[deliverable/linux.git] / drivers / scsi / NCR5380.c

/*
 * NCR 5380 generic driver routines.  These should make it *trivial*
 * to implement 5380 SCSI drivers under Linux with a non-trantor
 * architecture.
 *
 * Note that these routines also work with NR53c400 family chips.
 *
 * Copyright 1993, Drew Eckhardt
 * Visionary Computing
 * (Unix and Linux consulting and custom programming)
 * drew@colorado.edu
 * +1 (303) 666-5836
 *
 * For more information, please consult
 *
 * NCR 5380 Family
 * SCSI Protocol Controller
 * Databook
 *
 * NCR Microelectronics
 * 1635 Aeroplaza Drive
 * Colorado Springs, CO 80916
 * 1+ (719) 578-3400
 * 1+ (800) 334-5454
 */

/*
 * With contributions from Ray Van Tassle, Ingmar Baumgart,
 * Ronald van Cuijlenborg, Alan Cox and others.
 */

/*
 * Further development / testing that should be done :
 * 1.  Cleanup the NCR5380_transfer_dma function and DMA operation complete
 * code so that everything does the same thing that's done at the
 * end of a pseudo-DMA read operation.
 *
 * 4.  Test SCSI-II tagged queueing (I have no devices which support
 * tagged queueing)
 */

/*
 * Design
 *
 * This is a generic 5380 driver.  To use it on a different platform,
 * one simply writes appropriate system specific macros (ie, data
 * transfer - some PC's will use the I/O bus, 68K's must use
 * memory mapped) and drops this file in their 'C' wrapper.
 *
 * As far as command queueing, two queues are maintained for
 * each 5380 in the system - commands that haven't been issued yet,
 * and commands that are currently executing.  This means that an
 * unlimited number of commands may be queued, letting
 * more commands propagate from the higher driver levels giving higher
 * throughput.  Note that both I_T_L and I_T_L_Q nexuses are supported,
 * allowing multiple commands to propagate all the way to a SCSI-II device
 * while a command is already executing.
 *
 *
 * Issues specific to the NCR5380 :
 *
 * When used in a PIO or pseudo-dma mode, the NCR5380 is a braindead
 * piece of hardware that requires you to sit in a loop polling for
 * the REQ signal as long as you are connected.  Some devices are
 * brain dead (ie, many TEXEL CD ROM drives) and won't disconnect
 * while doing long seek operations. [...] These
 * broken devices are the exception rather than the rule and I'd rather
 * spend my time optimizing for the normal case.
 *
 * Architecture :
 *
 * At the heart of the design is a coroutine, NCR5380_main,
 * which is started from a workqueue for each NCR5380 host in the
 * system.  It attempts to establish I_T_L or I_T_L_Q nexuses by
 * removing the commands from the issue queue and calling
 * NCR5380_select() if a nexus is not established.
 *
 * Once a nexus is established, the NCR5380_information_transfer()
 * phase goes through the various phases as instructed by the target.
 * if the target goes into MSG IN and sends a DISCONNECT message,
 * the command structure is placed into the per instance disconnected
 * queue, and NCR5380_main tries to find more work.  If the target is
 * idle for too long, the system will try to sleep.
 *
 * If a command has disconnected, eventually an interrupt will trigger,
 * calling NCR5380_intr()  which will in turn call NCR5380_reselect
 * to reestablish a nexus.  This will run main if necessary.
 *
 * On command termination, the done function will be called as
 * appropriate.
 *
 * SCSI pointers are maintained in the SCp field of SCSI command
 * structures, being initialized after the command is connected
 * in NCR5380_select, and set as appropriate in NCR5380_information_transfer.
 * Note that in violation of the standard, an implicit SAVE POINTERS operation
 * is done, since some BROKEN disks fail to issue an explicit SAVE POINTERS.
 */

/*
 * Using this file :
 * This file a skeleton Linux SCSI driver for the NCR 5380 series
 * of chips.  To use it, you write an architecture specific functions
 * and macros and include this file in your driver.
 *
 * These macros control options :
 * AUTOPROBE_IRQ - if defined, the NCR5380_probe_irq() function will be
 * defined.
 *
 * AUTOSENSE - if defined, REQUEST SENSE will be performed automatically
 * for commands that return with a CHECK CONDITION status.
 *
 * DIFFERENTIAL - if defined, NCR53c81 chips will use external differential
 * transceivers.
 *
 * DONT_USE_INTR - if defined, never use interrupts, even if we probe or
 * override-configure an IRQ.
 *
 * PSEUDO_DMA - if defined, PSEUDO DMA is used during the data transfer phases.
 *
 * These macros MUST be defined :
 *
 * NCR5380_read(register)  - read from the specified register
 *
 * NCR5380_write(register, value) - write to the specific register
 *
 * NCR5380_implementation_fields  - additional fields needed for this
 * specific implementation of the NCR5380
 *
 * Either real DMA *or* pseudo DMA may be implemented
 *
 * NCR5380_dma_write_setup(instance, src, count) - initialize
 * NCR5380_dma_read_setup(instance, dst, count) - initialize
 * NCR5380_dma_residual(instance); - residual count
 *
 * The generic driver is initialized by calling NCR5380_init(instance),
 * after setting the appropriate host specific fields and ID.  If the
 * driver wishes to autoprobe for an IRQ line, the NCR5380_probe_irq(instance,
 * possible) function may be used.
 */

#ifndef NCR5380_io_delay
#define NCR5380_io_delay(x)
#endif

static int do_abort(struct Scsi_Host *);
static void do_reset(struct Scsi_Host *);

/**
 * initialize_SCp - init the scsi pointer field
 * @cmd: command block to set up
 *
 * Set up the internal fields in the SCSI command.
 */

static inline void initialize_SCp(struct scsi_cmnd *cmd)
{
        /*
         * Initialize the Scsi Pointer field so that all of the commands in the
         * various queues are valid.
         */

        if (scsi_bufflen(cmd)) {
                cmd->SCp.buffer = scsi_sglist(cmd);
                cmd->SCp.buffers_residual = scsi_sg_count(cmd) - 1;
                cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
                cmd->SCp.this_residual = cmd->SCp.buffer->length;
        } else {
                cmd->SCp.buffer = NULL;
                cmd->SCp.buffers_residual = 0;
                cmd->SCp.ptr = NULL;
                cmd->SCp.this_residual = 0;
        }

        cmd->SCp.Status = 0;
        cmd->SCp.Message = 0;
}

/**
 * NCR5380_poll_politely2 - wait for two chip register values
 * @instance: controller to poll
 * @reg1: 5380 register to poll
 * @bit1: Bitmask to check
 * @val1: Expected value
 * @reg2: Second 5380 register to poll
 * @bit2: Second bitmask to check
 * @val2: Second expected value
 * @wait: Time-out in jiffies
 *
 * Polls the chip in a reasonably efficient manner waiting for an
 * event to occur. After a short quick poll we begin to yield the CPU
 * (if possible). In irq contexts the time-out is arbitrarily limited.
 * Callers may hold locks as long as they are held in irq mode.
 *
 * Returns 0 if either or both event(s) occurred otherwise -ETIMEDOUT.
 */

static int NCR5380_poll_politely2(struct Scsi_Host *instance,
                                  int reg1, int bit1, int val1,
                                  int reg2, int bit2, int val2, int wait)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        unsigned long deadline = jiffies + wait;
        unsigned long n;

        /* Busy-wait for up to 10 ms */
        n = min(10000U, jiffies_to_usecs(wait));
        n *= hostdata->accesses_per_ms;
        n /= 2000;
        do {
                if ((NCR5380_read(reg1) & bit1) == val1)
                        return 0;
                if ((NCR5380_read(reg2) & bit2) == val2)
                        return 0;
                cpu_relax();
        } while (n--);

        if (irqs_disabled() || in_interrupt())
                return -ETIMEDOUT;

        /* Repeatedly sleep for 1 ms until deadline */
        while (time_is_after_jiffies(deadline)) {
                schedule_timeout_uninterruptible(1);
                if ((NCR5380_read(reg1) & bit1) == val1)
                        return 0;
                if ((NCR5380_read(reg2) & bit2) == val2)
                        return 0;
        }

        return -ETIMEDOUT;
}

static inline int NCR5380_poll_politely(struct Scsi_Host *instance,
                                        int reg, int bit, int val, int wait)
{
        return NCR5380_poll_politely2(instance, reg, bit, val,
                                                reg, bit, val, wait);
}

#if NDEBUG
static struct {
        unsigned char mask;
        const char *name;
} signals[] = {
        {SR_DBP, "PARITY"},
        {SR_RST, "RST"},
        {SR_BSY, "BSY"},
        {SR_REQ, "REQ"},
        {SR_MSG, "MSG"},
        {SR_CD, "CD"},
        {SR_IO, "IO"},
        {SR_SEL, "SEL"},
        {0, NULL}
},
basrs[] = {
        {BASR_ATN, "ATN"},
        {BASR_ACK, "ACK"},
        {0, NULL}
},
icrs[] = {
        {ICR_ASSERT_RST, "ASSERT RST"},
        {ICR_ASSERT_ACK, "ASSERT ACK"},
        {ICR_ASSERT_BSY, "ASSERT BSY"},
        {ICR_ASSERT_SEL, "ASSERT SEL"},
        {ICR_ASSERT_ATN, "ASSERT ATN"},
        {ICR_ASSERT_DATA, "ASSERT DATA"},
        {0, NULL}
},
mrs[] = {
        {MR_BLOCK_DMA_MODE, "MODE BLOCK DMA"},
        {MR_TARGET, "MODE TARGET"},
        {MR_ENABLE_PAR_CHECK, "MODE PARITY CHECK"},
        {MR_ENABLE_PAR_INTR, "MODE PARITY INTR"},
        {MR_ENABLE_EOP_INTR, "MODE EOP INTR"},
        {MR_MONITOR_BSY, "MODE MONITOR BSY"},
        {MR_DMA_MODE, "MODE DMA"},
        {MR_ARBITRATE, "MODE ARBITRATION"},
        {0, NULL}
};

