Expand PMF_FN_* macros.

[netbsd-mini2440.git] / sys / arch / sgimips / dev / scn.c

/*      $NetBSD: scn.c,v 1.1 2009/02/10 06:04:56 rumble Exp $ */

/*
 * Resurrected from the old pc532 port 1/18/2009.
 *
 * XXX- The locking in this is probably totally broken. I haven't attempted
 *      to get it right, but it seems to work okay anyhow.
 */

/*
 * Copyright (c) 1991, 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Portions of this software were 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. 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.
 *
 *      from: @(#)com.c 7.5 (Berkeley) 5/16/91
 */

/*
 * Copyright (c) 1996, 1997 Philip L. Budne.
 * Copyright (c) 1993 Philip A. Nelson.
 *
 * Portions of this software were 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.
 *
 *      from: @(#)com.c 7.5 (Berkeley) 5/16/91
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: scn.c,v 1.1 2009/02/10 06:04:56 rumble Exp $");

#include "opt_ddb.h"
#include "opt_kgdb.h"
#include "scn.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/ioctl.h>
#include <sys/select.h>
#include <sys/tty.h>
#include <sys/proc.h>
#include <sys/file.h>
#include <sys/uio.h>
#include <sys/kernel.h>
#include <sys/syslog.h>
#include <sys/types.h>
#include <sys/device.h>
#include <sys/malloc.h>
#include <sys/conf.h>
#include <sys/intr.h>
#ifdef KGDB
#include <sys/kgdb.h>
#endif
#include <sys/kauth.h>

#include <dev/cons.h>

#include <machine/autoconf.h>
#include <machine/machtype.h>

#include <sgimips/dev/scnreg.h>
#include <sgimips/dev/scnvar.h>

int     scn_match(device_t, struct cfdata *, void *);
void    scn_attach(device_t, device_t, void *);
int     scnparam(struct tty *, struct termios *);
void    scnstart(struct tty *);
int     scnhwiflow(struct tty *, int);

void    scncnprobe(struct consdev *);
void    scncninit(struct consdev *);
int     scncngetc(dev_t);
void    scncnputc(dev_t, int);
void    scncnpollc(dev_t, int);
int     scninit(dev_t, int);
void    scncnreinit(void *);

CFATTACH_DECL(scn, sizeof(struct scn_softc),
    scn_match, scn_attach, NULL, NULL);

extern struct cfdriver scn_cd;

dev_type_open(scnopen);
dev_type_close(scnclose);
dev_type_read(scnread);
dev_type_write(scnwrite);
dev_type_ioctl(scnioctl);
dev_type_stop(scnstop);
dev_type_tty(scntty);
dev_type_poll(scnpoll);

const struct cdevsw scn_cdevsw = {
        scnopen, scnclose, scnread, scnwrite, scnioctl,
        scnstop, scntty, scnpoll, nommap, ttykqfilter, D_TTY
};

struct consdev scn_cn = {
        scncnprobe,
        scncninit,
        scncngetc,
        scncnputc,
        scncnpollc,
        NULL,
        NULL,
        NULL,
        NODEV,
        CN_NORMAL
};

#ifndef CONSOLE_SPEED
#define CONSOLE_SPEED TTYDEF_SPEED
#endif

#ifndef SCNDEF_CFLAG
#define SCNDEF_CFLAG TTYDEF_CFLAG
#endif

#ifdef CPU30MHZ
#define RECOVER()       __asm volatile("bispsrw 0x800" : : : "cc")
#else
#define RECOVER()
#endif

int     scndefaultrate = TTYDEF_SPEED;
int     scnconsrate = CONSOLE_SPEED;

static inline struct scn_softc *
SOFTC(int unit)
{
        if (unit < 0 || unit >= scn_cd.cd_ndevs)
                return (NULL);
        return ((struct scn_softc *)scn_cd.cd_devs[unit]);
}

static int      scnintr(void *);
static void     scnrxintr(void *);
static int      scn_rxintr(struct scn_softc *);
static void     scnsoft(void *);
static void     scn_setchip(struct scn_softc *sc);
static int      scniter(int *, int, int*, int*, struct chan *, int);
static int      scn_config(int, int, int, int, u_char, u_char);
static void     scn_rxenable(struct scn_softc *);
static void     scn_rxdisable(struct scn_softc *);
static void     dcd_int(struct scn_softc *, struct tty *, u_char);
static void     scnoverrun(int, long *, const char *);
static u_char   opbits(struct scn_softc *, int);

static void *scnsir = NULL;             /* s/w intr cookie */
#define setsoftscn()    softint_schedule(scnsir)

#ifdef SCN_TIMING
/*
 * Keep timing info on latency of software interrupt used by
 * the ringbuf code to empty ring buffer.
 * "getinfo" program reads data from /dev/kmem.
 */
static struct timeval tstart;
#define NJITTER 100
int     scn_njitter = NJITTER;
int     scn_jitter[NJITTER];
#endif

#define SCN_CLOCK       3686400         /* input clock */

/* speed table groups ACR[7] */
#define GRP_A   0
#define GRP_B   ACR_BRG

/* combo of MR0[2:0] and ACR[7] */
#define MODE0A  MR0_MODE_0
#define MODE0B  (MR0_MODE_0|ACR_BRG)
#define MODE1A  MR0_MODE_1
#define MODE1B  (MR0_MODE_1|ACR_BRG)
#define MODE2A  MR0_MODE_2
#define MODE2B  (MR0_MODE_2|ACR_BRG)

#define ANYMODE -1
#define DEFMODE(C92) MODE0A             /* use MODE4A if 26c92? */

