Commit 6c9e92ef authored by Jean-Philippe Brucker's avatar Jean-Philippe Brucker Committed by Michael S. Tsirkin
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dt-bindings: virtio: Add virtio-pci-iommu node 



Some systems implement virtio-iommu as a PCI endpoint. The operating
system needs to discover the relationship between IOMMU and masters long
before the PCI endpoint gets probed. Add a PCI child node to describe the
virtio-iommu device.

The virtio-pci-iommu is conceptually split between a PCI programming
interface and a translation component on the parent bus. The latter
doesn't have a node in the device tree. The virtio-pci-iommu node
describes both, by linking the PCI endpoint to "iommus" property of DMA
master nodes and to "iommu-map" properties of bus nodes.

Reviewed-by: default avatarRob Herring <robh@kernel.org>
Reviewed-by: default avatarEric Auger <eric.auger@redhat.com>
Signed-off-by: default avatarJean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 8447d84e

Documentation/devicetree/bindings/virtio/iommu.txt

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* virtio IOMMU PCI device



When virtio-iommu uses the PCI transport, its programming interface is

discovered dynamically by the PCI probing infrastructure. However the

device tree statically describes the relation between IOMMU and DMA

masters. Therefore, the PCI root complex that hosts the virtio-iommu

contains a child node representing the IOMMU device explicitly.



Required properties:



- compatible:	Should be "virtio,pci-iommu"

- reg:		PCI address of the IOMMU. As defined in the PCI Bus

		Binding reference [1], the reg property is a five-cell

		address encoded as (phys.hi phys.mid phys.lo size.hi

		size.lo). phys.hi should contain the device's BDF as

		0b00000000 bbbbbbbb dddddfff 00000000. The other cells

		should be zero.

- #iommu-cells:	Each platform DMA master managed by the IOMMU is assigned

		an endpoint ID, described by the "iommus" property [2].

		For virtio-iommu, #iommu-cells must be 1.



Notes:



- DMA from the IOMMU device isn't managed by another IOMMU. Therefore the

  virtio-iommu node doesn't have an "iommus" property, and is omitted from

  the iommu-map property of the root complex.



Example:



pcie@10000000 {

	compatible = "pci-host-ecam-generic";

	...



	/* The IOMMU programming interface uses slot 00:01.0 */

	iommu0: iommu@0008 {

		compatible = "virtio,pci-iommu";

		reg = <0x00000800 0 0 0 0>;

		#iommu-cells = <1>;

	};



	/*

	 * The IOMMU manages all functions in this PCI domain except

	 * itself. Omit BDF 00:01.0.

	 */

	iommu-map = <0x0 &iommu0 0x0 0x8>

		    <0x9 &iommu0 0x9 0xfff7>;

};



pcie@20000000 {

	compatible = "pci-host-ecam-generic";

	...

	/*

	 * The IOMMU also manages all functions from this domain,

	 * with endpoint IDs 0x10000 - 0x1ffff

	 */

	iommu-map = <0x0 &iommu0 0x10000 0x10000>;

};



ethernet@fe001000 {

	...

	/* The IOMMU manages this platform device with endpoint ID 0x20000 */

	iommus = <&iommu0 0x20000>;

};



[1] Documentation/devicetree/bindings/pci/pci.txt

[2] Documentation/devicetree/bindings/iommu/iommu.txt

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