e1000e: Fix Runtime PM blocks EEE link negotiation in S5

Adding a function, and associated calls, to flush writes to (read) the LPIC
MAC register before entering the shutdown flow.  This fixes the problem
of the PHY never negotiating a 100M link (if both sides of the link support
EEE and 100M link) when Runtime PM is enabled.

Signed-off-by: Dave Ertman <david.m.ertman@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/e1000e/netdev.c

@@ -6033,6 +6033,28 @@ release:
 	return retval;
 }
 
+static void e1000e_flush_lpic(struct pci_dev *pdev)
+{
+	struct net_device *netdev = pci_get_drvdata(pdev);
+	struct e1000_adapter *adapter = netdev_priv(netdev);
+	struct e1000_hw *hw = &adapter->hw;
+	u32 ret_val;
+
+	pm_runtime_get_sync(netdev->dev.parent);
+
+	ret_val = hw->phy.ops.acquire(hw);
+	if (ret_val)
+		goto fl_out;
+
+	pr_info("EEE TX LPI TIMER: %08X\n",
+		er32(LPIC) >> E1000_LPIC_LPIET_SHIFT);
+
+	hw->phy.ops.release(hw);
+
+fl_out:
+	pm_runtime_put_sync(netdev->dev.parent);
+}
+
 static int e1000e_pm_freeze(struct device *dev)
 {
 	struct net_device *netdev = pci_get_drvdata(to_pci_dev(dev));
@@ -6333,6 +6355,8 @@ static int e1000e_pm_suspend(struct device *dev)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 
+	e1000e_flush_lpic(pdev);
+
 	e1000e_pm_freeze(dev);
 
 	return __e1000_shutdown(pdev, false);
@@ -6416,6 +6440,8 @@ static int e1000e_pm_runtime_suspend(struct device *dev)
 
 static void e1000_shutdown(struct pci_dev *pdev)
 {
+	e1000e_flush_lpic(pdev);
+
 	e1000e_pm_freeze(&pdev->dev);
 
 	__e1000_shutdown(pdev, false);