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SubjectRe: [PATCH 1/6] Docs: dt: add fsl-mc iommu-parent device-tree binding
On Mon, Mar 05, 2018 at 07:59:21PM +0530, Nipun Gupta wrote:
> The existing IOMMU bindings cannot be used to specify the relationship
> between fsl-mc devices and IOMMUs. This patch adds a binding for
> mapping fsl-mc devices to IOMMUs, using a new iommu-parent property.
>
> Signed-off-by: Nipun Gupta <nipun.gupta@nxp.com>
> ---
> .../devicetree/bindings/misc/fsl,qoriq-mc.txt | 31 ++++++++++++++++++++++
> 1 file changed, 31 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt b/Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt
> index 6611a7c..011c7d6 100644
> --- a/Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt
> +++ b/Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt
> @@ -9,6 +9,24 @@ blocks that can be used to create functional hardware objects/devices
> such as network interfaces, crypto accelerator instances, L2 switches,
> etc.
>
> +For an overview of the DPAA2 architecture and fsl-mc bus see:
> +drivers/staging/fsl-mc/README.txt
> +
> +As described in the above overview, all DPAA2 objects in a DPRC share the
> +same hardware "isolation context" and a 10-bit value called an ICID
> +(isolation context id) is expressed by the hardware to identify
> +the requester.
> +
> +The generic 'iommus' property is cannot be used to describe the relationship
> +between fsl-mc and IOMMUs, so an iommu-parent property is used to define
> +the same.

Why not? It is just a link between 2 nodes.

> +
> +For generic IOMMU bindings, see
> +Documentation/devicetree/bindings/iommu/iommu.txt.
> +
> +For arm-smmu binding, see:
> +Documentation/devicetree/bindings/iommu/arm,smmu.txt.
> +
> Required properties:
>
> - compatible
> @@ -88,14 +106,27 @@ Sub-nodes:
> Value type: <phandle>
> Definition: Specifies the phandle to the PHY device node associated
> with the this dpmac.
> +Optional properties:
> +
> +- iommu-parent: Maps the devices on fsl-mc bus to an IOMMU.
> + The property specifies the IOMMU behind which the devices on
> + fsl-mc bus are residing.

If you want a generic property, this should be documented in the common
binding.

Couldn't you have more than 1 IOMMU upstream of a MC?

>
> Example:
>
> + smmu: iommu@5000000 {
> + compatible = "arm,mmu-500";
> + #iommu-cells = <1>;
> + stream-match-mask = <0x7C00>;
> + ...
> + };
> +
> fsl_mc: fsl-mc@80c000000 {
> compatible = "fsl,qoriq-mc";
> reg = <0x00000008 0x0c000000 0 0x40>, /* MC portal base */
> <0x00000000 0x08340000 0 0x40000>; /* MC control reg */
> msi-parent = <&its>;
> + iommu-parent = <&smmu>;
> #address-cells = <3>;
> #size-cells = <1>;
>
> --
> 1.9.1
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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