[PATCH v3 1/2] ASoC: tas5805m: rework to avoid scheduling while atomic.

[Daniel Beer <daniel.beer@igorinstitute.com>]

There's some setup we need to do in order to get the DSP initialized,
and this can't be done until a bit-clock is ready. In an earlier version
of this driver, this work was done in a DAPM callback.

The DAPM callback doesn't guarantee that the bit-clock is running, so
the work was moved instead to the trigger callback. Unfortunately this
callback runs in atomic context, and the setup code needs to do I2C
transactions.

Here we use a work_struct to kick off the setup in a thread instead.

Fixes: ec45268467f4 ("ASoC: add support for TAS5805M digital amplifier")
Signed-off-by: Daniel Beer <daniel.beer@igorinstitute.com>
---
 sound/soc/codecs/tas5805m.c | 128 ++++++++++++++++++++++++------------
 1 file changed, 87 insertions(+), 41 deletions(-)

diff --git a/sound/soc/codecs/tas5805m.c b/sound/soc/codecs/tas5805m.c
index beb4ec629a03..6e2edf045446 100644
--- a/sound/soc/codecs/tas5805m.c
+++ b/sound/soc/codecs/tas5805m.c
@@ -154,6 +154,7 @@ static const uint32_t tas5805m_volume[] = {
 #define TAS5805M_VOLUME_MIN	0
 
 struct tas5805m_priv {
+	struct i2c_client		*i2c;
 	struct regulator		*pvdd;
 	struct gpio_desc		*gpio_pdn_n;
 
@@ -165,6 +166,9 @@ struct tas5805m_priv {
 	int				vol[2];
 	bool				is_powered;
 	bool				is_muted;
+
+	struct work_struct		work;
+	struct mutex			lock;
 };
 
 static void set_dsp_scale(struct regmap *rm, int offset, int vol)
@@ -181,13 +185,11 @@ static void set_dsp_scale(struct regmap *rm, int offset, int vol)
 	regmap_bulk_write(rm, offset, v, ARRAY_SIZE(v));
 }
 
-static void tas5805m_refresh(struct snd_soc_component *component)
+static void tas5805m_refresh(struct tas5805m_priv *tas5805m)
 {
-	struct tas5805m_priv *tas5805m =
-		snd_soc_component_get_drvdata(component);
 	struct regmap *rm = tas5805m->regmap;
 
-	dev_dbg(component->dev, "refresh: is_muted=%d, vol=%d/%d\n",
+	dev_dbg(&tas5805m->i2c->dev, "refresh: is_muted=%d, vol=%d/%d\n",
 		tas5805m->is_muted, tas5805m->vol[0], tas5805m->vol[1]);
 
 	regmap_write(rm, REG_PAGE, 0x00);
@@ -226,8 +228,11 @@ static int tas5805m_vol_get(struct snd_kcontrol *kcontrol,
 	struct tas5805m_priv *tas5805m =
 		snd_soc_component_get_drvdata(component);
 
+	mutex_lock(&tas5805m->lock);
 	ucontrol->value.integer.value[0] = tas5805m->vol[0];
 	ucontrol->value.integer.value[1] = tas5805m->vol[1];
+	mutex_unlock(&tas5805m->lock);
+
 	return 0;
 }
 
@@ -243,11 +248,13 @@ static int tas5805m_vol_put(struct snd_kcontrol *kcontrol,
 		snd_soc_kcontrol_component(kcontrol);
 	struct tas5805m_priv *tas5805m =
 		snd_soc_component_get_drvdata(component);
+	int ret = 0;
 
 	if (!(volume_is_valid(ucontrol->value.integer.value[0]) &&
 	      volume_is_valid(ucontrol->value.integer.value[1])))
 		return -EINVAL;
 
