iio: adc: at91: disable adc channel interrupt in timeout case

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>

diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index 75d2f73..596841a 100644 (file)
--- 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;