[RFC PATCH 2/8] dt-bindings: mailbox: Add bindings for RPMI shared memory transport

[Anup Patel <apatel@ventanamicro.com>]

Add device tree bindings for the common RISC-V Platform Management
Interface (RPMI) shared memory transport as a mailbox controller.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
---
 .../mailbox/riscv,rpmi-shmem-mbox.yaml        | 135 ++++++++++++++++++
 1 file changed, 135 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mailbox/riscv,rpmi-shmem-mbox.yaml

diff --git a/Documentation/devicetree/bindings/mailbox/riscv,rpmi-shmem-mbox.yaml b/Documentation/devicetree/bindings/mailbox/riscv,rpmi-shmem-mbox.yaml
new file mode 100644
index 000000000000..8d713ba7ffc7
--- /dev/null
+++ b/Documentation/devicetree/bindings/mailbox/riscv,rpmi-shmem-mbox.yaml
@@ -0,0 +1,135 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mailbox/riscv,sbi-mpxy-mbox.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: RISC-V Platform Management Interface (RPMI) shared memory mailbox
+
+maintainers:
+  - Anup Patel <anup@brainfault.org>
+
+description: |
+  The RISC-V Platform Management Interface (RPMI) [1] defines a common shared
+  memory based RPMI transport. This RPMI shared memory transport integrates as
+  mailbox controller in the SBI implementation or supervisor software whereas
+  each RPMI service group is mailbox client in the SBI implementation and
+  supervisor software.
+
+  ===========================================
+  References
+  ===========================================
+
+  [1] RISC-V Platform Management Interface (RPMI)
+      https://github.com/riscv-non-isa/riscv-rpmi/releases
+
+properties:
+  compatible:
+    const: riscv,rpmi-shmem-mbox
+
+  reg:
+    oneOf:
+      - items:
+        - description: A2P request queue base address
+        - description: P2A acknowledgment queue base address
+        - description: P2A request queue base address
+        - description: A2P acknowledgment queue base address
+        - description: A2P doorbell address
+      - items:
+        - description: A2P request queue base address
+        - description: P2A acknowledgment queue base address
+        - description: A2P doorbell address
+
+  reg-names:
+    oneOf:
+      - items:
+        - const: a2p-req
+        - const: p2a-ack
+        - const: p2a-req
+        - const: a2p-ack
+        - const: db-reg
+      - items:
+        - const: a2p-req
+        - const: p2a-ack
+        - const: db-reg
+
+  interrupts:
+    minItems: 1
+    maxItems: 1
+    description:
+      The RPMI shared memory transport supports wired interrupt specified by
+      this property as the P2A doorbell.
+
+  msi-parent:
+    description:
+      The RPMI shared memory transport supports MSI as P2A doorbell and this
+      property specifies the target MSI controller.
+
+  riscv,slot-size:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 64
+    description:
+      Power-of-2 RPMI slot size of the RPMI shared memory transport.
+
+  riscv,db-mask:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      Update only the register bits of doorbell defined by the mask (32 bit).
+      If this property is not present then mask is assumed to be 0xffffffff.
+
+  riscv,db-value:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      Value written to the doorbell register bits (32-bit access) specified
+      by the riscv,db-mask property. If this property is not present then
+      value is assumed to be 0x1.
+
+  "#mbox-cells":
+    const: 1
+    description:
+      The first cell specifies RPMI service group ID.
+
+required:
+  - compatible
+  - reg
+  - reg-names
+  - riscv,slot-size
+  - "#mbox-cells"
+
+anyOf:
+  - required:
+      - interrupts
+  - required:
+      - msi-parent
+
+additionalProperties: false
+
+examples:
+  - |
+    // Example 1 (RPMI shared memory with only 2 queues):
+    mailbox@10080000 {
+        compatible = "riscv,rpmi-shmem-mbox";
+        reg = <0x00 0x10080000 0x00 0x10000>,
+              <0x00 0x10090000 0x00 0x10000>,
+              <0x00 0x100a0000 0x00 0x4>;
+        reg-names = "a2p-req", "p2a-ack", "db-reg";
+        msi-parent = <&imsic_mlevel>;
+        riscv,slot-size = <64>;
+        #mbox-cells = <1>;
+    };
+  - |
+    // Example 2 (RPMI shared memory with only 4 queues):
+    mailbox@10001000 {
+        compatible = "riscv,rpmi-shmem-mbox";
+        reg = <0x00 0x10001000 0x00 0x800>,
+              <0x00 0x10001800 0x00 0x800>,
+              <0x00 0x10002000 0x00 0x800>,
+              <0x00 0x10002800 0x00 0x800>,
+              <0x00 0x10003000 0x00 0x4>;
+        reg-names = "a2p-req", "p2a-ack", "db-reg";
+        msi-parent = <&imsic_mlevel>;
+        riscv,slot-size = <64>;
+        riscv,db-mask = <0x00008000>;
+        riscv,db-value = <0x00008000>;
+        #mbox-cells = <1>;
+    };
-- 
2.43.0