+	mutex_lock(&tas5805m->lock);
 	if (tas5805m->vol[0] != ucontrol->value.integer.value[0] ||
 	    tas5805m->vol[1] != ucontrol->value.integer.value[1]) {
 		tas5805m->vol[0] = ucontrol->value.integer.value[0];
@@ -256,11 +263,12 @@ static int tas5805m_vol_put(struct snd_kcontrol *kcontrol,
 			tas5805m->vol[0], tas5805m->vol[1],
 			tas5805m->is_powered);
 		if (tas5805m->is_powered)
-			tas5805m_refresh(component);
-		return 1;
+			tas5805m_refresh(tas5805m);
+		ret = 1;
 	}
+	mutex_unlock(&tas5805m->lock);
 
-	return 0;
+	return ret;
 }
 
 static const struct snd_kcontrol_new tas5805m_snd_controls[] = {
@@ -294,54 +302,83 @@ static int tas5805m_trigger(struct snd_pcm_substream *substream, int cmd,
 	struct snd_soc_component *component = dai->component;
 	struct tas5805m_priv *tas5805m =
 		snd_soc_component_get_drvdata(component);
-	struct regmap *rm = tas5805m->regmap;
-	unsigned int chan, global1, global2;
 
 	switch (cmd) {
 	case SNDRV_PCM_TRIGGER_START:
 	case SNDRV_PCM_TRIGGER_RESUME:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
-		dev_dbg(component->dev, "DSP startup\n");
-
-		/* We mustn't issue any I2C transactions until the I2S
-		 * clock is stable. Furthermore, we must allow a 5ms
-		 * delay after the first set of register writes to
-		 * allow the DSP to boot before configuring it.
-		 */
-		usleep_range(5000, 10000);
-		send_cfg(rm, dsp_cfg_preboot,
-			ARRAY_SIZE(dsp_cfg_preboot));
-		usleep_range(5000, 15000);
-		send_cfg(rm, tas5805m->dsp_cfg_data,
-			tas5805m->dsp_cfg_len);
-
-		tas5805m->is_powered = true;
-		tas5805m_refresh(component);
+		dev_dbg(component->dev, "clock start\n");
+		schedule_work(&tas5805m->work);
 		break;
 
 	case SNDRV_PCM_TRIGGER_STOP:
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
-		dev_dbg(component->dev, "DSP shutdown\n");
+		break;
 
-		tas5805m->is_powered = false;
+	default:
+		return -EINVAL;
+	}
 
-		regmap_write(rm, REG_PAGE, 0x00);
-		regmap_write(rm, REG_BOOK, 0x00);
+	return 0;
+}
 
-		regmap_read(rm, REG_CHAN_FAULT, &chan);
-		regmap_read(rm, REG_GLOBAL_FAULT1, &global1);
-		regmap_read(rm, REG_GLOBAL_FAULT2, &global2);
+static void do_work(struct work_struct *work)
+{
+	struct tas5805m_priv *tas5805m =
+	       container_of(work, struct tas5805m_priv, work);
+	struct regmap *rm = tas5805m->regmap;
 
-		dev_dbg(component->dev,
-			"fault regs: CHAN=%02x, GLOBAL1=%02x, GLOBAL2=%02x\n",
-			chan, global1, global2);
+	dev_dbg(&tas5805m->i2c->dev, "DSP startup\n");
 
-		regmap_write(rm, REG_DEVICE_CTRL_2, DCTRL2_MODE_HIZ);
-		break;
+	mutex_lock(&tas5805m->lock);
+	/* We mustn't issue any I2C transactions until the I2S
+	 * clock is stable. Furthermore, we must allow a 5ms
+	 * delay after the first set of register writes to
+	 * allow the DSP to boot before configuring it.
+	 */
+	usleep_range(5000, 10000);
+	send_cfg(rm, dsp_cfg_preboot, ARRAY_SIZE(dsp_cfg_preboot));
+	usleep_range(5000, 15000);
+	send_cfg(rm, tas5805m->dsp_cfg_data, tas5805m->dsp_cfg_len);
+
+	tas5805m->is_powered = true;
+	tas5805m_refresh(tas5805m);
+	mutex_unlock(&tas5805m->lock);
+}
 
