775		specific code for a watchdog. For the 8xx
776		CPUs, the SIU Watchdog feature is enabled in the SYPCR
777		register.  When supported for a specific SoC is
778		available, then no further board specific code should
779		be needed to use it.
780
781		CONFIG_HW_WATCHDOG
782		When using a watchdog circuitry external to the used
783		SoC, then define this variable and provide board
784		specific code for the "hw_watchdog_reset" function.
785
786		CONFIG_AT91_HW_WDT_TIMEOUT
787		specify the timeout in seconds. default 2 seconds.
788
789- Real-Time Clock:
790
791		When CONFIG_CMD_DATE is selected, the type of the RTC
792		has to be selected, too. Define exactly one of the
793		following options:
794
795		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
796		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
797		CONFIG_RTC_MC146818	- use MC146818 RTC
798		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
799		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
800		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
801		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
802		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
803		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
804		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
805		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
806		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
807					  RV3029 RTC.
808
809		Note that if the RTC uses I2C, then the I2C interface
810		must also be configured. See I2C Support, below.
811
812- GPIO Support:
813		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
814
815		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
816		chip-ngpio pairs that tell the PCA953X driver the number of
817		pins supported by a particular chip.
818
819		Note that if the GPIO device uses I2C, then the I2C interface
820		must also be configured. See I2C Support, below.
821
822- I/O tracing:
823		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
824		accesses and can checksum them or write a list of them out
825		to memory. See the 'iotrace' command for details. This is
826		useful for testing device drivers since it can confirm that
827		the driver behaves the same way before and after a code
828		change. Currently this is supported on sandbox and arm. To
829		add support for your architecture, add '#include <iotrace.h>'
830		to the bottom of arch/<arch>/include/asm/io.h and test.
831
832		Example output from the 'iotrace stats' command is below.
833		Note that if the trace buffer is exhausted, the checksum will
834		still continue to operate.
835
836			iotrace is enabled
837			Start:  10000000	(buffer start address)
838			Size:   00010000	(buffer size)
839			Offset: 00000120	(current buffer offset)
840			Output: 10000120	(start + offset)
841			Count:  00000018	(number of trace records)
842			CRC32:  9526fb66	(CRC32 of all trace records)
843
844- Timestamp Support:
845
846		When CONFIG_TIMESTAMP is selected, the timestamp
847		(date and time) of an image is printed by image
848		commands like bootm or iminfo. This option is
849		automatically enabled when you select CONFIG_CMD_DATE .
850
851- Partition Labels (disklabels) Supported:
852		Zero or more of the following:
853		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
854		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
855		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
856				       bootloader.  Note 2TB partition limit; see
857				       disk/part_efi.c
858		CONFIG_SCSI) you must configure support for at
859		least one non-MTD partition type as well.
860
861- IDE Reset method:
862		CONFIG_IDE_RESET_ROUTINE - this is defined in several
863		board configurations files but used nowhere!
864
865		CONFIG_IDE_RESET - is this is defined, IDE Reset will
866		be performed by calling the function
867			ide_set_reset(int reset)
868		which has to be defined in a board specific file
869
870- ATAPI Support:
871		CONFIG_ATAPI
872
873		Set this to enable ATAPI support.
874
875- LBA48 Support
876		CONFIG_LBA48
877
878		Set this to enable support for disks larger than 137GB
879		Also look at CONFIG_SYS_64BIT_LBA.
880		Whithout these , LBA48 support uses 32bit variables and will 'only'
881		support disks up to 2.1TB.
882
883		CONFIG_SYS_64BIT_LBA:
884			When enabled, makes the IDE subsystem use 64bit sector addresses.
885			Default is 32bit.
886
887- SCSI Support:
888		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
889		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
890		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
891		maximum numbers of LUNs, SCSI ID's and target
892		devices.
893
894		The environment variable 'scsidevs' is set to the number of
895		SCSI devices found during the last scan.
896
897- NETWORK Support (PCI):
898		CONFIG_E1000
899		Support for Intel 8254x/8257x gigabit chips.
900
901		CONFIG_E1000_SPI
902		Utility code for direct access to the SPI bus on Intel 8257x.
903		This does not do anything useful unless you set at least one
904		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
905
906		CONFIG_E1000_SPI_GENERIC
907		Allow generic access to the SPI bus on the Intel 8257x, for
908		example with the "sspi" command.
909
910		CONFIG_EEPRO100
911		Support for Intel 82557/82559/82559ER chips.
912		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
913		write routine for first time initialisation.
914
915		CONFIG_TULIP
916		Support for Digital 2114x chips.
917		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
918		modem chip initialisation (KS8761/QS6611).
919
920		CONFIG_NATSEMI
921		Support for National dp83815 chips.
922
923		CONFIG_NS8382X
924		Support for National dp8382[01] gigabit chips.
925
926- NETWORK Support (other):
927
928		CONFIG_DRIVER_AT91EMAC
929		Support for AT91RM9200 EMAC.
930
931			CONFIG_RMII
932			Define this to use reduced MII inteface
933
934			CONFIG_DRIVER_AT91EMAC_QUIET
935			If this defined, the driver is quiet.
936			The driver doen't show link status messages.
937
938		CONFIG_CALXEDA_XGMAC
939		Support for the Calxeda XGMAC device
940
941		CONFIG_LAN91C96
942		Support for SMSC's LAN91C96 chips.
943
944			CONFIG_LAN91C96_USE_32_BIT
945			Define this to enable 32 bit addressing
946
947		CONFIG_SMC91111
948		Support for SMSC's LAN91C111 chip
949
950			CONFIG_SMC91111_BASE
951			Define this to hold the physical address
952			of the device (I/O space)
953
954			CONFIG_SMC_USE_32_BIT
955			Define this if data bus is 32 bits
956
957			CONFIG_SMC_USE_IOFUNCS
958			Define this to use i/o functions instead of macros
959			(some hardware wont work with macros)
960
961			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
962			Define this if you have more then 3 PHYs.
963
964		CONFIG_FTGMAC100
965		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
966
967			CONFIG_FTGMAC100_EGIGA
968			Define this to use GE link update with gigabit PHY.
969			Define this if FTGMAC100 is connected to gigabit PHY.
970			If your system has 10/100 PHY only, it might not occur
971			wrong behavior. Because PHY usually return timeout or
972			useless data when polling gigabit status and gigabit
973			control registers. This behavior won't affect the
974			correctnessof 10/100 link speed update.
975
976		CONFIG_SH_ETHER
977		Support for Renesas on-chip Ethernet controller
978
979			CONFIG_SH_ETHER_USE_PORT
980			Define the number of ports to be used
981
982			CONFIG_SH_ETHER_PHY_ADDR
983			Define the ETH PHY's address
984
985			CONFIG_SH_ETHER_CACHE_WRITEBACK
986			If this option is set, the driver enables cache flush.
987
988- PWM Support:
989		CONFIG_PWM_IMX
990		Support for PWM module on the imx6.
991
992- TPM Support:
993		CONFIG_TPM
994		Support TPM devices.
995
996		CONFIG_TPM_TIS_INFINEON
997		Support for Infineon i2c bus TPM devices. Only one device
998		per system is supported at this time.
999
1000			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1001			Define the burst count bytes upper limit
1002
1003		CONFIG_TPM_ST33ZP24
1004		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1005
1006			CONFIG_TPM_ST33ZP24_I2C
1007			Support for STMicroelectronics ST33ZP24 I2C devices.
1008			Requires TPM_ST33ZP24 and I2C.
1009
1010			CONFIG_TPM_ST33ZP24_SPI
1011			Support for STMicroelectronics ST33ZP24 SPI devices.
1012			Requires TPM_ST33ZP24 and SPI.
1013
1014		CONFIG_TPM_ATMEL_TWI
1015		Support for Atmel TWI TPM device. Requires I2C support.
1016
1017		CONFIG_TPM_TIS_LPC
1018		Support for generic parallel port TPM devices. Only one device
1019		per system is supported at this time.
1020
1021			CONFIG_TPM_TIS_BASE_ADDRESS
1022			Base address where the generic TPM device is mapped
1023			to. Contemporary x86 systems usually map it at
1024			0xfed40000.
1025
1026		CONFIG_TPM
1027		Define this to enable the TPM support library which provides
1028		functional interfaces to some TPM commands.
1029		Requires support for a TPM device.
1030
1031		CONFIG_TPM_AUTH_SESSIONS
1032		Define this to enable authorized functions in the TPM library.
1033		Requires CONFIG_TPM and CONFIG_SHA1.
1034
1035- USB Support:
1036		At the moment only the UHCI host controller is
1037		supported (PIP405, MIP405); define
1038		CONFIG_USB_UHCI to enable it.
1039		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1040		and define CONFIG_USB_STORAGE to enable the USB
1041		storage devices.
1042		Note:
1043		Supported are USB Keyboards and USB Floppy drives
1044		(TEAC FD-05PUB).
1045
1046		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1047		txfilltuning field in the EHCI controller on reset.
1048
1049		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1050		HW module registers.
1051
1052- USB Device:
1053		Define the below if you wish to use the USB console.
1054		Once firmware is rebuilt from a serial console issue the
1055		command "setenv stdin usbtty; setenv stdout usbtty" and
1056		attach your USB cable. The Unix command "dmesg" should print
1057		it has found a new device. The environment variable usbtty
1058		can be set to gserial or cdc_acm to enable your device to
1059		appear to a USB host as a Linux gserial device or a
1060		Common Device Class Abstract Control Model serial device.
1061		If you select usbtty = gserial you should be able to enumerate
1062		a Linux host by
1063		# modprobe usbserial vendor=0xVendorID product=0xProductID
1064		else if using cdc_acm, simply setting the environment
1065		variable usbtty to be cdc_acm should suffice. The following
1066		might be defined in YourBoardName.h
1067
1068			CONFIG_USB_DEVICE
1069			Define this to build a UDC device
1070
1071			CONFIG_USB_TTY
1072			Define this to have a tty type of device available to
1073			talk to the UDC device
1074
1075			CONFIG_USBD_HS
1076			Define this to enable the high speed support for usb
1077			device and usbtty. If this feature is enabled, a routine
1078			int is_usbd_high_speed(void)
1079			also needs to be defined by the driver to dynamically poll
1080			whether the enumeration has succeded at high speed or full
1081			speed.
1082
1083			CONFIG_SYS_CONSOLE_IS_IN_ENV
1084			Define this if you want stdin, stdout &/or stderr to
1085			be set to usbtty.
1086
1087		If you have a USB-IF assigned VendorID then you may wish to
1088		define your own vendor specific values either in BoardName.h
1089		or directly in usbd_vendor_info.h. If you don't define
1090		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1091		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1092		should pretend to be a Linux device to it's target host.
1093
1094			CONFIG_USBD_MANUFACTURER
1095			Define this string as the name of your company for
1096			- CONFIG_USBD_MANUFACTURER "my company"
1097
1098			CONFIG_USBD_PRODUCT_NAME
1099			Define this string as the name of your product
1100			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1101
1102			CONFIG_USBD_VENDORID
1103			Define this as your assigned Vendor ID from the USB
1104			Implementors Forum. This *must* be a genuine Vendor ID
1105			to avoid polluting the USB namespace.
1106			- CONFIG_USBD_VENDORID 0xFFFF
1107
1108			CONFIG_USBD_PRODUCTID
1109			Define this as the unique Product ID
1110			for your device
1111			- CONFIG_USBD_PRODUCTID 0xFFFF
1112
1113- ULPI Layer Support:
1114		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1115		the generic ULPI layer. The generic layer accesses the ULPI PHY
1116		via the platform viewport, so you need both the genric layer and
1117		the viewport enabled. Currently only Chipidea/ARC based
1118		viewport is supported.
1119		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1120		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1121		If your ULPI phy needs a different reference clock than the
1122		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1123		the appropriate value in Hz.
1124
1125- MMC Support:
1126		The MMC controller on the Intel PXA is supported. To
1127		enable this define CONFIG_MMC. The MMC can be
1128		accessed from the boot prompt by mapping the device
1129		to physical memory similar to flash. Command line is
1130		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1131		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1132
1133		CONFIG_SH_MMCIF
1134		Support for Renesas on-chip MMCIF controller
1135
1136			CONFIG_SH_MMCIF_ADDR
1137			Define the base address of MMCIF registers
1138
1139			CONFIG_SH_MMCIF_CLK
1140			Define the clock frequency for MMCIF
1141
1142		CONFIG_SUPPORT_EMMC_BOOT
1143		Enable some additional features of the eMMC boot partitions.
1144
1145- USB Device Firmware Update (DFU) class support:
1146		CONFIG_DFU_OVER_USB
1147		This enables the USB portion of the DFU USB class
1148
1149		CONFIG_DFU_MMC
1150		This enables support for exposing (e)MMC devices via DFU.
1151
1152		CONFIG_DFU_NAND
1153		This enables support for exposing NAND devices via DFU.
1154
1155		CONFIG_DFU_RAM
1156		This enables support for exposing RAM via DFU.
1157		Note: DFU spec refer to non-volatile memory usage, but
1158		allow usages beyond the scope of spec - here RAM usage,
1159		one that would help mostly the developer.
1160
1161		CONFIG_SYS_DFU_DATA_BUF_SIZE
1162		Dfu transfer uses a buffer before writing data to the
1163		raw storage device. Make the size (in bytes) of this buffer
1164		configurable. The size of this buffer is also configurable
1165		through the "dfu_bufsiz" environment variable.
1166
1167		CONFIG_SYS_DFU_MAX_FILE_SIZE
1168		When updating files rather than the raw storage device,
1169		we use a static buffer to copy the file into and then write
1170		the buffer once we've been given the whole file.  Define
1171		this to the maximum filesize (in bytes) for the buffer.
1172		Default is 4 MiB if undefined.
1173
1174		DFU_DEFAULT_POLL_TIMEOUT
1175		Poll timeout [ms], is the timeout a device can send to the
1176		host. The host must wait for this timeout before sending
1177		a subsequent DFU_GET_STATUS request to the device.
1178
1179		DFU_MANIFEST_POLL_TIMEOUT
1180		Poll timeout [ms], which the device sends to the host when
1181		entering dfuMANIFEST state. Host waits this timeout, before
1182		sending again an USB request to the device.
1183
1184- Journaling Flash filesystem support:
1185		CONFIG_JFFS2_NAND
1186		Define these for a default partition on a NAND device
1187
1188		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1189		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1190		Define these for a default partition on a NOR device
1191
1192- Keyboard Support:
1193		See Kconfig help for available keyboard drivers.
1194
1195		CONFIG_KEYBOARD
1196
1197		Define this to enable a custom keyboard support.
1198		This simply calls drv_keyboard_init() which must be
1199		defined in your board-specific files. This option is deprecated
1200		and is only used by novena. For new boards, use driver model
1201		instead.
1202
1203- Video support:
1204		CONFIG_FSL_DIU_FB
1205		Enable the Freescale DIU video driver.	Reference boards for
1206		SOCs that have a DIU should define this macro to enable DIU
1207		support, and should also define these other macros:
1208
1209			CONFIG_SYS_DIU_ADDR
1210			CONFIG_VIDEO
1211			CONFIG_CFB_CONSOLE
1212			CONFIG_VIDEO_SW_CURSOR
1213			CONFIG_VGA_AS_SINGLE_DEVICE
1214			CONFIG_VIDEO_LOGO
1215			CONFIG_VIDEO_BMP_LOGO
1216
1217		The DIU driver will look for the 'video-mode' environment
1218		variable, and if defined, enable the DIU as a console during
1219		boot.  See the documentation file doc/README.video for a
1220		description of this variable.
1221
1222- LCD Support:	CONFIG_LCD
1223
1224		Define this to enable LCD support (for output to LCD
1225		display); also select one of the supported displays
1226		by defining one of these:
1227
1228		CONFIG_ATMEL_LCD:
1229
1230			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1231
1232		CONFIG_NEC_NL6448AC33:
1233
1234			NEC NL6448AC33-18. Active, color, single scan.
1235
1236		CONFIG_NEC_NL6448BC20
1237
1238			NEC NL6448BC20-08. 6.5", 640x480.
1239			Active, color, single scan.
1240
1241		CONFIG_NEC_NL6448BC33_54
1242
1243			NEC NL6448BC33-54. 10.4", 640x480.
1244			Active, color, single scan.
1245
1246		CONFIG_SHARP_16x9
1247
1248			Sharp 320x240. Active, color, single scan.
1249			It isn't 16x9, and I am not sure what it is.
1250
1251		CONFIG_SHARP_LQ64D341
1252
1253			Sharp LQ64D341 display, 640x480.
1254			Active, color, single scan.
1255
1256		CONFIG_HLD1045
1257
1258			HLD1045 display, 640x480.
1259			Active, color, single scan.
1260
1261		CONFIG_OPTREX_BW
1262
1263			Optrex	 CBL50840-2 NF-FW 99 22 M5
1264			or
1265			Hitachi	 LMG6912RPFC-00T
1266			or
1267			Hitachi	 SP14Q002
1268
1269			320x240. Black & white.
1270
1271		CONFIG_LCD_ALIGNMENT
1272
1273		Normally the LCD is page-aligned (typically 4KB). If this is
1274		defined then the LCD will be aligned to this value instead.
1275		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1276		here, since it is cheaper to change data cache settings on
1277		a per-section basis.
1278
1279
1280		CONFIG_LCD_ROTATION
1281
1282		Sometimes, for example if the display is mounted in portrait
1283		mode or even if it's mounted landscape but rotated by 180degree,
1284		we need to rotate our content of the display relative to the
1285		framebuffer, so that user can read the messages which are
1286		printed out.
1287		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1288		initialized with a given rotation from "vl_rot" out of
1289		"vidinfo_t" which is provided by the board specific code.
1290		The value for vl_rot is coded as following (matching to
1291		fbcon=rotate:<n> linux-kernel commandline):
1292		0 = no rotation respectively 0 degree
1293		1 = 90 degree rotation
1294		2 = 180 degree rotation
1295		3 = 270 degree rotation
1296
1297		If CONFIG_LCD_ROTATION is not defined, the console will be
1298		initialized with 0degree rotation.
1299
1300		CONFIG_LCD_BMP_RLE8
1301
1302		Support drawing of RLE8-compressed bitmaps on the LCD.
1303
1304		CONFIG_I2C_EDID
1305
1306		Enables an 'i2c edid' command which can read EDID
1307		information over I2C from an attached LCD display.
