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authorLinus Torvalds <torvalds@linux-foundation.org>2025-03-25 15:00:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2025-03-25 15:00:18 -0700
commit7d20aa5c32ac8bd272b5470ddbd7ac6e0cb35714 (patch)
tree3efb2907bedf17f931b204adbe0cf466315a4124 /Documentation/admin-guide/pm
parent21e0ff5b10ec1b61fda435d42db4ba80d0cdfded (diff)
parentc5a55e427c947f013f08cbbf2be23bd4df2c9590 (diff)
Merge tag 'pm-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull power management updates from Rafael Wysocki: "These are dominated by cpufreq updates which in turn are dominated by updates related to boost support in the core and drivers and amd-pstate driver optimizations. Apart from the above, there are some cpuidle updates including a rework of the most recent idle intervals handling in the venerable menu governor that leads to significant improvements in some performance benchmarks, as the governor is now more likely to predict a shorter idle duration in some cases, and there are updates of the core device power management code, mostly related to system suspend and resume, that should help to avoid potential issues arising when the drivers of devices depending on one another want to use different optimizations. There is also a usual collection of assorted fixes and cleanups, including removal of some unused code. Specifics: - Manage sysfs attributes and boost frequencies efficiently from cpufreq core to reduce boilerplate code in drivers (Viresh Kumar) - Minor cleanups to cpufreq drivers (Aaron Kling, Benjamin Schneider, Dhananjay Ugwekar, Imran Shaik, zuoqian) - Migrate some cpufreq drivers to using for_each_present_cpu() (Jacky Bai) - cpufreq-qcom-hw DT binding fixes (Krzysztof Kozlowski) - Use str_enable_disable() helper in cpufreq_online() (Lifeng Zheng) - Optimize the amd-pstate driver to avoid cases where call paths end up calling the same writes multiple times and needlessly caching variables through code reorganization, locking overhaul and tracing adjustments (Mario Limonciello, Dhananjay Ugwekar) - Make it possible to avoid enabling capacity-aware scheduling (CAS) in the intel_pstate driver and relocate a check for out-of-band (OOB) platform handling in it to make it detect OOB before checking HWP availability (Rafael Wysocki) - Fix dbs_update() to avoid inadvertent conversions of negative integer values to unsigned int which causes CPU frequency selection to be inaccurate in some cases when the "conservative" cpufreq governor is in use (Jie Zhan) - Update the handling of the most recent idle intervals in the menu cpuidle governor to prevent useful information from being discarded by it in some cases and improve the prediction accuracy (Rafael Wysocki) - Make it possible to tell the intel_idle driver to ignore its built-in table of idle states for the given processor, clean up the handling of auto-demotion disabling on Baytrail and Cherrytrail chips in it, and update its MAINTAINERS entry (David Arcari, Artem Bityutskiy, Rafael Wysocki) - Make some cpuidle drivers use for_each_present_cpu() instead of for_each_possible_cpu() during initialization to avoid issues occurring when nosmp or maxcpus=0 are used (Jacky Bai) - Clean up the Energy Model handling code somewhat (Rafael Wysocki) - Use kfree_rcu() to simplify the handling of runtime Energy Model updates (Li RongQing) - Add an entry for the Energy Model framework to MAINTAINERS as properly maintained (Lukasz Luba) - Address RCU-related sparse warnings in the Energy Model code (Rafael Wysocki) - Remove ENERGY_MODEL dependency on SMP and allow it to be selected when DEVFREQ is set without CPUFREQ so it can be used on a wider range of systems (Jeson Gao) - Unify error handling during runtime suspend and runtime resume in the core to help drivers to implement more consistent runtime PM error handling (Rafael Wysocki) - Drop a redundant check from pm_runtime_force_resume() and rearrange documentation related to __pm_runtime_disable() (Rafael Wysocki) - Rework the handling of the "smart suspend" driver flag in the PM core to avoid issues