Lost one screen from triple multi monitor radeon setup.

[Ewano]

I have been running a stock Ubuntu 16.04 LTS with three monitors from a single Radeon HD 7770 card with no problems.

Description: Ubuntu 16.04.1 LTS
Release: 16.04

After not having used my system since approximately 20/12/2016, I used a simple script on 03/01/2017 to run updates then shut down the system as follows:

apt-get update
apt-get -y dist-upgrade
apt-get -y autoremove
shutdown -P now

Upon next start up, one of my screens remains dark in power saving mode. This screen is connected using a displayport cable.

At boot the BIOS splash screen is shown on the affected screen. During the boot process the screen is active until the login screen is presented - at which point the screen enters power saving mode.

Using the print screen to capture an image of my desktop, I can see that desktop is active and application windows are being created just fine. The monitor screen in question remains in power saving mode, and is unusable.

I tested with an alternate existing install on different hard drive which had also not been updated for some time. I swapped over the hard drive to this machine, let it boot through to a correctly functioning desktop to verify that there was no hardware fault. Once I had verified that the hardware functioned correctly, I again ran updates and rebooted the machine. After update this installation also exhibited the fault.

I can only assume that a bug has been introduced during the updates supplied between 20/12/2016 and 03/01/2017.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: xorg 1:7.7+13ubuntu3
ProcVersionSignature: Ubuntu 4.4.0-57.78-generic 4.4.35
Uname: Linux 4.4.0-57-generic x86_64
.tmp.unity_support_test.0:

ApportVersion: 2.20.1-0ubuntu2.4
Architecture: amd64
BootLog:

CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
CurrentDesktop: Unity
Date: Sat Jan 7 17:22:02 2017
DistUpgraded: Fresh install
DistroCodename: xenial
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes
GraphicsCard:
 Advanced Micro Devices, Inc. [AMD/ATI] Cape Verde XT [Radeon HD 7770/8760 / R7 250X] [1002:683d] (prog-if 00 [VGA controller])
   Subsystem: Micro-Star International Co., Ltd. [MSI] R7770-PMD1GD5 [1462:2710]
InstallationDate: Installed on 2016-09-28 (101 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
MachineType: To Be Filled By O.E.M. To Be Filled By O.E.M.
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-57-generic.efi.signed root=UUID=d1a7c988-d3b8-474e-ab61-437925f4454e ro quiet splash vt.handoff=7
SourcePackage: xorg
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 07/06/2012
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P2.00
dmi.board.name: A75M
dmi.board.vendor: ASRock
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP2.00:bd07/06/2012:svnToBeFilledByO.E.M.:pnToBeFilledByO.E.M.:pvrToBeFilledByO.E.M.:rvnASRock:rnA75M:rvr:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.name: To Be Filled By O.E.M.
dmi.product.version: To Be Filled By O.E.M.
dmi.sys.vendor: To Be Filled By O.E.M.
version.compiz: compiz 1:0.9.12.2+16.04.20160823-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.67-1ubuntu0.16.04.2
version.libgl1-mesa-dri: libgl1-mesa-dri 11.2.0-1ubuntu2.2
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 11.2.0-1ubuntu2.2
version.xserver-xorg-core: xserver-xorg-core 2:1.18.4-0ubuntu0.2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.10.1-1ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.7.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20160325-1ubuntu1.2
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.12-1build2
xserver.bootTime: Sat Jan 7 16:26:58 2017
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.version: 2:1.18.4-0ubuntu0.2
xserver.video_driver: radeon

[Ewano (i-launchpad-ewano-net)]

Update:

This fault was tracked down to a damaged display port cable. Some of the pins in one of the connectors were bent so badly that I have no idea how it was functioning. A replacement resurrected the affected display.

I can only conclude that there must have been some extra status checking code in one of the updates which introduced a test on the faulty lines. The test returned an erroneous result and triggered the driver to issue an "enter power save" command to that monitor.

This bug can be closed - and I can stop attempting to bisect the Xorg code..

[Ewano (i-launchpad-ewano-net)]

Not a bug. Code changes found a fault in hardware.