linux-kernel - Re: [PATCH 06/13] arm64: dts: mediatek: mt8188: Update VPPSYS node name and compatible

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Message-ID: <CAC=S1ni+pJJZhbjvVqhba5u1JqGv=dZTv8+KH4xburea2AG4Qg@mail.gmail.com>
Date: Tue, 10 Sep 2024 19:06:43 +0800
From: Fei Shao <fshao@...omium.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Matthias Brugger <matthias.bgg@...il.com>, Conor Dooley <conor+dt@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Rob Herring <robh@...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 06/13] arm64: dts: mediatek: mt8188: Update VPPSYS node
 name and compatible

On Tue, Sep 10, 2024 at 3:19 PM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On 10/09/2024 07:12, Fei Shao wrote:
> > On Mon, Sep 9, 2024 at 7:41 PM Krzysztof Kozlowski <krzk@...nel.org> wrote:
> >>
> >> On 09/09/2024 13:14, Fei Shao wrote:
> >>> Use and add "syscon" in VPPSYS node names and compatible to fix errors
> >>> from `make CHECK_DTBS=y mediatek/mt8188-evb.dtb`.
> >>>
> >>> Signed-off-by: Fei Shao <fshao@...omium.org>
> >>> ---
> >>>
> >>>  arch/arm64/boot/dts/mediatek/mt8188.dtsi | 8 ++++----
> >>>  1 file changed, 4 insertions(+), 4 deletions(-)
> >>>
> >>> diff --git a/arch/arm64/boot/dts/mediatek/mt8188.dtsi b/arch/arm64/boot/dts/mediatek/mt8188.dtsi
> >>> index 2900d78b7ceb..14e51a11f688 100644
> >>> --- a/arch/arm64/boot/dts/mediatek/mt8188.dtsi
> >>> +++ b/arch/arm64/boot/dts/mediatek/mt8188.dtsi
> >>> @@ -1799,8 +1799,8 @@ mfgcfg: clock-controller@...bf000 {
> >>>                       #clock-cells = <1>;
> >>>               };
> >>>
> >>> -             vppsys0: clock-controller@...00000 {
> >>> -                     compatible = "mediatek,mt8188-vppsys0";
> >>> +             vppsys0: syscon@...00000 {
> >>> +                     compatible = "mediatek,mt8188-vppsys0", "syscon";
> >>
> >> If this was working before, it looks like this is not a syscon and
> >> bindings need to be fixed.
> >
> > I guess it's because the binding was later updated in commit
> > 26bcd8a53098 ("dt-bindings: arm: mediatek: mmsys: Add VPPSYS
> > compatible for MT8188"), and the corresponding DT update was unnoticed
> > at the time.
> > If that makes sense then this should be a valid fix.
>
> Not necessarily. Why not fixing bindings? Prove that bindings are
> correct, not DTS, first.

MediaTek's mmsys doesn't merely control clocks, it also provides
display pipeline routing control and other misc control registers, so
it's appropriate to categorize it as a system controller over a clock
controller.
As for vdosys and vppsys, they are likely variants or aliases of mmsys
introduced in their newer SoCs.

That description was updated in commit 1a680aa888d6 ("dt-bindings:
mediatek: Update mmsys binding to reflect it is a system controller"),
so I just assumed it's correct without thinking much...

Regards,
Fei