Commit 9795a0dd authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

Merge back cpufreq material for v5.8.

parents 8c539776 33aa46f2

Documentation/admin-guide/pm/intel_pstate.rst

+19 −13
Original line number Diff line number Diff line
@@ -62,9 +62,10 @@ on the capabilities of the processor. 
Active Mode

-----------



This is the default operation mode of ``intel_pstate``.  If it works in this

mode, the ``scaling_driver`` policy attribute in ``sysfs`` for all ``CPUFreq``

policies contains the string "intel_pstate".

This is the default operation mode of ``intel_pstate`` for processors with

hardware-managed P-states (HWP) support.  If it works in this mode, the

``scaling_driver`` policy attribute in ``sysfs`` for all ``CPUFreq`` policies

contains the string "intel_pstate".



In this mode the driver bypasses the scaling governors layer of ``CPUFreq`` and

provides its own scaling algorithms for P-state selection.  Those algorithms
@@ -138,12 +139,13 @@ internal P-state selection logic to be less performance-focused. 
Active Mode Without HWP

~~~~~~~~~~~~~~~~~~~~~~~



This is the default operation mode for processors that do not support the HWP

feature.  It also is used by default with the ``intel_pstate=no_hwp`` argument

in the kernel command line.  However, in this mode ``intel_pstate`` may refuse

to work with the given processor if it does not recognize it.  [Note that

``intel_pstate`` will never refuse to work with any processor with the HWP

feature enabled.]

This operation mode is optional for processors that do not support the HWP

feature or when the ``intel_pstate=no_hwp`` argument is passed to the kernel in

the command line.  The active mode is used in those cases if the

``intel_pstate=active`` argument is passed to the kernel in the command line.

In this mode ``intel_pstate`` may refuse to work with processors that are not

recognized by it.  [Note that ``intel_pstate`` will never refuse to work with

any processor with the HWP feature enabled.]



In this mode ``intel_pstate`` registers utilization update callbacks with the

CPU scheduler in order to run a P-state selection algorithm, either
@@ -188,10 +190,14 @@ is not set. 
Passive Mode

------------



This mode is used if the ``intel_pstate=passive`` argument is passed to the

kernel in the command line (it implies the ``intel_pstate=no_hwp`` setting too).

Like in the active mode without HWP support, in this mode ``intel_pstate`` may

refuse to work with the given processor if it does not recognize it.

This is the default operation mode of ``intel_pstate`` for processors without

hardware-managed P-states (HWP) support.  It is always used if the

``intel_pstate=passive`` argument is passed to the kernel in the command line

regardless of whether or not the given processor supports HWP.  [Note that the

``intel_pstate=no_hwp`` setting implies ``intel_pstate=passive`` if it is used

without ``intel_pstate=active``.]  Like in the active mode without HWP support,

in this mode ``intel_pstate`` may refuse to work with processors that are not

recognized by it.



If the driver works in this mode, the ``scaling_driver`` policy attribute in

``sysfs`` for all ``CPUFreq`` policies contains the string "intel_cpufreq".

drivers/cpufreq/intel_pstate.c

+2 −1
Original line number Diff line number Diff line
@@ -2771,6 +2771,8 @@ static int __init intel_pstate_init(void) 
		pr_info("Invalid MSRs\n");

		return -ENODEV;

	}

	/* Without HWP start in the passive mode. */

	default_driver = &intel_cpufreq;



hwp_cpu_matched:

	/*
@@ -2816,7 +2818,6 @@ static int __init intel_pstate_setup(char *str) 
	if (!strcmp(str, "disable")) {

		no_load = 1;

	} else if (!strcmp(str, "passive")) {

		pr_info("Passive mode enabled\n");

		default_driver = &intel_cpufreq;

		no_hwp = 1;

	}