On Wed, Jul 18, 2012 at 2:10 PM, Chris Metcalf <cmetcalf@xxxxxxxxxx> wrote: > On 7/18/2012 12:50 PM, Bjorn Helgaas wrote: >> On Wed, Jul 18, 2012 at 10:15 AM, Chris Metcalf <cmetcalf@xxxxxxxxxx> wrote: >>> On 7/13/2012 1:25 PM, Bjorn Helgaas wrote: >>>> On Fri, Jul 13, 2012 at 11:52:11AM -0400, Chris Metcalf wrote: >>>>> We use the same pci_iomem_resource for different domains or host >>>>> bridges, but the MMIO apertures for each bridge do not overlap because >>>>> non-overlapping resource ranges are allocated for each domains. >>>> You should not use the same pci_iomem_resource for different host bridges >>>> because that tells the PCI core that everything in pci_iomem_resource is >>>> available for devices under every host bridge, which I doubt is the case. >>>> >>>> The fact that your firmware assigns non-overlapping resources is good and >>>> works now, but if the kernel ever needs to allocate resources itself, >>> Actually, we were not using any firmware. It was indeed the kernel which >>> allocates resources from the shared pci_iomem_resource. >> Wow. I wonder how that managed to work. Is there some information >> that would have helped the PCI core do the right allocations? Or >> maybe the host bridges forward everything they receive to PCI, >> regardless of address, and any given MMIO address is only routed to >> one of the host bridges because of the routing info in the page >> tables? > > Since each host bridge contains non-overlapping ranges in its bridge config > header, ioremap() locates the right host bridge for the target PCI resource > address and programs the host bridge info into the MMIO mapping. The end > result is the MMIO address is routed to the right host bridge. On Tile > processors, different host bridges are like separate IO devices, in > completely separate domains. > >> I guess in that case, the "apertures" would basically be >> defined by the page tables, not by the host bridges. But that still >> doesn't explain how we would assign non-overlapping ranges to each >> domain. > > Since all domains share the single resource, allocate_resource() "allocate > empty slot in the resource tree", giving non-overlapping ranges to each > devices. > > Just to confirm, I'm assuming I'll ask Linus to pull this code out of my > tile tree when the merge window opens, right? Would you like me to add > your name to the commit as acked or reviewed? Thanks! Yep, just ask Linus to pull it; I don't think there's any need to coordinate with my PCI tree since you're not using any interfaces we changed in this cycle. Reviewed-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