/* speed code for Counter/Timer (all modes, groups) */
#define USE_CT 0xd

/*
 * Rate table, ordered by speed, then mode.
 * NOTE: ordering of modes must be done carefully!
 */
struct tabent {
        int32_t speed;
        int16_t code;
        int16_t mode;
} table[] = {
        {     50, 0x0, MODE0A },
        {     75, 0x0, MODE0B },
        {    110, 0x1, MODE0A },
        {    110, 0x1, MODE0B },
        {    110, 0x1, MODE1A },
        {    110, 0x1, MODE1B },
        {    134, 0x2, MODE0A },        /* 134.5 */
        {    134, 0x2, MODE0B },        /* 134.5 */
        {    134, 0x2, MODE1A },        /* 134.5 */
        {    134, 0x2, MODE1B },        /* 134.5 */
        {    150, 0x3, MODE0A },
        {    150, 0x3, MODE0A },
        {    200, 0x3, MODE0A },
        {    300, 0x4, MODE0A },
        {    300, 0x4, MODE0B },
        {    300, 0x0, MODE1A },
        {    450, 0x0, MODE1B },
        {    600, 0x5, MODE0A },
        {    600, 0x5, MODE0B },
        {    880, 0x1, MODE2A },
        {    880, 0x1, MODE2B },
        {    900, 0x3, MODE1B },
        {   1050, 0x7, MODE0A },
        {   1050, 0x7, MODE1A },
        {   1076, 0x2, MODE2A },
        {   1076, 0x2, MODE2B },
        {   1200, 0x6, MODE0A },
        {   1200, 0x6, MODE0B },
        {   1200, 0x3, MODE1A },
        {   1800, 0xa, MODE0B },
        {   1800, 0x4, MODE1A },
        {   1800, 0x4, MODE1B },
        {   2000, 0x7, MODE0B },
        {   2000, 0x7, MODE1B },
        {   2400, 0x8, MODE0A },
        {   2400, 0x8, MODE0B },
        {   3600, 0x5, MODE1A },
        {   3600, 0x5, MODE1B },
        {   4800, 0x9, MODE2A },
        {   4800, 0x9, MODE2B },
        {   4800, 0x9, MODE0A },
        {   4800, 0x9, MODE0B },
        {   7200, 0xa, MODE0A },
        {   7200, 0x0, MODE2B },
        {   7200, 0x6, MODE1A },
        {   7200, 0x6, MODE1B },
        {   9600, 0xb, MODE2A },
        {   9600, 0xb, MODE2B },
        {   9600, 0xb, MODE0A },
        {   9600, 0xb, MODE0B },
        {   9600, 0xd, MODE1A },        /* use C/T as entre' to mode1 */
        {   9600, 0xd, MODE1B },        /* use C/T as entre' to mode1 */
        {  14400, 0x3, MODE2B },
        {  14400, 0x8, MODE1A },
        {  14400, 0x8, MODE1B },
        {  19200, 0x3, MODE2A },
        {  19200, 0xc, MODE2B },
        {  19200, 0xc, MODE0B },
        {  19200, 0xd, MODE1A },        /* use C/T as entre' to mode1 */
        {  19200, 0xd, MODE1B },        /* use C/T as entre' to mode1 */
        {  28800, 0x4, MODE2A },
        {  28800, 0x4, MODE2B },
        {  28800, 0x9, MODE1A },
        {  28800, 0x9, MODE1B },
        {  38400, 0xc, MODE2A },
        {  38400, 0xc, MODE0A },
        {  57600, 0x5, MODE2A },
        {  57600, 0x5, MODE2B },
        {  57600, 0xb, MODE1A },
        {  57600, 0xb, MODE1B },
        { 115200, 0x6, MODE2A },
        { 115200, 0x6, MODE2B },
        { 115200, 0xc, MODE1B },
        { 230400, 0xc, MODE1A }
};
#define TABENTRIES (sizeof(table)/sizeof(table[0]))

/*
 * boolean for speed codes which are identical in both A/B BRG groups
 * in all modes
 */
static u_char bothgroups[16] = {
        0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 0, 1, 1, 1
};

/*
 * Manually constructed divisors table
 * for minimum error (from some of Dave Rand's code)
 */
const struct {
        uint16_t speed;
        uint16_t div;
} divs[] = {
        {    50, 2303 },        /* 2304 is exact?? */
        {   110, 1047 },        /* Should be 1047.27 */
        {   134, 857 },         /* Should be 856.505576 */
        {  1050, 110 },         /* Should be 109.7142857 */
        {  2000, 57 }           /* Should be 57.6 */
};
#define DIVS (sizeof(divs)/sizeof(divs[0]))

/*
 * minor unit bit decode:
 * CxxxUUU
 *
 * C - carrier
 *      0 - delay open until carrier high
 *      1 - allow open with carrier low
 * UUU - unit 0-7
 */

#define DEV_UNIT(x)     (minor(x) & 0x7)
#define DEV_DIALOUT(x)  (minor(x) & 0x80)

extern struct tty *constty;

#define SCN_MAXDUART 4
static struct duart scn_duart[SCN_MAXDUART];

#ifdef KGDB
extern int kgdb_dev;
extern int kgdb_rate;
extern int kgdb_debug_init;
#endif

/* XXXXX - fix this */
#define splrtty() spltty()

/* RS-232 configuration routines */

/*
 * set chip parameters, or mark for delayed change.
 * called at spltty() or on TxEMPTY interrupt.
 *
 * Reads current values to avoid glitches from redundant sets.
 * Perhaps should save last value set to avoid read/write?  NOTE:
 * Would still need to do read if write not needed to advance MR
 * pointer.
 *
 * new 2/97 -plb
 */

static void
scn_setchip(struct scn_softc *sc)
{
        struct duart *dp;
        u_char acr, csr, mr1, mr2;
        int chan;

        if (sc->sc_tty && (sc->sc_tty->t_state & TS_BUSY)) {
                sc->sc_heldchanges = 1;
                return;
        }

        chan = sc->sc_channel;
        dp = sc->sc_duart;
        if (dp->type == SC26C92) {
                u_char nmr0a, mr0a;

                /* input rate high enough so 64 bit time watchdog not
                 * onerous? */
                if (dp->chan[chan].ispeed >= 1200) {
                        /* set FIFO threshold at 6 for other
                         * thresholds we could have to set MR1_FFULL
                         */
                        dp->chan[chan].mr0 |= MR0_RXWD | MR0_RXINT;
                } else {
                        dp->chan[chan].mr0 &= ~(MR0_RXWD | MR0_RXINT);
                }

                /* select BRG mode (MR0A only) */
                nmr0a = dp->chan[0].mr0 | (dp->mode & MR0_MODE);

                dp->base[CH_CR] = CR_CMD_MR0;
                RECOVER();

                mr0a = dp->base[CH_MR];
                if (mr0a != nmr0a) {
                        dp->base[CH_CR] = CR_CMD_MR0;
                        RECOVER();
                        dp->base[CH_MR] = nmr0a;
                }

                if (chan) {      /* channel B? */
                        u_char mr0b;

                        sc->sc_chbase[CH_CR] = CR_CMD_MR0;
                        RECOVER();
                        mr0b = dp->base[CH_MR];

                        if (dp->chan[chan].mr0 != mr0b) {
                                sc->sc_chbase[CH_CR] = CR_CMD_MR0;
                                RECOVER();
                                sc->sc_chbase[CH_MR] = dp->chan[chan].mr0;
                        }
                }
        } else {
                sc->sc_chbase[CH_CR] = CR_CMD_MR1;
                RECOVER();
        }

        mr1 = sc->sc_chbase[CH_MR];
        mr2 = sc->sc_chbase[CH_MR];
        if (mr1 != dp->chan[chan].new_mr1 ||
            mr2 != dp->chan[chan].new_mr2) {
                sc->sc_chbase[CH_CR] = CR_CMD_MR1;
                RECOVER();
                sc->sc_chbase[CH_MR] = dp->chan[chan].new_mr1;
                sc->sc_chbase[CH_MR] = dp->chan[chan].new_mr2;
        }

        acr = dp->acr | (dp->mode & ACR_BRG);
        dp->base[DU_ACR] = acr;         /* write-only reg! */

        /* set speed codes */
        csr = (dp->chan[chan].icode<<4) | dp->chan[chan].ocode;
        if (sc->sc_chbase[CH_CSR] != csr) {
                sc->sc_chbase[CH_CSR] = csr;
        }

        /* see if counter/timer in use */
        if (dp->counter &&
            (dp->chan[0].icode == USE_CT || dp->chan[0].ocode == USE_CT ||
             dp->chan[1].icode == USE_CT || dp->chan[1].ocode == USE_CT)) {

                /* program counter/timer only if necessary */
                if (dp->counter != dp->ocounter) {
                        uint16_t div;
#ifdef DIVS
                        int i;

                        /* look for precalculated rate, for minimum error */
                        for (i = 0; i < DIVS && divs[i].speed <= dp->counter; i++) {
                                if (divs[i].speed == dp->counter) {
                                        div = divs[i].div;
                                        goto found;
                                }
                        }
#endif

