screen remains blank after waking up from suspend

[Pierre Equoy]

Steps:
1. Suspend the computer by pressing the Sleep key(Fn+F2 on the keyboard here)
2. Press any key on the keyboard or the Power button to wake the device up

Expected results:
1. The system suspends and the Power button LED blinks
2. The system wakes up and user can log in.

Actual results:
1. The system suspends and the Power button LED blinks (OK)
2. The login screen appears and the screen is immediately turned off (NOK). User needs to move the mouse or enter a key to turn the screen on.

Additional information:

- In a few additional occasions, after performing this action several times (pressing the Sleep key to suspend the system, then wake it up), the system freezes at log in screen just before going to suspend mode. It has to be force-stopped and restarted.

- Please note that this problem does NOT happen when suspending from the User Menu or using the Power button and selecting Suspend.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: lightdm 1.10.4-0ubuntu2
ProcVersionSignature: Ubuntu 3.13.0-34.60-generic 3.13.11.4
Uname: Linux 3.13.0-34-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.7
Architecture: amd64
Date: Thu Mar 12 11:19:32 2015
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-stella-datong140729-kylin-trusty-amd64-20150205-2
InstallationDate: Installed on 2015-02-10 (29 days ago)
InstallationMedia: Ubuntu 14.04 "Trusty" - Build amd64 LIVE Binary 20150205-07:08
LightdmConfig:
 [SeatDefaults]
 autologin-guest=false
 autologin-user-timeout=0
 autologin-session=lightdm-autologin
 #autologin-user=u
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)

[TienFu Chen (ctf)]

This issue seems related to lp:1405349, not sure if it is the same root-cause.

[TienFu Chen (ctf)]

I can't reproduce this issue on vivid 0323 image.

[TienFu Chen (ctf)]

I can't reproduce this issue on stock 14.04.1, but instead sometimes the system halts when running into suspend.

[TienFu Chen (ctf)]

As stock 14.04.1 image can't reproduce this issue(instead it halts, but it should be another issue), I'm closing the oem priority bug here.

[Ubuntu Foundations Team Bug Bot (crichton)]

The attachment "adarshbug.txt" seems to be a patch. If it isn't, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are a member of the ~ubuntu-reviewers, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issues please contact him.]

[Daniel van Vugt (vanvugt)]

Ubuntu 14.04 (trusty) reached end of standard support in April 2019:

  https://wiki.ubuntu.com/Releases

If you would like to continue with free support then please update to a
newer Ubuntu version and tell us if the problem still occurs.

If you would like to continue with Ubuntu 14.04 then there is a paid
support option detailed at https://www.ubuntu.com/esm