Flashing LinuxBIOS on A-Test Boards

Warnings

YOU CAN BRICK YOUR MACHINE IF YOU FOLLOW ANY OF THESE STEPS!

The instructions here are for the A test boards. You can place an PLCC EEPROM into the (only) socket on the A test board, flash it with LinuxBIOS, and on reboot boot from the EEPROM chip containing your newly flashed LinuxBIOS. For now, this only covers flashing a PLCC chip.

Hardware

Currently there isn't any sane way to flash the ROM to the serial flash on the OLPC board without running a huge risk of bricking it. The only way to try out the ROM image right now is to write the image to a PLCC ROM chip and use that in the PLCC socket on the Rev A boards.

You will want to use 8Mbit ROM chips, like these.

Preparation

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) 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

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).