[hsw dp audio] Muting S/PDIF turns off DP

[Daniel Martin <consume.noise@gmail.com>]

Hi,

I've a bug here: when playing audio via the speakers of a monitor
attached to a DisplayPort and I mute the corresponding S/PDIF (i.e. with
alsamixer) then the monitor switches off into standby, unmuting the
S/PDIF turns the monitor back on.
When muting the S/PDIF while no audio is playing everything is fine.

There's no audio daemon running and my ~/.asoundrc contains only:

    pcm.!default {
        type hw
        card 0
        device 3
    }

I've already filed a fdo bug report (drm/intel) for this as I thought it
might be related to it:
    Bug 75729 - [hsw dp audio] Muting S/PDIF turns off DP
    https://bugs.freedesktop.org/show_bug.cgi?id=75729
Attached to this bug is a `alsa-info.log` too.

As stated in the bug report it's not a showstopper for me, but obviously
something seems to go wrong and maybe someone has an idea.

Thanks,
    Daniel Martin