1 files changed, 14 insertions, 2 deletions

diff --git a/sys/dev/em/if_em.c b/sys/dev/em/if_em.c
index 6cf1a7fc02d5c..2b233bbaf412c 100644
--- a/sys/dev/em/if_em.c
+++ b/sys/dev/em/if_em.c
@@ -3005,8 +3005,20 @@ em_enable_intr(struct adapter * adapter)
 static void
 em_disable_intr(struct adapter *adapter)
 {
-	E1000_WRITE_REG(&adapter->hw, IMC, 
-			(0xffffffff & ~E1000_IMC_RXSEQ));
+	/*
+	 * The first version of 82542 had an errata where when link was forced it
+	 * would stay up even up even if the cable was disconnected.  Sequence errors
+	 * were used to detect the disconnect and then the driver would unforce the link.
+	 * This code in the in the ISR.  For this to work correctly the Sequence error 
+	 * interrupt had to be enabled all the time.
+	 */
+
+	if (adapter->hw.mac_type == em_82542_rev2_0)
+	    E1000_WRITE_REG(&adapter->hw, IMC,
+	        (0xffffffff & ~E1000_IMC_RXSEQ));
+	else
+	    E1000_WRITE_REG(&adapter->hw, IMC,
+	        0xffffffff);
 	return;
 }