linux-kernel - Re: [PATCH 1/3] arm64: dts: mediatek: asurada: Add display regulators

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Date:   Fri, 9 Sep 2022 09:46:33 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     Chen-Yu Tsai <wenst@...omium.org>, kernel@...labora.com,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 1/3] arm64: dts: mediatek: asurada: Add display regulators

Il 08/09/22 19:11, Nícolas F. R. A. Prado ha scritto:
> Add the regulators present on the Asurada platform that are used to
> power the internal and external displays.
> 
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
> 
> ---
> 
>   .../boot/dts/mediatek/mt8192-asurada.dtsi     | 114 ++++++++++++++++++
>   1 file changed, 114 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi b/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi
> index 4b314435f8fd..1d99e470ea1a 100644
> --- a/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi
> +++ b/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi

..snip..

> @@ -56,6 +116,18 @@ pp3300_ldo_z: regulator-3v3-z {
>   		vin-supply = <&ppvar_sys>;
>   	};
>   

Can you please add a comment here advertising that this regulator
will not only provide power to the MIPI bridge, but *also* to the
display panel itself?

This is to make sure that everyone understands what's going on, and
also that we ourselves don't forget about that.

Probably something like:
/* pp3300_mipibrdg also enables pp3300_panel */

I would then propose to add a "regulator-fixed" that has no GPIO
but with vin-supply as this one.

pp3300_panel: regulator-3v3-panel {
	compatible = "regulator-fixed";
	regulator-name = "pp3300_panel";
	regulator-min-microvolt = <3300000>;
	regulator-max-microvolt = <3300000>;

	vin-supply = <&pp3300_mipibrdg>;
};

I would also test assigning this regulator to the panel node, as this
will make sure to cover future corner cases (think about PM suspend/resume).

P.S.: If you add the pp3300_panel regulator-fixed with that vin-supply,
       maybe the proposed comment would become a bit overkill. Your choice!

Cheers,
Angelo

> +	pp3300_mipibrdg: regulator-3v3-mipibrdg {
> +		compatible = "regulator-fixed";
> +		regulator-name = "pp3300_mipibrdg";
> +		pinctrl-names = "default";
> +		pinctrl-0 = <&pp3300_mipibrdg_en_pins>;
> +		regulator-min-microvolt = <3300000>;
> +		regulator-max-microvolt = <3300000>;
> +		enable-active-high;
> +		regulator-boot-on;
> +		gpio = <&pio 127 GPIO_ACTIVE_HIGH>;
> +	};
> +
>   	/* separately switched 3.3V power rail */
>   	pp3300_u: regulator-3v3-u {
>   		compatible = "regulator-fixed";