/* $NetBSD: sbscn.c,v 1.45 2021/01/04 18:19:53 thorpej Exp $ */

/*
 * Copyright 2000, 2001
 * Broadcom Corporation. All rights reserved.
 *
 * This software is furnished under license and may be used and copied only
 * in accordance with the following terms and conditions.  Subject to these
 * conditions, you may download, copy, install, use, modify and distribute
 * modified or unmodified copies of this software in source and/or binary
 * form. No title or ownership is transferred hereby.
 *
 * 1) Any source code used, modified or distributed must reproduce and
 *    retain this copyright notice and list of conditions as they appear in
 *    the source file.
 *
 * 2) No right is granted to use any trade name, trademark, or logo of
 *    Broadcom Corporation.  The "Broadcom Corporation" name may not be
 *    used to endorse or promote products derived from this software
 *    without the prior written permission of Broadcom Corporation.
 *
 * 3) THIS SOFTWARE IS PROVIDED "AS-IS" AND ANY EXPRESS OR IMPLIED
 *    WARRANTIES, INCLUDING BUT NOT LIMITED TO, ANY IMPLIED WARRANTIES OF
 *    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR
 *    NON-INFRINGEMENT ARE DISCLAIMED. IN NO EVENT SHALL BROADCOM BE LIABLE
 *    FOR ANY DAMAGES WHATSOEVER, AND IN PARTICULAR, BROADCOM SHALL NOT BE
 *    LIABLE FOR 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), EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/* from: $NetBSD: com.c,v 1.172 2000/05/03 19:19:04 thorpej Exp */

/*-
 * Copyright (c) 1998, 1999 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Charles M. Hannum.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

/*
 * Copyright (c) 1991 The Regents of the University of California.
 * All rights reserved.
 *
 * 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.
 *
 *      @(#)com.c       7.5 (Berkeley) 5/16/91
 */

/*
 * `sbscn' driver, supports SiByte SB-1250 SOC DUART.
 *
 * This DUART is quite similar in programming model to the scn2681/68681
 * DUARTs supported by the NetBSD/amiga `mfc' and NetBSD/pc532 `scn'
 * driver, but substantial rework would have been necessary to make
 * those drivers sane w.r.t. bus_space (which would then have been
 * required on NetBSD/sbmips very early on), and to accommodate the
 * different register mappings.
 *
 * So, another driver.  Eventually there should be One True Driver,
 * but we're not here to save the world.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: sbscn.c,v 1.45 2021/01/04 18:19:53 thorpej Exp $");

#define SBSCN_DEBUG

#include "opt_ddb.h"
#include "ioconf.h"

#ifdef RND_SBSCN
#include <sys/rndsource.h>
#endif

#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/conf.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/kmem.h>
#include <sys/vnode.h>
#include <sys/kauth.h>
#include <sys/intr.h>

#include <mips/sibyte/dev/sbobiovar.h>
#if 0
#include <mips/sibyte/dev/sbscnreg.h>
#endif
#include <mips/sibyte/dev/sbscnvar.h>
#include <dev/cons.h>
#include <mips/locore.h>

#include <evbmips/sbmips/systemsw.h>

void    sbscn_attach_channel(struct sbscn_softc *sc, int chan, int intr);
#if defined(DDB) || defined(KGDB)
static void sbscn_enable_debugport(struct sbscn_channel *ch);
#endif
void    sbscn_config(struct sbscn_channel *ch);
void    sbscn_shutdown(struct sbscn_channel *ch);
int     sbscn_speed(long, long *);
static int cflag2modes(tcflag_t, u_char *, u_char *);
int     sbscn_param(struct tty *, struct termios *);
void    sbscn_start(struct tty *);
int     sbscn_hwiflow(struct tty *, int);

void    sbscn_loadchannelregs(struct sbscn_channel *);
void    sbscn_dohwiflow(struct sbscn_channel *);
void    sbscn_break(struct sbscn_channel *, int);
void    sbscn_modem(struct sbscn_channel *, int);
void    tiocm_to_sbscn(struct sbscn_channel *, int, int);
int     sbscn_to_tiocm(struct sbscn_channel *);
void    sbscn_iflush(struct sbscn_channel *);

int     sbscn_init(u_long addr, int chan, int rate, tcflag_t cflag);
int     sbscn_common_getc(u_long addr, int chan);
void    sbscn_common_putc(u_long addr, int chan, int c);
void    sbscn_intr(void *arg, uint32_t status, vaddr_t pc);

int     sbscn_cngetc(dev_t dev);
void    sbscn_cnputc(dev_t dev, int c);
void    sbscn_cnpollc(dev_t dev, int on);

dev_type_open(sbscnopen);
dev_type_close(sbscnclose);
dev_type_read(sbscnread);
dev_type_write(sbscnwrite);
dev_type_ioctl(sbscnioctl);
dev_type_stop(sbscnstop);
dev_type_tty(sbscntty);
dev_type_poll(sbscnpoll);

const struct cdevsw sbscn_cdevsw = {
        .d_open = sbscnopen,
        .d_close = sbscnclose,
        .d_read = sbscnread,
        .d_write = sbscnwrite,
        .d_ioctl = sbscnioctl,
        .d_stop = sbscnstop,
        .d_tty = sbscntty,
        .d_poll = sbscnpoll,
        .d_mmap = nommap,
        .d_kqfilter = ttykqfilter,
        .d_discard = nodiscard,
        .d_flag = D_TTY
};

#define integrate       static inline
void    sbscn_soft(void *);
integrate void sbscn_rxsoft(struct sbscn_channel *, struct tty *);
integrate void sbscn_txsoft(struct sbscn_channel *, struct tty *);
integrate void sbscn_stsoft(struct sbscn_channel *, struct tty *);
integrate void sbscn_schedrx(struct sbscn_channel *);
void    sbscn_diag(void *);

/*
 * Make this an option variable one can patch.
 * But be warned:  this must be a power of 2!
 */
u_int sbscn_rbuf_size = SBSCN_RING_SIZE;

/* Stop input when 3/4 of the ring is full; restart when only 1/4 is full. */
u_int sbscn_rbuf_hiwat = (SBSCN_RING_SIZE * 1) / 4;
u_int sbscn_rbuf_lowat = (SBSCN_RING_SIZE * 3) / 4;

static int      sbscn_cons_present;
static int      sbscn_cons_attached;
static u_long   sbscn_cons_addr;
static int      sbscn_cons_chan;
static int      sbscn_cons_rate;
static tcflag_t sbscn_cons_cflag;

#ifdef KGDB
#include <sys/kgdb.h>

static int      sbscn_kgdb_present;
static int      sbscn_kgdb_attached;
static u_long   sbscn_kgdb_addr;
static int      sbscn_kgdb_chan;

int     sbscn_kgdb_getc(void *);
void    sbscn_kgdb_putc(void *, int);
#endif /* KGDB */

static int      sbscn_match(device_t, cfdata_t, void *);
static void     sbscn_attach(device_t, device_t, void *);

CFATTACH_DECL_NEW(sbscn, sizeof(struct sbscn_softc),
    sbscn_match, sbscn_attach, NULL, NULL);

#define READ_REG(rp)            (mips3_ld((register_t)(rp)))
#define WRITE_REG(rp, val)      (mips3_sd((register_t)(rp), (val)))