                        /* not found in table; calculate a value (rounding up) */
                        div = ((long)SCN_CLOCK/16/2 + dp->counter/2) / dp->counter;

                found:
                        /* halt before loading? may ALWAYS glitch?
                         * reload race may only sometimes glitch??
                         */
                        dp->base[DU_CTUR] = div >> 8;
                        dp->base[DU_CTLR] = div & 255;
                        if (dp->ocounter == 0) {
                                /* not previously used? */
                                u_char temp;
                                /* start C/T running */
                                temp = dp->base[DU_CSTRT];
                        }
                        dp->ocounter = dp->counter;
                }
        } else {
                /* counter not in use; mark as free */
                dp->counter = 0;
        }
        sc->sc_heldchanges = 0;

        /*
         * delay a tiny bit to try and avoid tx glitching.
         * I know we're at spltty(), but this is much better than the
         * old version used DELAY((96000 / out_speed) * 10000)
         * -plb
         */
        DELAY(10);
}

/*
 * iterator function for speeds.
 * (could be called "findnextcode")
 * Returns sequence of possible speed codes for a given rate.
 * should set index to zero before first call.
 *
 * Could be implemented as a "checkspeed()" function called
 * to evaluate table entries, BUT this allows more variety in
 * use of C/T with fewer table entries.
 */

static int
scniter(int *index, int wanted, int *counter, int *mode, struct chan *other,
    int c92)
{

        while (*index < TABENTRIES) {
                struct tabent *tp;

                tp = table + (*index)++;
                if (tp->speed != wanted)
                        continue;

                /* if not a 26C92 only look at MODE0 entries */
                if (!c92 && (tp->mode & MR0_MODE) != MR0_MODE_0)
                        continue;

                /*
                 * check mode;
                 * OK if this table entry for current mode, or mode not
                 * yet set, or other channel's rates are available in both
                 * A and B groups.
                 */

                if (tp->mode == *mode || *mode == ANYMODE ||
                    (other != NULL && (tp->mode & MR0_MODE) == (*mode & MR0_MODE) &&
                     bothgroups[other->icode] && bothgroups[other->ocode])) {
                        /*
                         * for future table entries specifying
                         * use of counter/timer
                         */
                        if (tp->code == USE_CT) {
                                if (*counter != wanted && *counter != 0)
                                        continue;       /* counter busy */
                                *counter = wanted;
                        }
                        *mode = tp->mode;
                        return tp->code;
                }
        }

        /* here after returning all applicable table entries */
        /* XXX return sequence of USE_CT with all possible modes?? */
        if ((*index)++ == TABENTRIES) {
                /* Max C/T rate (even on 26C92?) is 57600 */
                if (wanted <= 57600 && (*counter == wanted || *counter == 0)) {
                        *counter = wanted;
                        return USE_CT;
                }
        }

        return -1;                      /* FAIL */
}

/*
 * calculate configuration
 * rewritten 2/97 -plb
 */
static int
scn_config(int unit, int chan, int ispeed, int ospeed, u_char mr1, u_char mr2)
{
        struct scn_softc *sc;
        struct duart *dp;
        int other;              /* opposite of chan */
        int mode;
        int counter;
        int i, o;               /* input, output iterator indexes */
        int ic, oc;             /* input, output codes */
        struct chan *ocp;       /* other duart channel */
        struct tty *otp;        /* other channel tty struct */
        int c92;                /* true if duart is sc26c92 */
        int s;

        /* Set up softc pointer. */
        if (unit >= scn_cd.cd_ndevs)
                return ENXIO;
        sc = SOFTC(unit);
        chan = sc->sc_channel;
        other = chan ^ 1;
        dp = sc->sc_duart;
        ocp = &dp->chan[other];
        otp = ocp->tty;
        c92 = (dp->type == SC26C92);

        /*
         * Right now the first combination that works is used.
         * Perhaps it should search entire solution space for "best"
         * combination. For example, use heuristic weighting of mode
         * preferences, and use of counter timer?
         *
         * For example right now with 2681/2692 when default rate is
         * 9600 and other channel is closed setting 19200 will pick
         * mode 0a and use counter/timer.  Better solution might be
         * mode 0b, leaving counter/timer free!
         *
         * When other channel is open might want to prefer
         * leaving counter timer free, or not flipping A/B group?
         */
        if (otp && (otp->t_state & TS_ISOPEN)) {

                /*
                 * Other channel open;
                 * Find speed codes compatible with current mode/counter.
                 */

                i = 0;
                for (;;) {
                        mode = dp->mode;
                        counter = dp->counter;

                        /* NOTE: pass other chan pointer to allow group flipping */
                        ic = scniter(&i, ispeed, &counter, &mode, ocp, c92);
                        if (ic == -1)
                                break;

                        o = 0;
                        if ((oc = scniter(&o, ospeed, &counter,
                                          &mode, NULL, c92)) != -1) {
                                /*
                                 * take first match
                                 *
                                 * Perhaps calculate heuristic "score",
                                 * save score,codes,mode,counter if score
                                 * better than previous best?
                                 */
                                goto gotit;
                        }
                }
                /* XXX try looping for ospeed? */
        } else {
                /* other channel closed */
                int oo, oi;     /* other input, output iterators */
                int oic, ooc;   /* other input, output codes */

                /*
                 * Here when other channel closed.  Finds first
                 * combination that will allow other channel to be opened
                 * (with defaults) and fits our needs.
                 */
                oi = 0;
                for (;;) {
                        mode = ANYMODE;
                        counter = 0;

                        oic = scniter(&oi, ocp->ispeed, &counter, &mode, NULL, c92);
                        if (oic == -1)
                                break;

                        oo = 0;
                        while ((ooc = scniter(&oo, ocp->ospeed, &counter,
                                           &mode, NULL, c92)) != -1) {
                                i = 0;
                                while ((ic = scniter(&i, ispeed, &counter,
                                                  &mode, NULL, c92)) != -1) {
                                        o = 0;
                                        if ((oc = scniter(&o, ospeed, &counter,
                                                       &mode, NULL, c92)) != -1) {
                                                /*
                                                 * take first match
                                                 *
                                                 * Perhaps calculate heuristic
                                                 * "score", save
                                                 *     score,codes,mode,counter
                                                 * if score better than
                                                 * previous best?
                                                 */
                                                s = spltty();
                                                dp->chan[other].icode = oic;
                                                dp->chan[other].ocode = ooc;
                                                goto gotit2;
                                        }
                                }
                        }
                }
        }
        return EINVAL;

 gotit:
        s = spltty();
 gotit2:
        dp->chan[chan].new_mr1 = mr1;
        dp->chan[chan].new_mr2 = mr2;
        dp->chan[chan].ispeed = ispeed;
        dp->chan[chan].ospeed = ospeed;
        dp->chan[chan].icode = ic;
        dp->chan[chan].ocode = oc;
        if (mode == ANYMODE)            /* no mode selected?? */
                mode = DEFMODE(c92);
        dp->mode = mode;
        dp->counter = counter;

        scn_setchip(sc);                /* set chip now, if possible */
        splx(s);
        return (0);
}

int
scn_match(device_t parent, struct cfdata *cf, void *aux)
{
        struct mainbus_attach_args *ma = aux;

        if ((mach_type == MACH_SGI_IP6 || mach_type == MACH_SGI_IP10) &&
            ma->ma_addr == 0x1fb80004)
                return (1);

        return (0);
}

/*
 * No need to make scn_rx{en,dis}able too efficient,
 * they're only called on setup, open & close!
 */
static inline void
scn_rxenable(struct scn_softc *sc)
{
        struct duart *dp;
        int channel;

        dp = sc->sc_duart;
        channel = sc->sc_channel;

