ASoC: codecs/jz4770: Add missing gain control after DAC/ADC mixer

The capture and playback paths both have a configurable gain after their
respective mixer, which can be set from -31 dB to 0 dB in 32 steps.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20211125232543.117074-1-paul@crapouillou.netSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/jz4770.c

@@ -307,6 +307,7 @@ static const DECLARE_TLV_DB_MINMAX_MUTE(dac_tlv, -3100, 0);
 static const DECLARE_TLV_DB_SCALE(adc_tlv, 0, 100, 0);
 static const DECLARE_TLV_DB_MINMAX(out_tlv, -2500, 600);
 static const DECLARE_TLV_DB_SCALE(linein_tlv, -2500, 100, 0);
+static const DECLARE_TLV_DB_MINMAX(mixer_tlv, -3100, 0);
 
 /* Unconditional controls. */
 static const struct snd_kcontrol_new jz4770_codec_snd_controls[] = {
@@ -319,6 +320,14 @@ static const struct snd_kcontrol_new jz4770_codec_snd_controls[] = {
 	SOC_DOUBLE_R_TLV("Line In Bypass Playback Volume",
 			 JZ4770_CODEC_REG_GCR_LIBYL, JZ4770_CODEC_REG_GCR_LIBYR,
 			 REG_GCR_GAIN_OFFSET, REG_GCR_GAIN_MAX, 1, linein_tlv),
+
+	SOC_SINGLE_TLV("Mixer Capture Volume",
+		       JZ4770_CODEC_REG_GCR_MIXADC,
+		       REG_GCR_GAIN_OFFSET, REG_GCR_GAIN_MAX, 1, mixer_tlv),
+
+	SOC_SINGLE_TLV("Mixer Playback Volume",
+		       JZ4770_CODEC_REG_GCR_MIXDAC,
+		       REG_GCR_GAIN_OFFSET, REG_GCR_GAIN_MAX, 1, mixer_tlv),
 };
 
 static const struct snd_kcontrol_new jz4770_codec_pcm_playback_controls[] = {