/*
   * Adaptec 274x/284x/294x device driver firmware for Linux and FreeBSD.
   *
   * Copyright (c) 1994-2001 Justin T. Gibbs.
   * Copyright (c) 2000-2001 Adaptec Inc.
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions, and the following disclaimer,
   *    without modification.
   * 2. Redistributions in binary form must reproduce at minimum a disclaimer
   *    substantially similar to the "NO WARRANTY" disclaimer below
   *    ("Disclaimer") and any redistribution must be conditioned upon
   *    including a substantially similar Disclaimer requirement for further
   *    binary redistribution.
   * 3. Neither the names of the above-listed copyright holders nor the names
   *    of any contributors may be used to endorse or promote products derived
   *    from this software without specific prior written permission.
   *
   * Alternatively, this software may be distributed under the terms of the
   * GNU General Public License ("GPL") version 2 as published by the Free
   * Software Foundation.
   *
   * NO WARRANTY
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
   * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGES.
   *
   * $FreeBSD$
   */
  
  VERSION = "$Id: //depot/aic7xxx/aic7xxx/aic7xxx.seq#58 $"
  PATCH_ARG_LIST = "struct ahc_softc *ahc"
  PREFIX = "ahc_"
  
  #include "aic7xxx.reg"
  #include "scsi_message.h"
  
  /*
   * A few words on the waiting SCB list:
   * After starting the selection hardware, we check for reconnecting targets
   * as well as for our selection to complete just in case the reselection wins
   * bus arbitration.  The problem with this is that we must keep track of the
   * SCB that we've already pulled from the QINFIFO and started the selection
   * on just in case the reselection wins so that we can retry the selection at
   * a later time.  This problem cannot be resolved by holding a single entry
   * in scratch ram since a reconnecting target can request sense and this will
   * create yet another SCB waiting for selection.  The solution used here is to 
   * use byte 27 of the SCB as a pseudo-next pointer and to thread a list
   * of SCBs that are awaiting selection.  Since 0-0xfe are valid SCB indexes, 
   * SCB_LIST_NULL is 0xff which is out of range.  An entry is also added to
   * this list every time a request sense occurs or after completing a non-tagged
   * command for which a second SCB has been queued.  The sequencer will
   * automatically consume the entries.
   */
  
  bus_free_sel:
  	/*
  	 * Turn off the selection hardware.  We need to reset the
  	 * selection request in order to perform a new selection.
  	 */
  	and	SCSISEQ, TEMODE|ENSELI|ENRSELI|ENAUTOATNP;
  	and	SIMODE1, ~ENBUSFREE;
  poll_for_work:
  	call	clear_target_state;
  	and	SXFRCTL0, ~SPIOEN;
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		clr	SCSIBUSL;
  	}
  	test	SCSISEQ, ENSELO	jnz poll_for_selection;
  	if ((ahc->features & AHC_TWIN) != 0) {
  		xor	SBLKCTL,SELBUSB;	/* Toggle to the other bus */
  		test	SCSISEQ, ENSELO		jnz poll_for_selection;
  	}
  	cmp	WAITING_SCBH,SCB_LIST_NULL jne start_waiting;
  poll_for_work_loop:
  	if ((ahc->features & AHC_TWIN) != 0) {
  		xor	SBLKCTL,SELBUSB;	/* Toggle to the other bus */
  	}
  	test	SSTAT0, SELDO|SELDI	jnz selection;
  test_queue:
  	/* Has the driver posted any work for us? */
  BEGIN_CRITICAL;
  	if ((ahc->features & AHC_QUEUE_REGS) != 0) {
  		test	QOFF_CTLSTA, SCB_AVAIL jz poll_for_work_loop;
  	} else {
  		mov	A, QINPOS;
  		cmp	KERNEL_QINPOS, A je poll_for_work_loop;
  	}
  	mov	ARG_1, NEXT_QUEUED_SCB;
  
  	/*
  	 * We have at least one queued SCB now and we don't have any 
  	 * SCBs in the list of SCBs awaiting selection.  Allocate a
  	 * card SCB for the host's SCB and get to work on it.
  	 */
  	if ((ahc->flags & AHC_PAGESCBS) != 0) {
  		mov	ALLZEROS	call	get_free_or_disc_scb;
  	} else {
  		/* In the non-paging case, the SCBID == hardware SCB index */
  		mov	SCBPTR, ARG_1;
  	}
  	or	SEQ_FLAGS2, SCB_DMA;
  END_CRITICAL;
  dma_queued_scb:
  	/*
  	 * DMA the SCB from host ram into the current SCB location.
  	 */
  	mvi	DMAPARAMS, HDMAEN|DIRECTION|FIFORESET;
  	mov	ARG_1	call dma_scb;
  	/*
  	 * Check one last time to see if this SCB was canceled
  	 * before we completed the DMA operation.  If it was,
  	 * the QINFIFO next pointer will not match our saved
  	 * value.
  	 */
  	mov	A, ARG_1;
  BEGIN_CRITICAL;
  	cmp	NEXT_QUEUED_SCB, A jne abort_qinscb;
  	if ((ahc->flags & AHC_SEQUENCER_DEBUG) != 0) {
  		cmp	SCB_TAG, A je . + 2;
  		mvi	SCB_MISMATCH call set_seqint;
  	}
  	mov	NEXT_QUEUED_SCB, SCB_NEXT;
  	mov	SCB_NEXT,WAITING_SCBH;
  	mov	WAITING_SCBH, SCBPTR;
  	if ((ahc->features & AHC_QUEUE_REGS) != 0) {
  		mov	NONE, SNSCB_QOFF;
  	} else {
  		inc	QINPOS;
  	}
  	and	SEQ_FLAGS2, ~SCB_DMA;
  END_CRITICAL;
  start_waiting:
  	/*
  	 * Start the first entry on the waiting SCB list.
  	 */
  	mov	SCBPTR, WAITING_SCBH;
  	call	start_selection;
  
  poll_for_selection:
  	/*
  	 * Twin channel devices cannot handle things like SELTO
  	 * interrupts on the "background" channel.  So, while
  	 * selecting, keep polling the current channel until
  	 * either a selection or reselection occurs.
  	 */
  	test	SSTAT0, SELDO|SELDI	jz poll_for_selection;
  
  selection:
  	/*
  	 * We aren't expecting a bus free, so interrupt
  	 * the kernel driver if it happens.
  	 */
  	mvi	CLRSINT1,CLRBUSFREE;
  	if ((ahc->features & AHC_DT) == 0) {
  		or	SIMODE1, ENBUSFREE;
  	}
  
  	/*
  	 * Guard against a bus free after (re)selection
  	 * but prior to enabling the busfree interrupt.  SELDI
  	 * and SELDO will be cleared in that case.
  	 */
  	test	SSTAT0, SELDI|SELDO	jz bus_free_sel;
  	test	SSTAT0,SELDO	jnz select_out;
  select_in:
  	if ((ahc->flags & AHC_TARGETROLE) != 0) {
  		if ((ahc->flags & AHC_INITIATORROLE) != 0) {
  			test	SSTAT0, TARGET	jz initiator_reselect;
  		}
  		mvi	CLRSINT0, CLRSELDI;
  
  		/*
  		 * We've just been selected.  Assert BSY and
  		 * setup the phase for receiving messages
  		 * from the target.
  		 */
  		mvi	SCSISIGO, P_MESGOUT|BSYO;
  
  		/*
  		 * Setup the DMA for sending the identify and
  		 * command information.
  		 */
  		mvi	SEQ_FLAGS, CMDPHASE_PENDING;
  
  		mov     A, TQINPOS;
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			mvi	DINDEX, CCHADDR;
  			mvi	SHARED_DATA_ADDR call set_32byte_addr;
  			mvi	CCSCBCTL, CCSCBRESET;
  		} else {
  			mvi	DINDEX, HADDR;
  			mvi	SHARED_DATA_ADDR call set_32byte_addr;
  			mvi	DFCNTRL, FIFORESET;
  		}
  
  		/* Initiator that selected us */
  		and	SAVED_SCSIID, SELID_MASK, SELID;
  		/* The Target ID we were selected at */
  		if ((ahc->features & AHC_MULTI_TID) != 0) {
  			and	A, OID, TARGIDIN;
  		} else if ((ahc->features & AHC_ULTRA2) != 0) {
  			and	A, OID, SCSIID_ULTRA2;
  		} else {
  			and	A, OID, SCSIID;
  		}
  		or	SAVED_SCSIID, A;
  		if ((ahc->features & AHC_TWIN) != 0) {
  			test 	SBLKCTL, SELBUSB jz . + 2;
  			or	SAVED_SCSIID, TWIN_CHNLB;
  		}
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			mov	CCSCBRAM, SAVED_SCSIID;
  		} else {
  			mov	DFDAT, SAVED_SCSIID;
  		}
  
  		/*
  		 * If ATN isn't asserted, the target isn't interested
  		 * in talking to us.  Go directly to bus free.
  		 * XXX SCSI-1 may require us to assume lun 0 if
  		 * ATN is false.
  		 */
  		test	SCSISIGI, ATNI	jz	target_busfree;
  
  		/*
  		 * Watch ATN closely now as we pull in messages from the
  		 * initiator.  We follow the guidlines from section 6.5
  		 * of the SCSI-2 spec for what messages are allowed when.
  		 */
  		call	target_inb;
  
  		/*
  		 * Our first message must be one of IDENTIFY, ABORT, or
  		 * BUS_DEVICE_RESET.
  		 */
  		test	DINDEX, MSG_IDENTIFYFLAG jz host_target_message_loop;
  		/* Store for host */
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			mov	CCSCBRAM, DINDEX;
  		} else {
  			mov	DFDAT, DINDEX;
  		}
  		and	SAVED_LUN, MSG_IDENTIFY_LUNMASK, DINDEX;
  
  		/* Remember for disconnection decision */
  		test	DINDEX, MSG_IDENTIFY_DISCFLAG jnz . + 2;
  		/* XXX Honor per target settings too */
  		or	SEQ_FLAGS, NO_DISCONNECT;
  
  		test	SCSISIGI, ATNI	jz	ident_messages_done;
  		call	target_inb;
  		/*
  		 * If this is a tagged request, the tagged message must
  		 * immediately follow the identify.  We test for a valid
  		 * tag message by seeing if it is >= MSG_SIMPLE_Q_TAG and
  		 * < MSG_IGN_WIDE_RESIDUE.
  		 */
  		add	A, -MSG_SIMPLE_Q_TAG, DINDEX;
  		jnc	ident_messages_done_msg_pending;
  		add	A, -MSG_IGN_WIDE_RESIDUE, DINDEX;
  		jc	ident_messages_done_msg_pending;
  
  		/* Store for host */
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			mov	CCSCBRAM, DINDEX;
  		} else {
  			mov	DFDAT, DINDEX;
  		}
  		
  		/*
  		 * If the initiator doesn't feel like providing a tag number,
  		 * we've got a failed selection and must transition to bus
  		 * free.
  		 */
  		test	SCSISIGI, ATNI	jz	target_busfree;
  
  		/*
  		 * Store the tag for the host.
  		 */
  		call	target_inb;
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			mov	CCSCBRAM, DINDEX;
  		} else {
  			mov	DFDAT, DINDEX;
  		}
  		mov	INITIATOR_TAG, DINDEX;
  		or	SEQ_FLAGS, TARGET_CMD_IS_TAGGED;
  
  ident_messages_done:
  		/* Terminate the ident list */
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			mvi	CCSCBRAM, SCB_LIST_NULL;
  		} else {
  			mvi	DFDAT, SCB_LIST_NULL;
  		}
  		or	SEQ_FLAGS, TARG_CMD_PENDING;
  		test	SEQ_FLAGS2, TARGET_MSG_PENDING
  			jnz target_mesgout_pending;
  		test	SCSISIGI, ATNI jnz target_mesgout_continue;
  		jmp	target_ITloop;
  
  
  ident_messages_done_msg_pending:
  		or	SEQ_FLAGS2, TARGET_MSG_PENDING;
  		jmp	ident_messages_done;
  
