Diffstat (limited to 'Documentation')
3 files changed, 32 insertions, 3 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index a703b9e9aeb9..974e29f5da86 100644
@@ -136,6 +136,24 @@ Description: Discover cpuidle policy and mechanism
See files in Documentation/cpuidle/ for more information.
+Date: pre-git history
+Description: Discover and change clock speed of CPUs
+ Clock scaling allows you to change the clock speed of the
+ CPUs on the fly. This is a nice method to save battery
+ power, because the lower the clock speed, the less power
+ the CPU consumes.
+ There are many knobs to tweak in this directory.
+ See files in Documentation/cpu-freq/ for more information.
+ In particular, read Documentation/cpu-freq/user-guide.txt
+ to learn how to control the knobs.
Date: August 2008
diff --git a/Documentation/cpu-freq/cpu-drivers.txt b/Documentation/cpu-freq/cpu-drivers.txt
index 75a58d14d3cf..6c30e930c122 100644
@@ -92,9 +92,9 @@ policy->cpuinfo.max_freq - the minimum and maximum frequency
(in kHz) which is supported by
policy->cpuinfo.transition_latency the time it takes on this CPU to
- switch between two frequencies (if
- appropriate, else specify
+ switch between two frequencies in
+ nanoseconds (if appropriate, else
+ specify CPUFREQ_ETERNAL)
policy->cur The current operating frequency of
this CPU (if appropriate)
diff --git a/Documentation/cpu-freq/user-guide.txt b/Documentation/cpu-freq/user-guide.txt
index 2a5b850847c0..04f6b32993e6 100644
@@ -203,6 +203,17 @@ scaling_cur_freq : Current frequency of the CPU as determined by
the frequency the kernel thinks the CPU runs
+bios_limit : If the BIOS tells the OS to limit a CPU to
+ lower frequencies, the user can read out the
+ maximum available frequency from this file.
+ This typically can happen through (often not
+ intended) BIOS settings, restrictions
+ triggered through a service processor or other
+ BIOS/HW based implementations.
+ This does not cover thermal ACPI limitations
+ which can be detected through the generic
+ thermal driver.
If you have selected the "userspace" governor which allows you to
set the CPU operating frequency to a specific value, you can read out
the current frequency in