/*+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 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************************************************************************/

VERSION AIC7XXX_SEQ_VER "$Id: aic7xxx.seq,v 1.35 1996/05/21 18:32:22 gibbs Exp $"

#include "../../dev/aic7xxx/aic7xxx_reg.h"

/*
 * We can't just use ACCUM in the sequencer code because it
 * must be treated specially by the assembler, and it currently
 * looks for the symbol 'A'.  This is the only register defined in
 * the assembler's symbol space.
 */
A = ACCUM

/* 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 offsets, 
 * SCB_LIST_NULL is 0xff which is out of range.  The kernel driver must
 * add an entry to this list everytime a request sense occurs.  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	DFCNTRL
	clr	SCSISIGO		/* De-assert BSY */
/*
 * We jump to start after every bus free.
 */
start:
	and	FLAGS,0x0f		/* clear target specific flags */
	mvi	SCSISEQ,ENRSELI		/* Always allow reselection */
poll_for_work:
	/*
	 * Are we a twin channel device?
	 * For fairness, we check the other bus first,
	 * since we just finished a transaction on the
	 * current channel.
	 */
	test	FLAGS,TWIN_BUS	jz start2
	xor	SBLKCTL,SELBUSB			/* Toggle to the other bus */
	test	SSTAT0,SELDI	jnz reselect
	xor	SBLKCTL,SELBUSB			/* Toggle to the original bus */
start2:
	test	SSTAT0,SELDI	jnz reselect
	cmp	WAITING_SCBH,SCB_LIST_NULL jne start_waiting
	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.  Set the SCB
 * pointer from the FIFO so we see the right bank of SCB 
 * registers.
 */
	mov	SCBPTR,QINFIFO

/*
 * 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.  It may be benificial to make findscb a more general procedure
 * to see if the added cost of the search is negligible.  This code also 
 * assumes that the kernel driver will clear the active flags on board 
 * initialization, board reset, and a target SELTO.  Tagged commands
 * don't set the active bits since you can queue more than one command
 * at a time.  We do, however, look to see if there are any non-tagged
 * I/Os in progress, and requeue the command if there are.  Tagged and
 * non-tagged commands cannot be mixed to a single target.
 */

test_busy:
	mov	FUNCTION1,SCB_TCL
	mov	A,FUNCTION1
	test	SCB_TCL,0x88	jz test_a	/* Id < 8 && A channel */

	test	ACTIVE_B,A	jnz requeue
	test	SCB_CONTROL,TAG_ENB	jnz start_scb
	/* Mark the current target as busy */
	or	ACTIVE_B,A
	jmp	start_scb

/* Place the currently active SCB back on the queue for later processing */
requeue:
	mov	QINFIFO, SCBPTR
	jmp	poll_for_work

/*
 * Pull the first entry off of the waiting for selection list
 * We don't have to "test_busy" because only transactions that
 * have passed that test can be in the waiting_scb list.
 */
start_waiting:
	mov	SCBPTR,WAITING_SCBH
	jmp	start_scb2

test_a:
	test	ACTIVE_A,A jnz requeue
	test	SCB_CONTROL,TAG_ENB jnz start_scb
	/* Mark the current target as busy */
	or	ACTIVE_A,A

start_scb:
	mov	SCB_NEXT,WAITING_SCBH
	mov	WAITING_SCBH, SCBPTR
start_scb2:
	and	SINDEX,0xf7,SBLKCTL	/* Clear the channel select bit */
	and	A,0x08,SCB_TCL		/* Get new channel bit */
	or	SINDEX,A
	mov	SBLKCTL,SINDEX		/* select channel */
	mov	SCB_TCL	call initialize_scsiid

/*
 * Enable selection phase as an initiator, and do automatic ATN
 * after the selection.  We do this now so that we can overlap the
 * rest of our work to set up this target with the arbitration and
 * selection bus phases.
 */
start_selection:
	mvi	SCSISEQ,0x58		/* ENSELO|ENAUTOATNO|ENRSELI */

