Unable to connect to monitors via docking station with kernel 5.11
Originally reported on bugs.archlinux.org.
After an update to linux-5.11.2 I am not able to use the external monitors anymore. Instead I get lots of these errors:
kernel: i915 0000:00:02.0: [drm] ERROR Link Training Unsuccessful
and this error once:
kernel: i915 0000:00:02.0: [drm] ERROR CPU pipe C FIFO underrun
The docking station is a Dell WD19 connected via the USB-C connector. As a graphics adapter I have an Intel HD 620. Curiously on another machine with an Intel HD 630 the problem does not occur.
Downgrading to 5.10.16 gave me back the functionality for now. I also tried the 5.11.3 kernel version from testing, without success.
lspci -v output:
00:02.0 VGA compatible controller: Intel Corporation HD Graphics 620 (rev 02) (prog-if 00 [VGA controller])
Subsystem: Lenovo Device 224b
Flags: bus master, fast devsel, latency 0, IRQ 138
Memory at eb000000 (64-bit, non-prefetchable) [size=16M]
Memory at a0000000 (64-bit, prefetchable) [size=256M]
I/O ports at e000 [size=64]
Expansion ROM at 000c0000 [virtual] [disabled] [size=128K]
Capabilities: [40] Vendor Specific Information: Len=0c <?>
Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00
Capabilities: [ac] MSI: Enable+ Count=1/1 Maskable- 64bit-
Capabilities: [d0] Power Management version 2
Capabilities: [100] Process Address Space ID (PASID)
Capabilities: [200] Address Translation Service (ATS)
Capabilities: [300] Page Request Interface (PRI)
Kernel driver in use: i915
Kernel modules: i915Edited by Bodo Graumann