Re: [PATCH 2/2] arm64: dts: imx8mp: Add support for Data Modul i.MX8M Plus eDM SBC

[Marek Vasut <marex@denx.de>]

On 1/9/23 04:54, Shawn Guo wrote:

[...]

>>>> +		backlight = <&backlight>;
>>>> +		power-supply = <&reg_panel_vcc>;
>>>> +		/* Disabled by default, unless display board plugged in. */
>>>> +		status = "disabled";
>>>> +	};
>>>> +
>>>> +	reg_panel_vcc: regulator-panel-vcc {
>>>> +		compatible = "regulator-fixed";
>>>> +		pinctrl-names = "default";
>>>> +		pinctrl-0 = <&pinctrl_panel_vcc_reg>;
>>>> +		regulator-name = "PANEL_VCC";
>>>> +		regulator-min-microvolt = <5000000>;
>>>> +		regulator-max-microvolt = <5000000>;
>>>> +		gpio = <&gpio3 6 0>;
>>>
>>> GPIO_ACTIVE_HIGH?
>>
>> No, the 0 is correct and you're not the first one to wonder about this
>> oddity.
> 
> I understand that the polarity is ignored by Linux Kernel.  But it
> shouldn't prevent us from describing the polarity cell with defines
> for better readability.
> 
> I'm always looking for the pattern below when reviewing the device tree.
> 
> 	regulator-xxx {
> 		compatible = "regulator-fixed";
> 		...
> 		gpio = <&gpio3 6 GPIO_ACTIVE_HIGH>;
> 		enable-active-high;
> 	}
> 
> Or for low polarity:
> 
> 	regulator-xxx {
> 		compatible = "regulator-fixed";
> 		...
> 		gpio = <&gpio3 6 GPIO_ACTIVE_LOW>;
> 	}
> 
> The polarity define is helpful for me to validate whether
> `enable-active-high` property should present.

Maybe the best thing we can do to resolve this is to ask GPIO maintainer 
Linus what is the preferred way of describing this in DT -- whether with 
valid GPIO flags which are ignored or with 0 instead of GPIO flags ?