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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2020-06-01 15:19:39 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2020-06-01 15:19:39 +0200
commitac7ccfc75faf2d82fe3176a100ed032621335b62 (patch)
treed33e01819b18a9c393a031fb487ad97aa86d45b2 /Documentation/admin-guide/pm
parentf1ecbf79554d30baef4bef770b9500a1b7c51b82 (diff)
parent552abb884e97d26589964e5a8c7e736f852f95f0 (diff)
Merge branch 'pm-cpufreq'
* pm-cpufreq: cpufreq: Fix up cpufreq_boost_set_sw() cpufreq: fix minor typo in struct cpufreq_driver doc comment cpufreq: qoriq: Add platform dependencies clk: qoriq: add cpufreq platform device cpufreq: qoriq: convert to a platform driver cpufreq: qcom: fix wrong compatible binding cpufreq: imx-cpufreq-dt: support i.MX7ULP cpufreq: dt: Add support for r8a7742 cpufreq: Add i.MX7ULP to cpufreq-dt-platdev blacklist cpufreq: omap: Build driver by default for ARCH_OMAP2PLUS cpufreq: intel_pstate: Use passive mode by default without HWP
Diffstat (limited to 'Documentation/admin-guide/pm')
-rw-r--r--Documentation/admin-guide/pm/intel_pstate.rst32
1 files changed, 19 insertions, 13 deletions
diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin-guide/pm/intel_pstate.rst
index ad392f3aee06..39d80bc29ccd 100644
--- a/Documentation/admin-guide/pm/intel_pstate.rst
+++ b/Documentation/admin-guide/pm/intel_pstate.rst
@@ -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".