ASoC: nau8540: PGA short to ground

Change channel PGA input mode selection for better recording quality.
The patch shorts the inputs to ground with 12kOhm differentially
terminated.

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

sound/soc/codecs/nau8540.c

@@ -730,6 +730,13 @@ static void nau8540_init_regs(struct nau8540 *nau8540)
 	regmap_update_bits(regmap, NAU8540_REG_ADC_SAMPLE_RATE,
 		NAU8540_CH_SYNC | NAU8540_ADC_OSR_MASK,
 		NAU8540_CH_SYNC | NAU8540_ADC_OSR_64);
+	/* PGA input mode selection */
+	regmap_update_bits(regmap, NAU8540_REG_FEPGA1,
+		NAU8540_FEPGA1_MODCH2_SHT | NAU8540_FEPGA1_MODCH1_SHT,
+		NAU8540_FEPGA1_MODCH2_SHT | NAU8540_FEPGA1_MODCH1_SHT);
+	regmap_update_bits(regmap, NAU8540_REG_FEPGA2,
+		NAU8540_FEPGA2_MODCH4_SHT | NAU8540_FEPGA2_MODCH3_SHT,
+		NAU8540_FEPGA2_MODCH4_SHT | NAU8540_FEPGA2_MODCH3_SHT);
 }
 
 static int __maybe_unused nau8540_suspend(struct snd_soc_codec *codec)

sound/soc/codecs/nau8540.h

@@ -184,6 +184,18 @@
 #define NAU8540_PRECHARGE_DIS		(0x1 << 13)
 #define NAU8540_GLOBAL_BIAS_EN	(0x1 << 12)
 
+/* FEPGA1 (0x69) */
+#define NAU8540_FEPGA1_MODCH2_SHT_SFT	7
+#define NAU8540_FEPGA1_MODCH2_SHT	(0x1 << NAU8540_FEPGA1_MODCH2_SHT_SFT)
+#define NAU8540_FEPGA1_MODCH1_SHT_SFT	3
+#define NAU8540_FEPGA1_MODCH1_SHT	(0x1 << NAU8540_FEPGA1_MODCH1_SHT_SFT)
+
+/* FEPGA2 (0x6A) */
+#define NAU8540_FEPGA2_MODCH4_SHT_SFT	7
+#define NAU8540_FEPGA2_MODCH4_SHT	(0x1 << NAU8540_FEPGA2_MODCH4_SHT_SFT)
+#define NAU8540_FEPGA2_MODCH3_SHT_SFT	3
+#define NAU8540_FEPGA2_MODCH3_SHT	(0x1 << NAU8540_FEPGA2_MODCH3_SHT_SFT)
+
 
 /* System Clock Source */
 enum {