diff options
Diffstat (limited to 'src/device')
| -rw-r--r-- | src/device/pci_device.c | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/src/device/pci_device.c b/src/device/pci_device.c index 4b5e73b806..1075ef7e0e 100644 --- a/src/device/pci_device.c +++ b/src/device/pci_device.c @@ -1204,6 +1204,30 @@ static void pci_scan_hidden_device(struct device *dev) } /** + * A PCIe Downstream Port normally leads to a Link with only Device 0 on it + * (PCIe spec r5.0, sec 7.3.1). As an optimization, scan only for Device 0 in + * that situation. + * + * @param bus Pointer to the bus structure. + */ +static bool pci_bus_only_one_child(struct bus *bus) +{ + struct device *bridge = bus->dev; + u16 pcie_pos, pcie_flags_reg; + int pcie_type; + + pcie_pos = pci_find_capability(bridge, PCI_CAP_ID_PCIE); + if (!pcie_pos) + return false; + + pcie_flags_reg = pci_read_config16(bridge, pcie_pos + PCI_EXP_FLAGS); + + pcie_type = (pcie_flags_reg & PCI_EXP_FLAGS_TYPE) >> 4; + + return pciexp_is_downstream_port(pcie_type); +} + +/** * Scan a PCI bus. * * Determine the existence of devices and bridges on a PCI bus. If there are @@ -1232,6 +1256,9 @@ void pci_scan_bus(struct bus *bus, unsigned int min_devfn, post_code(0x24); + if (pci_bus_only_one_child(bus)) + max_devfn = MIN(max_devfn, 0x07); + /* * Probe all devices/functions on this bus with some optimization for * non-existence and single function devices. |