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[Ubuntu Foundations Team Bug Bot <1457781@xxxxxxxxxxxxxxxxxx>]

** Tags added: patch

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https://bugs.launchpad.net/bugs/1457781

Title:
  armhf: cpufreq doesn't autoload by default

Status in linux package in Ubuntu:
  Incomplete

Bug description:
  SRU Justification:

      Impact: upon boot, frequency scaling is not working.

      Fix: Apply the patches, recompile and reboot.

      Testcase: Try booting a beaglebone with and without a patched
  kernel.

  With this series applied there should be:

  ubuntu@beaglebone:~$ ls -la /sys/devices/system/cpu/cpu0/cpufreq/
  total 0
  drwxr-xr-x 3 root root    0 May 22 07:03 .
  drwxr-xr-x 5 root root    0 May 22 07:03 ..
  -r--r--r-- 1 root root 4096 May 22 07:03 affected_cpus
  -r-------- 1 root root 4096 May 22 07:03 cpuinfo_cur_freq
  -r--r--r-- 1 root root 4096 May 22 07:03 cpuinfo_max_freq
  -r--r--r-- 1 root root 4096 May 22 07:03 cpuinfo_min_freq
  -r--r--r-- 1 root root 4096 May 22 07:03 cpuinfo_transition_latency
  -r--r--r-- 1 root root 4096 May 22 07:03 related_cpus
  -r--r--r-- 1 root root 4096 May 22 07:03 scaling_available_frequencies
  -r--r--r-- 1 root root 4096 May 22 07:03 scaling_available_governors
  -r--r--r-- 1 root root 4096 May 22 07:03 scaling_cur_freq
  -r--r--r-- 1 root root 4096 May 22 07:03 scaling_driver
  -rw-r--r-- 1 root root 4096 May 22 04:43 scaling_governor
  -rw-r--r-- 1 root root 4096 May 22 07:03 scaling_max_freq
  -rw-r--r-- 1 root root 4096 May 22 07:03 scaling_min_freq
  -rw-r--r-- 1 root root 4096 May 22 07:03 scaling_setspeed
  drwxr-xr-x 2 root root    0 May 22 07:03 stats
  ubuntu@beaglebone:~$

  With an unpatched kernel, until the cpufreq module is loaded, that
  directory doesn't exist.

  ...

  While cpufreq support on armhf is available for a while, if support is
  compiled as a kernel module, the corresponding module doesn't autoload
  by default, and thus frequency scaling is not active upon boot until a
  user manually load it (or until /etc/modules is modified to forcibly
  load it).

  While in Trusty cpufreq was built-in on armhf, starting with Utopic we
  made support available as a kernel module, making people think that
  cpufreq was either broken or missing in their new kernels.

  To fix it, revert back that decision and make cpufreq compiled-in
  again on armhf - it affects Utopic and Vivid kernels.

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