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[netbsd-mini2440.git] / sys / dev / ic / sunscpal.c

/*      $NetBSD: sunscpal.c,v 1.24 2008/12/16 22:35:31 christos Exp $   */

/*
 * Copyright (c) 2001 Matthew Fredette
 * Copyright (c) 1995 David Jones, Gordon W. Ross
 * Copyright (c) 1994 Jarle Greipsland
 * 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. The name of the authors may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 * 4. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by
 *      David Jones and Gordon Ross
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``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 AUTHORS 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.
 */

/*
 * This is a machine-independent driver for the Sun "sc"
 * SCSI Bus Controller (SBC).
 *
 * This code should work with any memory-mapped card,
 * and can be shared by multiple adapters that address
 * the card with different register offset spacings.
 * (This can happen on the atari, for example.)
 *
 * Credits, history:
 *
 * Matthew Fredette completely copied revision 1.38 of
 * ncr5380sbc.c, and then heavily modified it to match
 * the Sun sc PAL.  The remaining credits are for
 * ncr5380sbc.c:
 *
 * David Jones is the author of most of the code that now
 * appears in this file, and was the architect of the
 * current overall structure (MI/MD code separation, etc.)
 *
 * Gordon Ross integrated the message phase code, added lots of
 * comments about what happens when and why (re. SCSI spec.),
 * debugged some reentrance problems, and added several new
 * "hooks" needed for the Sun3 "si" adapters.
 *
 * The message in/out code was taken nearly verbatim from
 * the aic6360 driver by Jarle Greipsland.
 *
 * Several other NCR5380 drivers were used for reference
 * while developing this driver, including work by:
 *   The Alice Group (mac68k port) namely:
 *       Allen K. Briggs, Chris P. Caputo, Michael L. Finch,
 *       Bradley A. Grantham, and Lawrence A. Kesteloot
 *   Michael L. Hitch (amiga drivers: sci.c)
 *   Leo Weppelman (atari driver: ncr5380.c)
 * There are others too.  Thanks, everyone.
 *
 * Transliteration to bus_space() performed 9/17/98 by
 * John Ruschmeyer (jruschme@exit109.com) for i386 'nca' driver.
 * Thank you all.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: sunscpal.c,v 1.24 2008/12/16 22:35:31 christos Exp $");

#include "opt_ddb.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/errno.h>
#include <sys/malloc.h>
#include <sys/device.h>
#include <sys/buf.h>
#include <sys/proc.h>

#include <dev/scsipi/scsi_all.h>
#include <dev/scsipi/scsipi_all.h>
#include <dev/scsipi/scsipi_debug.h>
#include <dev/scsipi/scsi_message.h>
#include <dev/scsipi/scsiconf.h>

#ifdef DDB
#include <ddb/db_output.h>
#endif

#include <dev/ic/sunscpalreg.h>
#include <dev/ic/sunscpalvar.h>

static void     sunscpal_reset_scsibus(struct sunscpal_softc *);
static void     sunscpal_sched(struct sunscpal_softc *);
static void     sunscpal_done(struct sunscpal_softc *);

static int      sunscpal_select(struct sunscpal_softc *, struct sunscpal_req *);
static void     sunscpal_reselect(struct sunscpal_softc *);

static int      sunscpal_msg_in(struct sunscpal_softc *);
static int      sunscpal_msg_out(struct sunscpal_softc *);
static int      sunscpal_data_xfer(struct sunscpal_softc *, int);
static int      sunscpal_command(struct sunscpal_softc *);
static int      sunscpal_status(struct sunscpal_softc *);
static void     sunscpal_machine(struct sunscpal_softc *);

void    sunscpal_abort(struct sunscpal_softc *);
void    sunscpal_cmd_timeout(void *);
/*
 * Action flags returned by the info_transfer functions:
 * (These determine what happens next.)
 */
#define ACT_CONTINUE    0x00    /* No flags: expect another phase */
#define ACT_DISCONNECT  0x01    /* Target is disconnecting */
#define ACT_CMD_DONE    0x02    /* Need to call scsipi_done() */
#define ACT_RESET_BUS   0x04    /* Need bus reset (cmd timeout) */
#define ACT_WAIT_DMA    0x10    /* Wait for DMA to complete */

/*****************************************************************
 * Debugging stuff
 *****************************************************************/

#ifndef DDB
/* This is used only in recoverable places. */
#ifndef Debugger
#define Debugger() printf("Debug: sunscpal.c:%d\n", __LINE__)
#endif
#endif

#ifdef  SUNSCPAL_DEBUG

#define SUNSCPAL_DBG_BREAK      1
#define SUNSCPAL_DBG_CMDS       2
#define SUNSCPAL_DBG_DMA        4
int sunscpal_debug = 0;
#define SUNSCPAL_BREAK() \
        do { if (sunscpal_debug & SUNSCPAL_DBG_BREAK) Debugger(); } while (0)
static void sunscpal_show_scsi_cmd(struct scsipi_xfer *);
#ifdef DDB
void    sunscpal_clear_trace(void);
void    sunscpal_show_trace(void);
void    sunscpal_show_req(struct sunscpal_req *);
void    sunscpal_show_state(void);
#endif  /* DDB */
#else   /* SUNSCPAL_DEBUG */

#define SUNSCPAL_BREAK()                /* nada */
#define sunscpal_show_scsi_cmd(xs) /* nada */

#endif  /* SUNSCPAL_DEBUG */

static const char *
phase_names[8] = {
        "DATA_OUT",
        "DATA_IN",
        "COMMAND",
        "STATUS",
        "UNSPEC1",
        "UNSPEC2",
        "MSG_OUT",
        "MSG_IN",
};

#ifdef SUNSCPAL_USE_BUS_DMA
static void sunscpal_dma_alloc(struct sunscpal_softc *);
static void sunscpal_dma_free(struct sunscpal_softc *);
static void sunscpal_dma_setup(struct sunscpal_softc *);
#else
#define sunscpal_dma_alloc(sc) (*sc->sc_dma_alloc)(sc)
#define sunscpal_dma_free(sc) (*sc->sc_dma_free)(sc)
#define sunscpal_dma_setup(sc) (*sc->sc_dma_setup)(sc)
#endif
static void sunscpal_minphys(struct buf *);

/*****************************************************************
 * Actual chip control
 *****************************************************************/

/*
 * XXX: These timeouts might need to be tuned...
 */

/* This one is used when waiting for a phase change. (X100uS.) */
int sunscpal_wait_phase_timo = 1000 * 10 * 300; /* 5 min. */

/* These are used in the following inline functions. */
int sunscpal_wait_req_timo = 1000 * 50; /* X2 = 100 mS. */
int sunscpal_wait_nrq_timo = 1000 * 25; /* X2 =  50 mS. */

static inline int sunscpal_wait_req(struct sunscpal_softc *);
static inline int sunscpal_wait_not_req(struct sunscpal_softc *);
static inline void sunscpal_sched_msgout(struct sunscpal_softc *, int);

/* Return zero on success. */
static inline int sunscpal_wait_req(struct sunscpal_softc *sc)
{
        int timo = sunscpal_wait_req_timo;

        for (;;) {
                if (SUNSCPAL_READ_2(sc, sunscpal_icr) & SUNSCPAL_ICR_REQUEST) {
                        timo = 0;       /* return 0 */
                        break;
                }
                if (--timo < 0)
                        break;  /* return -1 */
                delay(2);
        }
        return timo;
}

/* Return zero on success. */
static inline int sunscpal_wait_not_req(struct sunscpal_softc *sc)
{
        int timo = sunscpal_wait_nrq_timo;

        for (;;) {
                if ((SUNSCPAL_READ_2(sc, sunscpal_icr) &
                    SUNSCPAL_ICR_REQUEST) == 0) {
                        timo = 0;       /* return 0 */
                        break;
                }
                if (--timo < 0)
                        break;  /* return -1 */
                delay(2);
        }
        return timo;
}

/*
 * These functions control DMA functions in the chipset independent of
 * the host DMA implementation.
 */
static void sunscpal_dma_start(struct sunscpal_softc *);
static void sunscpal_dma_poll(struct sunscpal_softc *);
static void sunscpal_dma_stop(struct sunscpal_softc *);

static void
sunscpal_dma_start(struct sunscpal_softc *sc)
{
        struct sunscpal_req *sr = sc->sc_current;
        int xlen;
        uint16_t icr;

        xlen = sc->sc_reqlen;

        /* Let'er rip! */
        icr = SUNSCPAL_READ_2(sc, sunscpal_icr);
        icr |= SUNSCPAL_ICR_DMA_ENABLE |
            ((xlen & 1) ? 0 : SUNSCPAL_ICR_WORD_MODE) |
            ((sr->sr_flags & SR_IMMED) ? 0 : SUNSCPAL_ICR_INTERRUPT_ENABLE);
        SUNSCPAL_WRITE_2(sc, sunscpal_icr, icr);

        sc->sc_state |= SUNSCPAL_DOINGDMA;

#ifdef  SUNSCPAL_DEBUG
        if (sunscpal_debug & SUNSCPAL_DBG_DMA) {
                printf("%s: started, flags=0x%x\n",
                    __func__, sc->sc_state);
        }
#endif
}

#define ICR_MASK (SUNSCPAL_ICR_PARITY_ERROR | SUNSCPAL_ICR_BUS_ERROR | SUNSCPAL_ICR_INTERRUPT_REQUEST)
#define POLL_TIMO       50000   /* X100 = 5 sec. */

/*
 * Poll (spin-wait) for DMA completion.
 * Called right after xx_dma_start(), and
 * xx_dma_stop() will be called next.
 */
static void
sunscpal_dma_poll(struct sunscpal_softc *sc)
{
        struct sunscpal_req *sr = sc->sc_current;
        int tmo;

