Re: Re: [PATCH v1 2/3] media: cedrus: Set the platform driver data earlier

From: "Jernej Škrabec" <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>
Cc: kernel@collabora.com, stable@vger.kernel.org,
	linux-staging@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org,
	linux-sunxi@lists.linux.dev, 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	[thread overview]
Message-ID: <3448453.iIbC2pHGDl@kista> (raw)
In-Reply-To: <6a8f2555-1bd4-ac81-390e-b597e3c886f6@collabora.com>

Dne nedelja, 21. avgust 2022 ob 22:40:21 CEST je Dmitry Osipenko napisal(a):
> On 8/20/22 11:25, Jernej Škrabec wrote:
> > Dne petek, 19. avgust 2022 ob 17:37:20 CEST je Nicolas Dufresne 
napisal(a):
> >> Le vendredi 19 août 2022 à 06:17 +0200, Jernej Škrabec a écrit :
> >>> Dne četrtek, 18. avgust 2022 ob 22:33:07 CEST je Nicolas Dufresne
> > 
> > napisal(a):
> >>>> From: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> >>>> 
> >>>> 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 probe.
> >>> 
> >>> Does it even work without PM? Maybe it would be better if Cedrus would
> >>> select PM in Kconfig.
> >> 
> >> I cannot comment myself on this, but it does not seem to invalidate this
> >> Dmitry's fix.
> > 
> > If NULL pointer dereference happens only when PM is disabled, then it
> > does. I have PM always enabled and I never experienced above issue.
> 
> 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>

> 
> 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.
> 

Maybe in the future :)

Best regards,
Jernej

> --
> Best regards,
> Dmitry

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel