diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
index 069f9bf2489e..ce17eeefc2da 100644
--- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
+++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
@@ -943,8 +943,21 @@ drm_hdmi_connector_mode_valid(struct drm_connector *connector,
 			      const struct drm_display_mode *mode)
 {
 	unsigned long long clock;
+	enum drm_output_color_format fmt;
 
-	clock = drm_hdmi_compute_mode_clock(mode, 8, DRM_OUTPUT_COLOR_FORMAT_RGB444);
+	if (drm_mode_is_420_only(&connector->display_info, mode)) {
+		if (connector->ycbcr_420_allowed)
+			fmt = DRM_OUTPUT_COLOR_FORMAT_YCBCR420;
+		else
+			return MODE_NO_420;
+	} else if (drm_mode_is_420_also(&connector->display_info, mode) &&
+		   connector->ycbcr_420_allowed) {
+		fmt = DRM_OUTPUT_COLOR_FORMAT_YCBCR420;
+	} else {
+		fmt = DRM_OUTPUT_COLOR_FORMAT_RGB444;
+	}
+
+	clock = drm_hdmi_compute_mode_clock(mode, 8, fmt);
 	if (!clock)
 		return MODE_ERROR;