| Message ID | 1392128273-8614-4-git-send-email-lorenzo.pieralisi@arm.com |
|---|---|
| State | Superseded, archived |
| Headers | show |
Hi Lorenzo, This patch series looks nice and explains the ARM C state DT bindings clearly. Couples of thoughts below. On 2/11/14, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> wrote: > ARM based platforms implement a variety of power management schemes that > allow processors to enter idle states at run-time. > The parameters defining these idle states vary on a per-platform basis > forcing > the OS to hardcode the state parameters in platform specific static tables > whose size grows as the number of platforms supported in the kernel > increases > and hampers device drivers standardization. > > Therefore, this patch aims at standardizing idle state device tree bindings > for > ARM platforms. Bindings define idle state parameters inclusive of entry > methods > and state latencies, to allow operating systems to retrieve the > configuration > entries from the device tree and initialize the related power management > drivers, paving the way for common code in the kernel to deal with idle > states and removing the need for static data in current and previous kernel > versions. > > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > --- > Documentation/devicetree/bindings/arm/cpus.txt | 10 + > Documentation/devicetree/bindings/arm/idle-states.txt | 690 ++++++++++ > 2 files changed, 700 insertions(+) > > diff --git a/Documentation/devicetree/bindings/arm/cpus.txt > b/Documentation/devicetree/bindings/arm/cpus.txt > index 9130435..fb7f008 100644 > --- a/Documentation/devicetree/bindings/arm/cpus.txt > +++ b/Documentation/devicetree/bindings/arm/cpus.txt > @@ -191,6 +191,13 @@ nodes to be present and contain the properties > described below. > property identifying a 64-bit zero-initialised > memory location. > > + - cpu-idle-states > + Usage: Optional > + Value type: <prop-encoded-array> > + Definition: > + # List of phandles to cpu idle state nodes supported > + by this cpu [1]. > + > Example 1 (dual-cluster big.LITTLE system 32-bit): > > cpus { > @@ -382,3 +389,6 @@ cpus { > cpu-release-addr = <0 0x20000000>; > }; > }; > + > +[1] ARM Linux kernel documentation - idle state bindings > + Documentation/devicetree/bindings/arm/idle-states.txt > diff --git a/Documentation/devicetree/bindings/arm/idle-states.txt > b/Documentation/devicetree/bindings/arm/idle-states.txt > new file mode 100644 > index 0000000..f155e70 > --- /dev/null > +++ b/Documentation/devicetree/bindings/arm/idle-states.txt > @@ -0,0 +1,690 @@ > +========================================== > +ARM idle states binding description > +========================================== > + > +========================================== > +1 - Introduction > +========================================== > + > +ARM 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 OSPM 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. > + > +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: > + > +1 - Running > +2 - Idle_standby > +3 - Idle_retention > +4 - Sleep > +5 - Off > + > +ARM platforms implement the power states specified in the SBSA through > power > +management schemes that allow an OS PM implementation to put the processor > in > +different idle states (which include states 1 to 4 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 (eg entry latency) are platform specific and need to > be > +characterized with bindings that provide the required information to OSPM > +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. > + > +=========================================== > +2 - cpu-idle-states node > +=========================================== > + > +ARM processor idle states are defined within the cpu-idle-states node, > which is > +a direct child of the cpus node and provides a container where the > processor > +states, defined as device tree nodes, are listed. > + > +- cpu-idle-states node > + > + Usage: Optional - On ARM systems, 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 a cpu-idle-states node is not > + required. > + > + Description: cpu-idle-states node is a container node, where its > + subnodes describe the CPU idle states. > + > + Node name must be "cpu-idle-states". > + > + The cpu-idle-states node's parent node must be the cpus node. > + > + The cpu-idle-states node's child nodes can be: > + > + - one or more state nodes > + > + Any other configuration is considered invalid. > + > +The nodes describing the idle states (state) can only be defined within > the > +cpu-idle-states node. > + > +Any other configuration is consider invalid and therefore must be ignored. > + > +=========================================== > +2 - state node > +=========================================== > + > +A state node represents an idle state description and must be defined as > +follows: > + > +- state node > + > + Description: must be child of either the cpu-idle-states node or > + a state node. > + > + The state node name shall be "stateN", where N = {0, 1, ...