mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-28 11:18:45 +07:00
a3ea0153ec
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>
41 lines
1.6 KiB
Plaintext
41 lines
1.6 KiB
Plaintext
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
|