Comment # 23 on bug 1129027 from Stefan Dirsch

There are a 4 commits since xorg-server 1.20.4, which appear to be related to
atomic modesetting in X.Org modeset driver:

7a44e8d4007b9c3ca55a5cc3f5e98601565311c7
Author: Lyude Paul <lyude@redhat.com>
Date:   Tue Nov 13 20:14:10 2018 -0500

    modesetting: Actually disable CRTCs in legacy mode

d83efc47b7a524b4f8d4a993c27a3e402a98fa7c
Author: Keith Packard <keithp@keithp.com>
Date:   Tue Jun 26 16:34:29 2018 -0700

    xf86-video-modesetting: Lease planes as well if using atomic

4a11f66e4690f9e94dc61cb264f5ef78dbdb255a
Author: Keith Packard <keithp@keithp.com>
Date:   Tue Jun 26 14:05:31 2018 -0700

    xf86-video-modesetting: Don't enable UNIVERSAL_PLANES separately

c12f1bd4b76088ea66e3bec9ab9721a52b20cdf2
Author: Lyude Paul <lyude@redhat.com>
Date:   Thu Jun 7 20:30:34 2018 -0400

    modesetting: Also disable CRTC in drmmode_output_disable()