usb-c dock connected displays fail after suspend or blanking with kernel 5.11+
I have been using a Dell XPS 13 9300 laptop w/ Cable Matters USB-C docking station w/ two external monitors for over a year on Fedora versions 31-33 without any display issues. After updating from kernel 5.10.23 to 5.11.11, the external monitors rarely turn back on after waking from suspend or screen blanking. Usually (but not always), unplugging the laptop from the dock and reconnecting resolves the issue. The issue is reproducible ~3/4 times by either suspending the laptop, or allowing gnome to blank the screens after inactivity.
Last working kernel:
- kernel-5.10.23-200.fc33.x86_64
Issue present on:
- kernel-5.11.11-200.fc33.x86_64
- kernel-5.11.12-200.fc33.x86_64
- kernel-5.11.14-200.fc33.x86_64
- kernel-5.11.15-200.fc33.x86_64
- kernel-5.12.0-0.rc7.189.fc35.x86_64
This issue was first reported downstream (only noted suspend/sleep in downstream issue):
This is a Dell XPS 9300 (077Y9N) connected to a Cable Matters 201053 USB-C Docking Station which is connected to two external monitors via HDMI-to-HDMI.
$ uname -a
Linux monkfish 5.11.15-200.fc33.x86_64 #1 SMP Fri Apr 16 13:41:20 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
$ cat /etc/fedora-release
Fedora release 33 (Thirty Three)
$ grep 'model name' /proc/cpuinfo | uniq
model name : Intel(R) Core(TM) i7-1065G7 CPU @ 1.30GHzAttached is a log segment with drm.debug=0x1e log_buf_len=1M where the screen timeout was set to 1 minute of inactivity the log begins at 14:03:00, with the screen blanking a minute later around 14:04:00 and appears to complete blanking at 14:04:13. After 30 seconds a key was pressed on the keyboard to wake the screens back up (14:04:43). Neither of the external displays were woken up.