Commit 2d1ce5ec authored by Alexandru Gagniuc's avatar Alexandru Gagniuc Committed by Bjorn Helgaas
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PCI: Check for PCIe Link downtraining 



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: default avatarAlexandru 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: default avatarBjorn Helgaas <bhelgaas@google.com>
parent aa667c64

drivers/pci/pci.c

+20 −7
Original line number Diff line number Diff line
@@ -5264,14 +5264,16 @@ u32 pcie_bandwidth_capable(struct pci_dev *dev, enum pci_bus_speed *speed, 
}



/**

 * pcie_print_link_status - Report the PCI device's link speed and width

 * __pcie_print_link_status - Report the PCI device's link speed and width

 * @dev: PCI device to query

 * @verbose: Print info even when enough bandwidth is available

 *

 * Report the available bandwidth at the device.  If this is less than the

 * device is capable of, report the device's maximum possible bandwidth and

 * the upstream link that limits its performance to less than that.

 * If the available bandwidth at the device is less than the device is

 * capable of, report the device's maximum possible bandwidth and the

 * upstream link that limits its performance.  If @verbose, always print

 * the available bandwidth, even if the device isn't constrained.

 */

void pcie_print_link_status(struct pci_dev *dev)

void __pcie_print_link_status(struct pci_dev *dev, bool verbose)

{

	enum pcie_link_width width, width_cap;

	enum pci_bus_speed speed, speed_cap;
@@ -5281,11 +5283,11 @@ void pcie_print_link_status(struct pci_dev *dev) 
	bw_cap = pcie_bandwidth_capable(dev, &speed_cap, &width_cap);

	bw_avail = pcie_bandwidth_available(dev, &limiting_dev, &speed, &width);



	if (bw_avail >= bw_cap)

	if (bw_avail >= bw_cap && verbose)

		pci_info(dev, "%u.%03u Gb/s available PCIe bandwidth (%s x%d link)\n",

			 bw_cap / 1000, bw_cap % 1000,

			 PCIE_SPEED2STR(speed_cap), width_cap);

	else

	else if (bw_avail < bw_cap)

		pci_info(dev, "%u.%03u Gb/s available PCIe bandwidth, limited by %s x%d link at %s (capable of %u.%03u Gb/s with %s x%d link)\n",

			 bw_avail / 1000, bw_avail % 1000,

			 PCIE_SPEED2STR(speed), width,
@@ -5293,6 +5295,17 @@ void pcie_print_link_status(struct pci_dev *dev) 
			 bw_cap / 1000, bw_cap % 1000,

			 PCIE_SPEED2STR(speed_cap), width_cap);

}



/**

 * pcie_print_link_status - Report the PCI device's link speed and width

 * @dev: PCI device to query

 *

 * Report the available bandwidth at the device.

 */

void pcie_print_link_status(struct pci_dev *dev)

{

	__pcie_print_link_status(dev, true);

}

EXPORT_SYMBOL(pcie_print_link_status);



/**

drivers/pci/pci.h

+1 −0
Original line number Diff line number Diff line
@@ -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 {

drivers/pci/probe.c

+21 −0
Original line number Diff line number Diff line
@@ -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;

}

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