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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.

--- a/sys/src/9/sgi/etherseeq.c

+++ b/sys/src/9/sgi/etherseeq.c

@@ -110,6 +110,7 @@

 {

 	Rendez;

 	int	size;

+	int	free;

 	uchar*	base;

 	Desc*	head;

 	Desc*	tail;

@@ -119,9 +120,10 @@

 {

 	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 @@

 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 @@

 		io->ctl = Cnormal | Cover;

 	if(s & Cint) {

 		io->ctl = Cnormal | Cint;

+		txintr(ctlr);

 		wakeup(&ctlr->rx);

 	}

 }

@@ -164,12 +193,6 @@

 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 @@

 {

 	Ether *edev = arg;

 	Ctlr *ctlr;

-	Hio *io;

 	Block *b;

 	Desc *p;

 	int n;

@@ -187,12 +209,9 @@

 		;

 	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);

-		}

+	for(p = IO(Desc, ctlr->rx.head->next);; p = IO(Desc, p->next)){

+		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){

@@ -203,51 +222,36 @@

 			}

 		}

 		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);

-			}

+		while(ctlr->tx.free == 0)

+			sleep(&ctlr->tx, notbusy, ctlr);

+		ctlr->tx.free--;

-			p = IO(Desc, ctlr->tx.tail->next);

-			if(clean)

-				break;

-

-			io->xstat = Xdma;

-			tsleep(&ctlr->tx, return0, nil, 10);

-		}

-		clean--;

-

 		n = BLEN(b);

 		if(n > ETHERMAXTU)

 			n = ETHERMAXTU;

@@ -254,12 +258,14 @@

 		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 @@

 	int m;

 	r->size = n;

-	

+	r->free = n;

+

 	m = n*BY2PG/2;

 	b = xspanalloc(m, BY2PG, 0);

 	dcflush(b, m);

@@ -324,7 +331,7 @@

 	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);

@@ -336,7 +343,6 @@

 		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;

@@ -343,8 +349,10 @@

 	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;

 }