From 572eb81d5918543910122ef3c16ca74be1748b93 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Fri, 19 Jan 1996 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1996-01-19

---
 pc/main.c         |  6 ++++--
 port/devcons.c    |  7 +++++--
 port/devns16552.c | 23 ++++++++++++-----------
 3 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/pc/main.c b/pc/main.c
index 30c2d9571e6fcd46ad9846ece7afb446cb814c3e..da27294187ac11b4c40b2e2e2e92b68d8e428d6c 100644
--- a/pc/main.c
+++ b/pc/main.c
@@ -50,9 +50,9 @@ main(void)
 	screeninit();
 	printinit();
 	mmuinit();
+	trapinit();
 	ns16552install();
 	pageinit();
-	trapinit();
 	mathinit();
 	clockinit();
 	faultinit();
@@ -640,12 +640,14 @@ exit(int ispanic)
 {
 	up = 0;
 	print("exiting\n");
+	spllo();
 	if(ispanic){
 		if(cpuserver)
 			delay(10000);
 		else
 			for(;;);
-	}
+	} else
+		delay(1000);
 
 	(*arch->reset)();
 }
diff --git a/port/devcons.c b/port/devcons.c
index 0e7c0f7527aa95a719422fef5211b4f5af096354..13917bf2542a5e4ee5580b6bbfd2a0c1800f665f 100644
--- a/port/devcons.c
+++ b/port/devcons.c
@@ -193,8 +193,11 @@ echo(Rune r, char *buf, int n)
 	/*
 	 * ^p hack
 	 */
-	if(r==0x10 && cpuserver && !kbd.ctlpoff)
-		exit(0);
+	if(r==0x10 && cpuserver && !kbd.ctlpoff){
+		lock(&active);
+		active.exiting = 1;
+		unlock(&active);
+	}
 
 	/*
 	 * ^t hack BUG
diff --git a/port/devns16552.c b/port/devns16552.c
index 2e630451883819c9c81866e68ec0f86c8d3a1154..fa6952b0063f9c5cabe5a646ec396504f71fc3e5 100644
--- a/port/devns16552.c
+++ b/port/devns16552.c
@@ -80,7 +80,6 @@ struct Uart
 	uchar	sticky[8];	/* sticky write register values */
 	ulong	port;
 	Lock	plock;		/* for printing variable */
-	int	printing;	/* true if printing */
 	ulong	freq;		/* clock frequency */
 	int	opens;
 	uchar	mask;		/* bits/char */
@@ -418,7 +417,7 @@ ns16552kick(Uart *p)
 
 	x = splhi();
 	lock(&p->plock);
-	if(p->printing == 0 || (uartrdreg(p, Lstat) & Outready))
+	if((uartrdreg(p, Lstat) & Outready))
 	if(p->cts && p->blocked == 0)
 	if(p->op < p->oe || stageoutput(p)){
 		n = 0;
@@ -595,16 +594,16 @@ ns16552intr(int dev)
 					l = uartrdreg(p, Lstat) & Outready;
 				}while(l);
 			}
-			if(l)
-				p->printing = 0;
 			unlock(&p->plock);
 			break;
 	
 		case 0:	/* modem status */
 			ch = uartrdreg(p, Mstat);
 			if(ch & Ctsc){
-				p->cts = ch & Cts; /* clock gets output going again */
-				p->ctsbackoff += 1;
+				l = p->cts;
+				p->cts = ch & Cts;
+				if(l == 0 && p->cts)
+					p->ctsbackoff = 2; /* clock gets output going again */
 			}
 			break;
 	
@@ -623,7 +622,7 @@ ns16552intr(int dev)
  *  There's also a bit of code to get a stalled print going.
  *  It shouldn't happen, but it does.  Obviously I don't
  *  understand something.  Since it was there, I bundled a
- *  restart after flow control with it to give some histeresis
+ *  restart after flow control with it to give some hysteresis
  *  to the hardware flow control.  This makes compressing
  *  modems happier but will probably bother something else.
  *	 -- presotto
@@ -635,7 +634,7 @@ uartclock(void)
 	Uart *p;
 
 	for(p = uartalloc.elist; p; p = p->elist){
-		ns16552intr(p->dev);
+		/* this amortizes cost of qproduce to many chars */
 		if(haveinput){
 			n = p->ip - p->istage;
 			if(n > 0 && p->iq){
@@ -647,9 +646,11 @@ uartclock(void)
 					p->ip = p->istage;
 			}
 		}
-		if(p->ctsbackoff-- < 0){
-			p->ctsbackoff = 0;
-			ns16552kick(p);
+
+		/* this adds hysteresis to hardware flow control */
+		if(p->ctsbackoff){
+			if(--(p->ctsbackoff) == 0)
+				ns16552kick(p);
 		}
 	}
 	haveinput = 0;