} is > + the node number; state nodes which are siblings within a single common > + parent node must be given a unique and sequential N value, starting > + from 0. > + > + A state node can contain state child nodes. A state node with > + children represents a hierarchical state, which is a superset of > + the child states. Hierarchical states require all CPUs on which > + they are valid to request the state in order for it to be entered. > + > + A state node defines the following properties: > + > + - compatible > + Usage: Required > + Value type: <stringlist> > + Definition: Must be "arm,cpu-idle-state". > + > + - index > + Usage: Required > + Value type: <u32> > + Definition: It represents an idle state index, starting from 2. > + Index 0 represents the processor state "running" > + and index 1 represents processor mode > + "idle_standby", entered by executing a wfi > + instruction (SBSA,[3]); indexes 0 and 1 are > + standard ARM states that need not be described. > + > + - entry-method > + Usage: Required > + Value type: <stringlist> > + Definition: Describes the method by which a CPU enters the > + idle state. This property is required and must be > + one of: > + > + - "arm,psci-cpu-suspend" > + ARM PSCI firmware interface, CPU suspend > + method[2]. > + > + - "[vendor],[method]" > + An implementation dependent string with > + format "vendor,method", where vendor is a string > + denoting the name of the manufacturer and > + method is a string specifying the mechanism > + used to enter the idle state. > + > + - power-state > + Usage: See definition. > + Value type: <u32> > + Definition: Depends on the entry-method property value. > + If entry-method is "arm,psci-cpu-suspend": > + # Property is required and represents > + psci-power-state parameter. Please refer to > + [2] for PSCI bindings definition. > + > + - entry-latency > + Usage: Required > + Value type: <prop-encoded-array> > + Definition: u32 value representing worst case latency > + in microseconds required to enter the idle state. I liked your V2 version of OPP based latency more. However in this way also latency supplied can correspond to max OPP and based on the current OPP, the cpuidle driver can compute the new latency proportionately. In case of frequency this can be linear but may not be linear for residency. > + > + - exit-latency > + Usage: Required > + Value type: <prop-encoded-array> > + Definition: u32 value representing worst case latency > + in microseconds required to exit the idle state. > + > + - min-residency > + Usage: Required > + Value type: <prop-encoded-array> > + Definition: u32 value representing time in microseconds > + required for the CPU to be in the idle state to > + make up for the dynamic power consumed to > + enter/exit the idle state in order to break even > + in terms of power consumption compared to idle > + state index 1 (idle_standby). > + > + - power-domains > + Usage: Optional > + Value type: <prop-encoded-array> > + Definition: List of power domain specifiers ([1]) describing > + the power domains that are affected by the idle > + state entry. I can see power-domains used in 2 places. First in C state definitions and second in cpu node cache descriptions. I am not sure but if possible than this can be put in one place. > + > + - cache-state-retained > + Usage: See definition > + Value type: <none> > + Definition: if present cache memory is retained on power down, > + otherwise it is lost. Can the DT bindings support both retained and non-retained with different C states? The example shown does not use the retained flag. I guess than many combinations are possible. Processor retained, cache non-retained = C state 2 Processor non retained , cache retained = C state 3 Processor non retained, cache non retained = C state 4 > + > + - processor-state-retained > + Usage: See definition > + Value type: <none> > + Definition: if present CPU processor logic is retained on > + power down, otherwise it is lost. > + > +=========================================== > +3 - Examples > +=========================================== > + > +Example 1 (ARM 64-bit, 16-cpu system): > + > +pd_clusters: power-domain-clusters@80002000 { > + compatible = "arm,power-controller"; > + reg = <0x0 0x80002000 0x0 0x1000>; > + #power-domain-cells = <1>; > + #address-cells = <2>; > + #size-cells = <2>; > + > + pd_cores: power-domain-cores@80000000 { > + compatible = "arm,power-controller"; > + reg = <0x0 0x80000000 0x0 0x1000>; > + #power-domain-cells = <1>; > + }; > +}; > + > +cpus { > + #size-cells = <0>; > + #address-cells = <2>; > + > + cpu-idle-states { > + > + STATE0: state0 { > + compatible = "arm,cpu-idle-state"; > + index = <3>; > + entry-method = "arm,psci-cpu-suspend"; > + psci-power-state = <0x1010000>; > + entry-latency = <500>; > + exit-latency = <1000>; > + min-residency = <2500>; > + power-domains = <&pd_clusters 0>; > + STATE0_1: state0 { > + compatible = "arm,cpu-idle-state"; > + index = <2>; > + entry-method = "arm,psci-cpu-suspend"; > + psci-power-state = <0x0010000>; > + entry-latency = <200>; > + exit-latency = <400>; > + min-residency = <300>; > + power-domains = <&pd_cores 0>, > + <&pd_cores 1>, > + <&pd_cores 2>, > + <&pd_cores 3>, > + <&pd_cores 4>, > + <&pd_cores 5>, > + <&pd_cores 6>, > + <&pd_cores 7>; > + }; > + }; > + > + STATE1: state1 { > + compatible = "arm,cpu-idle-state"; > + index = <3>; > + entry-method = "arm,psci-cpu-suspend"; > + psci-power-state = <0x1010000>; > + entry-latency = <1000>; > + exit-latency = <3000>; > + min-residency = <6500>; > + power-domains = <&pd_clusters 1>; > + STATE1_0: state0 { > + compatible = "arm,cpu-idle-state"; > + index = <2>; > + entry-method = "arm,psci-cpu-suspend"; > + psci-power-state = <0x0010000>; > + entry-latency = <200>; > + exit-latency = <400>; > + min-residency = <500>; > + power-domains = <&pd_cores 8>, > + <&pd_cores 9>, > + <&pd_cores 10>, > + <&pd_cores 11>, > + <&pd_cores 12>, > + <&pd_cores 13>, > + <&pd_cores 14>, > + <&pd_cores 