https://bugs.freedesktop.org/show_bug.cgi?id=102985
--- Comment #5 from invergo bicom@invergo.net --- I am on commit 23d3505d648e and this now appears to be resolved: I can select 4k@60Hz (among several other new resolutions) without crashing. Furthermore, this also resolves a problem I hadn't mentioned of not having HDMI audio (didn't realize that it could be related).