forked from Minki/linux
mainlining shenanigans
51ebfc92b7
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:
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.