[alsa-devel] [PATCH] ASoC: codecs: dmic: Use channel map for configs with a single mic

[Matthias Kaehlcke]

The DMIC DAI driver specifies a number of 1 to 8 channels for each DAI.
The actual number of mics can currently not be configured in the device
tree or audio glue, but is derived from the min/max channels of the CPU
and codec DAI. A typical CPU DAI has two or more channels, in consequence
a single mic is treated as a stereo/multi channel device, even though
only one channel carries audio data.

This change adds the option to specify the number of used DMIC channels
in the device tree. If a single channel is used we export a channel map
that marks all unused channels as invalid to indicate userspace that the
capture device is mono.

Signed-off-by: Matthias Kaehlcke <mka at chromium.org>
---
 Documentation/devicetree/bindings/sound/dmic.txt |  2 +
 sound/soc/codecs/dmic.c                          | 72 +++++++++++++++++++++---
 2 files changed, 65 insertions(+), 9 deletions(-)

diff --git a/Documentation/devicetree/bindings/sound/dmic.txt b/Documentation/devicetree/bindings/sound/dmic.txt
index 54c8ef6498a8..f7bf65611453 100644
--- a/Documentation/devicetree/bindings/sound/dmic.txt
+++ b/Documentation/devicetree/bindings/sound/dmic.txt
@@ -7,10 +7,12 @@ Required properties:
 
 Optional properties:
 	- dmicen-gpios: GPIO specifier for dmic to control start and stop
+	- num-channels: Number of microphones on this DAI
 
 Example node:
 
 	dmic_codec: dmic at 0 {
 		compatible = "dmic-codec";
 		dmicen-gpios = <&gpio4 3 GPIO_ACTIVE_HIGH>;
+		num-channels = <1>;
 	};
diff --git a/sound/soc/codecs/dmic.c b/sound/soc/codecs/dmic.c
index b88a1ee66f80..c705a25b138e 100644
--- a/sound/soc/codecs/dmic.c
+++ b/sound/soc/codecs/dmic.c
@@ -29,24 +29,29 @@
 #include <sound/soc.h>
 #include <sound/soc-dapm.h>
 
+struct dmic {
+	struct gpio_desc *gpio_en;
+	int channels;
+};
+
 static int dmic_daiops_trigger(struct snd_pcm_substream *substream,
 		int cmd, struct snd_soc_dai *dai)
 {
-	struct gpio_desc *dmic_en = snd_soc_dai_get_drvdata(dai);
+	struct dmic *dmic = snd_soc_dai_get_drvdata(dai);
 
-	if (!dmic_en)
+	if (!dmic || !dmic->gpio_en)
 		return 0;
 
 	switch (cmd) {
 	case SNDRV_PCM_TRIGGER_START:
 	case SNDRV_PCM_TRIGGER_RESUME:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
-		gpiod_set_value(dmic_en, 1);
+		gpiod_set_value(dmic->gpio_en, 1);
 		break;
 	case SNDRV_PCM_TRIGGER_STOP:
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
-		gpiod_set_value(dmic_en, 0);
+		gpiod_set_value(dmic->gpio_en, 0);
 		break;
 	}
 
@@ -57,6 +62,42 @@ static const struct snd_soc_dai_ops dmic_dai_ops = {
 	.trigger	= dmic_daiops_trigger,
 };
 
+const struct snd_pcm_chmap_elem dmic_chmaps_single[] = {
+	{ .channels = 1,
+	  .map = { SNDRV_CHMAP_MONO } },
+	{ .channels = 2,
+	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_NA } },
+	{ .channels = 4,
+	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_NA,
+		   SNDRV_CHMAP_NA, SNDRV_CHMAP_NA } },
+	{ .channels = 6,
+	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_NA,
+		   SNDRV_CHMAP_NA, SNDRV_CHMAP_NA,
+		   SNDRV_CHMAP_NA, SNDRV_CHMAP_NA } },
+	{ .channels = 8,
+	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_NA,
+		   SNDRV_CHMAP_NA, SNDRV_CHMAP_NA,
+		   SNDRV_CHMAP_NA, SNDRV_CHMAP_NA,
+		   SNDRV_CHMAP_NA, SNDRV_CHMAP_NA } },
+	{ }
+};
+
+static int dmic_pcm_new(struct snd_soc_pcm_runtime *rtd,
+			      struct snd_soc_dai *dai)
+{
+	struct dmic *dmic = snd_soc_dai_get_drvdata(dai);
+	int err;
+
+	if (dmic->channels == 1) {
+		err = snd_pcm_add_chmap_ctls(rtd->pcm, SNDRV_PCM_STREAM_CAPTURE,
+					     dmic_chmaps_single, 8, 0, NULL);
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
+}
+
 static struct snd_soc_dai_driver dmic_dai = {
 	.name = "dmic-hifi",
 	.capture = {
@@ -69,18 +110,31 @@ static struct snd_soc_dai_driver dmic_dai = {
 			| SNDRV_PCM_FMTBIT_S16_LE,
 	},
 	.ops    = &dmic_dai_ops,
+	.pcm_new = dmic_pcm_new,
 };
 
 static int dmic_codec_probe(struct snd_soc_codec *codec)
 {
-	struct gpio_desc *dmic_en;
+	struct dmic *dmic;
+	int err;
+	u32 pval;
+
+	dmic = devm_kzalloc(codec->dev, sizeof(*dmic), GFP_KERNEL);
+	if (!dmic)
+		return -ENOMEM;
 
-	dmic_en = devm_gpiod_get_optional(codec->dev,
+	dmic->gpio_en = devm_gpiod_get_optional(codec->dev,
 					"dmicen", GPIOD_OUT_LOW);
-	if (IS_ERR(dmic_en))
-		return PTR_ERR(dmic_en);
+	if (IS_ERR(dmic->gpio_en))
+		return PTR_ERR(dmic->gpio_en);
+
+	err = of_property_read_u32(codec->dev->of_node, "num-channels", &pval);
+	if (!err)
+		dmic->channels = (int)pval;
+	else if (err != -ENOENT)
+		return err;
 
-	snd_soc_codec_set_drvdata(codec, dmic_en);
+	snd_soc_codec_set_drvdata(codec, dmic);
 
 	return 0;
 }
-- 
2.16.0.rc0.223.g4a4ac83678-goog