fix(fc): fix fc dma interrupt (#1476)

pass cpu_interrupts_v2/4-irq_and_dma.nes

ares/fc/apu/apu.hpp

@@ -148,13 +148,14 @@ struct APU : Thread {
     auto clock() -> n8;
 
     auto power(bool reset) -> void;
+    auto setDMABuffer(n8 data) -> void;
+    auto dmaAddress() -> n16 const { return 0x8000 | readAddress; }
 
     //serialization.cpp
     auto serialize(serializer&) -> void;
 
     n16 lengthCounter;
     n16 periodCounter;
-    n16 dmaDelayCounter;
     n1  irqPending;
     n4  period;
     n1  irqEnable;

ares/fc/apu/dmc.cpp

@@ -2,44 +2,19 @@ auto APU::DMC::start() -> void {
   if(lengthCounter == 0) {
     readAddress = 0x4000 + (addressLatch << 6);
     lengthCounter = (lengthLatch << 4) + 1;
+
+    if (!dmaBufferValid)
+      cpu.dmcDMAPending();
   }
 }
 
 auto APU::DMC::stop() -> void {
   lengthCounter = 0;
-  dmaDelayCounter = 0;
-  cpu.rdyLine(1);
-  cpu.rdyAddress(false);
 }
 
 auto APU::DMC::clock() -> n8 {
   n8 result = dacLatch;
 
-  if(dmaDelayCounter > 0) {
-    dmaDelayCounter--;
-
-    if(dmaDelayCounter == 1) {
-      cpu.rdyAddress(true, 0x8000 | readAddress);
-    } else if(dmaDelayCounter == 0) {
-      cpu.rdyLine(1);
-      cpu.rdyAddress(false);
-
-      dmaBuffer = cpu.io.openBus;
-      dmaBufferValid = true;
-      lengthCounter--;
-      readAddress++;
-
-      if(lengthCounter == 0) {
-        if(loopMode) {
-          start();
-        } else if(irqEnable) {
-          irqPending = true;
-          apu.setIRQ();
-        }
-      }
-    }
-  }
-
   if(--periodCounter == 0) {
     if(sampleValid) {
       s32 delta = (((sample >> bitCounter) & 1) << 2) - 2;
@@ -52,6 +27,9 @@ auto APU::DMC::clock() -> n8 {
         sampleValid = true;
         sample = dmaBuffer;
         dmaBufferValid = false;
+
+        if (lengthCounter > 0)
+          cpu.dmcDMAPending();
       } else {
         sampleValid = false;
       }
@@ -60,18 +38,12 @@ auto APU::DMC::clock() -> n8 {
     periodCounter = Region::PAL() ? dmcPeriodTablePAL[period] : dmcPeriodTableNTSC[period];
   }
 
-  if(lengthCounter > 0 && !dmaBufferValid && dmaDelayCounter == 0) {
-    cpu.rdyLine(0);
-    dmaDelayCounter = 4;
-  }
-
   return result;
 }
 
 auto APU::DMC::power(bool reset) -> void {
   lengthCounter = 0;
   periodCounter = Region::PAL() ? dmcPeriodTablePAL[0] : dmcPeriodTableNTSC[0];
-  dmaDelayCounter = 0;
   irqPending = 0;
   period = 0;
   irqEnable = 0;
@@ -86,3 +58,19 @@ auto APU::DMC::power(bool reset) -> void {
   sampleValid = 0;
   sample = 0;
 }
+
+auto APU::DMC::setDMABuffer(n8 data) -> void {
+  dmaBuffer = data;
+  dmaBufferValid = true;
+  lengthCounter--;
+  readAddress++;
+
+  if (lengthCounter == 0) {
+    if (loopMode) {
+      start();
+    } else if (irqEnable) {
+      irqPending = true;
+      apu.setIRQ();
+    }
+  }
+}

ares/fc/apu/serialization.cpp

@@ -70,7 +70,6 @@ auto APU::Noise::serialize(serializer& s) -> void {
 auto APU::DMC::serialize(serializer& s) -> void {
   s(lengthCounter);
   s(periodCounter);
-  s(dmaDelayCounter);
   s(irqPending);
   s(period);
   s(irqEnable);

ares/fc/cpu/cpu.cpp

@@ -34,6 +34,7 @@ auto CPU::main() -> void {
 
 auto CPU::step(u32 clocks) -> void {
   assert(clocks == rate());
+  io.oddCycle ^= 1;
   Thread::step(clocks);
   Thread::synchronize();
 }

ares/fc/cpu/cpu.hpp

@@ -49,15 +49,13 @@ struct CPU : MOS6502, Thread {
   auto irqPending() -> bool override;
   auto nmi(n16& vector) -> void override;
 