/*
 * 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.
 */
	test	SCB_CMDLEN,0xff jnz mk_identify	/* 0 Length Command? */

/*
 * The kernel has sent us an SCB with no command attached.  This implies
 * that the kernel wants to send a message of some sort to this target,
 * so we interrupt the driver, allow it to fill the message buffer, and
 * then go back into the arbitration loop
 */
	mvi     INTSTAT,AWAITING_MSG
	jmp     wait_for_selection

mk_identify:
	and	A,DISCENB,SCB_CONTROL	/* mask off disconnect privledge */

	and	MSG0,0x7,SCB_TCL	/* lun */
	or	MSG0,A			/* or in disconnect privledge */
	or	MSG0,MSG_IDENTIFY
	mvi	MSG_LEN, 1

	test	SCB_CONTROL,0xb0 jz  !message	/* WDTR, SDTR or TAG?? */
/*
 * 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:
	mvi	DINDEX, MSG1
	test	SCB_CONTROL,TAG_ENB jz mk_tag_done
	and	DINDIR,0x23,SCB_CONTROL
	mov	DINDIR,SCB_TAG

	add	MSG_LEN,COMP_MSG0,DINDEX	/* update message length */

mk_tag_done:

	test	SCB_CONTROL,0x90 jz !message	/* NEEDWDTR|NEEDSDTR */
	mov	DINDEX	call mk_dtr	/* build DTR message if needed */

!message:
wait_for_selection:
	test	SSTAT0,SELDO	jnz select 
	test	SSTAT0,SELDI	jz wait_for_selection

/*
 * 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.
 */
reselect:
	clr	MSG_LEN		/* Don't have anything in the mesg buffer */
	mov	SELID		call initialize_scsiid
	or	FLAGS,RESELECTED
	jmp	select2

/*
 * After the selection, remove this SCB from the "waiting for selection"
 * 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:
	mov	WAITING_SCBH,SCB_NEXT
	or	FLAGS,SELECTED
select2:
/*
 * Set CLRCHN here before the target has entered a data transfer mode -
 * with synchronous SCSI, if you do it later, you blow away some
 * data in the SCSI FIFO that the target has already sent to you.
 */
	or	SXFRCTL0,CLRCHN
/*
 * Initialize SCSIRATE with the appropriate value for this target.
 */
	call	ndx_dtr
	mov	SCSIRATE,SINDIR

/*
 * Initialize Ultra mode setting.
 */
	mov	FUNCTION1,SCSIID
	mov	A,FUNCTION1
	and	SINDEX,0xdf,SXFRCTL0		/* default to Ultra disabled */
	test	SCSIID, 0x80	 jnz ultra_b	/* Target ID > 7 */
	test	SBLKCTL, SELBUSB jnz ultra_b	/* Second channel device */
	test	ULTRA_ENB,A	 jz  set_sxfrctl0
	or	SINDEX, ULTRAEN  jmp set_sxfrctl0
ultra_b:
	test	ULTRA_ENB_B,A	 jz  set_sxfrctl0
	or	SINDEX, ULTRAEN

set_sxfrctl0:
	mov	SXFRCTL0,SINDEX

	mvi	SCSISEQ,ENAUTOATNP		/*
						 * ATN on parity errors
						 * for "in" phases
						 */
	mvi	CLRSINT1,CLRBUSFREE
	mvi	CLRSINT0,0x60			/* CLRSELDI|CLRSELDO */
/*
 * 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,BUSFREE	jnz p_busfree
	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. */

p_dataout:
	mvi	DMAPARAMS,0x7d			/*
						 * 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:
	mov	STCNT0,SCB_RESID_DCNT0
	mov	STCNT1,SCB_RESID_DCNT1
	mov	STCNT2,SCB_RESID_DCNT2
	jmp	data_phase_loop

p_datain:
	mvi	DMAPARAMS,0x79		/*
					 * WIDEODD|SCSIEN|SDMAEN|HDMAEN|
					 * !DIRECTION|FIFORESET
					 */
data_phase_init:
	call	assert

	test	FLAGS, DPHASE	jnz data_phase_reinit
	call	sg_scb2ram
	or	FLAGS, DPHASE		/* We have seen a data phase */

data_phase_loop:
/* If we are the last SG block, don't set wideodd. */
	cmp	SG_COUNT,0x01 jne data_phase_wideodd
	and	DMAPARAMS, 0xbf		/* Turn off WIDEODD */
data_phase_wideodd:
	mov	DMAPARAMS  call dma

