drm/probe-helper: Call drm_mode_validate_ycbcr420() before connector->mode_valid()

Make life easier for drivers by filtering out unwanted YCbCr 4:2:0
only modes prior to calling the connector->mode_valid() hook.
Currently drivers will still see YCbCr 4:2:0 only modes in said
hook, which will likely come as a suprise when the driver has
declared no support for such modes (via setting
connector->ycbcr_420_allowed to false).

Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/10992Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240516173324.18149-1-ville.syrjala@linux.intel.comReviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_probe_helper.c

@@ -474,6 +474,10 @@ static int __drm_helper_update_and_validate(struct drm_connector *connector,
 		if (mode->status != MODE_OK)
 			continue;
 
+		mode->status = drm_mode_validate_ycbcr420(mode, connector);
+		if (mode->status != MODE_OK)
+			continue;
+
 		ret = drm_mode_validate_pipeline(mode, connector, ctx,
 						 &mode->status);
 		if (ret) {
@@ -486,10 +490,6 @@ static int __drm_helper_update_and_validate(struct drm_connector *connector,
 			else
 				return -EDEADLK;
 		}
-
-		if (mode->status != MODE_OK)
-			continue;
-		mode->status = drm_mode_validate_ycbcr420(mode, connector);
 	}
 
 	return 0;