atari_ncr5380.c

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     * If SCSI-II tagged queuing is enabled, we also send a SIMPLE_QUEUE_TAG
     * message (2 bytes) with a tag ID that we increment with every command
     * until it wraps back to 0.
     *
     * XXX - it turns out that there are some broken SCSI-II devices,
     *	     which claim to support tagged queuing but fail when more than
     *	     some number of commands are issued at once.
     */

    /* Wait for start of REQ/ACK handshake */
    while (!(NCR5380_read(STATUS_REG) & SR_REQ));

    SEL_PRINTK("scsi%d: target %d selected, going into MESSAGE OUT phase.\n",
	       HOSTNO, cmd->target);
    tmp[0] = IDENTIFY(1, cmd->lun);

#ifdef SUPPORT_TAGS
    if (cmd->tag != TAG_NONE) {
	tmp[1] = hostdata->last_message = SIMPLE_QUEUE_TAG;
	tmp[2] = cmd->tag;
	len = 3;
    } else 
	len = 1;
#else
    len = 1;
    cmd->tag=0;
#endif /* SUPPORT_TAGS */

    /* Send message(s) */
    data = tmp;
    phase = PHASE_MSGOUT;
    NCR5380_transfer_pio(instance, &phase, &len, &data);
    SEL_PRINTK("scsi%d: nexus established.\n", HOSTNO);
    /* XXX need to handle errors here */
    hostdata->connected = cmd;
#ifndef SUPPORT_TAGS
    hostdata->busy[cmd->target] |= (1 << cmd->lun);
#endif    

    initialize_SCp(cmd);


    return 0;
}

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

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

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

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

    NCR5380_write(TARGET_COMMAND_REG, PHASE_SR_TO_TCR(p));

    do {
	/* 
	 * Wait for assertion of REQ, after which the phase bits will be 
	 * valid 
	 */
	while (!((tmp = NCR5380_read(STATUS_REG)) & SR_REQ));

	HSH_PRINTK("scsi%d: REQ detected\n", HOSTNO);

	/* Check for phase mismatch */	
	if ((tmp & PHASE_MASK) != p) {
	    PIO_PRINTK("scsi%d: phase mismatch\n", HOSTNO);
	    NCR_PRINT_PHASE(NDEBUG_PIO);
	    break;
	}

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

	++d;

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

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

	while (NCR5380_read(STATUS_REG) & SR_REQ);

	HSH_PRINTK("scsi%d: req false, handshake complete\n", HOSTNO);

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

    PIO_PRINTK("scsi%d: residual %d\n", HOSTNO, c);

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

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

/*
 * Function : do_abort (Scsi_Host *host)
 * 
 * Purpose : abort the currently established nexus.  Should only be 
 * 	called from a routine which can drop into a 
 * 
 * Returns : 0 on success, -1 on failure.
 */

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

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

    /* 
     * Wait for the target to indicate a valid phase by asserting 
     * REQ.  Once this happens, we'll have either a MSGOUT phase 
     * and can immediately send the ABORT message, or we'll have some 
     * other phase and will have to source/sink data.
     * 
     * We really don't care what value was on the bus or what value
     * the target sees, so we just handshake.
     */
    
    while (!(tmp = NCR5380_read(STATUS_REG)) & SR_REQ);

    NCR5380_write(TARGET_COMMAND_REG, PHASE_SR_TO_TCR(tmp));

    if ((tmp & PHASE_MASK) != PHASE_MSGOUT) {
	NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_ATN | 
		      ICR_ASSERT_ACK);
	while (NCR5380_read(STATUS_REG) & SR_REQ);
	NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_ATN);
    }
   
    tmp = ABORT;
    msgptr = &tmp;
    len = 1;
    phase = PHASE_MSGOUT;
    NCR5380_transfer_pio (host, &phase, &len, &msgptr);

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

    return len ? -1 : 0;
}

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


static int NCR5380_transfer_dma( struct Scsi_Host *instance, 
				 unsigned char *phase, int *count,
				 unsigned char **data)
{
    SETUP_HOSTDATA(instance);
    register int c = *count;
    register unsigned char p = *phase;
    register unsigned char *d = *data;
    unsigned char tmp;
    unsigned long flags;

