/**
 ** Supermodel
 ** A Sega Model 3 Arcade Emulator.
 ** Copyright 2011 Bart Trzynadlowski, Nik Henson 
 **
 ** This file is part of Supermodel.
 **
 ** Supermodel is free software: you can redistribute it and/or modify it under
 ** the terms of the GNU General Public License as published by the Free 
 ** Software Foundation, either version 3 of the License, or (at your option)
 ** any later version.
 **
 ** Supermodel is distributed in the hope that it will be useful, but WITHOUT
 ** ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 ** FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 ** more details.
 **
 ** You should have received a copy of the GNU General Public License along
 ** with Supermodel.  If not, see <http://www.gnu.org/licenses/>.
 **/
 
/*
 * 53C810.cpp
 * 
 * Implementation of the C53C810 class: NCR 53C810 SCSI controller.
 *
 * Notes:
 * ------
 * - VF3 does something weird: it writes DSP (triggering automatic code
 *   execution because MAN=0) and THEN sets single step mode, expecting an
 *   interrupt to occur. I suspect this is incorrect operation and that
 *   the SCRIPTS processor either enters single-step mode while the memory
 *   transfer is underway (though it is unlikely because it's such a short
 *   transfer), or that single step can occur even when the device is "halted"
 *   (which would mean the SCRIPTS processor executes an invalid instruction
 *   once or twice without the VF3 SCSI driver noticing). Unfortunately, the
 *   former is not feasible to emulate. If automatic SCRIPTS execution is
 *   disabled when single-stepping is enabled, Scud Race breaks (glitchy,
 *   jerky graphics). Enabling automatic execution and also allowing single
 *   stepping to occur when the processor is halted seems to work, but it 
 *   causes invalid instructions to be hit each time.
 * - pg 2-22 (42) of the manual has description of how to clear interrupts.
 *
 */

#include <cstring>
#include "Supermodel.h"


/******************************************************************************
 Save States
******************************************************************************/

void C53C810::SaveState(CBlockFile *SaveState)
{
  SaveState->NewBlock("53C810", __FILE__);
  SaveState->Write(Ctx.regs, sizeof(Ctx.regs));
  SaveState->Write(&Ctx.regTEMP, sizeof(Ctx.regTEMP));
  SaveState->Write(&Ctx.regDSP, sizeof(Ctx.regDSP));
  SaveState->Write(&Ctx.regDSPS, sizeof(Ctx.regDSPS));
  SaveState->Write(&Ctx.regDBC, sizeof(Ctx.regDBC));
  SaveState->Write(&Ctx.regDCMD, sizeof(Ctx.regDCMD));
  SaveState->Write(&Ctx.regDCNTL, sizeof(Ctx.regDCNTL));
  SaveState->Write(&Ctx.regDMODE, sizeof(Ctx.regDMODE));
  SaveState->Write(&Ctx.regDSTAT, sizeof(Ctx.regDSTAT));
  SaveState->Write(&Ctx.regISTAT, sizeof(Ctx.regISTAT));
}

void C53C810::LoadState(CBlockFile *SaveState)
{
  if (OKAY != SaveState->FindBlock("53C810"))
  {
    ErrorLog("Unable to load 53C810 state. Save state file is corrupt.");
    return;
  }
  
  SaveState->Read(Ctx.regs, sizeof(Ctx.regs));
  SaveState->Read(&Ctx.regTEMP, sizeof(Ctx.regTEMP));
  SaveState->Read(&Ctx.regDSP, sizeof(Ctx.regDSP));
  SaveState->Read(&Ctx.regDSPS, sizeof(Ctx.regDSPS));
  SaveState->Read(&Ctx.regDBC, sizeof(Ctx.regDBC));
  SaveState->Read(&Ctx.regDCMD, sizeof(Ctx.regDCMD));
  SaveState->Read(&Ctx.regDCNTL, sizeof(Ctx.regDCNTL));
  SaveState->Read(&Ctx.regDMODE, sizeof(Ctx.regDMODE));
  SaveState->Read(&Ctx.regDSTAT, sizeof(Ctx.regDSTAT));
  SaveState->Read(&Ctx.regISTAT, sizeof(Ctx.regISTAT));
}


