Messages in this thread | | | Date | Fri, 03 Jan 2014 09:29:06 -0800 | From | Randy Dunlap <> | Subject | Re: [PATCH] Documentation/cpu-freq: add intel-pstate.txt |
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On 01/03/14 03:31, Ramkumar Ramachandra wrote: > 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> > Cc: Rafael J. Wysocki <rjw@rjwysocki.net> > Cc: Viresh Kumar <viresh.kumar@linaro.org> > Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com> > --- > > Documentation/cpu-freq/intel-pstate.txt | 40 +++++++++++++++++++++++++++++++++ > 1 file changed, 40 insertions(+) > create mode 100644 Documentation/cpu-freq/intel-pstate.txt > > diff --git a/Documentation/cpu-freq/intel-pstate.txt b/Documentation/cpu-freq/intel-pstate.txt > new file mode 100644 > index 0000000..fda74ab > --- /dev/null > +++ b/Documentation/cpu-freq/intel-pstate.txt > @@ -0,0 +1,40 @@ > +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 > +assmuned to implement internal governors by the cpufreq core. All the
assumed
> +logic for selecting the current P state is contained within the driver
driver;
> +no external governor is used by the cpufreq core. > + > +Only 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 avail performance.
available
> + > + min_perf_pct: limits the minimum P state that will be requested by > + the driver stated as a percentage of the avail performance.
available
> + > + no_turbo: limits the driver to selecting P states below the turbo > + frequency range. > + > +The units for these for these files are purposely abstract and stated
drop duplicate "for these"
> +in terms of available performance and not frequency. In idea that
The idea
> +frequency can be set to a single frequency is a fiction for Intel Core
is fiction
> +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 >
-- ~Randy
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