linux-kernel - Re: [PATCH v3 3/8] drm/imagination: Use pwrseq for TH1520 GPU power management

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Message-ID: <59cc6827-1602-402a-9279-96ad6285cff4@kernel.org>
Date: Fri, 13 Jun 2025 08:44:26 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Michal Wilczynski <m.wilczynski@...sung.com>,
 Bartosz Golaszewski <brgl@...ev.pl>, Matt Coster <matt.coster@...tec.com>,
 "krzk+dt@...nel.org" <krzk+dt@...nel.org>
Cc: Drew Fustini <drew@...7.com>, Guo Ren <guoren@...nel.org>,
 Fu Wei <wefu@...hat.com>, Rob Herring <robh@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>,
 Frank Binns <frank.binns@...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 3/8] drm/imagination: Use pwrseq for TH1520 GPU power
 management

On 11/06/2025 14:01, Michal Wilczynski wrote:
> 
> However, this leads me back to a fundamental issue with the
> consumer side implementation in the generic pvr_device.c driver. The
> current fallback code is:
> 
> /*
>  * If the error is -EPROBE_DEFER, it's because the
>  * optional sequencer provider is not present
>  * and it's safe to fall back on manual power-up.
>  */
> if (pwrseq_err == -EPROBE_DEFER)
>         pvr_dev->pwrseq = NULL;
> 
> As Krzysztof noted, simply ignoring -EPROBE_DEFER is not ideal. But if I
> change this to a standard deferred probe, the pvr_device.c driver will

Why? You have specific compatible for executing such quirks only for
given platform.

> break on all other supported SoCs. It would wait indefinitely for a
> pwrseq-thead-gpu provider that will never appear on those platforms.
> 



Best regards,
Krzysztof