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From:   Eugen Hristev <eugen.hristev@microchip.com>
To:     <jic23@kernel.org>, <ludovic.desroches@microchip.com>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <linux-iio@vger.kernel.org>
CC:     <nicolas.ferre@microchip.com>,
        Eugen Hristev <eugen.hristev@microchip.com>,
        Maxime Ripard <maxime.ripard@bootlin.com>
Subject: [PATCH v2 1/2] iio: adc: at91: fix acking DRDY irq on simple conversions
Date:   Mon, 24 Sep 2018 10:51:43 +0300
Message-ID: <1537775504-7981-1-git-send-email-eugen.hristev@microchip.com>
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Sender: linux-kernel-owner@vger.kernel.org
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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>
---
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@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