fm10k: Report PCIe link properties with pcie_print_link_status()

Previously the driver used pcie_get_minimum_link() to warn when the NIC
is in a slot that can't supply as much bandwidth as the NIC could use.

pcie_get_minimum_link() can be misleading because it finds the slowest link
and the narrowest link (which may be different links) without considering
the total bandwidth of each link.  For a path with a 16 GT/s x1 link and a
2.5 GT/s x16 link, it returns 2.5 GT/s x1, which corresponds to 250 MB/s of
bandwidth, not the true available bandwidth of about 1969 MB/s for a
16 GT/s x1 link.

Use pcie_print_link_status() to report PCIe link speed and possible
limitations instead of implementing this in the driver itself.  This finds
the slowest link in the path to the device by computing the total bandwidth
of each link and compares that with the capabilities of the device.

Note that the driver previously used dev_warn() to suggest using a
different slot, but pcie_print_link_status() uses dev_info() because if the
platform has no faster slot available, the user can't do anything about the
warning and may not want to be bothered with it.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Jacob Keller <jacob.e.keller@intel.com>

drivers/net/ethernet/intel/fm10k/fm10k_pci.c

@@ -2120,91 +2120,6 @@ static int fm10k_sw_init(struct fm10k_intfc *interface,
 	return 0;
 }
 
-static void fm10k_slot_warn(struct fm10k_intfc *interface)
-{
-	enum pcie_link_width width = PCIE_LNK_WIDTH_UNKNOWN;
-	enum pci_bus_speed speed = PCI_SPEED_UNKNOWN;
-	struct fm10k_hw *hw = &interface->hw;
-	int max_gts = 0, expected_gts = 0;
-
-	if (pcie_get_minimum_link(interface->pdev, &speed, &width) ||
-	    speed == PCI_SPEED_UNKNOWN || width == PCIE_LNK_WIDTH_UNKNOWN) {
-		dev_warn(&interface->pdev->dev,
-			 "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 has less than 2% impact on throughput */
-		max_gts = 8 * width;
-		break;
-	default:
-		dev_warn(&interface->pdev->dev,
-			 "Unable to determine PCI Express bandwidth.\n");
-		return;
-	}
-
-	dev_info(&interface->pdev->dev,
-		 "PCI Express bandwidth of %dGT/s available\n",
-		 max_gts);
-	dev_info(&interface->pdev->dev,
-		 "(Speed:%s, Width: x%d, Encoding Loss:%s, Payload:%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"),
-		 hw->bus.width,
-		 (speed == PCIE_SPEED_2_5GT ? "20%" :
-		  speed == PCIE_SPEED_5_0GT ? "20%" :
-		  speed == PCIE_SPEED_8_0GT ? "<2%" :
-		  "Unknown"),
-		 (hw->bus.payload == fm10k_bus_payload_128 ? "128B" :
-		  hw->bus.payload == fm10k_bus_payload_256 ? "256B" :
-		  hw->bus.payload == fm10k_bus_payload_512 ? "512B" :
-		  "Unknown"));
-
-	switch (hw->bus_caps.speed) {
-	case fm10k_bus_speed_2500:
-		/* 8b/10b encoding reduces max throughput by 20% */
-		expected_gts = 2 * hw->bus_caps.width;
-		break;
-	case fm10k_bus_speed_5000:
-		/* 8b/10b encoding reduces max throughput by 20% */
-		expected_gts = 4 * hw->bus_caps.width;
-		break;
-	case fm10k_bus_speed_8000:
-		/* 128b/130b encoding has less than 2% impact on throughput */
-		expected_gts = 8 * hw->bus_caps.width;
-		break;
-	default:
-		dev_warn(&interface->pdev->dev,
-			 "Unable to determine expected PCI Express bandwidth.\n");
-		return;
-	}
-
-	if (max_gts >= expected_gts)
-		return;
-
-	dev_warn(&interface->pdev->dev,
-		 "This device requires %dGT/s of bandwidth for optimal performance.\n",
-		 expected_gts);
-	dev_warn(&interface->pdev->dev,
-		 "A %sslot with x%d lanes is suggested.\n",
-		 (hw->bus_caps.speed == fm10k_bus_speed_2500 ? "2.5GT/s " :
-		  hw->bus_caps.speed == fm10k_bus_speed_5000 ? "5.0GT/s " :
-		  hw->bus_caps.speed == fm10k_bus_speed_8000 ? "8.0GT/s " : ""),
-		 hw->bus_caps.width);
-}
-
 /**
  * fm10k_probe - Device Initialization Routine
  * @pdev: PCI device information struct
@@ -2326,7 +2241,7 @@ static int fm10k_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	mod_timer(&interface->service_timer, (HZ * 2) + jiffies);
 
 	/* print warning for non-optimal configurations */
-	fm10k_slot_warn(interface);
+	pcie_print_link_status(interface->pdev);
 
 	/* report MAC address for logging */
 	dev_info(&pdev->dev, "%pM\n", netdev->dev_addr);