        /* Outputs wire-ored and connected to ICU input for fast rx interrupt. */
        if (channel == 0)
                dp->opcr |= OPCR_OP4_RXRDYA;
        else
                dp->opcr |= OPCR_OP5_RXRDYB;
        dp->base[DU_OPCR] = dp->opcr;
        dp->imr |= sc->sc_rx_int;
        dp->base[DU_IMR] = dp->imr;
}

static inline void
scn_rxdisable(struct scn_softc *sc)
{
        struct duart *dp;
        int channel;

        dp = sc->sc_duart;
        channel = sc->sc_channel;

        /* Outputs wire-ored and connected to ICU input for fast rx interrupt. */
        if (channel == 0)
                dp->opcr &= ~OPCR_OP4_RXRDYA;
        else
                dp->opcr &= ~OPCR_OP5_RXRDYB;
        dp->base[DU_OPCR] = dp->opcr;
        dp->imr &= ~sc->sc_rx_int;
        dp->base[DU_IMR] = dp->imr;
}

void
scn_attach(device_t parent, device_t self, void *aux)
{
        struct mainbus_attach_args *ma = aux;
        struct scn_softc *sc;
        struct duart *duart;
        volatile u_char *ch_base;
        volatile u_char *duart_base;
        int channel;
        int speed;
        int s;
        int maj;
        u_char unit;
        u_char duartno;
        u_char delim = ':';
        u_char mr1, mr2;
        enum scntype scntype = SCNUNK;
        const char *duart_type = "Unknown";
        char *intrname;
        bool console, first;
        devmajor_t major;

        (void)major;

        sc = device_private(self);
        unit = device_unit(self);

        /* XXX - hard-coded */
        if (ma->ma_addr == 0x1fb80004)
                duartno = 1;
        else
                duartno = 0;
        channel = 0;
        console = 1;

        duart = sc->sc_duart = &scn_duart[duartno];
        duart->chan[channel].sc = sc;
        first = (duart->base == NULL);

        if (console) {
                sc->sc_isconsole = 1;
                sc->sc_swflags |= SCN_SW_SOFTCAR;       /* ignore carrier */
        }

        duart_base = (volatile u_char *)MIPS_PHYS_TO_KSEG1(ma->ma_addr);
        ch_base    = duart_base; /* XXX */

        if (first) {
                /* Probe DUART type */
                s = spltty();
                if (console) {
                        ch_base[CH_CR] = CR_DIS_TX;
                        delay(5 * 10000);
                }
                ch_base[CH_CR] = CR_CMD_MR1;
                RECOVER();
                mr1 = ch_base[CH_MR];
                mr2 = ch_base[CH_MR];
                ch_base[CH_CR] = CR_CMD_MR1;
                RECOVER();
                ch_base[CH_MR] = 1;
                ch_base[CH_MR] = 0;
                ch_base[CH_CR] = CR_CMD_MR1;
                RECOVER();
                if (ch_base[CH_MR] == 1) {
                        /* MR 2 selected */
                        ch_base[CH_CR] = CR_CMD_MR0;
                        RECOVER();
                        /* if 2681, MR2 still selected */
                        ch_base[CH_MR] = 1;
                        ch_base[CH_CR] = CR_CMD_MR1;
                        RECOVER();
                        ch_base[CH_MR] = 0; /* MR1 */
                        ch_base[CH_MR] = 0; /* MR2 */
                        ch_base[CH_CR] = CR_CMD_MR0;
                        RECOVER();
                        /* if 2681, MR2 still selected */
                        if((ch_base[CH_MR] & 1) == 1) {
                                duart_type = "sc26c92";
                                scntype = SC26C92;
                        } else {
                                /* 2681 treats as MR1 Select */
                                ch_base[CH_CR] = CR_CMD_RTS_OFF;
                                RECOVER();
                                ch_base[CH_MR] = 1;
                                ch_base[CH_MR] = 0;
                                ch_base[CH_CR] = CR_CMD_RTS_OFF;
                                RECOVER();
                                if (ch_base[CH_MR] == 1) {
                                        duart_type = "scn2681";
                                        scntype = SCN2681;
                                } else {
                                        duart_type = "scn2692";
                                        scntype = SCN2692;
                                }
                        }
                }

                /* If a 2681, the CR_CMD_MR0 is interpreted as a TX_RESET */
                if (console) {
                        ch_base[CH_CR] = CR_ENA_TX;
                        RECOVER();
                }
                ch_base[CH_CR] = CR_CMD_MR1;
                RECOVER();
                ch_base[CH_MR] = mr1;
                ch_base[CH_MR] = mr2;
                splx(s);

                intrname = malloc(sizeof("scnXX"), M_DEVBUF, M_NOWAIT);
                snprintf(intrname, sizeof("scnXX"), "scn%d", unit);

                /*
                 * On IP6 the console chip is duart1. The keyboard/mouse
                 * is duart0. Each chip has two channels and the channels
                 * share an interrupt. Duart0 is interrupt 0, duart1 is
                 * interrupt 1.
                 */
                if (duartno != 0 && duartno != 1)
                        panic("scn_attach: bad duartno: %d", duartno);
                cpu_intr_establish(duartno, IPL_TTY, scnintr, duart);

                printf("%c %s", delim, duart_type);
                delim = ',';

                duart->base = duart_base;
                duart->type = scntype;
        }
        /* Record channel, uart */
        sc->sc_channel = channel;
        sc->sc_chbase = ch_base;

        /* Initialize modem/interrupt bit masks */
        if (channel == 0) {
                sc->sc_op_rts = OP_RTSA;
                sc->sc_op_dtr = OP_DTRA;
                sc->sc_ip_cts = IP_CTSA;
                sc->sc_ip_dcd = IP_DCDA;

                sc->sc_tx_int = INT_TXA;
                sc->sc_rx_int = INT_RXA;
        } else {
                sc->sc_op_rts = OP_RTSB;
                sc->sc_op_dtr = OP_DTRB;
                sc->sc_ip_cts = IP_CTSB;
                sc->sc_ip_dcd = IP_DCDB;

                sc->sc_tx_int = INT_TXB;
                sc->sc_rx_int = INT_RXB;
        }

        /* Initialize counters */
        sc->sc_framing_errors = 0;
        sc->sc_fifo_overruns = 0;
        sc->sc_parity_errors = 0;
        sc->sc_breaks = 0;

        if (console) {
                DELAY(5 * 10000);       /* Let the output go out.... */
        }

        /*
         * Set up the hardware to a base state, in particular:
         * o reset transmitter and receiver
         * o set speeds and configurations
         * o receiver interrupts only (RxRDY and BREAK)
         */

        s = spltty();
        /* RTS off... */
        SCN_OP_BIC(sc, sc->sc_op_rts);  /* "istop" */

        ch_base[CH_CR] = CR_DIS_RX | CR_DIS_TX;
        RECOVER();
        ch_base[CH_CR] = CR_CMD_RESET_RX;
        RECOVER();
        ch_base[CH_CR] = CR_CMD_RESET_TX;
        RECOVER();
        ch_base[CH_CR] = CR_CMD_RESET_ERR;
        RECOVER();
        ch_base[CH_CR] = CR_CMD_RESET_BRK;
        RECOVER();
        ch_base[CH_CR] = CR_CMD_MR1;
        RECOVER();

        /* No receiver control of RTS. */
        ch_base[CH_MR] = 0;
        ch_base[CH_MR] = 0;

