Haze: Simplified VDP data reading to use read_word now that the RV bit of 32x is emulated (can use read-word on the 68k space without breaking Tempo Graphics)

Added a function to SH2 to allow the 32x to tell it when data is available to DMA, prevents excessive polling with high frequency timer in Chaotix, and improves performance in said game.

src/emu/cpu/sh2/sh2comn.c

@@ -106,6 +106,7 @@ static void sh2_timer_activate(sh2_state *sh2)
 	}
 }
 
+
 static TIMER_CALLBACK( sh2_timer_callback )
 {
 	sh2_state *sh2 = (sh2_state *)ptr;
@@ -157,6 +158,26 @@ static TIMER_CALLBACK( sh2_timer_callback )
 */
 
 
+
+void sh2_notify_dma_data_available(running_device *device)
+{
+	sh2_state *sh2 = GET_SH2(device);
+	//printf("call notify\n");
+	
+	for (int dma=0;dma<2;dma++)
+	{
+		//printf("sh2->dma_timer_active[dma] %04x\n",sh2->dma_timer_active[dma]);
+		
+		if (sh2->dma_timer_active[dma]==2) // 2 = stalled
+		{
+		//	printf("resuming stalled dma\n");
+			sh2->dma_timer_active[dma]=1;
+			timer_adjust_oneshot(sh2->dma_current_active_timer[dma], attotime_zero, dma);
+		}		
+	}
+
+}
+
 void sh2_do_dma(sh2_state *sh2, int dma)
 {
 	UINT32 dmadata;
@@ -165,10 +186,7 @@ void sh2_do_dma(sh2_state *sh2, int dma)
 
 	if (sh2->active_dma_count[dma] > 0)
 	{
-#ifdef USE_TIMER_FOR_DMA
+
-		 //schedule next DMA callback
-		timer_adjust_oneshot(sh2->dma_current_active_timer[dma], sh2->device->cycles_to_attotime(2), dma);
-#endif
 
 		// process current DMA
 		switch(sh2->active_dma_size[dma])
@@ -194,9 +212,18 @@ void sh2_do_dma(sh2_state *sh2, int dma)
 					int available = sh2->dma_callback_fifo_data_available(tempsrc, tempdst, 0, sh2->active_dma_size[dma]);
 	
 					if (!available)
+					{
+						//printf("dma stalled\n");
+						sh2->dma_timer_active[dma]=2;// mark as stalled
 						return;
+					}
 				}
-					
+			
+				#ifdef USE_TIMER_FOR_DMA
+				 //schedule next DMA callback
+				timer_adjust_oneshot(sh2->dma_current_active_timer[dma], sh2->device->cycles_to_attotime(2), dma);
+				#endif
+		
 
 				dmadata = sh2->program->read_byte(tempsrc);
 				if (sh2->dma_callback_kludge) dmadata = sh2->dma_callback_kludge(tempsrc, tempdst, dmadata, sh2->active_dma_size[dma]);
@@ -233,9 +260,18 @@ void sh2_do_dma(sh2_state *sh2, int dma)
 					int available = sh2->dma_callback_fifo_data_available(tempsrc, tempdst, 0, sh2->active_dma_size[dma]);
 	
 					if (!available)
+					{
+						//printf("dma stalled\n");
+						sh2->dma_timer_active[dma]=2;// mark as stalled
 						return;
+					}
 				}
 
+				#ifdef USE_TIMER_FOR_DMA
+				 //schedule next DMA callback
+				timer_adjust_oneshot(sh2->dma_current_active_timer[dma], sh2->device->cycles_to_attotime(2), dma);
+				#endif
+
 				// check: should this really be using read_word_32 / write_word_32?
 				dmadata	= sh2->program->read_word(tempsrc);
 				if (sh2->dma_callback_kludge) dmadata = sh2->dma_callback_kludge(tempsrc, tempdst, dmadata, sh2->active_dma_size[dma]);
@@ -271,9 +307,18 @@ void sh2_do_dma(sh2_state *sh2, int dma)
 					int available = sh2->dma_callback_fifo_data_available(tempsrc, tempdst, 0, sh2->active_dma_size[dma]);
 	
 					if (!available)
+					{
+						//printf("dma stalled\n");
+						sh2->dma_timer_active[dma]=2;// mark as stalled
 						return;
+					}
 				}
 
