On 2018-02-16 19:53, Matthias Kaehlcke wrote:
> On some systems a delay is needed after switching on the clocks, to allow
> the 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 after enabling the mic. A blocking delay
> can't be applied in dmic_daiops_trigger() since the function is called
> in atomic context. Instead use a DAPM event handler to set the enable
> GPIO and apply the delay in the handler.
> 
> Signed-off-by: Matthias Kaehlcke <m...@chromium.org>

Reviewed-by: Peter Ujfalusi <peter.ujfal...@ti.com>

> ---
> Changes in v3:
> - rebased on latest dmic topic branch
> 
> Changes in v2:
> - use DAPM event handler instead of _prepare() and get rid of
>   _trigger()
> - skip error check for optional 'wakeup-delay-ms' property
> - updated commit message
> 
>  .../devicetree/bindings/sound/dmic.txt        |  2 +
>  sound/soc/codecs/dmic.c                       | 63 ++++++++++---------
>  2 files changed, 37 insertions(+), 28 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/sound/dmic.txt 
> b/Documentation/devicetree/bindings/sound/dmic.txt
> index f7bf65611453..e957b4136716 100644
> --- a/Documentation/devicetree/bindings/sound/dmic.txt
> +++ b/Documentation/devicetree/bindings/sound/dmic.txt
> @@ -8,6 +8,7 @@ Required properties:
>  Optional properties:
>       - dmicen-gpios: GPIO specifier for dmic to control start and stop
>       - num-channels: Number of microphones on this DAI
> +     - wakeup-delay-ms: Delay (in ms) after enabling the DMIC
>  
>  Example node:
>  
> @@ -15,4 +16,5 @@ Example node:
>               compatible = "dmic-codec";
>               dmicen-gpios = <&gpio4 3 GPIO_ACTIVE_HIGH>;
>               num-channels = <1>;
> +             wakeup-delay-ms <50>;
>       };
> diff --git a/sound/soc/codecs/dmic.c b/sound/soc/codecs/dmic.c
> index 32a8f71d51f1..bac5bbb2dd59 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>
> @@ -29,34 +30,33 @@
>  #include <sound/soc.h>
>  #include <sound/soc-dapm.h>
>  
> -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 {
> +     struct gpio_desc *gpio_en;
> +     int wakeup_delay;
> +};
>  
> -     if (!dmic_en)
> -             return 0;
> +static int dmic_aif_event(struct snd_soc_dapm_widget *w,
> +                       struct snd_kcontrol *kcontrol, int event) {
> +     struct snd_soc_codec *codec = snd_soc_dapm_to_codec(w->dapm);
> +     struct dmic *dmic = snd_soc_codec_get_drvdata(codec);
>  
> -     switch (cmd) {
> -     case SNDRV_PCM_TRIGGER_START:
> -     case SNDRV_PCM_TRIGGER_RESUME:
> -     case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
> -             gpiod_set_value(dmic_en, 1);
> +     switch (event) {
> +     case SND_SOC_DAPM_POST_PMU:
> +             if (dmic->gpio_en)
> +                     gpiod_set_value(dmic->gpio_en, 1);
> +
> +             if (dmic->wakeup_delay)
> +                     msleep(dmic->wakeup_delay);
>               break;
> -     case SNDRV_PCM_TRIGGER_STOP:
> -     case SNDRV_PCM_TRIGGER_SUSPEND:
> -     case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
> -             gpiod_set_value(dmic_en, 0);
> +     case SND_SOC_DAPM_POST_PMD:
> +             if (dmic->gpio_en)
> +                     gpiod_set_value(dmic->gpio_en, 0);
>               break;
>       }
>  
>       return 0;
>  }
>  
> -static const struct snd_soc_dai_ops dmic_dai_ops = {
> -     .trigger        = dmic_daiops_trigger,
> -};
> -
>  static struct snd_soc_dai_driver dmic_dai = {
>       .name = "dmic-hifi",
>       .capture = {
> @@ -68,26 +68,33 @@ static struct snd_soc_dai_driver dmic_dai = {
>                       | SNDRV_PCM_FMTBIT_S24_LE
>                       | SNDRV_PCM_FMTBIT_S16_LE,
>       },
> -     .ops    = &dmic_dai_ops,
>  };
>  
>  static int dmic_component_probe(struct snd_soc_component *component)
>  {
> -     struct gpio_desc *dmic_en;
> +     struct dmic *dmic;
> +
> +     dmic = devm_kzalloc(component->dev, sizeof(*dmic), GFP_KERNEL);
> +     if (!dmic)
> +             return -ENOMEM;
> +
> +     dmic->gpio_en = devm_gpiod_get_optional(component->dev,
> +                                             "dmicen", GPIOD_OUT_LOW);
> +     if (IS_ERR(dmic->gpio_en))
> +             return PTR_ERR(dmic->gpio_en);
>  
> -     dmic_en = devm_gpiod_get_optional(component->dev,
> -                                     "dmicen", GPIOD_OUT_LOW);
> -     if (IS_ERR(dmic_en))
> -             return PTR_ERR(dmic_en);
> +     device_property_read_u32(component->dev, "wakeup-delay-ms",
> +                              &dmic->wakeup_delay);
>  
> -     snd_soc_component_set_drvdata(component, dmic_en);
> +     snd_soc_component_set_drvdata(component, dmic);
>  
>       return 0;
>  }
>  
>  static const struct snd_soc_dapm_widget dmic_dapm_widgets[] = {
> -     SND_SOC_DAPM_AIF_OUT("DMIC AIF", "Capture", 0,
> -                          SND_SOC_NOPM, 0, 0),
> +     SND_SOC_DAPM_AIF_OUT_E("DMIC AIF", "Capture", 0,
> +                            SND_SOC_NOPM, 0, 0, dmic_aif_event,
> +                            SND_SOC_DAPM_POST_PMU | SND_SOC_DAPM_POST_PMD),
>       SND_SOC_DAPM_INPUT("DMic"),
>  };
>  
> 

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