iio: dac: ad5421: 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/ad5421.c

@@ -62,12 +62,14 @@
  * @current_range:	current range which the device is configured for
  * @data:		spi transfer buffers
  * @fault_mask:		software masking of events
+ * @lock	lock to protect the data buffer during SPI ops
  */
 struct ad5421_state {
 	struct spi_device		*spi;
 	unsigned int			ctrl;
 	enum ad5421_current_range	current_range;
 	unsigned int			fault_mask;
+	struct mutex			lock;
 
 	/*
 	 * DMA (thus cache coherency maintenance) requires the
@@ -142,11 +144,12 @@ static int ad5421_write_unlocked(struct iio_dev *indio_dev,
 static int ad5421_write(struct iio_dev *indio_dev, unsigned int reg,
 	unsigned int val)
 {
+	struct ad5421_state *st = iio_priv(indio_dev);
 	int ret;
 
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&st->lock);
 	ret = ad5421_write_unlocked(indio_dev, reg, val);
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&st->lock);
 
 	return ret;
 }
@@ -166,7 +169,7 @@ static int ad5421_read(struct iio_dev *indio_dev, unsigned int reg)
 		},
 	};
 
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&st->lock);
 
 	st->data[0].d32 = cpu_to_be32((1 << 23) | (reg << 16));
 
@@ -174,7 +177,7 @@ static int ad5421_read(struct iio_dev *indio_dev, unsigned int reg)
 	if (ret >= 0)
 		ret = be32_to_cpu(st->data[1].d32) & 0xffff;
 
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&st->lock);
 
 	return ret;
 }
@@ -185,14 +188,14 @@ static int ad5421_update_ctrl(struct iio_dev *indio_dev, unsigned int set,
 	struct ad5421_state *st = iio_priv(indio_dev);
 	unsigned int ret;
 
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&st->lock);
 
 	st->ctrl &= ~clr;
 	st->ctrl |= set;
 
 	ret = ad5421_write_unlocked(indio_dev, AD5421_REG_CTRL, st->ctrl);
 
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&st->lock);
 
 	return ret;
 }
@@ -400,12 +403,12 @@ static int ad5421_write_event_config(struct iio_dev *indio_dev,
 		return -EINVAL;
 	}
 
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&st->lock);
 	if (state)
 		st->fault_mask |= mask;
 	else
 		st->fault_mask &= ~mask;
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&st->lock);
 
 	return 0;
 }
@@ -491,6 +494,8 @@ static int ad5421_probe(struct spi_device *spi)
 	indio_dev->channels = ad5421_channels;
 	indio_dev->num_channels = ARRAY_SIZE(ad5421_channels);
 
+	mutex_init(&st->lock);
+
 	st->ctrl = AD5421_CTRL_WATCHDOG_DISABLE |
 			AD5421_CTRL_AUTO_FAULT_READBACK;