Unity will act erratically after connecting to an external monitor [Intel Broadwell-U][8086:1616]

[Po-Hsu Lin]

CID: 201408-15444 Dell Vostro

The desktop will act erratically after connect to an external monitor,

* First thing is the content of "System Settings" will gone when the window is not in focus.
* The characters like "l", "i" will be missing from the console.
This won't back to normal even if you unplugged the monitor.
* The title of firefox also missing some characters, like R, U, x, z, F
But if you resize it to full screen, it will back to normal

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-3.16.0-31-generic 3.16.0-31.43~14.04.1
ProcVersionSignature: Ubuntu 3.16.0-31.43~14.04.1-generic 3.16.7-ckt5
Uname: Linux 3.16.0-31-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.14.1-0ubuntu3.7
Architecture: amd64
CurrentDesktop: Unity
Date: Fri Mar 20 05:18:26 2015
InstallationDate: Installed on 2015-03-20 (0 days ago)
InstallationMedia: Ubuntu 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1)
SourcePackage: linux-lts-utopic
UpgradeStatus: No upgrade log present (probably fresh install)

[Po-Hsu Lin (cypressyew)]

this issue still exist after reboot (without connecting to an external monitor), but quite random

[Po-Hsu Lin (cypressyew)]

00:02.0 VGA compatible controller [0300]: Intel Corporation Broadwell-U Integrated Graphics [8086:1616] (rev 08)

[Po-Hsu Lin (cypressyew)]

It seems that this issue does not exist in the drm-intel-nightly kernel at http://kernel.ubuntu.com/~kernel-ppa/mainline/drm-intel-nightly/current/

Verified with Linux 201408-15444 4.0.0-994-generic #201503240206

Also, this issue does not exist on another I+N system (201408-15447 Dell Vostro 3449)
even though that system looks like running on the Intel driver.

[Timo Aaltonen (tjaalton)]

Please try with 3.17 mainline, there might be some bugfixes missing from i915.ko. Check dmesg if you see a GPU hang mentioned there (the symptoms match)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Timo Aaltonen (tjaalton)]

the "upstream" bug is

https://bugs.launchpad.net/ubuntu/utopic/+source/linux/+bug/1374389

I'm building a test kernel for amd64 right now

[Timo Aaltonen (tjaalton)]

I've put an utopic kernel build here, can be tested on trusty too:

http://people.canonical.com/~tjaalton/utopic-fix/

[Timo Aaltonen (tjaalton)]

marked as a dupe of the other bug, file test results there