Machine: Lenovo X1 Gen 3 with OneLink Pro dock Monitor: Lenovo 4k monitor "Pro 2480mD" If I connect the monitor using the X1's built-in mini-DP with a DP1.2 compatible mini-DP to DP cable, things work fine (more/less, the monitor sometimes fails to come back from idle blanking but I'll file that as a separate issue). If I connect the monitor to the dock using the DP-DP cable coming with the monitor, the monitor doesn't sync. It displays an error about no sync. dmesg fills up with error messages from the driver which I will attach. $ uname -a Linux pasglop 4.3.0-rc4+ #1 SMP Tue Oct 6 11:46:15 AEDT 2015 x86_64 x86_64 x86_64 GNU/Linux git head is 1ff47c81ae9fcf16e40292478b7dd8c1d68130c1 from the drm-intel git tree using the nightly branch. If I use xrandr to use a lower resolution (1080p for example), I had it working once or twice. I tried to use 4k at 30Hz but that resulted in a driver crash taking out the internal panel as well (reproduceable) with a previous 4.3-rc kernel. I will update this with more tests of the above using this latest kernel.
Created attachment 118694 [details] dmesg with errors This is the dmesg after plugging, then unplugging the monitor, you can see all the master control interrupt errors.
I will do another dmesg with drm.debug in a minute. In the meantime, I tried --rate to use a 30Hz rate, and that did crash it. The symptom is a bit different that previous kernels though, the internal LCD didn't switch to displaying garbage, but it did hang. I recovered after a few seconds, but then all displays blinked (looked like it re-detected the external monitor) and this time everything hung. There was nothing in the sysfs "error" file after a reboot.
Created attachment 118695 [details] dmesg with drm.debug=0x1e New dmesg
I tried again --mode/--rate to set --output DP2-2 to 30Hz but that locked up immediately this time. Still nothing in the error file. I will try ssh'ing next time in case the machine is still responsive but that will have to wait possibly til tomorrow. Let me know if there's anything else I can do such as capturing registers etc... Note that it works in Windows, however the dock output in that case is limited to 30Hz (I believe the OneLink docks are DP1.1 only).
I've the same issue on an X1 Yoga with ubuntu xenial: marco@placebo:~/scripts$ uname -a Linux placebo 4.4.0-21-generic #37-Ubuntu SMP Mon Apr 18 18:33:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
Please try current v4.6-rc kernels or, if that fails, drm-intel-nightly branch of http://cgit.freedesktop.org/drm-intel
https://support.lenovo.com/gb/en/documents/pd029981 says the pro dock supports "DisplayPort with maximum resolution 2560x1600".
Dock does not support 4k not a bug
Except that it works in windows at 30Hz...
Tons of fixes since 4.3/4.4 times, please try latest components.
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