ASoC: tas2764: Wait for ramp-down after shutdown

When we shut down the amp, we need to wait for the built-in ramp-down
before we can remove the TDM clocks. There is no documented status
regiter to poll, so the best we can do is a delay. Datasheet says 5.9ms
for ramp-down and 1.5ms between shutdown and next startup, so let's do
6ms after mute and 2ms after shutdown. That gives us a cumulative 8ms
for ramp-down and guaratees the required minimum shutdown time.

Signed-off-by: Hector Martin <marcan@marcan.st>

Author: marcan

sound/soc/codecs/tas2764.c

@@ -164,6 +164,8 @@ static int tas2764_codec_suspend(struct snd_soc_component *component)
 	regcache_cache_only(tas2764->regmap, true);
 	regcache_mark_dirty(tas2764->regmap);
 
+	usleep_range(6000, 7000);
+
 	return 0;
 }
 
@@ -257,10 +259,16 @@ static int tas2764_mute(struct snd_soc_dai *dai, int mute, int direction)
 		return ret;
 
 	if (mute) {
+		/* Wait for ramp-down */
+		usleep_range(6000, 7000);
+
 		tas2764->dac_powered = false;
 		ret = tas2764_update_pwr_ctrl(tas2764);
 		if (ret)
 			return ret;
+
+		/* Wait a bit after shutdown */
+		usleep_range(2000, 3000);
 	}
 
 	return 0;