mmc: core: new discard feature support at eMMC v4.5

MMC v4.5 supports the DISCARD feature (CMD38).  It's different from
trim and there's no check bit.  Currently it's only supported at v4.5.

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index e85816e1634a..370472797fff 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -756,7 +756,9 @@ static int mmc_blk_issue_discard_rq(struct mmc_queue *mq, struct request *req)
         from = blk_rq_pos(req);
         nr = blk_rq_sectors(req);
 
-        if (mmc_can_trim(card))
+        if (mmc_can_discard(card))
+                arg = MMC_DISCARD_ARG;
+        else if (mmc_can_trim(card))
                 arg = MMC_TRIM_ARG;
         else
                 arg = MMC_ERASE_ARG;