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

Adrian Hunter
2022-03-14T06:54:23Z

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?

> Signed-off-by: Michael Wu <michael@allwinnertech.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

>
> string_get_size((u64)size, 512, STRING_UNITS_2,