[RFC PATCH 11/36] dt-bindings: arm: Add MPAM MSC binding
James Morse
james.morse at arm.com
Fri Jul 11 11:36:23 PDT 2025
From: Rob Herring <robh at 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 at arm.com>
Signed-off-by: Rob Herring <robh at kernel.org>
Signed-off-by: James Morse <james.morse at 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
diff --git a/Documentation/devicetree/bindings/arm/arm,mpam-msc.yaml b/Documentation/devicetree/bindings/arm/arm,mpam-msc.yaml
new file mode 100644
index 000000000000..9d542ecb1a7d
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/arm,mpam-msc.yaml
@@ -0,0 +1,227 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/arm,mpam-msc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Arm Memory System Resource Partitioning and Monitoring (MPAM)
+
+description: |
+ The Arm MPAM specification can be found here:
+
+ https://developer.arm.com/documentation/ddi0598/latest
+
+maintainers:
+ - Rob Herring <robh at kernel.org>
+
+properties:
+ compatible:
+ items:
+ - const: arm,mpam-msc # Further details are discoverable
+ - const: arm,mpam-memory-controller-msc
+
+ reg:
+ maxItems: 1
+ description: A memory region containing registers as defined in the MPAM
+ specification.
+
+ interrupts:
+ minItems: 1
+ items:
+ - description: error (optional)
+ - description: overflow (optional, only for monitoring)
+
+ interrupt-names:
+ oneOf:
+ - items:
+ - enum: [ error, overflow ]
+ - items:
+ - const: error
+ - const: overflow
+
+ arm,not-ready-us:
+ description: The maximum time in microseconds for monitoring data to be
+ accurate after a settings change. For more information, see the
+ Not-Ready (NRDY) bit description in the MPAM specification.
+
+ numa-node-id: true # see NUMA binding
+
+ '#address-cells':
+ const: 1
+
+ '#size-cells':
+ const: 0
+
+patternProperties:
+ '^ris@[0-9a-f]$':
+ type: object
+ additionalProperties: false
+ description: |
+ 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'
+ 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'
+ 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 at 0 {
+ next-level-cache = <&L2_0>;
+ };
+ cpu at 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>;
+
+ };
+
+ L3: cache-controller at 30000000 {
+ compatible = "arm,dsu-l3-cache", "cache";
+ cache-level = <3>;
+ cache-unified;
+
+ ranges = <0x0 0x30000000 0x800000>;
+ #address-cells = <1>;
+ #size-cells = <1>;
+
+ msc at 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 at 20000 {
+ compatible = "foo,a-memory-controller";
+ reg = <0x20000 0x1000>;
+
+ #address-cells = <1>;
+ #size-cells = <1>;
+ ranges;
+
+ msc at 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 at 40000 {
+ reg = <0x40000 0x1000>;
+
+ ranges;
+ #address-cells = <1>;
+ #size-cells = <1>;
+
+ msc at 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 at 2 {
+ compatible = "arm,mpam-cache";
+ reg = <0>;
+ // TODO: How to map to device(s)?
+ };
+ };
+ };
+
+ msc at 80000 {
+ compatible = "foo,a-standalone-msc";
+ reg = <0x80000 0x1000>;
+
+ clocks = <&clks 123>;
+
+ ranges;
+ #address-cells = <1>;
+ #size-cells = <1>;
+
+ msc at 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 at 0 {
+ compatible = "arm,mpam-cache";
+ reg = <0>;
+ arm,mpam-device = <&L2_0>;
+ };
+
+ ris at 1 {
+ compatible = "arm,mpam-memory";
+ reg = <1>;
+ arm,mpam-device = <&mem>;
+ };
+ };
+ };
+
+...
--
2.39.5
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