xref: /src/sys/arch/sun3/dev/zs.c

/*	$NetBSD: zs.c,v 1.18 1994/12/21 23:56:43 gwr Exp $	*/

/*
 * Copyright (c) 1994 Gordon W. Ross
 * Copyright (c) 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This software was developed by the Computer Systems Engineering group
 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
 * contributed to Berkeley.
 *
 * All advertising materials mentioning features or use of this software
 * must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Lawrence Berkeley Laboratory.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)zs.c	8.1 (Berkeley) 7/19/93
 */

/*
 * Zilog Z8530 (ZSCC) driver.
 *
 * Runs two tty ports (ttya and ttyb) on zs0,
 * and runs a keyboard and mouse on zs1.
 *
 * This driver knows far too much about chip to usage mappings.
 */
#define	NZS	2		/* XXX */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/device.h>
#include <sys/conf.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <sys/tty.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/syslog.h>

#include <machine/autoconf.h>
#include <machine/cpu.h>
#include <machine/isr.h>
#include <machine/obio.h>
#include <machine/mon.h>
#include <machine/eeprom.h>
#include <machine/kbd.h>

#include <dev/cons.h>

#include "zsreg.h"
#include "zsvar.h"

/*
 * The default parity REALLY needs to be the same as the PROM uses,
 * or you can not see messages done with printf during boot-up...
 */
#undef	TTYDEF_CFLAG
#define	TTYDEF_CFLAG	(CREAD | CS8 | HUPCL)

#ifdef KGDB
#include <machine/remote-sl.h>
#endif

#define	ZSMAJOR	12		/* XXX */

#define	ZS_KBD		2	/* XXX */
#define	ZS_MOUSE	3	/* XXX */

/* The Sun3 provides a 4.9152 MHz clock to the ZS chips. */
#define PCLK	(9600 * 512)	/* PCLK pin input clock rate */

/*
 * Select software interrupt levels.
 */
#define ZSSOFT_PRI	2	/* XXX - Want TTY_PRI */
#define ZSHARD_PRI	6	/* Wired on the CPU board... */

/*
 * Software state per found chip.  This would be called `zs_softc',
 * but the previous driver had a rather different zs_softc....
 */
struct zsinfo {
	struct	device zi_dev;		/* base device */
	volatile struct zsdevice *zi_zs;/* chip registers */
	struct	zs_chanstate zi_cs[2];	/* channel A and B software state */
};

struct tty *zs_tty[NZS * 2];		/* XXX should be dynamic */

/* Definition of the driver for autoconfig. */
static int	zs_match(struct device *, void *, void *);
static void	zs_attach(struct device *, struct device *, void *);

struct cfdriver zscd = {
	NULL, "zs", zs_match, zs_attach,
	DV_TTY, sizeof(struct zsinfo) };

/* Interrupt handlers. */
static int	zshard(int);
static int	zssoft(int);

struct zs_chanstate *zslist;

/* Routines called from other code. */
int zsopen(dev_t, int, int, struct proc *);
int zsclose(dev_t, int, int, struct proc *);
static void	zsiopen(struct tty *);
static void	zsiclose(struct tty *);
static void	zsstart(struct tty *);
void		zsstop(struct tty *, int);
static int	zsparam(struct tty *, struct termios *);

/* Routines purely local to this driver. */
static int	zs_getspeed(volatile struct zschan *);
static void	zs_reset(volatile struct zschan *, int, int);
static void	zs_modem(struct zs_chanstate *, int);
static void	zs_loadchannelregs(volatile struct zschan *, u_char *);
static u_char zs_read(volatile struct zschan *, u_char);
static u_char zs_write(volatile struct zschan *, u_char, u_char);

/* Console stuff. */
static volatile struct zschan *zs_conschan;

#ifdef KGDB
/* KGDB stuff.  Must reboot to change zs_kgdbunit. */
extern int kgdb_dev, kgdb_rate;
static int zs_kgdb_savedspeed;
static void zs_checkkgdb(int, struct zs_chanstate *, struct tty *);
#endif

/*
 * Console keyboard L1-A processing is done in the hardware interrupt code,
 * so we need to duplicate some of the console keyboard decode state.  (We
 * must not use the regular state as the hardware code keeps ahead of the
 * software state: the software state tracks the most recent ring input but
 * the hardware state tracks the most recent ZSCC input.)  See also kbd.h.
 */
static struct conk_state {	/* console keyboard state */
	char	conk_id;	/* true => ID coming up (console only) */
	char	conk_l1;	/* true => L1 pressed (console only) */
} zsconk_state;

int zshardscope;
int zsshortcuts;		/* number of "shortcut" software interrupts */

int zssoftpending;		/* We have done isr_soft_request() */

static struct zsdevice *zsaddr[NZS];	/* XXX, but saves work */

/* Default OBIO addresses. */
static int zs_physaddr[NZS] = { OBIO_ZS, OBIO_KEYBD_MS };

static u_char zs_init_reg[16] = {
	0,	/* 0: CMD (reset, etc.) */
	ZSWR1_RIE | ZSWR1_TIE | ZSWR1_SIE,
	0x18 + ZSHARD_PRI,	/* IVECT */
	ZSWR3_RX_8 | ZSWR3_RX_ENABLE,
	ZSWR4_CLK_X16 | ZSWR4_ONESB | ZSWR4_EVENP,
	ZSWR5_TX_8 | ZSWR5_TX_ENABLE,
	0,	/* 6: TXSYNC/SYNCLO */
	0,	/* 7: RXSYNC/SYNCHI */
	0,	/* 8: alias for data port */
	0,	/* 9: ZSWR9_MASTER_IE (later) */
	0,	/*10: Misc. TX/RX control bits */
	ZSWR11_TXCLK_BAUD | ZSWR11_RXCLK_BAUD,
	0,	/*12: BAUDLO (later) */
	0,	/*13: BAUDHI (later) */
	ZSWR14_BAUD_FROM_PCLK | ZSWR14_BAUD_ENA,
	ZSWR15_BREAK_IE | ZSWR15_DCD_IE,
};

/* Find PROM mappings (for console support). */
void zs_init()
{
	if (zsaddr[0] == NULL)
		zsaddr[0] = (struct zsdevice *)
			obio_find_mapping(OBIO_ZS, OBIO_ZS_SIZE);
	if (zsaddr[1] == NULL)
		zsaddr[1] = (struct zsdevice *)
			obio_find_mapping(OBIO_KEYBD_MS, OBIO_ZS_SIZE);
}

