Comment 12 for bug 1895665

Here is what happens as seen by pulseaudio -vvvv during the monitor sleep/wake cycle leading to disappearance of the HDMI output:

D: [pulseaudio] alsa-util.c: ELD info empty (for device=3)
D: [pulseaudio] module-alsa-card.c: Jack 'HDMI/DP,pcm=3 Jack' is now unplugged
D: [pulseaudio] device-port.c: Setting port hdmi-output-0 to status no
D: [pulseaudio] core-subscribe.c: Dropped redundant event due to change event.
D: [pulseaudio] module-switch-on-port-available.c: Trying to switch away from port hdmi-output-0, found no better option
I: [pulseaudio] core.c: default_sink: alsa_output.pci-0000_65_00.1.hdmi-stereo -> alsa_output.pci-0000_00_1f.3.iec958-stereo
D: [pulseaudio] card.c: Setting card alsa_card.pci-0000_65_00.1 profile output:hdmi-stereo to availability status no
D: [pulseaudio] core-subscribe.c: Dropped redundant event due to change event.
D: [pulseaudio] module-switch-on-port-available.c: Active profile output:hdmi-stereo on card alsa_card.pci-0000_65_00.1 became unavailable, switching to another profile
D: [pulseaudio] sink.c: alsa_output.pci-0000_65_00.1.hdmi-stereo: state: SUSPENDED -> UNLINKED
D: [pulseaudio] source.c: alsa_output.pci-0000_65_00.1.hdmi-stereo.monitor: state: SUSPENDED -> UNLINKED
D: [alsa-sink-HDMI 0] alsa-sink.c: Thread shutting down
I: [pulseaudio] sink.c: Freeing sink 1 "alsa_output.pci-0000_65_00.1.hdmi-stereo"
I: [pulseaudio] source.c: Freeing source 2 "alsa_output.pci-0000_65_00.1.hdmi-stereo.monitor"
D: [pulseaudio] card.c: alsa_card.pci-0000_65_00.1: active_profile: output:hdmi-stereo -> off
D: [pulseaudio] core-subscribe.c: Dropped redundant event due to change event.
D: [pulseaudio] alsa-util.c: ELD info empty (for device=3)
D: [pulseaudio] module-alsa-card.c: Jack 'HDMI/DP,pcm=3 Jack' is now unplugged
D: [pulseaudio] alsa-util.c: ELD info empty (for device=3)

Although slightly redundant, it looks all right.
Part of the problem seems to come from blacklisting HDMI monitors by default (not switching to them when they are plugged in). But that's the second part of the problem.

I: [pulseaudio] module-switch-on-connect.c: Refusing to switch to blacklisted sink alsa_output.pci-0000_65_00.1.hdmi-stereo

The first and major issue is the absence of any event detection when the DP monitor wakes up.

"pulseaudio -k" restarts the daemon, and probing at startup seems to find it again.