/**
 * NCR5380_print - print scsi bus signals
 * @instance: adapter state to dump
 *
 * Print the SCSI bus signals for debugging purposes
 */

static void NCR5380_print(struct Scsi_Host *instance)
{
        unsigned char status, data, basr, mr, icr, i;

        data = NCR5380_read(CURRENT_SCSI_DATA_REG);
        status = NCR5380_read(STATUS_REG);
        mr = NCR5380_read(MODE_REG);
        icr = NCR5380_read(INITIATOR_COMMAND_REG);
        basr = NCR5380_read(BUS_AND_STATUS_REG);

        printk("STATUS_REG: %02x ", status);
        for (i = 0; signals[i].mask; ++i)
                if (status & signals[i].mask)
                        printk(",%s", signals[i].name);
        printk("\nBASR: %02x ", basr);
        for (i = 0; basrs[i].mask; ++i)
                if (basr & basrs[i].mask)
                        printk(",%s", basrs[i].name);
        printk("\nICR: %02x ", icr);
        for (i = 0; icrs[i].mask; ++i)
                if (icr & icrs[i].mask)
                        printk(",%s", icrs[i].name);
        printk("\nMODE: %02x ", mr);
        for (i = 0; mrs[i].mask; ++i)
                if (mr & mrs[i].mask)
                        printk(",%s", mrs[i].name);
        printk("\n");
}

static struct {
        unsigned char value;
        const char *name;
} phases[] = {
        {PHASE_DATAOUT, "DATAOUT"},
        {PHASE_DATAIN, "DATAIN"},
        {PHASE_CMDOUT, "CMDOUT"},
        {PHASE_STATIN, "STATIN"},
        {PHASE_MSGOUT, "MSGOUT"},
        {PHASE_MSGIN, "MSGIN"},
        {PHASE_UNKNOWN, "UNKNOWN"}
};

/**
 * NCR5380_print_phase - show SCSI phase
 * @instance: adapter to dump
 *
 * Print the current SCSI phase for debugging purposes
 */

static void NCR5380_print_phase(struct Scsi_Host *instance)
{
        unsigned char status;
        int i;

        status = NCR5380_read(STATUS_REG);
        if (!(status & SR_REQ))
                shost_printk(KERN_DEBUG, instance, "REQ not asserted, phase unknown.\n");
        else {
                for (i = 0; (phases[i].value != PHASE_UNKNOWN) &&
                     (phases[i].value != (status & PHASE_MASK)); ++i)
                        ;
                shost_printk(KERN_DEBUG, instance, "phase %s\n", phases[i].name);
        }
}
#endif


static int probe_irq __initdata;

/**
 * probe_intr   -       helper for IRQ autoprobe
 * @irq: interrupt number
 * @dev_id: unused
 * @regs: unused
 *
 * Set a flag to indicate the IRQ in question was received. This is
 * used by the IRQ probe code.
 */

static irqreturn_t __init probe_intr(int irq, void *dev_id)
{
        probe_irq = irq;
        return IRQ_HANDLED;
}

/**
 * NCR5380_probe_irq    -       find the IRQ of an NCR5380
 * @instance: NCR5380 controller
 * @possible: bitmask of ISA IRQ lines
 *
 * Autoprobe for the IRQ line used by the NCR5380 by triggering an IRQ
 * and then looking to see what interrupt actually turned up.
 */

static int __init __maybe_unused NCR5380_probe_irq(struct Scsi_Host *instance,
                                                int possible)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        unsigned long timeout;
        int trying_irqs, i, mask;

        for (trying_irqs = 0, i = 1, mask = 2; i < 16; ++i, mask <<= 1)
                if ((mask & possible) && (request_irq(i, &probe_intr, 0, "NCR-probe", NULL) == 0))
                        trying_irqs |= mask;

        timeout = jiffies + msecs_to_jiffies(250);
        probe_irq = NO_IRQ;

        /*
         * A interrupt is triggered whenever BSY = false, SEL = true
         * and a bit set in the SELECT_ENABLE_REG is asserted on the
         * SCSI bus.
         *
         * Note that the bus is only driven when the phase control signals
         * (I/O, C/D, and MSG) match those in the TCR, so we must reset that
         * to zero.
         */

        NCR5380_write(TARGET_COMMAND_REG, 0);
        NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
        NCR5380_write(OUTPUT_DATA_REG, hostdata->id_mask);
        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_DATA | ICR_ASSERT_SEL);

        while (probe_irq == NO_IRQ && time_before(jiffies, timeout))
                schedule_timeout_uninterruptible(1);

        NCR5380_write(SELECT_ENABLE_REG, 0);
        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);

        for (i = 1, mask = 2; i < 16; ++i, mask <<= 1)
                if (trying_irqs & mask)
                        free_irq(i, NULL);

        return probe_irq;
}

/**
 * NCR58380_info - report driver and host information
 * @instance: relevant scsi host instance
 *
 * For use as the host template info() handler.
 */

static const char *NCR5380_info(struct Scsi_Host *instance)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);

        return hostdata->info;
}

static void prepare_info(struct Scsi_Host *instance)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);

        snprintf(hostdata->info, sizeof(hostdata->info),
                 "%s, io_port 0x%lx, n_io_port %d, "
                 "base 0x%lx, irq %d, "
                 "can_queue %d, cmd_per_lun %d, "
                 "sg_tablesize %d, this_id %d, "
                 "flags { %s%s%s}, "
                 "options { %s} ",
                 instance->hostt->name, instance->io_port, instance->n_io_port,
                 instance->base, instance->irq,
                 instance->can_queue, instance->cmd_per_lun,
                 instance->sg_tablesize, instance->this_id,
                 hostdata->flags & FLAG_DMA_FIXUP     ? "DMA_FIXUP "     : "",
                 hostdata->flags & FLAG_NO_PSEUDO_DMA ? "NO_PSEUDO_DMA " : "",
                 hostdata->flags & FLAG_TOSHIBA_DELAY ? "TOSHIBA_DELAY "  : "",
#ifdef AUTOPROBE_IRQ
                 "AUTOPROBE_IRQ "
#endif
#ifdef DIFFERENTIAL
                 "DIFFERENTIAL "
#endif
#ifdef PARITY
                 "PARITY "
#endif
                 "");
}

/**
 * NCR5380_init - initialise an NCR5380
 * @instance: adapter to configure
 * @flags: control flags
 *
 * Initializes *instance and corresponding 5380 chip,
 * with flags OR'd into the initial flags value.
 *
 * Notes : I assume that the host, hostno, and id bits have been
 * set correctly. I don't care about the irq and other fields.
 *
 * Returns 0 for success
 */

static int NCR5380_init(struct Scsi_Host *instance, int flags)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        int i;
        unsigned long deadline;

        hostdata->host = instance;
        hostdata->id_mask = 1 << instance->this_id;
        hostdata->id_higher_mask = 0;
        for (i = hostdata->id_mask; i <= 0x80; i <<= 1)
                if (i > hostdata->id_mask)
                        hostdata->id_higher_mask |= i;
        for (i = 0; i < 8; ++i)
                hostdata->busy[i] = 0;
        hostdata->dma_len = 0;

        spin_lock_init(&hostdata->lock);
        hostdata->connected = NULL;
        hostdata->sensing = NULL;
        INIT_LIST_HEAD(&hostdata->autosense);
        INIT_LIST_HEAD(&hostdata->unissued);
        INIT_LIST_HEAD(&hostdata->disconnected);

        hostdata->flags = flags;

        INIT_WORK(&hostdata->main_task, NCR5380_main);
        hostdata->work_q = alloc_workqueue("ncr5380_%d",
                                WQ_UNBOUND | WQ_MEM_RECLAIM,
                                1, instance->host_no);
        if (!hostdata->work_q)
                return -ENOMEM;

        prepare_info(instance);

        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
        NCR5380_write(MODE_REG, MR_BASE);
        NCR5380_write(TARGET_COMMAND_REG, 0);
        NCR5380_write(SELECT_ENABLE_REG, 0);

        /* Calibrate register polling loop */
        i = 0;
        deadline = jiffies + 1;
        do {
                cpu_relax();
        } while (time_is_after_jiffies(deadline));
        deadline += msecs_to_jiffies(256);
        do {
                NCR5380_read(STATUS_REG);
                ++i;
                cpu_relax();
        } while (time_is_after_jiffies(deadline));
        hostdata->accesses_per_ms = i / 256;

        return 0;
}

/**
 * NCR5380_maybe_reset_bus - Detect and correct bus wedge problems.
 * @instance: adapter to check
 *
 * If the system crashed, it may have crashed with a connected target and
 * the SCSI bus busy. Check for BUS FREE phase. If not, try to abort the
 * currently established nexus, which we know nothing about. Failing that
 * do a bus reset.
 *
 * Note that a bus reset will cause the chip to assert IRQ.
 *
 * Returns 0 if successful, otherwise -ENXIO.
 */

static int NCR5380_maybe_reset_bus(struct Scsi_Host *instance)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        int pass;

        for (pass = 1; (NCR5380_read(STATUS_REG) & SR_BSY) && pass <= 6; ++pass) {
                switch (pass) {
                case 1:
                case 3:
                case 5:
                        shost_printk(KERN_ERR, instance, "SCSI bus busy, waiting up to five seconds\n");
                        NCR5380_poll_politely(instance,
                                              STATUS_REG, SR_BSY, 0, 5 * HZ);
                        break;
                case 2:
                        shost_printk(KERN_ERR, instance, "bus busy, attempting abort\n");
                        do_abort(instance);
                        break;
                case 4:
                        shost_printk(KERN_ERR, instance, "bus busy, attempting reset\n");
                        do_reset(instance);
                        /* Wait after a reset; the SCSI standard calls for
                         * 250ms, we wait 500ms to be on the safe side.
                         * But some Toshiba CD-ROMs need ten times that.
                         */
                        if (hostdata->flags & FLAG_TOSHIBA_DELAY)
                                msleep(2500);
                        else
                                msleep(500);
                        break;
                case 6:
                        shost_printk(KERN_ERR, instance, "bus locked solid\n");
                        return -ENXIO;
                }
        }
        return 0;
}

