linux-kernel - Re: [PATCH 2/2] HID: i2c-hid: goodix: Add support for powered-in-suspend property

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Message-ID: <CAC=S1njkYWfvqs5x4nYk0YxoFEcivunKP1T0pG3pO_tapfHivA@mail.gmail.com>
Date:   Tue, 25 Apr 2023 16:36:50 +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 2/2] HID: i2c-hid: goodix: Add support for
 powered-in-suspend property

Hi,

On Tue, Apr 25, 2023 at 2:16 AM Doug Anderson <dianders@...omium.org> wrote:
>
> Hi,
>
> On Sun, Apr 23, 2023 at 8:38 PM Jeff LaBundy <jeff@...undy.com> wrote:
> >
> > > @@ -37,13 +38,34 @@ static int goodix_i2c_hid_power_up(struct i2chid_ops *ops)
> > >               container_of(ops, struct i2c_hid_of_goodix, ops);
> > >       int ret;
> > >
> > > -     ret = regulator_enable(ihid_goodix->vdd);
> > > -     if (ret)
> > > -             return ret;
> > > -
> > > -     ret = regulator_enable(ihid_goodix->vddio);
> > > -     if (ret)
> > > -             return ret;
> > > +     /*
> > > +      * This is to ensure that the reset GPIO will be asserted and the
> > > +      * regulators will be enabled for all cases.
> > > +      */
> > > +     if (ihid_goodix->powered_in_suspend) {
> > > +             /*
> > > +              * This is not mandatory, but we assert reset here (instead of
> > > +              * in power-down) to ensure that the device will have a clean
> > > +              * state later on just like the normal scenarios would have.
> > > +              *
> > > +              * Also, since the regulators were not disabled in power-down,
> > > +              * we don't need to enable them here.
> > > +              */
> > > +             gpiod_set_value_cansleep(ihid_goodix->reset_gpio, 1);
> > > +     } else {
> > > +             /*
> > > +              * In this case, the reset is already asserted (either in
> > > +              * probe or power-down).
> > > +              * All we need is to enable the regulators.
> > > +              */
> > > +             ret = regulator_enable(ihid_goodix->vdd);
> > > +             if (ret)
> > > +                     return ret;
> > > +
> > > +             ret = regulator_enable(ihid_goodix->vddio);
> > > +             if (ret)
> > > +                     return ret;
> > > +     }
> >
> > Please let me know in case I have misunderstood, but I don't see a need
> > to change the regulator_enable/disable() logic if this property is set.
> > If the regulators are truly always-on, the regulator core already knows
> > what to do and we should not duplicate that logic here.

Your understanding is totally right, let me restore that in the next
revision. Thanks!

Regards,
Fei

> >
> > Based on the alleged silicon erratum discussed in patch [1/2], it seems
> > we only want to control the behavior of the reset GPIO. Therefore, only
> > the calls to gpiod_set_value_cansleep() should be affected and the name
> > of the property updated to reflect what it's actually doing.
>
> This would be OK w/ me.