/*
 * input and output signals are actually the _inverse_ of the bits in the
 * input and output port registers!
 */
#define GET_INPUT_SIGNALS(ch) \
    ((~READ_REG(MIPS_PHYS_TO_KSEG1((ch)->ch_sc->sc_addr + 0x280))) & (ch)->ch_i_mask)
#define SET_OUTPUT_SIGNALS(ch, val)                                     \
    do {                                                                \
        int sigs_to_set, sigs_to_clr;                                   \
                                                                        \
        sigs_to_set = (ch)->ch_o_mask & val;                            \
        sigs_to_clr = (ch)->ch_o_mask & ~val;                           \
                                                                        \
        /* set signals by clearing op bits, and vice versa */           \
        WRITE_REG(MIPS_PHYS_TO_KSEG1((ch)->ch_sc->sc_addr + 0x2c0),     \
            sigs_to_set);                                               \
        WRITE_REG(MIPS_PHYS_TO_KSEG1((ch)->ch_sc->sc_addr + 0x2b0),     \
            sigs_to_clr);                                               \
    } while (0)

static int
sbscn_match(device_t parent, cfdata_t match, void *aux)
{
        struct sbobio_attach_args *sa = aux;

        if (sa->sa_locs.sa_type != SBOBIO_DEVTYPE_DUART)
                return (0);

        return 1;
}

static void
sbscn_attach(device_t parent, device_t self, void *aux)
{
        struct sbscn_softc *sc = device_private(self);
        struct sbobio_attach_args *sa = aux;
        int i;

        sc->sc_dev = self;
        sc->sc_addr = sa->sa_base + sa->sa_locs.sa_offset;

        aprint_normal("\n");
        for (i = 0; i < 2; i++)
                sbscn_attach_channel(sc, i, sa->sa_locs.sa_intr[i]);

        /* init duart_opcr */
        WRITE_REG(MIPS_PHYS_TO_KSEG1(sc->sc_addr + 0x270), 0);
        /* init duart_aux_ctrl */
        WRITE_REG(MIPS_PHYS_TO_KSEG1(sc->sc_addr + 0x210), 0x0f); /* XXX */
}

void
sbscn_attach_channel(struct sbscn_softc *sc, int chan, int intr)
{
        struct sbscn_channel *ch = &sc->sc_channels[chan];
        u_long chan_addr;
        struct tty *tp;

        ch->ch_sc = sc;
        ch->ch_num = chan;

        chan_addr = sc->sc_addr + (0x100 * chan);
        ch->ch_base = (void *)MIPS_PHYS_TO_KSEG1(chan_addr);
        ch->ch_isr_base =
            (void *)MIPS_PHYS_TO_KSEG1(sc->sc_addr + 0x220 + (0x20 * chan));
        ch->ch_imr_base =
            (void *)MIPS_PHYS_TO_KSEG1(sc->sc_addr + 0x230 + (0x20 * chan));
#ifdef XXXCGDnotyet
        ch->ch_inchg_base =
            (void *)MIPS_PHYS_TO_KSEG1(sc->sc_addr + 0x2d0 + (0x10 * chan));
#endif

        ch->ch_i_dcd = ch->ch_i_dcd_pin = 0 /* XXXCGD */;
        ch->ch_i_cts = ch->ch_i_cts_pin = 0 /* XXXCGD */;
        ch->ch_i_dsr = ch->ch_i_dsr_pin = 0 /* XXXCGD */;
        ch->ch_i_ri = ch->ch_i_ri_pin = 0 /* XXXCGD */;
        ch->ch_i_mask =
            ch->ch_i_dcd | ch->ch_i_cts | ch->ch_i_dsr | ch->ch_i_ri;
        ch->ch_o_dtr = ch->ch_o_dtr_pin = 0 /* XXXCGD */;
        ch->ch_o_rts = ch->ch_o_rts_pin = 0 /* XXXCGD */;
        ch->ch_o_mask = ch->ch_o_dtr | ch->ch_o_rts;

        ch->ch_intrhand = cpu_intr_establish(intr, IPL_SERIAL, sbscn_intr, ch);
        callout_init(&ch->ch_diag_callout, 0);

        /* Disable interrupts before configuring the device. */
        ch->ch_imr = 0;
        WRITE_REG(ch->ch_imr_base, ch->ch_imr);

        if (sbscn_cons_present &&
            sbscn_cons_addr == chan_addr && sbscn_cons_chan == chan) {
                sbscn_cons_attached = 1;

                /* Make sure the console is always "hardwired". */
                delay(1000);                    /* wait for output to finish */
                SET(ch->ch_hwflags, SBSCN_HW_CONSOLE);
                SET(ch->ch_swflags, TIOCFLAG_SOFTCAR);
        }

        tp = tty_alloc();
        tp->t_oproc = sbscn_start;
        tp->t_param = sbscn_param;
        tp->t_hwiflow = sbscn_hwiflow;

        ch->ch_tty = tp;
        ch->ch_rbuf = kmem_alloc(sbscn_rbuf_size << 1, KM_SLEEP);
        ch->ch_ebuf = ch->ch_rbuf + (sbscn_rbuf_size << 1);

        tty_attach(tp);

        if (ISSET(ch->ch_hwflags, SBSCN_HW_CONSOLE)) {
                int maj;

                /* locate the major number */
                maj = cdevsw_lookup_major(&sbscn_cdevsw);

                cn_tab->cn_dev = makedev(maj,
                    (device_unit(sc->sc_dev) << 1) + chan);

                aprint_normal_dev(sc->sc_dev, "channel %d: %s\n",
                    chan, "console");
        }

#ifdef KGDB
        /*
         * Allow kgdb to "take over" this port.  If this is
         * the kgdb device, it has exclusive use.
         */
        if (sbscn_kgdb_present &&
            sbscn_kgdb_addr == chan_addr && sbscn_kgdb_chan == chan) {
                sbscn_kgdb_attached = 1;

                SET(sc->sc_hwflags, SBSCN_HW_KGDB);
                aprint_normal_dev(sc->sc_dev, "channel %d: %s\n",
                    chan, "kgdb");
        }
#endif

        ch->ch_si = softint_establish(SOFTINT_SERIAL, sbscn_soft, ch);

#ifdef RND_SBSCN
        rnd_attach_source(&ch->ch_rnd_source, device_xname(sc->sc_dev),
                          RND_TYPE_TTY, RND_FLAG_COLLECT_TIME|
                                        RND_FLAG_ESTIMATE_TIME);
#endif

        sbscn_config(ch);

        SET(ch->ch_hwflags, SBSCN_HW_DEV_OK);
}

int
sbscn_speed(long speed, long *brcp)
{
#define divrnd(n, q)    (((n)*2/(q)+1)/2)       /* divide and round off */

        int x, err;
        int frequency = 100000000;

        *brcp = divrnd(frequency / 20, speed) - 1;

        if (speed <= 0)
                return (-1);
        x = divrnd(frequency / 20, speed);
        if (x <= 0)
                return (-1);
        err = divrnd(((quad_t)frequency) * 1000 / 20, speed * x) - 1000;
        if (err < 0)
                err = -err;
        if (err > SBSCN_TOLERANCE)
                return (-1);
        *brcp = x - 1;
        return (0);

