Remove too expensive bus_dmamap_sync(9) call in dc_rx_resync().

With this change, driver may not notice updated descriptor status
change when bounce buffers are active. However, rxeof() in next run
will handle the synchronization.

Change dc_rxeof() a bit to return the number of processed frames in
RX descriptor ring. Previously it returned the number of frames
that were successfully passed to upper stack which in turn means it
ignored frames that were discarded due to errors. The number of
processed frames in RX descriptor ring is used to detect whether
driver is out of sync with controller's current descriptor pointer.
Returning number of processed frames reduces unnecessary (probably
wrong) re-synchronization.

Reviewed by:	marius

1 files changed, 4 insertions, 10 deletions

diff --git a/sys/dev/dc/if_dc.c b/sys/dev/dc/if_dc.c
index c7fda43..bfc4401 100644
--- a/sys/dev/dc/if_dc.c
+++ b/sys/dev/dc/if_dc.c
@@ -2790,8 +2790,6 @@ dc_rx_resync(struct dc_softc *sc)
 	pos = sc->dc_cdata.dc_rx_prod;
 
 	for (i = 0; i < DC_RX_LIST_CNT; i++) {
-		bus_dmamap_sync(sc->dc_rx_ltag, sc->dc_rx_lmap,
-		    BUS_DMASYNC_POSTREAD | BUS_DMASYNC_POSTWRITE);
 		cur_rx = &sc->dc_ldata.dc_rx_list[pos];
 		if (!(le32toh(cur_rx->dc_status) & DC_RXSTAT_OWN))
 			break;
@@ -2862,6 +2860,7 @@ dc_rxeof(struct dc_softc *sc)
 		bus_dmamap_sync(sc->dc_rx_mtag, sc->dc_cdata.dc_rx_map[i],
 		    BUS_DMASYNC_POSTREAD);
 		total_len = DC_RXBYTES(rxstat);
+		rx_npkts++;
 
 		if (sc->dc_flags & DC_PNIC_RX_BUG_WAR) {
 			if ((rxstat & DC_WHOLEFRAME) != DC_WHOLEFRAME) {
@@ -2939,7 +2938,6 @@ dc_rxeof(struct dc_softc *sc)
 		DC_UNLOCK(sc);
 		(*ifp->if_input)(ifp, m);
 		DC_LOCK(sc);
-		rx_npkts++;
 	}
 
 	sc->dc_cdata.dc_rx_prod = i;
@@ -3263,7 +3261,7 @@ dc_intr(void *arg)
 	struct dc_softc *sc;
 	struct ifnet *ifp;
 	uint32_t r, status;
-	int curpkts, n;
+	int n;
 
 	sc = arg;
 
@@ -3293,9 +3291,7 @@ dc_intr(void *arg)
 		CSR_WRITE_4(sc, DC_ISR, status);
 
 		if (status & DC_ISR_RX_OK) {
-			curpkts = ifp->if_ipackets;
-			dc_rxeof(sc);
-			if (curpkts == ifp->if_ipackets) {
+			if (dc_rxeof(sc) == 0) {
 				while (dc_rx_resync(sc))
 					dc_rxeof(sc);
 			}
@@ -3319,9 +3315,7 @@ dc_intr(void *arg)
 		    || (status & DC_ISR_RX_NOBUF)) {
 			r = CSR_READ_4(sc, DC_FRAMESDISCARDED);
 			ifp->if_ierrors += (r & 0xffff) + ((r >> 17) & 0x7ff);
-			curpkts = ifp->if_ipackets;
-			dc_rxeof(sc);
-			if (curpkts == ifp->if_ipackets) {
+			if (dc_rxeof(sc) == 0) {
 				while (dc_rx_resync(sc))
 					dc_rxeof(sc);
 			}