fix tx ring accounting in myx_start.

turns out i was calculating the number of packets (not descriptors)
on the tx ring, and then using that as the free space for descriptors.

1 files changed, 24 insertions, 20 deletions

diff --git a/sys/dev/pci/if_myx.c b/sys/dev/pci/if_myx.c
index 0dbce5276b5..0c1b7d11740 100644
--- a/sys/dev/pci/if_myx.c
+++ b/sys/dev/pci/if_myx.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_myx.c,v 1.86 2015/11/19 12:46:08 dlg Exp $	*/
+/*	$OpenBSD: if_myx.c,v 1.87 2015/11/24 10:04:34 dlg Exp $	*/
 
 /*
  * Copyright (c) 2007 Reyk Floeter <reyk@openbsd.org>
@@ -146,7 +146,8 @@ struct myx_softc {
 	u_int32_t		 sc_tx_ring_offset;
 	u_int			 sc_tx_nsegs;
 	u_int32_t		 sc_tx_count; /* shadows ms_txdonecnt */
-	u_int			 sc_tx_ring_idx;
+	u_int			 sc_tx_ring_prod;
+	u_int			 sc_tx_ring_cons;
 
 	u_int			 sc_tx_prod;
 	u_int			 sc_tx_cons;
@@ -1032,7 +1033,8 @@ myx_up(struct myx_softc *sc)
 		printf("%s: unable to get tx ring size\n", DEVNAME(sc));
 		goto free_pad;
 	}
-	sc->sc_tx_ring_idx = 0;
+	sc->sc_tx_ring_prod = 0;
+	sc->sc_tx_ring_cons = 0;
 	sc->sc_tx_ring_count = r / sizeof(struct myx_tx_desc);
 	sc->sc_tx_nsegs = min(16, sc->sc_tx_ring_count / 4); /* magic */
 	sc->sc_tx_count = 0;
@@ -1439,17 +1441,15 @@ myx_start(struct ifnet *ifp)
 	    IFQ_IS_EMPTY(&ifp->if_snd))
 		return;
 
-	prod = sc->sc_tx_prod;
-	cons = sc->sc_tx_cons;
+	idx = sc->sc_tx_ring_prod;
 
 	/* figure out space */
-	free = prod;
-	if (cons >= prod)
+	free = sc->sc_tx_ring_cons;
+	if (free <= idx)
 		free += sc->sc_tx_ring_count;
-	free -= cons;
+	free -= idx;
 
-	/* keep track of our usage */
-	cons = prod;
+	cons = prod = sc->sc_tx_prod;
 
 	used = 0;
 
@@ -1478,7 +1478,7 @@ myx_start(struct ifnet *ifp)
 
 		map = ms->ms_map;
 		bus_dmamap_sync(sc->sc_dmat, map, 0,
-		    map->dm_mapsize, BUS_DMASYNC_POSTWRITE);
+		    map->dm_mapsize, BUS_DMASYNC_PREWRITE);
 
 		used += map->dm_nsegs + (map->dm_mapsize < 60 ? 1 : 0);
 
@@ -1490,7 +1490,6 @@ myx_start(struct ifnet *ifp)
 		return;
 
 	ms = &sc->sc_tx_slots[cons];
-	idx = sc->sc_tx_ring_idx;
 
 	for (;;) {
 		idx += ms->ms_map->dm_nsegs +
@@ -1537,26 +1536,27 @@ myx_start(struct ifnet *ifp)
 	txd.tx_flags = flags | MYXTXD_FLAGS_FIRST;
 
 	/* make sure the first descriptor is seen after the others */
-	myx_write_txd_tail(sc, ms, flags, offset, sc->sc_tx_ring_idx);
+	myx_write_txd_tail(sc, ms, flags, offset, sc->sc_tx_ring_prod);
 
 	myx_bus_space_write(sc,
-	    offset + sizeof(txd) * sc->sc_tx_ring_idx, &txd,
+	    offset + sizeof(txd) * sc->sc_tx_ring_prod, &txd,
 	    sizeof(txd) - sizeof(myx_bus_t));
 
 	bus_space_barrier(sc->sc_memt, sc->sc_memh, offset,
 	    sizeof(txd) * sc->sc_tx_ring_count, BUS_SPACE_BARRIER_WRITE);
 
 	myx_bus_space_write(sc,
-	    offset + sizeof(txd) * (sc->sc_tx_ring_idx + 1) - sizeof(myx_bus_t),
+	    offset + sizeof(txd) * (sc->sc_tx_ring_prod + 1) -
+	    sizeof(myx_bus_t),
 	    (u_int8_t *)&txd + sizeof(txd) - sizeof(myx_bus_t),
 	    sizeof(myx_bus_t));
 
 	bus_space_barrier(sc->sc_memt, sc->sc_memh,
-	    offset + sizeof(txd) * sc->sc_tx_ring_idx, sizeof(txd),
+	    offset + sizeof(txd) * sc->sc_tx_ring_prod, sizeof(txd),
 	    BUS_SPACE_BARRIER_WRITE);
 
 	/* commit */
-	sc->sc_tx_ring_idx = idx;
+	sc->sc_tx_ring_prod = idx;
 	sc->sc_tx_prod = prod;
 }
 
@@ -1688,16 +1688,16 @@ myx_txeof(struct myx_softc *sc, u_int32_t done_count)
 	struct ifnet *ifp = &sc->sc_ac.ac_if;
 	struct myx_slot *ms;
 	bus_dmamap_t map;
-	u_int free = 0;
-	u_int cons;
+	u_int idx, cons;
 
+	idx = sc->sc_tx_ring_cons;
 	cons = sc->sc_tx_cons;
 
 	do {
 		ms = &sc->sc_tx_slots[cons];
 		map = ms->ms_map;
 
-		free += map->dm_nsegs + (map->dm_mapsize < 60 ? 1 : 0);
+		idx += map->dm_nsegs + (map->dm_mapsize < 60 ? 1 : 0);
 
 		bus_dmamap_sync(sc->sc_dmat, map, 0,
 		    map->dm_mapsize, BUS_DMASYNC_POSTWRITE);
@@ -1710,6 +1710,10 @@ myx_txeof(struct myx_softc *sc, u_int32_t done_count)
 			cons = 0;
 	} while (++sc->sc_tx_count != done_count);
 
+	if (idx >= sc->sc_tx_ring_count)
+		idx -= sc->sc_tx_ring_count;
+
+	sc->sc_tx_ring_cons = idx;
 	sc->sc_tx_cons = cons;
 }