/**
 * NCR5380_exit - remove an NCR5380
 * @instance: adapter to remove
 *
 * Assumes that no more work can be queued (e.g. by NCR5380_intr).
 */

static void NCR5380_exit(struct Scsi_Host *instance)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);

        cancel_work_sync(&hostdata->main_task);
        destroy_workqueue(hostdata->work_q);
}

/**
 * complete_cmd - finish processing a command and return it to the SCSI ML
 * @instance: the host instance
 * @cmd: command to complete
 */

static void complete_cmd(struct Scsi_Host *instance,
                         struct scsi_cmnd *cmd)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);

        dsprintk(NDEBUG_QUEUES, instance, "complete_cmd: cmd %p\n", cmd);

        if (hostdata->sensing == cmd) {
                /* Autosense processing ends here */
                if ((cmd->result & 0xff) != SAM_STAT_GOOD) {
                        scsi_eh_restore_cmnd(cmd, &hostdata->ses);
                        set_host_byte(cmd, DID_ERROR);
                } else
                        scsi_eh_restore_cmnd(cmd, &hostdata->ses);
                hostdata->sensing = NULL;
        }

        hostdata->busy[scmd_id(cmd)] &= ~(1 << cmd->device->lun);

        cmd->scsi_done(cmd);
}

/**
 * NCR5380_queue_command - queue a command
 * @instance: the relevant SCSI adapter
 * @cmd: SCSI command
 *
 * cmd is added to the per-instance issue queue, with minor
 * twiddling done to the host specific fields of cmd.  If the
 * main coroutine is not running, it is restarted.
 */

static int NCR5380_queue_command(struct Scsi_Host *instance,
                                 struct scsi_cmnd *cmd)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        struct NCR5380_cmd *ncmd = scsi_cmd_priv(cmd);
        unsigned long flags;

#if (NDEBUG & NDEBUG_NO_WRITE)
        switch (cmd->cmnd[0]) {
        case WRITE_6:
        case WRITE_10:
                shost_printk(KERN_DEBUG, instance, "WRITE attempted with NDEBUG_NO_WRITE set\n");
                cmd->result = (DID_ERROR << 16);
                cmd->scsi_done(cmd);
                return 0;
        }
#endif /* (NDEBUG & NDEBUG_NO_WRITE) */

        cmd->result = 0;

        spin_lock_irqsave(&hostdata->lock, flags);

        /*
         * Insert the cmd into the issue queue. Note that REQUEST SENSE
         * commands are added to the head of the queue since any command will
         * clear the contingent allegiance condition that exists and the
         * sense data is only guaranteed to be valid while the condition exists.
         */

        if (cmd->cmnd[0] == REQUEST_SENSE)
                list_add(&ncmd->list, &hostdata->unissued);
        else
                list_add_tail(&ncmd->list, &hostdata->unissued);

        spin_unlock_irqrestore(&hostdata->lock, flags);

        dsprintk(NDEBUG_QUEUES, instance, "command %p added to %s of queue\n",
                 cmd, (cmd->cmnd[0] == REQUEST_SENSE) ? "head" : "tail");

        /* Kick off command processing */
        queue_work(hostdata->work_q, &hostdata->main_task);
        return 0;
}

/**
 * dequeue_next_cmd - dequeue a command for processing
 * @instance: the scsi host instance
 *
 * Priority is given to commands on the autosense queue. These commands
 * need autosense because of a CHECK CONDITION result.
 *
 * Returns a command pointer if a command is found for a target that is
 * not already busy. Otherwise returns NULL.
 */

static struct scsi_cmnd *dequeue_next_cmd(struct Scsi_Host *instance)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        struct NCR5380_cmd *ncmd;
        struct scsi_cmnd *cmd;

        if (hostdata->sensing || list_empty(&hostdata->autosense)) {
                list_for_each_entry(ncmd, &hostdata->unissued, list) {
                        cmd = NCR5380_to_scmd(ncmd);
                        dsprintk(NDEBUG_QUEUES, instance, "dequeue: cmd=%p target=%d busy=0x%02x lun=%llu\n",
                                 cmd, scmd_id(cmd), hostdata->busy[scmd_id(cmd)], cmd->device->lun);

                        if (!(hostdata->busy[scmd_id(cmd)] & (1 << cmd->device->lun))) {
                                list_del(&ncmd->list);
                                dsprintk(NDEBUG_QUEUES, instance,
                                         "dequeue: removed %p from issue queue\n", cmd);
                                return cmd;
                        }
                }
        } else {
                /* Autosense processing begins here */
                ncmd = list_first_entry(&hostdata->autosense,
                                        struct NCR5380_cmd, list);
                list_del(&ncmd->list);
                cmd = NCR5380_to_scmd(ncmd);
                dsprintk(NDEBUG_QUEUES, instance,
                         "dequeue: removed %p from autosense queue\n", cmd);
                scsi_eh_prep_cmnd(cmd, &hostdata->ses, NULL, 0, ~0);
                hostdata->sensing = cmd;
                return cmd;
        }
        return NULL;
}

static void requeue_cmd(struct Scsi_Host *instance, struct scsi_cmnd *cmd)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        struct NCR5380_cmd *ncmd = scsi_cmd_priv(cmd);

        if (hostdata->sensing == cmd) {
                scsi_eh_restore_cmnd(cmd, &hostdata->ses);
                list_add(&ncmd->list, &hostdata->autosense);
                hostdata->sensing = NULL;
        } else
                list_add(&ncmd->list, &hostdata->unissued);
}

/**
 * NCR5380_main - NCR state machines
 *
 * NCR5380_main is a coroutine that runs as long as more work can
 * be done on the NCR5380 host adapters in a system.  Both
 * NCR5380_queue_command() and NCR5380_intr() will try to start it
 * in case it is not running.
 */

static void NCR5380_main(struct work_struct *work)
{
        struct NCR5380_hostdata *hostdata =
                container_of(work, struct NCR5380_hostdata, main_task);
        struct Scsi_Host *instance = hostdata->host;
        int done;

        do {
                done = 1;

                spin_lock_irq(&hostdata->lock);
                while (!hostdata->connected && !hostdata->selecting) {
                        struct scsi_cmnd *cmd = dequeue_next_cmd(instance);

                        if (!cmd)
                                break;

                        dsprintk(NDEBUG_MAIN, instance, "main: dequeued %p\n", cmd);

                        /*
                         * Attempt to establish an I_T_L nexus here.
                         * On success, instance->hostdata->connected is set.
                         * On failure, we must add the command back to the
                         * issue queue so we can keep trying.
                         */
                        /*
                         * REQUEST SENSE commands are issued without tagged
                         * queueing, even on SCSI-II devices because the
                         * contingent allegiance condition exists for the
                         * entire unit.
                         */

                        if (!NCR5380_select(instance, cmd)) {
                                dsprintk(NDEBUG_MAIN, instance, "main: select complete\n");
                        } else {
                                dsprintk(NDEBUG_MAIN | NDEBUG_QUEUES, instance,
                                         "main: select failed, returning %p to queue\n", cmd);
                                requeue_cmd(instance, cmd);
                        }
                }
                if (hostdata->connected && !hostdata->dma_len) {
                        dsprintk(NDEBUG_MAIN, instance, "main: performing information transfer\n");
                        NCR5380_information_transfer(instance);
                        done = 0;
                }
                spin_unlock_irq(&hostdata->lock);
                if (!done)
                        cond_resched();
        } while (!done);
}

#ifndef DONT_USE_INTR

/**
 * NCR5380_intr - generic NCR5380 irq handler
 * @irq: interrupt number
 * @dev_id: device info
 *
 * Handle interrupts, reestablishing I_T_L or I_T_L_Q nexuses
 * from the disconnected queue, and restarting NCR5380_main()
 * as required.
 *
 * The chip can assert IRQ in any of six different conditions. The IRQ flag
 * is then cleared by reading the Reset Parity/Interrupt Register (RPIR).
 * Three of these six conditions are latched in the Bus and Status Register:
 * - End of DMA (cleared by ending DMA Mode)
 * - Parity error (cleared by reading RPIR)
 * - Loss of BSY (cleared by reading RPIR)
 * Two conditions have flag bits that are not latched:
 * - Bus phase mismatch (non-maskable in DMA Mode, cleared by ending DMA Mode)
 * - Bus reset (non-maskable)
 * The remaining condition has no flag bit at all:
 * - Selection/reselection
 *
 * Hence, establishing the cause(s) of any interrupt is partly guesswork.
 * In "The DP8490 and DP5380 Comparison Guide", National Semiconductor
 * claimed that "the design of the [DP8490] interrupt logic ensures
 * interrupts will not be lost (they can be on the DP5380)."
 * The L5380/53C80 datasheet from LOGIC Devices has more details.
 *
 * Checking for bus reset by reading RST is futile because of interrupt
 * latency, but a bus reset will reset chip logic. Checking for parity error
 * is unnecessary because that interrupt is never enabled. A Loss of BSY
 * condition will clear DMA Mode. We can tell when this occurs because the
 * the Busy Monitor interrupt is enabled together with DMA Mode.
 */

static irqreturn_t NCR5380_intr(int irq, void *dev_id)
{
        struct Scsi_Host *instance = dev_id;
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        int handled = 0;
        unsigned char basr;
        unsigned long flags;

        spin_lock_irqsave(&hostdata->lock, flags);

        basr = NCR5380_read(BUS_AND_STATUS_REG);
        if (basr & BASR_IRQ) {
                unsigned char mr = NCR5380_read(MODE_REG);
                unsigned char sr = NCR5380_read(STATUS_REG);

                dsprintk(NDEBUG_INTR, instance, "IRQ %d, BASR 0x%02x, SR 0x%02x, MR 0x%02x\n",
                         irq, basr, sr, mr);

                if ((NCR5380_read(CURRENT_SCSI_DATA_REG) & hostdata->id_mask) &&
                    (sr & (SR_SEL | SR_IO | SR_BSY | SR_RST)) == (SR_SEL | SR_IO)) {
                        /* Probably reselected */
                        NCR5380_write(SELECT_ENABLE_REG, 0);
                        NCR5380_read(RESET_PARITY_INTERRUPT_REG);

