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[Alberto Salvia Novella <es20490446e@xxxxxxxxx>]

** Changed in: linux (Ubuntu)
   Importance: Undecided => High

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https://bugs.launchpad.net/bugs/1427330

Title:
  AMD Kaveri APU/CPU frequency scaling not working on linux 3.19

Status in linux package in Ubuntu:
  Confirmed

Bug description:
  A few days ago, when Vivid was still at Linux 3.18 I tried the Linux
  4.0-rc1 kernel from mainline and noticed that CPU frequency scaling
  would have no effect on the actual processor speed. I went back to
  3.18 and everything worked fine.

  Now Ubuntu 15.04 moved to Linux 3.19 and it happens to have the same
  problem as with 4.0-rc1 from mainline.

  The cpufreq indicator shows that the frequencies are adapted but
  > watch sudo cpupower monitor
  reveals that the AMD A10 PRO-7350B CPUs are stuck at the lowest frequency level (about 1.1GHz).

  This observation is confirmed by a quick benchmark using octave.
  The following line is executed on Linux 3.18 in less than 4 seconds, while on Linux 3.19 it needs more than 8 seconds to complete.
  > time echo "a=rand(3000);a*a;" | octave -q

  ProblemType: Bug
  DistroRelease: Ubuntu 15.04
  Package: linux-image-3.19.0-7-generic 3.19.0-7.7
  ProcVersionSignature: Ubuntu 3.19.0-7.7-generic 3.19.0
  Uname: Linux 3.19.0-7-generic x86_64
  ApportVersion: 2.16.2-0ubuntu1
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC1:  marc       2515 F.... pulseaudio
   /dev/snd/controlC0:  marc       2515 F.... pulseaudio
  CurrentDesktop: Unity
  Date: Mon Mar  2 19:04:32 2015
  EcryptfsInUse: Yes
  InstallationDate: Installed on 2015-02-23 (7 days ago)
  InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Alpha amd64 (20150219)
  MachineType: Hewlett-Packard HP EliteBook 755 G2
  ProcFB: 0 radeondrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.19.0-7-generic root=UUID=1a54cd72-80fc-4716-a62e-4faa5dcc63e9 ro quiet splash vt.handoff=7
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 05/19/2014
  dmi.bios.vendor: Hewlett-Packard
  dmi.bios.version: M84 Ver. 01.01
  dmi.board.asset.tag: Base Board Asset Tag
  dmi.board.name: 221C
  dmi.board.vendor: Hewlett-Packard
  dmi.board.version: KBC Version 63.13
  dmi.chassis.asset.tag: CNU426C7YS
  dmi.chassis.type: 10
  dmi.chassis.vendor: Hewlett-Packard
  dmi.modalias: dmi:bvnHewlett-Packard:bvrM84Ver.01.01:bd05/19/2014:svnHewlett-Packard:pnHPEliteBook755G2:pvrA3009DD10303:rvnHewlett-Packard:rn221C:rvrKBCVersion63.13:cvnHewlett-Packard:ct10:cvr:
  dmi.product.name: HP EliteBook 755 G2
  dmi.product.version: A3009DD10303
  dmi.sys.vendor: Hewlett-Packard

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