[PATCH] mtd: cfi: Wait for Block Erase operation to finish

[Joakim Tjernlund]

>
> If an Erase Suspend Command (0xb0) is issued while a Block Erase operation
> (0x20, 0xd0) is in progress, Status Register bit 6 (SR.6) will be set to 1.
> After an Erase Resume Command (0xd0) is issued, SR.6 will be set back to 0.
>
> Unfortunately when inval_cache_and_wait_for_operation() is called to wait for
> a Block Erase operation to finish, it never checks that SR.6 = 0 before
> returning. Consequently it can (and does) return while a Block Erase operation
> is still suspended, resulting in random breakage.
>
> This patch ensures that when inval_cache_and_wait_for_operation() is called to
> wait for a Block Erase operation to finish (chip->state == FL_ERASING), it does
> not return until both SR.7 = 1 (as before) and SR.6 = 0.

Interesting but I do wonder, should not the
  if (chip->state != chip_state)
test just before the status test prevent this in the first place?

>
> Signed-off-by: Paul Parsons <lost.distance at yahoo.com>
> ---
>
> I found this after switching my HP iPAQ hx4700 from using jffs2 to ubifs. It
> then consistently reported "block erase error: (bad VPP)" errors. Intriguingly,
> the bootloader never reporting erase or programming failures; it turned out that
> the bootloader never issued Erase Suspend Commands.
>
> Should SR.6 = 0 also be checked after an Erase Suspend Command (0xb0) is issued?
> This should preclude an unnecessary (and perhaps unpredictable) subsequent Erase
> Resume Command (0xd0).
>
> --- clean-3.3-rc5/drivers/mtd/chips/cfi_cmdset_0001.c   2012-02-25 20:18:16.000000000 +0000
> +++ linux-3.3-rc5/drivers/mtd/chips/cfi_cmdset_0001.c   2012-02-28 03:13:30.521537614 +0000
> @@ -1211,6 +1211,7 @@ static int inval_cache_and_wait_for_oper
>  {
>     struct cfi_private *cfi = map->fldrv_priv;
>     map_word status, status_OK = CMD(0x80);
> +   map_word status_76 = (chip->state == FL_ERASING) ? CMD(0xc0) : CMD(0x80);

hmm, I wonder if you can get by without the chip->state test? Just always set it to 0xc0?

 Jocke