[RFC PATCH] dt-bindings: riscv: Add YAML documentation for PMU

[Anup Patel]

On Mon, Jul 27, 2020 at 1:57 PM Zong Li <zong.li at sifive.com> wrote:
>
> Add device tree bindings for performance monitor unit. It passes the
> dt_binding_check verification.
>
> Signed-off-by: Zong Li <zong.li at sifive.com>
> ---
>  .../devicetree/bindings/riscv/pmu.yaml        | 71 +++++++++++++++++++
>  1 file changed, 71 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/riscv/pmu.yaml
>
> diff --git a/Documentation/devicetree/bindings/riscv/pmu.yaml b/Documentation/devicetree/bindings/riscv/pmu.yaml
> new file mode 100644
> index 000000000000..0c49039a5d3b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/riscv/pmu.yaml
> @@ -0,0 +1,71 @@
> +# SPDX-License-Identifier: GPL-2.0
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/riscv/pmu.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: RISC-V Performance Monitor Units
> +
> +maintainers:
> +  - Zong Li <zong.li at sifive.com>
> +  - Paul Walmsley <paul.walmsley at sifive.com>
> +  - Palmer Dabbelt <palmer at dabbelt.com>
> +
> +properties:
> +  compatible:
> +    items:
> +      - const: riscv,pmu
> +
> +  riscv,width-hpmcntr:
> +    description: The width of hpmcounter CSRs. Default is 64.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +
> +  riscv,n-hpmcntr:
> +    description: The number of hpmcounter CSRs. Default is zero.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +
> +  riscv,hw-event-map:
> +    description: The mapping of generic hardware events to values of hpmcounter.
> +      The key is the encoding of generic hardware events, and the value is the
> +      actual value which is implemented by platform. If there is no a key-value
> +      pair for specific generic hardware event, view the generic hardware event
> +      as not supported. CYCLE and INSTRET be mapped by default, so we shouldn't
> +      list PERF_COUNT_HW_CPU_CYCLES and PERF_COUNT_HW_INSTRUCTIONS here.
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +
> +  riscv,hw-cache-event-map:
> +    description: The mapping of generic hardware cache events to values of
> +      hpmcounter. The key is encoding of generic hardware cache events, and the
> +      value is the actual value which is implemented by platform. If there is no
> +      a key-value pair for specific generic hardware cache event, view the
> +      generic hardware cache event as not supported.
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +
> +  riscv,hpmcntr-of-event:
> +    description: The mapping of platform hardware events to allowed hmpcounters.
> +      The key is the platform hardware event, and the value is the bitmap for
> +      hmpcounters which support this event. If there is no a key-value pair for
> +      specific platform hardware events, view the platform hardware events as
> +      supported by all hpmcounters.
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +
> +required:
> +  - compatible
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    pmu {
> +      compatible = "riscv,pmu";
> +      riscv,width-hpmcntr = <40>;
> +      riscv,n-hpmcntr = <2>;
> +      riscv,hw-event-map = <0x3 0x0202
> +                            0x4 0x4000>;
> +      riscv,hw-cache-event-map = <0x010201 0x0102
> +                                  0x010204 0x0802>;
> +      riscv,hpmcntr-of-event = <0x100 0x18
> +                                0x400 0x10>;
> +    };
> +
> +...
> --
> 2.27.0
>

I don't see the point of sending DT bindings documents
until the SBI PMU extension is defined and accepted
by everyone.

Regards,
Anup