Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin-guide/pm/intel_pstate.rst
index 8f1d3de..67e414e 100644
--- a/Documentation/admin-guide/pm/intel_pstate.rst
+++ b/Documentation/admin-guide/pm/intel_pstate.rst
@@ -1,10 +1,13 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
===============================================
``intel_pstate`` CPU Performance Scaling Driver
===============================================
-::
+:Copyright: |copy| 2017 Intel Corporation
- Copyright (c) 2017 Intel Corp., Rafael J. Wysocki <rafael.j.wysocki@intel.com>
+:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
General Information
@@ -20,11 +23,10 @@
For the processors supported by ``intel_pstate``, the P-state concept is broader
than just an operating frequency or an operating performance point (see the
-`LinuxCon Europe 2015 presentation by Kristen Accardi <LCEU2015_>`_ for more
+LinuxCon Europe 2015 presentation by Kristen Accardi [1]_ for more
information about that). For this reason, the representation of P-states used
by ``intel_pstate`` internally follows the hardware specification (for details
-refer to `Intel® 64 and IA-32 Architectures Software Developer’s Manual
-Volume 3: System Programming Guide <SDM_>`_). However, the ``CPUFreq`` core
+refer to Intel Software Developer’s Manual [2]_). However, the ``CPUFreq`` core
uses frequencies for identifying operating performance points of CPUs and
frequencies are involved in the user space interface exposed by it, so
``intel_pstate`` maps its internal representation of P-states to frequencies too
@@ -465,6 +467,13 @@
policy for the time interval between the last two invocations of the
driver's utilization update callback by the CPU scheduler for that CPU.
+One more policy attribute is present if the `HWP feature is enabled in the
+processor <Active Mode With HWP_>`_:
+
+``base_frequency``
+ Shows the base frequency of the CPU. Any frequency above this will be
+ in the turbo frequency range.
+
The meaning of these attributes in the `passive mode <Passive Mode_>`_ is the
same as for other scaling drivers.
@@ -488,7 +497,15 @@
2. Each individual CPU is affected by its own per-policy limits (that is, it
cannot be requested to run faster than its own per-policy maximum and it
- cannot be requested to run slower than its own per-policy minimum).
+ cannot be requested to run slower than its own per-policy minimum). The
+ effective performance depends on whether the platform supports per core
+ P-states, hyper-threading is enabled and on current performance requests
+ from other CPUs. When platform doesn't support per core P-states, the
+ effective performance can be more than the policy limits set on a CPU, if
+ other CPUs are requesting higher performance at that moment. Even with per
+ core P-states support, when hyper-threading is enabled, if the sibling CPU
+ is requesting higher performance, the other siblings will get higher
+ performance than their policy limits.
3. The global and per-policy limits can be set independently.
@@ -546,9 +563,9 @@
On the majority of systems supported by ``intel_pstate``, the ACPI tables
provided by the platform firmware contain ``_PSS`` objects returning information
-that can be used for CPU performance scaling (refer to the `ACPI specification`_
-for details on the ``_PSS`` objects and the format of the information returned
-by them).
+that can be used for CPU performance scaling (refer to the ACPI specification
+[3]_ for details on the ``_PSS`` objects and the format of the information
+returned by them).
The information returned by the ACPI ``_PSS`` objects is used by the
``acpi-cpufreq`` scaling driver. On systems supported by ``intel_pstate``
@@ -713,6 +730,14 @@
<idle>-0 [000] ..s. 2537.654843: intel_pstate_set_pstate <-intel_pstate_timer_func
-.. _LCEU2015: http://events.linuxfoundation.org/sites/events/files/slides/LinuxConEurope_2015.pdf
-.. _SDM: http://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-system-programming-manual-325384.html
-.. _ACPI specification: http://www.uefi.org/sites/default/files/resources/ACPI_6_1.pdf
+References
+==========
+
+.. [1] Kristen Accardi, *Balancing Power and Performance in the Linux Kernel*,
+ http://events.linuxfoundation.org/sites/events/files/slides/LinuxConEurope_2015.pdf
+
+.. [2] *Intel® 64 and IA-32 Architectures Software Developer’s Manual Volume 3: System Programming Guide*,
+ http://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-system-programming-manual-325384.html
+
+.. [3] *Advanced Configuration and Power Interface Specification*,
+ https://uefi.org/sites/default/files/resources/ACPI_6_3_final_Jan30.pdf