On Mon, Nov 14, 2011 at 09:44:50AM -0500, Prarit Bhargava wrote: > On 11/11/2011 03:35 PM, Don Dutile wrote: > We should make it work automatically, either with > >> some sort of machine-dependent quirk, or (preferably) with a change to > >> the generic algorithm so it can handle these "broken" topologies along > >> with all the correct ones. > > The problem is when I'm examining "this" PCIE bridge I have no knowledge of the remaining hierarchy below it. In order to find the broken topology we need to do a two pass enumeration (NO.) or minimally query all possible devices immediately connected to it. If we do that then what is the purpose of the only_one_child() check? We have enough information to do this quirk. pci_scan_slot calls pci_scan_single_device() for the devfn 0. We can look at the device we found and quirk the parent device. Something like this ... int pci_scan_slot(struct pci_bus *bus, int devfn) [...] dev = pci_scan_single_device(bus, devfn); if (!dev) return 0; if (!dev->is_added) nr++; + /* Quirk to fix NEC/Stratus broken PCIe topologies */ + if ((dev->pcie_type == PCI_EXP_TYPE_DOWNSTREAM) && + (bus->self->pcie_type == PCI_EXP_TYPE_DOWNSTREAM)) + bus->self->pcie_type = PCI_EXP_TYPE_UPSTREAM; if (pci_ari_enabled(bus)) next_fn = next_ari_fn; [...] As an aside, I'm quite shocked that this patch has been in the kernel for almost two years and this is the first time anybody's tested it on one of these systems. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- 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
