gdm started before GPU (DRM) is initialized

journald.log

Dec 29 22:42:58 newn kernel: [drm] radeon kernel modesetting enabled.
Dec 29 22:42:58 newn kernel: fb0: switching to radeondrmfb from EFI VGA
Dec 29 22:42:58 newn kernel: [drm] initializing kernel modesetting (PITCAIRN 0x1002:0x6811 0x1043:0x048D 0x00).
Dec 29 22:42:58 newn kernel: [drm] Detected VRAM RAM=2048M, BAR=256M
Dec 29 22:42:58 newn kernel: [drm] RAM width 256bits DDR
Dec 29 22:42:58 newn kernel: [drm] radeon: 2048M of VRAM memory ready
Dec 29 22:42:58 newn kernel: [drm] radeon: 2048M of GTT memory ready.
Dec 29 22:42:58 newn kernel: [drm] Loading pitcairn Microcode
Dec 29 22:42:58 newn kernel: [drm] Internal thermal controller with fan control
Dec 29 22:42:58 newn kernel: [drm] radeon: dpm initialized
Dec 29 22:42:58 newn kernel: [drm] Found VCE firmware/feedback version 50.0.1 / 17!
Dec 29 22:42:58 newn kernel: [drm] GART: num cpu pages 524288, num gpu pages 524288
Dec 29 22:42:58 newn kernel: [drm] PCIE gen 3 link speeds already enabled
Dec 29 22:42:58 newn kernel: [drm] PCIE GART of 2048M enabled (table at 0x00000000001D6000).
Dec 29 22:42:58 newn kernel: [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
Dec 29 22:42:58 newn kernel: [drm] Driver supports precise vblank timestamp query.
Dec 29 22:42:58 newn kernel: [drm] radeon: irq initialized.
Dec 29 22:42:58 newn kernel: [drm] ring test on 0 succeeded in 1 usecs
Dec 29 22:42:58 newn kernel: [drm] ring test on 1 succeeded in 1 usecs
Dec 29 22:42:58 newn kernel: [drm] ring test on 2 succeeded in 1 usecs
Dec 29 22:42:58 newn kernel: [drm] ring test on 3 succeeded in 4 usecs
Dec 29 22:42:58 newn kernel: [drm] ring test on 4 succeeded in 4 usecs
Dec 29 22:42:58 newn kernel: [drm] ring test on 5 succeeded in 2 usecs
Dec 29 22:42:58 newn kernel: [drm] UVD initialized successfully.
Dec 29 22:42:58 newn systemd[1]: Starting GNOME Display Manager...
Dec 29 22:42:59 newn systemd[1]: Started GNOME Display Manager.
Dec 29 22:42:59 newn dbus-daemon[639]: [system] Activating via systemd: service name='org.freedesktop.login1' unit='dbus-org.freedesktop.login1.service' requested by ':1.13' (uid=0 pid=754 comm="/usr/bin/gdm ")
Dec 29 22:42:59 newn kernel: [drm] ring test on 6 succeeded in 20 usecs
Dec 29 22:42:59 newn kernel: [drm] ring test on 7 succeeded in 3 usecs
Dec 29 22:42:59 newn kernel: [drm] VCE initialized successfully.
Dec 29 22:42:59 newn kernel: [drm] ib test on ring 0 succeeded in 0 usecs
Dec 29 22:42:59 newn kernel: [drm] ib test on ring 1 succeeded in 0 usecs
Dec 29 22:42:59 newn kernel: [drm] ib test on ring 2 succeeded in 0 usecs
Dec 29 22:42:59 newn kernel: [drm] ib test on ring 3 succeeded in 0 usecs
Dec 29 22:42:59 newn kernel: [drm] ib test on ring 4 succeeded in 0 usecs
Dec 29 22:42:59 newn kernel: [drm] ib test on ring 5 succeeded
Dec 29 22:42:59 newn dbus-daemon[639]: [system] Activating via systemd: service name='org.freedesktop.Accounts' unit='accounts-daemon.service' requested by ':1.13' (uid=0 pid=754 comm="/usr/bin/gdm ")
Dec 29 22:43:00 newn kernel: [drm] ib test on ring 6 succeeded
Dec 29 22:43:00 newn systemd-logind[717]: New session c1 of user gdm.
