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

[Michael Wu]

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@xxxxxxxxxxxxxxxxx>
> > ---
> >   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'?

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

--
Best Regards,
Michael Wu