1* virtio IOMMU PCI device 2 3When virtio-iommu uses the PCI transport, its programming interface is 4discovered dynamically by the PCI probing infrastructure. However the 5device tree statically describes the relation between IOMMU and DMA 6masters. Therefore, the PCI root complex that hosts the virtio-iommu 7contains a child node representing the IOMMU device explicitly. 8 9Required properties: 10 11- compatible: Should be "virtio,pci-iommu" 12- reg: PCI address of the IOMMU. As defined in the PCI Bus 13 Binding reference [1], the reg property is a five-cell 14 address encoded as (phys.hi phys.mid phys.lo size.hi 15 size.lo). phys.hi should contain the device's BDF as 16 0b00000000 bbbbbbbb dddddfff 00000000. The other cells 17 should be zero. 18- #iommu-cells: Each platform DMA master managed by the IOMMU is assigned 19 an endpoint ID, described by the "iommus" property [2]. 20 For virtio-iommu, #iommu-cells must be 1. 21 22Notes: 23 24- DMA from the IOMMU device isn't managed by another IOMMU. Therefore the 25 virtio-iommu node doesn't have an "iommus" property, and is omitted from 26 the iommu-map property of the root complex. 27 28Example: 29 30pcie@10000000 { 31 compatible = "pci-host-ecam-generic"; 32 ... 33 34 /* The IOMMU programming interface uses slot 00:01.0 */ 35 iommu0: iommu@0008 { 36 compatible = "virtio,pci-iommu"; 37 reg = <0x00000800 0 0 0 0>; 38 #iommu-cells = <1>; 39 }; 40 41 /* 42 * The IOMMU manages all functions in this PCI domain except 43 * itself. Omit BDF 00:01.0. 44 */ 45 iommu-map = <0x0 &iommu0 0x0 0x8> 46 <0x9 &iommu0 0x9 0xfff7>; 47}; 48 49pcie@20000000 { 50 compatible = "pci-host-ecam-generic"; 51 ... 52 /* 53 * The IOMMU also manages all functions from this domain, 54 * with endpoint IDs 0x10000 - 0x1ffff 55 */ 56 iommu-map = <0x0 &iommu0 0x10000 0x10000>; 57}; 58 59ethernet@fe001000 { 60 ... 61 /* The IOMMU manages this platform device with endpoint ID 0x20000 */ 62 iommus = <&iommu0 0x20000>; 63}; 64 65[1] Documentation/devicetree/bindings/pci/pci.txt 66[2] Documentation/devicetree/bindings/iommu/iommu.txt 67