Created attachment 143523 [details]
I have a NUC7i7BNH with the latest BIOS (0062) running Ubuntu 18.04 (uname -r = 4.18.0-15-generic). I have the NUC connected via USB-C to a dual DisplayPort adapter, to an Avocent SV340D KVM. Also tried kernel v5.0-rc7.
If I have the KVM on the switch for the NUC, everything works great. If I switch the KVM to another channel, and then switch back to the NUC, I only get black screens. The only solution is to hard reboot the NUC.
This relates to a bug I raised on https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1816269.
Specifically [ 135.089830] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun followed by a lot of thunderblot hotplug messages.
Ville, any comments here?
Any additional info I can provide here to help?
Thanks for asking. Can you please verify the issue with latest drmtip?
This is to ensure that this issue still persists with drmtip. This will be useful during investigation.
FWIW you can find prebuilt binary  for Ubuntu.
Created attachment 143696 [details]
@Lakshmi / @Kai-Heng
Tried cod/tip/drm-tip/2019-03-16 mainline build but still same issue.
When I switch over to another KVM input, and switch back to the NUC, black screen and can't do anything. The only way to recover is hard reboot of the NUC.
new dmesg attached.
Created attachment 143697 [details]
drm-tip install messages
drm-tip install messages
> new dmesg attached.
Can you please set kernel parameters drm.debug=0x1e log_buf_len=4M and attach the log from boot.
Created attachment 143731 [details]
dmesg with boot parameters
Thanks for the help. Please see attached file for dmesg with boot params.
Let me know what else I can provide.
This still isn't working for me - I even tried another KVM - is there anything further I can provide to help debug?
Hi @stuart, can you please provide display_info as well?
Will try reproducing the issue and get back to you.
(In reply to Stuart from comment #10)
> HI @Lakshmi,
> This still isn't working for me - I even tried another KVM - is there
> anything further I can provide to help debug?
(In reply to Swati Sharma from comment #11)
> Hi @stuart, can you please provide display_info as well?
> cat /sys/kernel/debug/dri/0/i915_display_info
> Will try reproducing the issue and get back to you.
No feedback from more than a month. Dropping the priority of the issue to Medium.
Stuart, can you please provide requested details?