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Date: Sun, 28 Jan 2024 10:24:02 +0100
From: Maxime Ripard <mripard@kernel.org>
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Subject: Re: Re: [PATCH] drm/atomic-helpers: remove legacy_cursor_update hacks
Message-ID: <vyh5wg2ltmrtqw2mhtyj2lii6i4eccrjjlynzpfg7x63tkrav6@cxbz3sasvjjm>
References: <20230216111214.3489223-1-daniel.vetter@ffwll.ch>
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On Thu, Jan 25, 2024 at 07:17:21PM +0100, Daniel Vetter wrote:
> On Tue, Jan 23, 2024 at 06:09:05AM +0000, Jason-JH Lin (=E6=9E=97=E7=9D=
=BF=E7=A5=A5) wrote:
> > Hi Maxime, Daniel,
> >=20
> > We encountered similar issue with mediatek SoCs.
> >=20
> > We have found that in drm_atomic_helper_commit_rpm(), when disabling
> > the cursor plane, the old_state->legacy_cursor_update in
> > drm_atomic_wait_for_vblank() is set to true.
> > As the result, we are not actually waiting for a vlbank to wait for our
> > hardware to close the cursor plane. Subsequently, the execution
> > proceeds to drm_atomic_helper_cleanup_planes() to  free the cursor
> > buffer. This can lead to use-after-free issues with our hardware.
> >=20
> > Could you please apply this patch to fix our problem?
> > Or are there any considerations for not applying this patch?
>=20
> Mostly it needs someone to collect a pile of acks/tested-by and then land
> it.
>=20
> I'd be _very_ happy if someone else can take care of that ...
>=20
> There's also the potential issue that it might slow down some of the
> legacy X11 use-cases that really needed a non-blocking cursor, but I think
> all the drivers where this matters have switched over to the async plane
> update stuff meanwhile. So hopefully that's good.

I think there was also a regression with msm no one really figured out?

Maxime

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