From 8280a33470f0a5fdd4782dbf61378c3d2fe4de86 Mon Sep 17 00:00:00 2001
From: Bruce Evans <bde@FreeBSD.org>
Date: Sun, 22 Nov 1998 10:47:42 +0000
Subject: [PATCH] Deleted the workaround for lockup of certain (hopefully no
 longer used) UARTs when their divisor latch registers are selected while they
 are doing output.  Waiting for (some) output to drain is not permitted for
 the TCSANOW case of tcsetattr().  NIST-PCTS easily detects bugs like this by
 testing at at speeds that no one would want to use (50 bps).

Deleted stale comments related to flushing i/o.  Flushing works properly
for 16550s according to NIST-PCTS (it can't work properly for 16450s).
This finishes fixing all sio(16550)-related bugs found by NIST-PCTS.
---
 sys/i386/isa/sio.c | 52 +---------------------------------------------
 1 file changed, 1 insertion(+), 51 deletions(-)

diff --git a/sys/i386/isa/sio.c b/sys/i386/isa/sio.c
index 4ede49ac960..729f5854b86 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 1.216 1998/10/22 05:58:40 bde Exp $
+ *	$Id: sio.c,v 1.217 1998/11/22 09:41:12 bde Exp $
  */
 
 #include "opt_comconsole.h"
@@ -2037,11 +2037,9 @@ comparam(tp, t)
 	int		divisor;
 	u_char		dlbh;
 	u_char		dlbl;
-	int		error;
 	Port_t		iobase;
 	int		s;
 	int		unit;
-	int		txtimeout;
 
 	/* do historical conversions */
 	if (t->c_ispeed == 0)
@@ -2107,54 +2105,8 @@ comparam(tp, t)
 		outb(iobase + com_fifo, com->fifo_image);
 	}
 
-	/*
-	 * Some UARTs lock up if the divisor latch registers are selected
-	 * while the UART is doing output (they refuse to transmit anything
-	 * more until given a hard reset).  Fix this by stopping filling
-	 * the device buffers and waiting for them to drain.  Reading the
-	 * line status port outside of siointr1() might lose an output
-	 * interrupt, but this will be fixed by (re)starting output.
-	 */
-	disable_intr();
-retry:
-	com->state &= ~CS_TTGO;
-	txtimeout = tp->t_timeout;
-	enable_intr();
-	while ((inb(com->line_status_port) & (LSR_TSRE | LSR_TXRDY))
-	       != (LSR_TSRE | LSR_TXRDY)) {
-		tp->t_state |= TS_SO_OCOMPLETE;
-		error = ttysleep(tp, TSA_OCOMPLETE(tp), TTIPRI | PCATCH,
-				 "siotx", hz / 100);
-		if (   txtimeout != 0
-		    && (!error || error	== EAGAIN)
-		    && (txtimeout -= hz	/ 100) <= 0
-		   )
-			error = EIO;
-		if (com->gone)
-			error = ENODEV;
-		if (error != 0 && error != EAGAIN) {
-			if (!(tp->t_state & TS_TTSTOP)) {
-				disable_intr();
-				com->state |= CS_TTGO;
-				enable_intr();
-			}
-			splx(s);
-			return (error);
-		}
-	}
-
 	disable_intr();		/* very important while com_data is hidden */
 
-	/*
-	 * XXX - clearing CS_TTGO is not sufficient to stop further output,
-	 * because siopoll() calls comstart() which usually sets it again
-	 * because TS_TTSTOP is clear.  Setting TS_TTSTOP would not be
-	 * sufficient, for similar reasons.
-	 */
-	if ((inb(com->line_status_port) & (LSR_TSRE | LSR_TXRDY))
-	    != (LSR_TSRE | LSR_TXRDY))
-		goto retry;
-
 	if (divisor != 0) {
 		outb(iobase + com_cfcr, cfcr | CFCR_DLAB);
 		/*
@@ -2346,7 +2298,6 @@ siostop(tp, rw)
 		    /* XXX avoid h/w bug. */
 		    if (!com->esp)
 #endif
-			/* XXX does this flush everything? */
 			outb(com->iobase + com_fifo,
 			     FIFO_XMT_RST | com->fifo_image);
 		com->obufs[0].l_queued = FALSE;
@@ -2362,7 +2313,6 @@ siostop(tp, rw)
 		    /* XXX avoid h/w bug. */
 		    if (!com->esp)
 #endif
-			/* XXX does this flush everything? */
 			outb(com->iobase + com_fifo,
 			     FIFO_RCV_RST | com->fifo_image);
 		com_events -= (com->iptr - com->ibuf);