linux-kernel - Re: [PATCH 3/9] regulator: mt6358: Merge VCN33

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Date:   Mon, 12 Jun 2023 18:34:37 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Chen-Yu Tsai <wenst@...omium.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/9] regulator: mt6358: Merge VCN33_* regulators

On Mon, Jun 12, 2023 at 12:19:01PM +0800, Chen-Yu Tsai wrote:
> On Sat, Jun 10, 2023 at 11:28 PM Conor Dooley <conor@...nel.org> wrote:

> > Ah, I see in the binding commit there's a "Luckily no device tree actually
> > uses them." Does that just cover the kernel, or does it consider other
> > operating systems/bootloaders?
> 
> That comment covers the upstream kernel and the downstream ChromeOS kernel
> specifically. The bootloader that ChromeOS uses (coreboot) doesn't use
> device trees. I don't know what MediaTek uses for their phones though.
> 
> AFAIK MediaTek only supports the Linux kernel, be it for Android or ChromeOS.
> There's not a large community around it, unlike some of the other ARM SoCs.
> 
> I did find an old v4.4 Android kernel [1] for the MediaTek Helio P60
> (MT6771) that is also paired with MT6358. There are no device tree
> references to the VCN33 regulator either. Only the definition exists
> in the mt6358.dtsi file, much like what we have upstream.
> 
> As far as the regulator driver goes, if it can't find a matching regulator
> node, it's the same as if the node doesn't exist, and therefore the given
> constraints are not ingested. If no constraints are ingested that can
> turn it on, and no consumer references to enable it either, we can say
> that the regulator is effectively unused.

Okay, that sounds reasonable. Seems like you've done your research,
so thanks for that!


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