summaryrefslogtreecommitdiffstats
path: root/Documentation/cpu-freq/intel-pstate.txt
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/cpu-freq/intel-pstate.txt')
-rw-r--r--Documentation/cpu-freq/intel-pstate.txt40
1 files changed, 40 insertions, 0 deletions
diff --git a/Documentation/cpu-freq/intel-pstate.txt b/Documentation/cpu-freq/intel-pstate.txt
new file mode 100644
index 000000000000..e742d21dbd96
--- /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