Arch Linux

Descprition:
Prime synchronization in nvidia drivers was broken since linux 5.4. Arch maintainers fixed this with patch, provided on the forum. But prime synchronization is still not working in nvidia-390xx. The same person wrote patch for 390xx drivers, so can it be added to nvidia-390xx (nvidia-390xx-dkms) package? It works for me, people on the forum also reports that it's fine. As well, base 5.5 patch should be dropped, that one isn't needed with this new version.

Enabling DRM kernel mode setting according to Arch Linux wiki instruction (https://wiki.archlinux.org/index.php/NVIDIA_Optimus#Tearing/Broken_VSync) doesn't help.

Running smth like xrandr --output eDP-1-1 --set "PRIME Synchronization" 1 doesn't help (screen blinks, prime synchronization does not turn on)

Creating a bug report for upstream isn't possible, because Nvidia doesn't support 390xx drivers (https://nvidia.custhelp.com/app/answers/detail/a_id/3142) and fixes only critical issues (tearing is not critical).

Creating this bug report was recommended by Sven-Hendrik Haase.

Additional info:
* nvidia-390xx-dkms-390.132-30, linux-5.5.6.arch1-1, xorg-server-1.20.7-1
* commit fixing such issue in nvidia package: https://git.archlinux.org/svntogit/packages.git/commit/trunk?h=packages/nvidia&id=4a4925b42f277bcdeac6d30cb9ae03f76440a1cf
* topic on archlinux forum: https://bbs.archlinux.org/viewtopic.php?id=251032
* patch for nvidia-390xx: https://gitlab.com/snippets/1943814

Steps to reproduce:
Install nvidia 390xx driver and start xorg-server on a discrete graphics card, then run xrandr -prop and get something like this: (see attached file)