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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Date:   Tue, 22 Sep 2020 10:25:32 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Michel Dänzer <michel@...nzer.net>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        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 Mon, Sep 21, 2020 at 04:48:05PM +0200, Michel Dänzer wrote:
>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.

Will drop it for now, thanks.

-- 
Thanks,
Sasha