                        dsprintk(NDEBUG_INTR, instance, "interrupt with SEL and IO\n");

                        if (!hostdata->connected) {
                                NCR5380_reselect(instance);
                                queue_work(hostdata->work_q, &hostdata->main_task);
                        }
                        if (!hostdata->connected)
                                NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
                } else {
                        /* Probably Bus Reset */
                        NCR5380_read(RESET_PARITY_INTERRUPT_REG);

                        dsprintk(NDEBUG_INTR, instance, "unknown interrupt\n");
                }
                handled = 1;
        } else {
                shost_printk(KERN_NOTICE, instance, "interrupt without IRQ bit\n");
        }

        spin_unlock_irqrestore(&hostdata->lock, flags);

        return IRQ_RETVAL(handled);
}

#endif

/*
 * Function : int NCR5380_select(struct Scsi_Host *instance,
 * struct scsi_cmnd *cmd)
 *
 * Purpose : establishes I_T_L or I_T_L_Q nexus for new or existing command,
 * including ARBITRATION, SELECTION, and initial message out for
 * IDENTIFY and queue messages.
 *
 * Inputs : instance - instantiation of the 5380 driver on which this
 * target lives, cmd - SCSI command to execute.
 *
 * Returns cmd if selection failed but should be retried,
 * NULL if selection failed and should not be retried, or
 * NULL if selection succeeded (hostdata->connected == cmd).
 *
 * Side effects :
 * If bus busy, arbitration failed, etc, NCR5380_select() will exit
 * with registers as they should have been on entry - ie
 * SELECT_ENABLE will be set appropriately, the NCR5380
 * will cease to drive any SCSI bus signals.
 *
 * If successful : I_T_L or I_T_L_Q nexus will be established,
 * instance->connected will be set to cmd.
 * SELECT interrupt will be disabled.
 *
 * If failed (no target) : cmd->scsi_done() will be called, and the
 * cmd->result host byte set to DID_BAD_TARGET.
 */

static struct scsi_cmnd *NCR5380_select(struct Scsi_Host *instance,
                                        struct scsi_cmnd *cmd)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        unsigned char tmp[3], phase;
        unsigned char *data;
        int len;
        int err;

        NCR5380_dprint(NDEBUG_ARBITRATION, instance);
        dsprintk(NDEBUG_ARBITRATION, instance, "starting arbitration, id = %d\n",
                 instance->this_id);

        /*
         * Arbitration and selection phases are slow and involve dropping the
         * lock, so we have to watch out for EH. An exception handler may
         * change 'selecting' to NULL. This function will then return NULL
         * so that the caller will forget about 'cmd'. (During information
         * transfer phases, EH may change 'connected' to NULL.)
         */
        hostdata->selecting = cmd;

        /*
         * Set the phase bits to 0, otherwise the NCR5380 won't drive the
         * data bus during SELECTION.
         */

        NCR5380_write(TARGET_COMMAND_REG, 0);

        /*
         * Start arbitration.
         */

        NCR5380_write(OUTPUT_DATA_REG, hostdata->id_mask);
        NCR5380_write(MODE_REG, MR_ARBITRATE);

        /* The chip now waits for BUS FREE phase. Then after the 800 ns
         * Bus Free Delay, arbitration will begin.
         */

        spin_unlock_irq(&hostdata->lock);
        err = NCR5380_poll_politely2(instance, MODE_REG, MR_ARBITRATE, 0,
                        INITIATOR_COMMAND_REG, ICR_ARBITRATION_PROGRESS,
                                               ICR_ARBITRATION_PROGRESS, HZ);
        spin_lock_irq(&hostdata->lock);
        if (!(NCR5380_read(MODE_REG) & MR_ARBITRATE)) {
                /* Reselection interrupt */
                goto out;
        }
        if (!hostdata->selecting) {
                /* Command was aborted */
                NCR5380_write(MODE_REG, MR_BASE);
                goto out;
        }
        if (err < 0) {
                NCR5380_write(MODE_REG, MR_BASE);
                shost_printk(KERN_ERR, instance,
                             "select: arbitration timeout\n");
                goto out;
        }
        spin_unlock_irq(&hostdata->lock);

        /* The SCSI-2 arbitration delay is 2.4 us */
        udelay(3);

        /* Check for lost arbitration */
        if ((NCR5380_read(INITIATOR_COMMAND_REG) & ICR_ARBITRATION_LOST) ||
            (NCR5380_read(CURRENT_SCSI_DATA_REG) & hostdata->id_higher_mask) ||
            (NCR5380_read(INITIATOR_COMMAND_REG) & ICR_ARBITRATION_LOST)) {
                NCR5380_write(MODE_REG, MR_BASE);
                dsprintk(NDEBUG_ARBITRATION, instance, "lost arbitration, deasserting MR_ARBITRATE\n");
                spin_lock_irq(&hostdata->lock);
                goto out;
        }

        /* After/during arbitration, BSY should be asserted.
         * IBM DPES-31080 Version S31Q works now
         * Tnx to Thomas_Roesch@m2.maus.de for finding this! (Roman)
         */
        NCR5380_write(INITIATOR_COMMAND_REG,
                      ICR_BASE | ICR_ASSERT_SEL | ICR_ASSERT_BSY);

        /*
         * Again, bus clear + bus settle time is 1.2us, however, this is
         * a minimum so we'll udelay ceil(1.2)
         */

        if (hostdata->flags & FLAG_TOSHIBA_DELAY)
                udelay(15);
        else
                udelay(2);

        spin_lock_irq(&hostdata->lock);

        /* NCR5380_reselect() clears MODE_REG after a reselection interrupt */
        if (!(NCR5380_read(MODE_REG) & MR_ARBITRATE))
                goto out;

        if (!hostdata->selecting) {
                NCR5380_write(MODE_REG, MR_BASE);
                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
                goto out;
        }

        dsprintk(NDEBUG_ARBITRATION, instance, "won arbitration\n");

        /*
         * Now that we have won arbitration, start Selection process, asserting
         * the host and target ID's on the SCSI bus.
         */

        NCR5380_write(OUTPUT_DATA_REG, hostdata->id_mask | (1 << scmd_id(cmd)));

        /*
         * Raise ATN while SEL is true before BSY goes false from arbitration,
         * since this is the only way to guarantee that we'll get a MESSAGE OUT
         * phase immediately after selection.
         */

        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_BSY |
                      ICR_ASSERT_DATA | ICR_ASSERT_ATN | ICR_ASSERT_SEL);
        NCR5380_write(MODE_REG, MR_BASE);

        /*
         * Reselect interrupts must be turned off prior to the dropping of BSY,
         * otherwise we will trigger an interrupt.
         */
        NCR5380_write(SELECT_ENABLE_REG, 0);

        spin_unlock_irq(&hostdata->lock);

        /*
         * The initiator shall then wait at least two deskew delays and release
         * the BSY signal.
         */
        udelay(1);        /* wingel -- wait two bus deskew delay >2*45ns */

        /* Reset BSY */
        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_DATA |
                      ICR_ASSERT_ATN | ICR_ASSERT_SEL);

        /*
         * Something weird happens when we cease to drive BSY - looks
         * like the board/chip is letting us do another read before the
         * appropriate propagation delay has expired, and we're confusing
         * a BSY signal from ourselves as the target's response to SELECTION.
         *
         * A small delay (the 'C++' frontend breaks the pipeline with an
         * unnecessary jump, making it work on my 386-33/Trantor T128, the
         * tighter 'C' code breaks and requires this) solves the problem -
         * the 1 us delay is arbitrary, and only used because this delay will
         * be the same on other platforms and since it works here, it should
         * work there.
         *
         * wingel suggests that this could be due to failing to wait
         * one deskew delay.
         */

        udelay(1);

        dsprintk(NDEBUG_SELECTION, instance, "selecting target %d\n", scmd_id(cmd));

        /*
         * The SCSI specification calls for a 250 ms timeout for the actual
         * selection.
         */

        err = NCR5380_poll_politely(instance, STATUS_REG, SR_BSY, SR_BSY,
                                    msecs_to_jiffies(250));

        if ((NCR5380_read(STATUS_REG) & (SR_SEL | SR_IO)) == (SR_SEL | SR_IO)) {
                spin_lock_irq(&hostdata->lock);
                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
                NCR5380_reselect(instance);
                if (!hostdata->connected)
                        NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
                shost_printk(KERN_ERR, instance, "reselection after won arbitration?\n");
                goto out;
        }

        if (err < 0) {
                spin_lock_irq(&hostdata->lock);
                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
                NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
                /* Can't touch cmd if it has been reclaimed by the scsi ML */
                if (hostdata->selecting) {
                        cmd->result = DID_BAD_TARGET << 16;
                        complete_cmd(instance, cmd);
                        dsprintk(NDEBUG_SELECTION, instance, "target did not respond within 250ms\n");
                        cmd = NULL;
                }
                goto out;
        }

        /*
         * No less than two deskew delays after the initiator detects the
         * BSY signal is true, it shall release the SEL signal and may
         * change the DATA BUS.                                     -wingel
         */

        udelay(1);

        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_ATN);