#undef  divrnd
}

#ifdef SBSCN_DEBUG
void    sbscn_status(struct sbscn_channel *, const char *);

int     sbscn_debug = 0 /* XXXCGD */;

void
sbscn_status(struct sbscn_channel *ch, const char *str)
{
        struct sbscn_softc *sc = ch->ch_sc;
        struct tty *tp = ch->ch_tty;

        aprint_normal_dev(sc->sc_dev,
            "chan %d: %s %sclocal  %sdcd %sts_carr_on %sdtr %stx_stopped\n",
            ch->ch_num, str,
            ISSET(tp->t_cflag, CLOCAL) ? "+" : "-",
            ISSET(ch->ch_iports, ch->ch_i_dcd) ? "+" : "-",
            ISSET(tp->t_state, TS_CARR_ON) ? "+" : "-",
            ISSET(ch->ch_oports, ch->ch_o_dtr) ? "+" : "-",
            ch->ch_tx_stopped ? "+" : "-");

        aprint_normal_dev(sc->sc_dev,
            "chan %d: %s %scrtscts %scts %sts_ttstop  %srts %xrx_flags\n",
            ch->ch_num, str,
            ISSET(tp->t_cflag, CRTSCTS) ? "+" : "-",
            ISSET(ch->ch_iports, ch->ch_i_cts) ? "+" : "-",
            ISSET(tp->t_state, TS_TTSTOP) ? "+" : "-",
            ISSET(ch->ch_oports, ch->ch_o_rts) ? "+" : "-",
            ch->ch_rx_flags);
}
#endif

#if defined(DDB) || defined(KGDB)
static void
sbscn_enable_debugport(struct sbscn_channel *ch)
{
        int s;

        /* Turn on line break interrupt, set carrier. */
        s = splserial();

#if 0   /* DO NOT turn on break interrupt at this time. */
        ch->ch_imr = 0x04;
#else
        ch->ch_imr = 0x00;
#endif
        WRITE_REG(ch->ch_imr_base, ch->ch_imr);
        SET(ch->ch_oports, ch->ch_o_dtr | ch->ch_o_rts);
        SET_OUTPUT_SIGNALS(ch, ch->ch_oports);

        splx(s);
}
#endif

void
sbscn_config(struct sbscn_channel *ch)
{

        /* Disable interrupts before configuring the device. */
        ch->ch_imr = 0x00;
        WRITE_REG(ch->ch_imr_base, ch->ch_imr);

#ifdef DDB
        if (ISSET(ch->ch_hwflags, SBSCN_HW_CONSOLE))
                sbscn_enable_debugport(ch);
#endif

#ifdef KGDB
        /*
         * Allow kgdb to "take over" this port.  If this is
         * the kgdb device, it has exclusive use.
         */
        if (ISSET(ch->ch_hwflags, SBSCN_HW_KGDB))
                sbscn_enable_debugport(ch);
#endif
}

void
sbscn_shutdown(struct sbscn_channel *ch)
{
        struct tty *tp = ch->ch_tty;
        int s;

        s = splserial();

        /* If we were asserting flow control, then deassert it. */
        SET(ch->ch_rx_flags, RX_IBUF_BLOCKED);
        sbscn_dohwiflow(ch);

        /* Clear any break condition set with TIOCSBRK. */
        sbscn_break(ch, 0);

        /*
         * Hang up if necessary.  Wait a bit, so the other side has time to
         * notice even if we immediately open the port again.
         * Avoid tsleeping above splhigh().
         */
        if (ISSET(tp->t_cflag, HUPCL)) {
                sbscn_modem(ch, 0);
                splx(s);
                /* XXX tsleep will only timeout */
                (void) tsleep(ch, TTIPRI, ttclos, hz);
                s = splserial();
        }

        /* Turn off interrupts. */
#ifdef DDB
        if (ISSET(ch->ch_hwflags, SBSCN_HW_CONSOLE))
#if 0   /* DO NOT turn on break interrupt at this time. */
                ch->ch_imr = 0x04; /* interrupt on break */
#else
                ch->ch_imr = 0x00;
#endif
        else
#endif
                ch->ch_imr = 0;
        WRITE_REG(ch->ch_imr_base, ch->ch_imr);

        splx(s);
}

int
sbscnopen(dev_t dev, int flag, int mode, struct lwp *l)
{
        int chan = SBSCN_CHAN(dev);
        struct sbscn_softc *sc;
        struct sbscn_channel *ch;
        struct tty *tp;
        int s, s2;
        int error;

        sc = device_lookup_private(&sbscn_cd, SBSCN_UNIT(dev));
        if (sc == NULL)
                return (ENXIO);
        ch = &sc->sc_channels[chan];
        if (!ISSET(ch->ch_hwflags, SBSCN_HW_DEV_OK) || ch->ch_rbuf == NULL)
                return (ENXIO);

#ifdef KGDB
        /*
         * If this is the kgdb port, no other use is permitted.
         */
        if (ISSET(ch->ch_hwflags, SBSCN_HW_KGDB))
                return (EBUSY);
#endif

        tp = ch->ch_tty;

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

        s = spltty();

        /*
         * Do the following iff this is a first open.
         */
        if (!ISSET(tp->t_state, TS_ISOPEN) && tp->t_wopen == 0) {
                struct termios t;

                tp->t_dev = dev;

                s2 = splserial();

                /* Turn on receive, break, and status change interrupts. */
#if 0   /* DO NOT turn on break or status change interrupt at this time. */
                ch->ch_imr = 0xe;
#else
                ch->ch_imr = 0x2;
#endif
                WRITE_REG(ch->ch_imr_base, ch->ch_imr);

                /* Fetch the current modem control status, needed later. */
                ch->ch_iports = GET_INPUT_SIGNALS(ch);
                ch->ch_iports_delta = 0;
                splx(s2);

                /*
                 * Initialize the termios status to the defaults.  Add in the
                 * sticky bits from TIOCSFLAGS.
                 */
                t.c_ispeed = 0;
                if (ISSET(ch->ch_hwflags, SBSCN_HW_CONSOLE)) {
                        t.c_ospeed = sbscn_cons_rate;
                        t.c_cflag = sbscn_cons_cflag;
                } else {
                        t.c_ospeed = TTYDEF_SPEED;
                        t.c_cflag = TTYDEF_CFLAG;
                }
                if (ISSET(ch->ch_swflags, TIOCFLAG_CLOCAL))
                        SET(t.c_cflag, CLOCAL);
                if (ISSET(ch->ch_swflags, TIOCFLAG_CRTSCTS))
                        SET(t.c_cflag, CRTSCTS);
                if (ISSET(ch->ch_swflags, TIOCFLAG_MDMBUF))
                        SET(t.c_cflag, MDMBUF);
                /* Make sure sbscn_param() will do something. */
                tp->t_ospeed = 0;
                (void) sbscn_param(tp, &t);
                tp->t_iflag = TTYDEF_IFLAG;
                tp->t_oflag = TTYDEF_OFLAG;
                tp->t_lflag = TTYDEF_LFLAG;
                ttychars(tp);
                ttsetwater(tp);

                s2 = splserial();

                /*
                 * Turn on DTR.  We must always do this, even if carrier is not
                 * present, because otherwise we'd have to use TIOCSDTR
                 * immediately after setting CLOCAL, which applications do not
                 * expect.  We always assert DTR while the device is open
                 * unless explicitly requested to deassert it.
                 */
                sbscn_modem(ch, 1);

                /* Clear the input ring, and unblock. */
                ch->ch_rbput = ch->ch_rbget = ch->ch_rbuf;
                ch->ch_rbavail = sbscn_rbuf_size;
                sbscn_iflush(ch);
                CLR(ch->ch_rx_flags, RX_ANY_BLOCK);
                sbscn_dohwiflow(ch);

#ifdef SBSCN_DEBUG
                if (sbscn_debug)
                        sbscn_status(ch, "sbscnopen  ");
#endif

                splx(s2);
        }

        splx(s);

        error = ttyopen(tp, SBSCN_DIALOUT(dev), ISSET(flag, O_NONBLOCK));
        if (error)
                goto bad;

        error = (*tp->t_linesw->l_open)(dev, tp);
        if (error)
                goto bad;

        return (0);

bad:
        if (!ISSET(tp->t_state, TS_ISOPEN) && tp->t_wopen == 0) {
                /*
                 * We failed to open the device, and nobody else had it opened.
                 * Clean up the state as appropriate.
                 */
                sbscn_shutdown(ch);
        }

        return (error);
}

int
sbscnclose(dev_t dev, int flag, int mode, struct lwp *l)
{
        struct sbscn_softc *sc = device_lookup_private(&sbscn_cd, SBSCN_UNIT(dev));
        struct sbscn_channel *ch = &sc->sc_channels[SBSCN_CHAN(dev)];
        struct tty *tp = ch->ch_tty;

