Re: [PATCH v4] mmc: Add quirk MMC_QUIRK_BROKEN_CACHE_FLUSH for Micron eMMC Q2J54A

[Ulf Hansson <ulf.hansson@linaro.org>]

On Sun, 1 Oct 2023 at 21:50, Bean Huo <beanhuo@iokpp.de> wrote:
>
> From: Bean Huo <beanhuo@micron.com>
>
> Micron MTFC4GACAJCN eMMC supports cache but requires that flush cache
> operation be allowed only after a write has occurred. Otherwise, the
> cache flush command or subsequent commands will time out.
>
> Signed-off-by: Bean Huo <beanhuo@micron.com>
> Signed-off-by: Rafael Beims <rafael.beims@toradex.com>
> Cc: stable@vger.kernel.org
>
> ---
> Changelog:
>
> v3--v4:
>     1. Add helper function for this quirk in drivers/mmc/core/card.h.
>     2. Set card->written_flag only for REQ_OP_WRITE.
> v2--v3:
>     1. Set card->written_flag in mmc_blk_mq_issue_rq().
> v1--v2:
>     1. Add Rafael's test-tag, and Co-developed-by.
>     2. Check host->card whether NULL or not in __mmc_start_request() before asserting host->card->->quirks
> ---
>  drivers/mmc/core/block.c  | 5 ++++-
>  drivers/mmc/core/card.h   | 4 ++++
>  drivers/mmc/core/mmc.c    | 5 +++++
>  drivers/mmc/core/quirks.h | 7 ++++---
>  include/linux/mmc/card.h  | 2 ++
>  5 files changed, 19 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index 3a8f27c3e310..dfa67d9c80bb 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -2381,8 +2381,11 @@ enum mmc_issued mmc_blk_mq_issue_rq(struct mmc_queue *mq, struct request *req)
>                         }
>                         ret = mmc_blk_cqe_issue_flush(mq, req);
>                         break;
> -               case REQ_OP_READ:
>                 case REQ_OP_WRITE:
> +                       if (mmc_card_broken_cache_flush(card) && !card->written_flag)

It looks superfluous to me to check mmc_card_broken_cache_flush() and
!card->written_flag. Just set the card->written_flag unconditionally.

> +                               card->written_flag = true;
> +                       fallthrough;
> +               case REQ_OP_READ:
>                         if (host->cqe_enabled)
>                                 ret = mmc_blk_cqe_issue_rw_rq(mq, req);
>                         else
> diff --git a/drivers/mmc/core/card.h b/drivers/mmc/core/card.h
> index 4edf9057fa79..b7754a1b8d97 100644
> --- a/drivers/mmc/core/card.h
> +++ b/drivers/mmc/core/card.h
> @@ -280,4 +280,8 @@ static inline int mmc_card_broken_sd_cache(const struct mmc_card *c)
>         return c->quirks & MMC_QUIRK_BROKEN_SD_CACHE;
>  }
>
> +static inline int mmc_card_broken_cache_flush(const struct mmc_card *c)
> +{
> +       return c->quirks & MMC_QUIRK_BROKEN_CACHE_FLUSH;
> +}
>  #endif
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 89cd48fcec79..47896c32086e 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1929,6 +1929,8 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
>         if (!oldcard)
>                 host->card = card;
>
> +       card->written_flag = false;
> +

How about doing this after a successful flush operation instead? In
other words in _mmc_flush_cache().

>         return 0;
>
>  free_card:
> @@ -2081,6 +2083,9 @@ static int _mmc_flush_cache(struct mmc_host *host)
>  {
>         int err = 0;
>
> +       if (mmc_card_broken_cache_flush(host->card) && !host->card->written_flag)
> +               return err;

return 0;

> +
>         if (_mmc_cache_enabled(host)) {
>                 err = mmc_switch(host->card, EXT_CSD_CMD_SET_NORMAL,
>                                  EXT_CSD_FLUSH_CACHE, 1,
> diff --git a/drivers/mmc/core/quirks.h b/drivers/mmc/core/quirks.h
> index 32b64b564fb1..5e68c8b4cdca 100644
> --- a/drivers/mmc/core/quirks.h
> +++ b/drivers/mmc/core/quirks.h
> @@ -110,11 +110,12 @@ static const struct mmc_fixup __maybe_unused mmc_blk_fixups[] = {
>                   MMC_QUIRK_TRIM_BROKEN),
>
>         /*
> -        * Micron MTFC4GACAJCN-1M advertises TRIM but it does not seems to
> -        * support being used to offload WRITE_ZEROES.
> +        * Micron MTFC4GACAJCN-1M supports TRIM but does not appear to suppor
> +        * WRITE_ZEROES offloading. It also supports caching, but the cache can
> +        * only be flushed after a write has occurred.
>          */
>         MMC_FIXUP("Q2J54A", CID_MANFID_MICRON, 0x014e, add_quirk_mmc,
> -                 MMC_QUIRK_TRIM_BROKEN),
> +                 MMC_QUIRK_TRIM_BROKEN | MMC_QUIRK_BROKEN_CACHE_FLUSH),
>
>         /*
>          * Kingston EMMC04G-M627 advertises TRIM but it does not seems to
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index daa2f40d9ce6..7b12eebc5586 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -295,7 +295,9 @@ struct mmc_card {
>  #define MMC_QUIRK_BROKEN_HPI   (1<<13)         /* Disable broken HPI support */
>  #define MMC_QUIRK_BROKEN_SD_DISCARD    (1<<14) /* Disable broken SD discard support */
>  #define MMC_QUIRK_BROKEN_SD_CACHE      (1<<15) /* Disable broken SD cache support */
> +#define MMC_QUIRK_BROKEN_CACHE_FLUSH   (1<<16) /* Don't flush cache until the write has occurred */
>
> +       bool                    written_flag;   /* Indicates eMMC has been written since power on */
>         bool                    reenable_cmdq;  /* Re-enable Command Queue */
>
>         unsigned int            erase_size;     /* erase size in sectors */
> --
> 2.34.1
>

Kind regards
Uffe