u-Boot readme

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u-Boot readme

벅스바니 2010. 2. 10. 10:00

Link:http://www.beattie-home.net/beattie/DSM-G600/U-Boot-README.html

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'

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 corresponding setting in the environment; if the corresponding environment variable is set, this overrides the settings in the card; that means:

If the SROM has a valid MAC address, and there is no address in the environment, the SROM's address is used.
If there is no valid address in the SROM, and a definition in theenvironment exists, then the value from the environment variable isused.
If both the SROM and the environment contain a MAC address, andboth addresses are the same, this MAC address is used.
If both the SROM and the environment contain a MAC address, and theaddresses differ, the value from the environment is used and awarning is printed.
If neither SROM nor the environment contain a MAC address, an erroris 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 canbe run with the same "initrd". This makes testing easier (you don'thave to build a new "zImage.initrd" Linux image when you justchange a file in your "initrd"). Also, a field-upgrade of thesoftware is easier now.

Building a Linux Image

With U-Boot, "normal" build targets like "zImage" or "bzImage" are not used. If you use recent kernel source, a new build target "uImage" will exist which automatically builds an image usable by U-Boot. Most older kernels also have support for a "pImage" target, which was introduced for our predecessor project PPCBoot and uses a 100% compatible format.

Example:

 make TQM850L_config
 make oldconfig
 make dep
 make uImage

The "uImage" build target uses a special tool (in 'tools/mkimage') to encapsulate a compressed Linux kernel image with header information, CRC32 checksum etc. for use with U-Boot. This is what we are doing:

* build a standard "vmlinux" kernel image (in ELF binary format):

* convert the kernel into a raw binary image:
 ${CROSS_COMPILE}-objcopy -O binary \
 -R .note -R .comment \
 -S vmlinux linux.bin

* compress the binary image:
 gzip -9 linux.bin

* package compressed binary image for U-Boot:
 mkimage -A ppc -O linux -T kernel -C gzip \
 -a 0 -e 0 -n "Linux Kernel Image" \
 -d linux.bin.gz uImage

The "mkimage" tool can also be used to create ramdisk images for use with U-Boot, either separated from the Linux kernel image, or combined into one file. "mkimage" encapsulates the images with a 64 byte header containing information about target architecture, operating system, image type, compression method, entry points, time stamp, CRC32 checksums, etc.

"mkimage" can be called in two ways: to verify existing images and print the header information, or to build new images.

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 later kernels have the entry point at 0x00000000.

So a typical call to build a U-Boot image would read:

-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
 > -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux.gz \
 > examples/uImage.TQM850L
 Image Name: 2.4.4 kernel for 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: 0x00000000

To verify the contents of the image (or check for corruption):

 -> tools/mkimage -l examples/uImage.TQM850L
 Image Name: 2.4.4 kernel for 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: 0x00000000

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/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux.gz
 -> tools/mkimage -n '2.4.4 kernel for TQM850L' \
 > -A ppc -O linux -T kernel -C none -a 0 -e 0 \
 > -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux \
 > examples/uImage.TQM850L-uncompressed
 Image Name: 2.4.4 kernel for 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: 0x00000000

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).

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