/**

 * $Id$

 *

 * Support for the miscellaneous ASIC functions (Primarily event multiplexing,

 * and DMA). 

 *

 * Copyright (c) 2005 Nathan Keynes.

 *

 * This program 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 2 of the License, or

 * (at your option) any later version.

 *

 * This program 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.

 */

#define MODULE asic_module

#include <assert.h>

#include <stdlib.h>

#include "dream.h"

#include "mem.h"

#include "sh4/intc.h"

#include "sh4/dmac.h"

#include "sh4/sh4.h"

#include "dreamcast.h"

#include "maple/maple.h"

#include "gdrom/ide.h"

#include "pvr2/pvr2.h"

#include "asic.h"

#define MMIO_IMPL

#include "asic.h"

/*

 * Open questions:

 *   1) Does changing the mask after event occurance result in the

 *      interrupt being delivered immediately?

 * TODO: Logic diagram of ASIC event/interrupt logic.

 *

 * ... don't even get me started on the "EXTDMA" page, about which, apparently,

 * practically nothing is publicly known...

 */

static void asic_check_cleared_events( void );

static void asic_init( void );

static void asic_reset( void );

static uint32_t asic_run_slice( uint32_t nanosecs );

static void asic_save_state( FILE *f );

static int asic_load_state( FILE *f );

static uint32_t g2_update_fifo_status( uint32_t slice_cycle );

struct dreamcast_module asic_module = { "ASIC", asic_init, asic_reset, NULL, asic_run_slice,

        NULL, asic_save_state, asic_load_state };

#define G2_BIT5_TICKS 60

#define G2_BIT4_TICKS 160

#define G2_BIT0_ON_TICKS 120

#define G2_BIT0_OFF_TICKS 420

struct asic_g2_state {

    int bit5_off_timer;

    int bit4_on_timer;

    int bit4_off_timer;

    int bit0_on_timer;

    int bit0_off_timer;

};

static struct asic_g2_state g2_state;

static uint32_t asic_run_slice( uint32_t nanosecs )

{

    g2_update_fifo_status(nanosecs);

    if( g2_state.bit5_off_timer <= (int32_t)nanosecs ) {

        g2_state.bit5_off_timer = -1;

    } else {

        g2_state.bit5_off_timer -= nanosecs;

    }

    if( g2_state.bit4_off_timer <= (int32_t)nanosecs ) {

        g2_state.bit4_off_timer = -1;

    } else {

        g2_state.bit4_off_timer -= nanosecs;

    }

    if( g2_state.bit4_on_timer <= (int32_t)nanosecs ) {

        g2_state.bit4_on_timer = -1;

    } else {

        g2_state.bit4_on_timer -= nanosecs;

    }

    if( g2_state.bit0_off_timer <= (int32_t)nanosecs ) {

        g2_state.bit0_off_timer = -1;

    } else {

        g2_state.bit0_off_timer -= nanosecs;

    }

    if( g2_state.bit0_on_timer <= (int32_t)nanosecs ) {

        g2_state.bit0_on_timer = -1;

    } else {

        g2_state.bit0_on_timer -= nanosecs;

    }

    return nanosecs;

}

static void asic_init( void )

{

    register_io_region( &mmio_region_ASIC );

    register_io_region( &mmio_region_EXTDMA );

    asic_reset();

}

static void asic_reset( void )

{

    memset( &g2_state, 0xFF, sizeof(g2_state) );

}    

static void asic_save_state( FILE *f )

{

    fwrite( &g2_state, sizeof(g2_state), 1, f );

}

static int asic_load_state( FILE *f )

{

    if( fread( &g2_state, sizeof(g2_state), 1, f ) != 1 )

        return 1;

    else

        return 0;

}

/**

 * Setup the timers for the 3 FIFO status bits following a write through the G2

 * bus from the SH4 side. The timing is roughly as follows: (times are

 * approximate based on software readings - I wouldn't take this as gospel but

 * it seems to be enough to fool most programs). 

 *    0ns: Bit 5 (Input fifo?) goes high immediately on the write

 *   40ns: Bit 5 goes low and bit 4 goes high

 *  120ns: Bit 4 goes low, bit 0 goes high

 *  240ns: Bit 0 goes low.

 *

 * Additional writes while the FIFO is in operation extend the time that the

 * bits remain high as one might expect, without altering the time at which

 * they initially go high.

