linux-kernel - Re: [PATCH v3] Fix IRQ issue by setting IRQ_DISABLE

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Date:   Wed, 26 Apr 2023 21:02:13 +0900
From:   Masahiro Honda <honda@...hatrax.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] Fix IRQ issue by setting IRQ_DISABLE_UNLAZY flag

Hi Jonathan,

On Sun, Apr 23, 2023 at 7:59 PM Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Thu, 20 Apr 2023 19:23:16 +0900
> Masahiro Honda <honda@...hatrax.com> wrote:
>
> > 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@...hatrax.com>
> > ---
> > v3:
> >  - 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 | 25 ++++++++++++++++++++-----
> >  1 file changed, 20 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
> > index d8570f620..215ecbedb 100644
> > --- a/drivers/iio/adc/ad_sigma_delta.c
> > +++ b/drivers/iio/adc/ad_sigma_delta.c
> > @@ -565,6 +565,14 @@ int ad_sd_validate_trigger(struct iio_dev *indio_dev, struct iio_trigger *trig)
> >  }
> >  EXPORT_SYMBOL_NS_GPL(ad_sd_validate_trigger, IIO_AD_SIGMA_DELTA);
> >
> > +static void ad_sd_free_irq(void *sd)
> > +{
> > +     struct ad_sigma_delta *sigma_delta = sd;
> > +
> > +     irq_clear_status_flags(sigma_delta->spi->irq, IRQ_DISABLE_UNLAZY);
> > +     free_irq(sigma_delta->spi->irq, sigma_delta);
> > +}
>
> Don't fuse the two operations unwinding like this.  Just register a callback that only
> does the irq_clear_status_flags immediately after setting them.  Then leave
> the orginally devm_request_irq call alone.  If it fails, the devm cleanup will
> deal with the irq_clear_status_flag for you.
>
> It almost never makes sense for a single devm call to unwind more than one function call in
> a driver.
>
> Otherwise this looks fine to me,
>
> Thanks,
>
> Jonathan
>

I understand. I'll fix it.

Thanks,