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+#
+# (C) Copyright 2000 - 2002
+# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+#
+# See file CREDITS for list of people who contributed to this
+# project.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation; either version 2 of
+# the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+# MA 02111-1307 USA
+#
+
+Summary:
+========
+
+This directory contains the source code for U-Boot, a monitor for
+Embedded PowerPC boards, which can be installed in a boot ROM and
+used to test the hardware or download and run application code.
+
+The development of U-Boot is closely related to Linux: some parts of
+the source code originate in the Linux source tree, we still have
+some header files in common, and special provision has been made to
+support booting of Linux images.
+
+Some attention has been paid to make this software easily
+configurable and extendable. For instance, all monitor commands are
+implemented with the same call interface, so that it's very easy to
+add new commands. Also, instead of permanently adding rarely used
+code (for instance hardware test utilities) to the monitor, you can
+load and run it dynamically.
+
+
+Status:
+=======
+
+In general, all boards for which a configuration option exists in the
+Makefile have been tested to some extent and can be considered
+"working". In fact, many of them are used in production systems.
+
+In case of problems see the CHANGELOG and CREDITS files to find out
+who contributed the specific port.
+
+Exception from this rule: the port to the Sandpoint 8240 has not been
+completed yet.
+
+
+Where to get help:
+==================
+
+In case you have questions about, problems with or contributions for
+U-Boot you should send a message to the U-Boot mailing list at
+<u-boot-users@lists.sourceforge.net>. There is also an archive of
+previous traffic on the mailing list - please search the archive
+before asking FAQ's. Please see
+http://lists.sourceforge.net/lists/listinfo/u-boot-users/
+
+
+Where we come from:
+===================
+
+- start from 8xxrom sources
+- clean up code
+- make it easier to add custom boards
+- make it possible to add other [PowerPC] CPUs
+- extend functions, especially:
+ * Provide extended interface to Linux boot loader
+ * S-Record download
+ * network boot
+ * PCMCIA / CompactFLash / ATA disk / SCSI ... boot
+- add other CPU families (starting with ARM)
+
+
+Directory Hierarchy:
+====================
+
+- board Board dependend files
+- common Misc architecture independend functions
+- cpu CPU specific files
+- disk Code for disk drive partition handling
+- doc Documentation (don't expect too much)
+- drivers Common used device drivers
+- dtt Digital Thermometer and Thermostat drivers
+- examples Example code for standalone applications, etc.
+- include Header Files
+- disk Harddisk interface code
+- net Networking code
+- ppc Files generic to PowerPC architecture
+- post Power On Self Test
+- post/arch Symlink to architecture specific Power On Self Test
+- post/arch-ppc PowerPC architecture specific Power On Self Test
+- post/cpu/mpc8260 MPC8260 CPU specific Power On Self Test
+- post/cpu/mpc8xx MPC8xx CPU specific Power On Self Test
+- rtc Real Time Clock drivers
+- tools Tools to build S-Record or U-Boot images, etc.
+
+- cpu/74xx_7xx Files specific to Motorola MPC74xx and 7xx CPUs
+- cpu/mpc8xx Files specific to Motorola MPC8xx CPUs
+- cpu/mpc824x Files specific to Motorola MPC824x CPUs
+- cpu/mpc8260 Files specific to Motorola MPC8260 CPU
+- cpu/ppc4xx Files specific to IBM 4xx CPUs
+
+- board/RPXClassic
+ Files specific to RPXClassic boards
+- board/RPXlite Files specific to RPXlite boards
+- board/c2mon Files specific to c2mon boards
+- board/cogent Files specific to Cogent boards
+ (need further configuration)
+ Files specific to CPCIISER4 boards
+- board/cpu86 Files specific to CPU86 boards
+- board/cray/ Files specific to boards manufactured by Cray
+- board/cray/L1 Files specific to L1 boards
+- board/cu824 Files specific to CU824 boards
+- board/ebony Files specific to IBM Ebony board
+- board/eric Files specific to ERIC boards
+- board/esd/ Files specific to boards manufactured by ESD
+- board/esd/adciop Files specific to ADCIOP boards
+- board/esd/ar405 Files specific to AR405 boards
+- board/esd/canbt Files specific to CANBT boards
+- board/esd/cpci405 Files specific to CPCI405 boards
+- board/esd/cpciiser4 Files specific to CPCIISER4 boards
+- board/esd/common Common files for ESD boards
+- board/esd/dasa_sim Files specific to DASA_SIM boards
+- board/esd/du405 Files specific to DU405 boards
+- board/esd/ocrtc Files specific to OCRTC boards
+- board/esd/pci405 Files specific to PCI405 boards
+- board/esteem192e
+ Files specific to ESTEEM192E boards
+- board/etx094 Files specific to ETX_094 boards
+- board/evb64260
+ Files specific to EVB64260 boards
+- board/fads Files specific to FADS boards
+- board/flagadm Files specific to FLAGADM boards
+- board/gen860t Files specific to GEN860T boards
+- board/genietv Files specific to GENIETV boards
+- board/gth Files specific to GTH boards
+- board/hermes Files specific to HERMES boards
+- board/hymod Files specific to HYMOD boards
+- board/icu862 Files specific to ICU862 boards
+- board/ip860 Files specific to IP860 boards
+- board/iphase4539
+ Files specific to Interphase4539 boards
+- board/ivm Files specific to IVMS8/IVML24 boards
+- board/lantec Files specific to LANTEC boards
+- board/lwmon Files specific to LWMON boards
+- board/mbx8xx Files specific to MBX boards
+- board/mpc8260ads
+ Files specific to MMPC8260ADS boards
+- board/mpl/ Files specific to boards manufactured by MPL
+- board/mpl/common Common files for MPL boards
+- board/mpl/pip405 Files specific to PIP405 boards
+- board/mpl/mip405 Files specific to MIP405 boards
+- board/musenki Files specific to MUSEKNI boards
+- board/mvs1 Files specific to MVS1 boards
+- board/nx823 Files specific to NX823 boards
+- board/oxc Files specific to OXC boards
+- board/pcippc2 Files specific to PCIPPC2/PCIPPC6 boards
+- board/pm826 Files specific to PM826 boards
+- board/ppmc8260
+ Files specific to PPMC8260 boards
+- board/rpxsuper
+ Files specific to RPXsuper boards
+- board/rsdproto
+ Files specific to RSDproto boards
+- board/sandpoint
+ Files specific to Sandpoint boards
+- board/sbc8260 Files specific to SBC8260 boards
+- board/sacsng Files specific to SACSng boards
+- board/siemens Files specific to boards manufactured by Siemens AG
+- board/siemens/CCM Files specific to CCM boards
+- board/siemens/IAD210 Files specific to IAD210 boards
+- board/siemens/SCM Files specific to SCM boards
+- board/siemens/pcu_e Files specific to PCU_E boards
+- board/sixnet Files specific to SIXNET boards
+- board/spd8xx Files specific to SPD8xxTS boards
+- board/tqm8260 Files specific to TQM8260 boards
+- board/tqm8xx Files specific to TQM8xxL boards
+- board/w7o Files specific to W7O boards
+- board/walnut405
+ Files specific to Walnut405 boards
+- board/westel/ Files specific to boards manufactured by Westel Wireless
+- board/westel/amx860 Files specific to AMX860 boards
+- board/utx8245 Files specific to UTX8245 boards
+
+Software Configuration:
+=======================
+
+Configuration is usually done using C preprocessor defines; the
+rationale behind that is to avoid dead code whenever possible.
+
+There are two classes of configuration variables:
+
+* Configuration _OPTIONS_:
+ These are selectable by the user and have names beginning with
+ "CONFIG_".
+
+* Configuration _SETTINGS_:
+ These depend on the hardware etc. and should not be meddled with if
+ you don't know what you're doing; they have names beginning with
+ "CFG_".
+
+Later we will add a configuration tool - probably similar to or even
+identical to what's used for the Linux kernel. Right now, we have to
+do the configuration by hand, which means creating some symbolic
+links and editing some configuration files. We use the TQM8xxL boards
+as an example here.
+
+
+Selection of Processor Architecture and Board Type:
+---------------------------------------------------
+
+For all supported boards there are ready-to-use default
+configurations available; just type "make <board_name>_config".
+
+Example: For a TQM823L module type:
+
+ cd u-boot
+ make TQM823L_config
+
+For the Cogent platform, you need to specify the cpu type as well;
+e.g. "make cogent_mpc8xx_config". And also configure the cogent
+directory according to the instructions in cogent/README.
+
+
+Configuration Options:
+----------------------
+
+Configuration depends on the combination of board and CPU type; all
+such information is kept in a configuration file
+"include/configs/<board_name>.h".
+
+Example: For a TQM823L module, all configuration settings are in
+"include/configs/TQM823L.h".
+
+
+The following options need to be configured:
+
+- CPU Type: Define exactly one of
+
+ PowerPC based CPUs:
+ -------------------
+ CONFIG_MPC823, CONFIG_MPC850, CONFIG_MPC855, CONFIG_MPC860
+ or CONFIG_MPC824X, CONFIG_MPC8260
+ or CONFIG_IOP480
+ or CONFIG_405GP
+ or CONFIG_440
+ or CONFIG_MPC74xx
+
+ ARM based CPUs:
+ ---------------
+ CONFIG_SA1110
+ CONFIG_ARM7
+ CONFIG_PXA250
+
+
+- Board Type: Define exactly one of
+
+ PowerPC based boards:
+ ---------------------
+
+ CONFIG_ADCIOP, CONFIG_ICU862 CONFIG_RPXsuper,
+ CONFIG_ADS860, CONFIG_IP860, CONFIG_SM850,
+ CONFIG_AMX860, CONFIG_IPHASE4539, CONFIG_SPD823TS,
+ CONFIG_AR405, CONFIG_IVML24, CONFIG_SXNI855T,
+ CONFIG_BAB7xx, CONFIG_IVML24_128, CONFIG_Sandpoint8240,
+ CONFIG_CANBT, CONFIG_IVML24_256, CONFIG_Sandpoint8245,
+ CONFIG_CCM, CONFIG_IVMS8, CONFIG_TQM823L,
+ CONFIG_CPCI405, CONFIG_IVMS8_128, CONFIG_TQM850L,
+ CONFIG_CPCI4052, CONFIG_IVMS8_256, CONFIG_TQM855L,
+ CONFIG_CPCIISER4, CONFIG_LANTEC, CONFIG_TQM860L,
+ CONFIG_CPU86, CONFIG_MBX, CONFIG_TQM8260,
+ CONFIG_CRAYL1, CONFIG_MBX860T, CONFIG_TTTech,
+ CONFIG_CU824, CONFIG_MHPC, CONFIG_UTX8245,
+ CONFIG_DASA_SIM, CONFIG_MIP405, CONFIG_W7OLMC,
+ CONFIG_DU405, CONFIG_MOUSSE, CONFIG_W7OLMG,
+ CONFIG_ELPPC, CONFIG_MPC8260ADS, CONFIG_WALNUT405,
+ CONFIG_ERIC, CONFIG_MUSENKI, CONFIG_ZUMA,
+ CONFIG_ESTEEM192E, CONFIG_MVS1, CONFIG_c2mon,
+ CONFIG_ETX094, CONFIG_NX823, CONFIG_cogent_mpc8260,
+ CONFIG_EVB64260, CONFIG_OCRTC, CONFIG_cogent_mpc8xx,
+ CONFIG_FADS823, CONFIG_ORSG, CONFIG_ep8260,
+ CONFIG_FADS850SAR, CONFIG_OXC, CONFIG_gw8260,
+ CONFIG_FADS860T, CONFIG_PCI405, CONFIG_hermes,
+ CONFIG_FLAGADM, CONFIG_PCIPPC2, CONFIG_hymod,
+ CONFIG_FPS850L, CONFIG_PCIPPC6, CONFIG_lwmon,
+ CONFIG_GEN860T, CONFIG_PIP405, CONFIG_pcu_e,
+ CONFIG_GENIETV, CONFIG_PM826, CONFIG_ppmc8260,
+ CONFIG_GTH, CONFIG_RPXClassic, CONFIG_rsdproto,
+ CONFIG_IAD210, CONFIG_RPXlite, CONFIG_sbc8260,
+ CONFIG_EBONY, CONFIG_sacsng
+
+ ARM based boards:
+ -----------------
+
+ CONFIG_HHP_CRADLE, CONFIG_DNP1110, CONFIG_EP7312,
+ CONFIG_IMPA7, CONFIG_LART, CONFIG_LUBBOCK,
+ CONFIG_SHANNON, CONFIG_SMDK2400, CONFIG_SMDK2410,
+ CONFIG_TRAB
+
+
+- CPU Module Type: (if CONFIG_COGENT is defined)
+ Define exactly one of
+ CONFIG_CMA286_60_OLD
+--- FIXME --- not tested yet:
+ CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
+ CONFIG_CMA287_23, CONFIG_CMA287_50
+
+- Motherboard Type: (if CONFIG_COGENT is defined)
+ Define exactly one of
+ CONFIG_CMA101, CONFIG_CMA102
+
+- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
+ Define one or more of
+ CONFIG_CMA302
+
+- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
+ Define one or more of
+ CONFIG_LCD_HEARTBEAT - update a character position on
+ the lcd display every second with
+ a "rotator" |\-/|\-/
+
+- MPC824X Family Member (if CONFIG_MPC824X is defined)
+ Define exactly one of
+ CONFIG_MPC8240, CONFIG_MPC8245
+
+- 8xx CPU Options: (if using an 8xx cpu)
+ Define one or more of
+ CONFIG_8xx_GCLK_FREQ - if get_gclk_freq() can not work e.g.
