driver:gpio: Added reset gpio to PI4IO

BCS 746-001106

drivers/staging/gpio/gpio-pi4ioe5v6408.c

@@ -66,6 +66,7 @@ struct pi4io_priv {
 	struct i2c_client *i2c;
 	struct regmap *regmap;
 	struct gpio_chip gpio;
+	struct gpio_desc *reset_gpio;
 };
 
 static int pi4io_gpio_get_direction(struct gpio_chip *chip, unsigned offset)
@@ -181,6 +182,27 @@ static int pi4io_gpio_setup(struct pi4io_priv *pi4io)
 	return 0;
 }
 
+static int pi4io_reset(struct pi4io_priv *pi4io)
+{
+	struct device *dev = &pi4io->i2c->dev;
+
+	if (pi4io->reset_gpio) {
+		dev_dbg(dev, "Performing reset");
+
+		/*
+		 * According to the datasheet, the reset time should
+		 * be 150 ns. However, when using 150 ns, the device
+		 * doesn't come up correctly.
+		 */
+		gpiod_set_value(pi4io->reset_gpio, 1);
+		udelay(150);
+		gpiod_set_value(pi4io->reset_gpio, 0);
+		udelay(150);
+	}
+
+	return 0;
+};
+
 static int pi4io_probe(
 	struct i2c_client *client, const struct i2c_device_id *id)
 {
@@ -196,6 +218,12 @@ static int pi4io_probe(
 	i2c_set_clientdata(client, pi4io);
 	pi4io->i2c = client;
 
+	pi4io->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
+	if (!pi4io->reset_gpio)
+		dev_warn(dev, "Could not get reset-gpios");
+
+	pi4io_reset(pi4io);
+
 	pi4io->regmap = devm_regmap_init_i2c(client, &pi4io_regmap);
 	ret = regmap_read(pi4io->regmap, PI4IO_CHIP_ID, &chip_id);
 	if (ret < 0) {