/*      $Id: at91dbgu.c,v 1.19 2022/10/26 23:38:06 riastradh Exp $      */
/*      $NetBSD: at91dbgu.c,v 1.19 2022/10/26 23:38:06 riastradh Exp $ */

/*
 *
 * Copyright (c) 1998, 1999, 2001, 2002, 2004 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jesse Off
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Ichiro FUKUHARA and Naoto Shimazaki.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by IWAMOTO Toshihiro.
 *
 * 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
 */

/*
 * TODO: hardware flow control
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: at91dbgu.c,v 1.19 2022/10/26 23:38:06 riastradh Exp $");

#include "opt_kgdb.h"

#include "rnd.h"
#ifdef RND_COM
#include <sys/rndsource.h>
#endif

/*
 * Override cnmagic(9) macro before including <sys/systm.h>.
 * We need to know if cn_check_magic triggered debugger, so set a flag.
 * Callers of cn_check_magic must declare int cn_trapped = 0;
 * XXX: this is *ugly*!
 */
#define cn_trap()                               \
        do {                                    \
                console_debugger();             \
                cn_trapped = 1;                 \
        } while (/* CONSTCOND */ 0)

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/types.h>
#include <sys/conf.h>
#include <sys/file.h>
#include <sys/device.h>
#include <sys/kernel.h>
#include <sys/kmem.h>
#include <sys/tty.h>
#include <sys/uio.h>
#include <sys/vnode.h>
#include <sys/kauth.h>

#include <machine/intr.h>
#include <sys/bus.h>

#include <ddb/db_active.h>

#include <arm/at91/at91reg.h>
#include <arm/at91/at91var.h>
#include <arm/at91/at91dbguvar.h>
#include <arm/at91/at91dbgureg.h>

#include <dev/cons.h>

static int      at91dbgu_match(device_t, cfdata_t, void *);
static void     at91dbgu_attach(device_t, device_t, void *);

static int      at91dbgu_param(struct tty *, struct termios *);
static void     at91dbgu_start(struct tty *);
static int      at91dbgu_hwiflow(struct tty *, int);

#if 0
static u_int    cflag2lcrhi(tcflag_t);
#endif
static void     at91dbgu_iflush(struct at91dbgu_softc *);
static void     at91dbgu_set(struct at91dbgu_softc *);

int             at91dbgu_cn_getc(dev_t);
void            at91dbgu_cn_putc(dev_t, int);
void            at91dbgu_cn_pollc(dev_t, int);

static void     at91dbgu_soft(void* arg);
inline static void      at91dbgu_txsoft(struct at91dbgu_softc *, struct tty *);
inline static void      at91dbgu_rxsoft(struct at91dbgu_softc *, struct tty *);

void            at91dbgu_cn_probe(struct consdev *);
void            at91dbgu_cn_init(struct consdev *);

static struct at91dbgu_cons_softc {
        bus_space_tag_t         sc_iot;
        bus_space_handle_t      sc_ioh;
        bus_addr_t              sc_hwbase;
        int                     sc_ospeed;
        tcflag_t                sc_cflag;
        int                     sc_attached;

        uint8_t                 *sc_rx_ptr;
        uint8_t                 sc_rx_fifo[64];
} dbgu_cn_sc;

static struct cnm_state at91dbgu_cnm_state;

CFATTACH_DECL_NEW(at91dbgu, sizeof(struct at91dbgu_softc),
              at91dbgu_match, at91dbgu_attach, NULL, NULL);

extern struct cfdriver at91dbgu_cd;

dev_type_open(at91dbgu_open);
dev_type_close(at91dbgu_close);
dev_type_read(at91dbgu_read);
dev_type_write(at91dbgu_write);
dev_type_ioctl(at91dbgu_ioctl);
dev_type_stop(at91dbgu_stop);
dev_type_tty(at91dbgu_tty);
dev_type_poll(at91dbgu_poll);

const struct cdevsw at91dbgu_cdevsw = {
        .d_open = at91dbgu_open,
        .d_close = at91dbgu_close,
        .d_read = at91dbgu_read,
        .d_write = at91dbgu_write,
        .d_ioctl = at91dbgu_ioctl,
        .d_stop = at91dbgu_stop,
        .d_tty = at91dbgu_tty,
        .d_poll = at91dbgu_poll,
        .d_mmap = nommap,
        .d_kqfilter = ttykqfilter,
        .d_discard = nodiscard,
        .d_flag = D_TTY
};

struct consdev at91dbgu_cons = {
        at91dbgu_cn_probe, NULL, at91dbgu_cn_getc, at91dbgu_cn_putc, at91dbgu_cn_pollc, NULL,
        NULL, NULL, NODEV, CN_REMOTE
};