        /* XXX This is for cons.c. */
        if (!ISSET(tp->t_state, TS_ISOPEN))
                return (0);

        (*tp->t_linesw->l_close)(tp, flag);
        ttyclose(tp);

        if (!ISSET(tp->t_state, TS_ISOPEN) && tp->t_wopen == 0) {
                /*
                 * Although we got a last close, the device may still be in
                 * use; e.g. if this was the dialout node, and there are still
                 * processes waiting for carrier on the non-dialout node.
                 */
                sbscn_shutdown(ch);
        }

        return (0);
}

int
sbscnread(dev_t dev, struct uio *uio, int flag)
{
        struct sbscn_softc *sc = device_lookup_private(&sbscn_cd, SBSCN_UNIT(dev));
        struct sbscn_channel *ch = &sc->sc_channels[SBSCN_CHAN(dev)];
        struct tty *tp = ch->ch_tty;

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

int
sbscnwrite(dev_t dev, struct uio *uio, int flag)
{
        struct sbscn_softc *sc = device_lookup_private(&sbscn_cd, SBSCN_UNIT(dev));
        struct sbscn_channel *ch = &sc->sc_channels[SBSCN_CHAN(dev)];
        struct tty *tp = ch->ch_tty;

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

int
sbscnpoll(dev_t dev, int events, struct lwp *l)
{
        struct sbscn_softc *sc = device_lookup_private(&sbscn_cd, SBSCN_UNIT(dev));
        struct sbscn_channel *ch = &sc->sc_channels[SBSCN_CHAN(dev)];
        struct tty *tp = ch->ch_tty;

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

struct tty *
sbscntty(dev_t dev)
{
        struct sbscn_softc *sc = device_lookup_private(&sbscn_cd, SBSCN_UNIT(dev));
        struct sbscn_channel *ch = &sc->sc_channels[SBSCN_CHAN(dev)];
        struct tty *tp = ch->ch_tty;

        return (tp);
}

int
sbscnioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
{
        struct sbscn_softc *sc = device_lookup_private(&sbscn_cd, SBSCN_UNIT(dev));
        struct sbscn_channel *ch = &sc->sc_channels[SBSCN_CHAN(dev)];
        struct tty *tp = ch->ch_tty;
        int error;
        int s;

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

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

        error = 0;

        s = splserial();

        switch (cmd) {
        case TIOCSBRK:
                sbscn_break(ch, 1);
                break;

        case TIOCCBRK:
                sbscn_break(ch, 0);
                break;

        case TIOCSDTR:
                sbscn_modem(ch, 1);
                break;

        case TIOCCDTR:
                sbscn_modem(ch, 0);
                break;

        case TIOCGFLAGS:
                *(int *)data = ch->ch_swflags;
                break;

        case TIOCSFLAGS:
                error = kauth_authorize_device_tty(l->l_cred,
                    KAUTH_DEVICE_TTY_PRIVSET, tp);
                if (error)
                        break;
                ch->ch_swflags = *(int *)data;
                break;

        case TIOCMSET:
        case TIOCMBIS:
        case TIOCMBIC:
                tiocm_to_sbscn(ch, cmd, *(int *)data);
                break;

        case TIOCMGET:
                *(int *)data = sbscn_to_tiocm(ch);
                break;

        default:
                error = EPASSTHROUGH;
                break;
        }

        splx(s);

#ifdef SBSCN_DEBUG
        if (sbscn_debug)
                sbscn_status(ch, "sbscn_ioctl ");
#endif

        return (error);
}

integrate void
sbscn_schedrx(struct sbscn_channel *ch)
{

        ch->ch_rx_ready = 1;

        /* Wake up the poller. */
        softint_schedule(ch->ch_si);
}

void
sbscn_break(struct sbscn_channel *ch, int onoff)
{

/* XXXCGD delay break until not busy */
        if (onoff)
                WRITE_REG(ch->ch_base + 0x50, 0x60);
        else
                WRITE_REG(ch->ch_base + 0x50, 0x70);

#if 0
        if (!ch->ch_heldchange) {
                if (ch->ch_tx_busy) {
                        ch->ch_heldtbc = ch->ch_tbc;
                        ch->ch_tbc = 0;
                        ch->ch_heldchange = 1;
                } else
                        sbscn_loadchannelregs(ch);
        }
#endif
}

void
sbscn_modem(struct sbscn_channel *ch, int onoff)
{

        if (ch->ch_o_dtr == 0)
                return;

        if (onoff)
                SET(ch->ch_oports, ch->ch_o_dtr);
        else
                CLR(ch->ch_oports, ch->ch_o_dtr);

        if (!ch->ch_heldchange) {
                if (ch->ch_tx_busy) {
                        ch->ch_heldtbc = ch->ch_tbc;
                        ch->ch_tbc = 0;
                        ch->ch_heldchange = 1;
                } else
                        sbscn_loadchannelregs(ch);
        }
}

void
tiocm_to_sbscn(struct sbscn_channel *ch, int how, int ttybits)
{
        u_char bits;

        bits = 0;
        if (ISSET(ttybits, TIOCM_DTR))
                SET(bits, ch->ch_o_dtr);
        if (ISSET(ttybits, TIOCM_RTS))
                SET(bits, ch->ch_o_rts);

        switch (how) {
        case TIOCMBIC:
                CLR(ch->ch_oports, bits);
                break;

        case TIOCMBIS:
                SET(ch->ch_oports, bits);
                break;

        case TIOCMSET:
                ch->ch_oports = bits;
                break;
        }

        if (!ch->ch_heldchange) {
                if (ch->ch_tx_busy) {
                        ch->ch_heldtbc = ch->ch_tbc;
                        ch->ch_tbc = 0;
                        ch->ch_heldchange = 1;
                } else
                        sbscn_loadchannelregs(ch);
        }
}

int
sbscn_to_tiocm(struct sbscn_channel *ch)
{
        u_char hwbits;
        int ttybits = 0;

        hwbits = ch->ch_oports;
        if (ISSET(hwbits, ch->ch_o_dtr))
                SET(ttybits, TIOCM_DTR);
        if (ISSET(hwbits, ch->ch_o_rts))
                SET(ttybits, TIOCM_RTS);

        hwbits = ch->ch_iports;
        if (ISSET(hwbits, ch->ch_i_dcd))
                SET(ttybits, TIOCM_CD);
        if (ISSET(hwbits, ch->ch_i_cts))
                SET(ttybits, TIOCM_CTS);
        if (ISSET(hwbits, ch->ch_i_dsr))
                SET(ttybits, TIOCM_DSR);
        if (ISSET(hwbits, ch->ch_i_ri))
                SET(ttybits, TIOCM_RI);

        if (ch->ch_imr != 0)
                SET(ttybits, TIOCM_LE);

        return (ttybits);
}

static int
cflag2modes(tcflag_t cflag, u_char *mode1p, u_char *mode2p)
{
        u_char mode1;
        u_char mode2;
        int err = 0;

        mode1 = mode2 = 0;

        switch (ISSET(cflag, CSIZE)) {
        case CS7:
                mode1 |= 2;                     /* XXX */
                break;
        default:
                err = -1;
                /* FALLTHRU for sanity */
        case CS8:
                mode1 |= 3;                     /* XXX */
                break;
        }
        if (!ISSET(cflag, PARENB))
                mode1 |= 2 << 3;
        else {
                mode1 |= 0 << 3;
                if (ISSET(cflag, PARODD))
                        mode1 |= 1 << 2;
        }

        if (ISSET(cflag, CSTOPB))
                mode2 |= 1 << 3;                /* two stop bits XXX not std */

        if (ISSET(cflag, CRTSCTS)) {
                mode1 |= 1 << 7;
                mode2 |= 1 << 4;
        }