1308
1309- Splash Screen Support: CONFIG_SPLASH_SCREEN
1310
1311		If this option is set, the environment is checked for
1312		a variable "splashimage". If found, the usual display
1313		of logo, copyright and system information on the LCD
1314		is suppressed and the BMP image at the address
1315		specified in "splashimage" is loaded instead. The
1316		console is redirected to the "nulldev", too. This
1317		allows for a "silent" boot where a splash screen is
1318		loaded very quickly after power-on.
1319
1320		CONFIG_SPLASHIMAGE_GUARD
1321
1322		If this option is set, then U-Boot will prevent the environment
1323		variable "splashimage" from being set to a problematic address
1324		(see doc/README.displaying-bmps).
1325		This option is useful for targets where, due to alignment
1326		restrictions, an improperly aligned BMP image will cause a data
1327		abort. If you think you will not have problems with unaligned
1328		accesses (for example because your toolchain prevents them)
1329		there is no need to set this option.
1330
1331		CONFIG_SPLASH_SCREEN_ALIGN
1332
1333		If this option is set the splash image can be freely positioned
1334		on the screen. Environment variable "splashpos" specifies the
1335		position as "x,y". If a positive number is given it is used as
1336		number of pixel from left/top. If a negative number is given it
1337		is used as number of pixel from right/bottom. You can also
1338		specify 'm' for centering the image.
1339
1340		Example:
1341		setenv splashpos m,m
1342			=> image at center of screen
1343
1344		setenv splashpos 30,20
1345			=> image at x = 30 and y = 20
1346
1347		setenv splashpos -10,m
1348			=> vertically centered image
1349			   at x = dspWidth - bmpWidth - 9
1350
1351- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1352
1353		If this option is set, additionally to standard BMP
1354		images, gzipped BMP images can be displayed via the
1355		splashscreen support or the bmp command.
1356
1357- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1358
1359		If this option is set, 8-bit RLE compressed BMP images
1360		can be displayed via the splashscreen support or the
1361		bmp command.
1362
1363- Compression support:
1364		CONFIG_GZIP
1365
1366		Enabled by default to support gzip compressed images.
1367
1368		CONFIG_BZIP2
1369
1370		If this option is set, support for bzip2 compressed
1371		images is included. If not, only uncompressed and gzip
1372		compressed images are supported.
1373
1374		NOTE: the bzip2 algorithm requires a lot of RAM, so
1375		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1376		be at least 4MB.
1377
1378- MII/PHY support:
1379		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1380
1381		The clock frequency of the MII bus
1382
1383		CONFIG_PHY_RESET_DELAY
1384
1385		Some PHY like Intel LXT971A need extra delay after
1386		reset before any MII register access is possible.
1387		For such PHY, set this option to the usec delay
1388		required. (minimum 300usec for LXT971A)
1389
1390		CONFIG_PHY_CMD_DELAY (ppc4xx)
1391
1392		Some PHY like Intel LXT971A need extra delay after
1393		command issued before MII status register can be read
1394
1395- IP address:
1396		CONFIG_IPADDR
1397
1398		Define a default value for the IP address to use for
1399		the default Ethernet interface, in case this is not
1400		determined through e.g. bootp.
1401		(Environment variable "ipaddr")
1402
1403- Server IP address:
1404		CONFIG_SERVERIP
1405
1406		Defines a default value for the IP address of a TFTP
1407		server to contact when using the "tftboot" command.
1408		(Environment variable "serverip")
1409
1410		CONFIG_KEEP_SERVERADDR
1411
1412		Keeps the server's MAC address, in the env 'serveraddr'
1413		for passing to bootargs (like Linux's netconsole option)
1414
1415- Gateway IP address:
1416		CONFIG_GATEWAYIP
1417
1418		Defines a default value for the IP address of the
1419		default router where packets to other networks are
1420		sent to.
1421		(Environment variable "gatewayip")
1422
1423- Subnet mask:
1424		CONFIG_NETMASK
1425
1426		Defines a default value for the subnet mask (or
1427		routing prefix) which is used to determine if an IP
1428		address belongs to the local subnet or needs to be
1429		forwarded through a router.
1430		(Environment variable "netmask")
1431
1432- Multicast TFTP Mode:
1433		CONFIG_MCAST_TFTP
1434
1435		Defines whether you want to support multicast TFTP as per
1436		rfc-2090; for example to work with atftp.  Lets lots of targets
1437		tftp down the same boot image concurrently.  Note: the Ethernet
1438		driver in use must provide a function: mcast() to join/leave a
1439		multicast group.
1440
1441- BOOTP Recovery Mode:
1442		CONFIG_BOOTP_RANDOM_DELAY
1443
1444		If you have many targets in a network that try to
1445		boot using BOOTP, you may want to avoid that all
1446		systems send out BOOTP requests at precisely the same
1447		moment (which would happen for instance at recovery
1448		from a power failure, when all systems will try to
1449		boot, thus flooding the BOOTP server. Defining
1450		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1451		inserted before sending out BOOTP requests. The
1452		following delays are inserted then:
1453
1454		1st BOOTP request:	delay 0 ... 1 sec
1455		2nd BOOTP request:	delay 0 ... 2 sec
1456		3rd BOOTP request:	delay 0 ... 4 sec
1457		4th and following
1458		BOOTP requests:		delay 0 ... 8 sec
1459
1460		CONFIG_BOOTP_ID_CACHE_SIZE
1461
1462		BOOTP packets are uniquely identified using a 32-bit ID. The
1463		server will copy the ID from client requests to responses and
1464		U-Boot will use this to determine if it is the destination of
1465		an incoming response. Some servers will check that addresses
1466		aren't in use before handing them out (usually using an ARP
1467		ping) and therefore take up to a few hundred milliseconds to
1468		respond. Network congestion may also influence the time it
1469		takes for a response to make it back to the client. If that
1470		time is too long, U-Boot will retransmit requests. In order
1471		to allow earlier responses to still be accepted after these
1472		retransmissions, U-Boot's BOOTP client keeps a small cache of
1473		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1474		cache. The default is to keep IDs for up to four outstanding
1475		requests. Increasing this will allow U-Boot to accept offers
1476		from a BOOTP client in networks with unusually high latency.
1477
1478- DHCP Advanced Options:
1479		You can fine tune the DHCP functionality by defining
1480		CONFIG_BOOTP_* symbols:
1481
1482		CONFIG_BOOTP_NISDOMAIN
1483		CONFIG_BOOTP_BOOTFILESIZE
1484		CONFIG_BOOTP_SEND_HOSTNAME
1485		CONFIG_BOOTP_NTPSERVER
1486		CONFIG_BOOTP_TIMEOFFSET
1487		CONFIG_BOOTP_VENDOREX
1488		CONFIG_BOOTP_MAY_FAIL
1489
1490		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1491		environment variable, not the BOOTP server.
1492
1493		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1494		after the configured retry count, the call will fail
1495		instead of starting over.  This can be used to fail over
1496		to Link-local IP address configuration if the DHCP server
1497		is not available.
1498
1499		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1500		to do a dynamic update of a DNS server. To do this, they
1501		need the hostname of the DHCP requester.
1502		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1503		of the "hostname" environment variable is passed as
1504		option 12 to the DHCP server.
1505
1506		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1507
1508		A 32bit value in microseconds for a delay between
1509		receiving a "DHCP Offer" and sending the "DHCP Request".
1510		This fixes a problem with certain DHCP servers that don't
1511		respond 100% of the time to a "DHCP request". E.g. On an
1512		AT91RM9200 processor running at 180MHz, this delay needed
1513		to be *at least* 15,000 usec before a Windows Server 2003
1514		DHCP server would reply 100% of the time. I recommend at
1515		least 50,000 usec to be safe. The alternative is to hope
1516		that one of the retries will be successful but note that
1517		the DHCP timeout and retry process takes a longer than
1518		this delay.
1519
1520 - Link-local IP address negotiation:
1521		Negotiate with other link-local clients on the local network
1522		for an address that doesn't require explicit configuration.
1523		This is especially useful if a DHCP server cannot be guaranteed
1524		to exist in all environments that the device must operate.
1525
1526		See doc/README.link-local for more information.
1527
1528 - MAC address from environment variables
1529
1530		FDT_SEQ_MACADDR_FROM_ENV
1531
1532		Fix-up device tree with MAC addresses fetched sequentially from
1533		environment variables. This config work on assumption that
1534		non-usable ethernet node of device-tree are either not present
1535		or their status has been marked as "disabled".
1536
1537 - CDP Options:
1538		CONFIG_CDP_DEVICE_ID
1539
1540		The device id used in CDP trigger frames.
1541
1542		CONFIG_CDP_DEVICE_ID_PREFIX
1543
1544		A two character string which is prefixed to the MAC address
1545		of the device.
1546
1547		CONFIG_CDP_PORT_ID
1548
1549		A printf format string which contains the ascii name of
1550		the port. Normally is set to "eth%d" which sets
1551		eth0 for the first Ethernet, eth1 for the second etc.
1552
1553		CONFIG_CDP_CAPABILITIES
1554
1555		A 32bit integer which indicates the device capabilities;
1556		0x00000010 for a normal host which does not forwards.
1557
1558		CONFIG_CDP_VERSION
1559
1560		An ascii string containing the version of the software.
1561
1562		CONFIG_CDP_PLATFORM
1563
1564		An ascii string containing the name of the platform.
1565
1566		CONFIG_CDP_TRIGGER
1567
1568		A 32bit integer sent on the trigger.
1569
1570		CONFIG_CDP_POWER_CONSUMPTION
1571
1572		A 16bit integer containing the power consumption of the
1573		device in .1 of milliwatts.
1574
1575		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1576
1577		A byte containing the id of the VLAN.
1578
1579- Status LED:	CONFIG_LED_STATUS
1580
1581		Several configurations allow to display the current
1582		status using a LED. For instance, the LED will blink
1583		fast while running U-Boot code, stop blinking as
1584		soon as a reply to a BOOTP request was received, and
1585		start blinking slow once the Linux kernel is running
1586		(supported by a status LED driver in the Linux
1587		kernel). Defining CONFIG_LED_STATUS enables this
1588		feature in U-Boot.
1589
1590		Additional options:
1591
1592		CONFIG_LED_STATUS_GPIO
1593		The status LED can be connected to a GPIO pin.
1594		In such cases, the gpio_led driver can be used as a
1595		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1596		to include the gpio_led driver in the U-Boot binary.
1597
1598		CONFIG_GPIO_LED_INVERTED_TABLE
1599		Some GPIO connected LEDs may have inverted polarity in which
1600		case the GPIO high value corresponds to LED off state and
1601		GPIO low value corresponds to LED on state.
1602		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1603		with a list of GPIO LEDs that have inverted polarity.
1604
1605- I2C Support:	CONFIG_SYS_I2C
1606
1607		This enable the NEW i2c subsystem, and will allow you to use
1608		i2c commands at the u-boot command line (as long as you set
1609		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1610		based realtime clock chips or other i2c devices. See
1611		common/cmd_i2c.c for a description of the command line
1612		interface.
1613
1614		ported i2c driver to the new framework:
1615		- drivers/i2c/soft_i2c.c:
1616		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1617		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1618		    for defining speed and slave address
1619		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1620		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1621		    for defining speed and slave address
1622		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1623		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1624		    for defining speed and slave address
1625		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1626		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1627		    for defining speed and slave address
1628
1629		- drivers/i2c/fsl_i2c.c:
1630		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1631		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1632		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1633		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1634		    bus.
1635		  - If your board supports a second fsl i2c bus, define
1636		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1637		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1638		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1639		    second bus.
1640
1641		- drivers/i2c/tegra_i2c.c:
1642		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1643		  - This driver adds 4 i2c buses with a fix speed from
1644		    100000 and the slave addr 0!
1645
1646		- drivers/i2c/ppc4xx_i2c.c
1647		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1648		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1649		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1650
1651		- drivers/i2c/i2c_mxc.c
1652		  - activate this driver with CONFIG_SYS_I2C_MXC
1653		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1654		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1655		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1656		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1657		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1658		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1659		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1660		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1661		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1662		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1663		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1664		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1665		If those defines are not set, default value is 100000
1666		for speed, and 0 for slave.
1667
1668		- drivers/i2c/rcar_i2c.c:
1669		  - activate this driver with CONFIG_SYS_I2C_RCAR
1670		  - This driver adds 4 i2c buses
1671
1672		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1673		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1674		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1675		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1676		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1677		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1678		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1679		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1680		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1681
1682		- drivers/i2c/sh_i2c.c:
1683		  - activate this driver with CONFIG_SYS_I2C_SH
1684		  - This driver adds from 2 to 5 i2c buses
1685
1686		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1687		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1688		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1689		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1690		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1691		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1692		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1693		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1694		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1695		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1696		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1697
1698		- drivers/i2c/omap24xx_i2c.c
1699		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1700		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1701		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1702		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1703		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1704		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1705		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1706		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1707		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1708		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1709		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1710
1711		- drivers/i2c/zynq_i2c.c
1712		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1713		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1714		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1715
1716		- drivers/i2c/s3c24x0_i2c.c:
1717		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1718		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1719		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1720		    with a fix speed from 100000 and the slave addr 0!
1721
1722		- drivers/i2c/ihs_i2c.c
1723		  - activate this driver with CONFIG_SYS_I2C_IHS
1724		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1725		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1726		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1727		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1728		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1729		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1730		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1731		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1732		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1733		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1734		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1735		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1736		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1737		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1738		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1739		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1740		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1741		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1742		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1743		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1744		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1745
1746		additional defines:
1747
1748		CONFIG_SYS_NUM_I2C_BUSES
1749		Hold the number of i2c buses you want to use.
1750
1751		CONFIG_SYS_I2C_DIRECT_BUS
1752		define this, if you don't use i2c muxes on your hardware.
1753		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1754		omit this define.
1755
1756		CONFIG_SYS_I2C_MAX_HOPS
1757		define how many muxes are maximal consecutively connected
1758		on one i2c bus. If you not use i2c muxes, omit this
1759		define.
1760
1761		CONFIG_SYS_I2C_BUSES
1762		hold a list of buses you want to use, only used if
1763		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1764		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1765		CONFIG_SYS_NUM_I2C_BUSES = 9:
1766
1767		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1768					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1769					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1770					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1771					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1772					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1773					{1, {I2C_NULL_HOP}}, \
1774					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1775					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1776					}
1777
1778		which defines
1779			bus 0 on adapter 0 without a mux
1780			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1781			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1782			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1783			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1784			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1785			bus 6 on adapter 1 without a mux
1786			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1787			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1788
1789		If you do not have i2c muxes on your board, omit this define.
1790
1791- Legacy I2C Support:
1792		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1793		then the following macros need to be defined (examples are
1794		from include/configs/lwmon.h):
1795
1796		I2C_INIT
1797
1798		(Optional). Any commands necessary to enable the I2C
1799		controller or configure ports.
1800
1801		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1802
1803		I2C_ACTIVE
1804
1805		The code necessary to make the I2C data line active
1806		(driven).  If the data line is open collector, this
1807		define can be null.
1808
1809		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1810
1811		I2C_TRISTATE
1812
1813		The code necessary to make the I2C data line tri-stated
1814		(inactive).  If the data line is open collector, this
1815		define can be null.
1816
1817		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1818
1819		I2C_READ
1820
1821		Code that returns true if the I2C data line is high,
1822		false if it is low.
1823
1824		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1825
1826		I2C_SDA(bit)
1827
1828		If <bit> is true, sets the I2C data line high. If it
1829		is false, it clears it (low).
1830
1831		eg: #define I2C_SDA(bit) \
1832			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1833			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1834
1835		I2C_SCL(bit)
1836
1837		If <bit> is true, sets the I2C clock line high. If it
1838		is false, it clears it (low).
1839
1840		eg: #define I2C_SCL(bit) \
1841			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1842			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1843
1844		I2C_DELAY
1845
1846		This delay is invoked four times per clock cycle so this
1847		controls the rate of data transfer.  The data rate thus
1848		is 1 / (I2C_DELAY * 4). Often defined to be something
1849		like:
1850
1851		#define I2C_DELAY  udelay(2)
1852
1853		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1854
1855		If your arch supports the generic GPIO framework (asm/gpio.h),
1856		then you may alternatively define the two GPIOs that are to be
1857		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1858		have GPIO-based defaults assigned to them as appropriate.
1859
1860		You should define these to the GPIO value as given directly to
1861		the generic GPIO functions.
1862
1863		CONFIG_SYS_I2C_INIT_BOARD
1864
1865		When a board is reset during an i2c bus transfer
1866		chips might think that the current transfer is still
1867		in progress. On some boards it is possible to access
1868		the i2c SCLK line directly, either by using the
1869		processor pin as a GPIO or by having a second pin
1870		connected to the bus. If this option is defined a
1871		custom i2c_init_board() routine in boards/xxx/board.c
1872		is run early in the boot sequence.
1873
1874		CONFIG_I2C_MULTI_BUS
1875
1876		This option allows the use of multiple I2C buses, each of which
1877		must have a controller.	 At any point in time, only one bus is
1878		active.	 To switch to a different bus, use the 'i2c dev' command.
1879		Note that bus numbering is zero-based.
1880
1881		CONFIG_SYS_I2C_NOPROBES
1882
1883		This option specifies a list of I2C devices that will be skipped
1884		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1885		is set, specify a list of bus-device pairs.  Otherwise, specify
1886		a 1D array of device addresses
1887
1888		e.g.
1889			#undef	CONFIG_I2C_MULTI_BUS
1890			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1891
1892		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1893
1894			#define CONFIG_I2C_MULTI_BUS
1895			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1896
1897		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1898
1899		CONFIG_SYS_SPD_BUS_NUM
1900
1901		If defined, then this indicates the I2C bus number for DDR SPD.
1902		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1903
1904		CONFIG_SYS_RTC_BUS_NUM
1905
1906		If defined, then this indicates the I2C bus number for the RTC.
1907		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1908
1909		CONFIG_SOFT_I2C_READ_REPEATED_START
1910
1911		defining this will force the i2c_read() function in
1912		the soft_i2c driver to perform an I2C repeated start
1913		between writing the address pointer and reading the
1914		data.  If this define is omitted the default behaviour
1915		of doing a stop-start sequence will be used.  Most I2C
1916		devices can use either method, but some require one or
1917		the other.
1918
1919- SPI Support:	CONFIG_SPI
1920
1921		Enables SPI driver (so far only tested with
1922		SPI EEPROM, also an instance works with Crystal A/D and
1923		D/As on the SACSng board)
1924
1925		CONFIG_SOFT_SPI
1926
1927		Enables a software (bit-bang) SPI driver rather than
1928		using hardware support. This is a general purpose
1929		driver that only requires three general I/O port pins
1930		(two outputs, one input) to function. If this is
1931		defined, the board configuration must define several
1932		SPI configuration items (port pins to use, etc). For
1933		an example, see include/configs/sacsng.h.