/* Exit if we had an underrun */
	test	SSTAT0,SDONE	jz data_phase_finish /* underrun STCNT != 0 */

/*
 * 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_NEXT0,SG_SIZEOF,SG_NEXT0
	adc	SG_NEXT1,A,SG_NEXT1

/*
 * 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:
	clr	HCNT2
	clr	HCNT1
	mvi	HCNT0,SG_SIZEOF

	mov	HADDR0,SG_NEXT0
	mov	HADDR1,SG_NEXT1
	mov	HADDR2,SG_NEXT2
	mov	HADDR3,SG_NEXT3

	or	DFCNTRL,0xd			/* HDMAEN|DIRECTION|FIFORESET */

/*
 * 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 preserving WIDEODD */
	and	DFCNTRL,WIDEODD
dma_finish2:
	test	DFCNTRL,HDMAENACK jnz dma_finish2

/*
 * Copy data from FIFO into SCB data pointer and data count.  This assumes
 * that the struct scatterlist has this structure (this and sizeof(struct
 * scatterlist) == 12 are asserted in aic7xxx.c for the Linux driver):
 *
 *	struct scatterlist {
 *		char *address;		four bytes, little-endian order
 *		...			four bytes, ignored
 *		unsigned short length;	two bytes, little-endian order
 *	}
 *
 *
 * In FreeBSD, the scatter list entry is only 8 bytes.
 * 
 * struct ahc_dma_seg {
 *       physaddr addr;                  four bytes, little-endian order
 *       long    len;                    four bytes, little endian order
 * };
 */

	mov	HADDR0,DFDAT
	mov	HADDR1,DFDAT
	mov	HADDR2,DFDAT
	mov	HADDR3,DFDAT
/*
 * For Linux, we must throw away four bytes since there is a 32bit gap
 * in the middle of a struct scatterlist.
 */
#ifdef __linux__
	mov	NONE,DFDAT
	mov	NONE,DFDAT
	mov	NONE,DFDAT
	mov	NONE,DFDAT
#endif
	mov	HCNT0,DFDAT
	mov	HCNT1,DFDAT
	mov	HCNT2,DFDAT

/* Load STCNT as well.  It is a mirror of HCNT */
	mov	STCNT0,HCNT0
	mov	STCNT1,HCNT1
	mov	STCNT2,HCNT2
        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_DCNT0,STCNT0
	mov	SCB_RESID_DCNT1,STCNT1
	mov	SCB_RESID_DCNT2,STCNT2
	mov	SCB_RESID_SGCNT, SG_COUNT
	jmp	ITloop

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

/*
 * Load HADDR and HCNT.
 */
	mov	HADDR0, SCB_CMDPTR0
	mov	HADDR1, SCB_CMDPTR1
	mov	HADDR2, SCB_CMDPTR2
	mov	HADDR3, SCB_CMDPTR3
	mov	HCNT0, SCB_CMDLEN
	clr	HCNT1
	clr	HCNT2

	mov	STCNT0, HCNT0
	mov	STCNT1, HCNT1
	mov	STCNT2, HCNT2

	mvi	0x3d		call dma	# SCSIEN|SDMAEN|HDMAEN|
						#   DIRECTION|FIFORESET
	jmp	ITloop

/*
 * Status phase.  Wait for the data byte to appear, then read it
 * and store it into the SCB.
 */
p_status:
	mvi	SCB_TARGET_STATUS	call inb_first
	jmp	mesgin_done

