264 lines
7.3 KiB
YAML
264 lines
7.3 KiB
YAML
# SPDX-License-Identifier: GPL-2.0
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%YAML 1.2
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---
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$id: http://devicetree.org/schemas/arm/psci.yaml#
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$schema: http://devicetree.org/meta-schemas/core.yaml#
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title: Power State Coordination Interface (PSCI)
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maintainers:
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- Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
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description: |+
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Firmware implementing the PSCI functions described in ARM document number
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ARM DEN 0022A ("Power State Coordination Interface System Software on ARM
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processors") can be used by Linux to initiate various CPU-centric power
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operations.
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Issue A of the specification describes functions for CPU suspend, hotplug
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and migration of secure software.
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Functions are invoked by trapping to the privilege level of the PSCI
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firmware (specified as part of the binding below) and passing arguments
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in a manner similar to that specified by AAPCS:
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r0 => 32-bit Function ID / return value
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{r1 - r3} => Parameters
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Note that the immediate field of the trapping instruction must be set
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to #0.
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[2] Power State Coordination Interface (PSCI) specification
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http://infocenter.arm.com/help/topic/com.arm.doc.den0022c/DEN0022C_Power_State_Coordination_Interface.pdf
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properties:
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$nodename:
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const: psci
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compatible:
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oneOf:
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- description:
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For implementations complying to PSCI versions prior to 0.2.
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const: arm,psci
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- description:
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For implementations complying to PSCI 0.2.
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Function IDs are not required and should be ignored by an OS with
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PSCI 0.2 support, but are permitted to be present for compatibility
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with existing software when "arm,psci" is later in the compatible
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list.
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minItems: 1
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items:
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- const: arm,psci-0.2
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- const: arm,psci
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- description:
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For implementations complying to PSCI 1.0.
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PSCI 1.0 is backward compatible with PSCI 0.2 with minor
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specification updates, as defined in the PSCI specification[2].
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minItems: 1
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items:
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- const: arm,psci-1.0
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- const: arm,psci-0.2
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- const: arm,psci
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method:
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description: The method of calling the PSCI firmware.
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$ref: /schemas/types.yaml#/definitions/string-array
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enum:
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- smc
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# HVC #0, with the register assignments specified in this binding.
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- hvc
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cpu_suspend:
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$ref: /schemas/types.yaml#/definitions/uint32
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description: Function ID for CPU_SUSPEND operation
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cpu_off:
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$ref: /schemas/types.yaml#/definitions/uint32
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description: Function ID for CPU_OFF operation
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cpu_on:
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$ref: /schemas/types.yaml#/definitions/uint32
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description: Function ID for CPU_ON operation
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migrate:
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$ref: /schemas/types.yaml#/definitions/uint32
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description: Function ID for MIGRATE operation
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arm,psci-suspend-param:
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$ref: /schemas/types.yaml#/definitions/uint32
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description: |
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power_state parameter to pass to the PSCI suspend call.
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Device tree nodes that require usage of PSCI CPU_SUSPEND function (ie
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idle state nodes with entry-method property is set to "psci", as per
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bindings in [1]) must specify this property.
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[1] Kernel documentation - ARM idle states bindings
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Documentation/devicetree/bindings/cpu/idle-states.yaml
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patternProperties:
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"^power-domain-":
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$ref: /schemas/power/power-domain.yaml#
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type: object
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description: |
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ARM systems can have multiple cores, sometimes in an hierarchical
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arrangement. This often, but not always, maps directly to the processor
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power topology of the system. Individual nodes in a topology have their
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own specific power states and can be better represented hierarchically.
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For these cases, the definitions of the idle states for the CPUs and the
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CPU topology, must conform to the binding in [3]. The idle states
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themselves must conform to the binding in [4] and must specify the
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arm,psci-suspend-param property.
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It should also be noted that, in PSCI firmware v1.0 the OS-Initiated
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(OSI) CPU suspend mode is introduced. Using a hierarchical representation
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helps to implement support for OSI mode and OS implementations may choose
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to mandate it.
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[3] Documentation/devicetree/bindings/power/power-domain.yaml
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[4] Documentation/devicetree/bindings/power/domain-idle-state.yaml
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required:
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- compatible
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- method
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allOf:
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- if:
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properties:
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compatible:
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contains:
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const: arm,psci
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then:
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required:
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- cpu_off
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- cpu_on
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additionalProperties: false
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examples:
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- |+
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// Case 1: PSCI v0.1 only.
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psci {
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compatible = "arm,psci";
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method = "smc";
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cpu_suspend = <0x95c10000>;
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cpu_off = <0x95c10001>;
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cpu_on = <0x95c10002>;
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migrate = <0x95c10003>;
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};
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- |+
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// Case 2: PSCI v0.2 only
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psci {
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compatible = "arm,psci-0.2";
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method = "smc";
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};
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- |+
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// Case 3: PSCI v0.2 and PSCI v0.1.
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/*
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* A DTB may provide IDs for use by kernels without PSCI 0.2 support,
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* enabling firmware and hypervisors to support existing and new kernels.
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* These IDs will be ignored by kernels with PSCI 0.2 support, which will
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* use the standard PSCI 0.2 IDs exclusively.
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*/
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psci {
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compatible = "arm,psci-0.2", "arm,psci";
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method = "hvc";
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cpu_on = <0x95c10002>;
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cpu_off = <0x95c10001>;
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};
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- |+
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// Case 4: CPUs and CPU idle states described using the hierarchical model.
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cpus {
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#size-cells = <0>;
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#address-cells = <1>;
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CPU0: cpu@0 {
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device_type = "cpu";
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compatible = "arm,cortex-a53";
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reg = <0x0>;
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enable-method = "psci";
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power-domains = <&CPU_PD0>;
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power-domain-names = "psci";
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};
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CPU1: cpu@1 {
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device_type = "cpu";
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compatible = "arm,cortex-a53";
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reg = <0x100>;
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enable-method = "psci";
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power-domains = <&CPU_PD1>;
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power-domain-names = "psci";
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};
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idle-states {
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CPU_PWRDN: cpu-power-down {
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compatible = "arm,idle-state";
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arm,psci-suspend-param = <0x0000001>;
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entry-latency-us = <10>;
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exit-latency-us = <10>;
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min-residency-us = <100>;
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};
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};
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domain-idle-states {
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CLUSTER_RET: cluster-retention {
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compatible = "domain-idle-state";
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arm,psci-suspend-param = <0x1000011>;
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entry-latency-us = <500>;
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exit-latency-us = <500>;
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min-residency-us = <2000>;
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};
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CLUSTER_PWRDN: cluster-power-down {
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compatible = "domain-idle-state";
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arm,psci-suspend-param = <0x1000031>;
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entry-latency-us = <2000>;
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exit-latency-us = <2000>;
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min-residency-us = <6000>;
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};
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};
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};
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psci {
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compatible = "arm,psci-1.0";
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method = "smc";
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CPU_PD0: power-domain-cpu0 {
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#power-domain-cells = <0>;
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domain-idle-states = <&CPU_PWRDN>;
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power-domains = <&CLUSTER_PD>;
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};
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CPU_PD1: power-domain-cpu1 {
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#power-domain-cells = <0>;
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domain-idle-states = <&CPU_PWRDN>;
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power-domains = <&CLUSTER_PD>;
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};
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CLUSTER_PD: power-domain-cluster {
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#power-domain-cells = <0>;
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domain-idle-states = <&CLUSTER_RET>, <&CLUSTER_PWRDN>;
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};
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};
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...
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