        /* Make sure DMA started successfully. */
        if (sc->sc_state & SUNSCPAL_ABORTING)
                return;

        /* Wait for any "DMA complete" or error bits. */
        tmo = POLL_TIMO;
        for (;;) {
                if (SUNSCPAL_READ_2(sc, sunscpal_icr) & ICR_MASK)
                        break;
                if (--tmo <= 0) {
                        printf("sc: DMA timeout (while polling)\n");
                        /* Indicate timeout as MI code would. */
                        sr->sr_flags |= SR_OVERDUE;
                        break;
                }
                delay(100);
        }
        SUNSCPAL_TRACE("sunscpal_dma_poll: waited %d\n", POLL_TIMO - tmo);

#ifdef  SUNSCPAL_DEBUG
        if (sunscpal_debug & SUNSCPAL_DBG_DMA) {
                char buffer[64];
                snprintb(buffer, sizeof(buffer),
                    SUNSCPAL_READ_2(sc, sunscpal_icr), SUNSCPAL_ICR_BITS);
                printf("%s: done, icr=%s\n", __func__, buffer);
        }
#endif
}

static void
sunscpal_dma_stop(struct sunscpal_softc *sc)
{
        struct sunscpal_req *sr = sc->sc_current;
        struct scsipi_xfer *xs = sr->sr_xs;
        int resid, ntrans;
        uint16_t icr;

        if ((sc->sc_state & SUNSCPAL_DOINGDMA) == 0) {
#ifdef  DEBUG
                printf("%s: DMA not running\n", __func__);
#endif
                return;
        }
        sc->sc_state &= ~SUNSCPAL_DOINGDMA;

        /* First, halt the DMA engine. */
        icr = SUNSCPAL_READ_2(sc, sunscpal_icr);
        icr &= ~(SUNSCPAL_ICR_DMA_ENABLE | SUNSCPAL_ICR_WORD_MODE |
            SUNSCPAL_ICR_INTERRUPT_ENABLE);
        SUNSCPAL_WRITE_2(sc, sunscpal_icr, icr);

#ifdef  SUNSCPAL_USE_BUS_DMA
        /*
         * XXX - this function is supposed to be independent of
         * the host's DMA implementation.
         */
 {
         sunscpal_dma_handle_t dh = sr->sr_dma_hand;

         /* sync the DMA map: */
         bus_dmamap_sync(sc->sunscpal_dmat, dh->dh_dmamap, 0, dh->dh_maplen,
             ((xs->xs_control & XS_CTL_DATA_OUT) == 0 ?
            BUS_DMASYNC_POSTREAD : BUS_DMASYNC_POSTWRITE));
 }
#endif /* SUNSCPAL_USE_BUS_DMA */


        if (icr & (SUNSCPAL_ICR_BUS_ERROR)) {
                char buffer[64];
                snprintb(buffer, sizeof(buffer), SUNSCPAL_ICR_BITS, icr);
                printf("sc: DMA error, icr=%s, reset\n", buffer);
                sr->sr_xs->error = XS_DRIVER_STUFFUP;
                sc->sc_state |= SUNSCPAL_ABORTING;
                goto out;
        }

        /* Note that timeout may have set the error flag. */
        if (sc->sc_state & SUNSCPAL_ABORTING)
                goto out;

        /* XXX: Wait for DMA to actually finish? */

        /*
         * Now try to figure out how much actually transferred
         */

        resid = SUNSCPAL_DMA_COUNT_FLIP(SUNSCPAL_READ_2(sc,
            sunscpal_dma_count));
        ntrans = sc->sc_reqlen - resid;

#ifdef  SUNSCPAL_DEBUG
        if (sunscpal_debug & SUNSCPAL_DBG_DMA) {
                printf("%s: resid=0x%x ntrans=0x%x\n",
                    __func__, resid, ntrans);
        }
#endif

        if (ntrans < sc->sc_min_dma_len) {
                printf("sc: DMA count: 0x%x\n", resid);
                sc->sc_state |= SUNSCPAL_ABORTING;
                goto out;
        }
        if (ntrans > sc->sc_datalen)
                panic("%s: excess transfer", __func__);

        /* Adjust data pointer */
        sc->sc_dataptr += ntrans;
        sc->sc_datalen -= ntrans;

        /*
         * After a read, we may need to clean-up
         * "Left-over bytes" (yuck!)
         */
        if (((xs->xs_control & XS_CTL_DATA_OUT) == 0) &&
            ((icr & SUNSCPAL_ICR_ODD_LENGTH) != 0)) {
#ifdef DEBUG
                printf("sc: Got Left-over bytes!\n");
#endif
                *(sc->sc_dataptr++) = SUNSCPAL_READ_1(sc, sunscpal_data);
                sc->sc_datalen--;
        }

 out:
        SUNSCPAL_WRITE_2(sc, sunscpal_dma_count, SUNSCPAL_DMA_COUNT_FLIP(0));

}

/* Ask the target for a MSG_OUT phase. */
static inline void
sunscpal_sched_msgout(struct sunscpal_softc *sc, int msg_code)
{
        /*
         * This controller does not allow you to assert ATN, which
         * will eventually leave us with no option other than to reset
         * the bus.  We keep this function as a placeholder, though,
         * and this printf will eventually go away or get #ifdef'ed:
         */
        printf("%s: trying to schedule 0x%0x\n", __func__, msg_code);
        sc->sc_msgpriq |= msg_code;
}

int
sunscpal_pio_out(struct sunscpal_softc *sc, int phase, int count, uint8_t *data)
{
        int resid;

        resid = count;
        while (resid > 0) {
                if (!SUNSCPAL_BUSY(sc)) {
                        SUNSCPAL_TRACE("pio_out: lost BSY, resid=%d\n", resid);
                        break;
                }
                if (sunscpal_wait_req(sc)) {
                        SUNSCPAL_TRACE("pio_out: no REQ, resid=%d\n", resid);
                        break;
                }
                if (SUNSCPAL_BUS_PHASE(SUNSCPAL_READ_2(sc, sunscpal_icr)) !=
                    phase)
                        break;

                /* Put the data on the bus. */
                if (data) {
                        SUNSCPAL_BYTE_WRITE(sc, phase, *data++);
                } else {
                        SUNSCPAL_BYTE_WRITE(sc, phase, 0);
                }

                --resid;
        }

        return count - resid;
}


int
sunscpal_pio_in(struct sunscpal_softc *sc, int phase, int count, uint8_t *data)
{
        int resid;

        resid = count;
        while (resid > 0) {
                if (!SUNSCPAL_BUSY(sc)) {
                        SUNSCPAL_TRACE("pio_in: lost BSY, resid=%d\n", resid);
                        break;
                }
                if (sunscpal_wait_req(sc)) {
                        SUNSCPAL_TRACE("pio_in: no REQ, resid=%d\n", resid);
                        break;
                }
                /* A phase change is not valid until AFTER REQ rises! */
                if (SUNSCPAL_BUS_PHASE(SUNSCPAL_READ_2(sc, sunscpal_icr)) !=
                    phase)
                        break;

                /* Read the data bus. */
                if (data)
                        *data++ = SUNSCPAL_BYTE_READ(sc, phase);
                else
                        (void)SUNSCPAL_BYTE_READ(sc, phase);

                --resid;
        }

        return count - resid;
}


void
sunscpal_init(struct sunscpal_softc *sc)
{
        int i, j;

#ifdef  SUNSCPAL_DEBUG
        sunscpal_debug_sc = sc;
#endif

        for (i = 0; i < SUNSCPAL_OPENINGS; i++)
                sc->sc_ring[i].sr_xs = NULL;
        for (i = 0; i < 8; i++)
                for (j = 0; j < 8; j++)
                        sc->sc_matrix[i][j] = NULL;

        sc->sc_prevphase = SUNSCPAL_PHASE_INVALID;
        sc->sc_state = SUNSCPAL_IDLE;

        SUNSCPAL_WRITE_2(sc, sunscpal_icr, 0);
        SUNSCPAL_WRITE_2(sc, sunscpal_dma_addr_h, 0);
        SUNSCPAL_WRITE_2(sc, sunscpal_dma_addr_l, 0);
        SUNSCPAL_WRITE_2(sc, sunscpal_dma_count, SUNSCPAL_DMA_COUNT_FLIP(0));

        SUNSCPAL_CLR_INTR(sc);

        /* Another hack (Er.. hook!) for anything that needs it: */
        if (sc->sc_intr_on) {
                SUNSCPAL_TRACE("init: intr ON\n", 0);
                sc->sc_intr_on(sc);
        }
}


static void
sunscpal_reset_scsibus(struct sunscpal_softc *sc)
{

        SUNSCPAL_TRACE("reset_scsibus, cur=0x%x\n", (long)sc->sc_current);

        SUNSCPAL_WRITE_2(sc, sunscpal_icr, SUNSCPAL_ICR_RESET);
        delay(500);
        SUNSCPAL_WRITE_2(sc, sunscpal_icr, 0);

        SUNSCPAL_CLR_INTR(sc);
        /* XXX - Need long delay here! */
        delay(100000);

        /* XXX - Need to cancel disconnected requests. */
}


/*
 * Interrupt handler for the SCSI Bus Controller (SBC)
 * This may also called for a DMA timeout (at splbio).
 */
int
sunscpal_intr(void *arg)
{
        struct sunscpal_softc *sc = arg;
        int claimed = 0;

        /*
         * Do not touch SBC regs here unless sc_current == NULL
         * or it will complain about "register conflict" errors.
         * Instead, just let sunscpal_machine() deal with it.
         */
        SUNSCPAL_TRACE("intr: top, state=%d\n", sc->sc_state);

        if (sc->sc_state == SUNSCPAL_IDLE) {
                /*
                 * Might be reselect.  sunscpal_reselect() will check,
                 * and set up the connection if so.  This will verify
                 * that sc_current == NULL at the beginning...
                 */

