linux-kernel - Re: [PATCH v5 1/7] dt-bindings: iommu: Add Qualcomm TBU bindings

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Date: Thu, 29 Feb 2024 18:53:47 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Georgi Djakov <quic_c_gdjako@...cinc.com>, robh+dt@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org, will@...nel.org,
 robin.murphy@....com, joro@...tes.org, iommu@...ts.linux.dev
Cc: devicetree@...r.kernel.org, andersson@...nel.org,
 konrad.dybcio@...aro.org, robdclark@...il.com,
 linux-arm-kernel@...ts.infradead.org, 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 v5 1/7] dt-bindings: iommu: Add Qualcomm TBU bindings

On 26/02/2024 18:22, 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). These TBUs have
> hardware debugging features that are specific and only present on
> Qualcomm hardware. Represent them as independent DT nodes. List all
> the resources that are needed to operate them (such as registers,
> clocks, power domains and interconnects).
> 
> Signed-off-by: Georgi Djakov <quic_c_gdjako@...cinc.com>
> ---
>  .../devicetree/bindings/iommu/qcom,tbu.yaml   | 65 +++++++++++++++++++
>  1 file changed, 65 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iommu/qcom,tbu.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iommu/qcom,tbu.yaml b/Documentation/devicetree/bindings/iommu/qcom,tbu.yaml
> new file mode 100644
> index 000000000000..6841ca9af21f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iommu/qcom,tbu.yaml
> @@ -0,0 +1,65 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iommu/qcom,tbu.yaml#
> +$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 with each client core.
> +
> +properties:
> +  compatible:
> +    const: qcom,qsmmuv500-tbu

Why we don't have SoC specific compatibles? If that's for SDM845, then
it should be qcom,sdm845-tbu or qcom,sdm845-qsmmuv500-tbu


> +
> +  reg:
> +    maxItems: 1
> +
> +  clocks:
> +    maxItems: 1
> +
> +  interconnects:
> +    maxItems: 1
> +
> +  power-domains:
> +    maxItems: 1
> +
> +  qcom,stream-id-range:
> +    description: Phandle of a SMMU device and Stream ID range (address and size) that is assigned by the TBU

Please wrap it according to coding style, so 80.

> +    $ref: /schemas/types.yaml#/definitions/phandle-array
> +    items:
> +      - items:
> +          - description: phandle of a smmu node
> +          - description: stream id base address
> +          - description: stream id size
> +
> +required:
> +  - compatible
> +  - reg
> +  - qcom,stream-id-range
> +
> +unevaluatedProperties: false

This should be additionalProperties: false

> +
> +examples:
Best regards,
Krzysztof