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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-01-14 23:12:08 +0100
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-01-14 23:12:08 +0100
commit51c4c4ce1df49b14bbfc334c6388cc9efe32c631 (patch)
treeb33a9a905b9b646c78be7df7c189e7f9c0f28f77 /Documentation
parent6cbd7ee10e2842a3d1f9b60abede1c8f3d1f1130 (diff)
parent22c73795b101597051924556dce019385a1e2fa0 (diff)
downloadop-kernel-dev-51c4c4ce1df49b14bbfc334c6388cc9efe32c631.zip
op-kernel-dev-51c4c4ce1df49b14bbfc334c6388cc9efe32c631.tar.gz
Merge back earlier 'pm-cpufreq' material.
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/ABI/testing/sysfs-devices-system-cpu24
-rw-r--r--Documentation/cpu-freq/intel-pstate.txt40
2 files changed, 64 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 468e4d4..d5a0d33 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -200,3 +200,27 @@ Description: address and size of the percpu note.
note of cpu#.
crash_notes_size: size of the note of cpu#.
+
+
+What: /sys/devices/system/cpu/intel_pstate/max_perf_pct
+ /sys/devices/system/cpu/intel_pstate/min_perf_pct
+ /sys/devices/system/cpu/intel_pstate/no_turbo
+Date: February 2013
+Contact: linux-pm@vger.kernel.org
+Description: Parameters for the Intel P-state driver
+
+ Logic for selecting the current P-state in Intel
+ Sandybridge+ processors. The three knobs control
+ limits for the P-state that will be requested by the
+ driver.
+
+ max_perf_pct: limits the maximum P state that will be requested by
+ the driver stated as a percentage of the available performance.
+
+ min_perf_pct: limits the minimum P state that will be requested by
+ the driver stated as a percentage of the available performance.
+
+ no_turbo: limits the driver to selecting P states below the turbo
+ frequency range.
+
+ More details can be found in Documentation/cpu-freq/intel-pstate.txt
diff --git a/Documentation/cpu-freq/intel-pstate.txt b/Documentation/cpu-freq/intel-pstate.txt
new file mode 100644
index 0000000..e742d21
--- /dev/null
+++ b/Documentation/cpu-freq/intel-pstate.txt
@@ -0,0 +1,40 @@
+Intel P-state driver
+--------------------
+
+This driver implements a scaling driver with an internal governor for
+Intel Core processors. The driver follows the same model as the
+Transmeta scaling driver (longrun.c) and implements the setpolicy()
+instead of target(). Scaling drivers that implement setpolicy() are
+assumed to implement internal governors by the cpufreq core. All the
+logic for selecting the current P state is contained within the
+driver; no external governor is used by the cpufreq core.
+
+Intel SandyBridge+ processors are supported.
+
+New sysfs files for controlling P state selection have been added to
+/sys/devices/system/cpu/intel_pstate/
+
+ max_perf_pct: limits the maximum P state that will be requested by
+ the driver stated as a percentage of the available performance.
+
+ min_perf_pct: limits the minimum P state that will be requested by
+ the driver stated as a percentage of the available performance.
+
+ no_turbo: limits the driver to selecting P states below the turbo
+ frequency range.
+
+For contemporary Intel processors, the frequency is controlled by the
+processor itself and the P-states exposed to software are related to
+performance levels. The idea that frequency can be set to a single
+frequency is fiction for Intel Core processors. Even if the scaling
+driver selects a single P state the actual frequency the processor
+will run at is selected by the processor itself.
+
+New debugfs files have also been added to /sys/kernel/debug/pstate_snb/
+
+ deadband
+ d_gain_pct
+ i_gain_pct
+ p_gain_pct
+ sample_rate_ms
+ setpoint
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