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sgtl5000 latency

Question asked by Dat Tran on Mar 14, 2019
Latest reply on Mar 14, 2019 by igorpadykov

Using an iMX6 and SGTL5000 for audio, I noticed a 400ms delay when snd_pcm_prepare() is called. Looking at the sgtl5000.c codec driver, there is a sleep of 400ms when the power management powers up and powers down. For some reason the call to power up is always called on snd_pcm_prepare() even when the audio codec power never went down. I added a state to keep track of it in the codec driver as a workaround to not delay unless necessary. While this workaround works, I don't think it's the best solution. Does someone know why the power up section of code is always called in the driver? Thanks

 

 

+diff --git a/sound/soc/codecs/sgtl5000.c b/sound/soc/codecs/sgtl5000.c
+index 6668845..3aaf384 100644
+--- a/sound/soc/codecs/sgtl5000.c
++++ b/sound/soc/codecs/sgtl5000.c
+@@ -152,6 +152,8 @@ static int mic_bias_event(struct snd_soc_dapm_widget *w,
+ static int power_vag_event(struct snd_soc_dapm_widget *w,
+  struct snd_kcontrol *kcontrol, int event)
+ {
++ static bool is_power_up = false;
++
+  struct snd_soc_codec *codec = snd_soc_dapm_to_codec(w->dapm);
+  const u32 mask = SGTL5000_DAC_POWERUP | SGTL5000_ADC_POWERUP;
+
+@@ -159,7 +161,12 @@ static int power_vag_event(struct snd_soc_dapm_widget *w,
+  case SND_SOC_DAPM_POST_PMU:
+   snd_soc_update_bits(codec, SGTL5000_CHIP_ANA_POWER,
+    SGTL5000_VAG_POWERUP, SGTL5000_VAG_POWERUP);
+-  msleep(400);
++
++  if (is_power_up == false)
++  {
++   msleep(400);
++   is_power_up = true;
++  }
+   break;
+
+  case SND_SOC_DAPM_PRE_PMD:
+@@ -173,6 +180,7 @@ static int power_vag_event(struct snd_soc_dapm_widget *w,
+    snd_soc_update_bits(codec, SGTL5000_CHIP_ANA_POWER,
+     SGTL5000_VAG_POWERUP, 0);
+    msleep(400);
++   is_power_up = false;
+   }
+   break;
+  default: 

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