1934
1935		CONFIG_HARD_SPI
1936
1937		Enables a hardware SPI driver for general-purpose reads
1938		and writes.  As with CONFIG_SOFT_SPI, the board configuration
1939		must define a list of chip-select function pointers.
1940		Currently supported on some MPC8xxx processors.	 For an
1941		example, see include/configs/mpc8349emds.h.
1942
1943		CONFIG_SYS_SPI_MXC_WAIT
1944		Timeout for waiting until spi transfer completed.
1945		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1946
1947- FPGA Support: CONFIG_FPGA
1948
1949		Enables FPGA subsystem.
1950
1951		CONFIG_FPGA_<vendor>
1952
1953		Enables support for specific chip vendors.
1954		(ALTERA, XILINX)
1955
1956		CONFIG_FPGA_<family>
1957
1958		Enables support for FPGA family.
1959		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1960
1961		CONFIG_FPGA_COUNT
1962
1963		Specify the number of FPGA devices to support.
1964
1965		CONFIG_SYS_FPGA_PROG_FEEDBACK
1966
1967		Enable printing of hash marks during FPGA configuration.
1968
1969		CONFIG_SYS_FPGA_CHECK_BUSY
1970
1971		Enable checks on FPGA configuration interface busy
1972		status by the configuration function. This option
1973		will require a board or device specific function to
1974		be written.
1975
1976		CONFIG_FPGA_DELAY
1977
1978		If defined, a function that provides delays in the FPGA
1979		configuration driver.
1980
1981		CONFIG_SYS_FPGA_CHECK_CTRLC
1982		Allow Control-C to interrupt FPGA configuration
1983
1984		CONFIG_SYS_FPGA_CHECK_ERROR
1985
1986		Check for configuration errors during FPGA bitfile
1987		loading. For example, abort during Virtex II
1988		configuration if the INIT_B line goes low (which
1989		indicated a CRC error).
1990
1991		CONFIG_SYS_FPGA_WAIT_INIT
1992
1993		Maximum time to wait for the INIT_B line to de-assert
1994		after PROB_B has been de-asserted during a Virtex II
1995		FPGA configuration sequence. The default time is 500
1996		ms.
1997
1998		CONFIG_SYS_FPGA_WAIT_BUSY
1999
2000		Maximum time to wait for BUSY to de-assert during
2001		Virtex II FPGA configuration. The default is 5 ms.
2002
2003		CONFIG_SYS_FPGA_WAIT_CONFIG
2004
2005		Time to wait after FPGA configuration. The default is
2006		200 ms.
2007
2008- Configuration Management:
2009		CONFIG_BUILD_TARGET
2010
2011		Some SoCs need special image types (e.g. U-Boot binary
2012		with a special header) as build targets. By defining
2013		CONFIG_BUILD_TARGET in the SoC / board header, this
2014		special image will be automatically built upon calling
2015		make / buildman.
2016
2017		CONFIG_IDENT_STRING
2018
2019		If defined, this string will be added to the U-Boot
2020		version information (U_BOOT_VERSION)
2021
2022- Vendor Parameter Protection:
2023
2024		U-Boot considers the values of the environment
2025		variables "serial#" (Board Serial Number) and
2026		"ethaddr" (Ethernet Address) to be parameters that
2027		are set once by the board vendor / manufacturer, and
2028		protects these variables from casual modification by
2029		the user. Once set, these variables are read-only,
2030		and write or delete attempts are rejected. You can
2031		change this behaviour:
2032
2033		If CONFIG_ENV_OVERWRITE is #defined in your config
2034		file, the write protection for vendor parameters is
2035		completely disabled. Anybody can change or delete
2036		these parameters.
2037
2038		Alternatively, if you define _both_ an ethaddr in the
2039		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2040		Ethernet address is installed in the environment,
2041		which can be changed exactly ONCE by the user. [The
2042		serial# is unaffected by this, i. e. it remains
2043		read-only.]
2044
2045		The same can be accomplished in a more flexible way
2046		for any variable by configuring the type of access
2047		to allow for those variables in the ".flags" variable
2048		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2049
2050- Protected RAM:
2051		CONFIG_PRAM
2052
2053		Define this variable to enable the reservation of
2054		"protected RAM", i. e. RAM which is not overwritten
2055		by U-Boot. Define CONFIG_PRAM to hold the number of
2056		kB you want to reserve for pRAM. You can overwrite
2057		this default value by defining an environment
2058		variable "pram" to the number of kB you want to
2059		reserve. Note that the board info structure will
2060		still show the full amount of RAM. If pRAM is
2061		reserved, a new environment variable "mem" will
2062		automatically be defined to hold the amount of
2063		remaining RAM in a form that can be passed as boot
2064		argument to Linux, for instance like that:
2065
2066			setenv bootargs ... mem=\${mem}
2067			saveenv
2068
2069		This way you can tell Linux not to use this memory,
2070		either, which results in a memory region that will
2071		not be affected by reboots.
2072
2073		*WARNING* If your board configuration uses automatic
2074		detection of the RAM size, you must make sure that
2075		this memory test is non-destructive. So far, the
2076		following board configurations are known to be
2077		"pRAM-clean":
2078
2079			IVMS8, IVML24, SPD8xx,
2080			HERMES, IP860, RPXlite, LWMON,
2081			FLAGADM
2082
2083- Access to physical memory region (> 4GB)
2084		Some basic support is provided for operations on memory not
2085		normally accessible to U-Boot - e.g. some architectures
2086		support access to more than 4GB of memory on 32-bit
2087		machines using physical address extension or similar.
2088		Define CONFIG_PHYSMEM to access this basic support, which
2089		currently only supports clearing the memory.
2090
2091- Error Recovery:
2092		CONFIG_NET_RETRY_COUNT
2093
2094		This variable defines the number of retries for
2095		network operations like ARP, RARP, TFTP, or BOOTP
2096		before giving up the operation. If not defined, a
2097		default value of 5 is used.
2098
2099		CONFIG_ARP_TIMEOUT
2100
2101		Timeout waiting for an ARP reply in milliseconds.
2102
2103		CONFIG_NFS_TIMEOUT
2104
2105		Timeout in milliseconds used in NFS protocol.
2106		If you encounter "ERROR: Cannot umount" in nfs command,
2107		try longer timeout such as
2108		#define CONFIG_NFS_TIMEOUT 10000UL
2109
2110- Command Interpreter:
2111		CONFIG_SYS_PROMPT_HUSH_PS2
2112
2113		This defines the secondary prompt string, which is
2114		printed when the command interpreter needs more input
2115		to complete a command. Usually "> ".
2116
2117	Note:
2118
2119		In the current implementation, the local variables
2120		space and global environment variables space are
2121		separated. Local variables are those you define by
2122		simply typing `name=value'. To access a local
2123		variable later on, you have write `$name' or
2124		`${name}'; to execute the contents of a variable
2125		directly type `$name' at the command prompt.
2126
2127		Global environment variables are those you use
2128		setenv/printenv to work with. To run a command stored
2129		in such a variable, you need to use the run command,
2130		and you must not use the '$' sign to access them.
2131
2132		To store commands and special characters in a
2133		variable, please use double quotation marks
2134		surrounding the whole text of the variable, instead
2135		of the backslashes before semicolons and special
2136		symbols.
2137
2138- Command Line Editing and History:
2139		CONFIG_CMDLINE_PS_SUPPORT
2140
2141		Enable support for changing the command prompt string
2142		at run-time. Only static string is supported so far.
2143		The string is obtained from environment variables PS1
2144		and PS2.
2145
2146- Default Environment:
2147		CONFIG_EXTRA_ENV_SETTINGS
2148
2149		Define this to contain any number of null terminated
2150		strings (variable = value pairs) that will be part of
2151		the default environment compiled into the boot image.
2152
2153		For example, place something like this in your
2154		board's config file:
2155
2156		#define CONFIG_EXTRA_ENV_SETTINGS \
2157			"myvar1=value1\0" \
2158			"myvar2=value2\0"
2159
2160		Warning: This method is based on knowledge about the
2161		internal format how the environment is stored by the
2162		U-Boot code. This is NOT an official, exported
2163		interface! Although it is unlikely that this format
2164		will change soon, there is no guarantee either.
2165		You better know what you are doing here.
2166
2167		Note: overly (ab)use of the default environment is
2168		discouraged. Make sure to check other ways to preset
2169		the environment like the "source" command or the
2170		boot command first.
2171
2172		CONFIG_DELAY_ENVIRONMENT
2173
2174		Normally the environment is loaded when the board is
2175		initialised so that it is available to U-Boot. This inhibits
2176		that so that the environment is not available until
2177		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2178		this is instead controlled by the value of
2179		/config/load-environment.
2180
2181- Serial Flash support
2182		Usage requires an initial 'sf probe' to define the serial
2183		flash parameters, followed by read/write/erase/update
2184		commands.
2185
2186		The following defaults may be provided by the platform
2187		to handle the common case when only a single serial
2188		flash is present on the system.
2189
2190		CONFIG_SF_DEFAULT_BUS		Bus identifier
2191		CONFIG_SF_DEFAULT_CS		Chip-select
2192		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2193		CONFIG_SF_DEFAULT_SPEED		in Hz
2194
2195
2196- TFTP Fixed UDP Port:
2197		CONFIG_TFTP_PORT
2198
2199		If this is defined, the environment variable tftpsrcp
2200		is used to supply the TFTP UDP source port value.
2201		If tftpsrcp isn't defined, the normal pseudo-random port
2202		number generator is used.
2203
2204		Also, the environment variable tftpdstp is used to supply
2205		the TFTP UDP destination port value.  If tftpdstp isn't
2206		defined, the normal port 69 is used.
2207
2208		The purpose for tftpsrcp is to allow a TFTP server to
2209		blindly start the TFTP transfer using the pre-configured
2210		target IP address and UDP port. This has the effect of
2211		"punching through" the (Windows XP) firewall, allowing
2212		the remainder of the TFTP transfer to proceed normally.
2213		A better solution is to properly configure the firewall,
2214		but sometimes that is not allowed.
2215
2216- Show boot progress:
2217		CONFIG_SHOW_BOOT_PROGRESS
2218
2219		Defining this option allows to add some board-
2220		specific code (calling a user-provided function
2221		"show_boot_progress(int)") that enables you to show
2222		the system's boot progress on some display (for
2223		example, some LED's) on your board. At the moment,
2224		the following checkpoints are implemented:
2225
2226
2227Legacy uImage format:
2228
2229  Arg	Where			When
2230    1	common/cmd_bootm.c	before attempting to boot an image
2231   -1	common/cmd_bootm.c	Image header has bad	 magic number
2232    2	common/cmd_bootm.c	Image header has correct magic number
2233   -2	common/cmd_bootm.c	Image header has bad	 checksum
2234    3	common/cmd_bootm.c	Image header has correct checksum
2235   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2236    4	common/cmd_bootm.c	Image data   has correct checksum
2237   -4	common/cmd_bootm.c	Image is for unsupported architecture
2238    5	common/cmd_bootm.c	Architecture check OK
2239   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2240    6	common/cmd_bootm.c	Image Type check OK
2241   -6	common/cmd_bootm.c	gunzip uncompression error
2242   -7	common/cmd_bootm.c	Unimplemented compression type
2243    7	common/cmd_bootm.c	Uncompression OK
2244    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2245   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2246
2247    9	common/image.c		Start initial ramdisk verification
2248  -10	common/image.c		Ramdisk header has bad	   magic number
2249  -11	common/image.c		Ramdisk header has bad	   checksum
2250   10	common/image.c		Ramdisk header is OK
2251  -12	common/image.c		Ramdisk data   has bad	   checksum
2252   11	common/image.c		Ramdisk data   has correct checksum
2253   12	common/image.c		Ramdisk verification complete, start loading
2254  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2255   13	common/image.c		Start multifile image verification
2256   14	common/image.c		No initial ramdisk, no multifile, continue.
2257
2258   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2259
2260  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2261  -31	post/post.c		POST test failed, detected by post_output_backlog()
2262  -32	post/post.c		POST test failed, detected by post_run_single()
2263
2264   34	common/cmd_doc.c	before loading a Image from a DOC device
2265  -35	common/cmd_doc.c	Bad usage of "doc" command
2266   35	common/cmd_doc.c	correct usage of "doc" command
2267  -36	common/cmd_doc.c	No boot device
2268   36	common/cmd_doc.c	correct boot device
2269  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2270   37	common/cmd_doc.c	correct chip ID found, device available
2271  -38	common/cmd_doc.c	Read Error on boot device
2272   38	common/cmd_doc.c	reading Image header from DOC device OK
2273  -39	common/cmd_doc.c	Image header has bad magic number
2274   39	common/cmd_doc.c	Image header has correct magic number
2275  -40	common/cmd_doc.c	Error reading Image from DOC device
2276   40	common/cmd_doc.c	Image header has correct magic number
2277   41	common/cmd_ide.c	before loading a Image from a IDE device
2278  -42	common/cmd_ide.c	Bad usage of "ide" command
2279   42	common/cmd_ide.c	correct usage of "ide" command
2280  -43	common/cmd_ide.c	No boot device
2281   43	common/cmd_ide.c	boot device found
2282  -44	common/cmd_ide.c	Device not available
2283   44	common/cmd_ide.c	Device available
2284  -45	common/cmd_ide.c	wrong partition selected
2285   45	common/cmd_ide.c	partition selected
2286  -46	common/cmd_ide.c	Unknown partition table
2287   46	common/cmd_ide.c	valid partition table found
2288  -47	common/cmd_ide.c	Invalid partition type
2289   47	common/cmd_ide.c	correct partition type
2290  -48	common/cmd_ide.c	Error reading Image Header on boot device
2291   48	common/cmd_ide.c	reading Image Header from IDE device OK
2292  -49	common/cmd_ide.c	Image header has bad magic number
2293   49	common/cmd_ide.c	Image header has correct magic number
2294  -50	common/cmd_ide.c	Image header has bad	 checksum
2295   50	common/cmd_ide.c	Image header has correct checksum
2296  -51	common/cmd_ide.c	Error reading Image from IDE device
2297   51	common/cmd_ide.c	reading Image from IDE device OK
2298   52	common/cmd_nand.c	before loading a Image from a NAND device
2299  -53	common/cmd_nand.c	Bad usage of "nand" command
2300   53	common/cmd_nand.c	correct usage of "nand" command
2301  -54	common/cmd_nand.c	No boot device
2302   54	common/cmd_nand.c	boot device found
2303  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2304   55	common/cmd_nand.c	correct chip ID found, device available
2305  -56	common/cmd_nand.c	Error reading Image Header on boot device
2306   56	common/cmd_nand.c	reading Image Header from NAND device OK
2307  -57	common/cmd_nand.c	Image header has bad magic number
2308   57	common/cmd_nand.c	Image header has correct magic number
2309  -58	common/cmd_nand.c	Error reading Image from NAND device
2310   58	common/cmd_nand.c	reading Image from NAND device OK
2311
2312  -60	common/env_common.c	Environment has a bad CRC, using default
2313
2314   64	net/eth.c		starting with Ethernet configuration.
2315  -64	net/eth.c		no Ethernet found.
2316   65	net/eth.c		Ethernet found.
2317
2318  -80	common/cmd_net.c	usage wrong
2319   80	common/cmd_net.c	before calling net_loop()
2320  -81	common/cmd_net.c	some error in net_loop() occurred
2321   81	common/cmd_net.c	net_loop() back without error
2322  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2323   82	common/cmd_net.c	trying automatic boot
2324   83	common/cmd_net.c	running "source" command
2325  -83	common/cmd_net.c	some error in automatic boot or "source" command
2326   84	common/cmd_net.c	end without errors
2327
2328FIT uImage format:
2329
2330  Arg	Where			When
2331  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2332 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2333  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2334 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2335  102	common/cmd_bootm.c	Kernel unit name specified
2336 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2337  103	common/cmd_bootm.c	Found configuration node
2338  104	common/cmd_bootm.c	Got kernel subimage node offset
2339 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2340  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2341 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2342  106	common/cmd_bootm.c	Architecture check OK
2343 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2344  107	common/cmd_bootm.c	Kernel subimage type OK
2345 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2346  108	common/cmd_bootm.c	Got kernel subimage data/size
2347 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2348 -109	common/cmd_bootm.c	Can't get kernel subimage type
2349 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2350 -111	common/cmd_bootm.c	Can't get kernel subimage os
2351 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2352 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2353
2354  120	common/image.c		Start initial ramdisk verification
2355 -120	common/image.c		Ramdisk FIT image has incorrect format
2356  121	common/image.c		Ramdisk FIT image has correct format
2357  122	common/image.c		No ramdisk subimage unit name, using configuration
2358 -122	common/image.c		Can't get configuration for ramdisk subimage
2359  123	common/image.c		Ramdisk unit name specified
2360 -124	common/image.c		Can't get ramdisk subimage node offset
2361  125	common/image.c		Got ramdisk subimage node offset
2362 -125	common/image.c		Ramdisk subimage hash verification failed
2363  126	common/image.c		Ramdisk subimage hash verification OK
2364 -126	common/image.c		Ramdisk subimage for unsupported architecture
2365  127	common/image.c		Architecture check OK
2366 -127	common/image.c		Can't get ramdisk subimage data/size
2367  128	common/image.c		Got ramdisk subimage data/size
2368  129	common/image.c		Can't get ramdisk load address
2369 -129	common/image.c		Got ramdisk load address
2370
2371 -130	common/cmd_doc.c	Incorrect FIT image format
2372  131	common/cmd_doc.c	FIT image format OK
2373
2374 -140	common/cmd_ide.c	Incorrect FIT image format
2375  141	common/cmd_ide.c	FIT image format OK
2376
2377 -150	common/cmd_nand.c	Incorrect FIT image format
2378  151	common/cmd_nand.c	FIT image format OK
2379
2380- Standalone program support:
2381		CONFIG_STANDALONE_LOAD_ADDR
2382
2383		This option defines a board specific value for the
2384		address where standalone program gets loaded, thus
2385		overwriting the architecture dependent default
2386		settings.
2387
2388- Frame Buffer Address:
2389		CONFIG_FB_ADDR
2390
2391		Define CONFIG_FB_ADDR if you want to use specific
2392		address for frame buffer.  This is typically the case
2393		when using a graphics controller has separate video
2394		memory.  U-Boot will then place the frame buffer at
2395		the given address instead of dynamically reserving it
2396		in system RAM by calling lcd_setmem(), which grabs
2397		the memory for the frame buffer depending on the
2398		configured panel size.
