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1 This document describes the generic device tree binding for IOMMUs and their
8 An IOMMU can provide the following services:
15 * Implement scatter-gather at page level granularity so that the device does
19   through the IOMMU and faulting when encountering accesses to unmapped
26 Device nodes compatible with this binding represent hardware with some of the
30 typically have a fixed association to the master device, whereas multiple-
33 The device tree node of the IOMMU device's parent bus must contain a valid
34 "dma-ranges" property that describes how the physical address space of the
43 The meaning of the IOMMU specifier is defined by the device tree binding of
44 the specific IOMMU. Below are a few examples of typical use-cases:
47   therefore no additional information needs to be encoded in the specifier.
48   This may also apply to multiple master IOMMU devices that do not allow the
51   In such cases the number of cells will usually be 1 as in the next case.
53   in order to enable translation for a given master. In such cases the single
54   address cell corresponds to the master device's ID. In some cases more than
56 - #iommu-cells = <4>: Some IOMMU devices allow the DMA window for masters to
57   be configured. The first cell of the address in this may contain the master
58   device's ID for example, while the second cell could contain the start of
59   the DMA window for the given device. The length of the DMA window is given
60   by the third and fourth cells.
63 definitions to represent their individual needs. Always refer to the specific
64 IOMMU binding for the exact meaning of the cells that make up the specifier.
75 - iommus: A list of phandle and IOMMU specifier pairs that describe the IOMMU
76   master interfaces of the device. One entry in the list describes one master
77   interface of the device.
79 When an "iommus" property is specified in a device tree node, the IOMMU will
80 be used for address translation. If a "dma-ranges" property exists in the
81 device's parent node it will be ignored. An exception to this rule is if the
82 referenced IOMMU is disabled, in which case the "dma-ranges" property of the
84 not guarantee that the IOMMU is really disabled since the hardware may not
86 disable the IOMMU's device tree node in the first place because it would
87 prevent any driver from properly setting up the translations.
93 One possible extension to the above is to use an "iommus" property along with
95 can be useful to describe how children on the bus relate to the IOMMU if they
96 are not explicitly listed in the device tree (e.g. PCI devices). However, the
123 		 * the same address translations because the IOMMU does not
148 		/* the specifier represents the ID of the master */
153 		/* device has master ID 42 in the IOMMU */
158 		/* device has master IDs 23 and 24 in the IOMMU */
168 			 * One cell for the master ID and one cell for the
169 			 * address of the DMA window. The length of the DMA
172 			 * The DMA window is the range addressable by the
173 			 * master (i.e. the I/O virtual address space).