mame/src/mess/machine/dccons.c

/*

    dc.c - Sega Dreamcast hardware

    MESS (DC home console) hardware overrides (GD-ROM drive etc)

    c230048 - 5 is written, want 6
    c0d9d9e - where bad happens, from routine @ c0da260

    c0d9d8e - R0 on return is the value to put in

    cfffee0 - stack location when bad happens

    TODO:
    - gdrom_alt_status is identical to normal status except that "but it does not clear DMA status information when it is accessed"

*/

#include "emu.h"
#include "cdrom.h"
#include "debugger.h"
#include "includes/dc.h"
#include "cpu/sh4/sh4.h"
#include "sound/aica.h"
#include "includes/dccons.h"

#define ATAPI_CYCLES_PER_SECTOR (5000)  // TBD for Dreamcast

WRITE_LINE_MEMBER(dc_cons_state::ata_interrupt)
{
	if (state)
		dc_sysctrl_regs[SB_ISTEXT] |= IST_EXT_GDROM;
	else
		dc_sysctrl_regs[SB_ISTEXT] &= ~IST_EXT_GDROM;

	dc_update_interrupt_status();
}

TIMER_CALLBACK_MEMBER(dc_cons_state::atapi_xfer_end )
{
	UINT8 sector_buffer[ 4096 ];

	atapi_timer->adjust(attotime::never);

	printf("atapi_xfer_end atapi_xferlen = %d\n", atapi_xferlen );

	//mame_printf_debug("ATAPI: xfer_end.  xferlen = %d\n", atapi_xferlen);

	m_ata->write_dmack(1);

	while (atapi_xferlen > 0 )
	{
		struct sh4_ddt_dma ddtdata;

		// get a sector from the SCSI device
		for (int i = 0; i < 2048/2; i++)
		{
			int d = m_ata->read_dma();
			sector_buffer[ i*2 ] = d & 0xff;
			sector_buffer[ (i*2)+1 ] = d >> 8;
		}

		atapi_xferlen -= 2048;

		// perform the DMA
		ddtdata.destination = atapi_xferbase;   // destination address
		ddtdata.length = 2048/4;
		ddtdata.size = 4;
		ddtdata.buffer = sector_buffer;
		ddtdata.direction=1;    // 0 source to buffer, 1 buffer to destination
		ddtdata.channel= -1;    // not used
		ddtdata.mode= -1;       // copy from/to buffer
		printf("ATAPI: DMA one sector to %x, %x remaining\n", atapi_xferbase, atapi_xferlen);
		sh4_dma_ddt(m_maincpu, &ddtdata);

		atapi_xferbase += 2048;
	}

	m_ata->write_dmack(0);

	g1bus_regs[SB_GDST]=0;
	dc_sysctrl_regs[SB_ISTNRM] |= IST_DMA_GDROM;
	dc_update_interrupt_status();
}

void dc_cons_state::dreamcast_atapi_init()
{
	atapi_timer = machine().scheduler().timer_alloc(timer_expired_delegate(FUNC(dc_cons_state::atapi_xfer_end),this));
	atapi_timer->adjust(attotime::never);
	save_item(NAME(atapi_xferlen));
	save_item(NAME(atapi_xferbase));
}

/*

 GDROM regsters:

 5f7018: alternate status/device control
 5f7080: data
 5f7084: error/features
 5f7088: interrupt reason/sector count
 5f708c: sector number
 5f7090: byte control low
 5f7094: byte control high
 5f7098: drive select
 5f709c: status/command

c002910 - ATAPI packet writes
c002796 - aux status read after that
c000776 - DMA triggered to c008000

*/

READ32_MEMBER(dc_cons_state::dc_mess_g1_ctrl_r )
{
	switch(offset)
	{
		case SB_GDSTARD:
			printf("G1CTRL: GDSTARD %08x\n", atapi_xferbase); // Hello Kitty reads here
			debugger_break(machine());
			return atapi_xferbase;
		case SB_GDST:
			break;
		case SB_GDLEND:
			//debugger_break(machine());
			return atapi_xferlen; // TODO: check me
		default:
			printf("G1CTRL:  Unmapped read %08x\n", 0x5f7400+offset*4);
			debugger_break(machine());
	}
	return g1bus_regs[offset];
}

WRITE32_MEMBER(dc_cons_state::dc_mess_g1_ctrl_w )
{
	g1bus_regs[offset] = data; // 5f7400+reg*4=dat
//  mame_printf_verbose("G1CTRL: [%08x=%x] write %" I64FMT "x to %x, mask %" I64FMT "x\n", 0x5f7400+reg*4, dat, data, offset, mem_mask);
	switch (offset)
	{
	case SB_GDST:
		if (data & 1 && g1bus_regs[SB_GDEN] == 1) // 0 -> 1
		{
			if (g1bus_regs[SB_GDDIR] == 0)
			{
				printf("G1CTRL: unsupported transfer\n");
				return;
			}

			atapi_xferbase = g1bus_regs[SB_GDSTAR];
			//atapi_timer->adjust(m_maincpu->cycles_to_attotime((ATAPI_CYCLES_PER_SECTOR * (atapi_xferlen/2048))));
			/* 12x * 75 Hz = 0,00(1) secs per sector */
			/* TODO: make DMA to be single step */
			atapi_timer->adjust(attotime::from_usec(1111*atapi_xferlen/2048));
//			atapi_regs[ATAPI_REG_SAMTAG] = GDROM_PAUSE_STATE | 0x80;
		}
		break;

	case SB_GDLEN:
		atapi_xferlen = data;
		break;

	// The following is required to unlock the GD-ROM. The original Japanese BIOS doesn't need it
	case GD_UNLOCK:
		if (data==0 || data==0x001fffff || data==0x42fe)
		{
//			atapi_regs[ATAPI_REG_SAMTAG] = GDROM_PAUSE_STATE | 0x80;
			printf("Unlocking GD-ROM! %x\n", data);
		}
		break;
	}
}