linux-kernel - Re: [PATCH v6 0/8] Add TH1520 GPU support with power sequencing

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Message-ID: <CAPDyKFrCeYxtqscX8Vr165HMOcSof_d62PMtRwt_yDyZ4ujSDQ@mail.gmail.com>
Date: Wed, 25 Jun 2025 12:09:59 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
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>, 
	Bartosz Golaszewski <brgl@...ev.pl>, 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, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH v6 0/8] Add TH1520 GPU support with power sequencing

On Mon, 23 Jun 2025 at 13:44, Michal Wilczynski
<m.wilczynski@...sung.com> wrote:
>
> This patch series introduces support for the Imagination IMG BXM-4-64
> GPU found on the T-HEAD TH1520 SoC. A key aspect of this support is
> managing the GPU's complex power-up and power-down sequence, which
> involves multiple clocks and resets.
>
> The TH1520 GPU requires a specific sequence to be followed for its
> clocks and resets to ensure correct operation. Initial discussions and
> an earlier version of this series explored managing this via the generic
> power domain (genpd) framework. However, following further discussions
> with kernel maintainers [1], the approach has been reworked to utilize
> the dedicated power sequencing (pwrseq) framework.
>
> This revised series now employs a new pwrseq provider driver
> (pwrseq-thead-gpu.c) specifically for the TH1520 GPU. This driver
> encapsulates the SoC specific power sequence details. The Imagination
> GPU driver (pvr_device.c) is updated to act as a consumer of this power
> sequencer, requesting the "gpu-power" target. The sequencer driver,
> during its match phase with the GPU device, acquires the necessary clock
> and reset handles from the GPU device node to perform the full sequence.
>
> This approach aligns with the goal of abstracting SoC specific power
> management details away from generic device drivers and leverages the
> pwrseq framework as recommended.
>
> The series is structured as follows:
>
> Patch 1: Introduces the pwrseq-thead-gpu auxiliary driver to manage the
>          GPU's power-on/off sequence.
> Patch 2: Adds device tree bindings for the gpu-clkgen reset to the
>          existing thead,th1520-aon binding.
> Patch 3: Extends the pm-domains driver to detect the gpu-clkgen reset
>          and spawn the pwrseq-thead-gpu auxiliary driver.
> Patch 4: Updates the Imagination DRM driver to utilize the pwrseq
>          framework for TH1520 GPU power management.
> Patch 5: Adds the thead,th1520-gpu compatible string to the PowerVR GPU
>          device tree bindings.
> Patch 6: Adds the gpu-clkgen reset property to the aon node in the
>          TH1520 device tree source.
> Patch 7: Adds the device tree node for the IMG BXM-4-64 GPU and its
>          required fixed-clock.
> Patch 8: Enables compilation of the Imagination PowerVR driver on the
>          RISC-V architecture.
>
> This patchset finishes the work started in bigger series [2] by adding
> all remaining GPU power sequencing piece. After this patchset the GPU
> probes correctly.
>
> This series supersedes the previous genpd based approach. Testing on
> T-HEAD TH1520 SoC indicates the new pwrseq based solution works
> correctly.

I have applied patch2 and patch3 for next via the pmdomain tree, thanks!

Note that, the DT patch (patch2) is also available on the immutable dt
branch, if it needs to be pulled into some other tree.

[...]

Kind regards
Uffe