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

  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
`powered-in-suspend` property in the driver that allows the driver to
determine whether the touchscreen is still powered in suspend, and
handle the reset GPIO accordingly as below:
- When set to true, the driver does not assert the reset GPIO in power
  down. To ensure a clean start and the consistent behavior, it does the
  assertion in power up instead.
  This is for designs with a dedicated always-on regulator.
- When set to false, 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@chromium.org>

---

 drivers/hid/i2c-hid/i2c-hid-of-goodix.c | 46 +++++++++++++++++++++----
 1 file changed, 39 insertions(+), 7 deletions(-)
  

Hi,

On Tue, Apr 18, 2023 at 5:51 AM Fei Shao <fshao@chromium.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
> `powered-in-suspend` property in the driver that allows the driver to
> determine whether the touchscreen is still powered in suspend, and
> handle the reset GPIO accordingly as below:
> - When set to true, the driver does not assert the reset GPIO in power
>   down. To ensure a clean start and the consistent behavior, it does the
>   assertion in power up instead.
>   This is for designs with a dedicated always-on regulator.
> - When set to false, 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@chromium.org>
>
> ---
>
>  drivers/hid/i2c-hid/i2c-hid-of-goodix.c | 46 +++++++++++++++++++++----
>  1 file changed, 39 insertions(+), 7 deletions(-)

I privately reviewed earlier versions of this patch, so it's
unsurprising that I have no comments. Assuming that the DT folks don't
have any objections to the bindings change, this LGTM.

Reviewed-by: Douglas Anderson <dianders@chromium.org>
  

Hi Fei,

On Tue, Apr 18, 2023 at 08:49:52PM +0800, Fei Shao 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
> `powered-in-suspend` property in the driver that allows the driver to
> determine whether the touchscreen is still powered in suspend, and
> handle the reset GPIO accordingly as below:
> - When set to true, the driver does not assert the reset GPIO in power
>   down. To ensure a clean start and the consistent behavior, it does the
>   assertion in power up instead.
>   This is for designs with a dedicated always-on regulator.
> - When set to false, 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@chromium.org>
> 
> ---
> 
>  drivers/hid/i2c-hid/i2c-hid-of-goodix.c | 46 +++++++++++++++++++++----
>  1 file changed, 39 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/hid/i2c-hid/i2c-hid-of-goodix.c b/drivers/hid/i2c-hid/i2c-hid-of-goodix.c
> index 0060e3dcd775..b438db8ca6f4 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 powered_in_suspend;
>  	const struct goodix_i2c_hid_timing_data *timings;
>  };
>  
> @@ -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.

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.

>  
>  	if (ihid_goodix->timings->post_power_delay_ms)
>  		msleep(ihid_goodix->timings->post_power_delay_ms);
> @@ -60,6 +82,13 @@ 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 or disable regulators if we're keeping the
> +	 * device powered in suspend.
> +	 */
> +	if (ihid_goodix->powered_in_suspend)
> +		return;
> +
>  	gpiod_set_value_cansleep(ihid_goodix->reset_gpio, 1);
>  	regulator_disable(ihid_goodix->vddio);
>  	regulator_disable(ihid_goodix->vdd);
> @@ -91,6 +120,9 @@ static int i2c_hid_of_goodix_probe(struct i2c_client *client)
>  	if (IS_ERR(ihid_goodix->vddio))
>  		return PTR_ERR(ihid_goodix->vddio);
>  
> +	ihid_goodix->powered_in_suspend =
> +		of_property_read_bool(client->dev.of_node, "powered-in-suspend");
> +
>  	ihid_goodix->timings = device_get_match_data(&client->dev);
>  
>  	return i2c_hid_core_probe(client, &ihid_goodix->ops, 0x0001, 0);
> -- 
> 2.40.0.634.g4ca3ef3211-goog
> 

Kind regards,
Jeff LaBundy
  

Hi,

On Sun, Apr 23, 2023 at 8:38 PM Jeff LaBundy <jeff@labundy.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.
>
> 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.
  

Hi,

On Tue, Apr 25, 2023 at 2:16 AM Doug Anderson <dianders@chromium.org> wrote:
>
> Hi,
>
> On Sun, Apr 23, 2023 at 8:38 PM Jeff LaBundy <jeff@labundy.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.