[RFC 2/6] dt-bindings: riscv: add riscv,isa-extension-* property and incompatible example

[Conor Dooley <conor@xxxxxxxxxx>]

From: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>

This dt-binding is illustrative *only*, it doesn't yet do what I want it
to do in terms of enforcement etc. I am yet to figure out exactly how to
wrangle the binding such that the individual properties have more
generous versions than the generic pattern property.
This binding *will* generate errors, and needs rework before it can
seriously be considered.
Nevertheless, it should demonstrate how I intend such a property be
used.

Not-signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
---
 .../devicetree/bindings/riscv/cpus.yaml       | 61 ++++++++++++++++++-
 1 file changed, 60 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
index 405915b04d69..cccb3b2ae23d 100644
--- a/Documentation/devicetree/bindings/riscv/cpus.yaml
+++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
@@ -100,6 +100,15 @@ properties:
       lowercase.
     $ref: "/schemas/types.yaml#/definitions/string"
     pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:[hsxz](?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
+    deprecated: true
+
+  riscv,isa-base:
+    description:
+      Identifies the base ISA supported by a hart.
+    $ref: "/schemas/types.yaml#/definitions/string"
+    enum:
+      - rv32i
+      - rv64i
 
   # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
   timebase-frequency: false
@@ -136,8 +145,32 @@ properties:
       DMIPS/MHz, relative to highest capacity-dmips-mhz
       in the system.
 
+  riscv,isa-extension-v:
+    description: RISC-V Vector extension
+    $ref: "/schemas/types.yaml#/definitions/string"
+    oneOf:
+      - const: v1.0.0
+        description: the original incarnation
+      - const: v1.0.1
+        description: backwards compat was broken here
+
+patternProperties:
+  "^riscv,isa-extension-*":
+    description:
+      Catch-all property for ISA extensions that do not need any special
+      handling, and of which all known versions are compatible with their
+      original revision.
+    $ref: "/schemas/types.yaml#/definitions/string"
+    enum:
+      - v1.0.0
+
+oneOf:
+  - required:
+      - riscv,isa-base
+  - required:
+      - riscv,isa
+
 required:
-  - riscv,isa
   - interrupt-controller
 
 additionalProperties: true
@@ -208,4 +241,30 @@ examples:
                 };
         };
     };
+
+  - |
+    // Example 3: Extension specification
+    cpus {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        cpu@0 {
+                device_type = "cpu";
+                reg = <0>;
+                compatible = "riscv";
+                riscv,isa-base = "rv64i";
+                riscv,isa-extension-i = "v1.0.0";
+                riscv,isa-extension-m = "v1.0.0";
+                riscv,isa-extension-a = "v1.0.0";
+                riscv,isa-extension-f = "v1.0.0";
+                riscv,isa-extension-d = "v1.0.0";
+                riscv,isa-extension-c = "v2.0.0";
+                riscv,isa-extension-v = "v1.0.1";
+                mmu-type = "riscv,sv48";
+                interrupt-controller {
+                        #interrupt-cells = <1>;
+                        interrupt-controller;
+                        compatible = "riscv,cpu-intc";
+                };
+        };
+    };
 ...
-- 
2.39.2