/*
 * 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_NOP		call mk_mesg	/* build NOP message */

p_mesgout_start:
/*
 * Set up automatic PIO transfer from MSG0.  Bit 3 in
 * SXFRCTL0 (SPIOEN) is already on.
 */
	mvi	SINDEX,MSG0
	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.
 *
 * Keep an eye out for a phase change, in case the target issues
 * a MESSAGE REJECT.
 */
p_mesgout_loop:
	test	SSTAT1,PHASEMIS	jnz p_mesgout_phasemis
	test	SSTAT0,SPIORDY	jz p_mesgout_loop
	cmp	DINDEX,1	jne p_mesgout_outb	/* last byte? */
	mvi	CLRSINT1,CLRATNO			/* drop ATN */
p_mesgout_outb:
	dec	DINDEX
	or	CLRSINT0, CLRSPIORDY
	mov	SCSIDATL,SINDIR
	
p_mesgout4:
	test	DINDEX,0xff	jnz p_mesgout_loop

/*
 * 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_snoop:
	test	SSTAT1,BUSFREE	jnz p_mesgout_done
	test	SSTAT1,REQINIT	jz p_mesgout_snoop

	test	SSTAT1,PHASEMIS	jnz p_mesgout_done

	or	SCSISIGO,ATNO			/* turn on ATNO */

	jmp	ITloop

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

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

	test	A,MSG_IDENTIFY		jnz mesgin_identify
	cmp	A,MSG_DISCONNECT	je mesgin_disconnect
	cmp	A,MSG_SDPTRS		je mesgin_sdptrs
	cmp	ALLZEROS,A		je mesgin_complete
	cmp	A,MSG_RDPTRS		je mesgin_rdptrs
	cmp	A,MSG_EXTENDED		je mesgin_extended
	cmp	A,MSG_REJECT		je mesgin_reject

rej_mesgin:
/*
 * We have no idea what this message in is, and there's no way
 * to pass it up to the kernel, so we issue a message reject and
 * hope for the best.  Since we're now using manual PIO mode to
 * read in the message, there should no longer be a race condition
 * present when we assert ATN.  In any case, rejection should be a
 * rare occurrence - signal the driver when it happens.
 */
	or	SCSISIGO,ATNO			/* turn on ATNO */
	mvi	INTSTAT,SEND_REJECT		/* let driver know */

	mvi	MSG_REJECT	call mk_mesg

mesgin_done:
	call	inb_last			/*ack & turn auto PIO back on*/
	jmp	ITloop


mesgin_complete:
/*
 * We got a "command complete" message, so put the SCB_TAG into QUEUEOUT,
 * and trigger a completion interrupt.  Check status for non zero return
 * and interrupt driver if needed.  This allows the driver to interpret
 * errors only when they occur instead of always uploading the scb.  If
 * the status is SCSI_CHECK, the driver will download a new scb requesting
 * sense to replace the old one, modify the "waiting for selection" SCB list
 * and set RETURN_1 to SEND_SENSE.  If RETURN_1 is set to SEND_SENSE the
 * sequencer imediately jumps to main loop where it will run down the waiting
 * SCB list and process the sense request.  If the kernel driver does not
 * wish to request sense, it need only clear RETURN_1, and the command is
 * allowed to complete.  We don't bother to post to the QOUTFIFO in the
 * error case 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	jz check_status
/*
 * If we have a residual count, interrupt and tell the host.  Other
 * alternatives are to pause the sequencer on all command completes (yuck),
 * dma the resid directly to the host (slick, we may have space to do it now)
 * or have the sequencer pause itself when it encounters a non-zero resid 
 * (unecessary pause just to flag the command -yuck-, but takes one instruction
 * and since it shouldn't happen that often is good enough for our purposes).  
 */
resid:
	mvi	INTSTAT,RESIDUAL

check_status:
	test	SCB_TARGET_STATUS,0xff	jz status_ok	/* Good Status? */
	mvi	INTSTAT,BAD_STATUS			/* let driver know */
	cmp	RETURN_1, SEND_SENSE	jne status_ok
	jmp	mesgin_done

