I guess the extra modes with the new code in drm-core-next are crucial 
for some, but it does generate a lot of extra non working modes for me.

With the previous behavior xrandr would list modes that all worked - 
although there are a few new ones that work on my monitor there are a 
lot that don't and for my TV I don't think any new one works.

I see from xorg log that the old DDC gethered modes are still listed - 
maybe if all these extra modes are needed/not being listed in error a 
new xrandr option to list "safe" modes or one to list the new modes with 
safe being default would be more user friendly.

Attached are xrandr --verbose before and after in case anyone is interested.

DVI-0 is a plasma 1920x1080 TV via hdmi (dvi adapter)

DVI-1 is a lcd 1920x1080 120Hz monitor.