+ no 32KHz reference PIT/RTC clock
+
+- Clock Interface:
+ CONFIG_CLOCKS_IN_MHZ
+
+ U-Boot stores all clock information in Hz
+ internally. For binary compatibility with older Linux
+ kernels (which expect the clocks passed in the
+ bd_info data to be in MHz) the environment variable
+ "clocks_in_mhz" can be defined so that U-Boot
+ converts clock data to MHZ before passing it to the
+ Linux kernel.
+
+ When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
+ "clocks_in_mhz=1" is automatically included in the
+ default environment.
+
+- Console Interface:
+ Depending on board, define exactly one serial port
+ (like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
+ CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
+ console by defining CONFIG_8xx_CONS_NONE
+
+ Note: if CONFIG_8xx_CONS_NONE is defined, the serial
+ port routines must be defined elsewhere
+ (i.e. serial_init(), serial_getc(), ...)
+
+ CONFIG_CFB_CONSOLE
+ Enables console device for a color framebuffer. Needs following
+ defines (cf. smiLynxEM, i8042, board/eltec/bab7xx)
+ VIDEO_FB_LITTLE_ENDIAN graphic memory organisation
+ (default big endian)
+ VIDEO_HW_RECTFILL graphic chip supports
+ rectangle fill
+ (cf. smiLynxEM)
+ VIDEO_HW_BITBLT graphic chip supports
+ bit-blit (cf. smiLynxEM)
+ VIDEO_VISIBLE_COLS visible pixel columns
+ (cols=pitch)
+ VIDEO_VISIBLE_ROWS visible pixel rows
+ VIDEO_PIXEL_SIZE bytes per pixel
+ VIDEO_DATA_FORMAT graphic data format
+ (0-5, cf. cfb_console.c)
+ VIDEO_FB_ADRS framebuffer address
+ VIDEO_KBD_INIT_FCT keyboard int fct
+ (i.e. i8042_kbd_init())
+ VIDEO_TSTC_FCT test char fct
+ (i.e. i8042_tstc)
+ VIDEO_GETC_FCT get char fct
+ (i.e. i8042_getc)
+ CONFIG_CONSOLE_CURSOR cursor drawing on/off
+ (requires blink timer
+ cf. i8042.c)
+ CFG_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
+ CONFIG_CONSOLE_TIME display time/date info in
+ upper right corner
+ (requires CFG_CMD_DATE)
+ CONFIG_VIDEO_LOGO display Linux logo in
+ upper left corner
+ CONFIG_CONSOLE_EXTRA_INFO
+ addional board info beside
+ the logo
+
+ When CONFIG_CFB_CONSOLE is defined, video console is
+ default i/o. Serial console can be forced with
+ environment 'console=serial'.
+
+- Console Baudrate:
+ CONFIG_BAUDRATE - in bps
+ Select one of the baudrates listed in
+ CFG_BAUDRATE_TABLE, see below.
+
+- Interrupt driven serial port input:
+ CONFIG_SERIAL_SOFTWARE_FIFO
+
+ PPC405GP only.
+ Use an interrupt handler for receiving data on the
+ serial port. It also enables using hardware handshake
+ (RTS/CTS) and UART's built-in FIFO. Set the number of
+ bytes the interrupt driven input buffer should have.
+
+ Set to 0 to disable this feature (this is the default).
+ This will also disable hardware handshake.
+
+- Boot Delay: CONFIG_BOOTDELAY - in seconds
+ Delay before automatically booting the default image;
+ set to -1 to disable autoboot.
+
+ See doc/README.autoboot for these options that
+ work with CONFIG_BOOTDELAY. None are required.
+ CONFIG_BOOT_RETRY_TIME
+ CONFIG_BOOT_RETRY_MIN
+ CONFIG_AUTOBOOT_KEYED
+ CONFIG_AUTOBOOT_PROMPT
+ CONFIG_AUTOBOOT_DELAY_STR
+ CONFIG_AUTOBOOT_STOP_STR
+ CONFIG_AUTOBOOT_DELAY_STR2
+ CONFIG_AUTOBOOT_STOP_STR2
+ CONFIG_ZERO_BOOTDELAY_CHECK
+ CONFIG_RESET_TO_RETRY
+
+- Autoboot Command:
+ CONFIG_BOOTCOMMAND
+ Only needed when CONFIG_BOOTDELAY is enabled;
+ define a command string that is automatically executed
+ when no character is read on the console interface
+ within "Boot Delay" after reset.
+
+ CONFIG_BOOTARGS
+ This can be used to pass arguments to the bootm
+ command. The value of CONFIG_BOOTARGS goes into the
+ environment value "bootargs".
+
+ CONFIG_RAMBOOT and CONFIG_NFSBOOT
+ The value of these goes into the environment as
+ "ramboot" and "nfsboot" respectively, and can be used
+ as a convenience, when switching between booting from
+ ram and nfs.
+
+- Pre-Boot Commands:
+ CONFIG_PREBOOT
+
+ When this option is #defined, the existence of the
+ environment variable "preboot" will be checked
+ immediately before starting the CONFIG_BOOTDELAY
+ countdown and/or running the auto-boot command resp.
+ entering interactive mode.
+
+ This feature is especially useful when "preboot" is
+ automatically generated or modified. For an example
+ see the LWMON board specific code: here "preboot" is
+ modified when the user holds down a certain
+ combination of keys on the (special) keyboard when
+ booting the systems
+
+- Serial Download Echo Mode:
+ CONFIG_LOADS_ECHO
+ If defined to 1, all characters received during a
+ serial download (using the "loads" command) are
+ echoed back. This might be needed by some terminal
+ emulations (like "cu"), but may as well just take
+ time on others. This setting #define's the initial
+ value of the "loads_echo" environment variable.
+
+- Kgdb Serial Baudrate: (if CFG_CMD_KGDB is defined)
+ CONFIG_KGDB_BAUDRATE
+ Select one of the baudrates listed in
+ CFG_BAUDRATE_TABLE, see below.
+
+- Monitor Functions:
+ CONFIG_COMMANDS
+ Most monitor functions can be selected (or
+ de-selected) by adjusting the definition of
+ CONFIG_COMMANDS; to select individual functions,
+ #define CONFIG_COMMANDS by "OR"ing any of the
+ following values:
+
+ #define enables commands:
+ -------------------------
+ CFG_CMD_ASKENV * ask for env variable
+ CFG_CMD_BDI bdinfo
+ CFG_CMD_BEDBUG Include BedBug Debugger
+ CFG_CMD_BOOTD bootd
+ CFG_CMD_CACHE icache, dcache
+ CFG_CMD_CONSOLE coninfo
+ CFG_CMD_DATE * support for RTC, date/time...
+ CFG_CMD_DHCP DHCP support
+ CFG_CMD_ECHO * echo arguments
+ CFG_CMD_EEPROM * EEPROM read/write support
+ CFG_CMD_ELF bootelf, bootvx
+ CFG_CMD_ENV saveenv
+ CFG_CMD_FDC * Floppy Disk Support
+ CFG_CMD_FLASH flinfo, erase, protect
+ CFG_CMD_FPGA FPGA device initialization support
+ CFG_CMD_I2C * I2C serial bus support
+ CFG_CMD_IDE * IDE harddisk support
+ CFG_CMD_IMI iminfo
+ CFG_CMD_IMMAP * IMMR dump support
+ CFG_CMD_IRQ * irqinfo
+ CFG_CMD_KGDB * kgdb
+ CFG_CMD_LOADB loadb
+ CFG_CMD_LOADS loads
+ CFG_CMD_MEMORY md, mm, nm, mw, cp, cmp, crc, base,
+ loop, mtest
+ CFG_CMD_MII MII utility commands
+ CFG_CMD_NET bootp, tftpboot, rarpboot
+ CFG_CMD_PCI * pciinfo
+ CFG_CMD_PCMCIA * PCMCIA support
+ CFG_CMD_REGINFO * Register dump
+ CFG_CMD_RUN run command in env variable
+ CFG_CMD_SCSI * SCSI Support
+ CFG_CMD_SETGETDCR Support for DCR Register access (4xx only)
+ CFG_CMD_SPI * SPI serial bus support
+ CFG_CMD_USB * USB support
+ CFG_CMD_BSP * Board SPecific functions
+ -----------------------------------------------
+ CFG_CMD_ALL all
+
+ CFG_CMD_DFL Default configuration; at the moment
+ this is includes all commands, except
+ the ones marked with "*" in the list
+ above.
+
+ If you don't define CONFIG_COMMANDS it defaults to
+ CFG_CMD_DFL in include/cmd_confdefs.h. A board can
+ override the default settings in the respective
+ include file.
+
+ EXAMPLE: If you want all functions except of network
+ support you can write:
+
+ #define CONFIG_COMMANDS (CFG_CMD_ALL & ~CFG_CMD_NET)
+
+
+ Note: Don't enable the "icache" and "dcache" commands
+ (configuration option CFG_CMD_CACHE) unless you know
+ what you (and your U-Boot users) are doing. Data
+ cache cannot be enabled on systems like the 8xx or
+ 8260 (where accesses to the IMMR region must be
+ uncached), and it cannot be disabled on all other
+ systems where we (mis-) use the data cache to hold an
+ initial stack and some data.
+
+
+ XXX - this list needs to get updated!
+
+- Watchdog:
+ CONFIG_WATCHDOG
+ If this variable is defined, it enables watchdog
+ support. There must support in the platform specific
+ code for a watchdog. For the 8xx and 8260 CPUs, the
+ SIU Watchdog feature is enabled in the SYPCR
+ register.
+
+- Real-Time Clock:
+
+ When CFG_CMD_DATE is selected, the type of the RTC
+ has to be selected, too. Define exactly one of the
+ following options:
+
+ CONFIG_RTC_MPC8xx - use internal RTC of MPC8xx
+ CONFIG_RTC_PCF8563 - use Philips PCF8563 RTC
+ CONFIG_RTC_MC146818 - use MC146818 RTC
+ CONFIG_RTC_DS1337 - use Maxim, Inc. DS1337 RTC
+
+- Timestamp Support:
+
+ When CONFIG_TIMESTAMP is selected, the timestamp
+ (date and time) of an image is printed by image
+ commands like bootm or iminfo. This option is
+ automatically enabled when you select CFG_CMD_DATE .
