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

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Message-ID: <DM6PR04MB6575C3B87DFA920EDCD994CCFC0F9@DM6PR04MB6575.namprd04.prod.outlook.com>
Date:   Mon, 14 Mar 2022 09:37:11 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Michael Wu <michael@...winnertech.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "porzio@...il.com" <porzio@...il.com>
CC:     "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        allwinner-opensource-support 
        <allwinner-opensource-support@...winnertech.com>
Subject: RE: [PATCH] mmc: block: enable cache-flushing when mmc cache is on

> On 14/03/2022 14:54, Adrian Hunter wrote:
> > On 12/03/2022 06:43, Michael Wu wrote:
> >> The mmc core enable cache on 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.
> >>
> >
> > Fixes tag?
> >
> 
> Hi Adrian,
> My patch intend to fix the cache problem brought by the following two
> patches:
> 
> Fixes: d0c97cfb81ebc ("mmc: core: Use CMD23 for multiblock transfers when
> we can.")
> Fixes: e9d5c746246c8 ("mmc/block: switch to using blk_queue_write_cache()")
> 
> I'm not sure if this is what you referred to ("Fixes tag"). Please correct me if I
> misunderstood.
> 
> >> Signed-off-by: Michael Wu <michael@...winnertech.com>
> >> ---
> >>   drivers/mmc/core/block.c | 20 ++++++++++++++------
> >>   1 file changed, 14 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> >> index 689eb9afeeed..1e508c079c1e 100644
> >> --- a/drivers/mmc/core/block.c
> >> +++ b/drivers/mmc/core/block.c
> >> @@ -2279,6 +2279,8 @@ 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 enable_cache = false;
> >> +    bool enable_fua = false;
> >>
> >>      devidx = ida_simple_get(&mmc_blk_ida, 0, max_devices, GFP_KERNEL);
> >>      if (devidx < 0) {
> >> @@ -2375,12 +2377,18 @@ 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 &&
> >> -        ((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);
> >> +    if (mmc_card_mmc(card)) {
> >> +            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;
> >> +                    enable_fua = true;
> >> +            }
> >> +
> >> +            if (mmc_cache_enabled(card->host))
> >> +                    enable_cache = true;
> >> +
> >> +            blk_queue_write_cache(md->queue.queue, enable_cache,
> >> + enable_fua);
> >>      }
> >
> > Seems like we should inform block layer about SD card cache also
> >
> 
> I saw another mail by Avri Altman, which says few days will be needed to ask
> internally. Shall I wait or make another change here on 'inform block layer
> about SD card cache'?
Please don't wait.

Thanks,
Avri

> 
> >>
> >>      string_get_size((u64)size, 512, STRING_UNITS_2,
> 
> --
> Best Regards,
> Michael Wu