If you have indeed
sudo cat /sys/module/nvidia_drm/parameters/modeset
Y
with kernel 4.15 then there’s more not working, I deducted the modeset=0 parameter indirectly from the missing lines in dmesg:
[drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[drm] No driver support for vblank timestamp query.