[PATCH] iio: dac: ad5755: Replace indio_dev->mlock with own device lock

[Sergiu Cuciurean <sergiu.cuciurean@xxxxxxxxxx>]

As part of the general cleanup of indio_dev->mlock, this change replaces
it with a local lock on the device's state structure.
This also changes some internal functions to pass the pointer to the
state-struct vs a ref to indio_dev just to access the state-struct again.

Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@xxxxxxxxxx>
---
 drivers/iio/dac/ad5755.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/iio/dac/ad5755.c b/drivers/iio/dac/ad5755.c
index 388ddd14bfd0..7723bd313fc6 100644
--- a/drivers/iio/dac/ad5755.c
+++ b/drivers/iio/dac/ad5755.c
@@ -82,6 +82,7 @@ struct ad5755_chip_info {
  * @pwr_down:	bitmask which contains  hether a channel is powered down or not
  * @ctrl:	software shadow of the channel ctrl registers
  * @channels:	iio channel spec for the device
+ * @lock	lock to protect the data buffer during SPI ops
  * @data:	spi transfer buffers
  */
 struct ad5755_state {
@@ -90,6 +91,7 @@ struct ad5755_state {
 	unsigned int			pwr_down;
 	unsigned int			ctrl[AD5755_NUM_CHANNELS];
 	struct iio_chan_spec		channels[AD5755_NUM_CHANNELS];
+	struct mutex			lock;
 
 	/*
 	 * DMA (thus cache coherency maintenance) requires the
@@ -174,11 +176,12 @@ static int ad5755_write_ctrl_unlocked(struct iio_dev *indio_dev,
 static int ad5755_write(struct iio_dev *indio_dev, unsigned int reg,
 	unsigned int val)
 {
+	struct ad5755_state *st = iio_priv(indio_dev);
 	int ret;
 
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&st->lock);
 	ret = ad5755_write_unlocked(indio_dev, reg, val);
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&st->lock);
 
 	return ret;
 }
@@ -186,11 +189,12 @@ static int ad5755_write(struct iio_dev *indio_dev, unsigned int reg,
 static int ad5755_write_ctrl(struct iio_dev *indio_dev, unsigned int channel,
 	unsigned int reg, unsigned int val)
 {
+	struct ad5755_state *st = iio_priv(indio_dev);
 	int ret;
 
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&st->lock);
 	ret = ad5755_write_ctrl_unlocked(indio_dev, channel, reg, val);
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&st->lock);
 
 	return ret;
 }
@@ -211,7 +215,7 @@ static int ad5755_read(struct iio_dev *indio_dev, unsigned int addr)
 		},
 	};
 
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&st->lock);
 
 	st->data[0].d32 = cpu_to_be32(AD5755_READ_FLAG | (addr << 16));
 	st->data[1].d32 = cpu_to_be32(AD5755_NOOP);
@@ -220,7 +224,7 @@ static int ad5755_read(struct iio_dev *indio_dev, unsigned int addr)
 	if (ret >= 0)
 		ret = be32_to_cpu(st->data[1].d32) & 0xffff;
 
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&st->lock);
 
 	return ret;
 }
@@ -246,7 +250,7 @@ static int ad5755_set_channel_pwr_down(struct iio_dev *indio_dev,
 	struct ad5755_state *st = iio_priv(indio_dev);
 	unsigned int mask = BIT(channel);
 
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&st->lock);
 
 	if ((bool)(st->pwr_down & mask) == pwr_down)
 		goto out_unlock;
@@ -266,7 +270,7 @@ static int ad5755_set_channel_pwr_down(struct iio_dev *indio_dev,
 	}
 
 out_unlock:
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&st->lock);
 
 	return 0;
 }
@@ -746,6 +750,8 @@ static int ad5755_probe(struct spi_device *spi)
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->num_channels = AD5755_NUM_CHANNELS;
 
+	mutex_init(&st->lock);
+
 	if (spi->dev.of_node)
 		pdata = ad5755_parse_dt(&spi->dev);
 	else
-- 
2.17.1