15>; > + }; > + }; > + }; > + > + CPU0: cpu@0 { > + device_type = "cpu"; > + compatible = "arm,cortex-a57"; > + reg = <0x0 0x0>; > + enable-method = "psci"; > + next-level-cache = <&L1_0>; > + cpu-idle-states = <&STATE0_1 &STATE0>; > + L1_0: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_0>; > + power-domain = <&pd_cores 0>; > + }; > + L2_0: l2-cache { > + compatible = "arm,arch-cache"; > + power-domain = <&pd_clusters 0>; > + }; > + }; > + > + CPU1: cpu@1 { > + device_type = "cpu"; > + compatible = "arm,cortex-a57"; > + reg = <0x0 0x1>; > + enable-method = "psci"; > + next-level-cache = <&L1_1>; > + cpu-idle-states = <&STATE0_1 &STATE0>; > + L1_1: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_0>; > + power-domain = <&pd_cores 1>; > + }; > + }; > + > + CPU2: cpu@100 { > + device_type = "cpu"; > + compatible = "arm,cortex-a57"; > + reg = <0x0 0x100>; > + enable-method = "psci"; > + next-level-cache = <&L1_2>; > + cpu-idle-states = <&STATE0_1 &STATE0>; > + L1_2: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_0>; > + power-domain = <&pd_cores 2>; > + }; > + }; > + > + CPU3: cpu@101 { > + device_type = "cpu"; > + compatible = "arm,cortex-a57"; > + reg = <0x0 0x101>; > + enable-method = "psci"; > + next-level-cache = <&L1_3>; > + cpu-idle-states = <&STATE0_1 &STATE0>; > + L1_3: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_0>; > + power-domain = <&pd_cores 3>; > + }; > + }; > + > + CPU4: cpu@10000 { > + device_type = "cpu"; > + compatible = "arm,cortex-a57"; > + reg = <0x0 0x10000>; > + enable-method = "psci"; > + next-level-cache = <&L1_4>; > + cpu-idle-states = <&STATE0_1 &STATE0>; > + L1_4: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_0>; > + power-domain = <&pd_cores 4>; > + }; > + }; > + > + CPU5: cpu@10001 { > + device_type = "cpu"; > + compatible = "arm,cortex-a57"; > + reg = <0x0 0x10001>; > + enable-method = "psci"; > + next-level-cache = <&L1_5>; > + cpu-idle-states = <&STATE0_1 &STATE0>; > + L1_5: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_0>; > + power-domain = <&pd_cores 5>; > + }; > + }; > + > + CPU6: cpu@10100 { > + device_type = "cpu"; > + compatible = "arm,cortex-a57"; > + reg = <0x0 0x10100>; > + enable-method = "psci"; > + next-level-cache = <&L1_6>; > + cpu-idle-states = <&STATE0_1 &STATE0>; > + L1_6: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_0>; > + power-domain = <&pd_cores 6>; > + }; > + }; > + > + CPU7: cpu@10101 { > + device_type = "cpu"; > + compatible = "arm,cortex-a57"; > + reg = <0x0 0x10101>; > + enable-method = "psci"; > + next-level-cache = <&L1_7>; > + cpu-idle-states = <&STATE0_1 &STATE0>; > + L1_7: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_0>; > + power-domain = <&pd_cores 7>; > + }; > + }; > + > + CPU8: cpu@100000000 { > + device_type = "cpu"; > + compatible = "arm,cortex-a53"; > + reg = <0x1 0x0>; > + enable-method = "psci"; > + next-level-cache = <&L1_8>; > + cpu-idle-states = <&STATE1_0 &STATE1>; > + L1_8: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_1>; > + power-domain = <&pd_cores 8>; > + }; > + L2_1: l2-cache { > + compatible = "arm,arch-cache"; > + power-domain = <&pd_clusters 1>; > + }; > + }; > + > + CPU9: cpu@100000001 { > + device_type = "cpu"; > + compatible = "arm,cortex-a53"; > + reg = <0x1 0x1>; > + enable-method = "psci"; > + next-level-cache = <&L1_9>; > + cpu-idle-states = <&STATE1_0 &STATE1>; > + L1_9: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_1>; > + power-domain = <&pd_cores 9>; > + }; > + }; > + > + CPU10: cpu@100000100 { > + device_type = "cpu"; > + compatible = "arm,cortex-a53"; > + reg = <0x1 0x100>; > + enable-method = "psci"; > + next-level-cache = <&L1_10>; > + cpu-idle-states = <&STATE1_0 &STATE1>; > + L1_10: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_1>; > + power-domain = <&pd_cores 10>; > + }; > + }; > + > + CPU11: cpu@100000101 { > + device_type = "cpu"; > + compatible = "arm,cortex-a53"; > + reg = <0x1 0x101>; > + enable-method = "psci"; > + next-level-cache = <&L1_11>; > + cpu-idle-states = <&STATE1_0 &STATE1>; > + L1_11: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_1>; > + power-domain = <&pd_cores 11>; > + }; > + }; > + > + CPU12: cpu@100010000 { > + device_type = "cpu"; > + compatible = "arm,cortex-a53"; > + reg = <0x1 0x10000>; > + enable-method = "psci"; > + next-level-cache = <&L1_12>; > + cpu-idle-states = <&STATE1_0 &STATE1>; > + L1_12: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_1>; > + power-domain = <&pd_cores 12>; > + }; > + }; > + > + CPU13: cpu@100010001 { > + device_type = "cpu"; > + compatible = "arm,cortex-a53"; > + reg = <0x1 0x10001>; > + enable-method = "psci"; > + next-level-cache = <&L1_13>; > + cpu-idle-states = <&STATE1_0 &STATE1>; > + L1_13: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_1>; > + power-domain = <&pd_cores 13>; > + }; > + }; > + > + CPU14: cpu@100010100 { > + device_type = "cpu"; > + compatible = "arm,cortex-a53"; > + reg = <0x1 0x10100>; > + enable-method = "psci"; > + next-level-cache = <&L1_14>; > + cpu-idle-states = <&STATE1_0 &STATE1>; > + L1_14: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_1>; > + power-domain = <&pd_cores 14>; > + }; > + }; > + > + CPU15: cpu@100010101 { > + device_type = "cpu"; > + compatible = "arm,cortex-a53"; > + reg = <0x1 0x10101>; > + enable-method = "psci"; > + next-level-cache = <&L1_15>; > + cpu-idle-states = <&STATE1_0 &STATE1>; > + L1_15: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_1>; > + power-domain = <&pd_cores 15>; > + }; > + }; > +}; > + > +Example 