/****************************************************************************
 * NS32K Monitor SCSI low-level driver
 * Bruce Culbertson
 * 8 March 1990
 * (This source is public domain source.)
 *
 * Originally written by Bruce Culbertson for a ns32016 port of Minix.
 * Adapted from that for the pc532 (ns32632) monitor.
 * Adapted from that for NetBSD/pc532 by Philip L. Bunde.
 *
 * Do not use DMA -- makes 32016 and pc532 versions compatible.
 * Do not use interrupts -- makes it harder for the user code to bomb
 * this code.
 ****************************************************************************/

#include "so.h"

#define OK 		0
#define NOT_OK		OK+1
#define	PRIVATE
#define PUBLIC
#define WR_ADR(adr,val)	(*((volatile unsigned char *)(adr))=(val))
#define RD_ADR(adr)	(*((volatile unsigned char *)(adr)))
#define AIC6250		0
#define DP8490		1
#define MAX_CACHE	0x10000

/* SCSI bus phases
 */
#define PH_ODATA	0
#define PH_IDATA	1
#define PH_CMD		2
#define PH_STAT		3
#define PH_IMSG		7
#define PH_NONE		8
#define PH_IN(phase)	((phase) & 1)

/* NCR5380 SCSI controller registers
 */
#define SC_CTL		0x30000000	/* base for control registers */
#define SC_DMA		0x38000000	/* base for data registers */
#define SC_CURDATA	SC_CTL+0
#define SC_OUTDATA	SC_CTL+0
#define SC_ICMD		SC_CTL+1
#define SC_MODE		SC_CTL+2
#define SC_TCMD		SC_CTL+3
#define SC_STAT1	SC_CTL+4
#define SC_STAT2	SC_CTL+5
#define SC_START_SEND	SC_CTL+5
#define SC_INDATA	SC_CTL+6
#define SC_RESETIP	SC_CTL+7
#define SC_START_RCV	SC_CTL+7

/* Bits in NCR5380 registers
 */
#define SC_A_RST	0x80
#define SC_A_SEL	0x04
#define SC_S_SEL	0x02
#define SC_S_REQ	0x20
#define SC_S_BSY	0x40
#define SC_S_BSYERR	0x04
#define SC_S_PHASE	0x08
#define SC_S_IRQ	0x10
#define SC_S_DRQ	0x40
#define SC_M_DMA	0x02
#define SC_M_BSY	0x04
#define SC_ENABLE_DB	0x01

/* Status of interrupt routine, returned in m1_i1 field of message.
 */
#define ISR_NOTDONE	0
#define ISR_OK		1
#define ISR_BSYERR	2
#define ISR_RSTERR	3
#define ISR_BADPHASE	4
#define ISR_TIMEOUT	5

#define ICU_ADR		0xfffffe00
#define ICU_IO		(ICU_ADR+20)
#define ICU_DIR		(ICU_ADR+21)
#define ICU_DATA	(ICU_ADR+19)
#define ICU_SCSI_BIT	0x80

/* Miscellaneous
 */
#define MAX_WAIT	2000000
#define SC_LOG_LEN	32

PRIVATE struct scsi_args	*sc_ptrs;
PRIVATE char			sc_cur_phase,
				sc_reset_done,
				sc_have_msg,
				sc_accept_int,
				sc_dma_dir;

long	sc_dma_port = SC_DMA,
	sc_dma_adr;

#ifdef DEBUG
struct sc_log {
  unsigned char stat1, stat2;
}				sc_log [SC_LOG_LEN],
				*sc_log_head = sc_log;
int				sc_spurious_int;
#endif
unsigned char
	sc_watchdog_error;		/* watch dog error */

/* error messages */
char *scsi_errors[] = {
  0,					/* ISR_NOTDONE */
  0,					/* ISR_OK */
  "busy error",				/* ISR_BSYERR */
  "reset error",			/* ISR_RSTERR */
  "NULL pointer for current phase",	/* ISR_BADPHASE */
  "timeout",				/* ISR_TIMEOUT */
};

