ixgbe: enable devices with internal switch to read pci parent

This patch modifies the driver to enable certain devices, which have an internal
switch, to read data from the physical slot rather than reading data from the
internal switch. The internal switch will always report the same PCI width and
speed, which is not useful compared to knowing the width and speed of the slot
the physical card is plugged into.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe_main.c

@@ -149,6 +149,52 @@ MODULE_DESCRIPTION("Intel(R) 10 Gigabit PCI Express Network Driver");
 MODULE_LICENSE("GPL");
 MODULE_VERSION(DRV_VERSION);
 
+static int ixgbe_read_pci_cfg_word_parent(struct ixgbe_adapter *adapter,
+					  u32 reg, u16 *value)
+{
+	int pos = 0;
+	struct pci_dev *parent_dev;
+	struct pci_bus *parent_bus;
+
+	parent_bus = adapter->pdev->bus->parent;
+	if (!parent_bus)
+		return -1;
+
+	parent_dev = parent_bus->self;
+	if (!parent_dev)
+		return -1;
+
+	pos = pci_find_capability(parent_dev, PCI_CAP_ID_EXP);
+	if (!pos)
+		return -1;
+
+	pci_read_config_word(parent_dev, pos + reg, value);
+	return 0;
+}
+
+static s32 ixgbe_get_parent_bus_info(struct ixgbe_adapter *adapter)
+{
+	struct ixgbe_hw *hw = &adapter->hw;
+	u16 link_status = 0;
+	int err;
+
+	hw->bus.type = ixgbe_bus_type_pci_express;
+
+	/* Get the negotiated link width and speed from PCI config space of the
+	 * parent, as this device is behind a switch
+	 */
+	err = ixgbe_read_pci_cfg_word_parent(adapter, 18, &link_status);
+
+	/* assume caller will handle error case */
+	if (err)
+		return err;
+
+	hw->bus.width = ixgbe_convert_bus_width(link_status);
+	hw->bus.speed = ixgbe_convert_bus_speed(link_status);
+
+	return 0;
+}
+
 static void ixgbe_service_event_schedule(struct ixgbe_adapter *adapter)
 {
 	if (!test_bit(__IXGBE_DOWN, &adapter->state) &&
@@ -7487,6 +7533,8 @@ static int ixgbe_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 
 	/* pick up the PCI bus settings for reporting later */
 	hw->mac.ops.get_bus_info(hw);
+	if (hw->device_id == IXGBE_DEV_ID_82599_SFP_SF_QP)
+		ixgbe_get_parent_bus_info(adapter);
 
 	/* print bus type/speed/width info */
 	e_dev_info("(PCI Express:%s:%s) %pM\n",