opp.txt

Generic OPP (Operating Performance Points) Bindings
----------------------------------------------------

Devices work at voltage-current-frequency combinations and some implementations
have the liberty of choosing these. These combinations are called Operating
Performance Points aka OPPs. This document defines bindings for these OPPs
applicable across wide range of devices. For illustration purpose, this document
uses CPU as a device.

This document contain multiple versions of OPP binding and only one of them
should be used per device.

Binding 1: operating-points
============================

This binding only supports voltage-frequency pairs.

Properties:
- operating-points: An array of 2-tuples items, and each item consists
  of frequency and voltage like <freq-kHz vol-uV>.
	freq: clock frequency in kHz
	vol: voltage in microvolt

Examples:

cpu@0 {
	compatible = "arm,cortex-a9";
	reg = <0>;
	next-level-cache = <&L2>;
	operating-points = <
		/* kHz    uV */
		792000  1100000
		396000  950000
		198000  850000
	>;
};


Binding 2: operating-points-v2
============================

* Property: operating-points-v2

Devices supporting OPPs must set their "operating-points-v2" property with
phandle to a OPP table in their DT node. The OPP core will use this phandle to
find the operating points for the device.

Devices may want to choose OPP tables at runtime and so can provide a list of
phandles here. But only *one* of them should be chosen at runtime. This must be
accompanied by a corresponding "operating-points-names" property, to uniquely
identify the OPP tables.

If required, this can be extended for SoC vendor specfic bindings. Such bindings
should be documented as Documentation/devicetree/bindings/power/<vendor>-opp.txt
and should have a compatible description like: "operating-points-v2-<vendor>".

Optional properties:
- operating-points-names: Names of OPP tables (required if multiple OPP
  tables are present), to uniquely identify them. The same list must be present
  for all the CPUs which are sharing clock/voltage rails and hence the OPP
  tables.

* OPP Table Node

This describes the OPPs belonging to a device. This node can have following
properties:

Required properties:
- compatible: Allow OPPs to express their compatibility. It should be:
  "operating-points-v2".

- OPP nodes: One or more OPP nodes describing voltage-current-frequency
  combinations. Their name isn't significant but their phandle can be used to
  reference an OPP.

Optional properties:
- opp-shared: Indicates that device nodes using this OPP Table Node's phandle
  switch their DVFS state together, i.e. they share clock/voltage/current lines.
  Missing property means devices have independent clock/voltage/current lines,
  but they share OPP tables.

- status: Marks the OPP table enabled/disabled.


* OPP Node

This defines voltage-current-frequency combinations along with other related
properties.

Required properties:
- opp-hz: Frequency in Hz, expressed as a 64-bit big-endian integer.

Optional properties:
- opp-microvolt: voltage in micro Volts.

  A single regulator's voltage is specified with an array of size one or three.
  Single entry is for target voltage and three entries are for <target min max>
  voltages.

  Entries for multiple regulators must be present in the same order as
  regulators are specified in device's DT node.

- opp-microamp: The maximum current drawn by the device in microamperes
  considering system specific parameters (such as transients, process, aging,
  maximum operating temperature range etc.) as necessary. This may be used to
  set the most efficient regulator operating mode.

  Should only be set if opp-microvolt is set for the OPP.

  Entries for multiple regulators must be present in the same order as
  regulators are specified in device's DT node. If this property isn't required
  for few regulators, then this should be marked as zero for them. If it isn't
  required for any regulator, then this property need not be present.

- clock-latency-ns: Specifies the maximum possible transition latency (in
  nanoseconds) for switching to this OPP from any other OPP.

- turbo-mode: Marks the OPP to be used only for turbo modes. Turbo mode is
  available on some platforms, where the device can run over its operating
  frequency for a short duration of time limited by the device's power, current
  and thermal limits.

- opp-suspend: Marks the OPP to be used during device suspend. Only one OPP in
  the table should have this.

- status: Marks the node enabled/disabled.

Example 1: Single cluster Dual-core ARM cortex A9, switch DVFS states together.