                /* Another hack (Er.. hook!) for anything that needs it: */
                if (sc->sc_intr_off) {
                        SUNSCPAL_TRACE("intr: for reselect, intr off\n", 0);
                    sc->sc_intr_off(sc);
                }

                sunscpal_reselect(sc);
        }

        /*
         * The remaining documented interrupt causes are a DMA complete
         * condition.
         *
         * The procedure is to let sunscpal_machine() figure out what
         * to do next.
         */
        if (sc->sc_state & SUNSCPAL_WORKING) {
                SUNSCPAL_TRACE("intr: call machine, cur=0x%x\n",
                    (long)sc->sc_current);
                /* This will usually free-up the nexus. */
                sunscpal_machine(sc);
                SUNSCPAL_TRACE("intr: machine done, cur=0x%x\n",
                    (long)sc->sc_current);
                claimed = 1;
        }

        /* Maybe we can run some commands now... */
        if (sc->sc_state == SUNSCPAL_IDLE) {
                SUNSCPAL_TRACE("intr: call sched, cur=0x%x\n",
                    (long)sc->sc_current);
                sunscpal_sched(sc);
                SUNSCPAL_TRACE("intr: sched done, cur=0x%x\n",
                    (long)sc->sc_current);
        }

        return claimed;
}


/*
 * Abort the current command (i.e. due to timeout)
 */
void
sunscpal_abort(struct sunscpal_softc *sc)
{

        /*
         * Finish it now.  If DMA is in progress, we
         * can not call sunscpal_sched_msgout() because
         * that hits the SBC (avoid DMA conflict).
         */

        /* Another hack (Er.. hook!) for anything that needs it: */
        if (sc->sc_intr_off) {
                SUNSCPAL_TRACE("abort: intr off\n", 0);
                sc->sc_intr_off(sc);
        }

        sc->sc_state |= SUNSCPAL_ABORTING;
        if ((sc->sc_state & SUNSCPAL_DOINGDMA) == 0) {
                sunscpal_sched_msgout(sc, SEND_ABORT);
        }
        SUNSCPAL_TRACE("abort: call machine, cur=0x%x\n",
            (long)sc->sc_current);
        sunscpal_machine(sc);
        SUNSCPAL_TRACE("abort: machine done, cur=0x%x\n",
            (long)sc->sc_current);

        /* Another hack (Er.. hook!) for anything that needs it: */
        if (sc->sc_intr_on) {
                SUNSCPAL_TRACE("abort: intr ON\n", 0);
                sc->sc_intr_on(sc);
        }
}

/*
 * Timeout handler, scheduled for each SCSI command.
 */
void
sunscpal_cmd_timeout(void *arg)
{
        struct sunscpal_req *sr = arg;
        struct scsipi_xfer *xs;
        struct scsipi_periph *periph;
        struct sunscpal_softc *sc;
        int s;

        s = splbio();

        /* Get all our variables... */
        xs = sr->sr_xs;
        if (xs == NULL) {
                printf("%s: no scsipi_xfer\n", __func__);
                goto out;
        }
        periph = xs->xs_periph;
        sc = device_private(periph->periph_channel->chan_adapter->adapt_dev);

        printf("%s: cmd timeout, targ=%d, lun=%d\n",
            device_xname(sc->sc_dev),
            sr->sr_target, sr->sr_lun);

        /*
         * Mark the overdue job as failed, and arrange for
         * sunscpal_machine to terminate it.  If the victim
         * is the current job, call sunscpal_machine() now.
         * Otherwise arrange for sunscpal_sched() to do it.
         */
        sr->sr_flags |= SR_OVERDUE;
        if (sc->sc_current == sr) {
                SUNSCPAL_TRACE("cmd_tmo: call abort, sr=0x%x\n", (long)sr);
                sunscpal_abort(sc);
        } else {
                /*
                 * The driver may be idle, or busy with another job.
                 * Arrange for sunscpal_sched() to do the deed.
                 */
                SUNSCPAL_TRACE("cmd_tmo: clear matrix, t/l=0x%02x\n",
                    (sr->sr_target << 4) | sr->sr_lun);
                sc->sc_matrix[sr->sr_target][sr->sr_lun] = NULL;
        }

        /*
         * We may have aborted the current job, or may have
         * already been idle. In either case, we should now
         * be idle, so try to start another job.
         */
        if (sc->sc_state == SUNSCPAL_IDLE) {
                SUNSCPAL_TRACE("cmd_tmo: call sched, cur=0x%x\n",
                    (long)sc->sc_current);
                sunscpal_sched(sc);
                SUNSCPAL_TRACE("cmd_tmo: sched done, cur=0x%x\n",
                    (long)sc->sc_current);
        }

 out:
        splx(s);
}


/*****************************************************************
 * Interface to higher level
 *****************************************************************/


/*
 * Enter a new SCSI command into the "issue" queue, and
 * if there is work to do, start it going.
 *
 * WARNING:  This can be called recursively!
 * (see comment in sunscpal_done)
 */
void
sunscpal_scsipi_request(struct scsipi_channel *chan, scsipi_adapter_req_t req,
    void *arg)
{
        struct scsipi_xfer *xs;
        struct scsipi_periph *periph;
        struct sunscpal_softc *sc;
        struct sunscpal_req *sr;
        int s, i, flags;

        sc = device_private(chan->chan_adapter->adapt_dev);

        switch (req) {
        case ADAPTER_REQ_RUN_XFER:
                xs = arg;
                periph = xs->xs_periph;
                flags = xs->xs_control;

                if (flags & XS_CTL_DATA_UIO)
                        panic("sunscpal: scsi data uio requested");

                s = splbio();

                if (flags & XS_CTL_POLL) {
                        /* Terminate any current command. */
                        sr = sc->sc_current;
                        if (sr != NULL) {
                                printf("%s: polled request aborting %d/%d\n",
                                    device_xname(sc->sc_dev), sr->sr_target,
                                    sr->sr_lun);
                                sunscpal_abort(sc);
                        }
                        if (sc->sc_state != SUNSCPAL_IDLE) {
                                panic("%s: polled request, abort failed",
                                    __func__);
                        }
                }

                /*
                 * Find lowest empty slot in ring buffer.
                 * XXX: What about "fairness" and cmd order?
                 */
                for (i = 0; i < SUNSCPAL_OPENINGS; i++)
                        if (sc->sc_ring[i].sr_xs == NULL)
                                goto new;

                xs->error = XS_RESOURCE_SHORTAGE;
                SUNSCPAL_TRACE("scsipi_cmd: no openings, rv=%d\n", rv);
                goto out;

 new:
                /* Create queue entry */
                sr = &sc->sc_ring[i];
                sr->sr_xs = xs;
                sr->sr_target = xs->xs_periph->periph_target;
                sr->sr_lun = xs->xs_periph->periph_lun;
                sr->sr_dma_hand = NULL;
                sr->sr_dataptr = xs->data;
                sr->sr_datalen = xs->datalen;
                sr->sr_flags = (flags & XS_CTL_POLL) ? SR_IMMED : 0;
                sr->sr_status = -1;     /* no value */
                sc->sc_ncmds++;

                SUNSCPAL_TRACE("scsipi_cmd: new sr=0x%x\n", (long)sr);

                if (flags & XS_CTL_POLL) {
                        /* Force this new command to be next. */
                        sc->sc_rr = i;
                }

                /*
                 * If we were idle, run some commands...
                 */
                if (sc->sc_state == SUNSCPAL_IDLE) {
                        SUNSCPAL_TRACE("scsipi_cmd: call sched, cur=0x%x\n",
                            (long)sc->sc_current);
                        sunscpal_sched(sc);
                        SUNSCPAL_TRACE("scsipi_cmd: sched done, cur=0x%x\n",
                            (long)sc->sc_current);
                }

                if (flags & XS_CTL_POLL) {
                        /* Make sure sunscpal_sched() finished it. */
                        if ((xs->xs_status & XS_STS_DONE) == 0)
                                panic("%s: poll didn't finish", __func__);
                }

 out:
                splx(s);
                return;

        case ADAPTER_REQ_GROW_RESOURCES:
                /* XXX Not supported. */
                return;

        case ADAPTER_REQ_SET_XFER_MODE:
            {
                /*
                 * We don't support Sync, Wide, or Tagged Queueing.
                 * Just callback now, to report this.
                 */
                struct scsipi_xfer_mode *xm = arg;

                xm->xm_mode = 0;
                xm->xm_period = 0;
                xm->xm_offset = 0;
                scsipi_async_event(chan, ASYNC_EVENT_XFER_MODE, xm);
                return;
            }
        }
}


/*
 * POST PROCESSING OF SCSI_CMD (usually current)
 * Called by sunscpal_sched(), sunscpal_machine()
 */
static void
sunscpal_done(struct sunscpal_softc *sc)
{
        struct  sunscpal_req *sr;
        struct  scsipi_xfer *xs;

#ifdef  DIAGNOSTIC
        if (sc->sc_state == SUNSCPAL_IDLE)
                panic("%s: state=idle", __func__);
        if (sc->sc_current == NULL)
                panic("%s: current=0", __func__);
#endif

        sr = sc->sc_current;
        xs = sr->sr_xs;

        SUNSCPAL_TRACE("done: top, cur=0x%x\n", (long)sc->sc_current);

