xref: /linux/drivers/scsi/NCR5380.c (revision c79c3c34f75d72a066e292b10aa50fc758c97c89)

// SPDX-License-Identifier: GPL-2.0
/*
 * 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.
 */

/* Ported to Atari by Roman Hodek and others. */

/* Adapted for the Sun 3 by Sam Creasey. */

/*
 * 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 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_xfer_len   - determine size of DMA/PDMA transfer
 * NCR5380_dma_send_setup - execute DMA/PDMA from memory to 5380
 * NCR5380_dma_recv_setup - execute DMA/PDMA from 5380 to memory
 * NCR5380_dma_residual   - residual byte count
 *
 * The generic driver is initialized by calling NCR5380_init(instance),
 * after setting the appropriate host specific fields and ID.
 */

#ifndef NCR5380_io_delay
#define NCR5380_io_delay(x)
#endif

#ifndef NCR5380_acquire_dma_irq
#define NCR5380_acquire_dma_irq(x)	(1)
#endif

#ifndef NCR5380_release_dma_irq
#define NCR5380_release_dma_irq(x)
#endif

static unsigned int disconnect_mask = ~0;
module_param(disconnect_mask, int, 0444);

static int do_abort(struct Scsi_Host *, unsigned int);
static void do_reset(struct Scsi_Host *);
static void bus_reset_cleanup(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.ptr = sg_virt(cmd->SCp.buffer);
		cmd->SCp.this_residual = cmd->SCp.buffer->length;
	} else {
		cmd->SCp.buffer = NULL;
		cmd->SCp.ptr = NULL;
		cmd->SCp.this_residual = 0;
	}

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

static inline void advance_sg_buffer(struct scsi_cmnd *cmd)
{
	struct scatterlist *s = cmd->SCp.buffer;

	if (!cmd->SCp.this_residual && s && !sg_is_last(s)) {
		cmd->SCp.buffer = sg_next(s);
		cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);
		cmd->SCp.this_residual = cmd->SCp.buffer->length;
	}
}

static inline void set_resid_from_SCp(struct scsi_cmnd *cmd)
{
	int resid = cmd->SCp.this_residual;
	struct scatterlist *s = cmd->SCp.buffer;

	if (s)
		while (!sg_is_last(s)) {
			s = sg_next(s);
			resid += s->length;
		}
	scsi_set_resid(cmd, resid);
}

/**
 * NCR5380_poll_politely2 - wait for two chip register values
 * @hostdata: host private data
 * @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, 0 if sleeping is not allowed
 *
 * 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 NCR5380_hostdata *hostdata,
                                  unsigned int reg1, u8 bit1, u8 val1,
                                  unsigned int reg2, u8 bit2, u8 val2,
                                  unsigned long wait)
{
	unsigned long n = hostdata->poll_loops;
	unsigned long deadline = jiffies + wait;

	do {
		if ((NCR5380_read(reg1) & bit1) == val1)
			return 0;
		if ((NCR5380_read(reg2) & bit2) == val2)
			return 0;
		cpu_relax();
	} while (n--);

	if (!wait)
		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;
}

#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_END_DMA_TRANSFER, "END OF DMA"},
	{BASR_DRQ, "DRQ"},
	{BASR_PARITY_ERROR, "PARITY ERROR"},
	{BASR_IRQ, "IRQ"},
	{BASR_PHASE_MATCH, "PHASE MATCH"},
	{BASR_BUSY_ERROR, "BUSY ERROR"},
	{BASR_ATN, "ATN"},
	{BASR_ACK, "ACK"},
	{0, NULL}
},
icrs[] = {
	{ICR_ASSERT_RST, "ASSERT RST"},
	{ICR_ARBITRATION_PROGRESS, "ARB. IN PROGRESS"},
	{ICR_ARBITRATION_LOST, "LOST ARB."},
	{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, "BLOCK DMA MODE"},
	{MR_TARGET, "TARGET"},
	{MR_ENABLE_PAR_CHECK, "PARITY CHECK"},
	{MR_ENABLE_PAR_INTR, "PARITY INTR"},
	{MR_ENABLE_EOP_INTR, "EOP INTR"},
	{MR_MONITOR_BSY, "MONITOR BSY"},
	{MR_DMA_MODE, "DMA MODE"},
	{MR_ARBITRATE, "ARBITRATE"},
	{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)
{
	struct NCR5380_hostdata *hostdata = shost_priv(instance);
	unsigned char status, basr, mr, icr, i;

