xref: /openbmc/u-boot/README (revision 60853a9b)
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_NAND
1150		This enables support for exposing NAND devices via DFU.
1151
1152		CONFIG_DFU_RAM
1153		This enables support for exposing RAM via DFU.
1154		Note: DFU spec refer to non-volatile memory usage, but
1155		allow usages beyond the scope of spec - here RAM usage,
1156		one that would help mostly the developer.
1157
1158		CONFIG_SYS_DFU_DATA_BUF_SIZE
1159		Dfu transfer uses a buffer before writing data to the
1160		raw storage device. Make the size (in bytes) of this buffer
1161		configurable. The size of this buffer is also configurable
1162		through the "dfu_bufsiz" environment variable.
1163
1164		CONFIG_SYS_DFU_MAX_FILE_SIZE
1165		When updating files rather than the raw storage device,
1166		we use a static buffer to copy the file into and then write
1167		the buffer once we've been given the whole file.  Define
1168		this to the maximum filesize (in bytes) for the buffer.
1169		Default is 4 MiB if undefined.
1170
1171		DFU_DEFAULT_POLL_TIMEOUT
1172		Poll timeout [ms], is the timeout a device can send to the
1173		host. The host must wait for this timeout before sending
1174		a subsequent DFU_GET_STATUS request to the device.
1175
1176		DFU_MANIFEST_POLL_TIMEOUT
1177		Poll timeout [ms], which the device sends to the host when
1178		entering dfuMANIFEST state. Host waits this timeout, before
1179		sending again an USB request to the device.
1180
1181- Journaling Flash filesystem support:
1182		CONFIG_JFFS2_NAND
1183		Define these for a default partition on a NAND device
1184
1185		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1186		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1187		Define these for a default partition on a NOR device
1188
1189- Keyboard Support:
1190		See Kconfig help for available keyboard drivers.
1191
1192		CONFIG_KEYBOARD
1193
1194		Define this to enable a custom keyboard support.
1195		This simply calls drv_keyboard_init() which must be
1196		defined in your board-specific files. This option is deprecated
1197		and is only used by novena. For new boards, use driver model
1198		instead.
1199
1200- Video support:
1201		CONFIG_FSL_DIU_FB
1202		Enable the Freescale DIU video driver.	Reference boards for
1203		SOCs that have a DIU should define this macro to enable DIU
1204		support, and should also define these other macros:
1205
1206			CONFIG_SYS_DIU_ADDR
1207			CONFIG_VIDEO
1208			CONFIG_CFB_CONSOLE
1209			CONFIG_VIDEO_SW_CURSOR
1210			CONFIG_VGA_AS_SINGLE_DEVICE
1211			CONFIG_VIDEO_LOGO
1212			CONFIG_VIDEO_BMP_LOGO
1213
1214		The DIU driver will look for the 'video-mode' environment
1215		variable, and if defined, enable the DIU as a console during
1216		boot.  See the documentation file doc/README.video for a
1217		description of this variable.
1218
1219- LCD Support:	CONFIG_LCD
1220
1221		Define this to enable LCD support (for output to LCD
1222		display); also select one of the supported displays
1223		by defining one of these:
1224
1225		CONFIG_ATMEL_LCD:
1226
1227			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1228
1229		CONFIG_NEC_NL6448AC33:
1230
1231			NEC NL6448AC33-18. Active, color, single scan.
1232
1233		CONFIG_NEC_NL6448BC20
1234
1235			NEC NL6448BC20-08. 6.5", 640x480.
1236			Active, color, single scan.
1237
1238		CONFIG_NEC_NL6448BC33_54
1239
1240			NEC NL6448BC33-54. 10.4", 640x480.
1241			Active, color, single scan.
1242
1243		CONFIG_SHARP_16x9
1244
1245			Sharp 320x240. Active, color, single scan.
1246			It isn't 16x9, and I am not sure what it is.
1247
1248		CONFIG_SHARP_LQ64D341
1249
1250			Sharp LQ64D341 display, 640x480.
1251			Active, color, single scan.
1252
1253		CONFIG_HLD1045
1254
1255			HLD1045 display, 640x480.
1256			Active, color, single scan.
1257
1258		CONFIG_OPTREX_BW
1259
1260			Optrex	 CBL50840-2 NF-FW 99 22 M5
1261			or
1262			Hitachi	 LMG6912RPFC-00T
1263			or
1264			Hitachi	 SP14Q002
1265
1266			320x240. Black & white.
1267
1268		CONFIG_LCD_ALIGNMENT
1269
1270		Normally the LCD is page-aligned (typically 4KB). If this is
1271		defined then the LCD will be aligned to this value instead.
1272		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1273		here, since it is cheaper to change data cache settings on
1274		a per-section basis.
1275
1276
1277		CONFIG_LCD_ROTATION
1278
1279		Sometimes, for example if the display is mounted in portrait
1280		mode or even if it's mounted landscape but rotated by 180degree,
1281		we need to rotate our content of the display relative to the
1282		framebuffer, so that user can read the messages which are
1283		printed out.
1284		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1285		initialized with a given rotation from "vl_rot" out of
1286		"vidinfo_t" which is provided by the board specific code.
1287		The value for vl_rot is coded as following (matching to
1288		fbcon=rotate:<n> linux-kernel commandline):
1289		0 = no rotation respectively 0 degree
1290		1 = 90 degree rotation
1291		2 = 180 degree rotation
1292		3 = 270 degree rotation
1293
1294		If CONFIG_LCD_ROTATION is not defined, the console will be
1295		initialized with 0degree rotation.
1296
1297		CONFIG_LCD_BMP_RLE8
1298
1299		Support drawing of RLE8-compressed bitmaps on the LCD.
1300
1301		CONFIG_I2C_EDID
1302
1303		Enables an 'i2c edid' command which can read EDID
1304		information over I2C from an attached LCD display.
1305
1306- Splash Screen Support: CONFIG_SPLASH_SCREEN
1307
1308		If this option is set, the environment is checked for
1309		a variable "splashimage". If found, the usual display
1310		of logo, copyright and system information on the LCD
1311		is suppressed and the BMP image at the address
1312		specified in "splashimage" is loaded instead. The
1313		console is redirected to the "nulldev", too. This
1314		allows for a "silent" boot where a splash screen is
1315		loaded very quickly after power-on.
1316
1317		CONFIG_SPLASHIMAGE_GUARD
1318
1319		If this option is set, then U-Boot will prevent the environment
1320		variable "splashimage" from being set to a problematic address
1321		(see doc/README.displaying-bmps).
1322		This option is useful for targets where, due to alignment
1323		restrictions, an improperly aligned BMP image will cause a data
1324		abort. If you think you will not have problems with unaligned
1325		accesses (for example because your toolchain prevents them)
1326		there is no need to set this option.
1327
1328		CONFIG_SPLASH_SCREEN_ALIGN
1329
1330		If this option is set the splash image can be freely positioned
1331		on the screen. Environment variable "splashpos" specifies the
1332		position as "x,y". If a positive number is given it is used as
1333		number of pixel from left/top. If a negative number is given it
1334		is used as number of pixel from right/bottom. You can also
1335		specify 'm' for centering the image.
1336
1337		Example:
1338		setenv splashpos m,m
1339			=> image at center of screen
1340
1341		setenv splashpos 30,20
1342			=> image at x = 30 and y = 20
1343
1344		setenv splashpos -10,m
1345			=> vertically centered image
1346			   at x = dspWidth - bmpWidth - 9
1347
1348- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1349
1350		If this option is set, additionally to standard BMP
1351		images, gzipped BMP images can be displayed via the
1352		splashscreen support or the bmp command.
1353
1354- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1355
1356		If this option is set, 8-bit RLE compressed BMP images
1357		can be displayed via the splashscreen support or the
1358		bmp command.
1359
1360- Compression support:
1361		CONFIG_GZIP
1362
1363		Enabled by default to support gzip compressed images.
1364
1365		CONFIG_BZIP2
1366
1367		If this option is set, support for bzip2 compressed
1368		images is included. If not, only uncompressed and gzip
1369		compressed images are supported.
1370
1371		NOTE: the bzip2 algorithm requires a lot of RAM, so
1372		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1373		be at least 4MB.
1374
1375- MII/PHY support:
1376		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1377
1378		The clock frequency of the MII bus
1379
1380		CONFIG_PHY_RESET_DELAY
1381
1382		Some PHY like Intel LXT971A need extra delay after
1383		reset before any MII register access is possible.
1384		For such PHY, set this option to the usec delay
1385		required. (minimum 300usec for LXT971A)
1386
1387		CONFIG_PHY_CMD_DELAY (ppc4xx)
1388
1389		Some PHY like Intel LXT971A need extra delay after
1390		command issued before MII status register can be read
1391
1392- IP address:
1393		CONFIG_IPADDR
1394
1395		Define a default value for the IP address to use for
1396		the default Ethernet interface, in case this is not
1397		determined through e.g. bootp.
1398		(Environment variable "ipaddr")
1399
1400- Server IP address:
1401		CONFIG_SERVERIP
1402
1403		Defines a default value for the IP address of a TFTP
1404		server to contact when using the "tftboot" command.
1405		(Environment variable "serverip")
1406
1407		CONFIG_KEEP_SERVERADDR
1408
1409		Keeps the server's MAC address, in the env 'serveraddr'
1410		for passing to bootargs (like Linux's netconsole option)
1411
1412- Gateway IP address:
1413		CONFIG_GATEWAYIP
1414
1415		Defines a default value for the IP address of the
1416		default router where packets to other networks are
1417		sent to.
1418		(Environment variable "gatewayip")
1419
1420- Subnet mask:
1421		CONFIG_NETMASK
1422
1423		Defines a default value for the subnet mask (or
1424		routing prefix) which is used to determine if an IP
1425		address belongs to the local subnet or needs to be
1426		forwarded through a router.
1427		(Environment variable "netmask")
1428
1429- BOOTP Recovery Mode:
1430		CONFIG_BOOTP_RANDOM_DELAY
1431
1432		If you have many targets in a network that try to
1433		boot using BOOTP, you may want to avoid that all
1434		systems send out BOOTP requests at precisely the same
1435		moment (which would happen for instance at recovery
1436		from a power failure, when all systems will try to
1437		boot, thus flooding the BOOTP server. Defining
1438		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1439		inserted before sending out BOOTP requests. The
1440		following delays are inserted then:
1441
1442		1st BOOTP request:	delay 0 ... 1 sec
1443		2nd BOOTP request:	delay 0 ... 2 sec
1444		3rd BOOTP request:	delay 0 ... 4 sec
1445		4th and following
1446		BOOTP requests:		delay 0 ... 8 sec
1447
1448		CONFIG_BOOTP_ID_CACHE_SIZE
1449
1450		BOOTP packets are uniquely identified using a 32-bit ID. The
1451		server will copy the ID from client requests to responses and
1452		U-Boot will use this to determine if it is the destination of
1453		an incoming response. Some servers will check that addresses
1454		aren't in use before handing them out (usually using an ARP
1455		ping) and therefore take up to a few hundred milliseconds to
1456		respond. Network congestion may also influence the time it
1457		takes for a response to make it back to the client. If that
1458		time is too long, U-Boot will retransmit requests. In order
1459		to allow earlier responses to still be accepted after these
1460		retransmissions, U-Boot's BOOTP client keeps a small cache of
1461		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1462		cache. The default is to keep IDs for up to four outstanding
1463		requests. Increasing this will allow U-Boot to accept offers
1464		from a BOOTP client in networks with unusually high latency.
1465
1466- DHCP Advanced Options:
1467		You can fine tune the DHCP functionality by defining
1468		CONFIG_BOOTP_* symbols:
1469
1470		CONFIG_BOOTP_NISDOMAIN
1471		CONFIG_BOOTP_BOOTFILESIZE
1472		CONFIG_BOOTP_SEND_HOSTNAME
1473		CONFIG_BOOTP_NTPSERVER
1474		CONFIG_BOOTP_TIMEOFFSET
1475		CONFIG_BOOTP_VENDOREX
1476		CONFIG_BOOTP_MAY_FAIL
1477
1478		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1479		environment variable, not the BOOTP server.
1480
1481		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1482		after the configured retry count, the call will fail
1483		instead of starting over.  This can be used to fail over
1484		to Link-local IP address configuration if the DHCP server
1485		is not available.
1486
1487		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1488		to do a dynamic update of a DNS server. To do this, they
1489		need the hostname of the DHCP requester.
1490		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1491		of the "hostname" environment variable is passed as
1492		option 12 to the DHCP server.
1493
1494		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1495
1496		A 32bit value in microseconds for a delay between
1497		receiving a "DHCP Offer" and sending the "DHCP Request".
1498		This fixes a problem with certain DHCP servers that don't
1499		respond 100% of the time to a "DHCP request". E.g. On an
1500		AT91RM9200 processor running at 180MHz, this delay needed
1501		to be *at least* 15,000 usec before a Windows Server 2003
1502		DHCP server would reply 100% of the time. I recommend at
1503		least 50,000 usec to be safe. The alternative is to hope
1504		that one of the retries will be successful but note that
1505		the DHCP timeout and retry process takes a longer than
1506		this delay.
1507
1508 - Link-local IP address negotiation:
1509		Negotiate with other link-local clients on the local network
1510		for an address that doesn't require explicit configuration.
1511		This is especially useful if a DHCP server cannot be guaranteed
1512		to exist in all environments that the device must operate.
1513
1514		See doc/README.link-local for more information.
1515
1516 - MAC address from environment variables
1517
1518		FDT_SEQ_MACADDR_FROM_ENV
1519
1520		Fix-up device tree with MAC addresses fetched sequentially from
1521		environment variables. This config work on assumption that
1522		non-usable ethernet node of device-tree are either not present
1523		or their status has been marked as "disabled".
1524
1525 - CDP Options:
1526		CONFIG_CDP_DEVICE_ID
1527
1528		The device id used in CDP trigger frames.
1529
1530		CONFIG_CDP_DEVICE_ID_PREFIX
1531
1532		A two character string which is prefixed to the MAC address
1533		of the device.
1534
1535		CONFIG_CDP_PORT_ID
1536
1537		A printf format string which contains the ascii name of
1538		the port. Normally is set to "eth%d" which sets
1539		eth0 for the first Ethernet, eth1 for the second etc.
1540
1541		CONFIG_CDP_CAPABILITIES
1542
1543		A 32bit integer which indicates the device capabilities;
1544		0x00000010 for a normal host which does not forwards.
1545
1546		CONFIG_CDP_VERSION
1547
1548		An ascii string containing the version of the software.
1549
1550		CONFIG_CDP_PLATFORM
1551
1552		An ascii string containing the name of the platform.
1553
1554		CONFIG_CDP_TRIGGER
1555
1556		A 32bit integer sent on the trigger.
1557
1558		CONFIG_CDP_POWER_CONSUMPTION
1559
1560		A 16bit integer containing the power consumption of the
1561		device in .1 of milliwatts.
1562
1563		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1564
1565		A byte containing the id of the VLAN.
1566
1567- Status LED:	CONFIG_LED_STATUS
1568
1569		Several configurations allow to display the current
1570		status using a LED. For instance, the LED will blink
1571		fast while running U-Boot code, stop blinking as
1572		soon as a reply to a BOOTP request was received, and
1573		start blinking slow once the Linux kernel is running
1574		(supported by a status LED driver in the Linux
1575		kernel). Defining CONFIG_LED_STATUS enables this
1576		feature in U-Boot.
1577
1578		Additional options:
1579
1580		CONFIG_LED_STATUS_GPIO
1581		The status LED can be connected to a GPIO pin.
1582		In such cases, the gpio_led driver can be used as a
1583		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1584		to include the gpio_led driver in the U-Boot binary.
1585
1586		CONFIG_GPIO_LED_INVERTED_TABLE
1587		Some GPIO connected LEDs may have inverted polarity in which
1588		case the GPIO high value corresponds to LED off state and
1589		GPIO low value corresponds to LED on state.
1590		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1591		with a list of GPIO LEDs that have inverted polarity.
1592
1593- I2C Support:	CONFIG_SYS_I2C
1594
1595		This enable the NEW i2c subsystem, and will allow you to use
1596		i2c commands at the u-boot command line (as long as you set
1597		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1598		based realtime clock chips or other i2c devices. See
1599		common/cmd_i2c.c for a description of the command line
1600		interface.
1601
1602		ported i2c driver to the new framework:
1603		- drivers/i2c/soft_i2c.c:
1604		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1605		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1606		    for defining speed and slave address
1607		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1608		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1609		    for defining speed and slave address
1610		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1611		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1612		    for defining speed and slave address
1613		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1614		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1615		    for defining speed and slave address
1616
1617		- drivers/i2c/fsl_i2c.c:
1618		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1619		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1620		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1621		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1622		    bus.
1623		  - If your board supports a second fsl i2c bus, define
1624		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1625		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1626		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1627		    second bus.
1628
1629		- drivers/i2c/tegra_i2c.c:
1630		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1631		  - This driver adds 4 i2c buses with a fix speed from
1632		    100000 and the slave addr 0!
