| 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. The |
| available (P states) performance may be reduced by the no_turbo |
| setting described below. |
| |
| min_perf_pct: limits the minimum P state that will be requested by |
| the driver stated as a percentage of the max (non-turbo) |
| performance level. |
| |
| 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 |
