Created attachment 851460 [details]
Xorg.0.log and dmesg

Initial summary:
black screen on initial X open on Kaveri Radeon R7, /dev/dri/card0: No such
file or directory with radeon.cik_support=0 amdgpu.cik_support=1

To reproduce:
1-boot with included on kernel cmdline radeon.cik_support=0
amdgpu.cik_support=1
2-wait for X to fail to start
3-login on a tty
4-systemctl restart xdm

Actual behavior:
1-X fails to start, finding no /dev/dri/card0, leaving login prompt on tty1 on
display screen
2-X starts normally using amdgpu DDX driver

Expected behavior:
1-X starts normally using amdgpu DDX driver

Tested with kernels 5.12.13, 5.11.16, 5.7.11
# inxi -SGIay
System:
  Host: asa88 Kernel: 5.12.13-1-default x86_64 bits: 64 compiler: gcc
  v: 11.1.1
  parameters: BOOT_IMAGE=/boot/vmlinuz root=LABEL=tvgp07stw noresume
  ipv6.disable=1 net.ifnames=0 mitigations=auto consoleblank=0
  radeon.cik_support=0 amdgpu.cik_support=1 video=1024x768@60
  video=1440x900@60 drm.debug=0x1e log_buf_len=1M
  Console: tty pts/0 DM: TDM Distro: openSUSE Tumbleweed 20210730
Graphics:
  Device-1: AMD Kaveri [Radeon R7 Graphics] vendor: ASUSTeK driver: amdgpu
  v: kernel alternate: radeon bus-ID: 00:01.0 chip-ID: 1002:130f
  class-ID: 0300
  Display: server: X.org 1.20.12 driver: loaded: vesa
  unloaded: fbdev,modesetting alternate: ati
  Message: Advanced graphics data unavailable for root.
Info:...inxi: 3.3.06

Comments:
1-without radeon.cik_support=0 amdgpu.cik_support=1 on cmdline, X cannot be
coaxed into using amdgpu DDX driver via /etc/X11/xorg.conf.d/*conf
2-without radeon.cik_support=0 amdgpu.cik_support=1, greeter startup completes
(normally, on first try) using modesetting DIX driver