1633
1634		- drivers/i2c/ppc4xx_i2c.c
1635		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1636		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1637		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1638
1639		- drivers/i2c/i2c_mxc.c
1640		  - activate this driver with CONFIG_SYS_I2C_MXC
1641		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1642		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1643		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1644		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1645		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1646		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1647		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1648		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1649		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1650		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1651		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1652		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1653		If those defines are not set, default value is 100000
1654		for speed, and 0 for slave.
1655
1656		- drivers/i2c/rcar_i2c.c:
1657		  - activate this driver with CONFIG_SYS_I2C_RCAR
1658		  - This driver adds 4 i2c buses
1659
1660		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1661		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1662		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1663		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1664		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1665		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1666		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1667		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1668		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1669
1670		- drivers/i2c/sh_i2c.c:
1671		  - activate this driver with CONFIG_SYS_I2C_SH
1672		  - This driver adds from 2 to 5 i2c buses
1673
1674		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1675		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1676		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1677		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1678		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1679		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1680		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1681		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1682		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1683		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1684		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1685
1686		- drivers/i2c/omap24xx_i2c.c
1687		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1688		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1689		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1690		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1691		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1692		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1693		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1694		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1695		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1696		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1697		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1698
1699		- drivers/i2c/zynq_i2c.c
1700		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1701		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1702		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1703
1704		- drivers/i2c/s3c24x0_i2c.c:
1705		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1706		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1707		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1708		    with a fix speed from 100000 and the slave addr 0!
1709
1710		- drivers/i2c/ihs_i2c.c
1711		  - activate this driver with CONFIG_SYS_I2C_IHS
1712		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1713		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1714		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1715		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1716		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1717		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1718		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1719		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1720		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1721		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1722		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1723		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1724		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1725		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1726		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1727		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1728		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1729		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1730		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1731		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1732		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1733
1734		additional defines:
1735
1736		CONFIG_SYS_NUM_I2C_BUSES
1737		Hold the number of i2c buses you want to use.
1738
1739		CONFIG_SYS_I2C_DIRECT_BUS
1740		define this, if you don't use i2c muxes on your hardware.
1741		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1742		omit this define.
1743
1744		CONFIG_SYS_I2C_MAX_HOPS
1745		define how many muxes are maximal consecutively connected
1746		on one i2c bus. If you not use i2c muxes, omit this
1747		define.
1748
1749		CONFIG_SYS_I2C_BUSES
1750		hold a list of buses you want to use, only used if
1751		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1752		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1753		CONFIG_SYS_NUM_I2C_BUSES = 9:
1754
1755		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1756					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1757					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1758					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1759					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1760					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1761					{1, {I2C_NULL_HOP}}, \
1762					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1763					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1764					}
1765
1766		which defines
1767			bus 0 on adapter 0 without a mux
1768			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1769			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1770			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1771			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1772			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1773			bus 6 on adapter 1 without a mux
1774			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1775			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1776
1777		If you do not have i2c muxes on your board, omit this define.
1778
1779- Legacy I2C Support:
1780		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1781		then the following macros need to be defined (examples are
1782		from include/configs/lwmon.h):
1783
1784		I2C_INIT
1785
1786		(Optional). Any commands necessary to enable the I2C
1787		controller or configure ports.
1788
1789		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1790
1791		I2C_ACTIVE
1792
1793		The code necessary to make the I2C data line active
1794		(driven).  If the data line is open collector, this
1795		define can be null.
1796
1797		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1798
1799		I2C_TRISTATE
1800
1801		The code necessary to make the I2C data line tri-stated
1802		(inactive).  If the data line is open collector, this
1803		define can be null.
1804
1805		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1806
1807		I2C_READ
1808
1809		Code that returns true if the I2C data line is high,
1810		false if it is low.
1811
1812		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1813
1814		I2C_SDA(bit)
1815
1816		If <bit> is true, sets the I2C data line high. If it
1817		is false, it clears it (low).
1818
1819		eg: #define I2C_SDA(bit) \
1820			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1821			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1822
1823		I2C_SCL(bit)
1824
1825		If <bit> is true, sets the I2C clock line high. If it
1826		is false, it clears it (low).
1827
1828		eg: #define I2C_SCL(bit) \
1829			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1830			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1831
1832		I2C_DELAY
1833
1834		This delay is invoked four times per clock cycle so this
1835		controls the rate of data transfer.  The data rate thus
1836		is 1 / (I2C_DELAY * 4). Often defined to be something
1837		like:
1838
1839		#define I2C_DELAY  udelay(2)
1840
1841		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1842
1843		If your arch supports the generic GPIO framework (asm/gpio.h),
1844		then you may alternatively define the two GPIOs that are to be
1845		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1846		have GPIO-based defaults assigned to them as appropriate.
1847
1848		You should define these to the GPIO value as given directly to
1849		the generic GPIO functions.
1850
1851		CONFIG_SYS_I2C_INIT_BOARD
1852
1853		When a board is reset during an i2c bus transfer
1854		chips might think that the current transfer is still
1855		in progress. On some boards it is possible to access
1856		the i2c SCLK line directly, either by using the
1857		processor pin as a GPIO or by having a second pin
1858		connected to the bus. If this option is defined a
1859		custom i2c_init_board() routine in boards/xxx/board.c
1860		is run early in the boot sequence.
1861
1862		CONFIG_I2C_MULTI_BUS
1863
1864		This option allows the use of multiple I2C buses, each of which
1865		must have a controller.	 At any point in time, only one bus is
1866		active.	 To switch to a different bus, use the 'i2c dev' command.
1867		Note that bus numbering is zero-based.
1868
1869		CONFIG_SYS_I2C_NOPROBES
1870
1871		This option specifies a list of I2C devices that will be skipped
1872		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1873		is set, specify a list of bus-device pairs.  Otherwise, specify
1874		a 1D array of device addresses
1875
1876		e.g.
1877			#undef	CONFIG_I2C_MULTI_BUS
1878			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1879
1880		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1881
1882			#define CONFIG_I2C_MULTI_BUS
1883			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1884
1885		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1886
1887		CONFIG_SYS_SPD_BUS_NUM
1888
1889		If defined, then this indicates the I2C bus number for DDR SPD.
1890		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1891
1892		CONFIG_SYS_RTC_BUS_NUM
1893
1894		If defined, then this indicates the I2C bus number for the RTC.
1895		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1896
1897		CONFIG_SOFT_I2C_READ_REPEATED_START
1898
1899		defining this will force the i2c_read() function in
1900		the soft_i2c driver to perform an I2C repeated start
1901		between writing the address pointer and reading the
1902		data.  If this define is omitted the default behaviour
1903		of doing a stop-start sequence will be used.  Most I2C
1904		devices can use either method, but some require one or
1905		the other.
1906
1907- SPI Support:	CONFIG_SPI
1908
1909		Enables SPI driver (so far only tested with
1910		SPI EEPROM, also an instance works with Crystal A/D and
1911		D/As on the SACSng board)
1912
1913		CONFIG_SOFT_SPI
1914
1915		Enables a software (bit-bang) SPI driver rather than
1916		using hardware support. This is a general purpose
1917		driver that only requires three general I/O port pins
1918		(two outputs, one input) to function. If this is
1919		defined, the board configuration must define several
1920		SPI configuration items (port pins to use, etc). For
1921		an example, see include/configs/sacsng.h.
1922
1923		CONFIG_SYS_SPI_MXC_WAIT
1924		Timeout for waiting until spi transfer completed.
1925		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1926
1927- FPGA Support: CONFIG_FPGA
1928
1929		Enables FPGA subsystem.
1930
1931		CONFIG_FPGA_<vendor>
1932
1933		Enables support for specific chip vendors.
1934		(ALTERA, XILINX)
1935
1936		CONFIG_FPGA_<family>
1937
1938		Enables support for FPGA family.
1939		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1940
1941		CONFIG_FPGA_COUNT
1942
1943		Specify the number of FPGA devices to support.
1944
1945		CONFIG_SYS_FPGA_PROG_FEEDBACK
1946
1947		Enable printing of hash marks during FPGA configuration.
1948
1949		CONFIG_SYS_FPGA_CHECK_BUSY
1950
1951		Enable checks on FPGA configuration interface busy
1952		status by the configuration function. This option
1953		will require a board or device specific function to
1954		be written.
1955
1956		CONFIG_FPGA_DELAY
1957
1958		If defined, a function that provides delays in the FPGA
1959		configuration driver.
1960
1961		CONFIG_SYS_FPGA_CHECK_CTRLC
1962		Allow Control-C to interrupt FPGA configuration
1963
1964		CONFIG_SYS_FPGA_CHECK_ERROR
1965
1966		Check for configuration errors during FPGA bitfile
1967		loading. For example, abort during Virtex II
1968		configuration if the INIT_B line goes low (which
1969		indicated a CRC error).
1970
1971		CONFIG_SYS_FPGA_WAIT_INIT
1972
1973		Maximum time to wait for the INIT_B line to de-assert
1974		after PROB_B has been de-asserted during a Virtex II
1975		FPGA configuration sequence. The default time is 500
1976		ms.
1977
1978		CONFIG_SYS_FPGA_WAIT_BUSY
1979
1980		Maximum time to wait for BUSY to de-assert during
1981		Virtex II FPGA configuration. The default is 5 ms.
1982
1983		CONFIG_SYS_FPGA_WAIT_CONFIG
1984
1985		Time to wait after FPGA configuration. The default is
1986		200 ms.
1987
1988- Configuration Management:
1989		CONFIG_BUILD_TARGET
1990
1991		Some SoCs need special image types (e.g. U-Boot binary
1992		with a special header) as build targets. By defining
1993		CONFIG_BUILD_TARGET in the SoC / board header, this
1994		special image will be automatically built upon calling
1995		make / buildman.
1996
1997		CONFIG_IDENT_STRING
1998
1999		If defined, this string will be added to the U-Boot
2000		version information (U_BOOT_VERSION)
2001
2002- Vendor Parameter Protection:
2003
2004		U-Boot considers the values of the environment
2005		variables "serial#" (Board Serial Number) and
2006		"ethaddr" (Ethernet Address) to be parameters that
2007		are set once by the board vendor / manufacturer, and
2008		protects these variables from casual modification by
2009		the user. Once set, these variables are read-only,
2010		and write or delete attempts are rejected. You can
2011		change this behaviour:
2012
2013		If CONFIG_ENV_OVERWRITE is #defined in your config
2014		file, the write protection for vendor parameters is
2015		completely disabled. Anybody can change or delete
2016		these parameters.
2017
2018		Alternatively, if you define _both_ an ethaddr in the
2019		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2020		Ethernet address is installed in the environment,
2021		which can be changed exactly ONCE by the user. [The
2022		serial# is unaffected by this, i. e. it remains
2023		read-only.]
2024
2025		The same can be accomplished in a more flexible way
2026		for any variable by configuring the type of access
2027		to allow for those variables in the ".flags" variable
2028		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2029
2030- Protected RAM:
2031		CONFIG_PRAM
2032
2033		Define this variable to enable the reservation of
2034		"protected RAM", i. e. RAM which is not overwritten
2035		by U-Boot. Define CONFIG_PRAM to hold the number of
2036		kB you want to reserve for pRAM. You can overwrite
2037		this default value by defining an environment
2038		variable "pram" to the number of kB you want to
2039		reserve. Note that the board info structure will
2040		still show the full amount of RAM. If pRAM is
2041		reserved, a new environment variable "mem" will
2042		automatically be defined to hold the amount of
2043		remaining RAM in a form that can be passed as boot
2044		argument to Linux, for instance like that:
2045
2046			setenv bootargs ... mem=\${mem}
2047			saveenv
2048
2049		This way you can tell Linux not to use this memory,
2050		either, which results in a memory region that will
2051		not be affected by reboots.
2052
2053		*WARNING* If your board configuration uses automatic
2054		detection of the RAM size, you must make sure that
2055		this memory test is non-destructive. So far, the
2056		following board configurations are known to be
2057		"pRAM-clean":
2058
2059			IVMS8, IVML24, SPD8xx,
2060			HERMES, IP860, RPXlite, LWMON,
2061			FLAGADM
2062
2063- Access to physical memory region (> 4GB)
2064		Some basic support is provided for operations on memory not
2065		normally accessible to U-Boot - e.g. some architectures
2066		support access to more than 4GB of memory on 32-bit
2067		machines using physical address extension or similar.
2068		Define CONFIG_PHYSMEM to access this basic support, which
2069		currently only supports clearing the memory.
2070
2071- Error Recovery:
2072		CONFIG_NET_RETRY_COUNT
2073
2074		This variable defines the number of retries for
2075		network operations like ARP, RARP, TFTP, or BOOTP
2076		before giving up the operation. If not defined, a
2077		default value of 5 is used.
2078
2079		CONFIG_ARP_TIMEOUT
2080
2081		Timeout waiting for an ARP reply in milliseconds.
2082
2083		CONFIG_NFS_TIMEOUT
2084
2085		Timeout in milliseconds used in NFS protocol.
2086		If you encounter "ERROR: Cannot umount" in nfs command,
2087		try longer timeout such as
2088		#define CONFIG_NFS_TIMEOUT 10000UL
2089
2090- Command Interpreter:
2091		CONFIG_SYS_PROMPT_HUSH_PS2
2092
2093		This defines the secondary prompt string, which is
2094		printed when the command interpreter needs more input
2095		to complete a command. Usually "> ".
2096
2097	Note:
2098
2099		In the current implementation, the local variables
2100		space and global environment variables space are
2101		separated. Local variables are those you define by
2102		simply typing `name=value'. To access a local
2103		variable later on, you have write `$name' or
2104		`${name}'; to execute the contents of a variable
2105		directly type `$name' at the command prompt.
2106
2107		Global environment variables are those you use
2108		setenv/printenv to work with. To run a command stored
2109		in such a variable, you need to use the run command,
2110		and you must not use the '$' sign to access them.
2111
2112		To store commands and special characters in a
2113		variable, please use double quotation marks
2114		surrounding the whole text of the variable, instead
2115		of the backslashes before semicolons and special
2116		symbols.
2117
2118- Command Line Editing and History:
2119		CONFIG_CMDLINE_PS_SUPPORT
2120
2121		Enable support for changing the command prompt string
2122		at run-time. Only static string is supported so far.
2123		The string is obtained from environment variables PS1
2124		and PS2.
2125
2126- Default Environment:
2127		CONFIG_EXTRA_ENV_SETTINGS
2128
2129		Define this to contain any number of null terminated
2130		strings (variable = value pairs) that will be part of
2131		the default environment compiled into the boot image.
2132
2133		For example, place something like this in your
2134		board's config file:
2135
2136		#define CONFIG_EXTRA_ENV_SETTINGS \
2137			"myvar1=value1\0" \
2138			"myvar2=value2\0"
2139
2140		Warning: This method is based on knowledge about the
2141		internal format how the environment is stored by the
2142		U-Boot code. This is NOT an official, exported
2143		interface! Although it is unlikely that this format
2144		will change soon, there is no guarantee either.
2145		You better know what you are doing here.
2146
2147		Note: overly (ab)use of the default environment is
2148		discouraged. Make sure to check other ways to preset
2149		the environment like the "source" command or the
2150		boot command first.
2151
2152		CONFIG_DELAY_ENVIRONMENT
2153
2154		Normally the environment is loaded when the board is
2155		initialised so that it is available to U-Boot. This inhibits
2156		that so that the environment is not available until
2157		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2158		this is instead controlled by the value of
2159		/config/load-environment.
2160
2161- Serial Flash support
2162		Usage requires an initial 'sf probe' to define the serial
2163		flash parameters, followed by read/write/erase/update
2164		commands.
2165
2166		The following defaults may be provided by the platform
2167		to handle the common case when only a single serial
2168		flash is present on the system.
2169
2170		CONFIG_SF_DEFAULT_BUS		Bus identifier
2171		CONFIG_SF_DEFAULT_CS		Chip-select
2172		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2173		CONFIG_SF_DEFAULT_SPEED		in Hz
2174
2175
2176- TFTP Fixed UDP Port:
2177		CONFIG_TFTP_PORT
2178
2179		If this is defined, the environment variable tftpsrcp
2180		is used to supply the TFTP UDP source port value.
2181		If tftpsrcp isn't defined, the normal pseudo-random port
2182		number generator is used.
2183
2184		Also, the environment variable tftpdstp is used to supply
2185		the TFTP UDP destination port value.  If tftpdstp isn't
2186		defined, the normal port 69 is used.
2187
2188		The purpose for tftpsrcp is to allow a TFTP server to
2189		blindly start the TFTP transfer using the pre-configured
2190		target IP address and UDP port. This has the effect of
2191		"punching through" the (Windows XP) firewall, allowing
2192		the remainder of the TFTP transfer to proceed normally.
2193		A better solution is to properly configure the firewall,
2194		but sometimes that is not allowed.
