[ubuntu] Skylake, Displayport and 4K woes (picture, no audio)

Ok. I've been fighting with this issue for weeks now.

I have fresh Intel NUC (http://www.intel.com/content/www/us/...nuc6i5syk.html) set up as a HTPC and coected to a UHD tv, which is capable of doing 3840x2160@60fps. The computer is coected with a DP1.2->HDMI 2.0 adapter (http://www.club-3d.com/index.php/pro...e-adapter.html) and even though the system doesn't automatically detect a 60Hz mode, I can get it to work with a modeline based on the displays EDID information.

Modeline "3840x2160" 533.28 3840 3888 3920 4000 2160 2163 2168 2222 +hsync -vsync

If I use a slightly "invalid" modeline, which has a much higher pixel clock and isn't a "reduced blanking" mode, I get a picture with some flickering pixels and clipping/popping audio.

"3840x2160_60.00" 594.000 3840 4016 4104 4400 2160 2168 2178 2250 +hsync +vsync

I tried a Windows to Go USB media to check if there is any difference, and 4K@60Hz works fine with audio, and apparently exactly the same info as the first listed modeline.

I just can't understand what to do next. Any help getting the modeline in order would be very welcome.