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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-09-08 01:01:14 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-09-08 01:01:14 -0300
commite5fd91f1ef340da553f7a79da9540c3db711c937 (patch)
treeb11842027dc6641da63f4bcc524f8678263304a3 /Documentation/cpu-freq/intel-pstate.txt
parent2a9b0348e685a63d97486f6749622b61e9e3292f (diff)
Linux-libre 4.2-gnu
Diffstat (limited to 'Documentation/cpu-freq/intel-pstate.txt')
-rw-r--r--Documentation/cpu-freq/intel-pstate.txt21
1 files changed, 11 insertions, 10 deletions
diff --git a/Documentation/cpu-freq/intel-pstate.txt b/Documentation/cpu-freq/intel-pstate.txt
index 655750743..be8d4006b 100644
--- a/Documentation/cpu-freq/intel-pstate.txt
+++ b/Documentation/cpu-freq/intel-pstate.txt
@@ -3,24 +3,25 @@ Intel P-state driver
This driver provides an interface to control the P state selection for
SandyBridge+ Intel processors. The driver can operate two different
-modes based on the processor model legacy and Hardware P state (HWP)
+modes based on the processor model, legacy mode and Hardware P state (HWP)
mode.
-In legacy mode the 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.
+In legacy mode, the Intel P-state implements two internal governors,
+performance and powersave, that differ from the general cpufreq governors of
+the same name (the general cpufreq governors implement target(), whereas the
+internal Intel P-state governors implement setpolicy()). The internal
+performance governor sets the max_perf_pct and min_perf_pct to 100; that is,
+the governor selects the highest available P state to maximize the performance
+of the core. The internal powersave governor selects the appropriate P state
+based on the current load on the CPU.
In HWP mode P state selection is implemented in the processor
itself. The driver provides the interfaces between the cpufreq core and
the processor to control P state selection based on user preferences
and reporting frequency to the cpufreq core. In this mode the
-internal governor code is disabled.
+internal Intel P-state governor code is disabled.
-In addtion to the interfaces provided by the cpufreq core for
+In addition to the interfaces provided by the cpufreq core for
controlling frequency the driver provides sysfs files for
controlling P state selection. These files have been added to
/sys/devices/system/cpu/intel_pstate/