https://bugs.freedesktop.org/show_bug.cgi?id=102300
--- Comment #7 from Michel Dänzer michel@daenzer.net --- According to the log file, the ASUS monitor only lists the 60 Hz 1920x1080 mode in its EDID. So it seems clear that's what the monitor wants to be fed, but for some reason we don't seem to be generating it properly.
Any chance you can try if a kernel built from the amd-staging-4.12 or amd-staging-drm-next branch of https://cgit.freedesktop.org/~agd5f/linux/ with CONFIG_DRM_AMD_DC=y works better?