/*
 * Match slave number to zs unit number, so that misconfiguration will
 * not set up the keyboard as ttya, etc.
 */
static int
zs_match(struct device *parent, void *vcf, void *args)
{
	struct cfdata *cf = vcf;
	struct confargs *ca = args;
	int unit, x;

	unit = cf->cf_unit;
	if (unit < 0 || unit >= NZS)
		return (0);

	if (ca->ca_paddr == -1)
		ca->ca_paddr = zs_physaddr[unit];
	if (ca->ca_intpri == -1)
		ca->ca_intpri = ZSHARD_PRI;

	/* The peek returns non-zero on error. */
	x = bus_peek(ca->ca_bustype, ca->ca_paddr, 1);
	return (x != -1);
}

/*
 * Attach a found zs.
 *
 * USE ROM PROPERTIES port-a-ignore-cd AND port-b-ignore-cd FOR
 * SOFT CARRIER, AND keyboard PROPERTY FOR KEYBOARD/MOUSE?
 */
static void
zs_attach(struct device *parent, struct device *self, void *args)
{
	struct cfdata *cf;
	struct confargs *ca;
	register int zs, unit;
	register struct zsinfo *zi;
	register struct zs_chanstate *cs;
	register volatile struct zsdevice *addr;
	register struct tty *tp, *ctp;
	int softcar;
	static int didintr;

	cf = self->dv_cfdata;
	zs = self->dv_unit;
	ca = args;

	printf(" softpri %d\n", ZSSOFT_PRI);

	if (zsaddr[zs] == NULL) {
		zsaddr[zs] = (struct zsdevice *)
			obio_alloc(ca->ca_paddr, OBIO_ZS_SIZE);
	}
	addr = zsaddr[zs];

	if (!didintr) {
		didintr = 1;
		isr_add_autovect(zssoft, NULL, ZSSOFT_PRI);
		isr_add_autovect(zshard, NULL, ZSHARD_PRI);
	}

	zi = (struct zsinfo *)self;
	zi->zi_zs = addr;
	unit = zs * 2;
	cs = zi->zi_cs;
	softcar = cf->cf_flags;

	if(!zs_tty[unit])
		zs_tty[unit] = ttymalloc();
	if(!zs_tty[unit+1])
		zs_tty[unit+1] = ttymalloc();

	/* link into interrupt list with order (A,B) (B=A+1) */
	cs[0].cs_next = &cs[1];
	cs[1].cs_next = zslist;
	zslist = cs;

	tp = zs_tty[unit];
	cs->cs_unit = unit;
	cs->cs_zc = &addr->zs_chan[CHAN_A];
	cs->cs_speed = zs_getspeed(cs->cs_zc);
#ifdef	DEBUG
	mon_printf("zs%da speed %d ",  zs, cs->cs_speed);
#endif
	cs->cs_softcar = softcar & 1;
	cs->cs_ttyp = tp;
	tp->t_dev = makedev(ZSMAJOR, unit);
	tp->t_oproc = zsstart;
	tp->t_param = zsparam;
	if (cs->cs_zc == zs_conschan) {
		/* This unit is the console. */
		cs->cs_consio = 1;
		cs->cs_brkabort = 1;
		cs->cs_softcar = 1;
		/* Call zsparam so interrupts get enabled. */
		tp->t_ispeed = tp->t_ospeed = cs->cs_speed;
		tp->t_cflag = TTYDEF_CFLAG;
		(void) zsparam(tp, &tp->t_termios);
	} else {
		/* Can not run kgdb on the console? */
#ifdef KGDB
		zs_checkkgdb(unit, cs, tp);
#endif
	}
#if 0
	/* XXX - Drop carrier here? -gwr */
	zs_modem(cs, cs->cs_softcar ? 1 : 0);
#endif

	if (unit == ZS_KBD) {
		/*
		 * Keyboard: tell /dev/kbd driver how to talk to us.
		 */
		tp->t_ispeed = tp->t_ospeed = cs->cs_speed;
		tp->t_cflag = CS8;
		/* zsparam called by zsiopen */
		kbd_serial(tp, zsiopen, zsiclose);
		cs->cs_conk = 1;		/* do L1-A processing */
	}
	unit++;
	cs++;
	tp = zs_tty[unit];

	cs->cs_unit = unit;
	cs->cs_zc = &addr->zs_chan[CHAN_B];
	cs->cs_speed = zs_getspeed(cs->cs_zc);
#ifdef	DEBUG
	mon_printf("zs%db speed %d\n", zs, cs->cs_speed);
#endif
	cs->cs_softcar = softcar & 2;
	cs->cs_ttyp = tp;
	tp->t_dev = makedev(ZSMAJOR, unit);
	tp->t_oproc = zsstart;
	tp->t_param = zsparam;
	if (cs->cs_zc == zs_conschan) {
		/* This unit is the console. */
		cs->cs_consio = 1;
		cs->cs_brkabort = 1;
		cs->cs_softcar = 1;
		tp->t_ispeed = tp->t_ospeed = cs->cs_speed;
		tp->t_cflag = TTYDEF_CFLAG;
		(void) zsparam(tp, &tp->t_termios);
	} else {
		/* Can not run kgdb on the console? */
#ifdef KGDB
		zs_checkkgdb(unit, cs, tp);
#endif
	}
#if 0
	/* XXX - Drop carrier here? -gwr */
	zs_modem(cs, cs->cs_softcar ? 1 : 0);
#endif

	if (unit == ZS_MOUSE) {
		/*
		 * Mouse: tell /dev/mouse driver how to talk to us.
		 */
		tp->t_ispeed = tp->t_ospeed = cs->cs_speed;
		tp->t_cflag = CS8;
		/* zsparam called by zsiopen */
		ms_serial(tp, zsiopen, zsiclose);
	}
}

/*
 * Put a channel in a known state.  Interrupts may be left disabled
 * or enabled, as desired.  (Used only by kgdb)
 */
static void
zs_reset(zc, inten, speed)
	volatile struct zschan *zc;
	int inten, speed;
{
	int tconst;
	u_char reg[16];

	bcopy(zs_init_reg, reg, 16);
	if (inten)
		reg[9] |= ZSWR9_MASTER_IE;

	tconst = BPS_TO_TCONST(PCLK / 16, speed);
	reg[12] = tconst;
	reg[13] = tconst >> 8;
	zs_loadchannelregs(zc, reg);
}

