[PATCH v2 1/2] iio: adc: at91: fix acking DRDY irq on simple conversions

On Tue, 25 Sep 2018 15:17:39 +0200
Ludovic Desroches [off-list ref] wrote:

On Mon, Sep 24, 2018 at 10:51:43AM +0300, Eugen Hristev wrote:

quoted

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 <redacted>
Signed-off-by: Eugen Hristev <redacted>  

Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com> 

Applied to the togreg branch of iio.git and marked for stable.

It's been broken long enough that I think it can wait for the merge window
coming in a few weeks time.

Thanks,

Jonathan

quoted

---
Hello Jonathan,

I moved this LCDR read/acknowledge into the IRQ handler after the conversion
value is being read.
Sorry about the noise to stable at vger, removed from message.

Thanks,
Eugen

 drivers/iio/adc/at91_adc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index 44b5168..e3be88e 100644
--- 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);
 	}

-- 
2.7.4