linux-kernel - Re: [PATCH v2 2/2] HID: i2c-hid: goodix: Add support for "goodix,no-reset-during-suspend" property

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Message-ID: <CAC=S1niMR5JBunfmMbV+FSqSOcR7rY3R4KH4Y7QQmz=LgciT2g@mail.gmail.com>
Date:   Wed, 26 Apr 2023 22:24:06 +0800
From:   Fei Shao <fshao@...omium.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Jeff LaBundy <jeff@...undy.com>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-mediatek <linux-mediatek@...ts.infradead.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Jiri Kosina <jikos@...nel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Stephen Kitt <steve@....org>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] HID: i2c-hid: goodix: Add support for
 "goodix,no-reset-during-suspend" property

On Wed, Apr 26, 2023 at 10:05 PM Doug Anderson <dianders@...omium.org> wrote:
>
> Hi,
>
> On Wed, Apr 26, 2023 at 2:33 AM Fei Shao <fshao@...omium.org> wrote:
> >
> > In the beginning, commit 18eeef46d359 ("HID: i2c-hid: goodix: Tie the
> > reset line to true state of the regulator") introduced a change to tie
> > the reset line of the Goodix touchscreen to the state of the regulator
> > to fix a power leakage issue in suspend.
> >
> > After some time, the change was deemed unnecessary and was reverted in
> > commit 557e05fa9fdd ("HID: i2c-hid: goodix: Stop tying the reset line to
> > the regulator") due to difficulties in managing regulator notifiers for
> > designs like Evoker, which provides a second power rail to touchscreen.
> >
> > However, the revert caused a power regression on another Chromebook
> > device Steelix in the field, which has a dedicated always-on regulator
> > for touchscreen and was covered by the workaround in the first commit.
> >
> > To address both cases, this patch adds the support for the new
> > "goodix,no-reset-during-suspend" property in the driver:
> > - When set to true, the driver does not assert the reset GPIO during
> >   power-down.
> >   Instead, the GPIO will be asserted during power-up to ensure the
> >   touchscreen always has a clean start and consistent behavior after
> >   resuming.
> >   This is for designs with a dedicated always-on regulator.
> > - When set to false or unset, the driver uses the original control flow
> >   and asserts GPIO and disable regulators normally.
> >   This is for the two-regulator and shared-regulator designs.
> >
> > Signed-off-by: Fei Shao <fshao@...omium.org>
> > Reviewed-by: Douglas Anderson <dianders@...omium.org>
> >
> > ---
> >
> > Changes in v2:
> > - Do not change the regulator_enable logic during power-up.
> >
> >  drivers/hid/i2c-hid/i2c-hid-of-goodix.c | 26 +++++++++++++++++++++++++
> >  1 file changed, 26 insertions(+)
> >
> > diff --git a/drivers/hid/i2c-hid/i2c-hid-of-goodix.c b/drivers/hid/i2c-hid/i2c-hid-of-goodix.c
> > index 0060e3dcd775..fc4532fcadcc 100644
> > --- a/drivers/hid/i2c-hid/i2c-hid-of-goodix.c
> > +++ b/drivers/hid/i2c-hid/i2c-hid-of-goodix.c
> > @@ -28,6 +28,7 @@ struct i2c_hid_of_goodix {
> >         struct regulator *vdd;
> >         struct regulator *vddio;
> >         struct gpio_desc *reset_gpio;
> > +       bool no_reset_during_suspend;
> >         const struct goodix_i2c_hid_timing_data *timings;
> >  };
> >
> > @@ -37,6 +38,20 @@ static int goodix_i2c_hid_power_up(struct i2chid_ops *ops)
> >                 container_of(ops, struct i2c_hid_of_goodix, ops);
> >         int ret;
> >
> > +       if (ihid_goodix->no_reset_during_suspend) {
> > +               /*
> > +                * This is not mandatory, but we assert reset here (instead of
> > +                * during power-down) to ensure the device will have a clean
> > +                * state after powering up, just like the normal scenarios will
> > +                * have.
> > +                *
> > +                * Note that in this case we assume the regulators should be
> > +                * (marked as) always-on, so the regulator core knows what to
> > +                * do with them in the following regulator_enable() calls
> > +                * despite regulator_disable() was not called previously.
> > +                */
> > +               gpiod_set_value_cansleep(ihid_goodix->reset_gpio, 1);
> > +       }
> >         ret = regulator_enable(ihid_goodix->vdd);
> >         if (ret)
> >                 return ret;
> > @@ -60,6 +75,14 @@ static void goodix_i2c_hid_power_down(struct i2chid_ops *ops)
> >         struct i2c_hid_of_goodix *ihid_goodix =
> >                 container_of(ops, struct i2c_hid_of_goodix, ops);
> >
> > +       /*
> > +        * Don't assert reset GPIO if it's set.
> > +        * Also, it's okay to skip the following regulator_disable() calls
> > +        * because the regulators should be always-on in this case.
> > +        */
> > +       if (ihid_goodix->no_reset_during_suspend)
> > +               return;
> > +
> >         gpiod_set_value_cansleep(ihid_goodix->reset_gpio, 1);
> >         regulator_disable(ihid_goodix->vddio);
> >         regulator_disable(ihid_goodix->vdd);
>
> I think the above is wrong. You should just skip the GPIO call when
> "no_reset_during_suspend", not the regulator calls. As your code is
> written, you'll enable the regulators over and over again in
> "power_up" and never in "power_down".

Agree, I'll resend v3. Thanks for the feedback!

Regards,
Fei

>
> -Doug