linux-kernel - Re: [PATCH v2] mmc: block: enable cache-flushing when mmc cache is on

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Date:   Mon, 4 Apr 2022 13:52:29 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Michael Wu <michael@...winnertech.com>
Cc:     axboe@...nel.dk, adrian.hunter@...el.com, avri.altman@....com,
        kch@...dia.com, beanhuo@...ron.com, swboyd@...omium.org,
        digetx@...il.com, bigeasy@...utronix.de, CLoehle@...erstone.com,
        cjb@...top.org, arnd@...db.de, andreiw@...orola.com,
        tgih.jun@...sung.com, jh80.chung@...sung.com,
        linus.walleij@...aro.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        allwinner-opensource-support@...winnertech.com
Subject: Re: [PATCH v2] mmc: block: enable cache-flushing when mmc cache is on

On Thu, 31 Mar 2022 at 09:32, Michael Wu <michael@...winnertech.com> wrote:
>
> The mmc core enables cache by default. But it only enables
> cache-flushing when host supports cmd23 and eMMC supports
> reliable-write.
> For hosts which do not support cmd23 or eMMCs which do not support
> reliable-write, the cache can not be flushed by `sync` command.
> This may leads to cache data lost.
> This patch enables cache-flushing as long as cache is enabled,
> no matter host supports cmd23 and/or eMMC supports reliable write
> or not.
> For SD cards, backwards compatibility is guaranteed. Newer components
> like SD5.0 which have cache are also supported in advance, which means
> this patch will also be applicable if SD5.0 cache is added to the mmc
> core in the future.

SD 5.0 cache support was added in the commit 130206a615a9 below. No
need to resend, I will take care of updating the commit message.

>
> Fixes: f4c5522b0a88 ("mmc: Reliable write support.")
> Fixes: 881d1c25f765 ("mmc: core: Add cache control for eMMC4.5 device")
> Fixes: 130206a615a9 ("mmc: core: Add support for cache ctrl for SD cards")
> Fixes: d0c97cfb81eb ("mmc: core: Use CMD23 for multiblock transfers when we can.")
> Fixes: e9d5c746246c ("mmc/block: switch to using blk_queue_write_cache()")

I will have a look at the above to see what makes sense to add - and
then I will add a stable tag too.

>
> Reviewed-by: Avri Altman <Avri.Altman@....com>
> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
>
> Signed-off-by: Michael Wu <michael@...winnertech.com>

Thanks, applied for fixes!

Kind regards
Uffe


> ---
>  drivers/mmc/core/block.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index 4e67c1403cc9..ec76ed82abb9 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -2350,6 +2350,8 @@ static struct mmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,
>         struct mmc_blk_data *md;
>         int devidx, ret;
>         char cap_str[10];
> +       bool cache_enabled = false;
> +       bool fua_enabled = false;
>
>         devidx = ida_simple_get(&mmc_blk_ida, 0, max_devices, GFP_KERNEL);
>         if (devidx < 0) {
> @@ -2429,13 +2431,17 @@ static struct mmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,
>                         md->flags |= MMC_BLK_CMD23;
>         }
>
> -       if (mmc_card_mmc(card) &&
> -           md->flags & MMC_BLK_CMD23 &&
> +       if (md->flags & MMC_BLK_CMD23 &&
>             ((card->ext_csd.rel_param & EXT_CSD_WR_REL_PARAM_EN) ||
>              card->ext_csd.rel_sectors)) {
>                 md->flags |= MMC_BLK_REL_WR;
> -               blk_queue_write_cache(md->queue.queue, true, true);
> +               fua_enabled = true;
> +               cache_enabled = true;
>         }
> +       if (mmc_cache_enabled(card->host))
> +               cache_enabled  = true;
> +
> +       blk_queue_write_cache(md->queue.queue, cache_enabled, fua_enabled);
>
>         string_get_size((u64)size, 512, STRING_UNITS_2,
>                         cap_str, sizeof(cap_str));
> --
> 2.29.0
>