iio: dac: ad5380: Replace indio_dev->mlock with own device lock

As part of the general cleanup of indio_dev->mlock, this change replaces
it with a local lock on the device's state structure.
Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dac/ad5380.c

@@ -51,6 +51,7 @@ struct ad5380_chip_info {
  * @vref_reg:		vref supply regulator
  * @vref:		actual reference voltage used in uA
  * @pwr_down:		whether the chip is currently in power down mode
+ * @lock		lock to protect the data buffer during regmap ops
  */
 
 struct ad5380_state {
@@ -59,6 +60,7 @@ struct ad5380_state {
 	struct regulator		*vref_reg;
 	int				vref;
 	bool				pwr_down;
+	struct mutex			lock;
 };
 
 enum ad5380_type {
@@ -98,7 +100,7 @@ static ssize_t ad5380_write_dac_powerdown(struct iio_dev *indio_dev,
 	if (ret)
 		return ret;
 
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&st->lock);
 
 	if (pwr_down)
 		ret = regmap_write(st->regmap, AD5380_REG_SF_PWR_DOWN, 0);
@@ -107,7 +109,7 @@ static ssize_t ad5380_write_dac_powerdown(struct iio_dev *indio_dev,
 
 	st->pwr_down = pwr_down;
 
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&st->lock);
 
 	return ret ? ret : len;
 }
@@ -390,6 +392,8 @@ static int ad5380_probe(struct device *dev, struct regmap *regmap,
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->num_channels = st->chip_info->num_channels;
 
+	mutex_init(&st->lock);
+
 	ret = ad5380_alloc_channels(indio_dev);
 	if (ret) {
 		dev_err(dev, "Failed to allocate channel spec: %d\n", ret);