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

	printk(KERN_DEBUG "SR =   0x%02x : ", status);
	for (i = 0; signals[i].mask; ++i)
		if (status & signals[i].mask)
			printk(KERN_CONT "%s, ", signals[i].name);
	printk(KERN_CONT "\nBASR = 0x%02x : ", basr);
	for (i = 0; basrs[i].mask; ++i)
		if (basr & basrs[i].mask)
			printk(KERN_CONT "%s, ", basrs[i].name);
	printk(KERN_CONT "\nICR =  0x%02x : ", icr);
	for (i = 0; icrs[i].mask; ++i)
		if (icr & icrs[i].mask)
			printk(KERN_CONT "%s, ", icrs[i].name);
	printk(KERN_CONT "\nMR =   0x%02x : ", mr);
	for (i = 0; mrs[i].mask; ++i)
		if (mr & mrs[i].mask)
			printk(KERN_CONT "%s, ", mrs[i].name);
	printk(KERN_CONT "\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)
{
	struct NCR5380_hostdata *hostdata = shost_priv(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

/**
 * NCR5380_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;
}

/**
 * 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;
	unsigned long accesses_per_ms;

	instance->max_lun = 7;

	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;

	snprintf(hostdata->info, sizeof(hostdata->info),
		"%s, irq %d, io_port 0x%lx, base 0x%lx, can_queue %d, cmd_per_lun %d, sg_tablesize %d, this_id %d, flags { %s%s%s}",
		instance->hostt->name, instance->irq, hostdata->io_port,
		hostdata->base, 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 " : "");

	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));
	accesses_per_ms = i / 256;
	hostdata->poll_loops = NCR5380_REG_POLL_TIME * accesses_per_ms / 2;

	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(hostdata,
			                      STATUS_REG, SR_BSY, 0, 5 * HZ);
			break;
		case 2:
			shost_printk(KERN_ERR, instance, "bus busy, attempting abort\n");
			do_abort(instance, 1);
			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 (status_byte(cmd->result) != GOOD) {
			scsi_eh_restore_cmnd(cmd, &hostdata->ses);
		} else {
			scsi_eh_restore_cmnd(cmd, &hostdata->ses);
			set_driver_byte(cmd, DRIVER_SENSE);
		}
		hostdata->sensing = NULL;
	}

	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);

	if (!NCR5380_acquire_dma_irq(instance)) {
		spin_unlock_irqrestore(&hostdata->lock, flags);

		return SCSI_MLQUEUE_HOST_BUSY;
	}

	/*
	 * 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;
}

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

	/* Caller does the locking needed to set & test these data atomically */
	if (list_empty(&hostdata->disconnected) &&
	    list_empty(&hostdata->unissued) &&
	    list_empty(&hostdata->autosense) &&
	    !hostdata->connected &&
	    !hostdata->selecting) {
		NCR5380_release_dma_irq(instance);
	}
}

/**
 * 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;
		}
		if (!hostdata->connected) {
			NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
			maybe_release_dma_irq(instance);
		}
		spin_unlock_irq(&hostdata->lock);
		if (!done)
			cond_resched();
	} while (!done);
}

