linux-kernel - [PATCH 5.10 052/103] iio: adc: ad7780: Fix IRQ flag

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Date:   Mon, 18 Oct 2021 15:24:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Alexandru Tachici <alexandru.tachici@...log.com>,
        Stable@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: [PATCH 5.10 052/103] iio: adc: ad7780: Fix IRQ flag

From: Alexandru Tachici <alexandru.tachici@...log.com>

commit e081102f3077aa716974ccebec97003c890d5641 upstream.

Correct IRQ flag here is falling.

In Sigma-Delta devices the SDO line is also used as an interrupt.
Leaving IRQ on level instead of falling might trigger a sample read
when the IRQ is enabled, as the SDO line is already low. Not sure
if SDO line will always immediately go high in ad_sd_buffer_postenable
before the IRQ is enabled.

Also the datasheet seem to explicitly say the falling edge of the SDO
should be used as an interrupt:
>>From the AD7780 datasheet: " The DOUT/Figure 22 RDY falling edge
can be used as an interrupt to a processor"

Fixes: da4d3d6bb9f6 ("iio: adc: ad-sigma-delta: Allow custom IRQ flags")
Signed-off-by: Alexandru Tachici <alexandru.tachici@...log.com>
Cc: <Stable@...r.kernel.org>
Link: https://lore.kernel.org/r/20210906065630.16325-3-alexandru.tachici@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/iio/adc/ad7780.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/iio/adc/ad7780.c
+++ b/drivers/iio/adc/ad7780.c
@@ -203,7 +203,7 @@ static const struct ad_sigma_delta_info
 	.set_mode = ad7780_set_mode,
 	.postprocess_sample = ad7780_postprocess_sample,
 	.has_registers = false,
-	.irq_flags = IRQF_TRIGGER_LOW,
+	.irq_flags = IRQF_TRIGGER_FALLING,
 };
 
 #define _AD7780_CHANNEL(_bits, _wordsize, _mask_all)		\