Fix up tx ring slot calculations so we store the mbuf and dma map with

the last slot of the packet rather than the first slot of the next.

ok dlg@

diff --git a/sys/dev/fdt/if_mvneta.c b/sys/dev/fdt/if_mvneta.c
index 2339ca8..9ee7a9c 100644 (file)
--- a/sys/dev/fdt/if_mvneta.c
+++ b/sys/dev/fdt/if_mvneta.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: if_mvneta.c,v 1.26 2022/06/05 02:54:18 dlg Exp $      */
+/*     $OpenBSD: if_mvneta.c,v 1.27 2022/07/19 21:49:22 jmatthew Exp $ */
 /*     $NetBSD: if_mvneta.c,v 1.41 2015/04/15 10:15:40 hsuenaga Exp $  */
 /*
  * Copyright (c) 2007, 2008, 2013 KIYOHARA Takashi
@@ -975,11 +975,15 @@ mvneta_start(struct ifqueue *ifq)
 
                mvneta_encap(sc, map, m, prod);
 
-               nprod = (prod + map->dm_nsegs) % MVNETA_TX_RING_CNT;
-               sc->sc_txbuf[prod].tb_map = sc->sc_txbuf[nprod].tb_map;
-               prod = nprod;
-               sc->sc_txbuf[prod].tb_map = map;
+               if (map->dm_nsegs > 1) {
+                       nprod = (prod + (map->dm_nsegs - 1)) %
+                           MVNETA_TX_RING_CNT;
+                       sc->sc_txbuf[prod].tb_map = sc->sc_txbuf[nprod].tb_map;
+                       prod = nprod;
+                       sc->sc_txbuf[prod].tb_map = map;
+               }
                sc->sc_txbuf[prod].tb_m = m;
+               prod = MVNETA_TX_RING_NEXT(prod);
 
                free -= map->dm_nsegs;