Hi,
I have the following situation: a laptop connected to a DELL WD22TB4 Thunderbolt dock, with two external screens connected to it.
~> inxi -e
System:
Host: C22URNQ Kernel: 6.17.0-rc2-4.g5e7fd49-vanilla arch: x86_64 bits: 64
Desktop: KDE Plasma v: 6.4.4 Distro: openSUSE Tumbleweed 20250905
Machine:
Type: Laptop System: Dell product: Latitude 5530 v: N/A
serial: <superuser required>
Mobo: Dell model: 0C6CYC v: A00 serial: <superuser required> UEFI: Dell
v: 1.31.1 date: 07/04/2025
Battery:
ID-1: BAT0 charge: 38.8 Wh (80.9%) condition: 48/58 Wh (82.7%)
CPU:
Info: 10-core (2-mt/8-st) model: 12th Gen Intel Core i7-1265U bits: 64
type: MST AMCP cache: L2: 6.5 MiB
Speed (MHz): avg: 400 min/max: 400/4800:3600 cores: 1: 400 2: 400 3: 400
4: 400 5: 400 6: 400 7: 400 8: 400 9: 400 10: 400 11: 400 12: 400
Graphics:
Device-1: Intel Alder Lake-UP3 GT2 [Iris Xe Graphics] driver: i915 v: kernel
Device-2: NVIDIA TU117M [GeForce MX550] driver: nouveau v: kernel
Device-3: Microdia Integrated_Webcam_HD driver: uvcvideo type: USB
Display: wayland server: X.org v: 1.21.1.15 with: Xwayland v: 24.1.8
compositor: kwin_wayland driver: X: loaded: intel unloaded: modesetting,vesa
dri: iris gpu: i915 resolution: 1: 2560x1440~60Hz 2: 1920x1080~60Hz
3: 1920x1080~60Hz
API: EGL v: 1.5 drivers: iris,swrast
platforms: gbm,wayland,x11,surfaceless,device
API: OpenGL v: 4.6 compat-v: 4.5 vendor: intel mesa v: 25.2.2
renderer: Mesa Intel Iris Xe Graphics (ADL GT2)
API: Vulkan v: 1.4.321 drivers: intel,llvmpipe surfaces: N/A
Info: Tools: api: eglinfo, glxinfo, vulkaninfo
de: kscreen-console,kscreen-doctor gpu: gputop, intel_gpu_top, lsgpu
wl: wayland-info x11: xdpyinfo, xprop, xrandr
Audio:
Device-1: Intel Alder Lake PCH-P High Definition Audio driver: snd_hda_intel
API: ALSA v: k6.17.0-rc2-4.g5e7fd49-vanilla status: kernel-api
Server-1: PipeWire v: 1.4.7 status: active
Network:
Device-1: Intel Alder Lake-P PCH CNVi WiFi driver: iwlwifi
IF: wlp0s20f3 state: up mac: 28:6b:35:15:ad:3d
Device-2: Intel Ethernet I219-LM driver: e1000e
IF: enp0s31f6 state: down mac: c8:4b:d6:60:90:cf
Device-3: Realtek RTL8153 Gigabit Ethernet Adapter driver: r8152 type: USB
IF: enp0s13f0u1u4u4 state: up speed: 1000 Mbps duplex: full
mac: c8:4b:d6:60:90:d0
Drives:
Local Storage: total: 953.87 GiB used: 381.95 GiB (40.0%)
ID-1: /dev/nvme0n1 vendor: Samsung model: PM9A1 NVMe 1024GB
size: 953.87 GiB
Partition:
[...]
Info:
Memory: total: 32 GiB note: est. available: 31.04 GiB used: 6.36 GiB (20.5%)
Processes: 371 Uptime: 0h 13m Shell: Bash inxi: 3.3.39
When booting with any kernel >6.7.7 (i.e., a long time ago!), the system does not let me configure my three screens as desired any longer:
- Left: Laptop screen at 1920x1080, 60Hz, 100% scaling
- Middle: P2415Q at 3840x2160, 60Hz, 175% scaling
- Right: U2414H at 1080x1920 (vertical), 60Hz, 100% scaling
With the old kernel 6.7.7 (preserved thanks to putting multiversion.kernels = latest,latest-1,6.7.7-1.1,running in /etc/zypp/zypp.conf), I can use this configuration perfectly on an otherwise up-to-date Tumbleweed. Of course I don’t want to keep running like this forever, so I’d like to ask for help with figuring out how to solve this.
When booting with any newer kernel (>6.8, all the way up to the 6.17.0-rc2 from tiwai’s drm-tip home repo), the SDDM login screen operates all 3 screens, but after entering the password and hitting enter, I only get a black screen. I then have to unplug the docking station from the laptop, at which point the TW plasma loading screen (lightbulb + loading spinner) shows up, and I get to the desktop shortly after. Upon reconnecting the dock, the left and middle screen work at their configured resolutions, but the right screen remains black.
In the plasma display configuration, when trying to enable the right screen, I get this error about “Couldn’t apply display configuration: The driver rejected the output configuration”
(The inxi output above shows one screen (a DELL P2415Q) operating at 2560x1440, which is the configuration I currently have to use due to my problem: I cannot configure this display to use 4k 60Hz — dropping the resolution allows all 3 displays.)
Coincidentally, this all started during the same TW update where Plasma 6 arrived (as this is when kernel 6.8 also reached my device), which I blamed at first. However, I found that Plasma 6+TW+kernel 6.7.7 actually worked perfectly (and have done ever since), so it doesn’t seem to be Plasma’s fault, at least immediately.
Things I’ve tried:
- Waiting for kernel/TW updates to fix it (works for 95% of my TW problems…) — no luck for the past ~year now!
- Deleting
~/.config/kwinoutputconfig.jsonand logging back in (like here) — no luck, still black screen at login and doesn’t allow me to configure my desired settings. - Updating firmware of all involved devices (BIOS, docking station); all up-to-date:
# fwupdmgr get-updates
Devices with no available firmware updates:
• 0000:00:1f.5
• 0000:00:1f.5-chip1
• BIOS1
• Bios DB Key
• Bios FW Aux Authority
• KEK CA
• Key Exchange Key
• Option ROM UEFI CA
• UEFI Device Firmware
• UEFI Device Firmware
• USB4 Retimer
• Windows Production PCA
Devices with the latest available firmware version:
• Package level of Dell dock
• RTS5413 in Dell dock
• RTS5487 in Dell dock
• VMM5331 in Dell dock
• WD22TB4
• PM9A1 NVMe Samsung 1024GB
• System Firmware
• UEFI CA
• UEFI dbx
• USB4 controller in Dell dock
• Unifying Receiver
No updates available
- Looking at the drm bugtracker for related i915 graphics driver bugs (involving this dock or similar ones, but also DisplayPort MST which seems to be involved — I’m speculating it’s some deep link training/bandwidth issue, which I don’t have the skills to debug
); there have been a few such reports (example), and their fixes have landed, but not made a difference for me. (This is the reason I’ve tried use the home:tiwai repo to get recent drm-tip kernel-vanilla builds to try…)
How can I go about debugging this further? Please let me know which additional information/command output would help (I’m sure there’s more stuff that could be helpful).
Thanks in advance!