/******************************************************************************
 SCRIPTS Emulation
******************************************************************************/

static inline UINT32 Fetch(struct NCR53C810Context *Ctx, UINT32 offset)
{
  UINT32 data = Ctx->Bus->Read32(Ctx->regDSP + offset);
  return FLIPENDIAN32(data);  // remember: bus is big endian, need to convert to little endian
}

//TODO: what happens if interrupt is executed in single step mode?
static bool SCRIPTS_Int_IntFly(struct NCR53C810Context *Ctx)
{
  Ctx->halt = true;   // halt SCRIPTS execution
  Ctx->regISTAT |= 1; // DMA interrupt pending
  Ctx->regDSTAT |= 4; // SCRIPTS interrupt instruction received
  Ctx->IRQ->Assert(Ctx->scsiIRQ); 
  if ((Ctx->regDBC&0x100000)) // INTFLY
    return ErrorLog("53C810 INTFLY instruction not emulated!");
  // DSP not incremented (VF3 relies on this)
  return OKAY;
}

static bool SCRIPTS_MoveMemory(struct NCR53C810Context *Ctx)
{
  UINT32    src, dest;
  unsigned  numBytes, i;

  // Get operands
  src = Ctx->regDSPS;
  dest = Ctx->regTEMP = Fetch(Ctx, 8);  // word 3
  numBytes = Ctx->regDBC;
  // Not implemented: illegal instruction interrupt when src and dest are not aligned the same way

  DebugLog("53C810: Move Memory %08X -> %08X, %X\n", src, dest, numBytes);
    
  // Perform a 32-bit copy if possible
  for (i = 0; i < (numBytes/4); i++)
  {
    Ctx->Bus->Write32(dest, Ctx->Bus->Read32(src));
    dest += 4;
    src += 4;
  }

  // Finish off the last few odd bytes
  numBytes &= 3;
  while (numBytes)
  {
    Ctx->Bus->Write8(dest++, Ctx->Bus->Read8(src++));
    --numBytes;
  }

  // Update registers
  Ctx->regDBC = 0;
  Ctx->regDSPS = src;
  Ctx->regTEMP = dest;
  Ctx->regDSP += 12;

  return OKAY;
}

// Invalid instruction handler
static bool SCRIPTS_Invalid(struct NCR53C810Context *Ctx)
{
  DebugLog("53C810 encountered an unrecognized instruction (%02X%06X, DSP=%08X)\n!", Ctx->regDCMD, Ctx->regDBC, Ctx->regDSP);
  return FAIL;
}

void C53C810::Run(bool singleStep)
{
  UINT32  op;
  int   i;
  
  if (singleStep)// && !Ctx.halt)
  {
    // Fetch instruction (first two words are always fetched)
    op = Fetch(&Ctx, 0);          // word 1
    Ctx.regDBC = op&0x00FFFFFF;
    Ctx.regDCMD = (op>>24)&0xFF;
    Ctx.regDSPS = Fetch(&Ctx, 4); // word 2
    
    // Single step
    OpTable[Ctx.regDCMD](&Ctx);
    
    // Issue IRQ and finish
    Ctx.regISTAT |= 1;            // DMA interrupt pending
    Ctx.regDSTAT |= 8;            // single step interrupt
    Ctx.IRQ->Assert(Ctx.scsiIRQ); // generate an interrupt
    DebugLog("53C810: Asserted IRQ\n");
  }
  else
  {
    // Automatic mode: run (as long as the processor is not halted)
    for (i = 0; (i < 100) && !Ctx.halt; i++)
    {
      // Fetch instruction (first two words are always fetched)
      op = Fetch(&Ctx, 0);          // word 1
      Ctx.regDBC = op&0x00FFFFFF;
      Ctx.regDCMD = (op>>24)&0xFF;
      Ctx.regDSPS = Fetch(&Ctx, 4); // word 2
    
