diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 82a4ceed3fcf..7c6bc5183b60 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1342,7 +1342,6 @@ MODULE_PARM_DESC(edid_fixup,
 
 static void drm_get_displayid(struct drm_connector *connector,
 			      struct edid *edid);
-static int validate_displayid(u8 *displayid, int length, int idx);
 
 static int drm_edid_block_checksum(const u8 *raw_edid)
 {
@@ -2927,17 +2926,49 @@ static u8 *drm_find_edid_extension(const struct edid *edid, int ext_id)
 	return edid_ext;
 }
 
+static bool drm_displayid_is_valid(u8 *displayid, unsigned int length)
+{
+	struct displayid_hdr *base;
+	u8 csum = 0;
+	int i;
+
+	base = (struct displayid_hdr *)displayid;
+
+	DRM_DEBUG_KMS("base revision 0x%x, length %d, %d %d\n",
+		      base->rev, base->bytes, base->prod_id, base->ext_count);
+
+	if (base->bytes + 5 > length)
+		return false;
+
+	for (i = 0; i <= base->bytes + 5; i++)
+		csum += displayid[i];
+
+	if (csum) {
+		DRM_NOTE("DisplayID checksum invalid, remainder is %d\n", csum);
+		return false;
+	}
+
+	return true;
+}
 
 static u8 *drm_find_displayid_extension(const struct edid *edid)
 {
-	return drm_find_edid_extension(edid, DISPLAYID_EXT);
+	u8 *ext = drm_find_edid_extension(edid, DISPLAYID_EXT);
+
+	if (!ext)
+		return NULL;
+
+	/*
+	 * Skip the EDID extension block tag number to return the DisplayID
+	 * data.
+	 */
+	return ext + 1;
 }
 
 static u8 *drm_find_cea_extension(const struct edid *edid)
 {
-	int ret;
-	int idx = 1;
-	int length = EDID_LENGTH;
+	int idx;
+	int length = EDID_LENGTH - 1;
 	struct displayid_block *block;
 	u8 *cea;
 	u8 *displayid;
@@ -2952,11 +2983,10 @@ static u8 *drm_find_cea_extension(const struct edid *edid)
 	if (!displayid)
 		return NULL;
 
-	ret = validate_displayid(displayid, length, idx);
-	if (ret)
+	if (!drm_displayid_is_valid(displayid, length))
 		return NULL;
 
-	idx += sizeof(struct displayid_hdr);
+	idx = sizeof(struct displayid_hdr);
 	for_each_displayid_db(displayid, block, idx, length) {
 		if (block->tag == DATA_BLOCK_CTA) {
 			cea = (u8 *)block;
@@ -4711,29 +4741,6 @@ u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edi
 	return quirks;
 }
 
-static int validate_displayid(u8 *displayid, int length, int idx)
-{
-	int i;
-	u8 csum = 0;
-	struct displayid_hdr *base;
-
-	base = (struct displayid_hdr *)&displayid[idx];
-
-	DRM_DEBUG_KMS("base revision 0x%x, length %d, %d %d\n",
-		      base->rev, base->bytes, base->prod_id, base->ext_count);
-
-	if (base->bytes + 5 > length - idx)
-		return -EINVAL;
-	for (i = idx; i <= base->bytes + 5; i++) {
-		csum += displayid[i];
-	}
-	if (csum) {
-		DRM_NOTE("DisplayID checksum invalid, remainder is %d\n", csum);
-		return -EINVAL;
-	}
-	return 0;
-}
-
 static struct drm_display_mode *drm_mode_displayid_detailed(struct drm_device *dev,
 							    struct displayid_detailed_timings_1 *timings)
 {
@@ -4809,9 +4816,8 @@ static int add_displayid_detailed_modes(struct drm_connector *connector,
 					struct edid *edid)
 {
 	u8 *displayid;
-	int ret;
-	int idx = 1;
-	int length = EDID_LENGTH;
+	int idx;
+	int length = EDID_LENGTH - 1;
 	struct displayid_block *block;
 	int num_modes = 0;
 
@@ -4819,11 +4825,10 @@ static int add_displayid_detailed_modes(struct drm_connector *connector,
 	if (!displayid)
 		return 0;
 
-	ret = validate_displayid(displayid, length, idx);
-	if (ret)
+	if (!drm_displayid_is_valid(displayid, length))
 		return 0;
 
-	idx += sizeof(struct displayid_hdr);
+	idx = sizeof(struct displayid_hdr);
 	for_each_displayid_db(displayid, block, idx, length) {
 		switch (block->tag) {
 		case DATA_BLOCK_TYPE_1_DETAILED_TIMING:
@@ -5424,23 +5429,17 @@ static int drm_parse_tiled_block(struct drm_connector *connector,
 	return 0;
 }
 
-static int drm_parse_display_id(struct drm_connector *connector,
-				u8 *displayid, int length,
-				bool is_edid_extension)
+static int drm_parse_displayid(struct drm_connector *connector,
+			       u8 *displayid, int length)
 {
-	/* if this is an EDID extension the first byte will be 0x70 */
-	int idx = 0;
 	struct displayid_block *block;
+	int idx;
 	int ret;
 
-	if (is_edid_extension)
-		idx = 1;
+	if (!drm_displayid_is_valid(displayid, length))
+		return -EINVAL;
 
-	ret = validate_displayid(displayid, length, idx);
-	if (ret)
-		return ret;
-
-	idx += sizeof(struct displayid_hdr);
+	idx = sizeof(struct displayid_hdr);
 	for_each_displayid_db(displayid, block, idx, length) {
 		DRM_DEBUG_KMS("block id 0x%x, rev %d, len %d\n",
 			      block->tag, block->rev, block->num_bytes);
@@ -5468,8 +5467,9 @@ static int drm_parse_display_id(struct drm_connector *connector,
 static void drm_get_displayid(struct drm_connector *connector,
 			      struct edid *edid)
 {
-	void *displayid = NULL;
+	void *displayid;
 	int ret;
+
 	connector->has_tile = false;
 	displayid = drm_find_displayid_extension(edid);
 	if (!displayid) {
@@ -5477,16 +5477,16 @@ static void drm_get_displayid(struct drm_connector *connector,
 		goto out_drop_ref;
 	}
 
-	ret = drm_parse_display_id(connector, displayid, EDID_LENGTH, true);
+	ret = drm_parse_displayid(connector, displayid, EDID_LENGTH - 1);
 	if (ret < 0)
 		goto out_drop_ref;
 	if (!connector->has_tile)
 		goto out_drop_ref;
 	return;
+
 out_drop_ref:
 	if (connector->tile_group) {
 		drm_mode_put_tile_group(connector->dev, connector->tile_group);
 		connector->tile_group = NULL;
 	}
-	return;
 }