        /* Initialize the uart structure if this is channel A. */
        if (first) {
                /* Disable all interrupts. */
                duart_base[DU_IMR] = duart->imr = 0;

                /* Output port config */
                duart_base[DU_OPCR] = duart->opcr = 0;

                /* Speeds... */
                duart->mode = 0;

                /*
                 * Set initial speed to an illegal code that can be changed to
                 * any other baud.
                 */
                duart->chan[0].icode = duart->chan[0].ocode = 0x2f;
                duart->chan[1].icode = duart->chan[1].ocode = 0x2f;
                duart->chan[0].ispeed = duart->chan[0].ospeed = 0;
                duart->chan[1].ispeed = duart->chan[1].ospeed = 0;

                duart->acr = 0;
                duart->acr |= ACR_CT_TCLK1;     /* timer mode 1x clk */
        }

        if (channel == 0) {
                duart->acr |= ACR_DELTA_DCDA;   /* Set CD int */
        } else {
                duart->acr |= ACR_DELTA_DCDB;   /* Set CD int */
        }

        if (scnsir == NULL) {
                /* software intr: calls tty code, hence IPL_TTY */
                scnsir = softint_establish(SOFTINT_SERIAL, scnsoft, NULL);
        }

        duart_base[DU_ACR] = (duart->mode & ACR_BRG) | duart->acr;

        if (console)
                speed = scnconsrate;
        else
                speed = scndefaultrate;

        scn_config(unit, channel, speed, speed, MR1_PNONE | MR1_CS8, MR2_STOP1);
        if (console) {
                maj = cdevsw_lookup_major(&scn_cdevsw);
                KASSERT(maj != NODEVMAJOR);
                shutdownhook_establish(scncnreinit, NULL);
                /* Make sure console can do scncngetc */
                duart_base[DU_OPSET] = channel ? (OP_RTSB | OP_DTRB) :
                        (OP_RTSA | OP_DTRA);
        }

        /* Turn on the receiver and transmitters */
        ch_base[CH_CR] = CR_ENA_RX | CR_ENA_TX;

        /* Set up the interrupts. */
        duart->imr |= INT_IP;
        scn_rxdisable(sc);
        splx(s);

        if (sc->sc_swflags) {
                printf("%c flags %d", delim, sc->sc_swflags);
                delim = ',';
        }

#ifdef KGDB
        major = cdevsw_lookup_major(&scn_cdevsw);
        KASSERT(major != NODEVMAJOR);
        if (kgdb_dev == makedev(major, unit)) {
                if (console)
                        kgdb_dev = NODEV; /* can't debug over console port */
                else {
                        scninit(kgdb_dev, kgdb_rate);
                        scn_rxenable(sc);
                        scn->sc_iskgdb = 1;
                        kgdb_attach(scncngetc, scncnputc, kgdb_dev);
                        if (kgdb_debug_init) {
                                printf("%c ", delim);
                                kgdb_connect(1);
                        } else
                                printf("%c kgdb enabled", delim);
                        delim = ',';
                }
        }
#endif
        printf("\n");
}

/* ARGSUSED */
int
scnopen(dev_t dev, int flags, int mode, struct lwp *l)
{
        struct tty *tp;
        int unit = DEV_UNIT(dev);
        struct scn_softc *sc;
        int error = 0;
        int hwset = 0;

        if (unit >= scn_cd.cd_ndevs)
                return ENXIO;
        sc = SOFTC(unit);
        if (!sc)
                return ENXIO;

        tp = sc->sc_tty;
        if (!tp) {
                tp = ttymalloc();
                sc->sc_tty = sc->sc_duart->chan[sc->sc_channel].tty = tp;
                tty_attach(tp);
        }

        tp->t_oproc = scnstart;
        tp->t_param = scnparam;
        tp->t_hwiflow = scnhwiflow;
        tp->t_dev = dev;

        if (kauth_authorize_device_tty(l->l_cred, KAUTH_DEVICE_TTY_OPEN, tp))
                return (EBUSY);

        mutex_spin_enter(&tty_lock);

        if ((tp->t_state & TS_ISOPEN) == 0 && tp->t_wopen == 0) {
                ttychars(tp);
                tp->t_iflag = TTYDEF_IFLAG;
                tp->t_oflag = TTYDEF_OFLAG;
                tp->t_cflag = SCNDEF_CFLAG;

                sc->sc_rx_blocked = 0;

                if (sc->sc_swflags & SCN_SW_CLOCAL)
                        tp->t_cflag |= CLOCAL;
                if (sc->sc_swflags & SCN_SW_CRTSCTS)
                        tp->t_cflag |= CCTS_OFLOW | CRTS_IFLOW;
                tp->t_lflag = TTYDEF_LFLAG;
                if (sc->sc_isconsole)
                        tp->t_ispeed = tp->t_ospeed = scnconsrate;
                else
                        tp->t_ispeed = tp->t_ospeed = scndefaultrate;
                scnparam(tp, &tp->t_termios);
                ttsetwater(tp);

                /* Turn on DTR and RTS. */
                SCN_OP_BIS(sc, sc->sc_op_rts | sc->sc_op_dtr);

                /* enable receiver interrupts */
                scn_rxenable(sc);
                hwset = 1;

                /* set carrier state; */
                if ((sc->sc_swflags & SCN_SW_SOFTCAR) || /* check ttyflags */
                    SCN_DCD(sc) ||                       /* check h/w */
                    DEV_DIALOUT(dev))
                        tp->t_state |= TS_CARR_ON;
                else
                        tp->t_state &= ~TS_CARR_ON;
        }

        mutex_spin_exit(&tty_lock);

        error = ttyopen(tp, SCN_DIALOUT(sc), flags & O_NONBLOCK);
if (error) printf("ttyopen failed line %d, error %d\n", __LINE__, error);
        if (error)
                goto bad;

        error = (*tp->t_linesw->l_open) (dev, tp);
if (error) printf("l_open failed line %d, error %d\n", __LINE__, error);
        if (error)
                goto bad;

        return (0);

bad:
        if ((tp->t_state & TS_ISOPEN) == 0 && tp->t_wopen == 0) {
                scn_rxdisable(sc);
                SCN_OP_BIC(sc, sc->sc_op_rts | sc->sc_op_dtr);
        }

        return (error);
}


/*ARGSUSED*/
int
scnclose(dev_t dev, int flags, int mode, struct lwp *l)
{
        int unit = DEV_UNIT(dev);
        struct scn_softc *sc = SOFTC(unit);
        struct tty *tp = sc->sc_tty;
        devmajor_t major;

        (void)major;

        if ((tp->t_state & TS_ISOPEN) == 0)
                return 0;

        (*tp->t_linesw->l_close) (tp, flags);

#ifdef KGDB
        /* do not disable interrupts if debugging */
        major = cdevsw_lookup_major(&scn_devsw);
        KASSERT(major != cdevsw_lookup_major);
        if (kgdb_dev != makedev(major, unit))
#endif
                if ((tp->t_state & TS_ISOPEN) == 0) {
                        scn_rxdisable(sc);
                }
        if ((tp->t_cflag & HUPCL) && (sc->sc_swflags & SCN_SW_SOFTCAR) == 0) {
                SCN_OP_BIC(sc, sc->sc_op_dtr);
                /* hold low for 1 second */
                tsleep(sc, TTIPRI, ttclos, hz);
        }
        SCN_CLRDIALOUT(sc);
        ttyclose(tp);

