On Sunday, January 05, 2014 03:51:14 PM 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.brande...@gmail.com> > Cc: Rafael J. Wysocki <r...@rjwysocki.net> > Cc: Randy Dunlap <rdun...@infradead.org> > Cc: Linux PM <linux...@vger.kernel.org> > Acked-by: Randy Dunlap <rdun...@infradead.org> > Signed-off-by: Ramkumar Ramachandra <artag...@gmail.com>
Queued up for 3.14, thanks! > --- > 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..e742d21 > --- /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 > +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. > + > + min_perf_pct: limits the minimum P state that will be requested by > + the driver stated as a percentage of the available performance. > + > + 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 > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
