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# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
%YAML 1.2
---
$id: http://devicetree.org/schemas/cpu/idle-states.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#
title: Idle states
maintainers:
- Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
- Anup Patel <anup@brainfault.org>
description: |+
==========================================
1 - Introduction
==========================================
ARM and RISC-V systems contain HW capable of managing power consumption
dynamically, where cores can be put in different low-power states (ranging
from simple wfi to power gating) according to OS PM policies. The CPU states
representing the range of dynamic idle states that a processor can enter at
run-time, can be specified through device tree bindings representing the
parameters required to enter/exit specific idle states on a given processor.
==========================================
2 - ARM idle states
==========================================
According to the Server Base System Architecture document (SBSA, [3]), the
power states an ARM CPU can be put into are identified by the following list:
- Running
- Idle_standby
- Idle_retention
- Sleep
- Off
The power states described in the SBSA document define the basic CPU states on
top of which ARM platforms implement power management schemes that allow an OS
PM implementation to put the processor in different idle states (which include
states listed above; "off" state is not an idle state since it does not have
wake-up capabilities, hence it is not considered in this document).
Idle state parameters (e.g. entry latency) are platform specific and need to
be characterized with bindings that provide the required information to OS PM
code so that it can build the required tables and use them at runtime.
The device tree binding definition for ARM idle states is the subject of this
document.
==========================================
3 - RISC-V idle states
==========================================
On RISC-V systems, the HARTs (or CPUs) [6] can be put in platform specific
suspend (or idle) states (ranging from simple WFI, power gating, etc). The
RISC-V SBI v0.3 (or higher) [7] hart state management extension provides a
standard mechanism for OS to request HART state transitions.
The platform specific suspend (or idle) states of a hart can be either
retentive or non-rententive in nature. A retentive suspend state will
preserve HART registers and CSR values for all privilege modes whereas
a non-retentive suspend state will not preserve HART registers and CSR
values.
===========================================
4 - idle-states definitions
===========================================
Idle states are characterized for a specific system through a set of
timing and energy related properties, that underline the HW behaviour
triggered upon idle states entry and exit.
The following diagram depicts the CPU execution phases and related timing
properties required to enter and exit an idle state:
..__[EXEC]__|__[PREP]__|__[ENTRY]__|__[IDLE]__|__[EXIT]__|__[EXEC]__..
| | | | |
|<------ entry ------->|
| latency |
|<- exit ->|
| latency |
|<-------- min-residency -------->|
|<------- wakeup-latency ------->|
Diagram 1: CPU idle state execution phases
EXEC: Normal CPU execution.
PREP: Preparation phase before committing the hardware to idle mode
like cache flushing. This is abortable on pending wake-up
event conditions. The abort latency is assumed to be negligible
(i.e. less than the ENTRY + EXIT duration). If aborted, CPU
goes back to EXEC. This phase is optional. If not abortable,
this should be included in the ENTRY phase instead.
ENTRY: The hardware is committed to idle mode. This period must run
to completion up to IDLE before anything else can happen.
IDLE: This is the actual energy-saving idle period. This may last
between 0 and infinite time, until a wake-up event occurs.
EXIT: Period during which the CPU is brought back to operational
mode (EXEC).
entry-latency: Worst case latency required to enter the idle state. The
exit-latency may be guaranteed only after entry-latency has passed.
min-residency: Minimum period, including preparation and entry, for a given
idle state to be worthwhile energywise.
wakeup-latency: Maximum delay between the signaling of a wake-up event and the
CPU being able to execute normal code again. If not specified, this is assumed
to be entry-latency + exit-latency.
These timing parameters can be used by an OS in different circumstances.
An idle CPU requires the expected min-residency time to select the most
appropriate idle state based on the expected expiry time of the next IRQ
(i.e. wake-up) that causes the CPU to return to the EXEC phase.
An operating system scheduler may need to compute the shortest wake-up delay
for CPUs in the system by detecting how long will it take to get a CPU out
of an idle state, e.g.:
wakeup-delay = exit-latency + max(entry-latency - (now - entry-timestamp), 0)
In other words, the scheduler can make its scheduling decision by selecting
(e.g. waking-up) the CPU with the shortest wake-up delay.
