it's seems like it's not possible to cap (limit) the framerate. Or is it?
If it's not currently possible, could you please implement it?
This would be useful for freesync without vsync and also power savings (radeon chill does it in windows). Shouldn't be complicated to implement?
Seems unrelated to the kernel and would have a better place in a compositor or in mesa.
If you disagree, please file a bug in https://gitlab.freedesktop.org/drm/misc.