/*
 * NCR5380_dma_complete - finish DMA transfer
 * @instance: the scsi host instance
 *
 * Called by the interrupt handler when DMA finishes or a phase
 * mismatch occurs (which would end the DMA transfer).
 */

static void NCR5380_dma_complete(struct Scsi_Host *instance)
{
	struct NCR5380_hostdata *hostdata = shost_priv(instance);
	int transferred;
	unsigned char **data;
	int *count;
	int saved_data = 0, overrun = 0;
	unsigned char p;

	if (hostdata->read_overruns) {
		p = hostdata->connected->SCp.phase;
		if (p & SR_IO) {
			udelay(10);
			if ((NCR5380_read(BUS_AND_STATUS_REG) &
			     (BASR_PHASE_MATCH | BASR_ACK)) ==
			    (BASR_PHASE_MATCH | BASR_ACK)) {
				saved_data = NCR5380_read(INPUT_DATA_REG);
				overrun = 1;
				dsprintk(NDEBUG_DMA, instance, "read overrun handled\n");
			}
		}
	}

#ifdef CONFIG_SUN3
	if ((sun3scsi_dma_finish(rq_data_dir(hostdata->connected->request)))) {
		pr_err("scsi%d: overrun in UDC counter -- not prepared to deal with this!\n",
		       instance->host_no);
		BUG();
	}

	if ((NCR5380_read(BUS_AND_STATUS_REG) & (BASR_PHASE_MATCH | BASR_ACK)) ==
	    (BASR_PHASE_MATCH | BASR_ACK)) {
		pr_err("scsi%d: BASR %02x\n", instance->host_no,
		       NCR5380_read(BUS_AND_STATUS_REG));
		pr_err("scsi%d: bus stuck in data phase -- probably a single byte overrun!\n",
		       instance->host_no);
		BUG();
	}
#endif

	NCR5380_write(MODE_REG, MR_BASE);
	NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
	NCR5380_read(RESET_PARITY_INTERRUPT_REG);

	transferred = hostdata->dma_len - NCR5380_dma_residual(hostdata);
	hostdata->dma_len = 0;

	data = (unsigned char **)&hostdata->connected->SCp.ptr;
	count = &hostdata->connected->SCp.this_residual;
	*data += transferred;
	*count -= transferred;

	if (hostdata->read_overruns) {
		int cnt, toPIO;

		if ((NCR5380_read(STATUS_REG) & PHASE_MASK) == p && (p & SR_IO)) {
			cnt = toPIO = hostdata->read_overruns;
			if (overrun) {
				dsprintk(NDEBUG_DMA, instance,
				         "Got an input overrun, using saved byte\n");
				*(*data)++ = saved_data;
				(*count)--;
				cnt--;
				toPIO--;
			}
			if (toPIO > 0) {
				dsprintk(NDEBUG_DMA, instance,
				         "Doing %d byte PIO to 0x%p\n", cnt, *data);
				NCR5380_transfer_pio(instance, &p, &cnt, data, 0);
				*count -= toPIO - cnt;
			}
		}
	}
}

/**
 * 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 __maybe_unused 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 ((mr & MR_DMA_MODE) || (mr & MR_MONITOR_BSY)) {
			/* Probably End of DMA, Phase Mismatch or Loss of BSY.
			 * We ack IRQ after clearing Mode Register. Workarounds
			 * for End of DMA errata need to happen in DMA Mode.
			 */

			dsprintk(NDEBUG_INTR, instance, "interrupt in DMA mode\n");

			if (hostdata->connected) {
				NCR5380_dma_complete(instance);
				queue_work(hostdata->work_q, &hostdata->main_task);
			} else {
				NCR5380_write(MODE_REG, MR_BASE);
				NCR5380_read(RESET_PARITY_INTERRUPT_REG);
			}
		} else 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);

			if (sr & SR_RST) {
				/* Certainly Bus Reset */
				shost_printk(KERN_WARNING, instance,
					     "bus reset interrupt\n");
				bus_reset_cleanup(instance);
			} else {
				dsprintk(NDEBUG_INTR, instance, "unknown interrupt\n");
			}
#ifdef SUN3_SCSI_VME
			dregs->csr |= CSR_DMA_ENABLE;
#endif
		}
		handled = 1;
	} else {
		dsprintk(NDEBUG_INTR, instance, "interrupt without IRQ bit\n");
#ifdef SUN3_SCSI_VME
		dregs->csr |= CSR_DMA_ENABLE;
#endif
	}

