On Thu, May 30, 2019 at 06:09:24PM +0100, Jean-Philippe Brucker wrote: > Some systems implement virtio-iommu as a PCI endpoint. The operating > system needs to discover the relationship between IOMMU and masters long > before the PCI endpoint gets probed. Add a PCI child node to describe the > virtio-iommu device. > > The virtio-pci-iommu is conceptually split between a PCI programming > interface and a translation component on the parent bus. The latter > doesn't have a node in the device tree. The virtio-pci-iommu node > describes both, by linking the PCI endpoint to "iommus" property of DMA > master nodes and to "iommu-map" properties of bus nodes. > > Reviewed-by: Rob Herring <robh@xxxxxxxxxx> > Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx> > Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx> So this is just an example right? We are not defining any new properties or anything like that. I think down the road for non dt platforms we want to put this info in the config space of the device. I do not think ACPI is the best option for this since not all systems have it. But that can wait. > --- > .../devicetree/bindings/virtio/iommu.txt | 66 +++++++++++++++++++ > 1 file changed, 66 insertions(+) > create mode 100644 Documentation/devicetree/bindings/virtio/iommu.txt > > diff --git a/Documentation/devicetree/bindings/virtio/iommu.txt b/Documentation/devicetree/bindings/virtio/iommu.txt > new file mode 100644 > index 000000000000..2407fea0651c > --- /dev/null > +++ b/Documentation/devicetree/bindings/virtio/iommu.txt > @@ -0,0 +1,66 @@ > +* virtio IOMMU PCI device > + > +When virtio-iommu uses the PCI transport, its programming interface is > +discovered dynamically by the PCI probing infrastructure. However the > +device tree statically describes the relation between IOMMU and DMA > +masters. Therefore, the PCI root complex that hosts the virtio-iommu > +contains a child node representing the IOMMU device explicitly. > + > +Required properties: > + > +- compatible: Should be "virtio,pci-iommu" > +- reg: PCI address of the IOMMU. As defined in the PCI Bus > + Binding reference [1], the reg property is a five-cell > + address encoded as (phys.hi phys.mid phys.lo size.hi > + size.lo). phys.hi should contain the device's BDF as > + 0b00000000 bbbbbbbb dddddfff 00000000. The other cells > + should be zero. > +- #iommu-cells: Each platform DMA master managed by the IOMMU is assigned > + an endpoint ID, described by the "iommus" property [2]. > + For virtio-iommu, #iommu-cells must be 1. > + > +Notes: > + > +- DMA from the IOMMU device isn't managed by another IOMMU. Therefore the > + virtio-iommu node doesn't have an "iommus" property, and is omitted from > + the iommu-map property of the root complex. > + > +Example: > + > +pcie@10000000 { > + compatible = "pci-host-ecam-generic"; > + ... > + > + /* The IOMMU programming interface uses slot 00:01.0 */ > + iommu0: iommu@0008 { > + compatible = "virtio,pci-iommu"; > + reg = <0x00000800 0 0 0 0>; > + #iommu-cells = <1>; > + }; > + > + /* > + * The IOMMU manages all functions in this PCI domain except > + * itself. Omit BDF 00:01.0. > + */ > + iommu-map = <0x0 &iommu0 0x0 0x8> > + <0x9 &iommu0 0x9 0xfff7>; > +}; > + > +pcie@20000000 { > + compatible = "pci-host-ecam-generic"; > + ... > + /* > + * The IOMMU also manages all functions from this domain, > + * with endpoint IDs 0x10000 - 0x1ffff > + */ > + iommu-map = <0x0 &iommu0 0x10000 0x10000>; > +}; > + > +ethernet@fe001000 { > + ... > + /* The IOMMU manages this platform device with endpoint ID 0x20000 */ > + iommus = <&iommu0 0x20000>; > +}; > + > +[1] Documentation/devicetree/bindings/pci/pci.txt > +[2] Documentation/devicetree/bindings/iommu/iommu.txt > -- > 2.21.0