[PATCH 4/9] dt-bindings: Add RISC-V incoming MSI controller bindings

[Anup Patel <apatel@ventanamicro.com>]

We add DT bindings document for RISC-V incoming MSI controller (IMSIC)
defined by the RISC-V advanced interrupt architecture (AIA) specification.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
---
 .../interrupt-controller/riscv,imsic.yaml     | 174 ++++++++++++++++++
 1 file changed, 174 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/interrupt-controller/riscv,imsic.yaml

diff --git a/Documentation/devicetree/bindings/interrupt-controller/riscv,imsic.yaml b/Documentation/devicetree/bindings/interrupt-controller/riscv,imsic.yaml
new file mode 100644
index 000000000000..05106eb1955e
--- /dev/null
+++ b/Documentation/devicetree/bindings/interrupt-controller/riscv,imsic.yaml
@@ -0,0 +1,174 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/interrupt-controller/riscv,imsic.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: RISC-V Incoming MSI Controller (IMSIC)
+
+maintainers:
+  - Anup Patel <anup@brainfault.org>
+
+description:
+  The RISC-V advanced interrupt architecture (AIA) defines a per-CPU incoming
+  MSI controller (IMSIC) for handling MSIs in a RISC-V platform. The RISC-V
+  AIA specification can be found at https://github.com/riscv/riscv-aia.
+
+  The IMSIC is a per-CPU (or per-HART) device with separate interrupt file
+  for each privilege level (machine or supervisor). The configuration of
+  a IMSIC interrupt file is done using AIA CSRs and it also has a 4KB MMIO
+  space to receive MSIs from devices. Each IMSIC interrupt file supports a
+  fixed number of interrupt identities (to distinguish MSIs from devices)
+  which is same for given privilege level across CPUs (or HARTs).
+
+  The arrangement of IMSIC interrupt files in MMIO space of a RISC-V platform
+  follows a particular scheme defined by the RISC-V AIA specification. A IMSIC
+  group is a set of IMSIC interrupt files co-located in MMIO space and we can
+  have multiple IMSIC groups (i.e. clusters, sockets, chiplets, etc) in a
+  RISC-V platform. The MSI target address of a IMSIC interrupt file at given
+  privilege level (machine or supervisor) encodes group index, HART index,
+  and guest index (shown below).
+
+  XLEN-1           >=24                                 12    0
+  |                  |                                  |     |
+  -------------------------------------------------------------
+  |xxxxxx|Group Index|xxxxxxxxxxx|HART Index|Guest Index|  0  |
+  -------------------------------------------------------------
+
+  The device tree of a RISC-V platform will have one IMSIC device tree node
+  for each privilege level (machine or supervisor) which collectively describe
+  IMSIC interrupt files at that privilege level across CPUs (or HARTs).
+
+allOf:
+  - $ref: /schemas/interrupt-controller.yaml#
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - vendor,chip-imsics
+      - const: riscv,imsics
+
+  reg:
+    minItems: 1
+    maxItems: 128
+    description:
+      Base address of each IMSIC group.
+
+  interrupt-controller: true
+
+  "#interrupt-cells":
+    const: 0
+
+  msi-controller: true
+
+  interrupts-extended:
+    minItems: 1
+    maxItems: 32768
+    description:
+      This property represents the set of CPUs (or HARTs) for which given
+      device tree node describes the IMSIC interrupt files. Each node pointed
+      to should be a riscv,cpu-intc node, which has a riscv node (i.e. RISC-V
+      HART) as parent.
+
+  riscv,num-ids:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 63
+    maximum: 2047
+    description:
+      Specifies how many interrupt identities are supported by IMSIC interrupt
+      file.
+
+  riscv,num-guest-ids:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 63
+    maximum: 2047
+    description:
+      Specifies how many interrupt identities are supported by IMSIC guest
+      interrupt file. When not specified the number of interrupt identities
+      supported by IMSIC guest file is assumed to be same as specified by
+      the riscv,num-ids property.
+
+  riscv,slow-ipi:
+    type: boolean
+    description:
+      The presence of this property implies that software interrupts (i.e.
+      IPIs) using IMSIC software injected MSIs is slower compared to other
+      software interrupt mechanisms (such as SBI IPI) on the underlying
+      RISC-V platform.
+
+  riscv,guest-index-bits:
+    minimum: 0
+    maximum: 7
+    description:
+      Specifies number of guest index bits in the MSI target address. When
+      not specified it is assumed to be 0.
+
+  riscv,hart-index-bits:
+    minimum: 0
+    maximum: 15
+    description:
+      Specifies number of HART index bits in the MSI target address. When
+      not specified it is estimated based on the interrupts-extended property.
+
+  riscv,group-index-bits:
+    minimum: 0
+    maximum: 7
+    description:
+      Specifies number of group index bits in the MSI target address. When
+      not specified it is assumed to be 0.
+
+  riscv,group-index-shift:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 24
+    maximum: 55
+    description:
+      Specifies the least significant bit of the group index bits in the
+      MSI target address. When not specified it is assumed to be 24.
+
+additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - interrupt-controller
+  - msi-controller
+  - interrupts-extended
+  - riscv,num-ids
+
+examples:
+  - |
+    // Example 1 (Machine-level IMSIC files with just one group):
+
+    imsic_mlevel: interrupt-controller@24000000 {
+      compatible = "vendor,chip-imsics", "riscv,imsics";
+      interrupts-extended = <&cpu1_intc 11>,
+                            <&cpu2_intc 11>,
+                            <&cpu3_intc 11>,
+                            <&cpu4_intc 11>;
+      reg = <0x28000000 0x4000>;
+      interrupt-controller;
+      #interrupt-cells = <0>;
+      msi-controller;
+      riscv,num-ids = <127>;
+    };
+
+  - |
+    // Example 2 (Supervisor-level IMSIC files with two groups):
+
+    imsic_slevel: interrupt-controller@28000000 {
+      compatible = "vendor,chip-imsics", "riscv,imsics";
+      interrupts-extended = <&cpu1_intc 9>,
+                            <&cpu2_intc 9>,
+                            <&cpu3_intc 9>,
+                            <&cpu4_intc 9>;
+      reg = <0x28000000 0x2000>, /* Group0 IMSICs */
+            <0x29000000 0x2000>; /* Group1 IMSICs */
+      interrupt-controller;
+      #interrupt-cells = <0>;
+      msi-controller;
+      riscv,num-ids = <127>;
+      riscv,group-index-bits = <1>;
+      riscv,group-index-shift = <24>;
+    };
+...
-- 
2.34.1