iio: adc: rockchip_saradc: 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>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20221004134909.1692021-8-nuno.sa@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/rockchip_saradc.c

@@ -5,6 +5,7 @@
  */
 
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/platform_device.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
@@ -49,6 +50,8 @@ struct rockchip_saradc {
 	struct clk		*clk;
 	struct completion	completion;
 	struct regulator	*vref;
+	/* lock to protect against multiple access to the device */
+	struct mutex		lock;
 	int			uv_vref;
 	struct reset_control	*reset;
 	const struct rockchip_saradc_data *data;
@@ -94,17 +97,17 @@ static int rockchip_saradc_read_raw(struct iio_dev *indio_dev,
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
-		mutex_lock(&indio_dev->mlock);
+		mutex_lock(&info->lock);
 
 		ret = rockchip_saradc_conversion(info, chan);
 		if (ret) {
 			rockchip_saradc_power_down(info);
-			mutex_unlock(&indio_dev->mlock);
+			mutex_unlock(&info->lock);
 			return ret;
 		}
 
 		*val = info->last_val;
-		mutex_unlock(&indio_dev->mlock);
+		mutex_unlock(&info->lock);
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		*val = info->uv_vref / 1000;
@@ -270,7 +273,7 @@ static irqreturn_t rockchip_saradc_trigger_handler(int irq, void *p)
 	int ret;
 	int i, j = 0;
 
-	mutex_lock(&i_dev->mlock);
+	mutex_lock(&info->lock);
 
 	for_each_set_bit(i, i_dev->active_scan_mask, i_dev->masklength) {
 		const struct iio_chan_spec *chan = &i_dev->channels[i];
@@ -287,7 +290,7 @@ static irqreturn_t rockchip_saradc_trigger_handler(int irq, void *p)
 
 	iio_push_to_buffers_with_timestamp(i_dev, &data, iio_get_time_ns(i_dev));
 out:
-	mutex_unlock(&i_dev->mlock);
+	mutex_unlock(&info->lock);
 
 	iio_trigger_notify_done(i_dev->trig);
 
@@ -478,6 +481,8 @@ static int rockchip_saradc_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	mutex_init(&info->lock);
+
 	return devm_iio_device_register(&pdev->dev, indio_dev);
 }