Defragment mbufs in the tx path to work around a (not fully understood)

issue on the StarFive JH7100 SoC where packets spanning multiple mbufs
are corrupted.  Makes ethernet work reliably on the StarFive VisionFive 1
board.

ok patrick@

diff --git a/sys/dev/fdt/if_dwge.c b/sys/dev/fdt/if_dwge.c
index eed03e3..c5c42ec 100644 (file)
--- a/sys/dev/fdt/if_dwge.c
+++ b/sys/dev/fdt/if_dwge.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: if_dwge.c,v 1.14 2023/01/14 17:02:57 kettenis Exp $   */
+/*     $OpenBSD: if_dwge.c,v 1.15 2023/02/26 13:28:12 kettenis Exp $   */
 /*
  * Copyright (c) 2008, 2019 Mark Kettenis <kettenis@openbsd.org>
  * Copyright (c) 2017 Patrick Wildt <patrick@blueri.se>
@@ -253,6 +253,7 @@ struct dwge_softc {
        int                     sc_phyloc;
        int                     sc_force_thresh_dma_mode;
        int                     sc_enh_desc;
+       int                     sc_defrag;
 
        struct dwge_dmamem      *sc_txring;
        struct dwge_buf         *sc_txbuf;
@@ -406,6 +407,16 @@ dwge_attach(struct device *parent, struct device *self, void *aux)
                        sc->sc_enh_desc = 1;
        }
 
+       /*
+        * The GMAC on the StarFive JH7100 (core version 3.70)
+        * sometimes transmits corrupted packets.  The exact
+        * conditions under which this happens are unclear, but
+        * defragmenting mbufs before transmitting them fixes the
+        * issue.
+        */
+       if (OF_is_compatible(faa->fa_node, "starfive,jh7100-gmac"))
+               sc->sc_defrag = 1;
+
        /* Power up PHY. */
        phy_supply = OF_getpropint(faa->fa_node, "phy-supply", 0);
        if (phy_supply)
@@ -1252,6 +1263,11 @@ dwge_encap(struct dwge_softc *sc, struct mbuf *m, int *idx, int *used)
        cur = frag = *idx;
        map = sc->sc_txbuf[cur].tb_map;
 
+       if (sc->sc_defrag) {
+               if (m_defrag(m, M_DONTWAIT))
+                       return (ENOBUFS);
+       }
+
        if (bus_dmamap_load_mbuf(sc->sc_dmat, map, m, BUS_DMA_NOWAIT)) {
                if (m_defrag(m, M_DONTWAIT))
                        return (EFBIG);