2399
2400		Please see board_init_f function.
2401
2402- Automatic software updates via TFTP server
2403		CONFIG_UPDATE_TFTP
2404		CONFIG_UPDATE_TFTP_CNT_MAX
2405		CONFIG_UPDATE_TFTP_MSEC_MAX
2406
2407		These options enable and control the auto-update feature;
2408		for a more detailed description refer to doc/README.update.
2409
2410- MTD Support (mtdparts command, UBI support)
2411		CONFIG_MTD_UBI_WL_THRESHOLD
2412		This parameter defines the maximum difference between the highest
2413		erase counter value and the lowest erase counter value of eraseblocks
2414		of UBI devices. When this threshold is exceeded, UBI starts performing
2415		wear leveling by means of moving data from eraseblock with low erase
2416		counter to eraseblocks with high erase counter.
2417
2418		The default value should be OK for SLC NAND flashes, NOR flashes and
2419		other flashes which have eraseblock life-cycle 100000 or more.
2420		However, in case of MLC NAND flashes which typically have eraseblock
2421		life-cycle less than 10000, the threshold should be lessened (e.g.,
2422		to 128 or 256, although it does not have to be power of 2).
2423
2424		default: 4096
2425
2426		CONFIG_MTD_UBI_BEB_LIMIT
2427		This option specifies the maximum bad physical eraseblocks UBI
2428		expects on the MTD device (per 1024 eraseblocks). If the
2429		underlying flash does not admit of bad eraseblocks (e.g. NOR
2430		flash), this value is ignored.
2431
2432		NAND datasheets often specify the minimum and maximum NVM
2433		(Number of Valid Blocks) for the flashes' endurance lifetime.
2434		The maximum expected bad eraseblocks per 1024 eraseblocks
2435		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2436		which gives 20 for most NANDs (MaxNVB is basically the total
2437		count of eraseblocks on the chip).
2438
2439		To put it differently, if this value is 20, UBI will try to
2440		reserve about 1.9% of physical eraseblocks for bad blocks
2441		handling. And that will be 1.9% of eraseblocks on the entire
2442		NAND chip, not just the MTD partition UBI attaches. This means
2443		that if you have, say, a NAND flash chip admits maximum 40 bad
2444		eraseblocks, and it is split on two MTD partitions of the same
2445		size, UBI will reserve 40 eraseblocks when attaching a
2446		partition.
2447
2448		default: 20
2449
2450		CONFIG_MTD_UBI_FASTMAP
2451		Fastmap is a mechanism which allows attaching an UBI device
2452		in nearly constant time. Instead of scanning the whole MTD device it
2453		only has to locate a checkpoint (called fastmap) on the device.
2454		The on-flash fastmap contains all information needed to attach
2455		the device. Using fastmap makes only sense on large devices where
2456		attaching by scanning takes long. UBI will not automatically install
2457		a fastmap on old images, but you can set the UBI parameter
2458		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2459		that fastmap-enabled images are still usable with UBI implementations
2460		without	fastmap support. On typical flash devices the whole fastmap
2461		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2462
2463		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2464		Set this parameter to enable fastmap automatically on images
2465		without a fastmap.
2466		default: 0
2467
2468		CONFIG_MTD_UBI_FM_DEBUG
2469		Enable UBI fastmap debug
2470		default: 0
2471
2472- SPL framework
2473		CONFIG_SPL
2474		Enable building of SPL globally.
2475
2476		CONFIG_SPL_LDSCRIPT
2477		LDSCRIPT for linking the SPL binary.
2478
2479		CONFIG_SPL_MAX_FOOTPRINT
2480		Maximum size in memory allocated to the SPL, BSS included.
2481		When defined, the linker checks that the actual memory
2482		used by SPL from _start to __bss_end does not exceed it.
2483		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2484		must not be both defined at the same time.
2485
2486		CONFIG_SPL_MAX_SIZE
2487		Maximum size of the SPL image (text, data, rodata, and
2488		linker lists sections), BSS excluded.
2489		When defined, the linker checks that the actual size does
2490		not exceed it.
2491
2492		CONFIG_SPL_TEXT_BASE
2493		TEXT_BASE for linking the SPL binary.
2494
2495		CONFIG_SPL_RELOC_TEXT_BASE
2496		Address to relocate to.  If unspecified, this is equal to
2497		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2498
2499		CONFIG_SPL_BSS_START_ADDR
2500		Link address for the BSS within the SPL binary.
2501
2502		CONFIG_SPL_BSS_MAX_SIZE
2503		Maximum size in memory allocated to the SPL BSS.
2504		When defined, the linker checks that the actual memory used
2505		by SPL from __bss_start to __bss_end does not exceed it.
2506		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2507		must not be both defined at the same time.
2508
2509		CONFIG_SPL_STACK
2510		Adress of the start of the stack SPL will use
2511
2512		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2513		When defined, SPL will panic() if the image it has
2514		loaded does not have a signature.
2515		Defining this is useful when code which loads images
2516		in SPL cannot guarantee that absolutely all read errors
2517		will be caught.
2518		An example is the LPC32XX MLC NAND driver, which will
2519		consider that a completely unreadable NAND block is bad,
2520		and thus should be skipped silently.
2521
2522		CONFIG_SPL_RELOC_STACK
2523		Adress of the start of the stack SPL will use after
2524		relocation.  If unspecified, this is equal to
2525		CONFIG_SPL_STACK.
2526
2527		CONFIG_SYS_SPL_MALLOC_START
2528		Starting address of the malloc pool used in SPL.
2529		When this option is set the full malloc is used in SPL and
2530		it is set up by spl_init() and before that, the simple malloc()
2531		can be used if CONFIG_SYS_MALLOC_F is defined.
2532
2533		CONFIG_SYS_SPL_MALLOC_SIZE
2534		The size of the malloc pool used in SPL.
2535
2536		CONFIG_SPL_OS_BOOT
2537		Enable booting directly to an OS from SPL.
2538		See also: doc/README.falcon
2539
2540		CONFIG_SPL_DISPLAY_PRINT
2541		For ARM, enable an optional function to print more information
2542		about the running system.
2543
2544		CONFIG_SPL_INIT_MINIMAL
2545		Arch init code should be built for a very small image
2546
2547		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2548		Partition on the MMC to load U-Boot from when the MMC is being
2549		used in raw mode
2550
2551		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2552		Sector to load kernel uImage from when MMC is being
2553		used in raw mode (for Falcon mode)
2554
2555		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2556		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2557		Sector and number of sectors to load kernel argument
2558		parameters from when MMC is being used in raw mode
2559		(for falcon mode)
2560
2561		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2562		Partition on the MMC to load U-Boot from when the MMC is being
2563		used in fs mode
2564
2565		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2566		Filename to read to load U-Boot when reading from filesystem
2567
2568		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2569		Filename to read to load kernel uImage when reading
2570		from filesystem (for Falcon mode)
2571
2572		CONFIG_SPL_FS_LOAD_ARGS_NAME
2573		Filename to read to load kernel argument parameters
2574		when reading from filesystem (for Falcon mode)
2575
2576		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2577		Set this for NAND SPL on PPC mpc83xx targets, so that
2578		start.S waits for the rest of the SPL to load before
2579		continuing (the hardware starts execution after just
2580		loading the first page rather than the full 4K).
2581
2582		CONFIG_SPL_SKIP_RELOCATE
2583		Avoid SPL relocation
2584
2585		CONFIG_SPL_NAND_BASE
2586		Include nand_base.c in the SPL.  Requires
2587		CONFIG_SPL_NAND_DRIVERS.
2588
2589		CONFIG_SPL_NAND_DRIVERS
2590		SPL uses normal NAND drivers, not minimal drivers.
2591
2592		CONFIG_SPL_NAND_IDENT
2593		SPL uses the chip ID list to identify the NAND flash.
2594		Requires CONFIG_SPL_NAND_BASE.
2595
2596		CONFIG_SPL_NAND_ECC
2597		Include standard software ECC in the SPL
2598
2599		CONFIG_SPL_NAND_SIMPLE
2600		Support for NAND boot using simple NAND drivers that
2601		expose the cmd_ctrl() interface.
2602
2603		CONFIG_SPL_UBI
2604		Support for a lightweight UBI (fastmap) scanner and
2605		loader
2606
2607		CONFIG_SPL_NAND_RAW_ONLY
2608		Support to boot only raw u-boot.bin images. Use this only
2609		if you need to save space.
2610
2611		CONFIG_SPL_COMMON_INIT_DDR
2612		Set for common ddr init with serial presence detect in
2613		SPL binary.
2614
2615		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2616		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2617		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2618		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2619		CONFIG_SYS_NAND_ECCBYTES
2620		Defines the size and behavior of the NAND that SPL uses
2621		to read U-Boot
2622
2623		CONFIG_SPL_NAND_BOOT
2624		Add support NAND boot
2625
2626		CONFIG_SYS_NAND_U_BOOT_OFFS
2627		Location in NAND to read U-Boot from
2628
2629		CONFIG_SYS_NAND_U_BOOT_DST
2630		Location in memory to load U-Boot to
2631
2632		CONFIG_SYS_NAND_U_BOOT_SIZE
2633		Size of image to load
2634
2635		CONFIG_SYS_NAND_U_BOOT_START
2636		Entry point in loaded image to jump to
2637
2638		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2639		Define this if you need to first read the OOB and then the
2640		data. This is used, for example, on davinci platforms.
2641
2642		CONFIG_SPL_RAM_DEVICE
2643		Support for running image already present in ram, in SPL binary
2644
2645		CONFIG_SPL_PAD_TO
2646		Image offset to which the SPL should be padded before appending
2647		the SPL payload. By default, this is defined as
2648		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2649		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2650		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2651
2652		CONFIG_SPL_TARGET
2653		Final target image containing SPL and payload.  Some SPLs
2654		use an arch-specific makefile fragment instead, for
2655		example if more than one image needs to be produced.
2656
2657		CONFIG_SPL_FIT_PRINT
2658		Printing information about a FIT image adds quite a bit of
2659		code to SPL. So this is normally disabled in SPL. Use this
2660		option to re-enable it. This will affect the output of the
2661		bootm command when booting a FIT image.
2662
2663- TPL framework
2664		CONFIG_TPL
2665		Enable building of TPL globally.
2666
2667		CONFIG_TPL_PAD_TO
2668		Image offset to which the TPL should be padded before appending
2669		the TPL payload. By default, this is defined as
2670		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2671		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2672		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2673
2674- Interrupt support (PPC):
2675
2676		There are common interrupt_init() and timer_interrupt()
2677		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2678		for CPU specific initialization. interrupt_init_cpu()
2679		should set decrementer_count to appropriate value. If
2680		CPU resets decrementer automatically after interrupt
2681		(ppc4xx) it should set decrementer_count to zero.
2682		timer_interrupt() calls timer_interrupt_cpu() for CPU
2683		specific handling. If board has watchdog / status_led
2684		/ other_activity_monitor it works automatically from
2685		general timer_interrupt().
2686
2687
2688Board initialization settings:
2689------------------------------
2690
2691During Initialization u-boot calls a number of board specific functions
2692to allow the preparation of board specific prerequisites, e.g. pin setup
2693before drivers are initialized. To enable these callbacks the
2694following configuration macros have to be defined. Currently this is
2695architecture specific, so please check arch/your_architecture/lib/board.c
2696typically in board_init_f() and board_init_r().
2697
2698- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2699- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2700- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2701- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2702
2703Configuration Settings:
2704-----------------------
2705
2706- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2707		Optionally it can be defined to support 64-bit memory commands.
2708
2709- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2710		undefine this when you're short of memory.
2711
2712- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2713		width of the commands listed in the 'help' command output.
2714
2715- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2716		prompt for user input.
2717
2718- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2719
2720- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2721
2722- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2723
2724- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2725		the application (usually a Linux kernel) when it is
2726		booted
2727
2728- CONFIG_SYS_BAUDRATE_TABLE:
2729		List of legal baudrate settings for this board.
2730
2731- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2732		Begin and End addresses of the area used by the
2733		simple memory test.
2734
2735- CONFIG_SYS_MEMTEST_SCRATCH:
2736		Scratch address used by the alternate memory test
2737		You only need to set this if address zero isn't writeable
2738
2739- CONFIG_SYS_MEM_RESERVE_SECURE
2740		Only implemented for ARMv8 for now.
2741		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2742		is substracted from total RAM and won't be reported to OS.
2743		This memory can be used as secure memory. A variable
2744		gd->arch.secure_ram is used to track the location. In systems
2745		the RAM base is not zero, or RAM is divided into banks,
2746		this variable needs to be recalcuated to get the address.
2747
2748- CONFIG_SYS_MEM_TOP_HIDE:
2749		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2750		this specified memory area will get subtracted from the top
2751		(end) of RAM and won't get "touched" at all by U-Boot. By
2752		fixing up gd->ram_size the Linux kernel should gets passed
2753		the now "corrected" memory size and won't touch it either.
2754		This should work for arch/ppc and arch/powerpc. Only Linux
2755		board ports in arch/powerpc with bootwrapper support that
2756		recalculate the memory size from the SDRAM controller setup
2757		will have to get fixed in Linux additionally.
2758
2759		This option can be used as a workaround for the 440EPx/GRx
2760		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2761		be touched.
2762
2763		WARNING: Please make sure that this value is a multiple of
2764		the Linux page size (normally 4k). If this is not the case,
2765		then the end address of the Linux memory will be located at a
2766		non page size aligned address and this could cause major
2767		problems.
2768
2769- CONFIG_SYS_LOADS_BAUD_CHANGE:
2770		Enable temporary baudrate change while serial download
2771
2772- CONFIG_SYS_SDRAM_BASE:
2773		Physical start address of SDRAM. _Must_ be 0 here.
2774
2775- CONFIG_SYS_FLASH_BASE:
2776		Physical start address of Flash memory.
2777
2778- CONFIG_SYS_MONITOR_BASE:
2779		Physical start address of boot monitor code (set by
2780		make config files to be same as the text base address
2781		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2782		CONFIG_SYS_FLASH_BASE when booting from flash.
2783
2784- CONFIG_SYS_MONITOR_LEN:
2785		Size of memory reserved for monitor code, used to
2786		determine _at_compile_time_ (!) if the environment is
2787		embedded within the U-Boot image, or in a separate
2788		flash sector.
2789
2790- CONFIG_SYS_MALLOC_LEN:
2791		Size of DRAM reserved for malloc() use.
2792
2793- CONFIG_SYS_MALLOC_F_LEN
2794		Size of the malloc() pool for use before relocation. If
2795		this is defined, then a very simple malloc() implementation
2796		will become available before relocation. The address is just
2797		below the global data, and the stack is moved down to make
2798		space.
2799
2800		This feature allocates regions with increasing addresses
2801		within the region. calloc() is supported, but realloc()
2802		is not available. free() is supported but does nothing.
2803		The memory will be freed (or in fact just forgotten) when
2804		U-Boot relocates itself.
2805
2806- CONFIG_SYS_MALLOC_SIMPLE
2807		Provides a simple and small malloc() and calloc() for those
2808		boards which do not use the full malloc in SPL (which is
2809		enabled with CONFIG_SYS_SPL_MALLOC_START).
2810
2811- CONFIG_SYS_NONCACHED_MEMORY:
2812		Size of non-cached memory area. This area of memory will be
2813		typically located right below the malloc() area and mapped
2814		uncached in the MMU. This is useful for drivers that would
2815		otherwise require a lot of explicit cache maintenance. For
2816		some drivers it's also impossible to properly maintain the
2817		cache. For example if the regions that need to be flushed
2818		are not a multiple of the cache-line size, *and* padding
2819		cannot be allocated between the regions to align them (i.e.
2820		if the HW requires a contiguous array of regions, and the
2821		size of each region is not cache-aligned), then a flush of
2822		one region may result in overwriting data that hardware has
2823		written to another region in the same cache-line. This can
2824		happen for example in network drivers where descriptors for
2825		buffers are typically smaller than the CPU cache-line (e.g.
2826		16 bytes vs. 32 or 64 bytes).
2827
2828		Non-cached memory is only supported on 32-bit ARM at present.
2829
2830- CONFIG_SYS_BOOTM_LEN:
2831		Normally compressed uImages are limited to an
2832		uncompressed size of 8 MBytes. If this is not enough,
2833		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2834		to adjust this setting to your needs.
2835
2836- CONFIG_SYS_BOOTMAPSZ:
2837		Maximum size of memory mapped by the startup code of
2838		the Linux kernel; all data that must be processed by
2839		the Linux kernel (bd_info, boot arguments, FDT blob if
2840		used) must be put below this limit, unless "bootm_low"
2841		environment variable is defined and non-zero. In such case
2842		all data for the Linux kernel must be between "bootm_low"
2843		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2844		variable "bootm_mapsize" will override the value of
2845		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2846		then the value in "bootm_size" will be used instead.
2847
2848- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2849		Enable initrd_high functionality.  If defined then the
2850		initrd_high feature is enabled and the bootm ramdisk subcommand
2851		is enabled.
2852
2853- CONFIG_SYS_BOOT_GET_CMDLINE:
2854		Enables allocating and saving kernel cmdline in space between
2855		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2856
2857- CONFIG_SYS_BOOT_GET_KBD:
2858		Enables allocating and saving a kernel copy of the bd_info in
2859		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2860
2861- CONFIG_SYS_MAX_FLASH_BANKS:
2862		Max number of Flash memory banks
2863
2864- CONFIG_SYS_MAX_FLASH_SECT:
2865		Max number of sectors on a Flash chip
2866
2867- CONFIG_SYS_FLASH_ERASE_TOUT:
2868		Timeout for Flash erase operations (in ms)
2869
2870- CONFIG_SYS_FLASH_WRITE_TOUT:
2871		Timeout for Flash write operations (in ms)
2872
2873- CONFIG_SYS_FLASH_LOCK_TOUT
2874		Timeout for Flash set sector lock bit operation (in ms)
2875
2876- CONFIG_SYS_FLASH_UNLOCK_TOUT
2877		Timeout for Flash clear lock bits operation (in ms)
2878
2879- CONFIG_SYS_FLASH_PROTECTION
2880		If defined, hardware flash sectors protection is used
2881		instead of U-Boot software protection.
2882
2883- CONFIG_SYS_DIRECT_FLASH_TFTP:
2884
2885		Enable TFTP transfers directly to flash memory;
2886		without this option such a download has to be
2887		performed in two steps: (1) download to RAM, and (2)
2888		copy from RAM to flash.
2889
2890		The two-step approach is usually more reliable, since
2891		you can check if the download worked before you erase
2892		the flash, but in some situations (when system RAM is
2893		too limited to allow for a temporary copy of the
2894		downloaded image) this option may be very useful.