The wake-up delay must take into account the entry latency if that period
has not expired. The abortable nature of the PREP period can be ignored
if it cannot be relied upon (e.g. the PREP deadline may occur much sooner than
the worst case since it depends on the CPU operating conditions, i.e. caches
state).
An OS has to reliably probe the wakeup-latency since some devices can enforce
latency constraint guarantees to work properly, so the OS has to detect the
worst case wake-up latency it can incur if a CPU is allowed to enter an
idle state, and possibly to prevent that to guarantee reliable device
functioning.
The min-residency time parameter deserves further explanation since it is
expressed in time units but must factor in energy consumption coefficients.
The energy consumption of a cpu when it enters a power state can be roughly
characterised by the following graph:
|
|
|
e |
n | /---
e | /------
r | /------
g | /-----
y | /------
| ----
| /|
| / |
| / |
| / |
| / |
| / |
|/ |
-----|-------+----------------------------------
0| 1 time(ms)
Graph 1: Energy vs time example
The graph is split in two parts delimited by time 1ms on the X-axis.
The graph curve with X-axis values = { x | 0 < x < 1ms } has a steep slope
and denotes the energy costs incurred while entering and leaving the idle
state.
The graph curve in the area delimited by X-axis values = {x | x > 1ms } has
shallower slope and essentially represents the energy consumption of the idle
state.
min-residency is defined for a given idle state as the minimum expected
residency time for a state (inclusive of preparation and entry) after
which choosing that state become the most energy efficient option. A good
way to visualise this, is by taking the same graph above and comparing some
states energy consumptions plots.
For sake of simplicity, let's consider a system with two idle states IDLE1,
and IDLE2:
|
|
|
| /-- IDLE1
e | /---
n | /----
e | /---
r | /-----/--------- IDLE2
g | /-------/---------
y | ------------ /---|
| / /---- |
| / /--- |
| / /---- |
| / /--- |
| --- |
| / |
| / |
|/ | time
---/----------------------------+------------------------
|IDLE1-energy < IDLE2-energy | IDLE2-energy < IDLE1-energy
|
IDLE2-min-residency
Graph 2: idle states min-residency example
In graph 2 above, that takes into account idle states entry/exit energy
costs, it is clear that if the idle state residency time (i.e. time till next
wake-up IRQ) is less than IDLE2-min-residency, IDLE1 is the better idle state
choice energywise.
This is mainly down to the fact that IDLE1 entry/exit energy costs are lower
than IDLE2.
However, the lower power consumption (i.e. shallower energy curve slope) of
idle state IDLE2 implies that after a suitable time, IDLE2 becomes more energy
efficient.
The time at which IDLE2 becomes more energy efficient than IDLE1 (and other
shallower states in a system with multiple idle states) is defined
IDLE2-min-residency and corresponds to the time when energy consumption of
IDLE1 and IDLE2 states breaks even.
The definitions provided in this section underpin the idle states
properties specification that is the subject of the following sections.
===========================================
5 - idle-states node
===========================================
The processor idle states are defined within the idle-states node, which is
a direct child of the cpus node [1] and provides a container where the
processor idle states, defined as device tree nodes, are listed.
On ARM systems, it is a container of processor idle states nodes. If the
system does not provide CPU power management capabilities, or the processor
just supports idle_standby, an idle-states node is not required.
===========================================
6 - Qualcomm specific STATES
===========================================
Idle states have different enter/exit latency and residency values.
The idle states supported by the QCOM SoC are defined as -
* Standby
* Retention
* Standalone Power Collapse (Standalone PC or SPC)
* Power Collapse (PC)
Standby: Standby does a little more in addition to architectural clock gating.
