> From: Mark Rutland <mark.rutland@xxxxxxx> > Date: Thu, Jul 23, 2015 at 11:52 AM [cut] > diff --git a/Documentation/devicetree/bindings/pci/pci-msi.txt > b/Documentation/devicetree/bindings/pci/pci-msi.txt > new file mode 100644 > index 0000000..9b3cc81 > --- /dev/null > +++ b/Documentation/devicetree/bindings/pci/pci-msi.txt > @@ -0,0 +1,220 @@ > +This document describes the generic device tree binding for describing the > +relationship between PCI devices and MSI controllers. > + > +Each PCI device under a root complex is uniquely identified by its Requester ID > +(AKA RID). A Requester ID is a triplet of a Bus number, Device number, and > +Function number. > + > +For the purpose of this document, when treated as a numeric value, a RID is > +formatted such that: > + > +* Bits [15:8] are the Bus number. > +* Bits [7:3] are the Device number. > +* Bits [2:0] are the Function number. > +* Any other bits required for padding must be zero. > + > +MSIs may be distinguished in part through the use of sideband data accompanying > +writes. In the case of PCI devices, this sideband data may be derived from the > +Requester ID. A mechanism is required to associate a device with both the MSI > +controllers it can address, and the sideband data that will be associated with > +its writes to those controllers. > + > +For generic MSI bindings, see > +Documentation/devicetree/bindings/interrupt-controller/msi.txt. > + > + > +PCI root complex > +================ > + > +Optional properties > +------------------- > + > +- msi-map: Maps a Requester ID to an MSI controller and associated > + msi-specifier data. The property is an arbitrary number of tuples of > + (rid-base,msi-controller,msi-base,length), where: > + > + * rid-base is a single cell describing the first RID matched by the entry. > + > + * msi-controller is a single phandle to an MSI controller > + > + * msi-base is an msi-specifier describing the msi-specifier produced for the > + first RID matched by the entry. > + > + * length is a single cell describing how many consecutive RIDs are matched > + following the rid-base. > + > + Any RID r in the interval [rid-base, rid-base + length) is associated with > + the listed msi-controller, with the msi-specifier (r - rid-base + msi-base). > + > +- msi-map-mask: A mask to be applied to each Requester ID prior to being mapped > + to an msi-specifier per the msi-map property. Can we extend the msi-map-mask definition to say: "A mask value of 0x0 is valid and indicates that no RIDs are _currently_ mapped to any msi-specifier." We have an SoC with a programmable hardware table in the PCI controller that maps requester ID to stream ID, so the overall msi-map (and iommu-map) definition fit into that scheme. But, we would like to be able make the RID->stream-ID mapping decision _lazily_, in Linux, based on actual usage of PCI devices. pcie@3600000 { compatible = "fsl,ls2085a-pcie", "snps,dw-pcie"; device_type = "pci"; ... msi-map = <0x0 &msi_a 0x7 4>, msi-map-mask = <0x0> }; That specifies the there are 4 stream IDs starting at stream ID 0x7, but the requester ID's are not mapped (because the mask is 0x0). This tells the PCI controller driver that there are 4 msi-specifiers (e.g. stream IDs) available and what they are. (same definition would apply to the iommu-map-mask) Thanks, Stuart ��.n��������+%������w��{.n����z�{��ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f