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[Bug 1899336] Re: Thinkpad T14s (AMD) external monitors on docking station no longer detected
Thx for the update.
interesting to see it was indeed a kernel/firmware issue.
I'll close this for now.
Please do raise further issues that are potentially a kernel issue via
** Changed in: linux (Ubuntu)
Status: Confirmed => Fix Released
** Changed in: ubuntubudgie
Status: New => Fix Released
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Thinkpad T14s (AMD) external monitors on docking station no longer
Status in Ubuntu Budgie:
Status in linux package in Ubuntu:
I run Ubuntu Budgie 20.04 on my Lenovo ThinkPad T14s with Ryzen 4750U
processor together with the "Lenovo ThinkPad USB-C Dock (Gen 2)"
The docking station is connected via USB-C to the system, supplies it
with power via USB Power Delivery and provides USB 3.1 Gen 2 (10
Gbit/s) connectivity (including an Ethernet controller and audio codec
running over the USB data path), as well as support for two monitors
via "DisplayPort alternate mode" of USB-C, so technically it will
configure the four high-speed lanes of USB-C as one lane for
SuperSpeed+ RX, one lane for SuperSpeed+ TX, and two lanes for
DisplayPort 1.4, the latter of which the docking station will then
demultiplex onto two full-size DisplayPort connectors like an MST hub.
So far, external monitors have worked fine most of the time. However,
for a couple of days now, I cannot get the system to detect the
external monitors connected to my docking station anymore.
The "BIOS" (EFI) boot screen (with the Lenovo logo) still shows up on
the external monitors. However, both the LUKS/dm-crypt pre-boot-
authentication screen (since I use full-disk-encryption) and also the
desktop after login show up on the internal display, even with the
laptop connected to the docking station, so it appears like the kernel
no longer detects the monitors connecting via "DisplayPort alternate
mode". Yesterday, I could get the monitors to show up by disconnecting
the laptop from the docking station and reconnecting it again. Today,
not even this appears to work. Sometimes the external monitors are
detected (and shown as "enabled") in the display settings of Budgie,
sometimes they do not even show up. Even when they show up and are
enabled, nothing is displayed on them. The monitors say they do not
receive a signal and I should check the connection. Unplugging and
replugging the cables from the docking station to the monitors does
not change anything.
Audio, Ethernet and USB runs fine over the docking station, just
DisplayPort does not. This is obviously very bad, since I now have to
work on the internal display even with the laptop docked.
I have the "amdgpu.exp_hw_support=1" in my kernel arguments (*) and
the Ryzen 4000 GPU appears to be recognized.
$ lspci -k
06:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Renoir (rev d1)
Subsystem: Lenovo Renoir
Kernel driver in use: amdgpu
Kernel modules: amdgpu
(*) When I installed Ubuntu Budgie 20.04, I needed to add this in
order to extend my desktop over the two external monitors. Without
this argument, the system only showed a single display in the
settings, the same content was displayed on all connected monitors
(mirrored) and there was no way to change that.
I have attached parts of "dmesg" output which I deem relevant.
$ uname -a
Linux thinkpad-t14s 5.4.0-48-generic #52-Ubuntu SMP Thu Sep 10 10:58:49 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
DistroRelease: Ubuntu 20.04
InstallationDate: Installed on 2020-07-27 (75 days ago)
InstallationMedia: Ubuntu-Budgie 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
MachineType: LENOVO 20UH001AGE
Package: linux (not installed)
ProcFB: 0 amdgpudrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.4.0-48-generic root=UUID=5b605ccb-8a29-46ee-b571-e0d61a323457 ro quiet splash amdgpu.exp_hw_support=1 vt.handoff=7
ProcVersionSignature: Ubuntu 5.4.0-48.52-generic 5.4.60
Uname: Linux 5.4.0-48-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm audio cdrom dip lpadmin lxd plugdev sambashare sudo
dmi.bios.version: R1CET36W(1.05 )
dmi.board.asset.tag: Not Available
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Information
dmi.product.family: ThinkPad T14s Gen 1
dmi.product.sku: LENOVO_MT_20UH_BU_Think_FM_ThinkPad T14s Gen 1
dmi.product.version: ThinkPad T14s Gen 1
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