Displayport audio and MST


I recently bought a Dell U3011 monitor (2560x1600) with MST support for daisy-chaining. The monitor also has an audio line-out that will send the DP audio stream to speakers - and the nvidia drivers detect that there is a valid audio target and everything works fine.

If I turn MST on in the monitor settings, the display works fine, but the audio device disappears and there’s no longer an ELD entry for it reported by alsa. In dmesg I see some lines like

[28609.766211] sound hdaudioC1D0: HDMI: invalid ELD data byte 9

but those aren’t consistent when I power cycle the display, so I’m not sure whether that means the ELD is hosed in MST mode (I guess the display could send different EDID/ELD blocks in each case) or whether something else is going on on the driver side.

Has anyone had any success with DP audio in MST mode?