[PATCH v2] Staging: iio: ade7758: expand buf_lock to cover both buffer and state protection

[Shreeya Patel <shreeya.patel23498@gmail.com>]

iio_dev->mlock is to be used only by the IIO core for protecting
device mode changes between INDIO_DIRECT and INDIO_BUFFER.

This patch replaces the use of mlock with the already established
buf_lock mutex.

Introducing 'unlocked' __ade7758_spi_write_reg_8 and
__ade7758_spi_read_reg_8 functions to be used by ade7758_write_samp_freq
and ade7758_read_samp_freq which avoids nested locks and maintains
atomicity between bus and device frequency changes.

Signed-off-by: Shreeya Patel <shreeya.patel23498@gmail.com>
---

Changes in v2
  -Add static keyword to newly introduced functions and remove some
added comments which are not required.


 drivers/staging/iio/meter/ade7758.h      |  2 +-
 drivers/staging/iio/meter/ade7758_core.c | 47 +++++++++++++++++++++++---------
 2 files changed, 35 insertions(+), 14 deletions(-)

diff --git a/drivers/staging/iio/meter/ade7758.h b/drivers/staging/iio/meter/ade7758.h
index 6ae78d8..2de81b5 100644
--- a/drivers/staging/iio/meter/ade7758.h
+++ b/drivers/staging/iio/meter/ade7758.h
@@ -111,7 +111,7 @@
  * @trig:		data ready trigger registered with iio
  * @tx:			transmit buffer
  * @rx:			receive buffer
- * @buf_lock:		mutex to protect tx and rx
+ * @buf_lock:		mutex to protect tx, rx, read and write frequency
  **/
 struct ade7758_state {
 	struct spi_device	*us;
diff --git a/drivers/staging/iio/meter/ade7758_core.c b/drivers/staging/iio/meter/ade7758_core.c
index 7b7ffe5..fed4684 100644
--- a/drivers/staging/iio/meter/ade7758_core.c
+++ b/drivers/staging/iio/meter/ade7758_core.c
@@ -24,17 +24,25 @@
 #include "meter.h"
 #include "ade7758.h"
 
-int ade7758_spi_write_reg_8(struct device *dev, u8 reg_address, u8 val)
+static int __ade7758_spi_write_reg_8(struct device *dev, u8 reg_address, u8 val)
 {
-	int ret;
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct ade7758_state *st = iio_priv(indio_dev);
 
-	mutex_lock(&st->buf_lock);
 	st->tx[0] = ADE7758_WRITE_REG(reg_address);
 	st->tx[1] = val;
 
-	ret = spi_write(st->us, st->tx, 2);
+	return spi_write(st->us, st->tx, 2);
+}
+
+int ade7758_spi_write_reg_8(struct device *dev, u8 reg_address, u8 val)
+{
+	int ret;
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct ade7758_state *st = iio_priv(indio_dev);
+
+	mutex_lock(&st->buf_lock);
+	ret = __ade7758_spi_write_reg_8(dev, reg_address, val);
 	mutex_unlock(&st->buf_lock);
 
 	return ret;
@@ -91,7 +99,7 @@ static int ade7758_spi_write_reg_24(struct device *dev, u8 reg_address,
 	return ret;
 }
 
-int ade7758_spi_read_reg_8(struct device *dev, u8 reg_address, u8 *val)
+static int __ade7758_spi_read_reg_8(struct device *dev, u8 reg_address, u8 *val)
 {
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct ade7758_state *st = iio_priv(indio_dev);
@@ -111,7 +119,6 @@ int ade7758_spi_read_reg_8(struct device *dev, u8 reg_address, u8 *val)
 		},
 	};
 
-	mutex_lock(&st->buf_lock);
 	st->tx[0] = ADE7758_READ_REG(reg_address);
 	st->tx[1] = 0;
 
@@ -124,7 +131,19 @@ int ade7758_spi_read_reg_8(struct device *dev, u8 reg_address, u8 *val)
 	*val = st->rx[0];
 
 error_ret:
+	return ret;
+}
+
+int ade7758_spi_read_reg_8(struct device *dev, u8 reg_address, u8 *val)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct ade7758_state *st = iio_priv(indio_dev);
+	int ret;
+
+	mutex_lock(&st->buf_lock);
+	ret = __ade7758_spi_read_reg_8(dev, reg_address, val);
 	mutex_unlock(&st->buf_lock);
+
 	return ret;
 }
 
@@ -470,7 +489,7 @@ static int ade7758_read_samp_freq(struct device *dev, int *val)
 	int ret;
 	u8 t;
 
-	ret = ade7758_spi_read_reg_8(dev, ADE7758_WAVMODE, &t);
+	ret = __ade7758_spi_read_reg_8(dev, ADE7758_WAVMODE, &t);
 	if (ret)
 		return ret;
 
@@ -503,14 +522,14 @@ static int ade7758_write_samp_freq(struct device *dev, int val)
 		goto out;
 	}
 
-	ret = ade7758_spi_read_reg_8(dev, ADE7758_WAVMODE, &reg);
+	ret = __ade7758_spi_read_reg_8(dev, ADE7758_WAVMODE, &reg);
 	if (ret)
 		goto out;
 
 	reg &= ~(5 << 3);
 	reg |= t << 5;
 
-	ret = ade7758_spi_write_reg_8(dev, ADE7758_WAVMODE, reg);
+	ret = __ade7758_spi_write_reg_8(dev, ADE7758_WAVMODE, reg);
 
 out:
 	return ret;
@@ -523,12 +542,13 @@ static int ade7758_read_raw(struct iio_dev *indio_dev,
 			    long mask)
 {
 	int ret;
+	struct ade7758_state *st = iio_priv(indio_dev);
 
 	switch (mask) {
 	case IIO_CHAN_INFO_SAMP_FREQ:
-		mutex_lock(&indio_dev->mlock);
+		mutex_lock(&st->buf_lock);
 		ret = ade7758_read_samp_freq(&indio_dev->dev, val);
-		mutex_unlock(&indio_dev->mlock);
+		mutex_unlock(&st->buf_lock);
 		return ret;
 	default:
 		return -EINVAL;
@@ -542,14 +562,15 @@ static int ade7758_write_raw(struct iio_dev *indio_dev,
 			     int val, int val2, long mask)
 {
 	int ret;
+	struct ade7758_state *st = iio_priv(indio_dev);
 
 	switch (mask) {
 	case IIO_CHAN_INFO_SAMP_FREQ:
 		if (val2)
 			return -EINVAL;
-		mutex_lock(&indio_dev->mlock);
+		mutex_lock(&st->buf_lock);
 		ret = ade7758_write_samp_freq(&indio_dev->dev, val);
-		mutex_unlock(&indio_dev->mlock);
+		mutex_unlock(&st->buf_lock);
 		return ret;
 	default:
 		return -EINVAL;
-- 
2.7.4