drm/edid: skip CTA extension scan in drm_edid_to_eld() just for CTA rev

The DisplayID CTA data block version does not necessarily match the CTA
revision. Simplify by postponing drm_edid_to_eld() slightly, and reusing
the CTA revision extracted by drm_parse_cea_ext().

By not bailing out early in drm_edid_to_eld() we may end up filling
meaningless data to the ELD. However, the main decision for audio is not
the ELD, but rather drm_detect_monitor_audio() called by drivers.

(Arguably a future cleanup could do that in drm_add_edid_modes() and
cache the result in the connector.)

Cc: Ville Syrjälä <ville.syrjala@linux.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/163ebbfd765066acbfc267256fb3b67fc711a78d.1651569697.git.jani.nikula@intel.com

drivers/gpu/drm/drm_edid.c

@@ -4863,10 +4863,10 @@ static void clear_eld(struct drm_connector *connector)
 static void drm_edid_to_eld(struct drm_connector *connector,
 			    const struct edid *edid)
 {
+	const struct drm_display_info *info = &connector->display_info;
 	const struct cea_db *db;
 	struct cea_db_iter iter;
 	uint8_t *eld = connector->eld;
-	const u8 *cea;
 	int total_sad_count = 0;
 	int mnl;
 
@@ -4875,16 +4875,10 @@ static void drm_edid_to_eld(struct drm_connector *connector,
 	if (!edid)
 		return;
 
-	cea = drm_find_cea_extension(edid);
-	if (!cea) {
-		DRM_DEBUG_KMS("ELD: no CEA Extension found\n");
-		return;
-	}
-
 	mnl = get_monitor_name(edid, &eld[DRM_ELD_MONITOR_NAME_STRING]);
 	DRM_DEBUG_KMS("ELD monitor %s\n", &eld[DRM_ELD_MONITOR_NAME_STRING]);
 
-	eld[DRM_ELD_CEA_EDID_VER_MNL] = cea[1] << DRM_ELD_CEA_EDID_VER_SHIFT;
+	eld[DRM_ELD_CEA_EDID_VER_MNL] = info->cea_rev << DRM_ELD_CEA_EDID_VER_SHIFT;
 	eld[DRM_ELD_CEA_EDID_VER_MNL] |= mnl;
 
 	eld[DRM_ELD_VER] = DRM_ELD_VER_CEA861D;
@@ -5821,8 +5815,6 @@ static int drm_edid_connector_update(struct drm_connector *connector,
 		return 0;
 	}
 
-	drm_edid_to_eld(connector, edid);
-
 	/*
 	 * CEA-861-F adds ycbcr capability map block, for HDMI 2.0 sinks.
 	 * To avoid multiple parsing of same block, lets parse that map
@@ -5830,6 +5822,9 @@ static int drm_edid_connector_update(struct drm_connector *connector,
 	 */
 	quirks = drm_add_display_info(connector, edid);
 
+	/* Depends on info->cea_rev set by drm_add_display_info() above */
+	drm_edid_to_eld(connector, edid);
+
 	/*
 	 * EDID spec says modes should be preferred in this order:
 	 * - preferred detailed mode