drm/edid: check for HF-SCDB block

Find HF-SCDB information in CEA extensions block. And retrieve
Max_TMDS_Character_Rate that support by sink device.

v2: HF-SCDB and HF-VSDBS carry the same SCDS data. Reuse
    drm_parse_hdmi_forum_vsdb() to parse this packet.

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Cc: intel-gfx <intel-gfx@lists.freedesktop.org>
Signed-off-by: Lee Shawn C <shawn.c.lee@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/2bf7110cdb56d5dda311480787faf472c9802de4.1651569697.git.jani.nikula@intel.com

drivers/gpu/drm/drm_edid.c

@@ -3471,6 +3471,7 @@ add_detailed_modes(struct drm_connector *connector, const struct edid *edid,
 #define EXT_VIDEO_CAPABILITY_BLOCK 0x00
 #define EXT_VIDEO_DATA_BLOCK_420	0x0E
 #define EXT_VIDEO_CAP_BLOCK_Y420CMDB 0x0F
+#define EXT_VIDEO_HF_SCDB_DATA_BLOCK	0x79
 #define EDID_BASIC_AUDIO	(1 << 6)
 #define EDID_CEA_YCRCB444	(1 << 5)
 #define EDID_CEA_YCRCB422	(1 << 4)
@@ -4402,6 +4403,20 @@ static bool cea_db_is_vcdb(const u8 *db)
 	return true;
 }
 
+static bool cea_db_is_hdmi_forum_scdb(const u8 *db)
+{
+	if (cea_db_tag(db) != USE_EXTENDED_TAG)
+		return false;
+
+	if (cea_db_payload_len(db) < 7)
+		return false;
+
+	if (cea_db_extended_tag(db) != EXT_VIDEO_HF_SCDB_DATA_BLOCK)
+		return false;
+
+	return true;
+}
+
 static bool cea_db_is_y420cmdb(const u8 *db)
 {
 	if (cea_db_tag(db) != USE_EXTENDED_TAG)
@@ -5363,7 +5378,8 @@ static void drm_parse_cea_ext(struct drm_connector *connector,
 
 		if (cea_db_is_hdmi_vsdb(db))
 			drm_parse_hdmi_vsdb_video(connector, db);
-		if (cea_db_is_hdmi_forum_vsdb(db))
+		if (cea_db_is_hdmi_forum_vsdb(db) ||
+		    cea_db_is_hdmi_forum_scdb(db))
 			drm_parse_hdmi_forum_vsdb(connector, db);
 		if (cea_db_is_microsoft_vsdb(db))
 			drm_parse_microsoft_vsdb(connector, db);