/ {
	cpus {
		#address-cells = <1>;
		#size-cells = <0>;

		cpu@0 {
			compatible = "arm,cortex-a9";
			reg = <0>;
			next-level-cache = <&L2>;
			clocks = <&clk_controller 0>;
			clock-names = "cpu";
			cpu-supply = <&cpu_supply0>;
			operating-points-v2 = <&cpu0_opp_table>;
		};

		cpu@1 {
			compatible = "arm,cortex-a9";
			reg = <1>;
			next-level-cache = <&L2>;
			clocks = <&clk_controller 0>;
			clock-names = "cpu";
			cpu-supply = <&cpu_supply0>;
			operating-points-v2 = <&cpu0_opp_table>;
		};
	};

	cpu0_opp_table: opp_table0 {
		compatible = "operating-points-v2";
		opp-shared;

		opp00 {
			opp-hz = /bits/ 64 <1000000000>;
			opp-microvolt = <970000 975000 985000>;
			opp-microamp = <70000>;
			clock-latency-ns = <300000>;
			opp-suspend;
		};
		opp01 {
			opp-hz = /bits/ 64 <1100000000>;
			opp-microvolt = <980000 1000000 1010000>;
			opp-microamp = <80000>;
			clock-latency-ns = <310000>;
		};
		opp02 {
			opp-hz = /bits/ 64 <1200000000>;
			opp-microvolt = <1025000>;
			clock-latency-ns = <290000>;
			turbo-mode;
		};
	};
};

Example 2: Single cluster, Quad-core Qualcom-krait, switches DVFS states
independently.

/ {
	cpus {
		#address-cells = <1>;
		#size-cells = <0>;

		cpu@0 {
			compatible = "qcom,krait";
			reg = <0>;
			next-level-cache = <&L2>;
			clocks = <&clk_controller 0>;
			clock-names = "cpu";
			cpu-supply = <&cpu_supply0>;
			operating-points-v2 = <&cpu_opp_table>;
		};

		cpu@1 {
			compatible = "qcom,krait";
			reg = <1>;
			next-level-cache = <&L2>;
			clocks = <&clk_controller 1>;
			clock-names = "cpu";
			cpu-supply = <&cpu_supply1>;
			operating-points-v2 = <&cpu_opp_table>;
		};

		cpu@2 {
			compatible = "qcom,krait";
			reg = <2>;
			next-level-cache = <&L2>;
			clocks = <&clk_controller 2>;
			clock-names = "cpu";
			cpu-supply = <&cpu_supply2>;
			operating-points-v2 = <&cpu_opp_table>;
		};

		cpu@3 {
			compatible = "qcom,krait";
			reg = <3>;
			next-level-cache = <&L2>;
			clocks = <&clk_controller 3>;
			clock-names = "cpu";
			cpu-supply = <&cpu_supply3>;
			operating-points-v2 = <&cpu_opp_table>;
		};
	};

	cpu_opp_table: opp_table {
		compatible = "operating-points-v2";

		/*
		 * Missing opp-shared property means CPUs switch DVFS states
		 * independently.
		 */

		opp00 {
			opp-hz = /bits/ 64 <1000000000>;
			opp-microvolt = <970000 975000 985000>;
			opp-microamp = <70000>;
			clock-latency-ns = <300000>;
			opp-suspend;
		};
		opp01 {
			opp-hz = /bits/ 64 <1100000000>;
			opp-microvolt = <980000 1000000 1010000>;
			opp-microamp = <80000>;
			clock-latency-ns = <310000>;
		};
		opp02 {
			opp-hz = /bits/ 64 <1200000000>;
			opp-microvolt = <1025000>;
			opp-microamp = <90000;
			lock-latency-ns = <290000>;
			turbo-mode;
		};
	};
};

Example 3: Dual-cluster, Dual-core per cluster. CPUs within a cluster switch
DVFS state together.

/ {
	cpus {
		#address-cells = <1>;
		#size-cells = <0>;

		cpu@0 {
			compatible = "arm,cortex-a7";
			reg = <0>;
			next-level-cache = <&L2>;
			clocks = <&clk_controller 0>;
			clock-names = "cpu";
			cpu-supply = <&cpu_supply0>;
			operating-points-v2 = <&cluster0_opp>;
		};

		cpu@1 {
			compatible = "arm,cortex-a7";
			reg = <1>;
			next-level-cache = <&L2>;
			clocks = <&clk_controller 0>;
			clock-names = "cpu";
			cpu-supply = <&cpu_supply0>;
			operating-points-v2 = <&cluster0_opp>;
		};

		cpu@100 {
			compatible = "arm,cortex-a15";
			reg = <100>;
			next-level-cache = <&L2>;
			clocks = <&clk_controller 1>;
			clock-names = "cpu";
			cpu-supply = <&cpu_supply1>;
			operating-points-v2 = <&cluster1_opp>;
		};

		cpu@101 {
			compatible = "arm,cortex-a15";
			reg = <101>;
			next-level-cache = <&L2>;
			clocks = <&clk_controller 1>;
			clock-names = "cpu";
			cpu-supply = <&cpu_supply1>;
			operating-points-v2 = <&cluster1_opp>;
		};
	};