#ifndef DEFAULT_COMSPEED
#define DEFAULT_COMSPEED 115200
#endif

#define COMUNIT(x)      TTUNIT(x)
#define COMDIALOUT(x)   TTDIALOUT(x)

#define COM_ISALIVE(sc) ((sc)->enabled != 0 && device_is_active((sc)->sc_dev))

static int
at91dbgu_match(device_t parent, cfdata_t match, void *aux)
{
        if (strcmp(match->cf_name, "at91dbgu") == 0)
                return 2;
        return 0;
}

static int
dbgu_intr(void* arg);

static void
at91dbgu_attach(device_t parent, device_t self, void *aux)
{
        struct at91dbgu_softc *sc = device_private(self);
        struct at91bus_attach_args *sa = aux;
        struct tty *tp;

        printf("\n");

        sc->sc_dev = self;
        bus_space_map(sa->sa_iot, sa->sa_addr, sa->sa_size, 0, &sc->sc_ioh);
        sc->sc_iot = sa->sa_iot;
        sc->sc_hwbase = sa->sa_addr;

        DBGUREG(DBGU_IDR) = -1;
        at91_intr_establish(sa->sa_pid, IPL_SERIAL, INTR_HIGH_LEVEL, dbgu_intr, sc);
        DBGU_INIT(AT91_MSTCLK, 115200U);

        if (sc->sc_iot == dbgu_cn_sc.sc_iot
            && sc->sc_hwbase == dbgu_cn_sc.sc_hwbase) {
                dbgu_cn_sc.sc_attached = 1;
                /* Make sure the console is always "hardwired". */
                delay(10000);   /* wait for output to finish */
                SET(sc->sc_hwflags, COM_HW_CONSOLE);
                SET(sc->sc_swflags, TIOCFLAG_SOFTCAR);
                SET(sc->sc_ier, DBGU_INT_RXRDY);
                DBGUREG(DBGU_IER) = DBGU_INT_RXRDY; // @@@@@
        }

        tp = tty_alloc();
        tp->t_oproc = at91dbgu_start;
        tp->t_param = at91dbgu_param;
        tp->t_hwiflow = at91dbgu_hwiflow;

        sc->sc_tty = tp;
        sc->sc_rbuf = kmem_alloc(AT91DBGU_RING_SIZE << 1, KM_SLEEP);
        sc->sc_rbput = sc->sc_rbget = sc->sc_rbuf;
        sc->sc_rbavail = AT91DBGU_RING_SIZE;
        sc->sc_ebuf = sc->sc_rbuf + (AT91DBGU_RING_SIZE << 1);
        sc->sc_tbc = 0;

        tty_attach(tp);

        if (ISSET(sc->sc_hwflags, COM_HW_CONSOLE)) {
                int maj;

                /* locate the major number */
                maj = cdevsw_lookup_major(&at91dbgu_cdevsw);

                cn_tab->cn_dev = makedev(maj, device_unit(sc->sc_dev));

                aprint_normal("%s: console (maj %u min %u cn_dev %#"PRIx64")\n",
                    device_xname(sc->sc_dev), maj, device_unit(sc->sc_dev),
                    cn_tab->cn_dev);
        }

        sc->sc_si = softint_establish(SOFTINT_SERIAL, at91dbgu_soft, sc);

#ifdef RND_COM
        rnd_attach_source(&sc->rnd_source, device_xname(sc->sc_dev),
                          RND_TYPE_TTY, RND_FLAG_DEFAULT);
#endif

        /* if there are no enable/disable functions, assume the device
           is always enabled */
        if (!sc->enable)
                sc->enabled = 1;

        /* XXX configure register */
        /* xxx_config(sc) */

        SET(sc->sc_hwflags, COM_HW_DEV_OK);
}

static int
at91dbgu_param(struct tty *tp, struct termios *t)
{
        struct at91dbgu_softc *sc
                = device_lookup_private(&at91dbgu_cd, COMUNIT(tp->t_dev));
        int s;

        if (COM_ISALIVE(sc) == 0)
                return (EIO);

