From: miod <miod@openbsd.org>
Date: Sun, 24 Aug 2008 14:51:22 +0000 (+0000)
Subject: Writing to the DTR register on KA60 resets the TCR register behind our back.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=2c6cde36080b06a7e3f6484d1771f0fa7f348ccb;p=openbsd

Writing to the DTR register on KA60 resets the TCR register behind our back.
Preserve it explicitely in dzmctl() and restore it after the DTR update.
(This problem was a real PITA to track down)
---

diff --git a/sys/arch/vax/qbus/dz.c b/sys/arch/vax/qbus/dz.c
index 355e2cfe96b..88f6848cd7e 100644
--- a/sys/arch/vax/qbus/dz.c
+++ b/sys/arch/vax/qbus/dz.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: dz.c,v 1.15 2008/08/15 22:50:25 miod Exp $	*/
+/*	$OpenBSD: dz.c,v 1.16 2008/08/24 14:51:22 miod Exp $	*/
 /*	$NetBSD: dz.c,v 1.23 2000/06/04 02:14:12 matt Exp $	*/
 /*
  * Copyright (c) 1996  Ken C. Wellsch.  All rights reserved.
@@ -252,12 +252,9 @@ dzxint(void *arg)
 		if (tp->t_state & TS_FLUSH)
 			tp->t_state &= ~TS_FLUSH;
 		else
-			ndflush (&tp->t_outq, cl->c_cc);
+			ndflush(&tp->t_outq, cl->c_cc);
 
-		if (tp->t_line)
-			(*linesw[tp->t_line].l_start)(tp);
-		else
-			dzstart(tp);
+		(*linesw[tp->t_line].l_start)(tp);
 	}
 }
 
@@ -449,9 +446,13 @@ dztty(dev_t dev)
 int
 dzstop(struct tty *tp, int flag)
 {
+	int s;
+
+	s = spltty();
 	if (tp->t_state & TS_BUSY)
 		if (!(tp->t_state & TS_TTSTOP))
 			tp->t_state |= TS_FLUSH;
+	splx(s);
 	return(0);
 }
 
@@ -561,14 +562,16 @@ dzmctl(struct dz_softc *sc, int line, int bits, int how)
 	unsigned status;
 	unsigned mbits;
 	unsigned bit;
+	int8_t tcr;
 	int s;
 
 	s = spltty();
 
-	mbits = 0;
-
+	tcr = DZ_READ_BYTE(sc, dr_tcr);
 	bit = (1 << line);
 
+	mbits = 0;
+
 	/* external signals as seen from the port */
 
 	status = DZ_READ_BYTE(sc, dr_dcd) | sc->sc_dsr;
@@ -624,6 +627,12 @@ dzmctl(struct dz_softc *sc, int line, int bits, int how)
 		DZ_WRITE_BYTE(sc, dr_break, sc->sc_brk);
 	}
 
+	/*
+	 * On VAXstation 35x0/38x0, writing to the DTR register apparently
+	 * affects the TCR register.  Restore its value unconditionally.
+	 */
+	DZ_WRITE_BYTE(sc, dr_tcr, tcr);
+
 	splx(s);
 	return (mbits);
 }