One black screen of two when both on 1080p60

[Andreas Morgenstern]

One display turns off when both outputs are set to 1920x1080@60.0. They both still work separately on that rate.
Forcing the one to "1920x1080@59.9" is functioning as a work-around.

The good kernel version was linux_3.19.0-21.21.
This Problem occurred in kernel linux_3.19.0-22.22 and linux_3.19.0-23.24.

GPU is: Radeon HD 6670 using the radeon open source driver.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: linux-image-3.19.0-23-generic 3.19.0-23.24
ProcVersionSignature: Ubuntu 3.19.0-23.24-generic 3.19.8-ckt2
Uname: Linux 3.19.0-23-generic x86_64
ApportVersion: 2.17.2-0ubuntu1.1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: andreas 3695 F.... pulseaudio
 /dev/snd/controlC1: andreas 3695 F.... pulseaudio
CurrentDesktop: Unity
Date: Thu Jul 23 15:12:26 2015
HibernationDevice: RESUME=UUID=4f0d7a88-5c8d-41c5-a44c-d195a257fd4e
InstallationDate: Installed on 2012-04-11 (1198 days ago)
InstallationMedia: Xubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
IwConfig:
 eth0 no wireless extensions.

 lo no wireless extensions.
MachineType: Dell Inc. OptiPlex 755
ProcFB: 0 radeondrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.19.0-23-generic root=UUID=4acbdc21-f685-460d-a0dc-f86e6f346bf3 ro plymouth:debug splash quiet drm.debug=0xe
RelatedPackageVersions:
 linux-restricted-modules-3.19.0-23-generic N/A
 linux-backports-modules-3.19.0-23-generic N/A
 linux-firmware 1.143.2
RfKill:

SourcePackage: linux
UpgradeStatus: Upgraded to vivid on 2015-04-27 (87 days ago)
dmi.bios.date: 04/30/2008
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A10
dmi.board.name: 0GM819
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 6
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA10:bd04/30/2008:svnDellInc.:pnOptiPlex755:pvr:rvnDellInc.:rn0GM819:rvr:cvnDellInc.:ct6:cvr:
dmi.product.name: OptiPlex 755
dmi.sys.vendor: Dell Inc.

-----

(From TJ):

$ xrandr -q
Screen 0: minimum 320 x 200, current 3600 x 1080, maximum 16384 x 16384
HDMI-0 connected primary 1680x1050+0+0 (normal left inverted right x axis y axis) 477mm x 268mm
   1920x1080 60.0 *+ 50.0 59.9 60.0
   1920x1080i 60.1 50.0 60.0
   1600x1200 60.0
   1680x1050 59.9
   1280x1024 75.0 60.0
   1440x900 59.9
   1280x960 60.0
   1366x768 59.8
   1152x864 75.0
   1280x720 60.0 50.0 59.9
   1024x768 75.1 70.1 60.0
   832x624 74.6
   800x600 72.2 75.0 60.3 56.2
   720x576 50.0
   720x480 60.0 59.9
   640x480 75.0 72.8 66.7 60.0 59.9
   720x400 70.1
DVI-0 connected 1920x1080+1680+0 (normal left inverted right x axis y axis) 477mm x 268mm
   1920x1080 60.0*+
   1280x1024 75.0 60.0
   1152x864 75.0
   1024x768 75.1 60.0
   800x600 75.0 60.3
   640x480 75.0 60.0
   720x400 70.1
VGA-0 disconnected (normal left inverted right x axis y axis)

# workaround
$ xrandr --output HDMI-0 --mode 1920x1080 --rate 59.9

[Robert Hooker (sarvatt)]

Since the regression started in 3.19.0-22.22 (https://launchpad.net/ubuntu/+source/linux/3.19.0-22.22), it looks like its a stable update regression. I noticed in the upstream stable 3.18.18 release a few radeon commits were reverted that we haven't reverted yet

      Revert "drm/radeon: don't share plls if monitors differ in audio support"
      Revert "drm/radeon: adjust pll when audio is not enabled"

https://lkml.org/lkml/2015/7/11/94

[Robert Hooker (sarvatt)]

should be fixed in v3.19.8-ckt3, that picked up both reverts

http://kernel.ubuntu.com/git/ubuntu/linux.git/commit/?h=linux-3.19.y&id=bdb01a9532b5a985631d04aefc10e0a421284f28
http://kernel.ubuntu.com/git/ubuntu/linux.git/commit/?h=linux-3.19.y&id=bde11f3705c3aef7cd03731bf531c92c67a07358

[TJ (tj)]

Attached is IRC log of report and diagnosis

[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream stable kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v3.19 stable kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

If you are unable to test the mainline kernel, for example it will not boot, please add the tag: 'kernel-unable-to-test-upstream'.
Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.19.8-ckt3-vivid/

[Andy Whitcroft (apw)]

This bug was nominated against a series that is no longer supported, ie vivid. The bug task representing the vivid nomination is being closed as Won't Fix.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.