I have a RX560 with DP (1.4), HDMI and DVI. I am connecting to a TCL P605, which has HDMI2.0 turned on for the input and it’s set as ‘computer’ input. With HDMI out, I get 4K60, 4:4:4 fine. When I switch out to DP with the Plugable DP-HDMI (active, using the same HDMI cable), I can get 4K60, but only 4:2:0.
Running Linux with the open source AMD driver and it currently only supports 8bit color, so I’m sure that’s not the problem.
Is it possible that because the card supports DP 1.4 that the active DP-HDMI is trying for 1.4 levels of bandwidth negotiation?
Any ideas on what to check?
Edit: Machine info:
Qt: 5.10.0, KDE Frameworks: 5.43.0, Plasma: 5.12.1, Tumbleweed" v.“20180218”
4.5 (Core Profile) Mesa 18.0.0-rc3
Radeon RX 560 Series (POLARIS11 / DRM 3.23.0 / 4.16.0-rc2-mike, LLVM 5.0.1)