freebsd-dev/sys/dev/aic7xxx/aic7xxx.seq

/*+M***********************************************************************
 *Adaptec 274x/284x/294x device driver for Linux and FreeBSD.
 *
 *Copyright (c) 1994 John Aycock
 *  The University of Calgary Department of Computer Science.
 *  All rights reserved.
 *
 *FreeBSD, Twin, Wide, 2 command per target support, tagged queuing,
 *SCB paging and other optimizations:
 *Copyright (c) 1994, 1995, 1996, 1997 Justin Gibbs. All rights reserved.
 *
 *Redistribution and use in source and binary forms, with or without
 *modification, are permitted provided that the following conditions
 *are met:
 *1. Redistributions of source code must retain the above copyright
 *   notice, this list of conditions, and the following disclaimer.
 *2. Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *3. All advertising materials mentioning features or use of this software
 *   must display the following acknowledgement:
 *     This product includes software developed by the University of Calgary
 *     Department of Computer Science and its contributors.
 *4. Neither the name of the University nor the names of its contributors
 *   may be used to endorse or promote products derived from this software
 *   without specific prior written permission.
 *
 *THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 *ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 *FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 *DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 *OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 *HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 *LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 *OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 *SUCH DAMAGE.
 *
 *-M************************************************************************/

#include <dev/aic7xxx/aic7xxx.reg>
#include <scsi/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 psuedo-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 everytime 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.
 */

/*
 * We assume that the kernel driver may reset us at any time, even in the
 * middle of a DMA, so clear DFCNTRL too.
 */
reset:
	clr	SCSISIGO;		/* De-assert BSY */
	/* Always allow reselection */
	mvi	SCSISEQ, ENRSELI|ENAUTOATNP;
	call	clear_target_state;
poll_for_work:
	test	SSTAT0,SELDI|SELDO	jnz selection;
	test	SCSISEQ, ENSELO	jnz poll_for_work;
.if ( TWIN_CHANNEL )
	/*
	 * Twin channel devices cannot handle things like SELTO
	 * interrupts on the "background" channel.  So, if we
	 * are selecting, keep polling the current channel util
	 * either a selection or reselection occurs.
	 */
	xor	SBLKCTL,SELBUSB;	/* Toggle to the other bus */
	test	SSTAT0,SELDI|SELDO	jnz selection;
	test	SCSISEQ, ENSELO	jnz poll_for_work;
	xor	SBLKCTL,SELBUSB;	/* Toggle back */
.endif
	cmp	WAITING_SCBH,SCB_LIST_NULL jne start_waiting;
test_queue:
	/* Has the driver posted any work for us? */
	mov	A, QCNTMASK;
	test	QINCNT,A	jz poll_for_work;

/*
 * We have at least one queued SCB now and we don't have any 
 * SCBs in the list of SCBs awaiting selection.  If we have
 * any SCBs available for use, pull the tag from the QINFIFO
 * and get to work on it.
 */
.if ( SCB_PAGING )
	mov	ALLZEROS	call	get_free_or_disc_scb;
	cmp	SINDEX, SCB_LIST_NULL	je poll_for_work;
.endif
dequeue_scb:
	mov	CUR_SCBID,QINFIFO;
.if !( SCB_PAGING )
	/* In the non-paging case, the SCBID == hardware SCB index */
	mov	SCBPTR, CUR_SCBID;
.endif
dma_queued_scb:
/*
 * DMA the SCB from host ram into the current SCB location.
 */
	mvi	DMAPARAMS, HDMAEN|DIRECTION|FIFORESET;
	mov	CUR_SCBID	call dma_scb;

/*
 * See if there is not already an active SCB for this target.  This code
 * locks out on a per target basis instead of target/lun.  Although this
 * is not ideal for devices that have multiple luns active at the same
 * time, it is faster than looping through all SCB's looking for active
 * commands.  We also don't have enough spare SCB space for us to store the
 * SCBID of the currently busy transaction for each target/lun making it
 * impossible to link up the SCBs.
 */
test_busy:
	test	SCB_CONTROL, TAG_ENB|ABORT_SCB jnz start_scb;
	mvi	SEQCTL, PAUSEDIS|FASTMODE;
	mov	SAVED_SCBPTR, SCBPTR;
	mov	SCB_TCL		call	index_untagged_scb;
	mov	ARG_1, SINDIR;			/*
						 * ARG_1 should
						 * now have the SCB ID of
						 * any active, non-tagged,
						 * command for this target.
						 */
	cmp	ARG_1, SCB_LIST_NULL je make_busy;
.if ( SCB_PAGING )
	/*
	 * Put this SCB back onto the free list.  It
	 * may be necessary to satisfy the search for
	 * the active SCB.
	 */
	mov	SCBPTR, SAVED_SCBPTR;
	call	add_scb_to_free_list;
	/* Find the active SCB */
	mov	ALLZEROS	call findSCB;
	/*
	 * If we couldn't find it, tell the kernel.  This should
	 * never happen.
	 */
	cmp	SINDEX, SCB_LIST_NULL	jne paged_busy_link;
	mvi	INTSTAT, NO_MATCH_BUSY;
paged_busy_link:
	/* Link us in */
	mov	SCB_LINKED_NEXT, CUR_SCBID;
	/* Put it back on the disconnected list */
	call	add_scb_to_disc_list;
	mvi	SEQCTL, FASTMODE;
	jmp	poll_for_work;
.endif
simple_busy_link:
	mov	SCBPTR, ARG_1;
	mov	SCB_LINKED_NEXT, CUR_SCBID;
	mvi	SEQCTL, FASTMODE;
	jmp	poll_for_work;
make_busy:
	mov	DINDIR, CUR_SCBID;
	mov	SCBPTR, SAVED_SCBPTR;
	mvi	SEQCTL, FASTMODE;

start_scb:
	/*
	 * Place us on the waiting list in case our selection
	 * doesn't win during bus arbitration.
	 */
	mov	SCB_NEXT,WAITING_SCBH;
	mov	WAITING_SCBH, SCBPTR;
start_waiting:
	/*
	 * Pull the first entry off of the waiting SCB list
	 * We don't have to "test_busy" because only transactions that
	 * have passed that test can be in the WAITING_SCB list.
	 */
	mov	SCBPTR, WAITING_SCBH;
	call	start_selection;
	jmp	poll_for_work;

start_selection:
	and	SINDEX,~SELBUSB,SBLKCTL;/* Clear the channel select bit */
	and	A,SELBUSB,SCB_TCL;	/* Get new channel bit */
	or	SINDEX,A;
	mov	SBLKCTL,SINDEX;		/* select channel */
initialize_scsiid:
	and	A, TID, SCB_TCL;	/* Get target ID */
	and	SCSIID, OID;		/* Clear old target */
	or	SCSIID, A;
	mvi	SCSISEQ, ENSELO|ENAUTOATNO|ENRSELI|ENAUTOATNP ret;
/*
 * 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.
 */
selection:
	test	SSTAT0, SELDI	jz select;
reselect:
	clr	MSG_LEN;	/* Don't have anything in the mesg buffer */
	mvi	CLRSINT0, CLRSELDI;
	/* XXX test for and handle ONE BIT condition */
	and	SAVED_TCL, SELID_MASK, SELID;
	or	SEQ_FLAGS,RESELECTED;
	jmp	select2;

/*
 * 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:
	/* Turn off the selection hardware */
	mvi	SCSISEQ, ENRSELI|ENAUTOATNP;	/*
						 * ATN on parity errors
						 * for "in" phases
						 */
	mvi	CLRSINT0, CLRSELDO;
	mov	SCBPTR, WAITING_SCBH;
	mov	WAITING_SCBH,SCB_NEXT;
	mov	SAVED_TCL, SCB_TCL;
/*
 * As soon as we get a successful selection, the target should go
 * into the message out phase since we have ATN asserted.  Prepare
 * the message to send.
 *
 * Messages are stored in scratch RAM starting with a length byte
 * followed by the message itself.
 */

mk_identify:
	and	MSG_OUT,0x7,SCB_TCL;	/* lun */
	and	A,DISCENB,SCB_CONTROL;	/* mask off disconnect privledge */
	or	MSG_OUT,A;		/* or in disconnect privledge */
	or	MSG_OUT,MSG_IDENTIFYFLAG;
	mvi	MSG_LEN, 1;

/*
 * 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.
 */
mk_tag:
	test	SCB_CONTROL,TAG_ENB jz  mk_message;
	and	MSG_OUT[1],TAG_ENB|SCB_TAG_TYPE,SCB_CONTROL;
	mov	MSG_OUT[2],SCB_TAG;
	add	MSG_LEN,2;	/* update message length */

/*
 * Interrupt the driver, and allow it to tweak the message buffer
 * if it asks.
 */
mk_message:
	test	SCB_CONTROL,MK_MESSAGE  jz select2;
	mvi     INTSTAT,AWAITING_MSG;

select2:
	mvi	CLRSINT1,CLRBUSFREE;
	or	SIMODE1, ENBUSFREE;		/*
						 * We aren't expecting a
						 * bus free, so interrupt
						 * the kernel driver if it
						 * happens.
						 */
/*
 * Initialize Ultra mode setting and clear the SCSI channel.
 */
	or	SXFRCTL0, CLRSTCNT|SPIOEN|CLRCHN;
.if ( ULTRA )
ultra:
	mvi	SINDEX, ULTRA_ENB+1;
	test	SAVED_TCL, 0x80		jnz ultra_2;	/* Target ID > 7 */
	dec	SINDEX;
ultra_2:
	mov     FUNCTION1,SAVED_TCL;
	mov     A,FUNCTION1;
	test	SINDIR, A	jz ndx_dtr;
	or	SXFRCTL0, FAST20;
.endif
 