2 (ARM 32-bit, 8-cpu system, two clusters): > + > +pd_clusters: power-domain-clusters@80002000 { > + compatible = "arm,power-controller"; > + reg = <0x80002000 0x1000>; > + #power-domain-cells = <1>; > + #address-cells = <1>; > + #size-cells = <1>; > + > + pd_cores: power-domain-cores@80000000 { > + compatible = "arm,power-controller"; > + reg = <0x80000000 0x1000>; > + #power-domain-cells = <1>; > + }; > +}; > + > +cpus { > + #size-cells = <0>; > + #address-cells = <1>; > + > + cpu-idle-states { > + > + STATE0: state0 { > + compatible = "arm,cpu-idle-state"; > + index = <3>; > + entry-method = "psci"; > + psci-power-state = <0x1010000>; > + entry-latency = <1000>; > + exit-latency = <1500>; > + min-residency = <1500>; > + power-domains = <&pd_clusters 0>; > + STATE0_1: state0 { > + compatible = "arm,cpu-idle-state"; > + index = <2>; > + entry-method = "psci"; > + psci-power-state = <0x0010000>; > + entry-latency = <400>; > + exit-latency = <500>; > + min-residency = <300>; > + power-domains = <&pd_cores 0>, > + <&pd_cores 1>, > + <&pd_cores 2>, > + <&pd_cores 3>; > + }; > + }; > + > + STATE1: state1 { > + compatible = "arm,cpu-idle-state"; > + index = <3>; > + entry-method = "psci"; > + psci-power-state = <0x1010000>; > + entry-latency = <800>; > + exit-latency = <2000>; > + min-residency = <6500>; > + power-domains = <&pd_clusters 1>; > + STATE1_0: state0 { > + compatible = "arm,cpu-idle-state"; > + index = <2>; > + entry-method = "psci"; > + psci-power-state = <0x0010000>; > + entry-latency = <300>; > + exit-latency = <500>; > + min-residency = <500>; > + power-domains = <&pd_cores 4>, > + <&pd_cores 5>, > + <&pd_cores 6>, > + <&pd_cores 7>; > + }; > + }; > + }; > + > + CPU0: cpu@0 { > + device_type = "cpu"; > + compatible = "arm,cortex-a15"; > + reg = <0x0>; > + next-level-cache = <&L1_0>; > + cpu-idle-states = <&STATE0_1 &STATE0>; > + L1_0: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_0>; > + power-domain = <&pd_cores 0>; > + }; > + L2_0: l2-cache { > + compatible = "arm,arch-cache"; > + power-domain = <&pd_clusters 0>; > + }; > + }; > + > + CPU1: cpu@1 { > + device_type = "cpu"; > + compatible = "arm,cortex-a15"; > + reg = <0x1>; > + next-level-cache = <&L1_1>; > + cpu-idle-states = <&STATE0_1 &STATE0>; > + L1_1: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_0>; > + power-domain = <&pd_cores 1>; > + }; > + }; > + > + CPU2: cpu@2 { > + device_type = "cpu"; > + compatible = "arm,cortex-a15"; > + reg = <0x2>; > + next-level-cache = <&L1_2>; > + cpu-idle-states = <&STATE0_1 &STATE0>; > + L1_2: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_0>; > + power-domain = <&pd_cores 2>; > + }; > + }; > + > + CPU3: cpu@3 { > + device_type = "cpu"; > + compatible = "arm,cortex-a15"; > + reg = <0x3>; > + next-level-cache = <&L1_3>; > + cpu-idle-states = <&STATE0_1 &STATE0>; > + L1_3: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_0>; > + power-domain = <&pd_cores 3>; > + }; > + }; > + > + CPU4: cpu@100 { > + device_type = "cpu"; > + compatible = "arm,cortex-a7"; > + reg = <0x100>; > + next-level-cache = <&L1_4>; > + cpu-idle-states = <&STATE1_0 &STATE1>; > + L1_4: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_1>; > + power-domain = <&pd_cores 4>; > + }; > + L2_1: l2-cache { > + compatible = "arm,arch-cache"; > + power-domain = <&pd_clusters 1>; > + }; > + }; > + > + CPU5: cpu@101 { > + device_type = "cpu"; > + compatible = "arm,cortex-a7"; > + reg = <0x101>; > + next-level-cache = <&L1_5>; > + cpu-idle-states = <&STATE1_0 &STATE1>; > + L1_5: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_1>; > + power-domain = <&pd_cores 5>; > + }; > + }; > + > + CPU6: cpu@102 { > + device_type = "cpu"; > + compatible = "arm,cortex-a7"; > + reg = <0x102>; > + next-level-cache = <&L1_6>; > + cpu-idle-states = <&STATE1_0 &STATE1>; > + L1_6: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_1>; > + power-domain = <&pd_cores 6>; > + }; > + }; > + > + CPU7: cpu@103 { > + device_type = "cpu"; > + compatible = "arm,cortex-a7"; > + reg = <0x103>; > + next-level-cache = <&L1_7>; > + cpu-idle-states = <&STATE1_0 &STATE1>; > + L1_7: l1-cache { > + compatible = "arm,arch-cache"; > + next-level-cache = <&L2_1>; > + power-domain = <&pd_cores 7>; > + }; > + }; > +}; > + > +=========================================== > +4 - References > +=========================================== > + > +[1] ARM Linux Kernel documentation - power domain bindings > + Documentation/devicetree/bindings/power/power_domain.txt > + > +[2] ARM Linux Kernel documentation - PSCI bindings > + Documentation/devicetree/bindings/arm/psci.txt > + > +[3] ARM Server Base System Architecture (SBSA) > + http://infocenter.arm.com/help/index.jsp > -- > 1.8.4 > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Feb 11, 2014 at 02:17:53PM +0000, Lorenzo Pieralisi wrote: > +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: > +1 - Running > +2 - Idle_standby > +3 - Idle_retention > +4 - Sleep > +5 - Off > +ARM platforms implement the power states specified in the SBSA through power > +management schemes that allow an OS PM implementation to put the processor in > +different idle states (which include states 1 to 4 above; "off" state is not > +an idle state since it does not have wake-up capabilities, hence it is not > +considered in this document). This is explicitly talking about SBSA - is there any restriction with regard to non-SBSA systems? I can't think of any right now and this seems purely informational but it might be worth mentioning that non-SBSA systems might potentially have other states if the intention is to allow that. > +- state node > + > + Description: must be child of either the cpu-idle-states node or > + a state node. > + > + The state node name shall be "stateN", where N = {0, 1, ...