From 04043fd8e3561a1bf2f3226ad267e89d423ca508 Mon Sep 17 00:00:00 2001 From: Bjorn Helgaas Date: Thu, 30 Nov 2017 15:22:39 -0600 Subject: [PATCH] PCI: Make PCI_SCAN_ALL_PCIE_DEVS work for Root as well as Downstream Ports BugLink: http://bugs.launchpad.net/bugs/1756094 PCIe Downstream Ports normally have only a Device 0 below them. To optimize enumeration, we don't scan for other devices *unless* the PCI_SCAN_ALL_PCIE_DEVS flag is set by set by quirks or the "pci=pcie_scan_all" kernel parameter. Previously PCI_SCAN_ALL_PCIE_DEVS only affected scanning below Switch Downstream Ports, not Root Ports. But the "Nemo" system, also known as the AmigaOne X1000, has a PA Semi Root Port whose link leads to an AMD/ATI SB600 South Bridge. The Root Port is a PCIe device, of course, but the SB600 contains only conventional PCI devices with no visible PCIe port. Simplify and restructure only_one_child() so that we scan for all possible devices below Root Ports as well as Switch Downstream Ports when PCI_SCAN_ALL_PCIE_DEVS is set. This is enough to make Nemo work with "pci=pcie_scan_all". We would also like to add a quirk to set PCI_SCAN_ALL_PCIE_DEVS automatically on Nemo so users wouldn't have to use the "pci=pcie_scan_all" parameter, but we don't have that yet. Link: https://lkml.kernel.org/r/CAErSpo55Q8Q=5p6_+uu7ahnw+53ibVDNRXxrzRV9QnUr_9EUfw@mail.gmail.com Link: https://bugzilla.kernel.org/show_bug.cgi?id=198057 Reported-and-Tested-by: Christian Zigotzky Signed-off-by: Bjorn Helgaas (cherry picked from commit d57f0b8c81393e7105331ac037fa465d5a45c65f) Signed-off-by: Manoj Iyer Signed-off-by: Seth Forshee --- drivers/pci/probe.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 3761b1303529..070476036846 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -2248,22 +2248,27 @@ static unsigned next_fn(struct pci_bus *bus, struct pci_dev *dev, unsigned fn) static int only_one_child(struct pci_bus *bus) { - struct pci_dev *parent = bus->self; + struct pci_dev *bridge = bus->self; - if (!parent || !pci_is_pcie(parent)) + /* + * Systems with unusual topologies set PCI_SCAN_ALL_PCIE_DEVS so + * we scan for all possible devices, not just Device 0. + */ + if (pci_has_flag(PCI_SCAN_ALL_PCIE_DEVS)) return 0; - if (pci_pcie_type(parent) == PCI_EXP_TYPE_ROOT_PORT) - return 1; /* - * PCIe downstream ports are bridges that normally lead to only a - * device 0, but if PCI_SCAN_ALL_PCIE_DEVS is set, scan all - * possible devices, not just device 0. See PCIe spec r3.0, - * sec 7.3.1. + * A PCIe Downstream Port normally leads to a Link with only Device + * 0 on it (PCIe spec r3.1, sec 7.3.1). As an optimization, scan + * only for Device 0 in that situation. + * + * Checking has_secondary_link is a hack to identify Downstream + * Ports because sometimes Switches are configured such that the + * PCIe Port Type labels are backwards. */ - if (parent->has_secondary_link && - !pci_has_flag(PCI_SCAN_ALL_PCIE_DEVS)) + if (bridge && pci_is_pcie(bridge) && bridge->has_secondary_link) return 1; + return 0; } -- 2.39.2