 */

void asic_g2_write_word()

{

    if( g2_state.bit5_off_timer < (int32_t)sh4r.slice_cycle ) {

        g2_state.bit5_off_timer = sh4r.slice_cycle + G2_BIT5_TICKS;

    } else {

        g2_state.bit5_off_timer += G2_BIT5_TICKS;

    }

    if( g2_state.bit4_on_timer < (int32_t)sh4r.slice_cycle ) {

        g2_state.bit4_on_timer = sh4r.slice_cycle + G2_BIT5_TICKS;

    }

    if( g2_state.bit4_off_timer < (int32_t)sh4r.slice_cycle ) {

        g2_state.bit4_off_timer = g2_state.bit4_on_timer + G2_BIT4_TICKS;

    } else {

        g2_state.bit4_off_timer += G2_BIT4_TICKS;

    }

    if( g2_state.bit0_on_timer < (int32_t)sh4r.slice_cycle ) {

        g2_state.bit0_on_timer = sh4r.slice_cycle + G2_BIT0_ON_TICKS;

    }

    if( g2_state.bit0_off_timer < (int32_t)sh4r.slice_cycle ) {

        g2_state.bit0_off_timer = g2_state.bit0_on_timer + G2_BIT0_OFF_TICKS;

    } else {

        g2_state.bit0_off_timer += G2_BIT0_OFF_TICKS;

    }

    MMIO_WRITE( ASIC, G2STATUS, MMIO_READ(ASIC, G2STATUS) | 0x20 );

}

static uint32_t g2_update_fifo_status( uint32_t nanos )

{

    uint32_t val = MMIO_READ( ASIC, G2STATUS );

    if( ((uint32_t)g2_state.bit5_off_timer) <= nanos ) {

        val = val & (~0x20);

        g2_state.bit5_off_timer = -1;

    }

    if( ((uint32_t)g2_state.bit4_on_timer) <= nanos ) {

        val = val | 0x10;

        g2_state.bit4_on_timer = -1;

    }

    if( ((uint32_t)g2_state.bit4_off_timer) <= nanos ) {

        val = val & (~0x10);

        g2_state.bit4_off_timer = -1;

    } 

    if( ((uint32_t)g2_state.bit0_on_timer) <= nanos ) {

        val = val | 0x01;

        g2_state.bit0_on_timer = -1;

    }

    if( ((uint32_t)g2_state.bit0_off_timer) <= nanos ) {

        val = val & (~0x01);

        g2_state.bit0_off_timer = -1;

    } 

    MMIO_WRITE( ASIC, G2STATUS, val );

    return val;

}   

static int g2_read_status() {

    return g2_update_fifo_status( sh4r.slice_cycle );

}

void asic_event( int event )

{

    int offset = ((event&0x60)>>3);

    int result = (MMIO_READ(ASIC, PIRQ0 + offset))  |=  (1<<(event&0x1F));

    if( result & MMIO_READ(ASIC, IRQA0 + offset) )

        intc_raise_interrupt( INT_IRQ13 );

    if( result & MMIO_READ(ASIC, IRQB0 + offset) )

        intc_raise_interrupt( INT_IRQ11 );

    if( result & MMIO_READ(ASIC, IRQC0 + offset) )

        intc_raise_interrupt( INT_IRQ9 );

    if( event >= 64 ) { /* Third word */

        asic_event( EVENT_CASCADE2 );

    } else if( event >= 32 ) { /* Second word */

        asic_event( EVENT_CASCADE1 );

    }

}

void asic_clear_event( int event ) {

    int offset = ((event&0x60)>>3);

    uint32_t result = MMIO_READ(ASIC, PIRQ0 + offset)  & (~(1<<(event&0x1F)));

    MMIO_WRITE( ASIC, PIRQ0 + offset, result );

    if( result == 0 ) {

        /* clear cascades if necessary */

        if( event >= 64 ) {

            MMIO_WRITE( ASIC, PIRQ0, MMIO_READ( ASIC, PIRQ0 ) & 0x7FFFFFFF );

        } else if( event >= 32 ) {

            MMIO_WRITE( ASIC, PIRQ0, MMIO_READ( ASIC, PIRQ0 ) & 0xBFFFFFFF );

        }

    }

    asic_check_cleared_events();

