sgi: new approach for etherseeq

touching transmit descriptors while dma is running causes the
front to fall off. new approach keeps a counter of free
descriptors in the Ring structure that is incremented
by txintr() when transmit completed.

txintr() will clean descriptors once dma has stopped and
restart dma when there are more descrtors in the chain.

1 files changed, 55 insertions, 47 deletions

diff --git a/sys/src/9/sgi/etherseeq.c b/sys/src/9/sgi/etherseeq.c
index 4f9d930ac..ce2036225 100644
--- a/sys/src/9/sgi/etherseeq.c
+++ b/sys/src/9/sgi/etherseeq.c
@@ -110,6 +110,7 @@ struct Ring
 {
 	Rendez;
 	int	size;
+	int	free;
 	uchar*	base;
 	Desc*	head;
 	Desc*	tail;
@@ -119,9 +120,10 @@ enum
 {
 	Eor=	1<<31,		/* end of ring */
 	Eop=	1<<30,
-	Ie=	1<<29,
+	Ioc=	1<<29,		/* interrupt on completion */
 	Busy=	1<<24,
 	Empty=	1<<14,		/* no data here */
+	Done=	1<<15,		/* transmit done */
 };
 
 enum {
@@ -141,6 +143,32 @@ struct Ctlr
 static ulong dummy;
 
 static void
+txintr(Ctlr *ctlr)
+{
+	Hio *io;
+	ulong s;
+	Desc *p;
+
+	io = ctlr->io;
+	s = io->xstat;
+	if((s & Xdma) != 0)
+		return;
+	p = IO(Desc, ctlr->tx.head->next);
+	while((p->count & Busy) != 0){
+		if((p->count & Done) == 0){
+			io->nxbdp = PADDR(p);
+			io->xstat = Xdma;
+			break;
+		}
+		ctlr->tx.head = p;
+		p->count = Eor|Eop;
+		p = IO(Desc, p->next);
+		ctlr->tx.free++;
+	}
+	wakeup(&ctlr->tx);
+}
+
+static void
 interrupt(Ureg *, void *arg)
 {
 	Ether *edev;
@@ -156,6 +184,7 @@ interrupt(Ureg *, void *arg)
 		io->ctl = Cnormal | Cover;
 	if(s & Cint) {
 		io->ctl = Cnormal | Cint;
+		txintr(ctlr);
 		wakeup(&ctlr->rx);
 	}
 }
@@ -164,12 +193,6 @@ static int
 notempty(void *arg)
 {
 	Ctlr *ctlr = arg;
-	Hio *io;
-
-	io = ctlr->io;
-	dummy = io->piocfg;
-	if((io->rstat & Rdma) == 0)
-		return 1;
 	return (IO(Desc, ctlr->rx.head->next)->count & Empty) == 0;
 }
 
@@ -178,7 +201,6 @@ rxproc(void *arg)
 {
 	Ether *edev = arg;
 	Ctlr *ctlr;
-	Hio *io;
 	Block *b;
 	Desc *p;
 	int n;
@@ -187,12 +209,9 @@ rxproc(void *arg)
 		;
 
 	ctlr = edev->ctlr;
-	io = ctlr->io;
 	for(p = IO(Desc, ctlr->rx.head->next);; p = IO(Desc, p->next)){
-		while((p->count & Empty) != 0){
-			io->rstat = Rdma;
-			tsleep(&ctlr->rx, notempty, ctlr, 500);
-		}
+		while((p->count & Empty) != 0)
+			sleep(&ctlr->rx, notempty, ctlr);
 		n = Rbsize - (p->count & 0x3fff)-3;
 		if(n >= ETHERMINTU){
 			if((p->base[n+2] & Rok) != 0){
@@ -203,50 +222,35 @@ rxproc(void *arg)
 			}
 		}
 		p->addr = PADDR(p->base);
-		p->count = Ie|Empty|Rbsize;
+		p->count = Ioc|Empty|Rbsize;
 		ctlr->rx.head = p;
 	}
 }
 
+static int
+notbusy(void *arg)
+{
+	Ctlr *ctlr = arg;
+	return ctlr->tx.free > 0;
+}
+
 static void
 txproc(void *arg)
 {
 	Ether *edev = arg;
 	Ctlr *ctlr;
-	Hio *io;
 	Block *b;
 	Desc *p;
-	int clean, n;
+	int n;
 
 	while(waserror())
 		;
 
 	ctlr = edev->ctlr;
-	io = ctlr->io;
-	clean = ctlr->tx.size / 2;
 	for(p = IO(Desc, ctlr->tx.tail->next); (b = qbread(edev->oq, 1000000)) != nil; p = IO(Desc, p->next)){
-		while(!clean){
-			splhi();
-			p = ctlr->tx.head;
-			dummy = io->piocfg;
-			ctlr->tx.head = IO(Desc, io->nxbdp & ~0xf);
-			spllo();
-			while(p != ctlr->tx.head){
-				if((p->count & Busy) == 0)
-					break;
-				clean++;
-				p->count = Eor|Eop;
-				p = IO(Desc, p->next);
-			}
-
-			p = IO(Desc, ctlr->tx.tail->next);
-			if(clean)
-				break;
-
-			io->xstat = Xdma;
-			tsleep(&ctlr->tx, return0, nil, 10);
-		}
-		clean--;
+		while(ctlr->tx.free == 0)
+			sleep(&ctlr->tx, notbusy, ctlr);
+		ctlr->tx.free--;
 
 		n = BLEN(b);
 		if(n > ETHERMAXTU)
@@ -254,12 +258,14 @@ txproc(void *arg)
 		memmove(p->base, b->rp, n);
 
 		p->addr = PADDR(p->base);
-		p->count = Eor|Eop|Busy|n;
+		p->count = Ioc|Eor|Eop|Busy|n;
 
-		ctlr->tx.tail->count &= ~Eor;
+		ctlr->tx.tail->count &= ~(Ioc|Eor);
 		ctlr->tx.tail = p;
 
-		io->xstat = Xdma;
+		splhi();
+		txintr(ctlr);
+		spllo();
 
 		freeb(b);
 	}
@@ -273,7 +279,8 @@ allocring(Ring *r, int n)
 	int m;
 
 	r->size = n;
-	
+	r->free = n;
+
 	m = n*BY2PG/2;
 	b = xspanalloc(m, BY2PG, 0);
 	dcflush(b, m);
@@ -324,7 +331,7 @@ init(Ether *edev)
 	p = ctlr->rx.head;
 	do {
 		p->addr = PADDR(p->base);
-		p->count = Ie|Empty|Rbsize;
+		p->count = Ioc|Empty|Rbsize;
 		p = IO(Desc, p->next);
 	} while(p != ctlr->rx.head);
 	io->crbdp = PADDR(p);
@@ -336,16 +343,17 @@ init(Ether *edev)
 		p->count = Eor|Eop;
 		p = IO(Desc, p->next);
 	} while(p != ctlr->tx.tail);
-	ctlr->tx.head = IO(Desc, p->next);
 	io->cxbdp = PADDR(p);
 	io->nxbdp = p->next;
 
 	for(i=0; i<6; i++)
 		io->eaddr[i] = edev->ea[i];
 
-	io->csx = 0; /* XIok | XImaxtry | XIcoll | XIunder; -- no interrupts needed */
+	io->csx = XIok | XImaxtry | XIcoll | XIunder;
 	io->csr = Rprom | RIok|RIend|RIshort|RIdrbl|RIcrc;
 
+	io->rstat = Rdma;
+
 	return 0;
 }