tracking of PCI address space
galak at kernel.crashing.org
Thu Apr 9 07:53:52 EST 2009
On Apr 8, 2009, at 4:49 PM, Ira Snyder wrote:
> On Wed, Apr 08, 2009 at 03:53:55PM -0500, Kumar Gala wrote:
>> I was wondering if we have anything that tracks regions associated
>> the "inbound" side of a pci_bus.
>> What I mean is on embedded PPC we have window/mapping registers for
>> inbound (accessing memory on the SoC) and outbound (access PCI device
>> MMIO, IO etc). The combination of the inbound & outbound convey what
>> exists in the PCI address space vs CPU physical address space (and
>> how to
>> map from one to the other). Today in the PPC land we only attach
>> outbound windows to the pci_bus. So technically the inbound side
>> information (like what subset of physical memory is visible on the
>> bus) seems to be lost.
> To the best of my knowledge there is no API to set inbound windows in
> Linux. I've been implementing a virtio-over-PCI driver which needs the
> inbound windows. I set them up myself during driver probe, using
> get_immrbase() to get the IMMR registers. This board is a PCI Slave /
> Agent, it doesn't even have PCI support compiled into the kernel.
I'm not concerned explicitly about setting up inbound windows, its
more about have a consistent view of the PCI address space which may
be different from the CPU physical address space.
I'm working on code to actually setup the inbound windows on 85xx/86xx
class devices (based on dma-ranges property in the device tree). As I
was thinking about this I realized that the send of ranges/dma-ranges
in the .dts and what we map to outbound vs inbound changes if we an
agent or host.
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