Displays fail to wake up when booting machine away from Display Port KVM switch

Submitted by dhruv.a.thakkar@leidos.com

Assigned to Nouveau Project

Link to original bug (#101559)

Description

Created attachment 132142
Xorg.0.log

Description of problem:

We are trying to solve an issue in which displays fail to wake up when booting a Rhel 7.3 machine (Machine A) connected to a Display Port KVM while the KVM is pointing to Machine B. The unusual bit is that xorg logs in /var/log/Xorg.0.log indicate that everything comes up correctly, and a "ps -ef |grep X|xinit" shows that X and xinit are up and running. If we boot Machine A while the KVM is pointing to it, the displays come up with no issues.

We have KMS parameters set to force the output of the video (video=DP-1:2560x1600D and video=DP-2:2560x1600D) as well as options to load the EDID information. These parameters have worked in the past for us when we used DVI connections through KVMs, but DisplayPort is not showing the same results. Note that we have additional kernel options added for extra debug information (log_buf_len=8M nouveau.debug=disp=trace,i2c=trace,bios=trace)

Using Xrandr and Udev rules with a script allow us to turn off and then back on the displays automatically, allowing us a workaround, but it still does not solve the core issue of that nouveau is not waking up the monitors.

Please see the attached logs/config files and diagram below for more information.

|Machine A| |Machine B|
\ /
\ /
\ _________ /
|DPort KVM|
|_________|
/ <br> / <br> / <br> |Monitor 2| |Monitor 1|

Attachment 132142, "Xorg.0.log":
log.nouveau