hat may occur when drivers using it depend on some other drivers and clean up the related PM core code (Rafael Wysocki, Colin Ian King) - Fix the handling of devices with the power.direct_complete flag set if device_suspend() returns an error for at least one device to avoid situations in which some of them may not be resumed (Rafael Wysocki) - Use mutex_trylock() in hibernate_compressor_param_set() to avoid a possible deadlock that may occur if the "compressor" hibernation module parameter is accessed during the registration of a new ieee80211 device (Lizhi Xu) - Suppress sleeping parent warning in device_pm_add() in the case when new children are added under a device with the power.direct_complete set after it has been processed by device_resume() (Xu Yang) - Remove needless return in three void functions related to system wakeup (Zijun Hu) - Replace deprecated kmap_atomic() with kmap_local_page() in the hibernation core code (David Reaver) - Remove unused helper functions related to system sleep (David Alan Gilbert) - Clean up s2idle_enter() so it does not lock and unlock CPU offline in vain and update comments in it (Ulf Hansson) - Clean up broken white space in dpm_wait_for_children() (Geert Uytterhoeven) - Update the cpupower utility to fix lib version-ing in it and memory leaks in error legs, remove hard-coded values, and implement CPU physical core querying (Thomas Renninger, John B. Wyatt IV, Shuah Khan, Yiwei Lin, Zhongqiu Han)" * tag 'pm-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (139 commits) PM: sleep: Fix bit masking operation dt-bindings: cpufreq: cpufreq-qcom-hw: Narrow properties on SDX75, SA8775p and SM8650 dt-bindings: cpufreq: cpufreq-qcom-hw: Drop redundant minItems:1 dt-bindings: cpufreq: cpufreq-qcom-hw: Add missing constraint for interrupt-names dt-bindings: cpufreq: cpufreq-qcom-hw: Add QCS8300 compatible cpufreq: Init cpufreq only for present CPUs PM: sleep: Fix handling devices with direct_complete set on errors cpuidle: Init cpuidle only for present CPUs PM: clk: Remove unused pm_clk_remove() PM: sleep: core: Fix indentation in dpm_wait_for_children() PM: s2idle: Extend comment in s2idle_enter() PM: s2idle: Drop redundant locks when entering s2idle PM: sleep: Remove unused pm_generic_ wrappers cpufreq: tegra186: Share policy per cluster cpupower: Make lib versioning scheme more obvious and fix version link PM: EM: Rework the depends on for CONFIG_ENERGY_MODEL PM: EM: Address RCU-related sparse warnings cpupower: Implement CPU physical core querying pm: cpupower: remove hard-coded topology depth values pm: cpupower: Fix cmd_monitor() error legs to free cpu_topology ...
Diffstat (limited to 'Documentation/admin-guide/pm')
-rw-r--r--Documentation/admin-guide/pm/cpuidle.rst29
-rw-r--r--Documentation/admin-guide/pm/intel_idle.rst18
-rw-r--r--Documentation/admin-guide/pm/intel_pstate.rst3
3 files changed, 33 insertions, 17 deletions
diff --git a/Documentation/admin-guide/pm/cpuidle.rst b/Documentation/admin-guide/pm/cpuidle.rst
index eb58d7a5affd..0c090b076224 100644
--- a/Documentation/admin-guide/pm/cpuidle.rst
+++ b/Documentation/admin-guide/pm/cpuidle.rst
@@ -275,20 +275,25 @@ values and, when predicting the idle duration next time, it computes the average
and variance of them. If the variance is small (smaller than 400 square
milliseconds) or it is small relative to the average (the average is greater
that 6 times the standard deviation), the average is regarded as the "typical
-interval" value. Otherwise, the longest of the saved observed idle duration
+interval" value. Otherwise, either the longest or the shortest (depending on
+which one is farther from the average) of the saved observed idle duration
values is discarded and the computation is repeated for the remaining ones.
+
Again, if the variance of them is small (in the above sense), the average is
taken as the "typical interval" value and so on, until either the "typical
-interval" is determined or too many data points are disregarded, in which case
-the "typical interval" is assumed to equal "infinity" (the maximum unsigned
-integer value).