  		/*
  		 * Pushed message loop to allow the kernel to
  		 * run it's own target mode message state engine.
  		 */
  host_target_message_loop:
  		mvi	HOST_MSG_LOOP call set_seqint;
  		cmp	RETURN_1, EXIT_MSG_LOOP	je target_ITloop;
  		test	SSTAT0, SPIORDY jz .;
  		jmp	host_target_message_loop;
  	}
  
  if ((ahc->flags & AHC_INITIATORROLE) != 0) {
  /*
   * Reselection has been initiated by a target. Make a note that we've been
   * reselected, but haven't seen an IDENTIFY message from the target yet.
   */
  initiator_reselect:
  	/* XXX test for and handle ONE BIT condition */
  	or	SXFRCTL0, SPIOEN|CLRSTCNT|CLRCHN;
  	and	SAVED_SCSIID, SELID_MASK, SELID;
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		and	A, OID, SCSIID_ULTRA2;
  	} else {
  		and	A, OID, SCSIID;
  	}
  	or	SAVED_SCSIID, A;
  	if ((ahc->features & AHC_TWIN) != 0) {
  		test	SBLKCTL, SELBUSB	jz . + 2;
  		or	SAVED_SCSIID, TWIN_CHNLB;
  	}
  	mvi	CLRSINT0, CLRSELDI;
  	jmp	ITloop;
  }
  
  abort_qinscb:
  	call	add_scb_to_free_list;
  	jmp	poll_for_work_loop;
  
  start_selection:
  	/*
  	 * If bus reset interrupts have been disabled (from a previous
  	 * reset), re-enable them now.  Resets are only of interest
  	 * when we have outstanding transactions, so we can safely
  	 * defer re-enabling the interrupt until, as an initiator,
  	 * we start sending out transactions again.
  	 */
  	test	SIMODE1, ENSCSIRST	jnz . + 3;
  	mvi	CLRSINT1, CLRSCSIRSTI;
  	or	SIMODE1, ENSCSIRST;
  	if ((ahc->features & AHC_TWIN) != 0) {
  		and	SINDEX,~SELBUSB,SBLKCTL;/* Clear channel select bit */
  		test	SCB_SCSIID, TWIN_CHNLB jz . + 2;
  		or	SINDEX, SELBUSB;
  		mov	SBLKCTL,SINDEX;		/* select channel */
  	}
  initialize_scsiid:
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		mov	SCSIID_ULTRA2, SCB_SCSIID;
  	} else if ((ahc->features & AHC_TWIN) != 0) {
  		and	SCSIID, TWIN_TID|OID, SCB_SCSIID;
  	} else {
  		mov	SCSIID, SCB_SCSIID;
  	}
  	if ((ahc->flags & AHC_TARGETROLE) != 0) {
  		mov	SINDEX, SCSISEQ_TEMPLATE;
  		test	SCB_CONTROL, TARGET_SCB jz . + 2;
  		or	SINDEX, TEMODE;
  		mov	SCSISEQ, SINDEX ret;
  	} else {
  		mov	SCSISEQ, SCSISEQ_TEMPLATE ret;
  	}
  
  /*
   * Initialize transfer settings with SCB provided settings.
   */
  set_transfer_settings:
  	if ((ahc->features & AHC_ULTRA) != 0) {
  		test	SCB_CONTROL, ULTRAENB jz . + 2;
  		or	SXFRCTL0, FAST20;
  	} 
  	/*
  	 * Initialize SCSIRATE with the appropriate value for this target.
  	 */
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		bmov	SCSIRATE, SCB_SCSIRATE, 2 ret;
  	} else {
  		mov	SCSIRATE, SCB_SCSIRATE ret;
  	}
  
  if ((ahc->flags & AHC_TARGETROLE) != 0) {
  /*
   * We carefully toggle SPIOEN to allow us to return the 
   * message byte we receive so it can be checked prior to
   * driving REQ on the bus for the next byte.
   */
  target_inb:
  	/*
  	 * Drive REQ on the bus by enabling SCSI PIO.
  	 */
  	or	SXFRCTL0, SPIOEN;
  	/* Wait for the byte */
  	test	SSTAT0, SPIORDY jz .;
  	/* Prevent our read from triggering another REQ */
  	and	SXFRCTL0, ~SPIOEN;
  	/* Save latched contents */
  	mov	DINDEX, SCSIDATL ret;
  }
  
  /*
   * After the selection, remove this SCB from the "waiting SCB"
   * list.  This is achieved by simply moving our "next" pointer into
   * WAITING_SCBH.  Our next pointer will be set to null the next time this
   * SCB is used, so don't bother with it now.
   */
  select_out:
  	/* Turn off the selection hardware */
  	and	SCSISEQ, TEMODE|ENSELI|ENRSELI|ENAUTOATNP, SCSISEQ;
  	mov	SCBPTR, WAITING_SCBH;
  	mov	WAITING_SCBH,SCB_NEXT;
  	mov	SAVED_SCSIID, SCB_SCSIID;
  	and	SAVED_LUN, LID, SCB_LUN;
  	call	set_transfer_settings;
  	if ((ahc->flags & AHC_TARGETROLE) != 0) {
  		test	SSTAT0, TARGET	jz initiator_select;
  
  		or	SXFRCTL0, CLRSTCNT|CLRCHN;
  
  		/*
  		 * Put tag in connonical location since not
  		 * all connections have an SCB.
  		 */
  		mov	INITIATOR_TAG, SCB_TARGET_ITAG;
  
  		/*
  		 * We've just re-selected an initiator.
  		 * Assert BSY and setup the phase for
  		 * sending our identify messages.
  		 */
  		mvi	P_MESGIN|BSYO call change_phase;
  		mvi	CLRSINT0, CLRSELDO;
  
  		/*
  		 * Start out with a simple identify message.
  		 */
  		or	SAVED_LUN, MSG_IDENTIFYFLAG call target_outb;
  
  		/*
  		 * If we are the result of a tagged command, send
  		 * a simple Q tag and the tag id.
  		 */
  		test	SCB_CONTROL, TAG_ENB	jz . + 3;
  		mvi	MSG_SIMPLE_Q_TAG call target_outb;
  		mov	SCB_TARGET_ITAG call target_outb;
  target_synccmd:
  		/*
  		 * Now determine what phases the host wants us
  		 * to go through.
  		 */
  		mov	SEQ_FLAGS, SCB_TARGET_PHASES;
  		
  		test	SCB_CONTROL, MK_MESSAGE	jz target_ITloop;
  		mvi	P_MESGIN|BSYO call change_phase;
  		jmp	host_target_message_loop;
  target_ITloop:
  		/*
  		 * Start honoring ATN signals now that
  		 * we properly identified ourselves.
  		 */
  		test	SCSISIGI, ATNI			jnz target_mesgout;
  		test	SEQ_FLAGS, CMDPHASE_PENDING	jnz target_cmdphase;
  		test	SEQ_FLAGS, DPHASE_PENDING	jnz target_dphase;
  		test	SEQ_FLAGS, SPHASE_PENDING	jnz target_sphase;
  
  		/*
  		 * No more work to do.  Either disconnect or not depending
  		 * on the state of NO_DISCONNECT.
  		 */
  		test	SEQ_FLAGS, NO_DISCONNECT jz target_disconnect; 
  		mvi	TARG_IMMEDIATE_SCB, SCB_LIST_NULL;
  		call	complete_target_cmd;
  		if ((ahc->flags & AHC_PAGESCBS) != 0) {
  			mov	ALLZEROS	call	get_free_or_disc_scb;
  		}
  		cmp	TARG_IMMEDIATE_SCB, SCB_LIST_NULL je .;
  		mvi	DMAPARAMS, HDMAEN|DIRECTION|FIFORESET;
  		mov	TARG_IMMEDIATE_SCB call dma_scb;
  		call	set_transfer_settings;
  		or	SXFRCTL0, CLRSTCNT|CLRCHN;
  		jmp	target_synccmd;
  
  target_mesgout:
  		mvi	SCSISIGO, P_MESGOUT|BSYO;
  target_mesgout_continue:
  		call	target_inb;
  target_mesgout_pending:
  		and	SEQ_FLAGS2, ~TARGET_MSG_PENDING;
  		/* Local Processing goes here... */
  		jmp	host_target_message_loop;
  		
  target_disconnect:
  		mvi	P_MESGIN|BSYO call change_phase;
  		test	SEQ_FLAGS, DPHASE	jz . + 2;
  		mvi	MSG_SAVEDATAPOINTER call target_outb;
  		mvi	MSG_DISCONNECT call target_outb;
  
  target_busfree_wait:
  		/* Wait for preceding I/O session to complete. */
  		test	SCSISIGI, ACKI jnz .;
  target_busfree:
  		and	SIMODE1, ~ENBUSFREE;
  		if ((ahc->features & AHC_ULTRA2) != 0) {
  			clr	SCSIBUSL;
  		}
  		clr	SCSISIGO;
  		mvi	LASTPHASE, P_BUSFREE;
  		call	complete_target_cmd;
  		jmp	poll_for_work;
  
  target_cmdphase:
  		/*
  		 * The target has dropped ATN (doesn't want to abort or BDR)
  		 * and we believe this selection to be valid.  If the ring
  		 * buffer for new commands is full, return busy or queue full.
  		 */
  		if ((ahc->features & AHC_HS_MAILBOX) != 0) {
  			and	A, HOST_TQINPOS, HS_MAILBOX;
  		} else {
  			mov	A, KERNEL_TQINPOS;
  		}
  		cmp	TQINPOS, A jne tqinfifo_has_space;
  		mvi	P_STATUS|BSYO call change_phase;
  		test	SEQ_FLAGS, TARGET_CMD_IS_TAGGED jz . + 3;
  		mvi	STATUS_QUEUE_FULL call target_outb;
  		jmp	target_busfree_wait;
  		mvi	STATUS_BUSY call target_outb;
  		jmp	target_busfree_wait;
  tqinfifo_has_space:	
  		mvi	P_COMMAND|BSYO call change_phase;
  		call	target_inb;
  		mov	A, DINDEX;
  		/* Store for host */
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			mov	CCSCBRAM, A;
  		} else {
  			mov	DFDAT, A;
  		}
  
  		/*
  		 * Determine the number of bytes to read
  		 * based on the command group code via table lookup.
  		 * We reuse the first 8 bytes of the TARG_SCSIRATE
  		 * BIOS array for this table. Count is one less than
  		 * the total for the command since we've already fetched
  		 * the first byte.
  		 */
  		shr	A, CMD_GROUP_CODE_SHIFT;
  		add	SINDEX, CMDSIZE_TABLE, A;
  		mov	A, SINDIR;
  
  		test	A, 0xFF jz command_phase_done;
  		or	SXFRCTL0, SPIOEN;
  command_loop:
  		test	SSTAT0, SPIORDY jz .;
  		cmp	A, 1 jne . + 2;
  		and	SXFRCTL0, ~SPIOEN;	/* Last Byte */
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			mov	CCSCBRAM, SCSIDATL;
  		} else {
  			mov	DFDAT, SCSIDATL;
  		}
  		dec	A;
  		test	A, 0xFF jnz command_loop;
  
  command_phase_done:
  		and	SEQ_FLAGS, ~CMDPHASE_PENDING;
  		jmp	target_ITloop;
  
  target_dphase:
  		/*
  		 * Data phases on the bus are from the
  		 * perspective of the initiator.  The dma
  		 * code looks at LASTPHASE to determine the
  		 * data direction of the DMA.  Toggle it for
  		 * target transfers.
  		 */
  		xor	LASTPHASE, IOI, SCB_TARGET_DATA_DIR;
  		or	SCB_TARGET_DATA_DIR, BSYO call change_phase;
  		jmp	p_data;
  
  target_sphase:
  		mvi	P_STATUS|BSYO call change_phase;
  		mvi	LASTPHASE, P_STATUS;
  		mov	SCB_SCSI_STATUS call target_outb;
  		/* XXX Watch for ATN or parity errors??? */
  		mvi	SCSISIGO, P_MESGIN|BSYO;
  		/* MSG_CMDCMPLT is 0, but we can't do an immediate of 0 */
  		mov	ALLZEROS call target_outb;
  		jmp	target_busfree_wait;
  	
  complete_target_cmd:
  		test	SEQ_FLAGS, TARG_CMD_PENDING	jnz . + 2;
  		mov	SCB_TAG jmp complete_post;
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			/* Set the valid byte */
  			mvi	CCSCBADDR, 24;
  			mov	CCSCBRAM, ALLONES;
  			mvi	CCHCNT, 28;
  			or	CCSCBCTL, CCSCBEN|CCSCBRESET;
  			test	CCSCBCTL, CCSCBDONE jz .;
  			clr	CCSCBCTL;
  		} else {
  			/* Set the valid byte */
  			or	DFCNTRL, FIFORESET;
  			mvi	DFWADDR, 3; /* Third 64bit word or byte 24 */
  			mov	DFDAT, ALLONES;
  			mvi	28	call set_hcnt;
  			or	DFCNTRL, HDMAEN|FIFOFLUSH;
  			call	dma_finish;
  		}
  		inc	TQINPOS;
  		mvi	INTSTAT,CMDCMPLT ret;
  	}
  
  if ((ahc->flags & AHC_INITIATORROLE) != 0) {
  initiator_select:
  	or	SXFRCTL0, SPIOEN|CLRSTCNT|CLRCHN;
  	/*
  	 * As soon as we get a successful selection, the target
  	 * should go into the message out phase since we have ATN
  	 * asserted.
  	 */
  	mvi	MSG_OUT, MSG_IDENTIFYFLAG;
  	mvi	SEQ_FLAGS, NO_CDB_SENT;
  	mvi	CLRSINT0, CLRSELDO;
  
