linux-kernel - Re: [PATCH v2 1/6] dt-bindings: iommu: Add Translation Buffer Unit bindings

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Message-ID: <20231127181347.GA1953740-robh@kernel.org>
Date:   Mon, 27 Nov 2023 12:13:47 -0600
From:   Rob Herring <robh@...nel.org>
To:     Georgi Djakov <quic_c_gdjako@...cinc.com>
Cc:     krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        will@...nel.org, robin.murphy@....com, joro@...tes.org,
        devicetree@...r.kernel.org, andersson@...nel.org,
        konrad.dybcio@...aro.org, linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, quic_cgoldswo@...cinc.com,
        quic_sukadev@...cinc.com, quic_pdaly@...cinc.com,
        quic_sudaraja@...cinc.com, djakov@...nel.org
Subject: Re: [PATCH v2 1/6] dt-bindings: iommu: Add Translation Buffer Unit
 bindings

On Fri, Nov 17, 2023 at 08:27:25PM -0800, Georgi Djakov wrote:
> The "apps_smmu" on the Qualcomm sdm845 platform is an implementation
> of the SMMU-500, that consists of a single TCU (Translation Control
> Unit) and multiple TBUs (Translation Buffer Units). The TCU is already
> being described in the generic SMMU DT schema. Add also bindings for
> the TBUs to describe their properties and resources that needs to be
> managed in order to operate them.
> 
> In this DT schema, the TBUs are modelled as child devices of the TCU
> and each of them is described with it's register space, clocks, power
> domains, interconnects etc.
> 
> Signed-off-by: Georgi Djakov <quic_c_gdjako@...cinc.com>
> ---
>  .../devicetree/bindings/iommu/arm,smmu.yaml   | 25 ++++++
>  .../bindings/iommu/qcom,qsmmuv500-tbu.yaml    | 89 +++++++++++++++++++
>  2 files changed, 114 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iommu/qcom,qsmmuv500-tbu.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
> index aa9e1c0895a5..f7f89be5f7a3 100644
> --- a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
> @@ -231,6 +231,18 @@ properties:
>        enabled for any given device.
>      $ref: /schemas/types.yaml#/definitions/phandle
>  
> +  '#address-cells':
> +    enum: [ 1, 2 ]
> +
> +  '#size-cells':
> +    enum: [ 1, 2 ]
> +
> +  ranges: true
> +
> +patternProperties:
> +  "^tbu@[0-9a-f]*":
> +    type: object
> +
>  required:
>    - compatible
>    - reg
> @@ -453,6 +465,19 @@ allOf:
>              - description: Voter clock required for HLOS SMMU access
>              - description: Interface clock required for register access
>  
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: qcom,smmu-500

Doesn't match your example. No failure either, so there's some problem 
with your schema. The issue is the tbu@ entry above has no constraint on 
child properties. Dropping it would solve the issue. However, having a 
TBU is not QCom specific, so that doesn't feel right.


> +    then:
> +      patternProperties:
> +        "^tbu@[0-9a-f]*":

'+' rather than '*' as 1 is the minimum, not 0.

> +          $ref: qcom,qsmmuv500-tbu.yaml
> +          unevaluatedProperties: false
> +      properties:
> +        ranges: true
> +
>    # Disallow clocks for all other platforms with specific compatibles
>    - if:
>        properties:
> diff --git a/Documentation/devicetree/bindings/iommu/qcom,qsmmuv500-tbu.yaml b/Documentation/devicetree/bindings/iommu/qcom,qsmmuv500-tbu.yaml
> new file mode 100644
> index 000000000000..4dc9d0ca33c9
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iommu/qcom,qsmmuv500-tbu.yaml
> @@ -0,0 +1,89 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iommu/qcom,qsmmuv500-tbu.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Qualcomm TBU (Translation Buffer Unit)
> +
> +maintainers:
> +  - Georgi Djakov <quic_c_gdjako@...cinc.com>
> +
> +description:
> +  The Qualcomm SMMU500 implementation consists of TCU and TBU. The TBU contains
> +  a Translation Lookaside Buffer (TLB) that caches page tables. TBUs provides
> +  debug features to trace and trigger debug transactions. There are multiple TBU
> +  instances distributes with each client core.
> +
> +properties:
> +  $nodename:
> +    pattern: "^tbu@[0-9a-f]+$"

Drop. You defined this in the parent already.

> +
> +  compatible:
> +    const: qcom,qsmmuv500-tbu
> +
> +  reg:
> +    items:
> +      - description: Address and size of the TBU's register space.
> +
> +  reg-names:
> +    items:
> +      - const: base

Not a useful name. Drop.

> +
> +  clocks:
> +    maxItems: 1
> +
> +  interconnects:
> +    maxItems: 1
> +
> +  power-domains:
> +    maxItems: 1
> +
> +  qcom,stream-id-range:
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +    description: Stream ID range (address and size) that is assigned by the TBU
> +    items:
> +      minItems: 2
> +      maxItems: 2

Perhaps implementations other than QCom's needs this?

Rob