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

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Message-ID: <CAMRc=McDb13ZOM5v5gYBAT40Z6eNd8am6gy=FysWU72cG1172w@mail.gmail.com>
Date: Wed, 4 Jun 2025 08:36:20 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Michal Wilczynski <m.wilczynski@...sung.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, Ulf Hansson <ulf.hansson@...aro.org>, 
	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>, 
	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 8:24 PM Michal Wilczynski
<m.wilczynski@...sung.com> wrote:
> >
> > 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.
>
> Sure - this can be done using existing AON node.
>
> To keep the pwrseq code organized in drivers/power/sequencing/, a
> similar approach to our th1520-pd driver interfacing with the AON
> firmware library (drivers/firmware/thead,th1520-aon.c) could work.
>
> The idea would be to treat code like pwrseq-thead-aon.c (changed from a
> current pwrseq-thead-gpu.c) as a library. It would export its necessary
> functions (e.g., for specific sequence init/deinit steps) using
> EXPORT_SYMBOL_GPL. The main AON driver would then call these to provide
> the pwrseq functionality.
>
> This will introduce a compile-time dependency, as expected.
>
> An alternative would be to keep the driver in drivers/power/sequencing/
> as a platform driver and start it up using, for example, an auxiliary
> bus. This is similar to what the JH7110 clock driver
> (drivers/clk/starfive/clk-starfive-jh7110-sys.c) is doing with a reset
> driver. This could offer a cleaner separation of roles if that's
> preferred.
>
> Please let me know which way would be preferred.

I forgot the auxiliary bus is a thing. Yeah, definitely use that, it's
more elegant than a library function IMO.

Bart