/*
 * Console support
 */

/*
 * Used by the kd driver to find out if it can work.
 */
int
zscnprobe_kbd()
{
	if (zsaddr[1] == NULL) {
		mon_printf("zscnprobe_kbd: zs1 not yet mapped\n");
		return CN_DEAD;
	}
	return CN_INTERNAL;
}

/*
 * This is the console probe routine for ttya and ttyb.
 */
static int
zscnprobe(struct consdev *cn, int unit)
{
	int maj, eeCons;

	if (zsaddr[0] == NULL) {
		mon_printf("zscnprobe: zs0 not mapped\n");
		cn->cn_pri = CN_DEAD;
		return 0;
	}
	/* XXX - Also try to make sure it exists? */

	/* locate the major number */
	for (maj = 0; maj < nchrdev; maj++)
		if (cdevsw[maj].d_open == (void*)zsopen)
			break;

	cn->cn_dev = makedev(maj, unit);

	/* Use EEPROM console setting to decide "remote" console. */
	eeCons = ee_get_byte(EE_CONS_OFFSET, 0);

	/* Hack: EE_CONS_TTYA + 1 == EE_CONS_TTYB */
	if (eeCons == (EE_CONS_TTYA + unit)) {
		cn->cn_pri = CN_REMOTE;
	} else {
		cn->cn_pri = CN_NORMAL;
	}
	return (0);
}

/* This is the constab entry for TTYA. */
int
zscnprobe_a(struct consdev *cn)
{
	return (zscnprobe(cn, 0));
}

/* This is the constab entry for TTYB. */
int
zscnprobe_b(struct consdev *cn)
{
	return (zscnprobe(cn, 1));
}

/* Called by kdcninit() or below. */
void
zs_set_conschan(unit, ab)
	int unit, ab;
{
	volatile struct zsdevice *addr;

	addr = zsaddr[unit];
	zs_conschan = ((ab == 0) ?
				   &addr->zs_chan[CHAN_A] :
				   &addr->zs_chan[CHAN_B] );
}

/* Attach as console.  Also set zs_conschan */
int
zscninit(struct consdev *cn)
{
	int ab = minor(cn->cn_dev) & 1;
	zs_set_conschan(0, ab);
	mon_printf("console on zs0 (tty%c)\n", 'a' + ab);
}


/*
 * Polled console input putchar.
 */
int
zscngetc(dev)
	dev_t dev;
{
	register volatile struct zschan *zc = zs_conschan;
	register int s, c;

	if (zc == NULL)
		return (0);

	s = splhigh();

	/* Wait for a character to arrive. */
	while ((zc->zc_csr & ZSRR0_RX_READY) == 0)
		ZS_DELAY();
	ZS_DELAY();

	c = zc->zc_data;
	ZS_DELAY();

	splx(s);

	/*
	 * This is used by the kd driver to read scan codes,
	 * so don't translate '\r' ==> '\n' here...
	 */
	return (c);
}

/*
 * Polled console output putchar.
 */
int
zscnputc(dev, c)
	dev_t dev;
	int c;
{
	register volatile struct zschan *zc = zs_conschan;
	register int s;

	if (zc == NULL) {
		s = splhigh();
		mon_putchar(c);
		splx(s);
		return (0);
	}
	s = splhigh();

	/* Wait for transmitter to become ready. */
	while ((zc->zc_csr & ZSRR0_TX_READY) == 0)
		ZS_DELAY();
	ZS_DELAY();

	zc->zc_data = c;
	ZS_DELAY();
	splx(s);
}

#ifdef KGDB
/*
 * The kgdb zs port, if any, was altered at boot time (see zs_kgdb_init).
 * Pick up the current speed and character size and restore the original
 * speed.
 */
static void
zs_checkkgdb(int unit, struct zs_chanstate *cs, struct tty *tp)
{

	if (kgdb_dev == makedev(ZSMAJOR, unit)) {
		tp->t_ispeed = tp->t_ospeed = kgdb_rate;
		tp->t_cflag = CS8;
		cs->cs_kgdb = 1;
		cs->cs_speed = zs_kgdb_savedspeed;
		(void) zsparam(tp, &tp->t_termios);
	}
}
#endif

/*
 * Compute the current baud rate given a ZSCC channel.
 */
static int
zs_getspeed(zc)
	register volatile struct zschan *zc;
{
	register int tconst;

	tconst = ZS_READ(zc, 12);
	tconst |= ZS_READ(zc, 13) << 8;
	return (TCONST_TO_BPS(PCLK / 16, tconst));
}


/*
 * Do an internal open.
 */
static void
zsiopen(struct tty *tp)
{

	(void) zsparam(tp, &tp->t_termios);
	ttsetwater(tp);
	tp->t_state = TS_ISOPEN | TS_CARR_ON;
}

/*
 * Do an internal close.  Eventually we should shut off the chip when both
 * ports on it are closed.
 */
static void
zsiclose(struct tty *tp)
{

	ttylclose(tp, 0);	/* ??? */
	ttyclose(tp);		/* ??? */
	tp->t_state = 0;
}


/*
 * Open a zs serial port.  This interface may not be used to open
 * the keyboard and mouse ports. (XXX)
 */
int
zsopen(dev_t dev, int flags, int mode, struct proc *p)
{
	register struct tty *tp;
	register struct zs_chanstate *cs;
	struct zsinfo *zi;
	int unit = minor(dev), zs = unit >> 1, error, s;

