[PATCH v2 03/19] iio: adc: at91-sama5d2_adc: lock around oversampling and sample freq

Claudiu Beznea
2022-06-28T15:18:55Z

.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>
---
drivers/iio/adc/at91-sama5d2_adc.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
index c3301c749164..40a95d2fd5c8 100644
--- 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;