ioremap_nocache(0xfffe0000, 0x00020000);

I used the program below to get a copy of Bios rom on a National Geode / CS5530 board. If I remember correctly this code depended on the chipset decoding the rom at this specific address range, the 'standard' address range was 0xC0000..0xFFFFF but not all the Rom was available here. If you wanted to write to the rom then it needed some other chipset bits set correctly as well.

You could also take a look at the linux-2.4.19/drivers/mtd/maps/{netsc520.c,sc520cdp.c}.

You could probably acomplish the same with the right 'dd if=/dev/mem of=bios.rom ...'

Jon Burgess

/* dumprom.c
*
* Dump BIOS Rom space to a file
*/
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <ctype.h>

// To read the full 4Mbit ROM it needs to be accessed at the 'high' address range
// Only 128Kb is available at 'low' address of 0xc0000
#define START 0xfff80000
#define LENGTH 0x00080000

int main(int argc, char *argv[])

{
     void *pmem;
     int fd, fd2;

     if (argc != 2)
     {
          printf("%s: <filename>\n", argv[0]);
          printf("Writes the BIOS memory space out to the file specifed\n");
          exit(1);
     }

     fd2 = open(argv[1], O_WRONLY | O_CREAT);
     if (!fd2)
          {
         perror("Error creating file");
         exit(1);
          }

     /* Get access BIOS memory space */
     fd = open("/dev/mem", O_RDONLY);
     if(!fd)
       {
         perror("Error opening /dev/mem");
               close(fd2);
         exit(1);
       }

     pmem = mmap(0, LENGTH, PROT_READ, MAP_SHARED, fd, START);
     if (pmem == MAP_FAILED)
       {
         perror("Error mapping /dev/mem");
               close(fd2);
               close(fd);
         exit(1);
       }

     if (write(fd2, pmem, LENGTH) == -1)
          {
               perror("Error writing data");
               close(fd2);
               close(fd);
               exit(2);
          }

     munmap(pmem, LENGTH);

     close(fd);
     close(fd2);

     exit(0);
}