+
+- Partition Support:
+ CONFIG_MAC_PARTITION and/or CONFIG_DOS_PARTITION
+ and/or CONFIG_ISO_PARTITION
+
+ If IDE or SCSI support is enabled (CFG_CMD_IDE or
+ CFG_CMD_SCSI) you must configure support for at least
+ one partition type as well.
+
+- IDE Reset method:
+ CONFIG_IDE_RESET_ROUTINE
+
+ Set this to define that instead of a reset Pin, the
+ routine ide_set_reset(int idereset) will be used.
+
+- ATAPI Support:
+ CONFIG_ATAPI
+
+ Set this to enable ATAPI support.
+
+- SCSI Support:
+ At the moment only there is only support for the
+ SYM53C8XX SCSI controller; define
+ CONFIG_SCSI_SYM53C8XX to enable it.
+
+ CFG_SCSI_MAX_LUN [8], CFG_SCSI_MAX_SCSI_ID [7] and
+ CFG_SCSI_MAX_DEVICE [CFG_SCSI_MAX_SCSI_ID *
+ CFG_SCSI_MAX_LUN] can be adjusted to define the
+ maximum numbers of LUNs, SCSI ID's and target
+ devices.
+ CFG_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
+
+- NETWORK Support (PCI):
+ CONFIG_EEPRO100
+ Support for Intel 82557/82559/82559ER chips.
+ Optional CONFIG_EEPRO100_SROM_WRITE enables eeprom
+ write routine for first time initialisation.
+
+ CONFIG_TULIP
+ Support for Digital 2114x chips.
+ Optional CONFIG_TULIP_SELECT_MEDIA for board specific
+ modem chip initialisation (KS8761/QS6611).
+
+ CONFIG_NATSEMI
+ Support for National dp83815 chips.
+
+ CONFIG_NS8382X
+ Support for National dp8382[01] gigabit chips.
+
+- USB Support:
+ At the moment only the UHCI host controller is
+ supported (PIP405, MIP405); define
+ CONFIG_USB_UHCI to enable it.
+ define CONFIG_USB_KEYBOARD to enable the USB Keyboard
+ end define CONFIG_USB_STORAGE to enable the USB
+ storage devices.
+ Note:
+ Supported are USB Keyboards and USB Floppy drives
+ (TEAC FD-05PUB).
+
+- Keyboard Support:
+ CONFIG_ISA_KEYBOARD
+
+ Define this to enable standard (PC-Style) keyboard
+ support
+
+ CONFIG_I8042_KBD
+ Standard PC keyboard driver with US (is default) and
+ GERMAN key layout (switch via environment 'keymap=de') support.
+ Export function i8042_kbd_init, i8042_tstc and i8042_getc
+ for cfb_console. Supports cursor blinking.
+
+- Video support:
+ CONFIG_VIDEO
+
+ Define this to enable video support (for output to
+ video).
+
+ CONFIG_VIDEO_CT69000
+
+ Enable Chips & Technologies 69000 Video chip
+
+ CONFIG_VIDEO_SMI_LYNXEM
+ Enable Silicon Motion SMI 712/710/810 Video chip
+ Videomode are selected via environment 'videomode' with
+ standard LiLo mode numbers.
+ Following modes are supported (* is default):
+
+ 800x600 1024x768 1280x1024
+ 256 (8bit) 303* 305 307
+ 65536 (16bit) 314 317 31a
+ 16,7 Mill (24bit) 315 318 31b
+ (i.e. setenv videomode 317; saveenv; reset;)
+
+- LCD Support: CONFIG_LCD
+
+ Define this to enable LCD support (for output to LCD
+ display); also select one of the supported displays
+ by defining one of these:
+
+ CONFIG_NEC_NL6648AC33:
+
+ NEC NL6648AC33-18. Active, color, single scan.
+
+ CONFIG_NEC_NL6648BC20
+
+ NEC NL6648BC20-08. 6.5", 640x480.
+ Active, color, single scan.
+
+ CONFIG_SHARP_16x9
+
+ Sharp 320x240. Active, color, single scan.
+ It isn't 16x9, and I am not sure what it is.
+
+ CONFIG_SHARP_LQ64D341
+
+ Sharp LQ64D341 display, 640x480.
+ Active, color, single scan.
+
+ CONFIG_HLD1045
+
+ HLD1045 display, 640x480.
+ Active, color, single scan.
+
+ CONFIG_OPTREX_BW
+
+ Optrex CBL50840-2 NF-FW 99 22 M5
+ or
+ Hitachi LMG6912RPFC-00T
+ or
+ Hitachi SP14Q002
+
+ 320x240. Black & white.
+
+ Normally display is black on white background; define
+ CFG_WHITE_ON_BLACK to get it inverted.
+
+- Ethernet address:
+ CONFIG_ETHADDR
+ CONFIG_ETH2ADDR
+ CONFIG_ETH3ADDR
+
+ Define a default value for ethernet address to use
+ for the respective ethernet interface, in case this
+ is not determined automatically.
+
+- IP address:
+ CONFIG_IPADDR
+
+ Define a default value for the IP address to use for
+ the default ethernet interface, in case this is not
+ determined through e.g. bootp.
+
+- Server IP address:
+ CONFIG_SERVERIP
+
+ Defines a default value for theIP address of a TFTP
+ server to contact when using the "tftboot" command.
+
+- BOOTP Recovery Mode:
+ CONFIG_BOOTP_RANDOM_DELAY
+
+ If you have many targets in a network that try to
+ boot using BOOTP, you may want to avoid that all
+ systems send out BOOTP requests at precisely the same
+ moment (which would happen for instance at recovery
+ from a power failure, when all systems will try to
+ boot, thus flooding the BOOTP server. Defining
+ CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
+ inserted before sending out BOOTP requests. The
+ following delays are insterted then:
+
+ 1st BOOTP request: delay 0 ... 1 sec
+ 2nd BOOTP request: delay 0 ... 2 sec
+ 3rd BOOTP request: delay 0 ... 4 sec
+ 4th and following
+ BOOTP requests: delay 0 ... 8 sec
+
+- Status LED: CONFIG_STATUS_LED
+
+ Several configurations allow to display the current
+ status using a LED. For instance, the LED will blink
+ fast while running U-Boot code, stop blinking as
+ soon as a reply to a BOOTP request was received, and
+ start blinking slow once the Linux kernel is running
+ (supported by a status LED driver in the Linux
+ kernel). Defining CONFIG_STATUS_LED enables this
+ feature in U-Boot.
+
+- CAN Support: CONFIG_CAN_DRIVER
+
+ Defining CONFIG_CAN_DRIVER enables CAN driver support
+ on those systems that support this (optional)
+ feature, like the TQM8xxL modules.
+
+- I2C Support: CONFIG_HARD_I2C | CONFIG_SOFT_I2C
+
+ Enables I2C serial bus commands. If this is selected,
+ either CONFIG_HARD_I2C or CONFIG_SOFT_I2C must be defined
+ to include the appropriate I2C driver.
+
+ See also: common/cmd_i2c.c for a description of the
+ command line interface.
+
+
+ CONFIG_HARD_I2C
+
+ Selects the CPM hardware driver for I2C.
+
+ CONFIG_SOFT_I2C
+
+ Use software (aka bit-banging) driver instead of CPM
+ or similar hardware support for I2C. This is configured
+ via the following defines.
+
+ I2C_INIT
+
+ (Optional). Any commands necessary to enable I2C
+ controller or configure ports.
+
+ I2C_PORT
+
+ (Only for MPC8260 CPU). The I/O port to use (the code
+ assumes both bits are on the same port). Valid values
+ are 0..3 for ports A..D.
+
+ I2C_ACTIVE
+
+ The code necessary to make the I2C data line active
+ (driven). If the data line is open collector, this
+ define can be null.
+
+ I2C_TRISTATE
+
+ The code necessary to make the I2C data line tri-stated
+ (inactive). If the data line is open collector, this
+ define can be null.
+
+ I2C_READ
+
+ Code that returns TRUE if the I2C data line is high,
+ FALSE if it is low.
+
+ I2C_SDA(bit)
+
+ If <bit> is TRUE, sets the I2C data line high. If it
+ is FALSE, it clears it (low).
+
+ I2C_SCL(bit)
+
+ If <bit> is TRUE, sets the I2C clock line high. If it
+ is FALSE, it clears it (low).
+
+ I2C_DELAY
+
+ This delay is invoked four times per clock cycle so this
+ controls the rate of data transfer. The data rate thus
+ is 1 / (I2C_DELAY * 4).
+
+- SPI Support: CONFIG_SPI
+
+ Enables SPI driver (so far only tested with
+ SPI EEPROM, also an instance works with Crystal A/D and
+ D/As on the SACSng board)
+
+ CONFIG_SPI_X
+
+ Enables extended (16-bit) SPI EEPROM addressing.
+ (symmetrical to CONFIG_I2C_X)
+
+ CONFIG_SOFT_SPI
+
+ Enables a software (bit-bang) SPI driver rather than
+ using hardware support. This is a general purpose
+ driver that only requires three general I/O port pins
+ (two outputs, one input) to function. If this is
+ defined, the board configuration must define several
+ SPI configuration items (port pins to use, etc). For
+ an example, see include/configs/sacsng.h.
+
+- FPGA Support: CONFIG_FPGA_COUNT
+
+ Specify the number of FPGA devices to support.
+
+ CONFIG_FPGA
+
+ Used to specify the types of FPGA devices. For
+ example,
+ #define CONFIG_FPGA CFG_XILINX_VIRTEX2
+
+ CFG_FPGA_PROG_FEEDBACK
+
+ Enable printing of hash marks during FPGA
+ configuration.
+
+ CFG_FPGA_CHECK_BUSY
+
+ Enable checks on FPGA configuration interface busy
+ status by the configuration function. This option
+ will require a board or device specific function to
+ be written.
+
+ CONFIG_FPGA_DELAY
+
+ If defined, a function that provides delays in the
+ FPGA configuration driver.
+
+ CFG_FPGA_CHECK_CTRLC
+
+ Allow Control-C to interrupt FPGA configuration
+
+ CFG_FPGA_CHECK_ERROR
+
+ Check for configuration errors during FPGA bitfile
+ loading. For example, abort during Virtex II
+ configuration if the INIT_B line goes low (which
+ indicated a CRC error).
+
+ CFG_FPGA_WAIT_INIT
+
+ Maximum time to wait for the INIT_B line to deassert
+ after PROB_B has been deasserted during a Virtex II
+ FPGA configuration sequence. The default time is 500 mS.
+
+ CFG_FPGA_WAIT_BUSY
+
+ Maximum time to wait for BUSY to deassert during
+ Virtex II FPGA configuration. The default is 5 mS.
+
+ CFG_FPGA_WAIT_CONFIG
+
+ Time to wait after FPGA configuration. The default is
+ 200 mS.
+
+- FPGA Support: CONFIG_FPGA_COUNT
+
+ Specify the number of FPGA devices to support.
+
+ CONFIG_FPGA
+
+ Used to specify the types of FPGA devices. For example,
+ #define CONFIG_FPGA CFG_XILINX_VIRTEX2
+
+ CFG_FPGA_PROG_FEEDBACK
+
+ Enable printing of hash marks during FPGA configuration.
+
+ CFG_FPGA_CHECK_BUSY
+
+ Enable checks on FPGA configuration interface busy
+ status by the configuration function. This option
+ will require a board or device specific function to
+ be written.
+
+ CONFIG_FPGA_DELAY
+
+ If defined, a function that provides delays in the FPGA
+ configuration driver.
+
+ CFG_FPGA_CHECK_CTRLC
+ Allow Control-C to interrupt FPGA configuration
+
+ CFG_FPGA_CHECK_ERROR
+
+ Check for configuration errors during FPGA bitfile
+ loading. For example, abort during Virtex II
+ configuration if the INIT_B line goes low (which
+ indicated a CRC error).
