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Message #01037
[Bug 1899336] [NEW] Thinkpad T14s (AMD) external monitors on docking station no longer detected
Public bug reported:
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)"
(40AS0090EU).
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,
since a few days, 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 displyed 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.
** Affects: ubuntubudgie
Importance: Undecided
Status: New
** Attachment added: "dmesg-2020-10-11.txt"
https://bugs.launchpad.net/bugs/1899336/+attachment/5420794/+files/dmesg-2020-10-11.txt
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https://bugs.launchpad.net/bugs/1899336
Title:
Thinkpad T14s (AMD) external monitors on docking station no longer
detected
Status in Ubuntu Budgie:
New
Bug description:
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)"
(40AS0090EU).
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,
since a few days, 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 displyed 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.
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