        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(sc->sc_swflags, TIOCFLAG_SOFTCAR) ||
            ISSET(sc->sc_hwflags, COM_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);

        s = splserial();

        sc->sc_brgr = (AT91_MSTCLK / 16 + t->c_ospeed / 2) / t->c_ospeed;
        
        /* And copy to tty. */
        tp->t_ispeed = 0;
        tp->t_ospeed = t->c_ospeed;
        tp->t_cflag = t->c_cflag;
        at91dbgu_set(sc);

        splx(s);

        /*
         * Update the tty layer's idea of the carrier bit.
         * We tell tty the carrier is always on.
         */
        (void) (*tp->t_linesw->l_modem)(tp, 1);

#ifdef COM_DEBUG
        if (com_debug)
                comstatus(sc, "comparam ");
#endif

        if (!ISSET(t->c_cflag, CHWFLOW)) {
                if (sc->sc_tx_stopped) {
                        sc->sc_tx_stopped = 0;
                        at91dbgu_start(tp);
                }
        }

        return (0);
}

static int
at91dbgu_hwiflow(struct tty *tp, int block)
{
        return (0);
}

static void
at91dbgu_filltx(struct at91dbgu_softc *sc)
{
#if 0
        bus_space_tag_t iot = sc->sc_iot;
        bus_space_handle_t ioh = sc->sc_ioh;
#endif
        int n;

        n = 0;
        while (DBGUREG(DBGU_SR) & DBGU_SR_TXRDY) {
                if (n >= sc->sc_tbc)
                        break;
                DBGUREG(DBGU_THR) = *(sc->sc_tba + n) & 0xff;
                n++;
        }
        sc->sc_tbc -= n;
        sc->sc_tba += n;
}

static void
at91dbgu_start(struct tty *tp)
{
        struct at91dbgu_softc *sc
                = device_lookup_private(&at91dbgu_cd, COMUNIT(tp->t_dev));
        int s;

        if (COM_ISALIVE(sc) == 0)
                return;

        s = spltty();
        if (ISSET(tp->t_state, TS_BUSY | TS_TIMEOUT | TS_TTSTOP))
                goto out;
        if (sc->sc_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();

                sc->sc_tba = tba;
                sc->sc_tbc = tbc;
        }

        SET(tp->t_state, TS_BUSY);
        sc->sc_tx_busy = 1;

        /* Output the first chunk of the contiguous buffer. */
        at91dbgu_filltx(sc);

        SET(sc->sc_ier, DBGU_INT_TXRDY);
        DBGUREG(DBGU_IER) = DBGU_INT_TXRDY;

out:
        splx(s);
        return;
}

static void
at91dbgu_break(struct at91dbgu_softc *sc, int onoff)
{
        // @@@ we must disconnect the TX pin from the DBGU and control
        // @@@ the pin directly to support this...
}

static void
at91dbgu_shutdown(struct at91dbgu_softc *sc)
{
        int s;

        s = splserial();

        /* Turn off interrupts. */
        DBGUREG(DBGU_IDR) = -1;

        /* Clear any break condition set with TIOCSBRK. */
        at91dbgu_break(sc, 0);
        at91dbgu_set(sc);

        if (sc->disable) {
#ifdef DIAGNOSTIC
                if (!sc->enabled)
                        panic("at91dbgu_shutdown: not enabled?");
#endif
                (*sc->disable)(sc);
                sc->enabled = 0;
        }
        splx(s);
}

int
at91dbgu_open(dev_t dev, int flag, int mode, struct lwp *l)
{
        struct at91dbgu_softc *sc;
        struct tty *tp;
        int s, s2;
        int error;

        sc = device_lookup_private(&at91dbgu_cd, COMUNIT(dev));
        if (sc == NULL || !ISSET(sc->sc_hwflags, COM_HW_DEV_OK) ||
                sc->sc_rbuf == NULL)
                return (ENXIO);

        if (!device_is_active(sc->sc_dev))
                return (ENXIO);