-  auto oamDMA() -> void;
+  auto dmcDMAPending() -> void;
+  auto dma(n16 address) -> void;
 
   auto nmiLine(bool) -> void;
   auto irqLine(bool) -> void;
   auto apuLine(bool) -> void;
 
-  auto rdyLine(bool) -> void;
-  auto rdyAddress(bool valid, n16 value = 0) -> void;
-
 //protected:
   struct IO {
     n1  interruptPending;
@@ -65,9 +63,8 @@ struct CPU : MOS6502, Thread {
     n1  nmiLine;
     n1  irqLine;
     n1  apuLine;
-    n1  rdyLine = 1;
-    n1  rdyAddressValid;
-    n16 rdyAddressValue;
+    n1  oddCycle;
+    n1  dmcDMAPending;
     n1  oamDMAPending;
     n8  oamDMAPage;
     n8  openBus;

ares/fc/cpu/serialization.cpp

@@ -7,9 +7,7 @@ auto CPU::serialize(serializer& s) -> void {
   s(io.nmiLine);
   s(io.irqLine);
   s(io.apuLine);
-  s(io.rdyLine);
-  s(io.rdyAddressValid);
-  s(io.rdyAddressValue);
+  s(io.dmcDMAPending);
   s(io.oamDMAPending);
   s(io.oamDMAPage);
   s(io.openBus);

ares/fc/cpu/timing.cpp

@@ -1,13 +1,6 @@
 auto CPU::read(n16 address) -> n8 {
-  if(io.oamDMAPending) {
-    io.oamDMAPending = 0;
-    read(address);
-    oamDMA();
-  }
-
-  while(io.rdyLine == 0) {
-    io.openBus = readBus(io.rdyAddressValid ? io.rdyAddressValue : address);
-    step(rate());
+  if(io.oamDMAPending || io.dmcDMAPending) {
+    dma(address);
   }
 
   io.openBus = readBus(address);
@@ -43,10 +36,63 @@ auto CPU::nmi(n16& vector) -> void {
   }
 }
 
-auto CPU::oamDMA() -> void {
-  for(u32 n : range(256)) {
-    n8 data = read(io.oamDMAPage << 8 | n);
-    write(0x2004, data);
+auto CPU::dmcDMAPending() -> void {
+  io.dmcDMAPending = 1;
+}
+
+auto CPU::dma(n16 address) -> void {
+  bool dmcReady = false;
+  bool oamWriteReady = false;
+  n8   oamCounter = 0;
+
+  // halt read
+  io.openBus = readBus(address);
+  step(rate());
+
+  while (io.dmcDMAPending || io.oamDMAPending) {
+    if (io.oddCycle) {
+      // put_cycle
+      if (io.oamDMAPending && oamWriteReady) {
+        if (io.dmcDMAPending)
+          dmcReady = true;
+
+        // oam write
+        writeBus(0x2004, io.openBus);
+        step(rate());
+
+        oamWriteReady = false;
+        if (++oamCounter == 0)
+          io.oamDMAPending = 0;
+      } else {
+        // oam (re)alignment cycle
+        // dmc alignment cycle
+        if (io.dmcDMAPending)
+          dmcReady = true;
+
+        io.openBus = readBus(address);
+        step(rate());
+      }
+    } else {
+      // get_cycle
+      if (io.dmcDMAPending && dmcReady) {
+        // dmc read
+        io.openBus = readBus(apu.dmc.dmaAddress());
+        step(rate());
+
+        apu.dmc.setDMABuffer(io.openBus);
+        io.dmcDMAPending = 0;
+        dmcReady = false;
+      } else if (io.oamDMAPending) {
+        // oam read
+        io.openBus = readBus(io.oamDMAPage << 8 | oamCounter);
+        step(rate());
+        oamWriteReady = true;
+      } else {
+        // dmc dummy read cycle
+        io.openBus = readBus(address);
+        step(rate());
+      }
+    }
   }
 }
 
@@ -65,12 +111,3 @@ auto CPU::apuLine(bool line) -> void {
   //level-sensitive
   io.apuLine = line;
 }
-
-auto CPU::rdyLine(bool line) -> void {
-  io.rdyLine = line;
-}
-
-auto CPU::rdyAddress(bool valid, n16 value) -> void {
-  io.rdyAddressValid = valid;
-  io.rdyAddressValue = value;
-}

ares/fc/system/serialization.cpp

@@ -1,4 +1,4 @@
-static const string SerializerVersion = "v140";
+static const string SerializerVersion = "v141";
 
 auto System::serialize(bool synchronize) -> serializer {
   if(synchronize) scheduler.enter(Scheduler::Mode::Synchronize);