diff --git a/common/spl/spl.c b/common/spl/spl.c
index 5a026b8..4313710 100644
--- a/common/spl/spl.c
+++ b/common/spl/spl.c
@@ -378,6 +378,10 @@
 
 void spl_set_bd(void)
 {
+	/*
+	 * NOTE: On some platforms (e.g. x86) bdata may be in flash and not
+	 * writeable.
+	 */
 	if (!gd->bd)
 		gd->bd = &bdata;
 }