linux-kernel - Re: [PATCH v2] Input: atmel_mxt_ts

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Date:   Mon, 30 Sep 2019 08:29:06 -0700
From:   Evan Green <evgreen@...omium.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Nick Dyer <nick@...anahar.org>,
        Jongpil Jung <jongpil19.jung@...sung.com>,
        Furquan Shaikh <furquan@...omium.org>,
        Rajat Jain <rajatja@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-input@...r.kernel.org
Subject: Re: [PATCH v2] Input: atmel_mxt_ts - Disable IRQ across suspend

On Fri, Sep 27, 2019 at 5:16 PM Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
>
> Hi Evan,
>
> On Tue, Sep 24, 2019 at 02:52:38PM -0700, Evan Green wrote:
> > Across suspend and resume, we are seeing error messages like the following:
> >
> > atmel_mxt_ts i2c-PRP0001:00: __mxt_read_reg: i2c transfer failed (-121)
> > atmel_mxt_ts i2c-PRP0001:00: Failed to read T44 and T5 (-121)
> >
> > This occurs because the driver leaves its IRQ enabled. Upon resume, there
> > is an IRQ pending, but the interrupt is serviced before both the driver and
> > the underlying I2C bus have been resumed. This causes EREMOTEIO errors.
> >
> > Disable the IRQ in suspend, and re-enable it on resume. If there are cases
> > where the driver enters suspend with interrupts disabled, that's a bug we
> > should fix separately.
> >
> > Signed-off-by: Evan Green <evgreen@...omium.org>
> > ---
> >
> > Changes in v2:
> >  - Enable and disable unconditionally (Dmitry)
> >
> >  drivers/input/touchscreen/atmel_mxt_ts.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
> > index 24c4b691b1c9..a58092488679 100644
> > --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> > +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> > @@ -3155,6 +3155,7 @@ static int __maybe_unused mxt_suspend(struct device *dev)
> >               mxt_stop(data);
> >
> >       mutex_unlock(&input_dev->mutex);
> > +     disable_irq(data->irq);
> >
> >       return 0;
> >  }
> > @@ -3174,6 +3175,7 @@ static int __maybe_unused mxt_resume(struct device *dev)
> >               mxt_start(data);
> >
> >       mutex_unlock(&input_dev->mutex);
> > +     enable_irq(data->irq);
>
> At least for older devices that do soft reset on resume we need
> interrupts to already work when we call mxt_start().
>
> In general, order of resume steps should mirror suspend.

Ok, I can move the enable_irq up towards the top of resume. I was
worried that a pending IRQ might not get handled correctly if
mxt_start() hadn't been called yet. But if we need IRQs for
mxt_start() to run anyway, then I guess it should be handled.
-Evan