Update Linux to v5.4.2
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+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+======================================
+Intel Performance and Energy Bias Hint
+======================================
+
+:Copyright: |copy| 2019 Intel Corporation
+
+:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
+
+
+.. kernel-doc:: arch/x86/kernel/cpu/intel_epb.c
+ :doc: overview
+
+Intel Performance and Energy Bias Attribute in ``sysfs``
+========================================================
+
+The Intel Performance and Energy Bias Hint (EPB) value for a given (logical) CPU
+can be checked or updated through a ``sysfs`` attribute (file) under
+:file:`/sys/devices/system/cpu/cpu<N>/power/`, where the CPU number ``<N>``
+is allocated at the system initialization time:
+
+``energy_perf_bias``
+ Shows the current EPB value for the CPU in a sliding scale 0 - 15, where
+ a value of 0 corresponds to a hint preference for highest performance
+ and a value of 15 corresponds to the maximum energy savings.
+
+ In order to update the EPB value for the CPU, this attribute can be
+ written to, either with a number in the 0 - 15 sliding scale above, or
+ with one of the strings: "performance", "balance-performance", "normal",
+ "balance-power", "power" that represent values reflected by their
+ meaning.
+
+ This attribute is present for all online CPUs supporting the EPB
+ feature.
+
+Note that while the EPB interface to the processor is defined at the logical CPU
+level, the physical register backing it may be shared by multiple CPUs (for
+example, SMT siblings or cores in one package). For this reason, updating the
+EPB value for one CPU may cause the EPB values for other CPUs to change.