Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20190924215238.184750-1-evgreen@chromium.org> <20190928001626.GT237523@dtor-ws>
In-Reply-To: <20190928001626.GT237523@dtor-ws>
From:   Evan Green <evgreen@chromium.org>
Date:   Mon, 30 Sep 2019 08:29:06 -0700
Message-ID: <CAE=gft46VXLL5z2o5QEnTBMOrzDnK_uuFiK4NMQV21PBpLxmfQ@mail.gmail.com>
Subject: Re: [PATCH v2] Input: atmel_mxt_ts - Disable IRQ across suspend
To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc:     Nick Dyer <nick@shmanahar.org>,
        Jongpil Jung <jongpil19.jung@samsung.com>,
        Furquan Shaikh <furquan@chromium.org>,
        Rajat Jain <rajatja@chromium.org>,
        LKML <linux-kernel@vger.kernel.org>, linux-input@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Sep 27, 2019 at 5:16 PM Dmitry Torokhov
<dmitry.torokhov@gmail.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@chromium.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