Bug in am29f040b.c causes flash device not to be recognised

[Peter Fox]

The following patch needs to be applied to am29f040b.c in the
utils/flash_and_burn directory:

----------------------
--- am29f040b-nv.c	Wed Nov  5 14:33:34 2003
+++ am29f040b.c	Wed Nov  5 14:20:26 2003
@@ -76,8 +76,8 @@
    *(bios + 0x2AA) = 0x55;
    *(bios + 0x555) = 0x90;

-	id1 = *(unsigned char *) bios;
-	id2 = *(unsigned char *) (bios + 0x01);
+	id1 = *(volatile unsigned char *) bios;
+	id2 = *(volatile unsigned char *) (bios + 0x01);

*bios = 0xF0;

----------------------

My C compiler was reordering the writes and reads, so that
the flash wasn't ready to give an id when the reads occurred.

I notice that all the other flash devices already seem to have
this correct.

[ron minnich]

I applied the fix in a slightly different way, can you test this for me?

It looks like this now:

int probe_29f040b (struct flashchip * flash)
{
        volatile unsigned char * bios = flash->virt_addr;
        unsigned char id1, id2;

*(bios + 0x555) = 0xAA;
        *(bios + 0x2AA) = 0x55;
        *(bios + 0x555) = 0x90;

id1 = * bios;
        id2 = * (bios + 0x01);

*bios = 0xF0;

myusec_delay(10);

printf("%s: id1 0x%x, id2 0x%x\n", __FUNCTION__, id1, id2);
        if (id1 == flash->manufacture_id && id2 == flash->model_id)
                return 1;

return 0;
}

ron

[Peter Fox]

That also works, here's the assembly difference between
my version with volatiles in the cast, and yours with
the bios type changed:

--- am29f040b-v.s       Wed Nov  5 14:20:34 2003
+++ am29f040b.s Thu Nov  6 08:54:13 2003
@@ -23,12 +23,12 @@
        subl    $24, %esp
        movl    8(%ebp), %edx
        movl    12(%edx), %eax
-       movb    $-86, 1365(%eax)
+       movb    $170, 1365(%eax)
        movb    $85, 682(%eax)
-       movb    $-112, 1365(%eax)
+       movb    $144, 1365(%eax)
        movzbl  (%eax), %esi
        movb    1(%eax), %bl
-       movb    $-16, (%eax)
+       movb    $240, (%eax)
        movzbl  %bl, %edi
        pushl   $10
        call    myusec_delay