+
+ CFG_FPGA_WAIT_INIT
+
+ Maximum time to wait for the INIT_B line to deassert
+ after PROB_B has been deasserted during a Virtex II
+ FPGA configuration sequence. The default time is 500
+ mS.
+
+ CFG_FPGA_WAIT_BUSY
+
+ Maximum time to wait for BUSY to deassert during
+ Virtex II FPGA configuration. The default is 5 mS.
+
+ CFG_FPGA_WAIT_CONFIG
+
+ Time to wait after FPGA configuration. The default is
+ 200 mS.
+
+- Configuration Management:
+ CONFIG_IDENT_STRING
+
+ If defined, this string will be added to the U-Boot
+ version information (U_BOOT_VERSION)
+
+- Vendor Parameter Protection:
+
+ U-Boot considers the values of the environment
+ variables "serial#" (Board Serial Number) and
+ "ethaddr" (Ethernet Address) to bb parameters that
+ are set once by the board vendor / manufacturer, and
+ protects these variables from casual modification by
+ the user. Once set, these variables are read-only,
+ and write or delete attempts are rejected. You can
+ change this behviour:
+
+ If CONFIG_ENV_OVERWRITE is #defined in your config
+ file, the write protection for vendor parameters is
+ completely disabled. Anybody can change or delte
+ these parameters.
+
+ Alternatively, if you #define _both_ CONFIG_ETHADDR
+ _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
+ ethernet address is installed in the environment,
+ which can be changed exactly ONCE by the user. [The
+ serial# is unaffected by this, i. e. it remains
+ read-only.]
+
+- Protected RAM:
+ CONFIG_PRAM
+
+ Define this variable to enable the reservation of
+ "protected RAM", i. e. RAM which is not overwritten
+ by U-Boot. Define CONFIG_PRAM to hold the number of
+ kB you want to reserve for pRAM. You can overwrite
+ this default value by defining an environment
+ variable "pram" to the number of kB you want to
+ reserve. Note that the board info structure will
+ still show the full amount of RAM. If pRAM is
+ reserved, a new environment variable "mem" will
+ automatically be defined to hold the amount of
+ remaining RAM in a form that can be passed as boot
+ argument to Linux, for instance like that:
+
+ setenv bootargs ... mem=\$(mem)
+ saveenv
+
+ This way you can tell Linux not to use this memory,
+ either, which results in a memory region that will
+ not be affected by reboots.
+
+ *WARNING* If your board configuration uses automatic
+ detection of the RAM size, you must make sure that
+ this memory test is non-destructive. So far, the
+ following board configurations are known to be
+ "pRAM-clean":
+
+ ETX094, IVMS8, IVML24, SPD8xx, TQM8xxL,
+ HERMES, IP860, RPXlite, LWMON, LANTEC,
+ PCU_E, FLAGADM, TQM8260
+
+- Error Recovery:
+ CONFIG_PANIC_HANG
+
+ Define this variable to stop the system in case of a
+ fatal error, so that you have to reset it manually.
+ This is probably NOT a good idea for an embedded
+ system where you want to system to reboot
+ automatically as fast as possible, but it may be
+ useful during development since you can try to debug
+ the conditions that lead to the situation.
+
+ CONFIG_NET_RETRY_COUNT
+
+ This variable defines the number of retries for
+ network operations like ARP, RARP, TFTP, or BOOTP
+ before giving up the operation. If not defined, a
+ default value of 5 is used.
+
+- Command Interpreter:
+ CFG_HUSH_PARSER
+
+ Define this variable to enable the "hush" shell (from
+ Busybox) as command line interpreter, thus enabling
+ powerful command line syntax like
+ if...then...else...fi conditionals or `&&' and '||'
+ constructs ("shell scripts").
+
+ If undefined, you get the old, much simpler behaviour
+ with a somewhat smaller memory footprint.
+
+
+ CFG_PROMPT_HUSH_PS2
+
+ This defines the secondary prompt string, which is
+ printed when the command interpreter needs more input
+ to complete a command. Usually "> ".
+
+ Note:
+
+ In the current implementation, the local variables
+ space and global environment variables space are
+ separated. Local variables are those you define by
+ simply typing like `name=value'. To access a local
+ variable later on, you have write `$name' or
+ `${name}'; variable directly by typing say `$name' at
+ the command prompt.
+
+ Global environment variables are those you use
+ setenv/printenv to work with. To run a command stored
+ in such a variable, you need to use the run command,
+ and you must not use the '$' sign to access them.
+
+ To store commands and special characters in a
+ variable, please use double quotation marks
+ surrounding the whole text of the variable, instead
+ of the backslashes before semicolons and special
+ symbols.
+
+- Default Environment
+ CONFIG_EXTRA_ENV_SETTINGS
+
+ Define this to contain any number of null terminated
+ strings (variable = value pairs) that will be part of
+ the default enviroment compiled into the boot image.
+ For example, place something like this in your
+ board's config file:
+
+ #define CONFIG_EXTRA_ENV_SETTINGS \
+ "myvar1=value1\0" \
+ "myvar2=value2\0"
+
+ Warning: This method is based on knowledge about the
+ internal format how the environment is stored by the
+ U-Boot code. This is NOT an official, expoerted
+ interface! Although it is unlikely that this format
+ will change soon, there is no guarantee either.
+ You better know what you are doing here.
+
+ Note: overly (ab)use of the default environment is
+ discouraged. Make sure to check other ways to preset
+ the environment like the autoscript function or the
+ boot command first.
+
+- Show boot progress
+ CONFIG_SHOW_BOOT_PROGRESS
+
+ Defining this option allows to add some board-
+ specific code (calling a user-provided function
+ "show_boot_progress(int)") that enables you to show
+ the system's boot progress on some display (for
+ example, some LED's) on your board. At the moment,
+ the following checkpoints are implemented:
+
+ Arg Where When
+ 1 common/cmd_bootm.c before attempting to boot an image
+ -1 common/cmd_bootm.c Image header has bad magic number
+ 2 common/cmd_bootm.c Image header has correct magic number
+ -2 common/cmd_bootm.c Image header has bad checksum
+ 3 common/cmd_bootm.c Image header has correct checksum
+ -3 common/cmd_bootm.c Image data has bad checksum
+ 4 common/cmd_bootm.c Image data has correct checksum
+ -4 common/cmd_bootm.c Image is for unsupported architecture
+ 5 common/cmd_bootm.c Architecture check OK
+ -5 common/cmd_bootm.c Wrong Image Type (not kernel, multi, standalone)
+ 6 common/cmd_bootm.c Image Type check OK
+ -6 common/cmd_bootm.c gunzip uncompression error
+ -7 common/cmd_bootm.c Unimplemented compression type
+ 7 common/cmd_bootm.c Uncompression OK
+ -8 common/cmd_bootm.c Wrong Image Type (not kernel, multi, standalone)
+ 8 common/cmd_bootm.c Image Type check OK
+ -9 common/cmd_bootm.c Unsupported OS (not Linux, BSD, VxWorks, QNX)
+ 9 common/cmd_bootm.c Start initial ramdisk verification
+ -10 common/cmd_bootm.c Ramdisk header has bad magic number
+ -11 common/cmd_bootm.c Ramdisk header has bad checksum
+ 10 common/cmd_bootm.c Ramdisk header is OK
+ -12 common/cmd_bootm.c Ramdisk data has bad checksum
+ 11 common/cmd_bootm.c Ramdisk data has correct checksum
+ 12 common/cmd_bootm.c Ramdisk verification complete, start loading
+ -13 common/cmd_bootm.c Wrong Image Type (not PPC Linux Ramdisk)
+ 13 common/cmd_bootm.c Start multifile image verification
+ 14 common/cmd_bootm.c No initial ramdisk, no multifile, continue.
+ 15 common/cmd_bootm.c All preparation done, transferring control to OS
+
+ -1 common/cmd_doc.c Bad usage of "doc" command
+ -1 common/cmd_doc.c No boot device
+ -1 common/cmd_doc.c Unknown Chip ID on boot device
+ -1 common/cmd_doc.c Read Error on boot device
+ -1 common/cmd_doc.c Image header has bad magic number
+
+ -1 common/cmd_ide.c Bad usage of "ide" command
+ -1 common/cmd_ide.c No boot device
+ -1 common/cmd_ide.c Unknown boot device
+ -1 common/cmd_ide.c Unknown partition table
+ -1 common/cmd_ide.c Invalid partition type
+ -1 common/cmd_ide.c Read Error on boot device
+ -1 common/cmd_ide.c Image header has bad magic number
+
+ -1 common/cmd_nvedit.c Environment not changable, but has bad CRC
+
+
+Modem Support:
+--------------
+
+[so far only for SMDK2400 board]
+
+- Modem support endable:
+ CONFIG_MODEM_SUPPORT
+
+- RTS/CTS Flow control enable:
+ CONFIG_HWFLOW
+
+- Modem debug support:
+ CONFIG_MODEM_SUPPORT_DEBUG
+
+ Enables debugging stuff (char screen[1024], dbg())
+ for modem support. Useful only with BDI2000.
+
+- General:
+
+ In the target system modem support is enabled when a
+ specific key (key combination) is pressed during
+ power-on. Otherwise U-Boot will boot normally
+ (autoboot). The key_pressed() fuction is called from
+ board_init(). Currently key_pressed() is a dummy
+ function, returning 1 and thus enabling modem
+ initialization.
+
+ If there are no modem init strings in the
+ environment, U-Boot proceed to autoboot; the
+ previous output (banner, info printfs) will be
+ supressed, though.
+
+ See also: doc/README.Modem
+
+
+
+
+Configuration Settings:
+-----------------------
+
+- CFG_LONGHELP: Defined when you want long help messages included;
+ undefine this when you're short of memory.
+
+- CFG_PROMPT: This is what U-Boot prints on the console to
+ prompt for user input.
+
+- CFG_CBSIZE: Buffer size for input from the Console
+
+- CFG_PBSIZE: Buffer size for Console output
+
+- CFG_MAXARGS: max. Number of arguments accepted for monitor commands
+
+- CFG_BARGSIZE: Buffer size for Boot Arguments which are passed to
+ the application (usually a Linux kernel) when it is
+ booted
+
+- CFG_BAUDRATE_TABLE:
+ List of legal baudrate settings for this board.
+
+- CFG_CONSOLE_INFO_QUIET
+ Suppress display of console information at boot.
+
+- CFG_CONSOLE_IS_IN_ENV
+ If the board specific function
+ extern int overwrite_console (void);
+ returns 1, the stdin, stderr and stdout are switched to the
+ serial port, else the settings in the environment are used.
+
+- CFG_CONSOLE_OVERWRITE_ROUTINE
+ Enable the call to overwrite_console().
+
+- CFG_CONSOLE_ENV_OVERWRITE
+ Enable overwrite of previous console environment settings.
+
+- CFG_MEMTEST_START, CFG_MEMTEST_END:
+ Begin and End addresses of the area used by the
+ simple memory test.
+
+- CFG_ALT_MEMTEST:
+ Enable an alternate, more extensive memory test.
+
+- CFG_TFTP_LOADADDR:
+ Default load address for network file downloads
+
+- CFG_LOADS_BAUD_CHANGE:
+ Enable temporary baudrate change while serial download
+
+- CFG_SDRAM_BASE:
+ Physical start address of SDRAM. _Must_ be 0 here.
+
+- CFG_MBIO_BASE:
+ Physical start address of Motherboard I/O (if using a
+ Cogent motherboard)
+
+- CFG_FLASH_BASE:
+ Physical start address of Flash memory.
+
+- CFG_MONITOR_BASE:
+ Physical start address of boot monitor code (set by
+ make config files to be same as the text base address
+ (TEXT_BASE) used when linking) - same as
+ CFG_FLASH_BASE when booting from flash.
+
+- CFG_MONITOR_LEN:
+ Size of memory reserved for monitor code
+
+- CFG_MALLOC_LEN:
+ Size of DRAM reserved for malloc() use.
