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Subject[PATCH] iio: adc: at91: disable adc channel interrupt in timeout case
Date
From: Georg Ottinger <g.ottinger@abatec.at>

Having a brief look at at91_adc_read_raw() it is obvious that in the case
of a timeout the setting of AT91_ADC_CHDR and AT91_ADC_IDR registers is
omitted. If 2 different channels are queried we can end up with a
situation where two interrupts are enabled, but only one interrupt is
cleared in the interrupt handler. Resulting in a interrupt loop and a
system hang.

Signed-off-by: Georg Ottinger <g.ottinger@abatec.at>
---
drivers/iio/adc/at91_adc.c | 28 +++++++++++++++++-----------
1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index 75d2f7358..596841a3c 100644
--- a/drivers/iio/adc/at91_adc.c
+++ b/drivers/iio/adc/at91_adc.c
@@ -704,23 +704,29 @@ static int at91_adc_read_raw(struct iio_dev *idev,
ret = wait_event_interruptible_timeout(st->wq_data_avail,
st->done,
msecs_to_jiffies(1000));
- if (ret == 0)
- ret = -ETIMEDOUT;
- if (ret < 0) {
- mutex_unlock(&st->lock);
- return ret;
- }
-
- *val = st->last_value;

+ /* Disable interrupts, regardless if adc conversion was
+ * successful or not
+ */
at91_adc_writel(st, AT91_ADC_CHDR,
AT91_ADC_CH(chan->channel));
at91_adc_writel(st, AT91_ADC_IDR, BIT(chan->channel));

- st->last_value = 0;
- st->done = false;
+ if (ret > 0) {
+ /* a valid conversion took place */
+ *val = st->last_value;
+ st->last_value = 0;
+ st->done = false;
+ ret = IIO_VAL_INT;
+ } else if (ret == 0) {
+ /* conversion timeout */
+ dev_err(&idev->dev, "ADC Channel %d timeout.\n",
+ chan->channel);
+ ret = -ETIMEDOUT;
+ }
+
mutex_unlock(&st->lock);
- return IIO_VAL_INT;
+ return ret;

case IIO_CHAN_INFO_SCALE:
*val = st->vref_mv;
--
2.17.1
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