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

From: Michel Dänzer
Date: Mon Sep 21 2020 - 10:54:49 EST


On 2020-09-21 4:40 p.m., Sasha Levin wrote:
From: Michel Dänzer <mdaenzer@xxxxxxxxxx>

[ 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@xxxxxxxx>
Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx>
Signed-off-by: Michel Dänzer <mdaenzer@xxxxxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

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