}

void asic_check_cleared_events( )

{

    int i, setA = 0, setB = 0, setC = 0;

    uint32_t bits;

    for( i=0; i<12; i+=4 ) {

        bits = MMIO_READ( ASIC, PIRQ0 + i );

        setA |= (bits & MMIO_READ(ASIC, IRQA0 + i ));

        setB |= (bits & MMIO_READ(ASIC, IRQB0 + i ));

        setC |= (bits & MMIO_READ(ASIC, IRQC0 + i ));

    }

    if( setA == 0 )

        intc_clear_interrupt( INT_IRQ13 );

    if( setB == 0 )

        intc_clear_interrupt( INT_IRQ11 );

    if( setC == 0 )

        intc_clear_interrupt( INT_IRQ9 );

}

void asic_event_mask_changed( )

{

    int i, setA = 0, setB = 0, setC = 0;

    uint32_t bits;

    for( i=0; i<12; i+=4 ) {

        bits = MMIO_READ( ASIC, PIRQ0 + i );

        setA |= (bits & MMIO_READ(ASIC, IRQA0 + i ));

        setB |= (bits & MMIO_READ(ASIC, IRQB0 + i ));

        setC |= (bits & MMIO_READ(ASIC, IRQC0 + i ));

    }

    if( setA == 0 ) 

        intc_clear_interrupt( INT_IRQ13 );

    else

        intc_raise_interrupt( INT_IRQ13 );

    if( setB == 0 )

        intc_clear_interrupt( INT_IRQ11 );

    else

        intc_raise_interrupt( INT_IRQ11 );

    if( setC == 0 )

        intc_clear_interrupt( INT_IRQ9 );

    else

        intc_raise_interrupt( INT_IRQ9 );

}

void g2_dma_transfer( int channel )

{

    uint32_t offset = channel << 5;

    if( MMIO_READ( EXTDMA, G2DMA0CTL1 + offset ) == 1 ) {

        if( MMIO_READ( EXTDMA, G2DMA0CTL2 + offset ) == 1 ) {

            uint32_t extaddr = MMIO_READ( EXTDMA, G2DMA0EXT + offset );

            uint32_t sh4addr = MMIO_READ( EXTDMA, G2DMA0SH4 + offset );

            uint32_t length = MMIO_READ( EXTDMA, G2DMA0SIZ + offset ) & 0x1FFFFFFF;

            uint32_t dir = MMIO_READ( EXTDMA, G2DMA0DIR + offset );

            // uint32_t mode = MMIO_READ( EXTDMA, G2DMA0MOD + offset );

            unsigned char buf[length];

            if( dir == 0 ) { /* SH4 to device */

                mem_copy_from_sh4( buf, sh4addr, length );

                mem_copy_to_sh4( extaddr, buf, length );

            } else { /* Device to SH4 */

                mem_copy_from_sh4( buf, extaddr, length );

                mem_copy_to_sh4( sh4addr, buf, length );

            }

            MMIO_WRITE( EXTDMA, G2DMA0CTL2 + offset, 0 );

            asic_event( EVENT_G2_DMA0 + channel );

        } else {

            MMIO_WRITE( EXTDMA, G2DMA0CTL2 + offset, 0 );

        }

    }

}

void asic_ide_dma_transfer( )

{	

    if( MMIO_READ( EXTDMA, IDEDMACTL2 ) == 1 ) {

        if( MMIO_READ( EXTDMA, IDEDMACTL1 ) == 1 ) {

            MMIO_WRITE( EXTDMA, IDEDMATXSIZ, 0 );

            uint32_t addr = MMIO_READ( EXTDMA, IDEDMASH4 );

            uint32_t length = MMIO_READ( EXTDMA, IDEDMASIZ );

            // int dir = MMIO_READ( EXTDMA, IDEDMADIR );

            uint32_t xfer = ide_read_data_dma( addr, length );

            MMIO_WRITE( EXTDMA, IDEDMATXSIZ, xfer );

            MMIO_WRITE( EXTDMA, IDEDMACTL2, 0 );

            asic_event( EVENT_IDE_DMA );            

        } else { /* 0 */

            MMIO_WRITE( EXTDMA, IDEDMACTL2, 0 );

        }

    }

}

void pvr_dma_transfer( )

