iio: gyro: adis16080: replace mlock with own lock

The lock is used to protect the buffer during reads. Though the spi
routines have their own locks, it may be the case that the buffer needs to
be protected before it's stored and passed to the IIO read hooks.

indio_dev's mlock was used before.
This change replaces it with the driver's own lock.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/gyro/adis16080.c

@@ -38,10 +38,12 @@ struct adis16080_chip_info {
  * @us:			actual spi_device to write data
  * @info:		chip specific parameters
  * @buf:		transmit or receive buffer
+ * @lock		lock to protect buffer during reads
  **/
 struct adis16080_state {
 	struct spi_device		*us;
 	const struct adis16080_chip_info *info;
+	struct mutex			lock;
 
 	__be16 buf ____cacheline_aligned;
 };
@@ -82,9 +84,9 @@ static int adis16080_read_raw(struct iio_dev *indio_dev,
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
-		mutex_lock(&indio_dev->mlock);
+		mutex_lock(&st->lock);
 		ret = adis16080_read_sample(indio_dev, chan->address, val);
-		mutex_unlock(&indio_dev->mlock);
+		mutex_unlock(&st->lock);
 		return ret ? ret : IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		switch (chan->type) {
@@ -196,6 +198,8 @@ static int adis16080_probe(struct spi_device *spi)
 	/* this is only used for removal purposes */
 	spi_set_drvdata(spi, indio_dev);
 
+	mutex_init(&st->lock);
+
 	/* Allocate the comms buffers */
 	st->us = spi;
 	st->info = &adis16080_chip_info[id->driver_data];