On Fri, Jul 11, 2025 at 06:36:23PM +0000, James Morse wrote:

From: Rob Herring <robh@kernel.org>

The binding is designed around the assumption that an MSC will be a
sub-block of something else such as a memory controller, cache controller,
or IOMMU. However, it's certainly possible a design does not have that
association or has a mixture of both, so the binding illustrates how we can
support that with RIS child nodes.

A key part of MPAM is we need to know about all of the MSCs in the system
before it can be enabled. This drives the need for the genericish
'arm,mpam-msc' compatible. Though we can't assume an MSC is accessible
until a h/w specific driver potentially enables the h/w.

Cc: James Morse <james.morse@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: James Morse <james.morse@arm.com>
---
 .../devicetree/bindings/arm/arm,mpam-msc.yaml | 227 ++++++++++++++++++
 1 file changed, 227 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/arm/arm,mpam-msc.yaml

Is there any DT based h/w using this? I'm not aware of any. I would 
prefer not merging this until there is. I have little insight whether 
these genericish compatibles will be sufficient, but I have lots of 
experience to say they won't be. I would also suspect that if anyone has 
started using this, they've just extended/modified it however they 
wanted and no feedback got to me.

'|' can be dropped.

+      RIS nodes for each RIS in an MSC. These nodes are required for each RIS
+      implementing known MPAM controls
+
+    properties:
+      compatible:
+        enum:
+            # Bulk storage for cache
+          - arm,mpam-cache
+            # Memory bandwidth
+          - arm,mpam-memory
+
+      reg:
+        minimum: 0
+        maximum: 0xf
+
+      cpus:
+        $ref: '/schemas/types.yaml#/definitions/phandle-array'

Don't need the type. It's in the core schemas now.

+        description:
+          Phandle(s) to the CPU node(s) this RIS belongs to. By default, the parent
+          device's affinity is used.
+
+      arm,mpam-device:
+        $ref: '/schemas/types.yaml#/definitions/phandle'

Don't need quotes. This should be a warning, but no testing happened 
because the DT list and maintainers weren't CCed.

+        description:
+          By default, the MPAM enabled device associated with a RIS is the MSC's
+          parent node. It is possible for each RIS to be associated with different
+          devices in which case 'arm,mpam-device' should be used.
+
+    required:
+      - compatible
+      - reg
+
+required:
+  - compatible
+  - reg
+
+dependencies:
+  interrupts: [ interrupt-names ]
+
+additionalProperties: false
+
+examples:
+  - |
+    /*
+    cpus {
+        cpu@0 {
+            next-level-cache = <&L2_0>;
+        };
+        cpu@100 {
+            next-level-cache = <&L2_1>;
+        };
+    };
+    */
+    L2_0: cache-controller-0 {
+        compatible = "cache";
+        cache-level = <2>;
+        cache-unified;
+        next-level-cache = <&L3>;
+
+    };
+
+    L2_1: cache-controller-1 {
+        compatible = "cache";
+        cache-level = <2>;
+        cache-unified;
+        next-level-cache = <&L3>;
+
+    };

All the above should be dropped. Not part of this binding.

+
+    L3: cache-controller@30000000 {
+        compatible = "arm,dsu-l3-cache", "cache";

Pretty sure this is a warning because that compatible doesn't exist.

+        cache-level = <3>;
+        cache-unified;
+
+        ranges = <0x0 0x30000000 0x800000>;
+        #address-cells = <1>;
+        #size-cells = <1>;
+
+        msc@10000 {
+            compatible = "arm,mpam-msc";
+
+            /* CPU affinity implied by parent cache node's  */
+            reg = <0x10000 0x2000>;
+            interrupts = <1>, <2>;
+            interrupt-names = "error", "overflow";
+            arm,not-ready-us = <1>;
+        };
+    };
+
+    mem: memory-controller@20000 {
+        compatible = "foo,a-memory-controller";
+        reg = <0x20000 0x1000>;
+
+        #address-cells = <1>;
+        #size-cells = <1>;
+        ranges;
+
+        msc@21000 {
+            compatible = "arm,mpam-memory-controller-msc", "arm,mpam-msc";
+            reg = <0x21000 0x1000>;
+            interrupts = <3>;
+            interrupt-names = "error";
+            arm,not-ready-us = <1>;
+            numa-node-id = <1>;
+        };
+    };
+
+    iommu@40000 {
+        reg = <0x40000 0x1000>;
+
+        ranges;
+        #address-cells = <1>;
+        #size-cells = <1>;
+
+        msc@41000 {
+            compatible = "arm,mpam-msc";
+            reg = <0 0x1000>;
+            interrupts = <5>, <6>;
+            interrupt-names = "error", "overflow";
+            arm,not-ready-us = <1>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            ris@2 {
+                compatible = "arm,mpam-cache";
+                reg = <0>;
+                // TODO: How to map to device(s)?
+            };
+        };
+    };
+
+    msc@80000 {
+        compatible = "foo,a-standalone-msc";
+        reg = <0x80000 0x1000>;
+
+        clocks = <&clks 123>;
+
+        ranges;
+        #address-cells = <1>;
+        #size-cells = <1>;
+
+        msc@10000 {
+            compatible = "arm,mpam-msc";
+
+            reg = <0x10000 0x2000>;
+            interrupts = <7>;
+            interrupt-names = "overflow";
+            arm,not-ready-us = <1>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            ris@0 {
+                compatible = "arm,mpam-cache";
+                reg = <0>;
+                arm,mpam-device = <&L2_0>;
+            };
+
+            ris@1 {
+                compatible = "arm,mpam-memory";
+                reg = <1>;
+                arm,mpam-device = <&mem>;
+            };
+        };
+    };
+
+...
-- 
2.39.5