diff options
author | Ramkumar Ramachandra <artagnon@gmail.com> | 2014-01-05 05:21:14 -0500 |
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committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2014-01-05 19:14:25 -0500 |
commit | a3ea0153eca2a9de88fec1141426b589e8c8a2a1 (patch) | |
tree | 2627fa63428d4ca4d3c694e9eca4473e1e3c9f1c /Documentation/cpu-freq | |
parent | 72e2adcdcb0fa389ee78558b612c73f49641ed40 (diff) |
Documentation / cpufreq: add intel-pstate.txt
The Intel P-state driver is currently undocumented. Add some
documentation based on the cover-letter sent with the original series.
Cc: Dirk Brandewie <dirk.brandewie@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/cpu-freq')
-rw-r--r-- | Documentation/cpu-freq/intel-pstate.txt | 40 |
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 @@ | |||
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 | ||