Index: head/sys/arm/allwinner/aw_mmc.c
===================================================================
--- head/sys/arm/allwinner/aw_mmc.c
+++ head/sys/arm/allwinner/aw_mmc.c
@@ -256,6 +256,8 @@
 		cts->proto_specific.mmc.host_f_min = sc->aw_host.f_min;
 		cts->proto_specific.mmc.host_f_max = sc->aw_host.f_max;
 		cts->proto_specific.mmc.host_caps = sc->aw_host.caps;
+		cts->proto_specific.mmc.host_max_data = (sc->aw_mmc_conf->dma_xferlen *
+		    AW_MMC_DMA_SEGS) / MMC_SECTOR_SIZE;
 		memcpy(&cts->proto_specific.mmc.ios, &sc->aw_host.ios, sizeof(struct mmc_ios));
 		ccb->ccb_h.status = CAM_REQ_CMP;
 		break;
Index: head/sys/cam/cam_ccb.h
===================================================================
--- head/sys/cam/cam_ccb.h
+++ head/sys/cam/cam_ccb.h
@@ -1051,6 +1051,7 @@
 #define MMC_CAP_8_BIT_DATA	(1 << 1) /* Can do 8-bit data transfers */
 #define MMC_CAP_HSPEED		(1 << 2) /* Can do High Speed transfers */
 	uint32_t host_caps;
+	uint32_t host_max_data;
 };
 
 /* Get/Set transfer rate/width/disconnection/tag queueing settings */
Index: head/sys/cam/mmc/mmc_da.c
===================================================================
--- head/sys/cam/mmc/mmc_da.c
+++ head/sys/cam/mmc/mmc_da.c
@@ -1195,6 +1195,27 @@
 	return (cts->host_caps);
 }
 
+static uint32_t
+sdda_get_max_data(struct cam_periph *periph, union ccb *ccb)
+{
+	struct ccb_trans_settings_mmc *cts;
+
+	cts = &ccb->cts.proto_specific.mmc;
+	memset(cts, 0, sizeof(struct ccb_trans_settings_mmc));
+
+	ccb->ccb_h.func_code = XPT_GET_TRAN_SETTINGS;
+	ccb->ccb_h.flags = CAM_DIR_NONE;
+	ccb->ccb_h.retry_count = 0;
+	ccb->ccb_h.timeout = 100;
+	ccb->ccb_h.cbfcnp = NULL;
+	xpt_action(ccb);
+
+	if (ccb->ccb_h.status != CAM_REQ_CMP)
+		panic("Cannot get host max data");
+	KASSERT(cts->host_max_data != 0, ("host_max_data == 0?!"));
+	return (cts->host_max_data);
+}
+
 static void
 sdda_start_init(void *context, union ccb *start_ccb)
 {
@@ -1420,7 +1441,6 @@
 	struct sdda_softc *sc = (struct sdda_softc *)periph->softc;
 	struct sdda_part *part;
 	struct ccb_pathinq cpi;
-	u_int maxio;
 
 	CAM_DEBUG(periph->path, CAM_DEBUG_PERIPH,
 	    ("Partition type '%s', size %ju %s\n",
@@ -1479,12 +1499,9 @@
 	part->disk->d_gone = sddadiskgonecb;
 	part->disk->d_name = part->name;
 	part->disk->d_drv1 = part;
-	maxio = cpi.maxio;		/* Honor max I/O size of SIM */
-	if (maxio == 0)
-		maxio = DFLTPHYS;	/* traditional default */
-	else if (maxio > MAXPHYS)
-		maxio = MAXPHYS;	/* for safety */
-	part->disk->d_maxsize = maxio;
+	part->disk->d_maxsize =
+	    MIN(MAXPHYS, sdda_get_max_data(periph,
+		    (union ccb *)&cpi) * mmc_get_sector_size(periph));
 	part->disk->d_unit = cnt;
 	part->disk->d_flags = 0;
 	strlcpy(part->disk->d_descr, sc->card_id_string,
Index: head/sys/dev/sdhci/sdhci.c
===================================================================
--- head/sys/dev/sdhci/sdhci.c
+++ head/sys/dev/sdhci/sdhci.c
@@ -2580,6 +2580,7 @@
 	case XPT_GET_TRAN_SETTINGS:
 	{
 		struct ccb_trans_settings *cts = &ccb->cts;
+		uint32_t max_data;
 
 		if (sdhci_debug > 1)
 			slot_printf(slot, "Got XPT_GET_TRAN_SETTINGS\n");
@@ -2593,6 +2594,19 @@
 		cts->proto_specific.mmc.host_f_min = slot->host.f_min;
 		cts->proto_specific.mmc.host_f_max = slot->host.f_max;
 		cts->proto_specific.mmc.host_caps = slot->host.caps;
+		/*
+		 * Re-tuning modes 1 and 2 restrict the maximum data length
+		 * per read/write command to 4 MiB.
+		 */
+		if (slot->opt & SDHCI_TUNING_ENABLED &&
+		    (slot->retune_mode == SDHCI_RETUNE_MODE_1 ||
+		    slot->retune_mode == SDHCI_RETUNE_MODE_2)) {
+			max_data = 4 * 1024 * 1024 / MMC_SECTOR_SIZE;
+		} else {
+			max_data = 65535;
+		}
+		cts->proto_specific.mmc.host_max_data = max_data;
+
 		memcpy(&cts->proto_specific.mmc.ios, &slot->host.ios, sizeof(struct mmc_ios));
 		ccb->ccb_h.status = CAM_REQ_CMP;
 		break;