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

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Message-ID: <aIPilIRYMgKcSjZW@JSANTO12-L01.ad.analog.com>
Date: Fri, 25 Jul 2025 17:01:24 -0300
From: Jonathan Santos <jonath4nns@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Nuno Sá <noname.nuno@...il.com>,
	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
Subject: Re: [PATCH] iio: adc: ad7768-1: disable IRQ autoenable

On 07/19, Jonathan Cameron wrote:
> 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?
> 

No, but oneshot mode is only enabled for a brief moment when reading the raw data. The rest of the time it stays in continuous conversion mode because datasheet says it is necessary to make configuration changes.

> > > 
> > > 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?
> 

After some debugging, i think the device gets the last interrupt before
getting into oneshot mode because I don't see any DRDY later. it should have a sync_in pulse after to
update the data value, as you said.

> 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.
> 

If we made something like this wouldn't sufice?

...
	reinit_completion(&st->completion);

	ret = ad7768_set_mode(st, AD7768_ONE_SHOT);
	if (ret < 0)
		return ret;

	enable_irq(st->spi->irq);
	ad7768_send_sync_pulse(st);

	ret = wait_for_completion_timeout(&st->completion,
					  msecs_to_jiffies(1000));
	disable_irq(st->spi->irq);
	if (!ret)
		return -ETIMEDOUT;
...


> > >  	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
> > >   
> > 
>