linux-kernel - Re: [PATCH 2/5] arm64: dts: renesas: r8a77960-salvator-x: Enable GPU support

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Message-ID: <CAMuHMdWyKeQq31GEK+-y4BoaZFcCxJNac63S7NoocMj1cYKniw@mail.gmail.com>
Date: Wed, 29 Oct 2025 15:58:13 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Marek Vasut <marek.vasut+renesas@...lbox.org>
Cc: linux-arm-kernel@...ts.infradead.org, Conor Dooley <conor+dt@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Magnus Damm <magnus.damm@...il.com>, 
	Rob Herring <robh@...nel.org>, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH 2/5] arm64: dts: renesas: r8a77960-salvator-x: Enable GPU support

Hi Marek,

On Wed, 29 Oct 2025 at 15:52, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> On Mon, 27 Oct 2025 at 22:13, Marek Vasut
> <marek.vasut+renesas@...lbox.org> wrote:
> > Enable GPU on Salvator-X with R-Car M3-W.
> >
> > Signed-off-by: Marek Vasut <marek.vasut+renesas@...lbox.org>
>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

(no cover letter, so just replying here)

I am a bit reluctant to queue this, as apparently there is a bug/race
condition in the PowerVR driver: if the firmware is not available,
the kernel may crash during boot due to a NULL pointer dereference.
I could trigger this on Salvator-X with R-Car M3-W after applying your
series to renesas-drivers-2025-10-28, and adding two debug prints:

--- a/drivers/pmdomain/core.c
+++ b/drivers/pmdomain/core.c
@@ -256,12 +256,14 @@ struct device *dev_to_genpd_dev(struct device *dev)
 static int genpd_stop_dev(const struct generic_pm_domain *genpd,
                          struct device *dev)
 {
+pr_info("==== %s/%s: stop\n", genpd->name, dev_name(dev));
        return GENPD_DEV_CALLBACK(genpd, int, stop, dev);
 }

 static int genpd_start_dev(const struct generic_pm_domain *genpd,
                           struct device *dev)
 {
+pr_info("==== %s/%s: start\n", genpd->name, dev_name(dev));
        return GENPD_DEV_CALLBACK(genpd, int, start, dev);
 }

See also my original report "drm/imagination: genpd_runtime_suspend()
crash"[1] on Gray Hawk Single.

[1] https://lore.kernel.org/all/CAMuHMdWapT40hV3c+CSBqFOW05aWcV1a6v_NiJYgoYi0i9_PDQ@mail.gmail.com

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds