Anything with Displayport 1.1 and higher can be Displayport ++ in which case, if you are going Displayport > HDMI with an adapter, the source will reconfigure itself to output a proper HDMI signal through the Displayport connector. In this case, it behaves exactly like HDMI. Including all the audio formats you would normally get with HDMI.

Just need to look at the back of the device and see if the ++ symbol is there. We use it a fair bit (mostly with Dell PCs actually) and never have a problem. Although in the early days it was a bit hit and miss. The dual mode ++ versions fixed all that.