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GBA DMA: Remove `hasStarted` flag

This commit is contained in:
Jeffrey Pfau 2016-12-19 16:55:47 -08:00
parent 1c93b75b7e
commit 81416863a5
2 changed files with 33 additions and 36 deletions
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68
src/gba/dma.c
View File

@ -91,7 +91,7 @@ uint16_t GBADMAWriteCNT_HI(struct GBA* gba, int dma, uint16_t control) {
void GBADMASchedule(struct GBA* gba, int number, struct GBADMA* info) { void GBADMASchedule(struct GBA* gba, int number, struct GBADMA* info) {
switch (GBADMARegisterGetTiming(info->reg)) { switch (GBADMARegisterGetTiming(info->reg)) {
case DMA_TIMING_NOW: case DMA_TIMING_NOW:
info->when = mTimingCurrentTime(&gba->timing) + 2 + 1; // XXX: Account for I cycle when writing info->when = mTimingCurrentTime(&gba->timing) + 3; // DMAs take 3 cycles to start
info->nextCount = info->count; info->nextCount = info->count;
break; break;
case DMA_TIMING_HBLANK: case DMA_TIMING_HBLANK:
@ -121,8 +121,8 @@ void GBADMARunHblank(struct GBA* gba, int32_t cycles) {
int i; int i;
for (i = 0; i < 4; ++i) { for (i = 0; i < 4; ++i) {
dma = &memory->dma[i]; dma = &memory->dma[i];
if (GBADMARegisterIsEnable(dma->reg) && GBADMARegisterGetTiming(dma->reg) == DMA_TIMING_HBLANK && !dma->hasStarted) { if (GBADMARegisterIsEnable(dma->reg) && GBADMARegisterGetTiming(dma->reg) == DMA_TIMING_HBLANK && !dma->nextCount) {
dma->when = mTimingCurrentTime(&gba->timing) + 2 + cycles; dma->when = mTimingCurrentTime(&gba->timing) + 3 + cycles;
dma->nextCount = dma->count; dma->nextCount = dma->count;
} }
} }
@ -135,8 +135,8 @@ void GBADMARunVblank(struct GBA* gba, int32_t cycles) {
int i; int i;
for (i = 0; i < 4; ++i) { for (i = 0; i < 4; ++i) {
dma = &memory->dma[i]; dma = &memory->dma[i];
if (GBADMARegisterIsEnable(dma->reg) && GBADMARegisterGetTiming(dma->reg) == DMA_TIMING_VBLANK && !dma->hasStarted) { if (GBADMARegisterIsEnable(dma->reg) && GBADMARegisterGetTiming(dma->reg) == DMA_TIMING_VBLANK && !dma->nextCount) {
dma->when = mTimingCurrentTime(&gba->timing) + 2 + cycles; dma->when = mTimingCurrentTime(&gba->timing) + 3 + cycles;
dma->nextCount = dma->count; dma->nextCount = dma->count;
} }
} }
@ -149,7 +149,27 @@ void _dmaEvent(struct mTiming* timing, void* context, uint32_t cyclesLate) {
struct GBA* gba = context; struct GBA* gba = context;
struct GBAMemory* memory = &gba->memory; struct GBAMemory* memory = &gba->memory;
struct GBADMA* dma = &memory->dma[memory->activeDMA]; struct GBADMA* dma = &memory->dma[memory->activeDMA];
GBADMAService(gba, memory->activeDMA, dma); if (dma->nextCount == dma->count) {
dma->when = mTimingCurrentTime(&gba->timing);
}
if (dma->nextCount & 0xFFFFF) {
GBADMAService(gba, memory->activeDMA, dma);
} else {
dma->nextCount = 0;
if (!GBADMARegisterIsRepeat(dma->reg) || GBADMARegisterGetTiming(dma->reg) == DMA_TIMING_NOW) {
dma->reg = GBADMARegisterClearEnable(dma->reg);
// Clear the enable bit in memory
memory->io[(REG_DMA0CNT_HI + memory->activeDMA * (REG_DMA1CNT_HI - REG_DMA0CNT_HI)) >> 1] &= 0x7FE0;
}