2895
2896- CONFIG_SYS_FLASH_CFI:
2897		Define if the flash driver uses extra elements in the
2898		common flash structure for storing flash geometry.
2899
2900- CONFIG_FLASH_CFI_DRIVER
2901		This option also enables the building of the cfi_flash driver
2902		in the drivers directory
2903
2904- CONFIG_FLASH_CFI_MTD
2905		This option enables the building of the cfi_mtd driver
2906		in the drivers directory. The driver exports CFI flash
2907		to the MTD layer.
2908
2909- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2910		Use buffered writes to flash.
2911
2912- CONFIG_FLASH_SPANSION_S29WS_N
2913		s29ws-n MirrorBit flash has non-standard addresses for buffered
2914		write commands.
2915
2916- CONFIG_SYS_FLASH_QUIET_TEST
2917		If this option is defined, the common CFI flash doesn't
2918		print it's warning upon not recognized FLASH banks. This
2919		is useful, if some of the configured banks are only
2920		optionally available.
2921
2922- CONFIG_FLASH_SHOW_PROGRESS
2923		If defined (must be an integer), print out countdown
2924		digits and dots.  Recommended value: 45 (9..1) for 80
2925		column displays, 15 (3..1) for 40 column displays.
2926
2927- CONFIG_FLASH_VERIFY
2928		If defined, the content of the flash (destination) is compared
2929		against the source after the write operation. An error message
2930		will be printed when the contents are not identical.
2931		Please note that this option is useless in nearly all cases,
2932		since such flash programming errors usually are detected earlier
2933		while unprotecting/erasing/programming. Please only enable
2934		this option if you really know what you are doing.
2935
2936- CONFIG_SYS_RX_ETH_BUFFER:
2937		Defines the number of Ethernet receive buffers. On some
2938		Ethernet controllers it is recommended to set this value
2939		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2940		buffers can be full shortly after enabling the interface
2941		on high Ethernet traffic.
2942		Defaults to 4 if not defined.
2943
2944- CONFIG_ENV_MAX_ENTRIES
2945
2946	Maximum number of entries in the hash table that is used
2947	internally to store the environment settings. The default
2948	setting is supposed to be generous and should work in most
2949	cases. This setting can be used to tune behaviour; see
2950	lib/hashtable.c for details.
2951
2952- CONFIG_ENV_FLAGS_LIST_DEFAULT
2953- CONFIG_ENV_FLAGS_LIST_STATIC
2954	Enable validation of the values given to environment variables when
2955	calling env set.  Variables can be restricted to only decimal,
2956	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2957	the variables can also be restricted to IP address or MAC address.
2958
2959	The format of the list is:
2960		type_attribute = [s|d|x|b|i|m]
2961		access_attribute = [a|r|o|c]
2962		attributes = type_attribute[access_attribute]
2963		entry = variable_name[:attributes]
2964		list = entry[,list]
2965
2966	The type attributes are:
2967		s - String (default)
2968		d - Decimal
2969		x - Hexadecimal
2970		b - Boolean ([1yYtT|0nNfF])
2971		i - IP address
2972		m - MAC address
2973
2974	The access attributes are:
2975		a - Any (default)
2976		r - Read-only
2977		o - Write-once
2978		c - Change-default
2979
2980	- CONFIG_ENV_FLAGS_LIST_DEFAULT
2981		Define this to a list (string) to define the ".flags"
2982		environment variable in the default or embedded environment.
2983
2984	- CONFIG_ENV_FLAGS_LIST_STATIC
2985		Define this to a list (string) to define validation that
2986		should be done if an entry is not found in the ".flags"
2987		environment variable.  To override a setting in the static
2988		list, simply add an entry for the same variable name to the
2989		".flags" variable.
2990
2991	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2992	regular expression. This allows multiple variables to define the same
2993	flags without explicitly listing them for each variable.
2994
2995- CONFIG_ENV_ACCESS_IGNORE_FORCE
2996	If defined, don't allow the -f switch to env set override variable
2997	access flags.
2998
2999The following definitions that deal with the placement and management
3000of environment data (variable area); in general, we support the
3001following configurations:
3002
3003- CONFIG_BUILD_ENVCRC:
3004
3005	Builds up envcrc with the target environment so that external utils
3006	may easily extract it and embed it in final U-Boot images.
3007
3008BE CAREFUL! The first access to the environment happens quite early
3009in U-Boot initialization (when we try to get the setting of for the
3010console baudrate). You *MUST* have mapped your NVRAM area then, or
3011U-Boot will hang.
3012
3013Please note that even with NVRAM we still use a copy of the
3014environment in RAM: we could work on NVRAM directly, but we want to
3015keep settings there always unmodified except somebody uses "saveenv"
3016to save the current settings.
3017
3018BE CAREFUL! For some special cases, the local device can not use
3019"saveenv" command. For example, the local device will get the
3020environment stored in a remote NOR flash by SRIO or PCIE link,
3021but it can not erase, write this NOR flash by SRIO or PCIE interface.
3022
3023- CONFIG_NAND_ENV_DST
3024
3025	Defines address in RAM to which the nand_spl code should copy the
3026	environment. If redundant environment is used, it will be copied to
3027	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3028
3029Please note that the environment is read-only until the monitor
3030has been relocated to RAM and a RAM copy of the environment has been
3031created; also, when using EEPROM you will have to use env_get_f()
3032until then to read environment variables.
3033
3034The environment is protected by a CRC32 checksum. Before the monitor
3035is relocated into RAM, as a result of a bad CRC you will be working
3036with the compiled-in default environment - *silently*!!! [This is
3037necessary, because the first environment variable we need is the
3038"baudrate" setting for the console - if we have a bad CRC, we don't
3039have any device yet where we could complain.]
3040
3041Note: once the monitor has been relocated, then it will complain if
3042the default environment is used; a new CRC is computed as soon as you
3043use the "saveenv" command to store a valid environment.
3044
3045- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3046		Echo the inverted Ethernet link state to the fault LED.
3047
3048		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3049		      also needs to be defined.
3050
3051- CONFIG_SYS_FAULT_MII_ADDR:
3052		MII address of the PHY to check for the Ethernet link state.
3053
3054- CONFIG_NS16550_MIN_FUNCTIONS:
3055		Define this if you desire to only have use of the NS16550_init
3056		and NS16550_putc functions for the serial driver located at
3057		drivers/serial/ns16550.c.  This option is useful for saving
3058		space for already greatly restricted images, including but not
3059		limited to NAND_SPL configurations.
3060
3061- CONFIG_DISPLAY_BOARDINFO
3062		Display information about the board that U-Boot is running on
3063		when U-Boot starts up. The board function checkboard() is called
3064		to do this.
3065
3066- CONFIG_DISPLAY_BOARDINFO_LATE
3067		Similar to the previous option, but display this information
3068		later, once stdio is running and output goes to the LCD, if
3069		present.
3070
3071- CONFIG_BOARD_SIZE_LIMIT:
3072		Maximum size of the U-Boot image. When defined, the
3073		build system checks that the actual size does not
3074		exceed it.
3075
3076Low Level (hardware related) configuration options:
3077---------------------------------------------------
3078
3079- CONFIG_SYS_CACHELINE_SIZE:
3080		Cache Line Size of the CPU.
3081
3082- CONFIG_SYS_CCSRBAR_DEFAULT:
3083		Default (power-on reset) physical address of CCSR on Freescale
3084		PowerPC SOCs.
3085
3086- CONFIG_SYS_CCSRBAR:
3087		Virtual address of CCSR.  On a 32-bit build, this is typically
3088		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3089
3090- CONFIG_SYS_CCSRBAR_PHYS:
3091		Physical address of CCSR.  CCSR can be relocated to a new
3092		physical address, if desired.  In this case, this macro should
3093		be set to that address.	 Otherwise, it should be set to the
3094		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3095		is typically relocated on 36-bit builds.  It is recommended
3096		that this macro be defined via the _HIGH and _LOW macros:
3097
3098		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3099			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3100
3101- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3102		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3103		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3104		used in assembly code, so it must not contain typecasts or
3105		integer size suffixes (e.g. "ULL").
3106
3107- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3108		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3109		used in assembly code, so it must not contain typecasts or
3110		integer size suffixes (e.g. "ULL").
3111
3112- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3113		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3114		forced to a value that ensures that CCSR is not relocated.
3115
3116- Floppy Disk Support:
3117		CONFIG_SYS_FDC_DRIVE_NUMBER
3118
3119		the default drive number (default value 0)
3120
3121		CONFIG_SYS_ISA_IO_STRIDE
3122
3123		defines the spacing between FDC chipset registers
3124		(default value 1)
3125
3126		CONFIG_SYS_ISA_IO_OFFSET
3127
3128		defines the offset of register from address. It
3129		depends on which part of the data bus is connected to
3130		the FDC chipset. (default value 0)
3131
3132		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3133		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3134		default value.
3135
3136		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3137		fdc_hw_init() is called at the beginning of the FDC
3138		setup. fdc_hw_init() must be provided by the board
3139		source code. It is used to make hardware-dependent
3140		initializations.
3141
3142- CONFIG_IDE_AHB:
3143		Most IDE controllers were designed to be connected with PCI
3144		interface. Only few of them were designed for AHB interface.
3145		When software is doing ATA command and data transfer to
3146		IDE devices through IDE-AHB controller, some additional
3147		registers accessing to these kind of IDE-AHB controller
3148		is required.
3149
3150- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3151		DO NOT CHANGE unless you know exactly what you're
3152		doing! (11-4) [MPC8xx systems only]
3153
3154- CONFIG_SYS_INIT_RAM_ADDR:
3155
3156		Start address of memory area that can be used for
3157		initial data and stack; please note that this must be
3158		writable memory that is working WITHOUT special
3159		initialization, i. e. you CANNOT use normal RAM which
3160		will become available only after programming the
3161		memory controller and running certain initialization
3162		sequences.
3163
3164		U-Boot uses the following memory types:
3165		- MPC8xx: IMMR (internal memory of the CPU)
3166
3167- CONFIG_SYS_GBL_DATA_OFFSET:
3168
3169		Offset of the initial data structure in the memory
3170		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3171		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3172		data is located at the end of the available space
3173		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3174		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3175		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3176		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3177
3178	Note:
3179		On the MPC824X (or other systems that use the data
3180		cache for initial memory) the address chosen for
3181		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3182		point to an otherwise UNUSED address space between
3183		the top of RAM and the start of the PCI space.
3184
3185- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3186
3187- CONFIG_SYS_OR_TIMING_SDRAM:
3188		SDRAM timing
3189
3190- CONFIG_SYS_MAMR_PTA:
3191		periodic timer for refresh
3192
3193- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3194  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3195  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3196  CONFIG_SYS_BR1_PRELIM:
3197		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3198
3199- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3200  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3201  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3202		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3203
3204- CONFIG_PCI_ENUM_ONLY
3205		Only scan through and get the devices on the buses.
3206		Don't do any setup work, presumably because someone or
3207		something has already done it, and we don't need to do it
3208		a second time.	Useful for platforms that are pre-booted
3209		by coreboot or similar.
3210
3211- CONFIG_PCI_INDIRECT_BRIDGE:
3212		Enable support for indirect PCI bridges.
3213
3214- CONFIG_SYS_SRIO:
3215		Chip has SRIO or not
3216
3217- CONFIG_SRIO1:
3218		Board has SRIO 1 port available
3219
3220- CONFIG_SRIO2:
3221		Board has SRIO 2 port available
3222
3223- CONFIG_SRIO_PCIE_BOOT_MASTER
3224		Board can support master function for Boot from SRIO and PCIE
3225
3226- CONFIG_SYS_SRIOn_MEM_VIRT:
3227		Virtual Address of SRIO port 'n' memory region
3228
3229- CONFIG_SYS_SRIOn_MEM_PHYS:
3230		Physical Address of SRIO port 'n' memory region
3231
3232- CONFIG_SYS_SRIOn_MEM_SIZE:
3233		Size of SRIO port 'n' memory region
3234
3235- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3236		Defined to tell the NAND controller that the NAND chip is using
3237		a 16 bit bus.
3238		Not all NAND drivers use this symbol.
3239		Example of drivers that use it:
3240		- drivers/mtd/nand/raw/ndfc.c
3241		- drivers/mtd/nand/raw/mxc_nand.c
3242
3243- CONFIG_SYS_NDFC_EBC0_CFG
3244		Sets the EBC0_CFG register for the NDFC. If not defined
3245		a default value will be used.
3246
3247- CONFIG_SPD_EEPROM
3248		Get DDR timing information from an I2C EEPROM. Common
3249		with pluggable memory modules such as SODIMMs
3250
3251  SPD_EEPROM_ADDRESS
3252		I2C address of the SPD EEPROM
3253
3254- CONFIG_SYS_SPD_BUS_NUM
3255		If SPD EEPROM is on an I2C bus other than the first
3256		one, specify here. Note that the value must resolve
3257		to something your driver can deal with.
3258
3259- CONFIG_SYS_DDR_RAW_TIMING
3260		Get DDR timing information from other than SPD. Common with
3261		soldered DDR chips onboard without SPD. DDR raw timing
3262		parameters are extracted from datasheet and hard-coded into
3263		header files or board specific files.
3264
3265- CONFIG_FSL_DDR_INTERACTIVE
3266		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3267
3268- CONFIG_FSL_DDR_SYNC_REFRESH
3269		Enable sync of refresh for multiple controllers.
3270
3271- CONFIG_FSL_DDR_BIST
3272		Enable built-in memory test for Freescale DDR controllers.
3273
3274- CONFIG_SYS_83XX_DDR_USES_CS0
3275		Only for 83xx systems. If specified, then DDR should
3276		be configured using CS0 and CS1 instead of CS2 and CS3.
3277
3278- CONFIG_RMII
3279		Enable RMII mode for all FECs.
3280		Note that this is a global option, we can't
3281		have one FEC in standard MII mode and another in RMII mode.
3282
3283- CONFIG_CRC32_VERIFY
3284		Add a verify option to the crc32 command.
3285		The syntax is:
3286
3287		=> crc32 -v <address> <count> <crc32>
3288
3289		Where address/count indicate a memory area
3290		and crc32 is the correct crc32 which the
3291		area should have.
3292
3293- CONFIG_LOOPW
3294		Add the "loopw" memory command. This only takes effect if
3295		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3296
3297- CONFIG_MX_CYCLIC
3298		Add the "mdc" and "mwc" memory commands. These are cyclic
3299		"md/mw" commands.
3300		Examples:
3301
3302		=> mdc.b 10 4 500
3303		This command will print 4 bytes (10,11,12,13) each 500 ms.
3304
3305		=> mwc.l 100 12345678 10
3306		This command will write 12345678 to address 100 all 10 ms.
3307
3308		This only takes effect if the memory commands are activated
3309		globally (CONFIG_CMD_MEMORY).
3310
3311- CONFIG_SKIP_LOWLEVEL_INIT
3312		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3313		low level initializations (like setting up the memory
3314		controller) are omitted and/or U-Boot does not
3315		relocate itself into RAM.
3316
3317		Normally this variable MUST NOT be defined. The only
3318		exception is when U-Boot is loaded (to RAM) by some
3319		other boot loader or by a debugger which performs
3320		these initializations itself.
3321
3322- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3323		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3324		to be skipped. The normal CP15 init (such as enabling the
3325		instruction cache) is still performed.
3326
3327- CONFIG_SPL_BUILD
3328		Modifies the behaviour of start.S when compiling a loader
3329		that is executed before the actual U-Boot. E.g. when
3330		compiling a NAND SPL.
3331
3332- CONFIG_TPL_BUILD
3333		Modifies the behaviour of start.S  when compiling a loader
3334		that is executed after the SPL and before the actual U-Boot.
3335		It is loaded by the SPL.
3336
3337- CONFIG_SYS_MPC85XX_NO_RESETVEC
3338		Only for 85xx systems. If this variable is specified, the section
3339		.resetvec is not kept and the section .bootpg is placed in the
3340		previous 4k of the .text section.
3341
3342- CONFIG_ARCH_MAP_SYSMEM
3343		Generally U-Boot (and in particular the md command) uses
3344		effective address. It is therefore not necessary to regard
3345		U-Boot address as virtual addresses that need to be translated
3346		to physical addresses. However, sandbox requires this, since
3347		it maintains its own little RAM buffer which contains all
3348		addressable memory. This option causes some memory accesses
3349		to be mapped through map_sysmem() / unmap_sysmem().
3350
3351- CONFIG_X86_RESET_VECTOR
3352		If defined, the x86 reset vector code is included. This is not
3353		needed when U-Boot is running from Coreboot.
3354
3355- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3356		Option to disable subpage write in NAND driver
3357		driver that uses this:
3358		drivers/mtd/nand/raw/davinci_nand.c
3359
3360Freescale QE/FMAN Firmware Support:
3361-----------------------------------
3362
3363The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3364loading of "firmware", which is encoded in the QE firmware binary format.
3365This firmware often needs to be loaded during U-Boot booting, so macros
3366are used to identify the storage device (NOR flash, SPI, etc) and the address
3367within that device.
3368
3369- CONFIG_SYS_FMAN_FW_ADDR
3370	The address in the storage device where the FMAN microcode is located.  The
3371	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3372	is also specified.
3373
3374- CONFIG_SYS_QE_FW_ADDR
3375	The address in the storage device where the QE microcode is located.  The
3376	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3377	is also specified.
3378
3379- CONFIG_SYS_QE_FMAN_FW_LENGTH
3380	The maximum possible size of the firmware.  The firmware binary format
3381	has a field that specifies the actual size of the firmware, but it
3382	might not be possible to read any part of the firmware unless some
3383	local storage is allocated to hold the entire firmware first.
3384
3385- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3386	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3387	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3388	virtual address in NOR flash.
3389
3390- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3391	Specifies that QE/FMAN firmware is located in NAND flash.
3392	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3393
3394- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3395	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3396	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3397
3398- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3399	Specifies that QE/FMAN firmware is located in the remote (master)
3400	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3401	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3402	window->master inbound window->master LAW->the ucode address in
3403	master's memory space.
3404
3405Freescale Layerscape Management Complex Firmware Support:
3406---------------------------------------------------------
3407The Freescale Layerscape Management Complex (MC) supports the loading of
3408"firmware".
3409This firmware often needs to be loaded during U-Boot booting, so macros
3410are used to identify the storage device (NOR flash, SPI, etc) and the address
3411within that device.
3412
3413- CONFIG_FSL_MC_ENET
3414	Enable the MC driver for Layerscape SoCs.
3415
3416Freescale Layerscape Debug Server Support:
3417-------------------------------------------
3418The Freescale Layerscape Debug Server Support supports the loading of
3419"Debug Server firmware" and triggering SP boot-rom.
