[v2] mtd: rawnand: mxc: set spare area size register explicitly

The v21 version of the NAND flash controller contains a Spare Area Size
Register (SPAS) at offset 0x10. Its setting defaults to the maximum
spare area size of 218 bytes. The size that is set in this register is
used by the controller when it calculates the ECC bytes internally in
hardware.

Usually, this register is updated from settings in the IIM fuses when
the system is booting from NAND flash. For other boot media, however,
the SPAS register remains at the default setting, which may not work for
the particular flash chip on the board. The same goes for flash chips
whose configuration cannot be set in the IIM fuses (e.g. chips with 2k
sector size and 128 bytes spare area size can't be configured in the IIM
fuses on imx25 systems).

Set the SPAS register explicitly during the preset operation. Derive the
register value from mtd->oobsize that was detected during probe by
decoding the flash chip's ID bytes.

While at it, rename the define for the spare area register's offset to
NFC_V21_RSLTSPARE_AREA. The register at offset 0x10 on v1 controllers is
different from the register on v21 controllers.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
Cc: stable@vger.kernel.org
---
changes in v2
   - fix the commit message
   - use '/ 2' instead of shift operator for division

BTW is it ok to keep a Reviewed-by tag when updating the patch?

 drivers/mtd/nand/raw/mxc_nand.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Hi Martin,

On Sun, 10 Jun 2018 15:31:27 +0200, Martin Kaiser <martin@kaiser.cx>
wrote:

> The v21 version of the NAND flash controller contains a Spare Area Size
> Register (SPAS) at offset 0x10. Its setting defaults to the maximum
> spare area size of 218 bytes. The size that is set in this register is
> used by the controller when it calculates the ECC bytes internally in
> hardware.
> 
> Usually, this register is updated from settings in the IIM fuses when
> the system is booting from NAND flash. For other boot media, however,
> the SPAS register remains at the default setting, which may not work for
> the particular flash chip on the board. The same goes for flash chips
> whose configuration cannot be set in the IIM fuses (e.g. chips with 2k
> sector size and 128 bytes spare area size can't be configured in the IIM
> fuses on imx25 systems).
> 
> Set the SPAS register explicitly during the preset operation. Derive the
> register value from mtd->oobsize that was detected during probe by
> decoding the flash chip's ID bytes.
> 
> While at it, rename the define for the spare area register's offset to
> NFC_V21_RSLTSPARE_AREA. The register at offset 0x10 on v1 controllers is
> different from the register on v21 controllers.
> 
> Signed-off-by: Martin Kaiser <martin@kaiser.cx>
> Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
> Cc: stable@vger.kernel.org
> ---

Thanks, I'm ok with the patch, I'll queue it to nand/next.

> changes in v2
>    - fix the commit message
>    - use '/ 2' instead of shift operator for division
> 
> BTW is it ok to keep a Reviewed-by tag when updating the patch?

I think so, at least for such minor updates it is okay :)

Regards,
Miquèl

Hi Martin,

On Sun, 10 Jun 2018 15:31:27 +0200
Martin Kaiser <martin@kaiser.cx> wrote:

> The v21 version of the NAND flash controller contains a Spare Area Size
> Register (SPAS) at offset 0x10. Its setting defaults to the maximum
> spare area size of 218 bytes. The size that is set in this register is
> used by the controller when it calculates the ECC bytes internally in
> hardware.
> 
> Usually, this register is updated from settings in the IIM fuses when
> the system is booting from NAND flash. For other boot media, however,
> the SPAS register remains at the default setting, which may not work for
> the particular flash chip on the board. The same goes for flash chips
> whose configuration cannot be set in the IIM fuses (e.g. chips with 2k
> sector size and 128 bytes spare area size can't be configured in the IIM
> fuses on imx25 systems).
> 
> Set the SPAS register explicitly during the preset operation. Derive the
> register value from mtd->oobsize that was detected during probe by
> decoding the flash chip's ID bytes.
> 
> While at it, rename the define for the spare area register's offset to
> NFC_V21_RSLTSPARE_AREA. The register at offset 0x10 on v1 controllers is
> different from the register on v21 controllers.
> 
> Signed-off-by: Martin Kaiser <martin@kaiser.cx>
> Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
> Cc: stable@vger.kernel.org

Hm, a Cc-stable tag without its associated Fixes tag, I don't like that.
Can you find which commit introduced this bug?

Thanks,

Boris

Hi Boris,

Thus wrote Boris Brezillon (boris.brezillon@bootlin.com):

> > Signed-off-by: Martin Kaiser <martin@kaiser.cx>
> > Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
> > Cc: stable@vger.kernel.org

> Hm, a Cc-stable tag without its associated Fixes tag, I don't like that.
> Can you find which commit introduced this bug?

the particular corner case that I fixed has never really worked. As my
fix updates the preset operation, I'd suggest adding a Fixes tag pointing
at the first commit that introduced the preset operation.

I'll resend my patch with this tag added.

Best regards,

   Martin