Re: [PATCH v2 02/18] dt-bindings: arm: add support for ARM System Control and Management Interface(SCMI) protocol

[Rob Herring]

On Fri, Aug 04, 2017 at 03:31:28PM +0100, Sudeep Holla wrote:
> This patch adds devicetree binding for System Control and Management
> Interface (SCMI) Message Protocol used between the Application Cores(AP)
> and the System Control Processor(SCP). The MHU peripheral provides a
> mechanism for inter-processor communication between SCP's M3 processor
> and AP.
> 
> SCP offers control and management of the core/cluster power states,
> various power domain DVFS including the core/cluster, certain system
> clocks configuration, thermal sensors and many others.
> 
> SCMI protocol is developed as better replacement to the existing SCPI
> which is not flexible and easily extensible.
> 
> Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> Cc: Mark Rutland <mark.rutland@xxxxxxx>
> Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
> ---
>  Documentation/devicetree/bindings/arm/arm,scmi.txt | 174 +++++++++++++++++++++
>  1 file changed, 174 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/arm,scmi.txt
> 
> diff --git a/Documentation/devicetree/bindings/arm/arm,scmi.txt b/Documentation/devicetree/bindings/arm/arm,scmi.txt
> new file mode 100644
> index 000000000000..33c16be58e72
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/arm,scmi.txt
> @@ -0,0 +1,174 @@
> +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:

Please define this is a subnode of /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.
> +- mbox-names: shall be "tx" or "rx"
> +- shmem : List of phandle pointing to the shared memory(SHM) area as per
> +	  generic mailbox client binding.
> +
> +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 uses the generic power domain binding[4].
> +
> +PM domain providers
> +===================
> +
> +Required properties:
> + - #power-domain-cells : Should be 1. Contains the device or the power
> +			 domain ID value used by SCMI commands.
> +
> +PM domain consumers
> +===================

How consumers work is already defined elsewhere.

> +
> +Required properties:
> + - power-domains : A phandle and PM domain specifier as defined by bindings of
> +                   the power controller specified by phandle.
> +
> +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[2].
> +
> +			 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 [3]
> +
> +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/thermal/thermal.txt
> +[3] Documentation/devicetree/bindings/sram/sram.txt
> +[4] Documentation/devicetree/bindings/power/power_domain.txt
> +
> +Example:
> +
> +sram: 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: mailbox0@40000000 {
> +	....
> +	#mbox-cells = <1>;
> +};
> +
> +scmi_protocol: scmi@2e000000 {

The unit address is not valid.

> +	compatible = "arm,scmi";
> +	method = "mailbox-doorbell";

Is this not implied by the mboxes property? 

> +	mboxes = <&mailbox 0 &mailbox 1>;
> +	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>;
> +		...
> +	};
> +};
> -- 
> 2.7.4
>