-
-If the "typical interval" computed this way is long enough, the governor obtains
-the time until the closest timer event with the assumption that the scheduler
-tick will be stopped. That time, referred to as the *sleep length* in what follows,
-is the upper bound on the time before the next CPU wakeup. It is used to determine
-the sleep length range, which in turn is needed to get the sleep length correction
-factor.
+interval" is determined or too many data points are disregarded. In the latter
+case, if the size of the set of data points still under consideration is
+sufficiently large, the next idle duration is not likely to be above the largest
+idle duration value still in that set, so that value is taken as the predicted
+next idle duration. Finally, if the set of data points still under
+consideration is too small, no prediction is made.
+
+If the preliminary prediction of the next idle duration computed this way is
+long enough, the governor obtains the time until the closest timer event with
+the assumption that the scheduler tick will be stopped. That time, referred to
+as the *sleep length* in what follows, is the upper bound on the time before the
+next CPU wakeup. It is used to determine the sleep length range, which in turn
+is needed to get the sleep length correction factor.
The ``menu`` governor maintains an array containing several correction factor
values that correspond to different sleep length ranges organized so that each
@@ -302,7 +307,7 @@ to 1 the correction factor becomes (it must fall between 0 and 1 inclusive).
The sleep length is multiplied by the correction factor for the range that it
falls into to obtain an approximation of the predicted idle duration that is
compared to the "typical interval" determined previously and the minimum of
-the two is taken as the idle duration prediction.
+the two is taken as the final idle duration prediction.
If the "typical interval" value is small, which means that the CPU is likely
to be woken up soon enough, the sleep length computation is skipped as it may
diff --git a/Documentation/admin-guide/pm/intel_idle.rst b/Documentation/admin-guide/pm/intel_idle.rst
index 39bd6ecce7de..5940528146eb 100644
--- a/Documentation/admin-guide/pm/intel_idle.rst
+++ b/Documentation/admin-guide/pm/intel_idle.rst
@@ -192,11 +192,19 @@ even if they have been enumerated (see :ref:`cpu-pm-qos` in
Documentation/admin-guide/pm/cpuidle.rst).
Setting ``max_cstate`` to 0 causes the ``intel_idle`` initialization to fail.
-The ``no_acpi`` and ``use_acpi`` module parameters (recognized by ``intel_idle``
-if the kernel has been configured with ACPI support) can be set to make the
-driver ignore the system's ACPI tables entirely or use them for all of the
-recognized processor models, respectively (they both are unset by default and
-``use_acpi`` has no effect if ``no_acpi`` is set).
+The ``no_acpi``, ``use_acpi`` and ``no_native`` module parameters are
+recognized by ``intel_idle`` if the kernel has been configured with ACPI
+support. In the case that ACPI is not configured these flags have no impact
+on functionality.
+
+``no_acpi`` - Do not use ACPI at all. Only native mode is available, no
+ACPI mode.
+
+``use_acpi`` - No-op in ACPI mode, the driver will consult ACPI tables for
+C-states on/off status in native mode.
+
+``no_native`` - Work only in ACPI mode, no native mode available (ignore
+all custom tables).
The value of the ``states_off`` module parameter (0 by default) represents a
list of idle states to be disabled by default in the form of a bitmask.
diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin-guide/pm/intel_pstate.rst
index bf13ad25a32f..78fc83ed2a7e 100644
--- a/Documentation/admin-guide/pm/intel_pstate.rst
+++ b/Documentation/admin-guide/pm/intel_pstate.rst
@@ -696,6 +696,9 @@ of them have to be prepended with the ``intel_pstate=`` prefix.
Use per-logical-CPU P-State limits (see `Coordination of P-state
Limits`_ for details).
+``no_cas``
+ Do not enable capacity-aware scheduling (CAS) which is enabled by
+ default on hybrid systems.
Diagnostics and Tuning
======================