FS#57653 - [linux] External monitor (docking station) fails to work with linux-4.15+ on Lenovo T470s

Attached to Project: Arch Linux
Opened by Paul Moore (pcmoore) - Monday, 26 February 2018, 19:58 GMT
Last edited by Doug Newgard (Scimmia) - Friday, 20 April 2018, 15:34 GMT
Task Type Bug Report
Category Kernel
Status Closed
Assigned To Tobias Powalowski (tpowa)
Jan Alexander Steffens (heftig)
Architecture x86_64
Severity Medium
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 3
Private No

Details

Description:

Starting with the Linux v4.15 packages (just verified with linux-4.15.5-1) my external monitor, connected via a docking station does not work (it goes into power save mode). The monitor works without problem on earlier kernels, including linux-4.14.15-1 (currently running kernel).

It all happens very quickly during boot, but it would appear that there is some initial text displayed during early boot, but the monitor is blank by the time that initramfs asks for a password (dm-crypt'd root partition).

Additional info:

* hardware information

Lenovo T470s
Intel Corporation HD Graphics 620
Standard Lenovo docking station, display connected via DisplayPort

* package version(s)

linux 4.15.5-1
mkinitcpio 24-2

* config and/or log files etc.

# cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-linux root=UUID=XXX rw cryptdevice=UUID=XXX:cryptoroot:allow-discards
# cat /etc/mkinitcpio.conf | grep -v "^#" | grep -v "^$"
MODULES=(i915)
BINARIES=()
FILES=()
HOOKS=(base keyboard udev autodetect modconf encrypt block filesystems fsck)

Steps to reproduce:

Install linux-4.15+, reboot.
This task depends upon

Closed by  Doug Newgard (Scimmia)
Friday, 20 April 2018, 15:34 GMT
Reason for closing:  Fixed
Additional comments about closing:  linux 4.16.2-2
Comment by Paul Moore (pcmoore) - Sunday, 11 March 2018, 16:41 GMT
Quick update: the problem persists with linux 4.15.7-1
Comment by Paul Moore (pcmoore) - Friday, 30 March 2018, 17:11 GMT
The problem persists with linux 4.15.13-1, linux-lts 4.14.30-1 works as expected
Comment by Ferran Pallarès (poinu) - Wednesday, 04 April 2018, 06:43 GMT
Seems related to https://bugzilla.redhat.com/show_bug.cgi?id=1549042. Are you able to boot?
Comment by Paul Moore (pcmoore) - Friday, 13 April 2018, 12:30 GMT
I'm still seeing the problem with linux 4.15.15-1, and linux-lts continues to work as expected with version 4.14.33-1.

I looked at the Fedora bug report from @poinu and it appears to be a similar problem, although I don't have a quick way to tell if the system fully boots while docked (laptop screen is not visible). The system does boot, and appears to work correctly, using a v4.15.x kernel if *undocked*.

Does anyone have an Arch kernel with the patch from the Fedora BZ? If so, I would be willing to test it ...
Comment by Paul Moore (pcmoore) - Friday, 20 April 2018, 15:21 GMT
This appears to be fixed in linux 4.16.2-2, I think we can close this now.

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