Lines Matching +full:idle +full:- +full:state
1 .. SPDX-License-Identifier: GPL-2.0
5 CPU Idle Time Management
13 CPU Idle Time Management Subsystem
18 cores) is idle after an interrupt or equivalent wakeup event, which means that
19 there are no tasks to run on it except for the special "idle" task associated
21 belongs to. That can be done by making the idle logical CPU stop fetching
23 depended on by it into an idle state in which they will draw less power.
25 However, there may be multiple different idle states that can be used in such a
28 particular idle state. That is the role of the CPU idle time management
35 units: *governors* responsible for selecting idle states to ask the processor
40 CPU Idle Time Governors
43 A CPU idle time (``CPUIdle``) governor is a bundle of policy code invoked when
44 one of the logical CPUs in the system turns out to be idle. Its role is to
45 select an idle state to ask the processor to enter in order to save some energy.
85 struct cpuidle_state objects representing idle states that the
89 code, and that causes the kernel to run the architecture-specific
90 default code for idle CPUs on the CPU in question instead of ``CPUIdle``
91 until the ``->enable()`` governor callback is invoked for that CPU
103 It is expected to reverse any changes made by the ``->enable()``
113 Called to select an idle state for the processor holding the (logical)
117 The list of idle states to take into consideration is represented by the
126 idle state. When the ``bool`` variable pointed to by it (which is set
128 processor will be asked to enter the selected idle state without
131 asking the processor to enter the idle state).
142 Called to allow the governor to evaluate the accuracy of the idle state
143 selection made by the ``->select()`` callback (when it was invoked last
145 idle state selections in the future.
149 account when selecting idle states. In order to obtain the current effective
152 :c:func:`cpuidle_governor_latency_req()`. Then, the governor's ``->select()``
153 callback must not return the index of an indle state whose
158 CPU Idle Time Management Drivers
161 CPU idle time management (``CPUIdle``) drivers provide an interface between the
167 idle states that the processor hardware can be asked to enter shared by all of
172 the ascending order (that is, index 0 should correspond to the idle state with
175 idle state represented by the struct cpuidle_state object holding it, this
176 sorting order should be the same as the ascending sorting order by the idle
177 state "depth".]
180 governors for computations related to idle state selection:
183 Minimum time to spend in this idle state including the time needed to
185 be saved by staying in a shallower idle state for the same amount of
189 Maximum time it will take a CPU asking the processor to enter this idle
190 state to start executing the first instruction after a wakeup from it,
194 Flags representing idle state properties. Currently, governors only use
196 does not represent a real idle state, but an interface to a software
198 any idle state at all. [There are other flags used by the ``CPUIdle``
203 enter this particular idle state:
214 :c:member:`states` array representing the idle state to ask the processor to
217 The analogous ``->enter_s2idle()`` callback in struct cpuidle_state is used
218 only for implementing the suspend-to-idle system-wide power management feature.
219 The difference between in and ``->enter()`` is that it must not re-enable
221 clock event devices, which the ``->enter()`` callback may do sometimes.
226 entries in the :c:member:`states` array represent "coupled" idle states (that
227 is, idle states that can only be asked for if multiple related logical CPUs are
228 idle), the :c:member:`safe_state_index` field in struct cpuidle_driver needs
229 to be the index of an idle state that is not "coupled" (that is, one that can be
230 asked for if only one logical CPU is idle).
238 are no "coupled" idle state entries in the driver's :c:member:`states` array,
254 ``sysfs`` interface to be created and the governor's ``->enable()`` callback to
270 lead to modifications of the list of available processor idle states (which can