status_ok:
/* First, mark this target as free. */
	test	SCB_CONTROL,TAG_ENB jnz test_immediate	/*
							 * Tagged commands
							 * don't busy the
							 * target.
							 */
	mov	FUNCTION1,SCB_TCL
	mov	A,FUNCTION1
	test	SCB_TCL,0x88 jz clear_a
	xor	ACTIVE_B,A
	jmp	test_immediate

clear_a:
	xor	ACTIVE_A,A

test_immediate:
	test    SCB_CMDLEN,0xff jnz complete  /* Immediate message complete */
/*
 * Pause the sequencer until the driver gets around to handling the command
 * complete.  This is so that any action that might require carefull timing
 * with the completion of this command can occur.
 */
	mvi	INTSTAT,IMMEDDONE
	jmp	start
complete:
	mov	QOUTFIFO,SCB_TAG
	mvi	INTSTAT,CMDCMPLT
	jmp	mesgin_done


/*
 * Is it an extended message?  We only support the synchronous and wide data
 * transfer request messages, which will probably be in response to
 * WDTR or SDTR message outs from us.  If it's not SDTR or WDTR, reject it -
 * apparently this can be done after any message in byte, according
 * to the SCSI-2 spec.
 */
mesgin_extended:
	mvi	ARG_1		call inb_next	/* extended message length */
	mvi	REJBYTE_EXT	call inb_next	/* extended message code */

	cmp	REJBYTE_EXT,MSG_SDTR	je p_mesginSDTR
	cmp	REJBYTE_EXT,MSG_WDTR	je p_mesginWDTR
	jmp	rej_mesgin

p_mesginWDTR:
	cmp	ARG_1,2		jne rej_mesgin	/* extended mesg length=2 */
	mvi	ARG_1		call inb_next	/* Width of bus */
	mvi	INTSTAT,WDTR_MSG		/* let driver know */
	test	RETURN_1,0xff jz mesgin_done	/* Do we need to send WDTR? */
	cmp	RETURN_1,SEND_REJ je rej_mesgin /*
						 * Bus width was too large 
						 * Reject it.
						 */

/* We didn't initiate the wide negotiation, so we must respond to the request */
	and	RETURN_1,0x7f			/* Clear the SEND_WDTR Flag */
	mvi	DINDEX,MSG0
	mvi	MSG0	call mk_wdtr		/* build WDTR message */
	or	SCSISIGO,ATNO			/* turn on ATNO */
	jmp	mesgin_done

p_mesginSDTR:
	cmp	ARG_1,3		jne rej_mesgin	/* extended mesg length=3 */
	mvi	ARG_1		call inb_next	/* xfer period */
	mvi	A		call inb_next	/* REQ/ACK offset */
	mvi	INTSTAT,SDTR_MSG		/* call driver to convert */

	test	RETURN_1,0xff	jz mesgin_done  /* Do we need to mk_sdtr/rej */
	cmp	RETURN_1,SEND_REJ je rej_mesgin /*
						 * Requested SDTR too small
						 * Reject it.
						 */
	clr	ARG_1				/* Use the scratch ram rate */
	mvi	DINDEX, MSG0
	mvi     MSG0     call mk_sdtr
	or	SCSISIGO,ATNO			/* 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
	test	FLAGS, PAGESCBS jz mesgin_done
/*
 * 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
	mvi	SEQCTL,0x50			/* PAUSEDIS|FASTMODE */
	mov	SCB_NEXT, DISCONNECTED_SCBH
	mov	DISCONNECTED_SCBH, SCBPTR
	cmp	SCB_NEXT,SCB_LIST_NULL je linkdone
	mov	SCBPTR,SCB_NEXT
	mov	SCB_PREV,DISCONNECTED_SCBH
	mov	SCBPTR,DISCONNECTED_SCBH
linkdone:
	mvi	SEQCTL,0x10			/* !PAUSEDIS|FASTMODE */
	jmp	mesgin_done

