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
with
the "inbound" side of a pci_bus.
What I mean is on embedded PPC we have window/mapping registers for
both
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
PCI
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.
- k
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