#if 0
        if ((tp->t_state & TS_ISOPEN) == 0) {
                ttyfree(tp);
                sc->sc_tty = (struct tty *) NULL;
        }
#endif

        return (0);
}

int
scnread(dev_t dev, struct uio *uio, int flags)
{
        struct scn_softc *sc = SOFTC(DEV_UNIT(dev));
        struct tty *tp = sc->sc_tty;

        return ((*tp->t_linesw->l_read) (tp, uio, flags));
}

int
scnwrite(dev_t dev, struct uio *uio, int flags)
{
        struct scn_softc *sc = SOFTC(DEV_UNIT(dev));
        struct tty *tp = sc->sc_tty;

        return ((*tp->t_linesw->l_write) (tp, uio, flags));
}

int
scnpoll(dev_t dev, int events, struct lwp *l)
{
        struct scn_softc *sc = SOFTC(DEV_UNIT(dev));
        struct tty *tp = sc->sc_tty;

        return ((*tp->t_linesw->l_poll)(tp, events, l));
}

struct tty *
scntty(dev_t dev)
{
        struct scn_softc *sc = SOFTC(DEV_UNIT(dev));

        return sc->sc_tty;
}

/* Worker routines for interrupt processing */
static inline void
dcd_int(struct scn_softc *sc, struct tty *tp, u_char new)
{

        if (sc->sc_swflags & SCN_SW_SOFTCAR)
                return;

#if 0
        printf("scn%d: dcd_int ip %x SCN_DCD %x new %x ipcr %x\n",
            sc->unit,
            sc->sc_duart->base[DU_IP],
            SCN_DCD(sc),
            new,
            sc->sc_duart->base[DU_IPCR]
            );
#endif

/* XXX set some flag to have some lower (soft) int call line discipline? */
        if (!(*tp->t_linesw->l_modem) (tp, new == 0? 1: 0)) {
                SCN_OP_BIC(sc, sc->sc_op_rts | sc->sc_op_dtr);
        }
}

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

        if (*ptime != time_second) {
                *ptime = time_second;
                log(LOG_WARNING, "scn%d: %s overrun\n", unit, what);
        }
}

/*
 * Try to block or unblock input using hardware flow-control.
 * This is called by kern/tty.c if MDMBUF|CRTSCTS is set, and
 * if this function returns non-zero, the TS_TBLOCK flag will
 * be set or cleared according to the "stop" arg passed.
 */
int
scnhwiflow(struct tty *tp, int stop)
{
        int unit = DEV_UNIT(tp->t_dev);
        struct scn_softc *sc = SOFTC(unit);
        int s;

        s = splrtty();
        if (!stop) {
                if (sc->sc_rbput - sc->sc_rbget - 1) {
                        setsoftscn();
                }
        }
        splx(s);
        return 1;
}

static int
scnintr(void *arg)
{
        struct duart *duart = arg;
        struct scn_softc *sc0 = duart->chan[0].sc;
        struct scn_softc *sc1 = duart->chan[1].sc;

        struct tty *tp0 = (sc0 != NULL) ? sc0->sc_tty : NULL;
        struct tty *tp1 = (sc1 != NULL) ? sc1->sc_tty : NULL;

        char rs_work;
        u_char rs_stat;
        u_char rs_ipcr;

        /* Check for RX interrupts first, since we cannot distinguish by irq. */
        scnrxintr(duart);

        do {
                /* Loop to pick up ALL pending interrupts for device. */
                rs_work = false;
                rs_stat = duart->base[DU_ISR];

/* channel a */
                if (tp0 != NULL) {
                        if ((rs_stat & INT_TXA) && (tp0->t_state & TS_BUSY)) {
                                /* output char done. */
                                tp0->t_state &= ~(TS_BUSY | TS_FLUSH);

                                /* disable tx ints */
                                duart->imr &= ~sc0->sc_tx_int;
                                duart->base[DU_IMR] = duart->imr;

                                if (sc0->sc_heldchanges) {
                                        scn_setchip(sc0);
                                }

                                (*tp0->t_linesw->l_start) (tp0);
                                rs_work = true;
                        }
                }
                /* channel b */
                if (tp1 != NULL) {
                        if ((rs_stat & INT_TXB) && (tp1->t_state & TS_BUSY)) {
                                /* output char done. */
                                tp1->t_state &= ~(TS_BUSY | TS_FLUSH);

                                /* disable tx ints */
                                duart->imr &= ~sc1->sc_tx_int;
                                duart->base[DU_IMR] = duart->imr;

                                if (sc1->sc_heldchanges) {
                                        scn_setchip(sc1);
                                }

                                (*tp1->t_linesw->l_start) (tp1);
                                rs_work = true;
                        }
                }
                if (rs_stat & INT_IP) {
                        rs_work = true;
                        rs_ipcr = duart->base[DU_IPCR];

                        if (rs_ipcr & IPCR_DELTA_DCDA && tp0 != NULL) {
                                dcd_int(sc0, tp0, rs_ipcr & IPCR_DCDA);
                        }
                        if (rs_ipcr & IPCR_DELTA_DCDB && tp1 != NULL) {
                                dcd_int(sc1, tp1, rs_ipcr & IPCR_DCDB);
                        }
                }
        } while (rs_work);

        return (1);     /* ? */
}

/*
 * Handle rxrdy/ffull interrupt: QUICKLY poll both channels (checking
 * status first) and stash data in a ring buffer.  Ring buffer scheme
 * borowed from sparc/zs.c requires NO interlock on data!
 *
 * This interrupt should NOT be included in spltty() mask since it
 * invokes NO tty code!  The whole point is to allow tty input as much
 * of the time as possible, while deferring "heavy" character
 * processing until later.
 *
 * see scn.hw.README and scnsoft() for more info.
 *
 * THIS ROUTINE SHOULD BE KEPT AS CLEAN AS POSSIBLE!!
 * IT'S A CANDIDATE FOR RECODING IN ASSEMBLER!!
 */
static inline int
scn_rxintr(struct scn_softc *sc)
{
        char sr;
        int i, n;
        int work;

        work = 0;
        i = sc->sc_rbput;
        while (work <= 10) {
#define SCN_GETCH(SC) \
                sr = (SC)->sc_chbase[CH_SR]; \
                if ((sr & SR_RX_RDY) == 0) \
                        break; \
                if (sr & (SR_PARITY | SR_FRAME | SR_BREAK | SR_OVERRUN)) \
                        goto exception; \
                work++; \
                (SC)->sc_rbuf[i++ & SCN_RING_MASK] = (SC)->sc_chbase[CH_DAT]

                SCN_GETCH(sc); SCN_GETCH(sc); SCN_GETCH(sc);
                /* XXX more here if 26C92? -plb */
                continue;
        exception:
#if defined(DDB)
                if (sc->sc_isconsole && (sr & SR_BREAK)) {
                        Debugger();
                        sr = sc->sc_chbase[CH_SR];
                }
#endif
#if defined(KGDB)
                if (sc->sc_iskgdb && (sr & SR_RX_RDY)) {
                        kgdb_connect(1);
                        sr = sc->sc_chbase[CH_SR];
                }
#endif
                work++;
                sc->sc_rbuf[i++ & SCN_RING_MASK] = (sr << 8) | sc->sc_chbase[CH_DAT];
                sc->sc_chbase[CH_CR] = CR_CMD_RESET_ERR;        /* resets break? */
                RECOVER();
        }
        /*
         * If ring is getting too full, try to block input.
         */
        n = i - sc->sc_rbget;
        if (sc->sc_rbhiwat && (n > sc->sc_rbhiwat)) {
                /* If not CRTSCTS sc_rbhiwat is such that this
                 *  never happens.
                 * Clear RTS
                 */
                SCN_OP_BIC(sc, sc->sc_op_rts);
                sc->sc_rx_blocked = 1;
        }
        sc->sc_rbput = i;

        return work;
}

static void
scnrxintr(void *arg)
{
        struct duart *duart = arg;
        int work = 0;

        if (duart->chan[0].sc != NULL)
                work += scn_rxintr(duart->chan[0].sc);
        if (duart->chan[1].sc != NULL)
                work += scn_rxintr(duart->chan[1].sc);
        if (work > 0) {
                setsoftscn();   /* trigger s/w intr */
#ifdef SCN_TIMING
                microtime(&tstart);
#endif
        }
}