        *mode1p = mode1;
        *mode2p = mode2;
        return (err);
}

int
sbscn_param(struct tty *tp, struct termios *t)
{
        struct sbscn_softc *sc = device_lookup_private(&sbscn_cd, SBSCN_UNIT(tp->t_dev));
        struct sbscn_channel *ch = &sc->sc_channels[SBSCN_CHAN(tp->t_dev)];
        long brc;
        u_char mode1, mode2;
        int s;

/* XXX reset to console parameters if console? */
#if 0
XXX disable, enable.
#endif

        /* Check requested parameters. */
        if (sbscn_speed(t->c_ospeed, &brc) < 0)
                return (EINVAL);
        if (t->c_ispeed && t->c_ispeed != t->c_ospeed)
                return (EINVAL);

        /*
         * For the console, always force CLOCAL and !HUPCL, so that the port
         * is always active.
         */
        if (ISSET(ch->ch_swflags, TIOCFLAG_SOFTCAR) ||
            ISSET(ch->ch_hwflags, SBSCN_HW_CONSOLE)) {
                SET(t->c_cflag, CLOCAL);
                CLR(t->c_cflag, HUPCL);
        }

        /*
         * If there were no changes, don't do anything.  This avoids dropping
         * input and improves performance when all we did was frob things like
         * VMIN and VTIME.
         */
        if (tp->t_ospeed == t->c_ospeed &&
            tp->t_cflag == t->c_cflag)
                return (0);

        if (cflag2modes(t->c_cflag, &mode1, &mode2) < 0)
                return (EINVAL);

        s = splserial();

        ch->ch_mode1 = mode1;
        ch->ch_mode2 = mode2;

        /*
         * If we're not in a mode that assumes a connection is present, then
         * ignore carrier changes.
         */
        if (ISSET(t->c_cflag, CLOCAL | MDMBUF))
                ch->ch_i_dcd = 0;
        else
                ch->ch_i_dcd = ch->ch_i_dcd_pin;
        /*
         * Set the flow control pins depending on the current flow control
         * mode.
         */
        if (ISSET(t->c_cflag, CRTSCTS)) {
                ch->ch_o_dtr = ch->ch_o_dtr_pin;
                ch->ch_o_rts = ch->ch_o_rts_pin;
                ch->ch_i_cts = ch->ch_i_cts_pin;
                /* hw controle enable bits in mod regs set by cflag2modes */
        } else if (ISSET(t->c_cflag, MDMBUF)) {
                /*
                 * For DTR/DCD flow control, make sure we don't toggle DTR for
                 * carrier detection.
                 */
                ch->ch_o_dtr = 0;
                ch->ch_o_rts = ch->ch_o_dtr_pin;
                ch->ch_i_cts = ch->ch_i_dcd_pin;
        } else {
                /*
                 * If no flow control, then always set RTS.  This will make
                 * the other side happy if it mistakenly thinks we're doing
                 * RTS/CTS flow control.
                 */
                ch->ch_o_dtr = ch->ch_o_dtr_pin | ch->ch_o_rts_pin;
                ch->ch_o_rts = 0;
                ch->ch_i_cts = 0;
                if (ISSET(ch->ch_oports, ch->ch_o_dtr_pin))
                        SET(ch->ch_oports, ch->ch_o_rts_pin);
                else
                        CLR(ch->ch_oports, ch->ch_o_rts_pin);
        }
        /* XXX maybe mask the ports which generate intrs? */

        ch->ch_brc = brc;

        /* XXX maybe set fifo-full receive mode if RTSCTS and high speed? */

        /* And copy to tty. */
        tp->t_ispeed = 0;
        tp->t_ospeed = t->c_ospeed;
        tp->t_cflag = t->c_cflag;

        if (!ch->ch_heldchange) {
                if (ch->ch_tx_busy) {
                        ch->ch_heldtbc = ch->ch_tbc;
                        ch->ch_tbc = 0;
                        ch->ch_heldchange = 1;
                } else
                        sbscn_loadchannelregs(ch);
        }

        if (!ISSET(t->c_cflag, CHWFLOW)) {
                /* Disable the high water mark. */
                ch->ch_r_hiwat = 0;
                ch->ch_r_lowat = 0;
                if (ISSET(ch->ch_rx_flags, RX_TTY_OVERFLOWED)) {
                        CLR(ch->ch_rx_flags, RX_TTY_OVERFLOWED);
                        sbscn_schedrx(ch);
                }
                if (ISSET(ch->ch_rx_flags, RX_TTY_BLOCKED|RX_IBUF_BLOCKED)) {
                        CLR(ch->ch_rx_flags, RX_TTY_BLOCKED|RX_IBUF_BLOCKED);
                        sbscn_dohwiflow(ch);
                }
        } else {
                ch->ch_r_hiwat = sbscn_rbuf_hiwat;
                ch->ch_r_lowat = sbscn_rbuf_lowat;
        }

        splx(s);

        /*
         * Update the tty layer's idea of the carrier bit, in case we changed
         * CLOCAL or MDMBUF.  We don't hang up here; we only do that by
         * explicit request.
         */
        (void) (*tp->t_linesw->l_modem)(tp,
            ISSET(ch->ch_iports, ch->ch_i_dcd));

#ifdef SBSCN_DEBUG
        if (sbscn_debug)
                sbscn_status(ch, "sbscnparam ");
#endif

        if (!ISSET(t->c_cflag, CHWFLOW)) {
                if (ch->ch_tx_stopped) {
                        ch->ch_tx_stopped = 0;
                        sbscn_start(tp);
                }
        }

        return (0);
}

void
sbscn_iflush(struct sbscn_channel *ch)
{
#ifdef DIAGNOSTIC
        int reg;
#endif
        int timo;

#ifdef DIAGNOSTIC
        reg = 0xffff;
#endif
        timo = 50000;
        /* flush any pending I/O */
        while (ISSET(READ_REG(ch->ch_base + 0x20), 0x01)
            && --timo)
#ifdef DIAGNOSTIC
                reg =
#else
                    (void)
#endif
                    READ_REG(ch->ch_base + 0x60);
#ifdef DIAGNOSTIC
        if (!timo)
                aprint_debug_dev(ch->ch_sc->sc_dev,
                    "sbscn_iflush timeout %02x\n", reg & 0xff);
#endif
}

void
sbscn_loadchannelregs(struct sbscn_channel *ch)
{

        /* XXXXX necessary? */
        sbscn_iflush(ch);

        WRITE_REG(ch->ch_imr_base, 0);

// XXX disable?
        WRITE_REG(ch->ch_base + 0x00, ch->ch_mode1);
        WRITE_REG(ch->ch_base + 0x10, ch->ch_mode2);
        WRITE_REG(ch->ch_base + 0x30, ch->ch_brc);

        ch->ch_oports_active = ch->ch_oports;
        SET_OUTPUT_SIGNALS(ch, ch->ch_oports_active);

