iio: adc: at91: fix acking DRDY irq on simple conversions

When doing simple conversions, the driver did not acknowledge the DRDY irq.
If this irq status is not acked, it will be left pending, and as soon as a
trigger is enabled, the irq handler will be called, it doesn't know why
this status has occurred because no channel is pending, and then it will go
int a irq loop and board will hang.
To avoid this situation, read the LCDR after a raw conversion is done.

Fixes: 0e589d5fb ("ARM: AT91: IIO: Add AT91 ADC driver.")
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
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 44b516863c9d4d220f3323ca580d98fbb6f8e772..e3be88e7192c25a178c4b5759fd15cbe42b106c6 100644 (file)
--- a/drivers/iio/adc/at91_adc.c
+++ b/drivers/iio/adc/at91_adc.c
@@ -279,6 +279,8 @@ static void handle_adc_eoc_trigger(int irq, struct iio_dev *idev)
                iio_trigger_poll(idev->trig);
        } else {
                st->last_value = at91_adc_readl(st, AT91_ADC_CHAN(st, st->chnb));
+               /* Needed to ACK the DRDY interruption */
+               at91_adc_readl(st, AT91_ADC_LCDR);
                st->done = true;
                wake_up_interruptible(&st->wq_data_avail);
        }