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Subject[PATCH] ASoC: dmic: Add optional wakeup delay
Date
On some systems a delay is needed after switching on the clocks, to allow
the DMIC output to stabilize and avoid a popping noise at the beginning
of the recording. Add the optional device tree property 'wakeup-delay-ms'
and apply the specified delay in the new dmic_daiops_prepare().

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
---
.../devicetree/bindings/sound/dmic.txt | 2 +
sound/soc/codecs/dmic.c | 54 ++++++++++++++-----
2 files changed, 42 insertions(+), 14 deletions(-)

diff --git a/Documentation/devicetree/bindings/sound/dmic.txt b/Documentation/devicetree/bindings/sound/dmic.txt
index 54c8ef6498a8..de741c6609d0 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
+ - wakeup-delay-ms: Delay (in ms) after enabling the DMIC

Example node:

dmic_codec: dmic@0 {
compatible = "dmic-codec";
dmicen-gpios = <&gpio4 3 GPIO_ACTIVE_HIGH>;
+ wakeup-delay-ms <50>;
};
diff --git a/sound/soc/codecs/dmic.c b/sound/soc/codecs/dmic.c
index b88a1ee66f80..11f6abf11074 100644
--- a/sound/soc/codecs/dmic.c
+++ b/sound/soc/codecs/dmic.c
@@ -19,6 +19,7 @@
*
*/

+#include <linux/delay.h>
#include <linux/gpio.h>
#include <linux/gpio/consumer.h>
#include <linux/platform_device.h>
@@ -29,24 +30,38 @@
#include <sound/soc.h>
#include <sound/soc-dapm.h>

+struct dmic {
+ struct gpio_desc *gpio_en;
+ int wakeup_delay;
+};
+
+static int dmic_daiops_prepare(struct snd_pcm_substream *substream,
+ struct snd_soc_dai *dai)
+{
+ struct dmic *dmic = snd_soc_dai_get_drvdata(dai);
+
+ if (dmic->gpio_en)
+ gpiod_set_value(dmic->gpio_en, 1);
+
+ if (dmic->wakeup_delay)
+ msleep(dmic->wakeup_delay);
+
+ return 0;
+}
+
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->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);
- 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;
}

@@ -54,6 +69,7 @@ static int dmic_daiops_trigger(struct snd_pcm_substream *substream,
}

static const struct snd_soc_dai_ops dmic_dai_ops = {
+ .prepare = dmic_daiops_prepare,
.trigger = dmic_daiops_trigger,
};

@@ -73,14 +89,24 @@ static struct snd_soc_dai_driver dmic_dai = {

static int dmic_codec_probe(struct snd_soc_codec *codec)
{
- struct gpio_desc *dmic_en;
+ struct dmic *dmic;
+ int err;
+
+ dmic = devm_kzalloc(codec->dev, sizeof(*dmic), GFP_KERNEL);
+ if (!dmic)
+ return -ENOMEM;
+
+ dmic->gpio_en = devm_gpiod_get_optional(codec->dev,
+ "dmicen", GPIOD_OUT_LOW);
+ if (IS_ERR(dmic->gpio_en))
+ return PTR_ERR(dmic->gpio_en);

- dmic_en = devm_gpiod_get_optional(codec->dev,
- "dmicen", GPIOD_OUT_LOW);
- if (IS_ERR(dmic_en))
- return PTR_ERR(dmic_en);
+ err = device_property_read_u32(codec->dev, "wakeup-delay-ms",
+ &dmic->wakeup_delay);
+ if (err && (err != -EINVAL))
+ return err;

- snd_soc_codec_set_drvdata(codec, dmic_en);
+ snd_soc_codec_set_drvdata(codec, dmic);

return 0;
}
--
2.16.1.291.g4437f3f132-goog
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