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

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Date:   Mon, 24 Sep 2018 10:51:43 +0300
From:   Eugen Hristev <eugen.hristev@...rochip.com>
To:     <jic23@...nel.org>, <ludovic.desroches@...rochip.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-iio@...r.kernel.org>
CC:     <nicolas.ferre@...rochip.com>,
        Eugen Hristev <eugen.hristev@...rochip.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>
Subject: [PATCH v2 1/2] 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@...tlin.com>
Signed-off-by: Eugen Hristev <eugen.hristev@...rochip.com>
---
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@...r, 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