diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
index 7062bcd78740b..4ddf77045759e 100644
--- a/drivers/gpu/drm/ast/ast_mode.c
+++ b/drivers/gpu/drm/ast/ast_mode.c
@@ -561,8 +561,9 @@ static int ast_primary_plane_helper_atomic_check(struct drm_plane *plane,
 	return 0;
 }
 
-void ast_primary_plane_helper_atomic_update(struct drm_plane *plane,
-					    struct drm_plane_state *old_state)
+static void
+ast_primary_plane_helper_atomic_update(struct drm_plane *plane,
+				       struct drm_plane_state *old_state)
 {
 	struct ast_private *ast = plane->dev->dev_private;
 	struct drm_plane_state *state = plane->state;