        /*
         * Clean up DMA resources for this command.
         */
        if (sr->sr_dma_hand) {
                SUNSCPAL_TRACE("done: dma_free, dh=0x%x\n",
                    (long)sr->sr_dma_hand);
                sunscpal_dma_free(sc);
        }
#ifdef  DIAGNOSTIC
        if (sr->sr_dma_hand)
                panic("%s: DMA free did not", __func__);
#endif

        if (sc->sc_state & SUNSCPAL_ABORTING) {
                SUNSCPAL_TRACE("done: aborting, error=%d\n", xs->error);
                if (xs->error == XS_NOERROR)
                        xs->error = XS_TIMEOUT;
        }

        SUNSCPAL_TRACE("done: check error=%d\n", (long)xs->error);

        /* If error is already set, ignore sr_status value. */
        if (xs->error != XS_NOERROR)
                goto finish;

        SUNSCPAL_TRACE("done: check status=%d\n", sr->sr_status);

        xs->status = sr->sr_status;
        switch (sr->sr_status) {
        case SCSI_OK:   /* 0 */
                break;

        case SCSI_CHECK:
        case SCSI_BUSY:
                xs->error = XS_BUSY;
                break;

        case -1:
                /* This is our "impossible" initial value. */
                /* fallthrough */
        default:
                printf("%s: target %d, bad status=%d\n",
                    device_xname(sc->sc_dev), sr->sr_target, sr->sr_status);
                xs->error = XS_DRIVER_STUFFUP;
                break;
        }

 finish:

        SUNSCPAL_TRACE("done: finish, error=%d\n", xs->error);

        /*
         * Dequeue the finished command, but don't clear sc_state until
         * after the call to scsipi_done(), because that may call back to
         * sunscpal_scsi_cmd() - unwanted recursion!
         *
         * Keeping sc->sc_state != idle terminates the recursion.
         */
#ifdef  DIAGNOSTIC
        if ((sc->sc_state & SUNSCPAL_WORKING) == 0)
                panic("%s: bad state", __func__);
#endif

        /* Clear our pointers to the request. */
        sc->sc_current = NULL;
        sc->sc_matrix[sr->sr_target][sr->sr_lun] = NULL;
        callout_stop(&sr->sr_xs->xs_callout);

        /* Make the request free. */
        sr->sr_xs = NULL;
        sc->sc_ncmds--;

        /* Tell common SCSI code it is done. */
        scsipi_done(xs);

        sc->sc_state = SUNSCPAL_IDLE;
        /* Now sunscpal_sched() may be called again. */
}


/*
 * Schedule a SCSI operation.  This routine should return
 * only after it achieves one of the following conditions:
 *      Busy (sc->sc_state != SUNSCPAL_IDLE)
 *      No more work can be started.
 */
static void
sunscpal_sched(struct sunscpal_softc *sc)
{
        struct sunscpal_req     *sr;
        struct scsipi_xfer *xs;
        int     target = 0, lun = 0;
        int     error, i;

        /* Another hack (Er.. hook!) for anything that needs it: */
        if (sc->sc_intr_off) {
                SUNSCPAL_TRACE("sched: top, intr off\n", 0);
                sc->sc_intr_off(sc);
        }

 next_job:
        /*
         * Grab the next job from queue.  Must be idle.
         */
#ifdef  DIAGNOSTIC
        if (sc->sc_state != SUNSCPAL_IDLE)
                panic("%s: not idle", __func__);
        if (sc->sc_current)
                panic("%s: current set", __func__);
#endif

        /*
         * Always start the search where we last looked.
         */
        i = sc->sc_rr;
        sr = NULL;
        do {
                if (sc->sc_ring[i].sr_xs) {
                        target = sc->sc_ring[i].sr_target;
                        lun = sc->sc_ring[i].sr_lun;
                        if (sc->sc_matrix[target][lun] == NULL) {
                                /*
                                 * Do not mark the  target/LUN busy yet,
                                 * because reselect may cause some other
                                 * job to become the current one, so we
                                 * might not actually start this job.
                                 * Instead, set sc_matrix later on.
                                 */
                                sc->sc_rr = i;
                                sr = &sc->sc_ring[i];
                                break;
                        }
                }
                i++;
                if (i == SUNSCPAL_OPENINGS)
                        i = 0;
        } while (i != sc->sc_rr);

        if (sr == NULL) {
                SUNSCPAL_TRACE("sched: no work, cur=0x%x\n",
                    (long)sc->sc_current);

                /* Another hack (Er.. hook!) for anything that needs it: */
                if (sc->sc_intr_on) {
                        SUNSCPAL_TRACE("sched: ret, intr ON\n", 0);
                        sc->sc_intr_on(sc);
                }

                return;         /* No more work to do. */
        }

        SUNSCPAL_TRACE("sched: select for t/l=0x%02x\n",
            (sr->sr_target << 4) | sr->sr_lun);

        sc->sc_state = SUNSCPAL_WORKING;
        error = sunscpal_select(sc, sr);
        if (sc->sc_current) {
                /* Lost the race!  reselected out from under us! */
                /* Work with the reselected job. */
                if (sr->sr_flags & SR_IMMED) {
                        printf("%s: reselected while polling (abort)\n",
                            device_xname(sc->sc_dev));
                        /* Abort the reselected job. */
                        sc->sc_state |= SUNSCPAL_ABORTING;
                        sc->sc_msgpriq |= SEND_ABORT;
                }
                sr = sc->sc_current;
                xs = sr->sr_xs;
                SUNSCPAL_TRACE("sched: reselect, new sr=0x%x\n", (long)sr);
                goto have_nexus;
        }

        /* Normal selection result.  Target/LUN is now busy. */
        sc->sc_matrix[target][lun] = sr;
        sc->sc_current = sr;    /* connected */
        xs = sr->sr_xs;

        /*
         * Initialize pointers, etc. for this job
         */
        sc->sc_dataptr  = sr->sr_dataptr;
        sc->sc_datalen  = sr->sr_datalen;
        sc->sc_prevphase = SUNSCPAL_PHASE_INVALID;
        sc->sc_msgpriq = SEND_IDENTIFY;
        sc->sc_msgoutq = 0;
        sc->sc_msgout  = 0;

        SUNSCPAL_TRACE("sched: select rv=%d\n", error);

        switch (error) {
        case XS_NOERROR:
                break;

        case XS_BUSY:
                /* XXX - Reset and try again. */
                printf("%s: select found SCSI bus busy, resetting...\n",
                    device_xname(sc->sc_dev));
                sunscpal_reset_scsibus(sc);
                /* fallthrough */
        case XS_SELTIMEOUT:
        default:
                xs->error = error;      /* from select */
                SUNSCPAL_TRACE("sched: call done, sr=0x%x\n", (long)sr);
                sunscpal_done(sc);

                /* Paranoia: clear everything. */
                sc->sc_dataptr = NULL;
                sc->sc_datalen = 0;
                sc->sc_prevphase = SUNSCPAL_PHASE_INVALID;
                sc->sc_msgpriq = 0;
                sc->sc_msgoutq = 0;
                sc->sc_msgout  = 0;

                goto next_job;
        }

        /*
         * Selection was successful.  Normally, this means
         * we are starting a new command.  However, this
         * might be the termination of an overdue job.
         */
        if (sr->sr_flags & SR_OVERDUE) {
                SUNSCPAL_TRACE("sched: overdue, sr=0x%x\n", (long)sr);
                sc->sc_state |= SUNSCPAL_ABORTING;
                sc->sc_msgpriq |= SEND_ABORT;
                goto have_nexus;
        }

        /*
         * OK, we are starting a new command.
         * Initialize and allocate resources for the new command.
         * Device reset is special (only uses MSG_OUT phase).
         * Normal commands start in MSG_OUT phase where we will
         * send and IDENDIFY message, and then expect CMD phase.
         */
#ifdef  SUNSCPAL_DEBUG
        if (sunscpal_debug & SUNSCPAL_DBG_CMDS) {
                printf("%s: begin, target=%d, LUN=%d\n", __func__,
                    xs->xs_periph->periph_target, xs->xs_periph->periph_lun);
                sunscpal_show_scsi_cmd(xs);
        }
#endif
        if (xs->xs_control & XS_CTL_RESET) {
                SUNSCPAL_TRACE("sched: cmd=reset, sr=0x%x\n", (long)sr);
                /* Not an error, so do not set SUNSCPAL_ABORTING */
                sc->sc_msgpriq |= SEND_DEV_RESET;
                goto have_nexus;
        }

#ifdef  DIAGNOSTIC
        if ((xs->xs_control & (XS_CTL_DATA_IN | XS_CTL_DATA_OUT)) == 0) {
                if (sc->sc_dataptr) {
                        printf("%s: ptr but no data in/out flags?\n",
                            device_xname(sc->sc_dev));
                        SUNSCPAL_BREAK();
                        sc->sc_dataptr = NULL;
                }
        }
#endif

        /* Allocate DMA space (maybe) */
        if (sc->sc_dataptr && (sc->sc_flags & SUNSCPAL_DISABLE_DMA) == 0 &&
                (sc->sc_datalen >= sc->sc_min_dma_len))
        {
                SUNSCPAL_TRACE("sched: dma_alloc, len=%d\n", sc->sc_datalen);
                sunscpal_dma_alloc(sc);
        }

        /*
         * Initialization hook called just after select,
         * at the beginning of COMMAND phase.
         * (but AFTER the DMA allocation is done)
         *
         * We need to set up the DMA engine BEFORE the target puts
         * the SCSI bus into any DATA phase.
         */
        if (sr->sr_dma_hand) {
                SUNSCPAL_TRACE("sched: dma_setup, dh=0x%x\n",
                    (long) sr->sr_dma_hand);
            sunscpal_dma_setup(sc);
        }

        /*
         * Schedule a timeout for the job we are starting.
         */
        if ((sr->sr_flags & SR_IMMED) == 0) {
                i = mstohz(xs->timeout);
                SUNSCPAL_TRACE("sched: set timeout=%d\n", i);
                callout_reset(&sr->sr_xs->xs_callout, i,
                    sunscpal_cmd_timeout, sr);
        }

 have_nexus:

        SUNSCPAL_TRACE("sched: call machine, cur=0x%x\n",
            (long)sc->sc_current);
        sunscpal_machine(sc);
        SUNSCPAL_TRACE("sched: machine done, cur=0x%x\n",
            (long)sc->sc_current);

        /*
         * What state did sunscpal_machine() leave us in?
         * Hopefully it sometimes completes a job...
         */
        if (sc->sc_state == SUNSCPAL_IDLE)
                goto next_job;

        return;         /* Have work in progress. */
}


/*
 *  Reselect handler: checks for reselection, and if we are being
 *      reselected, it sets up sc->sc_current.
 *
 *  We are reselected when:
 *      SEL is TRUE
 *      IO  is TRUE
 *      BSY is FALSE
 */
void
sunscpal_reselect(struct sunscpal_softc *sc)
{

        /*
         * This controller does not implement disconnect/reselect, so
         * we really don't have anything to do here.  We keep this
         * function as a placeholder, though.
         */
}

/*
 *  Select target: xs is the transfer that we are selecting for.
 *  sc->sc_current should be NULL.
 *
 *  Returns:
 *      sc->sc_current != NULL  ==> we were reselected (race!)
 *      XS_NOERROR              ==> selection worked
 *      XS_BUSY                 ==> lost arbitration
 *      XS_SELTIMEOUT           ==> no response to selection
 */
static int
sunscpal_select(struct sunscpal_softc *sc, struct sunscpal_req *sr)
{
        int timo, target_mask;
        u_short mode;

        /* Check for reselect */
        sunscpal_reselect(sc);
        if (sc->sc_current) {
                SUNSCPAL_TRACE("select: reselect, cur=0x%x\n",
                    (long)sc->sc_current);
                return XS_BUSY; /* reselected */
        }

        /*
         * Select the target.
         */
        target_mask = (1 << sr->sr_target);
        SUNSCPAL_WRITE_1(sc, sunscpal_data, target_mask);
        SUNSCPAL_WRITE_2(sc, sunscpal_icr, SUNSCPAL_ICR_SELECT);

        /*
         * Wait for the target to assert BSY.
         * SCSI spec. says wait for 250 mS.
         */
        for (timo = 25000;;) {
                if (SUNSCPAL_READ_2(sc, sunscpal_icr) & SUNSCPAL_ICR_BUSY)
                        goto success;
                if (--timo <= 0)
                        break;
                delay(10);
        }

        SUNSCPAL_WRITE_1(sc, sunscpal_data, 0);
        SUNSCPAL_WRITE_2(sc, sunscpal_icr, 0);

        SUNSCPAL_TRACE("select: device down, rc=%d\n", XS_SELTIMEOUT);
        return XS_SELTIMEOUT;

 success:

        /*
         * The target is now driving BSY, so we can stop
         * driving SEL and the data bus.  We do set up
         * whether or not this target needs parity.
         */
        mode = 0;
        if ((sc->sc_parity_disable & target_mask) == 0)
                mode |= SUNSCPAL_ICR_PARITY_ENABLE;
        SUNSCPAL_WRITE_2(sc, sunscpal_icr, mode);

        return XS_NOERROR;
}

/*****************************************************************
 * Functions to handle each info. transfer phase:
 *****************************************************************/

/*
 * The message system:
 *
 * This is a revamped message system that now should easier accommodate
 * new messages, if necessary.
 *
 * Currently we accept these messages:
 * IDENTIFY (when reselecting)
 * COMMAND COMPLETE # (expect bus free after messages marked #)
 * NOOP
 * MESSAGE REJECT
 * SYNCHRONOUS DATA TRANSFER REQUEST
 * SAVE DATA POINTER
 * RESTORE POINTERS
 * DISCONNECT #
 *
 * We may send these messages in prioritized order:
 * BUS DEVICE RESET #           if XS_CTL_RESET & xs->xs_control (or in
 *                              weird sits.)
 * MESSAGE PARITY ERROR         par. err. during MSGI
 * MESSAGE REJECT               If we get a message we don't know how to handle
 * ABORT #                      send on errors
 * INITIATOR DETECTED ERROR     also on errors (SCSI2) (during info xfer)
 * IDENTIFY                     At the start of each transfer
 * SYNCHRONOUS DATA TRANSFER REQUEST    if appropriate
 * NOOP                         if nothing else fits the bill ...
 */

/*
 * Precondition:
 * The SCSI bus is already in the MSGI phase and there is a message byte
 * on the bus, along with an asserted REQ signal.
 *
 * Our return value determines whether our caller, sunscpal_machine()
 * will expect to see another REQ (and possibly phase change).
 */
static int
sunscpal_msg_in(struct sunscpal_softc *sc)
{
        struct sunscpal_req *sr = sc->sc_current;
        struct scsipi_xfer *xs = sr->sr_xs;
        int n, phase;
        int act_flags;

        act_flags = ACT_CONTINUE;

        if (sc->sc_prevphase == SUNSCPAL_PHASE_MSG_IN) {
                /* This is a continuation of the previous message. */
                n = sc->sc_imp - sc->sc_imess;
                SUNSCPAL_TRACE("msg_in: continuation, n=%d\n", n);
                goto nextbyte;
        }

        /* This is a new MESSAGE IN phase.  Clean up our state. */
        sc->sc_state &= ~SUNSCPAL_DROP_MSGIN;

 nextmsg:
        n = 0;
        sc->sc_imp = &sc->sc_imess[n];

 nextbyte:
        /*
         * Read a whole message, but don't ack the last byte.  If we reject the
         * message, we have to assert ATN during the message transfer phase
         * itself.
         */
        for (;;) {
                /*
                 * Read a message byte.
                 * First, check BSY, REQ, phase...
                 */
                if (!SUNSCPAL_BUSY(sc)) {
                        SUNSCPAL_TRACE("msg_in: lost BSY, n=%d\n", n);
                        /* XXX - Assume the command completed? */
                        act_flags |= (ACT_DISCONNECT | ACT_CMD_DONE);
                        return act_flags;
                }
                if (sunscpal_wait_req(sc)) {
                        SUNSCPAL_TRACE("msg_in: BSY but no REQ, n=%d\n", n);
                        /* Just let sunscpal_machine() handle it... */
                        return act_flags;
                }
                phase = SUNSCPAL_BUS_PHASE(SUNSCPAL_READ_2(sc, sunscpal_icr));
                if (phase != SUNSCPAL_PHASE_MSG_IN) {
                        /*
                         * Target left MESSAGE IN, probably because it
                         * a) noticed our ATN signal, or
                         * b) ran out of messages.
                         */
                        return act_flags;
                }
                /* Still in MESSAGE IN phase, and REQ is asserted. */
                if ((SUNSCPAL_READ_2(sc, sunscpal_icr) &
                    SUNSCPAL_ICR_PARITY_ERROR) != 0) {
                        sunscpal_sched_msgout(sc, SEND_PARITY_ERROR);
                        sc->sc_state |= SUNSCPAL_DROP_MSGIN;
                }

                /* Gather incoming message bytes if needed. */
                if ((sc->sc_state & SUNSCPAL_DROP_MSGIN) == 0) {
                        if (n >= SUNSCPAL_MAX_MSG_LEN) {
                                sunscpal_sched_msgout(sc, SEND_REJECT);
                                sc->sc_state |= SUNSCPAL_DROP_MSGIN;
                        } else {
                                *sc->sc_imp++ =
                                    SUNSCPAL_READ_1(sc, sunscpal_cmd_stat);
                                n++;
                                /*
                                 * This testing is suboptimal, but most
                                 * messages will be of the one byte variety, so
                                 * it should not affect performance
                                 * significantly.
                                 */
                                if (n == 1 && MSG_IS1BYTE(sc->sc_imess[0]))
                                        goto have_msg;
                                if (n == 2 && MSG_IS2BYTE(sc->sc_imess[0]))
                                        goto have_msg;
                                if (n >= 3 && MSG_ISEXTENDED(sc->sc_imess[0]) &&
                                        n == sc->sc_imess[1] + 2)
                                        goto have_msg;
                        }
                }

                /*
                 * If we reach this spot we're either:
                 * a) in the middle of a multi-byte message, or
                 * b) dropping bytes.
                 */

                if (act_flags != ACT_CONTINUE)
                        return act_flags;

                /* back to nextbyte */
        }

 have_msg:
        /* We now have a complete message.  Parse it. */

        switch (sc->sc_imess[0]) {
        case MSG_CMDCOMPLETE:
                SUNSCPAL_TRACE("msg_in: CMDCOMPLETE\n", 0);
                /* Target is about to disconnect. */
                act_flags |= (ACT_DISCONNECT | ACT_CMD_DONE);
                break;

        case MSG_PARITY_ERROR:
                SUNSCPAL_TRACE("msg_in: PARITY_ERROR\n", 0);
                /* Resend the last message. */
                sunscpal_sched_msgout(sc, sc->sc_msgout);
                break;

        case MSG_MESSAGE_REJECT:
                /* The target rejects the last message we sent. */
                SUNSCPAL_TRACE("msg_in: got reject for 0x%x\n", sc->sc_msgout);
                switch (sc->sc_msgout) {
                case SEND_IDENTIFY:
                        /* Really old target controller? */
                        /* XXX ... */
                        break;
                case SEND_INIT_DET_ERR:
                        goto abort;
                }
                break;

        case MSG_NOOP:
                SUNSCPAL_TRACE("msg_in: NOOP\n", 0);
                break;

        case MSG_DISCONNECT:
                SUNSCPAL_TRACE("msg_in: DISCONNECT\n", 0);
                /* Target is about to disconnect. */
                act_flags |= ACT_DISCONNECT;
                if ((xs->xs_periph->periph_quirks & PQUIRK_AUTOSAVE) == 0)
                        break;
                /*FALLTHROUGH*/

        case MSG_SAVEDATAPOINTER:
                SUNSCPAL_TRACE("msg_in: SAVE_PTRS\n", 0);
                sr->sr_dataptr = sc->sc_dataptr;
                sr->sr_datalen = sc->sc_datalen;
                break;

        case MSG_RESTOREPOINTERS:
                SUNSCPAL_TRACE("msg_in: RESTORE_PTRS\n", 0);
                sc->sc_dataptr = sr->sr_dataptr;
                sc->sc_datalen = sr->sr_datalen;
                break;

        case MSG_EXTENDED:
                switch (sc->sc_imess[2]) {
                case MSG_EXT_SDTR:
                case MSG_EXT_WDTR:
                        /* This controller can not do synchronous mode. */
                        goto reject;
                default:
                        printf("%s: unrecognized MESSAGE EXTENDED; "
                            "sending REJECT\n",
                            device_xname(sc->sc_dev));
                        SUNSCPAL_BREAK();
                        goto reject;
                }
                break;

        default:
                SUNSCPAL_TRACE("msg_in: eh? imsg=0x%x\n", sc->sc_imess[0]);
                printf("%s: unrecognized MESSAGE; sending REJECT\n",
                    device_xname(sc->sc_dev));
                SUNSCPAL_BREAK();
                /* FALLTHROUGH */
        reject:
                sunscpal_sched_msgout(sc, SEND_REJECT);
                break;

        abort:
                sc->sc_state |= SUNSCPAL_ABORTING;
                sunscpal_sched_msgout(sc, SEND_ABORT);
                break;
        }

        /* Go get the next message, if any. */
        if (act_flags == ACT_CONTINUE)
                goto nextmsg;

        return act_flags;
}


/*
 * The message out (and in) stuff is a bit complicated:
 * If the target requests another message (sequence) without
 * having changed phase in between it really asks for a
 * retransmit, probably due to parity error(s).
 * The following messages can be sent:
 * IDENTIFY        @ These 4 stem from SCSI command activity
 * SDTR            @
 * WDTR            @
 * DEV_RESET       @
 * REJECT if MSGI doesn't make sense
 * PARITY_ERROR if parity error while in MSGI
 * INIT_DET_ERR if parity error while not in MSGI
 * ABORT if INIT_DET_ERR rejected
 * NOOP if asked for a message and there's nothing to send
 *
 * Note that we call this one with (sc_current == NULL)
 * when sending ABORT for unwanted reselections.
 */
static int
sunscpal_msg_out(struct sunscpal_softc *sc)
{
        /*
         * This controller does not allow you to assert ATN, which
         * means we will never get the opportunity to send messages to
         * the target (the bus will never enter this MSG_OUT phase).
         * This will eventually leave us with no option other than to
         * reset the bus.  We keep this function as a placeholder,
         * though, and this printf will eventually go away or get
         * #ifdef'ed:
         */
        printf("%s: bus is in MSG_OUT phase?\n", __func__);
        return ACT_CONTINUE | ACT_RESET_BUS;
}

/*
 * Handle command phase.
 */
static int
sunscpal_command(struct sunscpal_softc *sc)
{
        struct sunscpal_req *sr = sc->sc_current;
        struct scsipi_xfer *xs = sr->sr_xs;
        int len;

        /* Assume command can be sent in one go. */
        /* XXX: Do this using DMA, and get a phase change intr? */
        len = sunscpal_pio_out(sc, SUNSCPAL_PHASE_COMMAND, xs->cmdlen,
            (uint8_t *)xs->cmd);

        if (len != xs->cmdlen) {
#ifdef  SUNSCPAL_DEBUG
                printf("%s: short transfer: wanted %d got %d.\n",
                    __func__, xs->cmdlen, len);
                sunscpal_show_scsi_cmd(xs);
                SUNSCPAL_BREAK();
#endif
                if (len < 6) {
                        xs->error = XS_DRIVER_STUFFUP;
                        sc->sc_state |= SUNSCPAL_ABORTING;
                        sunscpal_sched_msgout(sc, SEND_ABORT);
                }

        }

        return ACT_CONTINUE;
}


/*
 * Handle either data_in or data_out
 */
static int
sunscpal_data_xfer(struct sunscpal_softc *sc, int phase)
{
        struct sunscpal_req *sr = sc->sc_current;
        struct scsipi_xfer *xs = sr->sr_xs;
        int expected_phase;
        int len;

        /*
         * When aborting a command, disallow any data phase.
         */
        if (sc->sc_state & SUNSCPAL_ABORTING) {
                printf("%s: aborting, bus phase=%s (reset)\n",
                    device_xname(sc->sc_dev), phase_names[(phase >> 8) & 7]);
                return ACT_RESET_BUS;   /* XXX */
        }

        /* Validate expected phase (data_in or data_out) */
        expected_phase = (xs->xs_control & XS_CTL_DATA_OUT) ?
            SUNSCPAL_PHASE_DATA_OUT : SUNSCPAL_PHASE_DATA_IN;
        if (phase != expected_phase) {
                printf("%s: data phase error\n", device_xname(sc->sc_dev));
                goto abort;
        }

        /* Make sure we have some data to move. */
        if (sc->sc_datalen <= 0) {
                /* Device needs padding. */
                if (phase == SUNSCPAL_PHASE_DATA_IN)
                        sunscpal_pio_in(sc, phase, 4096, NULL);
                else
                        sunscpal_pio_out(sc, phase, 4096, NULL);
                /* Make sure that caused a phase change. */
                if (SUNSCPAL_BUS_PHASE(SUNSCPAL_READ_2(sc, sunscpal_icr)) ==
                    phase) {
                        /* More than 4k is just too much! */
                        printf("%s: too much data padding\n",
                            device_xname(sc->sc_dev));
                        goto abort;
                }
                return ACT_CONTINUE;
        }

        /*
         * Attempt DMA only if dma_alloc gave us a DMA handle AND
         * there is enough left to transfer so DMA is worth while.
         */
        if (sr->sr_dma_hand && (sc->sc_datalen >= sc->sc_min_dma_len)) {
                /*
                 * OK, really start DMA.  Note, the MD start function
                 * is responsible for setting the TCMD register, etc.
                 * (Acknowledge the phase change there, not here.)
                 */
                SUNSCPAL_TRACE("data_xfer: dma_start, dh=0x%x\n",
                    (long)sr->sr_dma_hand);
                sunscpal_dma_start(sc);
                return ACT_WAIT_DMA;
        }

        /*
         * Doing PIO for data transfer.  (Possibly "Pseudo DMA")
         * XXX:  Do PDMA functions need to set tcmd later?
         */
        SUNSCPAL_TRACE("data_xfer: doing PIO, len=%d\n", sc->sc_datalen);
        if (phase == SUNSCPAL_PHASE_DATA_OUT) {
                len = sunscpal_pio_out(sc, phase,
                    sc->sc_datalen, sc->sc_dataptr);
        } else {
                len = sunscpal_pio_in(sc, phase,
                    sc->sc_datalen, sc->sc_dataptr);
        }
        sc->sc_dataptr += len;
        sc->sc_datalen -= len;

        SUNSCPAL_TRACE("data_xfer: did PIO, resid=%d\n", sc->sc_datalen);
        return ACT_CONTINUE;

 abort:
        sc->sc_state |= SUNSCPAL_ABORTING;
        sunscpal_sched_msgout(sc, SEND_ABORT);
        return ACT_CONTINUE;
}


static int
sunscpal_status(struct sunscpal_softc *sc)
{
        int len;
        uint8_t status;
        struct sunscpal_req *sr = sc->sc_current;

        len = sunscpal_pio_in(sc, SUNSCPAL_PHASE_STATUS, 1, &status);
        if (len) {
                sr->sr_status = status;
        } else {
                printf("%s: none?\n", __func__);
        }

        return ACT_CONTINUE;
}


/*
 * This is the big state machine that follows SCSI phase changes.
 * This is somewhat like a co-routine.  It will do a SCSI command,
 * and exit if the command is complete, or if it must wait, i.e.
 * for DMA to complete or for reselect to resume the job.
 *
 * The bus must be selected, and we need to know which command is
 * being undertaken.
 */
static void
sunscpal_machine(struct sunscpal_softc *sc)
{
        struct sunscpal_req *sr;
        struct scsipi_xfer *xs;
        int act_flags, phase, timo;

#ifdef  DIAGNOSTIC
        if (sc->sc_state == SUNSCPAL_IDLE)
                panic("%s: state=idle", __func__);
        if (sc->sc_current == NULL)
                panic("%s: no current cmd", __func__);
#endif

        sr = sc->sc_current;
        xs = sr->sr_xs;
        act_flags = ACT_CONTINUE;

        /*
         * This will be called by sunscpal_intr() when DMA is
         * complete.  Must stop DMA before touching the PAL or
         * there will be "register conflict" errors.
         */
        if ((sc->sc_state & SUNSCPAL_DOINGDMA) != 0) {
                /* Pick-up where where we left off... */
                goto dma_done;
        }

 next_phase:

        if (!SUNSCPAL_BUSY(sc)) {
                /* Unexpected disconnect */
                printf("%s: unexpected disconnect.\n", __func__);
                xs->error = XS_DRIVER_STUFFUP;
                act_flags |= (ACT_DISCONNECT | ACT_CMD_DONE);
                goto do_actions;
        }

