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Message-ID: <20250711214314.GA1376683-robh@kernel.org>
Date: Fri, 11 Jul 2025 16:43:14 -0500
From: Rob Herring <robh@...nel.org>
To: James Morse <james.morse@....com>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
Ben Horgan <ben.horgan@....com>,
Rohit Mathew <rohit.mathew@....com>,
Shanker Donthineni <sdonthineni@...dia.com>,
Zeng Heng <zengheng4@...wei.com>,
Lecopzer Chen <lecopzerc@...dia.com>,
Carl Worth <carl@...amperecomputing.com>,
shameerali.kolothum.thodi@...wei.com,
D Scott Phillips OS <scott@...amperecomputing.com>,
lcherian@...vell.com, bobo.shaobowang@...wei.com,
tan.shaopeng@...itsu.com, baolin.wang@...ux.alibaba.com,
Jamie Iles <quic_jiles@...cinc.com>,
Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
dfustini@...libre.com, amitsinght@...vell.com,
David Hildenbrand <david@...hat.com>,
Rex Nie <rex.nie@...uarmicro.com>,
Dave Martin <dave.martin@....com>, Koba Ko <kobak@...dia.com>
Subject: Re: [RFC PATCH 11/36] dt-bindings: arm: Add MPAM MSC binding
On Fri, Jul 11, 2025 at 06:36:23PM +0000, James Morse wrote:
> From: Rob Herring <robh@...nel.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@....com>
> Signed-off-by: Rob Herring <robh@...nel.org>
> Signed-off-by: James Morse <james.morse@....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.
> 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@...nel.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: |
'|' 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@...00000 {
> + 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@...00 {
> + 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@...00 {
> + compatible = "foo,a-memory-controller";
> + reg = <0x20000 0x1000>;
> +
> + #address-cells = <1>;
> + #size-cells = <1>;
> + ranges;
> +
> + msc@...00 {
> + 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@...00 {
> + reg = <0x40000 0x1000>;
> +
> + ranges;
> + #address-cells = <1>;
> + #size-cells = <1>;
> +
> + msc@...00 {
> + 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@...00 {
> + compatible = "foo,a-standalone-msc";
> + reg = <0x80000 0x1000>;
> +
> + clocks = <&clks 123>;
> +
> + ranges;
> + #address-cells = <1>;
> + #size-cells = <1>;
> +
> + msc@...00 {
> + 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
>
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