pci <-> device node mapping

[Anton Blanchard]

> I read it, but I don't know enough about PCI to follow the discussion.
> Does a PHB map to a PCI domain?  As mentioned above some current
> machines will get something like 50 or 100 PHB's (48 or 64 or 96,
> I would have to root around for the details), I'm presuming the
> various participants are aware of this?

On POWER4 and above each host bridge will be a PCI domain. We shouldnt
have a problem with large machines, although in the lab we have found
some arbitrary limits in things like the sym2 driver (we hit a limit at
32 adapters).

Once pci domains and the irq rework have made it in I want to build up a
massive machine to see where we fall apart.

> The other factoid, I guess you're probably aware of this, but the
> slots with EADS seem to have the bus numbers spaced out so that
> bus ID's were 32 apart. I don't know why it needs to be so sparse,
> I thought I heard somebody utter the words 'hot plug' in the same
> breath, but I'm no longer sure.

In theory you could hotplug in cards with pci-pci bridges, like the 4
port pcnet32. So to make life easy they space them out a lot.

Anton

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