Re: [PATCH 1/8] dt-bindings: display: panel: novatek,nt36672e: Document the reset GPIO polarity

[Vladimir Zapolskiy <vz@kernel.org>]

On 10/29/26 11:49, Krzysztof Kozlowski wrote:
> On Wed, Oct 28, 2026 at 10:27:35PM +0200, Vladimir Zapolskiy wrote:
>> On 10/28/26 16:59, Krzysztof Kozlowski wrote:
>>> On 28/10/2026 15:56, Vladimir Zapolskiy wrote:
>>>>> We might fix it at some point, so not sure if it is worth documenting in
>>>>> the binding. And what about usage of this binding in other projects
>>>>> which implement it correctly?
>>>>>
>>>>
>>>> In the upstream there is only one user qcm6490-idp.dts, and changing
>>>> the polarity will be an ABI breaking change, unfortunately.
>>>
>>> And all other projects?
>>>
>>
>> It might be a challenging task to check usage of "novatek,nt36672e"
>> compatible display panels in all other projects. I've asked about it:
>>
>> * https://chatgpt.com/uc/6ae25571-2ef0-83ea-81e5-2522e70c4a93
>>
>> The check gives this info:
>>
>> 1. Linux kernel - invalid GPIO polarity in the driver and qcm6490-idp.dts,
>> 2. Android - invalid GPIO polarity in the copied driver and qcm6490-idp.dts,
>> 3. FreeBSD - invalid GPIO polarity in the copied qcm6490-idp.dts, no driver.
>>
>> Please let me know, if there are other projects to check. To my
>> understanding the RESET_N polarity cannot be corrected anymore,
>> and the best option is to clearly document a difference between
>> the device and its dt-binding documentation.
> 
> It can be correct, just with impact so we choose not to, but
> nevertheless hardware wants different polarity, so you should not state
> in the binding the incorrect one.
> 
> This property corresponds to the hardware, not chosen SW implementation.
> 

Here by the hardware do you mean a "novatek,nt36672e" compatible panel
hardware, or a board hardware like sm8450-hdk?

Its the panel hardware property to get a reset signal with the proper
polarity (in the ideal world it's taken from the panel datasheet), then
1) this description is missing in the panel dt bindings documentation,
2) if added, this description would contradict to the panel datasheet.

It would make sense to document it, and that's the intention of this
particular proposed change.

-- 
Best wishes,
Vladimir