Forgot to mention that the processor is i9 9900k and the motherboard is ASUS WS Z390 PRO

Can you please verify the issue with drmtip and attach dmesg?
(https://cgit.freedesktop.org/drm-tip)

Hi! I have compiled the kernel and I am running it now. Still no sound. Attaching the dmesg output

Created attachment 144919 [details]
drm-tip dmesg output

What's interesting is that `pacmd list-sinks` seems to find something at least:

1 sink(s) available.
  * index: 2
	name: <alsa_output.pci-0000_00_1f.3.hdmi-stereo>
	driver: <module-alsa-card.c>
	flags: HARDWARE DECIBEL_VOLUME LATENCY DYNAMIC_LATENCY
	state: RUNNING
	suspend cause: (none)
	priority: 9030
	volume: front-left: 65536 / 100% / 0.00 dB,   front-right: 65536 / 100% / 0.00 dB
	        balance 0.00
	base volume: 65536 / 100% / 0.00 dB
	volume steps: 65537
	muted: no
	current latency: 25.02 ms
	max request: 4 KiB
	max rewind: 4 KiB
	monitor source: 2
	sample spec: s16le 2ch 44100Hz
	channel map: front-left,front-right
	             Stereo
	used by: 1
	linked by: 1
	configured latency: 25.01 ms; range is 0.50 .. 2000.00 ms
	card: 0 <alsa_card.pci-0000_00_1f.3>
	module: 6
	properties:
		alsa.resolution_bits = "16"
		device.api = "alsa"
		device.class = "sound"
		alsa.class = "generic"
		alsa.subclass = "generic-mix"
		alsa.name = "HDMI 0"
		alsa.id = "HDMI 0"
		alsa.subdevice = "0"
		alsa.subdevice_name = "subdevice #0"
		alsa.device = "3"
		alsa.card = "0"
		alsa.card_name = "HDA Intel PCH"
		alsa.long_card_name = "HDA Intel PCH at 0x6001110000 irq 192"
		alsa.driver_name = "snd_hda_intel"
		device.bus_path = "pci-0000:00:1f.3"
		sysfs.path = "/devices/pci0000:00/0000:00:1f.3/sound/card0"
		device.bus = "pci"
		device.vendor.id = "8086"
		device.vendor.name = "Intel Corporation"
		device.product.id = "a348"
		device.product.name = "Cannon Lake PCH cAVS"
		device.form_factor = "internal"
		device.string = "hdmi:0"
		device.buffering.buffer_size = "352800"
		device.buffering.fragment_size = "176400"
		device.access_mode = "mmap+timer"
		device.profile.name = "hdmi-stereo"
		device.profile.description = "Digital Stereo (HDMI)"
		device.description = "Built-in Audio Digital Stereo (HDMI)"
		alsa.mixer_name = "Realtek ALC1220"
		alsa.components = "HDA:10ec1168,10438724,00100101 HDA:8086280b,80860101,00100000"
		module-udev-detect.discovered = "1"
		device.icon_name = "audio-card-pci"
	ports:
		hdmi-output-0: HDMI / DisplayPort (priority 5900, latency offset 0 usec, available: yes)
			properties:
				device.icon_name = "video-display"
				device.product.name = "C27HG7x"
	active port: <hdmi-output-0>

Can you try with only one monitor connected?

* * *

Side note, the device has LSPCON.

Seems like there's a lot going on in the dmesg. Seems like DP-MST is involved.

The driver detects that the monitor supports audio:

[    3.691122] [drm:drm_detect_monitor_audio [drm]] Monitor has basic audio support
[    3.691853] [drm:drm_helper_probe_single_connector_modes [drm_kms_helper]] [CONNECTOR:86:DP-1] status updated from unknown to connected
[    3.691859] [drm:drm_add_display_info [drm]] non_desktop set to 0
[    3.691865] [drm:drm_add_edid_modes [drm]] ELD monitor C27HG7x
[    3.691870] [drm:drm_add_edid_modes [drm]] ELD size 32, SAD count 1

ELD seems fine.

However we get a first warn which seems CEC-related:

[    3.746353] [drm:drm_detect_monitor_audio [drm]] Monitor has basic audio support
[    3.747023] WARNING: CPU: 0 PID: 100 at kernel/kmod.c:137 __request_module+0x1e1/0x3a8
[    3.747023] Modules linked in: i915 drm_kms_helper drm igb crct10dif_pclmul crc32_pclmul crc32c_intel e1000e nvme dca nvme_core i2c_algo_bit ghash_clmulni_intel video wmi hid_microsoft ff_memless
[    3.747027] CPU: 0 PID: 100 Comm: kworker/u32:1 Tainted: G     U            5.3.0-rc2drmtip+ #1
[    3.747027] Hardware name: ASUSTeK COMPUTER INC. WS Z390 PRO/WS Z390 PRO, BIOS 0401 08/31/2018
[    3.747028] Workqueue: events_unbound async_run_entry_fn
[    3.747029] RIP: 0010:__request_module+0x1e1/0x3a8
[    3.747029] Code: 31 c9 ba 01 00 00 00 be 03 00 00 00 48 c7 c7 80 bc 44 b3 e8 21 0e 02 00 e9 8b fe ff ff e8 97 ee ff ff 84 c0 0f 84 72 fe ff ff <0f> 0b e9 6b fe ff ff 65 8b 05 11 96 f0 4d 89 c0 48 0f a3 05 3f 7f
[    3.747030] RSP: 0018:ffff9fd5404579f8 EFLAGS: 00010202
[    3.747030] RAX: ffff8c9e269e6901 RBX: 0000000000000001 RCX: 0000000000000000
[    3.747031] RDX: ffffffffb31a20e5 RSI: ffffffffb318bc30 RDI: ffff8c9e25c98000
[    3.747031] RBP: ffff9fd540457ad8 R08: ffff8c9e26112a23 R09: 0000000000000000
[    3.747031] R10: ffff9fd540457ae8 R11: ffff8c9e26112a23 R12: 0000000000000000
[    3.747031] R13: ffffffffb318bc30 R14: 0000000000000001 R15: ffff9fd540457ae8
[    3.747032] FS:  0000000000000000(0000) GS:ffff8c9e2d800000(0000) knlGS:0000000000000000
[    3.747032] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    3.747033] CR2: 00007fef5ad82fe0 CR3: 00000004b140a002 CR4: 00000000003606f0
[    3.747033] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    3.747033] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[    3.747034] Call Trace:
[    3.747037]  ? kvasprintf+0x7d/0xc0
[    3.747039]  ? kobject_set_name_vargs+0x6f/0x90
[    3.747041]  rc_map_get+0x30/0x60
[    3.747042]  rc_register_device+0x119/0x4e0
[    3.747043]  cec_register_adapter+0x21c/0x290
[    3.747046]  drm_dp_cec_set_edid+0x106/0x176 [drm_kms_helper]
[    3.747066]  intel_dp_detect+0x1b9/0x4c0 [i915]
[    3.747070]  drm_helper_probe_single_connector_modes+0xd7/0x6c0 [drm_kms_helper]
[    3.747075]  drm_client_modeset_probe+0x278/0x10f0 [drm]
[    3.747077]  ? update_load_avg+0x76/0x600
[    3.747077]  ? update_curr+0xe1/0x1d0
[    3.747080]  __drm_fb_helper_initial_config_and_unlock+0x42/0x440 [drm_kms_helper]
[    3.747081]  ? __switch_to+0x80/0x440
[    3.747101]  intel_fbdev_initial_config+0x14/0x30 [i915]
[    3.747102]  async_run_entry_fn+0x39/0x160
[    3.747104]  process_one_work+0x19d/0x340
[    3.747105]  worker_thread+0x50/0x3b0
[    3.747106]  kthread+0xfb/0x130
[    3.747107]  ? process_one_work+0x340/0x340
[    3.747108]  ? kthread_park+0x80/0x80
[    3.747109]  ret_from_fork+0x1f/0x40
[    3.747111] WARNING: CPU: 0 PID: 100 at kernel/kmod.c:137 __request_module+0x1e1/0x3a8
[    3.747111] ---[ end trace 5ed3e0cc2a55e722 ]---

And then a second warn which seems audio-related:

[    3.848226] [drm:intel_atomic_check [i915]] hw max bpp: 36, pipe bpp: 24, dithering: 0
[    3.848242] [drm:pipe_config_mismatch [i915]] fastset mismatch in has_audio unable to verify whether state matches exactly, forcing modeset (expected no, found yes)
[    3.848259] [drm:intel_atomic_check [i915]] New cdclk calculated to be logical 675000 kHz, actual 675000 kHz
[    3.848275] [drm:intel_atomic_check [i915]] New voltage level calculated to be logical 3, actual 3
[    3.848277] ------------[ cut here ]------------
[    3.848278] WARN_ON(was_visible)
[    3.848302] WARNING: CPU: 0 PID: 7 at drivers/gpu/drm/i915/display/intel_display.c:11521 intel_plane_atomic_calc_changes+0x24a/0x720 [i915]
[    3.848303] Modules linked in: i915 drm_kms_helper drm igb crct10dif_pclmul crc32_pclmul crc32c_intel e1000e nvme dca nvme_core i2c_algo_bit ghash_clmulni_intel video wmi hid_microsoft ff_memless
[    3.848307] CPU: 0 PID: 7 Comm: kworker/0:1 Tainted: G     U  W         5.3.0-rc2drmtip+ #1
[    3.848307] Hardware name: ASUSTeK COMPUTER INC. WS Z390 PRO/WS Z390 PRO, BIOS 0401 08/31/2018
[    3.848311] Workqueue: events output_poll_execute [drm_kms_helper]
[    3.848327] RIP: 0010:intel_plane_atomic_calc_changes+0x24a/0x720 [i915]
[    3.848328] Code: 84 54 fe ff ff 48 c7 c6 fb 2e 94 c0 48 c7 c7 9e 22 94 c0 44 88 5c 24 1c 88 44 24 18 4c 89 54 24 10 88 54 24 0c e8 d4 3d 85 f1 <0f> 0b 0f b6 54 24 0c 44 0f b6 5c 24 1c 0f b6 44 24 18 4c 8b 54 24
[    3.848329] RSP: 0018:ffff9fd540073b58 EFLAGS: 00010282
[    3.848330] RAX: 0000000000000000 RBX: ffff8c9e0c2aa800 RCX: 0000000000000000
[    3.848331] RDX: 0000000000000014 RSI: ffffffffb3bc1a94 RDI: 0000000000000246
[    3.848331] RBP: ffff8c9e0d9ba000 R08: 00000000e56010ed R09: 0000000000000014
[    3.848331] R10: ffffffffb3bc1e60 R11: 00000000b3bc1a7f R12: ffff8c9e088ae000
[    3.848332] R13: ffff8c9e0d883e00 R14: ffff8c9e2652c800 R15: 0000000000000001
[    3.848332] FS:  0000000000000000(0000) GS:ffff8c9e2d800000(0000) knlGS:0000000000000000
[    3.848333] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    3.848334] CR2: 00007fef5ad82fe0 CR3: 00000004b140a002 CR4: 00000000003606f0
[    3.848334] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    3.848335] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[    3.848335] Call Trace:
[    3.848341]  drm_atomic_helper_check_planes+0xec/0x1e0 [drm_kms_helper]
[    3.848358]  intel_atomic_check+0x7a5/0x14b0 [i915]
[    3.848366]  drm_atomic_check_only+0x54d/0x780 [drm]
[    3.848374]  drm_atomic_commit+0x13/0x50 [drm]
[    3.848380]  drm_client_modeset_commit_atomic+0x1d0/0x1f0 [drm]
[    3.848387]  drm_client_modeset_commit_force+0x50/0x150 [drm]
[    3.848391]  drm_fb_helper_restore_fbdev_mode_unlocked+0x49/0xa0 [drm_kms_helper]
[    3.848395]  drm_fb_helper_set_par+0x2c/0x50 [drm_kms_helper]
[    3.848398]  drm_fb_helper_hotplug_event.part.0+0x97/0xb0 [drm_kms_helper]
[    3.848402]  drm_kms_helper_hotplug_event+0x26/0x30 [drm_kms_helper]
[    3.848405]  output_poll_execute+0x1a9/0x1c0 [drm_kms_helper]
[    3.848407]  process_one_work+0x19d/0x340
[    3.848408]  worker_thread+0x50/0x3b0
[    3.848410]  kthread+0xfb/0x130
[    3.848411]  ? process_one_work+0x340/0x340
[    3.848412]  ? kthread_park+0x80/0x80
[    3.848413]  ret_from_fork+0x1f/0x40
[    3.848431] WARNING: CPU: 0 PID: 7 at drivers/gpu/drm/i915/display/intel_display.c:11521 intel_plane_atomic_calc_changes+0x24a/0x720 [i915]
[    3.848431] ---[ end trace 5ed3e0cc2a55e723 ]---

But then apparently we enable audio on pipe B:

[    4.140908] [drm:intel_audio_codec_enable [i915]] ELD on [CONNECTOR:100:DP-2], [ENCODER:99:DDI C]
[    4.140927] [drm:hsw_audio_codec_enable [i915]] Enable audio codec on transcoder B, 32 bytes ELD
[    4.140947] [drm:hsw_audio_config_update [i915]] using automatic Maud, Naud

And then another warning.

On pipe C, sometimes we get:

[   23.525625] [drm:i915_audio_component_get_eld [i915]] Not valid for port C

Yes, it does indeed work if I reboot with only one monitor connected.

It did *NOT* work if I only disconnected one monitor - although that was maybe expected from what I gathered in your comment.

And it continues to work after I hooked the second monitor after I rebooted.

Correction; it works even better if I only boot with one monitor connected.
When I connect the second monitor I get two HDMI/DisplayPort audio outputs - like expected.

@Simon, any further comments on this?

I'd say this is one more MST bug, which doesn't route audio correctly in some cases. Needs more investigation to figure out a fix.

Kim, If you don't mind can you verify the issue with latest drmtip?
Last verified 2 months ago, it would be good to know if the situation has changed with the latest drmtip.

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