/*
 * Save data pointers message?  Copy working values into the SCB,
 * usually in preparation for a disconnect.
 */
mesgin_sdptrs:
	call	sg_ram2scb
	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	FLAGS,0xef			/*
						 * !DPHASE we'll reload them
						 * the next time through
						 */
	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,SELID          
	and     SAVED_TCL,0xf7
	and     A,SELBUSB,SBLKCTL	/* B Channel?? */
	or      SAVED_TCL,A
	call	inb_last		/* ACK */

/*
 * Here we "snoop" the bus looking for a SIMPLE QUEUE TAG message.
 * If we get one, we use the tag returned to switch 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.
 */
	mvi	ARG_1,SCB_LIST_NULL	/* Default to no-tag */
snoop_tag_loop:
	test	SSTAT1,BUSFREE	jnz use_findSCB
	test	SSTAT1,REQINIT	jz snoop_tag_loop
	test	SSTAT1,PHASEMIS	jnz use_findSCB
	mvi	A		call inb_first
	cmp	A,MSG_SIMPLE_TAG jne use_findSCB
get_tag:
	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	abort_tag

/*
 * Ensure that the SCB the tag points to is for an SCB transaction
 * to the reconnecting target.
 */
	test	FLAGS, PAGESCBS	jz index_by_tag
	call	inb_last			/* Ack Tag */
use_findSCB:
	mov	ALLZEROS	call findSCB	  /* Have to search */
setup_SCB:
	and	SCB_CONTROL,0xfb	  /* clear disconnect bit in SCB */
	or	FLAGS,IDENTIFY_SEEN	  /* make note of IDENTIFY */
	jmp	ITloop
index_by_tag:
	mov	SCBPTR,ARG_1
	mov	A,SAVED_TCL
	cmp	SCB_TCL,A		jne abort_tag
	test	SCB_CONTROL,TAG_ENB	jz  abort_tag
	call	inb_last			/* Ack Successful tag */
	jmp	setup_SCB

abort_tag:
	or	SCSISIGO,ATNO			/* turn on ATNO */
	mvi	INTSTAT,ABORT_TAG 		/* let driver know */
	mvi	MSG_ABORT_TAG	call mk_mesg	/* ABORT TAG message */
	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 ]
 */

/*
 * Bus free phase.  It might be useful to interrupt the device
 * driver if we aren't expecting this.  For now, make sure that
 * ATN isn't being asserted and look for a new command.
 */
p_busfree:
	mvi	CLRSINT1,CLRATNO
	clr	LASTPHASE

/*
 * if this is an immediate command, perform a psuedo command complete to
 * notify the driver.
 */
	test	SCB_CMDLEN,0xff	jz status_ok
	jmp	start

/*
 * 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,0x50			/* 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,0x10			/* !PAUSEDIS|FASTMODE */
	mvi	INTSTAT,MSG_BUFFER_BUSY

mk_mesg1:
	mvi	MSG_LEN,1		/* length = 1 */
	mov	MSG0,SINDEX		/* 1-byte message */
	mvi	SEQCTL,0x10	ret	/* !PAUSEDIS|FASTMODE */

/*
 * 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:
	or	CLRSINT0, CLRSPIORDY
	mov	NONE,SCSIDATL			/*dummy read from latch to ACK*/
inb_next_wait:
	test	SSTAT1,PHASEMIS	jnz mesgin_phasemis
	test	SSTAT0,SPIORDY	jz inb_next_wait /* wait for next byte */
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
dma1:
	test	SSTAT0,DMADONE	jnz dma3
	test	SSTAT1,PHASEMIS	jz dma1		/* ie. underrun */

/*
 * 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.
 */
dma3:
	test	SINDEX,DIRECTION	jnz dma5
dma4:
	test	DFSTATUS,FIFOEMP	jz dma4