      // Execute!
      if (OpTable[Ctx.regDCMD](&Ctx) != OKAY)
        break;
    }
  }
}

// Insert instructions into the LUT under control of the mask
void C53C810::Insert(UINT8 mask, UINT8 op, bool (*Handler)(struct NCR53C810Context *))
{
  UINT32  i;

  for (i = 0; i < 256; i++)
  {
    if ((i&mask) == op)
      OpTable[i] = Handler;
  }
}

void C53C810::BuildOpTable(void)
{
  Insert(0, 0, &SCRIPTS_Invalid);
  Insert(0xE0, 0xC0, &SCRIPTS_MoveMemory);
  Insert(0xF8, 0x98, &SCRIPTS_Int_IntFly);
}


/******************************************************************************
 Register and PCI Access Handlers
******************************************************************************/

void C53C810::WriteRegister(unsigned reg, UINT8 data)
{
  if (reg >= 0x60)
  {
    ErrorLog("Write to invalid 53C810 register (%02X).", reg);
    return;
  }
  
  DebugLog("53C810 write: %02X=%02X (PC=%08X, LR=%08X)\n", reg, data, ppc_get_pc(), ppc_get_lr());
  
  // Dump everything into the register file
  Ctx.regs[reg&0xFF] = data;
  
  // Do something extra with the ones that we actually care about
  // TO-DO: prevent invalid/reserved/read-only registers from being written?
  switch(reg)
  {
  case 0x14:    // ISTAT
    Ctx.regISTAT = data;
    DebugLog("ISTAT=%02X\n", data);
    break;
  case 0x1C:    // TEMP 7-0
    Ctx.regTEMP &= 0xFFFFFF00;
    Ctx.regTEMP |= data;
    break;
  case 0x1D:    // TEMP 15-8
    Ctx.regTEMP &= 0xFFFF00FF;
    Ctx.regTEMP |= (data<<8);
    break;
  case 0x1E:    // TEMP 23-16
    Ctx.regTEMP &= 0xFF00FFFF;
    Ctx.regTEMP |= (data<<16);
    break;
  case 0x1F:    // TEMP 31-24
    Ctx.regTEMP &= 0x00FFFFFF;
    Ctx.regTEMP |= (data<<24);
    break;
  case 0x24:    // DBC 7-0
    Ctx.regDBC &= 0xFFFFFF00;
    Ctx.regDBC |= data;
    break;
  case 0x25:    // DBC 15-8
    Ctx.regDBC &= 0xFFFF00FF;
    Ctx.regDBC |= (data<<8);
    break;
  case 0x26:    // DBC 23-16
    Ctx.regDBC &= 0xFF00FFFF;
    Ctx.regDBC |= (data<<16);
    break;
  case 0x27:    // DCMD
    Ctx.regDCMD = data;
    break;  
  case 0x2C:    // DSP 7-0
    Ctx.regDSP &= 0xFFFFFF00;
    Ctx.regDSP |= data;
    break;
  case 0x2D:    // DSP 15-8
    Ctx.regDSP &= 0xFFFF00FF;
    Ctx.regDSP |= (data<<8);
    break;
  case 0x2E:    // DSP 23-16
    Ctx.regDSP &= 0xFF00FFFF;
    Ctx.regDSP |= (data<<16);
    break;
  case 0x2F:    // DSP 31-24
    Ctx.regDSP &= 0x00FFFFFF;
    Ctx.regDSP |= (data<<24);
    Ctx.halt = false; // writing this register un-halts 53C810 operation (pg.6-31 of LSI manual)
    if (!(Ctx.regDMODE&1))  // if MAN=0, start SCRIPTS automatically
    // To-Do: is this correct? Should single step really be tested first?
    //if (!(Ctx.regDCNTL&0x10) && !(Ctx.regDMODE&1))  // if MAN=0 and not single stepping, start SCRIPTS automatically
    {
      DebugLog("53C810: Automatically starting (PC=%08X, LR=%08X, single step=%d)\n", ppc_get_pc(), ppc_get_lr(), !!(Ctx.regDCNTL&0x10));
      Run(false);       // automatic
    }
    break;  
  case 0x30:    // DSPS 7-0
    Ctx.regDSPS &= 0xFFFFFF00;
    Ctx.regDSPS |= data;
    break;
  case 0x31:    // DSPS 15-8
    Ctx.regDSPS &= 0xFFFF00FF;
    Ctx.regDSPS |= (data<<8);
    break;
  case 0x32:    // DSPS 23-16
    Ctx.regDSPS &= 0xFF00FFFF;
    Ctx.regDSPS |= (data<<16);
    break;
  case 0x33:    // DSPS 31-24
    Ctx.regDSPS &= 0x00FFFFFF;
    Ctx.regDSPS |= (data<<24);
    break;
  case 0x38:    // DMODE
    Ctx.regDMODE = data;
    break;
  case 0x3B:    // DCNTL
    Ctx.regDCNTL = data;
    if ((Ctx.regDCNTL&0x14) == 0x14)    // single step
    {
      DebugLog("53C810: single step: %08X, (halt=%d)\n", Ctx.regDSP, Ctx.halt);
      Run(true);
    }
    else if ((Ctx.regDCNTL&0x04))     // start DMA bit
    {
      DebugLog("53C810: Manually starting\n");
      Run(false);
    }
    break;
  default:
    break;
  }
} 

