[PATCH v1] mmc: Add quirk MMC_QUIRK_BROKEN_CACHE_FLUSH for Micron eMMC Q2J54A

[Bean Huo <beanhuo@iokpp.de>]

From: Bean Huo <beanhuo@micron.com>

Micron MTFC4GACAJCN eMMC supports cache but requires that flush cache
operation be allowed only after a write has occurred. Otherwise, the
cache flush command or subsequent commands will time out.

Signed-off-by: Bean Huo <beanhuo@micron.com>
Cc: stable@vger.kernel.org
---
 drivers/mmc/core/core.c   | 6 ++++++
 drivers/mmc/core/mmc.c    | 5 +++++
 drivers/mmc/core/quirks.h | 7 ++++---
 include/linux/mmc/card.h  | 2 ++
 4 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 3d3e0ca52614..5f858eb5f62c 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -259,6 +259,12 @@ static void __mmc_start_request(struct mmc_host *host, struct mmc_request *mrq)
 		host->cqe_ops->cqe_off(host);
 
 	host->ops->request(host, mrq);
+
+	if (host->card->quirks & MMC_QUIRK_BROKEN_CACHE_FLUSH && !host->card->written_flag) {
+		if (mrq->cmd->opcode == MMC_WRITE_MULTIPLE_BLOCK ||
+		    mrq->cmd->opcode == MMC_WRITE_BLOCK)
+			host->card->written_flag = true;
+	}
 }
 
 static void mmc_mrq_pr_debug(struct mmc_host *host, struct mmc_request *mrq,
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 89cd48fcec79..a2edd065fa1b 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -1929,6 +1929,8 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
 	if (!oldcard)
 		host->card = card;
 
+	card->written_flag = false;
+
 	return 0;
 
 free_card:
@@ -2081,6 +2083,9 @@ static int _mmc_flush_cache(struct mmc_host *host)
 {
 	int err = 0;
 
+	if (host->card->quirks & MMC_QUIRK_BROKEN_CACHE_FLUSH && !host->card->written_flag)
+		return err;
+
 	if (_mmc_cache_enabled(host)) {
 		err = mmc_switch(host->card, EXT_CSD_CMD_SET_NORMAL,
 				 EXT_CSD_FLUSH_CACHE, 1,
diff --git a/drivers/mmc/core/quirks.h b/drivers/mmc/core/quirks.h
index 32b64b564fb1..5e68c8b4cdca 100644
--- a/drivers/mmc/core/quirks.h
+++ b/drivers/mmc/core/quirks.h
@@ -110,11 +110,12 @@ static const struct mmc_fixup __maybe_unused mmc_blk_fixups[] = {
 		  MMC_QUIRK_TRIM_BROKEN),
 
 	/*
-	 * Micron MTFC4GACAJCN-1M advertises TRIM but it does not seems to
-	 * support being used to offload WRITE_ZEROES.
+	 * Micron MTFC4GACAJCN-1M supports TRIM but does not appear to suppor
+	 * WRITE_ZEROES offloading. It also supports caching, but the cache can
+	 * only be flushed after a write has occurred.
 	 */
 	MMC_FIXUP("Q2J54A", CID_MANFID_MICRON, 0x014e, add_quirk_mmc,
-		  MMC_QUIRK_TRIM_BROKEN),
+		  MMC_QUIRK_TRIM_BROKEN | MMC_QUIRK_BROKEN_CACHE_FLUSH),
 
 	/*
 	 * Kingston EMMC04G-M627 advertises TRIM but it does not seems to
diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index daa2f40d9ce6..7b12eebc5586 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -295,7 +295,9 @@ struct mmc_card {
 #define MMC_QUIRK_BROKEN_HPI	(1<<13)		/* Disable broken HPI support */
 #define MMC_QUIRK_BROKEN_SD_DISCARD	(1<<14)	/* Disable broken SD discard support */
 #define MMC_QUIRK_BROKEN_SD_CACHE	(1<<15)	/* Disable broken SD cache support */
+#define MMC_QUIRK_BROKEN_CACHE_FLUSH	(1<<16)	/* Don't flush cache until the write has occurred */
 
+	bool			written_flag;	/* Indicates eMMC has been written since power on */
 	bool			reenable_cmdq;	/* Re-enable Command Queue */
 
 	unsigned int		erase_size;	/* erase size in sectors */
-- 
2.34.1