if (GBADMARegisterGetDestControl(dma->reg) == DMA_INCREMENT_RELOAD) {
dma->nextDest = dma->dest;
}
if (GBADMARegisterIsDoIRQ(dma->reg)) {
GBARaiseIRQ(gba, IRQ_DMA0 + memory->activeDMA);
}
GBADMAUpdate(gba);
}
} }
void GBADMAUpdate(struct GBA* gba) { void GBADMAUpdate(struct GBA* gba) {
@ -157,13 +177,11 @@ void GBADMAUpdate(struct GBA* gba) {
struct GBAMemory* memory = &gba->memory; struct GBAMemory* memory = &gba->memory;
memory->activeDMA = -1; memory->activeDMA = -1;
uint32_t currentTime = mTimingCurrentTime(&gba->timing); uint32_t currentTime = mTimingCurrentTime(&gba->timing);
for (i = 3; i >= 0; --i) { for (i = 0; i < 4; ++i) {
struct GBADMA* dma = &memory->dma[i]; struct GBADMA* dma = &memory->dma[i];
if (GBADMARegisterIsEnable(dma->reg) && dma->nextCount) { if (GBADMARegisterIsEnable(dma->reg) && dma->nextCount) {
if (dma->when < currentTime) {
dma->when = currentTime;
}
memory->activeDMA = i; memory->activeDMA = i;
break;
} }
} }
@ -187,7 +205,7 @@ void GBADMAService(struct GBA* gba, int number, struct GBADMA* info) {
int32_t cycles = 2; int32_t cycles = 2;
gba->cpuBlocked = true; gba->cpuBlocked = true;
if (info->hasStarted < 2) { if (info->count == info->nextCount) {
if (sourceRegion < REGION_CART0 || destRegion < REGION_CART0) { if (sourceRegion < REGION_CART0 || destRegion < REGION_CART0) {
cycles += 2; cycles += 2;
} }
@ -196,13 +214,6 @@ void GBADMAService(struct GBA* gba, int number, struct GBADMA* info) {
} else { } else {
cycles += memory->waitstatesNonseq16[sourceRegion] + memory->waitstatesNonseq16[destRegion]; cycles += memory->waitstatesNonseq16[sourceRegion] + memory->waitstatesNonseq16[destRegion];
} }
if (info->hasStarted < 1) {
info->hasStarted = info->count << 1;
info->when = mTimingCurrentTime(&gba->timing) + cycles;
GBADMAUpdate(gba);
return;
}
info->hasStarted = 2;
source &= -width; source &= -width;
dest &= -width; dest &= -width;
} else { } else {
@ -244,24 +255,11 @@ void GBADMAService(struct GBA* gba, int number, struct GBADMA* info) {
--wordsRemaining; --wordsRemaining;
gba->performingDMA = 0; gba->performingDMA = 0;
if (!wordsRemaining) {
info->hasStarted = 0;
if (!GBADMARegisterIsRepeat(info->reg) || GBADMARegisterGetTiming(info->reg) == DMA_TIMING_NOW) {
info->reg = GBADMARegisterClearEnable(info->reg);
// Clear the enable bit in memory
memory->io[(REG_DMA0CNT_HI + number * (REG_DMA1CNT_HI - REG_DMA0CNT_HI)) >> 1] &= 0x7FE0;
}
if (GBADMARegisterGetDestControl(info->reg) == DMA_INCREMENT_RELOAD) {
info->nextDest = info->dest;
}
if (GBADMARegisterIsDoIRQ(info->reg)) {
GBARaiseIRQ(gba, IRQ_DMA0 + number);
}
} else {
info->nextDest = dest;
}
info->nextCount = wordsRemaining; info->nextCount = wordsRemaining;
info->nextSource = source; info->nextSource = source;
info->nextDest = dest;
if (!wordsRemaining) {
info->nextCount |= 0x80000000;
}
GBADMAUpdate(gba); GBADMAUpdate(gba);
} }

1
src/gba/memory.h
View File

@ -109,7 +109,6 @@ struct GBADMA {
uint32_t nextDest; uint32_t nextDest;
int32_t nextCount; int32_t nextCount;
uint32_t when; uint32_t when;
int32_t hasStarted;
}; };
struct GBAMemory { struct GBAMemory {