2195
2196- Show boot progress:
2197		CONFIG_SHOW_BOOT_PROGRESS
2198
2199		Defining this option allows to add some board-
2200		specific code (calling a user-provided function
2201		"show_boot_progress(int)") that enables you to show
2202		the system's boot progress on some display (for
2203		example, some LED's) on your board. At the moment,
2204		the following checkpoints are implemented:
2205
2206
2207Legacy uImage format:
2208
2209  Arg	Where			When
2210    1	common/cmd_bootm.c	before attempting to boot an image
2211   -1	common/cmd_bootm.c	Image header has bad	 magic number
2212    2	common/cmd_bootm.c	Image header has correct magic number
2213   -2	common/cmd_bootm.c	Image header has bad	 checksum
2214    3	common/cmd_bootm.c	Image header has correct checksum
2215   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2216    4	common/cmd_bootm.c	Image data   has correct checksum
2217   -4	common/cmd_bootm.c	Image is for unsupported architecture
2218    5	common/cmd_bootm.c	Architecture check OK
2219   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2220    6	common/cmd_bootm.c	Image Type check OK
2221   -6	common/cmd_bootm.c	gunzip uncompression error
2222   -7	common/cmd_bootm.c	Unimplemented compression type
2223    7	common/cmd_bootm.c	Uncompression OK
2224    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2225   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2226
2227    9	common/image.c		Start initial ramdisk verification
2228  -10	common/image.c		Ramdisk header has bad	   magic number
2229  -11	common/image.c		Ramdisk header has bad	   checksum
2230   10	common/image.c		Ramdisk header is OK
2231  -12	common/image.c		Ramdisk data   has bad	   checksum
2232   11	common/image.c		Ramdisk data   has correct checksum
2233   12	common/image.c		Ramdisk verification complete, start loading
2234  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2235   13	common/image.c		Start multifile image verification
2236   14	common/image.c		No initial ramdisk, no multifile, continue.
2237
2238   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2239
2240  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2241  -31	post/post.c		POST test failed, detected by post_output_backlog()
2242  -32	post/post.c		POST test failed, detected by post_run_single()
2243
2244   34	common/cmd_doc.c	before loading a Image from a DOC device
2245  -35	common/cmd_doc.c	Bad usage of "doc" command
2246   35	common/cmd_doc.c	correct usage of "doc" command
2247  -36	common/cmd_doc.c	No boot device
2248   36	common/cmd_doc.c	correct boot device
2249  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2250   37	common/cmd_doc.c	correct chip ID found, device available
2251  -38	common/cmd_doc.c	Read Error on boot device
2252   38	common/cmd_doc.c	reading Image header from DOC device OK
2253  -39	common/cmd_doc.c	Image header has bad magic number
2254   39	common/cmd_doc.c	Image header has correct magic number
2255  -40	common/cmd_doc.c	Error reading Image from DOC device
2256   40	common/cmd_doc.c	Image header has correct magic number
2257   41	common/cmd_ide.c	before loading a Image from a IDE device
2258  -42	common/cmd_ide.c	Bad usage of "ide" command
2259   42	common/cmd_ide.c	correct usage of "ide" command
2260  -43	common/cmd_ide.c	No boot device
2261   43	common/cmd_ide.c	boot device found
2262  -44	common/cmd_ide.c	Device not available
2263   44	common/cmd_ide.c	Device available
2264  -45	common/cmd_ide.c	wrong partition selected
2265   45	common/cmd_ide.c	partition selected
2266  -46	common/cmd_ide.c	Unknown partition table
2267   46	common/cmd_ide.c	valid partition table found
2268  -47	common/cmd_ide.c	Invalid partition type
2269   47	common/cmd_ide.c	correct partition type
2270  -48	common/cmd_ide.c	Error reading Image Header on boot device
2271   48	common/cmd_ide.c	reading Image Header from IDE device OK
2272  -49	common/cmd_ide.c	Image header has bad magic number
2273   49	common/cmd_ide.c	Image header has correct magic number
2274  -50	common/cmd_ide.c	Image header has bad	 checksum
2275   50	common/cmd_ide.c	Image header has correct checksum
2276  -51	common/cmd_ide.c	Error reading Image from IDE device
2277   51	common/cmd_ide.c	reading Image from IDE device OK
2278   52	common/cmd_nand.c	before loading a Image from a NAND device
2279  -53	common/cmd_nand.c	Bad usage of "nand" command
2280   53	common/cmd_nand.c	correct usage of "nand" command
2281  -54	common/cmd_nand.c	No boot device
2282   54	common/cmd_nand.c	boot device found
2283  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2284   55	common/cmd_nand.c	correct chip ID found, device available
2285  -56	common/cmd_nand.c	Error reading Image Header on boot device
2286   56	common/cmd_nand.c	reading Image Header from NAND device OK
2287  -57	common/cmd_nand.c	Image header has bad magic number
2288   57	common/cmd_nand.c	Image header has correct magic number
2289  -58	common/cmd_nand.c	Error reading Image from NAND device
2290   58	common/cmd_nand.c	reading Image from NAND device OK
2291
2292  -60	common/env_common.c	Environment has a bad CRC, using default
2293
2294   64	net/eth.c		starting with Ethernet configuration.
2295  -64	net/eth.c		no Ethernet found.
2296   65	net/eth.c		Ethernet found.
2297
2298  -80	common/cmd_net.c	usage wrong
2299   80	common/cmd_net.c	before calling net_loop()
2300  -81	common/cmd_net.c	some error in net_loop() occurred
2301   81	common/cmd_net.c	net_loop() back without error
2302  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2303   82	common/cmd_net.c	trying automatic boot
2304   83	common/cmd_net.c	running "source" command
2305  -83	common/cmd_net.c	some error in automatic boot or "source" command
2306   84	common/cmd_net.c	end without errors
2307
2308FIT uImage format:
2309
2310  Arg	Where			When
2311  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2312 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2313  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2314 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2315  102	common/cmd_bootm.c	Kernel unit name specified
2316 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2317  103	common/cmd_bootm.c	Found configuration node
2318  104	common/cmd_bootm.c	Got kernel subimage node offset
2319 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2320  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2321 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2322  106	common/cmd_bootm.c	Architecture check OK
2323 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2324  107	common/cmd_bootm.c	Kernel subimage type OK
2325 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2326  108	common/cmd_bootm.c	Got kernel subimage data/size
2327 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2328 -109	common/cmd_bootm.c	Can't get kernel subimage type
2329 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2330 -111	common/cmd_bootm.c	Can't get kernel subimage os
2331 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2332 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2333
2334  120	common/image.c		Start initial ramdisk verification
2335 -120	common/image.c		Ramdisk FIT image has incorrect format
2336  121	common/image.c		Ramdisk FIT image has correct format
2337  122	common/image.c		No ramdisk subimage unit name, using configuration
2338 -122	common/image.c		Can't get configuration for ramdisk subimage
2339  123	common/image.c		Ramdisk unit name specified
2340 -124	common/image.c		Can't get ramdisk subimage node offset
2341  125	common/image.c		Got ramdisk subimage node offset
2342 -125	common/image.c		Ramdisk subimage hash verification failed
2343  126	common/image.c		Ramdisk subimage hash verification OK
2344 -126	common/image.c		Ramdisk subimage for unsupported architecture
2345  127	common/image.c		Architecture check OK
2346 -127	common/image.c		Can't get ramdisk subimage data/size
2347  128	common/image.c		Got ramdisk subimage data/size
2348  129	common/image.c		Can't get ramdisk load address
2349 -129	common/image.c		Got ramdisk load address
2350
2351 -130	common/cmd_doc.c	Incorrect FIT image format
2352  131	common/cmd_doc.c	FIT image format OK
2353
2354 -140	common/cmd_ide.c	Incorrect FIT image format
2355  141	common/cmd_ide.c	FIT image format OK
2356
2357 -150	common/cmd_nand.c	Incorrect FIT image format
2358  151	common/cmd_nand.c	FIT image format OK
2359
2360- Standalone program support:
2361		CONFIG_STANDALONE_LOAD_ADDR
2362
2363		This option defines a board specific value for the
2364		address where standalone program gets loaded, thus
2365		overwriting the architecture dependent default
2366		settings.
2367
2368- Frame Buffer Address:
2369		CONFIG_FB_ADDR
2370
2371		Define CONFIG_FB_ADDR if you want to use specific
2372		address for frame buffer.  This is typically the case
2373		when using a graphics controller has separate video
2374		memory.  U-Boot will then place the frame buffer at
2375		the given address instead of dynamically reserving it
2376		in system RAM by calling lcd_setmem(), which grabs
2377		the memory for the frame buffer depending on the
2378		configured panel size.
2379
2380		Please see board_init_f function.
2381
2382- Automatic software updates via TFTP server
2383		CONFIG_UPDATE_TFTP
2384		CONFIG_UPDATE_TFTP_CNT_MAX
2385		CONFIG_UPDATE_TFTP_MSEC_MAX
2386
2387		These options enable and control the auto-update feature;
2388		for a more detailed description refer to doc/README.update.
2389
2390- MTD Support (mtdparts command, UBI support)
2391		CONFIG_MTD_UBI_WL_THRESHOLD
2392		This parameter defines the maximum difference between the highest
2393		erase counter value and the lowest erase counter value of eraseblocks
2394		of UBI devices. When this threshold is exceeded, UBI starts performing
2395		wear leveling by means of moving data from eraseblock with low erase
2396		counter to eraseblocks with high erase counter.
2397
2398		The default value should be OK for SLC NAND flashes, NOR flashes and
2399		other flashes which have eraseblock life-cycle 100000 or more.
2400		However, in case of MLC NAND flashes which typically have eraseblock
2401		life-cycle less than 10000, the threshold should be lessened (e.g.,
2402		to 128 or 256, although it does not have to be power of 2).
2403
2404		default: 4096
2405
2406		CONFIG_MTD_UBI_BEB_LIMIT
2407		This option specifies the maximum bad physical eraseblocks UBI
2408		expects on the MTD device (per 1024 eraseblocks). If the
2409		underlying flash does not admit of bad eraseblocks (e.g. NOR
2410		flash), this value is ignored.
2411
2412		NAND datasheets often specify the minimum and maximum NVM
2413		(Number of Valid Blocks) for the flashes' endurance lifetime.
2414		The maximum expected bad eraseblocks per 1024 eraseblocks
2415		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2416		which gives 20 for most NANDs (MaxNVB is basically the total
2417		count of eraseblocks on the chip).
2418
2419		To put it differently, if this value is 20, UBI will try to
2420		reserve about 1.9% of physical eraseblocks for bad blocks
2421		handling. And that will be 1.9% of eraseblocks on the entire
2422		NAND chip, not just the MTD partition UBI attaches. This means
2423		that if you have, say, a NAND flash chip admits maximum 40 bad
2424		eraseblocks, and it is split on two MTD partitions of the same
2425		size, UBI will reserve 40 eraseblocks when attaching a
2426		partition.
2427
2428		default: 20
2429
2430		CONFIG_MTD_UBI_FASTMAP
2431		Fastmap is a mechanism which allows attaching an UBI device
2432		in nearly constant time. Instead of scanning the whole MTD device it
2433		only has to locate a checkpoint (called fastmap) on the device.
2434		The on-flash fastmap contains all information needed to attach
2435		the device. Using fastmap makes only sense on large devices where
2436		attaching by scanning takes long. UBI will not automatically install
2437		a fastmap on old images, but you can set the UBI parameter
2438		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2439		that fastmap-enabled images are still usable with UBI implementations
2440		without	fastmap support. On typical flash devices the whole fastmap
2441		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2442
2443		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2444		Set this parameter to enable fastmap automatically on images
2445		without a fastmap.
2446		default: 0
2447
2448		CONFIG_MTD_UBI_FM_DEBUG
2449		Enable UBI fastmap debug
2450		default: 0
2451
2452- SPL framework
2453		CONFIG_SPL
2454		Enable building of SPL globally.
2455
2456		CONFIG_SPL_LDSCRIPT
2457		LDSCRIPT for linking the SPL binary.
2458
2459		CONFIG_SPL_MAX_FOOTPRINT
2460		Maximum size in memory allocated to the SPL, BSS included.
2461		When defined, the linker checks that the actual memory
2462		used by SPL from _start to __bss_end does not exceed it.
2463		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2464		must not be both defined at the same time.
2465
2466		CONFIG_SPL_MAX_SIZE
2467		Maximum size of the SPL image (text, data, rodata, and
2468		linker lists sections), BSS excluded.
2469		When defined, the linker checks that the actual size does
2470		not exceed it.
2471
2472		CONFIG_SPL_TEXT_BASE
2473		TEXT_BASE for linking the SPL binary.
2474
2475		CONFIG_SPL_RELOC_TEXT_BASE
2476		Address to relocate to.  If unspecified, this is equal to
2477		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2478
2479		CONFIG_SPL_BSS_START_ADDR
2480		Link address for the BSS within the SPL binary.
2481
2482		CONFIG_SPL_BSS_MAX_SIZE
2483		Maximum size in memory allocated to the SPL BSS.
2484		When defined, the linker checks that the actual memory used
2485		by SPL from __bss_start to __bss_end does not exceed it.
2486		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2487		must not be both defined at the same time.
2488
2489		CONFIG_SPL_STACK
2490		Adress of the start of the stack SPL will use
2491
2492		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2493		When defined, SPL will panic() if the image it has
2494		loaded does not have a signature.
2495		Defining this is useful when code which loads images
2496		in SPL cannot guarantee that absolutely all read errors
2497		will be caught.
2498		An example is the LPC32XX MLC NAND driver, which will
2499		consider that a completely unreadable NAND block is bad,
2500		and thus should be skipped silently.
2501
2502		CONFIG_SPL_RELOC_STACK
2503		Adress of the start of the stack SPL will use after
2504		relocation.  If unspecified, this is equal to
2505		CONFIG_SPL_STACK.
2506
2507		CONFIG_SYS_SPL_MALLOC_START
2508		Starting address of the malloc pool used in SPL.
2509		When this option is set the full malloc is used in SPL and
2510		it is set up by spl_init() and before that, the simple malloc()
2511		can be used if CONFIG_SYS_MALLOC_F is defined.
2512
2513		CONFIG_SYS_SPL_MALLOC_SIZE
2514		The size of the malloc pool used in SPL.
2515
2516		CONFIG_SPL_OS_BOOT
2517		Enable booting directly to an OS from SPL.
2518		See also: doc/README.falcon
2519
2520		CONFIG_SPL_DISPLAY_PRINT
2521		For ARM, enable an optional function to print more information
2522		about the running system.
2523
2524		CONFIG_SPL_INIT_MINIMAL
2525		Arch init code should be built for a very small image
2526
2527		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2528		Partition on the MMC to load U-Boot from when the MMC is being
2529		used in raw mode
2530
2531		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2532		Sector to load kernel uImage from when MMC is being
2533		used in raw mode (for Falcon mode)
2534
2535		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2536		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2537		Sector and number of sectors to load kernel argument
2538		parameters from when MMC is being used in raw mode
2539		(for falcon mode)
2540
2541		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2542		Partition on the MMC to load U-Boot from when the MMC is being
2543		used in fs mode
2544
2545		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2546		Filename to read to load U-Boot when reading from filesystem
2547
2548		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2549		Filename to read to load kernel uImage when reading
2550		from filesystem (for Falcon mode)
2551
2552		CONFIG_SPL_FS_LOAD_ARGS_NAME
2553		Filename to read to load kernel argument parameters
2554		when reading from filesystem (for Falcon mode)
2555
2556		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2557		Set this for NAND SPL on PPC mpc83xx targets, so that
2558		start.S waits for the rest of the SPL to load before
2559		continuing (the hardware starts execution after just
2560		loading the first page rather than the full 4K).
2561
2562		CONFIG_SPL_SKIP_RELOCATE
2563		Avoid SPL relocation
2564
2565		CONFIG_SPL_NAND_BASE
2566		Include nand_base.c in the SPL.  Requires
2567		CONFIG_SPL_NAND_DRIVERS.
2568
2569		CONFIG_SPL_NAND_DRIVERS
2570		SPL uses normal NAND drivers, not minimal drivers.
2571
2572		CONFIG_SPL_NAND_IDENT
2573		SPL uses the chip ID list to identify the NAND flash.
2574		Requires CONFIG_SPL_NAND_BASE.
2575
2576		CONFIG_SPL_NAND_ECC
2577		Include standard software ECC in the SPL
2578
2579		CONFIG_SPL_NAND_SIMPLE
2580		Support for NAND boot using simple NAND drivers that
2581		expose the cmd_ctrl() interface.
2582
2583		CONFIG_SPL_UBI
2584		Support for a lightweight UBI (fastmap) scanner and
2585		loader
2586
2587		CONFIG_SPL_NAND_RAW_ONLY
2588		Support to boot only raw u-boot.bin images. Use this only
2589		if you need to save space.
