linux-kernel - [PATCH] iio: ad_sigma_delta: Add custom irq flags

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Date:   Mon, 6 Jan 2020 12:57:47 +0200
From:   Alexandru Tachici <alexandru.tachici@...log.com>
To:     <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <jic23@...nel.org>,
        Alexandru Tachici <alexandru.tachici@...log.com>
Subject: [PATCH] iio: ad_sigma_delta: Add custom irq flags

The data-sheet of AD7124, from the Sigma-Delta ADC family,
recommends that the falling edge of the DOUT line should be used for
an interrupt.

The ad_sigma_delta implementation hardcodes the irq trigger type
to low, assuming that all Sigma-Delta ADCs have the same interrupt-type.
This causes unwanted behaviour. If DOUT line is already low, the
interrupt will fire once, when enabled and the irq handler will send a
read request to the device. At this time the device has not yet finished
the previous conversion and will give a bad reading.

This patch allows drivers using the ad_sigma_delta layer to set the
irq trigger type to the one specified in the corresponding data-sheet.

Signed-off-by: Alexandru Tachici <alexandru.tachici@...log.com>
---
 drivers/iio/adc/ad_sigma_delta.c       | 9 ++++++++-
 include/linux/iio/adc/ad_sigma_delta.h | 2 ++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
index d10bd0c97233..0007df8d50fb 100644
--- a/drivers/iio/adc/ad_sigma_delta.c
+++ b/drivers/iio/adc/ad_sigma_delta.c
@@ -454,7 +454,7 @@ static int ad_sd_probe_trigger(struct iio_dev *indio_dev)
 
 	ret = request_irq(sigma_delta->spi->irq,
 			  ad_sd_data_rdy_trig_poll,
-			  IRQF_TRIGGER_LOW,
+			  sigma_delta->irq_flags,
 			  indio_dev->name,
 			  sigma_delta);
 	if (ret)
@@ -540,8 +540,15 @@ EXPORT_SYMBOL_GPL(ad_sd_cleanup_buffer_and_trigger);
 int ad_sd_init(struct ad_sigma_delta *sigma_delta, struct iio_dev *indio_dev,
 	struct spi_device *spi, const struct ad_sigma_delta_info *info)
 {
+	unsigned long set_trigger_flags;
+
 	sigma_delta->spi = spi;
 	sigma_delta->info = info;
+
+	set_trigger_flags = sigma_delta->irq_flags & IRQF_TRIGGER_MASK;
+	if (set_trigger_flags == IRQF_TRIGGER_NONE)
+		sigma_delta->irq_flags |= IRQF_TRIGGER_LOW;
+
 	iio_device_set_drvdata(indio_dev, sigma_delta);
 
 	return 0;
diff --git a/include/linux/iio/adc/ad_sigma_delta.h b/include/linux/iio/adc/ad_sigma_delta.h
index 5ba430cc9a87..94a91731c8e8 100644
--- a/include/linux/iio/adc/ad_sigma_delta.h
+++ b/include/linux/iio/adc/ad_sigma_delta.h
@@ -53,6 +53,7 @@ struct ad_sigma_delta_info {
  * struct ad_sigma_delta - Sigma Delta device struct
  * @spi: The spi device associated with the Sigma Delta device.
  * @trig: The IIO trigger associated with the Sigma Delta device.
+ * @irq_flags: flags for the interrupt used by the triggered buffer
  *
  * Most of the fields are private to the sigma delta library code and should not
  * be accessed by individual drivers.
@@ -60,6 +61,7 @@ struct ad_sigma_delta_info {
 struct ad_sigma_delta {
 	struct spi_device	*spi;
 	struct iio_trigger	*trig;
+	unsigned long		irq_flags;
 
 /* private: */
 	struct completion	completion;
-- 
2.20.1