+
+- CFG_BOOTMAPSZ:
+ Maximum size of memory mapped by the startup code of
+ the Linux kernel; all data that must be processed by
+ the Linux kernel (bd_info, boot arguments, eventually
+ initrd image) must be put below this limit.
+
+- CFG_MAX_FLASH_BANKS:
+ Max number of Flash memory banks
+
+- CFG_MAX_FLASH_SECT:
+ Max number of sectors on a Flash chip
+
+- CFG_FLASH_ERASE_TOUT:
+ Timeout for Flash erase operations (in ms)
+
+- CFG_FLASH_WRITE_TOUT:
+ Timeout for Flash write operations (in ms)
+
+- CFG_DIRECT_FLASH_TFTP:
+
+ Enable TFTP transfers directly to flash memory;
+ without this option such a download has to be
+ performed in two steps: (1) download to RAM, and (2)
+ copy from RAM to flash.
+
+ The two-step approach is usually more reliable, since
+ you can check if the download worked before you erase
+ the flash, but in some situations (when sytem RAM is
+ too limited to allow for a tempory copy of the
+ downloaded image) this option may be very useful.
+
+- CFG_FLASH_CFI:
+ Define if the flash driver uses extra elements in the
+ common flash structure for storing flash geometry
+
+The following definitions that deal with the placement and management
+of environment data (variable area); in general, we support the
+following configurations:
+
+- CFG_ENV_IS_IN_FLASH:
+
+ Define this if the environment is in flash memory.
+
+ a) The environment occupies one whole flash sector, which is
+ "embedded" in the text segment with the U-Boot code. This
+ happens usually with "bottom boot sector" or "top boot
+ sector" type flash chips, which have several smaller
+ sectors at the start or the end. For instance, such a
+ layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
+ such a case you would place the environment in one of the
+ 4 kB sectors - with U-Boot code before and after it. With
+ "top boot sector" type flash chips, you would put the
+ environment in one of the last sectors, leaving a gap
+ between U-Boot and the environment.
+
+ - CFG_ENV_OFFSET:
+
+ Offset of environment data (variable area) to the
+ beginning of flash memory; for instance, with bottom boot
+ type flash chips the second sector can be used: the offset
+ for this sector is given here.
+
+ CFG_ENV_OFFSET is used relative to CFG_FLASH_BASE.
+
+ - CFG_ENV_ADDR:
+
+ This is just another way to specify the start address of
+ the flash sector containing the environment (instead of
+ CFG_ENV_OFFSET).
+
+ - CFG_ENV_SECT_SIZE:
+
+ Size of the sector containing the environment.
+
+
+ b) Sometimes flash chips have few, equal sized, BIG sectors.
+ In such a case you don't want to spend a whole sector for
+ the environment.
+
+ - CFG_ENV_SIZE:
+
+ If you use this in combination with CFG_ENV_IS_IN_FLASH
+ and CFG_ENV_SECT_SIZE, you can specify to use only a part
+ of this flash sector for the environment. This saves
+ memory for the RAM copy of the environment.
+
+ It may also save flash memory if you decide to use this
+ when your environment is "embedded" within U-Boot code,
+ since then the remainder of the flash sector could be used
+ for U-Boot code. It should be pointed out that this is
+ STRONGLY DISCOURAGED from a robustness point of view:
+ updating the environment in flash makes it always
+ necessary to erase the WHOLE sector. If something goes
+ wrong before the contents has been restored from a copy in
+ RAM, your target system will be dead.
+
+ - CFG_ENV_ADDR_REDUND
+ CFG_ENV_SIZE_REDUND
+
+ These settings describe a second storage area used to hold
+ a redundand copy of the environment data, so that there is
+ a valid backup copy in case there is a power failur during
+ a "saveenv" operation.
+
+BE CAREFUL! Any changes to the flash layout, and some changes to the
+source code will make it necessary to adapt <board>/u-boot.lds*
+accordingly!
+
+
+- CFG_ENV_IS_IN_NVRAM:
+
+ Define this if you have some non-volatile memory device
+ (NVRAM, battery buffered SRAM) which you want to use for the
+ environment.
+
+ - CFG_ENV_ADDR:
+ - CFG_ENV_SIZE:
+
+ These two #defines are used to determin the memory area you
+ want to use for environment. It is assumed that this memory
+ can just be read and written to, without any special
+ provision.
+
+BE CAREFUL! The first access to the environment happens quite early
+in U-Boot initalization (when we try to get the setting of for the
+console baudrate). You *MUST* have mappend your NVRAM area then, or
+U-Boot will hang.
+
+Please note that even with NVRAM we still use a copy of the
+environment in RAM: we could work on NVRAM directly, but we want to
+keep settings there always unmodified except somebody uses "saveenv"
+to save the current settings.
+
+
+- CFG_ENV_IS_IN_EEPROM:
+
+ Use this if you have an EEPROM or similar serial access
+ device and a driver for it.
+
+ - CFG_ENV_OFFSET:
+ - CFG_ENV_SIZE:
+
+ These two #defines specify the offset and size of the
+ environment area within the total memory of your EEPROM.
+
+ - CFG_I2C_EEPROM_ADDR:
+ If defined, specified the chip address of the EEPROM device.
+ The default address is zero.
+
+ - CFG_EEPROM_PAGE_WRITE_BITS:
+ If defined, the number of bits used to address bytes in a
+ single page in the EEPROM device. A 64 byte page, for example
+ would require six bits.
+
+ - CFG_EEPROM_PAGE_WRITE_DELAY_MS:
+ If defined, the number of milliseconds to delay between
+ page writes. The default is zero milliseconds.
+
+ - CFG_I2C_EEPROM_ADDR_LEN:
+ The length in bytes of the EEPROM memory array address. Note
+ that this is NOT the chip address length!
+
+ - CFG_EEPROM_SIZE:
+ The size in bytes of the EEPROM device.
+
+ - CFG_I2C_EEPROM_ADDR:
+ If defined, specified the chip address of the EEPROM device.
+ The default address is zero.
+
+ - CFG_EEPROM_PAGE_WRITE_BITS:
+ If defined, the number of bits used to address bytes in a
+ single page in the EEPROM device. A 64 byte page, for example
+ would require six bits.
+
+ - CFG_EEPROM_PAGE_WRITE_DELAY_MS:
+ If defined, the number of milliseconds to delay between
+ page writes. The default is zero milliseconds.
+
+ - CFG_I2C_EEPROM_ADDR_LEN:
+ The length in bytes of the EEPROM memory array address. Note
+ that this is NOT the chip address length!
+
+ - CFG_EEPROM_SIZE:
+ The size in bytes of the EEPROM device.
+
+- CFG_SPI_INIT_OFFSET
+
+ Defines offset to the initial SPI buffer area in DPRAM. The
+ area is used at an early stage (ROM part) if the environment
+ is configured to reside in the SPI EEPROM: We need a 520 byte
+ scratch DPRAM area. It is used between the two initialization
+ calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
+ to be a good choice since it makes it far enough from the
+ start of the data area as well as from the stack pointer.
+
+Please note that the environment is read-only as long as the monitor
+has been relocated to RAM and a RAM copy of the environment has been
+created; also, when using EEPROM you will have to use getenv_r()
+until then to read environment variables.
+
+The environment is now protected by a CRC32 checksum. Before the
+monitor is relocated into RAM, as a result of a bad CRC you will be
+working with the compiled-in default environment - *silently*!!!
+[This is necessary, because the first environment variable we need is
+the "baudrate" setting for the console - if we have a bad CRC, we
+don't have any device yet where we could complain.]
+
+Note: once the monitor has been relocated, then it will complain if
+the default environment is used; a new CRC is computed as soon as you
+use the "setenv" command to modify / delete / add any environment
+variable [even when you try to delete a non-existing variable!].
+
+Note2: you must edit your u-boot.lds file to reflect this
+configuration.
+
+
+Many of the options are named exactly as the corresponding Linux
+kernel configuration options. The intention is to make it easier to
+build a config tool - later.
+
+Low Level (hardware related) configuration options:
+
+- CFG_CACHELINE_SIZE:
+ Cache Line Size of the CPU.
+
+- CFG_DEFAULT_IMMR:
+ Default address of the IMMR after system reset.
+ Needed on some 8260 systems (MPC8260ADS and RPXsuper)
+ to be able to adjust the position of the IMMR
+ register after a reset.
+
+- CFG_IMMR: Physical address of the Internal Memory Mapped
+ Register; DO NOT CHANGE! (11-4)
+ [MPC8xx systems only]
+
+- CFG_INIT_RAM_ADDR:
+
+ Start address of memory area tha can be used for
+ initial data and stack; please note that this must be
+ writable memory that is working WITHOUT special
+ initialization, i. e. you CANNOT use normal RAM which
+ will become available only after programming the
+ memory controller and running certain initialization
+ sequences.
+
+ U-Boot uses the following memory types:
+ - MPC8xx and MPC8260: IMMR (internal memory of the CPU)
+ - MPC824X: data cache
+ - PPC4xx: data cache
+
+- CFG_INIT_DATA_OFFSET:
+
+ Offset of the initial data structure in the memory
+ area defined by CFG_INIT_RAM_ADDR. Usually
+ CFG_INIT_DATA_OFFSET is chosen such that the initial
+ data is located at the end of the available space
+ (sometimes written as (CFG_INIT_RAM_END -
+ CFG_INIT_DATA_SIZE), and the initial stack is just
+ below that area (growing from (CFG_INIT_RAM_ADDR +
+ CFG_INIT_DATA_OFFSET) downward.
+
+ Note:
+ On the MPC824X (or other systems that use the data
+ cache for initial memory) the address chosen for
+ CFG_INIT_RAM_ADDR is basically arbitrary - it must
+ point to an otherwise UNUSED address space between
+ the top of RAM and the start of the PCI space.
+
+- CFG_SIUMCR: SIU Module Configuration (11-6)
+
+- CFG_SYPCR: System Protection Control (11-9)
+
+- CFG_TBSCR: Time Base Status and Control (11-26)
+
+- CFG_PISCR: Periodic Interrupt Status and Control (11-31)
+
+- CFG_PLPRCR: PLL, Low-Power, and Reset Control Register (15-30)
+
+- CFG_SCCR: System Clock and reset Control Register (15-27)
+
+- CFG_OR_TIMING_SDRAM:
+ SDRAM timing
+
+- CFG_MAMR_PTA:
+ periodic timer for refresh
+
+- CFG_DER: Debug Event Register (37-47)
+
+- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CFG_REMAP_OR_AM,
+ CFG_PRELIM_OR_AM, CFG_OR_TIMING_FLASH, CFG_OR0_REMAP,
+ CFG_OR0_PRELIM, CFG_BR0_PRELIM, CFG_OR1_REMAP, CFG_OR1_PRELIM,
+ CFG_BR1_PRELIM:
+ Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
+
+- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
+ CFG_OR_TIMING_SDRAM, CFG_OR2_PRELIM, CFG_BR2_PRELIM,
+ CFG_OR3_PRELIM, CFG_BR3_PRELIM:
+ Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
+
+- CFG_MAMR_PTA, CFG_MPTPR_2BK_4K, CFG_MPTPR_1BK_4K, CFG_MPTPR_2BK_8K,
+ CFG_MPTPR_1BK_8K, CFG_MAMR_8COL, CFG_MAMR_9COL:
+ Machine Mode Register and Memory Periodic Timer
+ Prescaler definitions (SDRAM timing)
+
+- CFG_I2C_UCODE_PATCH, CFG_I2C_DPMEM_OFFSET [0x1FC0]:
+ enable I2C microcode relocation patch (MPC8xx);
+ define relocation offset in DPRAM [DSP2]
+
+- CFG_SPI_UCODE_PATCH, CFG_SPI_DPMEM_OFFSET [0x1FC0]:
+ enable SPI microcode relocation patch (MPC8xx);
+ define relocation offset in DPRAM [SCC4]
+
+- CFG_USE_OSCCLK:
+ Use OSCM clock mode on MBX8xx board. Be careful,
+ wrong setting might damage your board. Read
+ doc/README.MBX before setting this variable!
