ASoC: simple-card: Support setting mclk via a fixed factor

Some platforms require that the codecs mclk is a fixed multiplication
factor of the audio stream rate. Add a optional property to the
binding to hold this factor and implement a hw_params() function to
make use of it.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Mark Brown <broonie@linaro.org>

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

@@ -15,6 +15,9 @@ Optional properties:
 					  Each entry is a pair of strings, the first being the
 					  connection's sink, the second being the connection's
 					  source.
+- simple-audio-card,mclk-fs             : Multiplication factor between stream rate and codec
+  					  mclk.
+
 Optional subnodes:
 
 - simple-audio-card,dai-link		: Container for dai-link level

sound/soc/generic/simple-card.c

@@ -24,9 +24,32 @@ struct simple_card_data {
 		struct asoc_simple_dai cpu_dai;
 		struct asoc_simple_dai codec_dai;
 	} *dai_props;
+	unsigned int mclk_fs;
 	struct snd_soc_dai_link dai_link[];	/* dynamically allocated */
 };
 
+static int asoc_simple_card_hw_params(struct snd_pcm_substream *substream,
+				      struct snd_pcm_hw_params *params)
+{
+	struct snd_soc_pcm_runtime *rtd = substream->private_data;
+	struct snd_soc_dai *codec_dai = rtd->codec_dai;
+	struct simple_card_data *priv = snd_soc_card_get_drvdata(rtd->card);
+	unsigned int mclk;
+	int ret = 0;
+
+	if (priv->mclk_fs) {
+		mclk = params_rate(params) * priv->mclk_fs;
+		ret = snd_soc_dai_set_sysclk(codec_dai, 0, mclk,
+					     SND_SOC_CLOCK_IN);
+	}
+
+	return ret;
+}
+
+static struct snd_soc_ops asoc_simple_card_ops = {
+	.hw_params = asoc_simple_card_hw_params,
+};
+
 static int __asoc_simple_card_dai_init(struct snd_soc_dai *dai,
 				       struct asoc_simple_dai *set)
 {
@@ -251,6 +274,7 @@ static int simple_card_dai_link_of(struct device_node *node,
 	sprintf(name, "%s-%s", dai_link->cpu_dai_name,
 				dai_link->codec_dai_name);
 	dai_link->name = dai_link->stream_name = name;
+	dai_link->ops = &asoc_simple_card_ops;
 
 	dev_dbg(dev, "\tname : %s\n", dai_link->stream_name);
 	dev_dbg(dev, "\tcpu : %s / %04x / %d\n",
@@ -300,6 +324,10 @@ static int asoc_simple_card_parse_of(struct device_node *node,
 			return ret;
 	}
 
+	/* Factor to mclk, used in hw_params() */
+	of_property_read_u32(node, "simple-audio-card,mclk-fs",
+			     &priv->mclk_fs);
+
 	dev_dbg(dev, "New simple-card: %s\n", priv->snd_card.name ?
 		priv->snd_card.name : "");