        /*
         * Since we followed the SCSI spec, and raised ATN while SEL
         * was true but before BSY was false during selection, the information
         * transfer phase should be a MESSAGE OUT phase so that we can send the
         * IDENTIFY message.
         *
         * If SCSI-II tagged queuing is enabled, we also send a SIMPLE_QUEUE_TAG
         * message (2 bytes) with a tag ID that we increment with every command
         * until it wraps back to 0.
         *
         * XXX - it turns out that there are some broken SCSI-II devices,
         * which claim to support tagged queuing but fail when more than
         * some number of commands are issued at once.
         */

        /* Wait for start of REQ/ACK handshake */

        err = NCR5380_poll_politely(instance, STATUS_REG, SR_REQ, SR_REQ, HZ);
        spin_lock_irq(&hostdata->lock);
        if (err < 0) {
                shost_printk(KERN_ERR, instance, "select: REQ timeout\n");
                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
                NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
                goto out;
        }
        if (!hostdata->selecting) {
                do_abort(instance);
                goto out;
        }

        dsprintk(NDEBUG_SELECTION, instance, "target %d selected, going into MESSAGE OUT phase.\n",
                 scmd_id(cmd));
        tmp[0] = IDENTIFY(((instance->irq == NO_IRQ) ? 0 : 1), cmd->device->lun);

        len = 1;
        cmd->tag = 0;

        /* Send message(s) */
        data = tmp;
        phase = PHASE_MSGOUT;
        NCR5380_transfer_pio(instance, &phase, &len, &data);
        dsprintk(NDEBUG_SELECTION, instance, "nexus established.\n");
        /* XXX need to handle errors here */

        hostdata->connected = cmd;
        hostdata->busy[cmd->device->id] |= 1 << cmd->device->lun;

        initialize_SCp(cmd);

        cmd = NULL;

out:
        if (!hostdata->selecting)
                return NULL;
        hostdata->selecting = NULL;
        return cmd;
}

/*
 * Function : int NCR5380_transfer_pio (struct Scsi_Host *instance,
 * unsigned char *phase, int *count, unsigned char **data)
 *
 * Purpose : transfers data in given phase using polled I/O
 *
 * Inputs : instance - instance of driver, *phase - pointer to
 * what phase is expected, *count - pointer to number of
 * bytes to transfer, **data - pointer to data pointer.
 *
 * Returns : -1 when different phase is entered without transferring
 * maximum number of bytes, 0 if all bytes are transferred or exit
 * is in same phase.
 *
 * Also, *phase, *count, *data are modified in place.
 *
 * XXX Note : handling for bus free may be useful.
 */

/*
 * Note : this code is not as quick as it could be, however it
 * IS 100% reliable, and for the actual data transfer where speed
 * counts, we will always do a pseudo DMA or DMA transfer.
 */

static int NCR5380_transfer_pio(struct Scsi_Host *instance,
                                unsigned char *phase, int *count,
                                unsigned char **data)
{
        unsigned char p = *phase, tmp;
        int c = *count;
        unsigned char *d = *data;

        /*
         * The NCR5380 chip will only drive the SCSI bus when the
         * phase specified in the appropriate bits of the TARGET COMMAND
         * REGISTER match the STATUS REGISTER
         */

        NCR5380_write(TARGET_COMMAND_REG, PHASE_SR_TO_TCR(p));

        do {
                /*
                 * Wait for assertion of REQ, after which the phase bits will be
                 * valid
                 */

                if (NCR5380_poll_politely(instance, STATUS_REG, SR_REQ, SR_REQ, HZ) < 0)
                        break;

                dsprintk(NDEBUG_HANDSHAKE, instance, "REQ asserted\n");

                /* Check for phase mismatch */
                if ((NCR5380_read(STATUS_REG) & PHASE_MASK) != p) {
                        dsprintk(NDEBUG_PIO, instance, "phase mismatch\n");
                        NCR5380_dprint_phase(NDEBUG_PIO, instance);
                        break;
                }

                /* Do actual transfer from SCSI bus to / from memory */
                if (!(p & SR_IO))
                        NCR5380_write(OUTPUT_DATA_REG, *d);
                else
                        *d = NCR5380_read(CURRENT_SCSI_DATA_REG);

                ++d;

                /*
                 * The SCSI standard suggests that in MSGOUT phase, the initiator
                 * should drop ATN on the last byte of the message phase
                 * after REQ has been asserted for the handshake but before
                 * the initiator raises ACK.
                 */

                if (!(p & SR_IO)) {
                        if (!((p & SR_MSG) && c > 1)) {
                                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_DATA);
                                NCR5380_dprint(NDEBUG_PIO, instance);
                                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE |
                                              ICR_ASSERT_DATA | ICR_ASSERT_ACK);
                        } else {
                                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE |
                                              ICR_ASSERT_DATA | ICR_ASSERT_ATN);
                                NCR5380_dprint(NDEBUG_PIO, instance);
                                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE |
                                              ICR_ASSERT_DATA | ICR_ASSERT_ATN | ICR_ASSERT_ACK);
                        }
                } else {
                        NCR5380_dprint(NDEBUG_PIO, instance);
                        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_ACK);
                }

                if (NCR5380_poll_politely(instance,
                                          STATUS_REG, SR_REQ, 0, 5 * HZ) < 0)
                        break;

                dsprintk(NDEBUG_HANDSHAKE, instance, "REQ negated, handshake complete\n");

/*
 * We have several special cases to consider during REQ/ACK handshaking :
 * 1.  We were in MSGOUT phase, and we are on the last byte of the
 * message.  ATN must be dropped as ACK is dropped.
 *
 * 2.  We are in a MSGIN phase, and we are on the last byte of the
 * message.  We must exit with ACK asserted, so that the calling
 * code may raise ATN before dropping ACK to reject the message.
 *
 * 3.  ACK and ATN are clear and the target may proceed as normal.
 */
                if (!(p == PHASE_MSGIN && c == 1)) {
                        if (p == PHASE_MSGOUT && c > 1)
                                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_ATN);
                        else
                                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
                }
        } while (--c);

        dsprintk(NDEBUG_PIO, instance, "residual %d\n", c);

        *count = c;
        *data = d;
        tmp = NCR5380_read(STATUS_REG);
        /* The phase read from the bus is valid if either REQ is (already)
         * asserted or if ACK hasn't been released yet. The latter applies if
         * we're in MSG IN, DATA IN or STATUS and all bytes have been received.
         */
        if ((tmp & SR_REQ) || ((tmp & SR_IO) && c == 0))
                *phase = tmp & PHASE_MASK;
        else
                *phase = PHASE_UNKNOWN;

        if (!c || (*phase == p))
                return 0;
        else
                return -1;
}

/**
 * do_reset - issue a reset command
 * @instance: adapter to reset
 *
 * Issue a reset sequence to the NCR5380 and try and get the bus
 * back into sane shape.
 *
 * This clears the reset interrupt flag because there may be no handler for
 * it. When the driver is initialized, the NCR5380_intr() handler has not yet
 * been installed. And when in EH we may have released the ST DMA interrupt.
 */

static void do_reset(struct Scsi_Host *instance)
{
        unsigned long flags;

        local_irq_save(flags);
        NCR5380_write(TARGET_COMMAND_REG,
                      PHASE_SR_TO_TCR(NCR5380_read(STATUS_REG) & PHASE_MASK));
        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_RST);
        udelay(50);
        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
        (void)NCR5380_read(RESET_PARITY_INTERRUPT_REG);
        local_irq_restore(flags);
}

/**
 * do_abort - abort the currently established nexus by going to
 * MESSAGE OUT phase and sending an ABORT message.
 * @instance: relevant scsi host instance
 *
 * Returns 0 on success, -1 on failure.
 */

static int do_abort(struct Scsi_Host *instance)
{
        unsigned char *msgptr, phase, tmp;
        int len;
        int rc;

        /* Request message out phase */
        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_ATN);

        /*
         * Wait for the target to indicate a valid phase by asserting
         * REQ.  Once this happens, we'll have either a MSGOUT phase
         * and can immediately send the ABORT message, or we'll have some
         * other phase and will have to source/sink data.
         *
         * We really don't care what value was on the bus or what value
         * the target sees, so we just handshake.
         */

        rc = NCR5380_poll_politely(instance, STATUS_REG, SR_REQ, SR_REQ, 10 * HZ);
        if (rc < 0)
                goto timeout;

        tmp = NCR5380_read(STATUS_REG) & PHASE_MASK;

        NCR5380_write(TARGET_COMMAND_REG, PHASE_SR_TO_TCR(tmp));

        if (tmp != PHASE_MSGOUT) {
                NCR5380_write(INITIATOR_COMMAND_REG,
                              ICR_BASE | ICR_ASSERT_ATN | ICR_ASSERT_ACK);
                rc = NCR5380_poll_politely(instance, STATUS_REG, SR_REQ, 0, 3 * HZ);
                if (rc < 0)
                        goto timeout;
                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_ATN);
        }

        tmp = ABORT;
        msgptr = &tmp;
        len = 1;
        phase = PHASE_MSGOUT;
        NCR5380_transfer_pio(instance, &phase, &len, &msgptr);

        /*
         * If we got here, and the command completed successfully,
         * we're about to go into bus free state.
         */

        return len ? -1 : 0;

timeout:
        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
        return -1;
}

/*
 * Function : int NCR5380_transfer_dma (struct Scsi_Host *instance,
 * unsigned char *phase, int *count, unsigned char **data)
 *
 * Purpose : transfers data in given phase using either real
 * or pseudo DMA.
 *
 * Inputs : instance - instance of driver, *phase - pointer to
 * what phase is expected, *count - pointer to number of
 * bytes to transfer, **data - pointer to data pointer.
 *
 * Returns : -1 when different phase is entered without transferring
 * maximum number of bytes, 0 if all bytes or transferred or exit
 * is in same phase.
 *
 * Also, *phase, *count, *data are modified in place.
 */


static int NCR5380_transfer_dma(struct Scsi_Host *instance,
                                unsigned char *phase, int *count,
                                unsigned char **data)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        register int c = *count;
        register unsigned char p = *phase;
        register unsigned char *d = *data;
        unsigned char tmp;
        int foo;

        if ((tmp = (NCR5380_read(STATUS_REG) & PHASE_MASK)) != p) {
                *phase = tmp;
                return -1;
        }

