Flashing LinuxBIOS on A-Test Boards

Warnings

If you are upgrading to Linux BIOS, you are on the wrong page (See Upgrading_to_LinuxBIOS).

You can "brick" your machine if you make any mistakes in following these steps, so please take care! Therefore, please do not preceed unless you are sure that you know what you are doing!

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This page documents how to flash LinuxBIOS on the OLPC board for development of LinuxBIOS using PLCC EEPROM chips; it is not intended for general users.

Hardware

These instructions are only for the revision "A" test boards. You can place a PLCC EEPROM into the (only) socket on the test board, flash it with LinuxBIOS, and reboot from the EEPROM chip containing your newly flashed LinuxBIOS.

For now, this only covers writing the image to this PLCC ROM chip and using it in that PLCC socket; there is no sane way to write to the serial flash (that which contains the normal BIOS) without a huge risk of bricking your device.

You will want to use 8-Mbit EEPROM chips.

Boot with normal BIOS and setup toolchain

Use your normal serial BIOS (currently, by Insyde Software) to boot into a Linux distribution. You'll need to build some software before you can flash your EEPROM chip with LinuxBIOS.

rdmsr

Build the rdmsr (read MSR, model specific register) tool by Ron Minnich:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

int main (int argc, char *argv[])
{
    unsigned char buf[8];
    int fd_msr, i;
    unsigned long addr = 0;

    if (argc < 2) {
        printf("usage:rdmsr reg\n");
        exit(1);
    }
    addr = strtoul(argv[1], NULL, 0);

    fd_msr = open("/dev/cpu/0/msr", O_RDONLY);
    lseek(fd_msr, addr, SEEK_SET);
    read(fd_msr, buf, 8);

    printf("MSR register 0x%lx => ", addr);
    for (i = 7; i > 0; i--)
        printf("%2.2x:", buf[i]);
    printf("%2.2x\n", buf[i]);

    return(0);
}

with:

% gcc rdmsr.c -o rdmsr

wrmsr

Build the wrmsr (write MSR) tool (also by Ron Minnich):

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

int main (int argc, char *argv[])
{
    unsigned char buf[8], *p;
    int fd_msr, i;
    unsigned long addr = 0;

    if (argc < 3) {
        printf("usage:wrmsr reg value\n");
        exit(1);
    }
    addr = strtoul(argv[1], NULL, 0);
    p = argv[2];

    printf("MSR register 0x%lx => ", addr);
    for (i = 7; i > 0; i--) {
        buf[i] = strtol(p, &p, 16);
        p++;
        printf("%2.2x:", buf[i]);
    }
    buf[i] = strtol(p, &p, 16);
    printf("%2.2x\n", buf[i]);

    fd_msr = open("/dev/cpu/0/msr", O_WRONLY);
    lseek(fd_msr, addr, SEEK_SET);
    if (write(fd_msr, buf, 8) < 0)
        perror("");

    return(0);
}

with:

% gcc wrmsr.c -o wrmsr

You may get some warnings; they're not important and may be ignored.

flashrom

Download the latest LinuxBIOS snapshot to get the flashrom utility. Unpack the archive, and go into the util/flashrom directory. After making sure you have your distribution's pciutils and pcituils-dev package installed, run make. This will build the flashrom utility; copy it into a convenient location (such as /usr/local/bin).

Flashing

Inserting the chip

EEPROM chip mounted correctly in socket

EEPROM chip, unmounted; pin 1 is dot facing up

Because the board will be booting from the EEPROM chip we insert, we cannot boot while a blank EEPROM chip is inserted (otherwise you will not be able to boot). Thus, you're going to have to insert the EEPROM chip while the machine is running.

Be quick and careful: and remember, pin 1 is the triangle/dot, and these must line up with the socket properly. See the pictures at the right for guidance.

If you're using an A test board and a PLCC EEPROM chip, go ahead and insert the chip now, before following the next few steps.

Enable writing to flash

On Linux, make sure you have the MSR kernel module loaded:

% modprobe msr

so you will have MSR device files. To enable PLCC writing on the OLPC board, you need to enable flash writing. Once you've built rdmsr and wrmsr, run:

% ./rdmsr 0x1808
% ./wrmsr 0x1808 22:ff:80:02:10:f7:bf:00
% ./rdmsr 0x1808

The first command will read the MSR 0x1808; the second will write a value to this register; the third will read the register again. The value read from the third command should match the one written in the second command. If wrmsr produces an error "Bad file descriptor", you forgot to load the MSR kernel module (see above).

Using flashrom

Once you've got flashrom working, you can now flash your LinuxBIOS image. Check that flashrom can see your writable flash chip:

% flashrom -V

You should see a note about a writable part being detected. If so, you can now write to the part, with the LinuxBIOS image you've built previously:

% flashrom -w linuxbios.rom

Once it's written, verify that it has been written properly:

% flashrom -v linuxbios.rom

Boot with LinuxBIOS

You can now reboot. Make sure you shutdown properly (your disk/filesystems must be in a consistent state, and been unmounted properly). On reboot you'll be greeted by the OLPC LinuxBIOS splash screen, where you can select boot method. Choose USB to boot from a USB disk, hopefully using one of the build images.

Newer versions of the rom (after Aug 10) will boot from NAND/USB without keyboard intervention. Press ESC during the progress bar to see the boot menu.--JordanCrouse (Talk to me!) 15:12, 11 August 2006 (EDT)