	spin_unlock_irqrestore(&hostdata->lock, flags);

	return IRQ_RETVAL(handled);
}

/**
 * NCR5380_select - attempt arbitration and selection for a given command
 * @instance: the Scsi_Host instance
 * @cmd: the scsi_cmnd to execute
 *
 * This routine establishes an I_T_L nexus for a SCSI command. This involves
 * ARBITRATION, SELECTION and MESSAGE OUT phases and an IDENTIFY message.
 *
 * Returns true if the operation should be retried.
 * Returns false if it should not be retried.
 *
 * 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 : the I_T_L nexus will be established, and
 * hostdata->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 bool NCR5380_select(struct Scsi_Host *instance, struct scsi_cmnd *cmd)
	__releases(&hostdata->lock) __acquires(&hostdata->lock)
{
	struct NCR5380_hostdata *hostdata = shost_priv(instance);
	unsigned char tmp[3], phase;
	unsigned char *data;
	int len;
	int err;
	bool ret = true;
	bool can_disconnect = instance->irq != NO_IRQ &&
			      cmd->cmnd[0] != REQUEST_SENSE &&
			      (disconnect_mask & BIT(scmd_id(cmd)));

	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 false
	 * 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(hostdata, 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);
		return false;
	}
	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);
		return false;
	}

	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(hostdata, 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);
		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);

		/* Can't touch cmd if it has been reclaimed by the scsi ML */
		if (!hostdata->selecting)
			return false;

		cmd->result = DID_BAD_TARGET << 16;
		complete_cmd(instance, cmd);
		dsprintk(NDEBUG_SELECTION, instance,
			"target did not respond within 250ms\n");
		ret = false;
		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.
	 */

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

	err = NCR5380_poll_politely(hostdata, 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);
		goto out;
	}
	if (!hostdata->selecting) {
		do_abort(instance, 0);
		return false;
	}

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

	len = 1;
	data = tmp;
	phase = PHASE_MSGOUT;
	NCR5380_transfer_pio(instance, &phase, &len, &data, 0);
	if (len) {
		NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
		cmd->result = DID_ERROR << 16;
		complete_cmd(instance, cmd);
		dsprintk(NDEBUG_SELECTION, instance, "IDENTIFY message transfer failed\n");
		ret = false;
		goto out;
	}

	dsprintk(NDEBUG_SELECTION, instance, "nexus established.\n");

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

#ifdef SUN3_SCSI_VME
	dregs->csr |= CSR_INTR;
#endif

	initialize_SCp(cmd);

	ret = false;

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

/*
 * 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,
 * can_sleep - 1 or 0 when sleeping is permitted or not, respectively.
 *
 * 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 int can_sleep)
{
	struct NCR5380_hostdata *hostdata = shost_priv(instance);
	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(hostdata, STATUS_REG, SR_REQ, SR_REQ,
					  HZ * can_sleep) < 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(hostdata,
		                          STATUS_REG, SR_REQ, 0, 5 * HZ * can_sleep) < 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)
{
	struct NCR5380_hostdata __maybe_unused *hostdata = shost_priv(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
 * @can_sleep: 1 or 0 when sleeping is permitted or not, respectively
 *
 * Returns 0 on success, negative error code on failure.
 */

static int do_abort(struct Scsi_Host *instance, unsigned int can_sleep)
{
	struct NCR5380_hostdata *hostdata = shost_priv(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(hostdata, STATUS_REG, SR_REQ, SR_REQ,
				   10 * HZ * can_sleep);
	if (rc < 0)
		goto out;

	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(hostdata, STATUS_REG, SR_REQ, 0,
					   3 * HZ * can_sleep);
		if (rc < 0)
			goto out;
		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, can_sleep);
	if (len)
		rc = -ENXIO;

