On Thu, Jul 09, 2015 at 12:10:11PM +0100, leizhen wrote: > On 2015/7/8 21:13, Robin Murphy wrote: > > On 07/07/15 04:30, Zhen Lei wrote: > >> For pci devices, only the root nodes have "iommus" property. So we > >> should traverse all of its sub nodes in of_xlate. > > > > I don't really follow this description; only the host controller is > > described in DT - the devices behind it are probed dynamically and don't > > have nodes to traverse. > > The devices behind host controller may have nodes, but have no "iommus" > property.
No, the PCI masters won't have nodes in the DT on arm/arm64 systems (it makes hotplug difficult). > I got this conclusion base on the original code as below: > > struct pci_bus *bus = pdev->bus; > > /* Walk up to the root bus */ > while (!pci_is_root_bus(bus)) > bus = bus->parent; So this walks up the PCI topology, created by probing the bus, until we get to the top-level bus... > /* Follow the "iommus" phandle from the host controller */ > of_node = of_parse_phandle(bus->bridge->parent->of_node, "iommus", 0); > if (!of_node) > return NULL; ... then we find the host controller device, which *does* have a device-tree node and use *that* to find out the IOMMU corresponding to the PCI device. Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
