dt-bindings: arm: add support for ARM System Control and Management Interface(SCMI) protocol

System Control and Management Interface (SCMI) Message Protocol

----------------------------------------------------------

The SCMI is intended to allow agents such as OSPM to manage various functions

that are provided by the hardware platform it is running on, including power

and performance functions.

This binding is intended to define the interface the firmware implementing

the SCMI as described in ARM document number ARM DUI 0922B ("ARM System Control

and Management Interface Platform Design Document")[0] provide for OSPM in

the device tree.

Required properties:

The scmi node with the following properties shall be under the /firmware/ node.

- compatible : shall be "arm,scmi"

- mboxes: List of phandle and mailbox channel specifiers. It should contain

	  exactly one or two mailboxes, one for transmitting messages("tx")

	  and another optional for receiving the notifications("rx") if

	  supported.

- shmem : List of phandle pointing to the shared memory(SHM) area as per

	  generic mailbox client binding.

- #address-cells : should be '1' if the device has sub-nodes, maps to

	  protocol identifier for a given sub-node.

- #size-cells : should be '0' as 'reg' property doesn't have any size

	  associated with it.

Optional properties:

- mbox-names: shall be "tx" or "rx" depending on mboxes entries.

See Documentation/devicetree/bindings/mailbox/mailbox.txt for more details

about the generic mailbox controller and client driver bindings.

The mailbox is the only permitted method of calling the SCMI firmware.

Mailbox doorbell is used as a mechanism to alert the presence of a

messages and/or notification.

Each protocol supported shall have a sub-node with corresponding compatible

as described in the following sections. If the platform supports dedicated

communication channel for a particular protocol, the 3 properties namely:

mboxes, mbox-names and shmem shall be present in the sub-node corresponding

to that protocol.

Clock/Performance bindings for the clocks/OPPs based on SCMI Message Protocol

------------------------------------------------------------

This binding uses the common clock binding[1].

Required properties:

- #clock-cells : Should be 1. Contains the Clock ID value used by SCMI commands.

Power domain bindings for the power domains based on SCMI Message Protocol

------------------------------------------------------------

This binding for the SCMI power domain providers uses the generic power

domain binding[2].

Required properties:

 - #power-domain-cells : Should be 1. Contains the device or the power

			 domain ID value used by SCMI commands.

Sensor bindings for the sensors based on SCMI Message Protocol

--------------------------------------------------------------

SCMI provides an API to access the various sensors on the SoC.

Required properties:

- #thermal-sensor-cells: should be set to 1. This property follows the

			 thermal device tree bindings[3].

			 Valid cell values are raw identifiers (Sensor ID)

			 as used by the firmware. Refer to  platform details

			 for your implementation for the IDs to use.

SRAM and Shared Memory for SCMI

-------------------------------

A small area of SRAM is reserved for SCMI communication between application

processors and SCP.

The properties should follow the generic mmio-sram description found in [4]

Each sub-node represents the reserved area for SCMI.

Required sub-node properties:

- reg : The base offset and size of the reserved area with the SRAM

- compatible : should be "arm,scmi-shmem" for Non-secure SRAM based

	       shared memory

[0] http://infocenter.arm.com/help/topic/com.arm.doc.den0056a/index.html

[1] Documentation/devicetree/bindings/clock/clock-bindings.txt

[2] Documentation/devicetree/bindings/power/power_domain.txt

[3] Documentation/devicetree/bindings/thermal/thermal.txt

[4] Documentation/devicetree/bindings/sram/sram.txt

Example:

sram@50000000 {

	compatible = "mmio-sram";

	reg = <0x0 0x50000000 0x0 0x10000>;

	#address-cells = <1>;

	#size-cells = <1>;

	ranges = <0 0x0 0x50000000 0x10000>;

	cpu_scp_lpri: scp-shmem@0 {

		compatible = "arm,scmi-shmem";

		reg = <0x0 0x200>;

	};

	cpu_scp_hpri: scp-shmem@200 {

		compatible = "arm,scmi-shmem";

		reg = <0x200 0x200>;

	};

};

mailbox@40000000 {

	....

	#mbox-cells = <1>;

	reg = <0x0 0x40000000 0x0 0x10000>;

};

firmware {

	...

	scmi {

		compatible = "arm,scmi";

		mboxes = <&mailbox 0 &mailbox 1>;

		mbox-names = "tx", "rx";

		shmem = <&cpu_scp_lpri &cpu_scp_hpri>;

		#address-cells = <1>;

		#size-cells = <0>;

		scmi_devpd: protocol@11 {

			reg = <0x11>;

			#power-domain-cells = <1>;

		};

		scmi_dvfs: protocol@13 {

			reg = <0x13>;

			#clock-cells = <1>;

		};

		scmi_clk: protocol@14 {

			reg = <0x14>;

			#clock-cells = <1>;

		};

		scmi_sensors0: protocol@15 {

			reg = <0x15>;

			#thermal-sensor-cells = <1>;

		};

	};

};

cpu@0 {

	...

	reg = <0 0>;

	clocks = <&scmi_dvfs 0>;

};

hdlcd@7ff60000 {

	...

	reg = <0 0x7ff60000 0 0x1000>;

	clocks = <&scmi_clk 4>;

	power-domains = <&scmi_devpd 1>;

};

thermal-zones {

	soc_thermal {

		polling-delay-passive = <100>;

		polling-delay = <1000>;

					/* sensor ID */

		thermal-sensors = <&scmi_sensors0 3>;

		...

	};

};

S:	Supported

F:	drivers/mfd/syscon.c

SYSTEM CONTROL & POWER INTERFACE (SCPI) Message Protocol drivers

SYSTEM CONTROL & POWER/MANAGEMENT INTERFACE (SCPI/SCMI) Message Protocol drivers

M:	Sudeep Holla <sudeep.holla@arm.com>

L:	linux-arm-kernel@lists.infradead.org

S:	Maintained

F:	Documentation/devicetree/bindings/arm/arm,scpi.txt

F:	Documentation/devicetree/bindings/arm/arm,sc[mp]i.txt

F:	drivers/clk/clk-scpi.c

F:	drivers/cpufreq/scpi-cpufreq.c

F:	drivers/firmware/arm_scpi.c