diff --git a/sound/soc/sh/rcar/scu.c b/sound/soc/sh/rcar/scu.c
index 076aa71bc102..1adc85825f4e 100644
--- a/sound/soc/sh/rcar/scu.c
+++ b/sound/soc/sh/rcar/scu.c
@@ -40,6 +40,20 @@ struct rsnd_scu {
  *
  */
 
+/*
+ * scu.c is caring...
+ *
+ * Gen1
+ *
+ * [mem] -> [SRU] -> [SSI]
+ *        |--------|
+ *
+ * Gen2
+ *
+ * [mem] -> [SCU] -> [SSIU] -> [SSI]
+ *        |-----------------|
+ */
+
 /*
  *	How to use SRC bypass mode for debugging
  *