Re: [PATCH] Revert "mtd: spi-nor: disable protection for Winbond flash at startup"

[Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>]

On 26 November 2015 at 13:27, Felix Fietkau <nbd@openwrt.org> wrote:
> This reverts commit c6fc2171b249e73745c497b578b417a2946f1b2f.
>
> This commit is breaking read access on at least s25fl064k, but also
> possibly other Spansion flash chips.
>
> Any mtd read seems to succeed, but simply returns a zero-filled buffer.
>
> Signed-off-by: Felix Fietkau <nbd@openwrt.org>
> ---
>  drivers/mtd/spi-nor/spi-nor.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 4988390..8b8842e 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -1194,14 +1194,13 @@ int spi_nor_scan(struct spi_nor *nor, const char *name, enum read_mode mode)
>         mutex_init(&nor->lock);
>
>         /*
> -        * Atmel, SST, Intel/Numonyx, and others serial NOR tend to power up
> -        * with the software protection bits set
> +        * Atmel, SST and Intel/Numonyx serial nor tend to power
> +        * up with the software protection bits set
>          */
>
>         if (JEDEC_MFR(info) == SNOR_MFR_ATMEL ||
>             JEDEC_MFR(info) == SNOR_MFR_INTEL ||
> -           JEDEC_MFR(info) == SNOR_MFR_SST ||
> -           JEDEC_MFR(info) == SNOR_MFR_WINBOND) {
> +           JEDEC_MFR(info) == SNOR_MFR_SST) {
>                 write_enable(nor);
>                 write_sr(nor, 0);
>         }

As Brian mentioned, this looks definitely fishy.

IIUC, the above statement is trying to unlock flashes that power-up as
locked. But you say your flash is still locked after booting? And
moreover, removing the unlock quirk fixes it?

I think a more complete description of your problem might help us fix
this the right way. Perhaps the above line clearing the status
register is wrong?
-- 
Ezequiel García, VanguardiaSur
www.vanguardiasur.com.ar