/*
 * Initialize SCSIRATE with the appropriate value for this target.
 * The SCSIRATE settings for each target are stored in an array
 * based at TARG_SCRATCH.
 */
ndx_dtr:
	shr	A,4,SAVED_TCL;
	test	SBLKCTL,SELBUSB	jz ndx_dtr_2;
	or	SAVED_TCL, SELBUSB; /* Add the channel bit while we're here */
	or	A,0x08;			/* Channel B entries add 8 */
ndx_dtr_2:
	add	SINDEX,TARG_SCRATCH,A;
	mov	SCSIRATE,SINDIR;


/*
 * Main loop for information transfer phases.  If BSY is false, then
 * we have a bus free condition, expected or not.  Otherwise, wait
 * for the target to assert REQ before checking MSG, C/D and I/O
 * for the bus phase.
 *
 */
ITloop:
	test	SSTAT1,REQINIT	jz ITloop;

	and	A,PHASE_MASK,SCSISIGI;
	mov	LASTPHASE,A;
	mov	SCSISIGO,A;

	cmp	ALLZEROS,A	je p_dataout;
	cmp	A,P_DATAIN	je p_datain;
	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	INTSTAT,BAD_PHASE;	/* unknown phase - signal driver */
	jmp	ITloop;			/* Try reading the bus again. */

await_busfree:
	and	SIMODE1, ~ENBUSFREE;
	mov	NONE, SCSIDATL;		/* Ack the last byte */
	call	clear_target_state;
	test	SSTAT1,REQINIT|BUSFREE	jz .;
	test	SSTAT1, BUSFREE jnz poll_for_work;
	mvi	INTSTAT, BAD_PHASE;
	
clear_target_state:
	clr	DFCNTRL;
	clr	SCSIRATE;		/*
					 * We don't know the target we will
					 * connect to, so default to narrow
					 * transfers to avoid parity problems.
					 */
	and	SXFRCTL0, ~FAST20;	
	mvi	LASTPHASE, P_BUSFREE;
	/* clear target specific flags */
	and	SEQ_FLAGS,~(RESELECTED|IDENTIFY_SEEN|TAGGED_SCB|DPHASE) ret;

p_dataout:
	mvi	DMAPARAMS, WIDEODD|SCSIEN|SDMAEN|HDMAEN|DIRECTION|FIFORESET;
	jmp	data_phase_init;

/*
 * If we re-enter the data phase after going through another phase, the
 * STCNT may have been cleared, so restore it from the residual field.
 */
data_phase_reinit:
	mvi	DINDEX, STCNT;
	mvi	SCB_RESID_DCNT	call bcopy_3;
	jmp	data_phase_loop;

p_datain:
	mvi	DMAPARAMS, WIDEODD|SCSIEN|SDMAEN|HDMAEN|FIFORESET;
data_phase_init:
	call	assert;			/*
					 * Ensure entering a data
					 * phase is okay - seen identify, etc.
					 */

	test	SEQ_FLAGS, DPHASE	jnz data_phase_reinit;

	/*
	 * Initialize the DMA address and counter from the SCB.
	 * Also set SG_COUNT and SG_NEXT in memory since we cannot
	 * modify the values in the SCB itself until we see a
	 * save data pointers message.
	 */
	mvi	DINDEX, HADDR;
	mvi	SCB_DATAPTR	call bcopy_7;

	call	set_stcnt_from_hcnt;

	mov	SG_COUNT,SCB_SGCOUNT;

	mvi	DINDEX, SG_NEXT;
	mvi	SCB_SGPTR	call bcopy_4;

data_phase_loop:
/* Guard against overruns */
	test	SG_COUNT, 0xff jnz data_phase_inbounds;
/*
 * Turn on 'Bit Bucket' mode, set the transfer count to
 * 16meg and let the target run until it changes phase.
 * When the transfer completes, notify the host that we
 * had an overrun.
 */
	or	SXFRCTL1,BITBUCKET;
	mvi	HCNT[0], 0xff;
	mvi	HCNT[1], 0xff;
	mvi	HCNT[2], 0xff;
	call	set_stcnt_from_hcnt;

data_phase_inbounds:
/* If we are the last SG block, ensure wideodd is off. */
	cmp	SG_COUNT,0x01 jne data_phase_wideodd;
	and	DMAPARAMS, ~WIDEODD;
data_phase_wideodd:
	mov	DMAPARAMS  call dma;

/* Go tell the host about any overruns */
	test	SXFRCTL1,BITBUCKET jnz data_phase_overrun;

/* Exit if we had an underrun.  dma clears SINDEX in this case. */
	test	SINDEX,0xff	jz data_phase_finish;

/*
 * Advance the scatter-gather pointers if needed 
 */
sg_advance:
	dec	SG_COUNT;	/* one less segment to go */

	test	SG_COUNT, 0xff	jz data_phase_finish; /* Are we done? */

	clr	A;			/* add sizeof(struct scatter) */
	add	SG_NEXT[0],SG_SIZEOF;
	adc	SG_NEXT[1],A;

