/**

  * $Id$

  *

  * 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 );

 }

 void mmio_region_ASIC_write( uint32_t reg, uint32_t val )

 {

     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 );

     }

 }

 int32_t mmio_region_ASIC_read( uint32_t reg )

 {

     int32_t val;

     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_WRITE_FN( EXTDMA, reg, val )

 {

     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 );

     }

 }

 MMIO_REGION_READ_FN( EXTDMA, reg )

 {

     uint32_t val;

     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;

     }

 }