V520 causes intermittent blanking on daisychained DP monitor, v515 ok

In Fedora linux with a GTX 1650. Symptom: the daisychained DP monitor works fine for 1 to 15 seconds, then goes black for 1 to 8s (usually around 2s), then comes back on, goto step 1. Never stops.

Upgrading to akmod-nvidia-3:520.56.06-1.fc35.x86_64 introduced this new monitor blanking-out / flickering bug. It only affects one of my 3 monitors, which is plugged in as the final monitor on a 2-monitor DP daisy chain.

akmod-nvidia-3:515.65.01-1.fc35.x86_64 does not have this problem. I dnf downgraded to 515 and the bug went away. Bug is definitely caused by some change between 515 and 520. Reproduced this many times. 515 installed/booted: no bug; 520 installed/booted: bug.

I tried putting in the latest nvidia-gpu-firmware from testing first, as that upgraded at the same time, but it didn’t affect anything. Bug persists with any version of nvidia-gpu-firmware.

Versions of packages that work:
akmod-nvidia-3:515.65.01-1.fc35.x86_64
nvidia-settings-3:515.65.01-1.fc35.x86_64
xorg-x11-drv-nvidia-3:515.65.01-1.fc35.x86_64
xorg-x11-drv-nvidia-kmodsrc-3:515.65.01-1.fc35.x86_64
xorg-x11-drv-nvidia-libs-3:515.65.01-1.fc35.i686
xorg-x11-drv-nvidia-libs-3:515.65.01-1.fc35.x86_64

Versions broken:
akmod-nvidia-3:520.56.06-1.fc35.x86_64
kmod-nvidia-5.18.11-100.fc35.x86_64-3:520.56.06-1.fc35.x86_64
nvidia-settings-3:520.56.06-1.fc35.x86_64
xorg-x11-drv-nvidia-3:520.56.06-1.fc35.x86_64
xorg-x11-drv-nvidia-kmodsrc-3:520.56.06-1.fc35.x86_64
xorg-x11-drv-nvidia-libs-3:520.56.06-1.fc35.i686
xorg-x11-drv-nvidia-libs-3:520.56.06-1.fc35.x86_64

will attach nvidia-bug-report.log.gz in a sec

nvidia-bug-report.log.gz (122.9 KB)