  	/*
  	 * Main loop for information transfer phases.  Wait for the
  	 * target to assert REQ before checking MSG, C/D and I/O for
  	 * the bus phase.
  	 */
  mesgin_phasemis:
  ITloop:
  	call	phase_lock;
  
  	mov	A, LASTPHASE;
  
  	test	A, ~P_DATAIN	jz p_data;
  	cmp	A,P_COMMAND	je p_command;
  	cmp	A,P_MESGOUT	je p_mesgout;
  	cmp	A,P_STATUS	je p_status;
  	cmp	A,P_MESGIN	je p_mesgin;
  
  	mvi	BAD_PHASE call set_seqint;
  	jmp	ITloop;			/* Try reading the bus again. */
  
  await_busfree:
  	and	SIMODE1, ~ENBUSFREE;
  	mov	NONE, SCSIDATL;		/* Ack the last byte */
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		clr	SCSIBUSL;	/* Prevent bit leakage durint SELTO */
  	}
  	and	SXFRCTL0, ~SPIOEN;
  	mvi	SEQ_FLAGS, NOT_IDENTIFIED|NO_CDB_SENT;
  	test	SSTAT1,REQINIT|BUSFREE	jz .;
  	test	SSTAT1, BUSFREE jnz poll_for_work;
  	mvi	MISSED_BUSFREE call set_seqint;
  }
  	
  clear_target_state:
  	/*
  	 * We assume that the kernel driver may reset us
  	 * at any time, even in the middle of a DMA, so
  	 * clear DFCNTRL too.
  	 */
  	clr	DFCNTRL;
  	or	SXFRCTL0, CLRSTCNT|CLRCHN;
  
  	/*
  	 * We don't know the target we will connect to,
  	 * so default to narrow transfers to avoid
  	 * parity problems.
  	 */
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		bmov	SCSIRATE, ALLZEROS, 2;
  	} else {
  		clr	SCSIRATE;
  		if ((ahc->features & AHC_ULTRA) != 0) {
  			and	SXFRCTL0, ~(FAST20);
  		}
  	}
  	mvi	LASTPHASE, P_BUSFREE;
  	/* clear target specific flags */
  	mvi	SEQ_FLAGS, NOT_IDENTIFIED|NO_CDB_SENT ret;
  
  sg_advance:
  	clr	A;			/* add sizeof(struct scatter) */
  	add	SCB_RESIDUAL_SGPTR[0],SG_SIZEOF;
  	adc	SCB_RESIDUAL_SGPTR[1],A;
  	adc	SCB_RESIDUAL_SGPTR[2],A;
  	adc	SCB_RESIDUAL_SGPTR[3],A ret;
  
  if ((ahc->features & AHC_CMD_CHAN) != 0) {
  disable_ccsgen:
  	test	CCSGCTL, CCSGEN jz return;
  	test	CCSGCTL, CCSGDONE jz .;
  disable_ccsgen_fetch_done:
  	clr	CCSGCTL;
  	test	CCSGCTL, CCSGEN jnz .;
  	ret;
  idle_loop:
  	/*
  	 * Do we need any more segments for this transfer?
  	 */
  	test	SCB_RESIDUAL_DATACNT[3], SG_LAST_SEG jnz return;
  
  	/* Did we just finish fetching segs? */
  	cmp	CCSGCTL, CCSGEN|CCSGDONE je idle_sgfetch_complete;
  
  	/* Are we actively fetching segments? */
  	test	CCSGCTL, CCSGEN jnz return;
  
  	/*
  	 * Do we have any prefetch left???
  	 */
  	cmp	CCSGADDR, SG_PREFETCH_CNT jne idle_sg_avail;
  
  	/*
  	 * Need to fetch segments, but we can only do that
  	 * if the command channel is completely idle.  Make
  	 * sure we don't have an SCB prefetch going on.
  	 */
  	test	CCSCBCTL, CCSCBEN jnz return;
  
  	/*
  	 * We fetch a "cacheline aligned" and sized amount of data
  	 * so we don't end up referencing a non-existent page.
  	 * Cacheline aligned is in quotes because the kernel will
  	 * set the prefetch amount to a reasonable level if the
  	 * cacheline size is unknown.
  	 */
  	mvi	CCHCNT, SG_PREFETCH_CNT;
  	and	CCHADDR[0], SG_PREFETCH_ALIGN_MASK, SCB_RESIDUAL_SGPTR;
  	bmov	CCHADDR[1], SCB_RESIDUAL_SGPTR[1], 3;
  	mvi	CCSGCTL, CCSGEN|CCSGRESET ret;
  idle_sgfetch_complete:
  	call	disable_ccsgen_fetch_done;
  	and	CCSGADDR, SG_PREFETCH_ADDR_MASK, SCB_RESIDUAL_SGPTR;
  idle_sg_avail:
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		/* Does the hardware have space for another SG entry? */
  		test	DFSTATUS, PRELOAD_AVAIL jz return;
  		bmov 	HADDR, CCSGRAM, 7;
  		bmov	SCB_RESIDUAL_DATACNT[3], CCSGRAM, 1;
  		if ((ahc->flags & AHC_39BIT_ADDRESSING) != 0) {
  			mov	SCB_RESIDUAL_DATACNT[3] call set_hhaddr;
  		}
  		call	sg_advance;
  		mov	SINDEX, SCB_RESIDUAL_SGPTR[0];
  		test	SCB_RESIDUAL_DATACNT[3], SG_LAST_SEG jz . + 2;
  		or	SINDEX, LAST_SEG;
  		mov	SG_CACHE_PRE, SINDEX;
  		/* Load the segment */
  		or	DFCNTRL, PRELOADEN;
  	}
  	ret;
  }
  
  if ((ahc->bugs & AHC_PCI_MWI_BUG) != 0 && ahc->pci_cachesize != 0) {
  /*
   * Calculate the trailing portion of this S/G segment that cannot
   * be transferred using memory write and invalidate PCI transactions.  
   * XXX Can we optimize this for PCI writes only???
   */
  calc_mwi_residual:
  	/*
  	 * If the ending address is on a cacheline boundary,
  	 * there is no need for an extra segment.
  	 */
  	mov	A, HCNT[0];
  	add	A, A, HADDR[0];
  	and	A, CACHESIZE_MASK;
  	test	A, 0xFF jz return;
  
  	/*
  	 * If the transfer is less than a cachline,
  	 * there is no need for an extra segment.
  	 */
  	test	HCNT[1], 0xFF	jnz calc_mwi_residual_final;
  	test	HCNT[2], 0xFF	jnz calc_mwi_residual_final;
  	add	NONE, INVERTED_CACHESIZE_MASK, HCNT[0];
  	jnc	return;
  
  calc_mwi_residual_final:
  	mov	MWI_RESIDUAL, A;
  	not	A;
  	inc	A;
  	add	HCNT[0], A;
  	adc	HCNT[1], -1;
  	adc	HCNT[2], -1 ret;
  }
  
  p_data:
  	test	SEQ_FLAGS,NOT_IDENTIFIED|NO_CDB_SENT jz p_data_allowed;
  	mvi	PROTO_VIOLATION call set_seqint;
  p_data_allowed:
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		mvi	DMAPARAMS, PRELOADEN|SCSIEN|HDMAEN;
  	} else {
  		mvi	DMAPARAMS, WIDEODD|SCSIEN|SDMAEN|HDMAEN|FIFORESET;
  	}
  	test	LASTPHASE, IOI jnz . + 2;
  	or	DMAPARAMS, DIRECTION;
  	if ((ahc->features & AHC_CMD_CHAN) != 0) {
  		/* We don't have any valid S/G elements */
  		mvi	CCSGADDR, SG_PREFETCH_CNT;
  	}
  	test	SEQ_FLAGS, DPHASE	jz data_phase_initialize;
  
  	/*
  	 * If we re-enter the data phase after going through another
  	 * phase, our transfer location has almost certainly been
  	 * corrupted by the interveining, non-data, transfers.  Ask
  	 * the host driver to fix us up based on the transfer residual.
  	 */
  	mvi	PDATA_REINIT	call set_seqint;
  	jmp	data_phase_loop;
  
  data_phase_initialize:
  	/* We have seen a data phase for the first time */
  	or	SEQ_FLAGS, DPHASE;
  
  	/*
  	 * Initialize the DMA address and counter from the SCB.
  	 * Also set SCB_RESIDUAL_SGPTR, including the LAST_SEG
  	 * flag in the highest byte of the data count.  We cannot
  	 * modify the saved values in the SCB until we see a save
  	 * data pointers message.
  	 */
  	if ((ahc->flags & AHC_39BIT_ADDRESSING) != 0) {
  		/* The lowest address byte must be loaded last. */
  		mov	SCB_DATACNT[3] call set_hhaddr;
  	}
  	if ((ahc->features & AHC_CMD_CHAN) != 0) {
  		bmov	HADDR, SCB_DATAPTR, 7;
  		bmov	SCB_RESIDUAL_DATACNT[3], SCB_DATACNT[3], 5;
  	} else {
  		mvi	DINDEX, HADDR;
  		mvi	SCB_DATAPTR	call bcopy_7;
  		mvi	DINDEX, SCB_RESIDUAL_DATACNT + 3;
  		mvi	SCB_DATACNT + 3 call bcopy_5;
  	}
  	if ((ahc->bugs & AHC_PCI_MWI_BUG) != 0 && ahc->pci_cachesize != 0) {
  		call	calc_mwi_residual;
  	}
  	and	SCB_RESIDUAL_SGPTR[0], ~SG_FULL_RESID;
  
  	if ((ahc->features & AHC_ULTRA2) == 0) {
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			bmov	STCNT, HCNT, 3;
  		} else {
  			call	set_stcnt_from_hcnt;
  		}
  	}
  
  data_phase_loop:
  	/* Guard against overruns */
  	test	SCB_RESIDUAL_SGPTR[0], SG_LIST_NULL jz data_phase_inbounds;
  
  	/*
  	 * Turn on `Bit Bucket' mode, wait until the target takes
  	 * us to another phase, and then notify the host.
  	 */
  	and	DMAPARAMS, DIRECTION;
  	mov	DFCNTRL, DMAPARAMS;
  	or	SXFRCTL1,BITBUCKET;
  	if ((ahc->features & AHC_DT) == 0) {
  		test	SSTAT1,PHASEMIS	jz .;
  	} else {
  		test	SCSIPHASE, DATA_PHASE_MASK jnz .;
  	}
  	and	SXFRCTL1, ~BITBUCKET;
  	mvi	DATA_OVERRUN call set_seqint;
  	jmp	ITloop;
  
  data_phase_inbounds:
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		mov	SINDEX, SCB_RESIDUAL_SGPTR[0];
  		test	SCB_RESIDUAL_DATACNT[3], SG_LAST_SEG jz . + 2;
  		or	SINDEX, LAST_SEG;
  		mov	SG_CACHE_PRE, SINDEX;
  		mov	DFCNTRL, DMAPARAMS;
  ultra2_dma_loop:
  		call	idle_loop;
  		/*
  		 * The transfer is complete if either the last segment
  		 * completes or the target changes phase.
  		 */
  		test	SG_CACHE_SHADOW, LAST_SEG_DONE jnz ultra2_dmafinish;
  		if ((ahc->features & AHC_DT) == 0) {
  			if ((ahc->flags & AHC_TARGETROLE) != 0) {
  				 /*
  				  * As a target, we control the phases,
  				  * so ignore PHASEMIS.
  				  */
  				test	SSTAT0, TARGET jnz ultra2_dma_loop;
  			}
  			if ((ahc->flags & AHC_INITIATORROLE) != 0) {
  				test	SSTAT1,PHASEMIS	jz ultra2_dma_loop;
  			}
  		} else {
  			test	DFCNTRL, SCSIEN jnz ultra2_dma_loop;
  		}
  