/*
 * Load a struct scatter and set up the data address and length.
 * If the working value of the SG count is nonzero, then
 * we need to load a new set of values.
 *
 * This, like all DMA's, assumes little-endian host data storage.
 */
sg_load:
	mvi	DINDEX, HADDR;
	mvi	SG_NEXT	call bcopy_4;

	mvi	HCNT[0],SG_SIZEOF;
	clr	HCNT[1];
	clr	HCNT[2];

	or	DFCNTRL, HDMAEN|DIRECTION|FIFORESET;

	call	dma_finish;

/*
 * Copy data from FIFO into SCB data pointer and data count.  This assumes
 * that the SG segments are of the form:
 *
 * struct ahc_dma_seg {
 *	u_int32_t	addr;		four bytes, little-endian order
 *	u_int32_t	len;		four bytes, little endian order
 * };
 */
	mvi	HADDR	call dfdat_in_7;

/* Load STCNT as well.  It is a mirror of HCNT */
	call	set_stcnt_from_hcnt;
	test	SSTAT1,PHASEMIS	jz data_phase_loop;

data_phase_finish:
/*
 * 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.
 */
	mov	SCB_RESID_DCNT[0],STCNT[0];
	mov	SCB_RESID_DCNT[1],STCNT[1];
	mov	SCB_RESID_DCNT[2],STCNT[2];
	mov	SCB_RESID_SGCNT, SG_COUNT;

	/* We have seen a data phase */
	or	SEQ_FLAGS, DPHASE;

	jmp	ITloop;

data_phase_overrun:
/*
 * Turn off BITBUCKET mode and notify the host
 */
	and	SXFRCTL1, ~BITBUCKET;
	mvi	INTSTAT,DATA_OVERRUN;
	jmp	ITloop;

/*
 * Command phase.  Set up the DMA registers and let 'er rip.
 */
p_command:
	call	assert;

/*
 * Load HADDR and HCNT.
 */
	mvi	DINDEX, HADDR;
	mvi	SCB_CMDPTR	call bcopy_5;
	clr	HCNT[1];
	clr	HCNT[2];

	call	set_stcnt_from_hcnt;

	mvi	(SCSIEN|SDMAEN|HDMAEN|DIRECTION|FIFORESET) call dma;
	jmp	ITloop;

/*
 * Status phase.  Wait for the data byte to appear, then read it
 * and store it into the SCB.
 */
p_status:
	call	assert;

	mov	SCB_TARGET_STATUS, SCSIDATL;
	jmp	ITloop;

/*
 * Message out phase.  If there is not an active message, but the target
 * took us into this phase anyway, build a no-op message and send it.
 */
p_mesgout:
	test	MSG_LEN, 0xff	jnz  p_mesgout_start;
	mvi	MSG_NOOP	call mk_mesg;	/* build NOP message */
p_mesgout_start:
/*
 * Set up automatic PIO transfer from MSG_OUT.  Bit 3 in
 * SXFRCTL0 (SPIOEN) is already on.
 */
	mvi	SINDEX,MSG_OUT;
	mov	DINDEX,MSG_LEN;

/*
 * When target asks for a byte, drop ATN if it's the last one in
 * the message.  Otherwise, keep going until the message is exhausted.
 * ATN must be dropped *at least* 90ns before we ack the last byte, so
 * the code is aranged to execute two instructions before the byte is
 * transferred to give a good margin of safety
 *
 * Keep an eye out for a phase change, in case the target issues
 * a MESSAGE REJECT.
 */
p_mesgout_loop:
	test	SSTAT1, REQINIT	jz p_mesgout_loop;
	and	LASTPHASE, PHASE_MASK, SCSISIGI;
	cmp	LASTPHASE, P_MESGOUT jne p_mesgout_done;
/*
 * If the next bus phase after ATN drops is a message out, it means
 * that the target is requesting that the last message(s) be resent.
 */
p_mesgout_dropatn:
	cmp	DINDEX,1	jne p_mesgout_testretry;/* last byte? */
	mvi	CLRSINT1,CLRATNO;			/* drop ATN */
p_mesgout_testretry:
	test	DINDEX,0xff	jnz p_mesgout_outb;
	or	SCSISIGO,ATNO,LASTPHASE;/* turn on ATN for the retry */
	jmp	p_mesgout_start;
p_mesgout_outb:
	dec	DINDEX;
	mov	SCSIDATL,SINDIR;
	jmp	p_mesgout_loop;

p_mesgout_done:
	mvi	CLRSINT1,CLRATNO;	/* Be sure to turn ATNO off */
	clr	MSG_LEN;		/* no active msg */
	jmp	ITloop;

/*
 * Message in phase.  Bytes are read using Automatic PIO mode.
 */
p_mesgin:
	mvi	ACCUM		call inb_first;	/* read the 1st message byte */
	mov	REJBYTE,A;			/* save it for the driver */