{

    sh4addr_t destaddr = MMIO_READ( ASIC, PVRDMADEST) &0x1FFFFFE0;

    uint32_t count = MMIO_READ( ASIC, PVRDMACNT );

    unsigned char *data = alloca( count );

    uint32_t rcount = DMAC_get_buffer( 2, data, count );

    if( rcount != count )

        WARN( "PVR received %08X bytes from DMA, expected %08X", rcount, count );

    pvr2_dma_write( destaddr, data, rcount );

    MMIO_WRITE( ASIC, PVRDMACTL, 0 );

    MMIO_WRITE( ASIC, PVRDMACNT, 0 );

    if( destaddr & 0x01000000 ) { /* Write to texture RAM */

        MMIO_WRITE( ASIC, PVRDMADEST, destaddr + rcount );

    }

    asic_event( EVENT_PVR_DMA );

}

void pvr_dma2_transfer()

{

    if( MMIO_READ( EXTDMA, PVRDMA2CTL2 ) == 1 ) {

        if( MMIO_READ( EXTDMA, PVRDMA2CTL1 ) == 1 ) {

            sh4addr_t extaddr = MMIO_READ( EXTDMA, PVRDMA2EXT );

            sh4addr_t sh4addr = MMIO_READ( EXTDMA, PVRDMA2SH4 );

            int dir = MMIO_READ( EXTDMA, PVRDMA2DIR );

            uint32_t length = MMIO_READ( EXTDMA, PVRDMA2SIZ );

            unsigned char buf[length];

            if( dir == 0 ) { /* SH4 to PVR */

                mem_copy_from_sh4( buf, sh4addr, length );

                mem_copy_to_sh4( extaddr, buf, length );

            } else { /* PVR to SH4 */

                mem_copy_from_sh4( buf, extaddr, length );

                mem_copy_to_sh4( sh4addr, buf, length );

            }

            MMIO_WRITE( EXTDMA, PVRDMA2CTL2, 0 );

            asic_event( EVENT_PVR_DMA2 );

        }

    }

}

void sort_dma_transfer( )

{

    sh4addr_t table_addr = MMIO_READ( ASIC, SORTDMATBL );

    sh4addr_t data_addr = MMIO_READ( ASIC, SORTDMADATA );

    int table_size = MMIO_READ( ASIC, SORTDMATSIZ );

    int addr_shift = MMIO_READ( ASIC, SORTDMAASIZ ) ? 5 : 0;

    int count = 1;

    uint32_t *table32 = (uint32_t *)mem_get_region( table_addr );

    uint16_t *table16 = (uint16_t *)table32;

    uint32_t next = table_size ? (*table32++) : (uint32_t)(*table16++);

    while(1) {

        next &= 0x07FFFFFF;

        if( next == 1 ) {

            next = table_size ? (*table32++) : (uint32_t)(*table16++);

            count++;

            continue;

        } else if( next == 2 ) {

            asic_event( EVENT_SORT_DMA );

            break;

        } 

        uint32_t *data = (uint32_t *)mem_get_region(data_addr + (next<<addr_shift));

        if( data == NULL ) {

            break;

        }

        uint32_t *poly = pvr2_ta_find_polygon_context(data, 128);

        if( poly == NULL ) {

            asic_event( EVENT_SORT_DMA_ERR );

            break;

        }

        uint32_t size = poly[6] & 0xFF;

        if( size == 0 ) {

            size = 0x100;

        }

        next = poly[7];

        pvr2_ta_write( (unsigned char *)data, size<<5 );

    }

    MMIO_WRITE( ASIC, SORTDMACNT, count );

    MMIO_WRITE( ASIC, SORTDMACTL, 0 );

}

gboolean asic_enable_ide_interface( gboolean enable )

{

    gboolean oldval = idereg.interface_enabled;

    idereg.interface_enabled = enable;

    return oldval;

}

MMIO_REGION_READ_FN( ASIC, reg )

{

    int32_t val;

    reg &= 0xFFF;

    switch( reg ) {

    case PIRQ0:

    case PIRQ1:

    case PIRQ2:

    case IRQA0:

    case IRQA1:

    case IRQA2:

    case IRQB0:

    case IRQB1:

    case IRQB2:

    case IRQC0:

    case IRQC1:

    case IRQC2:

    case MAPLE_STATE:

        val = MMIO_READ(ASIC, reg);

        return val;            

    case G2STATUS:

        return g2_read_status();

    default:

        val = MMIO_READ(ASIC, reg);

        return val;