+
+Building the Software:
+======================
+
+Building U-Boot has been tested in native PPC environments (on a
+PowerBook G3 running LinuxPPC 2000) and in cross environments
+(running RedHat 6.x and 7.x Linux on x86, Solaris 2.6 on a SPARC, and
+NetBSD 1.5 on x86).
+
+If you are not using a native PPC environment, it is assumed that you
+have the GNU cross compiling tools available in your path and named
+with a prefix of "powerpc-linux-". If this is not the case, (e.g. if
+you are using Monta Vista's Hard Hat Linux CDK 1.2) you must change
+the definition of CROSS_COMPILE in Makefile. For HHL on a 4xx CPU,
+change it to:
+
+ CROSS_COMPILE = ppc_4xx-
+
+
+U-Boot is intended to be simple to build. After installing the
+sources you must configure U-Boot for one specific board type. This
+is done by typing:
+
+ make NAME_config
+
+where "NAME_config" is the name of one of the existing
+configurations; the following names are supported:
+
+ ADCIOP_config GTH_config TQM850L_config
+ ADS860_config IP860_config TQM855L_config
+ AR405_config IVML24_config TQM860L_config
+ CANBT_config IVMS8_config WALNUT405_config
+ CPCI405_config LANTEC_config cogent_common_config
+ CPCIISER4_config MBX_config cogent_mpc8260_config
+ CU824_config MBX860T_config cogent_mpc8xx_config
+ ESTEEM192E_config RPXlite_config hermes_config
+ ETX094_config RPXsuper_config hymod_config
+ FADS823_config SM850_config lwmon_config
+ FADS850SAR_config SPD823TS_config pcu_e_config
+ FADS860T_config SXNI855T_config rsdproto_config
+ FPS850L_config Sandpoint8240_config sbc8260_config
+ GENIETV_config TQM823L_config PIP405_config
+ GEN860T_config EBONY_config
+
+Note: for some board special configuration names may exist; check if
+ additional information is available from the board vendor; for
+ instance, the TQM8xxL systems run normally at 50 MHz and use a
+ SCC for 10baseT ethernet; there are also systems with 80 MHz
+ CPU clock, and an optional Fast Ethernet module is available
+ for CPU's with FEC. You can select such additional "features"
+ when chosing the configuration, i. e.
+
+ make TQM860L_config
+ - will configure for a plain TQM860L, i. e. 50MHz, no FEC
+
+ make TQM860L_FEC_config
+ - will configure for a TQM860L at 50MHz with FEC for ethernet
+
+ make TQM860L_80MHz_config
+ - will configure for a TQM860L at 80 MHz, with normal 10baseT
+ interface
+
+ make TQM860L_FEC_80MHz_config
+ - will configure for a TQM860L at 80 MHz with FEC for ethernet
+
+ make TQM823L_LCD_config
+ - will configure for a TQM823L with U-Boot console on LCD
+
+ make TQM823L_LCD_80MHz_config
+ - will configure for a TQM823L at 80 MHz with U-Boot console on LCD
+
+ etc.
+
+
+
+Finally, type "make all", and you should get some working U-Boot
+images ready for downlod to / installation on your system:
+
+- "u-boot.bin" is a raw binary image
+- "u-boot" is an image in ELF binary format
+- "u-boot.srec" is in Motorola S-Record format
+
+
+Please be aware that the Makefiles assume you are using GNU make, so
+for instance on NetBSD you might need to use "gmake" instead of
+native "make".
+
+
+If the system board that you have is not listed, then you will need
+to port U-Boot to your hardware platform. To do this, follow these
+steps:
+
+1. Add a new configuration option for your board to the toplevel
+ "Makefile", using the existing entries as examples.
+2. Create a new directory to hold your board specific code. Add any
+ files you need.
+3. If you're porting U-Boot to a new CPU, then also create a new
+ directory to hold your CPU specific code. Add any files you need.
+4. Run "make config_name" with your new name.
+5. Type "make", and you should get a working "u-boot.srec" file
+ to be installed on your target system.
+ [Of course, this last step is much harder than it sounds.]
+
+
+Testing of U-Boot Modifications, Ports to New Hardware, etc.:
+==============================================================
+
+If you have modified U-Boot sources (for instance added a new board
+or support for new devices, a new CPU, etc.) you are expected to
+provide feedback to the other developers. The feedback normally takes
+the form of a "patch", i. e. a context diff against a certain (latest
+official or latest in CVS) version of U-Boot sources.
+
+But before you submit such a patch, please verify that your modifi-
+cation did not break existing code. At least make sure that *ALL* of
+the supported boards compile WITHOUT ANY compiler warnings. To do so,
+just run the "MAKEALL" script, which will configure and build U-Boot
+for ALL supported system. Be warned, this will take a while. You can
+select which (cross) compiler to use py passing a `CROSS_COMPILE'
+environment variable to the script, i. e. to use the cross tools from
+MontaVista's Hard Hat Linux you can type
+
+ CROSS_COMPILE=ppc_8xx- MAKEALL
+
+or to build on a native PowerPC system you can type
+
+ CROSS_COMPILE=' ' MAKEALL
+
+See also "U-Boot Porting Guide" below.
+
+
+
+Monitor Commands - Overview:
+============================
+
+go - start application at address 'addr'
+run - run commands in an environment variable
+bootm - boot application image from memory
+bootp - boot image via network using BootP/TFTP protocol
+tftpboot- boot image via network using TFTP protocol
+ and env variables "ipaddr" and "serverip"
+ (and eventually "gatewayip")
+rarpboot- boot image via network using RARP/TFTP protocol
+diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
+loads - load S-Record file over serial line
+loadb - load binary file over serial line (kermit mode)
+md - memory display
+mm - memory modify (auto-incrementing)
+nm - memory modify (constant address)
+mw - memory write (fill)
+cp - memory copy
+cmp - memory compare
+crc32 - checksum calculation
+imd - i2c memory display
+imm - i2c memory modify (auto-incrementing)
+inm - i2c memory modify (constant address)
+imw - i2c memory write (fill)
+icrc32 - i2c checksum calculation
+iprobe - probe to discover valid I2C chip addresses
+iloop - infinite loop on address range
+isdram - print SDRAM configuration information
+sspi - SPI utility commands
+base - print or set address offset
+printenv- print environment variables
+setenv - set environment variables
+saveenv - save environment variables to persistent storage
+protect - enable or disable FLASH write protection
+erase - erase FLASH memory
+flinfo - print FLASH memory information
+bdinfo - print Board Info structure
+iminfo - print header information for application image
+coninfo - print console devices and informations
+ide - IDE sub-system
+loop - infinite loop on address range
+mtest - simple RAM test
+icache - enable or disable instruction cache
+dcache - enable or disable data cache
+reset - Perform RESET of the CPU
+echo - echo args to console
+version - print monitor version
+help - print online help
+? - alias for 'help'
+
+
+Monitor Commands - Detailed Description:
+========================================
+
+TODO.
+
+For now: just type "help <command>".
+
+
+Environment Variables:
+======================
+
+U-Boot supports user configuration using Environment Variables which
+can be made persistent by saving to Flash memory.
+
+Environment Variables are set using "setenv", printed using
+"printenv", and saved to Flash using "saveenv". Using "setenv"
+without a value can be used to delete a variable from the
+environment. As long as you don't save the environment you are
+working with an in-memory copy. In case the Flash area containing the
+environment is erased by accident, a default environment is provided.
+
+Some configuration options can be set using Environment Variables:
+
+ baudrate - see CONFIG_BAUDRATE
+
+ bootdelay - see CONFIG_BOOTDELAY
+
+ bootcmd - see CONFIG_BOOTCOMMAND
+
+ bootargs - Boot arguments when booting an RTOS image
+
+ bootfile - Name of the image to load with TFTP
+
+ autoload - if set to "no" (any string beginning with 'n'),
+ "bootp" will just load perform a lookup of the
+ configuration from the BOOTP server, but not try to
+ load any image using TFTP
+
+ autostart - if set to "yes", an image loaded using the "bootp",
+ "rarpboot", "tftpboot" or "diskboot" commands will
+ be automatically started (by internally calling
+ "bootm")
+
+ initrd_high - restrict positioning of initrd images:
+ If this variable is not set, initrd images will be
+ copied to the highest possible address in RAM; this
+ is usually what you want since it allows for
+ maximum initrd size. If for some reason you want to
+ make sure that the initrd image is loaded below the
+ CFG_BOOTMAPSZ limit, you can set this environment
+ variable to a value of "no" or "off" or "0".
+ Alternatively, you can set it to a maximum upper
+ address to use (U-Boot will still check that it
+ does not overwrite the U-Boot stack and data).
+
+ For instance, when you have a system with 16 MB
+ RAM, and want to reseve 4 MB from use by Linux,
+ you can do this by adding "mem=12M" to the value of
+ the "bootargs" variable. However, now you must make
+ sure, that the initrd image is placed in the first
+ 12 MB as well - this can be done with
+
+ setenv initrd_high 00c00000
+
+ ipaddr - IP address; needed for tftpboot command
+
+ loadaddr - Default load address for commands like "bootp",
+ "rarpboot", "tftpboot" or "diskboot"
+
+ loads_echo - see CONFIG_LOADS_ECHO
+
+ serverip - TFTP server IP address; needed for tftpboot command
+
+ bootretry - see CONFIG_BOOT_RETRY_TIME
+
+ bootdelaykey - see CONFIG_AUTOBOOT_DELAY_STR
+
+ bootstopkey - see CONFIG_AUTOBOOT_STOP_STR
+
+
+The following environment variables may be used and automatically
+updated by the network boot commands ("bootp" and "rarpboot"),
+depending the information provided by your boot server:
+
+ bootfile - see above
+ dnsip - IP address of your Domain Name Server
+ gatewayip - IP address of the Gateway (Router) to use
+ hostname - Target hostname
+ ipaddr - see above
+ netmask - Subnet Mask
+ rootpath - Pathname of the root filesystem on the NFS server
+ serverip - see above
+
+
+There are two special Environment Variables:
+
+ serial# - contains hardware identification information such
+ as type string and/or serial number
+ ethaddr - Ethernet address
+
+These variables can be set only once (usually during manufacturing of
+the board). U-Boot refuses to delete or overwrite these variables
+once they have been set once.
+
+
+Please note that changes to some configuration parameters may take
+only effect after the next boot (yes, that's just like Windoze :-).
+
+
+Note for Redundant Ethernet Interfaces:
+=======================================
+
+Some boards come with redundand ethernet interfaces; U-Boot supports
+such configurations and is capable of automatic selection of a
+"working" interface when needed. MAC assignemnt works as follows:
+
+Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
+MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
+"eth1addr" (=>eth1), "eth2addr", ...
+
+If the network interface stores some valid MAC address (for instance
+in SROM), this is used as default address if there is NO correspon-
+ding setting in the environment; if the corresponding environment
+variable is set, this overrides the settings in the card; that means:
+
+o If the SROM has a valid MAC address, and there is no address in the
+ environment, the SROM's address is used.
+
+o If there is no valid address in the SROM, and a definition in the
+ environment exists, then the value from the environment variable is
+ used.
+
+o If both the SROM and the environment contain a MAC address, and
+ both addresses are the same, this MAC address is used.
+
+o If both the SROM and the environment contain a MAC address, and the
+ addresses differ, the value from the environment is used and a
+ warning is printed.
+
+o If neither SROM nor the environment contain a MAC address, an error
+ is raised.
+
+
+
+Image Formats:
+==============
+
+The "boot" commands of this monitor operate on "image" files which
+can be basicly anything, preceeded by a special header; see the
+definitions in include/image.h for details; basicly, the header
+defines the following image properties:
+
+* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
+ 4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
+ LynxOS, pSOS, QNX;
+ Currently supported: Linux, NetBSD, VxWorks, QNX).
+* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
+ IA64, MIPS, MIPS, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
+ Currently supported: PowerPC).
+* Compression Type (Provisions for uncompressed, gzip, bzip2;
+ Currently supported: uncompressed, gzip).
+* Load Address
+* Entry Point
+* Image Name
+* Image Timestamp
+
+The header is marked by a special Magic Number, and both the header
+and the data portions of the image are secured against corruption by
+CRC32 checksums.
+
+
+Linux Support:
+==============
+
+Although U-Boot should support any OS or standalone application
+easily, Linux has always been in the focus during the design of
+U-Boot.
+
+U-Boot includes many features that so far have been part of some
+special "boot loader" code within the Linux kernel. Also, any
+"initrd" images to be used are no longer part of one big Linux image;
+instead, kernel and "initrd" are separate images. This implementation
+serves serveral purposes:
+
+- the same features can be used for other OS or standalone
+ applications (for instance: using compressed images to reduce the
+ Flash memory footprint)
+
+- it becomes much easier to port new Linux kernel versions because
+ lots of low-level, hardware dependend stuff are done by U-Boot
+
+- the same Linux kernel image can now be used with different "initrd"
+ images; of course this also means that different kernel images can
+ be run with the same "initrd". This makes testing easier (you don't
+ have to build a new "zImage.initrd" Linux image when you just
+ change a file in your "initrd"). Also, a field-upgrade of the
+ software is easier now.
+
+
+Linux HOWTO:
+============
+
+Porting Linux to U-Boot based systems:
+---------------------------------------
+
+U-Boot cannot save you from doing all the necessary modifications to
+configure the Linux device drivers for use with your target hardware
+(no, we don't intend to provide a full virtual machine interface to
+Linux :-).
+
+But now you can ignore ALL boot loader code (in arch/ppc/mbxboot).
+
+Just make sure your machine specific header file (for instance
+include/asm-ppc/tqm8xx.h) includes the same definition of the Board
+Information structure as we define in include/u-boot.h, and make
+sure that your definition of IMAP_ADDR uses the same value as your
+U-Boot configuration in CFG_IMMR.
+
+
+Configuring the Linux kernel:
+-----------------------------
+
+No specific requirements for U-Boot. Make sure you have some root
+device (initial ramdisk, NFS) for your target system.
+
+
+Building a Linux Image:
+-----------------------
+
+No specific requirements for U-Boot. There is no need to add a
+"ramdisk.image.gz" file when building the kernel, even when you
+intend to run it with initial ramdisk.
+
+Example:
+
+ make TQM850L_config
+ make oldconfig
+ make dep
+ make zImage
+
+However, we don't use the 'zImage' (= 'arch/ppc/mbxboot/zvmlinux') we
+build this way. The 'zImage' includes the old boot loader code which
+we don't ned any more. Instead, we use the raw (compressed) Linux
+kernel image in 'arch/ppc/coffboot/vmlinux.gz'.
+
+There is a special tool (in 'tools/mkimage') to encapsulate this
+image with header information, CRC32 checksum etc. for use with
+U-Boot:
+
+In the first form (with "-l" option) mkimage lists the information
+contained in the header of an existing U-Boot image; this includes
+checksum verification:
+
+ tools/mkimage -l image
+ -l ==> list image header information
+
+The second form (with "-d" option) is used to build a U-Boot image
+from a "data file" which is used as image payload:
+
+ tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
+ -n name -d data_file image
+ -A ==> set architecture to 'arch'
+ -O ==> set operating system to 'os'
+ -T ==> set image type to 'type'
+ -C ==> set compression type 'comp'
+ -a ==> set load address to 'addr' (hex)
+ -e ==> set entry point to 'ep' (hex)
+ -n ==> set image name to 'name'
+ -d ==> use image data from 'datafile'
+
+Right now, all Linux kernels use the same load address (0x00000000),
+but the entry point address depends on the kernel version:
+
+- 2.2.x kernels have the entry point at 0x0000000C,
+- 2.3.x and 2.4.x kernels have the entry point at 0x00000000.
+
+So a typical call to build a U-Boot image would read:
+
+ -> tools/mkimage -n '2.2.13 for initrd on TQM850L' \
+ > -A ppc -O linux -T kernel -C gzip -a 00000000 -e 0000000C \
+ > -d /opt/mpc8xx/src/linux-2.2.13/arch/ppc/coffboot/vmlinux.gz \
+ > examples/image-2.2.13-initrd
+ Image Name: 2.2.13 for initrd on TQM850L
+ Created: Wed Jul 19 02:34:59 2000
+ Image Type: PowerPC Linux Kernel Image (gzip compressed)
+ Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
+ Load Address: 0x00000000
+ Entry Point: 0x0000000c
+
+To verify the contents of the image (or check for corruption):
+
+ -> tools/mkimage -l examples/image-2.2.13-initrd
+ Image Name: 2.2.13 for initrd on TQM850L
+ Created: Wed Jul 19 02:34:59 2000
+ Image Type: PowerPC Linux Kernel Image (gzip compressed)
+ Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
+ Load Address: 0x00000000
+ Entry Point: 0x0000000c
+
+NOTE: for embedded systems where boot time is critical you can trade
+speed for memory and install an UNCOMPRESSED image instead: this
+needs more space in Flash, but boots much faster since it does not
+need to be uncompressed:
+
+ -> gunzip /opt/mpc8xx/src/linux-2.2.13/arch/ppc/coffboot/vmlinux.gz
+ -> tools/mkimage -n '2.2.13 for initrd on TQM850L' \
+ > -A ppc -O linux -T kernel -C none -a 00000000 -e 0000000C \
+ > -d /opt/mpc8xx/src/linux-2.2.13/arch/ppc/coffboot/vmlinux \
+ > examples/image-2.2.13-initrd-uncompressed
+ Image Name: 2.2.13 for initrd on TQM850L
+ Created: Wed Jul 19 02:34:59 2000
+ Image Type: PowerPC Linux Kernel Image (uncompressed)
+ Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
+ Load Address: 0x00000000
+ Entry Point: 0x0000000c
+
+
+Similar you can build U-Boot images from a 'ramdisk.image.gz' file
+when your kernel is intended to use an initial ramdisk:
+
+ -> tools/mkimage -n 'Simple Ramdisk Image' \
+ > -A ppc -O linux -T ramdisk -C gzip \
+ > -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
+ Image Name: Simple Ramdisk Image
+ Created: Wed Jan 12 14:01:50 2000
+ Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
+ Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
+ Load Address: 0x00000000
+ Entry Point: 0x00000000
+
+
+Installing a Linux Image:
+-------------------------
+
+To downloading a U-Boot image over the serial (console) interface,
+you must convert the image to S-Record format:
+
+ objcopy -I binary -O srec examples/image examples/image.srec
+
+The 'objcopy' does not understand the information in the U-Boot
+image header, so the resulting S-Record file will be relative to
+address 0x00000000. To load it to a given address, you need to
+specify the target address as 'offset' parameter with the 'loads'
+command.
+
+Example: install the image to address 0x40100000 (which on the
+TQM8xxL is in the first Flash bank):
+
+ => erase 40100000 401FFFFF
+
+ .......... done
+ Erased 8 sectors
+
+ => loads 40100000
+ ## Ready for S-Record download ...
+ ~>examples/image.srec
+ 1 2 3 4 5 6 7 8 9 10 11 12 13 ...
+ ...
+ 15989 15990 15991 15992
+ [file transfer complete]
+ [connected]
+ ## Start Addr = 0x00000000
+
+
+You can check the success of the download using the 'iminfo' command;
+this includes a checksum verification so you can be sure no data
+corruption happened:
+
+ => imi 40100000
+
+ ## Checking Image at 40100000 ...
+ Image Name: 2.2.13 for initrd on TQM850L
+ Image Type: PowerPC Linux Kernel Image (gzip compressed)
+ Data Size: 335725 Bytes = 327 kB = 0 MB
+ Load Address: 00000000
+ Entry Point: 0000000c
+ Verifying Checksum ... OK
+
+
+
+Boot Linux:
+-----------
+
+The "bootm" command is used to boot an application that is stored in
+memory (RAM or Flash). In case of a Linux kernel image, the contents
+of the "bootargs" environment variable is passed to the kernel as
+parameters. You can check and modify this variable using the
+"printenv" and "setenv" commands:
+
+
+ => printenv bootargs
+ bootargs=root=/dev/ram
+
+ => setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
+
+ => printenv bootargs
+ bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
+
+ => bootm 40020000
+ ## Booting Linux kernel at 40020000 ...
+ Image Name: 2.2.13 for NFS on TQM850L
+ Image Type: PowerPC Linux Kernel Image (gzip compressed)
+ Data Size: 381681 Bytes = 372 kB = 0 MB
+ Load Address: 00000000
+ Entry Point: 0000000c
+ Verifying Checksum ... OK
+ Uncompressing Kernel Image ... OK
+ 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
+ Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
+ time_init: decrementer frequency = 187500000/60
+ Calibrating delay loop... 49.77 BogoMIPS
+ Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
+ ...
+
+If you want to boot a Linux kernel with initial ram disk, you pass
+the memory addreses of both the kernel and the initrd image (PPBCOOT
+format!) to the "bootm" command:
+
+ => imi 40100000 40200000
+
+ ## Checking Image at 40100000 ...
+ Image Name: 2.2.13 for initrd on TQM850L
+ Image Type: PowerPC Linux Kernel Image (gzip compressed)
+ Data Size: 335725 Bytes = 327 kB = 0 MB
+ Load Address: 00000000
+ Entry Point: 0000000c
+ Verifying Checksum ... OK
+
+ ## Checking Image at 40200000 ...
+ Image Name: Simple Ramdisk Image
+ Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
+ Data Size: 566530 Bytes = 553 kB = 0 MB
+ Load Address: 00000000
+ Entry Point: 00000000
+ Verifying Checksum ... OK
+
+ => bootm 40100000 40200000
+ ## Booting Linux kernel at 40100000 ...
+ Image Name: 2.2.13 for initrd on TQM850L
+ Image Type: PowerPC Linux Kernel Image (gzip compressed)
+ Data Size: 335725 Bytes = 327 kB = 0 MB
+ Load Address: 00000000
+ Entry Point: 0000000c
+ Verifying Checksum ... OK
+ Uncompressing Kernel Image ... OK
+ ## Loading RAMDisk Image at 40200000 ...
+ Image Name: Simple Ramdisk Image
+ Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
+ Data Size: 566530 Bytes = 553 kB = 0 MB
+ Load Address: 00000000
+ Entry Point: 00000000
+ Verifying Checksum ... OK
+ Loading Ramdisk ... OK
+ 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
+ Boot arguments: root=/dev/ram
+ time_init: decrementer frequency = 187500000/60
+ Calibrating delay loop... 49.77 BogoMIPS
+ ...
+ RAMDISK: Compressed image found at block 0
+ VFS: Mounted root (ext2 filesystem).
+
+ bash#
+
+
+Standalone HOWTO:
+=================
+
+One of the features of U-Boot is that you can dynamically load and
+run "standalone" applications, which can use some resources of
+U-Boot like console I/O functions or interrupt services.
+
+Two simple examples are included with the sources:
+
+"Hello World" Demo:
+-------------------
+
+'examples/hello_world.c' contains a small "Hello World" Demo
+application; it is automatically compiled when you build U-Boot.
+It's configured to run at address 0x00040004, so you can play with it
+like that:
+
+ => loads
+ ## Ready for S-Record download ...
+ ~>examples/hello_world.srec
+ 1 2 3 4 5 6 7 8 9 10 11 ...
+ [file transfer complete]
+ [connected]
+ ## Start Addr = 0x00040004
+
+ => go 40004 Hello World! This is a test.
+ ## Starting application at 0x00040004 ...
+ Hello World
+ argc = 7
+ argv[0] = "40004"
+ argv[1] = "Hello"
+ argv[2] = "World!"
+ argv[3] = "This"
+ argv[4] = "is"
+ argv[5] = "a"
+ argv[6] = "test."