	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_EXTENDED		je mesgin_extended;
	cmp	A,MSG_MESSAGE_REJECT	je mesgin_reject;
	cmp	A,MSG_NOOP		je mesgin_done;

rej_mesgin:
/*
 * We have no idea what this message in is, so we issue a message reject
 * and hope for the best.  In any case, rejection should be a rare
 * occurrence - signal the driver when it happens.
 */
	mvi	INTSTAT,SEND_REJECT;		/* let driver know */

	mvi	MSG_MESSAGE_REJECT	call mk_mesg;

mesgin_done:
	mov	NONE,SCSIDATL;		/*dummy read from latch to ACK*/
	jmp	ITloop;


mesgin_complete:
/*
 * We got a "command complete" message, so 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 NO_ERROR (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 and set
 * RETURN_1 to SEND_SENSE.  If RETURN_1 is set to SEND_SENSE we redownload
 * the SCB, and process it as the next command by adding it to the waiting list.
 * If the kernel driver does not wish to request sense, it need only clear
 * RETURN_1, and the command is allowed to complete normally.  We don't bother
 * to post to the QOUTFIFO in the error cases since it would require extra
 * work in the kernel driver to ensure that the entry was removed before the
 * command complete code tried processing it.
 */

/*
 * First check for residuals
 */
	test	SCB_RESID_SGCNT,0xff	jnz upload_scb;
	test	SCB_TARGET_STATUS,0xff	jz status_ok;	/* Good Status? */
upload_scb:
	mvi	DMAPARAMS, FIFORESET;
	mov	SCB_TAG		call dma_scb;
check_status:
	test	SCB_TARGET_STATUS,0xff	jz status_ok;	/* Just a residual? */
	mvi	INTSTAT,BAD_STATUS;			/* let driver know */
	cmp	RETURN_1, SEND_SENSE	jne status_ok;
	/* This SCB becomes the next to execute as it will retrieve sense */
	mov	SCB_LINKED_NEXT, SCB_TAG;
	jmp	dma_next_scb;

status_ok:
/* First, mark this target as free. */
	test	SCB_CONTROL,TAG_ENB jnz complete;	/*
							 * Tagged commands
							 * don't busy the
							 * target.
							 */
	mov	SAVED_SCBPTR, SCBPTR;
	mov	SAVED_LINKPTR, SCB_LINKED_NEXT;
	mov	SCB_TCL	call index_untagged_scb;
	mov	DINDIR, SAVED_LINKPTR;
	mov	SCBPTR, SAVED_SCBPTR;

complete:
	/* Post the SCB and issue an interrupt */
	mov	QOUTFIFO,SCB_TAG;
	mvi	INTSTAT,CMDCMPLT;
	test	SCB_CONTROL, ABORT_SCB jz dma_next_scb;
	mvi	INTSTAT, ABORT_CMDCMPLT;

dma_next_scb:
	cmp	SCB_LINKED_NEXT, SCB_LIST_NULL	je add_to_free_list;
.if !( SCB_PAGING )
	/* Only DMA on top of ourselves if we are the SCB to download */
	mov	A, SCB_LINKED_NEXT;
	cmp	SCB_TAG, A	je dma_next_scb2;
	mov	SCBPTR, A;
	jmp	add_to_waiting_list;
.endif
dma_next_scb2:
	mvi	DMAPARAMS, HDMAEN|DIRECTION|FIFORESET;
	mov	SCB_LINKED_NEXT		call dma_scb;
add_to_waiting_list:
	mov	SCB_NEXT,WAITING_SCBH;
	mov	WAITING_SCBH, SCBPTR;
	/*
	 * Prepare our selection hardware before the busfree so we have a
	 * high probability of winning arbitration.
	 */
	call	start_selection;
	jmp	await_busfree;
add_to_free_list:
	call	add_scb_to_free_list;
	jmp	await_busfree;

/*
 * Is it an extended message?  Copy the message to our message buffer and
 * notify the host.  The host will tell us whether to reject this message,
 * respond to it with the message that the host placed in our message buffer,
 * or simply to do nothing.
 */
mesgin_extended:
	mvi	MSGIN_EXT_LEN	 call inb_next;
	mov	A, MSGIN_EXT_LEN;
mesgin_extended_loop:
	mov	DINDEX	call	inb_next;
	dec	A;
	cmp	DINDEX, MSGIN_EXT_BYTES+3 jne mesgin_extended_loop_test;
	dec	DINDEX;		/* dump by repeatedly filling the last byte */
mesgin_extended_loop_test:
	test	A, 0xFF		jnz mesgin_extended_loop;
mesgin_extended_intr:
	mvi	INTSTAT,EXTENDED_MSG;		/* let driver know */
	cmp	RETURN_1,SEND_REJ je rej_mesgin;
	cmp	RETURN_1,SEND_MSG jne mesgin_done;
/* The kernel has setup a message to be sent */
	or	SCSISIGO,ATNO,LASTPHASE;	/* turn on ATNO */
	jmp	mesgin_done;

