[PATCH v2 2/3] dt-bindings: riscv: Add Worlds per-hart properties

[Yu-Chien Peter Lin]

Add per-hart DT properties for the RISC-V Worlds architecture:
riscv,pmwid, riscv,pmwidlist, and riscv,pmlwidlist. These
platform-defined values are primarily used by M-mode firmware
to configure World ID CSRs and restrict WID usage across
privilege levels.

Also add schema validation rules to enforce valid property
combinations based on the ISA extensions present.

Signed-off-by: Yu-Chien Peter Lin <peter.lin at sifive.com>
---
 .../devicetree/bindings/riscv/cpus.yaml       | 61 +++++++++++++++
 .../devicetree/bindings/riscv/worlds.yaml     | 77 +++++++++++++++++++
 2 files changed, 138 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/riscv/worlds.yaml

diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
index 5feeb2203050..5922a0307cfe 100644
--- a/Documentation/devicetree/bindings/riscv/cpus.yaml
+++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
@@ -26,6 +26,7 @@ description: |
 allOf:
   - $ref: /schemas/cpu.yaml#
   - $ref: extensions.yaml
+  - $ref: worlds.yaml
   - if:
       not:
         properties:
@@ -39,6 +40,44 @@ allOf:
       properties:
         thead,vlenb: false
 
+  - if:
+      properties:
+        riscv,isa-extensions:
+          not:
+            contains:
+              const: smwid
+    then:
+      properties:
+        riscv,pmwidlist: false
+
+  - if:
+      properties:
+        riscv,isa-extensions:
+          not:
+            contains:
+              const: smlwid
+    then:
+      properties:
+        riscv,pmlwidlist: false
+
+  - if:
+      allOf:
+        - properties:
+            riscv,isa-extensions:
+              not:
+                contains:
+                  const: smwid
+        - properties:
+            riscv,isa-extensions:
+              contains:
+                enum:
+                  - smlwid
+                  - smwiddeleg
+                  - sswid
+    then:
+      required:
+        - riscv,pmwid
+
 properties:
   compatible:
     oneOf:
@@ -120,6 +159,28 @@ properties:
       thead systems where the vector register length is not identical on all harts, or
       the vlenb CSR is not available.
 
+  riscv,pmwid:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      M-mode World ID (WID) for this hart, M-mode firmware may read this property
+      to identify the WID for M-mode. For a Worlds-aware platform without any Worlds
+      ISA implemented, this is the WID for all privilege modes.
+    minimum: 0
+    maximum: 63
+
+  riscv,pmwidlist:
+    $ref: /schemas/types.yaml#/definitions/uint64
+    description:
+      Optional bitmask of WIDs available for M-mode use on this hart; each set bit N
+      indicates WID N is available. Firmware may read this to select a platform
+      authorized WID.
+
+  riscv,pmlwidlist:
+    $ref: /schemas/types.yaml#/definitions/uint64
+    description:
+      Optional bitmask of WIDs available for S-mode and U-mode use on this hart; each
+      set bit N indicates WID N is available. Firmware may read this to select platform
+      authorized WIDs for lower-privilege modes.
   # RISC-V has multiple properties for cache op block sizes as the sizes
   # differ between individual CBO extensions
   cache-op-block-size: false
diff --git a/Documentation/devicetree/bindings/riscv/worlds.yaml b/Documentation/devicetree/bindings/riscv/worlds.yaml
new file mode 100644
index 000000000000..cc8b3747591e
--- /dev/null
+++ b/Documentation/devicetree/bindings/riscv/worlds.yaml
@@ -0,0 +1,77 @@
+# SPDX-License-Identifier: (GPL-2.0 OR MIT)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/riscv/worlds.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: RISC-V Worlds Extension
+
+maintainers:
+  - Yu-Chien Peter Lin <peter.lin at sifive.com>
+
+description: |
+  The RISC-V Worlds ISA extension, as described in the RISC-V Privileged
+  Specification, adds World ID tagging for context isolation.
+
+  This binding describes the system-wide Worlds configuration for the /cpus node
+  and is used alongside per-hart Worlds-related properties such as riscv,pmwid in
+  the RISC-V CPU binding and Worlds-related ISA extensions enumerated via
+  riscv,isa-extensions.
+
+select:
+  properties:
+    $nodename:
+      pattern: "^cpus$"
+
+properties:
+  riscv,nworlds:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: |
+      Number of World IDs (WIDs) supported by the platform. This is a system-wide
+      property that describes the total number of isolation contexts available.
+      Hardware components such as the WorldGuard Checker use this to determine
+      the valid range of WID values.
+    minimum: 2
+    maximum: 64
+
+additionalProperties: true
+
+examples:
+  - |
+    // Example: System with 4 World IDs
+    cpus {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        timebase-frequency = <1000000>;
+        riscv,nworlds = <4>;
+
+        cpu at 0 {
+            device_type = "cpu";
+            reg = <0>;
+            compatible = "sifive,bullet0", "riscv";
+            riscv,isa-base = "rv64i";
+            riscv,isa-extensions = "i", "m", "a", "f", "d", "c";
+            riscv,pmwid = <0>;
+
+            interrupt-controller {
+                #interrupt-cells = <1>;
+                compatible = "riscv,cpu-intc";
+                interrupt-controller;
+            };
+        };
+
+        cpu at 1 {
+            device_type = "cpu";
+            reg = <1>;
+            compatible = "sifive,bullet0", "riscv";
+            riscv,isa-base = "rv64i";
+            riscv,isa-extensions = "i", "m", "a", "f", "d", "c";
+            riscv,pmwid = <1>;
+
+            interrupt-controller {
+                #interrupt-cells = <1>;
+                compatible = "riscv,cpu-intc";
+                interrupt-controller;
+            };
+        };
+    };
-- 
2.43.7