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Subject[PATCH v5 05/14] PCI: Add pcie_print_link_status() to log link speed and whether it's limited
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From: Tal Gilboa <talgi@mellanox.com>

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]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
drivers/pci/pci.c | 29 +++++++++++++++++++++++++++++
include/linux/pci.h | 1 +
2 files changed, 30 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e00d56b12747..cec7aed09f6b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5283,6 +5283,35 @@ 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, "%d Mb/s available bandwidth (%s x%d link)\n",
+ bw_cap, PCIE_SPEED2STR(speed_cap), width_cap);
+ else
+ pci_info(dev, "%d Mb/s available bandwidth, limited by %s x%d link at %s (capable of %d Mb/s with %s x%d link)\n",
+ bw_avail, PCIE_SPEED2STR(speed), width,
+ limiting_dev ? pci_name(limiting_dev) : "<unknown>",
+ bw_cap, 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 f2bf2b7a66c7..38f7957121ef 100644
--- 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);
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