        NCR5380_write(TARGET_COMMAND_REG, PHASE_SR_TO_TCR(p));

        /*
         * Note : on my sample board, watch-dog timeouts occurred when interrupts
         * were not disabled for the duration of a single DMA transfer, from
         * before the setting of DMA mode to after transfer of the last byte.
         */

        if (hostdata->flags & FLAG_DMA_FIXUP)
                NCR5380_write(MODE_REG, MR_BASE | MR_DMA_MODE | MR_MONITOR_BSY);
        else
                NCR5380_write(MODE_REG, MR_BASE | MR_DMA_MODE | MR_MONITOR_BSY |
                                        MR_ENABLE_EOP_INTR);

        dprintk(NDEBUG_DMA, "scsi%d : mode reg = 0x%X\n", instance->host_no, NCR5380_read(MODE_REG));

        /*
         * On the PAS16 at least I/O recovery delays are not needed here.
         * Everyone else seems to want them.
         */

        if (p & SR_IO) {
                NCR5380_io_delay(1);
                NCR5380_write(START_DMA_INITIATOR_RECEIVE_REG, 0);
        } else {
                NCR5380_io_delay(1);
                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_DATA);
                NCR5380_io_delay(1);
                NCR5380_write(START_DMA_SEND_REG, 0);
                NCR5380_io_delay(1);
        }

/*
 * A note regarding the DMA errata workarounds for early NMOS silicon.
 *
 * For DMA sends, we want to wait until the last byte has been
 * transferred out over the bus before we turn off DMA mode.  Alas, there
 * seems to be no terribly good way of doing this on a 5380 under all
 * conditions.  For non-scatter-gather operations, we can wait until REQ
 * and ACK both go false, or until a phase mismatch occurs.  Gather-sends
 * are nastier, since the device will be expecting more data than we
 * are prepared to send it, and REQ will remain asserted.  On a 53C8[01] we
 * could test Last Byte Sent to assure transfer (I imagine this is precisely
 * why this signal was added to the newer chips) but on the older 538[01]
 * this signal does not exist.  The workaround for this lack is a watchdog;
 * we bail out of the wait-loop after a modest amount of wait-time if
 * the usual exit conditions are not met.  Not a terribly clean or
 * correct solution :-%
 *
 * DMA receive is equally tricky due to a nasty characteristic of the NCR5380.
 * If the chip is in DMA receive mode, it will respond to a target's
 * REQ by latching the SCSI data into the INPUT DATA register and asserting
 * ACK, even if it has _already_ been notified by the DMA controller that
 * the current DMA transfer has completed!  If the NCR5380 is then taken
 * out of DMA mode, this already-acknowledged byte is lost. This is
 * not a problem for "one DMA transfer per READ command", because
 * the situation will never arise... either all of the data is DMA'ed
 * properly, or the target switches to MESSAGE IN phase to signal a
 * disconnection (either operation bringing the DMA to a clean halt).
 * However, in order to handle scatter-receive, we must work around the
 * problem.  The chosen fix is to DMA fewer bytes, then check for the
 * condition before taking the NCR5380 out of DMA mode.  One or two extra
 * bytes are transferred via PIO as necessary to fill out the original
 * request.
 */

        if (p & SR_IO) {
                foo = NCR5380_dma_recv_setup(instance, d,
                        hostdata->flags & FLAG_DMA_FIXUP ? c - 1 : c);
                if (!foo && (hostdata->flags & FLAG_DMA_FIXUP)) {
                        /*
                         * The workaround was to transfer fewer bytes than we
                         * intended to with the pseudo-DMA read function, wait for
                         * the chip to latch the last byte, read it, and then disable
                         * pseudo-DMA mode.
                         *
                         * After REQ is asserted, the NCR5380 asserts DRQ and ACK.
                         * REQ is deasserted when ACK is asserted, and not reasserted
                         * until ACK goes false.  Since the NCR5380 won't lower ACK
                         * until DACK is asserted, which won't happen unless we twiddle
                         * the DMA port or we take the NCR5380 out of DMA mode, we
                         * can guarantee that we won't handshake another extra
                         * byte.
                         */

                        if (NCR5380_poll_politely(instance, BUS_AND_STATUS_REG,
                                                  BASR_DRQ, BASR_DRQ, HZ) < 0) {
                                foo = -1;
                                shost_printk(KERN_ERR, instance, "PDMA read: DRQ timeout\n");
                        }
                        if (NCR5380_poll_politely(instance, STATUS_REG,
                                                  SR_REQ, 0, HZ) < 0) {
                                foo = -1;
                                shost_printk(KERN_ERR, instance, "PDMA read: !REQ timeout\n");
                        }
                        d[c - 1] = NCR5380_read(INPUT_DATA_REG);
                }
        } else {
                foo = NCR5380_dma_send_setup(instance, d, c);
                if (!foo && (hostdata->flags & FLAG_DMA_FIXUP)) {
                        /*
                         * Wait for the last byte to be sent.  If REQ is being asserted for
                         * the byte we're interested, we'll ACK it and it will go false.
                         */
                        if (NCR5380_poll_politely2(instance,
                             BUS_AND_STATUS_REG, BASR_DRQ, BASR_DRQ,
                             BUS_AND_STATUS_REG, BASR_PHASE_MATCH, 0, HZ) < 0) {
                                foo = -1;
                                shost_printk(KERN_ERR, instance, "PDMA write: DRQ and phase timeout\n");
                        }
                }
        }
        NCR5380_write(MODE_REG, MR_BASE);
        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
        NCR5380_read(RESET_PARITY_INTERRUPT_REG);
        *data = d + c;
        *count = 0;
        *phase = NCR5380_read(STATUS_REG) & PHASE_MASK;
        return foo;
}

/*
 * Function : NCR5380_information_transfer (struct Scsi_Host *instance)
 *
 * Purpose : run through the various SCSI phases and do as the target
 * directs us to.  Operates on the currently connected command,
 * instance->connected.
 *
 * Inputs : instance, instance for which we are doing commands
 *
 * Side effects : SCSI things happen, the disconnected queue will be
 * modified if a command disconnects, *instance->connected will
 * change.
 *
 * XXX Note : we need to watch for bus free or a reset condition here
 * to recover from an unexpected bus free condition.
 */

static void NCR5380_information_transfer(struct Scsi_Host *instance)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        unsigned char msgout = NOP;
        int sink = 0;
        int len;
        int transfersize;
        unsigned char *data;
        unsigned char phase, tmp, extended_msg[10], old_phase = 0xff;
        struct scsi_cmnd *cmd;

        while ((cmd = hostdata->connected)) {
                struct NCR5380_cmd *ncmd = scsi_cmd_priv(cmd);

                tmp = NCR5380_read(STATUS_REG);
                /* We only have a valid SCSI phase when REQ is asserted */
                if (tmp & SR_REQ) {
                        phase = (tmp & PHASE_MASK);
                        if (phase != old_phase) {
                                old_phase = phase;
                                NCR5380_dprint_phase(NDEBUG_INFORMATION, instance);
                        }
                        if (sink && (phase != PHASE_MSGOUT)) {
                                NCR5380_write(TARGET_COMMAND_REG, PHASE_SR_TO_TCR(tmp));

                                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_ATN |
                                              ICR_ASSERT_ACK);
                                while (NCR5380_read(STATUS_REG) & SR_REQ)
                                        ;
                                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE |
                                              ICR_ASSERT_ATN);
                                sink = 0;
                                continue;
                        }

                        switch (phase) {
                        case PHASE_DATAOUT:
#if (NDEBUG & NDEBUG_NO_DATAOUT)
                                shost_printk(KERN_DEBUG, instance, "NDEBUG_NO_DATAOUT set, attempted DATAOUT aborted\n");
                                sink = 1;
                                do_abort(instance);
                                cmd->result = DID_ERROR << 16;
                                complete_cmd(instance, cmd);
                                hostdata->connected = NULL;
                                return;
#endif
                        case PHASE_DATAIN:
                                /*
                                 * If there is no room left in the current buffer in the
                                 * scatter-gather list, move onto the next one.
                                 */

                                if (!cmd->SCp.this_residual && cmd->SCp.buffers_residual) {
                                        ++cmd->SCp.buffer;
                                        --cmd->SCp.buffers_residual;
                                        cmd->SCp.this_residual = cmd->SCp.buffer->length;
                                        cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
                                        dsprintk(NDEBUG_INFORMATION, instance, "%d bytes and %d buffers left\n",
                                                 cmd->SCp.this_residual,
                                                 cmd->SCp.buffers_residual);
                                }

                                /*
                                 * The preferred transfer method is going to be
                                 * PSEUDO-DMA for systems that are strictly PIO,
                                 * since we can let the hardware do the handshaking.
                                 *
                                 * For this to work, we need to know the transfersize
                                 * ahead of time, since the pseudo-DMA code will sit
                                 * in an unconditional loop.
                                 */

                                transfersize = 0;
                                if (!cmd->device->borken)
                                        transfersize = NCR5380_dma_xfer_len(instance, cmd, phase);