When the WFI instruction is executed the ARM core would gate its internal
clocks. In addition to gating the clocks, QCOM cpus use this instruction as a
trigger to execute the SPM state machine. The SPM state machine waits for the
interrupt to trigger the core back in to active. This triggers the cache
hierarchy to enter standby states, when all cpus are idle. An interrupt brings
the SPM state machine out of its wait, the next step is to ensure that the
cache hierarchy is also out of standby, and then the cpu is allowed to resume
execution. This state is defined as a generic ARM WFI state by the ARM cpuidle
driver and is not defined in the DT. The SPM state machine should be
configured to execute this state by default and after executing every other
state below.
Retention: Retention is a low power state where the core is clock gated and
the memory and the registers associated with the core are retained. The
voltage may be reduced to the minimum value needed to keep the processor
registers active. The SPM should be configured to execute the retention
sequence and would wait for interrupt, before restoring the cpu to execution
state. Retention may have a slightly higher latency than Standby.
Standalone PC: A cpu can power down and warmboot if there is a sufficient time
between the time it enters idle and the next known wake up. SPC mode is used
to indicate a core entering a power down state without consulting any other
cpu or the system resources. This helps save power only on that core. The SPM
sequence for this idle state is programmed to power down the supply to the
core, wait for the interrupt, restore power to the core, and ensure the
system state including cache hierarchy is ready before allowing core to
resume. Applying power and resetting the core causes the core to warmboot
back into Elevation Level (EL) which trampolines the control back to the
kernel. Entering a power down state for the cpu, needs to be done by trapping
into a EL. Failing to do so, would result in a crash enforced by the warm boot
code in the EL for the SoC. On SoCs with write-back L1 cache, the cache has to
be flushed in s/w, before powering down the core.
Power Collapse: This state is similar to the SPC mode, but distinguishes
itself in that the cpu acknowledges and permits the SoC to enter deeper sleep
modes. In a hierarchical power domain SoC, this means L2 and other caches can
be flushed, system bus, clocks - lowered, and SoC main XO clock gated and
voltages reduced, provided all cpus enter this state. Since the span of low
power modes possible at this state is vast, the exit latency and the residency
of this low power mode would be considered high even though at a cpu level,
this essentially is cpu power down. The SPM in this state also may handshake
with the Resource power manager (RPM) processor in the SoC to indicate a
complete application processor subsystem shut down.
===========================================
7 - References
===========================================
[1] ARM Linux Kernel documentation - CPUs bindings
Documentation/devicetree/bindings/arm/cpus.yaml
[2] ARM Linux Kernel documentation - PSCI bindings
Documentation/devicetree/bindings/arm/psci.yaml
[3] ARM Server Base System Architecture (SBSA)
http://infocenter.arm.com/help/index.jsp
[4] ARM Architecture Reference Manuals
http://infocenter.arm.com/help/index.jsp
[5] ARM Linux Kernel documentation - Booting AArch64 Linux
Documentation/arch/arm64/booting.rst
[6] RISC-V Linux Kernel documentation - CPUs bindings
Documentation/devicetree/bindings/riscv/cpus.yaml
[7] RISC-V Supervisor Binary Interface (SBI)
http://github.com/riscv/riscv-sbi-doc/riscv-sbi.adoc
properties:
$nodename:
const: idle-states
entry-method:
description: |
Usage and definition depend on ARM architecture version.
On ARM v8 64-bit this property is required.
On ARM 32-bit systems this property is optional
This assumes that the "enable-method" property is set to "psci" in the cpu
node[5] that is responsible for setting up CPU idle management in the OS
implementation.
const: psci
patternProperties:
"^(cpu|cluster)-":
type: object
description: |
Each state node represents an idle state description and must be defined
as follows.
The idle state entered by executing the wfi instruction (idle_standby
SBSA,[3][4]) is considered standard on all ARM and RISC-V platforms and
therefore must not be listed.
In addition to the properties listed above, a state node may require
additional properties specific to the entry-method defined in the
idle-states node. Please refer to the entry-method bindings
documentation for properties definitions.
properties:
compatible:
oneOf:
- items:
- enum:
- qcom,idle-state-ret
- qcom,idle-state-spc
- qcom,idle-state-pc
- const: arm,idle-state
- enum:
- arm,idle-state
- riscv,idle-state
arm,psci-suspend-param:
$ref: /schemas/types.yaml#/definitions/uint32
description: |
power_state parameter to pass to the ARM PSCI suspend call.
