[PATCH v3 1/2] mmc: block: Issue flush only if allowed

[Avri Altman]

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 <bpe...@lytx.com>
Tested-by: Brendan Peter <bpe...@lytx.com>
Signed-off-by: Avri Altman <avri.alt...@wdc.com>
---
 drivers/mmc/core/block.c   | 7 +++++++
 drivers/mmc/core/mmc.c     | 2 +-
 drivers/mmc/core/mmc_ops.h | 5 +++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index 8bfd4d95b386..5b6501fc9fb7 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.c b/drivers/mmc/core/mmc.c
index 9ad4aa537867..e3da62ffcb5e 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -2037,7 +2037,7 @@ static int _mmc_flush_cache(struct mmc_card *card)
 {
        int err = 0;
 
-       if (card->ext_csd.cache_size > 0 && card->ext_csd.cache_ctrl & 1) {
+       if (mmc_flush_allowed(card)) {
                err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
                                 EXT_CSD_FLUSH_CACHE, 1,
                                 CACHE_FLUSH_TIMEOUT_MS);
diff --git a/drivers/mmc/core/mmc_ops.h b/drivers/mmc/core/mmc_ops.h
index 5782fdf4e8e9..2682bf66708a 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