Arch Linux

stairmast0r

Member

Registered: 2016-11-09

Posts: 1

[SOLVED] Dell E7470 issues with docking station and external displays

I have a Dell Latitude E7470 with Arch installed and working beautifully (for the most part). One glaring issue (or maybe two? I'm not sure if there's any correlation) is that my two external monitors are not detected when docking the laptop in the morning, after suspending and undocking the previous evening. It's an E-port docking station, with monitors connected by DP and DVI. When booting for the first time with the laptop docked, both displays are recognized and work fine in extended mode via xrandr. If I suspend, then undock, then redock and unsuspend, xrandr shows DP1-1 as connected and is able to show a picture on it after setting the mode, but DP1-2 is disconnected and the only solution so far is to reboot. The second issue is that when rebooting at this point, the system freezes immediately after running the reboot command and the caps lock light starts blinking, which is supposedly indicative of a memory problem. After forced rebooting, the displays work as intended again. All of these steps are completely reproducible. From reading, it looks like the Dell docks use a DisplayPort MST hub internally for all three ports (DP, DVI, VGA), thus the DP1-{1..3} notation in xrandr. None of these problems occur when running Windows, which leads me to believe it's a driver problem within Arch. I've dug up about as much as I can on this topic and haven't gotten anywhere. Hopefully somebody else has some experience with this and can offer some advice. Thank you!

UPDATE: I found one of the "plus" models of this dock around the office, which features two DP ports. Using both DP and no DVI, the problem seems to be resolved thus far. If it holds up after further testing, I'll mark this as solved.

UPDATE 2: xrandr gets a little bit weird, but with the right config script I can get all three displays working properly when using the new dock with 2x DP. Marking as solved.

Last edited by stairmast0r (2016-11-10 15:19:57)

anno2100

Member

Registered: 2016-10-22

Posts: 15

Re: [SOLVED] Dell E7470 issues with docking station and external displays

Hi stairmast0r

I run into pretty much the exact same problem with my Thinkpad T460s. Would you mind sharing your config script so I could do some debuging and testing from there?
Thanks a lot!

oyhel

Member

Registered: 2017-03-09

Posts: 1

Re: [SOLVED] Dell E7470 issues with docking station and external displays

Hi
I am facing the same problem with a Thinkpad T460s and the Ultra dock. Did you ever figure out how to get this working? Any help is much appreciated!