[PATCH v2 1/3] dt-bindings: regulator: Add RPMI voltage service bindings
Joshua Yeong
joshua.yeong at starfivetech.com
Wed Sep 23 00:00:12 PDT 2026
Add device tree bindings for the RISC-V Platform Management Interface
(RPMI) voltage service group, both for the supervisor-facing regulator
controller and for the SBI MPXY channel which the SBI implementation
uses to expose the service group.
Signed-off-by: Joshua Yeong <joshua.yeong at starfivetech.com>
---
Based on the RPMI device power series ("Add RISC-V RPMI device power
service support"), which has been applied for next. The cover letter
links the mail saying so.
.../regulator/riscv,rpmi-mpxy-voltage.yaml | 65 ++++++++
.../regulator/riscv,rpmi-voltage.yaml | 147 ++++++++++++++++++
2 files changed, 212 insertions(+)
create mode 100644 Documentation/devicetree/bindings/regulator/riscv,rpmi-mpxy-voltage.yaml
create mode 100644 Documentation/devicetree/bindings/regulator/riscv,rpmi-voltage.yaml
diff --git a/Documentation/devicetree/bindings/regulator/riscv,rpmi-mpxy-voltage.yaml b/Documentation/devicetree/bindings/regulator/riscv,rpmi-mpxy-voltage.yaml
new file mode 100644
index 000000000000..8cc53879cdf9
--- /dev/null
+++ b/Documentation/devicetree/bindings/regulator/riscv,rpmi-mpxy-voltage.yaml
@@ -0,0 +1,65 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/riscv,rpmi-mpxy-voltage.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: RISC-V RPMI voltage service group based message proxy
+
+maintainers:
+ - Joshua Yeong <joshua.yeong at starfivetech.com>
+
+description: |
+ The RISC-V Platform Management Interface (RPMI) [1] defines a
+ messaging protocol which is modular and extensible. The supervisor
+ software can send/receive RPMI messages via SBI MPXY extension [2]
+ or some dedicated supervisor-mode RPMI transport.
+
+ The RPMI specification [1] defines voltage service group for accessing
+ and controlling the voltage domains managed by a platform
+ microcontroller. The SBI implementation (machine mode firmware or
+ hypervisor) can implement an SBI MPXY channel to allow RPMI voltage
+ service group access to the supervisor software.
+
+ ===========================================
+ References
+ ===========================================
+
+ [1] RISC-V Platform Management Interface (RPMI) v1.0 (or higher)
+ https://github.com/riscv-non-isa/riscv-rpmi/releases
+
+ [2] RISC-V Supervisor Binary Interface (SBI) v3.0 (or higher)
+ https://github.com/riscv-non-isa/riscv-sbi-doc/releases
+
+properties:
+ compatible:
+ description:
+ Intended for use by the SBI implementation.
+ const: riscv,rpmi-mpxy-voltage
+
+ mboxes:
+ maxItems: 1
+ description:
+ Mailbox channel of the underlying RPMI transport.
+
+ riscv,sbi-mpxy-channel-id:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description:
+ The SBI MPXY channel id to be used for providing RPMI access to
+ the supervisor software.
+
+required:
+ - compatible
+ - mboxes
+ - riscv,sbi-mpxy-channel-id
+
+additionalProperties: false
+
+examples:
+ - |
+ voltage-service {
+ compatible = "riscv,rpmi-mpxy-voltage";
+ mboxes = <&rpmi_shmem_mbox 0x7>;
+ riscv,sbi-mpxy-channel-id = <0x1004>;
+ };
+...
diff --git a/Documentation/devicetree/bindings/regulator/riscv,rpmi-voltage.yaml b/Documentation/devicetree/bindings/regulator/riscv,rpmi-voltage.yaml
new file mode 100644
index 000000000000..6334ebd31dc8
--- /dev/null
+++ b/Documentation/devicetree/bindings/regulator/riscv,rpmi-voltage.yaml
@@ -0,0 +1,147 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/riscv,rpmi-voltage.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: RISC-V RPMI voltage service group based regulator controller
+
+maintainers:
+ - Joshua Yeong <joshua.yeong at starfivetech.com>
+
+description: |
+ The RISC-V Platform Management Interface (RPMI) [1] defines a
+ messaging protocol which is modular and extensible. The supervisor
+ software can send/receive RPMI messages via SBI MPXY extension [2]
+ or some dedicated supervisor-mode RPMI transport.
