If the modes are only in the CEA extension block then this is a core drm issue. The core EDID parser does not handles all of the CEA 4K modes yet. Patches were proposed by several people, but I don't think any of them have gone upstream yet due to various objections and bikeshedding. See: https://lists.freedesktop.org/archives/dri-devel/2016-May/107463.html https://lists.freedesktop.org/archives/dri-devel/2016-October/121434.html https://lists.freedesktop.org/archives/dri-devel/2016-November/122631.html