[PATCH 8/8] CPUFREQ: Add documentation for new average_freq cpufreq_stats sysfs file

[Thomas Renninger <trenn@suse.de>]

Signed-off-by: Thomas Renninger <trenn@suse.de>
Cc: <linux-acpi@vger.kernel.org>
Cc: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>
Cc: <cpufreq@vger.kernel.org>
---
 Documentation/cpu-freq/cpufreq-stats.txt |   17 +++++++++++++++++
 1 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/Documentation/cpu-freq/cpufreq-stats.txt b/Documentation/cpu-freq/cpufreq-stats.txt
index fc64749..aa05b65 100644
--- a/Documentation/cpu-freq/cpufreq-stats.txt
+++ b/Documentation/cpu-freq/cpufreq-stats.txt
@@ -44,11 +44,28 @@ the stats driver insertion.
 total 0
 drwxr-xr-x  2 root root    0 May 14 16:06 .
 drwxr-xr-x  3 root root    0 May 14 15:58 ..
+-r--r--r--  1 root root 4096 May 14 16:06 average_freq
 -r--r--r--  1 root root 4096 May 14 16:06 time_in_state
 -r--r--r--  1 root root 4096 May 14 16:06 total_trans
 -r--r--r--  1 root root 4096 May 14 16:06 trans_table
 --------------------------------------------------------------------------------
 
+-  average_freq
+Shows the average frequency the processor stayed in since the file was read
+the last time. Zero is shown if it is read the first time or "not supported".
+
+CONFIG_X86_AVERAGE_FREQUENCY=y config needs to be set and the processor must
+support overclocking of single cores (ida flag in /proc/cpuinfo).
+This is the only way to detect, monitor and optimze for the feature that the
+BIOS can overclock single CPU cores behind the kernel's back if thermal
+requirements are met (e.g. other cores of the socket run at low frequency or
+sleep).
+
+Also on multi-core processors the shown current CPU frequency the machine is
+running on in cpufreq/cpufreq_scaling_cur and /proc/cpuinfo can be wrong with
+current kernels if the frequency of several cores must be the same because of
+HW restritions. average_freq should show the real frequency.
+
 -  time_in_state
 This gives the amount of time spent in each of the frequencies supported by
 this CPU. The cat output will have "<frequency> <time>" pair in each line, which
-- 
1.6.0.2