Lines Matching +full:entry +full:- +full:latency
1 # SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
3 ---
4 $id: http://devicetree.org/schemas/cpu/idle-states.yaml#
5 $schema: http://devicetree.org/meta-schemas/core.yaml#
10 - Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
11 - Anup Patel <anup@brainfault.org>
15 1 - Introduction
18 ARM and RISC-V systems contain HW capable of managing power consumption
19 dynamically, where cores can be put in different low-power states (ranging
22 run-time, can be specified through device tree bindings representing the
26 2 - ARM idle states
32 - Running
33 - Idle_standby
34 - Idle_retention
35 - Sleep
36 - Off
42 wake-up capabilities, hence it is not considered in this document).
44 Idle state parameters (e.g. entry latency) are platform specific and need to
52 3 - RISC-V idle states
55 On RISC-V systems, the HARTs (or CPUs) [6] can be put in platform specific
57 RISC-V SBI v0.3 (or higher) [7] hart state management extension provides a
61 retentive or non-rententive in nature. A retentive suspend state will
63 a non-retentive suspend state will not preserve HART registers and CSR
67 4 - idle-states definitions
72 triggered upon idle states entry and exit.
77 ..__[EXEC]__|__[PREP]__|__[ENTRY]__|__[IDLE]__|__[EXIT]__|__[EXEC]__..
80 |<------ entry ------->|
81 | latency |
82 |<- exit ->|
83 | latency |
84 |<-------- min-residency -------->|
85 |<------- wakeup-latency ------->|
92 like cache flushing. This is abortable on pending wake-up
93 event conditions. The abort latency is assumed to be negligible
94 (i.e. less than the ENTRY + EXIT duration). If aborted, CPU
96 this should be included in the ENTRY phase instead.
98 ENTRY: The hardware is committed to idle mode. This period must run
101 IDLE: This is the actual energy-saving idle period. This may last
102 between 0 and infinite time, until a wake-up event occurs.
107 entry-latency: Worst case latency required to enter the idle state. The
108 exit-latency may be guaranteed only after entry-latency has passed.
110 min-residency: Minimum period, including preparation and entry, for a given
113 wakeup-latency: Maximum delay between the signaling of a wake-up event and the
115 to be entry-latency + exit-latency.
119 An idle CPU requires the expected min-residency time to select the most
121 (i.e. wake-up) that causes the CPU to return to the EXEC phase.
123 An operating system scheduler may need to compute the shortest wake-up delay
127 wakeup-delay = exit-latency + max(entry-latency - (now - entry-timestamp), 0)
130 (e.g. waking-up) the CPU with the shortest wake-up delay.
131 The wake-up delay must take into account the entry latency if that period
137 An OS has to reliably probe the wakeup-latency since some devices can enforce
138 latency constraint guarantees to work properly, so the OS has to detect the
139 worst case wake-up latency it can incur if a CPU is allowed to enter an
143 The min-residency time parameter deserves further explanation since it is
153 n | /---
154 e | /------
155 r | /------
156 g | /-----
157 y | /------
158 | ----
166 -----|-------+----------------------------------
171 The graph is split in two parts delimited by time 1ms on the X-axis.
172 The graph curve with X-axis values = { x | 0 < x < 1ms } has a steep slope
175 The graph curve in the area delimited by X-axis values = {x | x > 1ms } has
179 min-residency is defined for a given idle state as the minimum expected
180 residency time for a state (inclusive of preparation and entry) after
191 | /-- IDLE1
192 e | /---
193 n | /----
194 e | /---
195 r | /-----/--------- IDLE2
196 g | /-------/---------
197 y | ------------ /---|
198 | / /---- |
199 | / /--- |
200 | / /---- |
201 | / /--- |
202 | --- |
206 ---/----------------------------+------------------------
207 |IDLE1-energy < IDLE2-energy | IDLE2-energy < IDLE1-energy
209 IDLE2-min-residency
211 Graph 2: idle states min-residency example
213 In graph 2 above, that takes into account idle states entry/exit energy
215 wake-up IRQ) is less than IDLE2-min-residency, IDLE1 is the better idle state
218 This is mainly down to the fact that IDLE1 entry/exit energy costs are lower
227 IDLE2-min-residency and corresponds to the time when energy consumption of
234 5 - idle-states node
237 The processor idle states are defined within the idle-states node, which is
243 just supports idle_standby, an idle-states node is not required.
246 6 - Qualcomm specific STATES
249 Idle states have different enter/exit latency and residency values.
250 The idle states supported by the QCOM SoC are defined as -
275 state. Retention may have a slightly higher latency than Standby.
