r8169: reset bus if NIC isn't accessible after tx timeout

ASPM issues may result in the NIC not being accessible any longer.
In this case disabling ASPM may not work. Therefore detect this case
by checking whether register reads return ~0, and try to make the
NIC accessible again by resetting the secondary bus.

v2:
- add exception handling for the case that pci_reset_bus() fails
Suggested-by: Alexander Duyck <alexander.duyck@gmail.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/r8169_main.c

@@ -4532,6 +4532,16 @@ static void rtl_task(struct work_struct *work)
 		goto out_unlock;
 
 	if (test_and_clear_bit(RTL_FLAG_TASK_TX_TIMEOUT, tp->wk.flags)) {
+		/* if chip isn't accessible, reset bus to revive it */
+		if (RTL_R32(tp, TxConfig) == ~0) {
+			ret = pci_reset_bus(tp->pci_dev);
+			if (ret < 0) {
+				netdev_err(tp->dev, "Can't reset secondary PCI bus, detach NIC\n");
+				netif_device_detach(tp->dev);
+				goto out_unlock;
+			}
+		}
+
 		/* ASPM compatibility issues are a typical reason for tx timeouts */
 		ret = pci_disable_link_state(tp->pci_dev, PCIE_LINK_STATE_L1 |
 							  PCIE_LINK_STATE_L0S);