/*
 * Is it a disconnect message?  Set a flag in the SCB to remind us
 * and await the bus going free.
 */
mesgin_disconnect:
	or	SCB_CONTROL,DISCONNECTED;
.if ( SCB_PAGING )
	call	add_scb_to_disc_list;
.endif
	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.
 */
mesgin_sdptrs:
	test	SEQ_FLAGS, DPHASE	jz mesgin_done;
	mov	SCB_SGCOUNT,SG_COUNT;

	/* The SCB SGPTR becomes the next one we'll download */
	mvi	DINDEX, SCB_SGPTR;
	mvi	SG_NEXT	call bcopy_4;
	
	/* The SCB DATAPTR0 becomes the current SHADDR */
	mvi	DINDEX, SCB_DATAPTR;
	mvi	SHADDR		call bcopy_4;

/*
 * Use the residual number since STCNT is corrupted by any message transfer.
 */
	mvi	SCB_RESID_DCNT	call	bcopy_3;

	jmp	mesgin_done;

/*
 * 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.
 */
mesgin_rdptrs:
	and	SEQ_FLAGS, ~DPHASE;		/*
						 * We'll reload them
						 * the next time through
						 * the dataphase.
						 */
	jmp	mesgin_done;

/*
 * 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:
	test	A,0x78	jnz rej_mesgin;	/*!DiscPriv|!LUNTAR|!Reserved*/
	and	A,0x07;			/* lun in lower three bits */
	or      SAVED_TCL,A;		/* SAVED_TCL should be complete now */
	mov	SAVED_TCL call index_untagged_scb;
	mov	ARG_1, SINDIR;
	/* XXX Directly index in the non paging case */
	cmp	ARG_1,SCB_LIST_NULL	jne use_findSCB;
/*
 * 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, this requires using findSCB for both tagged
 * and 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.
 */
	mov	NONE,SCSIDATL;		/* ACK Identify MSG */
snoop_tag_loop:
	test	SSTAT1,REQINIT		jz snoop_tag_loop;
	and	LASTPHASE, PHASE_MASK, SCSISIGI;
	cmp	LASTPHASE, P_MESGIN	jne not_found;
	cmp	SCSIBUSL,MSG_SIMPLE_Q_TAG jne not_found;
get_tag:
	or	SEQ_FLAGS, TAGGED_SCB;
	mvi	ARG_1	call inb_next;	/* tag value */
/*
 * See if the tag is in range.  The tag is < SCBCOUNT if we add
 * the complement of SCBCOUNT to the incomming tag and there is
 * no carry.
 */
	mov	A,COMP_SCBCOUNT;
	add	SINDEX,A,ARG_1;
	jc	not_found;

.if ! ( SCB_PAGING )
	jmp index_by_tag;
.endif
/*
 * Ensure that the SCB the tag points to is for an SCB transaction
 * to the reconnecting target.
 */
use_findSCB:
	mov	ALLZEROS	call findSCB;	  /* Have to search */
	cmp	SINDEX, SCB_LIST_NULL	je not_found;
setup_SCB:
	and	SCB_CONTROL,~DISCONNECTED;
	or	SEQ_FLAGS,IDENTIFY_SEEN;	  /* make note of IDENTIFY */
	jmp	mesgin_done;
index_by_tag:
	mov	SCBPTR,ARG_1;
	mov	A, SAVED_TCL;
	cmp	SCB_TCL,A		jne not_found;
	test	SCB_CONTROL,TAG_ENB	jz  not_found;
	test	SCB_CONTROL,DISCONNECTED jz not_found;
	jmp	setup_SCB;

not_found:
	mvi	INTSTAT, NO_MATCH;
send_abort_msg:
	test	SEQ_FLAGS, TAGGED_SCB jnz send_abort_tag_msg;
	mvi	MSG_ABORT	call mk_mesg;
	jmp	send_abort_done;
send_abort_tag_msg:
	mvi	MSG_ABORT_TAG	call mk_mesg;	/* ABORT TAG message */
send_abort_done:
	/* If we don't have the tag ID yet, we're "looking ahead" at state
	 * that hasn't been processed, so don't ack.
	 */
	cmp	ARG_1, SCB_LIST_NULL	je ITloop;
	jmp	mesgin_done;

/*
 * Message reject?  Let the kernel driver handle this.  If we have an 
 * outstanding WDTR or SDTR negotiation, assume that it's a response from 
 * the target selecting 8bit or asynchronous transfer, otherwise just ignore 
 * it since we have no clue what it pertains to.
 */
mesgin_reject:
	mvi	INTSTAT, REJECT_MSG;
	jmp	mesgin_done;

/*
 * [ ADD MORE MESSAGE HANDLING HERE ]
 */

/*
 * Locking the driver out, build a one-byte message passed in SINDEX
 * if there is no active message already.  SINDEX is returned intact.
 */
mk_mesg:
	mvi	SEQCTL, PAUSEDIS|FASTMODE;
	test	MSG_LEN,0xff	jz mk_mesg1;	/* Should always succeed */
	
