https://bugs.freedesktop.org/show_bug.cgi?id=77274
--- Comment #9 from Daniele Peruzzi amnesiac2001@gmail.com --- I've compiled a new 3.14 vanilla kernel with this patch:
https://bugs.freedesktop.org/attachment.cgi?id=97049&action=edit
the result was that the audio over HDMI becomes working again but the above mentioned error in my dmesg is still there.