linux-kernel - Re: [PATCH v6 1/8] power: sequencing: Add T-HEAD TH1520 GPU power sequencer driver

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Message-ID: <CAMRc=MfPLZ7oMVjLv+_GMoC8X+O=k+mMrQKxELho0=+Z7=HApQ@mail.gmail.com>
Date: Mon, 23 Jun 2025 16:32:52 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Michal Wilczynski <m.wilczynski@...sung.com>
Cc: 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 v6 1/8] power: sequencing: Add T-HEAD TH1520 GPU power
 sequencer driver

On Mon, Jun 23, 2025 at 1:44 PM Michal Wilczynski
<m.wilczynski@...sung.com> wrote:
>
> Introduce the pwrseq-thead-gpu driver, a power sequencer provider for
> the Imagination BXM-4-64 GPU on the T-HEAD TH1520 SoC. This driver
> controls an auxiliary device instantiated by the AON power domain.
>
> The TH1520 GPU requires a specific sequence to correctly initialize and
> power down its resources:
>  - Enable GPU clocks (core and sys).
>  - De-assert the GPU clock generator reset (clkgen_reset).
>  - Introduce a short hardware-required delay.
>  - De-assert the GPU core reset. The power-down sequence performs these
>    steps in reverse.
>
> Implement this sequence via the pwrseq_power_on and pwrseq_power_off
> callbacks.
>
> Crucially, the driver's match function is called when a consumer (the
> Imagination GPU driver) requests the "gpu-power" target. During this
> match, the sequencer uses clk_bulk_get() and
> reset_control_get_exclusive() on the consumer's device to obtain handles
> to the GPU's "core" and "sys" clocks, and the GPU core reset.  These,
> along with clkgen_reset obtained from parent aon node, allow it to
> perform the complete sequence.
>
> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
> Signed-off-by: Michal Wilczynski <m.wilczynski@...sung.com>
> ---

[snip]

> +
> +       /* Additionally verify consumer device has AON as power-domain */
> +       if (pwr_spec.np != ctx->aon_node || pwr_spec.args[0] != TH1520_GPU_PD) {
> +               of_node_put(pwr_spec.np);
> +               return 0;
> +       }
> +
> +       of_node_put(pwr_spec.np);
> +
> +       /* If a consumer is already bound, only allow a re-match from it */
> +       if (ctx->consumer_node)
> +               return ctx->consumer_node == dev->of_node;
> +

That should be `!!(ctx->consumer_node == dev->of_node)` or preferably
`ctx->consumer_node == dev->of_node ? 1 : 0`. I can amend it when
applying if you have no objections. The rest looks good to me and I'd
like to pick it up into pwrseq/for-next in the next two days.

Bart

[snip]