ASoC: cs4270: pull reset GPIO low then high

Pull the RST line low then high when initializing the driver,
in order to force a reset of the chip.
Previously, the line was not pulled low, which could result in
the chip registers not resetting to their default values on boot.
Signed-off-by: Mike Willard <mwillard@izotope.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200401205454.79792-1-mwillard@izotope.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/cs4270.c

@@ -137,6 +137,9 @@ struct cs4270_private {
 
 	/* power domain regulators */
 	struct regulator_bulk_data supplies[ARRAY_SIZE(supply_names)];
+
+	/* reset gpio */
+	struct gpio_desc *reset_gpio;
 };
 
 static const struct snd_soc_dapm_widget cs4270_dapm_widgets[] = {
@@ -648,6 +651,22 @@ static const struct regmap_config cs4270_regmap = {
 	.volatile_reg =		cs4270_reg_is_volatile,
 };
 
+/**
+ * cs4270_i2c_remove - deinitialize the I2C interface of the CS4270
+ * @i2c_client: the I2C client object
+ *
+ * This function puts the chip into low power mode when the i2c device
+ * is removed.
+ */
+static int cs4270_i2c_remove(struct i2c_client *i2c_client)
+{
+	struct cs4270_private *cs4270 = i2c_get_clientdata(i2c_client);
+
+	gpiod_set_value_cansleep(cs4270->reset_gpio, 0);
+
+	return 0;
+}
+
 /**
  * cs4270_i2c_probe - initialize the I2C interface of the CS4270
  * @i2c_client: the I2C client object
@@ -660,7 +679,6 @@ static int cs4270_i2c_probe(struct i2c_client *i2c_client,
 	const struct i2c_device_id *id)
 {
 	struct cs4270_private *cs4270;
-	struct gpio_desc *reset_gpiod;
 	unsigned int val;
 	int ret, i;
 
@@ -679,10 +697,21 @@ static int cs4270_i2c_probe(struct i2c_client *i2c_client,
 	if (ret < 0)
 		return ret;
 
-	reset_gpiod = devm_gpiod_get_optional(&i2c_client->dev, "reset",
-					      GPIOD_OUT_HIGH);
-	if (PTR_ERR(reset_gpiod) == -EPROBE_DEFER)
-		return -EPROBE_DEFER;
+	/* reset the device */
+	cs4270->reset_gpio = devm_gpiod_get_optional(&i2c_client->dev, "reset",
+						     GPIOD_OUT_LOW);
+	if (IS_ERR(cs4270->reset_gpio)) {
+		dev_dbg(&i2c_client->dev, "Error getting CS4270 reset GPIO\n");
+		return PTR_ERR(cs4270->reset_gpio);
+	}
+
+	if (cs4270->reset_gpio) {
+		dev_dbg(&i2c_client->dev, "Found reset GPIO\n");
+		gpiod_set_value_cansleep(cs4270->reset_gpio, 1);
+	}
+
+	/* Sleep 500ns before i2c communications */
+	ndelay(500);
 
 	cs4270->regmap = devm_regmap_init_i2c(i2c_client, &cs4270_regmap);
 	if (IS_ERR(cs4270->regmap))
@@ -735,6 +764,7 @@ static struct i2c_driver cs4270_i2c_driver = {
 	},
 	.id_table = cs4270_id,
 	.probe = cs4270_i2c_probe,
+	.remove = cs4270_i2c_remove,
 };
 
 module_i2c_driver(cs4270_i2c_driver);