Comment # 20 on bug 1193397 from Kourosh P.

(In reply to Takashi Iwai from comment #16)
> Try to boot with monitor off, run X.  Then before turning on the monitor,
> enable the debug option of drm, run the following as root:
>    echo 0x1e > /sys/module/drm/parameters/debug
> 
> Then turn on the monitor, confirm the problem ('no signal').  Save the dmesg
> output at this stage.

dmesg | susepaste
https://susepaste.org/49240459

> Then move to VT1, restore the monitor out, and save the dmesg output again.
> After that, clear the drm debug option
>     echo 0 > /sys/module/drm/parameters/debug

I hope with "move to VT1" you mean CTRL+ALT+F1 and run the command, and not
rebooting the system with monitor ON this time.

I did go to TTY1, login, startx (X took a lot longer time to load but only the
mouse cursor is visible with screen showing black) waited few minutes and the
ddesktop came on for a split second and everything went black except the mouse
cursor being visible. I did dmesg:

dmesg | susepaste
https://susepaste.org/12185740

I had to move to TTY2 to be able to reboot the system safely (took a LONG
time).
Don't know if I should have done another dmesg output after a successful reboot
with monitor ON?!

> Upload the saved two dmesg outputs to Bugzilla.
> 
> BTW, when you boot with another desktop environment (such as icewm), does
> the problem persist?  I mean not to log out and switch from KDE, but login
> directly to icewm session (which should be available as fallback) at boot.