        /*
         * Wait for REQ before reading the phase.
         * Need to wait longer than usual here, because
         * some devices are just plain slow...
         */
        timo = sunscpal_wait_phase_timo;
        for (;;) {
                if (SUNSCPAL_READ_2(sc, sunscpal_icr) & SUNSCPAL_ICR_REQUEST)
                        break;
                if (--timo <= 0) {
                        if (sc->sc_state & SUNSCPAL_ABORTING) {
                                printf("%s: no REQ while aborting, reset\n",
                                    device_xname(sc->sc_dev));
                                act_flags |= ACT_RESET_BUS;
                                goto do_actions;
                        }
                        printf("%s: no REQ for next phase, abort\n",
                            device_xname(sc->sc_dev));
                        sc->sc_state |= SUNSCPAL_ABORTING;
                        sunscpal_sched_msgout(sc, SEND_ABORT);
                        goto next_phase;
                }
                delay(100);
        }

        phase = SUNSCPAL_BUS_PHASE(SUNSCPAL_READ_2(sc, sunscpal_icr));
        SUNSCPAL_TRACE("machine: phase=%s\n",
            (long)phase_names[(phase >> 8) & 7]);

        /*
         * We assume that the device knows what it's doing,
         * so any phase is good.
         */

        switch (phase) {

        case SUNSCPAL_PHASE_DATA_OUT:
        case SUNSCPAL_PHASE_DATA_IN:
                act_flags = sunscpal_data_xfer(sc, phase);
                break;

        case SUNSCPAL_PHASE_COMMAND:
                act_flags = sunscpal_command(sc);
                break;

        case SUNSCPAL_PHASE_STATUS:
                act_flags = sunscpal_status(sc);
                break;

        case SUNSCPAL_PHASE_MSG_OUT:
                act_flags = sunscpal_msg_out(sc);
                break;

        case SUNSCPAL_PHASE_MSG_IN:
                act_flags = sunscpal_msg_in(sc);
                break;

        default:
                printf("%s: Unexpected phase 0x%x\n", __func__, phase);
                sc->sc_state |= SUNSCPAL_ABORTING;
                sunscpal_sched_msgout(sc, SEND_ABORT);
                goto next_phase;

        } /* switch */
        sc->sc_prevphase = phase;

 do_actions:

        if (act_flags & ACT_WAIT_DMA) {
                act_flags &= ~ACT_WAIT_DMA;
                /* Wait for DMA to complete (polling, or interrupt). */
                if ((sr->sr_flags & SR_IMMED) == 0) {
                        SUNSCPAL_TRACE("machine: wait for DMA intr.\n", 0);
                        return;         /* will resume at dma_done */
                }
                /* Busy-wait for it to finish. */
                SUNSCPAL_TRACE("machine: dma_poll, dh=0x%x\n",
                    (long)sr->sr_dma_hand);
                sunscpal_dma_poll(sc);
 dma_done:
                /* Return here after interrupt. */
                if (sr->sr_flags & SR_OVERDUE)
                        sc->sc_state |= SUNSCPAL_ABORTING;
                SUNSCPAL_TRACE("machine: dma_stop, dh=0x%x\n",
                    (long)sr->sr_dma_hand);
                sunscpal_dma_stop(sc);
                SUNSCPAL_CLR_INTR(sc);  /* XXX */
                /*
                 * While DMA is running we can not touch the SBC,
                 * so various places just set SUNSCPAL_ABORTING and
                 * expect us the "kick it" when DMA is done.
                 */
                if (sc->sc_state & SUNSCPAL_ABORTING) {
                        sunscpal_sched_msgout(sc, SEND_ABORT);
                }
        }

        /*
         * Check for parity error.
         * XXX - better place to check?
         */
        if (SUNSCPAL_READ_2(sc, sunscpal_icr) & SUNSCPAL_ICR_PARITY_ERROR) {
                printf("%s: parity error!\n", device_xname(sc->sc_dev));
                /* XXX: sc->sc_state |= SUNSCPAL_ABORTING; */
                sunscpal_sched_msgout(sc, SEND_PARITY_ERROR);
        }

        if (act_flags == ACT_CONTINUE)
                goto next_phase;
        /* All other actions "break" from the loop. */

        SUNSCPAL_TRACE("machine: act_flags=0x%x\n", act_flags);

        if (act_flags & ACT_RESET_BUS) {
                act_flags |= ACT_CMD_DONE;
                /*
                 * Reset the SCSI bus, usually due to a timeout.
                 * The error code XS_TIMEOUT allows retries.
                 */
                sc->sc_state |= SUNSCPAL_ABORTING;
                printf("%s: reset SCSI bus for TID=%d LUN=%d\n",
                    device_xname(sc->sc_dev), sr->sr_target, sr->sr_lun);
                sunscpal_reset_scsibus(sc);
        }

        if (act_flags & ACT_CMD_DONE) {
                act_flags |= ACT_DISCONNECT;
                /* Need to call scsipi_done() */
                /* XXX: from the aic6360 driver, but why? */
                if (sc->sc_datalen < 0) {
                        printf("%s: %d extra bytes from %d:%d\n",
                            device_xname(sc->sc_dev), -sc->sc_datalen,
                            sr->sr_target, sr->sr_lun);
                        sc->sc_datalen = 0;
                }
                xs->resid = sc->sc_datalen;
                /* Note: this will clear sc_current */
                SUNSCPAL_TRACE("machine: call done, cur=0x%x\n", (long)sr);
                sunscpal_done(sc);
        }

        if (act_flags & ACT_DISCONNECT) {
                /*
                 * The device has dropped BSY (or will soon).
                 * We have to wait here for BSY to drop, otherwise
                 * the next command may decide we need a bus reset.
                 */
                timo = sunscpal_wait_req_timo;  /* XXX */
                for (;;) {
                        if (!SUNSCPAL_BUSY(sc))
                                goto busfree;
                        if (--timo <= 0)
                                break;
                        delay(2);
                }
                /* Device is sitting on the bus! */
                printf("%s: Target %d LUN %d stuck busy, resetting...\n",
                    device_xname(sc->sc_dev), sr->sr_target, sr->sr_lun);
                sunscpal_reset_scsibus(sc);
 busfree:
                SUNSCPAL_TRACE("machine: discon, waited %d\n",
                        sunscpal_wait_req_timo - timo);

                SUNSCPAL_WRITE_2(sc, sunscpal_icr, 0);

                if ((act_flags & ACT_CMD_DONE) == 0) {
                        SUNSCPAL_TRACE("machine: discon, cur=0x%x\n", (long)sr);
                }

                /*
                 * We may be here due to a disconnect message,
                 * in which case we did NOT call sunscpal_done,
                 * and we need to clear sc_current.
                 */
                sc->sc_state = SUNSCPAL_IDLE;
                sc->sc_current = NULL;

                /* Paranoia: clear everything. */
                sc->sc_dataptr = NULL;
                sc->sc_datalen = 0;
                sc->sc_prevphase = SUNSCPAL_PHASE_INVALID;
                sc->sc_msgpriq = 0;
                sc->sc_msgoutq = 0;
                sc->sc_msgout  = 0;

                /* Our caller will re-enable interrupts. */
        }
}


#ifdef  SUNSCPAL_DEBUG

static void
sunscpal_show_scsi_cmd(struct scsipi_xfer *xs)
{
        uint8_t *b = (uint8_t *)xs->cmd;
        int i = 0;

        scsipi_printaddr(xs->xs_periph);
        if ((xs->xs_control & XS_CTL_RESET) == 0) {
                printf("-");
                while (i < xs->cmdlen) {
                        if (i != 0)
                                printf(",");
                        printf("%x", b[i++]);
                }
                printf("-\n");
        } else {
                printf("-RESET-\n");
        }
}


int sunscpal_traceidx = 0;

#define TRACE_MAX       1024
struct trace_ent {
        char *msg;
        long  val;
} sunscpal_tracebuf[TRACE_MAX];

void
sunscpal_trace(char *msg, long val)
{
        struct trace_ent *tr;
        int s;

        s = splbio();

        tr = &sunscpal_tracebuf[sunscpal_traceidx];

        sunscpal_traceidx++;
        if (sunscpal_traceidx >= TRACE_MAX)
                sunscpal_traceidx = 0;

        tr->msg = msg;
        tr->val = val;

        splx(s);
}

#ifdef  DDB
void
sunscpal_clear_trace(void)
{

        sunscpal_traceidx = 0;
        memset((void *)sunscpal_tracebuf, 0, sizeof(sunscpal_tracebuf));
}

void
sunscpal_show_trace(void)
{
        struct trace_ent *tr;
        int idx;

        idx = sunscpal_traceidx;
        do {
                tr = &sunscpal_tracebuf[idx];
                idx++;
                if (idx >= TRACE_MAX)
                        idx = 0;
                if (tr->msg)
                        db_printf(tr->msg, tr->val);
        } while (idx != sunscpal_traceidx);
}

void
sunscpal_show_req(struct sunscpal_req *sr)
{
        struct scsipi_xfer *xs = sr->sr_xs;

        db_printf("TID=%d ",    sr->sr_target);
        db_printf("LUN=%d ",    sr->sr_lun);
        db_printf("dh=%p ",     sr->sr_dma_hand);
        db_printf("dptr=%p ",   sr->sr_dataptr);
        db_printf("dlen=0x%x ", sr->sr_datalen);
        db_printf("flags=%d ",  sr->sr_flags);
        db_printf("stat=%d ",   sr->sr_status);

        if (xs == NULL) {
                db_printf("(xs=NULL)\n");
                return;
        }
        db_printf("\n");
#ifdef  SCSIDEBUG
        show_scsipi_xs(xs);
#else
        db_printf("xs=%p\n", xs);
#endif
}

void
sunscpal_show_state(void)
{
        struct sunscpal_softc *sc;
        struct sunscpal_req *sr;
        int i, j, k;

        sc = sunscpal_debug_sc;

        if (sc == NULL) {
                db_printf("sunscpal_debug_sc == NULL\n");
                return;
        }

