ASoC: twl6040: Add digital mute support

To reduce pop noise during playback stream start and stop the codec needs
to have the digital_mute callback implemented.
The codec need to be muted before the CPU dai has been stopped (McPDM).
Stopping the McPDM will generate a pop on the codec since no signal on the
PDM bus means full negative amplitude.
By managing the mute/unmute state of the outputs we can decrease the amount
of pop noise when playback starts or stops.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

1 files changed, 90 insertions, 1 deletions

diff --git a/sound/soc/codecs/twl6040.c b/sound/soc/codecs/twl6040.c
index 9ea3dbccc0b3..44621ddc332d 100644
--- a/sound/soc/codecs/twl6040.c
+++ b/sound/soc/codecs/twl6040.c
@@ -75,6 +75,8 @@ struct twl6040_data {
         int pll_power_mode;
         int hs_power_mode;
         int hs_power_mode_locked;
+        bool dl1_unmuted;
+        bool dl2_unmuted;
         unsigned int clk_in;
         unsigned int sysclk;
         struct twl6040_jack_data hs_jack;
@@ -228,6 +230,25 @@ static int twl6040_read_reg_volatile(struct snd_soc_codec *codec,
         return value;
 }
 
+static bool twl6040_is_path_unmuted(struct snd_soc_codec *codec,
+                                    unsigned int reg)
+{
+        struct twl6040_data *priv = snd_soc_codec_get_drvdata(codec);
+
+        switch (reg) {
+        case TWL6040_REG_HSLCTL:
+        case TWL6040_REG_HSRCTL:
+        case TWL6040_REG_EARCTL:
+                /* DL1 path */
+                return priv->dl1_unmuted;
+        case TWL6040_REG_HFLCTL:
+        case TWL6040_REG_HFRCTL:
+                return priv->dl2_unmuted;
+        default:
+                return 1;
+        };
+}
+
 /*
  * write to the twl6040 register space
  */
@@ -240,7 +261,8 @@ static int twl6040_write(struct snd_soc_codec *codec,
                 return -EIO;
 
         twl6040_write_reg_cache(codec, reg, value);
-        if (likely(reg < TWL6040_REG_SW_SHADOW))
+        if (likely(reg < TWL6040_REG_SW_SHADOW) &&
+            twl6040_is_path_unmuted(codec, reg))
                 return twl6040_reg_write(twl6040, reg, value);
         else
                 return 0;
@@ -1034,11 +1056,78 @@ static int twl6040_set_dai_sysclk(struct snd_soc_dai *codec_dai,
         return 0;
 }
 
+static void twl6040_mute_path(struct snd_soc_codec *codec, enum twl6040_dai_id id,
+                             int mute)
+{
+        struct twl6040 *twl6040 = codec->control_data;
+        struct twl6040_data *priv = snd_soc_codec_get_drvdata(codec);
+        int hslctl, hsrctl, earctl;
+        int hflctl, hfrctl;
+
+        switch (id) {
+        case TWL6040_DAI_DL1:
+                hslctl = twl6040_read_reg_cache(codec, TWL6040_REG_HSLCTL);
+                hsrctl = twl6040_read_reg_cache(codec, TWL6040_REG_HSRCTL);
+                earctl = twl6040_read_reg_cache(codec, TWL6040_REG_EARCTL);
+
+                if (mute) {
+                        /* Power down drivers and DACs */
+                        earctl &= ~0x01;
+                        hslctl &= ~(TWL6040_HSDRVENA | TWL6040_HSDACENA);
+                        hsrctl &= ~(TWL6040_HSDRVENA | TWL6040_HSDACENA);
+
+                }
+
+                twl6040_reg_write(twl6040, TWL6040_REG_EARCTL, earctl);
+                twl6040_reg_write(twl6040, TWL6040_REG_HSLCTL, hslctl);
+                twl6040_reg_write(twl6040, TWL6040_REG_HSRCTL, hsrctl);
+                priv->dl1_unmuted = !mute;
+                break;
+        case TWL6040_DAI_DL2:
+                hflctl = twl6040_read_reg_cache(codec, TWL6040_REG_HFLCTL);
+                hfrctl = twl6040_read_reg_cache(codec, TWL6040_REG_HFRCTL);
+
+                if (mute) {
+                        /* Power down drivers and DACs */
+                        hflctl &= ~(TWL6040_HFDACENA | TWL6040_HFPGAENA |
+                                    TWL6040_HFDRVENA);
+                        hfrctl &= ~(TWL6040_HFDACENA | TWL6040_HFPGAENA |
+                                    TWL6040_HFDRVENA);
+                }
+
+                twl6040_reg_write(twl6040, TWL6040_REG_HFLCTL, hflctl);
+                twl6040_reg_write(twl6040, TWL6040_REG_HFRCTL, hfrctl);
+                priv->dl2_unmuted = !mute;
+                break;
+        default:
+                break;
+        };
+}
+
+static int twl6040_digital_mute(struct snd_soc_dai *dai, int mute)
+{
+        switch (dai->id) {
+        case TWL6040_DAI_LEGACY:
+                twl6040_mute_path(dai->codec, TWL6040_DAI_DL1, mute);
+                twl6040_mute_path(dai->codec, TWL6040_DAI_DL2, mute);
+                break;
+        case TWL6040_DAI_DL1:
+        case TWL6040_DAI_DL2:
+                twl6040_mute_path(dai->codec, dai->id, mute);
+                break;
+        default:
+                break;
+        }
+
+        return 0;
+}
+
 static const struct snd_soc_dai_ops twl6040_dai_ops = {
         .startup        = twl6040_startup,
         .hw_params      = twl6040_hw_params,
         .prepare        = twl6040_prepare,
         .set_sysclk     = twl6040_set_dai_sysclk,
+        .digital_mute   = twl6040_digital_mute,
 };
 
 static struct snd_soc_dai_driver twl6040_dai[] = {