diff --git a/drivers/mci/mci-core.c b/drivers/mci/mci-core.c
index 29c0d54..4e6b83b 100644
--- a/drivers/mci/mci-core.c
+++ b/drivers/mci/mci-core.c
@@ -1819,23 +1819,29 @@
 
 	/* "bus-width" is translated to MMC_CAP_*_BIT_DATA flags */
 	if (of_property_read_u32(np, "bus-width", &bus_width) < 0) {
+		/* If bus-width is missing we get the driver's default, which
+		 * is, unfortunately, not consistent from driver to driver.
+		 * Better to specify it in the device tree.  */
 		dev_dbg(host->hw_dev,
-			"\"bus-width\" property is missing, assuming 1 bit.\n");
-		bus_width = 1;
-	}
-
-	switch (bus_width) {
-	case 8:
-		host->host_caps |= MMC_CAP_8_BIT_DATA;
-		/* Hosts capable of 8-bit transfers can also do 4 bits */
-	case 4:
-		host->host_caps |= MMC_CAP_4_BIT_DATA;
-		break;
-	case 1:
-		break;
-	default:
-		dev_err(host->hw_dev,
-			"Invalid \"bus-width\" value %u!\n", bus_width);
+			"\"bus-width\" property missing, default is %d\n",
+			(host->host_caps & MMC_CAP_8_BIT_DATA) ? 8 :
+			(host->host_caps & MMC_CAP_4_BIT_DATA) ? 4 : 1);
+	} else {
+		/* Set data width caps to exactly those specified in the DT.
+		 * bus-width isn't a list, so widths smaller than the specified
+		 * value are implictly supported as well.  */
+		host->host_caps &= ~MMC_CAP_BIT_DATA_MASK;
+		switch (bus_width) {
+		case 8:
+			host->host_caps |= MMC_CAP_8_BIT_DATA;
+		case 4: /* note fall through from above */
+			host->host_caps |= MMC_CAP_4_BIT_DATA;
+		case 1:
+			break;
+		default:
+			dev_err(host->hw_dev,
+				"Invalid \"bus-width\" value %u!\n", bus_width);
+		}
 	}
 
 	/* f_max is obtained from the optional "max-frequency" property */
diff --git a/include/mci.h b/include/mci.h
index 41a757e..174d150 100644
--- a/include/mci.h
+++ b/include/mci.h
@@ -56,6 +56,8 @@
 #define MMC_CAP_SD_HIGHSPEED		(1 << 3)
 #define MMC_CAP_MMC_HIGHSPEED		(1 << 4)
 #define MMC_CAP_MMC_HIGHSPEED_52MHZ	(1 << 5)
+/* Mask of all caps for bus width */
+#define MMC_CAP_BIT_DATA_MASK		(MMC_CAP_4_BIT_DATA | MMC_CAP_8_BIT_DATA)
 
 #define SD_DATA_4BIT		0x00040000