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PCI: Check for PCIe Link downtraining

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When both ends of a PCIe Link are capable of a higher bandwidth than is
currently in use, the Link is said to be "downtrained".  A downtrained Link
may indicate hardware or configuration problems in the system, but it's
hard to identify such Links from userspace.

Refactor pcie_print_link_status() so it continues to always print PCIe
bandwidth information, as several NIC drivers desire.

Add a new internal __pcie_print_link_status() to emit a message only when a
device's bandwidth is constrained by the fabric and call it from the PCI
core for all devices, which identifies all downtrained Links.  It also
emits messages for a few cases that are technically not downtrained, such
as a x4 device in an open-ended x1 slot.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
[bhelgaas: changelog, move __pcie_print_link_status() declaration to
drivers/pci/, rename pcie_check_upstream_link() to
pcie_report_downtraining()]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Alexandru Gagniuc
2018-08-06 18:25:35 -05:00
committed by Bjorn Helgaas
parent aa667c6408
commit 2d1ce5ec21
3 changed files with 42 additions and 7 deletions
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drivers/pci/pci.h
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@@ -263,6 +263,7 @@ enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev);
enum pcie_link_width pcie_get_width_cap(struct pci_dev *dev);
u32 pcie_bandwidth_capable(struct pci_dev *dev, enum pci_bus_speed *speed,
enum pcie_link_width *width);
void __pcie_print_link_status(struct pci_dev *dev, bool verbose);
/* Single Root I/O Virtualization */
struct pci_sriov {