linux-kernel - Re: [PATCH v3 1/2] dt-bindings: iommu: add bindings for sprd iommu

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Date:   Thu, 4 Mar 2021 15:11:51 +0800
From:   Chunyan Zhang <zhang.lyra@...il.com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Rob Herring <robh@...nel.org>, Joerg Roedel <joro@...tes.org>,
        Linux IOMMU <iommu@...ts.linux-foundation.org>,
        DTML <devicetree@...r.kernel.org>,
        Baolin Wang <baolin.wang7@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Orson Zhai <orsonzhai@...il.com>,
        Sheng Xu <sheng.xu@...soc.com>,
        Chunyan Zhang <chunyan.zhang@...soc.com>
Subject: Re: [PATCH v3 1/2] dt-bindings: iommu: add bindings for sprd iommu

Hi Robin,

On Tue, 16 Feb 2021 at 23:10, Robin Murphy <robin.murphy@....com> wrote:
>
> >>>
> >>> On Wed, Feb 03, 2021 at 05:07:26PM +0800, Chunyan Zhang wrote:
> >>>> From: Chunyan Zhang <chunyan.zhang@...soc.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@...soc.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@...il.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"
>
> OK, so apparently the hardware is not quite as trivial as my initial
> impression, and you should have interrupts as well.

I've checked with my colleagues for this issue. And like I explained
before, one sprd IOMMU serves one master device only, so interrupts
are handled by master devices rather than IOMMUs.

Chunyan