linux-kernel - Re: [PATCH] iio: adc: ad7768-1: disable IRQ autoenable

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Message-ID: <20250719130844.7559e322@jic23-huawei>
Date: Sat, 19 Jul 2025 13:08:44 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Nuno Sá <noname.nuno@...il.com>
Cc: Jonathan Santos <Jonathan.Santos@...log.com>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org, lars@...afoo.de,
 Michael.Hennerich@...log.com, dlechner@...libre.com, nuno.sa@...log.com,
 andy@...nel.org, jonath4nns@...il.com
Subject: Re: [PATCH] iio: adc: ad7768-1: disable IRQ autoenable

On Fri, 18 Jul 2025 10:18:56 +0100
Nuno Sá <noname.nuno@...il.com> wrote:

> On Thu, Jul 17, 2025 at 10:33:07PM -0300, Jonathan Santos wrote:
> > The device continuously converts data while powered up, generating
> > interrupts in the background. Configure the IRQ to be enabled and
> > disabled manually as needed to avoid unnecessary CPU load.

This generates interrupts continuously even when in oneshot mode?

> > 
> > Signed-off-by: Jonathan Santos <Jonathan.Santos@...log.com>
> > ---  
> 
> LGTM,
> 
> Reviewed-by: Nuno Sá <nuno.sa@...log.com>
> 
> >  drivers/iio/adc/ad7768-1.c | 18 +++++++++++++++++-
> >  1 file changed, 17 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
> > index a2e061f0cb08..3eea03c004c3 100644
> > --- a/drivers/iio/adc/ad7768-1.c
> > +++ b/drivers/iio/adc/ad7768-1.c
> > @@ -395,8 +395,10 @@ static int ad7768_scan_direct(struct iio_dev *indio_dev)
> >  	if (ret < 0)
> >  		return ret;
> >  
> > +	enable_irq(st->spi->irq);

Looks racey to me in a number of ways.

Before this patch:
In continuous mode, reinit_completion called then interrupt before we enter
 oneshot mode. What was captured? 

After this patch
Oneshot mode starts - hardware interrupt happens but enable_irq() is not set
so we miss it - or do we get another pulse later?

I'm not sure how to solve this as a device generating a stream of garbage
interrupts is near impossible to deal with.

I'm not following the datasheet description of this features vs the code 
though. It refers to oneshot mode requiring a pulse on sync in which I can't
find.

> >  	ret = wait_for_completion_timeout(&st->completion,
> >  					  msecs_to_jiffies(1000));
> > +	disable_irq(st->spi->irq);
> >  	if (!ret)
> >  		return -ETIMEDOUT;
> >  
> > @@ -1130,7 +1132,21 @@ static const struct iio_buffer_setup_ops ad7768_buffer_ops = {
> >  	.predisable = &ad7768_buffer_predisable,
> >  };
> >  
> > +static int ad7768_set_trigger_state(struct iio_trigger *trig, bool enable)
> > +{
> > +	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
> > +	struct ad7768_state *st = iio_priv(indio_dev);
> > +
> > +	if (enable)
> > +		enable_irq(st->spi->irq);
> > +	else
> > +		disable_irq(st->spi->irq);
> > +
> > +	return 0;
> > +}
> > +
> >  static const struct iio_trigger_ops ad7768_trigger_ops = {
> > +	.set_trigger_state = ad7768_set_trigger_state,
> >  	.validate_device = iio_trigger_validate_own_device,
> >  };
> >  
> > @@ -1417,7 +1433,7 @@ static int ad7768_probe(struct spi_device *spi)
> >  
> >  	ret = devm_request_irq(&spi->dev, spi->irq,
> >  			       &ad7768_interrupt,
> > -			       IRQF_TRIGGER_RISING | IRQF_ONESHOT,
> > +			       IRQF_TRIGGER_RISING | IRQF_NO_AUTOEN,

Why drop oneshot?

> >  			       indio_dev->name, indio_dev);
> >  	if (ret)
> >  		return ret;
> > 
> > base-commit: 0a686b9c4f847dc21346df8e56d5b119918fefef
> > -- 
> > 2.34.1
> >   
>