        WRITE_REG(ch->ch_imr_base, ch->ch_imr);
}

int
sbscn_hwiflow(struct tty *tp, int block)
{
        struct sbscn_softc *sc = device_lookup_private(&sbscn_cd, SBSCN_UNIT(tp->t_dev));
        struct sbscn_channel *ch = &sc->sc_channels[SBSCN_CHAN(tp->t_dev)];
        int s;

        if (ch->ch_o_rts == 0)
                return (0);

        s = splserial();
        if (block) {
                if (!ISSET(ch->ch_rx_flags, RX_TTY_BLOCKED)) {
                        SET(ch->ch_rx_flags, RX_TTY_BLOCKED);
                        sbscn_dohwiflow(ch);
                }
        } else {
                if (ISSET(ch->ch_rx_flags, RX_TTY_OVERFLOWED)) {
                        CLR(ch->ch_rx_flags, RX_TTY_OVERFLOWED);
                        sbscn_schedrx(ch);
                }
                if (ISSET(ch->ch_rx_flags, RX_TTY_BLOCKED)) {
                        CLR(ch->ch_rx_flags, RX_TTY_BLOCKED);
                        sbscn_dohwiflow(ch);
                }
        }
        splx(s);
        return (1);
}

/*
 * (un)block input via hw flowcontrol
 */
void
sbscn_dohwiflow(struct sbscn_channel *ch)
{

        if (ch->ch_o_rts == 0)
                return;

        if (ISSET(ch->ch_rx_flags, RX_ANY_BLOCK)) {
                CLR(ch->ch_oports, ch->ch_o_rts);
                CLR(ch->ch_oports_active, ch->ch_o_rts);
        } else {
                SET(ch->ch_oports, ch->ch_o_rts);
                SET(ch->ch_oports_active, ch->ch_o_rts);
        }
        SET_OUTPUT_SIGNALS(ch, ch->ch_oports_active);
}

void
sbscn_start(struct tty *tp)
{
        struct sbscn_softc *sc = device_lookup_private(&sbscn_cd, SBSCN_UNIT(tp->t_dev));
        struct sbscn_channel *ch = &sc->sc_channels[SBSCN_CHAN(tp->t_dev)];
        int s;

        s = spltty();
        if (ISSET(tp->t_state, TS_BUSY | TS_TIMEOUT | TS_TTSTOP))
                goto out;
        if (ch->ch_tx_stopped)
                goto out;
        if (!ttypull(tp))
                goto out;

        /* Grab the first contiguous region of buffer space. */
        {
                u_char *tba;
                int tbc;

                tba = tp->t_outq.c_cf;
                tbc = ndqb(&tp->t_outq, 0);

                (void)splserial();

                ch->ch_tba = tba;
                ch->ch_tbc = tbc;
        }

        SET(tp->t_state, TS_BUSY);
        ch->ch_tx_busy = 1;

        /* Enable transmit completion interrupts if necessary. */
        if (!ISSET(ch->ch_imr, 0x1)) {
                SET(ch->ch_imr, 0x1);
                WRITE_REG(ch->ch_imr_base, ch->ch_imr);
        }

        /* Output the first chunk of the contiguous buffer. */
        {
                u_char c;

                while (ch->ch_tbc && READ_REG(ch->ch_base + 0x20) & 0x04) {
                        c = *ch->ch_tba++;
                        ch->ch_tbc--;
                        WRITE_REG(ch->ch_base + 0x70, c);
                }
        }
out:
        splx(s);
        return;
}

/*
 * Stop output on a line.
 */
void
sbscnstop(struct tty *tp, int flag)
{
        struct sbscn_softc *sc = device_lookup_private(&sbscn_cd, SBSCN_UNIT(tp->t_dev));
        struct sbscn_channel *ch = &sc->sc_channels[SBSCN_CHAN(tp->t_dev)];
        int s;

        s = splserial();
        if (ISSET(tp->t_state, TS_BUSY)) {
                /* Stop transmitting at the next chunk. */
                ch->ch_tbc = 0;
                ch->ch_heldtbc = 0;
                if (!ISSET(tp->t_state, TS_TTSTOP))
                        SET(tp->t_state, TS_FLUSH);
        }
        splx(s);
}

void
sbscn_diag(void *arg)
{
        struct sbscn_channel *ch = arg;
        struct sbscn_softc *sc = ch->ch_sc;
        int overflows, floods;
        int s;

        s = splserial();
        overflows = ch->ch_overflows;
        ch->ch_overflows = 0;
        floods = ch->ch_floods;
        ch->ch_floods = 0;
        ch->ch_errors = 0;
        splx(s);

        log(LOG_WARNING, "%s: channel %d: %d fifo overflow%s, %d ibuf flood%s\n",
            device_xname(sc->sc_dev), ch->ch_num,
            overflows, overflows == 1 ? "" : "s",
            floods, floods == 1 ? "" : "s");
}

integrate void
sbscn_rxsoft(struct sbscn_channel *ch, struct tty *tp)
{
        int (*rint)(int, struct tty *) = tp->t_linesw->l_rint;
        u_char *get, *end;
        u_int cc, scc;
        u_char sr;
        int code;
        int s;

        end = ch->ch_ebuf;
        get = ch->ch_rbget;
        scc = cc = sbscn_rbuf_size - ch->ch_rbavail;

        if (cc == sbscn_rbuf_size) {
                ch->ch_floods++;
                if (ch->ch_errors++ == 0)
                        callout_reset(&ch->ch_diag_callout, 60 * hz,
                            sbscn_diag, ch);
        }

        while (cc) {
                code = get[0];
                sr = get[1];
                if (ISSET(sr, 0xf0)) {
                        if (ISSET(sr, 0x10)) {
                                ch->ch_overflows++;
                                if (ch->ch_errors++ == 0)
                                        callout_reset(&ch->ch_diag_callout,
                                            60 * hz, sbscn_diag, ch);
                        }
                        if (ISSET(sr, 0xc0))
                                SET(code, TTY_FE);
                        if (ISSET(sr, 0x20))
                                SET(code, TTY_PE);
                }
                if ((*rint)(code, tp) == -1) {
                        /*
                         * The line discipline's buffer is out of space.
                         */
                        if (!ISSET(ch->ch_rx_flags, RX_TTY_BLOCKED)) {
                                /*
                                 * We're either not using flow control, or the
                                 * line discipline didn't tell us to block for
                                 * some reason.  Either way, we have no way to
                                 * know when there's more space available, so
                                 * just drop the rest of the data.
                                 */
                                get += cc << 1;
                                if (get >= end)
                                        get -= sbscn_rbuf_size << 1;
                                cc = 0;
                        } else {
                                /*
                                 * Don't schedule any more receive processing
                                 * until the line discipline tells us there's
                                 * space available (through comhwiflow()).
                                 * Leave the rest of the data in the input
                                 * buffer.
                                 */
                                SET(ch->ch_rx_flags, RX_TTY_OVERFLOWED);
                        }
                        break;
                }
                get += 2;
                if (get >= end)
                        get = ch->ch_rbuf;
                cc--;
        }

        if (cc != scc) {
                ch->ch_rbget = get;
                s = splserial();
                cc = ch->ch_rbavail += scc - cc;
                /* Buffers should be ok again, release possible block. */
                if (cc >= ch->ch_r_lowat) {
                        if (ISSET(ch->ch_rx_flags, RX_IBUF_OVERFLOWED)) {
                                CLR(ch->ch_rx_flags, RX_IBUF_OVERFLOWED);
                                SET(ch->ch_imr, 0x02);
                                WRITE_REG(ch->ch_imr_base, ch->ch_imr);
                        }
                        if (ISSET(ch->ch_rx_flags, RX_IBUF_BLOCKED)) {
                                CLR(ch->ch_rx_flags, RX_IBUF_BLOCKED);
                                sbscn_dohwiflow(ch);
                        }
                }
                splx(s);
        }
}