+				#ifdef USE_TIMER_FOR_DMA
+				 //schedule next DMA callback
+				timer_adjust_oneshot(sh2->dma_current_active_timer[dma], sh2->device->cycles_to_attotime(2), dma);
+				#endif
+
 				dmadata	= sh2->program->read_dword(tempsrc);
 				if (sh2->dma_callback_kludge) dmadata = sh2->dma_callback_kludge(tempsrc, tempdst, dmadata, sh2->active_dma_size[dma]);
 				sh2->program->write_dword(tempdst, dmadata);
@@ -307,9 +352,18 @@ void sh2_do_dma(sh2_state *sh2, int dma)
 					int available = sh2->dma_callback_fifo_data_available(tempsrc, tempdst, 0, sh2->active_dma_size[dma]);
 	
 					if (!available)
+					{
+						//printf("dma stalled\n");
+						sh2->dma_timer_active[dma]=2;// mark as stalled
 						fatalerror("SH2 dma_callback_fifo_data_available == 0 in unsupported mode");
+					}
 				}
 
+				#ifdef USE_TIMER_FOR_DMA
+				 //schedule next DMA callback
+				timer_adjust_oneshot(sh2->dma_current_active_timer[dma], sh2->device->cycles_to_attotime(2), dma);
+				#endif
+
 				dmadata = sh2->program->read_dword(tempsrc);
 				if (sh2->dma_callback_kludge) dmadata = sh2->dma_callback_kludge(tempsrc, tempdst, dmadata, sh2->active_dma_size[dma]);
 				sh2->program->write_dword(tempdst, dmadata);

src/emu/cpu/sh2/sh2comn.h

@@ -189,5 +189,6 @@ void sh2_recalc_irq(sh2_state *sh2);
 void sh2_set_irq_line(sh2_state *sh2, int irqline, int state);
 void sh2_exception(sh2_state *sh2, const char *message, int irqline);
 void sh2_do_dma(sh2_state *sh2, int dma);
+void sh2_notify_dma_data_available(running_device *device);
 
 #endif /* __SH2COMN_H__ */

src/mame/drivers/megadriv.c

@@ -75,6 +75,7 @@ On SegaC2 the VDP never turns on the IRQ6 enable register
 #include "cpu/m68000/m68000.h"
 #include "includes/megadriv.h"
 #include "cpu/sh2/sh2.h"
+#include "cpu/sh2/sh2comn.h"
 
 #define MEGADRIV_VDP_VRAM(address) megadrive_vdp_vram[(address)&0x7fff]
 
@@ -621,19 +622,17 @@ static UINT16 vdp_get_word_from_68k_mem_default(running_machine *machine, UINT32
 {
 	// should we limit the valid areas here?
 	// how does this behave with the segacd etc?
-	// with the 32x it seems to see the raw cart? - using 68k space causes the character to vanish
 	// svp uses it's own function elsewhere...
+	// note, the RV bit on 32x is important for this to work, because it causes a normal cart mapping - see tempo
+	address_space *space68k = machine->device<legacy_cpu_device>("maincpu")->space();
 