Dec 29 22:43:00 newn systemd[1001]: pam_unix(systemd-user:session): session opened for user gdm by (uid=0)
Dec 29 22:43:00 newn systemd[1]: Started Session c1 of user gdm.
Dec 29 22:43:00 newn gnome-shell[1042]: Failed to create backend: No drm devices found        <-- NB!!!!!!!!!!!!!!!!!!!!
Dec 29 22:43:00 newn kernel: [drm] ib test on ring 7 succeeded
Dec 29 22:43:00 newn kernel: [drm] Radeon Display Connectors
Dec 29 22:43:00 newn kernel: [drm] Connector 0:
Dec 29 22:43:00 newn kernel: [drm]   DP-1
Dec 29 22:43:00 newn kernel: [drm]   HPD4
Dec 29 22:43:00 newn kernel: [drm]   DDC: 0x6530 0x6530 0x6534 0x6534 0x6538 0x6538 0x653c 0x653c
Dec 29 22:43:00 newn kernel: [drm]   Encoders:
Dec 29 22:43:00 newn kernel: [drm]     DFP1: INTERNAL_UNIPHY2
Dec 29 22:43:00 newn kernel: [drm] Connector 1:
Dec 29 22:43:00 newn kernel: [drm]   HDMI-A-1
Dec 29 22:43:00 newn kernel: [drm]   HPD5
Dec 29 22:43:00 newn kernel: [drm]   DDC: 0x6540 0x6540 0x6544 0x6544 0x6548 0x6548 0x654c 0x654c
Dec 29 22:43:00 newn kernel: [drm]   Encoders:
Dec 29 22:43:00 newn kernel: [drm]     DFP2: INTERNAL_UNIPHY2
Dec 29 22:43:00 newn kernel: [drm] Connector 2:
Dec 29 22:43:00 newn kernel: [drm]   DVI-I-1
Dec 29 22:43:00 newn kernel: [drm]   HPD6
Dec 29 22:43:00 newn kernel: [drm]   DDC: 0x6580 0x6580 0x6584 0x6584 0x6588 0x6588 0x658c 0x658c
Dec 29 22:43:00 newn kernel: [drm]   Encoders:
Dec 29 22:43:00 newn kernel: [drm]     DFP3: INTERNAL_UNIPHY
Dec 29 22:43:00 newn kernel: [drm]     CRT1: INTERNAL_KLDSCP_DAC1
Dec 29 22:43:00 newn kernel: [drm] Connector 3:
Dec 29 22:43:00 newn kernel: [drm]   DVI-D-1
Dec 29 22:43:00 newn kernel: [drm]   HPD1
Dec 29 22:43:00 newn kernel: [drm]   DDC: 0x6570 0x6570 0x6574 0x6574 0x6578 0x6578 0x657c 0x657c
Dec 29 22:43:00 newn kernel: [drm]   Encoders:
Dec 29 22:43:00 newn kernel: [drm]     DFP4: INTERNAL_UNIPHY1
Dec 29 22:43:00 newn kernel: [drm] fb mappable at 0xE05E1000
Dec 29 22:43:00 newn kernel: [drm] vram apper at 0xE0000000
Dec 29 22:43:00 newn kernel: [drm] size 33177600
Dec 29 22:43:00 newn kernel: [drm] fb depth is 24
Dec 29 22:43:00 newn kernel: [drm]    pitch is 15360
Dec 29 22:43:00 newn kernel: fbcon: radeondrmfb (fb0) is primary device
Dec 29 22:43:01 newn kernel: radeon 0000:09:00.0: fb0: radeondrmfb frame buffer device
Dec 29 22:43:01 newn kernel: [drm] Initialized radeon 2.50.0 20080528 for 0000:09:00.0 on minor 0
Dec 29 22:43:01 newn kernel: [drm] amdgpu kernel modesetting enabled.