I'm not sure, but I think you need an active adaptor from DP1.2 to HDMI 2.0. One like this:
https://www.amazon.com/Club3D-Displayport-1-2-HDMI-CAC-1070/dp/B017BQ8I54
Please excuse my bad English.
Currently gaming on a PC with an i5-4670k@stock (for now), 16Gb RAM 1600 MHz and a GTX 1070
Steam / Live / NNID : jonxiquet Add me if you want, but I'm a single player gamer.