Explicitly check resolved speed/duplex. Just checking IFM_ACTIVE

does not guarantee established link. Also 1000baseT link report for
fast ethernet controller is not valid one so make sure gigabit link
is allowed for this controller.
Whenever we lost link, check whether Rx/Tx MACs were enabled. If both
MAC are not active, do not try to disable it again.

sys/dev/msk/if_msk.c

@@ -475,11 +475,25 @@ msk_miibus_statchg(device_t dev)
 	    (ifp->if_drv_flags & IFF_DRV_RUNNING) == 0)
 		return;
 
-	if (mii->mii_media_status & IFM_ACTIVE) {
-		if (IFM_SUBTYPE(mii->mii_media_active) != IFM_NONE)
+	sc_if->msk_flags &= ~MSK_FLAG_LINK;
+	if ((mii->mii_media_status & (IFM_AVALID | IFM_ACTIVE)) ==
+	    (IFM_AVALID | IFM_ACTIVE)) {
+		switch (IFM_SUBTYPE(mii->mii_media_active)) {
+		case IFM_10_T:
+		case IFM_100_TX:
 			sc_if->msk_flags |= MSK_FLAG_LINK;
-	} else
-		sc_if->msk_flags &= ~MSK_FLAG_LINK;
+			break;
+		case IFM_1000_T:
+		case IFM_1000_SX:
+		case IFM_1000_LX:
+		case IFM_1000_CX:
+			if ((sc_if->msk_flags & MSK_FLAG_FASTETHER) == 0)
+				sc_if->msk_flags |= MSK_FLAG_LINK;
+			break;
+		default:
+			break;
+		}
+	}
 
 	if ((sc_if->msk_flags & MSK_FLAG_LINK) != 0) {
 		/* Enable Tx FIFO Underrun. */
@@ -538,10 +552,12 @@ msk_miibus_statchg(device_t dev)
 		msk_phy_writereg(sc_if, PHY_ADDR_MARV, PHY_MARV_INT_MASK, 0);
 		/* Disable Rx/Tx MAC. */
 		gmac = GMAC_READ_2(sc, sc_if->msk_port, GM_GP_CTRL);
-		gmac &= ~(GM_GPCR_RX_ENA | GM_GPCR_TX_ENA);
-		GMAC_WRITE_2(sc, sc_if->msk_port, GM_GP_CTRL, gmac);
-		/* Read again to ensure writing. */
-		GMAC_READ_2(sc, sc_if->msk_port, GM_GP_CTRL);
+		if ((GM_GPCR_RX_ENA | GM_GPCR_TX_ENA) != 0) {
+			gmac &= ~(GM_GPCR_RX_ENA | GM_GPCR_TX_ENA);
+			GMAC_WRITE_2(sc, sc_if->msk_port, GM_GP_CTRL, gmac);
+			/* Read again to ensure writing. */
+			GMAC_READ_2(sc, sc_if->msk_port, GM_GP_CTRL);
+		}
 	}
 }