/*===========================================================================*
 *				exec_scsi_low				     * 
 *===========================================================================*/
/* Execute a generic SCSI command.  Passed pointers to eight buffers:
 * data-out, data-in, command, status, dummy, dummy, message-out, message-in.
 */
PUBLIC
int
exec_scsi_low (args, scsi_adr)
struct scsi_args *args;
long scsi_adr;
{
  int ret;

  sc_ptrs = args;			/* make pointers globally accessible */
  scCtlrSelect (DP8490);
  if (!sc_reset_done) sc_reset();
  /* TCMD has some undocumented behavior in initiator mode.  I think the
   * data bus cannot be enabled if i/o is asserted.
   */
  WR_ADR (SC_TCMD, 0);
  if (OK != sc_wait_bus_free ()) {	/* bus-free phase */
    printf("SCSI: bus not free\n");
    return NOT_OK;
  }
  sc_cur_phase = PH_NONE;
  sc_have_msg = 0;
  if (OK != sc_select (scsi_adr))	/* select phase */
    return NOT_OK;
  sc_watchdog_error = 0;
  ret = sc_receive ();			/* isr does the rest */
  if (ret == ISR_OK) return OK;
  else {
    sc_reset();
    printf("SCSI: %s\n", scsi_errors[ret]);
    return NOT_OK;
  }
}

/*===========================================================================*
 *				sc_reset				     * 
 *===========================================================================*/
/*
 * Reset SCSI bus.
 */
PRIVATE
sc_reset()
{
  volatile int i;

  WR_ADR (SC_MODE, 0);			/* get into harmless state */
  WR_ADR (SC_OUTDATA, 0);
  WR_ADR (SC_ICMD, SC_A_RST);		/* assert RST on SCSI bus */
  i = 200;				/* wait 25 usec */
  while (i--);
  WR_ADR (SC_ICMD, 0);			/* deassert RST, get off bus */
  sc_reset_done = 1;
}

/*===========================================================================*
 *				sc_wait_bus_free			     * 
 *===========================================================================*/
PRIVATE int
sc_wait_bus_free()
{
  int i = MAX_WAIT;
  volatile int j;

  while (i--) {
    /* Must be clear for 2 usec, so read twice */
    if (RD_ADR (SC_STAT1) & (SC_S_BSY | SC_S_SEL)) continue;
    for (j = 0; j < 25; ++j);
    if (RD_ADR (SC_STAT1) & (SC_S_BSY | SC_S_SEL)) continue;
    return OK;
  }
  sc_reset_done = 0;
  return NOT_OK;
}

/*===========================================================================*
 *				sc_select				     * 
 *===========================================================================*/
/* This duplicates much of the work that the interrupt routine would do on a
 * phase mismatch and, in fact, the original plan was to just do the select,
 * let a phase mismatch occur, and let the interrupt routine do the rest.
 * That didn't work because the 5380 did not reliably generate the phase
 * mismatch interrupt after selection.
 */
PRIVATE int
sc_select(adr)
long adr;
{
  int i, stat1;
  long new_ptr;

  WR_ADR (SC_OUTDATA, adr);		/* SCSI bus address */
  WR_ADR (SC_ICMD, SC_A_SEL | SC_ENABLE_DB);
  for (i = 0;; ++i) {			/* wait for target to assert SEL */
    stat1 = RD_ADR (SC_STAT1);
    if (stat1 & SC_S_BSY) break;	/* select successful */
    if (i > MAX_WAIT) {			/* timeout */
      printf("SCSI: SELECT timeout\n");
      sc_reset();
      return NOT_OK;
    }
  }
  WR_ADR (SC_ICMD, 0);			/* clear SEL, disable data out */
  WR_ADR (SC_OUTDATA, 0);
  for (i = 0;; ++i) {			/* wait for target to assert REQ */
    if (stat1 & SC_S_REQ) break;	/* target requesting transfer */
    if (i > MAX_WAIT) {			/* timeout */
      printf("SCSI: REQ timeout\n");
      sc_reset();
      return NOT_OK;
    }
    stat1 = RD_ADR (SC_STAT1);
  }
  sc_cur_phase = (stat1 >> 2) & 7;	/* get new phase from controller */
  if (sc_cur_phase != PH_CMD) {
    printf("SCSI: bad phase = %d\n", sc_cur_phase);
    sc_reset();
    return NOT_OK;
  }
  new_ptr = sc_ptrs->ptr[PH_CMD];
  if (new_ptr == 0) {
    printf("SCSI: NULL command pointer\n");
    sc_reset();
    return NOT_OK;
  }
  sc_accept_int = 1;
  sc_dma_setup (DISK_WRITE, new_ptr);
  WR_ADR (SC_TCMD, PH_CMD);
  WR_ADR (SC_ICMD, SC_ENABLE_DB);
  WR_ADR (SC_MODE, SC_M_BSY | SC_M_DMA);
  WR_ADR (SC_START_SEND, 0);
  return OK;
}

