small MI refactor in preparation of (eventually) implementing the RDRAM interface properly

src/backend/core/mmio/Interrupt.cpp

@@ -1,50 +1,50 @@
 #include <Core.hpp>
 
 namespace n64 {
-void MI::InterruptRaise(const Interrupt intr) {
-  switch (intr) {
+void MI::InterruptRaise(const Interrupt intType) {
+  switch (intType) {
   case Interrupt::VI:
-    miIntr.vi = true;
+    intr.vi = true;
     break;
   case Interrupt::SI:
-    miIntr.si = true;
+    intr.si = true;
     break;
   case Interrupt::PI:
-    miIntr.pi = true;
+    intr.pi = true;
     break;
   case Interrupt::AI:
-    miIntr.ai = true;
+    intr.ai = true;
     break;
   case Interrupt::DP:
-    miIntr.dp = true;
+    intr.dp = true;
     break;
   case Interrupt::SP:
-    miIntr.sp = true;
+    intr.sp = true;
     break;
   }
 
   UpdateInterrupt();
 }
 
-void MI::InterruptLower(const Interrupt intr) {
-  switch (intr) {
+void MI::InterruptLower(const Interrupt intType) {
+  switch (intType) {
   case Interrupt::VI:
-    miIntr.vi = false;
+    intr.vi = false;
     break;
   case Interrupt::SI:
-    miIntr.si = false;
+    intr.si = false;
     break;
   case Interrupt::PI:
-    miIntr.pi = false;
+    intr.pi = false;
     break;
   case Interrupt::AI:
-    miIntr.ai = false;
+    intr.ai = false;
     break;
   case Interrupt::DP:
-    miIntr.dp = false;
+    intr.dp = false;
     break;
   case Interrupt::SP:
-    miIntr.sp = false;
+    intr.sp = false;
     break;
   }
 
@@ -53,7 +53,7 @@ void MI::InterruptLower(const Interrupt intr) {
 
 void MI::UpdateInterrupt() const {
   n64::Registers& regs = n64::Core::GetRegs();
-  const bool interrupt = miIntr.raw & miIntrMask.raw;
+  const bool interrupt = intr.raw & intrMask.raw;
   regs.cop0.cause.ip2 = interrupt;
 }
 } // namespace n64

src/backend/core/mmio/MI.cpp

@@ -8,58 +8,36 @@ namespace n64 {
 MI::MI() { Reset(); }
 
 void MI::Reset() {
-  miIntrMask.raw = 0;
-  miIntr.raw = 0;
-  miMode = 0;
+  intrMask.raw = 0;
+  intr.raw = 0;
+  mode.raw = 0;
 }
 
 auto MI::Read(u32 paddr) const -> u32 {
   switch (paddr & 0xF) {
   case 0x0:
-    return miMode & 0x3FF;
+    return mode.raw & 0x3FF;
   case 0x4:
     return MI_VERSION_REG;
   case 0x8:
-    return miIntr.raw & 0x3F;
+    return intr.raw & 0x3F;
   case 0xC:
-    return miIntrMask.raw & 0x3F;
+    return intrMask.raw & 0x3F;
   default:
     panic("Unhandled MI[{:08X}] read", paddr);
   }
 }
 
 void MI::Write(u32 paddr, u32 val) {
-  switch (paddr & 0xF) {
-  case 0x0:
-    miMode &= 0xFFFFFF80;
-    miMode |= val & 0x7F;
-    if (val & (1 << 7)) {
-      miMode &= ~(1 << 7);
-    }
-
-    if (val & (1 << 8)) {
-      miMode |= 1 << 7;
-    }
-
-    if (val & (1 << 9)) {
-      miMode &= ~(1 << 8);
-    }
-
-    if (val & (1 << 10)) {
-      miMode |= 1 << 8;
-    }
-
-    if (val & (1 << 11)) {
+  switch (paddr & 0xF) { //-----------sc-cscs-cvvv-vvvv
+  case 0x0: //  ----|----|----|----|--uu|deer|rccc|cccc
+    mode.repeatCount = val & 0x7F;
+    mode.repeat = val & 0x100 ? 1 : val & 0x80 ? 0 : mode.repeat;
+    mode.ebus = val & 0x400 ? 1 : val & 0x200 ? 0 : mode.ebus;
+    mode.upper = val & 0x2000 ? 1 : val & 0x1000 ? 0 : mode.upper;
+    if(val & 0x800) {
       InterruptLower(Interrupt::DP);
     }
-
-    if (val & (1 << 12)) {
-      miMode &= ~(1 << 9);
-    }
-
-    if (val & (1 << 13)) {
-      miMode |= 1 << 9;
-    }
     break;
   case 0x4:
   case 0x8:
@@ -70,11 +48,11 @@ void MI::Write(u32 paddr, u32 val) {
       const int setbit = (bit << 1) + 1;
 
       if (val & (1 << clearbit)) {
-        miIntrMask.raw &= ~(1 << bit);
+        intrMask.raw &= ~(1 << bit);
       }
 
       if (val & (1 << setbit)) {
-        miIntrMask.raw |= 1 << bit;
+        intrMask.raw |= 1 << bit;
       }
     }
 

src/backend/core/mmio/MI.hpp

@@ -3,7 +3,8 @@
 
 namespace n64 {
 
-union MIIntr {
+struct MI {
+  union Intr {
     struct {
       unsigned sp : 1;
       unsigned si : 1;
@@ -14,9 +15,20 @@ union MIIntr {
       unsigned : 26;
     };
     u32 raw;
-};
+  };
+
+  union Mode {
+    struct {
+      unsigned repeatCount:7;
+      unsigned repeat:1;
+      unsigned ebus:1;
+      unsigned upper:1;
+      unsigned : 22;
+    };
+    
+    u32 raw;
+  };
 
-struct MI {
   enum class Interrupt : u8 { VI, SI, PI, AI, DP, SP };
 
   explicit MI();
@@ -27,7 +39,7 @@ struct MI {
   void InterruptLower(Interrupt intr);
   void UpdateInterrupt() const;
 
-  u32 miMode{};
-  MIIntr miIntr{}, miIntrMask{};
+  Mode mode{};
+  Intr intr{}, intrMask{};
 };
 } // namespace n64

src/backend/core/mmio/PI.cpp

@@ -426,7 +426,7 @@ auto PI::Read(u32 addr) const -> u32 {
       value |= (dmaBusy << 0); // Is PI DMA active? No, because it's instant
       value |= (ioBusy << 1); // Is PI IO busy? No, because it's instant
       value |= (0 << 2); // PI IO error?
-      value |= (mem.mmio.mi.miIntr.pi << 3); // PI interrupt?
+      value |= (mem.mmio.mi.intr.pi << 3); // PI interrupt?
       return value;
     }
   case 0x04600014:

src/backend/core/mmio/SI.cpp

@@ -28,7 +28,7 @@ auto SI::Read(u32 addr) const -> u32 {
       val |= status.dmaBusy;
       val |= (0 << 1);
       val |= (0 << 3);
-      val |= (mem.mmio.mi.miIntr.si << 12);
+      val |= (mem.mmio.mi.intr.si << 12);
       return val;
     }
   default: