linux-kernel - Re: [PATCH AUTOSEL 5.4 13/15] drm/amdgpu/dc: Require primary plane to be enabled whenever the CRTC is

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Message-ID: <1ee666b4-f1af-a19f-e03a-fdfc00698d2f@daenzer.net>
Date:   Mon, 21 Sep 2020 16:48:05 +0200
From:   Michel Dänzer <michel@...nzer.net>
To:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        Alex Deucher <alexander.deucher@....com>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>
Subject: Re: [PATCH AUTOSEL 5.4 13/15] drm/amdgpu/dc: Require primary plane to
 be enabled whenever the CRTC is

On 2020-09-21 4:40 p.m., Sasha Levin wrote:
> From: Michel Dänzer <mdaenzer@...hat.com>
> 
> [ Upstream commit 2f228aab21bbc74e90e267a721215ec8be51daf7 ]
> 
> Don't check drm_crtc_state::active for this either, per its
> documentation in include/drm/drm_crtc.h:
> 
>   * Hence drivers must not consult @active in their various
>   * &drm_mode_config_funcs.atomic_check callback to reject an atomic
>   * commit.
> 
> atomic_remove_fb disables the CRTC as needed for disabling the primary
> plane.
> 
> This prevents at least the following problems if the primary plane gets
> disabled (e.g. due to destroying the FB assigned to the primary plane,
> as happens e.g. with mutter in Wayland mode):
> 
> * The legacy cursor ioctl returned EINVAL for a non-0 cursor FB ID
>    (which enables the cursor plane).
> * If the cursor plane was enabled, changing the legacy DPMS property
>    value from off to on returned EINVAL.
> 
> v2:
> * Minor changes to code comment and commit log, per review feedback.
> 
> GitLab: https://gitlab.gnome.org/GNOME/mutter/-/issues/1108
> GitLab: https://gitlab.gnome.org/GNOME/mutter/-/issues/1165
> GitLab: https://gitlab.gnome.org/GNOME/mutter/-/issues/1344
> Suggested-by: Daniel Vetter <daniel.vetter@...ll.ch>
> Acked-by: Daniel Vetter <daniel.vetter@...ll.ch>
> Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@....com>
> Signed-off-by: Michel Dänzer <mdaenzer@...hat.com>
> Signed-off-by: Alex Deucher <alexander.deucher@....com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>

I'm a bit nervous about this getting backported so far back so quickly. 
I'd prefer waiting for 5.9 final first at least.


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