Re: [PATCH] mmc: add quirk to disable eMMC cache for Micron eMMC v5.0 cards

[Ulf Hansson]

+ Bean Huo, Luca Porzio

On Thu, 8 Apr 2021 at 19:59, Scott Branden <scott.branden@xxxxxxxxxxxx> wrote:
>
> From: Vladimir Olovyannikov <vladimir.olovyannikov@xxxxxxxxxxxx>
>
> In certain rare combination of operations, Micron eMMC v5.0 cards
> may experience data errors if internal cache is enabled.
> This may lead to eMMC related data errors.
> Introduce a quirk to disable cache on these eMMC cards.

Can you please elaborate on this, what combinations of operations are
you referring to - and what kind of data errors?

I have also looped in some of the Micron guys, to let them chim in.

>
> Signed-off-by: Vladimir Olovyannikov <vladimir.olovyannikov@xxxxxxxxxxxx>
> Signed-off-by: Scott Branden <scott.branden@xxxxxxxxxxxx>

Kind regards
Uffe

> ---
>  drivers/mmc/core/card.h   | 5 +++++
>  drivers/mmc/core/mmc.c    | 4 ++--
>  drivers/mmc/core/quirks.h | 8 ++++++++
>  include/linux/mmc/card.h  | 1 +
>  4 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/card.h b/drivers/mmc/core/card.h
> index 7bd392d55cfa..22cea63ac359 100644
> --- a/drivers/mmc/core/card.h
> +++ b/drivers/mmc/core/card.h
> @@ -222,4 +222,9 @@ static inline int mmc_card_broken_hpi(const struct mmc_card *c)
>         return c->quirks & MMC_QUIRK_BROKEN_HPI;
>  }
>
> +static inline int mmc_card_broken_cache(const struct mmc_card *c)
> +{
> +       return c->quirks & MMC_QUIRK_BROKEN_CACHE;
> +}
> +
>  #endif
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 8741271d3971..cd83b7f0e59c 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1820,12 +1820,12 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
>          * sudden power failure tests. Let's extend the timeout to a minimum of
>          * DEFAULT_CACHE_EN_TIMEOUT_MS and do it for all cards.
>          */
> -       if (card->ext_csd.cache_size > 0) {
> +       if (!mmc_card_broken_cache(card) && card->ext_csd.cache_size > 0) {
>                 unsigned int timeout_ms = MIN_CACHE_EN_TIMEOUT_MS;
>
>                 timeout_ms = max(card->ext_csd.generic_cmd6_time, timeout_ms);
>                 err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
> -                               EXT_CSD_CACHE_CTRL, 1, timeout_ms);
> +                                EXT_CSD_CACHE_CTRL, 1, timeout_ms);
>                 if (err && err != -EBADMSG)
>                         goto free_card;
>
> diff --git a/drivers/mmc/core/quirks.h b/drivers/mmc/core/quirks.h
> index d68e6e513a4f..23972d87c82a 100644
> --- a/drivers/mmc/core/quirks.h
> +++ b/drivers/mmc/core/quirks.h
> @@ -116,6 +116,14 @@ static const struct mmc_fixup __maybe_unused mmc_ext_csd_fixups[] = {
>         MMC_FIXUP_EXT_CSD_REV(CID_NAME_ANY, CID_MANFID_NUMONYX,
>                               0x014e, add_quirk, MMC_QUIRK_BROKEN_HPI, 6),
>
> +       /*
> +        * In certain rare combination of operations, Micron eMMC v5.0 cards
> +        * may experience data errors if internal cache is enabled.
> +        * Disabling cache for these cards eliminates the issue.
> +        */
> +       MMC_FIXUP_EXT_CSD_REV(CID_NAME_ANY, CID_MANFID_MICRON,
> +                             0x014e, add_quirk, MMC_QUIRK_BROKEN_CACHE, 7),
> +
>         END_FIXUP
>  };
>
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index f9ad35dd6012..22f256a4e54e 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -270,6 +270,7 @@ struct mmc_card {
>  #define MMC_QUIRK_BROKEN_IRQ_POLLING   (1<<11) /* Polling SDIO_CCCR_INTx could create a fake interrupt */
>  #define MMC_QUIRK_TRIM_BROKEN  (1<<12)         /* Skip trim */
>  #define MMC_QUIRK_BROKEN_HPI   (1<<13)         /* Disable broken HPI support */
> +#define MMC_QUIRK_BROKEN_CACHE (1<<14)         /* Disable broken cache */
>
>         bool                    reenable_cmdq;  /* Re-enable Command Queue */
>
> --
> 2.17.1
>