ASoC: pcm3168a: Update the RST gpio handling to align with documentation

The RST (reset-gpios) is low active so the driver must handle it
accordingly.

Add comments to explain clearly how the line is used.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20191120131753.6831-3-peter.ujfalusi@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/pcm3168a.c

@@ -707,11 +707,15 @@ int pcm3168a_probe(struct device *dev, struct regmap *regmap)
 	dev_set_drvdata(dev, pcm3168a);
 
 	/*
-	 * Request the RST gpio line as non exclusive as the same reset line
+	 * Request the reset (connected to RST pin) gpio line as non exclusive
-	 * might be connected to multiple pcm3168a codec
+	 * as the same reset line might be connected to multiple pcm3168a codec
+	 *
+	 * The RST is low active, we want the GPIO line to be high initially, so
+	 * request the initial level to LOW which in practice means DEASSERTED:
+	 * The deasserted level of GPIO_ACTIVE_LOW is HIGH.
 	 */
-	pcm3168a->gpio_rst = devm_gpiod_get_optional(dev, "rst",
+	pcm3168a->gpio_rst = devm_gpiod_get_optional(dev, "reset",
-						GPIOD_OUT_HIGH |
+						GPIOD_OUT_LOW |
 						GPIOD_FLAGS_BIT_NONEXCLUSIVE);
 	if (IS_ERR(pcm3168a->gpio_rst)) {
 		ret = PTR_ERR(pcm3168a->gpio_rst);
@@ -814,7 +818,13 @@ void pcm3168a_remove(struct device *dev)
 {
 	struct pcm3168a_priv *pcm3168a = dev_get_drvdata(dev);
 
-	gpiod_set_value_cansleep(pcm3168a->gpio_rst, 0);
+	/*
+	 * The RST is low active, we want the GPIO line to be low when the
+	 * driver is removed, so set level to 1 which in practice means
+	 * ASSERTED:
+	 * The asserted level of GPIO_ACTIVE_LOW is LOW.
+	 */
+	gpiod_set_value_cansleep(pcm3168a->gpio_rst, 1);
 	pm_runtime_disable(dev);
 #ifndef CONFIG_PM
 	pcm3168a_disable(dev);