diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index d5e77382697f1f182d1a73f5ec128474686509dd..5b47888c49a7811b6c5fbd562ac1c4f6c4778c79 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3580,11 +3580,12 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 		case 2:
 			y_min_scanlines = 8;
 			break;
-		default:
-			WARN(1, "Unsupported pixel depth for rotation");
 		case 4:
 			y_min_scanlines = 4;
 			break;
+		default:
+			MISSING_CASE(cpp);
+			return -EINVAL;
 		}
 	} else {
 		y_min_scanlines = 4;