Radeon GFX card fails on 3.16.0-28

[Jasper]

Expected behaviour, and behaviour on previous kernels (3.16.0-25 and before):
 Normal boot, ending in Lighdm login screen or in my case Kodi
Observed behaviour:
 Boot ends with blank screen, dmesg shows errors.

Hypothesus:
 This is a bug related to upgrading the kernel.

What I have done:
 Using apt-btrfs-snapshots I reverted until I found the upgrade that caused the problem. No X, or X related components were updated on this boundary. Changing the booted kernel did show the problem.
 Kernels tried that worked:
  vmlinuz-3.16.0-23-generic
  vmlinuz-3.16.0-24-generic
  vmlinuz-3.16.0-25-generic

Assuming that 'ubuntu-bug linux' has included enough information.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: linux-image-3.16.0-28-generic 3.16.0-28.38
ProcVersionSignature: Ubuntu 3.16.0-28.38-generic 3.16.7-ckt1
Uname: Linux 3.16.0-28-generic x86_64
ApportVersion: 2.15.1-0ubuntu1
Architecture: amd64
Date: Mon Dec 29 09:22:51 2014
HibernationDevice: RESUME=UUID=3493ba1a-188f-4b7d-b9cf-c404cb204ece
InstallationDate: Installed on 2014-05-31 (210 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140312)
IwConfig:
 eth0 no wireless extensions.

 eth1 no wireless extensions.

 lo no wireless extensions.
MachineType: HP ProLiant ML110 G7
ProcFB: 0 radeondrmfb
ProcKernelCmdLine: BOOT_IMAGE=/@/boot/vmlinuz-3.16.0-28-generic root=UUID=80479971-6f5f-49ed-9923-0ea40b093cb5 ro rootflags=subvol=@ quiet splash vt.handoff=7
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
 linux-restricted-modules-3.16.0-28-generic N/A
 linux-backports-modules-3.16.0-28-generic N/A
 linux-firmware 1.140
RfKill:
 0: hci0: Bluetooth
  Soft blocked: no
  Hard blocked: no
SourcePackage: linux
StagingDrivers: lirc_serial
UpgradeStatus: Upgraded to vivid on 2014-08-03 (146 days ago)
dmi.bios.date: 07/01/2013
dmi.bios.vendor: HP
dmi.bios.version: J01
dmi.chassis.type: 7
dmi.chassis.vendor: HP
dmi.modalias: dmi:bvnHP:bvrJ01:bd07/01/2013:svnHP:pnProLiantML110G7:pvr:cvnHP:ct7:cvr:
dmi.product.name: ProLiant ML110 G7
dmi.sys.vendor: HP

[Brad Figg (brad-figg)]

This change was made by a bot.

[penalvch (penalvch)]

Jasper, thank you for reporting this and helping make Ubuntu better. Could you please test the latest upstream kernel available from the very top line at the top of the page (the release names are irrelevant for testing, and please do not test the daily folder) following https://wiki.ubuntu.com/KernelMainlineBuilds ? It will allow additional upstream developers to examine the issue.

If the test did not allow you to test to the issue (ex. you couldn't boot into the OS) please make a comment in your report about this, and continue to test the next most recent kernel version until you can test to the issue. Once you've tested the upstream kernel, please comment on which kernel version specifically you tested. If this bug is fixed in the mainline kernel, please add the following tags:
kernel-fixed-upstream
kernel-fixed-upstream-VERSION-NUMBER

where VERSION-NUMBER is the version number of the kernel you tested exactly shown as:
kernel-fixed-upstream-3.19-rc1

This can be done by clicking on the yellow circle with a black pencil icon next to the word Tags located at the bottom of the bug description.

If the mainline kernel does not fix this bug, please add the following tags:
kernel-bug-exists-upstream
kernel-bug-exists-upstream-VERSION-NUMBER

Once testing of the upstream kernel is complete, please mark this bug's Status as Confirmed. Please let us know your results. Thank you for your understanding.

[Jasper (jasper-mackenzie)]

Thank you.
 Upstream kernel 3.19-rc2 (generic and low latency for Vivid) solved the issue.

[penalvch (penalvch)]

Jasper, the next step is to fully reverse commit bisect from kernel 3.16 to 3.19-rc2 in order to identify the last bad commit, followed immediately by the first good one. Once this commit has been identified, then it may be reviewed as a candidate for backporting into your release. Could you please do this following https://wiki.ubuntu.com/Kernel/KernelBisection#How_do_I_reverse_bisect_the_upstream_kernel.3F ? Please note, finding adjacent kernel versions is not fully commit bisecting.

Thank you for your understanding.

Helpful bug reporting tips:
https://wiki.ubuntu.com/ReportingBugs

[Jasper (jasper-mackenzie)]

All kernels from mainline worked (took a selection from 3.16.0 to 3.19)

It turns out that 3.16.0-28 works without
linus-image-extras-3.16.0-28-generic
 which contains
/lib/modules/3.16.0-28-generic/kernel/drivers/gpu/drm/radeon/radeon.ko
and
/lib/modules/3.16.0-28-generic/kernel/drivers/video/fbdev/aty/radeonfb.ko

But

3.16.0-29-generic (linux-image and linux-image-extra) from ...../ubuntu/pool/main/l/linux/ works perfectly.
So a blip eh

[penalvch (penalvch)]

Jasper, given the Proposed kernel addresses the issue, let this be marked Triaged for now. If it ends up this kernel is not pushed into Updates, pursuing a bisect may be revisited then.

[Jasper (jasper-mackenzie)]

Cheers.