Device tree nodes that require usage of PSCI CPU_SUSPEND function
(i.e. idle states node with entry-method property is set to "psci")
must specify this property.
riscv,sbi-suspend-param:
$ref: /schemas/types.yaml#/definitions/uint32
description: |
suspend_type parameter to pass to the RISC-V SBI HSM suspend call.
This property is required in idle state nodes of device tree meant
for RISC-V systems. For more details on the suspend_type parameter
refer the SBI specifiation v0.3 (or higher) [7].
local-timer-stop:
description:
If present the CPU local timer control logic is
lost on state entry, otherwise it is retained.
type: boolean
entry-latency-us:
description:
Worst case latency in microseconds required to enter the idle state.
exit-latency-us:
description:
Worst case latency in microseconds required to exit the idle state.
The exit-latency-us duration may be guaranteed only after
entry-latency-us has passed.
min-residency-us:
description:
Minimum residency duration in microseconds, inclusive of preparation
and entry, for this idle state to be considered worthwhile energy wise
(refer to section 2 of this document for a complete description).
wakeup-latency-us:
description: |
Maximum delay between the signaling of a wake-up event and the CPU
being able to execute normal code again. If omitted, this is assumed
to be equal to:
entry-latency-us + exit-latency-us
It is important to supply this value on systems where the duration of
PREP phase (see diagram 1, section 2) is non-neglibigle. In such
systems entry-latency-us + exit-latency-us will exceed
wakeup-latency-us by this duration.
idle-state-name:
$ref: /schemas/types.yaml#/definitions/string
description:
A string used as a descriptive name for the idle state.
additionalProperties: false
required:
- compatible
- entry-latency-us
- exit-latency-us
- min-residency-us
additionalProperties: false
examples:
- |
cpus {
#size-cells = <0>;
#address-cells = <2>;
cpu@0 {
device_type = "cpu";
compatible = "arm,cortex-a57";
reg = <0x0 0x0>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
<&CLUSTER_RETENTION_0>, <&CLUSTER_SLEEP_0>;
};
cpu@1 {
device_type = "cpu";
compatible = "arm,cortex-a57";
reg = <0x0 0x1>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
<&CLUSTER_RETENTION_0>, <&CLUSTER_SLEEP_0>;
};
cpu@100 {
device_type = "cpu";
compatible = "arm,cortex-a57";
reg = <0x0 0x100>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
<&CLUSTER_RETENTION_0>, <&CLUSTER_SLEEP_0>;
};
cpu@101 {
device_type = "cpu";
compatible = "arm,cortex-a57";
reg = <0x0 0x101>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
<&CLUSTER_RETENTION_0>, <&CLUSTER_SLEEP_0>;
};
cpu@10000 {
device_type = "cpu";
compatible = "arm,cortex-a57";
reg = <0x0 0x10000>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
<&CLUSTER_RETENTION_0>, <&CLUSTER_SLEEP_0>;
};
cpu@10001 {
device_type = "cpu";
compatible = "arm,cortex-a57";
reg = <0x0 0x10001>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
<&CLUSTER_RETENTION_0>, <&CLUSTER_SLEEP_0>;