UINT8 C53C810::ReadRegister(unsigned reg)
{
  UINT8 ret;
  
  if (reg >= 0x60)
  {
    ErrorLog("Read from invalid 53C810 register (%02X).", reg);
    return 0;
  }
  
  DebugLog("53C810 read: %02X (PC=%08X, LR=%08X)\n", reg, ppc_get_pc(), ppc_get_lr());
  
  // Some registers require special handling
  switch(reg)
  {
  case 0x0C:    // DSTAT
    // For now, we don't generate stacked interrupts, so always clear IRQ status
    ret = Ctx.regDSTAT;
    //TO-DO: manual says these should be cleared here but MAME never clears them. What's up with that?
    Ctx.regISTAT &= 0xFE; // clear DIP bit (DMA interrupt)
    Ctx.regDSTAT &= 0xF7; // clear SSI (single step interrupt)
    //Ctx.regISTAT |= 1;  // doing this is another way to fix VF3
    //Ctx.regDSTAT |= 8;
    Ctx.IRQ->Deassert(Ctx.scsiIRQ);
    //DebugLog("53C810: DSTAT read\n");
    return ret;
  case 0x14:    // ISTAT
    //DebugLog("53C810: ISTAT read\n");
    return Ctx.regISTAT;
  case 0x1C:    // TEMP 7-0
    return Ctx.regTEMP&0xFF;
  case 0x1D:    // TEMP 15-8
    return (Ctx.regTEMP>>8)&0xFF;
  case 0x1E:    // TEMP 23-16
    return (Ctx.regTEMP>>16)&0xFF;
  case 0x1F:    // TEMP 31-24
    return (Ctx.regTEMP>>24)&0xFF;
  case 0x24:    // DBC 7-0
    return Ctx.regDBC&0xFF;
  case 0x25:    // DBC 15-8
    return (Ctx.regDBC>>8)&0xFF;
  case 0x26:    // DBC 23-16
    return (Ctx.regDBC>>16)&0xFF;
  case 0x27:    // DCMD
    return Ctx.regDCMD;
  case 0x2C:    // DSP 7-0
    return Ctx.regDSP&0xFF;
  case 0x2D:    // DSP 15-8
    return (Ctx.regDSP>>8)&0xFF;
  case 0x2E:    // DSP 23-16
    return (Ctx.regDSP>>16)&0xFF;
  case 0x2F:    // DSP 31-24
    return (Ctx.regDSP>>24)&0xFF;
  case 0x30:    // DSPS 7-0
    return Ctx.regDSPS&0xFF;
  case 0x31:    // DSPS 15-8
    return (Ctx.regDSPS>>8)&0xFF;
  case 0x32:    // DSPS 23-16
    return (Ctx.regDSPS>>16)&0xFF;
  case 0x33:    // DSPS 31-24
    return (Ctx.regDSPS>>24)&0xFF;
  case 0x38:
    return Ctx.regDMODE;
  case 0x3B:    // DCNTL
    return Ctx.regDCNTL;
  default:  // get it from the register file
    break;
  }
  