+
+ The RPMI specification [1] defines voltage service group for accessing
+ and controlling the voltage domains managed by a platform
+ microcontroller. The supervisor software can access RPMI voltage
+ service group via SBI MPXY channel or some dedicated supervisor-mode
+ RPMI transport.
+
+ The voltage domains are discovered at runtime from the platform
+ microcontroller, which reports the name, the level format, the supported
+ levels and the always-on capability of each one, so none of that is
+ described here.
+
+ A consumer names a domain in one of two ways. The first is through a
+ "<name>-supply" phandle to a child of the optional "regulators" container,
+ whose "reg" is the domain's RPMI DOMAIN_ID. The second needs no child with
+ "#voltage-domain-cells" on the provider, a consumer lists
+ "voltage-domains = <&provider DOMAIN_ID>" and names each entry in
+ "voltage-domain-names", the way it names a voltage power domain. Both
+ properties belong to the consumer, so a consumer binding describes them
+ itself:
+
+ codec {
+ compatible = "vendor,codec";
+ vdd-supply = <&volt2_reg>;
+ };
+
+ phy {
+ compatible = "vendor,phy";
+ voltage-domains = <&rpmi_voltage 3>, <&rpmi_voltage 4>;
+ voltage-domain-names = "vdda", "vddio";
+ };
+
+ A child may also say what the board permits the rail to supply, which the
+ platform microcontroller has no way to express. A child that gives no
+ voltage constraint leaves the rail free to move within the levels the
+ domain advertises.
+
+ ===========================================
+ References
+ ===========================================
+
+ [1] RISC-V Platform Management Interface (RPMI) v1.0 (or higher)
+ https://github.com/riscv-non-isa/riscv-rpmi/releases
+
+ [2] RISC-V Supervisor Binary Interface (SBI) v3.0 (or higher)
+ https://github.com/riscv-non-isa/riscv-sbi-doc/releases
+
+properties:
+ compatible:
+ description:
+ Intended for use by the supervisor software.
+ const: riscv,rpmi-voltage
+
+ mboxes:
+ maxItems: 1
+ description:
+ Mailbox channel of the underlying RPMI transport or SBI message proxy channel.
+
+ "#voltage-domain-cells":
+ const: 1
+ description:
+ Lets a consumer name a domain by its RPMI DOMAIN_ID, the single cell of
+ a "voltage-domains" entry, without a child node for the domain.
+
+ regulators:
+ type: object
+ additionalProperties: false
+ description:
+ Optional container giving discovered domains a node of their own, for
+ consumers to reference and for board level constraints.
+
+ properties:
+ "#address-cells":
+ const: 1
+
+ "#size-cells":
+ const: 0
+
+ patternProperties:
+ "^regulator@[0-9a-f]+$":
+ type: object
+ $ref: regulator.yaml#
+ unevaluatedProperties: false
+
+ properties:
+ reg:
+ maxItems: 1
+ description:
+ RPMI DOMAIN_ID of the voltage domain this node describes.
+
+ required:
+ - reg
+
+ required:
+ - "#address-cells"
+ - "#size-cells"
+
+required:
+ - compatible
+ - mboxes
+
+additionalProperties: false
+
+examples:
+ - |
+ rpmi_voltage: rpmi-voltage {
+ compatible = "riscv,rpmi-voltage";
+ mboxes = <&mpxy_mbox 0x1004 0x0>;
+ #voltage-domain-cells = <1>;
+
+ regulators {
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ // A node only so that a consumer can name the domain with a
+ // "<name>-supply". Its voltage stays free to move within the
+ // advertised levels.
+ volt1_reg: regulator at 1 {
+ reg = <1>;
+ };
+
+ // A board level constraint. Equal bounds pin the rail, so the
+ // supervisor applies 1.8V and refuses to move it afterwards.
+ volt2_reg: regulator at 2 {
+ reg = <2>;
+ regulator-min-microvolt = <1800000>;
+ regulator-max-microvolt = <1800000>;
+ };
+ };
+ };
+...
--
2.43.0
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