Boot Freeze (amdgpu.cik_support=1, Mesa 20.0.0-devel, Ubuntu 18.04.3)

Hi,

with the newest Oibaf PPA Mesa 20.0.0-devel (git-8a135ff6 2020-01-24 bionic-oibaf-ppa) and radeon.cik_support=0 amdgpu.cik_support=1 as kernel options, Ubuntu 18.04.3 freezes on boot (Gnome 3.28.2, Kernel 4.15.0-74-generic).

Without the kernel options, the system boots just fine (aside from missing Vulkan support and worse OpenGL performance). The previous Oibaf Mesa version was working well with aforementioned kernel options including the Vulkan API. The GPU is an AMD (Kaveri) A10-7850K.

I have no experience with Kernel or Driver debugging, so the only thing I can offer for now is an excerpt from the boot log (journalctl -b | grep -i -E "drm|gpu") which seemed relevant (see below). If You give me some guidance/pointers I'm happy to produce any logs or debug info that You need.

  Jan 24 15:54:07 dtitx-pc kernel: [drm] VGACON disable radeon kernel modesetting.
  Jan 24 15:54:07 dtitx-pc kernel: [drm:radeon_init [radeon]] *ERROR* No UMS support in radeon module!
  Jan 24 15:54:07 dtitx-pc kernel: [drm:amdgpu_init [amdgpu]] *ERROR* VGACON disables amdgpu kernel modesetting.
  Jan 24 15:54:13 dtitx-pc systemd[1]: Starting Detect the available GPUs and deal with any system changes...
  Jan 24 15:54:13 dtitx-pc gpu-manager[834]: Error: can't open /lib/modules/4.15.0-74-generic/updates/dkms
  Jan 24 15:54:13 dtitx-pc systemd[1]: Started Detect the available GPUs and deal with any system changes.
  Jan 24 15:54:14 dtitx-pc gnome-shell[1100]: Failed to create backend: Could not find a primary drm kms device
  Jan 24 15:54:14 dtitx-pc /usr/lib/gdm3/gdm-x-session[1189]: (==) Automatically adding GPU devices
  Jan 24 15:54:14 dtitx-pc /usr/lib/gdm3/gdm-x-session[1189]: (==) Automatically binding GPU devices
  Jan 24 15:54:14 dtitx-pc /usr/lib/gdm3/gdm-x-session[1189]: (II) [KMS] drm report modesetting isn't supported.