PCI: Add pcie_print_link_status() to log link speed and whether it's limited

Add pcie_print_link_status().  This logs the current settings of the link
(speed, width, and total available bandwidth).

If the device is capable of more bandwidth but is limited by a slower
upstream link, we include information about the link that limits the
device's performance.

The user may be able to move the device to a different slot for better
performance.

This provides a unified method for all PCI devices to report status and
issues, instead of each device reporting in a different way, using
different code.

Signed-off-by: Tal Gilboa <talgi@mellanox.com>
[bhelgaas: changelog, reword log messages, print device capabilities when
not limited, print bandwidth in Gb/s]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 91138cbeb8537e01148664cee0bd8b0d7cfb130c..e7a3917ed38969671f9f1536cf1a1ef537b277d6 100644 (file)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5288,6 +5288,38 @@ u32 pcie_bandwidth_capable(struct pci_dev *dev, enum pci_bus_speed *speed,
        return *width * PCIE_SPEED2MBS_ENC(*speed);
 }
 
+/**
+ * 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.  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.
+ */
+void pcie_print_link_status(struct pci_dev *dev)
+{
+       enum pcie_link_width width, width_cap;
+       enum pci_bus_speed speed, speed_cap;
+       struct pci_dev *limiting_dev = NULL;
+       u32 bw_avail, bw_cap;
+
+       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)
+               pci_info(dev, "%u.%03u Gb/s available bandwidth (%s x%d link)\n",
+                        bw_cap / 1000, bw_cap % 1000,
+                        PCIE_SPEED2STR(speed_cap), width_cap);
+       else
+               pci_info(dev, "%u.%03u Gb/s available 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,
+                        limiting_dev ? pci_name(limiting_dev) : "<unknown>",
+                        bw_cap / 1000, bw_cap % 1000,
+                        PCIE_SPEED2STR(speed_cap), width_cap);
+}
+EXPORT_SYMBOL(pcie_print_link_status);
+
 /**
  * pci_select_bars - Make BAR mask from the type of resource
  * @dev: the PCI device for which BAR mask is made

diff --git a/include/linux/pci.h b/include/linux/pci.h
index f2bf2b7a66c77a61708577775c3b1c54860e7727..38f7957121ef736ba8d5bed750e2278738352e10 100644 (file)
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1086,6 +1086,7 @@ int pcie_get_minimum_link(struct pci_dev *dev, enum pci_bus_speed *speed,
 u32 pcie_bandwidth_available(struct pci_dev *dev, struct pci_dev **limiting_dev,
                             enum pci_bus_speed *speed,
                             enum pcie_link_width *width);
+void pcie_print_link_status(struct pci_dev *dev);
 void pcie_flr(struct pci_dev *dev);
 int __pci_reset_function_locked(struct pci_dev *dev);
 int pci_reset_function(struct pci_dev *dev);