ASoC: rt5640: Allow configuration of LOUT to mono differential mode

LOUT output can produce either single-ended stereo signals, or mono
differential signal. Some applications are wired to use LOUT in mono
differential mode. Allow to configure it via device property.

Signed-off-by: Ondrej Jirman <megi@xff.cz>
Signed-off-by: Jarrah Gosbell <kernel@undef.tools>
Link: https://lore.kernel.org/r/20221209105621.39237-1-kernel@undef.tools
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/rt5640.c

@@ -2717,6 +2717,10 @@ static int rt5640_probe(struct snd_soc_component *component)
 		snd_soc_component_update_bits(component, RT5640_IN1_IN2,
 					      RT5640_IN_DF2, RT5640_IN_DF2);
 
+	if (device_property_read_bool(component->dev, "realtek,lout-differential"))
+		snd_soc_component_update_bits(component, RT5640_DUMMY1,
+					      RT5640_EN_LOUT_DF, RT5640_EN_LOUT_DF);
+
 	if (device_property_read_u32(component->dev, "realtek,dmic1-data-pin",
 				     &val) == 0 && val) {
 		dmic1_data_pin = val - 1;

sound/soc/codecs/rt5640.h

@@ -1978,6 +1978,8 @@
 #define RT5640_ZCD_HP_EN			(0x1 << 15)
 
 /* General Control 1 (0xfa) */
+#define RT5640_EN_LOUT_DF			(0x1 << 14)
+#define RT5640_EN_LOUT_DF_SFT			14
 #define RT5640_M_MONO_ADC_L			(0x1 << 13)
 #define RT5640_M_MONO_ADC_L_SFT			13
 #define RT5640_M_MONO_ADC_R			(0x1 << 12)