Merge back cpufreq material for v5.8.

Documentation/admin-guide/pm/intel_pstate.rst

···
 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
···
 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
···
 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

···
 		pr_info("Invalid MSRs\n");
 		return -ENODEV;
 	}
+	/* Without HWP start in the passive mode. */
+	default_driver = &intel_cpufreq;
 
 hwp_cpu_matched:
 	/*
···
 	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;
 	}