Index: if_em.c
===================================================================
RCS file: /pool/ncvs/src/sys/dev/em/if_em.c,v
retrieving revision 1.122
diff -u -r1.122 if_em.c
--- if_em.c	27 Jul 2006 00:43:34 -0000	1.122
+++ if_em.c	29 Jul 2006 06:53:18 -0000
@@ -214,6 +214,7 @@
 static void	em_txeof(struct em_softc *);
 static int	em_allocate_receive_structures(struct em_softc *);
 static int	em_allocate_transmit_structures(struct em_softc *);
+static __inline void em_discard_rxbuf(struct em_softc *, int);
 static int	em_rxeof(struct em_softc *, int);
 #ifndef __NO_STRICT_ALIGNMENT
 static int	em_fixup_rx(struct em_softc *);
@@ -227,7 +228,7 @@
 static void	em_set_multi(struct em_softc *);
 static void	em_print_hw_stats(struct em_softc *);
 static void	em_update_link_status(struct em_softc *);
-static int	em_get_buf(int i, struct em_softc *, struct mbuf *);
+static int	em_get_buf(struct em_softc *, int i);
 static void	em_enable_vlans(struct em_softc *);
 static void	em_disable_vlans(struct em_softc *);
 static int	em_encap(struct em_softc *, struct mbuf **);
@@ -2732,46 +2733,49 @@
  *
  **********************************************************************/
 static int
-em_get_buf(int i, struct em_softc *sc, struct mbuf *mp)
+em_get_buf(struct em_softc *sc, int i)
 {
-	struct ifnet		*ifp = sc->ifp;
+	struct mbuf		*m;
 	bus_dma_segment_t	segs[1];
+	bus_dmamap_t		map;
 	struct em_buffer	*rx_buffer;
 	int			error, nsegs;
 
-	if (mp == NULL) {
-		mp = m_getcl(M_DONTWAIT, MT_DATA, M_PKTHDR);
-		if (mp == NULL) {
-			sc->mbuf_cluster_failed++;
-			return (ENOBUFS);
-		}
-		mp->m_len = mp->m_pkthdr.len = MCLBYTES;
-	} else {
-		mp->m_len = mp->m_pkthdr.len = MCLBYTES;
-		mp->m_data = mp->m_ext.ext_buf;
-		mp->m_next = NULL;
-	}
-
-	if (ifp->if_mtu <= ETHERMTU)
-		m_adj(mp, ETHER_ALIGN);
-
-	rx_buffer = &sc->rx_buffer_area[i];
+	m = m_getcl(M_DONTWAIT, MT_DATA, M_PKTHDR);
+	if (m == NULL) {
+		sc->mbuf_cluster_failed++;
+		return (ENOBUFS);
+	}
+	m->m_len = m->m_pkthdr.len = MCLBYTES;
+	if (sc->hw.max_frame_size <= (MCLBYTES - ETHER_ALIGN))
+		m_adj(m, ETHER_ALIGN);
 
 	/*
 	 * Using memory from the mbuf cluster pool, invoke the
 	 * bus_dma machinery to arrange the memory mapping.
 	 */
-	error = bus_dmamap_load_mbuf_sg(sc->rxtag, rx_buffer->map,
-	    mp, segs, &nsegs, 0);
+	error = bus_dmamap_load_mbuf_sg(sc->rxtag, sc->rx_sparemap,
+	    m, segs, &nsegs, 0);
 	if (error != 0) {
-		m_free(mp);
+		m_free(m);
 		return (error);
 	}
 	/* If nsegs is wrong then the stack is corrupt. */
 	KASSERT(nsegs == 1, ("Too many segments returned!"));
-	rx_buffer->m_head = mp;
-	sc->rx_desc_base[i].buffer_addr = htole64(segs[0].ds_addr);
+
+	rx_buffer = &sc->rx_buffer_area[i];
+	if (rx_buffer->m_head != NULL)
+		bus_dmamap_unload(sc->rxtag, rx_buffer->map);
+
+	map = rx_buffer->map;
+	rx_buffer->map = sc->rx_sparemap;
+	sc->rx_sparemap = map;
 	bus_dmamap_sync(sc->rxtag, rx_buffer->map, BUS_DMASYNC_PREREAD);
+	rx_buffer->m_head = m;
+
+	sc->rx_desc_base[i].buffer_addr = htole64(segs[0].ds_addr);
+	/* Zero out the receive descriptors status. */
+	sc->rx_desc_base[i].status = 0;
 
 	return (0);
 }
@@ -2818,6 +2822,12 @@
 		goto fail;
 	}
 
+	error = bus_dmamap_create(sc->rxtag, BUS_DMA_NOWAIT, &sc->rx_sparemap);
+	if (error) {
+		device_printf(dev, "%s: bus_dmamap_create failed: %d\n",
+		    __func__, error);
+		goto fail;
+	}
 	rx_buffer = sc->rx_buffer_area;
 	for (i = 0; i < sc->num_rx_desc; i++, rx_buffer++) {
 		error = bus_dmamap_create(sc->rxtag, BUS_DMA_NOWAIT,
@@ -2830,7 +2840,7 @@
 	}
 
 	for (i = 0; i < sc->num_rx_desc; i++) {
-		error = em_get_buf(i, sc, NULL);
+		error = em_get_buf(sc, i);
 		if (error)
 			goto fail;
 	}
@@ -2965,6 +2975,12 @@
 