#ifdef	DEBUG
	mon_printf("zs_open\n");
#endif
	if (zs >= zscd.cd_ndevs || (zi = zscd.cd_devs[zs]) == NULL ||
	    unit == ZS_KBD || unit == ZS_MOUSE)
		return (ENXIO);
	cs = &zi->zi_cs[unit & 1];
	tp = cs->cs_ttyp;
	s = spltty();
	if ((tp->t_state & TS_ISOPEN) == 0) {
		ttychars(tp);
		tp->t_iflag = TTYDEF_IFLAG;
		tp->t_oflag = TTYDEF_OFLAG;
		tp->t_cflag = TTYDEF_CFLAG;
		tp->t_lflag = TTYDEF_LFLAG;
		tp->t_ispeed = tp->t_ospeed = cs->cs_speed;
		(void) zsparam(tp, &tp->t_termios);
		ttsetwater(tp);
	} else if (tp->t_state & TS_XCLUDE && p->p_ucred->cr_uid != 0) {
		splx(s);
		return (EBUSY);
	}
	error = 0;
#ifdef	DEBUG
	mon_printf("wait for carrier...\n");
#endif
	for (;;) {
		/* loop, turning on the device, until carrier present */
		zs_modem(cs, 1);
		/* May never get status intr if carrier already on. -gwr */
		if (cs->cs_zc->zc_csr & ZSRR0_DCD)
			tp->t_state |= TS_CARR_ON;
		if (cs->cs_softcar)
			tp->t_state |= TS_CARR_ON;
		if (flags & O_NONBLOCK || tp->t_cflag & CLOCAL ||
		    tp->t_state & TS_CARR_ON)
			break;
		tp->t_state |= TS_WOPEN;
		if (error = ttysleep(tp, (caddr_t)&tp->t_rawq, TTIPRI | PCATCH,
		    ttopen, 0))
			break;
	}
#ifdef	DEBUG
	mon_printf("...carrier %s\n",
			   (tp->t_state & TS_CARR_ON) ? "on" : "off");
#endif
	splx(s);
	if (error == 0)
		error = linesw[tp->t_line].l_open(dev, tp);
	if (error)
		zs_modem(cs, 0);
	return (error);
}

/*
 * Close a zs serial port.
 */
int
zsclose(dev_t dev, int flags, int mode, struct proc *p)
{
	register struct zs_chanstate *cs;
	register struct tty *tp;
	struct zsinfo *zi;
	int unit = minor(dev), s;

#ifdef	DEBUG
	mon_printf("zs_close\n");
#endif
	zi = zscd.cd_devs[unit >> 1];
	cs = &zi->zi_cs[unit & 1];
	tp = cs->cs_ttyp;
	linesw[tp->t_line].l_close(tp, flags);
	if (tp->t_cflag & HUPCL || tp->t_state & TS_WOPEN ||
	    (tp->t_state & TS_ISOPEN) == 0) {
		zs_modem(cs, 0);
		/* hold low for 1 second */
		(void) tsleep((caddr_t)cs, TTIPRI, ttclos, hz);
	}
	if (cs->cs_creg[5] & ZSWR5_BREAK)
	{
		s = splzs();
		cs->cs_preg[5] &= ~ZSWR5_BREAK;
		cs->cs_creg[5] &= ~ZSWR5_BREAK;
		ZS_WRITE(cs->cs_zc, 5, cs->cs_creg[5]);
		splx(s);
	}
	ttyclose(tp);
#ifdef KGDB
	/* Reset the speed if we're doing kgdb on this port */
	if (cs->cs_kgdb) {
		tp->t_ispeed = tp->t_ospeed = kgdb_rate;
		(void) zsparam(tp, &tp->t_termios);
	}
#endif
	return (0);
}

/*
 * Read/write zs serial port.
 */
int
zsread(dev_t dev, struct uio *uio, int flags)
{
	register struct tty *tp = zs_tty[minor(dev)];

	return (linesw[tp->t_line].l_read(tp, uio, flags));
}

int
zswrite(dev_t dev, struct uio *uio, int flags)
{
	register struct tty *tp = zs_tty[minor(dev)];

	return (linesw[tp->t_line].l_write(tp, uio, flags));
}

/*
 * ZS hardware interrupt.  Scan all ZS channels.  NB: we know here that
 * channels are kept in (A,B) pairs.
 *
 * Do just a little, then get out; set a software interrupt if more
 * work is needed.
 *
 * We deliberately ignore the vectoring Zilog gives us, and match up
 * only the number of `reset interrupt under service' operations, not
 * the order.
 */
/* ARGSUSED */
int
zshard(int intrarg)
{
	register struct zs_chanstate *a;
#define	b (a + 1)
	register volatile struct zschan *zc;
	register int rr3, intflags = 0, v, i;
	static int zsrint(struct zs_chanstate *, volatile struct zschan *);
	static int zsxint(struct zs_chanstate *, volatile struct zschan *);
	static int zssint(struct zs_chanstate *, volatile struct zschan *);

	for (a = zslist; a != NULL; a = b->cs_next) {
		rr3 = ZS_READ(a->cs_zc, 3);

		/* XXX - This should loop to empty the on-chip fifo. */
		if (rr3 & (ZSRR3_IP_A_RX|ZSRR3_IP_A_TX|ZSRR3_IP_A_STAT)) {
			intflags |= 2;
			zc = a->cs_zc;
			i = a->cs_rbput;
			if (rr3 & ZSRR3_IP_A_RX && (v = zsrint(a, zc)) != 0) {
				a->cs_rbuf[i++ & ZLRB_RING_MASK] = v;
				intflags |= 1;
			}
			if (rr3 & ZSRR3_IP_A_TX && (v = zsxint(a, zc)) != 0) {
				a->cs_rbuf[i++ & ZLRB_RING_MASK] = v;
				intflags |= 1;
			}
			if (rr3 & ZSRR3_IP_A_STAT && (v = zssint(a, zc)) != 0) {
				a->cs_rbuf[i++ & ZLRB_RING_MASK] = v;
				intflags |= 1;
			}
			a->cs_rbput = i;
		}

		/* XXX - This should loop to empty the on-chip fifo. */
		if (rr3 & (ZSRR3_IP_B_RX|ZSRR3_IP_B_TX|ZSRR3_IP_B_STAT)) {
			intflags |= 2;
			zc = b->cs_zc;
			i = b->cs_rbput;
			if (rr3 & ZSRR3_IP_B_RX && (v = zsrint(b, zc)) != 0) {
				b->cs_rbuf[i++ & ZLRB_RING_MASK] = v;
				intflags |= 1;
			}
			if (rr3 & ZSRR3_IP_B_TX && (v = zsxint(b, zc)) != 0) {
				b->cs_rbuf[i++ & ZLRB_RING_MASK] = v;
				intflags |= 1;
			}
			if (rr3 & ZSRR3_IP_B_STAT && (v = zssint(b, zc)) != 0) {
				b->cs_rbuf[i++ & ZLRB_RING_MASK] = v;
				intflags |= 1;
			}
			b->cs_rbput = i;
		}
	}
#undef b
	if (intflags & 1) {
		if (zssoftpending == 0) {
			zssoftpending = ZSSOFT_PRI;
			isr_soft_request(ZSSOFT_PRI);
		}
	}
	return (intflags & 2);
}

static int
zsrint(register struct zs_chanstate *cs, register volatile struct zschan *zc)
{
	register int c = zc->zc_data;

	if (cs->cs_conk) {
		register struct conk_state *conk = &zsconk_state;

