Public bug reported:
Running on a NUC5i7RYH, latest BIOS. ASUS Monitor connected via Display Port or
HDMI
Running Xubuntu 16.04 - latest all current patches
Sometimes the monitor remains blanked even when the session has
reactivated.
I have been able to reproduce this problem by letting the monitor remain
in the 'blanked' state for > 60 minutes, or powering off the monitor.
When the monitor is powered back on and the session is woken up with
mouse or keyboard input, it does wake up but the monitor remains
blanked.
I was able to prove to myself the session was awake by leaving it with
terminal opened to full screen with VIM running on an NFS mounted file
system. I could type and save at the black monitor screen and see that
the file got updates from a different system. So the session is "live"
but the computer has forgotten to re-establish the DisplayPort link.
An error appears in the lightdm logs about setting a CRTC, if you
activate an alternate terminal (say with CTL-ALT-F1) and try `xrandr
--output DP1 --auto` it also registers that CRTC error. HOWEVER, if you
ssh in from a different machine, tell bash to export DISPLAY=:0 (set
$DISPLAY to ':0') and then type 'xrandr --output DP1 --auto' the screen
turns on again! This also happens on a Gigabyte BRIX system (same NUC
reference design but in that case a core i3 rather than a Core i7).
To reproduce, turn off the monitor, wait an hour, and turn it on again.
You can also kill HUP the lightdm process and that will restart a new
session (but open windows in the previous session are lost).
So interesting questions, why does typing xrandr "locally" give you the
error but running it from an ssh session work?
Since xrandr and restarting the session can both "fix" the problem, the
driver seems to know how to turn the display on if told correctly.
How can I find out where the code is getting the CRTC error?
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: lightdm 1.18.1-0ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-22.39-generic 4.4.8
Uname: Linux 4.4.0-22-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
CurrentDesktop: XFCE
Date: Thu May 12 20:33:01 2016
InstallationDate: Installed on 2016-05-08 (4 days ago)
InstallationMedia: Xubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
LightdmDisplayLog: (II) AIGLX: Suspending AIGLX clients for VT switch
LightdmLog:
[+80180.09s] DEBUG: Seat seat0 changes active session to
[+80189.53s] DEBUG: Seat seat0 changes active session to 64
[+80222.67s] DEBUG: Seat seat0 changes active session to c4
[+80222.67s] DEBUG: Session c4 is already active
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)
** Affects: lightdm (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug xenial
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https://bugs.launchpad.net/bugs/1581302
Title:
Monitor remains blanked with Intel Graphics
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