	/*
	 * Hmmm.  For some reason the mesg buffer is in use.
	 * Tell the driver.  It should look at SINDEX to find
	 * out what we wanted to use the buffer for and resolve
	 * the conflict.
	 */
	mvi	SEQCTL,FASTMODE;
	mvi	INTSTAT,MSG_BUFFER_BUSY;

mk_mesg1:
	or	SCSISIGO,ATNO,LASTPHASE;/* turn on ATNO */
	mvi	MSG_LEN,1;		/* length = 1 */
	mov	MSG_OUT,SINDEX;		/* 1-byte message */
	mvi	SEQCTL,FASTMODE	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:
	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;
	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*/

mesgin_phasemis:
/*
 * We expected to receive another byte, but the target changed phase
 */
	mvi	INTSTAT, MSGIN_PHASEMIS;
	jmp	ITloop;

/*
 * DMA data transfer.  HADDR and HCNT must be loaded first, and
 * SINDEX should contain the value to load DFCNTRL with - 0x3d for
 * host->scsi, or 0x39 for scsi->host.  The SCSI channel is cleared
 * during initialization.
 */
dma:
	mov	DFCNTRL,SINDEX;
dma_loop:
	test	SSTAT0,DMADONE	jnz dma_dmadone;
	test	SSTAT1,PHASEMIS	jz dma_loop;	/* ie. underrun */
dma_phasemis:
	test	SSTAT0,SDONE	jnz dma_checkfifo;
	mov	SINDEX,ALLZEROS;		/* Notify caller of phasemiss */

/*
 * 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 the DMA enables off and make sure that the DMA enables are 
 * actually off first lest we get an ILLSADDR.
 */
dma_dmadone:
	and	DFCNTRL, ~(SCSIEN|SDMAEN|HDMAEN);
dma_halt:
	test	DFCNTRL, (SCSIEN|SDMAEN|HDMAEN)	jnz dma_halt; 
return:
	ret;

/*
 * Assert that if we've been reselected, then we've seen an IDENTIFY
 * message.
 */
assert:
	test	SEQ_FLAGS,RESELECTED	jz return;	/* reselected? */
	test	SEQ_FLAGS,IDENTIFY_SEEN	jnz return;	/* seen IDENTIFY? */

	mvi	INTSTAT,NO_IDENT 	ret;	/* no - tell the kernel */

/*
 * Locate a disconnected SCB either by SAVED_TCL (ARG_1 is SCB_LIST_NULL)
 * or by the SCBIDn ARG_1.  The search begins at the SCB index passed in
 * via SINDEX.  If the SCB cannot be found, SINDEX will be SCB_LIST_NULL,
 * otherwise, SCBPTR is set to the proper SCB.
 */
findSCB:
	mov	SCBPTR,SINDEX;			/* switch to next SCB */
	mov	A, ARG_1;			/* Tag passed in ARG_1 */
	cmp	SCB_TAG,A	jne findSCB_loop;
	test	SCB_CONTROL,DISCONNECTED jnz foundSCB;/*should be disconnected*/
findSCB_loop:
	inc	SINDEX;
	mov	A,SCBCOUNT;
	cmp	SINDEX,A	jne findSCB;
/*
 * We didn't find it.  If we're paging, pull an SCB and DMA down the
 * one we want.  If we aren't paging or the SCB we dma down has the
 * abort flag set, return not found.
 */
.if ( SCB_PAGING )
	mov	ALLZEROS	call	get_free_or_disc_scb;
	mvi	DMAPARAMS, HDMAEN|DIRECTION|FIFORESET;
	mov	ARG_1	call dma_scb;
	test	SCB_CONTROL, ABORT_SCB jz return;
.endif
find_error:
	mvi	SINDEX, SCB_LIST_NULL ret;
foundSCB:
	test	SCB_CONTROL, ABORT_SCB jnz find_error;
.if ( SCB_PAGING )
rem_scb_from_disc_list:
/* Remove this SCB from the disconnection list */
	cmp	SCB_NEXT,SCB_LIST_NULL je unlink_prev;
	mov	SAVED_LINKPTR, SCB_PREV;
	mov	SCBPTR, SCB_NEXT;
	mov	SCB_PREV, SAVED_LINKPTR;
	mov	SCBPTR, SINDEX;
unlink_prev:
	cmp	SCB_PREV,SCB_LIST_NULL	je rHead;/* At the head of the list */
	mov	SAVED_LINKPTR, SCB_NEXT;
	mov	SCBPTR, SCB_PREV;
	mov	SCB_NEXT, SAVED_LINKPTR;
	mov	SCBPTR, SINDEX ret;
rHead:
	mov	DISCONNECTED_SCBH,SCB_NEXT ret;
.else
	ret;
.endif

set_stcnt_from_hcnt:
	mov	STCNT[0], HCNT[0];
	mov	STCNT[1], HCNT[1];
	mov	STCNT[2], HCNT[2] ret;

