Created attachment 141689 [details]
DMESG with nvkm_dp_train_pattern failure. At 3468 is the manual re-plug
My computer (X10DAX motherboard, Nvidia GTX 980, dual Xeon E5) fails to come back if it goes to DPMS standby with:
WARNING: CPU: 3 PID: 8 at drivers/gpu/drm/nouveau/include/nvkm/subdev/i2c.h:170 nvkm_dp_train_pattern+0x12e/0x150 [nouveau]
I am running 4.18.9 of the kernel.
The GTX 980s are hooked to dual Dell P2715Q monitors. The monitors have a steady glowing power LED until I attempt to resume by moving the mouse at which point they say not connected and the power led starts flashing.
If I remove the re-insert the DP cable(s) the monitors come back.
Note that I am doing no suspending nor hibernation.
Created attachment 141690 [details]
Xorg logfile. Failed resume at 2290 and manual plug event at 3468
There have been a variety of DP-MST-related fixes recently, both in nouveau as well as the drm subsystem courtesy of Lyude. Could you try 4.19-rc4 or later? (No clue if those fixes affect your situation, but easy enough to check.)
Created attachment 141691 [details]
dmesg with 4.19-rc4 plus
Same general issue. Got some new "gr:" lines. Full dmesg attached.
A few things I have noticed:
* The unplug/replug monitor thing doesn't always fix it. Sometimes they just stay off.
* If I run "xset dpms force standby" and wait 5-10 seconds and move the mouse it seems to always come back (5 tests).
* If I run "xset dpms force standby" and wait 40 seconds and move the mouse it seems to NOT come back (3 tests).