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

commit bc1b45326223e7e890053cf6266357adfa61942d upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index 15109728cae79dde2ca248db0f92a97cc62f1849..8882b80419f6e348082811309b2ccce90a9d68cd 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);
        }