  ultra2_dmafinish:
  		/*
  		 * The transfer has terminated either due to a phase
  		 * change, and/or the completion of the last segment.
  		 * We have two goals here.  Do as much other work
  		 * as possible while the data fifo drains on a read
  		 * and respond as quickly as possible to the standard
  		 * messages (save data pointers/disconnect and command
  		 * complete) that usually follow a data phase.
  		 */
  		if ((ahc->bugs & AHC_AUTOFLUSH_BUG) != 0) {
  			/*
  			 * On chips with broken auto-flush, start
  			 * the flushing process now.  We'll poke
  			 * the chip from time to time to keep the
  			 * flush process going as we complete the
  			 * data phase.
  			 */
  			or	DFCNTRL, FIFOFLUSH;
  		}
  		/*
  		 * We assume that, even though data may still be
  		 * transferring to the host, that the SCSI side of
  		 * the DMA engine is now in a static state.  This
  		 * allows us to update our notion of where we are
  		 * in this transfer.
  		 *
  		 * If, by chance, we stopped before being able
  		 * to fetch additional segments for this transfer,
  		 * yet the last S/G was completely exhausted,
  		 * call our idle loop until it is able to load
  		 * another segment.  This will allow us to immediately
  		 * pickup on the next segment on the next data phase.
  		 *
  		 * If we happened to stop on the last segment, then
  		 * our residual information is still correct from
  		 * the idle loop and there is no need to perform
  		 * any fixups.
  		 */
  ultra2_ensure_sg:
  		test	SG_CACHE_SHADOW, LAST_SEG jz ultra2_shvalid;
  		/* Record if we've consumed all S/G entries */
  		test	SSTAT2, SHVALID	jnz residuals_correct;
  		or	SCB_RESIDUAL_SGPTR[0], SG_LIST_NULL;
  		jmp	residuals_correct;
  
  ultra2_shvalid:
  		test	SSTAT2, SHVALID	jnz sgptr_fixup;
  		call	idle_loop;
  		jmp	ultra2_ensure_sg;
  
  sgptr_fixup:
  		/*
  		 * Fixup the residual next S/G pointer.  The S/G preload
  		 * feature of the chip allows us to load two elements
  		 * in addition to the currently active element.  We
  		 * store the bottom byte of the next S/G pointer in
  		 * the SG_CACEPTR register so we can restore the
  		 * correct value when the DMA completes.  If the next
  		 * sg ptr value has advanced to the point where higher
  		 * bytes in the address have been affected, fix them
  		 * too.
  		 */
  		test	SG_CACHE_SHADOW, 0x80 jz sgptr_fixup_done;
  		test	SCB_RESIDUAL_SGPTR[0], 0x80 jnz sgptr_fixup_done;
  		add	SCB_RESIDUAL_SGPTR[1], -1;
  		adc	SCB_RESIDUAL_SGPTR[2], -1; 
  		adc	SCB_RESIDUAL_SGPTR[3], -1;
  sgptr_fixup_done:
  		and	SCB_RESIDUAL_SGPTR[0], SG_ADDR_MASK, SG_CACHE_SHADOW;
  		/* We are not the last seg */
  		and	SCB_RESIDUAL_DATACNT[3], ~SG_LAST_SEG;
  residuals_correct:
  		/*
  		 * Go ahead and shut down the DMA engine now.
  		 * In the future, we'll want to handle end of
  		 * transfer messages prior to doing this, but this
  		 * requires similar restructuring for pre-ULTRA2
  		 * controllers.
  		 */
  		test	DMAPARAMS, DIRECTION jnz ultra2_fifoempty;
  ultra2_fifoflush:
  		if ((ahc->features & AHC_DT) == 0) {
  			if ((ahc->bugs & AHC_AUTOFLUSH_BUG) != 0) {
  				/*
  				 * On Rev A of the aic7890, the autoflush
  				 * feature doesn't function correctly.
  				 * Perform an explicit manual flush.  During
  				 * a manual flush, the FIFOEMP bit becomes
  				 * true every time the PCI FIFO empties
  				 * regardless of the state of the SCSI FIFO.
  				 * It can take up to 4 clock cycles for the
  				 * SCSI FIFO to get data into the PCI FIFO
  				 * and for FIFOEMP to de-assert.  Here we
  				 * guard against this condition by making
  				 * sure the FIFOEMP bit stays on for 5 full
  				 * clock cycles.
  				 */
  				or	DFCNTRL, FIFOFLUSH;
  				test	DFSTATUS, FIFOEMP jz ultra2_fifoflush;
  				test	DFSTATUS, FIFOEMP jz ultra2_fifoflush;
  				test	DFSTATUS, FIFOEMP jz ultra2_fifoflush;
  				test	DFSTATUS, FIFOEMP jz ultra2_fifoflush;
  			}
  			test	DFSTATUS, FIFOEMP jz ultra2_fifoflush;
  		} else {
  			/*
  			 * We enable the auto-ack feature on DT capable
  			 * controllers.  This means that the controller may
  			 * have already transferred some overrun bytes into
  			 * the data FIFO and acked them on the bus.  The only
  			 * way to detect this situation is to wait for
  			 * LAST_SEG_DONE to come true on a completed transfer
  			 * and then test to see if the data FIFO is non-empty.
  			 */
  			test	SCB_RESIDUAL_SGPTR[0], SG_LIST_NULL
  				jz ultra2_wait_fifoemp;
  			test	SG_CACHE_SHADOW, LAST_SEG_DONE jz .;
  			/*
  			 * FIFOEMP can lag LAST_SEG_DONE.  Wait a few
  			 * clocks before calling this an overrun.
  			 */
  			test	DFSTATUS, FIFOEMP jnz ultra2_fifoempty;
  			test	DFSTATUS, FIFOEMP jnz ultra2_fifoempty;
  			test	DFSTATUS, FIFOEMP jnz ultra2_fifoempty;
  			/* Overrun */
  			jmp	data_phase_loop;
  ultra2_wait_fifoemp:
  			test	DFSTATUS, FIFOEMP jz .;
  		}
  ultra2_fifoempty:
  		/* Don't clobber an inprogress host data transfer */
  		test	DFSTATUS, MREQPEND	jnz ultra2_fifoempty;
  ultra2_dmahalt:
  		and     DFCNTRL, ~(SCSIEN|HDMAEN);
  		test	DFCNTRL, SCSIEN|HDMAEN jnz .;
  		if ((ahc->flags & AHC_39BIT_ADDRESSING) != 0) {
  			/*
  			 * Keep HHADDR cleared for future, 32bit addressed
  			 * only, DMA operations.
  			 *
  			 * Due to bayonette style S/G handling, our residual
  			 * data must be "fixed up" once the transfer is halted.
  			 * Here we fixup the HSHADDR stored in the high byte
  			 * of the residual data cnt.  By postponing the fixup,
  			 * we can batch the clearing of HADDR with the fixup.
  			 * If we halted on the last segment, the residual is
  			 * already correct.   If we are not on the last
  			 * segment, copy the high address directly from HSHADDR.
  			 * We don't need to worry about maintaining the
  			 * SG_LAST_SEG flag as it will always be false in the
  			 * case where an update is required.
  			 */
  			or	DSCOMMAND1, HADDLDSEL0;
  			test	SG_CACHE_SHADOW, LAST_SEG jnz . + 2;
  			mov	SCB_RESIDUAL_DATACNT[3], SHADDR;
  			clr	HADDR;
  			and	DSCOMMAND1, ~HADDLDSEL0;
  		}
  	} else {
  		/* If we are the last SG block, tell the hardware. */
  		if ((ahc->bugs & AHC_PCI_MWI_BUG) != 0
  		  && ahc->pci_cachesize != 0) {
  			test	MWI_RESIDUAL, 0xFF jnz dma_mid_sg;
  		}
  		test	SCB_RESIDUAL_DATACNT[3], SG_LAST_SEG jz dma_mid_sg;
  		if ((ahc->flags & AHC_TARGETROLE) != 0) {
  			test	SSTAT0, TARGET jz dma_last_sg;
  			if ((ahc->bugs & AHC_TMODE_WIDEODD_BUG) != 0) {
  				test	DMAPARAMS, DIRECTION jz dma_mid_sg;
  			}
  		}
  dma_last_sg:
  		and	DMAPARAMS, ~WIDEODD;
  dma_mid_sg:
  		/* Start DMA data transfer. */
  		mov	DFCNTRL, DMAPARAMS;
  dma_loop:
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			call	idle_loop;
  		}
  		test	SSTAT0,DMADONE	jnz dma_dmadone;
  		test	SSTAT1,PHASEMIS	jz dma_loop;	/* ie. underrun */
  dma_phasemis:
  		/*
  		 * We will be "done" DMAing when the transfer count goes to
  		 * zero, or the target changes the phase (in light of this,
  		 * it makes sense that the DMA circuitry doesn't ACK when
  		 * PHASEMIS is active).  If we are doing a SCSI->Host transfer,
  		 * the data FIFO should be flushed auto-magically on STCNT=0
  		 * or a phase change, so just wait for FIFO empty status.
  		 */
  dma_checkfifo:
  		test	DFCNTRL,DIRECTION	jnz dma_fifoempty;
  dma_fifoflush:
  		test	DFSTATUS,FIFOEMP	jz dma_fifoflush;
  dma_fifoempty:
  		/* Don't clobber an inprogress host data transfer */
  		test	DFSTATUS, MREQPEND	jnz dma_fifoempty;
  
  		/*
  		 * Now shut off the DMA and make sure that the DMA
  		 * hardware has actually stopped.  Touching the DMA
  		 * counters, etc. while a DMA is active will result
  		 * in an ILLSADDR exception.
  		 */
  dma_dmadone:
  		and	DFCNTRL, ~(SCSIEN|SDMAEN|HDMAEN);
  dma_halt:
  		/*
  		 * Some revisions of the aic78XX have a problem where, if the
  		 * data fifo is full, but the PCI input latch is not empty, 
  		 * HDMAEN cannot be cleared.  The fix used here is to drain
  		 * the prefetched but unused data from the data fifo until
  		 * there is space for the input latch to drain.
  		 */
  		if ((ahc->bugs & AHC_PCI_2_1_RETRY_BUG) != 0) {
  			mov	NONE, DFDAT;
  		}
  		test	DFCNTRL, (SCSIEN|SDMAEN|HDMAEN) jnz dma_halt;
  
  		/* See if we have completed this last segment */
  		test	STCNT[0], 0xff	jnz data_phase_finish;
  		test	STCNT[1], 0xff	jnz data_phase_finish;
  		test	STCNT[2], 0xff	jnz data_phase_finish;
  
  		/*
  		 * Advance the scatter-gather pointers if needed 
  		 */
  		if ((ahc->bugs & AHC_PCI_MWI_BUG) != 0
  		  && ahc->pci_cachesize != 0) {
  			test	MWI_RESIDUAL, 0xFF jz no_mwi_resid;
  			/*
  			 * Reload HADDR from SHADDR and setup the
  			 * count to be the size of our residual.
  			 */
  			if ((ahc->features & AHC_CMD_CHAN) != 0) {
  				bmov	HADDR, SHADDR, 4;
  				mov	HCNT, MWI_RESIDUAL;
  				bmov	HCNT[1], ALLZEROS, 2;
  			} else {
  				mvi	DINDEX, HADDR;
  				mvi	SHADDR call bcopy_4;
  				mov	MWI_RESIDUAL call set_hcnt;
  			}
  			clr	MWI_RESIDUAL;
  			jmp	sg_load_done;
  no_mwi_resid:
  		}
  		test	SCB_RESIDUAL_DATACNT[3], SG_LAST_SEG jz sg_load;
  		or	SCB_RESIDUAL_SGPTR[0], SG_LIST_NULL;
  		jmp	data_phase_finish;
  sg_load:
  		/*
  		 * Load the next SG element's data address and length
  		 * into the DMA engine.  If we don't have hardware
  		 * to perform a prefetch, we'll have to fetch the
  		 * segment from host memory first.
  		 */
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			/* Wait for the idle loop to complete */
  			test	CCSGCTL, CCSGEN jz . + 3;
  			call	idle_loop;
  			test	CCSGCTL, CCSGEN jnz . - 1;
  			bmov 	HADDR, CCSGRAM, 7;
  			/*
  			 * Workaround for flaky external SCB RAM
  			 * on certain aic7895 setups.  It seems
  			 * unable to handle direct transfers from
  			 * S/G ram to certain SCB locations.
  			 */
  			mov	SINDEX, CCSGRAM;
  			mov	SCB_RESIDUAL_DATACNT[3], SINDEX;
  		} else {
  			if ((ahc->flags & AHC_39BIT_ADDRESSING) != 0) {
  				mov	ALLZEROS call set_hhaddr;
  			}
  			mvi	DINDEX, HADDR;
  			mvi	SCB_RESIDUAL_SGPTR	call bcopy_4;
  
  			mvi	SG_SIZEOF	call set_hcnt;
  
  			or	DFCNTRL, HDMAEN|DIRECTION|FIFORESET;
  
  			call	dma_finish;
  
  			mvi	DINDEX, HADDR;
  			call	dfdat_in_7;
  			mov	SCB_RESIDUAL_DATACNT[3], DFDAT;
  		}
  
  		if ((ahc->flags & AHC_39BIT_ADDRESSING) != 0) {
  			mov	SCB_RESIDUAL_DATACNT[3] call set_hhaddr;
  
