Bug 89895

Summary: [HSW] HDMI/DP audio doesn't work with DP MST
Product: DRI Reporter: Sree Harsha Totakura <freedesktop>
Component: DRM/IntelAssignee: Dhinakaran Pandiyan <dhinakaran.pandiyan>
Status: CLOSED FIXED QA Contact: Intel GFX Bugs mailing list <intel-gfx-bugs>
Severity: normal    
Priority: medium CC: airlied, intel-gfx-bugs, james.ausmus, leho, marius.c.vlad, mrechte, noodles, paul
Version: unspecified   
Hardware: x86-64 (AMD64)   
OS: Linux (All)   
Whiteboard:
i915 platform: BDW, HSW, IVB, SKL, SNB i915 features: display/audio, display/DP MST
Attachments:
Description Flags
Kernel dmesg output for 4.0.1-gentoo with "drm.debug=14" none

Description Sree Harsha Totakura 2015-04-03 18:27:28 UTC 
Hi,

I hope this is the right section to report this bug; if not, please redirect me to the appropriate one.

I am having trouble getting audio via HDMI/DP working.  My setup has a Thinkpad Ultra dock which has a Synaptics DP MST hub connected to a Dell U2415 monitor via DP.

`aplay -l' reports:
**** List of PLAYBACK Hardware Devices ****
card 0: HDMI [HDA Intel HDMI], device 3: HDMI 0 [HDMI 0]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA Intel HDMI], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA Intel HDMI], device 8: HDMI 2 [HDMI 2]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 0: ALC3232 Analog [ALC3232 Analog]
  Subdevices: 0/1
  Subdevice #0: subdevice #0

So, the cards are being detected correctly.  However, I do not see that the monitor is being detected as connected as per ELD, even though I could use the monitor for video.

$ ls -1 /proc/asound/card0
codec#0
eld#0.0
eld#0.1
eld#0.2
id
pcm3p
pcm7p
pcm8p

$ cat /proc/asound/card0/eld*
monitor_present		0
eld_valid		0
monitor_present		0
eld_valid		0
monitor_present		0
eld_valid		0

Could it be that the DP MST Hub in the dock is misbehaving or not transmitting ELD?  If so, how can I verify that?
Comment 1 Jani Nikula 2015-04-07 10:56:26 UTC 
It would help considerably if you indicated which kernel version you're running.

Please attach dmesg with drm.debug=14 module parameter set, from boot to trying to use audio.
Comment 2 Chris Wilson 2015-04-07 15:42:32 UTC 
It is a known issue that audio does not work with DP-MST at the moment. Dave didn't get as far as figuring out the audio transport side of MST...
Comment 3 James Ausmus 2015-05-11 21:38:06 UTC 
(In reply to Chris Wilson from comment #2)
> It is a known issue that audio does not work with DP-MST at the moment. Dave
> didn't get as far as figuring out the audio transport side of MST...

Is this still the case? If so, is the root issue independent of the audio driver side, but rather a drm generic MST implementation issue?
Comment 4 Jani Nikula 2015-05-12 08:59:15 UTC 
CC Dave.
Comment 6 Paul Moore 2015-05-12 12:52:01 UTC 
I'm having the same problem, starting with Linux Kernel commit  0e32b39c ("drm/i915: add DP 1.2 MST support (v0.7)") and continuing through at least Linux 4.0.1, the latest kernel I've tried.

I'm attaching my dmesg output with my 4.0.1-gentoo kernel build with drm.debug=14 on the kernel command line.
Comment 7 Paul Moore 2015-05-12 12:52:45 UTC 
Created attachment 115719 [details]
Kernel dmesg output for 4.0.1-gentoo with "drm.debug=14"
Comment 8 Dave Airlie 2015-05-13 23:26:06 UTC 
As Jani pointed out, I've done initial enablement 

http://cgit.freedesktop.org/~airlied/linux/log/?h=dp-mst-audio

though the audio developers are quiet and the hardware seems to have some strange behaviour.
Comment 9 Paul Moore 2015-06-23 18:39:21 UTC 
I see you keep rebasing your DP audio fixes, any luck with the audio developers?  It would be really nice to get this upstream.
Comment 10 Paul Moore 2015-07-12 20:05:23 UTC 
Just a quick update that Dave's five patches in the git repo below, on top of the Gentoo 4.1.2 (sys-kernels/gentoo-sources-4.1.2) appear to work correctly for me after some quick testing.
Comment 11 Jani Nikula 2015-10-23 12:23:44 UTC 
*** Bug 90531 has been marked as a duplicate of this bug. ***
Comment 12 Dhinakaran Pandiyan 2017-01-04 00:13:44 UTC 
DP audio has been enabled on i915[1]. Please create a new bug if there are problems with it.


[1]
commit 7f9e77545b92bcb894b8e2be5646535e8ba8da9e
Author: Libin Yang <libin.yang@intel.com>
Date:   Mon Nov 28 20:07:07 2016 +0800

    drm/i915: enable dp mst audio

    This patch adds support for DP MST audio in i915.

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