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[Bug 1467190] Re: No audio over DisplayPort MST

To: kernel-packages@xxxxxxxxxxxxxxxxxxx
From: "Christopher M. Penalver" <christopher.m.penalver@xxxxxxxxx>
Date: Sun, 27 Dec 2015 02:40:31 -0000
Reply-to: Bug 1467190 <1467190@xxxxxxxxxxxxxxxxxx>
Sender: bounces@xxxxxxxxxxxxx

** Changed in: linux-lts-vivid (Ubuntu)
   Importance: Undecided => Medium

** Changed in: linux-lts-vivid (Ubuntu)
       Status: Confirmed => Triaged

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https://bugs.launchpad.net/bugs/1467190

Title:
  No audio over DisplayPort MST

Status in linux-lts-vivid package in Ubuntu:
  Triaged

Bug description:
  I have a Lenovo ThinkPad E540 with an Intel Haswell (4th Gen) HD
  graphics controller connected to a OneLink Pro Dock. The Dock uses
  DisplayPort (DP) 1.2 MST (multi stream transport) to provide both a DP
  and a DVI port. My monitor is connected to the DP.

  When I used kernels <= 3.16 audio worked fine, but the monitor would
  flicker heavily. So I installed linux-lts-vivid (3.19) which fixed the
  graphics problem (now I can see various DP? outputs in xrandr as
  opposed to one before), but there is no DP audio output to chose
  anymore.

  I also tested the latest mainline kernel 4.1-rc8, where this bug still
  exists. To further investigate I got these version's kernel sources,
  applied 4 patches by Dave Airlie from the intel-gfx mailing list [1]
  and tested this build (4.1-rc8+), which fixed the problem! I can play
  sound over DP, the same way I can over HDMI or DP without MST.

  I hope it is possible to backport these changes!

  [1] haswell displayport MST audio support
      http://www.spinics.net/lists/intel-gfx/msg68973.html

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: linux-image-3.19.0-22-generic 3.19.0-22.22~14.04.1
  ProcVersionSignature: Ubuntu 3.19.0-22.22~14.04.1-generic 3.19.8-ckt1
  Uname: Linux 3.19.0-22-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.11
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Sun Jun 21 01:44:30 2015
  InstallationDate: Installed on 2014-01-06 (530 days ago)
  InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
  SourcePackage: linux-lts-vivid
  UpgradeStatus: Upgraded to trusty on 2014-06-12 (373 days ago)

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