};
cpu@10100 {
device_type = "cpu";
compatible = "arm,cortex-a57";
reg = <0x0 0x10100>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
<&CLUSTER_RETENTION_0>, <&CLUSTER_SLEEP_0>;
};
cpu@10101 {
device_type = "cpu";
compatible = "arm,cortex-a57";
reg = <0x0 0x10101>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_0_0>, <&CPU_SLEEP_0_0>,
<&CLUSTER_RETENTION_0>, <&CLUSTER_SLEEP_0>;
};
cpu@100000000 {
device_type = "cpu";
compatible = "arm,cortex-a53";
reg = <0x1 0x0>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
<&CLUSTER_RETENTION_1>, <&CLUSTER_SLEEP_1>;
};
cpu@100000001 {
device_type = "cpu";
compatible = "arm,cortex-a53";
reg = <0x1 0x1>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
<&CLUSTER_RETENTION_1>, <&CLUSTER_SLEEP_1>;
};
cpu@100000100 {
device_type = "cpu";
compatible = "arm,cortex-a53";
reg = <0x1 0x100>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
<&CLUSTER_RETENTION_1>, <&CLUSTER_SLEEP_1>;
};
cpu@100000101 {
device_type = "cpu";
compatible = "arm,cortex-a53";
reg = <0x1 0x101>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
<&CLUSTER_RETENTION_1>, <&CLUSTER_SLEEP_1>;
};
cpu@100010000 {
device_type = "cpu";
compatible = "arm,cortex-a53";
reg = <0x1 0x10000>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
<&CLUSTER_RETENTION_1>, <&CLUSTER_SLEEP_1>;
};
cpu@100010001 {
device_type = "cpu";
compatible = "arm,cortex-a53";
reg = <0x1 0x10001>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
<&CLUSTER_RETENTION_1>, <&CLUSTER_SLEEP_1>;
};
cpu@100010100 {
device_type = "cpu";
compatible = "arm,cortex-a53";
reg = <0x1 0x10100>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
<&CLUSTER_RETENTION_1>, <&CLUSTER_SLEEP_1>;
};
cpu@100010101 {
device_type = "cpu";
compatible = "arm,cortex-a53";
reg = <0x1 0x10101>;
enable-method = "psci";
cpu-idle-states = <&CPU_RETENTION_1_0>, <&CPU_SLEEP_1_0>,
<&CLUSTER_RETENTION_1>, <&CLUSTER_SLEEP_1>;
};
idle-states {
entry-method = "psci";
CPU_RETENTION_0_0: cpu-retention-0-0 {
compatible = "arm,idle-state";
arm,psci-suspend-param = <0x0010000>;
entry-latency-us = <20>;
exit-latency-us = <40>;
min-residency-us = <80>;
};
CLUSTER_RETENTION_0: cluster-retention-0 {
compatible = "arm,idle-state";
local-timer-stop;
arm,psci-suspend-param = <0x1010000>;
entry-latency-us = <50>;
exit-latency-us = <100>;
min-residency-us = <250>;
wakeup-latency-us = <130>;
};
CPU_SLEEP_0_0: cpu-sleep-0-0 {
compatible = "arm,idle-state";
local-timer-stop;
arm,psci-suspend-param = <0x0010000>;
entry-latency-us = <250>;
exit-latency-us = <500>;
min-residency-us = <950>;
};
CLUSTER_SLEEP_0: cluster-sleep-0 {
compatible = "arm,idle-state";
local-timer-stop;
arm,psci-suspend-param = <0x1010000>;
entry-latency-us = <600>;
exit-latency-us = <1100>;
min-residency-us = <2700>;
wakeup-latency-us = <1500>;
};
CPU_RETENTION_1_0: cpu-retention-1-0 {
compatible = "arm,idle-state";
arm,psci-suspend-param = <0x0010000>;
entry-latency-us = <20>;
exit-latency-us = <40>;
min-residency-us = <90>;