/*
 * Now shut the DMA enables off and make sure that the DMA enables are 
 * actually off first lest we get an ILLSADDR.
 */
dma5:
	/* disable DMA, but maintain WIDEODD */
	and	DFCNTRL,WIDEODD
dma6:
	test	DFCNTRL,0x38	jnz dma6  /* SCSIENACK|SDMAENACK|HDMAENACK */

	ret

/*
 * Common SCSI initialization for selection and reselection.  Expects
 * the target SCSI ID to be in the upper four bits of SINDEX, and A's
 * contents are stomped on return.
 */
initialize_scsiid:
	and	SINDEX,0xf0		/* Get target ID */
	and	A,0x0f,SCSIID
	or	SINDEX,A
	mov	SCSIID,SINDEX ret

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

	mvi	INTSTAT,NO_IDENT 	ret	/* no - cause a kernel panic */

/*
 * Locate the SCB matching the target ID/channel/lun in SAVED_TCL, and the tag
 * value in ARG_1.  If ARG_1 == SCB_LIST_NULL, we're looking for a non-tagged
 * SCB.  Have the kernel print a warning message if it can't be found, and
 * generate an ABORT/ABORT_TAG message to the target.  SINDEX should be
 * cleared on call.
 */
findSCB:
	mov	A,SAVED_TCL
	mov	SCBPTR,SINDEX			/* switch to next SCB */
	mvi	SEQCTL,0x50			/* PAUSEDIS|FASTMODE */
	cmp	SCB_TCL,A	jne findSCB1 /* target ID/channel/lun match? */
	test	SCB_CONTROL,DISCONNECTED jz findSCB1 /*should be disconnected*/
	test	SCB_CONTROL,TAG_ENB jnz findTaggedSCB
	cmp	ARG_1,SCB_LIST_NULL je foundSCB
	jmp	findSCB1
findTaggedSCB:
	mov	A, ARG_1			/* Tag passed in ARG_1 */
	cmp	SCB_TAG,A	jne findSCB1	/* Found it? */
foundSCB:
	test	FLAGS,PAGESCBS	jz foundSCB_ret
/* 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
	mvi	SEQCTL,0x10	ret		/* !PAUSEDIS|FASTMODE */
rHead:
	mov	DISCONNECTED_SCBH,SCB_NEXT
foundSCB_ret:
	mvi	SEQCTL,0x10	ret		/* !PAUSEDIS|FASTMODE */

findSCB1:
	mvi	SEQCTL,0x10			/* !PAUSEDIS|FASTMODE */
	inc	SINDEX
	mov	A,SCBCOUNT
	cmp	SINDEX,A	jne findSCB

	mvi	INTSTAT,NO_MATCH		/* not found - signal kernel */
	cmp	RETURN_1,SCB_PAGEDIN je return
	or	SCSISIGO,ATNO			/* assert ATNO */
	cmp	ARG_1,SCB_LIST_NULL jne find_abort_tag
	mvi	MSG_ABORT	call mk_mesg
	jmp	ITloop
find_abort_tag:
	mvi	MSG_ABORT_TAG	call mk_mesg
	jmp	ITloop

/*
 * Make a working copy of the scatter-gather parameters from the SCB.
 */
sg_scb2ram:
	mov	HADDR0, SCB_DATAPTR0
	mov	HADDR1, SCB_DATAPTR1
	mov	HADDR2, SCB_DATAPTR2
	mov	HADDR3, SCB_DATAPTR3
	mov	HCNT0, SCB_DATACNT0
	mov	HCNT1, SCB_DATACNT1
	mov	HCNT2, SCB_DATACNT2

	mov	STCNT0, HCNT0
	mov	STCNT1, HCNT1
	mov	STCNT2, HCNT2

	mov	SG_COUNT,SCB_SGCOUNT

	mov	SG_NEXT0, SCB_SGPTR0
	mov	SG_NEXT1, SCB_SGPTR1
	mov	SG_NEXT2, SCB_SGPTR2
	mov	SG_NEXT3, SCB_SGPTR3 ret