2590
2591		CONFIG_SPL_COMMON_INIT_DDR
2592		Set for common ddr init with serial presence detect in
2593		SPL binary.
2594
2595		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2596		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2597		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2598		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2599		CONFIG_SYS_NAND_ECCBYTES
2600		Defines the size and behavior of the NAND that SPL uses
2601		to read U-Boot
2602
2603		CONFIG_SPL_NAND_BOOT
2604		Add support NAND boot
2605
2606		CONFIG_SYS_NAND_U_BOOT_OFFS
2607		Location in NAND to read U-Boot from
2608
2609		CONFIG_SYS_NAND_U_BOOT_DST
2610		Location in memory to load U-Boot to
2611
2612		CONFIG_SYS_NAND_U_BOOT_SIZE
2613		Size of image to load
2614
2615		CONFIG_SYS_NAND_U_BOOT_START
2616		Entry point in loaded image to jump to
2617
2618		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2619		Define this if you need to first read the OOB and then the
2620		data. This is used, for example, on davinci platforms.
2621
2622		CONFIG_SPL_RAM_DEVICE
2623		Support for running image already present in ram, in SPL binary
2624
2625		CONFIG_SPL_PAD_TO
2626		Image offset to which the SPL should be padded before appending
2627		the SPL payload. By default, this is defined as
2628		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2629		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2630		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2631
2632		CONFIG_SPL_TARGET
2633		Final target image containing SPL and payload.  Some SPLs
2634		use an arch-specific makefile fragment instead, for
2635		example if more than one image needs to be produced.
2636
2637		CONFIG_SPL_FIT_PRINT
2638		Printing information about a FIT image adds quite a bit of
2639		code to SPL. So this is normally disabled in SPL. Use this
2640		option to re-enable it. This will affect the output of the
2641		bootm command when booting a FIT image.
2642
2643- TPL framework
2644		CONFIG_TPL
2645		Enable building of TPL globally.
2646
2647		CONFIG_TPL_PAD_TO
2648		Image offset to which the TPL should be padded before appending
2649		the TPL payload. By default, this is defined as
2650		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2651		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2652		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2653
2654- Interrupt support (PPC):
2655
2656		There are common interrupt_init() and timer_interrupt()
2657		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2658		for CPU specific initialization. interrupt_init_cpu()
2659		should set decrementer_count to appropriate value. If
2660		CPU resets decrementer automatically after interrupt
2661		(ppc4xx) it should set decrementer_count to zero.
2662		timer_interrupt() calls timer_interrupt_cpu() for CPU
2663		specific handling. If board has watchdog / status_led
2664		/ other_activity_monitor it works automatically from
2665		general timer_interrupt().
2666
2667
2668Board initialization settings:
2669------------------------------
2670
2671During Initialization u-boot calls a number of board specific functions
2672to allow the preparation of board specific prerequisites, e.g. pin setup
2673before drivers are initialized. To enable these callbacks the
2674following configuration macros have to be defined. Currently this is
2675architecture specific, so please check arch/your_architecture/lib/board.c
2676typically in board_init_f() and board_init_r().
2677
2678- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2679- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2680- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2681- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2682
2683Configuration Settings:
2684-----------------------
2685
2686- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2687		Optionally it can be defined to support 64-bit memory commands.
2688
2689- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2690		undefine this when you're short of memory.
2691
2692- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2693		width of the commands listed in the 'help' command output.
2694
2695- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2696		prompt for user input.
2697
2698- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2699
2700- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2701
2702- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2703
2704- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2705		the application (usually a Linux kernel) when it is
2706		booted
2707
2708- CONFIG_SYS_BAUDRATE_TABLE:
2709		List of legal baudrate settings for this board.
2710
2711- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2712		Begin and End addresses of the area used by the
2713		simple memory test.
2714
2715- CONFIG_SYS_MEMTEST_SCRATCH:
2716		Scratch address used by the alternate memory test
2717		You only need to set this if address zero isn't writeable
2718
2719- CONFIG_SYS_MEM_RESERVE_SECURE
2720		Only implemented for ARMv8 for now.
2721		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2722		is substracted from total RAM and won't be reported to OS.
2723		This memory can be used as secure memory. A variable
2724		gd->arch.secure_ram is used to track the location. In systems
2725		the RAM base is not zero, or RAM is divided into banks,
2726		this variable needs to be recalcuated to get the address.
2727
2728- CONFIG_SYS_MEM_TOP_HIDE:
2729		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2730		this specified memory area will get subtracted from the top
2731		(end) of RAM and won't get "touched" at all by U-Boot. By
2732		fixing up gd->ram_size the Linux kernel should gets passed
2733		the now "corrected" memory size and won't touch it either.
2734		This should work for arch/ppc and arch/powerpc. Only Linux
2735		board ports in arch/powerpc with bootwrapper support that
2736		recalculate the memory size from the SDRAM controller setup
2737		will have to get fixed in Linux additionally.
2738
2739		This option can be used as a workaround for the 440EPx/GRx
2740		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2741		be touched.
2742
2743		WARNING: Please make sure that this value is a multiple of
2744		the Linux page size (normally 4k). If this is not the case,
2745		then the end address of the Linux memory will be located at a
2746		non page size aligned address and this could cause major
2747		problems.
2748
2749- CONFIG_SYS_LOADS_BAUD_CHANGE:
2750		Enable temporary baudrate change while serial download
2751
2752- CONFIG_SYS_SDRAM_BASE:
2753		Physical start address of SDRAM. _Must_ be 0 here.
2754
2755- CONFIG_SYS_FLASH_BASE:
2756		Physical start address of Flash memory.
2757
2758- CONFIG_SYS_MONITOR_BASE:
2759		Physical start address of boot monitor code (set by
2760		make config files to be same as the text base address
2761		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2762		CONFIG_SYS_FLASH_BASE when booting from flash.
2763
2764- CONFIG_SYS_MONITOR_LEN:
2765		Size of memory reserved for monitor code, used to
2766		determine _at_compile_time_ (!) if the environment is
2767		embedded within the U-Boot image, or in a separate
2768		flash sector.
2769
2770- CONFIG_SYS_MALLOC_LEN:
2771		Size of DRAM reserved for malloc() use.
2772
2773- CONFIG_SYS_MALLOC_F_LEN
2774		Size of the malloc() pool for use before relocation. If
2775		this is defined, then a very simple malloc() implementation
2776		will become available before relocation. The address is just
2777		below the global data, and the stack is moved down to make
2778		space.
2779
2780		This feature allocates regions with increasing addresses
2781		within the region. calloc() is supported, but realloc()
2782		is not available. free() is supported but does nothing.
2783		The memory will be freed (or in fact just forgotten) when
2784		U-Boot relocates itself.
2785
2786- CONFIG_SYS_MALLOC_SIMPLE
2787		Provides a simple and small malloc() and calloc() for those
2788		boards which do not use the full malloc in SPL (which is
2789		enabled with CONFIG_SYS_SPL_MALLOC_START).
2790
2791- CONFIG_SYS_NONCACHED_MEMORY:
2792		Size of non-cached memory area. This area of memory will be
2793		typically located right below the malloc() area and mapped
2794		uncached in the MMU. This is useful for drivers that would
2795		otherwise require a lot of explicit cache maintenance. For
2796		some drivers it's also impossible to properly maintain the
2797		cache. For example if the regions that need to be flushed
2798		are not a multiple of the cache-line size, *and* padding
2799		cannot be allocated between the regions to align them (i.e.
2800		if the HW requires a contiguous array of regions, and the
2801		size of each region is not cache-aligned), then a flush of
2802		one region may result in overwriting data that hardware has
2803		written to another region in the same cache-line. This can
2804		happen for example in network drivers where descriptors for
2805		buffers are typically smaller than the CPU cache-line (e.g.
2806		16 bytes vs. 32 or 64 bytes).
2807
2808		Non-cached memory is only supported on 32-bit ARM at present.
2809
2810- CONFIG_SYS_BOOTM_LEN:
2811		Normally compressed uImages are limited to an
2812		uncompressed size of 8 MBytes. If this is not enough,
2813		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2814		to adjust this setting to your needs.
2815
2816- CONFIG_SYS_BOOTMAPSZ:
2817		Maximum size of memory mapped by the startup code of
2818		the Linux kernel; all data that must be processed by
2819		the Linux kernel (bd_info, boot arguments, FDT blob if
2820		used) must be put below this limit, unless "bootm_low"
2821		environment variable is defined and non-zero. In such case
2822		all data for the Linux kernel must be between "bootm_low"
2823		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2824		variable "bootm_mapsize" will override the value of
2825		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2826		then the value in "bootm_size" will be used instead.
2827
2828- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2829		Enable initrd_high functionality.  If defined then the
2830		initrd_high feature is enabled and the bootm ramdisk subcommand
2831		is enabled.
2832
2833- CONFIG_SYS_BOOT_GET_CMDLINE:
2834		Enables allocating and saving kernel cmdline in space between
2835		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2836
2837- CONFIG_SYS_BOOT_GET_KBD:
2838		Enables allocating and saving a kernel copy of the bd_info in
2839		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2840
2841- CONFIG_SYS_MAX_FLASH_BANKS:
2842		Max number of Flash memory banks
2843
2844- CONFIG_SYS_MAX_FLASH_SECT:
2845		Max number of sectors on a Flash chip
2846
2847- CONFIG_SYS_FLASH_ERASE_TOUT:
2848		Timeout for Flash erase operations (in ms)
2849
2850- CONFIG_SYS_FLASH_WRITE_TOUT:
2851		Timeout for Flash write operations (in ms)
2852
2853- CONFIG_SYS_FLASH_LOCK_TOUT
2854		Timeout for Flash set sector lock bit operation (in ms)
2855
2856- CONFIG_SYS_FLASH_UNLOCK_TOUT
2857		Timeout for Flash clear lock bits operation (in ms)
2858
2859- CONFIG_SYS_FLASH_PROTECTION
2860		If defined, hardware flash sectors protection is used
2861		instead of U-Boot software protection.
2862
2863- CONFIG_SYS_DIRECT_FLASH_TFTP:
2864
2865		Enable TFTP transfers directly to flash memory;
2866		without this option such a download has to be
2867		performed in two steps: (1) download to RAM, and (2)
2868		copy from RAM to flash.
2869
2870		The two-step approach is usually more reliable, since
2871		you can check if the download worked before you erase
2872		the flash, but in some situations (when system RAM is
2873		too limited to allow for a temporary copy of the
2874		downloaded image) this option may be very useful.
2875
2876- CONFIG_SYS_FLASH_CFI:
2877		Define if the flash driver uses extra elements in the
2878		common flash structure for storing flash geometry.
2879
2880- CONFIG_FLASH_CFI_DRIVER
2881		This option also enables the building of the cfi_flash driver
2882		in the drivers directory
2883
2884- CONFIG_FLASH_CFI_MTD
2885		This option enables the building of the cfi_mtd driver
2886		in the drivers directory. The driver exports CFI flash
2887		to the MTD layer.
2888
2889- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2890		Use buffered writes to flash.
2891
2892- CONFIG_FLASH_SPANSION_S29WS_N
2893		s29ws-n MirrorBit flash has non-standard addresses for buffered
2894		write commands.
2895
2896- CONFIG_SYS_FLASH_QUIET_TEST
2897		If this option is defined, the common CFI flash doesn't
2898		print it's warning upon not recognized FLASH banks. This
2899		is useful, if some of the configured banks are only
2900		optionally available.
2901
2902- CONFIG_FLASH_SHOW_PROGRESS
2903		If defined (must be an integer), print out countdown
2904		digits and dots.  Recommended value: 45 (9..1) for 80
2905		column displays, 15 (3..1) for 40 column displays.
2906
2907- CONFIG_FLASH_VERIFY
2908		If defined, the content of the flash (destination) is compared
2909		against the source after the write operation. An error message
2910		will be printed when the contents are not identical.
2911		Please note that this option is useless in nearly all cases,
2912		since such flash programming errors usually are detected earlier
2913		while unprotecting/erasing/programming. Please only enable
2914		this option if you really know what you are doing.
2915
2916- CONFIG_SYS_RX_ETH_BUFFER:
2917		Defines the number of Ethernet receive buffers. On some
2918		Ethernet controllers it is recommended to set this value
2919		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2920		buffers can be full shortly after enabling the interface
2921		on high Ethernet traffic.
2922		Defaults to 4 if not defined.
2923
2924- CONFIG_ENV_MAX_ENTRIES
2925
2926	Maximum number of entries in the hash table that is used
2927	internally to store the environment settings. The default
2928	setting is supposed to be generous and should work in most
2929	cases. This setting can be used to tune behaviour; see
2930	lib/hashtable.c for details.
2931
2932- CONFIG_ENV_FLAGS_LIST_DEFAULT
2933- CONFIG_ENV_FLAGS_LIST_STATIC
2934	Enable validation of the values given to environment variables when
2935	calling env set.  Variables can be restricted to only decimal,
2936	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2937	the variables can also be restricted to IP address or MAC address.
2938
2939	The format of the list is:
2940		type_attribute = [s|d|x|b|i|m]
2941		access_attribute = [a|r|o|c]
2942		attributes = type_attribute[access_attribute]
2943		entry = variable_name[:attributes]
2944		list = entry[,list]
2945
2946	The type attributes are:
2947		s - String (default)
2948		d - Decimal
2949		x - Hexadecimal
2950		b - Boolean ([1yYtT|0nNfF])
2951		i - IP address
2952		m - MAC address
2953
2954	The access attributes are:
2955		a - Any (default)
2956		r - Read-only
2957		o - Write-once
2958		c - Change-default
2959
2960	- CONFIG_ENV_FLAGS_LIST_DEFAULT
2961		Define this to a list (string) to define the ".flags"
2962		environment variable in the default or embedded environment.
2963
2964	- CONFIG_ENV_FLAGS_LIST_STATIC
2965		Define this to a list (string) to define validation that
2966		should be done if an entry is not found in the ".flags"
2967		environment variable.  To override a setting in the static
2968		list, simply add an entry for the same variable name to the
2969		".flags" variable.
2970
2971	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2972	regular expression. This allows multiple variables to define the same
2973	flags without explicitly listing them for each variable.
2974
2975- CONFIG_ENV_ACCESS_IGNORE_FORCE
2976	If defined, don't allow the -f switch to env set override variable
2977	access flags.
2978
2979The following definitions that deal with the placement and management
2980of environment data (variable area); in general, we support the
2981following configurations:
2982
2983- CONFIG_BUILD_ENVCRC:
2984
2985	Builds up envcrc with the target environment so that external utils
2986	may easily extract it and embed it in final U-Boot images.
2987
2988BE CAREFUL! The first access to the environment happens quite early
2989in U-Boot initialization (when we try to get the setting of for the
2990console baudrate). You *MUST* have mapped your NVRAM area then, or
2991U-Boot will hang.
2992
2993Please note that even with NVRAM we still use a copy of the
2994environment in RAM: we could work on NVRAM directly, but we want to
2995keep settings there always unmodified except somebody uses "saveenv"
2996to save the current settings.
2997
2998BE CAREFUL! For some special cases, the local device can not use
2999"saveenv" command. For example, the local device will get the
3000environment stored in a remote NOR flash by SRIO or PCIE link,
3001but it can not erase, write this NOR flash by SRIO or PCIE interface.
3002
3003- CONFIG_NAND_ENV_DST
3004
3005	Defines address in RAM to which the nand_spl code should copy the
3006	environment. If redundant environment is used, it will be copied to
3007	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3008
3009Please note that the environment is read-only until the monitor
3010has been relocated to RAM and a RAM copy of the environment has been
3011created; also, when using EEPROM you will have to use env_get_f()
3012until then to read environment variables.
3013
3014The environment is protected by a CRC32 checksum. Before the monitor
3015is relocated into RAM, as a result of a bad CRC you will be working
3016with the compiled-in default environment - *silently*!!! [This is
3017necessary, because the first environment variable we need is the
3018"baudrate" setting for the console - if we have a bad CRC, we don't
3019have any device yet where we could complain.]
3020
3021Note: once the monitor has been relocated, then it will complain if
3022the default environment is used; a new CRC is computed as soon as you
3023use the "saveenv" command to store a valid environment.
3024
3025- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3026		Echo the inverted Ethernet link state to the fault LED.
3027
3028		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3029		      also needs to be defined.
3030
3031- CONFIG_SYS_FAULT_MII_ADDR:
3032		MII address of the PHY to check for the Ethernet link state.
3033
3034- CONFIG_NS16550_MIN_FUNCTIONS:
3035		Define this if you desire to only have use of the NS16550_init
3036		and NS16550_putc functions for the serial driver located at
3037		drivers/serial/ns16550.c.  This option is useful for saving
3038		space for already greatly restricted images, including but not
3039		limited to NAND_SPL configurations.
3040
3041- CONFIG_DISPLAY_BOARDINFO
3042		Display information about the board that U-Boot is running on
3043		when U-Boot starts up. The board function checkboard() is called
3044		to do this.
3045
3046- CONFIG_DISPLAY_BOARDINFO_LATE
3047		Similar to the previous option, but display this information
3048		later, once stdio is running and output goes to the LCD, if
3049		present.