                                if (transfersize) {
                                        len = transfersize;
                                        if (NCR5380_transfer_dma(instance, &phase,
                                            &len, (unsigned char **)&cmd->SCp.ptr)) {
                                                /*
                                                 * If the watchdog timer fires, all future
                                                 * accesses to this device will use the
                                                 * polled-IO.
                                                 */
                                                scmd_printk(KERN_INFO, cmd,
                                                        "switching to slow handshake\n");
                                                cmd->device->borken = 1;
                                                sink = 1;
                                                do_abort(instance);
                                                cmd->result = DID_ERROR << 16;
                                                /* XXX - need to source or sink data here, as appropriate */
                                        } else
                                                cmd->SCp.this_residual -= transfersize - len;
                                } else {
                                        /* Break up transfer into 3 ms chunks,
                                         * presuming 6 accesses per handshake.
                                         */
                                        transfersize = min((unsigned long)cmd->SCp.this_residual,
                                                           hostdata->accesses_per_ms / 2);
                                        len = transfersize;
                                        NCR5380_transfer_pio(instance, &phase, &len,
                                                             (unsigned char **)&cmd->SCp.ptr);
                                        cmd->SCp.this_residual -= transfersize - len;
                                }
                                return;
                        case PHASE_MSGIN:
                                len = 1;
                                data = &tmp;
                                NCR5380_transfer_pio(instance, &phase, &len, &data);
                                cmd->SCp.Message = tmp;

                                switch (tmp) {
                                case ABORT:
                                case COMMAND_COMPLETE:
                                        /* Accept message by clearing ACK */
                                        sink = 1;
                                        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
                                        dsprintk(NDEBUG_QUEUES, instance,
                                                 "COMMAND COMPLETE %p target %d lun %llu\n",
                                                 cmd, scmd_id(cmd), cmd->device->lun);

                                        hostdata->connected = NULL;

                                        cmd->result &= ~0xffff;
                                        cmd->result |= cmd->SCp.Status;
                                        cmd->result |= cmd->SCp.Message << 8;

                                        if (cmd->cmnd[0] == REQUEST_SENSE)
                                                complete_cmd(instance, cmd);
                                        else {
                                                if (cmd->SCp.Status == SAM_STAT_CHECK_CONDITION ||
                                                    cmd->SCp.Status == SAM_STAT_COMMAND_TERMINATED) {
                                                        dsprintk(NDEBUG_QUEUES, instance, "autosense: adding cmd %p to tail of autosense queue\n",
                                                                 cmd);
                                                        list_add_tail(&ncmd->list,
                                                                      &hostdata->autosense);
                                                } else
                                                        complete_cmd(instance, cmd);
                                        }

                                        /*
                                         * Restore phase bits to 0 so an interrupted selection,
                                         * arbitration can resume.
                                         */
                                        NCR5380_write(TARGET_COMMAND_REG, 0);

                                        /* Enable reselect interrupts */
                                        NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
                                        return;
                                case MESSAGE_REJECT:
                                        /* Accept message by clearing ACK */
                                        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
                                        switch (hostdata->last_message) {
                                        case HEAD_OF_QUEUE_TAG:
                                        case ORDERED_QUEUE_TAG:
                                        case SIMPLE_QUEUE_TAG:
                                                cmd->device->simple_tags = 0;
                                                hostdata->busy[cmd->device->id] |= (1 << (cmd->device->lun & 0xFF));
                                                break;
                                        default:
                                                break;
                                        }
                                        break;
                                case DISCONNECT:
                                        /* Accept message by clearing ACK */
                                        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
                                        hostdata->connected = NULL;
                                        list_add(&ncmd->list, &hostdata->disconnected);
                                        dsprintk(NDEBUG_INFORMATION | NDEBUG_QUEUES,
                                                 instance, "connected command %p for target %d lun %llu moved to disconnected queue\n",
                                                 cmd, scmd_id(cmd), cmd->device->lun);

                                        /*
                                         * Restore phase bits to 0 so an interrupted selection,
                                         * arbitration can resume.
                                         */
                                        NCR5380_write(TARGET_COMMAND_REG, 0);

                                        /* Enable reselect interrupts */
                                        NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
                                        return;
                                        /*
                                         * The SCSI data pointer is *IMPLICITLY* saved on a disconnect
                                         * operation, in violation of the SCSI spec so we can safely
                                         * ignore SAVE/RESTORE pointers calls.
                                         *
                                         * Unfortunately, some disks violate the SCSI spec and
                                         * don't issue the required SAVE_POINTERS message before
                                         * disconnecting, and we have to break spec to remain
                                         * compatible.
                                         */
                                case SAVE_POINTERS:
                                case RESTORE_POINTERS:
                                        /* Accept message by clearing ACK */
                                        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
                                        break;
                                case EXTENDED_MESSAGE:
                                        /*
                                         * Start the message buffer with the EXTENDED_MESSAGE
                                         * byte, since spi_print_msg() wants the whole thing.
                                         */
                                        extended_msg[0] = EXTENDED_MESSAGE;
                                        /* Accept first byte by clearing ACK */
                                        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);

                                        spin_unlock_irq(&hostdata->lock);

                                        dsprintk(NDEBUG_EXTENDED, instance, "receiving extended message\n");

                                        len = 2;
                                        data = extended_msg + 1;
                                        phase = PHASE_MSGIN;
                                        NCR5380_transfer_pio(instance, &phase, &len, &data);
                                        dsprintk(NDEBUG_EXTENDED, instance, "length %d, code 0x%02x\n",
                                                 (int)extended_msg[1],
                                                 (int)extended_msg[2]);

                                        if (!len && extended_msg[1] > 0 &&
                                            extended_msg[1] <= sizeof(extended_msg) - 2) {
                                                /* Accept third byte by clearing ACK */
                                                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
                                                len = extended_msg[1] - 1;
                                                data = extended_msg + 3;
                                                phase = PHASE_MSGIN;

                                                NCR5380_transfer_pio(instance, &phase, &len, &data);
                                                dsprintk(NDEBUG_EXTENDED, instance, "message received, residual %d\n",
                                                         len);

                                                switch (extended_msg[2]) {
                                                case EXTENDED_SDTR:
                                                case EXTENDED_WDTR:
                                                case EXTENDED_MODIFY_DATA_POINTER:
                                                case EXTENDED_EXTENDED_IDENTIFY:
                                                        tmp = 0;
                                                }
                                        } else if (len) {
                                                shost_printk(KERN_ERR, instance, "error receiving extended message\n");
                                                tmp = 0;
                                        } else {
                                                shost_printk(KERN_NOTICE, instance, "extended message code %02x length %d is too long\n",
                                                             extended_msg[2], extended_msg[1]);
                                                tmp = 0;
                                        }

                                        spin_lock_irq(&hostdata->lock);
                                        if (!hostdata->connected)
                                                return;

                                        /* Fall through to reject message */

                                        /*
                                         * If we get something weird that we aren't expecting,
                                         * reject it.
                                         */
                                default:
                                        if (!tmp) {
                                                shost_printk(KERN_ERR, instance, "rejecting message ");
                                                spi_print_msg(extended_msg);
                                                printk("\n");
                                        } else if (tmp != EXTENDED_MESSAGE)
                                                scmd_printk(KERN_INFO, cmd,
                                                            "rejecting unknown message %02x\n",
                                                            tmp);
                                        else
                                                scmd_printk(KERN_INFO, cmd,
                                                            "rejecting unknown extended message code %02x, length %d\n",
                                                            extended_msg[1], extended_msg[0]);

                                        msgout = MESSAGE_REJECT;
                                        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_ATN);
                                        break;
                                } /* switch (tmp) */
                                break;
                        case PHASE_MSGOUT:
                                len = 1;
                                data = &msgout;
                                hostdata->last_message = msgout;
                                NCR5380_transfer_pio(instance, &phase, &len, &data);
                                if (msgout == ABORT) {
                                        hostdata->connected = NULL;
                                        cmd->result = DID_ERROR << 16;
                                        complete_cmd(instance, cmd);
                                        NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
                                        return;
                                }
                                msgout = NOP;
                                break;
                        case PHASE_CMDOUT:
                                len = cmd->cmd_len;
                                data = cmd->cmnd;
                                /*
                                 * XXX for performance reasons, on machines with a
                                 * PSEUDO-DMA architecture we should probably
                                 * use the dma transfer function.
                                 */
                                NCR5380_transfer_pio(instance, &phase, &len, &data);
                                break;
                        case PHASE_STATIN:
                                len = 1;
                                data = &tmp;
                                NCR5380_transfer_pio(instance, &phase, &len, &data);
                                cmd->SCp.Status = tmp;
                                break;
                        default:
                                shost_printk(KERN_ERR, instance, "unknown phase\n");
                                NCR5380_dprint(NDEBUG_ANY, instance);
                        } /* switch(phase) */
                } else {
                        spin_unlock_irq(&hostdata->lock);
                        NCR5380_poll_politely(instance, STATUS_REG, SR_REQ, SR_REQ, HZ);
                        spin_lock_irq(&hostdata->lock);
                }
        }
}

/*
 * Function : void NCR5380_reselect (struct Scsi_Host *instance)
 *
 * Purpose : does reselection, initializing the instance->connected
 * field to point to the scsi_cmnd for which the I_T_L or I_T_L_Q
 * nexus has been reestablished,
 *
 * Inputs : instance - this instance of the NCR5380.
 */

static void NCR5380_reselect(struct Scsi_Host *instance)
{
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        unsigned char target_mask;
        unsigned char lun, phase;
        int len;
        unsigned char msg[3];
        unsigned char *data;
        struct NCR5380_cmd *ncmd;
        struct scsi_cmnd *tmp;

        /*
         * Disable arbitration, etc. since the host adapter obviously
         * lost, and tell an interrupted NCR5380_select() to restart.
         */

        NCR5380_write(MODE_REG, MR_BASE);

        target_mask = NCR5380_read(CURRENT_SCSI_DATA_REG) & ~(hostdata->id_mask);

        dsprintk(NDEBUG_RESELECTION, instance, "reselect\n");

        /*
         * At this point, we have detected that our SCSI ID is on the bus,
         * SEL is true and BSY was false for at least one bus settle delay
         * (400 ns).
         *
         * We must assert BSY ourselves, until the target drops the SEL
         * signal.
         */

