linux-kernel - Re: [PATCH v3 1/8] dt-bindings: power: Add T-HEAD TH1520 GPU power sequencer

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Message-ID: <CAMRc=MfXashaEscE1vF_P6cs9iOCBerfNFiB4yC+TX76fZ87nA@mail.gmail.com>
Date: Tue, 3 Jun 2025 15:35:16 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Michal Wilczynski <m.wilczynski@...sung.com>, Drew Fustini <drew@...7.com>, Guo Ren <guoren@...nel.org>, 
	Fu Wei <wefu@...hat.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Philipp Zabel <p.zabel@...gutronix.de>, Frank Binns <frank.binns@...tec.com>, 
	Matt Coster <matt.coster@...tec.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>, 
	Ulf Hansson <ulf.hansson@...aro.org>, Marek Szyprowski <m.szyprowski@...sung.com>, 
	linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v3 1/8] dt-bindings: power: Add T-HEAD TH1520 GPU power sequencer

On Tue, Jun 3, 2025 at 3:19 PM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On Mon, Jun 02, 2025 at 10:29:13PM GMT, Michal Wilczynski wrote:
> > >> +description: |
> > >> +  This binding describes the power sequencer for the T-HEAD TH1520 GPU.
> > >> +  This sequencer handles the specific power-up and power-down sequences
> > >> +  required by the GPU, including managing clocks and resets from both the
> > >> +  sequencer and the GPU device itself.
> > >> +
> > >> +properties:
> > >> +  compatible:
> > >> +    const: thead,th1520-gpu-pwrseq
> > >> +
> > >
> > > Before I review the rest: is this actually a physical device that
> > > takes care of the power sequencing? Some kind of a power management
> > > unit for the GPU? If so, I bet it's not called "power sequencer" so
> > > let's use its actual name as per the datasheet?
> >
> > Hi Bart,
> > Thanks for your feedback.
> >
> > The hardware block responsible for powering up the components in the
> > TH1520 SoC datasheet is called AON (Always On). However, we already have
> > a DT node named aon that serves as a power domain provider
> > (Documentation/devicetree/bindings/firmware/thead,th1520-aon.yaml).
>
> So no. One device, one device node (sometimes with cildren nodes). You
> do not get another device node just because someone wrote incomplete
> binding or because driver looks differently.
>
> >
> > Following the discussion [1] about needing a separate DT node for the
> > power sequencing capabilities of this AON block, and thinking further
> > about it, I think the binding should be more generic. The AON block can
> > manage power sequences for more than just the GPU (e.g. NPU, AUDIO,
> > DSP).
> >
> > The compatible string could be updated like so:
> > "thead,th1520-aon-pwrseq"
>
> Should not be separate node, you already have one for AON.
>

Agreed. And as far as implementation goes, you can have the same
driver be a PM domain AND pwrseq provider. It just has to bind to the
device node that represents an actual component, not a made-up
"convenience" node.

Bartosz