iio: pressure: bmp280: add reset GPIO line handling

On the APQ8060 Dragonboard the reset line to the BMP085 pressure
sensor is not deasserted on boot, so the driver needs to handle
this. For a simple GPIO line supplied as a descriptor (from a board
file, device tree or ACPI) this does the trick.
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

drivers/iio/pressure/bmp280.c

@@ -23,6 +23,7 @@
 #include <linux/delay.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
+#include <linux/gpio/consumer.h>
 
 /* BMP280 specific registers */
 #define BMP280_REG_HUMIDITY_LSB		0xFE
@@ -1024,6 +1025,7 @@ static int bmp280_probe(struct i2c_client *client,
 	struct iio_dev *indio_dev;
 	struct bmp280_data *data;
 	unsigned int chip_id;
+	struct gpio_desc *gpiod;
 
 	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
 	if (!indio_dev)
@@ -1063,6 +1065,14 @@ static int bmp280_probe(struct i2c_client *client,
 		return -EINVAL;
 	}
 
+	/* Bring chip out of reset if there is an assigned GPIO line */
+	gpiod = devm_gpiod_get(&client->dev, "reset", GPIOD_OUT_HIGH);
+	/* Deassert the signal */
+	if (!IS_ERR(gpiod)) {
+		dev_info(&client->dev, "release reset\n");
+		gpiod_set_value(gpiod, 0);
+	}
+
 	data->regmap = devm_regmap_init_i2c(client,
 					data->chip_info->regmap_config);
 	if (IS_ERR(data->regmap)) {