arm64: renesas: salvator-x: Sound DVC support

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/r8a7795-salvator-x.dts

@@ -8,6 +8,29 @@
  * kind, whether express or implied.
  */
 
+/*
+ * SSI-AK4613
+ *
+ * This command is required when Playback/Capture
+ *
+ *	amixer set "DVC Out" 100%
+ *	amixer set "DVC In" 100%
+ *
+ * You can use Mute
+ *
+ *	amixer set "DVC Out Mute" on
+ *	amixer set "DVC In Mute" on
+ *
+ * You can use Volume Ramp
+ *
+ *	amixer set "DVC Out Ramp Up Rate"   "0.125 dB/64 steps"
+ *	amixer set "DVC Out Ramp Down Rate" "0.125 dB/512 steps"
+ *	amixer set "DVC Out Ramp" on
+ *	aplay xxx.wav &
+ *	amixer set "DVC Out"  80%  // Volume Down
+ *	amixer set "DVC Out" 100%  // Volume Up
+ */
+
 /dts-v1/;
 #include "r8a7795.dtsi"
 
@@ -136,8 +159,8 @@ &rcar_sound {
 
 	rcar_sound,dai {
 		dai0 {
-			playback = <&ssi0 &src0>;
-			capture  = <&ssi1 &src1>;
+			playback = <&ssi0 &src0 &dvc0>;
+			capture  = <&ssi1 &src1 &dvc1>;
 		};
 	};
 };