};
CLUSTER_RETENTION_1: cluster-retention-1 {
compatible = "arm,idle-state";
local-timer-stop;
arm,psci-suspend-param = <0x1010000>;
entry-latency-us = <50>;
exit-latency-us = <100>;
min-residency-us = <270>;
wakeup-latency-us = <100>;
};
CPU_SLEEP_1_0: cpu-sleep-1-0 {
compatible = "arm,idle-state";
local-timer-stop;
arm,psci-suspend-param = <0x0010000>;
entry-latency-us = <70>;
exit-latency-us = <100>;
min-residency-us = <300>;
wakeup-latency-us = <150>;
};
CLUSTER_SLEEP_1: cluster-sleep-1 {
compatible = "arm,idle-state";
local-timer-stop;
arm,psci-suspend-param = <0x1010000>;
entry-latency-us = <500>;
exit-latency-us = <1200>;
min-residency-us = <3500>;
wakeup-latency-us = <1300>;
};
};
};
- |
// Example 2 (ARM 32-bit, 8-cpu system, two clusters):
cpus {
#size-cells = <0>;
#address-cells = <1>;
cpu@0 {
device_type = "cpu";
compatible = "arm,cortex-a15";
reg = <0x0>;
cpu-idle-states = <&cpu_sleep_0_0>, <&cluster_sleep_0>;
};
cpu@1 {
device_type = "cpu";
compatible = "arm,cortex-a15";
reg = <0x1>;
cpu-idle-states = <&cpu_sleep_0_0>, <&cluster_sleep_0>;
};
cpu@2 {
device_type = "cpu";
compatible = "arm,cortex-a15";
reg = <0x2>;
cpu-idle-states = <&cpu_sleep_0_0>, <&cluster_sleep_0>;
};
cpu@3 {
device_type = "cpu";
compatible = "arm,cortex-a15";
reg = <0x3>;
cpu-idle-states = <&cpu_sleep_0_0>, <&cluster_sleep_0>;
};
cpu@100 {
device_type = "cpu";
compatible = "arm,cortex-a7";
reg = <0x100>;
cpu-idle-states = <&cpu_sleep_1_0>, <&cluster_sleep_1>;
};
cpu@101 {
device_type = "cpu";
compatible = "arm,cortex-a7";
reg = <0x101>;
cpu-idle-states = <&cpu_sleep_1_0>, <&cluster_sleep_1>;
};
cpu@102 {
device_type = "cpu";
compatible = "arm,cortex-a7";
reg = <0x102>;
cpu-idle-states = <&cpu_sleep_1_0>, <&cluster_sleep_1>;
};
cpu@103 {
device_type = "cpu";
compatible = "arm,cortex-a7";
reg = <0x103>;
cpu-idle-states = <&cpu_sleep_1_0>, <&cluster_sleep_1>;
};
idle-states {
cpu_sleep_0_0: cpu-sleep-0-0 {
compatible = "arm,idle-state";
local-timer-stop;
entry-latency-us = <200>;
exit-latency-us = <100>;
min-residency-us = <400>;
wakeup-latency-us = <250>;
};
cluster_sleep_0: cluster-sleep-0 {
compatible = "arm,idle-state";
local-timer-stop;
entry-latency-us = <500>;
exit-latency-us = <1500>;
min-residency-us = <2500>;
wakeup-latency-us = <1700>;
};
cpu_sleep_1_0: cpu-sleep-1-0 {
compatible = "arm,idle-state";
local-timer-stop;
entry-latency-us = <300>;
exit-latency-us = <500>;
min-residency-us = <900>;
wakeup-latency-us = <600>;
};
cluster_sleep_1: cluster-sleep-1 {
compatible = "arm,idle-state";
local-timer-stop;
entry-latency-us = <800>;
exit-latency-us = <2000>;
min-residency-us = <6500>;
wakeup-latency-us = <2300>;
};
};
};
- |
// Example 3 (RISC-V 64-bit, 4-cpu systems, two clusters):
cpus {
#size-cells = <0>;
#address-cells = <1>;
cpu@0 {
device_type = "cpu";
compatible = "riscv";
reg = <0x0>;
riscv,isa = "rv64imafdc";
mmu-type = "riscv,sv48";
cpu-idle-states = <&CPU_RET_0_0>, <&CPU_NONRET_0_0>,
<&CLUSTER_RET_0>, <&CLUSTER_NONRET_0>;
cpu_intc0: interrupt-controller {