3420This firmware often needs to be loaded during U-Boot booting.
3421
3422- CONFIG_SYS_MC_RSV_MEM_ALIGN
3423	Define alignment of reserved memory MC requires
3424
3425Reproducible builds
3426-------------------
3427
3428In order to achieve reproducible builds, timestamps used in the U-Boot build
3429process have to be set to a fixed value.
3430
3431This is done using the SOURCE_DATE_EPOCH environment variable.
3432SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3433option for U-Boot or an environment variable in U-Boot.
3434
3435SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3436
3437Building the Software:
3438======================
3439
3440Building U-Boot has been tested in several native build environments
3441and in many different cross environments. Of course we cannot support
3442all possibly existing versions of cross development tools in all
3443(potentially obsolete) versions. In case of tool chain problems we
3444recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3445which is extensively used to build and test U-Boot.
3446
3447If you are not using a native environment, it is assumed that you
3448have GNU cross compiling tools available in your path. In this case,
3449you must set the environment variable CROSS_COMPILE in your shell.
3450Note that no changes to the Makefile or any other source files are
3451necessary. For example using the ELDK on a 4xx CPU, please enter:
3452
3453	$ CROSS_COMPILE=ppc_4xx-
3454	$ export CROSS_COMPILE
3455
3456Note: If you wish to generate Windows versions of the utilities in
3457      the tools directory you can use the MinGW toolchain
3458      (http://www.mingw.org).  Set your HOST tools to the MinGW
3459      toolchain and execute 'make tools'.  For example:
3460
3461       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3462
3463      Binaries such as tools/mkimage.exe will be created which can
3464      be executed on computers running Windows.
3465
3466U-Boot is intended to be simple to build. After installing the
3467sources you must configure U-Boot for one specific board type. This
3468is done by typing:
3469
3470	make NAME_defconfig
3471
3472where "NAME_defconfig" is the name of one of the existing configu-
3473rations; see boards.cfg for supported names.
3474
3475Note: for some board special configuration names may exist; check if
3476      additional information is available from the board vendor; for
3477      instance, the TQM823L systems are available without (standard)
3478      or with LCD support. You can select such additional "features"
3479      when choosing the configuration, i. e.
3480
3481      make TQM823L_defconfig
3482	- will configure for a plain TQM823L, i. e. no LCD support
3483
3484      make TQM823L_LCD_defconfig
3485	- will configure for a TQM823L with U-Boot console on LCD
3486
3487      etc.
3488
3489
3490Finally, type "make all", and you should get some working U-Boot
3491images ready for download to / installation on your system:
3492
3493- "u-boot.bin" is a raw binary image
3494- "u-boot" is an image in ELF binary format
3495- "u-boot.srec" is in Motorola S-Record format
3496
3497By default the build is performed locally and the objects are saved
3498in the source directory. One of the two methods can be used to change
3499this behavior and build U-Boot to some external directory:
3500
35011. Add O= to the make command line invocations:
3502
3503	make O=/tmp/build distclean
3504	make O=/tmp/build NAME_defconfig
3505	make O=/tmp/build all
3506
35072. Set environment variable KBUILD_OUTPUT to point to the desired location:
3508
3509	export KBUILD_OUTPUT=/tmp/build
3510	make distclean
3511	make NAME_defconfig
3512	make all
3513
3514Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3515variable.
3516
3517User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3518setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3519For example to treat all compiler warnings as errors:
3520
3521	make KCFLAGS=-Werror
3522
3523Please be aware that the Makefiles assume you are using GNU make, so
3524for instance on NetBSD you might need to use "gmake" instead of
3525native "make".
3526
3527
3528If the system board that you have is not listed, then you will need
3529to port U-Boot to your hardware platform. To do this, follow these
3530steps:
3531
35321.  Create a new directory to hold your board specific code. Add any
3533    files you need. In your board directory, you will need at least
3534    the "Makefile" and a "<board>.c".
35352.  Create a new configuration file "include/configs/<board>.h" for
3536    your board.
35373.  If you're porting U-Boot to a new CPU, then also create a new
3538    directory to hold your CPU specific code. Add any files you need.
35394.  Run "make <board>_defconfig" with your new name.
35405.  Type "make", and you should get a working "u-boot.srec" file
3541    to be installed on your target system.
35426.  Debug and solve any problems that might arise.
3543    [Of course, this last step is much harder than it sounds.]
3544
3545
3546Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3547==============================================================
3548
3549If you have modified U-Boot sources (for instance added a new board
3550or support for new devices, a new CPU, etc.) you are expected to
3551provide feedback to the other developers. The feedback normally takes
3552the form of a "patch", i. e. a context diff against a certain (latest
3553official or latest in the git repository) version of U-Boot sources.
3554
3555But before you submit such a patch, please verify that your modifi-
3556cation did not break existing code. At least make sure that *ALL* of
3557the supported boards compile WITHOUT ANY compiler warnings. To do so,
3558just run the buildman script (tools/buildman/buildman), which will
3559configure and build U-Boot for ALL supported system. Be warned, this
3560will take a while. Please see the buildman README, or run 'buildman -H'
3561for documentation.
3562
3563
3564See also "U-Boot Porting Guide" below.
3565
3566
3567Monitor Commands - Overview:
3568============================
3569
3570go	- start application at address 'addr'
3571run	- run commands in an environment variable
3572bootm	- boot application image from memory
3573bootp	- boot image via network using BootP/TFTP protocol
3574bootz   - boot zImage from memory
3575tftpboot- boot image via network using TFTP protocol
3576	       and env variables "ipaddr" and "serverip"
3577	       (and eventually "gatewayip")
3578tftpput - upload a file via network using TFTP protocol
3579rarpboot- boot image via network using RARP/TFTP protocol
3580diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3581loads	- load S-Record file over serial line
3582loadb	- load binary file over serial line (kermit mode)
3583md	- memory display
3584mm	- memory modify (auto-incrementing)
3585nm	- memory modify (constant address)
3586mw	- memory write (fill)
3587cp	- memory copy
3588cmp	- memory compare
3589crc32	- checksum calculation
3590i2c	- I2C sub-system
3591sspi	- SPI utility commands
3592base	- print or set address offset
3593printenv- print environment variables
3594setenv	- set environment variables
3595saveenv - save environment variables to persistent storage
3596protect - enable or disable FLASH write protection
3597erase	- erase FLASH memory
3598flinfo	- print FLASH memory information
3599nand	- NAND memory operations (see doc/README.nand)
3600bdinfo	- print Board Info structure
3601iminfo	- print header information for application image
3602coninfo - print console devices and informations
3603ide	- IDE sub-system
3604loop	- infinite loop on address range
3605loopw	- infinite write loop on address range
3606mtest	- simple RAM test
3607icache	- enable or disable instruction cache
3608dcache	- enable or disable data cache
3609reset	- Perform RESET of the CPU
3610echo	- echo args to console
3611version - print monitor version
3612help	- print online help
3613?	- alias for 'help'
3614
3615
3616Monitor Commands - Detailed Description:
3617========================================
3618
3619TODO.
3620
3621For now: just type "help <command>".
3622
3623
3624Environment Variables:
3625======================
3626
3627U-Boot supports user configuration using Environment Variables which
3628can be made persistent by saving to Flash memory.
3629
3630Environment Variables are set using "setenv", printed using
3631"printenv", and saved to Flash using "saveenv". Using "setenv"
3632without a value can be used to delete a variable from the
3633environment. As long as you don't save the environment you are
3634working with an in-memory copy. In case the Flash area containing the
3635environment is erased by accident, a default environment is provided.
3636
3637Some configuration options can be set using Environment Variables.
3638
3639List of environment variables (most likely not complete):
3640
3641  baudrate	- see CONFIG_BAUDRATE
3642
3643  bootdelay	- see CONFIG_BOOTDELAY
3644
3645  bootcmd	- see CONFIG_BOOTCOMMAND
3646
3647  bootargs	- Boot arguments when booting an RTOS image
3648
3649  bootfile	- Name of the image to load with TFTP
3650
3651  bootm_low	- Memory range available for image processing in the bootm
3652		  command can be restricted. This variable is given as
3653		  a hexadecimal number and defines lowest address allowed
3654		  for use by the bootm command. See also "bootm_size"
3655		  environment variable. Address defined by "bootm_low" is
3656		  also the base of the initial memory mapping for the Linux
3657		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3658		  bootm_mapsize.
3659
3660  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3661		  This variable is given as a hexadecimal number and it
3662		  defines the size of the memory region starting at base
3663		  address bootm_low that is accessible by the Linux kernel
3664		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3665		  as the default value if it is defined, and bootm_size is
3666		  used otherwise.
3667
3668  bootm_size	- Memory range available for image processing in the bootm
3669		  command can be restricted. This variable is given as
3670		  a hexadecimal number and defines the size of the region
3671		  allowed for use by the bootm command. See also "bootm_low"
3672		  environment variable.
3673
3674  updatefile	- Location of the software update file on a TFTP server, used
3675		  by the automatic software update feature. Please refer to
3676		  documentation in doc/README.update for more details.
3677
3678  autoload	- if set to "no" (any string beginning with 'n'),
3679		  "bootp" will just load perform a lookup of the
3680		  configuration from the BOOTP server, but not try to
3681		  load any image using TFTP
3682
3683  autostart	- if set to "yes", an image loaded using the "bootp",
3684		  "rarpboot", "tftpboot" or "diskboot" commands will
3685		  be automatically started (by internally calling
3686		  "bootm")
3687
3688		  If set to "no", a standalone image passed to the
3689		  "bootm" command will be copied to the load address
3690		  (and eventually uncompressed), but NOT be started.
3691		  This can be used to load and uncompress arbitrary
3692		  data.
3693
3694  fdt_high	- if set this restricts the maximum address that the
3695		  flattened device tree will be copied into upon boot.
3696		  For example, if you have a system with 1 GB memory
3697		  at physical address 0x10000000, while Linux kernel
3698		  only recognizes the first 704 MB as low memory, you
3699		  may need to set fdt_high as 0x3C000000 to have the
3700		  device tree blob be copied to the maximum address
3701		  of the 704 MB low memory, so that Linux kernel can
3702		  access it during the boot procedure.
3703
3704		  If this is set to the special value 0xFFFFFFFF then
3705		  the fdt will not be copied at all on boot.  For this
3706		  to work it must reside in writable memory, have
3707		  sufficient padding on the end of it for u-boot to
3708		  add the information it needs into it, and the memory
3709		  must be accessible by the kernel.
3710
3711  fdtcontroladdr- if set this is the address of the control flattened
3712		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3713		  defined.
3714
3715  i2cfast	- (PPC405GP|PPC405EP only)
3716		  if set to 'y' configures Linux I2C driver for fast
3717		  mode (400kHZ). This environment variable is used in
3718		  initialization code. So, for changes to be effective
3719		  it must be saved and board must be reset.
3720
3721  initrd_high	- restrict positioning of initrd images:
3722		  If this variable is not set, initrd images will be
3723		  copied to the highest possible address in RAM; this
3724		  is usually what you want since it allows for
3725		  maximum initrd size. If for some reason you want to
3726		  make sure that the initrd image is loaded below the
3727		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3728		  variable to a value of "no" or "off" or "0".
3729		  Alternatively, you can set it to a maximum upper
3730		  address to use (U-Boot will still check that it
3731		  does not overwrite the U-Boot stack and data).
3732
3733		  For instance, when you have a system with 16 MB
3734		  RAM, and want to reserve 4 MB from use by Linux,
3735		  you can do this by adding "mem=12M" to the value of
3736		  the "bootargs" variable. However, now you must make
3737		  sure that the initrd image is placed in the first
3738		  12 MB as well - this can be done with
3739
3740		  setenv initrd_high 00c00000
3741
3742		  If you set initrd_high to 0xFFFFFFFF, this is an
3743		  indication to U-Boot that all addresses are legal
3744		  for the Linux kernel, including addresses in flash
3745		  memory. In this case U-Boot will NOT COPY the
3746		  ramdisk at all. This may be useful to reduce the
3747		  boot time on your system, but requires that this
3748		  feature is supported by your Linux kernel.
3749
3750  ipaddr	- IP address; needed for tftpboot command
3751
3752  loadaddr	- Default load address for commands like "bootp",
3753		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3754
3755  loads_echo	- see CONFIG_LOADS_ECHO
3756
3757  serverip	- TFTP server IP address; needed for tftpboot command
3758
3759  bootretry	- see CONFIG_BOOT_RETRY_TIME
3760
3761  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3762
3763  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3764
3765  ethprime	- controls which interface is used first.
3766
3767  ethact	- controls which interface is currently active.
3768		  For example you can do the following
3769
3770		  => setenv ethact FEC
3771		  => ping 192.168.0.1 # traffic sent on FEC
3772		  => setenv ethact SCC
3773		  => ping 10.0.0.1 # traffic sent on SCC
3774
3775  ethrotate	- When set to "no" U-Boot does not go through all
3776		  available network interfaces.
3777		  It just stays at the currently selected interface.
3778
3779  netretry	- When set to "no" each network operation will
3780		  either succeed or fail without retrying.
3781		  When set to "once" the network operation will
3782		  fail when all the available network interfaces
3783		  are tried once without success.
3784		  Useful on scripts which control the retry operation
3785		  themselves.
3786
3787  npe_ucode	- set load address for the NPE microcode
3788
3789  silent_linux  - If set then Linux will be told to boot silently, by
3790		  changing the console to be empty. If "yes" it will be
3791		  made silent. If "no" it will not be made silent. If
3792		  unset, then it will be made silent if the U-Boot console
3793		  is silent.
3794
3795  tftpsrcp	- If this is set, the value is used for TFTP's
3796		  UDP source port.
3797
3798  tftpdstp	- If this is set, the value is used for TFTP's UDP
3799		  destination port instead of the Well Know Port 69.
3800
3801  tftpblocksize - Block size to use for TFTP transfers; if not set,
3802		  we use the TFTP server's default block size
3803
3804  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3805		  seconds, minimum value is 1000 = 1 second). Defines
3806		  when a packet is considered to be lost so it has to
3807		  be retransmitted. The default is 5000 = 5 seconds.
3808		  Lowering this value may make downloads succeed
3809		  faster in networks with high packet loss rates or
3810		  with unreliable TFTP servers.
3811
3812  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3813		  unit, minimum value = 0). Defines how many timeouts
3814		  can happen during a single file transfer before that
3815		  transfer is aborted. The default is 10, and 0 means
3816		  'no timeouts allowed'. Increasing this value may help
3817		  downloads succeed with high packet loss rates, or with
3818		  unreliable TFTP servers or client hardware.
3819
3820  vlan		- When set to a value < 4095 the traffic over
3821		  Ethernet is encapsulated/received over 802.1q
3822		  VLAN tagged frames.
3823
3824  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3825		  Unsigned value, in milliseconds. If not set, the period will
3826		  be either the default (28000), or a value based on
3827		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3828		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3829
3830The following image location variables contain the location of images
3831used in booting. The "Image" column gives the role of the image and is
3832not an environment variable name. The other columns are environment
3833variable names. "File Name" gives the name of the file on a TFTP
3834server, "RAM Address" gives the location in RAM the image will be
3835loaded to, and "Flash Location" gives the image's address in NOR
3836flash or offset in NAND flash.
3837
3838*Note* - these variables don't have to be defined for all boards, some
3839boards currently use other variables for these purposes, and some
3840boards use these variables for other purposes.
3841
3842Image		    File Name	     RAM Address       Flash Location
3843-----		    ---------	     -----------       --------------
3844u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3845Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3846device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3847ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3848
3849The following environment variables may be used and automatically
3850updated by the network boot commands ("bootp" and "rarpboot"),
3851depending the information provided by your boot server:
3852
3853  bootfile	- see above
3854  dnsip		- IP address of your Domain Name Server
3855  dnsip2	- IP address of your secondary Domain Name Server
3856  gatewayip	- IP address of the Gateway (Router) to use
3857  hostname	- Target hostname
3858  ipaddr	- see above
3859  netmask	- Subnet Mask
3860  rootpath	- Pathname of the root filesystem on the NFS server
3861  serverip	- see above
3862
3863
3864There are two special Environment Variables:
3865
3866  serial#	- contains hardware identification information such
3867		  as type string and/or serial number
3868  ethaddr	- Ethernet address
3869
3870These variables can be set only once (usually during manufacturing of
3871the board). U-Boot refuses to delete or overwrite these variables
3872once they have been set once.
3873
3874
3875Further special Environment Variables:
3876
3877  ver		- Contains the U-Boot version string as printed
3878		  with the "version" command. This variable is
3879		  readonly (see CONFIG_VERSION_VARIABLE).
3880
3881
3882Please note that changes to some configuration parameters may take
3883only effect after the next boot (yes, that's just like Windoze :-).
3884
3885
3886Callback functions for environment variables:
3887---------------------------------------------
3888
3889For some environment variables, the behavior of u-boot needs to change
3890when their values are changed.  This functionality allows functions to
3891be associated with arbitrary variables.  On creation, overwrite, or
3892deletion, the callback will provide the opportunity for some side
3893effect to happen or for the change to be rejected.
3894
3895The callbacks are named and associated with a function using the
3896U_BOOT_ENV_CALLBACK macro in your board or driver code.
3897
3898These callbacks are associated with variables in one of two ways.  The
3899static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3900in the board configuration to a string that defines a list of
3901associations.  The list must be in the following format:
3902
3903	entry = variable_name[:callback_name]
3904	list = entry[,list]
3905
3906If the callback name is not specified, then the callback is deleted.
3907Spaces are also allowed anywhere in the list.
3908
3909Callbacks can also be associated by defining the ".callbacks" variable
3910with the same list format above.  Any association in ".callbacks" will
3911override any association in the static list. You can define
3912CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3913".callbacks" environment variable in the default or embedded environment.
3914
3915If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3916regular expression. This allows multiple variables to be connected to
3917the same callback without explicitly listing them all out.
3918
3919The signature of the callback functions is:
3920
3921    int callback(const char *name, const char *value, enum env_op op, int flags)
3922
3923* name - changed environment variable
3924* value - new value of the environment variable
3925* op - operation (create, overwrite, or delete)
3926* flags - attributes of the environment variable change, see flags H_* in
3927  include/search.h
3928
3929The return value is 0 if the variable change is accepted and 1 otherwise.
