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Subject[PATCH v5 13/14] ixgbe: Report PCIe link properties with pcie_print_link_status()
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From: Bjorn Helgaas <bhelgaas@google.com>

Use pcie_print_link_status() to report PCIe link speed and possible
limitations instead of implementing this in the driver itself.

Note that pcie_get_minimum_link() can return misleading information because
it finds the slowest link and the narrowest link without considering the
total bandwidth of the link. If the path contains a 16 GT/s x1 link and a
2.5 GT/s x16 link, pcie_get_minimum_link() returns 2.5 GT/s x1, which
corresponds to 250 MB/s of bandwidth, not the actual available bandwidth of
about 2000 MB/s for a 16 GT/s x1 link.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 47 +------------------------
1 file changed, 1 insertion(+), 46 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 0da5aa2c8aba..38bb9c17d333 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -270,9 +270,6 @@ static void ixgbe_check_minimum_link(struct ixgbe_adapter *adapter,
int expected_gts)
{
struct ixgbe_hw *hw = &adapter->hw;
- int max_gts = 0;
- enum pci_bus_speed speed = PCI_SPEED_UNKNOWN;
- enum pcie_link_width width = PCIE_LNK_WIDTH_UNKNOWN;
struct pci_dev *pdev;

/* Some devices are not connected over PCIe and thus do not negotiate
@@ -288,49 +285,7 @@ static void ixgbe_check_minimum_link(struct ixgbe_adapter *adapter,
else
pdev = adapter->pdev;

- if (pcie_get_minimum_link(pdev, &speed, &width) ||
- speed == PCI_SPEED_UNKNOWN || width == PCIE_LNK_WIDTH_UNKNOWN) {
- e_dev_warn("Unable to determine PCI Express bandwidth.\n");
- return;
- }
-
- switch (speed) {
- case PCIE_SPEED_2_5GT:
- /* 8b/10b encoding reduces max throughput by 20% */
- max_gts = 2 * width;
- break;
- case PCIE_SPEED_5_0GT:
- /* 8b/10b encoding reduces max throughput by 20% */
- max_gts = 4 * width;
- break;
- case PCIE_SPEED_8_0GT:
- /* 128b/130b encoding reduces throughput by less than 2% */
- max_gts = 8 * width;
- break;
- default:
- e_dev_warn("Unable to determine PCI Express bandwidth.\n");
- return;
- }
-
- e_dev_info("PCI Express bandwidth of %dGT/s available\n",
- max_gts);
- e_dev_info("(Speed:%s, Width: x%d, Encoding Loss:%s)\n",
- (speed == PCIE_SPEED_8_0GT ? "8.0GT/s" :
- speed == PCIE_SPEED_5_0GT ? "5.0GT/s" :
- speed == PCIE_SPEED_2_5GT ? "2.5GT/s" :
- "Unknown"),
- width,
- (speed == PCIE_SPEED_2_5GT ? "20%" :
- speed == PCIE_SPEED_5_0GT ? "20%" :
- speed == PCIE_SPEED_8_0GT ? "<2%" :
- "Unknown"));
-
- if (max_gts < expected_gts) {
- e_dev_warn("This is not sufficient for optimal performance of this card.\n");
- e_dev_warn("For optimal performance, at least %dGT/s of bandwidth is required.\n",
- expected_gts);
- e_dev_warn("A slot with more lanes and/or higher speed is suggested.\n");
- }
+ pcie_print_link_status(pdev);
}

static void ixgbe_service_event_schedule(struct ixgbe_adapter *adapter)
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