diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
index f8cd094efa3c0bd6f75b52a0410b0910d8026a76..271a00b81264c9959a394399bf2507abb354da8b 100644
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -175,13 +175,13 @@ static int
 drm_dp_mst_rad_to_str(const u8 rad[8], u8 lct, char *out, size_t len)
 {
 	int i;
-	u8 unpacked_rad[16];
+	u8 unpacked_rad[16] = {};
 
-	for (i = 0; i < lct; i++) {
+	for (i = 1; i < lct; i++) {
 		if (i % 2)
-			unpacked_rad[i] = rad[i / 2] >> 4;
+			unpacked_rad[i] = rad[(i - 1) / 2] >> 4;
 		else
-			unpacked_rad[i] = rad[i / 2] & BIT_MASK(4);
+			unpacked_rad[i] = rad[(i - 1) / 2] & 0xF;
 	}
 
 	/* TODO: Eventually add something to printk so we can format the rad
diff --git a/include/drm/display/drm_dp_mst_helper.h b/include/drm/display/drm_dp_mst_helper.h
index a80ba457a858f36ac2110a6fdd91d8a1570b58e1..6398a6b50bd1b7be256c8fc07e18fbfabc6bdb00 100644
--- a/include/drm/display/drm_dp_mst_helper.h
+++ b/include/drm/display/drm_dp_mst_helper.h
@@ -222,6 +222,13 @@ struct drm_dp_mst_branch {
 	 */
 	struct list_head destroy_next;
 
+	/**
+	 * @rad: Relative Address of the MST branch.
+	 * For &drm_dp_mst_topology_mgr.mst_primary, it's rad[8] are all 0,
+	 * unset and unused. For MST branches connected after mst_primary,
+	 * in each element of rad[] the nibbles are ordered by the most
+	 * signifcant 4 bits first and the least significant 4 bits second.
+	 */
 	u8 rad[8];
 	u8 lct;
 	int num_ports;