notro
commented
2 years ago I tried disabling fbdev for the USB adapter, to see if the 'No available CRTC for monitor' message went away. It didn't.
$ echo 0 | sudo tee /sys/module/drm_kms_helper/parameters/fbdev_emulation
# plug in, plug out, plug in
$ journalctl -l --no-pager --boot /usr/bin/gnome-shell -g "No available CRTC"
april 28 14:27:26 pi-ubuntu-x86 gnome-shell[1092]: Failed to use suggested monitor configuration: No available CRTC for monitor 'SAM S24D590' not found
april 28 14:27:26 pi-ubuntu-x86 gnome-shell[1092]: Failed to use linear monitor configuration: No available CRTC for monitor 'SAM S24D590' not found
april 28 14:27:27 pi-ubuntu-x86 gnome-shell[1092]: Failed to use linear monitor configuration: No available CRTC for monitor 'SAM S24D590' not found
$ sudo cat /sys/kernel/debug/dri/1/state
plane[31]: plane-0
crtc=(null)
fb=0
crtc-pos=0x0+0+0
src-pos=0.000000x0.000000+0.000000+0.000000
rotation=1
normalized-zpos=0
color-encoding=ITU-R BT.601 YCbCr
color-range=YCbCr limited range
crtc[33]: crtc-0
enable=0
active=0
self_refresh_active=0
planes_changed=0
mode_changed=0
active_changed=0
connectors_changed=0
color_mgmt_changed=0
plane_mask=0
connector_mask=0
encoder_mask=0
mode: "": 0 0 0 0 0 0 0 0 0 0 0x0 0x0
connector[36]: HDMI-A-3
crtc=(null)
self_refresh_aware=0
connector[41]: HDMI-A-4
crtc=(null)
self_refresh_aware=0
Unplugging and then plugging in the adapter does not work. The display comes up as black and backlit. But when rebooting the splash comes up.
This was working on Ubuntu 20.04, but there the DRM device was not released so the DRM minor was bumped each time and not reused.
gnome-shell log:
(full log)
The black display is controlled by fbdev (fbcon) as this shows:
gnome-shell has an fd open:
kernel log:
This shows the reboot splash
Do the same with debug enabled: /etc/environment
log: https://gist.github.com/notro/a11be18408e9daddbf84b318f949e8e1