#interrupt-cells = <1>;
compatible = "riscv,cpu-intc";
interrupt-controller;
};
};
cpu@1 {
device_type = "cpu";
compatible = "riscv";
reg = <0x1>;
riscv,isa = "rv64imafdc";
mmu-type = "riscv,sv48";
cpu-idle-states = <&CPU_RET_0_0>, <&CPU_NONRET_0_0>,
<&CLUSTER_RET_0>, <&CLUSTER_NONRET_0>;
cpu_intc1: interrupt-controller {
#interrupt-cells = <1>;
compatible = "riscv,cpu-intc";
interrupt-controller;
};
};
cpu@10 {
device_type = "cpu";
compatible = "riscv";
reg = <0x10>;
riscv,isa = "rv64imafdc";
mmu-type = "riscv,sv48";
cpu-idle-states = <&CPU_RET_1_0>, <&CPU_NONRET_1_0>,
<&CLUSTER_RET_1>, <&CLUSTER_NONRET_1>;
cpu_intc10: interrupt-controller {
#interrupt-cells = <1>;
compatible = "riscv,cpu-intc";
interrupt-controller;
};
};
cpu@11 {
device_type = "cpu";
compatible = "riscv";
reg = <0x11>;
riscv,isa = "rv64imafdc";
mmu-type = "riscv,sv48";
cpu-idle-states = <&CPU_RET_1_0>, <&CPU_NONRET_1_0>,
<&CLUSTER_RET_1>, <&CLUSTER_NONRET_1>;
cpu_intc11: interrupt-controller {
#interrupt-cells = <1>;
compatible = "riscv,cpu-intc";
interrupt-controller;
};
};
idle-states {
CPU_RET_0_0: cpu-retentive-0-0 {
compatible = "riscv,idle-state";
riscv,sbi-suspend-param = <0x10000000>;
entry-latency-us = <20>;
exit-latency-us = <40>;
min-residency-us = <80>;
};
CPU_NONRET_0_0: cpu-nonretentive-0-0 {
compatible = "riscv,idle-state";
riscv,sbi-suspend-param = <0x90000000>;
entry-latency-us = <250>;
exit-latency-us = <500>;
min-residency-us = <950>;
};
CLUSTER_RET_0: cluster-retentive-0 {
compatible = "riscv,idle-state";
riscv,sbi-suspend-param = <0x11000000>;
local-timer-stop;
entry-latency-us = <50>;
exit-latency-us = <100>;
min-residency-us = <250>;
wakeup-latency-us = <130>;
};
CLUSTER_NONRET_0: cluster-nonretentive-0 {
compatible = "riscv,idle-state";
riscv,sbi-suspend-param = <0x91000000>;
local-timer-stop;
entry-latency-us = <600>;
exit-latency-us = <1100>;
min-residency-us = <2700>;
wakeup-latency-us = <1500>;
};
CPU_RET_1_0: cpu-retentive-1-0 {
compatible = "riscv,idle-state";
riscv,sbi-suspend-param = <0x10000010>;
entry-latency-us = <20>;
exit-latency-us = <40>;
min-residency-us = <80>;
};
CPU_NONRET_1_0: cpu-nonretentive-1-0 {
compatible = "riscv,idle-state";
riscv,sbi-suspend-param = <0x90000010>;
entry-latency-us = <250>;
exit-latency-us = <500>;
min-residency-us = <950>;
};
CLUSTER_RET_1: cluster-retentive-1 {
compatible = "riscv,idle-state";
riscv,sbi-suspend-param = <0x11000010>;
local-timer-stop;
entry-latency-us = <50>;
exit-latency-us = <100>;
min-residency-us = <250>;
wakeup-latency-us = <130>;
};
CLUSTER_NONRET_1: cluster-nonretentive-1 {
compatible = "riscv,idle-state";
riscv,sbi-suspend-param = <0x91000010>;
local-timer-stop;
entry-latency-us = <600>;
exit-latency-us = <1100>;
min-residency-us = <2700>;
wakeup-latency-us = <1500>;
};
};
};
// Example 4 - Qualcomm SPC
idle-states {
cpu_spc: cpu-spc {
compatible = "qcom,idle-state-spc", "arm,idle-state";
entry-latency-us = <150>;
exit-latency-us = <200>;
min-residency-us = <2000>;
};
};
...