iio: adc: at91-sama5d2_adc: lock around oversampling and sample freq

.read_raw()/.write_raw() could be called asynchronously from user space
or other in kernel drivers. Without locking on st->lock these could be
called asynchronously while there is a conversion in progress. Read will
be harmless but changing registers while conversion is in progress may
lead to inconsistent results. Thus, to avoid this lock st->lock.

Fixes: 27e177190891 ("iio:adc:at91_adc8xx: introduce new atmel adc driver")
Fixes: 6794e23fa3fe ("iio: adc: at91-sama5d2_adc: add support for oversampling resolution")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220803102855.2191070-4-claudiu.beznea@microchip.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
index 08d1f806c839861c18681759af0181fc49529bc3..3734ddc82952c5dcd0f130b7ee8cad496b2d4cb9 100644 (file)
--- a/drivers/iio/adc/at91-sama5d2_adc.c
+++ b/drivers/iio/adc/at91-sama5d2_adc.c
@@ -1542,10 +1542,10 @@ static int at91_adc_read_info_raw(struct iio_dev *indio_dev,
                ret = at91_adc_read_position(st, chan->channel,
                                             &tmp_val);
                *val = tmp_val;
-               mutex_unlock(&st->lock);
-               iio_device_release_direct_mode(indio_dev);
                if (ret > 0)
                        ret = at91_adc_adjust_val_osr(st, val);
+               mutex_unlock(&st->lock);
+               iio_device_release_direct_mode(indio_dev);
 
                return ret;
        }
@@ -1558,10 +1558,10 @@ static int at91_adc_read_info_raw(struct iio_dev *indio_dev,
                ret = at91_adc_read_pressure(st, chan->channel,
                                             &tmp_val);
                *val = tmp_val;
-               mutex_unlock(&st->lock);
-               iio_device_release_direct_mode(indio_dev);
                if (ret > 0)
                        ret = at91_adc_adjust_val_osr(st, val);
+               mutex_unlock(&st->lock);
+               iio_device_release_direct_mode(indio_dev);
 
                return ret;
        }
@@ -1650,16 +1650,20 @@ static int at91_adc_write_raw(struct iio_dev *indio_dev,
                /* if no change, optimize out */
                if (val == st->oversampling_ratio)
                        return 0;
+               mutex_lock(&st->lock);
                st->oversampling_ratio = val;
                /* update ratio */
                at91_adc_config_emr(st);
+               mutex_unlock(&st->lock);
                return 0;
        case IIO_CHAN_INFO_SAMP_FREQ:
                if (val < st->soc_info.min_sample_rate ||
                    val > st->soc_info.max_sample_rate)
                        return -EINVAL;
 
+               mutex_lock(&st->lock);
                at91_adc_setup_samp_freq(indio_dev, val);
+               mutex_unlock(&st->lock);
                return 0;
        default:
                return -EINVAL;