Hi! Thx for reporting your problem! On 31.03.24 07:59, Andrei Gaponenko wrote: > > I noticed a regression with the mailine kernel pre-compiled by EPEL. > > I have just tried linux-6.9-rc1.tar.gz from kernel.org, and it still > misbehaves. > > 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. With a "good" kernel everything works. With a > "broken" 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. > > Everything worked with EPEL mainline kernels up to and including > kernel-ml-6.7.9-1.el9.elrepo.x86_64 > > The breakage is observed in > > kernel-ml-6.8.1-1.el9.elrepo.x86_64 > kernel-ml-6.8.2-1.el9.elrepo.x86_64 > linux-6.9-rc1.tar.gz from kernel.org (with olddefconfig) > > Other tests: using an HDMI cable instead of the Display Port cable > between the monitor and the dock does not change things, 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. Does you laptop offer a HDMI or DP connector? Have you tried if that that works any better? If it does not, then the DRM developers might be willing to look into this. Anyway: could you try to bisect the problem as described in https://docs.kernel.org/admin-guide/verify-bugs-and-bisect-regressions.html I strongly suspect that this will be needed to get this resolved: this could be caused by various subsystems, so no developer might be willing to look into this without a bisection result. :-/ Ciao, Thorsten > Operating System: AlmaLinux 9.3 (Shamrock Pampas Cat) > > uname -mi: x86_64 x86_64 > > Laptop: Dell Precision 5470/02RK6V > > 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 > > dmesg and kernel config are attached to > https://bugzilla.kernel.org/show_bug.cgi?id=218663 > > #regzbot introduced: v6.7.9..v6.8.1 > > Andrei > >