3050
3051- CONFIG_BOARD_SIZE_LIMIT:
3052		Maximum size of the U-Boot image. When defined, the
3053		build system checks that the actual size does not
3054		exceed it.
3055
3056Low Level (hardware related) configuration options:
3057---------------------------------------------------
3058
3059- CONFIG_SYS_CACHELINE_SIZE:
3060		Cache Line Size of the CPU.
3061
3062- CONFIG_SYS_CCSRBAR_DEFAULT:
3063		Default (power-on reset) physical address of CCSR on Freescale
3064		PowerPC SOCs.
3065
3066- CONFIG_SYS_CCSRBAR:
3067		Virtual address of CCSR.  On a 32-bit build, this is typically
3068		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3069
3070- CONFIG_SYS_CCSRBAR_PHYS:
3071		Physical address of CCSR.  CCSR can be relocated to a new
3072		physical address, if desired.  In this case, this macro should
3073		be set to that address.	 Otherwise, it should be set to the
3074		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3075		is typically relocated on 36-bit builds.  It is recommended
3076		that this macro be defined via the _HIGH and _LOW macros:
3077
3078		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3079			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3080
3081- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3082		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3083		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3084		used in assembly code, so it must not contain typecasts or
3085		integer size suffixes (e.g. "ULL").
3086
3087- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3088		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3089		used in assembly code, so it must not contain typecasts or
3090		integer size suffixes (e.g. "ULL").
3091
3092- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3093		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3094		forced to a value that ensures that CCSR is not relocated.
3095
3096- Floppy Disk Support:
3097		CONFIG_SYS_FDC_DRIVE_NUMBER
3098
3099		the default drive number (default value 0)
3100
3101		CONFIG_SYS_ISA_IO_STRIDE
3102
3103		defines the spacing between FDC chipset registers
3104		(default value 1)
3105
3106		CONFIG_SYS_ISA_IO_OFFSET
3107
3108		defines the offset of register from address. It
3109		depends on which part of the data bus is connected to
3110		the FDC chipset. (default value 0)
3111
3112		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3113		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3114		default value.
3115
3116		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3117		fdc_hw_init() is called at the beginning of the FDC
3118		setup. fdc_hw_init() must be provided by the board
3119		source code. It is used to make hardware-dependent
3120		initializations.
3121
3122- CONFIG_IDE_AHB:
3123		Most IDE controllers were designed to be connected with PCI
3124		interface. Only few of them were designed for AHB interface.
3125		When software is doing ATA command and data transfer to
3126		IDE devices through IDE-AHB controller, some additional
3127		registers accessing to these kind of IDE-AHB controller
3128		is required.
3129
3130- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3131		DO NOT CHANGE unless you know exactly what you're
3132		doing! (11-4) [MPC8xx systems only]
3133
3134- CONFIG_SYS_INIT_RAM_ADDR:
3135
3136		Start address of memory area that can be used for
3137		initial data and stack; please note that this must be
3138		writable memory that is working WITHOUT special
3139		initialization, i. e. you CANNOT use normal RAM which
3140		will become available only after programming the
3141		memory controller and running certain initialization
3142		sequences.
3143
3144		U-Boot uses the following memory types:
3145		- MPC8xx: IMMR (internal memory of the CPU)
3146
3147- CONFIG_SYS_GBL_DATA_OFFSET:
3148
3149		Offset of the initial data structure in the memory
3150		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3151		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3152		data is located at the end of the available space
3153		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3154		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3155		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3156		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3157
3158	Note:
3159		On the MPC824X (or other systems that use the data
3160		cache for initial memory) the address chosen for
3161		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3162		point to an otherwise UNUSED address space between
3163		the top of RAM and the start of the PCI space.
3164
3165- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3166
3167- CONFIG_SYS_OR_TIMING_SDRAM:
3168		SDRAM timing
3169
3170- CONFIG_SYS_MAMR_PTA:
3171		periodic timer for refresh
3172
3173- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3174  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3175  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3176  CONFIG_SYS_BR1_PRELIM:
3177		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3178
3179- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3180  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3181  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3182		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3183
3184- CONFIG_PCI_ENUM_ONLY
3185		Only scan through and get the devices on the buses.
3186		Don't do any setup work, presumably because someone or
3187		something has already done it, and we don't need to do it
3188		a second time.	Useful for platforms that are pre-booted
3189		by coreboot or similar.
3190
3191- CONFIG_PCI_INDIRECT_BRIDGE:
3192		Enable support for indirect PCI bridges.
3193
3194- CONFIG_SYS_SRIO:
3195		Chip has SRIO or not
3196
3197- CONFIG_SRIO1:
3198		Board has SRIO 1 port available
3199
3200- CONFIG_SRIO2:
3201		Board has SRIO 2 port available
3202
3203- CONFIG_SRIO_PCIE_BOOT_MASTER
3204		Board can support master function for Boot from SRIO and PCIE
3205
3206- CONFIG_SYS_SRIOn_MEM_VIRT:
3207		Virtual Address of SRIO port 'n' memory region
3208
3209- CONFIG_SYS_SRIOn_MEM_PHYS:
3210		Physical Address of SRIO port 'n' memory region
3211
3212- CONFIG_SYS_SRIOn_MEM_SIZE:
3213		Size of SRIO port 'n' memory region
3214
3215- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3216		Defined to tell the NAND controller that the NAND chip is using
3217		a 16 bit bus.
3218		Not all NAND drivers use this symbol.
3219		Example of drivers that use it:
3220		- drivers/mtd/nand/raw/ndfc.c
3221		- drivers/mtd/nand/raw/mxc_nand.c
3222
3223- CONFIG_SYS_NDFC_EBC0_CFG
3224		Sets the EBC0_CFG register for the NDFC. If not defined
3225		a default value will be used.
3226
3227- CONFIG_SPD_EEPROM
3228		Get DDR timing information from an I2C EEPROM. Common
3229		with pluggable memory modules such as SODIMMs
3230
3231  SPD_EEPROM_ADDRESS
3232		I2C address of the SPD EEPROM
3233
3234- CONFIG_SYS_SPD_BUS_NUM
3235		If SPD EEPROM is on an I2C bus other than the first
3236		one, specify here. Note that the value must resolve
3237		to something your driver can deal with.
3238
3239- CONFIG_SYS_DDR_RAW_TIMING
3240		Get DDR timing information from other than SPD. Common with
3241		soldered DDR chips onboard without SPD. DDR raw timing
3242		parameters are extracted from datasheet and hard-coded into
3243		header files or board specific files.
3244
3245- CONFIG_FSL_DDR_INTERACTIVE
3246		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3247
3248- CONFIG_FSL_DDR_SYNC_REFRESH
3249		Enable sync of refresh for multiple controllers.
3250
3251- CONFIG_FSL_DDR_BIST
3252		Enable built-in memory test for Freescale DDR controllers.
3253
3254- CONFIG_SYS_83XX_DDR_USES_CS0
3255		Only for 83xx systems. If specified, then DDR should
3256		be configured using CS0 and CS1 instead of CS2 and CS3.
3257
3258- CONFIG_RMII
3259		Enable RMII mode for all FECs.
3260		Note that this is a global option, we can't
3261		have one FEC in standard MII mode and another in RMII mode.
3262
3263- CONFIG_CRC32_VERIFY
3264		Add a verify option to the crc32 command.
3265		The syntax is:
3266
3267		=> crc32 -v <address> <count> <crc32>
3268
3269		Where address/count indicate a memory area
3270		and crc32 is the correct crc32 which the
3271		area should have.
3272
3273- CONFIG_LOOPW
3274		Add the "loopw" memory command. This only takes effect if
3275		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3276
3277- CONFIG_MX_CYCLIC
3278		Add the "mdc" and "mwc" memory commands. These are cyclic
3279		"md/mw" commands.
3280		Examples:
3281
3282		=> mdc.b 10 4 500
3283		This command will print 4 bytes (10,11,12,13) each 500 ms.
3284
3285		=> mwc.l 100 12345678 10
3286		This command will write 12345678 to address 100 all 10 ms.
3287
3288		This only takes effect if the memory commands are activated
3289		globally (CONFIG_CMD_MEMORY).
3290
3291- CONFIG_SKIP_LOWLEVEL_INIT
3292		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3293		low level initializations (like setting up the memory
3294		controller) are omitted and/or U-Boot does not
3295		relocate itself into RAM.
3296
3297		Normally this variable MUST NOT be defined. The only
3298		exception is when U-Boot is loaded (to RAM) by some
3299		other boot loader or by a debugger which performs
3300		these initializations itself.
3301
3302- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3303		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3304		to be skipped. The normal CP15 init (such as enabling the
3305		instruction cache) is still performed.
3306
3307- CONFIG_SPL_BUILD
3308		Modifies the behaviour of start.S when compiling a loader
3309		that is executed before the actual U-Boot. E.g. when
3310		compiling a NAND SPL.
3311
3312- CONFIG_TPL_BUILD
3313		Modifies the behaviour of start.S  when compiling a loader
3314		that is executed after the SPL and before the actual U-Boot.
3315		It is loaded by the SPL.
3316
3317- CONFIG_SYS_MPC85XX_NO_RESETVEC
3318		Only for 85xx systems. If this variable is specified, the section
3319		.resetvec is not kept and the section .bootpg is placed in the
3320		previous 4k of the .text section.
3321
3322- CONFIG_ARCH_MAP_SYSMEM
3323		Generally U-Boot (and in particular the md command) uses
3324		effective address. It is therefore not necessary to regard
3325		U-Boot address as virtual addresses that need to be translated
3326		to physical addresses. However, sandbox requires this, since
3327		it maintains its own little RAM buffer which contains all
3328		addressable memory. This option causes some memory accesses
3329		to be mapped through map_sysmem() / unmap_sysmem().
3330
3331- CONFIG_X86_RESET_VECTOR
3332		If defined, the x86 reset vector code is included. This is not
3333		needed when U-Boot is running from Coreboot.
3334
3335- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3336		Option to disable subpage write in NAND driver
3337		driver that uses this:
3338		drivers/mtd/nand/raw/davinci_nand.c
3339
3340Freescale QE/FMAN Firmware Support:
3341-----------------------------------
3342
3343The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3344loading of "firmware", which is encoded in the QE firmware binary format.
3345This firmware often needs to be loaded during U-Boot booting, so macros
3346are used to identify the storage device (NOR flash, SPI, etc) and the address
3347within that device.
3348
3349- CONFIG_SYS_FMAN_FW_ADDR
3350	The address in the storage device where the FMAN microcode is located.  The
3351	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3352	is also specified.
3353
3354- CONFIG_SYS_QE_FW_ADDR
3355	The address in the storage device where the QE microcode is located.  The
3356	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3357	is also specified.
3358
3359- CONFIG_SYS_QE_FMAN_FW_LENGTH
3360	The maximum possible size of the firmware.  The firmware binary format
3361	has a field that specifies the actual size of the firmware, but it
3362	might not be possible to read any part of the firmware unless some
3363	local storage is allocated to hold the entire firmware first.
3364
3365- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3366	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3367	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3368	virtual address in NOR flash.
3369
3370- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3371	Specifies that QE/FMAN firmware is located in NAND flash.
3372	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3373
3374- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3375	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3376	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3377
3378- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3379	Specifies that QE/FMAN firmware is located in the remote (master)
3380	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3381	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3382	window->master inbound window->master LAW->the ucode address in
3383	master's memory space.
3384
3385Freescale Layerscape Management Complex Firmware Support:
3386---------------------------------------------------------
3387The Freescale Layerscape Management Complex (MC) supports the loading of
3388"firmware".
3389This firmware often needs to be loaded during U-Boot booting, so macros
3390are used to identify the storage device (NOR flash, SPI, etc) and the address
3391within that device.
3392
3393- CONFIG_FSL_MC_ENET
3394	Enable the MC driver for Layerscape SoCs.
3395
3396Freescale Layerscape Debug Server Support:
3397-------------------------------------------
3398The Freescale Layerscape Debug Server Support supports the loading of
3399"Debug Server firmware" and triggering SP boot-rom.
3400This firmware often needs to be loaded during U-Boot booting.
3401
3402- CONFIG_SYS_MC_RSV_MEM_ALIGN
3403	Define alignment of reserved memory MC requires
3404
3405Reproducible builds
3406-------------------
3407
3408In order to achieve reproducible builds, timestamps used in the U-Boot build
3409process have to be set to a fixed value.
3410
3411This is done using the SOURCE_DATE_EPOCH environment variable.
3412SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3413option for U-Boot or an environment variable in U-Boot.
3414
3415SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3416
3417Building the Software:
3418======================
3419
3420Building U-Boot has been tested in several native build environments
3421and in many different cross environments. Of course we cannot support
3422all possibly existing versions of cross development tools in all
3423(potentially obsolete) versions. In case of tool chain problems we
3424recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3425which is extensively used to build and test U-Boot.
3426
3427If you are not using a native environment, it is assumed that you
3428have GNU cross compiling tools available in your path. In this case,
3429you must set the environment variable CROSS_COMPILE in your shell.
3430Note that no changes to the Makefile or any other source files are
3431necessary. For example using the ELDK on a 4xx CPU, please enter:
3432
3433	$ CROSS_COMPILE=ppc_4xx-
3434	$ export CROSS_COMPILE
3435
3436Note: If you wish to generate Windows versions of the utilities in
3437      the tools directory you can use the MinGW toolchain
3438      (http://www.mingw.org).  Set your HOST tools to the MinGW
3439      toolchain and execute 'make tools'.  For example:
3440
3441       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3442
3443      Binaries such as tools/mkimage.exe will be created which can
3444      be executed on computers running Windows.
3445
3446U-Boot is intended to be simple to build. After installing the
3447sources you must configure U-Boot for one specific board type. This
3448is done by typing:
3449
3450	make NAME_defconfig
3451
3452where "NAME_defconfig" is the name of one of the existing configu-
3453rations; see boards.cfg for supported names.
3454
3455Note: for some board special configuration names may exist; check if
3456      additional information is available from the board vendor; for
3457      instance, the TQM823L systems are available without (standard)
3458      or with LCD support. You can select such additional "features"
3459      when choosing the configuration, i. e.
3460
3461      make TQM823L_defconfig
3462	- will configure for a plain TQM823L, i. e. no LCD support
3463
3464      make TQM823L_LCD_defconfig
3465	- will configure for a TQM823L with U-Boot console on LCD
3466
3467      etc.
3468
3469
3470Finally, type "make all", and you should get some working U-Boot
3471images ready for download to / installation on your system:
3472
3473- "u-boot.bin" is a raw binary image
3474- "u-boot" is an image in ELF binary format
3475- "u-boot.srec" is in Motorola S-Record format
3476
3477By default the build is performed locally and the objects are saved
3478in the source directory. One of the two methods can be used to change
3479this behavior and build U-Boot to some external directory:
3480
34811. Add O= to the make command line invocations:
3482
3483	make O=/tmp/build distclean
3484	make O=/tmp/build NAME_defconfig
3485	make O=/tmp/build all
3486
34872. Set environment variable KBUILD_OUTPUT to point to the desired location:
3488
3489	export KBUILD_OUTPUT=/tmp/build
3490	make distclean
3491	make NAME_defconfig
3492	make all
3493
3494Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3495variable.
3496
3497User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3498setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3499For example to treat all compiler warnings as errors:
3500
3501	make KCFLAGS=-Werror
3502
3503Please be aware that the Makefiles assume you are using GNU make, so
3504for instance on NetBSD you might need to use "gmake" instead of
3505native "make".
3506
3507
3508If the system board that you have is not listed, then you will need
3509to port U-Boot to your hardware platform. To do this, follow these
3510steps:
3511
35121.  Create a new directory to hold your board specific code. Add any
3513    files you need. In your board directory, you will need at least
3514    the "Makefile" and a "<board>.c".
35152.  Create a new configuration file "include/configs/<board>.h" for
3516    your board.
35173.  If you're porting U-Boot to a new CPU, then also create a new
3518    directory to hold your CPU specific code. Add any files you need.
35194.  Run "make <board>_defconfig" with your new name.
35205.  Type "make", and you should get a working "u-boot.srec" file
3521    to be installed on your target system.
35226.  Debug and solve any problems that might arise.
3523    [Of course, this last step is much harder than it sounds.]
3524
3525
3526Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3527==============================================================
3528
3529If you have modified U-Boot sources (for instance added a new board
3530or support for new devices, a new CPU, etc.) you are expected to
3531provide feedback to the other developers. The feedback normally takes
3532the form of a "patch", i. e. a context diff against a certain (latest
3533official or latest in the git repository) version of U-Boot sources.
3534
3535But before you submit such a patch, please verify that your modifi-
3536cation did not break existing code. At least make sure that *ALL* of
3537the supported boards compile WITHOUT ANY compiler warnings. To do so,
3538just run the buildman script (tools/buildman/buildman), which will
3539configure and build U-Boot for ALL supported system. Be warned, this
3540will take a while. Please see the buildman README, or run 'buildman -H'
3541for documentation.
