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| author | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2017-01-05 02:53:12 +0100 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2017-02-04 00:05:31 +0100 |
| commit | fb1fe1041c04ee5ba362cf239e83a7c559beb0f3 (patch) | |
| tree | 96b859d52c8d1a11d2a2b8a9d12b02fd2390d9a0 /Documentation/cpu-freq | |
| parent | 0c30b65b3c8e5b8c72f39497aa8c61a662b6bcc0 (diff) | |
| download | lwn-fb1fe1041c04ee5ba362cf239e83a7c559beb0f3.tar.gz lwn-fb1fe1041c04ee5ba362cf239e83a7c559beb0f3.zip | |
cpufreq: intel_pstate: Operation mode control from sysfs
Make it possible to change the operation mode of intel_pstate with
the help of a new sysfs attribute called "status".
There are three possible configurations that can be selected using
this attribute:
"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). [This is the same mode
the driver can be started in by passing intel_pstate=passive
in the kernel command line.]
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) feature is enabled, it is not possible
to change the driver's operation mode and attempts to write to this
attribute will fail.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/cpu-freq')
| -rw-r--r-- | Documentation/cpu-freq/intel-pstate.txt | 15 |
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. |