mmc: MMC-4.5 Data Tag Support

MMC-4.5 data tag feature will be used to store the file system meta-data
in the tagged region of eMMC. This will improve the write and subsequent
read transfer time for the meta data.

Signed-off-by: Saugata Das <saugata.das@linaro.org>
Tested-by: Venkatraman S <svenkatr@ti.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/card/block.c

@@ -1080,6 +1080,7 @@ static void mmc_blk_rw_rq_prep(struct mmc_queue_req *mqrq,
 	struct mmc_blk_request *brq = &mqrq->brq;
 	struct request *req = mqrq->req;
 	struct mmc_blk_data *md = mq->data;
+	bool do_data_tag;
 
 	/*
 	 * Reliable writes are used to implement Forced Unit Access and
@@ -1155,6 +1156,16 @@ static void mmc_blk_rw_rq_prep(struct mmc_queue_req *mqrq,
 	if (do_rel_wr)
 		mmc_apply_rel_rw(brq, card, req);
 
+	/*
+	 * Data tag is used only during writing meta data to speed
+	 * up write and any subsequent read of this meta data
+	 */
+	do_data_tag = (card->ext_csd.data_tag_unit_size) &&
+		(req->cmd_flags & REQ_META) &&
+		(rq_data_dir(req) == WRITE) &&
+		((brq->data.blocks * brq->data.blksz) >=
+		 card->ext_csd.data_tag_unit_size);
+
 	/*
 	 * Pre-defined multi-block transfers are preferable to
 	 * open ended-ones (and necessary for reliable writes).
@@ -1173,13 +1184,13 @@ static void mmc_blk_rw_rq_prep(struct mmc_queue_req *mqrq,
 	 * We'll avoid using CMD23-bounded multiblock writes for
 	 * these, while retaining features like reliable writes.
 	 */
-
-	if ((md->flags & MMC_BLK_CMD23) &&
-	    mmc_op_multi(brq->cmd.opcode) &&
-	    (do_rel_wr || !(card->quirks & MMC_QUIRK_BLK_NO_CMD23))) {
+	if ((md->flags & MMC_BLK_CMD23) && mmc_op_multi(brq->cmd.opcode) &&
+	    (do_rel_wr || !(card->quirks & MMC_QUIRK_BLK_NO_CMD23) ||
+	     do_data_tag)) {
 		brq->sbc.opcode = MMC_SET_BLOCK_COUNT;
 		brq->sbc.arg = brq->data.blocks |
-			(do_rel_wr ? (1 << 31) : 0);
+			(do_rel_wr ? (1 << 31) : 0) |
+			(do_data_tag ? (1 << 29) : 0);
 		brq->sbc.flags = MMC_RSP_R1 | MMC_CMD_AC;
 		brq->mrq.sbc = &brq->sbc;
 	}

drivers/mmc/core/mmc.c

@@ -519,6 +519,20 @@ static int mmc_read_ext_csd(struct mmc_card *card, u8 *ext_csd)
 			ext_csd[EXT_CSD_CACHE_SIZE + 1] << 8 |
 			ext_csd[EXT_CSD_CACHE_SIZE + 2] << 16 |
 			ext_csd[EXT_CSD_CACHE_SIZE + 3] << 24;
+
+		if (ext_csd[EXT_CSD_DATA_SECTOR_SIZE] == 1)
+			card->ext_csd.data_sector_size = 4096;
+		else
+			card->ext_csd.data_sector_size = 512;
+
+		if ((ext_csd[EXT_CSD_DATA_TAG_SUPPORT] & 1) &&
+		    (ext_csd[EXT_CSD_TAG_UNIT_SIZE] <= 8)) {
+			card->ext_csd.data_tag_unit_size =
+			((unsigned int) 1 << ext_csd[EXT_CSD_TAG_UNIT_SIZE]) *
+			(card->ext_csd.data_sector_size);
+		} else {
+			card->ext_csd.data_tag_unit_size = 0;
+		}
 	}
 
 out:

include/linux/mmc/card.h

@@ -71,6 +71,8 @@ struct mmc_ext_csd {
 	bool			hpi_en;			/* HPI enablebit */
 	bool			hpi;			/* HPI support bit */
 	unsigned int		hpi_cmd;		/* cmd used as HPI */
+	unsigned int            data_sector_size;       /* 512 bytes or 4KB */
+	unsigned int            data_tag_unit_size;     /* DATA TAG UNIT size */
 	unsigned int		boot_ro_lock;		/* ro lock support */
 	bool			boot_ro_lockable;
 	u8			raw_partition_support;	/* 160 */

include/linux/mmc/mmc.h

@@ -274,6 +274,7 @@ struct _mmc_csd {
 #define EXT_CSD_FLUSH_CACHE		32      /* W */
 #define EXT_CSD_CACHE_CTRL		33      /* R/W */
 #define EXT_CSD_POWER_OFF_NOTIFICATION	34	/* R/W */
+#define EXT_CSD_DATA_SECTOR_SIZE	61	/* R */
 #define EXT_CSD_GP_SIZE_MULT		143	/* R/W */
 #define EXT_CSD_PARTITION_ATTRIBUTE	156	/* R/W */
 #define EXT_CSD_PARTITION_SUPPORT	160	/* RO */
@@ -315,6 +316,8 @@ struct _mmc_csd {
 #define EXT_CSD_POWER_OFF_LONG_TIME	247	/* RO */
 #define EXT_CSD_GENERIC_CMD6_TIME	248	/* RO */
 #define EXT_CSD_CACHE_SIZE		249	/* RO, 4 bytes */
+#define EXT_CSD_TAG_UNIT_SIZE		498	/* RO */
+#define EXT_CSD_DATA_TAG_SUPPORT	499	/* RO */
 #define EXT_CSD_HPI_FEATURES		503	/* RO */
 
 /*