3542
3543
3544See also "U-Boot Porting Guide" below.
3545
3546
3547Monitor Commands - Overview:
3548============================
3549
3550go	- start application at address 'addr'
3551run	- run commands in an environment variable
3552bootm	- boot application image from memory
3553bootp	- boot image via network using BootP/TFTP protocol
3554bootz   - boot zImage from memory
3555tftpboot- boot image via network using TFTP protocol
3556	       and env variables "ipaddr" and "serverip"
3557	       (and eventually "gatewayip")
3558tftpput - upload a file via network using TFTP protocol
3559rarpboot- boot image via network using RARP/TFTP protocol
3560diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3561loads	- load S-Record file over serial line
3562loadb	- load binary file over serial line (kermit mode)
3563md	- memory display
3564mm	- memory modify (auto-incrementing)
3565nm	- memory modify (constant address)
3566mw	- memory write (fill)
3567cp	- memory copy
3568cmp	- memory compare
3569crc32	- checksum calculation
3570i2c	- I2C sub-system
3571sspi	- SPI utility commands
3572base	- print or set address offset
3573printenv- print environment variables
3574setenv	- set environment variables
3575saveenv - save environment variables to persistent storage
3576protect - enable or disable FLASH write protection
3577erase	- erase FLASH memory
3578flinfo	- print FLASH memory information
3579nand	- NAND memory operations (see doc/README.nand)
3580bdinfo	- print Board Info structure
3581iminfo	- print header information for application image
3582coninfo - print console devices and informations
3583ide	- IDE sub-system
3584loop	- infinite loop on address range
3585loopw	- infinite write loop on address range
3586mtest	- simple RAM test
3587icache	- enable or disable instruction cache
3588dcache	- enable or disable data cache
3589reset	- Perform RESET of the CPU
3590echo	- echo args to console
3591version - print monitor version
3592help	- print online help
3593?	- alias for 'help'
3594
3595
3596Monitor Commands - Detailed Description:
3597========================================
3598
3599TODO.
3600
3601For now: just type "help <command>".
3602
3603
3604Environment Variables:
3605======================
3606
3607U-Boot supports user configuration using Environment Variables which
3608can be made persistent by saving to Flash memory.
3609
3610Environment Variables are set using "setenv", printed using
3611"printenv", and saved to Flash using "saveenv". Using "setenv"
3612without a value can be used to delete a variable from the
3613environment. As long as you don't save the environment you are
3614working with an in-memory copy. In case the Flash area containing the
3615environment is erased by accident, a default environment is provided.
3616
3617Some configuration options can be set using Environment Variables.
3618
3619List of environment variables (most likely not complete):
3620
3621  baudrate	- see CONFIG_BAUDRATE
3622
3623  bootdelay	- see CONFIG_BOOTDELAY
3624
3625  bootcmd	- see CONFIG_BOOTCOMMAND
3626
3627  bootargs	- Boot arguments when booting an RTOS image
3628
3629  bootfile	- Name of the image to load with TFTP
3630
3631  bootm_low	- Memory range available for image processing in the bootm
3632		  command can be restricted. This variable is given as
3633		  a hexadecimal number and defines lowest address allowed
3634		  for use by the bootm command. See also "bootm_size"
3635		  environment variable. Address defined by "bootm_low" is
3636		  also the base of the initial memory mapping for the Linux
3637		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3638		  bootm_mapsize.
3639
3640  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3641		  This variable is given as a hexadecimal number and it
3642		  defines the size of the memory region starting at base
3643		  address bootm_low that is accessible by the Linux kernel
3644		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3645		  as the default value if it is defined, and bootm_size is
3646		  used otherwise.
3647
3648  bootm_size	- Memory range available for image processing in the bootm
3649		  command can be restricted. This variable is given as
3650		  a hexadecimal number and defines the size of the region
3651		  allowed for use by the bootm command. See also "bootm_low"
3652		  environment variable.
3653
3654  updatefile	- Location of the software update file on a TFTP server, used
3655		  by the automatic software update feature. Please refer to
3656		  documentation in doc/README.update for more details.
3657
3658  autoload	- if set to "no" (any string beginning with 'n'),
3659		  "bootp" will just load perform a lookup of the
3660		  configuration from the BOOTP server, but not try to
3661		  load any image using TFTP
3662
3663  autostart	- if set to "yes", an image loaded using the "bootp",
3664		  "rarpboot", "tftpboot" or "diskboot" commands will
3665		  be automatically started (by internally calling
3666		  "bootm")
3667
3668		  If set to "no", a standalone image passed to the
3669		  "bootm" command will be copied to the load address
3670		  (and eventually uncompressed), but NOT be started.
3671		  This can be used to load and uncompress arbitrary
3672		  data.
3673
3674  fdt_high	- if set this restricts the maximum address that the
3675		  flattened device tree will be copied into upon boot.
3676		  For example, if you have a system with 1 GB memory
3677		  at physical address 0x10000000, while Linux kernel
3678		  only recognizes the first 704 MB as low memory, you
3679		  may need to set fdt_high as 0x3C000000 to have the
3680		  device tree blob be copied to the maximum address
3681		  of the 704 MB low memory, so that Linux kernel can
3682		  access it during the boot procedure.
3683
3684		  If this is set to the special value 0xFFFFFFFF then
3685		  the fdt will not be copied at all on boot.  For this
3686		  to work it must reside in writable memory, have
3687		  sufficient padding on the end of it for u-boot to
3688		  add the information it needs into it, and the memory
3689		  must be accessible by the kernel.
3690
3691  fdtcontroladdr- if set this is the address of the control flattened
3692		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3693		  defined.
3694
3695  i2cfast	- (PPC405GP|PPC405EP only)
3696		  if set to 'y' configures Linux I2C driver for fast
3697		  mode (400kHZ). This environment variable is used in
3698		  initialization code. So, for changes to be effective
3699		  it must be saved and board must be reset.
3700
3701  initrd_high	- restrict positioning of initrd images:
3702		  If this variable is not set, initrd images will be
3703		  copied to the highest possible address in RAM; this
3704		  is usually what you want since it allows for
3705		  maximum initrd size. If for some reason you want to
3706		  make sure that the initrd image is loaded below the
3707		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3708		  variable to a value of "no" or "off" or "0".
3709		  Alternatively, you can set it to a maximum upper
3710		  address to use (U-Boot will still check that it
3711		  does not overwrite the U-Boot stack and data).
3712
3713		  For instance, when you have a system with 16 MB
3714		  RAM, and want to reserve 4 MB from use by Linux,
3715		  you can do this by adding "mem=12M" to the value of
3716		  the "bootargs" variable. However, now you must make
3717		  sure that the initrd image is placed in the first
3718		  12 MB as well - this can be done with
3719
3720		  setenv initrd_high 00c00000
3721
3722		  If you set initrd_high to 0xFFFFFFFF, this is an
3723		  indication to U-Boot that all addresses are legal
3724		  for the Linux kernel, including addresses in flash
3725		  memory. In this case U-Boot will NOT COPY the
3726		  ramdisk at all. This may be useful to reduce the
3727		  boot time on your system, but requires that this
3728		  feature is supported by your Linux kernel.
3729
3730  ipaddr	- IP address; needed for tftpboot command
3731
3732  loadaddr	- Default load address for commands like "bootp",
3733		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3734
3735  loads_echo	- see CONFIG_LOADS_ECHO
3736
3737  serverip	- TFTP server IP address; needed for tftpboot command
3738
3739  bootretry	- see CONFIG_BOOT_RETRY_TIME
3740
3741  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3742
3743  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3744
3745  ethprime	- controls which interface is used first.
3746
3747  ethact	- controls which interface is currently active.
3748		  For example you can do the following
3749
3750		  => setenv ethact FEC
3751		  => ping 192.168.0.1 # traffic sent on FEC
3752		  => setenv ethact SCC
3753		  => ping 10.0.0.1 # traffic sent on SCC
3754
3755  ethrotate	- When set to "no" U-Boot does not go through all
3756		  available network interfaces.
3757		  It just stays at the currently selected interface.
3758
3759  netretry	- When set to "no" each network operation will
3760		  either succeed or fail without retrying.
3761		  When set to "once" the network operation will
3762		  fail when all the available network interfaces
3763		  are tried once without success.
3764		  Useful on scripts which control the retry operation
3765		  themselves.
3766
3767  npe_ucode	- set load address for the NPE microcode
3768
3769  silent_linux  - If set then Linux will be told to boot silently, by
3770		  changing the console to be empty. If "yes" it will be
3771		  made silent. If "no" it will not be made silent. If
3772		  unset, then it will be made silent if the U-Boot console
3773		  is silent.
3774
3775  tftpsrcp	- If this is set, the value is used for TFTP's
3776		  UDP source port.
3777
3778  tftpdstp	- If this is set, the value is used for TFTP's UDP
3779		  destination port instead of the Well Know Port 69.
3780
3781  tftpblocksize - Block size to use for TFTP transfers; if not set,
3782		  we use the TFTP server's default block size
3783
3784  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3785		  seconds, minimum value is 1000 = 1 second). Defines
3786		  when a packet is considered to be lost so it has to
3787		  be retransmitted. The default is 5000 = 5 seconds.
3788		  Lowering this value may make downloads succeed
3789		  faster in networks with high packet loss rates or
3790		  with unreliable TFTP servers.
3791
3792  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3793		  unit, minimum value = 0). Defines how many timeouts
3794		  can happen during a single file transfer before that
3795		  transfer is aborted. The default is 10, and 0 means
3796		  'no timeouts allowed'. Increasing this value may help
3797		  downloads succeed with high packet loss rates, or with
3798		  unreliable TFTP servers or client hardware.
3799
3800  vlan		- When set to a value < 4095 the traffic over
3801		  Ethernet is encapsulated/received over 802.1q
3802		  VLAN tagged frames.
3803
3804  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3805		  Unsigned value, in milliseconds. If not set, the period will
3806		  be either the default (28000), or a value based on
3807		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3808		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3809
3810The following image location variables contain the location of images
3811used in booting. The "Image" column gives the role of the image and is
3812not an environment variable name. The other columns are environment
3813variable names. "File Name" gives the name of the file on a TFTP
3814server, "RAM Address" gives the location in RAM the image will be
3815loaded to, and "Flash Location" gives the image's address in NOR
3816flash or offset in NAND flash.
3817
3818*Note* - these variables don't have to be defined for all boards, some
3819boards currently use other variables for these purposes, and some
3820boards use these variables for other purposes.
3821
3822Image		    File Name	     RAM Address       Flash Location
3823-----		    ---------	     -----------       --------------
3824u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3825Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3826device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3827ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3828
3829The following environment variables may be used and automatically
3830updated by the network boot commands ("bootp" and "rarpboot"),
3831depending the information provided by your boot server:
3832
3833  bootfile	- see above
3834  dnsip		- IP address of your Domain Name Server
3835  dnsip2	- IP address of your secondary Domain Name Server
3836  gatewayip	- IP address of the Gateway (Router) to use
3837  hostname	- Target hostname
3838  ipaddr	- see above
3839  netmask	- Subnet Mask
3840  rootpath	- Pathname of the root filesystem on the NFS server
3841  serverip	- see above
3842
3843
3844There are two special Environment Variables:
3845
3846  serial#	- contains hardware identification information such
3847		  as type string and/or serial number
3848  ethaddr	- Ethernet address
3849
3850These variables can be set only once (usually during manufacturing of
3851the board). U-Boot refuses to delete or overwrite these variables
3852once they have been set once.
3853
3854
3855Further special Environment Variables:
3856
3857  ver		- Contains the U-Boot version string as printed
3858		  with the "version" command. This variable is
3859		  readonly (see CONFIG_VERSION_VARIABLE).
3860
3861
3862Please note that changes to some configuration parameters may take
3863only effect after the next boot (yes, that's just like Windoze :-).
3864
3865
3866Callback functions for environment variables:
3867---------------------------------------------
3868
3869For some environment variables, the behavior of u-boot needs to change
3870when their values are changed.  This functionality allows functions to
3871be associated with arbitrary variables.  On creation, overwrite, or
3872deletion, the callback will provide the opportunity for some side
3873effect to happen or for the change to be rejected.
3874
3875The callbacks are named and associated with a function using the
3876U_BOOT_ENV_CALLBACK macro in your board or driver code.
3877
3878These callbacks are associated with variables in one of two ways.  The
3879static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3880in the board configuration to a string that defines a list of
3881associations.  The list must be in the following format:
3882
3883	entry = variable_name[:callback_name]
3884	list = entry[,list]
3885
3886If the callback name is not specified, then the callback is deleted.
3887Spaces are also allowed anywhere in the list.
3888
3889Callbacks can also be associated by defining the ".callbacks" variable
3890with the same list format above.  Any association in ".callbacks" will
3891override any association in the static list. You can define
3892CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3893".callbacks" environment variable in the default or embedded environment.
3894
3895If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3896regular expression. This allows multiple variables to be connected to
3897the same callback without explicitly listing them all out.
3898
3899The signature of the callback functions is:
3900
3901    int callback(const char *name, const char *value, enum env_op op, int flags)
3902
3903* name - changed environment variable
3904* value - new value of the environment variable
3905* op - operation (create, overwrite, or delete)
3906* flags - attributes of the environment variable change, see flags H_* in
3907  include/search.h
3908
3909The return value is 0 if the variable change is accepted and 1 otherwise.
3910
3911Command Line Parsing:
3912=====================
3913
3914There are two different command line parsers available with U-Boot:
3915the old "simple" one, and the much more powerful "hush" shell:
3916
3917Old, simple command line parser:
3918--------------------------------
3919
3920- supports environment variables (through setenv / saveenv commands)
3921- several commands on one line, separated by ';'
3922- variable substitution using "... ${name} ..." syntax
3923- special characters ('$', ';') can be escaped by prefixing with '\',
3924  for example:
3925	setenv bootcmd bootm \${address}
3926- You can also escape text by enclosing in single apostrophes, for example:
3927	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3928
3929Hush shell:
3930-----------
3931
3932- similar to Bourne shell, with control structures like
3933  if...then...else...fi, for...do...done; while...do...done,
3934  until...do...done, ...
3935- supports environment ("global") variables (through setenv / saveenv
3936  commands) and local shell variables (through standard shell syntax
3937  "name=value"); only environment variables can be used with "run"
3938  command
3939
3940General rules:
3941--------------
3942
3943(1) If a command line (or an environment variable executed by a "run"
3944    command) contains several commands separated by semicolon, and
3945    one of these commands fails, then the remaining commands will be
3946    executed anyway.
3947
3948(2) If you execute several variables with one call to run (i. e.
3949    calling run with a list of variables as arguments), any failing
3950    command will cause "run" to terminate, i. e. the remaining
3951    variables are not executed.
3952
3953Note for Redundant Ethernet Interfaces:
3954=======================================
3955
3956Some boards come with redundant Ethernet interfaces; U-Boot supports
3957such configurations and is capable of automatic selection of a
3958"working" interface when needed. MAC assignment works as follows:
3959
3960Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3961MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3962"eth1addr" (=>eth1), "eth2addr", ...
3963
3964If the network interface stores some valid MAC address (for instance
3965in SROM), this is used as default address if there is NO correspon-
3966ding setting in the environment; if the corresponding environment
3967variable is set, this overrides the settings in the card; that means:
3968
3969o If the SROM has a valid MAC address, and there is no address in the
3970  environment, the SROM's address is used.
3971
3972o If there is no valid address in the SROM, and a definition in the
3973  environment exists, then the value from the environment variable is
3974  used.
3975
3976o If both the SROM and the environment contain a MAC address, and
3977  both addresses are the same, this MAC address is used.
3978
3979o If both the SROM and the environment contain a MAC address, and the
3980  addresses differ, the value from the environment is used and a
3981  warning is printed.
3982
3983o If neither SROM nor the environment contain a MAC address, an error
3984  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
3985  a random, locally-assigned MAC is used.
3986
3987If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
3988will be programmed into hardware as part of the initialization process.	 This
3989may be skipped by setting the appropriate 'ethmacskip' environment variable.
3990The naming convention is as follows:
3991"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
3992
3993Image Formats:
3994==============
3995
3996U-Boot is capable of booting (and performing other auxiliary operations on)
3997images in two formats:
3998
3999New uImage format (FIT)
4000-----------------------
4001
4002Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4003to Flattened Device Tree). It allows the use of images with multiple
4004components (several kernels, ramdisks, etc.), with contents protected by
4005SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4006
4007
4008Old uImage format
4009-----------------
4010
4011Old image format is based on binary files which can be basically anything,
4012preceded by a special header; see the definitions in include/image.h for
4013details; basically, the header defines the following image properties:
4014
4015* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4016  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4017  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4018  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4019  INTEGRITY).
4020* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4021  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4022  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4023* Compression Type (uncompressed, gzip, bzip2)
4024* Load Address
4025* Entry Point
4026* Image Name
4027* Image Timestamp
4028
4029The header is marked by a special Magic Number, and both the header
4030and the data portions of the image are secured against corruption by
4031CRC32 checksums.
