iio: ltc2983: add support for optional reset gpio

Check if an optional reset gpio is present and if so, make sure to reset
the device.
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20210825084149.11587-1-nuno.sa@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/temperature/ltc2983.c

@@ -1470,6 +1470,7 @@ static int ltc2983_probe(struct spi_device *spi)
 {
 	struct ltc2983_data *st;
 	struct iio_dev *indio_dev;
+	struct gpio_desc *gpio;
 	const char *name = spi_get_device_id(spi)->name;
 	int ret;
 
@@ -1494,6 +1495,16 @@ static int ltc2983_probe(struct spi_device *spi)
 	if (ret)
 		return ret;
 
+	gpio = devm_gpiod_get_optional(&st->spi->dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(gpio))
+		return PTR_ERR(gpio);
+
+	if (gpio) {
+		/* bring the device out of reset */
+		usleep_range(1000, 1200);
+		gpiod_set_value_cansleep(gpio, 0);
+	}
+
 	ret = ltc2983_setup(st, true);
 	if (ret)
 		return ret;