drm/i915: Tighten DRRS capability reporting

Only report DRRS capability for the connector if its fixed_modes
list contains at least two modes capable of seamless DRRS switch
between them.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221003113249.16213-6-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/display/intel_panel.c

@@ -147,10 +147,25 @@ int intel_panel_get_modes(struct intel_connector *connector)
 	return num_modes;
 }
 
+static bool has_drrs_modes(struct intel_connector *connector)
+{
+	const struct drm_display_mode *mode1;
+
+	list_for_each_entry(mode1, &connector->panel.fixed_modes, head) {
+		const struct drm_display_mode *mode2 = mode1;
+
+		list_for_each_entry_continue(mode2, &connector->panel.fixed_modes, head) {
+			if (is_alt_drrs_mode(mode1, mode2))
+				return true;
+		}
+	}
+
+	return false;
+}
+
 enum drrs_type intel_panel_drrs_type(struct intel_connector *connector)
 {
-	if (list_empty(&connector->panel.fixed_modes) ||
-	    list_is_singular(&connector->panel.fixed_modes))
+	if (!has_drrs_modes(connector))
 		return DRRS_TYPE_NONE;
 
 	return connector->panel.vbt.drrs_type;