integrate void
sbscn_txsoft(struct sbscn_channel *ch, struct tty *tp)
{

        CLR(tp->t_state, TS_BUSY);
        if (ISSET(tp->t_state, TS_FLUSH))
                CLR(tp->t_state, TS_FLUSH);
        else
                ndflush(&tp->t_outq, (int)(ch->ch_tba - tp->t_outq.c_cf));
        (*tp->t_linesw->l_start)(tp);
}

integrate void
sbscn_stsoft(struct sbscn_channel *ch, struct tty *tp)
{
        u_char iports, delta;
        int s;

        s = splserial();
        iports = ch->ch_iports;
        delta = ch->ch_iports_delta;
        ch->ch_iports_delta = 0;
        splx(s);

        if (ISSET(delta, ch->ch_i_dcd)) {
                /*
                 * Inform the tty layer that carrier detect changed.
                 */
                (void) (*tp->t_linesw->l_modem)(tp,
                    ISSET(iports, ch->ch_i_dcd));
        }

        if (ISSET(delta, ch->ch_i_cts)) {
                /* Block or unblock output according to flow control. */
                if (ISSET(iports, ch->ch_i_cts)) {
                        ch->ch_tx_stopped = 0;
                        (*tp->t_linesw->l_start)(tp);
                } else {
                        ch->ch_tx_stopped = 1;
                }
        }

#ifdef SBSCN_DEBUG
        if (sbscn_debug)
                sbscn_status(ch, "sbscn_stsoft");
#endif
}

void
sbscn_soft(void *arg)
{
        struct sbscn_channel *ch = arg;
        struct tty *tp = ch->ch_tty;

        if (ch->ch_rx_ready) {
                ch->ch_rx_ready = 0;
                sbscn_rxsoft(ch, tp);
        }

        if (ch->ch_st_check) {
                ch->ch_st_check = 0;
                sbscn_stsoft(ch, tp);
        }

        if (ch->ch_tx_done) {
                ch->ch_tx_done = 0;
                sbscn_txsoft(ch, tp);
        }
}

void
sbscn_intr(void *arg, uint32_t status, vaddr_t pc)
{
        struct sbscn_channel *ch = arg;
        u_char *put, *end;
        u_int cc;
        u_char isr, sr;

        /* read ISR */
        isr = READ_REG(ch->ch_isr_base) & ch->ch_imr;
        if (isr == 0)
                return;

        end = ch->ch_ebuf;
        put = ch->ch_rbput;
        cc = ch->ch_rbavail;

        do {
                u_char  iports, delta;

                if (isr & 0x02) {

                        sr = READ_REG(ch->ch_base + 0x20);
                        /* XXX sr 0x01 bit must be set at this point */

#if defined(DDB) || defined(KGDB)
                        if ((sr & 0x80) == 0x80) {
#ifdef DDB
                                if (ISSET(ch->ch_hwflags, SBSCN_HW_CONSOLE)) {
                                        (void)READ_REG(ch->ch_base + 0x60);
                                        console_debugger();
                                        continue;
                                }
#endif
#ifdef KGDB
                                if (ISSET(ch->ch_hwflags, SBSCN_HW_KGDB)) {
                                        (void)READ_REG(ch->ch_base + 0x60);
                                        kgdb_connect(1);
                                        continue;
                                }
#endif
                        }
#endif /* DDB || KGDB */

                        if (!ISSET(ch->ch_rx_flags, RX_IBUF_OVERFLOWED)) {
                                while (cc > 0) {
                                        put[0] = READ_REG(ch->ch_base + 0x60);
                                        put[1] = sr;
                                        put += 2;
                                        if (put >= end)
                                                put = ch->ch_rbuf;
                                        cc--;

                                        sr = READ_REG(ch->ch_base + 0x20);
                                        if (!ISSET(sr, 0x02))
                                                break;
                                }

                                /*
                                 * Current string of incoming characters ended
                                 * because no more data was available or we
                                 * ran out of space.  Schedule a receive event
                                 * if any data was received.  If we're out of
                                 * space, turn off receive interrupts.
                                 */
                                ch->ch_rbput = put;
                                ch->ch_rbavail = cc;
                                if (!ISSET(ch->ch_rx_flags, RX_TTY_OVERFLOWED))
                                        ch->ch_rx_ready = 1;

                                /*
                                 * See if we are in danger of overflowing a
                                 * buffer. If so, use hardware flow control
                                 * to ease the pressure.
                                 */
                                if (!ISSET(ch->ch_rx_flags, RX_IBUF_BLOCKED) &&
                                    cc < ch->ch_r_hiwat) {
                                        SET(ch->ch_rx_flags, RX_IBUF_BLOCKED);
                                        sbscn_dohwiflow(ch);
                                }

                                /*
                                 * If we're out of space, disable receive
                                 * interrupts until the queue has drained
                                 * a bit.
                                 */
                                if (!cc) {
                                        SET(ch->ch_rx_flags,
                                            RX_IBUF_OVERFLOWED);
                                        CLR(ch->ch_imr, 0x02);
                                        WRITE_REG(ch->ch_imr_base, ch->ch_imr);
                                }
                        } else {
                                /* XXX panic? */
                                CLR(ch->ch_imr, 0x02);
                                WRITE_REG(ch->ch_imr_base, ch->ch_imr);
                                continue;
                        }
                }

                if (isr & 0x01) {
                        CLR(ch->ch_imr, 0x01);
                        WRITE_REG(ch->ch_imr_base, ch->ch_imr);
                }

#if 0
XXX
                if (isr & 0x08) {
                        clear input signal change!
                }
#endif
                iports = GET_INPUT_SIGNALS(ch);
                delta = iports ^ ch->ch_iports;
                ch->ch_iports = iports;

                /*
                 * Process normal status changes
                 */
                if (ISSET(delta, ch->ch_i_mask)) {
                        SET(ch->ch_iports_delta, delta);

                        /*
                         * Stop output immediately if we lose the output
                         * flow control signal or carrier detect.
                         */
                        if (ISSET(~iports, ch->ch_i_mask)) {
                                ch->ch_tbc = 0;
                                ch->ch_heldtbc = 0;
#ifdef SBSCN_DEBUG
                                if (sbscn_debug)
                                        sbscn_status(ch, "sbscn_intr  ");
#endif
                        }

                        ch->ch_st_check = 1;
                }
        } while ((isr = (READ_REG(ch->ch_isr_base) & ch->ch_imr)) != 0);

        /*
         * Done handling any receive interrupts and status changes, and
         * clearing the tx-ready interrupt if it was set.  See if data can
         * be transmitted as well. Schedule tx done event if no data left
         * and tty was marked busy.
         */
        sr = READ_REG(ch->ch_base + 0x20);
        if (ISSET(sr, 0x4)) {

                /*
                 * If we've delayed a parameter change, do it now, and restart
                 * output.
                 */
                if (ch->ch_heldchange) {
                        sbscn_loadchannelregs(ch);
                        ch->ch_heldchange = 0;
                        ch->ch_tbc = ch->ch_heldtbc;
                        ch->ch_heldtbc = 0;
                }

                /* Output the next chunk of the contiguous buffer, if any. */
                if (ch->ch_tbc > 0) {
                        int wrote1;
                        u_char c;

