Bug #1899336 “Thinkpad T14s (AMD) external monitors on docking s...” : Bugs : Ubuntu Budgie

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Andre Plötze (andrepxx) wrote on 2020-10-11:

#1

dmesg-2020-10-11.txt Edit (16.2 KiB, text/plain)

Andre Plötze (andrepxx) on 2020-10-11

description:

updated

Andre Plötze (andrepxx) on 2020-10-11

description:

updated

Revision history for this message

fossfreedom (fossfreedom) wrote on 2020-10-11: Re: [Bug 1899336] Re: Thinkpad T14s (AMD) external monitors on docking station no longer detected

#2

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That kernel was released on the 21st Sept. So it could be a kernel issue.

Suggest boot with an earlier kernel to see if things begin to work again.

Press shift and hold immediately on boot to display grub. Choose the
advances options and select an earlier kernel to boot with.

On Sun, 11 Oct 2020, 12:30 Andre Plötze, <email address hidden> wrote:

> ** Description changed:
>
> 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
> + 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 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
> ar...

That kernel was released on the 21st Sept. So it could be a kernel issue.

Suggest boot with an earlier kernel to see if things begin to work again.

Press shift and hold immediately on boot to display grub. Choose the
advances options and select an earlier kernel to boot with.

On Sun, 11 Oct 2020, 12:30 Andre Plötze, <1899336@bugs.launchpad.net> wrote:

> ** Description changed:
>
>   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
> + 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 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.
>
>   $ 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
>   $
>
> --
> You received this bug notification because you are subscribed to Ubuntu
> Budgie.
> 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,
>   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 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.
>
>   $ 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
>   $
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/ubuntubudgie/+bug/1899336/+subscriptions
>

Revision history for this message

Andre Plötze (andrepxx) wrote on 2020-10-11:

#3

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Okay, I just did some analysis work.

I had kernels 5.4.0-47 and 5.4.0-48 on my system and with both at first external monitors didn't appear to work.

Then I installed 5.4.0-45 and 5.4.0-42 as well, so I got four kernel versions on my system. Then I tried booting with each kernel version both with laptop lid closed and opened several times. These are the results.

--- SNIP ---

Kernel 5.4.0-42, lid open:
- LUKS authentication: displayed on internal and external screens
- login screen: displayed on internal and external screens
- Budgie desktop: only displayed on internal screen, external screens do not show up under display settings

Kernel 5.4.0-42, lid closed:
- crashes during LUKS pre-boot authentication

Kernel 5.4.0-45, lid open:
- LUKS authentication: displayed on internal and external screens
- login screen: displayed on internal and external screens
- Budgie desktop: only displayed on internal screen, external screens do not show up under display settings

Kernel 5.4.0-45, lid closed:
- LUKS authentication: shows up on external screens most of the time, sometimes crashes during pre-boot authentication
- Login screen: most of the time shows up on external screens, sometimes does not show up on external screens, but then shows up on internal screen after lid is opened
- Budgie desktop: most of the time only displayed on internal screen, external screens do not show up under display settings, rarely shows up on external screens, switching to internal screen after lid is opened

Kernel 5.4.0-47, lid open:
- LUKS authentication: only displayed on internal screen
- Login screen: displayed on internal and external screen
- Budgie desktop: only displayed on internal screen, no external screen recognized

Kernel 5.4.0-47, lid closed:
- LUKS authentication: shows up on external screens
- Login screen: shows up on external screens
- Budgie desktop: either does not show up on external screens and does not show on internal screen after laptop lid is opened, or shows up on external screens and switches to internal screen after laptop lid is opened

Kernel 5.4.0-48, lid open:
- LUKS authentication: only displayed on internal screen
- Login screen: displayed on internal and external screen
- Budgie desktop: only displayed on internal screen, no external screen recognized

Kernel 5.4.0-48, lid closed:
- LUKS authentication: shows up on external screens
- Login screen: shows up on external screens
- Budgie desktop: either does not show up on external screens and does not show on internal screen after laptop lid is opened, or shows up on external screens and switches to internal screen after laptop lid is opened

--- SNIP ---

Man, that's horrible. I somehow guess I could do this another hundred times and still get different results. It somehow appears like there's a race condition during device enumeration or something like that, which would be a kernel issue then, and will probably be horrible to trace down.

However, assuming that this is a problem with device enumeration, some behaviour appears odd. First, reconnecting the dock does not appear to help alleviate the issue, which is kinda weird if it's a problem with device enumeration, since I would...