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

    if (atari_read_overruns && (p & SR_IO)) {
	c -= atari_read_overruns;
    }

    DMA_PRINTK("scsi%d: initializing DMA for %s, %d bytes %s %p\n",
	       HOSTNO, (p & SR_IO) ? "reading" : "writing",
	       c, (p & SR_IO) ? "to" : "from", d);

    NCR5380_write(TARGET_COMMAND_REG, PHASE_SR_TO_TCR(p));

#ifdef REAL_DMA
    NCR5380_write(MODE_REG, MR_BASE | MR_DMA_MODE | MR_ENABLE_EOP_INTR | MR_MONITOR_BSY);
#endif /* def REAL_DMA  */

    if (IS_A_TT()) {
	/* On the Medusa, it is a must to initialize the DMA before
	 * starting the NCR. This is also the cleaner way for the TT.
	 */
	save_flags(flags);
	cli();
	hostdata->dma_len = (p & SR_IO) ?
	    NCR5380_dma_read_setup(instance, d, c) : 
	    NCR5380_dma_write_setup(instance, d, c);
	restore_flags(flags);
    }
    
    if (p & SR_IO)
	NCR5380_write(START_DMA_INITIATOR_RECEIVE_REG, 0);
    else {
	NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_DATA);
	NCR5380_write(START_DMA_SEND_REG, 0);
    }

    if (!IS_A_TT()) {
	/* On the Falcon, the DMA setup must be done after the last */
	/* NCR access, else the DMA setup gets trashed!
	 */
	save_flags(flags);
	cli();
	hostdata->dma_len = (p & SR_IO) ?
	    NCR5380_dma_read_setup(instance, d, c) : 
	    NCR5380_dma_write_setup(instance, d, c);
	restore_flags(flags);
    }
    return 0;
}
#endif /* defined(REAL_DMA) */

/*
 * Function : NCR5380_information_transfer (struct Scsi_Host *instance)
 *
 * Purpose : run through the various SCSI phases and do as the target 
 * 	directs us to.  Operates on the currently connected command, 
 *	instance->connected.
 *
 * Inputs : instance, instance for which we are doing commands
 *
 * Side effects : SCSI things happen, the disconnected queue will be 
 *	modified if a command disconnects, *instance->connected will
 *	change.
 *
 * XXX Note : we need to watch for bus free or a reset condition here 
 * 	to recover from an unexpected bus free condition.
 */
 
static void NCR5380_information_transfer (struct Scsi_Host *instance)
{
    SETUP_HOSTDATA(instance);
    unsigned long flags;
    unsigned char msgout = NOP;
    int sink = 0;
    int len;
#if defined(REAL_DMA)
    int transfersize;
#endif
    unsigned char *data;
    unsigned char phase, tmp, extended_msg[10], old_phase=0xff;
    Scsi_Cmnd *cmd = (Scsi_Cmnd *) hostdata->connected;

    while (1) {
	tmp = NCR5380_read(STATUS_REG);
	/* We only have a valid SCSI phase when REQ is asserted */
	if (tmp & SR_REQ) {
	    phase = (tmp & PHASE_MASK); 
	    if (phase != old_phase) {
		old_phase = phase;
		NCR_PRINT_PHASE(NDEBUG_INFORMATION);
	    }
	    
	    if (sink && (phase != PHASE_MSGOUT)) {
		NCR5380_write(TARGET_COMMAND_REG, PHASE_SR_TO_TCR(tmp));

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

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

		if (!cmd->SCp.this_residual && cmd->SCp.buffers_residual) {
		    ++cmd->SCp.buffer;
		    --cmd->SCp.buffers_residual;
		    cmd->SCp.this_residual = cmd->SCp.buffer->length;
		    cmd->SCp.ptr = cmd->SCp.buffer->address;
		    /* ++roman: Try to merge some scatter-buffers if
		     * they are at contiguous physical addresses.
		     */
		    merge_contiguous_buffers( cmd );
		    INF_PRINTK("scsi%d: %d bytes and %d buffers left\n",
			       HOSTNO, cmd->SCp.this_residual,
			       cmd->SCp.buffers_residual);
		}

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

/* ++roman: I suggest, this should be
 *   #if def(REAL_DMA)
 * instead of leaving REAL_DMA out.
 */

#if defined(REAL_DMA)
		if (!cmd->device->borken &&
		    (transfersize = NCR5