If RX lockup workaround is enabled, fxp(4) will periodically reset

the controller to workaround silicon bug of i82557. Each reset will
re-establish link which in turn triggers MII status change
callback. The callback will try to reconfigure controller if the
controller is not i82557 to enable flow-control. This caused
endless link UP/DOWN when the workaround was enabled on non-i82557
controller.

To fix the issue, apply RX lockup workaround only for i82557.
Previously it blindly checked undocumented EEPROM location such
that it sometimes enabled the workaround for other controllers. At
this time, only i82557 is known to have the silicon bug.
This fixes a regression introduced in r215906 which enabled flow
control support for all controllers except i82557.

Reported by:	Karl Denninger (karl <> denninger dot net)
Tested by:	Karl Denninger (karl <> denninger dot net)
MFC after:	3 days

1 files changed, 6 insertions, 4 deletions

diff --git a/sys/dev/fxp/if_fxp.c b/sys/dev/fxp/if_fxp.c
index 6ccac920470c..fe9c0bd9ca62 100644
--- a/sys/dev/fxp/if_fxp.c
+++ b/sys/dev/fxp/if_fxp.c
@@ -526,10 +526,12 @@ fxp_attach(device_t dev)
 	}
 
 	/* Receiver lock-up workaround detection. */
-	fxp_read_eeprom(sc, &data, 3, 1);
-	if ((data & 0x03) != 0x03) {
-		sc->flags |= FXP_FLAG_RXBUG;
-		device_printf(dev, "Enabling Rx lock-up workaround\n");
+	if (sc->revision < FXP_REV_82558_A4) {
+		fxp_read_eeprom(sc, &data, 3, 1);
+		if ((data & 0x03) != 0x03) {
+			sc->flags |= FXP_FLAG_RXBUG;
+			device_printf(dev, "Enabling Rx lock-up workaround\n");
+		}
 	}
 
 	/*