3930
3931Command Line Parsing:
3932=====================
3933
3934There are two different command line parsers available with U-Boot:
3935the old "simple" one, and the much more powerful "hush" shell:
3936
3937Old, simple command line parser:
3938--------------------------------
3939
3940- supports environment variables (through setenv / saveenv commands)
3941- several commands on one line, separated by ';'
3942- variable substitution using "... ${name} ..." syntax
3943- special characters ('$', ';') can be escaped by prefixing with '\',
3944  for example:
3945	setenv bootcmd bootm \${address}
3946- You can also escape text by enclosing in single apostrophes, for example:
3947	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3948
3949Hush shell:
3950-----------
3951
3952- similar to Bourne shell, with control structures like
3953  if...then...else...fi, for...do...done; while...do...done,
3954  until...do...done, ...
3955- supports environment ("global") variables (through setenv / saveenv
3956  commands) and local shell variables (through standard shell syntax
3957  "name=value"); only environment variables can be used with "run"
3958  command
3959
3960General rules:
3961--------------
3962
3963(1) If a command line (or an environment variable executed by a "run"
3964    command) contains several commands separated by semicolon, and
3965    one of these commands fails, then the remaining commands will be
3966    executed anyway.
3967
3968(2) If you execute several variables with one call to run (i. e.
3969    calling run with a list of variables as arguments), any failing
3970    command will cause "run" to terminate, i. e. the remaining
3971    variables are not executed.
3972
3973Note for Redundant Ethernet Interfaces:
3974=======================================
3975
3976Some boards come with redundant Ethernet interfaces; U-Boot supports
3977such configurations and is capable of automatic selection of a
3978"working" interface when needed. MAC assignment works as follows:
3979
3980Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3981MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3982"eth1addr" (=>eth1), "eth2addr", ...
3983
3984If the network interface stores some valid MAC address (for instance
3985in SROM), this is used as default address if there is NO correspon-
3986ding setting in the environment; if the corresponding environment
3987variable is set, this overrides the settings in the card; that means:
3988
3989o If the SROM has a valid MAC address, and there is no address in the
3990  environment, the SROM's address is used.
3991
3992o If there is no valid address in the SROM, and a definition in the
3993  environment exists, then the value from the environment variable is
3994  used.
3995
3996o If both the SROM and the environment contain a MAC address, and
3997  both addresses are the same, this MAC address is used.
3998
3999o If both the SROM and the environment contain a MAC address, and the
4000  addresses differ, the value from the environment is used and a
4001  warning is printed.
4002
4003o If neither SROM nor the environment contain a MAC address, an error
4004  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4005  a random, locally-assigned MAC is used.
4006
4007If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4008will be programmed into hardware as part of the initialization process.	 This
4009may be skipped by setting the appropriate 'ethmacskip' environment variable.
4010The naming convention is as follows:
4011"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4012
4013Image Formats:
4014==============
4015
4016U-Boot is capable of booting (and performing other auxiliary operations on)
4017images in two formats:
4018
4019New uImage format (FIT)
4020-----------------------
4021
4022Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4023to Flattened Device Tree). It allows the use of images with multiple
4024components (several kernels, ramdisks, etc.), with contents protected by
4025SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4026
4027
4028Old uImage format
4029-----------------
4030
4031Old image format is based on binary files which can be basically anything,
4032preceded by a special header; see the definitions in include/image.h for
4033details; basically, the header defines the following image properties:
4034
4035* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4036  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4037  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4038  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4039  INTEGRITY).
4040* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4041  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4042  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4043* Compression Type (uncompressed, gzip, bzip2)
4044* Load Address
4045* Entry Point
4046* Image Name
4047* Image Timestamp
4048
4049The header is marked by a special Magic Number, and both the header
4050and the data portions of the image are secured against corruption by
4051CRC32 checksums.
4052
4053
4054Linux Support:
4055==============
4056
4057Although U-Boot should support any OS or standalone application
4058easily, the main focus has always been on Linux during the design of
4059U-Boot.
4060
4061U-Boot includes many features that so far have been part of some
4062special "boot loader" code within the Linux kernel. Also, any
4063"initrd" images to be used are no longer part of one big Linux image;
4064instead, kernel and "initrd" are separate images. This implementation
4065serves several purposes:
4066
4067- the same features can be used for other OS or standalone
4068  applications (for instance: using compressed images to reduce the
4069  Flash memory footprint)
4070
4071- it becomes much easier to port new Linux kernel versions because
4072  lots of low-level, hardware dependent stuff are done by U-Boot
4073
4074- the same Linux kernel image can now be used with different "initrd"
4075  images; of course this also means that different kernel images can
4076  be run with the same "initrd". This makes testing easier (you don't
4077  have to build a new "zImage.initrd" Linux image when you just
4078  change a file in your "initrd"). Also, a field-upgrade of the
4079  software is easier now.
4080
4081
4082Linux HOWTO:
4083============
4084
4085Porting Linux to U-Boot based systems:
4086---------------------------------------
4087
4088U-Boot cannot save you from doing all the necessary modifications to
4089configure the Linux device drivers for use with your target hardware
4090(no, we don't intend to provide a full virtual machine interface to
4091Linux :-).
4092
4093But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4094
4095Just make sure your machine specific header file (for instance
4096include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4097Information structure as we define in include/asm-<arch>/u-boot.h,
4098and make sure that your definition of IMAP_ADDR uses the same value
4099as your U-Boot configuration in CONFIG_SYS_IMMR.
4100
4101Note that U-Boot now has a driver model, a unified model for drivers.
4102If you are adding a new driver, plumb it into driver model. If there
4103is no uclass available, you are encouraged to create one. See
4104doc/driver-model.
4105
4106
4107Configuring the Linux kernel:
4108-----------------------------
4109
4110No specific requirements for U-Boot. Make sure you have some root
4111device (initial ramdisk, NFS) for your target system.
4112
4113
4114Building a Linux Image:
4115-----------------------
4116
4117With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4118not used. If you use recent kernel source, a new build target
4119"uImage" will exist which automatically builds an image usable by
4120U-Boot. Most older kernels also have support for a "pImage" target,
4121which was introduced for our predecessor project PPCBoot and uses a
4122100% compatible format.
4123
4124Example:
4125
4126	make TQM850L_defconfig
4127	make oldconfig
4128	make dep
4129	make uImage
4130
4131The "uImage" build target uses a special tool (in 'tools/mkimage') to
4132encapsulate a compressed Linux kernel image with header	 information,
4133CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4134
4135* build a standard "vmlinux" kernel image (in ELF binary format):
4136
4137* convert the kernel into a raw binary image:
4138
4139	${CROSS_COMPILE}-objcopy -O binary \
4140				 -R .note -R .comment \
4141				 -S vmlinux linux.bin
4142
4143* compress the binary image:
4144
4145	gzip -9 linux.bin
4146
4147* package compressed binary image for U-Boot:
4148
4149	mkimage -A ppc -O linux -T kernel -C gzip \
4150		-a 0 -e 0 -n "Linux Kernel Image" \
4151		-d linux.bin.gz uImage
4152
4153
4154The "mkimage" tool can also be used to create ramdisk images for use
4155with U-Boot, either separated from the Linux kernel image, or
4156combined into one file. "mkimage" encapsulates the images with a 64
4157byte header containing information about target architecture,
4158operating system, image type, compression method, entry points, time
4159stamp, CRC32 checksums, etc.
4160
4161"mkimage" can be called in two ways: to verify existing images and
4162print the header information, or to build new images.
4163
4164In the first form (with "-l" option) mkimage lists the information
4165contained in the header of an existing U-Boot image; this includes
4166checksum verification:
4167
4168	tools/mkimage -l image
4169	  -l ==> list image header information
4170
4171The second form (with "-d" option) is used to build a U-Boot image
4172from a "data file" which is used as image payload:
4173
4174	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4175		      -n name -d data_file image
4176	  -A ==> set architecture to 'arch'
4177	  -O ==> set operating system to 'os'
4178	  -T ==> set image type to 'type'
4179	  -C ==> set compression type 'comp'
4180	  -a ==> set load address to 'addr' (hex)
4181	  -e ==> set entry point to 'ep' (hex)
4182	  -n ==> set image name to 'name'
4183	  -d ==> use image data from 'datafile'
4184
4185Right now, all Linux kernels for PowerPC systems use the same load
4186address (0x00000000), but the entry point address depends on the
4187kernel version:
4188
4189- 2.2.x kernels have the entry point at 0x0000000C,
4190- 2.3.x and later kernels have the entry point at 0x00000000.
4191
4192So a typical call to build a U-Boot image would read:
4193
4194	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4195	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4196	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4197	> examples/uImage.TQM850L
4198	Image Name:   2.4.4 kernel for TQM850L
4199	Created:      Wed Jul 19 02:34:59 2000
4200	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4201	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4202	Load Address: 0x00000000
4203	Entry Point:  0x00000000
4204
4205To verify the contents of the image (or check for corruption):
4206
4207	-> tools/mkimage -l examples/uImage.TQM850L
4208	Image Name:   2.4.4 kernel for TQM850L
4209	Created:      Wed Jul 19 02:34:59 2000
4210	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4211	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4212	Load Address: 0x00000000
4213	Entry Point:  0x00000000
4214
4215NOTE: for embedded systems where boot time is critical you can trade
4216speed for memory and install an UNCOMPRESSED image instead: this
4217needs more space in Flash, but boots much faster since it does not
4218need to be uncompressed:
4219
4220	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4221	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4222	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4223	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4224	> examples/uImage.TQM850L-uncompressed
4225	Image Name:   2.4.4 kernel for TQM850L
4226	Created:      Wed Jul 19 02:34:59 2000
4227	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4228	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4229	Load Address: 0x00000000
4230	Entry Point:  0x00000000
4231
4232
4233Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4234when your kernel is intended to use an initial ramdisk:
4235
4236	-> tools/mkimage -n 'Simple Ramdisk Image' \
4237	> -A ppc -O linux -T ramdisk -C gzip \
4238	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4239	Image Name:   Simple Ramdisk Image
4240	Created:      Wed Jan 12 14:01:50 2000
4241	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4242	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4243	Load Address: 0x00000000
4244	Entry Point:  0x00000000
4245
4246The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4247option performs the converse operation of the mkimage's second form (the "-d"
4248option). Given an image built by mkimage, the dumpimage extracts a "data file"
4249from the image:
4250
4251	tools/dumpimage -i image -T type -p position data_file
4252	  -i ==> extract from the 'image' a specific 'data_file'
4253	  -T ==> set image type to 'type'
4254	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4255
4256
4257Installing a Linux Image:
4258-------------------------
4259
4260To downloading a U-Boot image over the serial (console) interface,
4261you must convert the image to S-Record format:
4262
4263	objcopy -I binary -O srec examples/image examples/image.srec
4264
4265The 'objcopy' does not understand the information in the U-Boot
4266image header, so the resulting S-Record file will be relative to
4267address 0x00000000. To load it to a given address, you need to
4268specify the target address as 'offset' parameter with the 'loads'
4269command.
4270
4271Example: install the image to address 0x40100000 (which on the
4272TQM8xxL is in the first Flash bank):
4273
4274	=> erase 40100000 401FFFFF
4275
4276	.......... done
4277	Erased 8 sectors
4278
4279	=> loads 40100000
4280	## Ready for S-Record download ...
4281	~>examples/image.srec
4282	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4283	...
4284	15989 15990 15991 15992
4285	[file transfer complete]
4286	[connected]
4287	## Start Addr = 0x00000000
4288
4289
4290You can check the success of the download using the 'iminfo' command;
4291this includes a checksum verification so you can be sure no data
4292corruption happened:
4293
4294	=> imi 40100000
4295
4296	## Checking Image at 40100000 ...
4297	   Image Name:	 2.2.13 for initrd on TQM850L
4298	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4299	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4300	   Load Address: 00000000
4301	   Entry Point:	 0000000c
4302	   Verifying Checksum ... OK
4303
4304
4305Boot Linux:
4306-----------
4307
4308The "bootm" command is used to boot an application that is stored in
4309memory (RAM or Flash). In case of a Linux kernel image, the contents
4310of the "bootargs" environment variable is passed to the kernel as
4311parameters. You can check and modify this variable using the
4312"printenv" and "setenv" commands:
4313
4314
4315	=> printenv bootargs
4316	bootargs=root=/dev/ram
4317
4318	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4319
4320	=> printenv bootargs
4321	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4322
4323	=> bootm 40020000
4324	## Booting Linux kernel at 40020000 ...
4325	   Image Name:	 2.2.13 for NFS on TQM850L
4326	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4327	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4328	   Load Address: 00000000
4329	   Entry Point:	 0000000c
4330	   Verifying Checksum ... OK
4331	   Uncompressing Kernel Image ... OK
4332	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
4333	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4334	time_init: decrementer frequency = 187500000/60
4335	Calibrating delay loop... 49.77 BogoMIPS
4336	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4337	...
4338
4339If you want to boot a Linux kernel with initial RAM disk, you pass
4340the memory addresses of both the kernel and the initrd image (PPBCOOT
4341format!) to the "bootm" command:
4342
4343	=> imi 40100000 40200000
4344
4345	## Checking Image at 40100000 ...
4346	   Image Name:	 2.2.13 for initrd on TQM850L
4347	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4348	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4349	   Load Address: 00000000
4350	   Entry Point:	 0000000c
4351	   Verifying Checksum ... OK
4352
4353	## Checking Image at 40200000 ...
4354	   Image Name:	 Simple Ramdisk Image
4355	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4356	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4357	   Load Address: 00000000
4358	   Entry Point:	 00000000
4359	   Verifying Checksum ... OK
4360
4361	=> bootm 40100000 40200000
4362	## Booting Linux kernel at 40100000 ...
4363	   Image Name:	 2.2.13 for initrd on TQM850L
4364	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4365	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4366	   Load Address: 00000000
4367	   Entry Point:	 0000000c
4368	   Verifying Checksum ... OK
4369	   Uncompressing Kernel Image ... OK
4370	## Loading RAMDisk Image at 40200000 ...
4371	   Image Name:	 Simple Ramdisk Image
4372	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4373	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4374	   Load Address: 00000000
4375	   Entry Point:	 00000000
4376	   Verifying Checksum ... OK
4377	   Loading Ramdisk ... OK
4378	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
4379	Boot arguments: root=/dev/ram
4380	time_init: decrementer frequency = 187500000/60
4381	Calibrating delay loop... 49.77 BogoMIPS
4382	...
4383	RAMDISK: Compressed image found at block 0
4384	VFS: Mounted root (ext2 filesystem).
4385
4386	bash#
4387
4388Boot Linux and pass a flat device tree:
4389-----------
4390
4391First, U-Boot must be compiled with the appropriate defines. See the section
4392titled "Linux Kernel Interface" above for a more in depth explanation. The
4393following is an example of how to start a kernel and pass an updated
4394flat device tree:
4395
4396=> print oftaddr
4397oftaddr=0x300000
4398=> print oft
4399oft=oftrees/mpc8540ads.dtb
4400=> tftp $oftaddr $oft
4401Speed: 1000, full duplex
4402Using TSEC0 device
4403TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4404Filename 'oftrees/mpc8540ads.dtb'.
4405Load address: 0x300000
4406Loading: #
4407done
4408Bytes transferred = 4106 (100a hex)
4409=> tftp $loadaddr $bootfile
4410Speed: 1000, full duplex
4411Using TSEC0 device
4412TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4413Filename 'uImage'.
4414Load address: 0x200000
4415Loading:############
4416done
4417Bytes transferred = 1029407 (fb51f hex)
4418=> print loadaddr
4419loadaddr=200000
4420=> print oftaddr
4421oftaddr=0x300000
4422=> bootm $loadaddr - $oftaddr
4423## Booting image at 00200000 ...
4424   Image Name:	 Linux-2.6.17-dirty
4425   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4426   Data Size:	 1029343 Bytes = 1005.2 kB
4427   Load Address: 00000000
4428   Entry Point:	 00000000
4429   Verifying Checksum ... OK
4430   Uncompressing Kernel Image ... OK
4431Booting using flat device tree at 0x300000
4432Using MPC85xx ADS machine description
4433Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4434[snip]
4435
4436
4437More About U-Boot Image Types:
4438------------------------------
4439
4440U-Boot supports the following image types:
4441
4442   "Standalone Programs" are directly runnable in the environment
4443	provided by U-Boot; it is expected that (if they behave
4444	well) you can continue to work in U-Boot after return from
4445	the Standalone Program.
4446   "OS Kernel Images" are usually images of some Embedded OS which
4447	will take over control completely. Usually these programs
4448	will install their own set of exception handlers, device
4449	drivers, set up the MMU, etc. - this means, that you cannot
4450	expect to re-enter U-Boot except by resetting the CPU.
4451   "RAMDisk Images" are more or less just data blocks, and their
4452	parameters (address, size) are passed to an OS kernel that is
4453	being started.
4454   "Multi-File Images" contain several images, typically an OS
4455	(Linux) kernel image and one or more data images like
4456	RAMDisks. This construct is useful for instance when you want
4457	to boot over the network using BOOTP etc., where the boot
4458	server provides just a single image file, but you want to get
4459	for instance an OS kernel and a RAMDisk image.
4460
4461	"Multi-File Images" start with a list of image sizes, each
4462	image size (in bytes) specified by an "uint32_t" in network
4463	byte order. This list is terminated by an "(uint32_t)0".
4464	Immediately after the terminating 0 follow the images, one by
4465	one, all aligned on "uint32_t" boundaries (size rounded up to
4466	a multiple of 4 bytes).
4467
4468   "Firmware Images" are binary images containing firmware (like
4469	U-Boot or FPGA images) which usually will be programmed to
4470	flash memory.
4471
4472   "Script files" are command sequences that will be executed by
4473	U-Boot's command interpreter; this feature is especially
4474	useful when you configure U-Boot to use a real shell (hush)
4475	as command interpreter.
4476
4477Booting the Linux zImage:
4478-------------------------
4479
4480On some platforms, it's possible to boot Linux zImage. This is done
4481using the "bootz" command. The syntax of "bootz" command is the same
4482as the syntax of "bootm" command.
4483
4484Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4485kernel with raw initrd images. The syntax is slightly different, the
4486address of the initrd must be augmented by it's size, in the following
4487format: "<initrd addres>:<initrd size>".
4488
4489
4490Standalone HOWTO:
4491=================
4492
4493One of the features of U-Boot is that you can dynamically load and
4494run "standalone" applications, which can use some resources of
4495U-Boot like console I/O functions or interrupt services.
4496
4497Two simple examples are included with the sources:
4498
4499"Hello World" Demo:
4500-------------------
4501
4502'examples/hello_world.c' contains a small "Hello World" Demo
4503application; it is automatically compiled when you build U-Boot.
4504It's configured to run at address 0x00040004, so you can play with it
4505like that:
4506
4507	=> loads
4508	## Ready for S-Record download ...