/*
 * Here on soft interrupt (at spltty) to empty ring buffers.
 *
 * Dave's original scheme was to use the DUART receiver timeout
 * interrupt. This requires 2692's (which my board doesn't have), and
 * I also liked the idea of using the C/T to generate alternate and/or
 * arbitrary bauds. -plb
 *
 * The ringbuffer code comes from Chris Torek's SPARC 44bsd zs driver
 * (hence the LBL notice on top of this file), DOES NOT require
 * interlocking with interrupt levels!
 *
 * The 44bsd sparc/zs driver reads the ring buffer from a separate
 * zssoftint, while the SunOS 4.x zs driver appears to use
 * timeout()'s.  timeouts seem to be too slow to deal with high data
 * rates.  I know, I tried them.
 * -plb.
 */
static void
scnsoft(void *arg)
{
        int s, unit;
#ifdef SCN_TIMING
        struct timeval tend;
        u_long  t;

        microtime(&tend);
        t = (tend.tv_sec - tstart.tv_sec) * 1000000 + (tend.tv_usec - tstart.tv_usec);
        t = (t + tick / 20) / (tick / 10);
        if (t >= NJITTER - 1) {
                t = NJITTER - 1;
        }
        scn_jitter[t]++;
#endif

        for (unit = 0; unit < scn_cd.cd_ndevs; unit++) {
                struct scn_softc *sc;
                struct tty *tp;
                int n, get;

                sc = SOFTC(unit);
                if (sc == NULL) {
                        continue;
                }
                tp = sc->sc_tty;
#ifdef KGDB
                if (tp == NULL) {
                        sc->sc_rbget = sc->sc_rbput;
                        continue;
                }
#endif
                if (tp == NULL || tp->t_state & TS_TBLOCK) {
                        continue;
                }


                get = sc->sc_rbget;

                /* NOTE: fetch from rbput is atomic */
                while (get != (n = sc->sc_rbput)) {
                        /*
                         * 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 > SCN_RING_SIZE) {
                                scnoverrun(unit, &sc->sc_rotime, "ring");
                                get += n - SCN_RING_SIZE;
                                n = SCN_RING_SIZE;
                                sc->sc_ring_overruns++;
                        }
                        while (--n >= 0) {
                                int c, sr;

                                if (tp->t_state & TS_TBLOCK) {
                                        sc->sc_rbget = get;
                                        goto done;
                                }
                                /* Race to keep ahead of incoming interrupts. */
                                c = sc->sc_rbuf[get++ & SCN_RING_MASK];

                                sr = c >> 8;    /* extract status */
                                c &= 0xff;      /* leave just character */

                                if (sr & SR_OVERRUN) {
                                        scnoverrun(unit, &sc->sc_fotime, "fifo");
                                        sc->sc_fifo_overruns++;
                                }
                                if (sr & SR_PARITY) {
                                        c |= TTY_PE;
                                        sc->sc_parity_errors++;
                                }
                                if (sr & SR_FRAME) {
                                        c |= TTY_FE;
                                        sc->sc_framing_errors++;
                                }
                                if (sr & SR_BREAK) {
#if 0
                                        /*
                                         * See DDB_CHECK() comments in
                                         * scnrxintr()
                                         */
                                        if (sc->sc_isconsole)
                                                Debugger();
#endif
                                        c = TTY_FE | 0;
                                        sc->sc_breaks++;
                                }

                                (*tp->t_linesw->l_rint) (c, tp);

                                if (sc->sc_rx_blocked && n < SCN_RING_THRESH) {
                                        s = splrtty();
                                        sc->sc_rx_blocked = 0;
                                        SCN_OP_BIS(sc, sc->sc_op_rts);
                                        splx(s);
                                }

                        }
                        sc->sc_rbget = get;
                }
        done: ;
        }
}

/* Convert TIOCM_xxx bits to output port bits. */
static unsigned char
opbits(struct scn_softc *sc, int tioc_bits)
{

        return ((((tioc_bits) & TIOCM_DTR) ? sc->sc_op_dtr : 0) |
            (((tioc_bits) & TIOCM_RTS) ? sc->sc_op_rts : 0));
}

int
scnioctl(dev_t dev, u_long cmd, void *data, int flags, struct lwp *l)
{
        int unit = DEV_UNIT(dev);
        struct scn_softc *sc = SOFTC(unit);
        struct tty *tp = sc->sc_tty;
        int error;

        error = (*tp->t_linesw->l_ioctl) (tp, cmd, data, flags, l);
        if (error != EPASSTHROUGH)
                return (error);

        error = ttioctl(tp, cmd, data, flags, l);
        if (error != EPASSTHROUGH)
                return (error);

        switch (cmd) {
        case TIOCSBRK:
                sc->sc_chbase[CH_CR] = CR_CMD_START_BRK;
                break;

        case TIOCCBRK:
                sc->sc_chbase[CH_CR] = CR_CMD_STOP_BRK;
                break;

        case TIOCSDTR:
                SCN_OP_BIS(sc, sc->sc_op_dtr | sc->sc_op_rts);
                break;

        case TIOCCDTR:
                SCN_OP_BIC(sc, sc->sc_op_dtr | sc->sc_op_rts);
                break;

        case TIOCMSET: {
                        int     s;
                        unsigned char sbits, cbits;

                        /* set bits */
                        sbits = opbits(sc, *(int *) data);

                        /* get bits to clear */
                        cbits = ~sbits & (sc->sc_op_dtr | sc->sc_op_rts);

                        s = spltty();
                        if (sbits) {
                                SCN_OP_BIS(sc, sbits);
                        }
                        if (cbits) {
                                SCN_OP_BIC(sc, cbits);
                        }
                        splx(s);
                        break;
                }

        case TIOCMBIS:
                SCN_OP_BIS(sc, opbits(sc, *(int *) data));
                break;

        case TIOCMBIC:
                SCN_OP_BIC(sc, opbits(sc, *(int *) data));
                break;

        case TIOCMGET: {
                        int     bits;
                        unsigned char ip, op;

                        /* s = spltty(); */
                        ip = sc->sc_duart->base[DU_IP];
                        /*
                         * XXX sigh; cannot get op current state!! even if
                         * maintained in private, RTS is done in h/w!!
                         */
                        op = 0;
                        /* splx(s); */

                        bits = 0;
                        if (ip & sc->sc_ip_dcd)
                                bits |= TIOCM_CD;
                        if (ip & sc->sc_ip_cts)
                                bits |= TIOCM_CTS;

#if 0
                        if (op & sc->sc_op_dtr)
                                bits |= TIOCM_DTR;
                        if (op & sc->sc_op_rts)
                                bits |= TIOCM_RTS;
#endif

