[REGRESSION] external monitor+Dell dock stopped working
Hello,
I see several reports here concerning external monitors and docks, but they all seem to be about different issues than what I encountered.
The default setup: a laptop is connected to a dock, Dell WD22TB4, via a USB-C cable. The dock is connected to an external monitor via a Display Port cable. All cable connections are made before I boot the laptop. With a "good" kernel everything works. With a "bad" kernel, the external monitor is still correctly identified by the system and is shown as enabled in plasma systemsettings. The system also behaves like the monitor is working, for example, one can move the mouse pointer off the laptop screen. However the external monitor screen stays black, and it eventually goes to sleep. This is 100% reproducible.
Using an HDMI cable instead of the Display Port cable between the monitor and the dock does not change things, I get the black screen with the newer kernels.
Using a small HDMI-to-USB-C adapter instead of the dock results in a working system, even with the newer kernels. So the breakage appears to be specific to the Dell WD22TB4 dock.
git bisect log is attached.
I am also attaching a snapshot of "git bisect visualize", which shows that between the "good" and the "bad" commits there is a range of drm/i915 commits that I could not test. Each "bisect skip" means compilation failed. They all failed with the same error:
ERROR: modpost: "devm_regmap_add_irq_chip" [drivers/mfd/cs42l43.ko] undefined!
Hardware name: Dell Inc. Precision 5470/02RK6V, BIOS 1.8.0 10/07/2022
Operating System: AlmaLinux 9.3 (Shamrock Pampas Cat)
uname -a Linux linux-141537 6.7.9-1.el9.elrepo.x86_64 #1 (moved) SMP PREEMPT_DYNAMIC Wed Mar 6 13:47:56 EST 2024 x86_64 x86_64 x86_64 GNU/Linux
lspci -vnn -d :*:0300 is attached
dmesg with debug information is attached (from a "bad" kernel)
lsusb |grep dock Bus 003 Device 007: ID 413c:b06e Dell Computer Corp. Dell dock Bus 003 Device 008: ID 413c:b06f Dell Computer Corp. Dell dock Bus 003 Device 006: ID 0bda:5413 Realtek Semiconductor Corp. Dell dock Bus 003 Device 005: ID 0bda:5487 Realtek Semiconductor Corp. Dell dock Bus 002 Device 004: ID 0bda:0413 Realtek Semiconductor Corp. Dell dock Bus 002 Device 003: ID 0bda:0487 Realtek Semiconductor Corp. Dell dock
Originally filed at https://bugzilla.kernel.org/show_bug.cgi?id=218663
dmesg-6.7.0-rc2-local-00357-g221d6546bd16
config-6.7.0-rc2-local-00357-g221d6546bd16
