https://bugs.freedesktop.org/show_bug.cgi?id=80162
--- Comment #2 from Pierre Ossman pierre-bugzilla@ossman.eu --- Thanks. Going through the vendor verbs revealed the issue. Multichannel mode was getting reset on suspend, and was not properly reinitialised by the driver on resume.
Will prepare a patch for the ALSA folks. I guess you can close this bug entry as invalid.