TWxSoftware/twx-linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

PCI: Check for PCIe Link downtraining

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files
drivers/pci/probe.c
+21
View File
@@ -2223,6 +2223,25 @@ static struct pci_dev *pci_scan_device(struct pci_bus *bus, int devfn)
return dev;
}
static void pcie_report_downtraining(struct pci_dev *dev)
{
if (!pci_is_pcie(dev))
return;
/* Look from the device up to avoid downstream ports with no devices */
if ((pci_pcie_type(dev) != PCI_EXP_TYPE_ENDPOINT) &&
(pci_pcie_type(dev) != PCI_EXP_TYPE_LEG_END) &&
(pci_pcie_type(dev) != PCI_EXP_TYPE_UPSTREAM))
return;
/* Multi-function PCIe devices share the same link/status */
if (PCI_FUNC(dev->devfn) != 0 || dev->is_virtfn)
return;
/* Print link status only if the device is constrained by the fabric */
__pcie_print_link_status(dev, false);
}
static void pci_init_capabilities(struct pci_dev *dev)
{
/* Enhanced Allocation */
@@ -2258,6 +2277,8 @@ static void pci_init_capabilities(struct pci_dev *dev)
/* Advanced Error Reporting */
pci_aer_init(dev);
pcie_report_downtraining(dev);
if (pci_probe_reset_function(dev) == 0)
dev->reset_fn = 1;
}