From 848a02fc419bea8853bc3c055edaeba40e1c2f31 Mon Sep 17 00:00:00 2001
From: Pyun YongHyeon <yongari@FreeBSD.org>
Date: Wed, 16 Mar 2011 17:09:51 +0000
Subject: [PATCH] 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
---
 sys/dev/dc/if_dc.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/sys/dev/dc/if_dc.c b/sys/dev/dc/if_dc.c
index c7fda434a6c..bfc440174eb 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);
 			}