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[Bug 1568573] Re: [Lenovo Thinkpad T460] Ultra Dock external displays not detected after suspend/resume cycle


The 4.7-rc1 kernel was not bootable on my system. However, I have been
testing with 4.6.0-996-generic #201605082201 from drm-next and the
behavior is better. With the drm-next kernel, I am able to dock/undock
the laptop multiple times without a freeze and the displays are
recognized and can be setup. The configured display layout is applied
successfully on docking, unlike with the 4.4.0-22 kernel. I do have one
persistent issue with the drm-next kernel, I have to change to a VT and
back to get display output after docking - but I don't think its related
to this issue. This intel stuff sure seems like a mess.

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  [Lenovo Thinkpad T460] Ultra Dock external displays not detected after
  suspend/resume cycle

Status in linux package in Ubuntu:

Bug description:
  System is Thinkpad T460, Skylake graphics, Thinkpad Ultra dock. DVI and HDMI displays connected via dock. 4.4.0-18.

  After a suspend-resume cycle, when the laptop is docked the dock
  connected external displays are not initialized/connected. If I
  disconnect the displays from the dock and connect them directly to the
  laptop, they are initialized successfully and can be configured via
  xrandr etc.

  If the laptop is power cycled, the displays can be used normally until
  the next suspend-resume cycle.

  Example from relevant dmesg:
  [drm:intel_dp_link_training_clock_recovery [i915_bpo]] *ERROR* too many voltage retries, give up
  [drm:intel_dp_link_training_clock_recovery [i915_bpo]] *ERROR* too many voltage retries, give up
  [drm:intel_dp_link_training_clock_recovery [i915_bpo]] *ERROR* too many voltage retries, give up
  [drm:intel_dp_start_link_train [i915_bpo]] *ERROR* failed to train DP, aborting
  [drm:intel_dp_set_idle_link_train [i915_bpo]] *ERROR* Timed out waiting for DP idle patterns
  [drm:intel_dp_link_training_clock_recovery [i915_bpo]] *ERROR* too many voltage retries, give up
  [drm:intel_dp_link_training_clock_recovery [i915_bpo]] *ERROR* too many voltage retries, give up
  [drm:intel_dp_link_training_clock_recovery [i915_bpo]] *ERROR* too many voltage retries, give up

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: linux-image-4.4.0-18-generic 4.4.0-18.34
  ProcVersionSignature: Ubuntu 4.4.0-18.34-generic 4.4.6
  Uname: Linux 4.4.0-18-generic x86_64
  ApportVersion: 2.20.1-0ubuntu1
  Architecture: amd64
   /dev/snd/controlC0:  ryan       1838 F.... pulseaudio
  Date: Sun Apr 10 09:39:32 2016
  HibernationDevice: RESUME=UUID=04e04e17-3976-4daa-a1dd-2dd369aee83d
  InstallationDate: Installed on 2015-09-21 (201 days ago)
  InstallationMedia: It
   Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
   Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
  MachineType: LENOVO 20FNCTO1WW
   PATH=(custom, no user)
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-18-generic root=/dev/mapper/it--vg-root ro quiet
  PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No PulseAudio daemon running, or not running as session daemon.
   linux-restricted-modules-4.4.0-18-generic N/A
   linux-backports-modules-4.4.0-18-generic  N/A
   linux-firmware                            1.157
  SourcePackage: linux
  UpgradeStatus: Upgraded to xenial on 2016-02-24 (45 days ago)
  dmi.bios.date: 03/09/2016
  dmi.bios.vendor: LENOVO
  dmi.bios.version: R06ET35W (1.09 )
  dmi.board.asset.tag: Not Available
  dmi.board.name: 20FNCTO1WW
  dmi.board.vendor: LENOVO
  dmi.board.version: SDK0J40697 WIN
  dmi.chassis.asset.tag: No Asset Information
  dmi.chassis.type: 10
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: None
  dmi.modalias: dmi:bvnLENOVO:bvrR06ET35W(1.09):bd03/09/2016:svnLENOVO:pn20FNCTO1WW:pvrThinkPadT460:rvnLENOVO:rn20FNCTO1WW:rvrSDK0J40697WIN:cvnLENOVO:ct10:cvrNone:
  dmi.product.name: 20FNCTO1WW
  dmi.product.version: ThinkPad T460
  dmi.sys.vendor: LENOVO

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