Make sure the rx ring lwm is set to at least 4. As far as we know, all

hardware variants need at least 4 descriptors on the rx ring to be able to
receive packets.  Should fix the issue reported by Christian Schulte on
bugs@.

ok mikeb@, sthen@

diff --git a/sys/dev/pci/if_em.c b/sys/dev/pci/if_em.c
index cc55e79..908e74f 100644 (file)
--- a/sys/dev/pci/if_em.c
+++ b/sys/dev/pci/if_em.c
@@ -31,7 +31,7 @@ POSSIBILITY OF SUCH DAMAGE.
 
 ***************************************************************************/
 
-/* $OpenBSD: if_em.c,v 1.296 2015/05/12 02:33:39 jsg Exp $ */
+/* $OpenBSD: if_em.c,v 1.297 2015/05/12 20:20:18 kettenis Exp $ */
 /* $FreeBSD: if_em.c,v 1.46 2004/09/29 18:28:28 mlaier Exp $ */
 
 #include <dev/pci/if_em.h>
@@ -2599,6 +2599,7 @@ int
 em_setup_receive_structures(struct em_softc *sc)
 {
        struct ifnet *ifp = &sc->interface_data.ac_if;
+       u_int lwm;
 
        memset(sc->rx_desc_base, 0,
            sizeof(struct em_rx_desc) * sc->num_rx_desc);
@@ -2610,8 +2611,8 @@ em_setup_receive_structures(struct em_softc *sc)
        sc->next_rx_desc_to_check = 0;
        sc->last_rx_desc_filled = sc->num_rx_desc - 1;
 
-       if_rxr_init(&sc->rx_ring, 2 * ((ifp->if_hardmtu / MCLBYTES) + 1),
-           sc->num_rx_desc);
+       lwm = max(4, 2 * ((ifp->if_hardmtu / MCLBYTES) + 1));
+       if_rxr_init(&sc->rx_ring, lwm, sc->num_rx_desc);
 
        if (em_rxfill(sc) == 0) {
                printf("%s: unable to fill any rx descriptors\n",