Documentation: add DT binding for ARM System Control and Power Interface(SCPI) protocol

System Control and Power Interface (SCPI) Message Protocol

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

Firmware implementing the SCPI described in ARM document number ARM DUI 0922B

("ARM Compute Subsystem SCP: Message Interface Protocols")[0] can be used

by Linux to initiate various system control and power operations.

Required properties:

- compatible : should be "arm,scpi"

- mboxes: List of phandle and mailbox channel specifiers

	  All the channels reserved by remote SCP firmware for use by

	  SCPI message protocol should be specified in any order

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

	  processors using these mailboxes for IPC, one for each mailbox

	  SHM can be any memory reserved for the purpose of this communication

	  between the processors.

See Documentation/devicetree/bindings/mailbox/mailbox.txt

for more details about the generic mailbox controller and

client driver bindings.

Clock bindings for the clocks based on SCPI Message Protocol

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

This binding uses the common clock binding[1].

Container Node

==============

Required properties:

- compatible : should be "arm,scpi-clocks"

	       All the clocks provided by SCP firmware via SCPI message

	       protocol much be listed as sub-nodes under this node.

Sub-nodes

=========

Required properties:

- compatible : shall include one of the following

	"arm,scpi-dvfs-clocks" - all the clocks that are variable and index based.

		These clocks don't provide an entire range of values between the

		limits but only discrete points within the range. The firmware

		provides the mapping for each such operating frequency and the

		index associated with it. The firmware also manages the

		voltage scaling appropriately with the clock scaling.

	"arm,scpi-variable-clocks" - all the clocks that are variable and provide full

		range within the specified range. The firmware provides the

		range of values within a specified range.

Other required properties for all clocks(all from common clock binding):

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

- clock-output-names : shall be the corresponding names of the outputs.

- clock-indices: The identifying number for the clocks(i.e.clock_id) in the

	node. It can be non linear and hence provide the mapping of identifiers

	into the clock-output-names array.

SRAM and Shared Memory for SCPI

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

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

processors and SCP.

Required properties:

- compatible : should be "arm,juno-sram-ns" for Non-secure SRAM on Juno

The rest of the properties should follow the generic mmio-sram description

found in ../../misc/sysram.txt

Each sub-node represents the reserved area for SCPI.

Required sub-node properties:

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

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

	       shared memory on Juno platforms

[0] http://infocenter.arm.com/help/topic/com.arm.doc.dui0922b/index.html

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

Example:

sram: sram@50000000 {

	compatible = "arm,juno-sram-ns", "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,juno-scp-shmem";

		reg = <0x0 0x200>;

	};

	cpu_scp_hpri: scp-shmem@200 {

		compatible = "arm,juno-scp-shmem";

		reg = <0x200 0x200>;

	};

};

mailbox: mailbox0@40000000 {

	....

	#mbox-cells = <1>;

};

scpi_protocol: scpi@2e000000 {

	compatible = "arm,scpi";

	mboxes = <&mailbox 0 &mailbox 1>;

	shmem = <&cpu_scp_lpri &cpu_scp_hpri>;

	clocks {

		compatible = "arm,scpi-clocks";

		scpi_dvfs: scpi_clocks@0 {

			compatible = "arm,scpi-dvfs-clocks";

			#clock-cells = <1>;

			clock-indices = <0>, <1>, <2>;

			clock-output-names = "atlclk", "aplclk","gpuclk";

		};

		scpi_clk: scpi_clocks@3 {

			compatible = "arm,scpi-variable-clocks";

			#clock-cells = <1>;

			clock-indices = <3>, <4>;

			clock-output-names = "pxlclk0", "pxlclk1";

		};

	};

};

cpu@0 {

	...

	reg = <0 0>;

	clocks = <&scpi_dvfs 0>;

};

hdlcd@7ff60000 {

	...

	reg = <0 0x7ff60000 0 0x1000>;

	clocks = <&scpi_clk 4>;

};

In the above example, the #clock-cells is set to 1 as required.

scpi_dvfs has 3 output clocks namely: atlclk, aplclk, and gpuclk with 0,

1 and 2 as clock-indices. scpi_clk has 2 output clocks namely: pxlclk0

and pxlclk1 with 3 and 4 as clock-indices.

The first consumer in the example is cpu@0 and it has '0' as the clock

specifier which points to the first entry in the output clocks of

scpi_dvfs i.e. "atlclk".

Similarly the second example is hdlcd@7ff60000 and it has pxlclk1 as input

clock. '4' in the clock specifier here points to the second entry

in the output clocks of scpi_clocks  i.e. "pxlclk1"

S:	Supported

S:	Supported

F:	arch/score/

F:	arch/score/

SYSTEM CONTROL & POWER INTERFACE (SCPI) 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

SCSI CDROM DRIVER

SCSI CDROM DRIVER

M:	Jens Axboe <axboe@kernel.dk>

M:	Jens Axboe <axboe@kernel.dk>

L:	linux-scsi@vger.kernel.org

L:	linux-scsi@vger.kernel.org