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

        tp = sc->sc_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();

                if (sc->enable) {
                        if ((*sc->enable)(sc)) {
                                splx(s2);
                                splx(s);
                                printf("%s: device enable failed\n",
                                       device_xname(sc->sc_dev));
                                return (EIO);
                        }
                        sc->enabled = 1;
#if 0
/* XXXXXXXXXXXXXXX */
                        com_config(sc);
#endif
                }

                /* Turn on interrupts. */
                sc->sc_ier |= DBGU_INT_RXRDY;
                DBGUREG(DBGU_IER) = DBGU_INT_RXRDY;

#if 0
                /* Fetch the current modem control status, needed later. */
                sc->sc_msr = bus_space_read_1(sc->sc_iot, sc->sc_ioh, com_msr);

                /* Clear PPS capture state on first open. */
                sc->sc_ppsmask = 0;
                sc->ppsparam.mode = 0;
#endif

                splx(s2);

                /*
                 * Initialize the termios status to the defaults.  Add in the
                 * sticky bits from TIOCSFLAGS.
                 */
                t.c_ispeed = 0;
                if (ISSET(sc->sc_hwflags, COM_HW_CONSOLE)) {
                        t.c_ospeed = dbgu_cn_sc.sc_ospeed;
                        t.c_cflag = dbgu_cn_sc.sc_cflag;
                } else {
                        t.c_ospeed = TTYDEF_SPEED;
                        t.c_cflag = TTYDEF_CFLAG;
                }
                if (ISSET(sc->sc_swflags, TIOCFLAG_CLOCAL))
                        SET(t.c_cflag, CLOCAL);
                if (ISSET(sc->sc_swflags, TIOCFLAG_CRTSCTS))
                        SET(t.c_cflag, CRTSCTS);
                if (ISSET(sc->sc_swflags, TIOCFLAG_MDMBUF))
                        SET(t.c_cflag, MDMBUF);
                /* Make sure at91dbgu_param() will do something. */
                tp->t_ospeed = 0;
                (void) at91dbgu_param(tp, &t);
                tp->t_iflag = TTYDEF_IFLAG;
                tp->t_oflag = TTYDEF_OFLAG;
                tp->t_lflag = TTYDEF_LFLAG;
                ttychars(tp);
                ttsetwater(tp);

                s2 = splserial();

                /* Clear the input ring, and unblock. */
                sc->sc_rbput = sc->sc_rbget = sc->sc_rbuf;
                sc->sc_rbavail = AT91DBGU_RING_SIZE;
                at91dbgu_iflush(sc);
                CLR(sc->sc_rx_flags, RX_ANY_BLOCK);

#ifdef COM_DEBUG
                if (at91dbgu_debug)
                        comstatus(sc, "at91dbgu_open  ");
#endif

                splx(s2);
        }
        
        splx(s);

        error = ttyopen(tp, COMDIALOUT(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.
                 */
                at91dbgu_shutdown(sc);
        }

        return (error);
}

int
at91dbgu_close(dev_t dev, int flag, int mode, struct lwp *l)
{
        struct at91dbgu_softc *sc = device_lookup_private(&at91dbgu_cd, COMUNIT(dev));
        struct tty *tp = sc->sc_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 (COM_ISALIVE(sc) == 0)
                return (0);

        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.
                 */
                at91dbgu_shutdown(sc);
        }

        return (0);
}

int
at91dbgu_read(dev_t dev, struct uio *uio, int flag)
{
        struct at91dbgu_softc *sc = device_lookup_private(&at91dbgu_cd, COMUNIT(dev));
        struct tty *tp = sc->sc_tty;

        if (COM_ISALIVE(sc) == 0)
                return (EIO);
 
        return ((*tp->t_linesw->l_read)(tp, uio, flag));
}

int
at91dbgu_write(dev_t dev, struct uio *uio, int flag)
{
        struct at91dbgu_softc *sc = device_lookup_private(&at91dbgu_cd, COMUNIT(dev));
        struct tty *tp = sc->sc_tty;

        if (COM_ISALIVE(sc) == 0)
                return (EIO);
 
        return ((*tp->t_linesw->l_write)(tp, uio, flag));
}

int
at91dbgu_poll(dev_t dev, int events, struct lwp *l)
{
        struct at91dbgu_softc *sc = device_lookup_private(&at91dbgu_cd, COMUNIT(dev));
        struct tty *tp = sc->sc_tty;

        if (COM_ISALIVE(sc) == 0)
                return (EIO);
 
        return ((*tp->t_linesw->l_poll)(tp, events, l));
}

struct tty *
at91dbgu_tty(dev_t dev)
{
        struct at91dbgu_softc *sc = device_lookup_private(&at91dbgu_cd, COMUNIT(dev));
        struct tty *tp = sc->sc_tty;

        return (tp);
}

int
at91dbgu_ioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
{
        struct at91dbgu_softc *sc = device_lookup_private(&at91dbgu_cd, COMUNIT(dev));
        struct tty *tp = sc->sc_tty;
        int error;
        int s;

        if (COM_ISALIVE(sc) == 0)
                return (EIO);