} is > + the node number; state nodes which are siblings within a single common > + parent node must be given a unique and sequential N value, starting > + from 0. This came up with the CPU bindings as well but I'm really not convinced that making the naming of the nodes important is great - it's not normal for DT and it makes the usual enumeration code not work. Can we not just have a property for state number in the node instead and allow the name to be anything? It seems we even have the index property already... > + - compatible > + Usage: Required > + Value type: <stringlist> > + Definition: Must be "arm,cpu-idle-state". Do we really need this given that the location in the tree is fixed - what would we extend it with in future? > + - index > + Usage: Required > + Value type: <u32> > + Definition: It represents an idle state index, starting from 2. > + Index 0 represents the processor state "running" > + and index 1 represents processor mode > + "idle_standby", entered by executing a wfi > + instruction (SBSA,[3]); indexes 0 and 1 are > + standard ARM states that need not be described. ...but other numbers are valid. > + - entry-method > + Usage: Required > + Value type: <stringlist> > + Definition: Describes the method by which a CPU enters the > + idle state. This property is required and must be > + one of: > + > + - "arm,psci-cpu-suspend" > + ARM PSCI firmware interface, CPU suspend > + method[2]. > + > + - "[vendor],[method]" > + An implementation dependent string with > + format "vendor,method", where vendor is a string > + denoting the name of the manufacturer and > + method is a string specifying the mechanism > + used to enter the idle state. Might be worth reversing these - arm,psci-cpu-suspend is just an example of a (hopefully very widely used) vendor method. Given that everyone is supposed to be using PSCI might it even be worth making it the default and the property optional? > + - power-state > + Usage: See definition. > + Value type: <u32> > + Definition: Depends on the entry-method property value. > + If entry-method is "arm,psci-cpu-suspend": > + # Property is required and represents > + psci-power-state parameter. Please refer to > + [2] for PSCI bindings definition. Should we just have the entry method nodes define their own properties for this stuff? I guess this goes back to the comment I made on some other binding that it might be cleaner to have an explicit PSCI binding rather than put PSCI explicitly in indiidual bindings. > + - entry-latency > + Usage: Required > + Value type: <prop-encoded-array> > + Definition: u32 value representing worst case latency > + in microseconds required to enter the idle state. Why is this defined as an array? > + - cache-state-retained > + Usage: See definition > + Value type: <none> > + Definition: if present cache memory is retained on power down, > + otherwise it is lost. Might be better to define which caches? > + STATE1: state1 { > + compatible = "arm,cpu-idle-state"; Even if we stick with the node name being meaningful it'd be nice to replace the STATEN here with a meaningful state name to improve legibility.
diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt index 9130435..fb7f008 100644 --- a/Documentation/devicetree/bindings/arm/cpus.txt +++ b/Documentation/devicetree/bindings/arm/cpus.txt @@ -191,6 +191,13 @@ nodes to be present and contain the properties described below. property identifying a 64-bit zero-initialised memory location. + - cpu-idle-states + Usage: Optional + Value type: <prop-encoded-array> + Definition: + # List of phandles to cpu idle state nodes supported + by this cpu [1]. + Example 1 (dual-cluster big.LITTLE system 32-bit): cpus { @@ -382,3 +389,6 @@ cpus { cpu-release-addr = <0 0x20000000>; }; }; + +[1] ARM Linux kernel documentation - idle state bindings + Documentation/devicetree/bindings/arm/idle-states.txt diff --git a/Documentation/devicetree/bindings/arm/idle-states.txt b/Documentation/devicetree/bindings/arm/idle-states.txt new file mode 100644 index 0000000..f155e70 --- /dev/null +++ b/Documentation/devicetree/bindings/arm/idle-states.txt @@ -0,0 +1,690 @@ +========================================== +ARM idle states binding description +========================================== + +========================================== +1 - Introduction +========================================== + +ARM 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 OSPM 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. + +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: + +1 - Running +2 - Idle_standby +3 - Idle_retention +4 - Sleep +5 - Off + +ARM platforms implement the power states specified in the SBSA through power +management schemes that allow an OS PM implementation to put the processor in +different idle states (which include states 1 to 4 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 (eg entry latency) are platform specific and need to be +characterized with bindings that provide the required information to OSPM +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. + +=========================================== +2 - cpu-idle-states node +=========================================== + +ARM processor idle states are defined within the cpu-idle-states