+ argv[7] = "<NULL>"
+ Hit any key to exit ...
+
+ ## Application terminated, rc = 0x0
+
+Another example, which demonstrates how to register a CPM interrupt
+handler with the U-Boot code, can be found in 'examples/timer.c'.
+Here, a CPM timer is set up to generate an interrupt every second.
+The interrupt service routine is trivial, just printing a '.'
+character, but this is just a demo program. The application can be
+controlled by the following keys:
+
+ ? - print current values og the CPM Timer registers
+ b - enable interrupts and start timer
+ e - stop timer and disable interrupts
+ q - quit application
+
+ => loads
+ ## Ready for S-Record download ...
+ ~>examples/timer.srec
+ 1 2 3 4 5 6 7 8 9 10 11 ...
+ [file transfer complete]
+ [connected]
+ ## Start Addr = 0x00040004
+
+ => go 40004
+ ## Starting application at 0x00040004 ...
+ TIMERS=0xfff00980
+ Using timer 1
+ tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
+
+Hit 'b':
+ [q, b, e, ?] Set interval 1000000 us
+ Enabling timer
+Hit '?':
+ [q, b, e, ?] ........
+ tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
+Hit '?':
+ [q, b, e, ?] .
+ tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
+Hit '?':
+ [q, b, e, ?] .
+ tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
+Hit '?':
+ [q, b, e, ?] .
+ tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
+Hit 'e':
+ [q, b, e, ?] ...Stopping timer
+Hit 'q':
+ [q, b, e, ?] ## Application terminated, rc = 0x0
+
+
+NetBSD Notes:
+=============
+
+Starting at version 0.9.2, U-Boot supports NetBSD both as host
+(build U-Boot) and target system (boots NetBSD/mpc8xx).
+
+Building requires a cross environment; it is known to work on
+NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
+need gmake since the Makefiles are not compatible with BSD make).
+Note that the cross-powerpc package does not install include files;
+attempting to build U-Boot will fail because <machine/ansi.h> is
+missing. This file has to be installed and patched manually:
+
+ # cd /usr/pkg/cross/powerpc-netbsd/include
+ # mkdir powerpc
+ # ln -s powerpc machine
+ # cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
+ # ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST
+
+Native builds *don't* work due to incompatibilities between native
+and U-Boot include files.
+
+Booting assumes that (the first part of) the image booted is a
+stage-2 loader which in turn loads and then invokes the kernel
+proper. Loader sources will eventually appear in the NetBSD source
+tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
+meantime, send mail to bruno@exet-ag.de and/or wd@denx.de for
+details.
+
+
+Implementation Internals:
+=========================
+
+The following is not intended to be a complete description of every
+implementation detail. However, it should help to understand the
+inner workings of U-Boot and make it easier to port it to custom
+hardware.
+
+
+Initial Stack, Global Data:
+---------------------------
+
+The implementation of U-Boot is complicated by the fact that U-Boot
+starts running out of ROM (flash memory), usually without access to
+system RAM (because the memory controller is not initialized yet).
+This means that we don't have writable Data or BSS segments, and BSS
+is not initialized as zero. To be able to get a C environment working
+at all, we have to allocate at least a minimal stack. Implementation
+options for this are defined and restricted by the CPU used: Some CPU
+models provide on-chip memory (like the IMMR area on MPC8xx and
+MPC826x processors), on others (parts of) the data cache can be
+locked as (mis-) used as memory, etc.
+
+It is essential to remember this, since it has some impact on the C
+code for the initialization procedures:
+
+* Initialized global data (data segment) is read-only. Do not attempt
+ to write it.
+
+* Do not use any unitialized global data (or implicitely initialized
+ as zero data - BSS segment) at all - this is undefined, initiali-
+ zation is performed later (when relocationg to RAM).
+
+* Stack space is very limited. Avoid big data buffers or things like
+ that.
+
+Having only the stack as writable memory limits means we cannot use
+normal global data to share information beween the code. But it
+turned out that the implementation of U-Boot can be greatly
+simplified by making a global data structure (gd_t) available to all
+functions. We could pass a pointer to this data as argument to _all_
+functions, but this would bloat the code. Instead we use a feature of
+the GCC compiler (Global Register Variables) to share the data: we
+place a pointer (gd) to the global data into a register which we
+reserve for this purpose.
+
+When chosing a register for such a purpose we are restricted by the
+relevant (E)ABI specifications for the current architecture, and by
+GCC's implementation.
+
+For PowerPC, the following registers have specific use:
+ R1: stack pointer
+ R2: TOC pointer
+ R3-R4: parameter passing and return values
+ R5-R10: parameter passing
+ R13: small data area pointer
+ R30: GOT pointer
+ R31: frame pointer
+
+ (U-Boot also uses R14 as internal GOT pointer.)
+
+ ==> U-Boot will use R29 to hold a pointer to the global data
+
+ Note: on PPC, we could use a static initializer (since the
+ address of the global data structure is known at compile time),
+ but it turned out that reserving a register results in somewhat
+ smaller code - although the code savings are not that big (on
+ average for all boards 752 bytes for the whole U-Boot image,
+ 624 text + 127 data).
+
+On ARM, the following registers are used:
+
+ R0: function argument word/integer result
+ R1-R3: function argument word
+ R9: GOT pointer
+ R10: stack limit (used only if stack checking if enabled)
+ R11: argument (frame) pointer
+ R12: temporary workspace
+ R13: stack pointer
+ R14: link register
+ R15: program counter
+
+ ==> U-Boot will use R8 to hold a pointer to the global data
+
+
+
+Memory Management:
+------------------
+
+U-Boot runs in system state and uses physical addresses, i.e. the
+MMU is not used either for address mapping nor for memory protection.
+
+The available memory is mapped to fixed addresses using the memory
+controller. In this process, a contiguous block is formed for each
+memory type (Flash, SDRAM, SRAM), even when it consists of several
+physical memory banks.
+
+U-Boot is installed in the first 128 kB of the first Flash bank (on
+TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
+booting and sizing and initializing DRAM, the code relocates itself
+to the upper end of DRAM. Immediately below the U-Boot code some
+memory is reserved for use by malloc() [see CFG_MALLOC_LEN
+configuration setting]. Below that, a structure with global Board
+Info data is placed, followed by the stack (growing downward).
+
+Additionally, some exception handler code is copied to the low 8 kB
+of DRAM (0x00000000 ... 0x00001FFF).
+
+So a typical memory configuration with 16 MB of DRAM could look like
+this:
+
+ 0x0000 0000 Exception Vector code
+ :
+ 0x0000 1FFF
+ 0x0000 2000 Free for Application Use
+ :
+ :
+
+ :
+ :
+ 0x00FB FF20 Monitor Stack (Growing downward)
+ 0x00FB FFAC Board Info Data and permanent copy of global data
+ 0x00FC 0000 Malloc Arena
+ :
+ 0x00FD FFFF
+ 0x00FE 0000 RAM Copy of Monitor Code
+ ... eventually: LCD or video framebuffer
+ ... eventually: pRAM (Protected RAM - unchanged by reset)
+ 0x00FF FFFF [End of RAM]
+
+
+System Initialization:
+----------------------
+
+In the reset configuration, U-Boot starts at the reset entry point
+(on most PowerPC systens at address 0x00000100). Because of the reset
+configuration for CS0# this is a mirror of the onboard Flash memory.
+To be able to re-map memory U-Boot then jumps to it's link address.
+To be able to implement the initialization code in C, a (small!)
+initial stack is set up in the internal Dual Ported RAM (in case CPUs
+which provide such a feature like MPC8xx or MPC8260), or in a locked
+part of the data cache. After that, U-Boot initializes the CPU core,
+the caches and the SIU.
+
+Next, all (potentially) available memory banks are mapped using a
+preliminary mapping. For example, we put them on 512 MB boundaries
+(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
+on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
+programmed for SDRAM access. Using the temporary configuration, a
+simple memory test is run that determines the size of the SDRAM
+banks.
+
+When there is more than one SDRAM bank, and the banks are of
+different size, the larger is mapped first. For equal size, the first
+bank (CS2#) is mapped first. The first mapping is always for address
+0x00000000, with any additional banks following immediately to create
+contiguous memory starting from 0.
+
+Then, the monitor installs itself at the upper end of the SDRAM area
+and allocates memory for use by malloc() and for the global Board
+Info data; also, the exception vector code is copied to the low RAM
+pages, and the final stack is set up.
+
+Only after this relocation will you have a "normal" C environment;
+until that you are restricted in several ways, mostly because you are
+running from ROM, and because the code will have to be relocated to a
+new address in RAM.
+
+
+U-Boot Porting Guide:
+----------------------
+
+[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
+list, Octover 2002]
+
+
+int main (int argc, char *argv[])
+{
+ sighandler_t no_more_time;
+
+ signal (SIGALRM, no_more_time);
+ alarm (PROJECT_DEADLINE - toSec (3 * WEEK));
+
+ if (available_money > available_manpower) {
+ pay consultant to port U-Boot;
+ return 0;
+ }
+
+ Download latest U-Boot source;
+
+ if (clueless) {
+ email ("Hi, I am new to U-Boot, how do I get started?");
+ }
+
+ while (learning) {
+ Read the README file in the top level directory;
+ Read http://www.denx.de/re/DPLG.html
+ Read the source, Luke;
+ }
+
+ if (available_money > toLocalCurrency ($2500)) {
+ Buy a BDI2000;
+ } else {
+ Add a lot of aggravation and time;
+ }
+
+ Create your own board support subdirectory;
+
+ while (!running) {
+ do {
+ Add / modify source code;
+ } until (compiles);
+ Debug;
+ if (clueless)
+ email ("Hi, I am having problems...");
+ }
+ Send patch file to Wolfgang;
+
+ return 0;
+}
+
+void no_more_time (int sig)
+{
+ hire_a_guru();
+}
+
+
+
+Coding Standards:
+-----------------
+
+All contributions to U-Boot should conform to the Linux kernel
+coding style; see the file "Documentation/CodingStyle" in your Linux
+kernel source directory.
+
+Please note that U-Boot is implemented in C (and to some small parts
+in Assembler); no C++ is used, so please do not use C++ style
+comments (//) in your code.
+
+Submissions which do not conform to the standards may be returned
+with a request to reformat the changes.
+
+
+Submitting Patches:
+-------------------
+
+Since the number of patches for U-Boot is growing, we need to
+establish some rules. Submissions which do not conform to these rules
+may be rejected, even when they contain important and valuable stuff.
+
+
+When you send a patch, please include the following information with
+it:
+
+* For bug fixes: a description of the bug and how your patch fixes
+ this bug. Please try to include a way of demonstrating that the
+ patch actually fixes something.
+
+* For new features: a description of the feature and your
+ implementation.
+
+* A CHANGELOG entry as plaintext (separate from the patch)
+
+* For major contributions, your entry to the CREDITS file
+
+* When you add support for a new board, don't forget to add this
+ board to the MAKEALL script, too.
+
+* If your patch adds new configuration options, don't forget to
+ document these in the README file.
+
+* The patch itself. If you are accessing the CVS repository use "cvs
+ update; cvs diff -puRN"; else, use "diff -purN OLD NEW". If your
+ version of diff does not support these options, then get the latest
+ version of GNU diff.
+
+ We accept patches as plain text, MIME attachments or as uuencoded
+ gzipped text.
+
+Notes:
+
+* Before sending the patch, run the MAKEALL script on your patched
+ source tree and make sure that no errors or warnings are reported
+ for any of the boards.
+
+* Keep your modifications to the necessary minimum: A patch
+ containing several unrelated changes or arbitrary reformats will be
+ returned with a request to re-formatting / split it.
+
+* If you modify existing code, make sure that your new code does not
+ add to the memory footprint of the code ;-) Small is beautiful!
+ When adding new features, these should compile conditionally only
+ (using #ifdef), and the resulting code with the new feature
+ disabled must not need more memory than the old code without your
+ modification.