[PATCH 02/15] iio: adc: ad799x: do not use internal iio_dev lock

["Nuno Sá" <nuno.sa@analog.com>]

'mlock' was being grabbed when setting the device frequency. In order to
not introduce any functional change a new lock is added. With that in
mind, the lock also needs to be grabbed in the places where 'mlock' is.

On the other places the lock was being used, we can just drop
it since we are only doing one i2c bus read/write which is already
safe.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
---
 drivers/iio/adc/ad799x.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/adc/ad799x.c b/drivers/iio/adc/ad799x.c
index 262bd7665b33..838ba8e77de1 100644
--- a/drivers/iio/adc/ad799x.c
+++ b/drivers/iio/adc/ad799x.c
@@ -28,6 +28,7 @@
 #include <linux/types.h>
 #include <linux/err.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/bitops.h>
 
 #include <linux/iio/iio.h>
@@ -125,6 +126,8 @@ struct ad799x_state {
 	const struct ad799x_chip_config	*chip_config;
 	struct regulator		*reg;
 	struct regulator		*vref;
+	/* lock to protect against multiple access to the device */
+	struct mutex			lock;
 	unsigned			id;
 	u16				config;
 
@@ -290,7 +293,9 @@ static int ad799x_read_raw(struct iio_dev *indio_dev,
 		ret = iio_device_claim_direct_mode(indio_dev);
 		if (ret)
 			return ret;
+		mutex_lock(&st->lock);
 		ret = ad799x_scan_direct(st, chan->scan_index);
+		mutex_unlock(&st->lock);
 		iio_device_release_direct_mode(indio_dev);
 
 		if (ret < 0)
@@ -351,7 +356,8 @@ static ssize_t ad799x_write_frequency(struct device *dev,
 	if (ret)
 		return ret;
 
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&st->lock);
+
 	ret = i2c_smbus_read_byte_data(st->client, AD7998_CYCLE_TMR_REG);
 	if (ret < 0)
 		goto error_ret_mutex;
@@ -373,7 +379,7 @@ static ssize_t ad799x_write_frequency(struct device *dev,
 	ret = len;
 
 error_ret_mutex:
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&st->lock);
 
 	return ret;
 }
@@ -407,6 +413,8 @@ static int ad799x_write_event_config(struct iio_dev *indio_dev,
 	if (ret)
 		return ret;
 
+	mutex_lock(&st->lock);
+
 	if (state)
 		st->config |= BIT(chan->scan_index) << AD799X_CHANNEL_SHIFT;
 	else
@@ -418,6 +426,7 @@ static int ad799x_write_event_config(struct iio_dev *indio_dev,
 		st->config &= ~AD7998_ALERT_EN;
 
 	ret = ad799x_write_config(st, st->config);
+	mutex_unlock(&st->lock);
 	iio_device_release_direct_mode(indio_dev);
 	return ret;
 }
@@ -454,11 +463,9 @@ static int ad799x_write_event_value(struct iio_dev *indio_dev,
 	if (val < 0 || val > GENMASK(chan->scan_type.realbits - 1, 0))
 		return -EINVAL;
 
-	mutex_lock(&indio_dev->mlock);
 	ret = i2c_smbus_write_word_swapped(st->client,
 		ad799x_threshold_reg(chan, dir, info),
 		val << chan->scan_type.shift);
-	mutex_unlock(&indio_dev->mlock);
 
 	return ret;
 }
@@ -473,10 +480,8 @@ static int ad799x_read_event_value(struct iio_dev *indio_dev,
 	int ret;
 	struct ad799x_state *st = iio_priv(indio_dev);
 
-	mutex_lock(&indio_dev->mlock);
 	ret = i2c_smbus_read_word_swapped(st->client,
 		ad799x_threshold_reg(chan, dir, info));
-	mutex_unlock(&indio_dev->mlock);
 	if (ret < 0)
 		return ret;
 	*val = (ret >> chan->scan_type.shift) &
@@ -785,6 +790,7 @@ static int ad799x_probe(struct i2c_client *client,
 		return -ENOMEM;
 
 	st = iio_priv(indio_dev);
+	mutex_init(&st->lock);
 	/* this is only used for device removal purposes */
 	i2c_set_clientdata(client, indio_dev);
 
-- 
2.37.3