mmc: block: Issue a cache flush only when it's enabled

In command queueing mode, the cache isn't flushed via the mmc_flush_cache()
function, but instead by issuing a CMDQ_TASK_MGMT (CMD48) with a
FLUSH_CACHE opcode. In this path, we need to check if cache has been
enabled, before deciding to flush the cache, along the lines of what's
being done in mmc_flush_cache().

To fix this problem, let's add a new bus ops callback ->cache_enabled() and
implement it for the mmc bus type. In this way, the mmc block device driver
can call it to know whether cache flushing should be done.

Fixes: 1e8e55b670 (mmc: block: Add CQE support)
Cc: stable@vger.kernel.org
Reported-by: Brendan Peter <bpeter@lytx.com>
Signed-off-by: Avri Altman <avri.altman@wdc.com>
Tested-by: Brendan Peter <bpeter@lytx.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20210425060207.2591-2-avri.altman@wdc.com
Link: https://lore.kernel.org/r/20210425060207.2591-3-avri.altman@wdc.com
[Ulf: Squashed the two patches and made some minor updates]
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/block.c

@@ -2237,6 +2237,10 @@ 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_cache_enabled(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:

drivers/mmc/core/core.h

@@ -29,6 +29,7 @@ struct mmc_bus_ops {
 	int (*shutdown)(struct mmc_host *);
 	int (*hw_reset)(struct mmc_host *);
 	int (*sw_reset)(struct mmc_host *);
+	bool (*cache_enabled)(struct mmc_host *);
 };
 
 void mmc_attach_bus(struct mmc_host *host, const struct mmc_bus_ops *ops);
@@ -163,4 +164,12 @@ static inline void mmc_post_req(struct mmc_host *host, struct mmc_request *mrq,
 		host->ops->post_req(host, mrq, err);
 }
 
+static inline bool mmc_cache_enabled(struct mmc_host *host)
+{
+	if (host->bus_ops->cache_enabled)
+		return host->bus_ops->cache_enabled(host);
+
+	return false;
+}
+
 #endif

drivers/mmc/core/mmc.c

@@ -2029,6 +2029,12 @@ static void mmc_detect(struct mmc_host *host)
 	}
 }
 
+static bool _mmc_cache_enabled(struct mmc_host *host)
+{
+	return host->card->ext_csd.cache_size > 0 &&
+	       host->card->ext_csd.cache_ctrl & 1;
+}
+
 static int _mmc_suspend(struct mmc_host *host, bool is_suspend)
 {
 	int err = 0;
@@ -2208,6 +2214,7 @@ static const struct mmc_bus_ops mmc_ops = {
 	.alive = mmc_alive,
 	.shutdown = mmc_shutdown,
 	.hw_reset = _mmc_hw_reset,
+	.cache_enabled = _mmc_cache_enabled,
 };
 
 /*

drivers/mmc/core/mmc_ops.c

@@ -968,9 +968,7 @@ 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_cache_enabled(card->host)) {
 		err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
 				 EXT_CSD_FLUSH_CACHE, 1,
 				 MMC_CACHE_FLUSH_TIMEOUT_MS);