/*
 * 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.
 */
sg_ram2scb:
	test	FLAGS, DPHASE	jz return
	mov	SCB_SGCOUNT,SG_COUNT

	mov	SCB_SGPTR0,SG_NEXT0
	mov	SCB_SGPTR1,SG_NEXT1
	mov	SCB_SGPTR2,SG_NEXT2
	mov	SCB_SGPTR3,SG_NEXT3
	
	mov	SCB_DATAPTR0,SHADDR0
	mov	SCB_DATAPTR1,SHADDR1
	mov	SCB_DATAPTR2,SHADDR2
	mov	SCB_DATAPTR3,SHADDR3

/*
 * Use the residual number since STCNT is corrupted by any message transfer
 */
	mov	SCB_DATACNT0,SCB_RESID_DCNT0
	mov	SCB_DATACNT1,SCB_RESID_DCNT1
	mov	SCB_DATACNT2,SCB_RESID_DCNT2 ret

/*
 * Add the array base TARG_SCRATCH to the target offset (the target address
 * is in SCSIID), and return the result in SINDEX.  The accumulator
 * contains the 3->8 decoding of the target ID on return.
 */
ndx_dtr:
	shr	A,SCSIID,4
	test	SBLKCTL,SELBUSB	jz ndx_dtr_2
	or	A,0x08		/* Channel B entries add 8 */
ndx_dtr_2:
	add	SINDEX,TARG_SCRATCH,A ret

/*
 * If we need to negotiate transfer parameters, build the WDTR or SDTR message
 * starting at the address passed in SINDEX.  DINDEX is modified on return.
 * The SCSI-II spec requires that Wide negotiation occur first and you can
 * only negotiat one or the other at a time otherwise in the event of a message
 * reject, you wouldn't be able to tell which message was the culpret.
 */
mk_dtr:
	test	SCB_CONTROL,NEEDWDTR jnz  mk_wdtr_16bit
	mvi	ARG_1, MAXOFFSET	/* Force an offset of 15 or 8 if WIDE */

mk_sdtr:
	mvi	DINDIR,1		/* extended message */
	mvi	DINDIR,3		/* extended message length = 3 */
	mvi	DINDIR,1		/* SDTR code */
	call	sdtr_to_rate
	mov	DINDIR,RETURN_1		/* REQ/ACK transfer period */
	cmp	ARG_1, MAXOFFSET je mk_sdtr_max_offset
	and	DINDIR,0x0f,SINDIR	/* Sync Offset */

mk_sdtr_done:
	add	MSG_LEN,COMP_MSG0,DINDEX ret	/* update message length */

mk_sdtr_max_offset:
/*
 * We're initiating sync negotiation, so request the max offset we can (15 or 8)
 */
	/* Talking to a WIDE device? */
	test	SCSIRATE, WIDEXFER	jnz wmax_offset	
	mvi	DINDIR, MAX_OFFSET_8BIT
	jmp	mk_sdtr_done

wmax_offset:
	mvi	DINDIR, MAX_OFFSET_16BIT
	jmp	mk_sdtr_done

mk_wdtr_16bit:
	mvi	ARG_1,BUS_16_BIT
mk_wdtr:
	mvi	DINDIR,1		/* extended message */
	mvi	DINDIR,2		/* extended message length = 2 */
	mvi	DINDIR,3		/* WDTR code */
	mov	DINDIR,ARG_1		/* bus width */

	add	MSG_LEN,COMP_MSG0,DINDEX ret	/* update message length */
	
sdtr_to_rate:
	call	ndx_dtr			/* index scratch space for target */
	shr	A,SINDIR,0x4
	dec	SINDEX			/* Preserve SINDEX */
	and	A,0x7
	clr	RETURN_1
sdtr_to_rate_loop:
	test	A,0x0f	jz sdtr_to_rate_done
	add	RETURN_1,0x19
	dec	A	
	jmp	sdtr_to_rate_loop
sdtr_to_rate_done:
	shr	RETURN_1,0x2
	add	RETURN_1,0x19
	test	SXFRCTL0,ULTRAEN jz return
	shr	RETURN_1,0x1
return:
	ret