iio: adc: ltc2947-core: do not use internal iio_dev lock

The iio_device lock is only meant for internal use. Hence define a
device local lock to protect against concurrent accesses.

While at it, properly include "mutex.h" for mutex related APIs.
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20221004134909.1692021-6-nuno.sa@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ltc2497-core.c

@@ -10,6 +10,7 @@
 #include <linux/iio/iio.h>
 #include <linux/iio/driver.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/regulator/consumer.h>
 
 #include "ltc2497.h"
@@ -81,9 +82,9 @@ static int ltc2497core_read_raw(struct iio_dev *indio_dev,
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
-		mutex_lock(&indio_dev->mlock);
+		mutex_lock(&ddata->lock);
 		ret = ltc2497core_read(ddata, chan->address, val);
-		mutex_unlock(&indio_dev->mlock);
+		mutex_unlock(&ddata->lock);
 		if (ret < 0)
 			return ret;
 
@@ -214,6 +215,8 @@ int ltc2497core_probe(struct device *dev, struct iio_dev *indio_dev)
 	ddata->addr_prev = LTC2497_CONFIG_DEFAULT;
 	ddata->time_prev = ktime_get();
 
+	mutex_init(&ddata->lock);
+
 	ret = iio_device_register(indio_dev);
 	if (ret < 0)
 		goto err_array_unregister;

drivers/iio/adc/ltc2497.h

@@ -12,6 +12,8 @@ struct ltc2497_chip_info {
 struct ltc2497core_driverdata {
 	struct regulator *ref;
 	ktime_t	time_prev;
+	/* lock to protect against multiple access to the device */
+	struct mutex lock;
 	const struct ltc2497_chip_info	*chip_info;
 	u8 addr_prev;
 	int (*result_and_measure)(struct ltc2497core_driverdata *ddata,