linux-kernel - Re: [PATCH v7 4/6] drm: Refuse to async flip with atomic prop changes

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Message-ID: <745e35ee-d617-9ce0-8b4e-795c84a5af48@mailbox.org>
Date:   Mon, 23 Oct 2023 10:42:45 +0200
From:   Michel Dänzer <michel.daenzer@...lbox.org>
To:     Simon Ser <contact@...rsion.fr>
Cc:     pierre-eric.pelloux-prayer@....com,
        André Almeida <andrealmeid@...lia.com>,
        'Marek Olšák' <maraeo@...il.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        Pekka Paalanen <ppaalanen@...il.com>,
        dri-devel@...ts.freedesktop.org, kernel-dev@...lia.com,
        alexander.deucher@....com, hwentlan@....com,
        christian.koenig@....com, joshua@...ggi.es
Subject: Re: [PATCH v7 4/6] drm: Refuse to async flip with atomic prop changes

On 10/23/23 10:27, Simon Ser wrote:
> On Sunday, October 22nd, 2023 at 12:12, Michel Dänzer <michel.daenzer@...lbox.org> wrote:
>> On 10/17/23 14:16, Simon Ser wrote:
>>
>>> After discussing with André it seems like we missed a plane type check
>>> here. We need to make sure FB_ID changes are only allowed on primary
>>> planes.
>>
>> Can you elaborate why that's needed?
> 
> 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.

That should be handled in the driver's atomic_check then?

Async flips of overlay planes would be useful e.g. for presenting a windowed application with tearing, while the rest of the desktop is tear-free.


-- 
Earthling Michel Dänzer            |                  https://redhat.com
Libre software enthusiast          |         Mesa and Xwayland developer