-	default:
-		return -EINVAL;
+static int tas5805m_dac_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 tas5805m_priv *tas5805m =
+		snd_soc_component_get_drvdata(component);
+	struct regmap *rm = tas5805m->regmap;
+
+	if (event & SND_SOC_DAPM_PRE_PMD) {
+		unsigned int chan, global1, global2;
+
+		dev_dbg(component->dev, "DSP shutdown\n");
+		cancel_work_sync(&tas5805m->work);
+
+		mutex_lock(&tas5805m->lock);
+		if (tas5805m->is_powered) {
+			tas5805m->is_powered = false;
+
+			regmap_write(rm, REG_PAGE, 0x00);
+			regmap_write(rm, REG_BOOK, 0x00);
+
+			regmap_read(rm, REG_CHAN_FAULT, &chan);
+			regmap_read(rm, REG_GLOBAL_FAULT1, &global1);
+			regmap_read(rm, REG_GLOBAL_FAULT2, &global2);
+
+			dev_dbg(component->dev, "fault regs: CHAN=%02x, "
+				"GLOBAL1=%02x, GLOBAL2=%02x\n",
+				chan, global1, global2);
+
+			regmap_write(rm, REG_DEVICE_CTRL_2, DCTRL2_MODE_HIZ);
+		}
+		mutex_unlock(&tas5805m->lock);
 	}
 
 	return 0;
@@ -354,7 +391,8 @@ static const struct snd_soc_dapm_route tas5805m_audio_map[] = {
 
 static const struct snd_soc_dapm_widget tas5805m_dapm_widgets[] = {
 	SND_SOC_DAPM_AIF_IN("DAC IN", "Playback", 0, SND_SOC_NOPM, 0, 0),
-	SND_SOC_DAPM_DAC("DAC", NULL, SND_SOC_NOPM, 0, 0),
+	SND_SOC_DAPM_DAC_E("DAC", NULL, SND_SOC_NOPM, 0, 0,
+		tas5805m_dac_event, SND_SOC_DAPM_PRE_PMD),
 	SND_SOC_DAPM_OUTPUT("OUT")
 };
 
@@ -375,11 +413,14 @@ static int tas5805m_mute(struct snd_soc_dai *dai, int mute, int direction)
 	struct tas5805m_priv *tas5805m =
 		snd_soc_component_get_drvdata(component);
 
+	mutex_lock(&tas5805m->lock);
 	dev_dbg(component->dev, "set mute=%d (is_powered=%d)\n",
 		mute, tas5805m->is_powered);
+
 	tas5805m->is_muted = mute;
 	if (tas5805m->is_powered)
-		tas5805m_refresh(component);
+		tas5805m_refresh(tas5805m);
+	mutex_unlock(&tas5805m->lock);
 
 	return 0;
 }
@@ -434,6 +475,7 @@ static int tas5805m_i2c_probe(struct i2c_client *i2c)
 	if (!tas5805m)
 		return -ENOMEM;
 
+	tas5805m->i2c = i2c;
 	tas5805m->pvdd = devm_regulator_get(dev, "pvdd");
 	if (IS_ERR(tas5805m->pvdd)) {
 		dev_err(dev, "failed to get pvdd supply: %ld\n",
@@ -507,6 +549,9 @@ static int tas5805m_i2c_probe(struct i2c_client *i2c)
 	gpiod_set_value(tas5805m->gpio_pdn_n, 1);
 	usleep_range(10000, 15000);
 
+	INIT_WORK(&tas5805m->work, do_work);
+	mutex_init(&tas5805m->lock);
+
 	/* Don't register through devm. We need to be able to unregister
 	 * the component prior to deasserting PDN#
 	 */
@@ -527,6 +572,7 @@ static void tas5805m_i2c_remove(struct i2c_client *i2c)
 	struct device *dev = &i2c->dev;
 	struct tas5805m_priv *tas5805m = dev_get_drvdata(dev);
 
+	cancel_work_sync(&tas5805m->work);
 	snd_soc_unregister_component(dev);
 	gpiod_set_value(tas5805m->gpio_pdn_n, 0);
 	usleep_range(10000, 15000);
-- 
2.38.1