[PATCH v4] Fix IRQ issue by setting IRQ_DISABLE_UNLAZY flag

[Masahiro Honda <honda@mechatrax.com>]

The Sigma-Delta ADCs supported by this driver can use SDO as an interrupt
line to indicate the completion of a conversion. However, some devices
cannot properly detect the completion of a conversion by an interrupt.
This is for the reason mentioned in the following commit.

commit e9849777d0e2 ("genirq: Add flag to force mask in
                      disable_irq[_nosync]()")

A read operation is performed by an extra interrupt before the completion
of a conversion. This patch fixes the issue by setting IRQ_DISABLE_UNLAZY
flag.

Signed-off-by: Masahiro Honda <honda@mechatrax.com>
---
v4:
 - Remove the callback.
v3: https://lore.kernel.org/linux-iio/20230420102316.757-1-honda@mechatrax.com/
 - Remove the Kconfig option.
v2: https://lore.kernel.org/linux-iio/20230414102744.150-1-honda@mechatrax.com/
 - Rework commit message.
 - Add a new entry in the Kconfig.
 - Call irq_clear_status_flags(irq, IRQ_DISABLE_UNLAZY) when freeing the IRQ.
v1: https://lore.kernel.org/linux-iio/20230306044737.862-1-honda@mechatrax.com/

 drivers/iio/adc/ad_sigma_delta.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
index d8570f6207..7e21928707 100644
--- a/drivers/iio/adc/ad_sigma_delta.c
+++ b/drivers/iio/adc/ad_sigma_delta.c
@@ -584,6 +584,10 @@ static int devm_ad_sd_probe_trigger(struct device *dev, struct iio_dev *indio_de
 	init_completion(&sigma_delta->completion);
 
 	sigma_delta->irq_dis = true;
+
+	/* the IRQ core clears IRQ_DISABLE_UNLAZY flag when freeing an IRQ */
+	irq_set_status_flags(sigma_delta->spi->irq, IRQ_DISABLE_UNLAZY);
+
 	ret = devm_request_irq(dev, sigma_delta->spi->irq,
 			       ad_sd_data_rdy_trig_poll,
 			       sigma_delta->info->irq_flags | IRQF_NO_AUTOEN,
-- 
2.34.1