                        *(int *) data = bits;
                        break;
                }

        case TIOCGFLAGS:{
                        int     bits = 0;

                        if (sc->sc_swflags & SCN_SW_SOFTCAR)
                                bits |= TIOCFLAG_SOFTCAR;
                        if (sc->sc_swflags & SCN_SW_CLOCAL)
                                bits |= TIOCFLAG_CLOCAL;
                        if (sc->sc_swflags & SCN_SW_CRTSCTS)
                                bits |= TIOCFLAG_CRTSCTS;
                        if (sc->sc_swflags & SCN_SW_MDMBUF)
                                bits |= TIOCFLAG_MDMBUF;

                        *(int *) data = bits;
                        break;
                }
        case TIOCSFLAGS:{
                        int     userbits, driverbits = 0;

                        error = kauth_authorize_device_tty(l->l_cred,
                            KAUTH_DEVICE_TTY_PRIVSET, tp);
                        if (error != 0)
                                return (EPERM);

                        userbits = *(int *) data;
                        if (userbits & TIOCFLAG_SOFTCAR)
                                driverbits |= SCN_SW_SOFTCAR;
                        if (userbits & TIOCFLAG_CLOCAL)
                                driverbits |= SCN_SW_CLOCAL;
                        if (userbits & TIOCFLAG_CRTSCTS)
                                driverbits |= SCN_SW_CRTSCTS;
                        if (userbits & TIOCFLAG_MDMBUF)
                                driverbits |= SCN_SW_MDMBUF;

                        sc->sc_swflags = driverbits;

                        break;
                }

        default:
                return (EPASSTHROUGH);
        }
        return (0);
}

int
scnparam(struct tty *tp, struct termios *t)
{
        int cflag = t->c_cflag;
        int unit = DEV_UNIT(tp->t_dev);
        char mr1, mr2;
        int error;
        struct scn_softc *sc = SOFTC(unit);

        /* Is this a hang up? */
        if (t->c_ospeed == B0) {
                SCN_OP_BIC(sc, sc->sc_op_dtr);
                /* leave DTR down. see comment in scnclose() -plb */
                return (0);
        }
        mr1 = mr2 = 0;

        /* Parity? */
        if (cflag & PARENB) {
                if ((cflag & PARODD) == 0)
                        mr1 |= MR1_PEVEN;
                else
                        mr1 |= MR1_PODD;
        } else
                mr1 |= MR1_PNONE;

        /* Stop bits. */
        if (cflag & CSTOPB)
                mr2 |= MR2_STOP2;
        else
                mr2 |= MR2_STOP1;

        /* Data bits. */
        switch (cflag & CSIZE) {
        case CS5:
                mr1 |= MR1_CS5;
                break;
        case CS6:
                mr1 |= MR1_CS6;
                break;
        case CS7:
                mr1 |= MR1_CS7;
                break;
        case CS8:
        default:
                mr1 |= MR1_CS8;
                break;
        }

        if (cflag & CCTS_OFLOW)
                mr2 |= MR2_TXCTS;

        if (cflag & CRTS_IFLOW) {
                mr1 |= MR1_RXRTS;
                sc->sc_rbhiwat = SCN_RING_HIWAT;
        } else {
                sc->sc_rbhiwat = 0;
        }

        error = scn_config(unit, sc->sc_channel, t->c_ispeed,
            t->c_ospeed, mr1, mr2);

        /* If successful, copy to tty */
        if (!error) {
                tp->t_ispeed = t->c_ispeed;
                tp->t_ospeed = t->c_ospeed;
                tp->t_cflag = cflag;
        }
        return (error);
}

/*
 * Start or restart a transmission.
 */
void
scnstart(struct tty *tp)
{
        int s, c;
        int unit = DEV_UNIT(tp->t_dev);
        struct scn_softc *sc = SOFTC(unit);

        s = spltty();
        if (tp->t_state & (TS_BUSY | TS_TIMEOUT | TS_TTSTOP))
                goto out;
        if (!ttypull(tp))
                goto out;

        tp->t_state |= TS_BUSY;

        while (sc->sc_chbase[CH_SR] & SR_TX_RDY) {
                if ((c = getc(&tp->t_outq)) == -1)
                        break;
                sc->sc_chbase[CH_DAT] = c;
        }
        sc->sc_duart->imr |= (sc->sc_tx_int | sc->sc_rx_int);
        sc->sc_duart->base[DU_IMR] = sc->sc_duart->imr;

out:
        splx(s);
}

/*
 * Stop output on a line.
 */
/*ARGSUSED*/
void
scnstop(struct tty *tp, int flags)
{
        int s;

        s = spltty();
        if (tp->t_state & TS_BUSY) {
                if ((tp->t_state & TS_TTSTOP) == 0)
                        tp->t_state |= TS_FLUSH;
        }
        splx(s);
}

/*
 * Following are all routines needed for SCN to act as console.
 */

void
scncnprobe(struct consdev *cn)
{
}

void
scncnreinit(void *v)
{
        volatile u_char *du_base =
            (volatile u_char *)MIPS_PHYS_TO_KSEG1(0x1fb80004);

        du_base[DU_OPSET] =
            SCN_CONSCHAN ? (OP_RTSB | OP_DTRB) : (OP_RTSA | OP_DTRA);
}

void
scncninit(struct consdev *cn)
{
        devmajor_t major;

        /* initialize required fields */
        major = cdevsw_lookup_major(&scn_cdevsw);
        KASSERT(major != NODEV);
        cn->cn_dev = makedev(major, SCN_CONSOLE);
        cn->cn_pri = CN_REMOTE;

        scninit(cn->cn_dev, scnconsrate);
}

/* Used by scncninit and kgdb startup. */
int
scninit(dev_t dev, int rate)
{
/* XXX - maintain PROM's settings */
#if 0
        volatile u_char *du_base =
            (volatile u_char *)MIPS_PHYS_TO_KSEG1(0x1fb80004);
        int unit = DEV_UNIT(dev);

        du_base[DU_OPSET] =
            SCN_CONSCHAN ? (OP_RTSB | OP_DTRB) : (OP_RTSA | OP_DTRA);
        scn_config(unit, SCN_CONSCHAN, rate, rate,
            MR1_PNONE | MR1_CS8, MR2_STOP1);
#endif
        return (0);
}

/*
 * Console kernel input character routine.
 */
int
scncngetc(dev_t dev)
{
        volatile u_char *ch_base =
            (volatile u_char *)MIPS_PHYS_TO_KSEG1(0x1fb80004);
        char c;
        int s;

        s = spltty();

        while ((ch_base[CH_SR] & SR_RX_RDY) == 0)
                ;
        c = ch_base[CH_DAT];

        splx(s);
        return c;
}

void
scncnpollc(dev_t dev, int on)
{
}

/*
 * Console kernel output character routine.
 */
void
scncnputc(dev_t dev, int c)
{
        volatile u_char *ch_base =
            (volatile u_char *)MIPS_PHYS_TO_KSEG1(0x1fb80004);
        volatile u_char *du_base =
            (volatile u_char *)MIPS_PHYS_TO_KSEG1(0x1fb80004);
        int s;

        s = spltty();

        if (c == '\n')
                scncnputc(dev, '\r');

        while ((ch_base[CH_SR] & SR_TX_RDY) == 0)
                ;
        ch_base[CH_DAT] = c;
        while ((ch_base[CH_SR] & SR_TX_RDY) == 0)
                ;
        du_base[DU_ISR];

        splx(s);
}