Re: [PATCH v2 7/8] dt-bindings: riscv: Add generic CBQRI controller binding

[Conor Dooley]

On Wed, Jun 24, 2026 at 06:38:35PM -0700, Drew Fustini wrote:
> Document the generic compatibles for capacity and bandwidth controllers
> that implement the RISC-V CBQRI specification. The binding also
> describes the common riscv,cbqri-rcid and riscv,cbqri-mcid properties,
> and the optional riscv,cbqri-cache phandle that links a capacity
> controller to the cache whose capacity it allocates.
> 
> Assisted-by: Claude:claude-opus-4-8
> Co-developed-by: Adrien Ricciardi <aricciardi@xxxxxxxxxxxx>
> Signed-off-by: Adrien Ricciardi <aricciardi@xxxxxxxxxxxx>
> Signed-off-by: Drew Fustini <fustini@xxxxxxxxxx>
> ---
>  .../devicetree/bindings/riscv/riscv,cbqri.yaml     | 97 ++++++++++++++++++++++
>  MAINTAINERS                                        |  1 +
>  2 files changed, 98 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/riscv/riscv,cbqri.yaml b/Documentation/devicetree/bindings/riscv/riscv,cbqri.yaml
> new file mode 100644
> index 0000000000000000000000000000000000000000..5d6be645381780e187b39e60c3bb487fdf2cfb69
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/riscv/riscv,cbqri.yaml
> @@ -0,0 +1,97 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/riscv/riscv,cbqri.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: RISC-V Capacity and Bandwidth QoS Register Interface (CBQRI) controller
> +
> +description: |
> +  The RISC-V CBQRI specification defines capacity-controller and
> +  bandwidth-controller register blocks that allocate cache capacity and memory
> +  bandwidth to resource-control IDs (RCIDs) and monitor usage per
> +  monitoring-counter ID (MCID):
> +  https://github.com/riscv-non-isa/riscv-cbqri/blob/main/riscv-cbqri.pdf
> +
> +  Allocation and monitoring share one register block, and a controller may
> +  implement either or both. A driver discovers which at runtime from the
> +  capabilities register, so the compatible names only the controller type. It
> +  does not distinguish allocation-only, monitoring-only or combined
> +  controllers, and no property declares monitoring support.
> +
> +maintainers:
> +  - Drew Fustini <fustini@xxxxxxxxxx>
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - items:
> +          - description: Tenstorrent Ascalon Shared Cache
> +            const: tenstorrent,ascalon-sc-cbqri
> +          - const: riscv,cbqri-capacity-controller
> +      - enum:
> +          - riscv,cbqri-capacity-controller
> +          - riscv,cbqri-bandwidth-controller

Please modify this, as has been done for other riscv spec related
bindings, to let people get away without using device-specific
compatibles.

In this case, you can just delete the first entry from this enum, since
it already has a user and only have to implement this feedback for the
second entry.

pw-bot: changes-requested

> +
> +  reg:
> +    maxItems: 1
> +    description:
> +      The CBQRI controller register block.
> +
> +  riscv,cbqri-rcid:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      The maximum number of RCIDs the controller supports. RCIDs are the
> +      resource-control IDs that allocation operations target.
> +
> +  riscv,cbqri-mcid:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      The maximum number of MCIDs the controller supports. MCIDs are the
> +      monitoring-counter IDs that usage-monitoring operations target. Present
> +      on controllers that implement monitoring.
> +
> +  riscv,cbqri-cache:
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +    description:
> +      Phandle to the cache node whose capacity this controller allocates.
> +      Applies to capacity controllers that back a CPU cache. The cache level
> +      and the harts sharing it are taken from that node's cache topology.

Architecturally, is it impossible for a capacity controller to control
more than one cache?

> +
> +required:
> +  - compatible
> +  - reg
> +
> +allOf:
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: tenstorrent,ascalon-sc-cbqri
> +    then:
> +      required:
> +        - riscv,cbqri-rcid
> +        - riscv,cbqri-cache
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    l2_cache: l2-cache {
> +        compatible = "cache";
> +        cache-level = <2>;
> +        cache-unified;
> +        cache-size = <0xc00000>;
> +        cache-sets = <512>;
> +        cache-block-size = <64>;
> +    };
> +
> +    cache-controller@a21a00c0 {
> +        compatible = "tenstorrent,ascalon-sc-cbqri",
> +                     "riscv,cbqri-capacity-controller";

Is this or is this not a cache controller?
The compatible and fact that the property points to an actual cache
controller suggests that this is not.

Cheers,
Conor.

> +        reg = <0xa21a00c0 0xf40>;
> +        riscv,cbqri-rcid = <16>;
> +        riscv,cbqri-cache = <&l2_cache>;
> +    };
> +
> +...
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 9e1092165046c773771b055869030bc1bdb64b16..64a95a4d795a57033d3f36200d98cfb4a013ab94 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -23298,6 +23298,7 @@ M:	Drew Fustini <fustini@xxxxxxxxxx>
>  R:	yunhui cui <cuiyunhui@xxxxxxxxxxxxx>
>  L:	linux-riscv@xxxxxxxxxxxxxxxxxxx
>  S:	Supported
> +F:	Documentation/devicetree/bindings/riscv/riscv,cbqri.yaml
>  F:	arch/riscv/include/asm/qos.h
>  F:	arch/riscv/include/asm/resctrl.h
>  F:	arch/riscv/kernel/qos.c
> 
> -- 
> 2.34.1
>

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