[alsa-devel] [PATCH] ASoC: da7219: Add delays to capture path to remove DC offset noise

[Adam Thomson]

On some platforms it has been noted that a pop noise can be
witnessed when capturing audio, mainly for first time after a
headset jack has been inserted. This is due to a DC offset in the
Mic PGA and so to avoid this delays are required when powering
up the capture path.

This commit rectifies the problem by adding delays post Mic PGA and
post Mixin PGA. The post Mic PGA delay is determined based on
Mic Bias voltage, and is only applied the first time after a
headset jack is inserted.

Signed-off-by: Adam Thomson <Adam.Thomson.Opensource at diasemi.com>
---
 sound/soc/codecs/da7219-aad.c |  5 +++++
 sound/soc/codecs/da7219.c     | 44 +++++++++++++++++++++++++++++++++++++------
 sound/soc/codecs/da7219.h     |  8 ++++++--
 3 files changed, 49 insertions(+), 8 deletions(-)

diff --git a/sound/soc/codecs/da7219-aad.c b/sound/soc/codecs/da7219-aad.c
index a49ab75..2c7d508 100644
--- a/sound/soc/codecs/da7219-aad.c
+++ b/sound/soc/codecs/da7219-aad.c
@@ -59,6 +59,7 @@ static void da7219_aad_btn_det_work(struct work_struct *work)
 		container_of(work, struct da7219_aad_priv, btn_det_work);
 	struct snd_soc_component *component = da7219_aad->component;
 	struct snd_soc_dapm_context *dapm = snd_soc_component_get_dapm(component);
+	struct da7219_priv *da7219 = snd_soc_component_get_drvdata(component);
 	u8 statusa, micbias_ctrl;
 	bool micbias_up = false;
 	int retries = 0;
@@ -86,6 +87,8 @@ static void da7219_aad_btn_det_work(struct work_struct *work)
 	if (retries >= DA7219_AAD_MICBIAS_CHK_RETRIES)
 		dev_warn(component->dev, "Mic bias status check timed out");
 
+	da7219->micbias_on_event = true;
+
 	/*
 	 * Mic bias pulse required to enable mic, must be done before enabling
 	 * button detection to prevent erroneous button readings.
@@ -439,6 +442,8 @@ static irqreturn_t da7219_aad_irq_thread(int irq, void *data)
 			snd_soc_component_update_bits(component, DA7219_ACCDET_CONFIG_1,
 					    DA7219_BUTTON_CONFIG_MASK, 0);
 
+			da7219->micbias_on_event = false;
+
 			/* Disable mic bias */
 			snd_soc_dapm_disable_pin(dapm, "Mic Bias");
 			snd_soc_dapm_sync(dapm);
diff --git a/sound/soc/codecs/da7219.c b/sound/soc/codecs/da7219.c
index c0144f2..e46e9f4 100644
--- a/sound/soc/codecs/da7219.c
+++ b/sound/soc/codecs/da7219.c
@@ -768,6 +768,30 @@ static int da7219_tonegen_freq_put(struct snd_kcontrol *kcontrol,
  * DAPM Events
  */
 
+static int da7219_mic_pga_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 da7219_priv *da7219 = snd_soc_component_get_drvdata(component);
+
+	switch (event) {
+	case SND_SOC_DAPM_POST_PMU:
+		if (da7219->micbias_on_event) {
+			/*
+			 * Delay only for first capture after bias enabled to
+			 * avoid possible DC offset related noise.
+			 */
+			da7219->micbias_on_event = false;
+			msleep(da7219->mic_pga_delay);
+		}
+		break;
+	default:
+		break;
+	}
+
+	return 0;
+}
+
 static int da7219_dai_event(struct snd_soc_dapm_widget *w,
 			    struct snd_kcontrol *kcontrol, int event)
 {
@@ -937,12 +961,12 @@ static int da7219_gain_ramp_event(struct snd_soc_dapm_widget *w,
 	SND_SOC_DAPM_INPUT("MIC"),
 
 	/* Input PGAs */
-	SND_SOC_DAPM_PGA("Mic PGA", DA7219_MIC_1_CTRL,
-			 DA7219_MIC_1_AMP_EN_SHIFT, DA7219_NO_INVERT,
-			 NULL, 0),
-	SND_SOC_DAPM_PGA("Mixin PGA", DA7219_MIXIN_L_CTRL,
-			 DA7219_MIXIN_L_AMP_EN_SHIFT, DA7219_NO_INVERT,
-			 NULL, 0),
+	SND_SOC_DAPM_PGA_E("Mic PGA", DA7219_MIC_1_CTRL,
+			   DA7219_MIC_1_AMP_EN_SHIFT, DA7219_NO_INVERT,
+			   NULL, 0, da7219_mic_pga_event, SND_SOC_DAPM_POST_PMU),
+	SND_SOC_DAPM_PGA_E("Mixin PGA", DA7219_MIXIN_L_CTRL,
+			   DA7219_MIXIN_L_AMP_EN_SHIFT, DA7219_NO_INVERT,
+			   NULL, 0, da7219_settling_event, SND_SOC_DAPM_POST_PMU),
 
 	/* Input Filters */
 	SND_SOC_DAPM_ADC("ADC", NULL, DA7219_ADC_L_CTRL, DA7219_ADC_L_EN_SHIFT,
@@ -1847,6 +1871,14 @@ static void da7219_handle_pdata(struct snd_soc_component *component)
 
 		snd_soc_component_write(component, DA7219_MICBIAS_CTRL, micbias_lvl);
 
+		/*
+		 * Calculate delay required to compensate for DC offset in
+		 * Mic PGA, based on Mic Bias voltage.
+		 */
+		da7219->mic_pga_delay =  DA7219_MIC_PGA_BASE_DELAY +
+					(pdata->micbias_lvl *
+					 DA7219_MIC_PGA_OFFSET_DELAY);
+
 		/* Mic */
 		switch (pdata->mic_amp_in_sel) {
 		case DA7219_MIC_AMP_IN_SEL_DIFF:
diff --git a/sound/soc/codecs/da7219.h b/sound/soc/codecs/da7219.h
index 1b00023..3a00686 100644
--- a/sound/soc/codecs/da7219.h
+++ b/sound/soc/codecs/da7219.h
@@ -781,8 +781,10 @@
 #define DA7219_SYS_STAT_CHECK_DELAY	50
 
 /* Power up/down Delays */
-#define DA7219_SETTLING_DELAY	40
-#define DA7219_MIN_GAIN_DELAY	30
+#define DA7219_SETTLING_DELAY		40
+#define DA7219_MIN_GAIN_DELAY		30
+#define DA7219_MIC_PGA_BASE_DELAY	100
+#define DA7219_MIC_PGA_OFFSET_DELAY	40
 
 enum da7219_clk_src {
 	DA7219_CLKSRC_MCLK = 0,
@@ -828,6 +830,8 @@ struct da7219_priv {
 
 	bool master;
 	bool alc_en;
+	bool micbias_on_event;
+	unsigned int mic_pga_delay;
 	u8 gain_ramp_ctrl;
 };
 
-- 
1.9.1