drm: dw-hdmi-i2s: add .get_dai_id callback for ALSA SoC

ALSA SoC needs to know connected DAI ID for probing.
It is not a big problem if device/driver was only for sound,
but getting DAI ID will be difficult if device includes both
Video/Sound, like HDMI.
To solve this issue, this patch adds new .get_dai_id callback
on hdmi_codec_ops.
dw-hdmi-i2s will assume that HDMI sound will be connected
to reg = <2>. Then, ALSA SoC side will recognized it as DAI 0

	ports {
		#address-cells = <1>;
		#size-cells = <0>;
		port@0 {
			reg = <0>;
			/* HDMI Video IN */
		};
		port@1 {
			reg = <1>;
			/* HDMI OUT */
		};
		port@2 {
			reg = <2>;
			/* HDMI Sound IN */
		};
	};
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/display/bridge/renesas,dw-hdmi.txt

@@ -25,7 +25,8 @@ Required properties:
 - clock-names: Shall contain "iahb" and "isfr" as defined in dw_hdmi.txt.
 - ports: See dw_hdmi.txt. The DWC HDMI shall have one port numbered 0
   corresponding to the video input of the controller and one port numbered 1
-  corresponding to its HDMI output. Each port shall have a single endpoint.
+  corresponding to its HDMI output, and one port numbered 2 corresponding to
+  sound input of the controller. Each port shall have a single endpoint.
 
 Optional properties:
 
@@ -59,6 +60,12 @@ Example:
 					remote-endpoint = <&hdmi0_con>;
 				};
 			};
+			port@2 {
+				reg = <2>;
+				rcar_dw_hdmi0_sound_in: endpoint {
+					remote-endpoint = <&hdmi_sound_out>;
+				};
+			};
 		};
 	};
 

drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c

@@ -82,9 +82,30 @@ static void dw_hdmi_i2s_audio_shutdown(struct device *dev, void *data)
 	hdmi_write(audio, HDMI_AUD_CONF0_SW_RESET, HDMI_AUD_CONF0);
 }
 
+static int dw_hdmi_i2s_get_dai_id(struct snd_soc_component *component,
+				  struct device_node *endpoint)
+{
+	struct of_endpoint of_ep;
+	int ret;
+
+	ret = of_graph_parse_endpoint(endpoint, &of_ep);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * HDMI sound should be located as reg = <2>
+	 * Then, it is sound port 0
+	 */
+	if (of_ep.port == 2)
+		return 0;
+
+	return -EINVAL;
+}
+
 static struct hdmi_codec_ops dw_hdmi_i2s_ops = {
 	.hw_params	= dw_hdmi_i2s_hw_params,
 	.audio_shutdown	= dw_hdmi_i2s_audio_shutdown,
+	.get_dai_id	= dw_hdmi_i2s_get_dai_id,
 };
 
 static int snd_dw_hdmi_probe(struct platform_device *pdev)