0001 * virtio IOMMU PCI device
0002
0003 When virtio-iommu uses the PCI transport, its programming interface is
0004 discovered dynamically by the PCI probing infrastructure. However the
0005 device tree statically describes the relation between IOMMU and DMA
0006 masters. Therefore, the PCI root complex that hosts the virtio-iommu
0007 contains a child node representing the IOMMU device explicitly.
0008
0009 Required properties:
0010
0011 - compatible: Should be "virtio,pci-iommu"
0012 - reg: PCI address of the IOMMU. As defined in the PCI Bus
0013 Binding reference [1], the reg property is a five-cell
0014 address encoded as (phys.hi phys.mid phys.lo size.hi
0015 size.lo). phys.hi should contain the device's BDF as
0016 0b00000000 bbbbbbbb dddddfff 00000000. The other cells
0017 should be zero.
0018 - #iommu-cells: Each platform DMA master managed by the IOMMU is assigned
0019 an endpoint ID, described by the "iommus" property [2].
0020 For virtio-iommu, #iommu-cells must be 1.
0021
0022 Notes:
0023
0024 - DMA from the IOMMU device isn't managed by another IOMMU. Therefore the
0025 virtio-iommu node doesn't have an "iommus" property, and is omitted from
0026 the iommu-map property of the root complex.
0027
0028 Example:
0029
0030 pcie@10000000 {
0031 compatible = "pci-host-ecam-generic";
0032 ...
0033
0034 /* The IOMMU programming interface uses slot 00:01.0 */
0035 iommu0: iommu@0008 {
0036 compatible = "virtio,pci-iommu";
0037 reg = <0x00000800 0 0 0 0>;
0038 #iommu-cells = <1>;
0039 };
0040
0041 /*
0042 * The IOMMU manages all functions in this PCI domain except
0043 * itself. Omit BDF 00:01.0.
0044 */
0045 iommu-map = <0x0 &iommu0 0x0 0x8>
0046 <0x9 &iommu0 0x9 0xfff7>;
0047 };
0048
0049 pcie@20000000 {
0050 compatible = "pci-host-ecam-generic";
0051 ...
0052 /*
0053 * The IOMMU also manages all functions from this domain,
0054 * with endpoint IDs 0x10000 - 0x1ffff
0055 */
0056 iommu-map = <0x0 &iommu0 0x10000 0x10000>;
0057 };
0058
0059 ethernet@fe001000 {
0060 ...
0061 /* The IOMMU manages this platform device with endpoint ID 0x20000 */
0062 iommus = <&iommu0 0x20000>;
0063 };
0064
0065 [1] Documentation/devicetree/bindings/pci/pci.txt
0066 [2] Documentation/devicetree/bindings/iommu/iommu.txt