288 code in the EL for the SoC. On SoCs with write-back L1 cache, the cache has to
294 be flushed, system bus, clocks - lowered, and SoC main XO clock gated and
296 power modes possible at this state is vast, the exit latency and the residency
303 7 - References
306 [1] ARM Linux Kernel documentation - CPUs bindings
309 [2] ARM Linux Kernel documentation - PSCI bindings
318 [5] ARM Linux Kernel documentation - Booting AArch64 Linux
321 [6] RISC-V Linux Kernel documentation - CPUs bindings
324 [7] RISC-V Supervisor Binary Interface (SBI)
325 http://github.com/riscv/riscv-sbi-doc/riscv-sbi.adoc
329 const: idle-states
331 entry-method:
335 On ARM v8 64-bit this property is required.
336 On ARM 32-bit systems this property is optional
338 This assumes that the "enable-method" property is set to "psci" in the cpu
344 "^(cpu|cluster)-":
351 SBSA,[3][4]) is considered standard on all ARM and RISC-V platforms and
355 additional properties specific to the entry-method defined in the
356 idle-states node. Please refer to the entry-method bindings
362 - items:
363 - enum:
364 - qcom,idle-state-ret
365 - qcom,idle-state-spc
366 - qcom,idle-state-pc
367 - const: arm,idle-state
368 - enum:
369 - arm,idle-state
370 - riscv,idle-state
372 arm,psci-suspend-param:
378 (i.e. idle states node with entry-method property is set to "psci")
381 riscv,sbi-suspend-param:
384 suspend_type parameter to pass to the RISC-V SBI HSM suspend call.
387 for RISC-V systems. For more details on the suspend_type parameter
390 local-timer-stop:
393 lost on state entry, otherwise it is retained.
396 entry-latency-us:
398 Worst case latency in microseconds required to enter the idle state.
400 exit-latency-us:
402 Worst case latency in microseconds required to exit the idle state.
403 The exit-latency-us duration may be guaranteed only after
404 entry-latency-us has passed.
406 min-residency-us:
409 and entry, for this idle state to be considered worthwhile energy wise
412 wakeup-latency-us:
414 Maximum delay between the signaling of a wake-up event and the CPU
418 entry-latency-us + exit-latency-us
421 PREP phase (see diagram 1, section 2) is non-neglibigle. In such
422 systems entry-latency-us + exit-latency-us will exceed
423 wakeup-latency-us by this duration.
425 idle-state-name:
433 - compatible
434 - entry-latency-us
435 - exit-latency-us
436 - min-residency-us
441 - |
444 #size-cells = <0>;
445 #address-cells = <2>;
449 compatible = "arm,cortex-a57";
451 enable-method = "psci";
452 cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
458 compatible = "arm,cortex-a57";
460 enable-method = "psci";
461 cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
467 compatible = "arm,cortex-a57";
469 enable-method = "psci";
470 cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
476 compatible = "arm,cortex-a57";
478 enable-method = "psci";
479 cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
485 compatible = "arm,cortex-a57";
487 enable-method = "psci";
488 cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
494 compatible = "arm,cortex-a57";
496 enable-method = "psci";
497 cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
503 compatible = "arm,cortex-a57";
505 enable-method = "psci";
506 cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
512 compatible = "arm,cortex-a57";
514 enable-method = "psci";
515 cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
521 compatible = "arm,cortex-a53";
523 enable-method = "psci";
524 cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
530 compatible = "arm,cortex-a53";
532 enable-method = "psci";
533 cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
539 compatible = "arm,cortex-a53";
541 enable-method = "psci";
542 cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
