ASoC: simple-card: add support for aux devices

Add device tree property to define auxiliary devices to be added to
simle-audio-card.

Together with proper audio routing definition, this allows to use
simple-card in setups where separate amplifier chip is connected to
codec's output.
Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/simple-card.txt

@@ -22,6 +22,8 @@ Optional properties:
 					  headphones are attached.
 - simple-audio-card,mic-det-gpio	: Reference to GPIO that signals when
 					  a microphone is attached.
+- simple-audio-card,aux-devs		: List of phandles pointing to auxiliary devices, such
+					  as amplifiers, to be added to the sound card.
 
 Optional subnodes:
 
@@ -162,3 +164,38 @@ sound {
 		};
 	};
 };
+
+Example 3 - route audio from IMX6 SSI2 through TLV320DAC3100 codec
+through TPA6130A2 amplifier to headphones:
+
+&i2c0 {
+	codec: tlv320dac3100@18 {
+		compatible = "ti,tlv320dac3100";
+		...
+	}
+
+	amp: tpa6130a2@60 {
+		compatible = "ti,tpa6130a2";
+		...
+	}
+}
+
+sound {
+	compatible = "simple-audio-card";
+	...
+	simple-audio-card,widgets =
+		"Headphone", "Headphone Jack";
+	simple-audio-card,routing =
+		"Headphone Jack", "HPLEFT",
+		"Headphone Jack", "HPRIGHT",
+		"LEFTIN", "HPL",
+		"RIGHTIN", "HPR";
+	simple-audio-card,aux-devs = <&amp>;
+	simple-audio-card,cpu {
+		sound-dai = <&ssi2>;
+	};
+	simple-audio-card,codec {
+		sound-dai = <&codec>;
+		clocks = ...
+	};
+};

sound/soc/generic/simple-card.c

@@ -318,6 +318,36 @@ static int asoc_simple_card_dai_link_of(struct device_node *node,
 	return ret;
 }
 
+static int asoc_simple_card_parse_aux_devs(struct device_node *node,
+					   struct simple_card_data *priv)
+{
+	struct device *dev = simple_priv_to_dev(priv);
+	struct device_node *aux_node;
+	int i, n, len;
+
+	if (!of_find_property(node, PREFIX "aux-devs", &len))
+		return 0;		/* Ok to have no aux-devs */
+
+	n = len / sizeof(__be32);
+	if (n <= 0)
+		return -EINVAL;
+
+	priv->snd_card.aux_dev = devm_kzalloc(dev,
+			n * sizeof(*priv->snd_card.aux_dev), GFP_KERNEL);
+	if (!priv->snd_card.aux_dev)
+		return -ENOMEM;
+
+	for (i = 0; i < n; i++) {
+		aux_node = of_parse_phandle(node, PREFIX "aux-devs", i);
+		if (!aux_node)
+			return -EINVAL;
+		priv->snd_card.aux_dev[i].codec_of_node = aux_node;
+	}
+
+	priv->snd_card.num_aux_devs = n;
+	return 0;
+}
+
 static int asoc_simple_card_parse_of(struct device_node *node,
 				     struct simple_card_data *priv)
 {
@@ -372,6 +402,10 @@ static int asoc_simple_card_parse_of(struct device_node *node,
 	}
 
 	ret = asoc_simple_card_parse_card_name(&priv->snd_card, PREFIX);
+	if (ret < 0)
+		goto card_parse_end;
+
+	ret = asoc_simple_card_parse_aux_devs(node, priv);
 
 card_parse_end:
 	of_node_put(dai_link);