iio: adc: at91-sama5d2_adc: exit from write_raw() when buffers are enabled

When buffers are enabled conversion may start asynchronously thus
allowing changes on actual hardware could lead to bad behavior. Thus
do not allow changing oversampling ratio and sample frequency when
if iio_device_claim_direct_mode() returns with error.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220803102855.2191070-6-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 e2c82c5a2fac0cf72500724e25c69fe9a0a51f4a..64943d8ea86926cc336c0f69dbfbc4b326b5c817 100644 (file)
--- a/drivers/iio/adc/at91-sama5d2_adc.c
+++ b/drivers/iio/adc/at91-sama5d2_adc.c
@@ -1641,6 +1641,7 @@ static int at91_adc_write_raw(struct iio_dev *indio_dev,
                              int val, int val2, long mask)
 {
        struct at91_adc_state *st = iio_priv(indio_dev);
+       int ret;
 
        switch (mask) {
        case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
@@ -1650,20 +1651,29 @@ static int at91_adc_write_raw(struct iio_dev *indio_dev,
                /* if no change, optimize out */
                if (val == st->oversampling_ratio)
                        return 0;
+
+               ret = iio_device_claim_direct_mode(indio_dev);
+               if (ret)
+                       return ret;
                mutex_lock(&st->lock);
                st->oversampling_ratio = val;
                /* update ratio */
                at91_adc_config_emr(st);
                mutex_unlock(&st->lock);
+               iio_device_release_direct_mode(indio_dev);
                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;
 
+               ret = iio_device_claim_direct_mode(indio_dev);
+               if (ret)
+                       return ret;
                mutex_lock(&st->lock);
                at91_adc_setup_samp_freq(indio_dev, val);
                mutex_unlock(&st->lock);
+               iio_device_release_direct_mode(indio_dev);
                return 0;
        default:
                return -EINVAL;