[PATCH] ASoC: max98357a: move control of SD_MODE back to DAI ops

[Tzung-Bi Shih]

Partially reverts commit 128f825aeab7 ("ASoC: max98357a: move control
of SD_MODE to DAPM").

In order to have mute control of max98357 from machine drivers, commit
128f825aeab7 ("ASoC: max98357a: move control of SD_MODE to DAPM")
moves the control of SD_MODE from DAI ops to DAPM events.  However, pop
noise has been observed on rk3399-gru-kevin boards due to this commit.

The commit 128f825aeab7 caused sequence of DAI clocks and SD_MODE
changed on rk3399-gru-kevin boards.

With the commit 128f825aeab7:
- SD_MODE will be set to 1 before DAI clocks start.
- SD_MODE will be set to 0 after DAI clocks stop.
As a result, pop noise.

Moves the control of SD_MODE back to DAI ops.  In the meantime, uses an
additional flag in DAPM event to provide chance of mute control for
machine drivers.

Signed-off-by: Tzung-Bi Shih <tzungbi at google.com>
---

This patch addresses the reported issue in the thread
https://lkml.org/lkml/2020/7/16/427

 sound/soc/codecs/max98357a.c | 50 ++++++++++++++++++++++++++++--------
 1 file changed, 40 insertions(+), 10 deletions(-)

diff --git a/sound/soc/codecs/max98357a.c b/sound/soc/codecs/max98357a.c
index 4f431133d0bb..918812763884 100644
--- a/sound/soc/codecs/max98357a.c
+++ b/sound/soc/codecs/max98357a.c
@@ -23,36 +23,61 @@
 struct max98357a_priv {
 	struct gpio_desc *sdmode;
 	unsigned int sdmode_delay;
+	int sdmode_switch;
 };
 
-static int max98357a_sdmode_event(struct snd_soc_dapm_widget *w,
-		struct snd_kcontrol *kcontrol, int event)
+static int max98357a_daiops_trigger(struct snd_pcm_substream *substream,
+		int cmd, struct snd_soc_dai *dai)
 {
-	struct snd_soc_component *component =
-		snd_soc_dapm_to_component(w->dapm);
+	struct snd_soc_component *component = dai->component;
 	struct max98357a_priv *max98357a =
 		snd_soc_component_get_drvdata(component);
 
 	if (!max98357a->sdmode)
 		return 0;
 
-	if (event & SND_SOC_DAPM_POST_PMU) {
-		msleep(max98357a->sdmode_delay);
-		gpiod_set_value(max98357a->sdmode, 1);
-		dev_dbg(component->dev, "set sdmode to 1");
-	} else if (event & SND_SOC_DAPM_PRE_PMD) {
+	switch (cmd) {
+	case SNDRV_PCM_TRIGGER_START:
+	case SNDRV_PCM_TRIGGER_RESUME:
+	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
+		mdelay(max98357a->sdmode_delay);
+		if (max98357a->sdmode_switch) {
+			gpiod_set_value(max98357a->sdmode, 1);
+			dev_dbg(component->dev, "set sdmode to 1");
+		}
+		break;
+	case SNDRV_PCM_TRIGGER_STOP:
+	case SNDRV_PCM_TRIGGER_SUSPEND:
+	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 		gpiod_set_value(max98357a->sdmode, 0);
 		dev_dbg(component->dev, "set sdmode to 0");
+		break;
 	}
 
 	return 0;
 }
 
+static int max98357a_sdmode_event(struct snd_soc_dapm_widget *w,
+		struct snd_kcontrol *kcontrol, int event)
+{
+	struct snd_soc_component *component =
+		snd_soc_dapm_to_component(w->dapm);
+	struct max98357a_priv *max98357a =
+		snd_soc_component_get_drvdata(component);
+
+	if (event & SND_SOC_DAPM_POST_PMU)
+		max98357a->sdmode_switch = 1;
+	else if (event & SND_SOC_DAPM_POST_PMD)
+		max98357a->sdmode_switch = 0;
+
+	return 0;
+}
+
 static const struct snd_soc_dapm_widget max98357a_dapm_widgets[] = {
 	SND_SOC_DAPM_OUTPUT("Speaker"),
 	SND_SOC_DAPM_OUT_DRV_E("SD_MODE", SND_SOC_NOPM, 0, 0, NULL, 0,
 			max98357a_sdmode_event,
-			SND_SOC_DAPM_POST_PMU | SND_SOC_DAPM_PRE_PMD),
+			SND_SOC_DAPM_POST_PMU | SND_SOC_DAPM_POST_PMD),
 };
 
 static const struct snd_soc_dapm_route max98357a_dapm_routes[] = {
@@ -71,6 +96,10 @@ static const struct snd_soc_component_driver max98357a_component_driver = {
 	.non_legacy_dai_naming	= 1,
 };
 
+static const struct snd_soc_dai_ops max98357a_dai_ops = {
+	.trigger        = max98357a_daiops_trigger,
+};
+
 static struct snd_soc_dai_driver max98357a_dai_driver = {
 	.name = "HiFi",
 	.playback = {
@@ -90,6 +119,7 @@ static struct snd_soc_dai_driver max98357a_dai_driver = {
 		.channels_min	= 1,
 		.channels_max	= 2,
 	},
+	.ops    = &max98357a_dai_ops,
 };
 
 static int max98357a_platform_probe(struct platform_device *pdev)
-- 
2.28.0.rc0.105.gf9edc3c819-goog