 	INIT_DEBUGOUT("free_receive_structures: begin");
 
+	if (sc->rx_sparemap) {
+		bus_dmamap_sync(sc->rxtag, sc->rx_sparemap,
+		    BUS_DMASYNC_POSTREAD);
+		bus_dmamap_destroy(sc->rxtag, sc->rx_sparemap);
+		sc->rx_sparemap = NULL;
+	}
 	if (sc->rx_buffer_area != NULL) {
 		rx_buffer = sc->rx_buffer_area;
 		for (i = 0; i < sc->num_rx_desc; i++, rx_buffer++) {
@@ -2995,6 +3011,26 @@
 	}
 }
 
+static __inline void
+em_discard_rxbuf(struct em_softc *sc, int i)
+{
+	struct mbuf *m;
+
+	/* Reuse loaded DMA map and just updates mbuf chain */
+	m = sc->rx_buffer_area[i].m_head;
+	m->m_len = m->m_pkthdr.len = MCLBYTES;
+	m->m_data = m->m_ext.ext_buf;
+	m->m_next = NULL;
+	if (sc->hw.max_frame_size <= (MCLBYTES - ETHER_ALIGN))
+		m_adj(m, ETHER_ALIGN);
+	if (sc->fmp != NULL)
+		m_freem(sc->fmp);
+	sc->fmp = NULL;
+	sc->lmp = NULL;
+	/* Zero out the receive descriptors status. */
+	sc->rx_desc_base[i].status = 0;
+}
+
 /*********************************************************************
  *
  *  This routine executes in interrupt context. It replenishes
@@ -3033,10 +3069,12 @@
 		struct mbuf *m = NULL;
 
 		mp = sc->rx_buffer_area[i].m_head;
+		/*
+		 * Can't defer bus_dmamap_sync(9) because TBI_ACCEPT
+		 * needs to access the last received byte in the mbuf.
+		 */
 		bus_dmamap_sync(sc->rxtag, sc->rx_buffer_area[i].map,
 		    BUS_DMASYNC_POSTREAD);
-		bus_dmamap_unload(sc->rxtag,
-		    sc->rx_buffer_area[i].map);
 
 		accept_frame = 1;
 		prev_len_adj = 0;
@@ -3075,14 +3113,9 @@
 		}
 
 		if (accept_frame) {
-			if (em_get_buf(i, sc, NULL) == ENOBUFS) {
-				sc->dropped_pkts++;
-				em_get_buf(i, sc, mp);
-				if (sc->fmp != NULL)
-					m_freem(sc->fmp);
-				sc->fmp = NULL;
-				sc->lmp = NULL;
-				break;
+			if (em_get_buf(sc, i) != 0) {
+				ifp->if_iqdrops++;
+				goto discard;
 			}
 
 			/* Assign correct length to the current fragment */
@@ -3116,7 +3149,8 @@
 				em_receive_checksum(sc, current_desc,
 				    sc->fmp);
 #ifndef __NO_STRICT_ALIGNMENT
-				if (ifp->if_mtu > ETHERMTU &&
+				if (sc->hw.max_frame_size >
+				    (MCLBYTES - ETHER_ALIGN) &&
 				    em_fixup_rx(sc) != 0)
 					goto skip;
 #endif
@@ -3132,16 +3166,10 @@
 				sc->lmp = NULL;
 			}
 		} else {
-			sc->dropped_pkts++;
-			em_get_buf(i, sc, mp);
-			if (sc->fmp != NULL)
-				m_freem(sc->fmp);
-			sc->fmp = NULL;
-			sc->lmp = NULL;
+discard:
+			em_discard_rxbuf(sc, i);
 		}
 
-		/* Zero out the receive descriptors status. */
-		current_desc->status = 0;
 		bus_dmamap_sync(sc->rxdma.dma_tag, sc->rxdma.dma_map,
 		    BUS_DMASYNC_PREREAD | BUS_DMASYNC_PREWRITE);
 
Index: if_em.h
===================================================================
RCS file: /pool/ncvs/src/sys/dev/em/if_em.h,v
retrieving revision 1.45
diff -u -r1.45 if_em.h
--- if_em.h	20 Jul 2006 04:18:45 -0000	1.45
+++ if_em.h	29 Jul 2006 06:53:24 -0000
@@ -314,6 +314,7 @@
 	int			rx_process_limit;
 	struct em_buffer	*rx_buffer_area;
 	bus_dma_tag_t		rxtag;
+	bus_dmamap_t		rx_sparemap;
 
 	/* First/last mbuf pointers, for collecting multisegment RX packets. */
 	struct mbuf	       *fmp;