Comment 10 for bug 1674304

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Rogério Vinhal Nunes (rogeriovn) wrote : Re: PRIME synchronization not working with xserver-1.19.x

So, I just upgraded to 17.04 with Xorg 1.19.3 and nvidia 375.xx drivers. By default, Ubuntu installed a modprobe.d file to set drm modeset = 0 for the nvidia kernel module and that seem to prevent Prime Synchronization from working.

I tried to change the modeset to 1 so I could finally try the synchronization configuration, but that froze the system hard as long as lightdm booted. I installed gnome with gdm3 and I could get to gdm3 and try to login to gnome with no avail. But after a few tries (without changing anything) it just logged in, but prime synchronization was off for both the laptop screen as my TV. I did the "modprobe -v nvidia-drm" to check the modeset and it was 1, but whenever I tried to set the Prime Synchronization via xrandr, the screen went black for a sec and came back, but xrandr --verbose still displayed Prime Synchronization off.

Why is that cat /etc/modprobe.d/nvidia-graphics-drivers.conf with the "options nvidia_375_drm modeset=0"? Why does changing it to 1 freeze the whole system thereafter?