Re: tracking of PCI address space

[Kumar Gala]

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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