		/*
		 * Check here for console abort function, so that we
		 * can abort even when interrupts are locking up the
		 * machine.
		 */
		if (c == KBD_RESET) {
			conk->conk_id = 1;	/* ignore next byte */
			conk->conk_l1 = 0;
		} else if (conk->conk_id)
			conk->conk_id = 0;	/* stop ignoring bytes */
		else if (c == KBD_L1)
			conk->conk_l1 = 1;	/* L1 went down */
		else if (c == (KBD_L1|KBD_UP))
			conk->conk_l1 = 0;	/* L1 went up */
		else if (c == KBD_A && conk->conk_l1) {
			zsabort();
			conk->conk_l1 = 0;	/* we never see the up */
			goto clearit;		/* eat the A after L1-A */
		}
	}
#ifdef KGDB
	if (c == FRAME_START && cs->cs_kgdb &&
	    (cs->cs_ttyp->t_state & TS_ISOPEN) == 0) {
		zskgdb(cs->cs_unit);
		goto clearit;
	}
#endif
	/* compose receive character and status */
	c <<= 8;
	c |= ZS_READ(zc, 1);

	/* clear receive error & interrupt condition */
	zc->zc_csr = ZSWR0_RESET_ERRORS;
	zc->zc_csr = ZSWR0_CLR_INTR;

	return (ZRING_MAKE(ZRING_RINT, c));

clearit:
	zc->zc_csr = ZSWR0_RESET_ERRORS;
	zc->zc_csr = ZSWR0_CLR_INTR;
	return (0);
}

static int
zsxint(register struct zs_chanstate *cs, register volatile struct zschan *zc)
{
	register int i = cs->cs_tbc;

	if (i == 0) {
		zc->zc_csr = ZSWR0_RESET_TXINT;
		zc->zc_csr = ZSWR0_CLR_INTR;
		return (ZRING_MAKE(ZRING_XINT, 0));
	}
	cs->cs_tbc = i - 1;
	zc->zc_data = *cs->cs_tba++;
	zc->zc_csr = ZSWR0_CLR_INTR;
	return (0);
}

static int
zssint(register struct zs_chanstate *cs, register volatile struct zschan *zc)
{
	register int rr0;

	rr0 = zc->zc_csr;
	zc->zc_csr = ZSWR0_RESET_STATUS;
	zc->zc_csr = ZSWR0_CLR_INTR;
	/*
	 * The chip's hardware flow control is, as noted in zsreg.h,
	 * busted---if the DCD line goes low the chip shuts off the
	 * receiver (!).  If we want hardware CTS flow control but do
	 * not have it, and carrier is now on, turn HFC on; if we have
	 * HFC now but carrier has gone low, turn it off.
	 */
	if (rr0 & ZSRR0_DCD) {
		if (cs->cs_ttyp->t_cflag & CCTS_OFLOW &&
		    (cs->cs_creg[3] & ZSWR3_HFC) == 0) {
			cs->cs_creg[3] |= ZSWR3_HFC;
			ZS_WRITE(zc, 3, cs->cs_creg[3]);
		}
	} else {
		if (cs->cs_creg[3] & ZSWR3_HFC) {
			cs->cs_creg[3] &= ~ZSWR3_HFC;
			ZS_WRITE(zc, 3, cs->cs_creg[3]);
		}
	}
	if ((rr0 & ZSRR0_BREAK) && cs->cs_brkabort) {
		/* Wait for end of break to avoid PROM abort. */
		while (zc->zc_csr & ZSRR0_BREAK)
			ZS_DELAY();
		zsabort();
		return (0);
	}
	return (ZRING_MAKE(ZRING_SINT, rr0));
}

zsabort()
{
#ifdef DDB
	Debugger();
#else
	printf("stopping on keyboard abort\n");
	sun3_rom_abort();
#endif
}

#ifdef KGDB
/*
 * KGDB framing character received: enter kernel debugger.  This probably
 * should time out after a few seconds to avoid hanging on spurious input.
 */
zskgdb(int unit)
{

	printf("zs%d%c: kgdb interrupt\n", unit >> 1, (unit & 1) + 'a');
	kgdb_connect(1);
}
#endif

/*
 * Print out a ring or fifo overrun error message.
 */
static void
zsoverrun(int unit, long *ptime, char *what)
{

	if (*ptime != time.tv_sec) {
		*ptime = time.tv_sec;
		log(LOG_WARNING, "zs%d%c: %s overrun\n", unit >> 1,
		    (unit & 1) + 'a', what);
	}
}

/*
 * ZS software interrupt.  Scan all channels for deferred interrupts.
 */
int
zssoft(int arg)
{
	register struct zs_chanstate *cs;
	register volatile struct zschan *zc;
	register struct linesw *line;
	register struct tty *tp;
	register int get, n, c, cc, unit, s;

	if (zssoftpending == 0)
		return (0);

	zssoftpending = 0;
	isr_soft_clear(ZSSOFT_PRI);

	for (cs = zslist; cs != NULL; cs = cs->cs_next) {
		get = cs->cs_rbget;
again:
		n = cs->cs_rbput;	/* atomic */
		if (get == n)		/* nothing more on this line */
			continue;
		unit = cs->cs_unit;	/* set up to handle interrupts */
		zc = cs->cs_zc;
		tp = cs->cs_ttyp;
		line = &linesw[tp->t_line];
		/*
		 * Compute the number of interrupts in the receive ring.
		 * If the count is overlarge, we lost some events, and
		 * must advance to the first valid one.  It may get
		 * overwritten if more data are arriving, but this is
		 * too expensive to check and gains nothing (we already
		 * lost out; all we can do at this point is trade one
		 * kind of loss for another).
		 */
		n -= get;
		if (n > ZLRB_RING_SIZE) {
			zsoverrun(unit, &cs->cs_rotime, "ring");
			get += n - ZLRB_RING_SIZE;
			n = ZLRB_RING_SIZE;
		}
		while (--n >= 0) {
			/* race to keep ahead of incoming interrupts */
			c = cs->cs_rbuf[get++ & ZLRB_RING_MASK];
			switch (ZRING_TYPE(c)) {

