dt-bindings: virtio-mmio: Add IOMMU description (8447d84e) · Commits · 戴 / test

The nature of a virtio-mmio node is discovered by the virtio driver at probe time. However the DMA relation between devices must be described statically. When a virtio-mmio node is a virtio-iommu device, it needs an "#iommu-cells" property as specified by bindings/iommu/iommu.txt. Otherwise, the virtio-mmio device may perform DMA through an IOMMU, which requires an "iommus" property. Describe these requirements in the device-tree bindings documentation. Reviewed-by:

Rob Herring <robh@kernel.org> Reviewed-by:

Eric Auger <eric.auger@redhat.com> Signed-off-by:

Jean-Philippe Brucker <jean-philippe.brucker@arm.com> Signed-off-by:

Michael S. Tsirkin <mst@redhat.com>

Documentation/devicetree/bindings/virtio/mmio.txt

+30 −0

Original line number	Diff line number	Diff line
		@@ -8,10 +8,40 @@ Required properties:
		- reg: control registers base address and size including configuration space
		- interrupts: interrupt generated by the device

		Required properties for virtio-iommu:

		- #iommu-cells: When the node corresponds to a virtio-iommu device, it is
		linked to DMA masters using the "iommus" or "iommu-map"
		properties [1][2]. #iommu-cells specifies the size of the
		"iommus" property. For virtio-iommu #iommu-cells must be
		1, each cell describing a single endpoint ID.

		Optional properties:

		- iommus: If the device accesses memory through an IOMMU, it should
		have an "iommus" property [1]. Since virtio-iommu itself
		does not access memory through an IOMMU, the "virtio,mmio"
		node cannot have both an "#iommu-cells" and an "iommus"
		property.

		Example:

		virtio_block@3000 {
		compatible = "virtio,mmio";
		reg = <0x3000 0x100>;
		interrupts = <41>;

		/* Device has endpoint ID 23 */
		iommus = <&viommu 23>
		}

		viommu: iommu@3100 {
		compatible = "virtio,mmio";
		reg = <0x3100 0x100>;
		interrupts = <42>;

		#iommu-cells = <1>
		}

		[1] Documentation/devicetree/bindings/iommu/iommu.txt
		[2] Documentation/devicetree/bindings/pci/pci-iommu.txt

Admin message