/*===========================================================================*
 *				scsi_interrupt				     *
 *===========================================================================*/
/* SCSI interrupt handler.
 */
PUBLIC
int
scsi_interrupt()
{
  unsigned char stat2, dummy;
  long new_ptr;
  int ret = ISR_NOTDONE;

  stat2 = RD_ADR (SC_STAT2);		/* get status before clearing request */

# ifdef DEBUG				/* debugging log of interrupts */
  sc_log_head->stat1 = RD_ADR (SC_STAT1);
  sc_log_head->stat2 = stat2;
  if (++sc_log_head >= sc_log + SC_LOG_LEN) sc_log_head = sc_log;
  sc_log_head->stat1 = sc_log_head->stat2 = 0xff;
# endif

  for (;;) {
    dummy = RD_ADR (SC_RESETIP);	/* clear interrupt request */
    if (!sc_accept_int ||		/* return if spurious interrupt */
        (!sc_watchdog_error &&
         (stat2 & SC_S_BSYERR) == 0 && (stat2 & SC_S_PHASE) == 1))
    {
#     ifdef DEBUG
        ++sc_spurious_int;
#     endif
      return ret;
    }
    RD_ADR (SC_MODE) &= ~SC_M_DMA;	/* clear DMA mode */
    WR_ADR (SC_ICMD, 0);		/* disable data bus */
    if (sc_cur_phase != PH_NONE) {	/* if did DMA, save the new pointer */
      new_ptr = sc_dma_adr;		/* fetch new pointer from DMA cntlr */
      if (sc_cur_phase == PH_IMSG &&	/* have message? */
        new_ptr != sc_ptrs->ptr[PH_IMSG]) sc_have_msg = 1;
      sc_ptrs->ptr[sc_cur_phase] =	/* save pointer */
        new_ptr;
    }
    if (sc_watchdog_error) ret = ISR_TIMEOUT;
    else if (stat2 & SC_S_BSYERR) {	/* target deasserted BSY? */
      if (sc_have_msg) ret = ISR_OK;
      else ret = ISR_BSYERR;
    } else if (!(stat2 & SC_S_PHASE)) {	/* if phase mismatch, setup new phase */
      sc_cur_phase = 			/* get new phase from controller */
        (RD_ADR (SC_STAT1) >> 2) & 7;
      new_ptr = sc_ptrs->ptr[sc_cur_phase];
      if (new_ptr == 0) ret = ISR_BADPHASE;
      else {
        WR_ADR (SC_TCMD, sc_cur_phase);	/* write new phase into TCMD */
        if (PH_IN (sc_cur_phase)) {	/* set DMA controller */
          sc_dma_setup (DISK_READ, new_ptr);
          RD_ADR (SC_MODE) |= SC_M_DMA;
          WR_ADR (SC_START_RCV, 0);	/* tell SCSI to start DMA */
	} else {
          sc_dma_setup (DISK_WRITE, new_ptr);
	  RD_ADR (SC_MODE) |= SC_M_DMA;
	  WR_ADR (SC_ICMD, SC_ENABLE_DB);
	  WR_ADR (SC_START_SEND, 0);
	}
      }
    } else ret = ISR_RSTERR;
    if (ret != ISR_NOTDONE) {		/* if done, send message to task */
      sc_watchdog_error = 0;
      sc_accept_int = 0;
      WR_ADR (SC_MODE, 0);		/* clear monbsy, dma */
      break;				/* reti re-enables ints */
    }
    if (0 == ((stat2 =			/* check for another interrupt */
      RD_ADR (SC_STAT2)) & SC_S_IRQ)) 
    {
      break;
    }
  }
  return ret;
}

