- Improved the TX performance with polling(4) by only checking the

  status registers for error conditions and updating statistics
  when there are cycles left (inspired by the nge(4) driver).

- Removed the TX list counter and the producer/consumer gap; it's
  enough to just ensure we don't reuse the last (free) descriptor,
  as the chip may not have read its next pointer yet.  If we reuse
  it, the TX may stall under a heavy TX load with polling enabled.

- Dropped code to recharge the watchdog timer, it's pointless; the
  watchdog routine will re-init the chip and both RX and TX lists.

2 files changed, 11 insertions, 16 deletions

diff --git a/sys/pci/if_ste.c b/sys/pci/if_ste.c
index 9c375f8..1062aed 100644
--- a/sys/pci/if_ste.c
+++ b/sys/pci/if_ste.c
@@ -651,7 +651,7 @@ ste_poll(struct ifnet *ifp, enum poll_cmd cmd, int count)
 	if (ifp->if_snd.ifq_head != NULL)
 		ste_start(ifp);
 
-	if (cmd == POLL_AND_CHECK_STATUS) { /* also check status register */
+	if (sc->rxcycles > 0 && cmd == POLL_AND_CHECK_STATUS) {
 		u_int16_t status;
 
 		status = CSR_READ_2(sc, STE_ISR_ACK);
@@ -923,21 +923,15 @@ ste_txeof(sc)
 
 		m_freem(cur_tx->ste_mbuf);
 		cur_tx->ste_mbuf = NULL;
-
+		ifp->if_flags &= ~IFF_OACTIVE;
 		ifp->if_opackets++;
 
-		sc->ste_cdata.ste_tx_cnt--;
 		STE_INC(idx, STE_TX_LIST_CNT);
 	}
 
-	if (idx != sc->ste_cdata.ste_tx_cons) {
-		sc->ste_cdata.ste_tx_cons = idx;
-		ifp->if_flags &= ~IFF_OACTIVE;
-		if (idx == sc->ste_cdata.ste_tx_prod)
-			ifp->if_timer = 0;
-		else if (ifp->if_timer == 0)
-			ifp->if_timer = 5;
-	}
+	sc->ste_cdata.ste_tx_cons = idx;
+	if (idx == sc->ste_cdata.ste_tx_prod)
+		ifp->if_timer = 0;
 }
 
 static void
@@ -1302,7 +1296,6 @@ ste_init_tx_list(sc)
 
 	cd->ste_tx_prod = 0;
 	cd->ste_tx_cons = 0;
-	cd->ste_tx_cnt = 0;
 
 	return;
 }
@@ -1637,8 +1630,12 @@ ste_start(ifp)
 	idx = sc->ste_cdata.ste_tx_prod;
 
 	while(sc->ste_cdata.ste_tx_chain[idx].ste_mbuf == NULL) {
-
-		if ((STE_TX_LIST_CNT - sc->ste_cdata.ste_tx_cnt) < 3) {
+		/*
+		 * We cannot re-use the last (free) descriptor;
+		 * the chip may not have read its ste_next yet.
+		 */
+		if (STE_NEXT(idx, STE_TX_LIST_CNT) ==
+		    sc->ste_cdata.ste_tx_cons) {
 			ifp->if_flags |= IFF_OACTIVE;
 			break;
 		}
@@ -1683,7 +1680,6 @@ ste_start(ifp)
 		BPF_MTAP(ifp, cur_tx->ste_mbuf);
 
 		STE_INC(idx, STE_TX_LIST_CNT);
-		sc->ste_cdata.ste_tx_cnt++;
 		ifp->if_timer = 5;
 	}
 	sc->ste_cdata.ste_tx_prod = idx;
diff --git a/sys/pci/if_stereg.h b/sys/pci/if_stereg.h
index 90350b4..213c82d 100644
--- a/sys/pci/if_stereg.h
+++ b/sys/pci/if_stereg.h
@@ -501,7 +501,6 @@ struct ste_chain_data {
 
 	int			ste_tx_prod;
 	int			ste_tx_cons;
-	int			ste_tx_cnt;
 };
 
 struct ste_softc {