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dt-bindings: arm: add support for ARM System Control and Management Interface(SCMI) protocol
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: Mark Rutland <mark.rutland@arm.com> Acked-by: Rob Herring <robh@kernel.org> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
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‎Documentation/devicetree/bindings/arm/arm,scmi.txt

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System Control and Management Interface (SCMI) Message Protocol
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----------------------------------------------------------
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The SCMI is intended to allow agents such as OSPM to manage various functions
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that are provided by the hardware platform it is running on, including power
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and performance functions.
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This binding is intended to define the interface the firmware implementing
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the SCMI as described in ARM document number ARM DUI 0922B ("ARM System Control
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and Management Interface Platform Design Document")[0] provide for OSPM in
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the device tree.
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Required properties:
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The scmi node with the following properties shall be under the /firmware/ node.
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- compatible : shall be "arm,scmi"
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- mboxes: List of phandle and mailbox channel specifiers. It should contain
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exactly one or two mailboxes, one for transmitting messages("tx")
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and another optional for receiving the notifications("rx") if
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supported.
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- shmem : List of phandle pointing to the shared memory(SHM) area as per
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generic mailbox client binding.
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- #address-cells : should be '1' if the device has sub-nodes, maps to
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protocol identifier for a given sub-node.
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- #size-cells : should be '0' as 'reg' property doesn't have any size
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associated with it.
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Optional properties:
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- mbox-names: shall be "tx" or "rx" depending on mboxes entries.
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See Documentation/devicetree/bindings/mailbox/mailbox.txt for more details
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about the generic mailbox controller and client driver bindings.
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The mailbox is the only permitted method of calling the SCMI firmware.
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Mailbox doorbell is used as a mechanism to alert the presence of a
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messages and/or notification.
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Each protocol supported shall have a sub-node with corresponding compatible
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as described in the following sections. If the platform supports dedicated
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communication channel for a particular protocol, the 3 properties namely:
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mboxes, mbox-names and shmem shall be present in the sub-node corresponding
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to that protocol.
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Clock/Performance bindings for the clocks/OPPs based on SCMI Message Protocol
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------------------------------------------------------------
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This binding uses the common clock binding[1].
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Required properties:
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- #clock-cells : Should be 1. Contains the Clock ID value used by SCMI commands.
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Power domain bindings for the power domains based on SCMI Message Protocol
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------------------------------------------------------------
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This binding for the SCMI power domain providers uses the generic power
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domain binding[2].
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Required properties:
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- #power-domain-cells : Should be 1. Contains the device or the power
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domain ID value used by SCMI commands.
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Sensor bindings for the sensors based on SCMI Message Protocol
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--------------------------------------------------------------
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SCMI provides an API to access the various sensors on the SoC.
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Required properties:
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- #thermal-sensor-cells: should be set to 1. This property follows the
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thermal device tree bindings[3].
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Valid cell values are raw identifiers (Sensor ID)
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as used by the firmware. Refer to platform details
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for your implementation for the IDs to use.
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SRAM and Shared Memory for SCMI
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-------------------------------
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A small area of SRAM is reserved for SCMI communication between application
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processors and SCP.
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The properties should follow the generic mmio-sram description found in [4]
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Each sub-node represents the reserved area for SCMI.
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Required sub-node properties:
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- reg : The base offset and size of the reserved area with the SRAM
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- compatible : should be "arm,scmi-shmem" for Non-secure SRAM based
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shared memory
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[0] http://infocenter.arm.com/help/topic/com.arm.doc.den0056a/index.html
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[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
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[2] Documentation/devicetree/bindings/power/power_domain.txt
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[3] Documentation/devicetree/bindings/thermal/thermal.txt
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[4] Documentation/devicetree/bindings/sram/sram.txt
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Example:
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sram@50000000 {
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compatible = "mmio-sram";
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reg = <0x0 0x50000000 0x0 0x10000>;
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#address-cells = <1>;
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#size-cells = <1>;
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ranges = <0 0x0 0x50000000 0x10000>;
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cpu_scp_lpri: scp-shmem@0 {
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compatible = "arm,scmi-shmem";
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reg = <0x0 0x200>;
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};
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cpu_scp_hpri: scp-shmem@200 {
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compatible = "arm,scmi-shmem";
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reg = <0x200 0x200>;
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};
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};
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mailbox@40000000 {
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....
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#mbox-cells = <1>;
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reg = <0x0 0x40000000 0x0 0x10000>;
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};
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firmware {
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...
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scmi {
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compatible = "arm,scmi";
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mboxes = <&mailbox 0 &mailbox 1>;
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mbox-names = "tx", "rx";
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shmem = <&cpu_scp_lpri &cpu_scp_hpri>;
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#address-cells = <1>;
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#size-cells = <0>;
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scmi_devpd: protocol@11 {
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reg = <0x11>;
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#power-domain-cells = <1>;
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};
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scmi_dvfs: protocol@13 {
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reg = <0x13>;
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#clock-cells = <1>;
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};
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scmi_clk: protocol@14 {
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reg = <0x14>;
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#clock-cells = <1>;
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};
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scmi_sensors0: protocol@15 {
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reg = <0x15>;
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#thermal-sensor-cells = <1>;
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};
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};
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};
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cpu@0 {
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...
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reg = <0 0>;
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clocks = <&scmi_dvfs 0>;
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};
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hdlcd@7ff60000 {
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...
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reg = <0 0x7ff60000 0 0x1000>;
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clocks = <&scmi_clk 4>;
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power-domains = <&scmi_devpd 1>;
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};
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thermal-zones {
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soc_thermal {
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polling-delay-passive = <100>;
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polling-delay = <1000>;
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/* sensor ID */
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thermal-sensors = <&scmi_sensors0 3>;
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...
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};
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};

‎MAINTAINERS

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@@ -13379,11 +13379,11 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd.git
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S: Supported
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F: drivers/mfd/syscon.c
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SYSTEM CONTROL & POWER INTERFACE (SCPI) Message Protocol drivers
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SYSTEM CONTROL & POWER/MANAGEMENT INTERFACE (SCPI/SCMI) Message Protocol drivers
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M: Sudeep Holla <sudeep.holla@arm.com>
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L: linux-arm-kernel@lists.infradead.org
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S: Maintained
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F: Documentation/devicetree/bindings/arm/arm,scpi.txt
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F: Documentation/devicetree/bindings/arm/arm,sc[mp]i.txt
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F: drivers/clk/clk-scpi.c
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F: drivers/cpufreq/scpi-cpufreq.c
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F: drivers/firmware/arm_scpi.c

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