        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:
                at91dbgu_break(sc, 1);
                break;

        case TIOCCBRK:
                at91dbgu_break(sc, 0);
                break;

        case TIOCGFLAGS:
                *(int *)data = sc->sc_swflags;
                break;

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

        default:
                error = EPASSTHROUGH;
                break;
        }

        splx(s);

        return (error);
}

/*
 * Stop output on a line.
 */
void
at91dbgu_stop(struct tty *tp, int flag)
{
        struct at91dbgu_softc *sc
                = device_lookup_private(&at91dbgu_cd, COMUNIT(tp->t_dev));
        int s;

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

#if 0
static u_int
cflag2lcrhi(tcflag_t cflag)
{
        uint32_t        mr;

        switch (cflag & CSIZE) {
        default:
                mr = 0x0;
                break;
        }
#if 0
        mr |= (cflag & PARENB) ? LinCtrlHigh_PEN : 0;
        mr |= (cflag & PARODD) ? 0 : LinCtrlHigh_EPS;
        mr |= (cflag & CSTOPB) ? LinCtrlHigh_STP2 : 0;
        mr |= LinCtrlHigh_FEN;  /* FIFO always enabled */
#endif
        mr |= DBGU_MR_PAR_NONE;
        return (mr);
}
#endif

static void
at91dbgu_iflush(struct at91dbgu_softc *sc)
{
#if 0
        bus_space_tag_t iot = sc->sc_iot;
        bus_space_handle_t ioh = sc->sc_ioh;
#endif
#ifdef DIAGNOSTIC
        int reg;
#endif
        int timo;

#ifdef DIAGNOSTIC
        reg = 0xffff;
#endif
        timo = 50000;
        /* flush any pending I/O */
        while (DBGUREG(DBGU_SR) & DBGU_SR_RXRDY
               && --timo)
#ifdef DIAGNOSTIC
                reg =
#else
                        (void)
#endif
                        DBGUREG(DBGU_RHR);
#ifdef DIAGNOSTIC
        if (!timo)
                printf("%s: com_iflush timeout %02x\n", device_xname(sc->sc_dev),
                       reg);
#endif
}

static void
at91dbgu_set(struct at91dbgu_softc *sc)
{
        DBGUREG(DBGU_MR) = DBGU_MR_PAR_NONE;
        DBGUREG(DBGU_BRGR) = sc->sc_brgr;
        DBGUREG(DBGU_CR) = DBGU_CR_TXEN | DBGU_CR_RXEN; // @@@ just in case
}

void
at91dbgu_cn_attach(bus_space_tag_t iot, bus_addr_t iobase, bus_space_handle_t ioh,
                   int ospeed, tcflag_t cflag);
void
at91dbgu_cn_attach(bus_space_tag_t iot, bus_addr_t iobase, bus_space_handle_t ioh,
                   int ospeed, tcflag_t cflag)
{
        cn_tab = &at91dbgu_cons;
        cn_init_magic(&at91dbgu_cnm_state);
        cn_set_magic("\047\001");

        dbgu_cn_sc.sc_iot = iot;
        dbgu_cn_sc.sc_ioh = ioh;
        dbgu_cn_sc.sc_hwbase = iobase;
        dbgu_cn_sc.sc_ospeed = ospeed;
        dbgu_cn_sc.sc_cflag = cflag;

