Uncorrectable bitflips with Linux 4.12 on SAMA5D2

[Romain Izard]

Hi Boris,

2017-07-17 20:20 GMT+02:00 Boris Brezillon <boris.brezillon at free-electrons.com>:
> Le Mon, 17 Jul 2017 19:48:09 +0200,
> Boris Brezillon <boris.brezillon at free-electrons.com> a écrit :
>
>> +Ludovic, Nicolas and Alexandre
>>
>> Hi Romain,
>>
>> Le Mon, 17 Jul 2017 18:11:26 +0200,
>> Romain Izard <romain.izard.pro at gmail.com> a écrit :
>>
>> > Hello,
>> >
>> > On a custom board based on Microchip's SAMA5D2 SoC, I am encountering
>> > ECC problems with the NAND Flash controller. The board is currently
>> > working with Linux v4.9.x, but it does not with Linux 4.12.
>> >
>> > Some pages on the NAND Flash memory chip of the device have bitflips.
>> > With Linux 4.9.x, the bitflips are fixed by the PMECC code, but with
>> > Linux 4.12, the errors are reported as uncorrectable.
>> >
>> > From my end, I updated the board's device tree to include the
>> > sama5d2.dtsi as it exists in Linux 4.12, but the rest of the file is
>> > the same as for Linux 4.9. From my understanding, it should be
>> > sufficient as the legacy DTB binding for the NAND controller is
>> > supported.
>>
>> I know Ludovic add some problems with the NAND controller on sama5d2,
>> but it was with the new bindings (see the fixes here [1]).
>>
>> Your problem seems a bit different since you're using the backward
>> compat code.
>
> Can you try with the following patch applied?
>
> --->8---
> From cb95a16cdd497137872c44d5dd4e251ec73c79c1 Mon Sep 17 00:00:00 2001
> From: Boris Brezillon <boris.brezillon at free-electrons.com>
> Date: Mon, 17 Jul 2017 20:09:59 +0200
> Subject: [PATCH] mtd: nand: atmel: Fix DT backward compatibility in pmecc.c
>
> PMECC caps extraction from old DT bindings is broken, thus leading to
> erroneous EL registers offset, which in turn make HW ECC unusable on
> sama5d2 when old bindings are in use.
>
> Passing the NAND dev node instead of the NFC node to of_match_node()
> solves the problem.
>
> Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>
> Fixes: f88fc122cc34 ("mtd: nand: Cleanup/rework the atmel_nand driver")
> Cc: <stable at vger.kernel.org>
> ---
>  drivers/mtd/nand/atmel/pmecc.c | 21 ++++++---------------
>  1 file changed, 6 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/mtd/nand/atmel/pmecc.c b/drivers/mtd/nand/atmel/pmecc.c
> index 55a8ee5306ea..8c210a5776bc 100644
> --- a/drivers/mtd/nand/atmel/pmecc.c
> +++ b/drivers/mtd/nand/atmel/pmecc.c
> @@ -945,6 +945,7 @@ struct atmel_pmecc *devm_atmel_pmecc_get(struct device *userdev)
>                  */
>                 struct platform_device *pdev = to_platform_device(userdev);
>                 const struct atmel_pmecc_caps *caps;
> +               const struct of_device_id *match;
>
>                 /* No PMECC engine available. */
>                 if (!of_property_read_bool(userdev->of_node,
> @@ -953,21 +954,11 @@ struct atmel_pmecc *devm_atmel_pmecc_get(struct device *userdev)
>
>                 caps = &at91sam9g45_caps;
>
> -               /*
> -                * Try to find the NFC subnode and extract the associated caps
> -                * from there.
> -                */
> -               np = of_find_compatible_node(userdev->of_node, NULL,
> -                                            "atmel,sama5d3-nfc");
> -               if (np) {
> -                       const struct of_device_id *match;
> -
> -                       match = of_match_node(atmel_pmecc_legacy_match, np);
> -                       if (match && match->data)
> -                               caps = match->data;
> -
> -                       of_node_put(np);
> -               }
> +               /* Find the caps associated to the NAND dev node. */
> +               match = of_match_node(atmel_pmecc_legacy_match,
> +                                     userdev->of_node);
> +               if (match && match->data)
> +                       caps = match->data;
>
>                 pmecc = atmel_pmecc_create(pdev, caps, 1, 2);
>         }


The proposed patch fixes my issue. Thank you for your quick response!

You can add my:
Tested-by: Romain Izard <romain.izard.pro at gmail.com>

Best regards,
-- 
Romain Izard