  			/*
  			 * The lowest address byte must be loaded
  			 * last as it triggers the computation of
  			 * some items in the PCI block.  The ULTRA2
  			 * chips do this on PRELOAD.
  			 */
  			mov	HADDR, HADDR;
  		}
  		if ((ahc->bugs & AHC_PCI_MWI_BUG) != 0
  		  && ahc->pci_cachesize != 0) {
  			call calc_mwi_residual;
  		}
  
  		/* Point to the new next sg in memory */
  		call	sg_advance;
  
  sg_load_done:
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			bmov	STCNT, HCNT, 3;
  		} else {
  			call	set_stcnt_from_hcnt;
  		}
  
  		if ((ahc->flags & AHC_TARGETROLE) != 0) {
  			test	SSTAT0, TARGET jnz data_phase_loop;
  		}
  	}
  data_phase_finish:
  	/*
  	 * If the target has left us in data phase, loop through
  	 * the dma code again.  In the case of ULTRA2 adapters,
  	 * we should only loop if there is a data overrun.  For
  	 * all other adapters, we'll loop after each S/G element
  	 * is loaded as well as if there is an overrun.
  	 */
  	if ((ahc->flags & AHC_TARGETROLE) != 0) {
  		test	SSTAT0, TARGET jnz data_phase_done;
  	}
  	if ((ahc->flags & AHC_INITIATORROLE) != 0) {
  		test	SSTAT1, REQINIT jz .;
  		if ((ahc->features & AHC_DT) == 0) {
  			test	SSTAT1,PHASEMIS	jz data_phase_loop;
  		} else {
  			test	SCSIPHASE, DATA_PHASE_MASK jnz data_phase_loop;
  		}
  	}
  
  data_phase_done:
  	/*
  	 * After a DMA finishes, save the SG and STCNT residuals back into
  	 * the SCB.  We use STCNT instead of HCNT, since it's a reflection
  	 * of how many bytes were transferred on the SCSI (as opposed to the
  	 * host) bus.
  	 */
  	if ((ahc->features & AHC_CMD_CHAN) != 0) {
  		/* Kill off any pending prefetch */
  		call	disable_ccsgen;
  	}
  
  	if ((ahc->features & AHC_ULTRA2) == 0) {
  		/*
  		 * Clear the high address byte so that all other DMA
  		 * operations, which use 32bit addressing, can assume
  		 * HHADDR is 0.
  		 */
  		if ((ahc->flags & AHC_39BIT_ADDRESSING) != 0) {
  			mov	ALLZEROS call set_hhaddr;
  		}
  	}
  
  	/*
  	 * Update our residual information before the information is
  	 * lost by some other type of SCSI I/O (e.g. PIO).  If we have
  	 * transferred all data, no update is needed.
  	 *
  	 */
  	test	SCB_RESIDUAL_SGPTR, SG_LIST_NULL jnz residual_update_done;
  	if ((ahc->bugs & AHC_PCI_MWI_BUG) != 0
  	  && ahc->pci_cachesize != 0) {
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			test	MWI_RESIDUAL, 0xFF jz bmov_resid;
  		}
  		mov	A, MWI_RESIDUAL;
  		add	SCB_RESIDUAL_DATACNT[0], A, STCNT[0];
  		clr	A;
  		adc	SCB_RESIDUAL_DATACNT[1], A, STCNT[1];
  		adc	SCB_RESIDUAL_DATACNT[2], A, STCNT[2];
  		clr	MWI_RESIDUAL;
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			jmp	. + 2;
  bmov_resid:
  			bmov	SCB_RESIDUAL_DATACNT, STCNT, 3;
  		}
  	} else if ((ahc->features & AHC_CMD_CHAN) != 0) {
  		bmov	SCB_RESIDUAL_DATACNT, STCNT, 3;
  	} else {
  		mov	SCB_RESIDUAL_DATACNT[0], STCNT[0];
  		mov	SCB_RESIDUAL_DATACNT[1], STCNT[1];
  		mov	SCB_RESIDUAL_DATACNT[2], STCNT[2];
  	}
  residual_update_done:
  	/*
  	 * Since we've been through a data phase, the SCB_RESID* fields
  	 * are now initialized.  Clear the full residual flag.
  	 */
  	and	SCB_SGPTR[0], ~SG_FULL_RESID;
  
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		/* Clear the channel in case we return to data phase later */
  		or	SXFRCTL0, CLRSTCNT|CLRCHN;
  		or	SXFRCTL0, CLRSTCNT|CLRCHN;
  	}
  
  	if ((ahc->flags & AHC_TARGETROLE) != 0) {
  		test	SEQ_FLAGS, DPHASE_PENDING jz ITloop;
  		and	SEQ_FLAGS, ~DPHASE_PENDING;
  		/*
  		 * For data-in phases, wait for any pending acks from the
  		 * initiator before changing phase.  We only need to
  		 * send Ignore Wide Residue messages for data-in phases.
  		 */
  		test	DFCNTRL, DIRECTION jz target_ITloop;
  		test	SSTAT1, REQINIT	jnz .;
  		test	SCB_LUN, SCB_XFERLEN_ODD jz target_ITloop;
  		test	SCSIRATE, WIDEXFER jz target_ITloop;
  		/*
  		 * Issue an Ignore Wide Residue Message.
  		 */
  		mvi	P_MESGIN|BSYO call change_phase;
  		mvi	MSG_IGN_WIDE_RESIDUE call target_outb;
  		mvi	1 call target_outb;
  		jmp	target_ITloop;
  	} else {
  		jmp	ITloop;
  	}
  
  if ((ahc->flags & AHC_INITIATORROLE) != 0) {
  /*
   * Command phase.  Set up the DMA registers and let 'er rip.
   */
  p_command:
  	test	SEQ_FLAGS, NOT_IDENTIFIED jz p_command_okay;
  	mvi	PROTO_VIOLATION call set_seqint;
  p_command_okay:
  
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		bmov	HCNT[0], SCB_CDB_LEN,  1;
  		bmov	HCNT[1], ALLZEROS, 2;
  		mvi	SG_CACHE_PRE, LAST_SEG;
  	} else if ((ahc->features & AHC_CMD_CHAN) != 0) {
  		bmov	STCNT[0], SCB_CDB_LEN, 1;
  		bmov	STCNT[1], ALLZEROS, 2;
  	} else {
  		mov	STCNT[0], SCB_CDB_LEN;
  		clr	STCNT[1];
  		clr	STCNT[2];
  	}
  	add	NONE, -13, SCB_CDB_LEN;
  	mvi	SCB_CDB_STORE jnc p_command_embedded;
  p_command_from_host:
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		bmov	HADDR[0], SCB_CDB_PTR, 4;
  		mvi	DFCNTRL, (PRELOADEN|SCSIEN|HDMAEN|DIRECTION);
  	} else {
  		if ((ahc->features & AHC_CMD_CHAN) != 0) {
  			bmov	HADDR[0], SCB_CDB_PTR, 4;
  			bmov	HCNT, STCNT, 3;
  		} else {
  			mvi	DINDEX, HADDR;
  			mvi	SCB_CDB_PTR call bcopy_4;
  			mov	SCB_CDB_LEN call set_hcnt;
  		}
  		mvi	DFCNTRL, (SCSIEN|SDMAEN|HDMAEN|DIRECTION|FIFORESET);
  	}
  	jmp	p_command_xfer;
  p_command_embedded:
  	/*
  	 * The data fifo seems to require 4 byte aligned
  	 * transfers from the sequencer.  Force this to
  	 * be the case by clearing HADDR[0] even though
  	 * we aren't going to touch host memory.
  	 */
  	clr	HADDR[0];
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		mvi	DFCNTRL, (PRELOADEN|SCSIEN|DIRECTION);
  		bmov	DFDAT, SCB_CDB_STORE, 12; 
  	} else if ((ahc->features & AHC_CMD_CHAN) != 0) {
  		if ((ahc->flags & AHC_SCB_BTT) != 0) {
  			/*
  			 * On the 7895 the data FIFO will
  			 * get corrupted if you try to dump
  			 * data from external SCB memory into
  			 * the FIFO while it is enabled.  So,
  			 * fill the fifo and then enable SCSI
  			 * transfers.
  			 */
  			mvi	DFCNTRL, (DIRECTION|FIFORESET);
  		} else {
  			mvi	DFCNTRL, (SCSIEN|SDMAEN|DIRECTION|FIFORESET);
  		}
  		bmov	DFDAT, SCB_CDB_STORE, 12; 
  		if ((ahc->flags & AHC_SCB_BTT) != 0) {
  			mvi	DFCNTRL, (SCSIEN|SDMAEN|DIRECTION|FIFOFLUSH);
  		} else {
  			or	DFCNTRL, FIFOFLUSH;
  		}
  	} else {
  		mvi	DFCNTRL, (SCSIEN|SDMAEN|DIRECTION|FIFORESET);
  		call	copy_to_fifo_6;
  		call	copy_to_fifo_6;
  		or	DFCNTRL, FIFOFLUSH;
  	}
  p_command_xfer:
  	and	SEQ_FLAGS, ~NO_CDB_SENT;
  	if ((ahc->features & AHC_DT) == 0) {
  		test	SSTAT0, SDONE jnz . + 2;
  		test    SSTAT1, PHASEMIS jz . - 1;
  		/*
  		 * Wait for our ACK to go-away on it's own
  		 * instead of being killed by SCSIEN getting cleared.
  		 */
  		test	SCSISIGI, ACKI jnz .;
  	} else {
  		test	DFCNTRL, SCSIEN jnz .;
  	}
  	test	SSTAT0, SDONE jnz p_command_successful;
  	/*
  	 * Don't allow a data phase if the command
  	 * was not fully transferred.
  	 */
  	or	SEQ_FLAGS, NO_CDB_SENT;
  p_command_successful:
  	and	DFCNTRL, ~(SCSIEN|SDMAEN|HDMAEN);
  	test	DFCNTRL, (SCSIEN|SDMAEN|HDMAEN) jnz .;
  	jmp	ITloop;
  
  /*
   * Status phase.  Wait for the data byte to appear, then read it
   * and store it into the SCB.
   */
  p_status:
  	test	SEQ_FLAGS, NOT_IDENTIFIED jnz mesgin_proto_violation;
  p_status_okay:
  	mov	SCB_SCSI_STATUS, SCSIDATL;
  	or	SCB_CONTROL, STATUS_RCVD;
  	jmp	ITloop;
  
  /*
   * Message out phase.  If MSG_OUT is MSG_IDENTIFYFLAG, build a full
   * indentify message sequence and send it to the target.  The host may
   * override this behavior by setting the MK_MESSAGE bit in the SCB
   * control byte.  This will cause us to interrupt the host and allow
   * it to handle the message phase completely on its own.  If the bit
   * associated with this target is set, we will also interrupt the host,
   * thereby allowing it to send a message on the next selection regardless
   * of the transaction being sent.
   * 
   * If MSG_OUT is == HOST_MSG, also interrupt the host and take a message.
   * This is done to allow the host to send messages outside of an identify
   * sequence while protecting the seqencer from testing the MK_MESSAGE bit
   * on an SCB that might not be for the current nexus. (For example, a
   * BDR message in response to a bad reselection would leave us pointed to
   * an SCB that doesn't have anything to do with the current target).
   *
   * Otherwise, treat MSG_OUT as a 1 byte message to send (abort, abort tag,
   * bus device reset).
   *
   * When there are no messages to send, MSG_OUT should be set to MSG_NOOP,
   * in case the target decides to put us in this phase for some strange
   * reason.
   */
  p_mesgout_retry:
  	/* Turn on ATN for the retry */
  	if ((ahc->features & AHC_DT) == 0) {
  		or	SCSISIGO, ATNO, LASTPHASE;
  	} else {
  		mvi	SCSISIGO, ATNO;
  	}
  p_mesgout:
  	mov	SINDEX, MSG_OUT;
  	cmp	SINDEX, MSG_IDENTIFYFLAG jne p_mesgout_from_host;
  	test	SCB_CONTROL,MK_MESSAGE	jnz host_message_loop;
  p_mesgout_identify:
  	or	SINDEX, MSG_IDENTIFYFLAG|DISCENB, SAVED_LUN;
  	test	SCB_CONTROL, DISCENB jnz . + 2;
  	and	SINDEX, ~DISCENB;
  /*
   * Send a tag message if TAG_ENB is set in the SCB control block.
   * Use SCB_TAG (the position in the kernel's SCB array) as the tag value.
   */
  p_mesgout_tag:
  	test	SCB_CONTROL,TAG_ENB jz  p_mesgout_onebyte;
  	mov	SCSIDATL, SINDEX;	/* Send the identify message */
  	call	phase_lock;
  	cmp	LASTPHASE, P_MESGOUT	jne p_mesgout_done;
  	and	SCSIDATL,TAG_ENB|SCB_TAG_TYPE,SCB_CONTROL;
  	call	phase_lock;
  	cmp	LASTPHASE, P_MESGOUT	jne p_mesgout_done;
  	mov	SCB_TAG	jmp p_mesgout_onebyte;
  /*
   * Interrupt the driver, and allow it to handle this message
   * phase and any required retries.
   */
  p_mesgout_from_host:
  	cmp	SINDEX, HOST_MSG	jne p_mesgout_onebyte;
  	jmp	host_message_loop;
  
  p_mesgout_onebyte:
  	mvi	CLRSINT1, CLRATNO;
  	mov	SCSIDATL, SINDEX;
  
