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From:   Jernej =?utf-8?B?xaBrcmFiZWM=?= <jernej.skrabec@gmail.com>
To:     linux-media@vger.kernel.org, Maxime Ripard <mripard@kernel.org>,
        Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Chen-Yu Tsai <wens@csie.org>,
        Samuel Holland <samuel@sholland.org>,
        Nicolas Dufresne <nicolas.dufresne@collabora.com>,
        Dmitry Osipenko <dmitry.osipenko@collabora.com>
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        linux-staging@lists.linux.dev,
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        linux-kernel@vger.kernel.org
Subject: Re: Re: [PATCH v1 2/3] media: cedrus: Set the platform driver data earlier
Date:   Thu, 25 Aug 2022 23:04:50 +0200
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Dne nedelja, 21. avgust 2022 ob 22:40:21 CEST je Dmitry Osipenko napisal(a):
> On 8/20/22 11:25, Jernej =C5=A0krabec wrote:
> > Dne petek, 19. avgust 2022 ob 17:37:20 CEST je Nicolas Dufresne=20
napisal(a):
> >> Le vendredi 19 ao=C3=BBt 2022 =C3=A0 06:17 +0200, Jernej =C5=A0krabec =
a =C3=A9crit :
> >>> Dne =C4=8Detrtek, 18. avgust 2022 ob 22:33:07 CEST je Nicolas Dufresne
> >=20
> > napisal(a):
> >>>> From: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> >>>>=20
> >>>> The cedrus_hw_resume() crashes with NULL deference on driver probe if
> >>>> runtime PM is disabled because it uses platform data that hasn't been
> >>>> set up yet. Fix this by setting the platform data earlier during pro=
be.
> >>>=20
> >>> Does it even work without PM? Maybe it would be better if Cedrus would
> >>> select PM in Kconfig.
> >>=20
> >> I cannot comment myself on this, but it does not seem to invalidate th=
is
> >> Dmitry's fix.
> >=20
> > If NULL pointer dereference happens only when PM is disabled, then it
> > does. I have PM always enabled and I never experienced above issue.
>=20
> Originally this fix was needed when I changed cedrus_hw_probe() to do
> the rpm-resume while was debugging the hang issue and then also noticed
> that the !PM should be broken. It's a good common practice for all
> drivers to have the drv data set early to avoid such problems, hence it
> won't hurt to make this change anyways.

Ok, as others pointed out, this is still a good thing, so:

Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>


>=20
> In practice nobody disables PM other than for debugging purposes and !PM
> handling is often broken in drivers. I assume that it might be even
> better to enable PM for all Allwiner SoCs and remove !PM handling from
> all the affected drivers, like it was done for Tegra some time ago.
>=20

Maybe in the future :)

Best regards,
Jernej

> --
> Best regards,
> Dmitry