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+* Generic PCI host controller
+
+Firmware-initialised PCI host controllers and PCI emulations, such as the
+virtio-pci implementations found in kvmtool and other para-virtualised
+systems, do not require driver support for complexities such as regulator
+and clock management. In fact, the controller may not even require the
+configuration of a control interface by the operating system, instead
+presenting a set of fixed windows describing a subset of IO, Memory and
+Configuration Spaces.
+
+Such a controller can be described purely in terms of the standardized device
+tree bindings communicated in pci.txt:
+
+
+Properties of the host controller node:
+
+- compatible : Must be "pci-host-cam-generic" or "pci-host-ecam-generic"
+ depending on the layout of configuration space (CAM vs
+ ECAM respectively).
+
+- device_type : Must be "pci".
+
+- ranges : As described in IEEE Std 1275-1994, but must provide
+ at least a definition of non-prefetchable memory. One
+ or both of prefetchable Memory and IO Space may also
+ be provided.
+
+- bus-range : Optional property (also described in IEEE Std 1275-1994)
+ to indicate the range of bus numbers for this controller.
+ If absent, defaults to <0 255> (i.e. all buses).
+
+- #address-cells : Must be 3.
+
+- #size-cells : Must be 2.
+
+- reg : The Configuration Space base address and size, as accessed
+ from the parent bus.
+
+
+Properties of the /chosen node:
+
+- linux,pci-probe-only
+ : Optional property which takes a single-cell argument.
+ If '0', then Linux will assign devices in its usual manner,
+ otherwise it will not try to assign devices and instead use
+ them as they are configured already.
+
+Configuration Space is assumed to be memory-mapped (as opposed to being
+accessed via an ioport) and laid out with a direct correspondence to the
+geography of a PCI bus address by concatenating the various components to
+form an offset.
+
+For CAM, this 24-bit offset is:
+
+ cfg_offset(bus, device, function, register) =
+ bus << 16 | device << 11 | function << 8 | register
+
+Whilst ECAM extends this by 4 bits to accomodate 4k of function space:
+
+ cfg_offset(bus, device, function, register) =
+ bus << 20 | device << 15 | function << 12 | register
+
+Interrupt mapping is exactly as described in `Open Firmware Recommended
+Practice: Interrupt Mapping' and requires the following properties:
+
+- #interrupt-cells : Must be 1
+
+- interrupt-map : <see aforementioned specification>
+
+- interrupt-map-mask : <see aforementioned specification>
+
+
+Example:
+
+pci {
+ compatible = "pci-host-cam-generic"
+ device_type = "pci";
+ #address-cells = <3>;
+ #size-cells = <2>;
+ bus-range = <0x0 0x1>;
+
+ // CPU_PHYSICAL(2) SIZE(2)
+ reg = <0x0 0x40000000 0x0 0x1000000>;
+
+ // BUS_ADDRESS(3) CPU_PHYSICAL(2) SIZE(2)
+ ranges = <0x01000000 0x0 0x01000000 0x0 0x01000000 0x0 0x00010000>,
+ <0x02000000 0x0 0x41000000 0x0 0x41000000 0x0 0x3f000000>;
+
+
+ #interrupt-cells = <0x1>;
+
+ // PCI_DEVICE(3) INT#(1) CONTROLLER(PHANDLE) CONTROLLER_DATA(3)
+ interrupt-map = < 0x0 0x0 0x0 0x1 &gic 0x0 0x4 0x1
+ 0x800 0x0 0x0 0x1 &gic 0x0 0x5 0x1
+ 0x1000 0x0 0x0 0x1 &gic 0x0 0x6 0x1
+ 0x1800 0x0 0x0 0x1 &gic 0x0 0x7 0x1>;
+
+ // PCI_DEVICE(3) INT#(1)
+ interrupt-map-mask = <0xf800 0x0 0x0 0x7>;
+}