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

[Yu-Chien Peter Lin <peter.lin@sifive.com>]

Add per-hart DT properties for 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.

Signed-off-by: Yu-Chien Peter Lin <peter.lin@sifive.com>
---
 .../devicetree/bindings/riscv/cpus.yaml       | 21 +++++
 .../devicetree/bindings/riscv/worlds.yaml     | 77 +++++++++++++++++++
 2 files changed, 98 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..4b5778b6d3e7 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:
@@ -120,11 +121,31 @@ 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:
+      Platform-defined M-mode World ID (WID) assigned to this hart.
+    minimum: 0
+    maximum: 63
+
+  riscv,pmwidlist:
+    $ref: /schemas/types.yaml#/definitions/uint64
+    description:
+      Platform-defined bitmap of M-mode World IDs (WIDs) that this hart may use.
+
+  riscv,pmlwidlist:
+    $ref: /schemas/types.yaml#/definitions/uint64
+    description:
+      Platform-defined bitmap of World IDs (WIDs) that S-mode and U-mode may use
+      on this hart.
+
   # RISC-V has multiple properties for cache op block sizes as the sizes
   # differ between individual CBO extensions
   cache-op-block-size: false
   # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
   timebase-frequency: false
+  # RISC-V requires 'riscv,nworlds' in /cpus, so disallow it here
+  riscv,nworlds: false
 
   interrupt-controller:
     type: object
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@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@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@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