Comment # 29 on bug 69729 from Rafał Miłecki

Are you sure you tested 3.11.4? It should work just like 3.12-rc3.

Can you install radeontool and provide output of "avivotools regs hdmi" command
when:

1) Playing audio with 3.11.4 (remember about radeon.audio=1)
2) Playing audio with 3.12-rc3