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

Michael Wu
2022-03-14T09:21:12Z

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@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
>

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