                        wrote1 = 0;
                        while (ch->ch_tbc &&
                            READ_REG(ch->ch_base + 0x20) & 0x04) {
                                wrote1 = 1;
                                c = *ch->ch_tba++;
                                ch->ch_tbc--;
                                WRITE_REG(ch->ch_base + 0x70, c);
                        }
                        if (wrote1) {
                                SET(ch->ch_imr, 0x01);
                                WRITE_REG(ch->ch_imr_base, ch->ch_imr);
                        }
                } else {
                        /*
                         * transmit completion interrupts already disabled,
                         * mark the channel tx state as done.
                         */
                        if (ch->ch_tx_busy) {
                                ch->ch_tx_busy = 0;
                                ch->ch_tx_done = 1;
                        }
                }
        }

        /* Wake up the poller. */
        softint_schedule(ch->ch_si);

#ifdef RND_SBSCN
        rnd_add_uint32(&ch->ch_rnd_source, isr | sr);
#endif
}

/*
 * The following functions are polled getc and putc routines, shared
 * by the console and kgdb glue.
 */

int
sbscn_common_getc(u_long addr, int chan)
{
        int s = splhigh();
        u_long base = MIPS_PHYS_TO_KSEG1(addr + (chan * 0x100));
        int c;

        /* block until a character becomes available */
        while ((READ_REG(base + 0x20) & 0x01) == 0)
                continue;

        c = READ_REG(base + 0x60) & 0xff;
        splx(s);
        return (c);
}

void
sbscn_common_putc(u_long addr, int chan, int c)
{
        int s = splhigh();
        int timo;
        u_long base = MIPS_PHYS_TO_KSEG1(addr + (chan * 0x100));

        /* wait for any pending transmission to finish */
        timo = 1500000;
        while ((READ_REG(base + 0x20) & 0x08) == 0 && --timo)
                continue;

        WRITE_REG(base + 0x70, c);

        /* wait for this transmission to complete */
        timo = 15000000;
        while ((READ_REG(base + 0x20) & 0x08) == 0 && --timo)
                continue;

        splx(s);
}

/*
 * Initialize UART for use as console or KGDB line.
 */
int
sbscn_init(u_long addr, int chan, int rate, tcflag_t cflag)
{
#if 1
        u_long chanregbase = MIPS_PHYS_TO_KSEG1(addr + (chan * 0x100));
        u_long imaskreg = MIPS_PHYS_TO_KSEG1(addr + 0x230 + (chan * 0x20));
        u_char mode1, mode2;
        u_long brc;
        volatile int timo;

        WRITE_REG(imaskreg, 0);                 /* disable channel intrs */

        /* XXX should we really do the following?  how about only if enabled? */
        /* wait for any pending transmission to finish */
        timo = 1500000;
        while ((READ_REG(chanregbase + 0x20) & 0x08) == 0 && --timo)
                continue;

        /* XXX: wait a little.  THIS SHOULD NOT BE NECESSARY!!! (?) */
        timo = 1500000;
        while (--timo)
                ;

        WRITE_REG(chanregbase + 0x50, 2 << 4);  /* reset receiver */
        WRITE_REG(chanregbase + 0x50, 3 << 4);  /* reset transmitter */

        /* set up the line for use */
        (void)cflag2modes(cflag, &mode1, &mode2);
        (void)sbscn_speed(rate, &brc);
        WRITE_REG(chanregbase + 0x00, mode1);
        WRITE_REG(chanregbase + 0x10, mode2);
        WRITE_REG(chanregbase + 0x30, brc);

        /* enable transmit and receive */
#define M_DUART_RX_EN                   0x01
#define M_DUART_TX_EN                   0x04
        WRITE_REG(chanregbase + 0x50,M_DUART_RX_EN | M_DUART_TX_EN);
#endif

        /* XXX: wait a little.  THIS SHOULD NOT BE NECESSARY!!! (?) */
        timo = 1500000;
        while (--timo)
                ;

#if 0 /* XXXCGD */
        bus_space_handle_t ioh;

        if (bus_space_map(iot, iobase, COM_NPORTS, 0, &ioh))
                return (ENOMEM); /* ??? */

        bus_space_write_1(iot, ioh, com_lcr, LCR_EERS);
        bus_space_write_1(iot, ioh, com_efr, 0);
        bus_space_write_1(iot, ioh, com_lcr, LCR_DLAB);
        rate = comspeed(rate, frequency);
        bus_space_write_1(iot, ioh, com_dlbl, rate);
        bus_space_write_1(iot, ioh, com_dlbh, rate >> 8);
        bus_space_write_1(iot, ioh, com_lcr, cflag2lcr(cflag));
        bus_space_write_1(iot, ioh, com_mcr, MCR_DTR | MCR_RTS);
        bus_space_write_1(iot, ioh, com_fifo,
            FIFO_ENABLE | FIFO_RCV_RST | FIFO_XMT_RST | FIFO_TRIGGER_1);
        bus_space_write_1(iot, ioh, com_ier, 0);

        *iohp = ioh;
        return (0);
#endif /* XXXCGD */
        /* XXXCGD */
        return (0);
}

/*
 * Following are all routines needed for sbscn to act as console
 */
int
sbscn_cnattach(u_long addr, int chan, int rate, tcflag_t cflag)
{
        int res;
        static struct consdev sbscn_cons = {
                NULL, NULL, sbscn_cngetc, sbscn_cnputc, sbscn_cnpollc, NULL,
                    NULL, NULL, NODEV, CN_NORMAL
        };

        res = sbscn_init(addr, chan, rate, cflag);
        if (res)
                return (res);

        cn_tab = &sbscn_cons;

        sbscn_cons_present = 1;
        sbscn_cons_addr = addr;
        sbscn_cons_chan = chan;
        sbscn_cons_rate = rate;
        sbscn_cons_cflag = cflag;

        return (0);
}

int
sbscn_cngetc(dev_t dev)
{

        return (sbscn_common_getc(sbscn_cons_addr, sbscn_cons_chan));
}

/*
 * Console kernel output character routine.
 */
void
sbscn_cnputc(dev_t dev, int c)
{

        sbscn_common_putc(sbscn_cons_addr, sbscn_cons_chan, c);
}

void
sbscn_cnpollc(dev_t dev, int on)
{

}

#ifdef KGDB
int
sbscn_kgdb_attach(u_long addr, int chan, int rate, tcflag_t cflag)
{
        int res;

        if (!sbscn_cons_present &&
            sbscn_cons_addr == addr && sbscn_cons_chan == chan)
                return (EBUSY); /* cannot share with console */

        res = sbscn_init(addr, chan, rate, cflag);
        if (res)
                return (res);

        kgdb_attach(sbscn_kgdb_getc, sbscn_kgdb_putc, NULL);
        kgdb_dev = 123; /* unneeded, only to satisfy some tests */

        sbscn_kgdb_present = 1;
        sbscn_kgdb_addr = addr;
        sbscn_kgdb_chan = chan;

        return (0);
}

/* ARGSUSED */
int
sbscn_kgdb_getc(void *arg)
{

        return (sbscn_common_getc(sbscn_kgdb_addr, sbscn_kgdb_chan));
}

/* ARGSUSED */
void
sbscn_kgdb_putc(void *arg, int c)
{

        sbscn_common_getc(sbscn_kgdb_addr, sbscn_kgdb_chan, c);
}
#endif /* KGDB */

/*
 * helper function to identify the sbscn channels used by
 * console or KGDB (and not yet autoconf attached)
 */
int
sbscn_is_console(u_long addr, int chan)
{

        if (sbscn_cons_present && !sbscn_cons_attached &&
            sbscn_cons_addr == addr && sbscn_cons_chan == chan)
                return (1);
#ifdef KGDB
        if (sbscn_kgdb_present && !sbscn_kgdb_attached &&
            sbscn_kgdb_addr == addr && sbscn_kgdb_chan == chan)
                return (1);
#endif
        return (0);
}