Numonyx NOR bug

[Joakim Tjernlund]

>
> I found a little problem with mtd drivers running on a LTIB linux
> distribution on a custom board equipped with a Freescale Coldfire and a
> Numonyx NOR Axcell M29EW flash memory. The do_erase_oneblock() function
> sometimes fails because the chip_good() functions returns zero reading a
> data word different from 0xffff. I spent some time debugging and finally
> I solved the problem adding a new chip state "FL_ERASE_STARTING" and
> setting it after the erase block command sequence as follows :
>
>    cfi_send_gen_cmd(0xAA, cfi->addr_unlock1, chip->start, map, cfi,
> cfi->device_type, NULL);
>    cfi_send_gen_cmd(0x55, cfi->addr_unlock2, chip->start, map, cfi,
> cfi->device_type, NULL);
>    cfi_send_gen_cmd(0x80, cfi->addr_unlock1, chip->start, map, cfi,
> cfi->device_type, NULL);
>    cfi_send_gen_cmd(0xAA, cfi->addr_unlock1, chip->start, map, cfi,
> cfi->device_type, NULL);
>    cfi_send_gen_cmd(0x55, cfi->addr_unlock2, chip->start, map, cfi,
> cfi->device_type, NULL);
>    map_write(map, CMD(0x30), adr);
>
>    chip->state = FL_ERASE_STARTING;
>
>    INVALIDATE_CACHE_UDELAY(map, chip,
>                         adr, len,
>                         chip->erase_time);
>
>    chip->state = FL_ERASING;
>    chip->erase_suspended = 0;
>    chip->in_progress_block_addr = adr;
>
>    timeo = jiffies + (HZ*20);
>
>    for (;;) {
>
> This works because the Numonyx chip probably does not accept the erase
> suspend command during the erase block time-out (the 50 us after the
> command sequence has been sent and before the erase starts). In fact the
> INVALIDATE_CACHE_UDELAY() macro unlocks the mutex and lets
> reading/writing functions to suspend the erasing too soon calling the
> get_chip(). With the FL_ERASE_STARTING state get_chip() does not give
> the access to reading/writing functions during the
> INVALIDATE_CACHE_UDELAY() sleeping period (chip->erase_time).
> Anyone into the same problem?
>
> Thanks for reading!
> Leonardo

Sounds similar to what we found some time ago, check out
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=ecf3fde07c8dcb92a1bf3fbdfe70905d85cd00e1
for a fix