Re: [PATCH 02/11] arm64: dts: qcom: sc8280xp-arcata: Enable backlight

[Jérôme de Bretagne <jerome.debretagne@gmail.com>]

On 5/21/26 10:48, Konrad Dybcio wrote:
> On 5/21/26 12:26 AM, Jérôme de Bretagne wrote:
>> On 5/20/26 18:40, Jérôme de Bretagne via B4 Relay wrote:
>>> From: Jérôme de Bretagne <jerome.debretagne@gmail.com>
>>>
>>> Add backlight nodes and enable backlight so that it can be controlled
>>> with the corresponding buttons found on Surface Pro Type Cover keyboards.
>>>
>>> The nodes are almost identical to the ones from the ThinkPad X13s with
>>> a different enable GPIO for the vreg_edp_bl node.
>>>
>>> The difference was found by looking at the output of /sys/kernel/debug/gpio
>>> on the ThinkPad X13s to see the properties of its enable gpio9:
> 
> [...]
> 
>> and ... backlight still works! It can also be enabled/disabled with:
>>    /sys/class/backlight/backlight/bl_power
>> as expected.
>>
>> I have no clue why both gpio6 on pmc8280_2 and gpio6 on pmc8280c can enable and disable the backlight. Is it a common scenario?
> 
> Could it be that one of them is an ENABLE_BL pin, while the other one
> enables the regulator?
> 
> Konrad

I've looked at more device trees and seen that quite a few of them
simply don't have a "power-supply = <&vreg_edp_bl>" property in their
backlight node. Trying a similar approach, the backlight still works
so the gpio6 I was adding wasn't used (or even useful).

I will send a simpler patch in v2, removing the power-supply property
and the vreg_edp_bl & edp_bl_reg_en nodes.

Jérôme