diff --git a/mm/cma.h b/mm/cma.h
index 4986128..33c0b51 100644
--- a/mm/cma.h
+++ b/mm/cma.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: GPL-2.0 */
 #ifndef __MM_CMA_H__
 #define __MM_CMA_H__