        db_printf("sc_ncmds=%d\n",      sc->sc_ncmds);
        k = -1; /* which is current? */
        for (i = 0; i < SUNSCPAL_OPENINGS; i++) {
                sr = &sc->sc_ring[i];
                if (sr->sr_xs) {
                        if (sr == sc->sc_current)
                                k = i;
                        db_printf("req %d: (sr=%p)", i, sr);
                        sunscpal_show_req(sr);
                }
        }
        db_printf("sc_rr=%d, current=%d\n", sc->sc_rr, k);

        db_printf("Active request matrix:\n");
        for(i = 0; i < 8; i++) {                /* targets */
                for (j = 0; j < 8; j++) {       /* LUN */
                        sr = sc->sc_matrix[i][j];
                        if (sr) {
                                db_printf("TID=%d LUN=%d sr=%p\n", i, j, sr);
                        }
                }
        }

        db_printf("sc_state=0x%x\n",    sc->sc_state);
        db_printf("sc_current=%p\n",    sc->sc_current);
        db_printf("sc_dataptr=%p\n",    sc->sc_dataptr);
        db_printf("sc_datalen=0x%x\n",  sc->sc_datalen);

        db_printf("sc_prevphase=%d\n",  sc->sc_prevphase);
        db_printf("sc_msgpriq=0x%x\n",  sc->sc_msgpriq);
}
#endif  /* DDB */
#endif  /* SUNSCPAL_DEBUG */

void
sunscpal_attach(struct sunscpal_softc *sc, int options)
{

        /*
         * Handle our options.
         */
        aprint_normal(": options=0x%x\n", options);
        sc->sc_parity_disable = (options & SUNSCPAL_OPT_NO_PARITY_CHK);
        if (options & SUNSCPAL_OPT_DISABLE_DMA)
                sc->sc_flags |= SUNSCPAL_DISABLE_DMA;

        /*
         * Fill in the adapter.
         */
        memset(&sc->sc_adapter, 0, sizeof(sc->sc_adapter));
        sc->sc_adapter.adapt_dev = sc->sc_dev;
        sc->sc_adapter.adapt_nchannels = 1;
        sc->sc_adapter.adapt_openings = SUNSCPAL_OPENINGS;
        sc->sc_adapter.adapt_max_periph = 1;
        sc->sc_adapter.adapt_request = sunscpal_scsipi_request;
        sc->sc_adapter.adapt_minphys = sunscpal_minphys;
        if (options & SUNSCPAL_OPT_FORCE_POLLING)
                sc->sc_adapter.adapt_flags |= SCSIPI_ADAPT_POLL_ONLY;

        sc->sc_channel.chan_adapter = &sc->sc_adapter;
        sc->sc_channel.chan_bustype = &scsi_bustype;
        sc->sc_channel.chan_channel = 0;
        sc->sc_channel.chan_ntargets = 8;
        sc->sc_channel.chan_nluns = 8;
        sc->sc_channel.chan_id = 7;

        /*
         * Add reference to adapter so that we drop the reference after
         * config_found() to make sure the adatper is disabled.
         */
        if (scsipi_adapter_addref(&sc->sc_adapter) != 0) {
                aprint_error_dev(sc->sc_dev, "unable to enable controller\n");
                return;
        }

        sunscpal_init(sc);      /* Init chip and driver */
        sunscpal_reset_scsibus(sc);

        /*
         * Ask the adapter what subunits are present
         */
        (void)config_found(sc->sc_dev, &sc->sc_channel, scsiprint);
        scsipi_adapter_delref(&sc->sc_adapter);
}

int
sunscpal_detach(struct sunscpal_softc *sc, int flags)
{

        return EOPNOTSUPP;
}

static void
sunscpal_minphys(struct buf *bp)
{

        if (bp->b_bcount > SUNSCPAL_MAX_DMA_LEN) {
#ifdef  SUNSCPAL_DEBUG
                if (sunscpal_debug & SUNSCPAL_DBG_DMA) {
                        printf("%s: len = 0x%lx.\n", __func__, bp->b_bcount);
                        Debugger();
                }
#endif
                bp->b_bcount = SUNSCPAL_MAX_DMA_LEN;
        }
        return minphys(bp);
}

#ifdef SUNSCPAL_USE_BUS_DMA

/*
 * Allocate a DMA handle and put it in sr->sr_dma_hand.  Prepare
 * for DMA transfer.
 */
static void
sunscpal_dma_alloc(struct sunscpal_softc *sc)
{
        struct sunscpal_req *sr = sc->sc_current;
        sunscpal_dma_handle_t dh;
        int i, xlen;
        u_long addr;

#ifdef  DIAGNOSTIC
        if (sr->sr_dma_hand != NULL)
                panic("%s: already have DMA handle", __func__);
#endif

        addr = (u_long)sc->sc_dataptr;
        xlen = sc->sc_datalen;

        /* If the DMA start addr is misaligned then do PIO */
        if ((addr & 1) || (xlen & 1)) {
                printf("%s: misaligned.\n", __func__);
                return;
        }

        /* Make sure our caller checked sc_min_dma_len. */
        if (xlen < sc->sc_min_dma_len)
                panic("%s: xlen=0x%x", __func__, xlen);

        /*
         * Never attempt single transfers of more than 63k, because
         * our count register is only 16 bits.
         * This should never happen since already bounded by minphys().
         * XXX - Should just segment these...
         */
        if (xlen > SUNSCPAL_MAX_DMA_LEN) {
                printf("%s: excessive xlen=0x%x\n", __func__, xlen);
                Debugger();
                sc->sc_datalen = xlen = SUNSCPAL_MAX_DMA_LEN;
        }

        /* Find free DMA handle.  Guaranteed to find one since we have
           as many DMA handles as the driver has processes. */
        for (i = 0; i < SUNSCPAL_OPENINGS; i++) {
                if ((sc->sc_dma_handles[i].dh_flags & SUNSCDH_BUSY) == 0)
                        goto found;
        }
        panic("%s: no free DMA handles.", device_xname(sc->sc_dev));
 found:

        dh = &sc->sc_dma_handles[i];
        dh->dh_flags = SUNSCDH_BUSY;
        dh->dh_mapaddr = (uint8_t *)addr;
        dh->dh_maplen  = xlen;
        dh->dh_dvma = 0;

        /* Load the DMA map. */
        if (bus_dmamap_load(sc->sunscpal_dmat, dh->dh_dmamap,
            dh->dh_mapaddr, dh->dh_maplen, NULL, BUS_DMA_NOWAIT) != 0) {
                /* Can't load map */
                printf("%s: can't DMA %p/0x%x\n", __func__,
                    dh->dh_mapaddr, dh->dh_maplen);
                dh->dh_flags = 0;
                return;
        }

        /* success */
        sr->sr_dma_hand = dh;
}

static void
sunscpal_dma_free(struct sunscpal_softc *sc)
{
        struct sunscpal_req *sr = sc->sc_current;
        sunscpal_dma_handle_t dh = sr->sr_dma_hand;

#ifdef  DIAGNOSTIC
        if (dh == NULL)
                panic("%s: no DMA handle", __func__);
#endif

        if (sc->sc_state & SUNSCPAL_DOINGDMA)
                panic("%s: free while in progress", __func__);

        if (dh->dh_flags & SUNSCDH_BUSY) {
                /* XXX - Should separate allocation and mapping. */
                /* Give back the DVMA space. */
                bus_dmamap_unload(sc->sunscpal_dmat, dh->dh_dmamap);
                dh->dh_flags = 0;
        }
        sr->sr_dma_hand = NULL;
}

/*
 * This function is called during the SELECT phase that
 * precedes a COMMAND phase, in case we need to setup the
 * DMA engine before the bus enters a DATA phase.
 *
 * On the sc version, setup the start address and the count.
 */
static void
sunscpal_dma_setup(struct sunscpal_softc *sc)
{
        struct sunscpal_req *sr = sc->sc_current;
        struct scsipi_xfer *xs = sr->sr_xs;
        sunscpal_dma_handle_t dh = sr->sr_dma_hand;
        long data_pa;
        int xlen;

        /*
         * Get the DVMA mapping for this segment.
         * XXX - Should separate allocation and mapin.
         */
        data_pa = dh->dh_dvma;
        data_pa += (sc->sc_dataptr - dh->dh_mapaddr);
        if (data_pa & 1)
                panic("%s: bad pa=0x%lx", __func__, data_pa);
        xlen = sc->sc_datalen;
        if (xlen & 1)
                panic("%s: bad xlen=0x%x", __func__, xlen);
        sc->sc_reqlen = xlen;   /* XXX: or less? */

#ifdef  SUNSCPAL_DEBUG
        if (sunscpal_debug & SUNSCPAL_DBG_DMA) {
                printf("%s: dh=%p, pa=0x%lx, xlen=0x%x\n",
                    __func__, dh, data_pa, xlen);
        }
#endif

        /* sync the DMA map: */
        bus_dmamap_sync(sc->sunscpal_dmat, dh->dh_dmamap, 0, dh->dh_maplen,
            ((xs->xs_control & XS_CTL_DATA_OUT) == 0 ?
            BUS_DMASYNC_PREREAD : BUS_DMASYNC_PREWRITE));

        /* Load the start address and the count. */
        SUNSCPAL_WRITE_2(sc, sunscpal_dma_addr_h, (data_pa >> 16) & 0xFFFF);
        SUNSCPAL_WRITE_2(sc, sunscpal_dma_addr_l, (data_pa >> 0) & 0xFFFF);
        SUNSCPAL_WRITE_2(sc, sunscpal_dma_count, SUNSCPAL_DMA_COUNT_FLIP(xlen));
}

#endif /* SUNSCPAL_USE_BUS_DMA */