e1000e: delay second read of PHY_STATUS register on failure of first read

Some PHYs may require two reads of the PHY_STATUS register to determine the
link status.  If the PHY is being accessed by another thread it is possible
the first read could timeout and fail.  In this case, put a delay in so
the second read will pick up the correct link status.
Signed-off-by: NBruce Allan <bruce.w.allan@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/e1000e/phy.c

@@ -1531,7 +1531,12 @@ s32 e1000e_phy_has_link_generic(struct e1000_hw *hw, u32 iterations,
 		 */
 		ret_val = e1e_rphy(hw, PHY_STATUS, &phy_status);
 		if (ret_val)
-			break;
+			/*
+			 * If the first read fails, another entity may have
+			 * ownership of the resources, wait and try again to
+			 * see if they have relinquished the resources yet.
+			 */
+			udelay(usec_interval);
 		ret_val = e1e_rphy(hw, PHY_STATUS, &phy_status);
 		if (ret_val)
 			break;