/*===========================================================================*
 *				sc_dma_setup				     *
 *===========================================================================*/
/* Fake DMA setup.  Just store pointers and direction in global variables.
 *
 * The pseudo-DMA is subtler than it looks because of the cache.
 *
 * 1)	When accessing I/O devices through a cache, some mechanism is
 *	necessary to ensure you access the device rather than the cache.
 *	On the 32532, the IODEC signal is supposed to be asserted for I/O
 *	addresses to accomplish this.  However, a bug makes this much
 *	slower than necessary and severely hurts pseudo-DMA performance.
 *	Hence, IODEC is not asserted for the SCSI DMA port.
 *
 * 2)	Because of (1), we must devise our own method of forcing the
 *	SCSI DMA port to be read.  0x8000000 addresses have been decoded
 *	to all access this port.  By always using new addresses to access
 *	the DMA port (wrapping only after reading MAX_CACHE bytes), we
 *	force cache misses and, hence, device reads.  Since the cache
 *	is write-through, we do not need to worry about writes.
 *
 * 3)	It is possible to miss the last few bytes of a transfer if
 *	bus transfer size is not considered.  The loop in sc_receive()
 *	transfers data until the interrupt signal is asserted.  If
 *	bytes are transferred, the attempt to move the first byte of a
 *	double word causes the whole word to be read into the cache.
 *	Then the byte is transferred.  If reading the double word
 *	completed the SCSI transfer, then the loop exits since
 *	interrupt is asserted.  However, the last few bytes have only
 *	been moved into the cache -- they have not been moved to the
 *	DMA destination.
 *
 * 4)	It is also possible to miss the first few bytes of a transfer.
 *	If the address used to access pseudo-dma port is not double word
 *	aligned, the whole double word is read into the cache, and then
 *	data is moved from the middle of the word (i.e. something other
 *	than the first bytes read from the SCSI controller) by the
 *	pseudo-dma loop in sc_receive().
 */
sc_dma_setup (dir, adr)
int dir;
long adr;
{
  if (sc_dma_port > SC_DMA + MAX_CACHE) sc_dma_port = SC_DMA;
  sc_dma_dir = dir;
  sc_dma_adr = adr;
}

/*===========================================================================*
 *				sc_receive				     *
 *===========================================================================*/
/* Replacement for Minix receive(), which waits for a message.  This code
 * spins, waiting for data to transfer or interrupt requests to handle.
 * See sc_dma_setup for details.
 */
int
sc_receive()
{
  int stat2, isr_ret;

  for (;;) {
    stat2 = RD_ADR (SC_STAT2);
    if (stat2 & SC_S_IRQ) {
      if (ISR_NOTDONE != (isr_ret = scsi_interrupt())) break;
    } else if (stat2 & SC_S_DRQ) {	/* test really not necessary on pc532 */
      if (sc_dma_dir == DISK_READ)
	*((long *)sc_dma_adr)++ = *((volatile long *)sc_dma_port)++;
      else *((volatile long *)sc_dma_port)++ = *((long *)sc_dma_adr)++;
    }
  }
  return isr_ret;
}

/*===========================================================================*
 *				scCtlrSelect
 *===========================================================================*/
/* Select a SCSI device.
 */
scCtlrSelect (ctlr)
int ctlr;
{
  RD_ADR (ICU_IO) &= ~ICU_SCSI_BIT;	/* i/o, not port */
  RD_ADR (ICU_DIR) &= ~ICU_SCSI_BIT;	/* output */
  if (ctlr == DP8490)
    RD_ADR (ICU_DATA) &= ~ICU_SCSI_BIT;	/* select = 0 for 8490 */
  else
    RD_ADR (ICU_DATA) |= ICU_SCSI_BIT;	/* select = 1 for AIC6250 */
}