4509	~>examples/hello_world.srec
4510	1 2 3 4 5 6 7 8 9 10 11 ...
4511	[file transfer complete]
4512	[connected]
4513	## Start Addr = 0x00040004
4514
4515	=> go 40004 Hello World! This is a test.
4516	## Starting application at 0x00040004 ...
4517	Hello World
4518	argc = 7
4519	argv[0] = "40004"
4520	argv[1] = "Hello"
4521	argv[2] = "World!"
4522	argv[3] = "This"
4523	argv[4] = "is"
4524	argv[5] = "a"
4525	argv[6] = "test."
4526	argv[7] = "<NULL>"
4527	Hit any key to exit ...
4528
4529	## Application terminated, rc = 0x0
4530
4531Another example, which demonstrates how to register a CPM interrupt
4532handler with the U-Boot code, can be found in 'examples/timer.c'.
4533Here, a CPM timer is set up to generate an interrupt every second.
4534The interrupt service routine is trivial, just printing a '.'
4535character, but this is just a demo program. The application can be
4536controlled by the following keys:
4537
4538	? - print current values og the CPM Timer registers
4539	b - enable interrupts and start timer
4540	e - stop timer and disable interrupts
4541	q - quit application
4542
4543	=> loads
4544	## Ready for S-Record download ...
4545	~>examples/timer.srec
4546	1 2 3 4 5 6 7 8 9 10 11 ...
4547	[file transfer complete]
4548	[connected]
4549	## Start Addr = 0x00040004
4550
4551	=> go 40004
4552	## Starting application at 0x00040004 ...
4553	TIMERS=0xfff00980
4554	Using timer 1
4555	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4556
4557Hit 'b':
4558	[q, b, e, ?] Set interval 1000000 us
4559	Enabling timer
4560Hit '?':
4561	[q, b, e, ?] ........
4562	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4563Hit '?':
4564	[q, b, e, ?] .
4565	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4566Hit '?':
4567	[q, b, e, ?] .
4568	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4569Hit '?':
4570	[q, b, e, ?] .
4571	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4572Hit 'e':
4573	[q, b, e, ?] ...Stopping timer
4574Hit 'q':
4575	[q, b, e, ?] ## Application terminated, rc = 0x0
4576
4577
4578Minicom warning:
4579================
4580
4581Over time, many people have reported problems when trying to use the
4582"minicom" terminal emulation program for serial download. I (wd)
4583consider minicom to be broken, and recommend not to use it. Under
4584Unix, I recommend to use C-Kermit for general purpose use (and
4585especially for kermit binary protocol download ("loadb" command), and
4586use "cu" for S-Record download ("loads" command).  See
4587http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4588for help with kermit.
4589
4590
4591Nevertheless, if you absolutely want to use it try adding this
4592configuration to your "File transfer protocols" section:
4593
4594	   Name	   Program			Name U/D FullScr IO-Red. Multi
4595	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4596	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4597
4598
4599NetBSD Notes:
4600=============
4601
4602Starting at version 0.9.2, U-Boot supports NetBSD both as host
4603(build U-Boot) and target system (boots NetBSD/mpc8xx).
4604
4605Building requires a cross environment; it is known to work on
4606NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4607need gmake since the Makefiles are not compatible with BSD make).
4608Note that the cross-powerpc package does not install include files;
4609attempting to build U-Boot will fail because <machine/ansi.h> is
4610missing.  This file has to be installed and patched manually:
4611
4612	# cd /usr/pkg/cross/powerpc-netbsd/include
4613	# mkdir powerpc
4614	# ln -s powerpc machine
4615	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4616	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4617
4618Native builds *don't* work due to incompatibilities between native
4619and U-Boot include files.
4620
4621Booting assumes that (the first part of) the image booted is a
4622stage-2 loader which in turn loads and then invokes the kernel
4623proper. Loader sources will eventually appear in the NetBSD source
4624tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4625meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4626
4627
4628Implementation Internals:
4629=========================
4630
4631The following is not intended to be a complete description of every
4632implementation detail. However, it should help to understand the
4633inner workings of U-Boot and make it easier to port it to custom
4634hardware.
4635
4636
4637Initial Stack, Global Data:
4638---------------------------
4639
4640The implementation of U-Boot is complicated by the fact that U-Boot
4641starts running out of ROM (flash memory), usually without access to
4642system RAM (because the memory controller is not initialized yet).
4643This means that we don't have writable Data or BSS segments, and BSS
4644is not initialized as zero. To be able to get a C environment working
4645at all, we have to allocate at least a minimal stack. Implementation
4646options for this are defined and restricted by the CPU used: Some CPU
4647models provide on-chip memory (like the IMMR area on MPC8xx and
4648MPC826x processors), on others (parts of) the data cache can be
4649locked as (mis-) used as memory, etc.
4650
4651	Chris Hallinan posted a good summary of these issues to the
4652	U-Boot mailing list:
4653
4654	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4655	From: "Chris Hallinan" <clh@net1plus.com>
4656	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4657	...
4658
4659	Correct me if I'm wrong, folks, but the way I understand it
4660	is this: Using DCACHE as initial RAM for Stack, etc, does not
4661	require any physical RAM backing up the cache. The cleverness
4662	is that the cache is being used as a temporary supply of
4663	necessary storage before the SDRAM controller is setup. It's
4664	beyond the scope of this list to explain the details, but you
4665	can see how this works by studying the cache architecture and
4666	operation in the architecture and processor-specific manuals.
4667
4668	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4669	is another option for the system designer to use as an
4670	initial stack/RAM area prior to SDRAM being available. Either
4671	option should work for you. Using CS 4 should be fine if your
4672	board designers haven't used it for something that would
4673	cause you grief during the initial boot! It is frequently not
4674	used.
4675
4676	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4677	with your processor/board/system design. The default value
4678	you will find in any recent u-boot distribution in
4679	walnut.h should work for you. I'd set it to a value larger
4680	than your SDRAM module. If you have a 64MB SDRAM module, set
4681	it above 400_0000. Just make sure your board has no resources
4682	that are supposed to respond to that address! That code in
4683	start.S has been around a while and should work as is when
4684	you get the config right.
4685
4686	-Chris Hallinan
4687	DS4.COM, Inc.
4688
4689It is essential to remember this, since it has some impact on the C
4690code for the initialization procedures:
4691
4692* Initialized global data (data segment) is read-only. Do not attempt
4693  to write it.
4694
4695* Do not use any uninitialized global data (or implicitly initialized
4696  as zero data - BSS segment) at all - this is undefined, initiali-
4697  zation is performed later (when relocating to RAM).
4698
4699* Stack space is very limited. Avoid big data buffers or things like
4700  that.
4701
4702Having only the stack as writable memory limits means we cannot use
4703normal global data to share information between the code. But it
4704turned out that the implementation of U-Boot can be greatly
4705simplified by making a global data structure (gd_t) available to all
4706functions. We could pass a pointer to this data as argument to _all_
4707functions, but this would bloat the code. Instead we use a feature of
4708the GCC compiler (Global Register Variables) to share the data: we
4709place a pointer (gd) to the global data into a register which we
4710reserve for this purpose.
4711
4712When choosing a register for such a purpose we are restricted by the
4713relevant  (E)ABI  specifications for the current architecture, and by
4714GCC's implementation.
4715
4716For PowerPC, the following registers have specific use:
4717	R1:	stack pointer
4718	R2:	reserved for system use
4719	R3-R4:	parameter passing and return values
4720	R5-R10: parameter passing
4721	R13:	small data area pointer
4722	R30:	GOT pointer
4723	R31:	frame pointer
4724
4725	(U-Boot also uses R12 as internal GOT pointer. r12
4726	is a volatile register so r12 needs to be reset when
4727	going back and forth between asm and C)
4728
4729    ==> U-Boot will use R2 to hold a pointer to the global data
4730
4731    Note: on PPC, we could use a static initializer (since the
4732    address of the global data structure is known at compile time),
4733    but it turned out that reserving a register results in somewhat
4734    smaller code - although the code savings are not that big (on
4735    average for all boards 752 bytes for the whole U-Boot image,
4736    624 text + 127 data).
4737
4738On ARM, the following registers are used:
4739
4740	R0:	function argument word/integer result
4741	R1-R3:	function argument word
4742	R9:	platform specific
4743	R10:	stack limit (used only if stack checking is enabled)
4744	R11:	argument (frame) pointer
4745	R12:	temporary workspace
4746	R13:	stack pointer
4747	R14:	link register
4748	R15:	program counter
4749
4750    ==> U-Boot will use R9 to hold a pointer to the global data
4751
4752    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4753
4754On Nios II, the ABI is documented here:
4755	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4756
4757    ==> U-Boot will use gp to hold a pointer to the global data
4758
4759    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4760    to access small data sections, so gp is free.
4761
4762On NDS32, the following registers are used:
4763
4764	R0-R1:	argument/return
4765	R2-R5:	argument
4766	R15:	temporary register for assembler
4767	R16:	trampoline register
4768	R28:	frame pointer (FP)
4769	R29:	global pointer (GP)
4770	R30:	link register (LP)
4771	R31:	stack pointer (SP)
4772	PC:	program counter (PC)
4773
4774    ==> U-Boot will use R10 to hold a pointer to the global data
4775
4776NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4777or current versions of GCC may "optimize" the code too much.
4778
4779On RISC-V, the following registers are used:
4780
4781	x0: hard-wired zero (zero)
4782	x1: return address (ra)
4783	x2:	stack pointer (sp)
4784	x3:	global pointer (gp)
4785	x4:	thread pointer (tp)
4786	x5:	link register (t0)
4787	x8:	frame pointer (fp)
4788	x10-x11:	arguments/return values (a0-1)
4789	x12-x17:	arguments (a2-7)
4790	x28-31:	 temporaries (t3-6)
4791	pc:	program counter (pc)
4792
4793    ==> U-Boot will use gp to hold a pointer to the global data
4794
4795Memory Management:
4796------------------
4797
4798U-Boot runs in system state and uses physical addresses, i.e. the
4799MMU is not used either for address mapping nor for memory protection.
4800
4801The available memory is mapped to fixed addresses using the memory
4802controller. In this process, a contiguous block is formed for each
4803memory type (Flash, SDRAM, SRAM), even when it consists of several
4804physical memory banks.
4805
4806U-Boot is installed in the first 128 kB of the first Flash bank (on
4807TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4808booting and sizing and initializing DRAM, the code relocates itself
4809to the upper end of DRAM. Immediately below the U-Boot code some
4810memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4811configuration setting]. Below that, a structure with global Board
4812Info data is placed, followed by the stack (growing downward).
4813
4814Additionally, some exception handler code is copied to the low 8 kB
4815of DRAM (0x00000000 ... 0x00001FFF).
4816
4817So a typical memory configuration with 16 MB of DRAM could look like
4818this:
4819
4820	0x0000 0000	Exception Vector code
4821	      :
4822	0x0000 1FFF
4823	0x0000 2000	Free for Application Use
4824	      :
4825	      :
4826
4827	      :
4828	      :
4829	0x00FB FF20	Monitor Stack (Growing downward)
4830	0x00FB FFAC	Board Info Data and permanent copy of global data
4831	0x00FC 0000	Malloc Arena
4832	      :
4833	0x00FD FFFF
4834	0x00FE 0000	RAM Copy of Monitor Code
4835	...		eventually: LCD or video framebuffer
4836	...		eventually: pRAM (Protected RAM - unchanged by reset)
4837	0x00FF FFFF	[End of RAM]
4838
4839
4840System Initialization:
4841----------------------
4842
4843In the reset configuration, U-Boot starts at the reset entry point
4844(on most PowerPC systems at address 0x00000100). Because of the reset
4845configuration for CS0# this is a mirror of the on board Flash memory.
4846To be able to re-map memory U-Boot then jumps to its link address.
4847To be able to implement the initialization code in C, a (small!)
4848initial stack is set up in the internal Dual Ported RAM (in case CPUs
4849which provide such a feature like), or in a locked part of the data
4850cache. After that, U-Boot initializes the CPU core, the caches and
4851the SIU.
4852
4853Next, all (potentially) available memory banks are mapped using a
4854preliminary mapping. For example, we put them on 512 MB boundaries
4855(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4856on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4857programmed for SDRAM access. Using the temporary configuration, a
4858simple memory test is run that determines the size of the SDRAM
4859banks.
4860
4861When there is more than one SDRAM bank, and the banks are of
4862different size, the largest is mapped first. For equal size, the first
4863bank (CS2#) is mapped first. The first mapping is always for address
48640x00000000, with any additional banks following immediately to create
4865contiguous memory starting from 0.
4866
4867Then, the monitor installs itself at the upper end of the SDRAM area
4868and allocates memory for use by malloc() and for the global Board
4869Info data; also, the exception vector code is copied to the low RAM
4870pages, and the final stack is set up.
4871
4872Only after this relocation will you have a "normal" C environment;
4873until that you are restricted in several ways, mostly because you are
4874running from ROM, and because the code will have to be relocated to a
4875new address in RAM.
4876
4877
4878U-Boot Porting Guide:
4879----------------------
4880
4881[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4882list, October 2002]
4883
4884
4885int main(int argc, char *argv[])
4886{
4887	sighandler_t no_more_time;
4888
4889	signal(SIGALRM, no_more_time);
4890	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4891
4892	if (available_money > available_manpower) {
4893		Pay consultant to port U-Boot;
4894		return 0;
4895	}
4896
4897	Download latest U-Boot source;
4898
4899	Subscribe to u-boot mailing list;
4900
4901	if (clueless)
4902		email("Hi, I am new to U-Boot, how do I get started?");
4903
4904	while (learning) {
4905		Read the README file in the top level directory;
4906		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4907		Read applicable doc/*.README;
4908		Read the source, Luke;
4909		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4910	}
4911
4912	if (available_money > toLocalCurrency ($2500))
4913		Buy a BDI3000;
4914	else
4915		Add a lot of aggravation and time;
4916
4917	if (a similar board exists) {	/* hopefully... */
4918		cp -a board/<similar> board/<myboard>
4919		cp include/configs/<similar>.h include/configs/<myboard>.h
4920	} else {
4921		Create your own board support subdirectory;
4922		Create your own board include/configs/<myboard>.h file;
4923	}
4924	Edit new board/<myboard> files
4925	Edit new include/configs/<myboard>.h
4926
4927	while (!accepted) {
4928		while (!running) {
4929			do {
4930				Add / modify source code;
4931			} until (compiles);
4932			Debug;
4933			if (clueless)
4934				email("Hi, I am having problems...");
4935		}
4936		Send patch file to the U-Boot email list;
4937		if (reasonable critiques)
4938			Incorporate improvements from email list code review;
4939		else
4940			Defend code as written;
4941	}
4942
4943	return 0;
4944}
4945
4946void no_more_time (int sig)
4947{
4948      hire_a_guru();
4949}
4950
4951
4952Coding Standards:
4953-----------------
4954
4955All contributions to U-Boot should conform to the Linux kernel
4956coding style; see the kernel coding style guide at
4957https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4958script "scripts/Lindent" in your Linux kernel source directory.
4959
4960Source files originating from a different project (for example the
4961MTD subsystem) are generally exempt from these guidelines and are not
4962reformatted to ease subsequent migration to newer versions of those
4963sources.
4964
4965Please note that U-Boot is implemented in C (and to some small parts in
4966Assembler); no C++ is used, so please do not use C++ style comments (//)
4967in your code.
4968
4969Please also stick to the following formatting rules:
4970- remove any trailing white space
4971- use TAB characters for indentation and vertical alignment, not spaces
4972- make sure NOT to use DOS '\r\n' line feeds
4973- do not add more than 2 consecutive empty lines to source files
4974- do not add trailing empty lines to source files
4975
4976Submissions which do not conform to the standards may be returned
4977with a request to reformat the changes.
4978
4979
4980Submitting Patches:
4981-------------------
4982
4983Since the number of patches for U-Boot is growing, we need to
4984establish some rules. Submissions which do not conform to these rules
4985may be rejected, even when they contain important and valuable stuff.
4986
4987Please see http://www.denx.de/wiki/U-Boot/Patches for details.
4988
4989Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4990see https://lists.denx.de/listinfo/u-boot
4991
4992When you send a patch, please include the following information with
4993it:
4994
4995* For bug fixes: a description of the bug and how your patch fixes
4996  this bug. Please try to include a way of demonstrating that the
4997  patch actually fixes something.
4998
4999* For new features: a description of the feature and your
5000  implementation.
5001
5002* A CHANGELOG entry as plaintext (separate from the patch)
5003
5004* For major contributions, add a MAINTAINERS file with your
5005  information and associated file and directory references.
5006
5007* When you add support for a new board, don't forget to add a
5008  maintainer e-mail address to the boards.cfg file, too.
5009
5010* If your patch adds new configuration options, don't forget to
5011  document these in the README file.
5012
5013* The patch itself. If you are using git (which is *strongly*
5014  recommended) you can easily generate the patch using the
5015  "git format-patch". If you then use "git send-email" to send it to
5016  the U-Boot mailing list, you will avoid most of the common problems
5017  with some other mail clients.
5018
5019  If you cannot use git, use "diff -purN OLD NEW". If your version of
5020  diff does not support these options, then get the latest version of
5021  GNU diff.
5022
5023  The current directory when running this command shall be the parent
5024  directory of the U-Boot source tree (i. e. please make sure that
5025  your patch includes sufficient directory information for the
5026  affected files).
5027
5028  We prefer patches as plain text. MIME attachments are discouraged,
5029  and compressed attachments must not be used.
5030
5031* If one logical set of modifications affects or creates several
5032  files, all these changes shall be submitted in a SINGLE patch file.
5033
5034* Changesets that contain different, unrelated modifications shall be
5035  submitted as SEPARATE patches, one patch per changeset.
5036
5037
5038Notes:
5039
5040* Before sending the patch, run the buildman script on your patched
5041  source tree and make sure that no errors or warnings are reported
5042  for any of the boards.
5043
5044* Keep your modifications to the necessary minimum: A patch
5045  containing several unrelated changes or arbitrary reformats will be
5046  returned with a request to re-formatting / split it.
5047
5048* If you modify existing code, make sure that your new code does not
5049  add to the memory footprint of the code ;-) Small is beautiful!
5050  When adding new features, these should compile conditionally only
5051  (using #ifdef), and the resulting code with the new feature
5052  disabled must not need more memory than the old code without your
5053  modification.
5054
5055* Remember that there is a size limit of 100 kB per message on the
5056  u-boot mailing list. Bigger patches will be moderated. If they are
5057  reasonable and not too big, they will be acknowledged. But patches
5058  bigger than the size limit should be avoided.
5059