Documentation/cpu-freq/intel-pstate.txt

   1 Intel P-state driver
   2 --------------------
   3
   4 This driver implements a scaling driver with an internal governor for
   5 Intel Core processors.  The driver follows the same model as the
   6 Transmeta scaling driver (longrun.c) and implements the setpolicy()
   7 instead of target().  Scaling drivers that implement setpolicy() are
   8 assumed to implement internal governors by the cpufreq core. All the
   9 logic for selecting the current P state is contained within the
  10 driver; no external governor is used by the cpufreq core.
  11
  12 Intel SandyBridge+ processors are supported.
  13
  14 New sysfs files for controlling P state selection have been added to
  15 /sys/devices/system/cpu/intel_pstate/
  16
  17       max_perf_pct: limits the maximum P state that will be requested by
  18       the driver stated as a percentage of the available performance.
  19
  20       min_perf_pct: limits the minimum P state that will be  requested by
  21       the driver stated as a percentage of the available performance.
  22
  23       no_turbo: limits the driver to selecting P states below the turbo
  24       frequency range.
  25
  26 For contemporary Intel processors, the frequency is controlled by the
  27 processor itself and the P-states exposed to software are related to
  28 performance levels.  The idea that frequency can be set to a single
  29 frequency is fiction for Intel Core processors. Even if the scaling
  30 driver selects a single P state the actual frequency the processor
  31 will run at is selected by the processor itself.
  32
  33 New debugfs files have also been added to /sys/kernel/debug/pstate_snb/
  34
  35       deadband
  36       d_gain_pct
  37       i_gain_pct
  38       p_gain_pct
  39       sample_rate_ms
  40       setpoint