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: <CAD=FV=VY+01V7hBfUeZKR3OnnTcNuuYb-vhLWGgdS5jb4QTLBQ@mail.gmail.com>
Date:   Wed, 26 Apr 2023 07:05:03 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Fei Shao <fshao@...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

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".

-Doug