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

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Date:   Fri, 8 Jan 2021 19:33:24 +0800
From:   Chunyan Zhang <zhang.lyra@...il.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Joerg Roedel <joro@...tes.org>, 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>,
        Kevin Tang <kevin.tang@...soc.com>
Subject: Re: [RFC PATCH 1/2] dt-bindings: iommu: add bindings for sprd iommu

On Fri, 8 Jan 2021 at 10:25, Rob Herring <robh@...nel.org> wrote:
>
> On Wed, Dec 23, 2020 at 07:16:32PM +0800, Chunyan Zhang wrote:
> > From: Chunyan Zhang <chunyan.zhang@...soc.com>
> >
> > This patch only adds bindings to support display iommu, support for others
> > would be added once finished tests with those devices, such as Image
> > codec(jpeg) processor, a few signal processors, including VSP(video),
> > GSP(graphic), ISP(image), and camera CPP, etc.
> >
> > Signed-off-by: Chunyan Zhang <chunyan.zhang@...soc.com>
> > ---
> >  .../devicetree/bindings/iommu/sprd,iommu.yaml | 44 +++++++++++++++++++
> >  1 file changed, 44 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..4d9a578a7cc9
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iommu/sprd,iommu.yaml
> > @@ -0,0 +1,44 @@
> > +# 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-disp
>
> Needs to be Soc specific.

All SoCs so far use the same iommu IP, there's a little different
among different iommu users.

> Is this block specific to display subsys or
> that just happens to be where the instance is?

This iommu driver can serve many subsystem devices, such as Video,
Camera, Image, etc., but they have their own iommu module which looks
like a subdevice embedded in the master devices.
I will add more compatible strings for those devices when needed.
For now, only this one was listed here because I just tested this
iommu driver with DPU only.

Thanks for the review.

Chunyan

>
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  "#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
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - "#iommu-cells"
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    iommu_disp: iommu@...00000 {
> > +      compatible = "sprd,iommu-disp";
> > +      reg = <0x63000000 0x880>;
> > +      #iommu-cells = <0>;
> > +    };
> > +
> > +...
> > --
> > 2.25.1
> >