when we use a fifo we always seem to need to know how much of the fifo is

ready to be used, and we need to decrement that "ready" count as we go over
the fifo. this diff moves that ready counter into the tht_fifo struct.

the ready value is calculated when we read the fifo pointers off the
hardware, and decremented by fifo_read or fifo_write as we work through it.
each of the loops over the fifos checks it directly to see if there's
anything left to work on.

1 files changed, 19 insertions, 21 deletions

diff --git a/sys/dev/pci/if_tht.c b/sys/dev/pci/if_tht.c
index 225d304977c..2d6bafa652d 100644
--- a/sys/dev/pci/if_tht.c
+++ b/sys/dev/pci/if_tht.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_tht.c,v 1.54 2007/04/23 09:59:01 dlg Exp $ */
+/*	$OpenBSD: if_tht.c,v 1.55 2007/04/23 11:24:07 dlg Exp $ */
 
 /*
  * Copyright (c) 2007 David Gwynne <dlg@openbsd.org>
@@ -358,6 +358,7 @@ struct tht_fifo {
 	int			tf_len;
 	int			tf_rptr;
 	int			tf_wptr;
+	int			tf_ready;
 };
 
 struct tht_pkt {
@@ -910,7 +911,7 @@ tht_start(struct ifnet *ifp)
 		bus_dmamap_sync(sc->sc_thtc->sc_dmat, pkt->tp_dmap, 0,
 		    pkt->tp_dmap->dm_mapsize, BUS_DMASYNC_PREWRITE);
 
-	} while (tht_fifo_ready(sc, &sc->sc_txt) <= THT_FIFO_DESC_LEN);
+	} while (sc->sc_txt.tf_ready > THT_FIFO_DESC_LEN);
 
 	tht_fifo_post(sc, &sc->sc_txt);
 }
@@ -963,17 +964,14 @@ tht_txf(struct tht_softc *sc)
 	bus_dmamap_t			dmap;
 	struct tht_tx_free		txf;
 	struct tht_pkt			*pkt;
-	int				ready;
 
-	ready = sc->sc_txf.tf_len - tht_fifo_ready(sc, &sc->sc_txf);
-	if (ready == 0)
+	if (tht_fifo_ready(sc, &sc->sc_txf) <= sizeof(txf))
 		return;
 
 	tht_fifo_pre(sc, &sc->sc_txf);
 
 	for (;;) {
 		tht_fifo_read(sc, &sc->sc_txf, &txf, sizeof(txf));
-		ready -= sizeof(txf);
 
 		pkt = &sc->sc_tx_list.tpl_pkts[txf.uid];
 		dmap = pkt->tp_dmap;
@@ -985,7 +983,8 @@ tht_txf(struct tht_softc *sc)
 		m_freem(pkt->tp_m);
 
 		tht_pkt_put(&sc->sc_rx_list, pkt);
-	} while (ready > 0);
+
+	} while (sc->sc_txf.tf_ready > sizeof(txf));
 
 	tht_fifo_post(sc, &sc->sc_txf);
 }
@@ -1038,7 +1037,7 @@ tht_rxf_fill(struct tht_softc *sc, int wait)
 		bus_dmamap_sync(dmat, dmap, 0, dmap->dm_mapsize,
 		    BUS_DMASYNC_PREREAD);
 
-		if (tht_fifo_ready(sc, &sc->sc_rxf) <= THT_FIFO_DESC_LEN)
+		if (sc->sc_rxf.tf_ready <= THT_FIFO_DESC_LEN)
 			goto done;
 	}
 
@@ -1079,18 +1078,16 @@ tht_rxd(struct tht_softc *sc)
 	struct tht_rx_desc		rxd;
 	struct tht_pkt			*pkt;
 	struct mbuf			*m;
-	int				ready, bc;
+	int				bc;
 	u_int32_t			flags;
 
-	ready = sc->sc_rxd.tf_len - tht_fifo_ready(sc, &sc->sc_rxd);
-	if (ready == 0)
+	if (tht_fifo_ready(sc, &sc->sc_rxd) < sizeof(rxd))
 		return;
 
 	tht_fifo_pre(sc, &sc->sc_rxd);
 
 	do {
 		tht_fifo_read(sc, &sc->sc_rxd, &rxd, sizeof(rxd));
-		ready -= sizeof(rxd);
 
 		flags = letoh32(rxd.flags);
 		bc = THT_RXD_FLAGS_BC(flags) * 8;
@@ -1122,11 +1119,10 @@ tht_rxd(struct tht_softc *sc)
 			static u_int32_t pad;
 
 			tht_fifo_read(sc, &sc->sc_rxd, &pad, sizeof(pad));
-			ready -= sizeof(pad);
 			bc -= sizeof(pad);
 		}
 
-	} while (ready > 0);
+	} while (sc->sc_rxd.tf_ready >= sizeof(rxd));
 
 	tht_fifo_post(sc, &sc->sc_rxd);
 }
@@ -1193,22 +1189,20 @@ tht_fifo_free(struct tht_softc *sc, struct tht_fifo *tf)
 size_t
 tht_fifo_ready(struct tht_softc *sc, struct tht_fifo *tf)
 {
-	int				ready;
-
 	if (tf->tf_desc->tfd_write) {
 		tf->tf_rptr = tht_read(sc, tf->tf_desc->tfd_rptr);
 		tf->tf_rptr &= THT_FIFO_PTR_MASK;
-		ready = tf->tf_rptr - tf->tf_wptr;
+		tf->tf_ready = tf->tf_rptr - tf->tf_wptr;
 	} else {
 		tf->tf_wptr = tht_read(sc, tf->tf_desc->tfd_wptr);
 		tf->tf_wptr &= THT_FIFO_PTR_MASK;
-		ready = tf->tf_wptr - tf->tf_rptr;
+		tf->tf_ready = tf->tf_wptr - tf->tf_rptr;
 	}
 
-	if (ready <= 0)
-		ready += tf->tf_len;
+	if (tf->tf_ready <= 0)
+		tf->tf_ready += tf->tf_len;
 
-	return (ready);
+	return (tf->tf_ready);
 }
 
 void
@@ -1226,6 +1220,8 @@ tht_fifo_read(struct tht_softc *sc, struct tht_fifo *tf,
 	u_int8_t			*desc = buf;
 	size_t				len;
 
+	tf->tf_ready -= buflen;
+
 	len = tf->tf_len - tf->tf_rptr;
 
 	if (len < buflen) {
@@ -1249,6 +1245,8 @@ tht_fifo_write(struct tht_softc *sc, struct tht_fifo *tf,
 	u_int8_t			*desc = buf;
 	size_t				len;
 
+	tf->tf_ready -= buflen;
+
 	len = tf->tf_len - tf->tf_wptr;
 
 	if (len < buflen) {