linux-kernel - Re: [PATCH v3 1/2] dt-bindings: input: goodix: Add "goodix,no-reset-during-suspend" property

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Date:   Wed, 26 Apr 2023 20:01:43 -0500
From:   Jeff LaBundy <jeff@...undy.com>
To:     Fei Shao <fshao@...omium.org>
Cc:     Douglas Anderson <dianders@...omium.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-mediatek <linux-mediatek@...ts.infradead.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        devicetree@...r.kernel.org, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] dt-bindings: input: goodix: Add
 "goodix,no-reset-during-suspend" property

Hi Fei,

On Wed, Apr 26, 2023 at 10:44:21PM +0800, Fei Shao wrote:
> We observed that on Chromebook device Steelix, if Goodix GT7375P
> touchscreen is powered in suspend (because, for example, it connects to
> an always-on regulator) and with the reset GPIO asserted, it will
> introduce about 14mW power leakage.
> 
> To address that, we add this property to skip reset during suspend.
> If it's set, the driver will stop asserting the reset GPIO during
> power-down. Refer to the comments in the driver for details.
> 
> Signed-off-by: Fei Shao <fshao@...omium.org>
> Reviewed-by: Douglas Anderson <dianders@...omium.org>
> Reviewed-by: Matthias Brugger <matthias.bgg@...il.com>
> ---

Reviewed-by: Jeff LaBundy <jeff@...undy.com>

> 
> (no changes since v2)
> 
> Changes in v2:
> - Use a more accurate property name and with "goodix," prefix.
> 
>  .../devicetree/bindings/input/goodix,gt7375p.yaml        | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml b/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml
> index ce18d7dadae2..1edad1da1196 100644
> --- a/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml
> +++ b/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml
> @@ -43,6 +43,15 @@ properties:
>        itself as long as it allows the main board to make signals compatible
>        with what the touchscreen is expecting for its IO rails.
>  
> +  goodix,no-reset-during-suspend:
> +    description:
> +      Set this to true to enforce the driver to not assert the reset GPIO
> +      during suspend.
> +      Due to potential touchscreen hardware flaw, back-powering could happen in
> +      suspend if the power supply is on and with active-low reset GPIO asserted.
> +      This property is used to avoid the back-powering issue.
> +    type: boolean
> +
>  required:
>    - compatible
>    - reg
> -- 
> 2.40.1.495.gc816e09b53d-goog
> 

Many thanks to you and Doug for the informative discussion.

Kind regards,
Jeff LaBundy