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Date:   Mon, 23 Oct 2023 08:44:46 +0000
To:     =?utf-8?Q?Michel_D=C3=A4nzer?= <michel.daenzer@mailbox.org>
From:   Simon Ser <contact@emersion.fr>
Cc:     pierre-eric.pelloux-prayer@amd.com,
        =?utf-8?Q?Andr=C3=A9_Almeida?= <andrealmeid@igalia.com>,
        =?utf-8?Q?=27Marek_Ol=C5=A1=C3=A1k=27?= <maraeo@gmail.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org,
        Pekka Paalanen <ppaalanen@gmail.com>,
        dri-devel@lists.freedesktop.org, kernel-dev@igalia.com,
        alexander.deucher@amd.com, hwentlan@amd.com,
        christian.koenig@amd.com, joshua@froggi.es
Subject: Re: [PATCH v7 4/6] drm: Refuse to async flip with atomic prop changes
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On Monday, October 23rd, 2023 at 10:42, Michel D=C3=A4nzer <michel.daenzer@=
mailbox.org> wrote:

> On 10/23/23 10:27, Simon Ser wrote:
>=20
> > On Sunday, October 22nd, 2023 at 12:12, Michel D=C3=A4nzer michel.daenz=
er@mailbox.org wrote:
> >=20
> > > On 10/17/23 14:16, Simon Ser wrote:
> > >=20
> > > > After discussing with Andr=C3=A9 it seems like we missed a plane ty=
pe check
> > > > here. We need to make sure FB_ID changes are only allowed on primar=
y
> > > > planes.
> > >=20
> > > Can you elaborate why that's needed?
> >=20
> > Current drivers are in general not prepared to perform async page-flips
> > on planes other than primary. For instance I don't think i915 has logic
> > to perform async page-flip on an overlay plane FB_ID change.
>=20
>=20
> That should be handled in the driver's atomic_check then?
>=20
> Async flips of overlay planes would be useful e.g. for presenting a windo=
wed application with tearing, while the rest of the desktop is tear-free.

Yes, that would be useful, but requires more work. Small steps: first
expose what the legacy uAPI can do in atomic, then later extend that in
some drivers.