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

out:
	NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
	return rc;
}

/*
 * 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);
	int c = *count;
	unsigned char p = *phase;
	unsigned char *d = *data;
	unsigned char tmp;
	int result = 0;

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

	hostdata->connected->SCp.phase = p;

	if (p & SR_IO) {
		if (hostdata->read_overruns)
			c -= hostdata->read_overruns;
		else if (hostdata->flags & FLAG_DMA_FIXUP)
			--c;
	}

	dsprintk(NDEBUG_DMA, instance, "initializing DMA %s: length %d, address %p\n",
	         (p & SR_IO) ? "receive" : "send", c, d);

#ifdef CONFIG_SUN3
	/* send start chain */
	sun3scsi_dma_start(c, *data);
#endif

	NCR5380_write(TARGET_COMMAND_REG, PHASE_SR_TO_TCR(p));
	NCR5380_write(MODE_REG, MR_BASE | MR_DMA_MODE | MR_MONITOR_BSY |
	                        MR_ENABLE_EOP_INTR);

	if (!(hostdata->flags & FLAG_LATE_DMA_SETUP)) {
		/* On the Medusa, it is a must to initialize the DMA before
		 * starting the NCR. This is also the cleaner way for the TT.
		 */
		if (p & SR_IO)
			result = NCR5380_dma_recv_setup(hostdata, d, c);
		else
			result = NCR5380_dma_send_setup(hostdata, d, c);
	}

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

	if (p & SR_IO) {
		NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
		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);
	}

#ifdef CONFIG_SUN3
#ifdef SUN3_SCSI_VME
	dregs->csr |= CSR_DMA_ENABLE;
#endif
	sun3_dma_active = 1;
#endif

	if (hostdata->flags & FLAG_LATE_DMA_SETUP) {
		/* On the Falcon, the DMA setup must be done after the last
		 * NCR access, else the DMA setup gets trashed!
		 */
		if (p & SR_IO)
			result = NCR5380_dma_recv_setup(hostdata, d, c);
		else
			result = NCR5380_dma_send_setup(hostdata, d, c);
	}

	/* On failure, NCR5380_dma_xxxx_setup() returns a negative int. */
	if (result < 0)
		return result;

	/* For real DMA, result is the byte count. DMA interrupt is expected. */
	if (result > 0) {
		hostdata->dma_len = result;
		return 0;
	}

	/* The result is zero iff pseudo DMA send/receive was completed. */
	hostdata->dma_len = c;

/*
 * 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 (hostdata->flags & FLAG_DMA_FIXUP) {
		if (p & SR_IO) {
			/*
			 * 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(hostdata, BUS_AND_STATUS_REG,
			                          BASR_DRQ, BASR_DRQ, 0) < 0) {
				result = -1;
				shost_printk(KERN_ERR, instance, "PDMA read: DRQ timeout\n");
			}
			if (NCR5380_poll_politely(hostdata, STATUS_REG,
			                          SR_REQ, 0, 0) < 0) {
				result = -1;
				shost_printk(KERN_ERR, instance, "PDMA read: !REQ timeout\n");
			}
			d[*count - 1] = NCR5380_read(INPUT_DATA_REG);
		} else {
			/*
			 * 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(hostdata,
			     BUS_AND_STATUS_REG, BASR_DRQ, BASR_DRQ,
			     BUS_AND_STATUS_REG, BASR_PHASE_MATCH, 0, 0) < 0) {
				result = -1;
				shost_printk(KERN_ERR, instance, "PDMA write: DRQ and phase timeout\n");
			}
		}
	}

	NCR5380_dma_complete(instance);
	return result;
}

/*
 * 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)
	__releases(&hostdata->lock) __acquires(&hostdata->lock)
{
	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;