			case ZRING_RINT:
				c = ZRING_VALUE(c);
				if (c & ZSRR1_DO)
					zsoverrun(unit, &cs->cs_fotime, "fifo");
				cc = c >> 8;
				if (c & ZSRR1_FE)
					cc |= TTY_FE;
				if (c & ZSRR1_PE)
					cc |= TTY_PE;
				/*
				 * this should be done through
				 * bstreams	XXX gag choke
				 */
				if (unit == ZS_KBD)
					kbd_rint(cc);
				else if (unit == ZS_MOUSE)
					ms_rint(cc);
				else
					line->l_rint(cc, tp);
				break;

			case ZRING_XINT:
				/*
				 * Transmit done: change registers and resume,
				 * or clear BUSY.
				 */
				if (cs->cs_heldchange) {
					s = splzs();
					c = zc->zc_csr;
					if ((c & ZSRR0_DCD) == 0)
						cs->cs_preg[3] &= ~ZSWR3_HFC;
					bcopy((caddr_t)cs->cs_preg,
					    (caddr_t)cs->cs_creg, 16);
					zs_loadchannelregs(zc, cs->cs_creg);
					splx(s);
					cs->cs_heldchange = 0;
					if (cs->cs_heldtbc &&
					    (tp->t_state & TS_TTSTOP) == 0) {
						cs->cs_tbc = cs->cs_heldtbc - 1;
						zc->zc_data = *cs->cs_tba++;
						goto again;
					}
				}
				tp->t_state &= ~TS_BUSY;
				if (tp->t_state & TS_FLUSH)
					tp->t_state &= ~TS_FLUSH;
				else
					ndflush(&tp->t_outq, cs->cs_tba -
						(caddr_t) tp->t_outq.c_cf);
				line->l_start(tp);
				break;

			case ZRING_SINT:
				/*
				 * Status line change.  HFC bit is run in
				 * hardware interrupt, to avoid locking
				 * at splzs here.
				 */
				c = ZRING_VALUE(c);
				if ((c ^ cs->cs_rr0) & ZSRR0_DCD) {
					cc = (c & ZSRR0_DCD) != 0;
					if (line->l_modem(tp, cc) == 0)
						zs_modem(cs, cc);
				}
				cs->cs_rr0 = c;
				break;

			default:
				log(LOG_ERR, "zs%d%c: bad ZRING_TYPE (%x)\n",
				    unit >> 1, (unit & 1) + 'a', c);
				break;
			}
		}
		cs->cs_rbget = get;
		goto again;
	}
	return (1);
}

int
zsioctl(dev_t dev, int cmd, caddr_t data, int flag, struct proc *p)
{
	int unit = minor(dev);
	struct zsinfo *zi = zscd.cd_devs[unit >> 1];
	register struct zs_chanstate *cs = &zi->zi_cs[unit & 1];
	register struct tty *tp = cs->cs_ttyp;
	register int error, s;

	error = linesw[tp->t_line].l_ioctl(tp, cmd, data, flag, p);
	if (error >= 0)
		return (error);
	error = ttioctl(tp, cmd, data, flag, p);
	if (error >= 0)
		return (error);

	switch (cmd) {

	case TIOCSBRK:
		s = splzs();
		cs->cs_preg[5] |= ZSWR5_BREAK;
		cs->cs_creg[5] |= ZSWR5_BREAK;
		ZS_WRITE(cs->cs_zc, 5, cs->cs_creg[5]);
		splx(s);
		break;

	case TIOCCBRK:
		s = splzs();
		cs->cs_preg[5] &= ~ZSWR5_BREAK;
		cs->cs_creg[5] &= ~ZSWR5_BREAK;
		ZS_WRITE(cs->cs_zc, 5, cs->cs_creg[5]);
		splx(s);
		break;

	case TIOCGFLAGS: {
		int bits = 0;

		if (cs->cs_softcar)
			bits |= TIOCFLAG_SOFTCAR;
		if (cs->cs_creg[15] & ZSWR15_DCD_IE)
			bits |= TIOCFLAG_CLOCAL;
		if (cs->cs_creg[3] & ZSWR3_HFC)
			bits |= TIOCFLAG_CRTSCTS;
		*(int *)data = bits;
		break;
	}

	case TIOCSFLAGS: {
		int userbits, driverbits = 0;

		error = suser(p->p_ucred, &p->p_acflag);
		if (error != 0)
			return (EPERM);

		userbits = *(int *)data;

		/*
		 * can have `local' or `softcar', and `rtscts' or `mdmbuf'
		 * defaulting to software flow control.
		 */
		if (userbits & TIOCFLAG_SOFTCAR && userbits & TIOCFLAG_CLOCAL)
			return(EINVAL);
		if (userbits & TIOCFLAG_MDMBUF)	/* don't support this (yet?) */
			return(ENXIO);

		s = splzs();
		if ((userbits & TIOCFLAG_SOFTCAR) ||
			(cs->cs_zc == zs_conschan))
		{
			cs->cs_softcar = 1;	/* turn on softcar */
			cs->cs_preg[15] &= ~ZSWR15_DCD_IE; /* turn off dcd */
			cs->cs_creg[15] &= ~ZSWR15_DCD_IE;
			ZS_WRITE(cs->cs_zc, 15, cs->cs_creg[15]);
		} else if (userbits & TIOCFLAG_CLOCAL) {
			cs->cs_softcar = 0; 	/* turn off softcar */
			cs->cs_preg[15] |= ZSWR15_DCD_IE; /* turn on dcd */
			cs->cs_creg[15] |= ZSWR15_DCD_IE;
			ZS_WRITE(cs->cs_zc, 15, cs->cs_creg[15]);
			tp->t_termios.c_cflag |= CLOCAL;
		}
		if (userbits & TIOCFLAG_CRTSCTS) {
			cs->cs_preg[15] |= ZSWR15_CTS_IE;
			cs->cs_creg[15] |= ZSWR15_CTS_IE;
			ZS_WRITE(cs->cs_zc, 15, cs->cs_creg[15]);
			cs->cs_preg[3] |= ZSWR3_HFC;
			cs->cs_creg[3] |= ZSWR3_HFC;
			ZS_WRITE(cs->cs_zc, 3, cs->cs_creg[3]);
			tp->t_termios.c_cflag |= CRTSCTS;
		} else {
			/* no mdmbuf, so we must want software flow control */
			cs->cs_preg[15] &= ~ZSWR15_CTS_IE;
			cs->cs_creg[15] &= ~ZSWR15_CTS_IE;
			ZS_WRITE(cs->cs_zc, 15, cs->cs_creg[15]);
			cs->cs_preg[3] &= ~ZSWR3_HFC;
			cs->cs_creg[3] &= ~ZSWR3_HFC;
			ZS_WRITE(cs->cs_zc, 3, cs->cs_creg[3]);
			tp->t_termios.c_cflag &= ~CRTSCTS;
		}
		splx(s);
		break;
	}

	case TIOCSDTR:
	case TIOCCDTR:
	case TIOCMSET:
	case TIOCMBIS:
	case TIOCMBIC:
	case TIOCMGET:
	default:
		return (ENOTTY);
	}
	return (0);
}

