linux-kernel - Re: [PATCH v4] Fix IRQ issue by setting IRQ_DISABLE

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Message-ID: <CA+Tz-SHF9+GxVD+U88tTxG4LYCC9BXSQKpVHL3E0eni+fRrgkQ@mail.gmail.com>
Date:   Mon, 8 May 2023 18:45:36 +0900
From:   Masahiro Honda <honda@...hatrax.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Nuno Sá <noname.nuno@...il.com>,
        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 v4] Fix IRQ issue by setting IRQ_DISABLE_UNLAZY flag

Hi Jonathan,

Thank you for your advice.

On Sun, May 7, 2023 at 11:45 PM Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Wed, 03 May 2023 10:09:28 +0200
> Nuno Sá <noname.nuno@...il.com> wrote:
>
> Patch title should be something like the following so it's easy to see what
> is affected when looking at a long list of patches.
>
> iio: adc: ad_sigma_delta: Fix IRQ issue by setting IRQ_DISABLE_UNLAZY flag.
>

I'll fix the title.

>
> > On Tue, 2023-05-02 at 19:29 +0900, Masahiro Honda 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>
> > > ---
> >
> > Reviewed-by: Nuno Sá <nuno.sa@...log.com>
>
> Fixes tag?  We'll want to know how far to backport this.  I assume it's
> limited by the above commit as these drivers are older than that.
>

I'll try to add a fixes tag.

> I'm also not totally sure what this 'looks like' for a user.  What happens?
> Fail to read, wrong value, lock up or something else?  It would be helpful
> to include that information in case anyone else runs into this.
>

I'll add information to the commit message.

Regards,

Masahiro


> Actual change looks right to me.
>
> Thanks,
>
> Jonathan
>
>
> >
> > > 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,
> >
>