        DBGU_INIT(AT91_MSTCLK, ospeed);
}

void at91dbgu_attach_cn(bus_space_tag_t iot, int ospeed, int cflag)
{
        bus_space_handle_t ioh;
        bus_space_map(iot, AT91DBGU_BASE, AT91DBGU_SIZE, 0, &ioh);
        at91dbgu_cn_attach(iot, AT91DBGU_BASE, ioh, ospeed, cflag);
}

void
at91dbgu_cn_probe(struct consdev *cp)
{
        cp->cn_pri = CN_REMOTE;
}

void
at91dbgu_cn_pollc(dev_t dev, int on)
{
        if (on) {
                // enable polling mode
                DBGUREG(DBGU_IDR) = DBGU_INT_RXRDY;
        } else {
                // disable polling mode
                DBGUREG(DBGU_IER) = DBGU_INT_RXRDY;
        }
}

void
at91dbgu_cn_putc(dev_t dev, int c)
{
#if 0
        bus_space_tag_t         iot = dbgu_cn_sc.sc_iot;
        bus_space_handle_t      ioh = dbgu_cn_sc.sc_ioh;
#endif
        DBGU_PUTC(c);

#ifdef DEBUG
        if (c == '\r') {
                int s = splserial();
                while((DBGUREG(DBGU_SR) & DBGU_SR_TXEMPTY) == 0) {
                        splx(s);
                        s = splserial();
                }
                splx(s);
        }
#endif

}

int
at91dbgu_cn_getc(dev_t dev)
{
        int                     c, sr;
        int                     s;
#if 0
        bus_space_tag_t         iot = dbgu_cn_sc.sc_iot;
        bus_space_handle_t      ioh = dbgu_cn_sc.sc_ioh;
#endif

        s = splserial();

        while ((c = DBGU_PEEKC()) == -1) {
          splx(s);
          s = splserial();
        }
                ;
        sr = DBGUREG(DBGU_SR);
        if (ISSET(sr, DBGU_SR_FRAME) && c == 0) {
                DBGUREG(DBGU_CR) = DBGU_CR_RSTSTA;      // reset status bits
                c = CNC_BREAK;
        }
        if (!db_active) {
                int cn_trapped __unused = 0;

                cn_check_magic(dev, c, at91dbgu_cnm_state);
        }
        splx(s);

        c &= 0xff;

        return (c);
}

inline static void
at91dbgu_txsoft(struct at91dbgu_softc *sc, 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)(sc->sc_tba - tp->t_outq.c_cf));
        (*tp->t_linesw->l_start)(tp);
}

inline static void
at91dbgu_rxsoft(struct at91dbgu_softc *sc, struct tty *tp)
{
        int (*rint)(int, struct tty *) = tp->t_linesw->l_rint;
        u_char *get, *end;
        u_int cc, scc;
        u_char sts;
        int code;
        int s;

        end = sc->sc_ebuf;
        get = sc->sc_rbget;
        scc = cc = AT91DBGU_RING_SIZE - sc->sc_rbavail;
#if 0
        if (cc == AT91DBGU_RING_SIZE) {
                sc->sc_floods++;
                if (sc->sc_errors++ == 0)
                        callout_reset(&sc->sc_diag_callout, 60 * hz,
                            comdiag, sc);
        }
#endif
        while (cc) {
                code = get[0];
                sts = get[1];
                if (ISSET(sts, DBGU_SR_PARE | DBGU_SR_FRAME | DBGU_SR_OVRE)) {
#if 0
                        if (ISSET(lsr, DR_ROR)) {
                                sc->sc_overflows++;
                                if (sc->sc_errors++ == 0)
                                        callout_reset(&sc->sc_diag_callout,
                                            60 * hz, comdiag, sc);
                        }
#endif
                        if (ISSET(sts, (DBGU_SR_FRAME | DBGU_SR_OVRE)))
                                SET(code, TTY_FE);
                        if (ISSET(sts, DBGU_SR_PARE))
                                SET(code, TTY_PE);
                }
                if ((*rint)(code, tp) == -1) {
                        /*
                         * The line discipline's buffer is out of space.
                         */
                        if (!ISSET(sc->sc_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 -= AT91DBGU_RING_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(sc->sc_rx_flags, RX_TTY_OVERFLOWED);
                        }
                        break;
                }
                get += 2;
                if (get >= end)
                        get = sc->sc_rbuf;
                cc--;
        }

        if (cc != scc) {
                sc->sc_rbget = get;
                s = splserial();
                