  /*
   * If the next bus phase after ATN drops is message out, it means
   * that the target is requesting that the last message(s) be resent.
   */
  	call	phase_lock;
  	cmp	LASTPHASE, P_MESGOUT	je p_mesgout_retry;
  
  p_mesgout_done:
  	mvi	CLRSINT1,CLRATNO;	/* Be sure to turn ATNO off */
  	mov	LAST_MSG, MSG_OUT;
  	mvi	MSG_OUT, MSG_NOOP;	/* No message left */
  	jmp	ITloop;
  
  /*
   * Message in phase.  Bytes are read using Automatic PIO mode.
   */
  p_mesgin:
  	mvi	ACCUM		call inb_first;	/* read the 1st message byte */
  
  	test	A,MSG_IDENTIFYFLAG	jnz mesgin_identify;
  	cmp	A,MSG_DISCONNECT	je mesgin_disconnect;
  	cmp	A,MSG_SAVEDATAPOINTER	je mesgin_sdptrs;
  	cmp	ALLZEROS,A		je mesgin_complete;
  	cmp	A,MSG_RESTOREPOINTERS	je mesgin_rdptrs;
  	cmp	A,MSG_IGN_WIDE_RESIDUE	je mesgin_ign_wide_residue;
  	cmp	A,MSG_NOOP		je mesgin_done;
  
  /*
   * Pushed message loop to allow the kernel to
   * run it's own message state engine.  To avoid an
   * extra nop instruction after signaling the kernel,
   * we perform the phase_lock before checking to see
   * if we should exit the loop and skip the phase_lock
   * in the ITloop.  Performing back to back phase_locks
   * shouldn't hurt, but why do it twice...
   */
  host_message_loop:
  	mvi	HOST_MSG_LOOP call set_seqint;
  	call	phase_lock;
  	cmp	RETURN_1, EXIT_MSG_LOOP	je ITloop + 1;
  	jmp	host_message_loop;
  
  mesgin_ign_wide_residue:
  if ((ahc->features & AHC_WIDE) != 0) {
  	test	SCSIRATE, WIDEXFER jz mesgin_reject;
  	/* Pull the residue byte */
  	mvi	ARG_1	call inb_next;
  	cmp	ARG_1, 0x01 jne mesgin_reject;
  	test	SCB_RESIDUAL_SGPTR[0], SG_LIST_NULL jz . + 2;
  	test	SCB_LUN, SCB_XFERLEN_ODD jnz mesgin_done;
  	mvi	IGN_WIDE_RES call set_seqint;
  	jmp	mesgin_done;
  }
  
  mesgin_proto_violation:
  	mvi	PROTO_VIOLATION call set_seqint;
  	jmp	mesgin_done;
  mesgin_reject:
  	mvi	MSG_MESSAGE_REJECT	call mk_mesg;
  mesgin_done:
  	mov	NONE,SCSIDATL;		/*dummy read from latch to ACK*/
  	jmp	ITloop;
  
  /*
   * We received a "command complete" message.  Put the SCB_TAG into the QOUTFIFO,
   * and trigger a completion interrupt.  Before doing so, check to see if there
   * is a residual or the status byte is something other than STATUS_GOOD (0).
   * In either of these conditions, we upload the SCB back to the host so it can
   * process this information.  In the case of a non zero status byte, we 
   * additionally interrupt the kernel driver synchronously, allowing it to
   * decide if sense should be retrieved.  If the kernel driver wishes to request
   * sense, it will fill the kernel SCB with a request sense command, requeue
   * it to the QINFIFO and tell us not to post to the QOUTFIFO by setting 
   * RETURN_1 to SEND_SENSE.
   */
  mesgin_complete:
  
  	/*
  	 * If ATN is raised, we still want to give the target a message.
  	 * Perhaps there was a parity error on this last message byte.
  	 * Either way, the target should take us to message out phase
  	 * and then attempt to complete the command again.  We should use a
  	 * critical section here to guard against a timeout triggering
  	 * for this command and setting ATN while we are still processing
  	 * the completion.
  	test	SCSISIGI, ATNI jnz mesgin_done;
  	 */
  
  	/*
  	 * If we are identified and have successfully sent the CDB,
  	 * any status will do.  Optimize this fast path.
  	 */
  	test	SCB_CONTROL, STATUS_RCVD jz mesgin_proto_violation;
  	test	SEQ_FLAGS, NOT_IDENTIFIED|NO_CDB_SENT jz complete_accepted; 
  
  	/*
  	 * If the target never sent an identify message but instead went
  	 * to mesgin to give an invalid message, let the host abort us.
  	 */
  	test	SEQ_FLAGS, NOT_IDENTIFIED jnz mesgin_proto_violation;
  
  	/*
  	 * If we recevied good status but never successfully sent the
  	 * cdb, abort the command.
  	 */
  	test	SCB_SCSI_STATUS,0xff	jnz complete_accepted;
  	test	SEQ_FLAGS, NO_CDB_SENT jnz mesgin_proto_violation;
  
  complete_accepted:
  	/*
  	 * See if we attempted to deliver a message but the target ingnored us.
  	 */
  	test	SCB_CONTROL, MK_MESSAGE jz . + 2;
  	mvi	MKMSG_FAILED call set_seqint;
  
  	/*
  	 * Check for residuals
  	 */
  	test	SCB_SGPTR, SG_LIST_NULL jnz check_status;/* No xfer */
  	test	SCB_SGPTR, SG_FULL_RESID jnz upload_scb;/* Never xfered */
  	test	SCB_RESIDUAL_SGPTR, SG_LIST_NULL jz upload_scb;
  check_status:
  	test	SCB_SCSI_STATUS,0xff	jz complete;	/* Good Status? */
  upload_scb:
  	or	SCB_SGPTR, SG_RESID_VALID;
  	mvi	DMAPARAMS, FIFORESET;
  	mov	SCB_TAG		call dma_scb;
  	test	SCB_SCSI_STATUS, 0xff	jz complete;	/* Just a residual? */
  	mvi	BAD_STATUS call set_seqint;		/* let driver know */
  	cmp	RETURN_1, SEND_SENSE	jne complete;
  	call	add_scb_to_free_list;
  	jmp	await_busfree;
  complete:
  	mov	SCB_TAG call complete_post;
  	jmp	await_busfree;
  }
  
  complete_post:
  	/* Post the SCBID in SINDEX and issue an interrupt */
  	call	add_scb_to_free_list;
  	mov	ARG_1, SINDEX;
  	if ((ahc->features & AHC_QUEUE_REGS) != 0) {
  		mov	A, SDSCB_QOFF;
  	} else {
  		mov	A, QOUTPOS;
  	}
  	mvi	QOUTFIFO_OFFSET call post_byte_setup;
  	mov	ARG_1 call post_byte;
  	if ((ahc->features & AHC_QUEUE_REGS) == 0) {
  		inc 	QOUTPOS;
  	}
  	mvi	INTSTAT,CMDCMPLT ret;
  
  if ((ahc->flags & AHC_INITIATORROLE) != 0) {
  /*
   * Is it a disconnect message?  Set a flag in the SCB to remind us
   * and await the bus going free.  If this is an untagged transaction
   * store the SCB id for it in our untagged target table for lookup on
   * a reselection.
   */
  mesgin_disconnect:
  	/*
  	 * If ATN is raised, we still want to give the target a message.
  	 * Perhaps there was a parity error on this last message byte
  	 * or we want to abort this command.  Either way, the target
  	 * should take us to message out phase and then attempt to
  	 * disconnect again.
  	 * XXX - Wait for more testing.
  	test	SCSISIGI, ATNI jnz mesgin_done;
  	 */
  	test	SEQ_FLAGS, NOT_IDENTIFIED|NO_CDB_SENT
  		jnz mesgin_proto_violation;
  	or	SCB_CONTROL,DISCONNECTED;
  	if ((ahc->flags & AHC_PAGESCBS) != 0) {
  		call	add_scb_to_disc_list;
  	}
  	test	SCB_CONTROL, TAG_ENB jnz await_busfree;
  	mov	ARG_1, SCB_TAG;
  	and	SAVED_LUN, LID, SCB_LUN;
  	mov	SCB_SCSIID	call set_busy_target;
  	jmp	await_busfree;
  
  /*
   * Save data pointers message:
   * Copying RAM values back to SCB, for Save Data Pointers message, but
   * only if we've actually been into a data phase to change them.  This
   * protects against bogus data in scratch ram and the residual counts
   * since they are only initialized when we go into data_in or data_out.
   * Ack the message as soon as possible.  For chips without S/G pipelining,
   * we can only ack the message after SHADDR has been saved.  On these
   * chips, SHADDR increments with every bus transaction, even PIO.
   */
  mesgin_sdptrs:
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		mov	NONE,SCSIDATL;		/*dummy read from latch to ACK*/
  		test	SEQ_FLAGS, DPHASE	jz ITloop;
  	} else {
  		test	SEQ_FLAGS, DPHASE	jz mesgin_done;
  	}
  
  	/*
  	 * If we are asked to save our position at the end of the
  	 * transfer, just mark us at the end rather than perform a
  	 * full save.
  	 */
  	test	SCB_RESIDUAL_SGPTR[0], SG_LIST_NULL jz mesgin_sdptrs_full;
  	or	SCB_SGPTR, SG_LIST_NULL;
  	if ((ahc->features & AHC_ULTRA2) != 0) {
  		jmp	ITloop;
  	} else {
  		jmp	mesgin_done;
  	}
  
  mesgin_sdptrs_full:
  
  	/*
  	 * The SCB_SGPTR becomes the next one we'll download,
  	 * and the SCB_DATAPTR becomes the current SHADDR.
  	 * Use the residual number since STCNT is corrupted by
  	 * any message transfer.
  	 */
  	if ((ahc->features & AHC_CMD_CHAN) != 0) {
  		bmov	SCB_DATAPTR, SHADDR, 4;
  		if ((ahc->features & AHC_ULTRA2) == 0) {
  			mov	NONE,SCSIDATL;	/*dummy read from latch to ACK*/
  		}
  		bmov	SCB_DATACNT, SCB_RESIDUAL_DATACNT, 8;
  	} else {
  		mvi	DINDEX, SCB_DATAPTR;
  		mvi	SHADDR call bcopy_4;
  		mov	NONE,SCSIDATL;	/*dummy read from latch to ACK*/
  		mvi	SCB_RESIDUAL_DATACNT call bcopy_8;
  	}
  	jmp	ITloop;
  
  /*
   * Restore pointers message?  Data pointers are recopied from the
   * SCB anytime we enter a data phase for the first time, so all
   * we need to do is clear the DPHASE flag and let the data phase
   * code do the rest.  We also reset/reallocate the FIFO to make
   * sure we have a clean start for the next data or command phase.
   */
  mesgin_rdptrs:
  	and	SEQ_FLAGS, ~DPHASE;		/*
  						 * We'll reload them
  						 * the next time through
  						 * the dataphase.
  						 */
  	or	SXFRCTL0, CLRSTCNT|CLRCHN;
  	jmp	mesgin_done;
  
  /*
   * Index into our Busy Target table.  SINDEX and DINDEX are modified
   * upon return.  SCBPTR may be modified by this action.
   */
  set_busy_target:
  	shr	DINDEX, 4, SINDEX;
  	if ((ahc->flags & AHC_SCB_BTT) != 0) {
  		mov	SCBPTR, SAVED_LUN;
  		add	DINDEX, SCB_64_BTT;
  	} else {
  		add	DINDEX, BUSY_TARGETS;
  	}
  	mov	DINDIR, ARG_1 ret;
  
