Index: sbin/camcontrol/camcontrol.c
===================================================================
--- sbin/camcontrol/camcontrol.c
+++ sbin/camcontrol/camcontrol.c
@@ -7791,6 +7791,8 @@
 		mmc_d.len = mmc_data_len;
 		mmc_d.data = mmc_data;
 		mmc_d.flags = MMC_DATA_READ;
+		mmc_d.block_size = 0;
+		mmc_d.block_count = 0;
 	} else flags |= CAM_DIR_NONE;
 
 	cam_fill_mmcio(&ccb->mmcio,
Index: sys/cam/mmc/mmc_da.c
===================================================================
--- sys/cam/mmc/mmc_da.c
+++ sys/cam/mmc/mmc_da.c
@@ -889,6 +889,7 @@
 	struct mmc_data d;
 
 	KASSERT(buf_len == 512, ("Buffer for ext csd must be 512 bytes"));
+	memset(&d, 0, sizeof(d));
 	d.data = rawextcsd;
 	d.len = buf_len;
 	d.flags = MMC_DATA_READ;
@@ -1013,6 +1014,7 @@
 	int err;
 
 	memset(res, 0, 64);
+	memset(&mmc_d, 0, sizeof(mmc_d));
 	mmc_d.len = 64;
 	mmc_d.data = res;
 	mmc_d.flags = MMC_DATA_READ;
@@ -1807,6 +1809,7 @@
 		mmcio->cmd.data->data = bp->bio_data;
 		mmcio->cmd.data->len = 512 * count;
 		mmcio->cmd.data->flags = (bp->bio_cmd == BIO_READ ? MMC_DATA_READ : MMC_DATA_WRITE);
+		mmcio->cmd.data->block_count = mmcio->cmd.data->block_size = 0;
 		/* Direct h/w to issue CMD12 upon completion */
 		if (count > 1) {
 			mmcio->cmd.data->flags |= MMC_DATA_MULTI;
Index: sys/dev/mmc/mmcreg.h
===================================================================
--- sys/dev/mmc/mmcreg.h
+++ sys/dev/mmc/mmcreg.h
@@ -190,6 +190,8 @@
 
 struct mmc_data {
 	size_t len;		/* size of the data */
+	size_t block_size;      /* block size for CMD53 */
+	size_t block_count;     /* block count for CMD53 */
 	size_t xfer_len;
 	void *data;		/* data buffer */
 	uint32_t	flags;
@@ -546,7 +548,11 @@
 #define	SD_IO_RW_LEN(x)		(((x) & 0xFF) << 0)
 
 #define	SD_IOE_RW_LEN(x)	(((x) & 0x1FF) << 0)
+#define	SD_IOE_RW_ADR(x)	(((x) & 0x1FFFF) << 9)
+#define	SD_IOE_RW_INCR		(1u << 26)
 #define	SD_IOE_RW_BLK		(1u << 27)
+#define	SD_IOE_RW_FUNC(x)	(((x) & 0x7) << 28)
+#define	SD_IOE_RW_WR		(1u << 31)
 
 /* Card Common Control Registers (CCCR) */
 #define	SD_IO_CCCR_START		0x00000
@@ -561,11 +567,15 @@
 #define	 CCCR_BUS_WIDTH_4		(1 << 1)
 #define	 CCCR_BUS_WIDTH_1		(1 << 0)
 #define	SD_IO_CCCR_CARDCAP		0x08
-#define	SD_IO_CCCR_CISPTR		0x09	/* XXX 9-10, 10-11, or 9-12 */
-
+#define  CCCR_CC_SMB                    (1 << 1)
+#define	SD_IO_CCCR_CISPTR		0x09    /* 0x09 - 0x0B */
+#define SD_IO_CCCR_FN0_BLKSZ            0x10    /* 0x10 - 0x11 */
 /* Function Basic Registers (FBR) */
 #define	SD_IO_FBR_START			0x00100
 #define	SD_IO_FBR_SIZE			0x00700
+#define SD_IO_FBR_START_F(n)            (SD_IO_FBR_START + (n-1) * 0x00100)
+#define SD_IO_FBR_CIS_OFFSET            0x9
+#define SD_IO_FBR_IOBLKSZ               0x10
 
 /* Card Information Structure (CIS) */
 #define	SD_IO_CIS_START			0x01000