forked from Minki/linux
f6225c3a0c
Make the offset from the beginning of the "reg" property be from the starting bus number, rather than zero. Hoist the invariant size calculation out of the mapping for loop. Update host-generic-pci.txt to clarify the semantics of the "reg" property with respect to non-zero starting bus numbers. Signed-off-by: David Daney <david.daney@cavium.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Rob Herring <robh@kernel.org>
102 lines
3.7 KiB
Plaintext
102 lines
3.7 KiB
Plaintext
* Generic PCI host controller
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Firmware-initialised PCI host controllers and PCI emulations, such as the
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virtio-pci implementations found in kvmtool and other para-virtualised
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systems, do not require driver support for complexities such as regulator
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and clock management. In fact, the controller may not even require the
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configuration of a control interface by the operating system, instead
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presenting a set of fixed windows describing a subset of IO, Memory and
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Configuration Spaces.
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Such a controller can be described purely in terms of the standardized device
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tree bindings communicated in pci.txt:
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Properties of the host controller node:
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- compatible : Must be "pci-host-cam-generic" or "pci-host-ecam-generic"
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depending on the layout of configuration space (CAM vs
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ECAM respectively).
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- device_type : Must be "pci".
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- ranges : As described in IEEE Std 1275-1994, but must provide
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at least a definition of non-prefetchable memory. One
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or both of prefetchable Memory and IO Space may also
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be provided.
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- bus-range : Optional property (also described in IEEE Std 1275-1994)
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to indicate the range of bus numbers for this controller.
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If absent, defaults to <0 255> (i.e. all buses).
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- #address-cells : Must be 3.
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- #size-cells : Must be 2.
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- reg : The Configuration Space base address and size, as accessed
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from the parent bus. The base address corresponds to
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the first bus in the "bus-range" property. If no
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"bus-range" is specified, this will be bus 0 (the default).
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Properties of the /chosen node:
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- linux,pci-probe-only
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: Optional property which takes a single-cell argument.
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If '0', then Linux will assign devices in its usual manner,
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otherwise it will not try to assign devices and instead use
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them as they are configured already.
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Configuration Space is assumed to be memory-mapped (as opposed to being
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accessed via an ioport) and laid out with a direct correspondence to the
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geography of a PCI bus address by concatenating the various components to
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form an offset.
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For CAM, this 24-bit offset is:
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cfg_offset(bus, device, function, register) =
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bus << 16 | device << 11 | function << 8 | register
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Whilst ECAM extends this by 4 bits to accommodate 4k of function space:
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cfg_offset(bus, device, function, register) =
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bus << 20 | device << 15 | function << 12 | register
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Interrupt mapping is exactly as described in `Open Firmware Recommended
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Practice: Interrupt Mapping' and requires the following properties:
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- #interrupt-cells : Must be 1
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- interrupt-map : <see aforementioned specification>
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- interrupt-map-mask : <see aforementioned specification>
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Example:
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pci {
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compatible = "pci-host-cam-generic"
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device_type = "pci";
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#address-cells = <3>;
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#size-cells = <2>;
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bus-range = <0x0 0x1>;
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// CPU_PHYSICAL(2) SIZE(2)
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reg = <0x0 0x40000000 0x0 0x1000000>;
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// BUS_ADDRESS(3) CPU_PHYSICAL(2) SIZE(2)
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ranges = <0x01000000 0x0 0x01000000 0x0 0x01000000 0x0 0x00010000>,
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<0x02000000 0x0 0x41000000 0x0 0x41000000 0x0 0x3f000000>;
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#interrupt-cells = <0x1>;
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// PCI_DEVICE(3) INT#(1) CONTROLLER(PHANDLE) CONTROLLER_DATA(3)
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interrupt-map = < 0x0 0x0 0x0 0x1 &gic 0x0 0x4 0x1
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0x800 0x0 0x0 0x1 &gic 0x0 0x5 0x1
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0x1000 0x0 0x0 0x1 &gic 0x0 0x6 0x1
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0x1800 0x0 0x0 0x1 &gic 0x0 0x7 0x1>;
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// PCI_DEVICE(3) INT#(1)
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interrupt-map-mask = <0xf800 0x0 0x0 0x7>;
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}
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