  /*
   * Identify message?  For a reconnecting target, this tells us the lun
   * that the reconnection is for - find the correct SCB and switch to it,
   * clearing the "disconnected" bit so we don't "find" it by accident later.
   */
  mesgin_identify:
  	/*
  	 * Determine whether a target is using tagged or non-tagged
  	 * transactions by first looking at the transaction stored in
  	 * the busy target array.  If there is no untagged transaction
  	 * for this target or the transaction is for a different lun, then
  	 * this must be a tagged transaction.
  	 */
  	shr	SINDEX, 4, SAVED_SCSIID;
  	and	SAVED_LUN, MSG_IDENTIFY_LUNMASK, A;
  	if ((ahc->flags & AHC_SCB_BTT) != 0) {
  		add	SINDEX, SCB_64_BTT;
  		mov	SCBPTR, SAVED_LUN;
  		if ((ahc->flags & AHC_SEQUENCER_DEBUG) != 0) {
  			add	NONE, -SCB_64_BTT, SINDEX;
  			jc	. + 2;
  			mvi	INTSTAT, OUT_OF_RANGE;
  			nop;
  			add	NONE, -(SCB_64_BTT + 16), SINDEX;
  			jnc	. + 2;
  			mvi	INTSTAT, OUT_OF_RANGE;
  			nop;
  		}
  	} else {
  		add	SINDEX, BUSY_TARGETS;
  		if ((ahc->flags & AHC_SEQUENCER_DEBUG) != 0) {
  			add	NONE, -BUSY_TARGETS, SINDEX;
  			jc	. + 2;
  			mvi	INTSTAT, OUT_OF_RANGE;
  			nop;
  			add	NONE, -(BUSY_TARGETS + 16), SINDEX;
  			jnc	. + 2;
  			mvi	INTSTAT, OUT_OF_RANGE;
  			nop;
  		}
  	}
  	mov	ARG_1, SINDIR;
  	cmp	ARG_1, SCB_LIST_NULL	je snoop_tag;
  	if ((ahc->flags & AHC_PAGESCBS) != 0) {
  		mov	ARG_1 call findSCB;
  	} else {
  		mov	SCBPTR, ARG_1;
  	}
  	if ((ahc->flags & AHC_SCB_BTT) != 0) {
  		jmp setup_SCB_id_lun_okay;
  	} else {
  		/*
  		 * We only allow one untagged command per-target
  		 * at a time.  So, if the lun doesn't match, look
  		 * for a tag message.
  		 */
  		and	A, LID, SCB_LUN;
  		cmp	SAVED_LUN, A	je setup_SCB_id_lun_okay;
  		if ((ahc->flags & AHC_PAGESCBS) != 0) {
  			/*
  			 * findSCB removes the SCB from the
  			 * disconnected list, so we must replace
  			 * it there should this SCB be for another
  			 * lun.
  			 */
  			call	cleanup_scb;
  		}
  	}
  
  /*
   * Here we "snoop" the bus looking for a SIMPLE QUEUE TAG message.
   * If we get one, we use the tag returned to find the proper
   * SCB.  With SCB paging, we must search for non-tagged
   * transactions since the SCB may exist in any slot.  If we're not
   * using SCB paging, we can use the tag as the direct index to the
   * SCB.
   */
  snoop_tag:
  	if ((ahc->flags & AHC_SEQUENCER_DEBUG) != 0) {
  		or	SEQ_FLAGS, 0x80;
  	}
  	mov	NONE,SCSIDATL;		/* ACK Identify MSG */
  	call	phase_lock;
  	if ((ahc->flags & AHC_SEQUENCER_DEBUG) != 0) {
  		or	SEQ_FLAGS, 0x1;
  	}
  	cmp	LASTPHASE, P_MESGIN	jne not_found;
  	if ((ahc->flags & AHC_SEQUENCER_DEBUG) != 0) {
  		or	SEQ_FLAGS, 0x2;
  	}
  	cmp	SCSIBUSL,MSG_SIMPLE_Q_TAG jne not_found;
  get_tag:
  	if ((ahc->flags & AHC_PAGESCBS) != 0) {
  		mvi	ARG_1	call inb_next;	/* tag value */
  		mov	ARG_1	call findSCB;
  	} else {
  		mvi	ARG_1	call inb_next;	/* tag value */
  		mov	SCBPTR, ARG_1;
  	}
  
  /*
   * Ensure that the SCB the tag points to is for
   * an SCB transaction to the reconnecting target.
   */
  setup_SCB:
  	if ((ahc->flags & AHC_SEQUENCER_DEBUG) != 0) {
  		or	SEQ_FLAGS, 0x4;
  	}
  	mov	A, SCB_SCSIID;
  	cmp	SAVED_SCSIID, A	jne not_found_cleanup_scb;
  	if ((ahc->flags & AHC_SEQUENCER_DEBUG) != 0) {
  		or	SEQ_FLAGS, 0x8;
  	}
  setup_SCB_id_okay:
  	and	A, LID, SCB_LUN;
  	cmp	SAVED_LUN, A	jne not_found_cleanup_scb;
  setup_SCB_id_lun_okay:
  	if ((ahc->flags & AHC_SEQUENCER_DEBUG) != 0) {
  		or	SEQ_FLAGS, 0x10;
  	}
  	test	SCB_CONTROL,DISCONNECTED jz not_found_cleanup_scb;
  	and	SCB_CONTROL,~DISCONNECTED;
  	test	SCB_CONTROL, TAG_ENB	jnz setup_SCB_tagged;
  	if ((ahc->flags & AHC_SCB_BTT) != 0) {
  		mov	A, SCBPTR;
  	}
  	mvi	ARG_1, SCB_LIST_NULL;
  	mov	SAVED_SCSIID	call	set_busy_target;
  	if ((ahc->flags & AHC_SCB_BTT) != 0) {
  		mov	SCBPTR, A;
  	}
  setup_SCB_tagged:
  	clr	SEQ_FLAGS;	/* make note of IDENTIFY */
  	call	set_transfer_settings;
  	/* See if the host wants to send a message upon reconnection */
  	test	SCB_CONTROL, MK_MESSAGE jz mesgin_done;
  	mvi	HOST_MSG	call mk_mesg;
  	jmp	mesgin_done;
  
  not_found_cleanup_scb:
  	if ((ahc->flags & AHC_PAGESCBS) != 0) {
  		call	cleanup_scb;
  	}
  not_found:
  	mvi	NO_MATCH call set_seqint;
  	jmp	mesgin_done;
  
  mk_mesg:
  	if ((ahc->features & AHC_DT) == 0) {
  		or	SCSISIGO, ATNO, LASTPHASE;
  	} else {
  		mvi	SCSISIGO, ATNO;
  	}
  	mov	MSG_OUT,SINDEX ret;
  
  /*
   * Functions to read data in Automatic PIO mode.
   *
   * According to Adaptec's documentation, an ACK is not sent on input from
   * the target until SCSIDATL is read from.  So we wait until SCSIDATL is
   * latched (the usual way), then read the data byte directly off the bus
   * using SCSIBUSL.  When we have pulled the ATN line, or we just want to
   * acknowledge the byte, then we do a dummy read from SCISDATL.  The SCSI
   * spec guarantees that the target will hold the data byte on the bus until
   * we send our ACK.
   *
   * The assumption here is that these are called in a particular sequence,
   * and that REQ is already set when inb_first is called.  inb_{first,next}
   * use the same calling convention as inb.
   */
  inb_next_wait_perr:
  	mvi	PERR_DETECTED call set_seqint;
  	jmp	inb_next_wait;
  inb_next:
  	mov	NONE,SCSIDATL;		/*dummy read from latch to ACK*/
  inb_next_wait:
  	/*
  	 * If there is a parity error, wait for the kernel to
  	 * see the interrupt and prepare our message response
  	 * before continuing.
  	 */
  	test	SSTAT1, REQINIT	jz inb_next_wait;
  	test	SSTAT1, SCSIPERR jnz inb_next_wait_perr;
  inb_next_check_phase:
  	and	LASTPHASE, PHASE_MASK, SCSISIGI;
  	cmp	LASTPHASE, P_MESGIN jne mesgin_phasemis;
  inb_first:
  	mov	DINDEX,SINDEX;
  	mov	DINDIR,SCSIBUSL	ret;		/*read byte directly from bus*/
  inb_last:
  	mov	NONE,SCSIDATL ret;		/*dummy read from latch to ACK*/
  }
  
  if ((ahc->flags & AHC_TARGETROLE) != 0) {
  /*
   * Change to a new phase.  If we are changing the state of the I/O signal,
   * from out to in, wait an additional data release delay before continuing.
   */
  change_phase:
  	/* Wait for preceding I/O session to complete. */
  	test	SCSISIGI, ACKI jnz .;
  
  	/* Change the phase */
  	and	DINDEX, IOI, SCSISIGI;
  	mov	SCSISIGO, SINDEX;
  	and	A, IOI, SINDEX;
  
  	/*
  	 * If the data direction has changed, from
  	 * out (initiator driving) to in (target driving),
  	 * we must wait at least a data release delay plus
  	 * the normal bus settle delay. [SCSI III SPI 10.11.0]
  	 */
  	cmp 	DINDEX, A je change_phase_wait;
  	test	SINDEX, IOI jz change_phase_wait;
  	call	change_phase_wait;
  change_phase_wait:
  	nop;
  	nop;
  	nop;
  	nop ret;
  
  /*
   * Send a byte to an initiator in Automatic PIO mode.
   */
  target_outb:
  	or	SXFRCTL0, SPIOEN;
  	test	SSTAT0, SPIORDY	jz .;
  	mov	SCSIDATL, SINDEX;
  	test	SSTAT0, SPIORDY	jz .;
  	and	SXFRCTL0, ~SPIOEN ret;
  }
  	
  /*
   * Locate a disconnected SCB by SCBID.  Upon return, SCBPTR and SINDEX will
   * be set to the position of the SCB.  If the SCB cannot be found locally,
   * it will be paged in from host memory.  RETURN_2 stores the address of the
   * preceding SCB in the disconnected list which can be used to speed up
   * removal of the found SCB from the disconnected list.
   */
  if ((ahc->flags & AHC_PAGESCBS) != 0) {
  BEGIN_CRITICAL;
  findSCB:
  	mov	A, SINDEX;			/* Tag passed in SINDEX */
  	cmp	DISCONNECTED_SCBH, SCB_LIST_NULL je findSCB_notFound;
  	mov	SCBPTR, DISCONNECTED_SCBH;	/* Initialize SCBPTR */
  	mvi	ARG_2, SCB_LIST_NULL;		/* Head of list */
  	jmp	findSCB_loop;
  findSCB_next:
  	cmp	SCB_NEXT, SCB_LIST_NULL je findSCB_notFound;
  	mov	ARG_2, SCBPTR;
  	mov	SCBPTR,SCB_NEXT;
  findSCB_loop:
  	cmp	SCB_TAG, A	jne findSCB_next;
  rem_scb_from_disc_list:
  	cmp	ARG_2, SCB_LIST_NULL	je rHead;
  	mov	DINDEX, SCB_NEXT;
  	mov	SINDEX, SCBPTR;
  	mov	SCBPTR, ARG_2;
  	mov	SCB_NEXT, DINDEX;
  	mov	SCBPTR, SINDEX ret;
  rHead:
  	mov	DISCONNECTED_SCBH,SCB_NEXT ret;
  END_CRITICAL;
  findSCB_notFound:
  	/*
  	 * We didn't find it.  Page in the SCB.
  	 */
  	mov	ARG_1, A; /* Save tag */
  	mov	ALLZEROS call get_free_or_disc_scb;
  	mvi	DMAPARAMS, HDMAEN|DIRECTION|FIFORESET;
  	mov	ARG_1	jmp dma_scb;
  }
  
