Commit patch to supress spurious link change events. Apparently, with

copper NICs, a link change event is posted whenever MII autopolling is
toggled off and on, which happens whenever someone calls
bge_miibus_readreg() or bge_miibus_writereg() to access the PHY
registers. This means anytime someone called the SIOCGIFMEDIA ioctl
on a bge interface, the link would reset. Even a simple "ifconfig bge0"
would do it, though other apps like dhclient or the PPPoE daemon could
trigger it as well. An obvious symptom of this problem is lots of
"bgeX: gigabit link up" messages appearing on the console for no
apparent reason.

Through experimentation, I determined that when a real link change
event occurs, the BGE_MIMODE_AUTOPOLL in the BGE_MI_MODE register
is always set, so now if we have a copper NIC and an link change
event occurs and the BGE_MIMODE_AUTOPOLL bit is clear, we ignore
the event.

Note that this does not apply to the original BCM5700 chip since we
use a different method for sensing link changes with that chip (the
status block method was broken), nor to fiber optic NICs since they
don't use the GMII PHY access registers.

1 files changed, 11 insertions, 2 deletions

diff --git a/sys/dev/bge/if_bge.c b/sys/dev/bge/if_bge.c
index 5468423..71ad6ab 100644
--- a/sys/dev/bge/if_bge.c
+++ b/sys/dev/bge/if_bge.c
@@ -2802,7 +2802,7 @@ bge_intr(xsc)
 	struct bge_softc *sc;
 	struct ifnet *ifp;
 	u_int32_t statusword;
-	u_int32_t status;
+	u_int32_t status, mimode;
 
 	sc = xsc;
 	ifp = &sc->arpcom.ac_if;
@@ -2863,10 +2863,19 @@ bge_intr(xsc)
 			 * that sometimes appear on fiber NICs during
 			 * periods of heavy traffic. (There should be no
 			 * effect on copper NICs.)
+			 *
+			 * If we do have a copper NIC (bge_tbi == 0) then
+			 * check that the AUTOPOLL bit is set before
+			 * processing the event as a real link change.
+			 * Turning AUTOPOLL on and off in the MII read/write
+			 * functions will often trigger a link status
+			 * interrupt for no reason.
 			 */
 			status = CSR_READ_4(sc, BGE_MAC_STS);
+			mimode = CSR_READ_4(sc, BGE_MI_MODE);
 			if (!(status & (BGE_MACSTAT_PORT_DECODE_ERROR|
-			    BGE_MACSTAT_MI_COMPLETE))) {
+			    BGE_MACSTAT_MI_COMPLETE)) && (!sc->bge_tbi &&
+			    (mimode & BGE_MIMODE_AUTOPOLL))) {
 				sc->bge_link = 0;
 				callout_stop(&sc->bge_stat_ch);
 				bge_tick_locked(sc);