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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 <chzigotzky@xenosoft.de> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.