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Date:   Thu, 4 Feb 2021 17:25:49 -0600
From:   Rob Herring <robh@kernel.org>
To:     Chunyan Zhang <zhang.lyra@gmail.com>
Cc:     Robin Murphy <robin.murphy@arm.com>,
        Joerg Roedel <joro@8bytes.org>,
        iommu@lists.linux-foundation.org, devicetree@vger.kernel.org,
        Baolin Wang <baolin.wang7@gmail.com>,
        linux-kernel@vger.kernel.org, Orson Zhai <orsonzhai@gmail.com>,
        Sheng Xu <sheng.xu@unisoc.com>,
        Chunyan Zhang <chunyan.zhang@unisoc.com>
Subject: Re: [PATCH v3 1/2] dt-bindings: iommu: add bindings for sprd iommu
Message-ID: <20210204232549.GA1305874@robh.at.kernel.org>
References: <20210203090727.789939-1-zhang.lyra@gmail.com>
 <20210203090727.789939-2-zhang.lyra@gmail.com>
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On Wed, Feb 03, 2021 at 05:07:26PM +0800, Chunyan Zhang wrote:
> From: Chunyan Zhang <chunyan.zhang@unisoc.com>
> 
> This iommu module can be used by Unisoc's multimedia devices, such as
> display, Image codec(jpeg) and a few signal processors, including
> VSP(video), GSP(graphic), ISP(image), and CPP(camera pixel processor), etc.
> 
> Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
> ---
>  .../devicetree/bindings/iommu/sprd,iommu.yaml | 72 +++++++++++++++++++
>  1 file changed, 72 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iommu/sprd,iommu.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iommu/sprd,iommu.yaml b/Documentation/devicetree/bindings/iommu/sprd,iommu.yaml
> new file mode 100644
> index 000000000000..4fc99e81fa66
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iommu/sprd,iommu.yaml
> @@ -0,0 +1,72 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +# Copyright 2020 Unisoc Inc.
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iommu/sprd,iommu.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Unisoc IOMMU and Multi-media MMU
> +
> +maintainers:
> +  - Chunyan Zhang <zhang.lyra@gmail.com>
> +
> +properties:
> +  compatible:
> +    enum:
> +      - sprd,iommu-v1
> +
> +  "#iommu-cells":
> +    const: 0
> +    description:
> +      Unisoc IOMMUs are all single-master IOMMU devices, therefore no
> +      additional information needs to associate with its master device.
> +      Please refer to the generic bindings document for more details,
> +      Documentation/devicetree/bindings/iommu/iommu.txt
> +
> +  reg:
> +    maxItems: 1
> +    description:
> +      Not required if 'sprd,iommu-regs' is defined.
> +
> +  clocks:
> +    description:
> +      Reference to a gate clock phandle, since access to some of IOMMUs are
> +      controlled by gate clock, but this is not required.
> +
> +  sprd,iommu-regs:
> +    $ref: /schemas/types.yaml#/definitions/phandle-array
> +    description:
> +      Reference to a syscon phandle plus 1 cell, the syscon defines the
> +      register range used by the iommu and the media device, the cell
> +      defines the offset for iommu registers. Since iommu module shares
> +      the same register range with the media device which uses it.
> +
> +required:
> +  - compatible
> +  - "#iommu-cells"
> +
> +oneOf:
> +  - required:
> +      - reg
> +  - required:
> +      - sprd,iommu-regs
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    iommu_disp: iommu-disp {
> +      compatible = "sprd,iommu-v1";
> +      sprd,iommu-regs = <&dpu_regs 0x800>;

If the IOMMU is contained within another device, then it should just be 
a child node of that device. Or just make 'dpu_regs' an IOMMU provider 
(i.e. just add #iommu-cells to it).

> +      #iommu-cells = <0>;
> +    };
> +
> +  - |
> +    iommu_jpg: iommu-jpg {
> +      compatible = "sprd,iommu-v1";
> +      sprd,iommu-regs = <&jpg_regs 0x300>;
> +      #iommu-cells = <0>;
> +      clocks = <&mm_gate 1>;
> +    };
> +
> +...
> -- 
> 2.25.1
>