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[Rafael David Tinoco <inaddy@xxxxxxxxxx>]

Collaborative Power Control = Enabled

enables "pcc-cpufreq" as the "core communication" between cpufreq driver
AND firmware.

https://www.kernel.org/doc/Documentation/cpu-freq/pcc-cpufreq.txt

This is an interface used by HP extensively (HP servers tend to use
extensively ACPI and interfaces between OS and firmware).

Judging by comments on commit:

https://lkml.org/lkml/2014/3/20/799

We can see that intel_pstates might actually fail to initialize cpufreq
if it ever calls the cpufreq driver initialization and gets an error.

We might be getting a "0" from:

drivers/cpufreq/pcc-cpufreq.c -> pcc_get_freq()

which is called in the code (from commit given):

policy->cur = cpufreq_driver->get(policy->cpu);

During the cpufreq initialization function (__cpufreq_add_dev).

* This is actual the latest code in the kernel and they assume sometimes
intel_pstates can fail to initialize cpufreq (even for other cpufreq
drivers). If it fails it gives us that warning message pointed out. A
workaround could be trying to "disable" and "enable" the core by putting
it offline and online again * (Kernel code does not attempt to
initialize cpufreq for a second time, for example).

It looks like HP ROM engineering team might want to debug this.

-- 
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Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1447763

Title:
  HP Proliant Servers suffer from cpufreq initialization failure for
  some cpu cores

Status in linux package in Ubuntu:
  In Progress

Bug description:
  It was brought to my attention the following:

  Ubuntu Trusty Kernel 3.13 is suffering from cpufreq initialization
  failure for some cpu cores on Proliant Servers.

  /sys/devices/system/cpu# for cpu in `ls -1d cpu[0-9]*`; do ls -ld $cpu/cpufreq; done 
  drwxr-xr-x 2 root root 0 Apr 2 16:15 cpu0/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu1/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu10/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu11/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu12/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu13/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu14/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu15/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu16/cpufreq 
  ls: cannot access cpu17/cpufreq: No such file or directory 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu18/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu19/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu2/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu20/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu21/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu22/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu23/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu24/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu25/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu26/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu27/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu28/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu29/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu3/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu30/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu31/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu4/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu5/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu6/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu7/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu8/cpufreq 
  drwxr-xr-x 2 root root 0 Apr 2 16:16 cpu9/cpufreq 

  With the following message:

  [ 2.465616] pcc-cpufreq: (v1.10.00) driver loaded with frequency limits: 1200 MHz, 2200 MHz 
  [ 2.474810] cpufreq: __cpufreq_add_dev: ->get() failed 

  Disabling Collaborative Power Control into firmware setup mitigates
  the issue.

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