#ifdef SUN3_SCSI_VME
	dregs->csr |= CSR_INTR;
#endif

	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);
			}
#ifdef CONFIG_SUN3
			if (phase == PHASE_CMDOUT &&
			    sun3_dma_setup_done != cmd) {
				int count;

				advance_sg_buffer(cmd);

				count = sun3scsi_dma_xfer_len(hostdata, cmd);

				if (count > 0) {
					if (rq_data_dir(cmd->request))
						sun3scsi_dma_send_setup(hostdata,
						                        cmd->SCp.ptr, count);
					else
						sun3scsi_dma_recv_setup(hostdata,
						                        cmd->SCp.ptr, count);
					sun3_dma_setup_done = cmd;
				}
#ifdef SUN3_SCSI_VME
				dregs->csr |= CSR_INTR;
#endif
			}
#endif /* CONFIG_SUN3 */

			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, 0);
				cmd->result = DID_ERROR << 16;
				complete_cmd(instance, cmd);
				hostdata->connected = NULL;
				hostdata->busy[scmd_id(cmd)] &= ~(1 << cmd->device->lun);
				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.
				 */

				advance_sg_buffer(cmd);
				dsprintk(NDEBUG_INFORMATION, instance,
					"this residual %d, sg ents %d\n",
					cmd->SCp.this_residual,
					sg_nents(cmd->SCp.buffer));

				/*
				 * 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(hostdata, cmd);

				if (transfersize > 0) {
					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;
						do_reset(instance);
						bus_reset_cleanup(instance);
					}
				} else {
					/* Transfer a small chunk so that the
					 * irq mode lock is not held too long.
					 */
					transfersize = min(cmd->SCp.this_residual,
							   NCR5380_PIO_CHUNK_SIZE);
					len = transfersize;
					NCR5380_transfer_pio(instance, &phase, &len,
					                     (unsigned char **)&cmd->SCp.ptr,
							     0);
					cmd->SCp.this_residual -= transfersize - len;
				}
#ifdef CONFIG_SUN3
				if (sun3_dma_setup_done == cmd)
					sun3_dma_setup_done = NULL;
#endif
				return;
			case PHASE_MSGIN:
				len = 1;
				data = &tmp;
				NCR5380_transfer_pio(instance, &phase, &len, &data, 0);
				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;
					hostdata->busy[scmd_id(cmd)] &= ~(1 << cmd->device->lun);

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

					set_resid_from_SCp(cmd);

					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);

					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);

#ifdef SUN3_SCSI_VME
					dregs->csr |= CSR_DMA_ENABLE;
#endif
					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, 1);
					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, 1);
						dsprintk(NDEBUG_EXTENDED, instance, "message received, residual %d\n",
						         len);

						switch (extended_msg[2]) {
						case EXTENDED_SDTR:
						case EXTENDED_WDTR:
							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;

					/* Reject message */
					fallthrough;
				default:
					/*
					 * If we get something weird that we aren't expecting,
					 * log it.
					 */
					if (tmp == EXTENDED_MESSAGE)
						scmd_printk(KERN_INFO, cmd,
						            "rejecting unknown extended message code %02x, length %d\n",
						            extended_msg[2], extended_msg[1]);
					else if (tmp)
						scmd_printk(KERN_INFO, cmd,
						            "rejecting unknown message code %02x\n",
						            tmp);

					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, 0);
				if (msgout == ABORT) {
					hostdata->connected = NULL;
					hostdata->busy[scmd_id(cmd)] &= ~(1 << cmd->device->lun);
					cmd->result = DID_ERROR << 16;
					complete_cmd(instance, cmd);
					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, 0);
				break;
			case PHASE_STATIN:
				len = 1;
				data = &tmp;
				NCR5380_transfer_pio(instance, &phase, &len, &data, 0);
				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(hostdata, 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;
	unsigned char msg[3];
	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);
	if (!target_mask || target_mask & (target_mask - 1)) {
		shost_printk(KERN_WARNING, instance,
			     "reselect: bad target_mask 0x%02x\n", target_mask);
		return;
	}

