[PATCH 4.19 44/96] iio: adc: at91: disable adc channel interrupt in timeout case

Greg Kroah-Hartman
2019-04-24T17:31:10Z

From: Georg Ottinger <g.ottinger@abatec.at>

commit 09c6bdee51183a575bf7546890c8c137a75a2b44 upstream.

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>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/iio/adc/at91_adc.c | 28 +++++++++++++++++-----------
1 file changed, 17 insertions(+), 11 deletions(-)

--- 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_
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;