Adaptive Sync/VRR not working in multi-head with a non-freesync monitor

Ilya Trukhanov lahvuun at
Tue Jan 8 12:41:48 UTC 2019

Tried Unigine Valley with bspwm and Plasma, Freesync does not get
engaged when second monitor (without Freesync support) is in use.
If I turn it off with e.g.

$ xrandr --output HDMI-A-0 --off

Freesync immediately starts working. Once I turn the monitor back on,
Freesync is gone.

Looking through one of the patches at
I found this:

> Per-CRTC support is gone for enabling variable refresh.
> A window must cover the entire X screen in order to flip
> so every CRTC must be enabled or disabled at the same time.

If I understood correctly, in case of multi-head, a window must span
across all monitors, with all monitors having Freesync support.
Therefore, my setup won't work in this case. However, it *does* work on
Windows (albeit only one monitor has Freesync working, obviously).

Am I missing something obvious?
Or is this some kind of X design limitation?
Are there any possible workarounds to achieve the same functionality as
on Windows?

I would greatly appreciate some clarification on this topic. Thank you!
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