ASoC: tas2770: Add zero-fill and pull-down controls

Expose the bits that control the behavior of the SDOUT pin when not
actively transmitting slot data. Zero-fill is useful when there is a
single amp on the SDOUT bus (e.g. Apple machines with mono speakers or a
single stereo pair, where L/R are on separate buses).

Pull-down is useful, though not perfect, when multiple amps share a
bus. It typically takes around 2 bits for the line to transition from
high to low after going Hi-Z, with the pull-down.

Signed-off-by: Hector Martin <marcan@marcan.st>

Author: marcan

sound/soc/codecs/tas2770.c

@@ -654,11 +654,24 @@ static int tas2770_codec_probe(struct snd_soc_component *component)
 
 	if (tas2770->pdm_slot != -1) {
 		ret = tas2770_set_pdm_transmit(tas2770, tas2770->pdm_slot);
-
 		if (ret < 0)
 			return ret;
 	}
 
+	ret = snd_soc_component_update_bits(component, TAS2770_TDM_CFG_REG4,
+					    TAS2770_TDM_CFG_REG4_TX_FILL,
+					    tas2770->sdout_zfill ? 0 :
+					    TAS2770_TDM_CFG_REG4_TX_FILL);
+	if (ret < 0)
+		return ret;
+
+	ret = snd_soc_component_update_bits(component, TAS2770_DIN_PD,
+					    TAS2770_DIN_PD_SDOUT,
+					    tas2770->sdout_pd ?
+					    TAS2770_DIN_PD_SDOUT : 0);
+	if (ret < 0)
+		return ret;
+
 	return 0;
 }
 
@@ -811,6 +824,9 @@ static int tas2770_parse_dt(struct device *dev, struct tas2770_priv *tas2770)
 	if (rc)
 		tas2770->pdm_slot = -1;
 
+	tas2770->sdout_pd = fwnode_property_read_bool(dev->fwnode, "ti,sdout-pull-down");
+	tas2770->sdout_zfill = fwnode_property_read_bool(dev->fwnode, "ti,sdout-zero-fill");
+
 	tas2770->sdz_reg = devm_regulator_get(dev, "SDZ");
 	if (IS_ERR(tas2770->sdz_reg))
 		return dev_err_probe(dev, PTR_ERR(tas2770->sdz_reg),

sound/soc/codecs/tas2770.h

@@ -67,6 +67,14 @@
 #define TAS2770_TDM_CFG_REG3_RXS_SHIFT 0x4
 #define TAS2770_TDM_CFG_REG3_30_MASK  GENMASK(3, 0)
 #define TAS2770_TDM_CFG_REG3_30_SHIFT 0
+    /* TDM Configuration Reg4 */
+#define TAS2770_TDM_CFG_REG4  TAS2770_REG(0X0, 0x0E)
+#define TAS2770_TDM_CFG_REG4_TX_LSB_CFG BIT(7)
+#define TAS2770_TDM_CFG_REG4_TX_KEEPER_CFG BIT(6)
+#define TAS2770_TDM_CFG_REG4_TX_KEEPER BIT(5)
+#define TAS2770_TDM_CFG_REG4_TX_FILL BIT(4)
+#define TAS2770_TDM_CFG_REG4_TX_OFFSET_MASK GENMASK(3, 1)
+#define TAS2770_TDM_CFG_REG4_TX_EDGE_FALLING BIT(0)
     /* TDM Configuration Reg5 */
 #define TAS2770_TDM_CFG_REG5  TAS2770_REG(0X0, 0x0F)
 #define TAS2770_TDM_CFG_REG5_VSNS_MASK  BIT(6)
@@ -115,6 +123,9 @@
 #define TAS2770_TEMP_LSB  TAS2770_REG(0X0, 0x2A)
     /* Interrupt Configuration */
 #define TAS2770_INT_CFG  TAS2770_REG(0X0, 0x30)
+    /* Data In Pull-Down */
+#define TAS2770_DIN_PD  TAS2770_REG(0X0, 0x31)
+#define TAS2770_DIN_PD_SDOUT BIT(7)
     /* Misc IRQ */
 #define TAS2770_MISC_IRQ  TAS2770_REG(0X0, 0x32)
     /* Clock Configuration */
@@ -145,6 +156,8 @@ struct tas2770_priv {
 	int v_sense_slot;
 	int i_sense_slot;
 	int pdm_slot;
+	bool sdout_pd;
+	bool sdout_zfill;
 	bool dac_powered;
 	bool unmuted;
 };