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;

dma_scb:
	/*
	 * SCB index is in SINDEX.  Determine the physical address in
	 * the host where this SCB is located and load HADDR with it.
	 */
	shr	DINDEX, 3, SINDEX;
	shl	A, 5, SINDEX;
	add	HADDR[0], A, HSCB_ADDR[0];
	mov	A, DINDEX;
	adc	HADDR[1], A, HSCB_ADDR[1];
	clr	A;
	adc	HADDR[2], A, HSCB_ADDR[2];
	adc	HADDR[3], A, HSCB_ADDR[3];
	/* Setup Count */
	mvi	HCNT[0], 28;
	clr	HCNT[1];
	clr	HCNT[2];
	mov	DFCNTRL, DMAPARAMS;
	test	DMAPARAMS, DIRECTION	jnz dma_scb_fromhost;
	/* Fill it with the SCB data */
	call	copy_scb_tofifo;
	or	DFCNTRL, HDMAEN|FIFOFLUSH;
dma_scb_fromhost:
	call	dma_finish;
	/* If we were putting the SCB, we are done */
	test	DMAPARAMS, DIRECTION	jz	return;
	mvi	SCB_CONTROL  call dfdat_in_7;
	call	dfdat_in_7_continued;
	call	dfdat_in_7_continued;
	jmp	dfdat_in_7_continued;
dfdat_in_7:
	mov     DINDEX,SINDEX;
dfdat_in_7_continued:
	mov	DINDIR,DFDAT;
	mov	DINDIR,DFDAT;
	mov	DINDIR,DFDAT;
	mov	DINDIR,DFDAT;
	mov	DINDIR,DFDAT;
	mov	DINDIR,DFDAT;
	mov	DINDIR,DFDAT ret;

copy_scb_tofifo:
	mvi	SCB_CONTROL call dfdat_out_7;
	call	dfdat_out_7;
	call	dfdat_out_7;
dfdat_out_7:
	mov	DFDAT,SINDIR;
	mov	DFDAT,SINDIR;
	mov	DFDAT,SINDIR;
	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;
	/* Turn off DMA */
	and	DFCNTRL, ~HDMAEN;
	test	DFCNTRL, HDMAEN jnz .;
	ret;

index_untagged_scb:
	mov	DINDEX, SINDEX;
	shr	DINDEX, 4;
	and	DINDEX, 0x03;			/* Bottom two bits of tid */
	add	DINDEX, SCB_BUSYTARGETS;
	shr	A, 6, SINDEX;			/* Target ID divided by 4 */
	test	SINDEX, SELBUSB jz index_untagged_scb2;
	add	A, 2;				/* Add 2 positions */
index_untagged_scb2:
	mov	SCBPTR, A;			/*
						 * Select the SCB with this 
						 * target's information.
						 */
	mov	SINDEX, DINDEX	ret;

add_scb_to_free_list:
	mov	SCB_NEXT, FREE_SCBH;
	mvi	SCB_TAG, SCB_LIST_NULL;
	mov	FREE_SCBH, SCBPTR ret;

.if ( SCB_PAGING )
get_free_or_disc_scb:
	cmp	FREE_SCBH, SCB_LIST_NULL jne dequeue_free_scb;
	cmp	DISCONNECTED_SCBH, SCB_LIST_NULL jne dequeue_disc_scb;
return_error:
	mvi	SINDEX, SCB_LIST_NULL	ret;
dequeue_disc_scb:
	mov	SCBPTR, DISCONNECTED_SCBH;
/*
 * If we have a residual, then we are in the middle of some I/O
 * and we have to send this SCB back up to the kernel so that the
 * saved data pointers and residual information isn't lost.
 */
	test	SCB_RESID_SGCNT,0xff	jnz dma_up_scb;
	cmp	SCB_LINKED_NEXT, SCB_LIST_NULL je unlink_disc_scb;
dma_up_scb:
	mvi	DMAPARAMS, FIFORESET;
	mov	SCB_TAG		call dma_scb;
unlink_disc_scb:
	/* jmp instead of call since we want to return anyway */
	mov	SCBPTR	jmp rem_scb_from_disc_list;
dequeue_free_scb:
	mov	SCBPTR, FREE_SCBH;
	mov	FREE_SCBH, SCB_NEXT ret;

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.
 */
	mvi	SCB_PREV, SCB_LIST_NULL;
	mov	SCB_NEXT, DISCONNECTED_SCBH;
	mov	DISCONNECTED_SCBH, SCBPTR;
	cmp	SCB_NEXT,SCB_LIST_NULL je return;
	mov	SCBPTR,SCB_NEXT;
	mov	SCB_PREV,DISCONNECTED_SCBH;
	mov	SCBPTR,DISCONNECTED_SCBH ret;
.endif