"link training failed": nouveau does not recover from monitor suspend
Submitted by Dan Callaghan
Assigned to Nouveau Project
When my monitor wakes up from "power save mode" (DPMS suspend) nouveau does not display any output and the monitor goes back to power save after a few seconds. The kernel says:
kernel: nouveau E[ PDISP][0000:03:00.0][0x00000006] 02:0006:0f42: link training failed
The behaviour of the monitor might be a bit dodgy. When booting the machine I have to mash buttons on the monitor to keep it awake until the firmware starts displaying an image, otherwise I will get no output from the firmware at all.
When the monitor goes into power save mode, it stays awake showing a message "Power save mode" for about 3 seconds, then it actually powers down (its LED turns orange). I have noticed that nouveau can recover if I shake the mouse during those three seconds, but it can't recover if I let the monitor power all the way down.
Complete logs to follow.
Lenovo Thinkstation P500, all legacy/CSM features disabled ("pure UEFI")
Nvidia Quadro K620 (GM107/NV117)
Thinkvision 2840m connected via Displayport
Kernel is 4.2.0 plus Fedora patches plus these four commits suggested by Ben Skeggs: