ixgbe: Filter out spurious link up indication

Add delayed link state recheck to filter false link up indication
caused by transceiver with no fiber cable attached.
Signed-off-by: Sebastian Czapla <sebastianx.czapla@intel.com>
Tested-by: Sunitha Mekala <sunithax.d.mekala@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

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

@@ -3292,13 +3292,14 @@ static bool ixgbe_need_crosstalk_fix(struct ixgbe_hw *hw)
 s32 ixgbe_check_mac_link_generic(struct ixgbe_hw *hw, ixgbe_link_speed *speed,
 				 bool *link_up, bool link_up_wait_to_complete)
 {
+	bool crosstalk_fix_active = ixgbe_need_crosstalk_fix(hw);
 	u32 links_reg, links_orig;
 	u32 i;
 
 	/* If Crosstalk fix enabled do the sanity check of making sure
 	 * the SFP+ cage is full.
 	 */
-	if (ixgbe_need_crosstalk_fix(hw)) {
+	if (crosstalk_fix_active) {
 		u32 sfp_cage_full;
 
 		switch (hw->mac.type) {
@@ -3346,10 +3347,24 @@ s32 ixgbe_check_mac_link_generic(struct ixgbe_hw *hw, ixgbe_link_speed *speed,
 			links_reg = IXGBE_READ_REG(hw, IXGBE_LINKS);
 		}
 	} else {
-		if (links_reg & IXGBE_LINKS_UP)
+		if (links_reg & IXGBE_LINKS_UP) {
+			if (crosstalk_fix_active) {
+				/* Check the link state again after a delay
+				 * to filter out spurious link up
+				 * notifications.
+				 */
+				mdelay(5);
+				links_reg = IXGBE_READ_REG(hw, IXGBE_LINKS);
+				if (!(links_reg & IXGBE_LINKS_UP)) {
+					*link_up = false;
+					*speed = IXGBE_LINK_SPEED_UNKNOWN;
+					return 0;
+				}
+			}
 			*link_up = true;
-		else
+		} else {
 			*link_up = false;
+		}
 	}
 
 	switch (links_reg & IXGBE_LINKS_SPEED_82599) {