linux-kernel - Re: [PATCH v1] mmc: Add quirk MMC_QUIRK_BROKEN_CACHE

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Message-ID: <CAPDyKFrt4r88RhCg1XigFtd8xSrLLbHeD31ZAEA0aUDkNzRxGQ@mail.gmail.com>
Date:   Thu, 14 Sep 2023 15:59:10 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Bean Huo <beanhuo@...pp.de>
Cc:     adrian.hunter@...el.com, beanhuo@...ron.com,
        jakub.kwapisz@...adex.com, rafael.beims@...adex.com,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v1] mmc: Add quirk MMC_QUIRK_BROKEN_CACHE_FLUSH for Micron
 eMMC Q2J54A

On Wed, 13 Sept 2023 at 20:57, Bean Huo <beanhuo@...pp.de> wrote:
>
> From: Bean Huo <beanhuo@...ron.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.

This needs some more explanation I think. What does "after a write" really mean?

According to the changes below, we are tracking only whether a write
has been done and then we set host->card->written_flag = true - keep
it like that forever.

What happens beyond a power cycle for example? Like in the recovery
path or in the system wide suspend/resume path? Does the flag need to
be reset in those cases too?

Kind regards
Uffe

>
> Signed-off-by: Bean Huo <beanhuo@...ron.com>
> Cc: stable@...r.kernel.org
> ---
>  drivers/mmc/core/core.c   | 6 ++++++
>  drivers/mmc/core/mmc.c    | 5 +++++
>  drivers/mmc/core/quirks.h | 7 ++++---
>  include/linux/mmc/card.h  | 2 ++
>  4 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 3d3e0ca52614..5f858eb5f62c 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -259,6 +259,12 @@ static void __mmc_start_request(struct mmc_host *host, struct mmc_request *mrq)
>                 host->cqe_ops->cqe_off(host);
>
>         host->ops->request(host, mrq);
> +
> +       if (host->card->quirks & MMC_QUIRK_BROKEN_CACHE_FLUSH && !host->card->written_flag) {
> +               if (mrq->cmd->opcode == MMC_WRITE_MULTIPLE_BLOCK ||
> +                   mrq->cmd->opcode == MMC_WRITE_BLOCK)
> +                       host->card->written_flag = true;
> +       }
>  }
>
>  static void mmc_mrq_pr_debug(struct mmc_host *host, struct mmc_request *mrq,
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 89cd48fcec79..a2edd065fa1b 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;
> +
>         return 0;
>
>  free_card:
> @@ -2081,6 +2083,9 @@ static int _mmc_flush_cache(struct mmc_host *host)
>  {
>         int err = 0;
>
> +       if (host->card->quirks & MMC_QUIRK_BROKEN_CACHE_FLUSH && !host->card->written_flag)
> +               return err;
> +
>         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
>