/*
 * Start or restart transmission.
 */
static void
zsstart(register struct tty *tp)
{
	register struct zs_chanstate *cs;
	register int s, nch;
	int unit = minor(tp->t_dev);
	struct zsinfo *zi = zscd.cd_devs[unit >> 1];

	cs = &zi->zi_cs[unit & 1];
	s = spltty();

	/*
	 * If currently active or delaying, no need to do anything.
	 */
	if (tp->t_state & (TS_TIMEOUT | TS_BUSY | TS_TTSTOP))
		goto out;

	/*
	 * If there are sleepers, and output has drained below low
	 * water mark, awaken.
	 */
	if (tp->t_outq.c_cc <= tp->t_lowat) {
		if (tp->t_state & TS_ASLEEP) {
			tp->t_state &= ~TS_ASLEEP;
			wakeup((caddr_t)&tp->t_outq);
		}
		selwakeup(&tp->t_wsel);
	}

	nch = ndqb(&tp->t_outq, 0);	/* XXX */
	if (nch) {
		register char *p = tp->t_outq.c_cf;

		/* mark busy, enable tx done interrupts, & send first byte */
		tp->t_state |= TS_BUSY;
		(void) splzs();
		cs->cs_preg[1] |= ZSWR1_TIE;
		cs->cs_creg[1] |= ZSWR1_TIE;
		ZS_WRITE(cs->cs_zc, 1, cs->cs_creg[1]);
		cs->cs_zc->zc_data = *p;
		cs->cs_tba = p + 1;
		cs->cs_tbc = nch - 1;
	} else {
		/*
		 * Nothing to send, turn off transmit done interrupts.
		 * This is useful if something is doing polled output.
		 */
		(void) splzs();
		cs->cs_preg[1] &= ~ZSWR1_TIE;
		cs->cs_creg[1] &= ~ZSWR1_TIE;
		ZS_WRITE(cs->cs_zc, 1, cs->cs_creg[1]);
	}
out:
	splx(s);
}

/*
 * Stop output, e.g., for ^S or output flush.
 */
void
zsstop(register struct tty *tp, int flag)
{
	register struct zs_chanstate *cs;
	register int s, unit = minor(tp->t_dev);
	struct zsinfo *zi = zscd.cd_devs[unit >> 1];

	cs = &zi->zi_cs[unit & 1];
	s = splzs();
	if (tp->t_state & TS_BUSY) {
		/*
		 * Device is transmitting; must stop it.
		 */
		cs->cs_tbc = 0;
		if ((tp->t_state & TS_TTSTOP) == 0)
			tp->t_state |= TS_FLUSH;
	}
	splx(s);
}

/*
 * Set ZS tty parameters from termios.
 */
static int
zsparam(register struct tty *tp, register struct termios *t)
{
	int unit = minor(tp->t_dev);
	struct zsinfo *zi = zscd.cd_devs[unit >> 1];
	register struct zs_chanstate *cs = &zi->zi_cs[unit & 1];
	register int tmp, tmp5, cflag, s;

	/*
	 * Because PCLK is only run at 4.9 MHz, the fastest we
	 * can go is 51200 baud (this corresponds to TC=1).
	 * This is somewhat unfortunate as there is no real
	 * reason we should not be able to handle higher rates.
	 */
	tmp = t->c_ospeed;
	if (tmp < 0 || (t->c_ispeed && t->c_ispeed != tmp))
		return (EINVAL);
	if (tmp == 0) {
		/* stty 0 => drop DTR and RTS */
		zs_modem(cs, 0);
		return (0);
	}
	tmp = BPS_TO_TCONST(PCLK / 16, tmp);
	if (tmp < 2)
		return (EINVAL);

	cflag = t->c_cflag;
	tp->t_ispeed = tp->t_ospeed = TCONST_TO_BPS(PCLK / 16, tmp);
	tp->t_cflag = cflag;

	/*
	 * Block interrupts so that state will not
	 * be altered until we are done setting it up.
	 */
	s = splzs();
	bcopy(zs_init_reg, cs->cs_preg, 16);
	cs->cs_preg[12] = tmp;
	cs->cs_preg[13] = tmp >> 8;
	cs->cs_preg[9] |= ZSWR9_MASTER_IE;
	switch (cflag & CSIZE) {
	case CS5:
		tmp = ZSWR3_RX_5;
		tmp5 = ZSWR5_TX_5;
		break;
	case CS6:
		tmp = ZSWR3_RX_6;
		tmp5 = ZSWR5_TX_6;
		break;
	case CS7:
		tmp = ZSWR3_RX_7;
		tmp5 = ZSWR5_TX_7;
		break;
	case CS8:
	default:
		tmp = ZSWR3_RX_8;
		tmp5 = ZSWR5_TX_8;
		break;
	}

	/*
	 * Output hardware flow control on the chip is horrendous: if
	 * carrier detect drops, the receiver is disabled.  Hence we
	 * can only do this when the carrier is on.
	 */
	if (cflag & CCTS_OFLOW && cs->cs_zc->zc_csr & ZSRR0_DCD)
		tmp |= ZSWR3_HFC | ZSWR3_RX_ENABLE;
	else
		tmp |= ZSWR3_RX_ENABLE;
	cs->cs_preg[3] = tmp;
	cs->cs_preg[5] = tmp5 | ZSWR5_TX_ENABLE | ZSWR5_DTR | ZSWR5_RTS;

	tmp = ZSWR4_CLK_X16 | (cflag & CSTOPB ? ZSWR4_TWOSB : ZSWR4_ONESB);
	if ((cflag & PARODD) == 0)
		tmp |= ZSWR4_EVENP;
	if (cflag & PARENB)
		tmp |= ZSWR4_PARENB;
	cs->cs_preg[4] = tmp;

