if we have to bounce a buffer, clear our anything already setup in
the map before trying again.

riastradh@ noticed that a map had two types of mbuf types, and this
seems to avoid it as seen on eqos(4) on quartz64.

add a couple more event counts for bus dma events.


Index: sys/arch/arm/arm32/bus_dma.c
===================================================================
RCS file: /cvsroot/src/sys/arch/arm/arm32/bus_dma.c,v
retrieving revision 1.134
diff -p -u -r1.134 bus_dma.c
--- sys/arch/arm/arm32/bus_dma.c	20 Dec 2021 13:58:58 -0000	1.134
+++ sys/arch/arm/arm32/bus_dma.c	6 Feb 2022 09:27:28 -0000
@@ -71,6 +71,8 @@ static struct evcnt bus_dma_write_bounce
 	EVCNT_INITIALIZER(EVCNT_TYPE_MISC, NULL, "busdma", "write bounces");
 static struct evcnt bus_dma_bounced_unloads =
 	EVCNT_INITIALIZER(EVCNT_TYPE_MISC, NULL, "busdma", "bounced unloads");
+static struct evcnt bus_dma_bounced_mbuf_loads =
+	EVCNT_INITIALIZER(EVCNT_TYPE_MISC, NULL, "busdma", "bounced mbuf loads");
 static struct evcnt bus_dma_unloads =
 	EVCNT_INITIALIZER(EVCNT_TYPE_MISC, NULL, "busdma", "unloads");
 static struct evcnt bus_dma_bounced_destroys =
@@ -93,6 +95,8 @@ static struct evcnt bus_dma_sync_postrea
 	EVCNT_INITIALIZER(EVCNT_TYPE_MISC, NULL, "busdma", "sync postreadwrite");
 static struct evcnt bus_dma_sync_postwrite =
 	EVCNT_INITIALIZER(EVCNT_TYPE_MISC, NULL, "busdma", "sync postwrite");
+static struct evcnt bus_dma_inrange_fail =
+	EVCNT_INITIALIZER(EVCNT_TYPE_MISC, NULL, "busdma", "inrange check failed");
 
 static struct evcnt bus_dma_sync_coherent_prereadwrite =
 	EVCNT_INITIALIZER(EVCNT_TYPE_MISC, NULL, "busdma", "sync coherent prereadwrite");
@@ -118,6 +122,7 @@ EVCNT_ATTACH_STATIC(bus_dma_unloads);
 EVCNT_ATTACH_STATIC(bus_dma_bounced_unloads);
 EVCNT_ATTACH_STATIC(bus_dma_destroys);
 EVCNT_ATTACH_STATIC(bus_dma_bounced_destroys);
+EVCNT_ATTACH_STATIC(bus_dma_bounced_mbuf_loads);
 EVCNT_ATTACH_STATIC(bus_dma_sync_prereadwrite);
 EVCNT_ATTACH_STATIC(bus_dma_sync_preread_begin);
 EVCNT_ATTACH_STATIC(bus_dma_sync_preread);
@@ -126,6 +131,7 @@ EVCNT_ATTACH_STATIC(bus_dma_sync_prewrit
 EVCNT_ATTACH_STATIC(bus_dma_sync_postread);
 EVCNT_ATTACH_STATIC(bus_dma_sync_postreadwrite);
 EVCNT_ATTACH_STATIC(bus_dma_sync_postwrite);
+EVCNT_ATTACH_STATIC(bus_dma_inrange_fail);
 
 EVCNT_ATTACH_STATIC(bus_dma_sync_coherent_prereadwrite);
 EVCNT_ATTACH_STATIC(bus_dma_sync_coherent_preread);
@@ -210,8 +216,10 @@ _bus_dmamap_load_paddr(bus_dma_tag_t t, 
 		/* XXX cache last result? */
 		const struct arm32_dma_range * const dr =
 		    _bus_dma_paddr_inrange(t->_ranges, t->_nranges, paddr);
-		if (dr == NULL)
+		if (dr == NULL) {
+			STAT_INCR(inrange_fail);
 			return EINVAL;
+		}
 
 		/*
 		 * If this region is coherent, mark the segment as coherent.
@@ -310,6 +318,7 @@ _bus_dma_load_bouncebuf(bus_dma_tag_t t,
 	 */
 	cookie->id_origbuf = buf;
 	cookie->id_origbuflen = buflen;
+	KASSERT(map->dm_nsegs == 0);
 	error = _bus_dmamap_load_buffer(t, map, cookie->id_bouncebuf,
 	    buflen, vm, flags);
 	if (error)
@@ -552,6 +561,11 @@ _bus_dmamap_load(bus_dma_tag_t t, bus_dm
 #ifdef _ARM32_NEED_BUS_DMA_BOUNCE
 	struct arm32_bus_dma_cookie * const cookie = map->_dm_cookie;
 	if (cookie != NULL && (cookie->id_flags & _BUS_DMA_MIGHT_NEED_BOUNCE)) {
+		/* Since we're trying again, clear the previous attempt. */
+		map->dm_mapsize = 0;
+		map->dm_nsegs = 0;
+		map->_dm_buftype = _BUS_DMA_BUFTYPE_INVALID;
+		map->_dm_flags |= _BUS_DMAMAP_COHERENT;
 		error = _bus_dma_load_bouncebuf(t, map, buf, buflen,
 		    _BUS_DMA_BUFTYPE_LINEAR, flags);
 	}
@@ -696,8 +710,14 @@ _bus_dmamap_load_mbuf(bus_dma_tag_t t, b
 #ifdef _ARM32_NEED_BUS_DMA_BOUNCE
 	struct arm32_bus_dma_cookie * const cookie = map->_dm_cookie;
 	if (cookie != NULL && (cookie->id_flags & _BUS_DMA_MIGHT_NEED_BOUNCE)) {
+		/* Since we're trying again, clear the previous attempt. */
+		map->dm_mapsize = 0;
+		map->dm_nsegs = 0;
+		map->_dm_buftype = _BUS_DMA_BUFTYPE_INVALID;
+		map->_dm_flags |= _BUS_DMAMAP_COHERENT;
 		error = _bus_dma_load_bouncebuf(t, map, m0, m0->m_pkthdr.len,
 		    _BUS_DMA_BUFTYPE_MBUF, flags);
+		STAT_INCR(bounced_mbuf_loads);
 	}
 #endif
 	return error;