[PATCH 02/16] iio: adc: at91-sama5d2_adc: lock around oversampling and sample freq

Claudiu Beznea
2022-06-09T08:30:04Z

.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 | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
index 32b6f157b803..a672a520cdc0 100644
--- a/drivers/iio/adc/at91-sama5d2_adc.c
+++ b/drivers/iio/adc/at91-sama5d2_adc.c
@@ -1542,10 +1542,11 @@ 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;
+ ret = at91_adc_adjust_val_osr(st, val);
mutex_unlock(&st->lock);
iio_device_release_direct_mode(indio_dev);

- return at91_adc_adjust_val_osr(st, val);
+ return ret;
}
if (chan->type == IIO_PRESSURE) {
ret = iio_device_claim_direct_mode(indio_dev);
@@ -1556,10 +1557,11 @@ 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;
+ ret = at91_adc_adjust_val_osr(st, val);
mutex_unlock(&st->lock);
iio_device_release_direct_mode(indio_dev);

- return at91_adc_adjust_val_osr(st, val);
+ return ret;
}

/* in this case we have a voltage channel */
@@ -1620,11 +1622,15 @@ static int at91_adc_read_raw(struct iio_dev *indio_dev,
return IIO_VAL_FRACTIONAL_LOG2;

case IIO_CHAN_INFO_SAMP_FREQ:
+ mutex_lock(&st->lock);
*val = at91_adc_get_sample_freq(st);
+ mutex_unlock(&st->lock);
return IIO_VAL_INT;

case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+ mutex_lock(&st->lock);
*val = st->oversampling_ratio;
+ mutex_unlock(&st->lock);
return IIO_VAL_INT;

default:
@@ -1644,18 +1650,23 @@ static int at91_adc_write_raw(struct iio_dev *indio_dev,
(val != AT91_OSR_16SAMPLES))
return -EINVAL;
/* if no change, optimize out */
+ mutex_lock(&st->lock);
if (val == st->oversampling_ratio)
- return 0;
+ goto unlock;
st->oversampling_ratio = val;
/* update ratio */
at91_adc_config_emr(st);
+unlock:
+ 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;
--
2.34.1