	cluster0_opp: opp_table0 {
		compatible = "operating-points-v2";
		opp-shared;

		opp00 {
			opp-hz = /bits/ 64 <1000000000>;
			opp-microvolt = <970000 975000 985000>;
			opp-microamp = <70000>;
			clock-latency-ns = <300000>;
			opp-suspend;
		};
		opp01 {
			opp-hz = /bits/ 64 <1100000000>;
			opp-microvolt = <980000 1000000 1010000>;
			opp-microamp = <80000>;
			clock-latency-ns = <310000>;
		};
		opp02 {
			opp-hz = /bits/ 64 <1200000000>;
			opp-microvolt = <1025000>;
			opp-microamp = <90000>;
			clock-latency-ns = <290000>;
			turbo-mode;
		};
	};

	cluster1_opp: opp_table1 {
		compatible = "operating-points-v2";
		opp-shared;

		opp10 {
			opp-hz = /bits/ 64 <1300000000>;
			opp-microvolt = <1045000 1050000 1055000>;
			opp-microamp = <95000>;
			clock-latency-ns = <400000>;
			opp-suspend;
		};
		opp11 {
			opp-hz = /bits/ 64 <1400000000>;
			opp-microvolt = <1075000>;
			opp-microamp = <100000>;
			clock-latency-ns = <400000>;
		};
		opp12 {
			opp-hz = /bits/ 64 <1500000000>;
			opp-microvolt = <1010000 1100000 1110000>;
			opp-microamp = <95000>;
			clock-latency-ns = <400000>;
			turbo-mode;
		};
	};
};

Example 4: Handling multiple regulators

/ {
	cpus {
		cpu@0 {
			compatible = "arm,cortex-a7";
			...

			cpu-supply = <&cpu_supply0>, <&cpu_supply1>, <&cpu_supply2>;
			operating-points-v2 = <&cpu0_opp_table>;
		};
	};

	cpu0_opp_table: opp_table0 {
		compatible = "operating-points-v2";
		opp-shared;

		opp00 {
			opp-hz = /bits/ 64 <1000000000>;
			opp-microvolt = <970000>, /* Supply 0 */
					<960000>, /* Supply 1 */
					<960000>; /* Supply 2 */
			opp-microamp =  <70000>,  /* Supply 0 */
					<70000>,  /* Supply 1 */
					<70000>;  /* Supply 2 */
			clock-latency-ns = <300000>;
		};

		/* OR */

		opp00 {
			opp-hz = /bits/ 64 <1000000000>;
			opp-microvolt = <970000 975000 985000>, /* Supply 0 */
					<960000 965000 975000>, /* Supply 1 */
					<960000 965000 975000>; /* Supply 2 */
			opp-microamp =  <70000>,		/* Supply 0 */
					<70000>,		/* Supply 1 */
					<70000>;		/* Supply 2 */
			clock-latency-ns = <300000>;
		};

		/* OR */

		opp00 {
			opp-hz = /bits/ 64 <1000000000>;
			opp-microvolt = <970000 975000 985000>, /* Supply 0 */
					<960000 965000 975000>, /* Supply 1 */
					<960000 965000 975000>; /* Supply 2 */
			opp-microamp =  <70000>,		/* Supply 0 */
					<0>,			/* Supply 1 doesn't need this */
					<70000>;		/* Supply 2 */
			clock-latency-ns = <300000>;
		};
	};
};

Example 5: Multiple OPP tables

/ {
	cpus {
		cpu@0 {
			compatible = "arm,cortex-a7";
			...

			cpu-supply = <&cpu_supply>
			operating-points-v2 = <&cpu0_opp_table_slow>, <&cpu0_opp_table_fast>;
			operating-points-names = "slow", "fast";
		};
	};

	cpu0_opp_table_slow: opp_table_slow {
		compatible = "operating-points-v2";
		status = "okay";
		opp-shared;

		opp00 {
			opp-hz = /bits/ 64 <600000000>;
			...
		};

		opp01 {
			opp-hz = /bits/ 64 <800000000>;
			...
		};
	};

	cpu0_opp_table_fast: opp_table_fast {
		compatible = "operating-points-v2";
		status = "okay";
		opp-shared;

		opp10 {
			opp-hz = /bits/ 64 <1000000000>;
			...
		};

		opp11 {
			opp-hz = /bits/ 64 <1100000000>;
			...
		};
	};
};