PCI: Enumerate switches below PCI-to-PCIe bridges A PCI-to-PCIe bridge (a "reverse bridge") has a PCI or PCI-X primary interface and a PCI Express secondary interface. The PCIe interface is a Downstream Port that originates a Link. See the "PCI Express to PCI/PCI-X Bridge Specification", rev 1.0, sections 1.2 and A.6. The bug report below involves a PCI-to-PCIe bridge and a PCIe switch below the bridge: 00:1e.0 Intel 82801 PCI Bridge to [bus 01-0a] 01:00.0 Pericom PI7C9X111SL PCIe-to-PCI Reversible Bridge to [bus 02-0a] 02:00.0 Pericom Device 8608 [PCIe Upstream Port] to [bus 03-0a] 03:01.0 Pericom Device 8608 [PCIe Downstream Port] to [bus 0a] 01:00.0 is configured as a PCI-to-PCIe bridge (despite the name printed by lspci). As we traverse a PCIe hierarchy, device connections alternate between PCIe Links and internal Switch logic. Previously we did not recognize that 01:00.0 had a secondary link, so we thought the 02:00.0 Upstream Port *did* have a secondary link. In fact, it's the other way around: 01:00.0 has a secondary link, and 02:00.0 has internal Switch logic on its secondary side. When we thought 02:00.0 had a secondary link, the pci_scan_slot() -> only_one_child() path assumed 02:00.0 could have only one child, so 03:00.0 was the only possible downstream device. But 03:00.0 doesn't exist, so we didn't look for any other devices on bus 03. Booting with "pci=pcie_scan_all" is a workaround, but we don't want users to have to do that. Recognize that PCI-to-PCIe bridges originate links on their secondary interfaces. Link: https://bugzilla.kernel.org/show_bug.cgi?id=189361 Fixes: d0751b98dfa3 ("PCI: Add dev->has_secondary_link to track downstream PCIe links") Tested-by: Blake Moore <blake.moore@xxxxxx> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> CC: stable@xxxxxxxxxxxxxxx # v4.2+ diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index e164b5c9f0f0..204960e70333 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -1169,6 +1169,7 @@ void set_pcie_port_type(struct pci_dev *pdev) pos = pci_find_capability(pdev, PCI_CAP_ID_EXP); if (!pos) return; + pdev->pcie_cap = pos; pci_read_config_word(pdev, pos + PCI_EXP_FLAGS, ®16); pdev->pcie_flags_reg = reg16; @@ -1176,13 +1177,14 @@ void set_pcie_port_type(struct pci_dev *pdev) pdev->pcie_mpss = reg16 & PCI_EXP_DEVCAP_PAYLOAD; /* - * A Root Port is always the upstream end of a Link. No PCIe - * component has two Links. Two Links are connected by a Switch - * that has a Port on each Link and internal logic to connect the - * two Ports. + * A Root Port or a PCI-to-PCIe bridge is always the upstream end + * of a Link. No PCIe component has two Links. Two Links are + * connected by a Switch that has a Port on each Link and internal + * logic to connect the two Ports. */ type = pci_pcie_type(pdev); - if (type == PCI_EXP_TYPE_ROOT_PORT) + if (type == PCI_EXP_TYPE_ROOT_PORT || + type == PCI_EXP_TYPE_PCIE_BRIDGE) pdev->has_secondary_link = 1; else if (type == PCI_EXP_TYPE_UPSTREAM || type == PCI_EXP_TYPE_DOWNSTREAM) { -- 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