4032
4033
4034Linux Support:
4035==============
4036
4037Although U-Boot should support any OS or standalone application
4038easily, the main focus has always been on Linux during the design of
4039U-Boot.
4040
4041U-Boot includes many features that so far have been part of some
4042special "boot loader" code within the Linux kernel. Also, any
4043"initrd" images to be used are no longer part of one big Linux image;
4044instead, kernel and "initrd" are separate images. This implementation
4045serves several purposes:
4046
4047- the same features can be used for other OS or standalone
4048  applications (for instance: using compressed images to reduce the
4049  Flash memory footprint)
4050
4051- it becomes much easier to port new Linux kernel versions because
4052  lots of low-level, hardware dependent stuff are done by U-Boot
4053
4054- the same Linux kernel image can now be used with different "initrd"
4055  images; of course this also means that different kernel images can
4056  be run with the same "initrd". This makes testing easier (you don't
4057  have to build a new "zImage.initrd" Linux image when you just
4058  change a file in your "initrd"). Also, a field-upgrade of the
4059  software is easier now.
4060
4061
4062Linux HOWTO:
4063============
4064
4065Porting Linux to U-Boot based systems:
4066---------------------------------------
4067
4068U-Boot cannot save you from doing all the necessary modifications to
4069configure the Linux device drivers for use with your target hardware
4070(no, we don't intend to provide a full virtual machine interface to
4071Linux :-).
4072
4073But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4074
4075Just make sure your machine specific header file (for instance
4076include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4077Information structure as we define in include/asm-<arch>/u-boot.h,
4078and make sure that your definition of IMAP_ADDR uses the same value
4079as your U-Boot configuration in CONFIG_SYS_IMMR.
4080
4081Note that U-Boot now has a driver model, a unified model for drivers.
4082If you are adding a new driver, plumb it into driver model. If there
4083is no uclass available, you are encouraged to create one. See
4084doc/driver-model.
4085
4086
4087Configuring the Linux kernel:
4088-----------------------------
4089
4090No specific requirements for U-Boot. Make sure you have some root
4091device (initial ramdisk, NFS) for your target system.
4092
4093
4094Building a Linux Image:
4095-----------------------
4096
4097With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4098not used. If you use recent kernel source, a new build target
4099"uImage" will exist which automatically builds an image usable by
4100U-Boot. Most older kernels also have support for a "pImage" target,
4101which was introduced for our predecessor project PPCBoot and uses a
4102100% compatible format.
4103
4104Example:
4105
4106	make TQM850L_defconfig
4107	make oldconfig
4108	make dep
4109	make uImage
4110
4111The "uImage" build target uses a special tool (in 'tools/mkimage') to
4112encapsulate a compressed Linux kernel image with header	 information,
4113CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4114
4115* build a standard "vmlinux" kernel image (in ELF binary format):
4116
4117* convert the kernel into a raw binary image:
4118
4119	${CROSS_COMPILE}-objcopy -O binary \
4120				 -R .note -R .comment \
4121				 -S vmlinux linux.bin
4122
4123* compress the binary image:
4124
4125	gzip -9 linux.bin
4126
4127* package compressed binary image for U-Boot:
4128
4129	mkimage -A ppc -O linux -T kernel -C gzip \
4130		-a 0 -e 0 -n "Linux Kernel Image" \
4131		-d linux.bin.gz uImage
4132
4133
4134The "mkimage" tool can also be used to create ramdisk images for use
4135with U-Boot, either separated from the Linux kernel image, or
4136combined into one file. "mkimage" encapsulates the images with a 64
4137byte header containing information about target architecture,
4138operating system, image type, compression method, entry points, time
4139stamp, CRC32 checksums, etc.
4140
4141"mkimage" can be called in two ways: to verify existing images and
4142print the header information, or to build new images.
4143
4144In the first form (with "-l" option) mkimage lists the information
4145contained in the header of an existing U-Boot image; this includes
4146checksum verification:
4147
4148	tools/mkimage -l image
4149	  -l ==> list image header information
4150
4151The second form (with "-d" option) is used to build a U-Boot image
4152from a "data file" which is used as image payload:
4153
4154	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4155		      -n name -d data_file image
4156	  -A ==> set architecture to 'arch'
4157	  -O ==> set operating system to 'os'
4158	  -T ==> set image type to 'type'
4159	  -C ==> set compression type 'comp'
4160	  -a ==> set load address to 'addr' (hex)
4161	  -e ==> set entry point to 'ep' (hex)
4162	  -n ==> set image name to 'name'
4163	  -d ==> use image data from 'datafile'
4164
4165Right now, all Linux kernels for PowerPC systems use the same load
4166address (0x00000000), but the entry point address depends on the
4167kernel version:
4168
4169- 2.2.x kernels have the entry point at 0x0000000C,
4170- 2.3.x and later kernels have the entry point at 0x00000000.
4171
4172So a typical call to build a U-Boot image would read:
4173
4174	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4175	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4176	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4177	> examples/uImage.TQM850L
4178	Image Name:   2.4.4 kernel for TQM850L
4179	Created:      Wed Jul 19 02:34:59 2000
4180	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4181	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4182	Load Address: 0x00000000
4183	Entry Point:  0x00000000
4184
4185To verify the contents of the image (or check for corruption):
4186
4187	-> tools/mkimage -l examples/uImage.TQM850L
4188	Image Name:   2.4.4 kernel for TQM850L
4189	Created:      Wed Jul 19 02:34:59 2000
4190	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4191	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4192	Load Address: 0x00000000
4193	Entry Point:  0x00000000
4194
4195NOTE: for embedded systems where boot time is critical you can trade
4196speed for memory and install an UNCOMPRESSED image instead: this
4197needs more space in Flash, but boots much faster since it does not
4198need to be uncompressed:
4199
4200	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4201	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4202	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4203	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4204	> examples/uImage.TQM850L-uncompressed
4205	Image Name:   2.4.4 kernel for TQM850L
4206	Created:      Wed Jul 19 02:34:59 2000
4207	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4208	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4209	Load Address: 0x00000000
4210	Entry Point:  0x00000000
4211
4212
4213Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4214when your kernel is intended to use an initial ramdisk:
4215
4216	-> tools/mkimage -n 'Simple Ramdisk Image' \
4217	> -A ppc -O linux -T ramdisk -C gzip \
4218	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4219	Image Name:   Simple Ramdisk Image
4220	Created:      Wed Jan 12 14:01:50 2000
4221	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4222	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4223	Load Address: 0x00000000
4224	Entry Point:  0x00000000
4225
4226The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4227option performs the converse operation of the mkimage's second form (the "-d"
4228option). Given an image built by mkimage, the dumpimage extracts a "data file"
4229from the image:
4230
4231	tools/dumpimage -i image -T type -p position data_file
4232	  -i ==> extract from the 'image' a specific 'data_file'
4233	  -T ==> set image type to 'type'
4234	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4235
4236
4237Installing a Linux Image:
4238-------------------------
4239
4240To downloading a U-Boot image over the serial (console) interface,
4241you must convert the image to S-Record format:
4242
4243	objcopy -I binary -O srec examples/image examples/image.srec
4244
4245The 'objcopy' does not understand the information in the U-Boot
4246image header, so the resulting S-Record file will be relative to
4247address 0x00000000. To load it to a given address, you need to
4248specify the target address as 'offset' parameter with the 'loads'
4249command.
4250
4251Example: install the image to address 0x40100000 (which on the
4252TQM8xxL is in the first Flash bank):
4253
4254	=> erase 40100000 401FFFFF
4255
4256	.......... done
4257	Erased 8 sectors
4258
4259	=> loads 40100000
4260	## Ready for S-Record download ...
4261	~>examples/image.srec
4262	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4263	...
4264	15989 15990 15991 15992
4265	[file transfer complete]
4266	[connected]
4267	## Start Addr = 0x00000000
4268
4269
4270You can check the success of the download using the 'iminfo' command;
4271this includes a checksum verification so you can be sure no data
4272corruption happened:
4273
4274	=> imi 40100000
4275
4276	## Checking Image at 40100000 ...
4277	   Image Name:	 2.2.13 for initrd on TQM850L
4278	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4279	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4280	   Load Address: 00000000
4281	   Entry Point:	 0000000c
4282	   Verifying Checksum ... OK
4283
4284
4285Boot Linux:
4286-----------
4287
4288The "bootm" command is used to boot an application that is stored in
4289memory (RAM or Flash). In case of a Linux kernel image, the contents
4290of the "bootargs" environment variable is passed to the kernel as
4291parameters. You can check and modify this variable using the
4292"printenv" and "setenv" commands:
4293
4294
4295	=> printenv bootargs
4296	bootargs=root=/dev/ram
4297
4298	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4299
4300	=> printenv bootargs
4301	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4302
4303	=> bootm 40020000
4304	## Booting Linux kernel at 40020000 ...
4305	   Image Name:	 2.2.13 for NFS on TQM850L
4306	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4307	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4308	   Load Address: 00000000
4309	   Entry Point:	 0000000c
4310	   Verifying Checksum ... OK
4311	   Uncompressing Kernel Image ... OK
4312	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
4313	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4314	time_init: decrementer frequency = 187500000/60
4315	Calibrating delay loop... 49.77 BogoMIPS
4316	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4317	...
4318
4319If you want to boot a Linux kernel with initial RAM disk, you pass
4320the memory addresses of both the kernel and the initrd image (PPBCOOT
4321format!) to the "bootm" command:
4322
4323	=> imi 40100000 40200000
4324
4325	## Checking Image at 40100000 ...
4326	   Image Name:	 2.2.13 for initrd on TQM850L
4327	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4328	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4329	   Load Address: 00000000
4330	   Entry Point:	 0000000c
4331	   Verifying Checksum ... OK
4332
4333	## Checking Image at 40200000 ...
4334	   Image Name:	 Simple Ramdisk Image
4335	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4336	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4337	   Load Address: 00000000
4338	   Entry Point:	 00000000
4339	   Verifying Checksum ... OK
4340
4341	=> bootm 40100000 40200000
4342	## Booting Linux kernel at 40100000 ...
4343	   Image Name:	 2.2.13 for initrd on TQM850L
4344	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4345	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4346	   Load Address: 00000000
4347	   Entry Point:	 0000000c
4348	   Verifying Checksum ... OK
4349	   Uncompressing Kernel Image ... OK
4350	## Loading RAMDisk Image at 40200000 ...
4351	   Image Name:	 Simple Ramdisk Image
4352	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4353	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4354	   Load Address: 00000000
4355	   Entry Point:	 00000000
4356	   Verifying Checksum ... OK
4357	   Loading Ramdisk ... OK
4358	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
4359	Boot arguments: root=/dev/ram
4360	time_init: decrementer frequency = 187500000/60
4361	Calibrating delay loop... 49.77 BogoMIPS
4362	...
4363	RAMDISK: Compressed image found at block 0
4364	VFS: Mounted root (ext2 filesystem).
4365
4366	bash#
4367
4368Boot Linux and pass a flat device tree:
4369-----------
4370
4371First, U-Boot must be compiled with the appropriate defines. See the section
4372titled "Linux Kernel Interface" above for a more in depth explanation. The
4373following is an example of how to start a kernel and pass an updated
4374flat device tree:
4375
4376=> print oftaddr
4377oftaddr=0x300000
4378=> print oft
4379oft=oftrees/mpc8540ads.dtb
4380=> tftp $oftaddr $oft
4381Speed: 1000, full duplex
4382Using TSEC0 device
4383TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4384Filename 'oftrees/mpc8540ads.dtb'.
4385Load address: 0x300000
4386Loading: #
4387done
4388Bytes transferred = 4106 (100a hex)
4389=> tftp $loadaddr $bootfile
4390Speed: 1000, full duplex
4391Using TSEC0 device
4392TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4393Filename 'uImage'.
4394Load address: 0x200000
4395Loading:############
4396done
4397Bytes transferred = 1029407 (fb51f hex)
4398=> print loadaddr
4399loadaddr=200000
4400=> print oftaddr
4401oftaddr=0x300000
4402=> bootm $loadaddr - $oftaddr
4403## Booting image at 00200000 ...
4404   Image Name:	 Linux-2.6.17-dirty
4405   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4406   Data Size:	 1029343 Bytes = 1005.2 kB
4407   Load Address: 00000000
4408   Entry Point:	 00000000
4409   Verifying Checksum ... OK
4410   Uncompressing Kernel Image ... OK
4411Booting using flat device tree at 0x300000
4412Using MPC85xx ADS machine description
4413Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4414[snip]
4415
4416
4417More About U-Boot Image Types:
4418------------------------------
4419
4420U-Boot supports the following image types:
4421
4422   "Standalone Programs" are directly runnable in the environment
4423	provided by U-Boot; it is expected that (if they behave
4424	well) you can continue to work in U-Boot after return from
4425	the Standalone Program.
4426   "OS Kernel Images" are usually images of some Embedded OS which
4427	will take over control completely. Usually these programs
4428	will install their own set of exception handlers, device
4429	drivers, set up the MMU, etc. - this means, that you cannot
4430	expect to re-enter U-Boot except by resetting the CPU.
4431   "RAMDisk Images" are more or less just data blocks, and their
4432	parameters (address, size) are passed to an OS kernel that is
4433	being started.
4434   "Multi-File Images" contain several images, typically an OS
4435	(Linux) kernel image and one or more data images like
4436	RAMDisks. This construct is useful for instance when you want
4437	to boot over the network using BOOTP etc., where the boot
4438	server provides just a single image file, but you want to get
4439	for instance an OS kernel and a RAMDisk image.
4440
4441	"Multi-File Images" start with a list of image sizes, each
4442	image size (in bytes) specified by an "uint32_t" in network
4443	byte order. This list is terminated by an "(uint32_t)0".
4444	Immediately after the terminating 0 follow the images, one by
4445	one, all aligned on "uint32_t" boundaries (size rounded up to
4446	a multiple of 4 bytes).
4447
4448   "Firmware Images" are binary images containing firmware (like
4449	U-Boot or FPGA images) which usually will be programmed to
4450	flash memory.
4451
4452   "Script files" are command sequences that will be executed by
4453	U-Boot's command interpreter; this feature is especially
4454	useful when you configure U-Boot to use a real shell (hush)
4455	as command interpreter.
4456
4457Booting the Linux zImage:
4458-------------------------
4459
4460On some platforms, it's possible to boot Linux zImage. This is done
4461using the "bootz" command. The syntax of "bootz" command is the same
4462as the syntax of "bootm" command.
4463
4464Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4465kernel with raw initrd images. The syntax is slightly different, the
4466address of the initrd must be augmented by it's size, in the following
4467format: "<initrd addres>:<initrd size>".
4468
4469
4470Standalone HOWTO:
4471=================
4472
4473One of the features of U-Boot is that you can dynamically load and
4474run "standalone" applications, which can use some resources of
4475U-Boot like console I/O functions or interrupt services.
4476
4477Two simple examples are included with the sources:
4478
4479"Hello World" Demo:
4480-------------------
4481
4482'examples/hello_world.c' contains a small "Hello World" Demo
4483application; it is automatically compiled when you build U-Boot.
4484It's configured to run at address 0x00040004, so you can play with it
4485like that:
4486
4487	=> loads
4488	## Ready for S-Record download ...
4489	~>examples/hello_world.srec
4490	1 2 3 4 5 6 7 8 9 10 11 ...
4491	[file transfer complete]
4492	[connected]
4493	## Start Addr = 0x00040004
4494
4495	=> go 40004 Hello World! This is a test.
4496	## Starting application at 0x00040004 ...
4497	Hello World
4498	argc = 7
4499	argv[0] = "40004"
4500	argv[1] = "Hello"
4501	argv[2] = "World!"
4502	argv[3] = "This"
4503	argv[4] = "is"
4504	argv[5] = "a"
4505	argv[6] = "test."
4506	argv[7] = "<NULL>"
4507	Hit any key to exit ...
4508
4509	## Application terminated, rc = 0x0
4510
4511Another example, which demonstrates how to register a CPM interrupt
4512handler with the U-Boot code, can be found in 'examples/timer.c'.
4513Here, a CPM timer is set up to generate an interrupt every second.
4514The interrupt service routine is trivial, just printing a '.'
4515character, but this is just a demo program. The application can be
4516controlled by the following keys:
4517
4518	? - print current values og the CPM Timer registers
4519	b - enable interrupts and start timer
4520	e - stop timer and disable interrupts
4521	q - quit application
4522
4523	=> loads
4524	## Ready for S-Record download ...
4525	~>examples/timer.srec
4526	1 2 3 4 5 6 7 8 9 10 11 ...
4527	[file transfer complete]
4528	[connected]
4529	## Start Addr = 0x00040004
4530
4531	=> go 40004
4532	## Starting application at 0x00040004 ...
4533	TIMERS=0xfff00980
4534	Using timer 1
4535	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4536
4537Hit 'b':
4538	[q, b, e, ?] Set interval 1000000 us
4539	Enabling timer
4540Hit '?':
4541	[q, b, e, ?] ........
