[PATCH v2] drm/amdgpu/dc: Require primary plane to be enabled whenever the CRTC is

[Michel Dänzer]

On 2020-09-07 9:57 a.m., Daniel Vetter wrote:
> On Fri, Sep 04, 2020 at 12:43:04PM +0200, Michel Dänzer wrote:
>> From: Michel Dänzer <mdaenzer at redhat.com>
>>
>> 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 at ffwll.ch>
>> Signed-off-by: Michel Dänzer <mdaenzer at redhat.com>
> 
> Commit message agrees with my understand of this maze now, so:
> 
> Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>

Thanks Daniel!


Nick / Harry, any more feedback? If not, can you apply this?


P.S. Since DCN doesn't make a distinction between primary or overlay 
planes in hardware, could ChromiumOS achieve the same effect with only 
the primary plane instead of only an overlay plane? If so, maybe there's 
no need for the "black plane hack".


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