EDID confusion with LG 4K TV as monitor running X rather than wayland
Submitted by Tom Horsley
Assigned to Nouveau Project
Link to original bug (#110631)
Description
Starting with fedora 28 and going through fedora 30, the nouveau driver produces a bad signal when trying to display X on my LG OLEDB6P 4K television.
Weirdly, with what is presumably the same driver, it displays a full UHD resolution when running wayland rather than X. (I really don't understand why something as low level as the video timing would be different between wayland and X, but if someone does know, they probably know where the bug is too :-).
This isn't restricted to fedora either. I've just been testing a multi-boot USB stick, and the drivers on the ubuntu 19.04 live CD and the System Rescue CD 6.0.3 produce the same "bad signal" errors on this monitor.
For details (like X log files) see:
https://bugzilla.redhat.com/show_bug.cgi?id=1575391
and
https://bugzilla.redhat.com/show_bug.cgi?id=1648608
If I add nomodeset and forcevesa kernel parameters, I can boot and see (lower resolution) video rather than a black screen.
Switching to the nvidia binary drivers makes the display work properly again.
Booting the USB stick on different systems with more conventional resolution monitors, nouveau works fine.