4542	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4543Hit '?':
4544	[q, b, e, ?] .
4545	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4546Hit '?':
4547	[q, b, e, ?] .
4548	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4549Hit '?':
4550	[q, b, e, ?] .
4551	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4552Hit 'e':
4553	[q, b, e, ?] ...Stopping timer
4554Hit 'q':
4555	[q, b, e, ?] ## Application terminated, rc = 0x0
4556
4557
4558Minicom warning:
4559================
4560
4561Over time, many people have reported problems when trying to use the
4562"minicom" terminal emulation program for serial download. I (wd)
4563consider minicom to be broken, and recommend not to use it. Under
4564Unix, I recommend to use C-Kermit for general purpose use (and
4565especially for kermit binary protocol download ("loadb" command), and
4566use "cu" for S-Record download ("loads" command).  See
4567http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4568for help with kermit.
4569
4570
4571Nevertheless, if you absolutely want to use it try adding this
4572configuration to your "File transfer protocols" section:
4573
4574	   Name	   Program			Name U/D FullScr IO-Red. Multi
4575	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4576	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4577
4578
4579NetBSD Notes:
4580=============
4581
4582Starting at version 0.9.2, U-Boot supports NetBSD both as host
4583(build U-Boot) and target system (boots NetBSD/mpc8xx).
4584
4585Building requires a cross environment; it is known to work on
4586NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4587need gmake since the Makefiles are not compatible with BSD make).
4588Note that the cross-powerpc package does not install include files;
4589attempting to build U-Boot will fail because <machine/ansi.h> is
4590missing.  This file has to be installed and patched manually:
4591
4592	# cd /usr/pkg/cross/powerpc-netbsd/include
4593	# mkdir powerpc
4594	# ln -s powerpc machine
4595	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4596	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4597
4598Native builds *don't* work due to incompatibilities between native
4599and U-Boot include files.
4600
4601Booting assumes that (the first part of) the image booted is a
4602stage-2 loader which in turn loads and then invokes the kernel
4603proper. Loader sources will eventually appear in the NetBSD source
4604tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4605meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4606
4607
4608Implementation Internals:
4609=========================
4610
4611The following is not intended to be a complete description of every
4612implementation detail. However, it should help to understand the
4613inner workings of U-Boot and make it easier to port it to custom
4614hardware.
4615
4616
4617Initial Stack, Global Data:
4618---------------------------
4619
4620The implementation of U-Boot is complicated by the fact that U-Boot
4621starts running out of ROM (flash memory), usually without access to
4622system RAM (because the memory controller is not initialized yet).
4623This means that we don't have writable Data or BSS segments, and BSS
4624is not initialized as zero. To be able to get a C environment working
4625at all, we have to allocate at least a minimal stack. Implementation
4626options for this are defined and restricted by the CPU used: Some CPU
4627models provide on-chip memory (like the IMMR area on MPC8xx and
4628MPC826x processors), on others (parts of) the data cache can be
4629locked as (mis-) used as memory, etc.
4630
4631	Chris Hallinan posted a good summary of these issues to the
4632	U-Boot mailing list:
4633
4634	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4635	From: "Chris Hallinan" <clh@net1plus.com>
4636	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4637	...
4638
4639	Correct me if I'm wrong, folks, but the way I understand it
4640	is this: Using DCACHE as initial RAM for Stack, etc, does not
4641	require any physical RAM backing up the cache. The cleverness
4642	is that the cache is being used as a temporary supply of
4643	necessary storage before the SDRAM controller is setup. It's
4644	beyond the scope of this list to explain the details, but you
4645	can see how this works by studying the cache architecture and
4646	operation in the architecture and processor-specific manuals.
4647
4648	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4649	is another option for the system designer to use as an
4650	initial stack/RAM area prior to SDRAM being available. Either
4651	option should work for you. Using CS 4 should be fine if your
4652	board designers haven't used it for something that would
4653	cause you grief during the initial boot! It is frequently not
4654	used.
4655
4656	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4657	with your processor/board/system design. The default value
4658	you will find in any recent u-boot distribution in
4659	walnut.h should work for you. I'd set it to a value larger
4660	than your SDRAM module. If you have a 64MB SDRAM module, set
4661	it above 400_0000. Just make sure your board has no resources
4662	that are supposed to respond to that address! That code in
4663	start.S has been around a while and should work as is when
4664	you get the config right.
4665
4666	-Chris Hallinan
4667	DS4.COM, Inc.
4668
4669It is essential to remember this, since it has some impact on the C
4670code for the initialization procedures:
4671
4672* Initialized global data (data segment) is read-only. Do not attempt
4673  to write it.
4674
4675* Do not use any uninitialized global data (or implicitly initialized
4676  as zero data - BSS segment) at all - this is undefined, initiali-
4677  zation is performed later (when relocating to RAM).
4678
4679* Stack space is very limited. Avoid big data buffers or things like
4680  that.
4681
4682Having only the stack as writable memory limits means we cannot use
4683normal global data to share information between the code. But it
4684turned out that the implementation of U-Boot can be greatly
4685simplified by making a global data structure (gd_t) available to all
4686functions. We could pass a pointer to this data as argument to _all_
4687functions, but this would bloat the code. Instead we use a feature of
4688the GCC compiler (Global Register Variables) to share the data: we
4689place a pointer (gd) to the global data into a register which we
4690reserve for this purpose.
4691
4692When choosing a register for such a purpose we are restricted by the
4693relevant  (E)ABI  specifications for the current architecture, and by
4694GCC's implementation.
4695
4696For PowerPC, the following registers have specific use:
4697	R1:	stack pointer
4698	R2:	reserved for system use
4699	R3-R4:	parameter passing and return values
4700	R5-R10: parameter passing
4701	R13:	small data area pointer
4702	R30:	GOT pointer
4703	R31:	frame pointer
4704
4705	(U-Boot also uses R12 as internal GOT pointer. r12
4706	is a volatile register so r12 needs to be reset when
4707	going back and forth between asm and C)
4708
4709    ==> U-Boot will use R2 to hold a pointer to the global data
4710
4711    Note: on PPC, we could use a static initializer (since the
4712    address of the global data structure is known at compile time),
4713    but it turned out that reserving a register results in somewhat
4714    smaller code - although the code savings are not that big (on
4715    average for all boards 752 bytes for the whole U-Boot image,
4716    624 text + 127 data).
4717
4718On ARM, the following registers are used:
4719
4720	R0:	function argument word/integer result
4721	R1-R3:	function argument word
4722	R9:	platform specific
4723	R10:	stack limit (used only if stack checking is enabled)
4724	R11:	argument (frame) pointer
4725	R12:	temporary workspace
4726	R13:	stack pointer
4727	R14:	link register
4728	R15:	program counter
4729
4730    ==> U-Boot will use R9 to hold a pointer to the global data
4731
4732    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4733
4734On Nios II, the ABI is documented here:
4735	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4736
4737    ==> U-Boot will use gp to hold a pointer to the global data
4738
4739    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4740    to access small data sections, so gp is free.
4741
4742On NDS32, the following registers are used:
4743
4744	R0-R1:	argument/return
4745	R2-R5:	argument
4746	R15:	temporary register for assembler
4747	R16:	trampoline register
4748	R28:	frame pointer (FP)
4749	R29:	global pointer (GP)
4750	R30:	link register (LP)
4751	R31:	stack pointer (SP)
4752	PC:	program counter (PC)
4753
4754    ==> U-Boot will use R10 to hold a pointer to the global data
4755
4756NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4757or current versions of GCC may "optimize" the code too much.
4758
4759On RISC-V, the following registers are used:
4760
4761	x0: hard-wired zero (zero)
4762	x1: return address (ra)
4763	x2:	stack pointer (sp)
4764	x3:	global pointer (gp)
4765	x4:	thread pointer (tp)
4766	x5:	link register (t0)
4767	x8:	frame pointer (fp)
4768	x10-x11:	arguments/return values (a0-1)
4769	x12-x17:	arguments (a2-7)
4770	x28-31:	 temporaries (t3-6)
4771	pc:	program counter (pc)
4772
4773    ==> U-Boot will use gp to hold a pointer to the global data
4774
4775Memory Management:
4776------------------
4777
4778U-Boot runs in system state and uses physical addresses, i.e. the
4779MMU is not used either for address mapping nor for memory protection.
4780
4781The available memory is mapped to fixed addresses using the memory
4782controller. In this process, a contiguous block is formed for each
4783memory type (Flash, SDRAM, SRAM), even when it consists of several
4784physical memory banks.
4785
4786U-Boot is installed in the first 128 kB of the first Flash bank (on
4787TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4788booting and sizing and initializing DRAM, the code relocates itself
4789to the upper end of DRAM. Immediately below the U-Boot code some
4790memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4791configuration setting]. Below that, a structure with global Board
4792Info data is placed, followed by the stack (growing downward).
4793
4794Additionally, some exception handler code is copied to the low 8 kB
4795of DRAM (0x00000000 ... 0x00001FFF).
4796
4797So a typical memory configuration with 16 MB of DRAM could look like
4798this:
4799
4800	0x0000 0000	Exception Vector code
4801	      :
4802	0x0000 1FFF
4803	0x0000 2000	Free for Application Use
4804	      :
4805	      :
4806
4807	      :
4808	      :
4809	0x00FB FF20	Monitor Stack (Growing downward)
4810	0x00FB FFAC	Board Info Data and permanent copy of global data
4811	0x00FC 0000	Malloc Arena
4812	      :
4813	0x00FD FFFF
4814	0x00FE 0000	RAM Copy of Monitor Code
4815	...		eventually: LCD or video framebuffer
4816	...		eventually: pRAM (Protected RAM - unchanged by reset)
4817	0x00FF FFFF	[End of RAM]
4818
4819
4820System Initialization:
4821----------------------
4822
4823In the reset configuration, U-Boot starts at the reset entry point
4824(on most PowerPC systems at address 0x00000100). Because of the reset
4825configuration for CS0# this is a mirror of the on board Flash memory.
4826To be able to re-map memory U-Boot then jumps to its link address.
4827To be able to implement the initialization code in C, a (small!)
4828initial stack is set up in the internal Dual Ported RAM (in case CPUs
4829which provide such a feature like), or in a locked part of the data
4830cache. After that, U-Boot initializes the CPU core, the caches and
4831the SIU.
4832
4833Next, all (potentially) available memory banks are mapped using a
4834preliminary mapping. For example, we put them on 512 MB boundaries
4835(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4836on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4837programmed for SDRAM access. Using the temporary configuration, a
4838simple memory test is run that determines the size of the SDRAM
4839banks.
4840
4841When there is more than one SDRAM bank, and the banks are of
4842different size, the largest is mapped first. For equal size, the first
4843bank (CS2#) is mapped first. The first mapping is always for address
48440x00000000, with any additional banks following immediately to create
4845contiguous memory starting from 0.
4846
4847Then, the monitor installs itself at the upper end of the SDRAM area
4848and allocates memory for use by malloc() and for the global Board
4849Info data; also, the exception vector code is copied to the low RAM
4850pages, and the final stack is set up.
4851
4852Only after this relocation will you have a "normal" C environment;
4853until that you are restricted in several ways, mostly because you are
4854running from ROM, and because the code will have to be relocated to a
4855new address in RAM.
4856
4857
4858U-Boot Porting Guide:
4859----------------------
4860
4861[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4862list, October 2002]
4863
4864
4865int main(int argc, char *argv[])
4866{
4867	sighandler_t no_more_time;
4868
4869	signal(SIGALRM, no_more_time);
4870	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4871
4872	if (available_money > available_manpower) {
4873		Pay consultant to port U-Boot;
4874		return 0;
4875	}
4876
4877	Download latest U-Boot source;
4878
4879	Subscribe to u-boot mailing list;
4880
4881	if (clueless)
4882		email("Hi, I am new to U-Boot, how do I get started?");
4883
4884	while (learning) {
4885		Read the README file in the top level directory;
4886		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4887		Read applicable doc/*.README;
4888		Read the source, Luke;
4889		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4890	}
4891
4892	if (available_money > toLocalCurrency ($2500))
4893		Buy a BDI3000;
4894	else
4895		Add a lot of aggravation and time;
4896
4897	if (a similar board exists) {	/* hopefully... */
4898		cp -a board/<similar> board/<myboard>
4899		cp include/configs/<similar>.h include/configs/<myboard>.h
4900	} else {
4901		Create your own board support subdirectory;
4902		Create your own board include/configs/<myboard>.h file;
4903	}
4904	Edit new board/<myboard> files
4905	Edit new include/configs/<myboard>.h
4906
4907	while (!accepted) {
4908		while (!running) {
4909			do {
4910				Add / modify source code;
4911			} until (compiles);
4912			Debug;
4913			if (clueless)
4914				email("Hi, I am having problems...");
4915		}
4916		Send patch file to the U-Boot email list;
4917		if (reasonable critiques)
4918			Incorporate improvements from email list code review;
4919		else
4920			Defend code as written;
4921	}
4922
4923	return 0;
4924}
4925
4926void no_more_time (int sig)
4927{
4928      hire_a_guru();
4929}
4930
4931
4932Coding Standards:
4933-----------------
4934
4935All contributions to U-Boot should conform to the Linux kernel
4936coding style; see the kernel coding style guide at
4937https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4938script "scripts/Lindent" in your Linux kernel source directory.
4939
4940Source files originating from a different project (for example the
4941MTD subsystem) are generally exempt from these guidelines and are not
4942reformatted to ease subsequent migration to newer versions of those
4943sources.
4944
4945Please note that U-Boot is implemented in C (and to some small parts in
4946Assembler); no C++ is used, so please do not use C++ style comments (//)
4947in your code.
4948
4949Please also stick to the following formatting rules:
4950- remove any trailing white space
4951- use TAB characters for indentation and vertical alignment, not spaces
4952- make sure NOT to use DOS '\r\n' line feeds
4953- do not add more than 2 consecutive empty lines to source files
4954- do not add trailing empty lines to source files
4955
4956Submissions which do not conform to the standards may be returned
4957with a request to reformat the changes.
4958
4959
4960Submitting Patches:
4961-------------------
4962
4963Since the number of patches for U-Boot is growing, we need to
4964establish some rules. Submissions which do not conform to these rules
4965may be rejected, even when they contain important and valuable stuff.
4966
4967Please see http://www.denx.de/wiki/U-Boot/Patches for details.
4968
4969Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4970see https://lists.denx.de/listinfo/u-boot
4971
4972When you send a patch, please include the following information with
4973it:
4974
4975* For bug fixes: a description of the bug and how your patch fixes
4976  this bug. Please try to include a way of demonstrating that the
4977  patch actually fixes something.
4978
4979* For new features: a description of the feature and your
4980  implementation.
4981
4982* A CHANGELOG entry as plaintext (separate from the patch)
4983
4984* For major contributions, add a MAINTAINERS file with your
4985  information and associated file and directory references.
4986
4987* When you add support for a new board, don't forget to add a
4988  maintainer e-mail address to the boards.cfg file, too.
4989
4990* If your patch adds new configuration options, don't forget to
4991  document these in the README file.
4992
4993* The patch itself. If you are using git (which is *strongly*
4994  recommended) you can easily generate the patch using the
4995  "git format-patch". If you then use "git send-email" to send it to
4996  the U-Boot mailing list, you will avoid most of the common problems
4997  with some other mail clients.
4998
4999  If you cannot use git, use "diff -purN OLD NEW". If your version of
5000  diff does not support these options, then get the latest version of
5001  GNU diff.
5002
5003  The current directory when running this command shall be the parent
5004  directory of the U-Boot source tree (i. e. please make sure that
5005  your patch includes sufficient directory information for the
5006  affected files).
5007
5008  We prefer patches as plain text. MIME attachments are discouraged,
5009  and compressed attachments must not be used.
5010
5011* If one logical set of modifications affects or creates several
5012  files, all these changes shall be submitted in a SINGLE patch file.
5013
5014* Changesets that contain different, unrelated modifications shall be
5015  submitted as SEPARATE patches, one patch per changeset.
5016
5017
5018Notes:
5019
5020* Before sending the patch, run the buildman script on your patched
5021  source tree and make sure that no errors or warnings are reported
5022  for any of the boards.
5023
5024* Keep your modifications to the necessary minimum: A patch
5025  containing several unrelated changes or arbitrary reformats will be
5026  returned with a request to re-formatting / split it.
5027
5028* If you modify existing code, make sure that your new code does not
5029  add to the memory footprint of the code ;-) Small is beautiful!
5030  When adding new features, these should compile conditionally only
5031  (using #ifdef), and the resulting code with the new feature
5032  disabled must not need more memory than the old code without your
5033  modification.
5034
5035* Remember that there is a size limit of 100 kB per message on the
5036  u-boot mailing list. Bigger patches will be moderated. If they are
5037  reasonable and not too big, they will be acknowledged. But patches
5038  bigger than the size limit should be avoided.
5039