diff options
Diffstat (limited to 'Documentation/cpu-freq/intel-pstate.txt')
| -rw-r--r-- | Documentation/cpu-freq/intel-pstate.txt | 21 |
1 files changed, 11 insertions, 10 deletions
diff --git a/Documentation/cpu-freq/intel-pstate.txt b/Documentation/cpu-freq/intel-pstate.txt index 655750743fb0..be8d4006bf76 100644 --- a/Documentation/cpu-freq/intel-pstate.txt +++ b/Documentation/cpu-freq/intel-pstate.txt | |||
| @@ -3,24 +3,25 @@ Intel P-state driver | |||
| 3 | 3 | ||
| 4 | This driver provides an interface to control the P state selection for | 4 | This driver provides an interface to control the P state selection for |
| 5 | SandyBridge+ Intel processors. The driver can operate two different | 5 | SandyBridge+ Intel processors. The driver can operate two different |
| 6 | modes based on the processor model legacy and Hardware P state (HWP) | 6 | modes based on the processor model, legacy mode and Hardware P state (HWP) |
| 7 | mode. | 7 | mode. |
| 8 | 8 | ||
| 9 | In legacy mode the driver implements a scaling driver with an internal | 9 | In legacy mode, the Intel P-state implements two internal governors, |
| 10 | governor for Intel Core processors. The driver follows the same model | 10 | performance and powersave, that differ from the general cpufreq governors of |
| 11 | as the Transmeta scaling driver (longrun.c) and implements the | 11 | the same name (the general cpufreq governors implement target(), whereas the |
| 12 | setpolicy() instead of target(). Scaling drivers that implement | 12 | internal Intel P-state governors implement setpolicy()). The internal |
| 13 | setpolicy() are assumed to implement internal governors by the cpufreq | 13 | performance governor sets the max_perf_pct and min_perf_pct to 100; that is, |
| 14 | core. All the logic for selecting the current P state is contained | 14 | the governor selects the highest available P state to maximize the performance |
| 15 | within the driver; no external governor is used by the cpufreq core. | 15 | of the core. The internal powersave governor selects the appropriate P state |
| 16 | based on the current load on the CPU. | ||
| 16 | 17 | ||
| 17 | In HWP mode P state selection is implemented in the processor | 18 | In HWP mode P state selection is implemented in the processor |
| 18 | itself. The driver provides the interfaces between the cpufreq core and | 19 | itself. The driver provides the interfaces between the cpufreq core and |
| 19 | the processor to control P state selection based on user preferences | 20 | the processor to control P state selection based on user preferences |
| 20 | and reporting frequency to the cpufreq core. In this mode the | 21 | and reporting frequency to the cpufreq core. In this mode the |
| 21 | internal governor code is disabled. | 22 | internal Intel P-state governor code is disabled. |
| 22 | 23 | ||
| 23 | In addtion to the interfaces provided by the cpufreq core for | 24 | In addition to the interfaces provided by the cpufreq core for |
| 24 | controlling frequency the driver provides sysfs files for | 25 | controlling frequency the driver provides sysfs files for |
| 25 | controlling P state selection. These files have been added to | 26 | controlling P state selection. These files have been added to |
| 26 | /sys/devices/system/cpu/intel_pstate/ | 27 | /sys/devices/system/cpu/intel_pstate/ |