node, which is +a direct child of the cpus node and provides a container where the processor +states, defined as device tree nodes, are listed. + +- cpu-idle-states node + + Usage: Optional - On ARM systems, 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 a cpu-idle-states node is not + required. + + Description: cpu-idle-states node is a container node, where its + subnodes describe the CPU idle states. + + Node name must be "cpu-idle-states". + + The cpu-idle-states node's parent node must be the cpus node. + + The cpu-idle-states node's child nodes can be: + + - one or more state nodes + + Any other configuration is considered invalid. + +The nodes describing the idle states (state) can only be defined within the +cpu-idle-states node. + +Any other configuration is consider invalid and therefore must be ignored. + +=========================================== +2 - state node +=========================================== + +A state node represents an idle state description and must be defined as +follows: + +- state node + + Description: must be child of either the cpu-idle-states node or + a state node. + + The state node name shall be "stateN", where N = {0, 1, ...} is + the node number; state nodes which are siblings within a single common + parent node must be given a unique and sequential N value, starting + from 0. + + A state node can contain state child nodes. A state node with + children represents a hierarchical state, which is a superset of + the child states. Hierarchical states require all CPUs on which + they are valid to request the state in order for it to be entered. + + A state node defines the following properties: + + - compatible + Usage: Required + Value type: <stringlist> + Definition: Must be "arm,cpu-idle-state". + + - index + Usage: Required + Value type: <u32> + Definition: It represents an idle state index, starting from 2. + Index 0 represents the processor state "running" + and index 1 represents processor mode + "idle_standby", entered by executing a wfi + instruction (SBSA,[3]); indexes 0 and 1 are + standard ARM states that need not be described. + + - entry-method + Usage: Required + Value type: <stringlist> + Definition: Describes the method by which a CPU enters the + idle state. This property is required and must be + one of: + + - "arm,psci-cpu-suspend" + ARM PSCI firmware interface, CPU suspend + method[2]. + + - "[vendor],[method]" + An implementation dependent string with + format "vendor,method", where vendor is a string + denoting the name of the manufacturer and + method is a string specifying the mechanism + used to enter the idle state. + + - power-state + Usage: See definition. + Value type: <u32> + Definition: Depends on the entry-method property value. + If entry-method is "arm,psci-cpu-suspend": + # Property is required and represents + psci-power-state parameter. Please refer to + [2] for PSCI bindings definition. + + - entry-latency + Usage: Required + Value type: <prop-encoded-array> + Definition: u32 value representing worst case latency + in microseconds required to enter the idle state. + + - exit-latency + Usage: Required + Value type: <prop-encoded-array> + Definition: u32 value representing worst case latency + in microseconds required to exit the idle state. + + - min-residency + Usage: Required + Value type: <prop-encoded-array> + Definition: u32 value representing time in microseconds + required for the CPU to be in the idle state to + make up for the dynamic power consumed to + enter/exit the idle state in order to break even + in terms of power consumption compared to idle + state index 1 (idle_standby). + + - power-domains + Usage: Optional + Value type: <prop-encoded-array> + Definition: List of power domain specifiers ([1]) describing + the power domains that are affected by the idle + state entry. + + - cache-state-retained + Usage: See definition + Value type: <none> + Definition: if present cache memory is retained on power down, + otherwise it is lost. + + - processor-state-retained + Usage: See definition + Value type: <none> + Definition: if present CPU processor logic is retained on + power down, otherwise it is lost. + +=========================================== +3 - Examples +=========================================== + +Example 1 (ARM 64-bit, 16-cpu system): + +pd_clusters: power-domain-clusters@80002000 { + compatible = "arm,power-controller"; + reg = <0x0 0x80002000 0x0 0x1000>; + #power-domain-cells = <1>; + #address-cells = <2>; + #size-cells = <2>; + + pd_cores: power-domain-cores@80000000 { + compatible = "arm,power-controller"; + reg = <0x0 0x80000000 0x0 0x1000>; + #power-domain-cells = <1>; + }; +}; + +cpus { + #size-cells = <0>; + #address-cells = <2>; + + cpu-idle-states { + + STATE0: state0 { + compatible = "arm,cpu-idle-state"; + index = <3>; + entry-method = "arm,psci-cpu-suspend"; + psci-power-state = <0x1010000>; + entry-latency = <500>; + exit-latency = <1000>; + min-residency = <2500>; + power-domains = <&pd_clusters 0>; + STATE0_1: state0 { + compatible = "arm,cpu-idle-state"; + index = <2>; + entry-method = "arm,psci-cpu-suspend"; + psci-power-state = <0x0010000>; + entry-latency = <200>; + exit-latency = <400>; + min-residency = <300>; + power-domains = <&pd_cores 0>, + <&pd_cores 1>, + <&pd_cores 2>, + <&pd_cores 3>, + <&pd_cores 4>, + <&pd_cores 5>, + <&pd_cores 6>, + <&pd_cores 7>; + }; + }; + + STATE1: state1 { + compatible = "arm,cpu-idle-state"; + index = <3>; + entry-method = "arm,psci-cpu-suspend"; + psci-power-state = <0x1010000>; + entry-latency = <1000>; + exit-latency = <3000>; + min-residency = <6500>; + power-domains = <&pd_clusters 1>; + STATE1_0: state0 { + compatible = "arm,cpu-idle-state"; + index = <2>; + entry-method = "arm,psci-cpu-suspend"; + psci-power-state = <0x0010000>; + entry-latency = <200>; + exit-latency = <400>; + min-residency = <500>; + power-domains = <&pd_cores 8>, + <&pd_cores 9>, + <&pd_cores 10>, + <&pd_cores 11>, + <&pd_cores 12>, + <&pd_cores 13>, + <&pd_cores 14>, + <&pd_cores 15>; + }; + }; + }; + + CPU0: cpu@0 { + device_type = "cpu"; + compatible = "arm,cortex-a57"; + reg = <0x0 0x0>; + enable-method = "psci"; + next-level-cache = <&L1_0>; + cpu-idle-states = <&STATE0_1 &STATE0>; + L1_0: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_0>; + power-domain = <&pd_cores 0>; + }; + L2_0: l2-cache { + compatible = "arm,arch-cache"; + power-domain = <&pd_clusters 0>; + }; + }; + + CPU1: cpu@1 { + device_type = "cpu"; + compatible = "arm,cortex-a57"; + reg = <0x0 0x1>; + enable-method = "psci"; + next-level-cache = <&L1_1>; + cpu-idle-states = <&STATE0_1 &STATE0>; + L1_1: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_0>; + power-domain = <&pd_cores 1>; + }; + }; + + CPU2: cpu@100 { + device_type = "cpu"; + compatible = "arm,cortex-a57"; + reg = <0x0 0x100>; + enable-method = "psci"; + next-level-cache = <&L1_2>; + cpu-idle-states = <&STATE0_1 &STATE0>; + L1_2: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_0>; + power-domain = <&pd_cores 2>; + }; + }; + + CPU3: cpu@101 { + device_type = "cpu"; + compatible = "arm,cortex-a57"; + reg = <0x0 0x101>; + enable-method = "psci"; + next-level-cache = <&L1_3>; + cpu-idle-states = <&STATE0_1 &STATE0>; + L1_3: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_0>; + power-domain = <&pd_cores 3>; + }; + }; + + CPU4: cpu@10000 { + device_type = "cpu"; + compatible = "arm,cortex-a57"; + reg = <0x0 0x10000>; + enable-method = "psci"; + next-level-cache = <&L1_4>; + cpu-idle-states = <&STATE0_1 &STATE0>; + L1_4: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_0>; + power-domain = <&pd_cores 4>; + }; + }; + + CPU5: cpu@10001 { + device_type = "cpu"; + compatible = "arm,cortex-a57"; + reg = <0x0 0x10001>; + enable-method = "psci"; + next-level-cache = <&L1_5>; + cpu-idle-states = <&STATE0_1 &STATE0>; + L1_5: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_0>; + power-domain = <&pd_cores 5>; + }; + }; + + CPU6: cpu@10100 { + device_type = "cpu"; + compatible = "arm,cortex-a57"; + reg = <0x0 0x10100>; + enable-method = "psci"; + next-level-cache = <&L1_6>; + cpu-idle-states = <&STATE0_1 &STATE0>; + L1_6: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_0>; + power-domain = <&pd_cores 6>; + }; + }; + + CPU7: cpu@10101 { + device_type = "cpu"; + compatible = "arm,cortex-a57"; + reg = <0x0 0x10101>; + enable-method = "psci"; + next-level-cache = <&L1_7>; + cpu-idle-states = <&STATE0_1 &STATE0>; + L1_7: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_0>; + power-domain = <&pd_cores 7>; + }; + }; + + CPU8: cpu@100000000 { + device_type = "cpu"; + compatible = "arm,cortex-a53"; + reg = <0x1 0x0>; + enable-method = "psci"; + next-level-cache = <&L1_8>; + cpu-idle-states = <&STATE1_0 &STATE1>; + L1_8: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_1>; + power-domain = <&pd_cores 8>; + }; + L2_1: l2-cache { + compatible = "arm,arch-cache"; + power-domain = <&pd_clusters 1>; + }; + }; + + CPU9: cpu@100000001 { + device_type = "cpu"; + compatible = "arm,cortex-a53"; + reg = <0x1 0x1>; + enable-method = "psci"; + next-level-cache = <&L1_9>; + cpu-idle-states = <&STATE1_0 &STATE1>; + L1_9: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_1>; + power-domain = <&pd_cores 9>; + }; + }; + + CPU10: cpu@100000100 { + device_type = "cpu"; + compatible = "arm,cortex-a53"; + reg = <0x1 0x100>; + enable-method = "psci"; + next-level-cache = <&L1_10>; + cpu-idle-states = <&STATE1_0 &STATE1>; + L1_10: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_1>; + power-domain = <&pd_cores 10>; + }; + }; + + CPU11: cpu@100000101 { + device_type = "cpu"; + compatible = "arm,cortex-a53"; + reg = <0x1 0x101>; + enable-method = "psci"; + next-level-cache = <&L1_11>; + cpu-idle-states = <&STATE1_0 &STATE1>; + L1_11: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_1>; + power-domain = <&pd_cores 11>; + }; + }; + + CPU12: cpu@100010000 { + device_type = "cpu"; + compatible = "arm,cortex-a53"; + reg = <0x1 0x10000>; + enable-method = "psci"; + next-level-cache = <&L1_12>; + cpu-idle-states = <&STATE1_0 &STATE1>; + L1_12: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_1>; + power-domain = <&pd_cores 12>; + }; + }; + + CPU13: cpu@100010001 { + device_type = "cpu"; + compatible = "arm,cortex-a53"; + reg = <0x1 0x10001>; + enable-method = "psci"; + next-level-cache = <&L1_13>; + cpu-idle-states = <&STATE1_0 &STATE1>; + L1_13: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_1>; + power-domain = <&pd_cores 13>; + }; + }; + + CPU14: cpu@100010100 { + device_type = "cpu"; + compatible = "arm,cortex-a53"; + reg = <0x1 0x10100>; + enable-method = "psci"; + next-level-cache = <&L1_14>; + cpu-idle-states = <&STATE1_0 &STATE1>; + L1_14: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_1>; + power-domain = <&pd_cores 14>; + }; + }; + + CPU15: cpu@100010101 { + device_type = "cpu"; + compatible = "arm,cortex-a53"; + reg = <0x1 0x10101>; + enable-method = "psci"; + next-level-cache = <&L1_15>; + cpu-idle-states = <&STATE1_0 &STATE1>; + L1_15: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_1>; + power-domain = <&pd_cores 15>; + }; + }; +}; + +Example 2 (ARM 32-bit, 8-cpu system, two clusters): + +pd_clusters: power-domain-clusters@80002000 { + compatible = "arm,power-controller"; + reg = <0x80002000 0x1000>; + #power-domain-cells = <1>; + #address-cells = <1>; + #size-cells = <1>; + + pd_cores: power-domain-cores@80000000 { + compatible = "arm,power-controller"; + reg = <0x80000000 0x1000>; + #power-domain-cells = <1>; + }; +}; + +cpus { + #size-cells = <0>; + #address-cells = <1>; + + cpu-idle-states { + + STATE0: state0 { + compatible = "arm,cpu-idle-state"; + index = <3>; + entry-method = "psci"; + psci-power-state = <0x1010000>; + entry-latency = <1000>; + exit-latency = <1500>; + min-residency = <1500>; + power-domains = <&pd_clusters 0>; + STATE0_1: state0 { + compatible = "arm,cpu-idle-state"; + index = <2>; + entry-method = "psci"; + psci-power-state = <0x0010000>; + entry-latency = <400>; + exit-latency = <500>; + min-residency = <300>; + power-domains = <&pd_cores 0>, + <&pd_cores 1>, + <&pd_cores 2>, + <&pd_cores 3>; + }; + }; + + STATE1: state1 { + compatible = "arm,cpu-idle-state"; + index = <3>; + entry-method = "psci"; + psci-power-state = <0x1010000>; + entry-latency = <800>; + exit-latency = <2000>; + min-residency = <6500>; + power-domains = <&pd_clusters 1>; + STATE1_0: state0 { + compatible = "arm,cpu-idle-state"; + index = <2>; + entry-method = "psci"; + psci-power-state = <0x0010000>; + entry-latency = <300>; + exit-latency = <500>; + min-residency = <500>; + power-domains = <&pd_cores 4>, + <&pd_cores 5>, + <&pd_cores 6>, + <&pd_cores 7>; + }; + }; + }; + + CPU0: cpu@0 { + device_type = "cpu"; + compatible = "arm,cortex-a15"; + reg = <0x0>; + next-level-cache = <&L1_0>; + cpu-idle-states = <&STATE0_1 &STATE0>; + L1_0: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_0>; + power-domain = <&pd_cores 0>; + }; + L2_0: l2-cache { + compatible = "arm,arch-cache"; + power-domain = <&pd_clusters 0>; + }; + }; + + CPU1: cpu@1 { + device_type = "cpu"; + compatible = "arm,cortex-a15"; + reg = <0x1>; + next-level-cache = <&L1_1>; + cpu-idle-states = <&STATE0_1 &STATE0>; + L1_1: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_0>; + power-domain = <&pd_cores 1>; + }; + }; + + CPU2: cpu@2 { + device_type = "cpu"; + compatible = "arm,cortex-a15"; + reg = <0x2>; + next-level-cache = <&L1_2>; + cpu-idle-states = <&STATE0_1 &STATE0>; + L1_2: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_0>; + power-domain = <&pd_cores 2>; + }; + }; + + CPU3: cpu@3 { + device_type = "cpu"; + compatible = "arm,cortex-a15"; + reg = <0x3>; + next-level-cache = <&L1_3>; + cpu-idle-states = <&STATE0_1 &STATE0>; + L1_3: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_0>; + power-domain = <&pd_cores 3>; + }; + }; + + CPU4: cpu@100 { + device_type = "cpu"; + compatible = "arm,cortex-a7"; + reg = <0x100>; + next-level-cache = <&L1_4>; + cpu-idle-states = <&STATE1_0 &STATE1>; + L1_4: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_1>; + power-domain = <&pd_cores 4>; + }; + L2_1: l2-cache { + compatible = "arm,arch-cache"; + power-domain = <&pd_clusters 1>; + }; + }; + + CPU5: cpu@101 { + device_type = "cpu"; + compatible = "arm,cortex-a7"; + reg = <0x101>; + next-level-cache = <&L1_5>; + cpu-idle-states = <&STATE1_0 &STATE1>; + L1_5: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_1>; + power-domain = <&pd_cores 5>; + }; + }; + + CPU6: cpu@102 { + device_type = "cpu"; + compatible = "arm,cortex-a7"; + reg = <0x102>; + next-level-cache = <&L1_6>; + cpu-idle-states = <&STATE1_0 &STATE1>; + L1_6: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_1>; + power-domain = <&pd_cores 6>; + }; + }; + + CPU7: cpu@103 { + device_type = "cpu"; + compatible = "arm,cortex-a7"; + reg = <0x103>; + next-level-cache = <&L1_7>; + cpu-idle-states = <&STATE1_0 &STATE1>; + L1_7: l1-cache { + compatible = "arm,arch-cache"; + next-level-cache = <&L2_1>; + power-domain = <&pd_cores 7>; + }; + }; +}; + +=========================================== +4 - References +=========================================== + +[1] ARM Linux Kernel documentation - power domain bindings + Documentation/devicetree/bindings/power/power_domain.txt + +[2] ARM Linux Kernel documentation - PSCI bindings + Documentation/devicetree/bindings/arm/psci.txt + +[3] ARM Server Base System Architecture (SBSA) + http://infocenter.arm.com/help/index.jsp
ARM based platforms implement a variety of power management schemes that allow processors to enter idle states at run-time. The parameters defining these idle states vary on a per-platform basis forcing the OS to hardcode the state parameters in platform specific static tables whose size grows as the number of platforms supported in the kernel increases and hampers device drivers standardization. Therefore, this patch aims at standardizing idle state device tree bindings for ARM platforms. Bindings define idle state parameters inclusive of entry methods and state latencies, to allow operating systems to retrieve the configuration entries from the device tree and initialize the related power management drivers, paving the way for common code in the kernel to deal with idle states and removing the need for static data in current and previous kernel versions. Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> --- Documentation/devicetree/bindings/arm/cpus.txt | 10 + Documentation/devicetree/bindings/arm/idle-states.txt | 690 ++++++++++ 2 files changed, 700 insertions(+)