    }

}

MMIO_REGION_READ_DEFSUBFNS(ASIC)

MMIO_REGION_WRITE_FN( ASIC, reg, val )

{

    reg &= 0xFFF;

    switch( reg ) {

    case PIRQ1:

        break; /* Treat this as read-only for the moment */

    case PIRQ0:

        val = val & 0x3FFFFFFF; /* Top two bits aren't clearable */

        MMIO_WRITE( ASIC, reg, MMIO_READ(ASIC, reg)&~val );

        asic_check_cleared_events();

        break;

    case PIRQ2:

        /* Clear any events */

        val = MMIO_READ(ASIC, reg)&(~val);

        MMIO_WRITE( ASIC, reg, val );

        if( val == 0 ) { /* all clear - clear the cascade bit */

            MMIO_WRITE( ASIC, PIRQ0, MMIO_READ( ASIC, PIRQ0 ) & 0x7FFFFFFF );

        }

        asic_check_cleared_events();

        break;

    case IRQA0:

    case IRQA1:

    case IRQA2:

    case IRQB0:

    case IRQB1:

    case IRQB2:

    case IRQC0:

    case IRQC1:

    case IRQC2:

        MMIO_WRITE( ASIC, reg, val );

        asic_event_mask_changed();

        break;

    case SYSRESET:

        if( val == 0x7611 ) {

            dreamcast_reset();

        } else {

            WARN( "Unknown value %08X written to SYSRESET port", val );

        }

        break;

    case MAPLE_STATE:

        MMIO_WRITE( ASIC, reg, val );

        if( val & 1 ) {

            uint32_t maple_addr = MMIO_READ( ASIC, MAPLE_DMA) &0x1FFFFFE0;

            maple_handle_buffer( maple_addr );

            MMIO_WRITE( ASIC, reg, 0 );

        }

        break;

    case PVRDMADEST:

        MMIO_WRITE( ASIC, reg, (val & 0x03FFFFE0) | 0x10000000 );

        break;

    case PVRDMACNT: 

        MMIO_WRITE( ASIC, reg, val & 0x00FFFFE0 );

        break;

    case PVRDMACTL: /* Initiate PVR DMA transfer */

        val = val & 0x01;

        MMIO_WRITE( ASIC, reg, val );

        if( val == 1 ) {

            pvr_dma_transfer();

        }

        break;

    case SORTDMATBL: case SORTDMADATA:

        MMIO_WRITE( ASIC, reg, (val & 0x0FFFFFE0) | 0x08000000 );

        break;

    case SORTDMATSIZ: case SORTDMAASIZ:

        MMIO_WRITE( ASIC, reg, (val & 1) );

        break;

    case SORTDMACTL:

        val = val & 1;

        MMIO_WRITE( ASIC, reg, val );

        if( val == 1 ) {

            sort_dma_transfer();

        }

        break;

    case MAPLE_DMA:

        MMIO_WRITE( ASIC, reg, val );

        break;

    default:

        MMIO_WRITE( ASIC, reg, val );

    }

}

MMIO_REGION_READ_FN( EXTDMA, reg )

{

    uint32_t val;

    reg &= 0xFFF;

    if( !idereg.interface_enabled && IS_IDE_REGISTER(reg) ) {

        return 0xFFFFFFFF; /* disabled */

    }

    switch( reg ) {

    case IDEALTSTATUS: 

        val = idereg.status;

        return val;

    case IDEDATA: return ide_read_data_pio( );

    case IDEFEAT: return idereg.error;

    case IDECOUNT:return idereg.count;

    case IDELBA0: return ide_get_drive_status();

    case IDELBA1: return idereg.lba1;

    case IDELBA2: return idereg.lba2;

    case IDEDEV: return idereg.device;

    case IDECMD:

        val = ide_read_status();

        return val;

    default:

        val = MMIO_READ( EXTDMA, reg );

        return val;

    }

}

MMIO_REGION_READ_DEFSUBFNS(EXTDMA)

MMIO_REGION_WRITE_FN( EXTDMA, reg, val )

