staging: iio: adis16060: Remove iio_dev mlock and refactor code

The IIO subsystem is redefining iio_dev->mlock to be used by
the IIO core only for protecting device operating mode changes.
ie. Changes between INDIO_DIRECT_MODE, INDIO_BUFFER_* modes.

In this driver, mlock was being used to protect hardware state changes.

In the driver, buf_lock protects both the adis16060_spi_write() and
adis16060_spi_read() functions and both are always called in
pair. First write, then read. Refactor the code to have
one single function adis16060_spi_write_than_read() protected by
the buf_lock.  This removes the need for additional locking via
mlock, so this locking is removed.

Signed-off-by: simran singhal <singhalsimran0@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/gyro/adis16060_core.c

@@ -40,25 +40,20 @@ struct adis16060_state {
 
 static struct iio_dev *adis16060_iio_dev;
 
-static int adis16060_spi_write(struct iio_dev *indio_dev, u8 val)
+static int adis16060_spi_write_than_read(struct iio_dev *indio_dev,
+					 u8 conf, u16 *val)
 {
 	int ret;
 	struct adis16060_state *st = iio_priv(indio_dev);
 
 	mutex_lock(&st->buf_lock);
-	st->buf[2] = val; /* The last 8 bits clocked in are latched */
+	st->buf[2] = conf; /* The last 8 bits clocked in are latched */
 	ret = spi_write(st->us_w, st->buf, 3);
-	mutex_unlock(&st->buf_lock);
 
-	return ret;
-}
-
-static int adis16060_spi_read(struct iio_dev *indio_dev, u16 *val)
-{
-	int ret;
-	struct adis16060_state *st = iio_priv(indio_dev);
-
-	mutex_lock(&st->buf_lock);
+	if (ret < 0) {
+		mutex_unlock(&st->buf_lock);
+		return ret;
+	}
 
 	ret = spi_read(st->us_r, st->buf, 3);
 
@@ -86,17 +81,11 @@ static int adis16060_read_raw(struct iio_dev *indio_dev,
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
-		/* Take the iio_dev status lock */
-		mutex_lock(&indio_dev->mlock);
-		ret = adis16060_spi_write(indio_dev, chan->address);
+		ret = adis16060_spi_write_than_read(indio_dev,
+						    chan->address, &tval);
 		if (ret < 0)
-			goto out_unlock;
+			return ret;
 
-		ret = adis16060_spi_read(indio_dev, &tval);
-		if (ret < 0)
-			goto out_unlock;
-
-		mutex_unlock(&indio_dev->mlock);
 		*val = tval;
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_OFFSET:
@@ -110,10 +99,6 @@ static int adis16060_read_raw(struct iio_dev *indio_dev,
 	}
 
 	return -EINVAL;
-
-out_unlock:
-	mutex_unlock(&indio_dev->mlock);
-	return ret;
 }
 
 static const struct iio_info adis16060_info = {