ThinkPad T14s external display not working on ThinkPad USB-C Dock Gen2
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux (Ubuntu) |
Fix Released
|
Undecided
|
Unassigned |
Bug Description
laptop: ThinkPad T14s Gen 1 - AMD Ryzen 7 PRO 4750U
docking station: ThinkPad USB-C Dock 2. Gen.
external display: NE MultiSync EA275UHD
OS: Ubuntu 20.10 - kernel 5.8.0
Plugging the external display into one of the docking station's two DisplayPort connectors leads to the screen resolution changing on the laptop's builtin display and the external display waking up but showing no picture and displaying "no-signal" after a bit.
Plugging the external display into the docking station's HDMI connector leads to no visible reaction on either the external nor the builtin display.
Plugging the external display into the laptop's builtin HDMI connector works as expected. The external display is recognized and shows an image.
I have recorded the output on `dmesg` during the steps mentioned above and inserted explanations using `echo MSG >/dev/kmsg`. The output follows at the end of the message. I believe `ubuntu-bug` should also attach the full log.
All above modes of connection work as expected with the same laptop, dock, and display on Windows 10 (installed as dual boot along side Ubuntu).
All above modes of connection also work as expected with an older laptop (ThinkPad T470s - Ubuntu 20.04 - kernel 5.4.0), and the same dock and display.
This leads me to believe that this is not a hardware issue.
The following bug seems related, but seems to have been observed on faulty hardware according to its author. Therefore, I decided to open a separate bug report. https:/
```
[ 343.372511] plugging DisplayPort into dock port 1
[ 352.666113] [drm] DP Alt mode state on HPD: 1
[ 352.749192] [drm] DM_MST: starting TM on aconnector: 000000002105a317 [id: 75]
[ 352.858482] [drm] amdgpu_
[ 352.888400] [drm] amdgpu_
[ 352.892555] [drm] amdgpu_
[ 352.896719] [drm] amdgpu_
[ 352.900876] [drm] amdgpu_
[ 352.905596] [drm] amdgpu_
[ 352.910323] [drm] amdgpu_
[ 352.914485] [drm] amdgpu_
[ 377.353566] plugged in - no signal
[ 396.728970] unplugging
[ 403.001418] [drm] DM_MST: stopping TM on aconnector: 000000002105a317 [id: 75]
[ 415.576397] unplugged
[ 431.500729] plugging DisplayPort into dock port 2
[ 437.607724] [drm] DP Alt mode state on HPD: 1
[ 437.681116] [drm] DM_MST: starting TM on aconnector: 000000002105a317 [id: 75]
[ 437.790303] [drm] amdgpu_
[ 437.820138] [drm] amdgpu_
[ 437.824305] [drm] amdgpu_
[ 437.828462] [drm] amdgpu_
[ 437.832619] [drm] amdgpu_
[ 437.837029] [drm] amdgpu_
[ 437.841984] [drm] amdgpu_
[ 437.846144] [drm] amdgpu_
[ 458.999849] plugged in - no signal
[ 465.702949] unplugging
[ 476.127418] [drm] DM_MST: stopping TM on aconnector: 000000002105a317 [id: 75]
[ 476.956491] [drm] Failed to add display topology, DTM TA is not initialized.
[ 488.792533] unplugged
[ 529.801179] plugging HDMI into dock
[ 536.721076] [drm] DP Alt mode state on HPD: 1
[ 536.792947] [drm] DM_MST: starting TM on aconnector: 000000002105a317 [id: 75]
[ 536.901958] [drm] amdgpu_
[ 536.906123] [drm] amdgpu_
[ 536.910288] [drm] amdgpu_
[ 536.914611] [drm] amdgpu_
[ 536.919568] [drm] amdgpu_
[ 536.923725] [drm] amdgpu_
[ 536.927888] [drm] amdgpu_
[ 536.932047] [drm] amdgpu_
[ 536.936451] [drm] amdgpu_
[ 536.941486] [drm] amdgpu_
[ 536.945651] [drm] amdgpu_
[ 536.949808] [drm] amdgpu_
[ 537.010093] [drm:drm_
[ 592.844147] plugged in - display does not react
[ 597.998141] unplugging
[ 604.657060] [drm] DM_MST: stopping TM on aconnector: 000000002105a317 [id: 75]
[ 612.058516] unplugged
[ 630.409181] plugging HDMI into laptop
[ 637.125592] [drm] Failed to add display topology, DTM TA is not initialized.
[ 639.077839] [drm] Failed to add display topology, DTM TA is not initialized.
[ 639.192248] [drm] Failed to add display topology, DTM TA is not initialized.
[ 683.221820] plugged in - working
[ 690.347738] unplugging
[ 694.212298] [drm] Failed to add display topology, DTM TA is not initialized.
[ 725.466488] unplugged
```
ProblemType: Bug
DistroRelease: Ubuntu 20.10
Package: linux-image-
ProcVersionSign
Uname: Linux 5.8.0-33-generic x86_64
ApportVersion: 2.20.11-0ubuntu50.2
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/
/dev/snd/
/dev/snd/
/dev/snd/
CasperMD5CheckR
CurrentDesktop: ubuntu:GNOME
Date: Mon Dec 14 22:11:01 2020
InstallationDate: Installed on 2020-12-12 (2 days ago)
InstallationMedia: Ubuntu 20.10 "Groovy Gorilla" - Release amd64 (20201022)
MachineType: LENOVO 20UHCTO1WW
ProcFB: 0 amdgpudrmfb
ProcKernelCmdLine: BOOT_IMAGE=
RelatedPackageV
linux-
linux-
linux-firmware 1.190.2
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/15/2020
dmi.bios.release: 1.25
dmi.bios.vendor: LENOVO
dmi.bios.version: R1CET56W(1.25 )
dmi.board.
dmi.board.name: 20UHCTO1WW
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.
dmi.ec.
dmi.modalias: dmi:bvnLENOVO:
dmi.product.family: ThinkPad T14s Gen 1
dmi.product.name: 20UHCTO1WW
dmi.product.sku: LENOVO_
dmi.product.
dmi.sys.vendor: LENOVO
This change was made by a bot.