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-rw-r--r--Documentation/cpu-freq/intel-pstate.txt15
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/cpu-freq/intel-pstate.txt b/Documentation/cpu-freq/intel-pstate.txt
index 1953994ef5e6..3fdcdfd968ba 100644
--- a/Documentation/cpu-freq/intel-pstate.txt
+++ b/Documentation/cpu-freq/intel-pstate.txt
@@ -85,6 +85,21 @@ Sysfs will show :
Refer to "Intel® 64 and IA-32 Architectures Software Developer’s Manual
Volume 3: System Programming Guide" to understand ratios.
+There is one more sysfs attribute in /sys/devices/system/cpu/intel_pstate/
+that can be used for controlling the operation mode of the driver:
+
+ status: Three settings are possible:
+ "off" - The driver is not in use at this time.
+ "active" - The driver works as a P-state governor (default).
+ "passive" - The driver works as a regular cpufreq one and collaborates
+ with the generic cpufreq governors (it sets P-states as
+ requested by those governors).
+ The current setting is returned by reads from this attribute. Writing one
+ of the above strings to it changes the operation mode as indicated by that
+ string, if possible. If HW-managed P-states (HWP) are enabled, it is not
+ possible to change the driver's operation mode and attempts to write to
+ this attribute will fail.
+
cpufreq sysfs for Intel P-State
Since this driver registers with cpufreq, cpufreq sysfs is also presented.