ASoC: nau8540: reset state machine for channel phase sync

The four channel ADCs in NAU85L40 have difference control registers,
it is hard to synchronous these four channels without correct sequence.
The phase difference will not be a constant and not to conjecture easily.
It may be 2.55 degree, or more ,or less.
Intended to prevent phase difference of channels, the solution as follows:
(1)Channel_Sync need to be enabled.
(2)Do soft reset without affecting register when recording done.

Signed-off-by: John Hsu <KCHSU0@nuvoton.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/nau8540.c

@@ -233,6 +233,19 @@ static SOC_ENUM_SINGLE_DECL(
 static const struct snd_kcontrol_new digital_ch1_mux =
 	SOC_DAPM_ENUM("Digital CH1 Select", digital_ch1_enum);
 
+static int aiftx_power_control(struct snd_soc_dapm_widget *w,
+		struct snd_kcontrol *k, int  event)
+{
+	struct snd_soc_codec *codec = snd_soc_dapm_to_codec(w->dapm);
+	struct nau8540 *nau8540 = snd_soc_codec_get_drvdata(codec);
+
+	if (SND_SOC_DAPM_EVENT_OFF(event)) {
+		regmap_write(nau8540->regmap, NAU8540_REG_RST, 0x0001);
+		regmap_write(nau8540->regmap, NAU8540_REG_RST, 0x0000);
+	}
+	return 0;
+}
+
 static const struct snd_soc_dapm_widget nau8540_dapm_widgets[] = {
 	SND_SOC_DAPM_SUPPLY("MICBIAS2", NAU8540_REG_MIC_BIAS, 11, 0, NULL, 0),
 	SND_SOC_DAPM_SUPPLY("MICBIAS1", NAU8540_REG_MIC_BIAS, 10, 0, NULL, 0),
@@ -270,7 +283,8 @@ static const struct snd_soc_dapm_widget nau8540_dapm_widgets[] = {
 	SND_SOC_DAPM_MUX("Digital CH1 Mux",
 		SND_SOC_NOPM, 0, 0, &digital_ch1_mux),
 
-	SND_SOC_DAPM_AIF_OUT("AIFTX", "Capture", 0, SND_SOC_NOPM, 0, 0),
+	SND_SOC_DAPM_AIF_OUT_E("AIFTX", "Capture", 0, SND_SOC_NOPM, 0, 0,
+		aiftx_power_control, SND_SOC_DAPM_POST_PMD),
 };
 
 static const struct snd_soc_dapm_route nau8540_dapm_routes[] = {
@@ -710,9 +724,12 @@ static void nau8540_init_regs(struct nau8540 *nau8540)
 	regmap_update_bits(regmap, NAU8540_REG_CLOCK_CTRL,
 		NAU8540_CLK_ADC_EN | NAU8540_CLK_I2S_EN,
 		NAU8540_CLK_ADC_EN | NAU8540_CLK_I2S_EN);
-	/* ADC OSR selection, CLK_ADC = Fs * OSR */
+	/* ADC OSR selection, CLK_ADC = Fs * OSR;
+	 * Channel time alignment enable.
+	 */
 	regmap_update_bits(regmap, NAU8540_REG_ADC_SAMPLE_RATE,
-		NAU8540_ADC_OSR_MASK, NAU8540_ADC_OSR_64);
+		NAU8540_CH_SYNC | NAU8540_ADC_OSR_MASK,
+		NAU8540_CH_SYNC | NAU8540_ADC_OSR_64);
 }
 
 static int __maybe_unused nau8540_suspend(struct snd_soc_codec *codec)

sound/soc/codecs/nau8540.h

@@ -165,6 +165,7 @@
 #define NAU8540_TDM_TX_MASK		0xf
 
 /* ADC_SAMPLE_RATE (0x3A) */
+#define NAU8540_CH_SYNC		(0x1 << 14)
 #define NAU8540_ADC_OSR_MASK		0x3
 #define NAU8540_ADC_OSR_256		0x3
 #define NAU8540_ADC_OSR_128		0x2