        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_BSY);
        if (NCR5380_poll_politely(instance,
                                  STATUS_REG, SR_SEL, 0, 2 * HZ) < 0) {
                NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
                return;
        }
        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);

        /*
         * Wait for target to go into MSGIN.
         */

        if (NCR5380_poll_politely(instance,
                                  STATUS_REG, SR_REQ, SR_REQ, 2 * HZ) < 0) {
                do_abort(instance);
                return;
        }

        len = 1;
        data = msg;
        phase = PHASE_MSGIN;
        NCR5380_transfer_pio(instance, &phase, &len, &data);

        if (len) {
                do_abort(instance);
                return;
        }

        if (!(msg[0] & 0x80)) {
                shost_printk(KERN_ERR, instance, "expecting IDENTIFY message, got ");
                spi_print_msg(msg);
                printk("\n");
                do_abort(instance);
                return;
        }
        lun = msg[0] & 0x07;

        /*
         * We need to add code for SCSI-II to track which devices have
         * I_T_L_Q nexuses established, and which have simple I_T_L
         * nexuses so we can chose to do additional data transfer.
         */

        /*
         * Find the command corresponding to the I_T_L or I_T_L_Q  nexus we
         * just reestablished, and remove it from the disconnected queue.
         */

        tmp = NULL;
        list_for_each_entry(ncmd, &hostdata->disconnected, list) {
                struct scsi_cmnd *cmd = NCR5380_to_scmd(ncmd);

                if (target_mask == (1 << scmd_id(cmd)) &&
                    lun == (u8)cmd->device->lun) {
                        list_del(&ncmd->list);
                        tmp = cmd;
                        break;
                }
        }

        if (tmp) {
                dsprintk(NDEBUG_RESELECTION | NDEBUG_QUEUES, instance,
                         "reselect: removed %p from disconnected queue\n", tmp);
        } else {
                shost_printk(KERN_ERR, instance, "target bitmask 0x%02x lun %d not in disconnected queue.\n",
                             target_mask, lun);
                /*
                 * Since we have an established nexus that we can't do anything
                 * with, we must abort it.
                 */
                do_abort(instance);
                return;
        }

        /* Accept message by clearing ACK */
        NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);

        hostdata->connected = tmp;
        dsprintk(NDEBUG_RESELECTION, instance, "nexus established, target %d, lun %llu, tag %d\n",
                 scmd_id(tmp), tmp->device->lun, tmp->tag);
}

/**
 * list_find_cmd - test for presence of a command in a linked list
 * @haystack: list of commands
 * @needle: command to search for
 */

static bool list_find_cmd(struct list_head *haystack,
                          struct scsi_cmnd *needle)
{
        struct NCR5380_cmd *ncmd;

        list_for_each_entry(ncmd, haystack, list)
                if (NCR5380_to_scmd(ncmd) == needle)
                        return true;
        return false;
}

/**
 * list_remove_cmd - remove a command from linked list
 * @haystack: list of commands
 * @needle: command to remove
 */

static bool list_del_cmd(struct list_head *haystack,
                         struct scsi_cmnd *needle)
{
        if (list_find_cmd(haystack, needle)) {
                struct NCR5380_cmd *ncmd = scsi_cmd_priv(needle);

                list_del(&ncmd->list);
                return true;
        }
        return false;
}

/**
 * NCR5380_abort - scsi host eh_abort_handler() method
 * @cmd: the command to be aborted
 *
 * Try to abort a given command by removing it from queues and/or sending
 * the target an abort message. This may not succeed in causing a target
 * to abort the command. Nonetheless, the low-level driver must forget about
 * the command because the mid-layer reclaims it and it may be re-issued.
 *
 * The normal path taken by a command is as follows. For EH we trace this
 * same path to locate and abort the command.
 *
 * unissued -> selecting -> [unissued -> selecting ->]... connected ->
 * [disconnected -> connected ->]...
 * [autosense -> connected ->] done
 *
 * If cmd was not found at all then presumably it has already been completed,
 * in which case return SUCCESS to try to avoid further EH measures.
 *
 * If the command has not completed yet, we must not fail to find it.
 * We have no option but to forget the aborted command (even if it still
 * lacks sense data). The mid-layer may re-issue a command that is in error
 * recovery (see scsi_send_eh_cmnd), but the logic and data structures in
 * this driver are such that a command can appear on one queue only.
 *
 * The lock protects driver data structures, but EH handlers also use it
 * to serialize their own execution and prevent their own re-entry.
 */

static int NCR5380_abort(struct scsi_cmnd *cmd)
{
        struct Scsi_Host *instance = cmd->device->host;
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        unsigned long flags;
        int result = SUCCESS;

        spin_lock_irqsave(&hostdata->lock, flags);

#if (NDEBUG & NDEBUG_ANY)
        scmd_printk(KERN_INFO, cmd, __func__);
#endif
        NCR5380_dprint(NDEBUG_ANY, instance);
        NCR5380_dprint_phase(NDEBUG_ANY, instance);

        if (list_del_cmd(&hostdata->unissued, cmd)) {
                dsprintk(NDEBUG_ABORT, instance,
                         "abort: removed %p from issue queue\n", cmd);
                cmd->result = DID_ABORT << 16;
                cmd->scsi_done(cmd); /* No tag or busy flag to worry about */
                goto out;
        }

        if (hostdata->selecting == cmd) {
                dsprintk(NDEBUG_ABORT, instance,
                         "abort: cmd %p == selecting\n", cmd);
                hostdata->selecting = NULL;
                cmd->result = DID_ABORT << 16;
                complete_cmd(instance, cmd);
                goto out;
        }

        if (list_del_cmd(&hostdata->disconnected, cmd)) {
                dsprintk(NDEBUG_ABORT, instance,
                         "abort: removed %p from disconnected list\n", cmd);
                /* Can't call NCR5380_select() and send ABORT because that
                 * means releasing the lock. Need a bus reset.
                 */
                set_host_byte(cmd, DID_ERROR);
                complete_cmd(instance, cmd);
                result = FAILED;
                goto out;
        }

        if (hostdata->connected == cmd) {
                dsprintk(NDEBUG_ABORT, instance, "abort: cmd %p is connected\n", cmd);
                hostdata->connected = NULL;
                hostdata->dma_len = 0;
                if (do_abort(instance)) {
                        set_host_byte(cmd, DID_ERROR);
                        complete_cmd(instance, cmd);
                        result = FAILED;
                        goto out;
                }
                set_host_byte(cmd, DID_ABORT);
                complete_cmd(instance, cmd);
                goto out;
        }

        if (list_del_cmd(&hostdata->autosense, cmd)) {
                dsprintk(NDEBUG_ABORT, instance,
                         "abort: removed %p from sense queue\n", cmd);
                set_host_byte(cmd, DID_ERROR);
                complete_cmd(instance, cmd);
        }

out:
        if (result == FAILED)
                dsprintk(NDEBUG_ABORT, instance, "abort: failed to abort %p\n", cmd);
        else
                dsprintk(NDEBUG_ABORT, instance, "abort: successfully aborted %p\n", cmd);

        queue_work(hostdata->work_q, &hostdata->main_task);
        spin_unlock_irqrestore(&hostdata->lock, flags);

        return result;
}


/**
 * NCR5380_bus_reset - reset the SCSI bus
 * @cmd: SCSI command undergoing EH
 *
 * Returns SUCCESS
 */

static int NCR5380_bus_reset(struct scsi_cmnd *cmd)
{
        struct Scsi_Host *instance = cmd->device->host;
        struct NCR5380_hostdata *hostdata = shost_priv(instance);
        int i;
        unsigned long flags;
        struct NCR5380_cmd *ncmd;

        spin_lock_irqsave(&hostdata->lock, flags);

#if (NDEBUG & NDEBUG_ANY)
        scmd_printk(KERN_INFO, cmd, __func__);
#endif
        NCR5380_dprint(NDEBUG_ANY, instance);
        NCR5380_dprint_phase(NDEBUG_ANY, instance);

        do_reset(instance);

        /* reset NCR registers */
        NCR5380_write(MODE_REG, MR_BASE);
        NCR5380_write(TARGET_COMMAND_REG, 0);
        NCR5380_write(SELECT_ENABLE_REG, 0);

        /* After the reset, there are no more connected or disconnected commands
         * and no busy units; so clear the low-level status here to avoid
         * conflicts when the mid-level code tries to wake up the affected
         * commands!
         */

        if (list_del_cmd(&hostdata->unissued, cmd)) {
                cmd->result = DID_RESET << 16;
                cmd->scsi_done(cmd);
        }

        if (hostdata->selecting) {
                hostdata->selecting->result = DID_RESET << 16;
                complete_cmd(instance, hostdata->selecting);
                hostdata->selecting = NULL;
        }

        list_for_each_entry(ncmd, &hostdata->disconnected, list) {
                struct scsi_cmnd *cmd = NCR5380_to_scmd(ncmd);

                set_host_byte(cmd, DID_RESET);
                cmd->scsi_done(cmd);
        }
        INIT_LIST_HEAD(&hostdata->disconnected);

        list_for_each_entry(ncmd, &hostdata->autosense, list) {
                struct scsi_cmnd *cmd = NCR5380_to_scmd(ncmd);

                set_host_byte(cmd, DID_RESET);
                cmd->scsi_done(cmd);
        }
        INIT_LIST_HEAD(&hostdata->autosense);

        if (hostdata->connected) {
                set_host_byte(hostdata->connected, DID_RESET);
                complete_cmd(instance, hostdata->connected);
                hostdata->connected = NULL;
        }

        for (i = 0; i < 8; ++i)
                hostdata->busy[i] = 0;
        hostdata->dma_len = 0;

        queue_work(hostdata->work_q, &hostdata->main_task);
        spin_unlock_irqrestore(&hostdata->lock, flags);

        return SUCCESS;
}