	/*
	 * If nothing is being transmitted, set up new current values,
	 * else mark them as pending.
	 */
	if (cs->cs_heldchange == 0) {
		if (cs->cs_ttyp->t_state & TS_BUSY) {
			cs->cs_heldtbc = cs->cs_tbc;
			cs->cs_tbc = 0;
			cs->cs_heldchange = 1;
		} else {
			bcopy((caddr_t)cs->cs_preg, (caddr_t)cs->cs_creg, 16);
			zs_loadchannelregs(cs->cs_zc, cs->cs_creg);
		}
	}
	splx(s);
	return (0);
}

/*
 * Raise or lower modem control (DTR/RTS) signals.  If a character is
 * in transmission, the change is deferred.
 */
static void
zs_modem(struct zs_chanstate *cs, int onoff)
{
	int s, bis, and;

	if (onoff) {
		bis = ZSWR5_DTR | ZSWR5_RTS;
		and = ~0;
	} else {
		bis = 0;
		and = ~(ZSWR5_DTR | ZSWR5_RTS);
	}
	s = splzs();
	cs->cs_preg[5] = (cs->cs_preg[5] | bis) & and;
	if (cs->cs_heldchange == 0) {
		if (cs->cs_ttyp->t_state & TS_BUSY) {
			cs->cs_heldtbc = cs->cs_tbc;
			cs->cs_tbc = 0;
			cs->cs_heldchange = 1;
		} else {
			cs->cs_creg[5] = (cs->cs_creg[5] | bis) & and;
			ZS_WRITE(cs->cs_zc, 5, cs->cs_creg[5]);
		}
	}
	splx(s);
}

/*
 * Write the given register set to the given zs channel in the proper order.
 * The channel must not be transmitting at the time.  The receiver will
 * be disabled for the time it takes to write all the registers.
 */
static void
zs_loadchannelregs(volatile struct zschan *zc, u_char *reg)
{
	int i;

	zc->zc_csr = ZSM_RESET_ERR;	/* reset error condition */
	ZS_DELAY();

#if 1	/* XXX - Is this really a good idea? -gwr */
	i = zc->zc_data;		/* drain fifo */
	ZS_DELAY();
	i = zc->zc_data;
	ZS_DELAY();
	i = zc->zc_data;
	ZS_DELAY();
#endif

	/* baud clock divisor, stop bits, parity */
	ZS_WRITE(zc, 4, reg[4]);

	/* misc. TX/RX control bits */
	ZS_WRITE(zc, 10, reg[10]);

	/* char size, enable (RX/TX) */
	ZS_WRITE(zc, 3, reg[3] & ~ZSWR3_RX_ENABLE);
	ZS_WRITE(zc, 5, reg[5] & ~ZSWR5_TX_ENABLE);

	/* interrupt enables: TX, TX, STATUS */
	ZS_WRITE(zc, 1, reg[1]);

	/* interrupt vector */
	ZS_WRITE(zc, 2, reg[2]);

	/* master interrupt control */
	ZS_WRITE(zc, 9, reg[9]);

	/* clock mode control */
	ZS_WRITE(zc, 11, reg[11]);

	/* baud rate (lo/hi) */
	ZS_WRITE(zc, 12, reg[12]);
	ZS_WRITE(zc, 13, reg[13]);

	/* Misc. control bits */
	ZS_WRITE(zc, 14, reg[14]);

	/* which lines cause status interrupts */
	ZS_WRITE(zc, 15, reg[15]);

	/* char size, enable (RX/TX)*/
	ZS_WRITE(zc, 3, reg[3]);
	ZS_WRITE(zc, 5, reg[5]);
}

static u_char
zs_read(zc, reg)
	volatile struct zschan *zc;
	u_char reg;
{
	u_char val;

	zc->zc_csr = reg;
	ZS_DELAY();
	val = zc->zc_csr;
	ZS_DELAY();
	return val;
}

static u_char
zs_write(zc, reg, val)
	volatile struct zschan *zc;
	u_char reg, val;
{
	zc->zc_csr = reg;
	ZS_DELAY();
	zc->zc_csr = val;
	ZS_DELAY();
	return val;
}

#ifdef KGDB
/*
 * Get a character from the given kgdb channel.  Called at splhigh().
 * XXX - Add delays, or combine with zscngetc()...
 */
static int
zs_kgdb_getc(void *arg)
{
	register volatile struct zschan *zc = (volatile struct zschan *)arg;

	while ((zc->zc_csr & ZSRR0_RX_READY) == 0)
		continue;
	return (zc->zc_data);
}

/*
 * Put a character to the given kgdb channel.  Called at splhigh().
 */
static void
zs_kgdb_putc(void *arg, int c)
{
	register volatile struct zschan *zc = (volatile struct zschan *)arg;

	while ((zc->zc_csr & ZSRR0_TX_READY) == 0)
		continue;
	zc->zc_data = c;
}

/*
 * Set up for kgdb; called at boot time before configuration.
 * KGDB interrupts will be enabled later when zs0 is configured.
 */
void
zs_kgdb_init()
{
	volatile struct zsdevice *addr;
	volatile struct zschan *zc;
	int unit, zs;

	if (major(kgdb_dev) != ZSMAJOR)
		return;
	unit = minor(kgdb_dev);
	/*
	 * Unit must be 0 or 1 (zs0).
	 */
	if ((unsigned)unit >= ZS_KBD) {
		printf("zs_kgdb_init: bad minor dev %d\n", unit);
		return;
	}
	zs = unit >> 1;
	unit &= 1;

	if (zsaddr[0] == NULL)
		panic("kbdb_attach: zs0 not yet mapped");
	addr = zsaddr[0];

	zc = unit == 0 ? &addr->zs_chan[CHAN_A] : &addr->zs_chan[CHAN_B];
	zs_kgdb_savedspeed = zs_getspeed(zc);
	printf("zs_kgdb_init: attaching zs%d%c at %d baud\n",
	    zs, unit + 'a', kgdb_rate);
	zs_reset(zc, 1, kgdb_rate);
	kgdb_attach(zs_kgdb_getc, zs_kgdb_putc, (void *)zc);
}
#endif /* KGDB */