[PATCH v2 1/2] 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>
---
 drivers/mmc/core/block.c   | 7 +++++++
 drivers/mmc/core/mmc_ops.c | 4 +---
 drivers/mmc/core/mmc_ops.h | 5 +++++
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index fe5892d30778..6800feb70c92 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -1476,6 +1476,11 @@ static int mmc_blk_cqe_issue_flush(struct mmc_queue *mq, struct request *req)
 	struct mmc_queue_req *mqrq = req_to_mmc_queue_req(req);
 	struct mmc_request *mrq = mmc_blk_cqe_prep_dcmd(mqrq, req);
 
+	if (mmc_card_mmc(mq->card) && !mmc_flush_allowed(mq->card)) {
+		blk_mq_end_request(req, BLK_STS_OK);
+		return -EPERM;
+	}
+
 	mrq->cmd->opcode = MMC_SWITCH;
 	mrq->cmd->arg = (MMC_SWITCH_MODE_WRITE_BYTE << 24) |
 			(EXT_CSD_FLUSH_CACHE << 16) |
@@ -2226,6 +2231,8 @@ enum mmc_issued mmc_blk_mq_issue_rq(struct mmc_queue *mq, struct request *req)
 		switch (req_op(req)) {
 		case REQ_OP_FLUSH:
 			ret = mmc_blk_cqe_issue_flush(mq, req);
+			if (ret == -EPERM)
+				return MMC_REQ_FINISHED;
 			break;
 		case REQ_OP_READ:
 		case REQ_OP_WRITE:
diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
index f413474f0f80..9c2a665be034 100644
--- a/drivers/mmc/core/mmc_ops.c
+++ b/drivers/mmc/core/mmc_ops.c
@@ -967,9 +967,7 @@ int mmc_flush_cache(struct mmc_card *card)
 {
 	int err = 0;
 
-	if (mmc_card_mmc(card) &&
-			(card->ext_csd.cache_size > 0) &&
-			(card->ext_csd.cache_ctrl & 1)) {
+	if (mmc_card_mmc(card) && mmc_flush_allowed(card)) {
 		err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
 				 EXT_CSD_FLUSH_CACHE, 1,
 				 MMC_CACHE_FLUSH_TIMEOUT_MS);
diff --git a/drivers/mmc/core/mmc_ops.h b/drivers/mmc/core/mmc_ops.h
index 632009260e51..bf2b315addd7 100644
--- a/drivers/mmc/core/mmc_ops.h
+++ b/drivers/mmc/core/mmc_ops.h
@@ -19,6 +19,11 @@ enum mmc_busy_cmd {
 struct mmc_host;
 struct mmc_card;
 
+static inline bool mmc_flush_allowed(struct mmc_card *card)
+{
+	return card->ext_csd.cache_size > 0 && (card->ext_csd.cache_ctrl & 1);
+}
+
 int mmc_select_card(struct mmc_card *card);
 int mmc_deselect_cards(struct mmc_host *host);
 int mmc_set_dsr(struct mmc_host *host);
-- 
2.25.1