	/*
	 * 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(hostdata,
	                          STATUS_REG, SR_SEL, 0, 0) < 0) {
		shost_printk(KERN_ERR, instance, "reselect: !SEL timeout\n");
		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(hostdata,
	                          STATUS_REG, SR_REQ, SR_REQ, 0) < 0) {
		if ((NCR5380_read(STATUS_REG) & (SR_BSY | SR_SEL)) == 0)
			/* BUS FREE phase */
			return;
		shost_printk(KERN_ERR, instance, "reselect: REQ timeout\n");
		do_abort(instance, 0);
		return;
	}

#ifdef CONFIG_SUN3
	/* acknowledge toggle to MSGIN */
	NCR5380_write(TARGET_COMMAND_REG, PHASE_SR_TO_TCR(PHASE_MSGIN));

	/* peek at the byte without really hitting the bus */
	msg[0] = NCR5380_read(CURRENT_SCSI_DATA_REG);
#else
	{
		int len = 1;
		unsigned char *data = msg;
		unsigned char phase = PHASE_MSGIN;

		NCR5380_transfer_pio(instance, &phase, &len, &data, 0);

		if (len) {
			do_abort(instance, 0);
			return;
		}
	}
#endif /* CONFIG_SUN3 */

	if (!(msg[0] & 0x80)) {
		shost_printk(KERN_ERR, instance, "expecting IDENTIFY message, got ");
		spi_print_msg(msg);
		printk("\n");
		do_abort(instance, 0);
		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 {
		int target = ffs(target_mask) - 1;

		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.
		 */
		if (do_abort(instance, 0) == 0)
			hostdata->busy[target] &= ~(1 << lun);
		return;
	}

#ifdef CONFIG_SUN3
	if (sun3_dma_setup_done != tmp) {
		int count;

		advance_sg_buffer(tmp);

		count = sun3scsi_dma_xfer_len(hostdata, tmp);

		if (count > 0) {
			if (rq_data_dir(tmp->request))
				sun3scsi_dma_send_setup(hostdata,
				                        tmp->SCp.ptr, count);
			else
				sun3scsi_dma_recv_setup(hostdata,
				                        tmp->SCp.ptr, count);
			sun3_dma_setup_done = tmp;
		}
	}

	NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_ACK);
#endif /* CONFIG_SUN3 */

	/* 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\n",
	         scmd_id(tmp), tmp->device->lun);
}

/**
 * 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, 0) < 0) {
			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);
		complete_cmd(instance, cmd);
	}

out:
	if (result == FAILED)
		dsprintk(NDEBUG_ABORT, instance, "abort: failed to abort %p\n", cmd);
	else {
		hostdata->busy[scmd_id(cmd)] &= ~(1 << cmd->device->lun);
		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;
}


static void bus_reset_cleanup(struct Scsi_Host *instance)
{
	struct NCR5380_hostdata *hostdata = shost_priv(instance);
	int i;
	struct NCR5380_cmd *ncmd;

	/* 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 (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);
		complete_cmd(instance, cmd);
	}
	INIT_LIST_HEAD(&hostdata->disconnected);

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

		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);
}

/**
 * NCR5380_host_reset - reset the SCSI host
 * @cmd: SCSI command undergoing EH
 *
 * Returns SUCCESS
 */

static int NCR5380_host_reset(struct scsi_cmnd *cmd)
{
	struct Scsi_Host *instance = cmd->device->host;
	struct NCR5380_hostdata *hostdata = shost_priv(instance);
	unsigned long flags;
	struct NCR5380_cmd *ncmd;

	spin_lock_irqsave(&hostdata->lock, flags);

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

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

		scmd->result = DID_RESET << 16;
		scmd->scsi_done(scmd);
	}
	INIT_LIST_HEAD(&hostdata->unissued);

	do_reset(instance);
	bus_reset_cleanup(instance);

	spin_unlock_irqrestore(&hostdata->lock, flags);

	return SUCCESS;
}