                cc = sc->sc_rbavail += scc - cc;
                /* Buffers should be ok again, release possible block. */
                if (cc >= 1) {
                        if (ISSET(sc->sc_rx_flags, RX_IBUF_OVERFLOWED)) {
                                CLR(sc->sc_rx_flags, RX_IBUF_OVERFLOWED);
                                DBGUREG(DBGU_IER) = DBGU_INT_RXRDY;
                        }
                        if (ISSET(sc->sc_rx_flags, RX_IBUF_BLOCKED)) {
                                CLR(sc->sc_rx_flags, RX_IBUF_BLOCKED);
#if 0
                                com_hwiflow(sc);
#endif
                        }
                }
                splx(s);
        }
}

static void
at91dbgu_soft(void* arg)
{
        struct at91dbgu_softc *sc = arg;

        if (COM_ISALIVE(sc) == 0)
                return;

        if (sc->sc_rx_ready) {
                sc->sc_rx_ready = 0;
                at91dbgu_rxsoft(sc, sc->sc_tty);
        }
        if (sc->sc_tx_done) {
                sc->sc_tx_done = 0;
                at91dbgu_txsoft(sc, sc->sc_tty);
        }
}


static int
dbgu_intr(void* arg)
{
        struct at91dbgu_softc *sc = arg;
#if 0
        bus_space_tag_t iot = sc->sc_iot;
        bus_space_handle_t ioh = sc->sc_ioh;
#endif
        u_char *put, *end;
        u_int cc;
        uint32_t imr, sr;
        int c = 0;
        imr = DBGUREG(DBGU_IMR);
#if 0
        if (!imr)
                return 0;
#endif
        sr = DBGUREG(DBGU_SR);
        if (!(sr & imr)) {
                if (sr & DBGU_SR_RXRDY) {
//                      printf("sr=0x%08x imr=0x%08x\n", sr, imr);
                }
                return 0;
        }

        end = sc->sc_ebuf;
        put = sc->sc_rbput;
        cc = sc->sc_rbavail;

        // ok, we DO have some interrupts to serve!
        if (sr & DBGU_SR_RXRDY) {
                int cn_trapped = 0;

                c = DBGUREG(DBGU_RHR);
                if (ISSET(sr, (DBGU_SR_OVRE | DBGU_SR_FRAME | DBGU_SR_PARE)))
                        DBGUREG(DBGU_CR) = DBGU_CR_RSTSTA;
                if (ISSET(sr, DBGU_SR_FRAME) && c == 0) {
                        c = CNC_BREAK;
                }
                if (!db_active)
                        cn_check_magic(cn_tab->cn_dev, c, at91dbgu_cnm_state);
                if (!cn_trapped && cc) {
                        put[0] = c & 0xff;
                        put[1] = sr & 0xff;
                        put += 2;
                        if (put >= end)
                                put = sc->sc_rbuf;
                        cc--;
                        /*
                         * 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.
                         */
                        sc->sc_rbput = put;
                        sc->sc_rbavail = cc;
                        if (!ISSET(sc->sc_rx_flags, RX_TTY_OVERFLOWED))
                                sc->sc_rx_ready = 1;

                        /*
                         * See if we are in danger of overflowing a buffer. If
                         * so, use hardware flow control to ease the pressure.
                         */

                        /* but at91dbgu cannot (yet). X-( */

                        /*
                         * If we're out of space, disable receive interrupts
                         * until the queue has drained a bit.
                         */
                        if (!cc) {
                                SET(sc->sc_rx_flags, RX_IBUF_OVERFLOWED);
                        }
                }
        }

        /*
         * Done handling any receive interrupts. See if data can be
         * transmitted as well. Schedule tx done event if no data left
         * and tty was marked busy.
         */

        if (ISSET(sr, DBGU_SR_TXRDY) && sc->sc_tbc > 0) {
                /* Output the next chunk of the contiguous buffer, if any. */
                at91dbgu_filltx(sc);
        } else {
                /* Disable transmit completion interrupts if necessary. */
                DBGUREG(DBGU_IDR) = DBGU_INT_TXRDY;
                if (sc->sc_tx_busy) {
                        sc->sc_tx_busy = 0;
                        sc->sc_tx_done = 1;
                }
        }

        /* Wake up the poller. */
        softint_schedule(sc->sc_si);
#if 0
#ifdef RND_COM
        rnd_add_uint32(&sc->rnd_source, imr ^ sr ^ c);
#endif
#endif

        return (1);
}