3  * Timer events oriented CPU idle governor
15  * wakeups from idle states.  Moreover, information about what happened in the
17  * idle state with target residency within the (known) time till the closest
19  * the upcoming CPU idle period and, if not, then which of the shallower idle
23  * which can be covered by taking a few most recent idle time intervals of the
25  * consider idle duration values greater than the sleep length, because the
29  * Thus this governor estimates whether or not the prospective idle duration of
31  * an idle state for it accordingly.
35  * idle states provided by the %CPUIdle driver in the ascending order.  That is,
37  * the second idle state (idle state 1), the second bin spans from the target
38  * residency of idle state 1 up to, but not including, the target residency of
39  * idle state 2, the third bin spans from the target residency of idle state 2
40  * up to, but not including, the target residency of idle state 3 and so on.
41  * The last bin spans from the target residency of the deepest idle state
45  * They are updated every time before selecting an idle state for the given CPU
49  * sleep length and the idle duration measured after CPU wakeup fall into the
52  * situations in which the measured idle duration is so much shorter than the
53  * sleep length that the bin it falls into corresponds to an idle state
57  * In order to select an idle state for a CPU, the governor takes the following
61  * 1. Find the deepest CPU idle state whose target residency does not exceed
62  *    the current sleep length (the candidate idle state) and compute 2 sums as
66  *      and all of the deeper idle states (it represents the cases in which the
67  *      CPU was idle long enough to avoid being intercepted if the sleep length
70  *    - The sum of the "intercepts" metrics for all of the idle states shallower
72  *      idle long enough to avoid being intercepted if the sleep length had been
76  *    up early, so look for an alternative idle state to select.
78  *    - Traverse the idle states shallower than the candidate one in the
82  *      of the idle states between it and the candidate one (including the
89  *      not exceeded the idle duration in over a half of the relevant cases),
90  *      select the given idle state instead of the candidate one.
122  * @time_span_ns: Time between idle state selection and post-wakeup update.
124  * @state_bins: Idle state data bins for this CPU.
153 		 * enough to the closest timer event expected at the idle state  in teo_update()
162 		 * (saved) time till the next timer event and the measured idle  in teo_update()
184 	 * find the bins that the sleep length and the measured idle duration  in teo_update()
225 	 * If the measured idle duration falls into the same bin as the sleep  in teo_update()
228 	 * the measured idle duration.  in teo_update()
246  * teo_find_shallower_state - Find shallower idle state matching given duration.
249  * @state_idx: Index of the capping idle state.
250  * @duration_ns: Idle duration value to match.
272  * teo_select - Selects the next idle state to enter.
321 		 * Update the sums of idle state mertics for all of the states  in teo_select()
351 		 * Only one idle state is enabled, so use it, but do not  in teo_select()
362 	 * If the sum of the intercepts metric for all of the idle states  in teo_select()
365 	 * all of the deeper states a shallower idle state is likely to be a  in teo_select()
373 		 * Look for the deepest idle state whose target residency had  in teo_select()
374 		 * not exceeded the idle duration in over a half of the relevant  in teo_select()
432 	 * idle state shallower than the current candidate one.  in teo_select()
478 	 * one or the expected idle duration is shorter than the tick period  in teo_select()
511 	 * nets, assume that the CPU might have been idle for the entire sleep  in teo_reflect()