Re: [PATCH v2.1 1/3] perf: Add Arm CMN-600 DT binding

From: Rob Herring <robh@kernel.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org, patrik.berglund@arm.com,
	tuanphan@os.amperecomputing.com, tsahee@amazon.com,
	harb@amperecomputing.com,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	james.yang@arm.com, Will Deacon <will@kernel.org>,
	"Saidi, Ali" <alisaidi@amazon.com>
Subject: Re: [PATCH v2.1 1/3] perf: Add Arm CMN-600 DT binding
Date: Fri, 18 Sep 2020 12:54:19 -0600	[thread overview]
Message-ID: <CAL_JsqKQUyp4tUrw149yF5PHgz6HQ3_Szy1PD=L8=pzU_vWotw@mail.gmail.com> (raw)
In-Reply-To: <3647765303e8936d45a69fe7c1f92b8d1b45de4b.1600452762.git.robin.murphy@arm.com>

On Fri, Sep 18, 2020 at 12:24 PM Robin Murphy <robin.murphy@arm.com> wrote:
>
> Document the requirements for the CMN-600 DT binding. The internal
> topology is almost entirely discoverable by walking a tree of ID
> registers, but sadly both the starting point for that walk and the
> exact format of those registers are configuration-dependent and not
> discoverable from some sane fixed location. Oh well.
>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
>
> fix up $id as well, oops...
>
>  .../devicetree/bindings/perf/arm,cmn.yaml     | 57 +++++++++++++++++++
>  1 file changed, 57 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/perf/arm,cmn.yaml

Do you expect this to cover more than cmn-600? If not, use the
compatible string for the file name.

>
> diff --git a/Documentation/devicetree/bindings/perf/arm,cmn.yaml b/Documentation/devicetree/bindings/perf/arm,cmn.yaml
> new file mode 100644
> index 000000000000..e4fcc0de25e2
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/perf/arm,cmn.yaml
> @@ -0,0 +1,57 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +# Copyright 2020 Arm Ltd.
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/perf/arm,cmn.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Arm CMN (Coherent Mesh Network) Performance Monitors
> +
> +maintainers:
> +  - Robin Murphy <robin.murphy@arm.com>
> +
> +properties:
> +  compatible:
> +    const: arm,cmn-600
> +
> +  reg:
> +    items:
> +      - description: Physical address of the base (PERIPHBASE) and
> +          size (up to 64MB) of the configuration address space.
> +
> +  interrupts:
> +    minItems: 1
> +    maxItems: 4
> +    items:
> +      - description: Overflow interrupt for DTC0
> +      - description: Overflow interrupt for DTC1
> +      - description: Overflow interrupt for DTC2
> +      - description: Overflow interrupt for DTC3
> +    description: One interrupt for each DTC domain implemented must
> +      be specified, in order. DTC0 is always present.

What's DTC?

> +
> +  arm,root-node:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: Offset from PERIPHBASE of the configuration
> +      discovery node (see TRM definition of ROOTNODEBASE).

You can enforce some alignment:

multipleOf: 0x4000

> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +  - arm,root-node
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +    #include <dt-bindings/interrupt-controller/irq.h>
> +    pmu@50000000 {
> +        compatible = "arm,cmn-600";
> +        reg = <0x50000000 0x4000000>;
> +        /* 4x2 mesh with one DTC, and CFG node at 0,1,1,0 */
> +        interrupts = <GIC_SPI 46 IRQ_TYPE_LEVEL_HIGH>;
> +        arm,root-node = <0x104000>;
> +    };
> +...
> --
> 2.28.0.dirty

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