 	if (( source >= 0x000000 ) && ( source <= 0x3fffff ))
 	{
-		UINT16 *rom = (UINT16*)memory_region(machine, "maincpu");
+		return space68k->read_word(source);
-		return rom[(source&0x3fffff)>>1];
 	}
 	else if (( source >= 0xe00000 ) && ( source <= 0xffffff ))
 	{
-//      mame_printf_debug("dma\n");
+		return space68k->read_word(source);
-	//  return ((megadrive_ram[(source&0xffff)>>1]&0xff00)>>8)|((megadrive_ram[(source&0xffff)>>1]&0x00ff)<<8);
-		return megadrive_ram[(source&0xffff)>>1];
 	}
 	else
 	{
@@ -2366,6 +2365,10 @@ static WRITE16_HANDLER( _32x_68k_a15112_w )
 			{
 				current_fifo_block = fifo_block_b;
 				current_fifo_readblock = fifo_block_a;
+				// incase we have a stalled DMA in progress, let the SH2 know there is data available
+				sh2_notify_dma_data_available(space->machine->device("32x_master_sh2"));
+				sh2_notify_dma_data_available(space->machine->device("32x_slave_sh2"));
+				
 			}
 			current_fifo_write_pos = 0;
 		}
@@ -2377,6 +2380,10 @@ static WRITE16_HANDLER( _32x_68k_a15112_w )
 			{
 				current_fifo_block = fifo_block_a;
 				current_fifo_readblock = fifo_block_b;
+				// incase we have a stalled DMA in progress, let the SH2 know there is data available
+				sh2_notify_dma_data_available(space->machine->device("32x_master_sh2"));
+				sh2_notify_dma_data_available(space->machine->device("32x_slave_sh2"));
+
 			}
 
 			current_fifo_write_pos = 0;
@@ -2395,7 +2402,7 @@ static WRITE16_HANDLER( _32x_68k_a15112_w )
  F = Fifo FULL
  K = 68k CPU Write mode (0 = no, 1 = CPU write)
  0 = always 0? no, marsch test wants it to be latched or 1
- R = RV (0 = no operation, 1 = DMA Start allowed)
+ R = RV (0 = no operation, 1 = DMA Start allowed) <-- RV bit actually affects memory mapping, this is misleading..  it just sets the memory up in a suitable way to use the genesis VDP DMA
 
 */
 
@@ -2420,8 +2427,21 @@ static WRITE16_HANDLER( _32x_68k_a15106_w )
 		a15106_reg = data & 0x7;
 
         if (a15106_reg & 0x1) /* NBA Jam TE relies on this */
+		{
+			
+			// install the game rom in the normal 0x000000-0x03fffff space used by the genesis - this allows VDP DMA operations to work as they have to be from this area or RAM
+			// it should also UNMAP the banked rom area...
 			memory_install_rom(space, 0x0000100, 0x03fffff, 0, 0, memory_region(space->machine, "gamecart") + 0x100);
-
+		}
+		else
+		{
+			// we should be careful and map back any rom overlay (hint) and backup ram too I think...
+			
+			// this is actually blank / nop area
+			// we should also map the banked area back (we don't currently unmap it tho)
+			memory_install_rom(space, 0x0000100, 0x03fffff, 0, 0, memory_region(space->machine, "maincpu")+0x100);
+		}
+		
 		//printf("_32x_68k_a15106_w %04x\n", data);
 		/*
         if (a15106_reg & 0x4)
@@ -3087,7 +3107,7 @@ static WRITE16_HANDLER( _32x_sh2_common_4004_w )
 
 static READ16_HANDLER( _32x_sh2_common_4006_r )
 {
-	printf("DREQ read!\n");
+	//printf("DREQ read!\n"); // tempo reads it, shut up for now
 	return 0;
 }
 
@@ -6810,7 +6830,6 @@ ROM_START( 32x_bios )
 
 	ROM_REGION16_BE( 0x400000, "maincpu", ROMREGION_ERASE00 )
 	// temp, rom should only be visible here when one of the regs is set, tempo needs it
-	ROM_COPY( "gamecart", 0x0, 0x0, 0x400000)
 	ROM_COPY( "32x_68k_bios", 0x0, 0x0, 0x100)
 
 	ROM_REGION( 0x400000, "32x_master_sh2", 0 ) /* SH2 Code */