linux-kernel - Re: [PATCH v2 1/2] dt-bindings: input: touchscreen: goodix: Add no-reset-pull-up property

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Message-ID: <87selrt1vl.fsf@geanix.com>
Date: Tue, 29 Apr 2025 17:37:34 +0200
From: Esben Haabendal <esben@...nix.com>
To: "Conor Dooley" <conor@...nel.org>
Cc: "Dmitry Torokhov" <dmitry.torokhov@...il.com>,  "Rob Herring"
 <robh@...nel.org>,  "Krzysztof Kozlowski" <krzk+dt@...nel.org>,  "Conor
 Dooley" <conor+dt@...nel.org>,  "Hans de Goede" <hdegoede@...hat.com>,
  <linux-input@...r.kernel.org>,  <devicetree@...r.kernel.org>,
  <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] dt-bindings: input: touchscreen: goodix: Add
 no-reset-pull-up property

"Conor Dooley" <conor@...nel.org> writes:

> On Tue, Apr 29, 2025 at 11:56:11AM +0200, Esben Haabendal wrote:
>> This should be added for boards where there is no pull-up on the reset pin,
>> as the driver will otherwise switch the reset signal to high-impedance to
>> save power, which obviously not safe without pull-up.
>> 
>> Signed-off-by: Esben Haabendal <esben@...nix.com>
>> ---
>>  Documentation/devicetree/bindings/input/touchscreen/goodix.yaml | 4 ++++
>>  1 file changed, 4 insertions(+)
>> 
>> diff --git a/Documentation/devicetree/bindings/input/touchscreen/goodix.yaml b/Documentation/devicetree/bindings/input/touchscreen/goodix.yaml
>> index eb4992f708b70fef93bd4b59b9565123f7c6ad5d..21ac13046b6e021eeb403d854aabc945801dd29f 100644
>> --- a/Documentation/devicetree/bindings/input/touchscreen/goodix.yaml
>> +++ b/Documentation/devicetree/bindings/input/touchscreen/goodix.yaml
>> @@ -45,6 +45,10 @@ properties:
>>    reset-gpios:
>>      maxItems: 1
>>  
>> +  goodix,no-reset-pull-up:
>> +    type: boolean
>> +    description: There is no pull-up on reset pin
>
> I have to wonder, why are these system using the reset property if the
> reset is not usable? Shouldn't the property be omitted?

The reset are fully functional. It just have to be controlled in
push-pull mode.

Because of the lack of external pull-up, configuring the reset gpio as
input (to save power) puts the reset pin in an unknown state.

/Esben