  // Register file should be up to date
  return Ctx.regs[reg&0xFF];
} 

UINT32 C53C810::ReadPCIConfigSpace(unsigned device, unsigned reg, unsigned bits, unsigned offset)
{
  UINT32  d;
  
  if ((bits==8))
  {
    DebugLog("53C810 %d-bit PCI read request for reg=%02X\n", bits, reg);
    return 0;
  }
  
  switch (reg)
  {
  case 0x00:  // Device ID and Vendor ID
    d = 0x00011000; // 0x1000 = LSI Logic
    switch (bits)
    {
    case 8:
      d >>= (3-offset)*8; // offset will be 0-3; select appropriate byte
      d &= 0xFF;
      break;
    case 16:
      d >>= (2-offset)*8; // offset will be 0 or 2 only; select either high or low word
      d &= 0xFFFF;
      break;
    default:
      break;
    }
    return d;
  default:
    DebugLog("53C810 PCI read request for reg=%02X (%d-bit)\n", reg, bits);
    break;
  }

  return 0;
}
  
void C53C810::WritePCIConfigSpace(unsigned device, unsigned reg, unsigned bits, unsigned offset, UINT32 data)
{
  DebugLog("53C810 PCI %d-bit write request for reg=%02X, data=%08X\n", bits, reg, data);
}

void C53C810::Reset(void)
{
  memset(Ctx.regs, 0, sizeof(Ctx.regs));
  Ctx.regs[0x00] = 0xC0;  // SCNTL0
  Ctx.regs[0x0C] = 0x80;  // DSTAT
  Ctx.regs[0x0F] = 0x02;  // SSTAT2
  Ctx.regs[0x18] = 0xFF;  // reserved
  Ctx.regs[0x19] = 0xF0;  // CTEST1
  Ctx.regs[0x1A] = 0x01;  // CTEST2
  Ctx.regs[0x46] = 0x60;  // MACNTL
  Ctx.regs[0x47] = 0x0F;  // GPCNTL
  Ctx.regs[0x4C] = 0x03;  // STEST0 
  Ctx.regTEMP = 0;
  Ctx.regDSP = 0;
  Ctx.regDSPS = 0;
  Ctx.regDBC = 0;
  Ctx.regDCMD = 0;
  Ctx.regDCNTL = 0;
  Ctx.regDMODE = 0;
  Ctx.regDSTAT = 0x80;  // DMA FIFO empty
  Ctx.regISTAT = 0;
  Ctx.halt = false;
  
  DebugLog("53C810 reset\n");
}


/******************************************************************************
 Configuration, Initialization, and Shutdown
******************************************************************************/

void C53C810::Init(CBus *BusObjectPtr, CIRQ *IRQObjectPtr, unsigned scsiIRQBit)
{
  Ctx.Bus = BusObjectPtr; 
  Ctx.IRQ = IRQObjectPtr;
  Ctx.scsiIRQ = scsiIRQBit;
}

C53C810::C53C810(void)
{ 
  BuildOpTable();
  Ctx.Bus = NULL;
  Ctx.IRQ = NULL;
  scsiIRQ = 0;
  DebugLog("Built 53C810\n");
}

C53C810::~C53C810(void)
{ 
  Ctx.Bus = NULL;
  Ctx.IRQ = NULL;
  DebugLog("Destroyed 53C810\n");
}