548 compatible = "arm,cortex-a53";
550 enable-method = "psci";
551 cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
557 compatible = "arm,cortex-a53";
559 enable-method = "psci";
560 cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
566 compatible = "arm,cortex-a53";
568 enable-method = "psci";
569 cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
575 compatible = "arm,cortex-a53";
577 enable-method = "psci";
578 cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
584 compatible = "arm,cortex-a53";
586 enable-method = "psci";
587 cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
591 idle-states {
592 entry-method = "psci";
594 CPU_RETENTION_0_0: cpu-retention-0-0 {
595 compatible = "arm,idle-state";
596 arm,psci-suspend-param = <0x0010000>;
597 entry-latency-us = <20>;
598 exit-latency-us = <40>;
599 min-residency-us = <80>;
602 CLUSTER_RETENTION_0: cluster-retention-0 {
603 compatible = "arm,idle-state";
604 local-timer-stop;
605 arm,psci-suspend-param = <0x1010000>;
606 entry-latency-us = <50>;
607 exit-latency-us = <100>;
608 min-residency-us = <250>;
609 wakeup-latency-us = <130>;
612 CPU_SLEEP_0_0: cpu-sleep-0-0 {
613 compatible = "arm,idle-state";
614 local-timer-stop;
615 arm,psci-suspend-param = <0x0010000>;
616 entry-latency-us = <250>;
617 exit-latency-us = <500>;
618 min-residency-us = <950>;
621 CLUSTER_SLEEP_0: cluster-sleep-0 {
622 compatible = "arm,idle-state";
623 local-timer-stop;
624 arm,psci-suspend-param = <0x1010000>;
625 entry-latency-us = <600>;
626 exit-latency-us = <1100>;
627 min-residency-us = <2700>;
628 wakeup-latency-us = <1500>;
631 CPU_RETENTION_1_0: cpu-retention-1-0 {
632 compatible = "arm,idle-state";
633 arm,psci-suspend-param = <0x0010000>;
634 entry-latency-us = <20>;
635 exit-latency-us = <40>;
636 min-residency-us = <90>;
639 CLUSTER_RETENTION_1: cluster-retention-1 {
640 compatible = "arm,idle-state";
641 local-timer-stop;
642 arm,psci-suspend-param = <0x1010000>;
643 entry-latency-us = <50>;
644 exit-latency-us = <100>;
645 min-residency-us = <270>;
646 wakeup-latency-us = <100>;
649 CPU_SLEEP_1_0: cpu-sleep-1-0 {
650 compatible = "arm,idle-state";
651 local-timer-stop;
652 arm,psci-suspend-param = <0x0010000>;
653 entry-latency-us = <70>;
654 exit-latency-us = <100>;
655 min-residency-us = <300>;
656 wakeup-latency-us = <150>;
659 CLUSTER_SLEEP_1: cluster-sleep-1 {
660 compatible = "arm,idle-state";
661 local-timer-stop;
662 arm,psci-suspend-param = <0x1010000>;
663 entry-latency-us = <500>;
664 exit-latency-us = <1200>;
665 min-residency-us = <3500>;
666 wakeup-latency-us = <1300>;
671 - |
672 // Example 2 (ARM 32-bit, 8-cpu system, two clusters):
675 #size-cells = <0>;
676 #address-cells = <1>;
680 compatible = "arm,cortex-a15";
682 cpu-idle-states = <&cpu_sleep_0_0>, <&cluster_sleep_0>;
687 compatible = "arm,cortex-a15";
689 cpu-idle-states = <&cpu_sleep_0_0>, <&cluster_sleep_0>;
694 compatible = "arm,cortex-a15";
696 cpu-idle-states = <&cpu_sleep_0_0>, <&cluster_sleep_0>;
701 compatible = "arm,cortex-a15";
703 cpu-idle-states = <&cpu_sleep_0_0>, <&cluster_sleep_0>;
708 compatible = "arm,cortex-a7";
710 cpu-idle-states = <&cpu_sleep_1_0>, <&cluster_sleep_1>;
715 compatible = "arm,cortex-a7";
717 cpu-idle-states = <&cpu_sleep_1_0>, <&cluster_sleep_1>;
722 compatible = "arm,cortex-a7";
724 cpu-idle-states = <&cpu_sleep_1_0>, <&cluster_sleep_1>;
729 compatible = "arm,cortex-a7";
731 cpu-idle-states = <&cpu_sleep_1_0>, <&cluster_sleep_1>;
734 idle-states {
735 cpu_sleep_0_0: cpu-sleep-0-0 {
736 compatible = "arm,idle-state";
737 local-timer-stop;
738 entry-latency-us = <200>;
739 exit-latency-us = <100>;
740 min-residency-us = <400>;
741 wakeup-latency-us = <250>;
744 cluster_sleep_0: cluster-sleep-0 {