  /*
   * Prepare the hardware to post a byte to host memory given an
   * index of (A + (256 * SINDEX)) and a base address of SHARED_DATA_ADDR.
   */
  post_byte_setup:
  	mov	ARG_2, SINDEX;
  	if ((ahc->features & AHC_CMD_CHAN) != 0) {
  		mvi	DINDEX, CCHADDR;
  		mvi	SHARED_DATA_ADDR call	set_1byte_addr;
  		mvi	CCHCNT, 1;
  		mvi	CCSCBCTL, CCSCBRESET ret;
  	} else {
  		mvi	DINDEX, HADDR;
  		mvi	SHARED_DATA_ADDR call	set_1byte_addr;
  		mvi	1	call set_hcnt;
  		mvi	DFCNTRL, FIFORESET ret;
  	}
  
  post_byte:
  	if ((ahc->features & AHC_CMD_CHAN) != 0) {
  		bmov	CCSCBRAM, SINDEX, 1;
  		or	CCSCBCTL, CCSCBEN|CCSCBRESET;
  		test	CCSCBCTL, CCSCBDONE jz .;
  		clr	CCSCBCTL ret;
  	} else {
  		mov	DFDAT, SINDEX;
  		or	DFCNTRL, HDMAEN|FIFOFLUSH;
  		jmp	dma_finish;
  	}
  
  phase_lock_perr:
  	mvi	PERR_DETECTED call set_seqint;
  phase_lock:     
  	/*
  	 * If there is a parity error, wait for the kernel to
  	 * see the interrupt and prepare our message response
  	 * before continuing.
  	 */
  	test	SSTAT1, REQINIT jz phase_lock;
  	test	SSTAT1, SCSIPERR jnz phase_lock_perr;
  phase_lock_latch_phase:
  	if ((ahc->features & AHC_DT) == 0) {
  		and	SCSISIGO, PHASE_MASK, SCSISIGI;
  	}
  	and	LASTPHASE, PHASE_MASK, SCSISIGI ret;
  
  if ((ahc->features & AHC_CMD_CHAN) == 0) {
  set_hcnt:
  	mov	HCNT[0], SINDEX;
  clear_hcnt:
  	clr	HCNT[1];
  	clr	HCNT[2] ret;
  
  set_stcnt_from_hcnt:
  	mov	STCNT[0], HCNT[0];
  	mov	STCNT[1], HCNT[1];
  	mov	STCNT[2], HCNT[2] ret;
  
  bcopy_8:
  	mov	DINDIR, SINDIR;
  bcopy_7:
  	mov	DINDIR, SINDIR;
  	mov	DINDIR, SINDIR;
  bcopy_5:
  	mov	DINDIR, SINDIR;
  bcopy_4:
  	mov	DINDIR, SINDIR;
  bcopy_3:
  	mov	DINDIR, SINDIR;
  	mov	DINDIR, SINDIR;
  	mov	DINDIR, SINDIR ret;
  }
  
  if ((ahc->flags & AHC_TARGETROLE) != 0) {
  /*
   * Setup addr assuming that A is an index into
   * an array of 32byte objects, SINDEX contains
   * the base address of that array, and DINDEX
   * contains the base address of the location
   * to store the indexed address.
   */
  set_32byte_addr:
  	shr	ARG_2, 3, A;
  	shl	A, 5;
  	jmp	set_1byte_addr;
  }
  
  /*
   * Setup addr assuming that A is an index into
   * an array of 64byte objects, SINDEX contains
   * the base address of that array, and DINDEX
   * contains the base address of the location
   * to store the indexed address.
   */
  set_64byte_addr:
  	shr	ARG_2, 2, A;
  	shl	A, 6;
  
  /*
   * Setup addr assuming that A + (ARG_2 * 256) is an
   * index into an array of 1byte objects, SINDEX contains
   * the base address of that array, and DINDEX contains
   * the base address of the location to store the computed
   * address.
   */
  set_1byte_addr:
  	add     DINDIR, A, SINDIR;
  	mov     A, ARG_2;
  	adc	DINDIR, A, SINDIR;
  	clr	A;
  	adc	DINDIR, A, SINDIR;
  	adc	DINDIR, A, SINDIR ret;
  
  /*
   * Either post or fetch an SCB from host memory based on the
   * DIRECTION bit in DMAPARAMS. The host SCB index is in SINDEX.
   */
  dma_scb:
  	mov	A, SINDEX;
  	if ((ahc->features & AHC_CMD_CHAN) != 0) {
  		mvi	DINDEX, CCHADDR;
  		mvi	HSCB_ADDR call set_64byte_addr;
  		mov	CCSCBPTR, SCBPTR;
  		test	DMAPARAMS, DIRECTION jz dma_scb_tohost;
  		if ((ahc->flags & AHC_SCB_BTT) != 0) {
  			mvi	CCHCNT, SCB_DOWNLOAD_SIZE_64;
  		} else {
  			mvi	CCHCNT, SCB_DOWNLOAD_SIZE;
  		}
  		mvi	CCSCBCTL, CCARREN|CCSCBEN|CCSCBDIR|CCSCBRESET;
  		cmp	CCSCBCTL, CCSCBDONE|ARRDONE|CCARREN|CCSCBEN|CCSCBDIR jne .;
  		jmp	dma_scb_finish;
  dma_scb_tohost:
  		mvi	CCHCNT, SCB_UPLOAD_SIZE;
  		if ((ahc->features & AHC_ULTRA2) == 0) {
  			mvi	CCSCBCTL, CCSCBRESET;
  			bmov	CCSCBRAM, SCB_BASE, SCB_UPLOAD_SIZE;
  			or	CCSCBCTL, CCSCBEN|CCSCBRESET;
  			test	CCSCBCTL, CCSCBDONE jz .;
  		} else if ((ahc->bugs & AHC_SCBCHAN_UPLOAD_BUG) != 0) {
  			mvi	CCSCBCTL, CCARREN|CCSCBRESET;
  			cmp	CCSCBCTL, ARRDONE|CCARREN jne .;
  			mvi	CCHCNT, SCB_UPLOAD_SIZE;
  			mvi	CCSCBCTL, CCSCBEN|CCSCBRESET;
  			cmp	CCSCBCTL, CCSCBDONE|CCSCBEN jne .;
  		} else {
  			mvi	CCSCBCTL, CCARREN|CCSCBEN|CCSCBRESET;
  			cmp	CCSCBCTL, CCSCBDONE|ARRDONE|CCARREN|CCSCBEN jne .;
  		}
  dma_scb_finish:
  		clr	CCSCBCTL;
  		test	CCSCBCTL, CCARREN|CCSCBEN jnz .;
  		ret;
  	} else {
  		mvi	DINDEX, HADDR;
  		mvi	HSCB_ADDR call set_64byte_addr;
  		mvi	SCB_DOWNLOAD_SIZE call set_hcnt;
  		mov	DFCNTRL, DMAPARAMS;
  		test	DMAPARAMS, DIRECTION	jnz dma_scb_fromhost;
  		/* Fill it with the SCB data */
  copy_scb_tofifo:
  		mvi	SINDEX, SCB_BASE;
  		add	A, SCB_DOWNLOAD_SIZE, SINDEX;
  copy_scb_tofifo_loop:
  		call	copy_to_fifo_8;
  		cmp	SINDEX, A jne copy_scb_tofifo_loop;
  		or	DFCNTRL, HDMAEN|FIFOFLUSH;
  		jmp	dma_finish;
  dma_scb_fromhost:
  		mvi	DINDEX, SCB_BASE;
  		if ((ahc->bugs & AHC_PCI_2_1_RETRY_BUG) != 0) {
  			/*
  			 * The PCI module will only issue a PCI
  			 * retry if the data FIFO is empty.  If the
  			 * host disconnects in the middle of a
  			 * transfer, we must empty the fifo of all
  			 * available data to force the chip to
  			 * continue the transfer.  This does not
  			 * happen for SCSI transfers as the SCSI module
  			 * will drain the FIFO as data are made available.
  			 * When the hang occurs, we know that a multiple
  			 * of 8 bytes is in the FIFO because the PCI
  			 * module has an 8 byte input latch that only
  			 * dumps to the FIFO when HCNT == 0 or the
  			 * latch is full.
  			 */
  			clr	A;
  			/* Wait for at least 8 bytes of data to arrive. */
  dma_scb_hang_fifo:
  			test	DFSTATUS, FIFOQWDEMP jnz dma_scb_hang_fifo;
  dma_scb_hang_wait:
  			test	DFSTATUS, MREQPEND jnz dma_scb_hang_wait;
  			test	DFSTATUS, HDONE	jnz dma_scb_hang_dma_done;
  			test	DFSTATUS, HDONE	jnz dma_scb_hang_dma_done;
  			test	DFSTATUS, HDONE	jnz dma_scb_hang_dma_done;
  			/*
  			 * The PCI module no longer intends to perform
  			 * a PCI transaction.  Drain the fifo.
  			 */
  dma_scb_hang_dma_drain_fifo:
  			not	A, HCNT;
  			add	A, SCB_DOWNLOAD_SIZE+SCB_BASE+1;
  			and	A, ~0x7;
  			mov	DINDIR,DFDAT;
  			cmp	DINDEX, A jne . - 1;
  			cmp	DINDEX, SCB_DOWNLOAD_SIZE+SCB_BASE
  				je	dma_finish_nowait;
  			/* Restore A as the lines left to transfer. */
  			add	A, -SCB_BASE, DINDEX;
  			shr	A, 3;
  			jmp	dma_scb_hang_fifo;
  dma_scb_hang_dma_done:
  			and	DFCNTRL, ~HDMAEN;
  			test	DFCNTRL, HDMAEN jnz .;
  			add	SEQADDR0, A;
  		} else {
  			call	dma_finish;
  		}
  		call	dfdat_in_8;
  		call	dfdat_in_8;
  		call	dfdat_in_8;
  dfdat_in_8:
  		mov	DINDIR,DFDAT;
  dfdat_in_7:
  		mov	DINDIR,DFDAT;
  		mov	DINDIR,DFDAT;
  		mov	DINDIR,DFDAT;
  		mov	DINDIR,DFDAT;
  		mov	DINDIR,DFDAT;
  dfdat_in_2:
  		mov	DINDIR,DFDAT;
  		mov	DINDIR,DFDAT ret;
  	}
  
  copy_to_fifo_8:
  	mov	DFDAT,SINDIR;
  	mov	DFDAT,SINDIR;
  copy_to_fifo_6:
  	mov	DFDAT,SINDIR;
  copy_to_fifo_5:
  	mov	DFDAT,SINDIR;
  copy_to_fifo_4:
  	mov	DFDAT,SINDIR;
  	mov	DFDAT,SINDIR;
  	mov	DFDAT,SINDIR;
  	mov	DFDAT,SINDIR ret;
  
  /*
   * Wait for DMA from host memory to data FIFO to complete, then disable
   * DMA and wait for it to acknowledge that it's off.
   */
  dma_finish:
  	test	DFSTATUS,HDONE	jz dma_finish;
  dma_finish_nowait:
  	/* Turn off DMA */
  	and	DFCNTRL, ~HDMAEN;
  	test	DFCNTRL, HDMAEN jnz .;
  	ret;
  
  /*
   * Restore an SCB that failed to match an incoming reselection
   * to the correct/safe state.  If the SCB is for a disconnected
   * transaction, it must be returned to the disconnected list.
   * If it is not in the disconnected state, it must be free.
   */
  cleanup_scb:
  	if ((ahc->flags & AHC_PAGESCBS) != 0) {
  		test	SCB_CONTROL,DISCONNECTED jnz add_scb_to_disc_list;
  	}
  add_scb_to_free_list:
  	if ((ahc->flags & AHC_PAGESCBS) != 0) {
  BEGIN_CRITICAL;
  		mov	SCB_NEXT, FREE_SCBH;
  		mvi	SCB_TAG, SCB_LIST_NULL;
  		mov	FREE_SCBH, SCBPTR ret;
  END_CRITICAL;
  	} else {
  		mvi	SCB_TAG, SCB_LIST_NULL ret;
  	}
  
  if ((ahc->flags & AHC_39BIT_ADDRESSING) != 0) {
  set_hhaddr:
  	or	DSCOMMAND1, HADDLDSEL0;
  	and	HADDR, SG_HIGH_ADDR_BITS, SINDEX;
  	and	DSCOMMAND1, ~HADDLDSEL0 ret;
  }
  
  if ((ahc->flags & AHC_PAGESCBS) != 0) {
  get_free_or_disc_scb:
  BEGIN_CRITICAL;
  	cmp	FREE_SCBH, SCB_LIST_NULL jne dequeue_free_scb;
  	cmp	DISCONNECTED_SCBH, SCB_LIST_NULL jne dequeue_disc_scb;
  return_error:
  	mvi	NO_FREE_SCB call set_seqint;
  	mvi	SINDEX, SCB_LIST_NULL	ret;
  dequeue_disc_scb:
  	mov	SCBPTR, DISCONNECTED_SCBH;
  	mov	DISCONNECTED_SCBH, SCB_NEXT;
  END_CRITICAL;
  	mvi	DMAPARAMS, FIFORESET;
  	mov	SCB_TAG	jmp dma_scb;
  BEGIN_CRITICAL;
  dequeue_free_scb:
  	mov	SCBPTR, FREE_SCBH;
  	mov	FREE_SCBH, SCB_NEXT ret;
  END_CRITICAL;
  
  add_scb_to_disc_list:
  /*
   * Link this SCB into the DISCONNECTED list.  This list holds the
   * candidates for paging out an SCB if one is needed for a new command.
   * Modifying the disconnected list is a critical(pause dissabled) section.
   */
  BEGIN_CRITICAL;
  	mov	SCB_NEXT, DISCONNECTED_SCBH;
  	mov	DISCONNECTED_SCBH, SCBPTR ret;
  END_CRITICAL;
  }
  set_seqint:
  	mov	INTSTAT, SINDEX;
  	nop;
  return:
  	ret;