[PATCH v5 2/2] mmc: block: Issue flush only if allowed

[Avri Altman <avri.altman@wdc.com>]

The cache may be flushed to the nonvolatile storage by writing to
FLUSH_CACHE byte (EXT_CSD byte [32]). When in command queueing mode, the
cache may be flushed by issuing a CMDQ_TASK_ DEV_MGMT (CMD48) with a
FLUSH_CACHE op-code.  Either way, verify that The cache function is
turned ON before doing so.

fixes: 1e8e55b67030 (mmc: block: Add CQE support)

Reported-by: Brendan Peter <bpeter@lytx.com>
Tested-by: Brendan Peter <bpeter@lytx.com>
Signed-off-by: Avri Altman <avri.altman@wdc.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
---
 drivers/mmc/core/block.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index 6cd5d03bcc64..e3062bbf110e 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -2198,6 +2198,11 @@ static int mmc_blk_wait_for_idle(struct mmc_queue *mq, struct mmc_host *host)
 	return mmc_blk_rw_wait(mq, NULL);
 }
 
+static bool mmc_blk_cache_disabled(struct mmc_host *host)
+{
+	return !mmc_cache_enabled(host);
+}
+
 enum mmc_issued mmc_blk_mq_issue_rq(struct mmc_queue *mq, struct request *req)
 {
 	struct mmc_blk_data *md = mq->blkdata;
@@ -2237,6 +2242,10 @@ enum mmc_issued mmc_blk_mq_issue_rq(struct mmc_queue *mq, struct request *req)
 	case MMC_ISSUE_ASYNC:
 		switch (req_op(req)) {
 		case REQ_OP_FLUSH:
+			if (mmc_blk_cache_disabled(host)) {
+				blk_mq_end_request(req, BLK_STS_OK);
+				return MMC_REQ_FINISHED;
+			}
 			ret = mmc_blk_cqe_issue_flush(mq, req);
 			break;
 		case REQ_OP_READ:
-- 
2.25.1