745 compatible = "arm,idle-state";
746 local-timer-stop;
747 entry-latency-us = <500>;
748 exit-latency-us = <1500>;
749 min-residency-us = <2500>;
750 wakeup-latency-us = <1700>;
753 cpu_sleep_1_0: cpu-sleep-1-0 {
754 compatible = "arm,idle-state";
755 local-timer-stop;
756 entry-latency-us = <300>;
757 exit-latency-us = <500>;
758 min-residency-us = <900>;
759 wakeup-latency-us = <600>;
762 cluster_sleep_1: cluster-sleep-1 {
763 compatible = "arm,idle-state";
764 local-timer-stop;
765 entry-latency-us = <800>;
766 exit-latency-us = <2000>;
767 min-residency-us = <6500>;
768 wakeup-latency-us = <2300>;
773 - |
774 // Example 3 (RISC-V 64-bit, 4-cpu systems, two clusters):
777 #size-cells = <0>;
778 #address-cells = <1>;
785 mmu-type = "riscv,sv48";
786 cpu-idle-states = <&CPU_RET_0_0>, <&CPU_NONRET_0_0>,
789 cpu_intc0: interrupt-controller {
790 #interrupt-cells = <1>;
791 compatible = "riscv,cpu-intc";
792 interrupt-controller;
801 mmu-type = "riscv,sv48";
802 cpu-idle-states = <&CPU_RET_0_0>, <&CPU_NONRET_0_0>,
805 cpu_intc1: interrupt-controller {
806 #interrupt-cells = <1>;
807 compatible = "riscv,cpu-intc";
808 interrupt-controller;
817 mmu-type = "riscv,sv48";
818 cpu-idle-states = <&CPU_RET_1_0>, <&CPU_NONRET_1_0>,
821 cpu_intc10: interrupt-controller {
822 #interrupt-cells = <1>;
823 compatible = "riscv,cpu-intc";
824 interrupt-controller;
833 mmu-type = "riscv,sv48";
834 cpu-idle-states = <&CPU_RET_1_0>, <&CPU_NONRET_1_0>,
837 cpu_intc11: interrupt-controller {
838 #interrupt-cells = <1>;
839 compatible = "riscv,cpu-intc";
840 interrupt-controller;
844 idle-states {
845 CPU_RET_0_0: cpu-retentive-0-0 {
846 compatible = "riscv,idle-state";
847 riscv,sbi-suspend-param = <0x10000000>;
848 entry-latency-us = <20>;
849 exit-latency-us = <40>;
850 min-residency-us = <80>;
853 CPU_NONRET_0_0: cpu-nonretentive-0-0 {
854 compatible = "riscv,idle-state";
855 riscv,sbi-suspend-param = <0x90000000>;
856 entry-latency-us = <250>;
857 exit-latency-us = <500>;
858 min-residency-us = <950>;
861 CLUSTER_RET_0: cluster-retentive-0 {
862 compatible = "riscv,idle-state";
863 riscv,sbi-suspend-param = <0x11000000>;
864 local-timer-stop;
865 entry-latency-us = <50>;
866 exit-latency-us = <100>;
867 min-residency-us = <250>;
868 wakeup-latency-us = <130>;
871 CLUSTER_NONRET_0: cluster-nonretentive-0 {
872 compatible = "riscv,idle-state";
873 riscv,sbi-suspend-param = <0x91000000>;
874 local-timer-stop;
875 entry-latency-us = <600>;
876 exit-latency-us = <1100>;
877 min-residency-us = <2700>;
878 wakeup-latency-us = <1500>;
881 CPU_RET_1_0: cpu-retentive-1-0 {
882 compatible = "riscv,idle-state";
883 riscv,sbi-suspend-param = <0x10000010>;
884 entry-latency-us = <20>;
885 exit-latency-us = <40>;
886 min-residency-us = <80>;
889 CPU_NONRET_1_0: cpu-nonretentive-1-0 {
890 compatible = "riscv,idle-state";
891 riscv,sbi-suspend-param = <0x90000010>;
892 entry-latency-us = <250>;
893 exit-latency-us = <500>;
894 min-residency-us = <950>;
897 CLUSTER_RET_1: cluster-retentive-1 {
898 compatible = "riscv,idle-state";
899 riscv,sbi-suspend-param = <0x11000010>;
900 local-timer-stop;
901 entry-latency-us = <50>;
902 exit-latency-us = <100>;
903 min-residency-us = <250>;
904 wakeup-latency-us = <130>;
907 CLUSTER_NONRET_1: cluster-nonretentive-1 {
908 compatible = "riscv,idle-state";
909 riscv,sbi-suspend-param = <0x91000010>;
910 local-timer-stop;
911 entry-latency-us = <600>;
912 exit-latency-us = <1100>;
913 min-residency-us = <2700>;
914 wakeup-latency-us = <1500>;
919 // Example 4 - Qualcomm SPC
920 idle-states {
921 cpu_spc: cpu-spc {
922 compatible = "qcom,idle-state-spc", "arm,idle-state";
923 entry-latency-us = <150>;
924 exit-latency-us = <200>;
925 min-residency-us = <2000>;