Fixed sloppy clearing of TS_BUSY. Don't clear it until the transmitter

is completely empty.  There is no interrupt for output completion, so
poll for it every 10 ms after output is nearly complete.  Now ttywait()
works right.

Reminded by:	NIST-PCTS

1 files changed, 33 insertions, 3 deletions

diff --git a/sys/i386/isa/sio.c b/sys/i386/isa/sio.c
index 5cc1f6c..d4125c3 100644
--- a/sys/i386/isa/sio.c
+++ b/sys/i386/isa/sio.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)com.c	7.5 (Berkeley) 5/16/91
- *	$Id: sio.c,v 1.150 1996/11/30 14:51:04 bde Exp $
+ *	$Id: sio.c,v 1.151 1996/11/30 15:03:05 bde Exp $
  */
 
 #include "opt_comconsole.h"
@@ -285,6 +285,7 @@ static	int	espattach	__P((struct isa_device *isdp, struct com_s *com,
 				     Port_t esp_port));
 #endif
 static	int	sioattach	__P((struct isa_device *dev));
+static	timeout_t siobusycheck;
 static	timeout_t siodtrwakeup;
 static	void	comhardclose	__P((struct com_s *com));
 static	void	siointr1	__P((struct com_s *com));
@@ -1274,6 +1275,35 @@ siowrite(dev, uio, flag)
 }
 
 static void
+siobusycheck(chan)
+	void	*chan;
+{
+	struct com_s	*com;
+	int		s;
+
+	com = (struct com_s *)chan;
+
+	/*
+	 * Clear TS_BUSY if low-level output is complete.
+	 * spl locking is sufficient because siointr1() does not set CS_BUSY.
+	 * If siointr() clears CS_BUSY after we look at it, then we'll get
+	 * called again.  Reading the line status port outside of siointr1()
+	 * is safe because CS_BUSY is clear so there are no output interrupts
+	 * to lose.
+	 */
+	s = spltty();
+	if (com->state & CS_BUSY)
+		;		/* False alarm. */
+	else if ((inb(com->line_status_port) & (LSR_TSRE | LSR_TXRDY))
+	    == (LSR_TSRE | LSR_TXRDY)) {
+		com->tp->t_state &= ~TS_BUSY;
+		ttwwakeup(com->tp);
+	} else
+		timeout(siobusycheck, com, hz / 100);
+	splx(s);
+}
+
+static void
 siodtrwakeup(chan)
 	void	*chan;
 {
@@ -1753,9 +1783,9 @@ repeat:
 			disable_intr();
 			com_events -= LOTS_OF_EVENTS;
 			com->state &= ~CS_ODONE;
-			if (!(com->state & CS_BUSY))
-				com->tp->t_state &= ~TS_BUSY;
 			enable_intr();
+			if (!(com->state & CS_BUSY))
+				timeout(siobusycheck, com, hz / 100);
 			(*linesw[tp->t_line].l_start)(tp);
 		}
 		if (incc <= 0 || !(tp->t_state & TS_ISOPEN) ||