{

    reg &= 0xFFF;

    if( !idereg.interface_enabled && IS_IDE_REGISTER(reg) ) {

        return; /* disabled */

    }

    switch( reg ) {

    case IDEALTSTATUS: /* Device control */

        ide_write_control( val );

        break;

    case IDEDATA:

        ide_write_data_pio( val );

        break;

    case IDEFEAT:

        if( ide_can_write_regs() )

            idereg.feature = (uint8_t)val;

        break;

    case IDECOUNT:

        if( ide_can_write_regs() )

            idereg.count = (uint8_t)val;

        break;

    case IDELBA0:

        if( ide_can_write_regs() )

            idereg.lba0 = (uint8_t)val;

        break;

    case IDELBA1:

        if( ide_can_write_regs() )

            idereg.lba1 = (uint8_t)val;

        break;

    case IDELBA2:

        if( ide_can_write_regs() )

            idereg.lba2 = (uint8_t)val;

        break;

    case IDEDEV:

        if( ide_can_write_regs() )

            idereg.device = (uint8_t)val;

        break;

    case IDECMD:

        if( ide_can_write_regs() || val == IDE_CMD_NOP ) {

            ide_write_command( (uint8_t)val );

        }

        break;

    case IDEDMASH4:

        MMIO_WRITE( EXTDMA, reg, val & 0x1FFFFFE0 );

        break;

    case IDEDMASIZ:

        MMIO_WRITE( EXTDMA, reg, val & 0x01FFFFFE );

        break;

    case IDEDMADIR:

        MMIO_WRITE( EXTDMA, reg, val & 1 );

        break;

    case IDEDMACTL1:

    case IDEDMACTL2:

        MMIO_WRITE( EXTDMA, reg, val & 0x01 );

        asic_ide_dma_transfer( );

        break;

    case IDEACTIVATE:

        if( val == 0x001FFFFF ) {

            idereg.interface_enabled = TRUE;

            /* Conventional wisdom says that this is necessary but not

             * sufficient to enable the IDE interface.

             */

        } else if( val == 0x000042FE ) {

            idereg.interface_enabled = FALSE;

        }

        break;

    case G2DMA0EXT: case G2DMA0SH4: case G2DMA0SIZ:

    case G2DMA1EXT: case G2DMA1SH4: case G2DMA1SIZ:

    case G2DMA2EXT: case G2DMA2SH4: case G2DMA2SIZ:

    case G2DMA3EXT: case G2DMA3SH4: case G2DMA3SIZ:

        MMIO_WRITE( EXTDMA, reg, val & 0x9FFFFFE0 );

        break;

    case G2DMA0MOD: case G2DMA1MOD: case G2DMA2MOD: case G2DMA3MOD:

        MMIO_WRITE( EXTDMA, reg, val & 0x07 );

        break;

    case G2DMA0DIR: case G2DMA1DIR: case G2DMA2DIR: case G2DMA3DIR:

        MMIO_WRITE( EXTDMA, reg, val & 0x01 );

        break;

    case G2DMA0CTL1:

    case G2DMA0CTL2:

        MMIO_WRITE( EXTDMA, reg, val & 1);

        g2_dma_transfer( 0 );

        break;

    case G2DMA0STOP:

        MMIO_WRITE( EXTDMA, reg, val & 0x37 );

        break;

    case G2DMA1CTL1:

    case G2DMA1CTL2:

        MMIO_WRITE( EXTDMA, reg, val & 1);

        g2_dma_transfer( 1 );

        break;

    case G2DMA1STOP:

        MMIO_WRITE( EXTDMA, reg, val & 0x37 );

        break;

    case G2DMA2CTL1:

    case G2DMA2CTL2:

        MMIO_WRITE( EXTDMA, reg, val &1 );

        g2_dma_transfer( 2 );

        break;

    case G2DMA2STOP:

        MMIO_WRITE( EXTDMA, reg, val & 0x37 );

        break;

    case G2DMA3CTL1:

    case G2DMA3CTL2:

        MMIO_WRITE( EXTDMA, reg, val &1 );

        g2_dma_transfer( 3 );

        break;

    case G2DMA3STOP:

        MMIO_WRITE( EXTDMA, reg, val & 0x37 );

        break;

    case PVRDMA2CTL1:

    case PVRDMA2CTL2:

        MMIO_WRITE( EXTDMA, reg, val & 1 );

        pvr_dma2_transfer();

        break;

    default:

        MMIO_WRITE( EXTDMA, reg, val );

    }

}