Timers: Correctly handle sync mode 0/3 for timer 2

src/core/timers.cpp

@@ -64,7 +64,7 @@ struct CounterState
 
 } // namespace
 
-static void UpdateCountingEnabled(CounterState& cs);
+static void UpdateCountingEnabled(u32 index, CounterState& cs);
 static void CheckForIRQ(u32 index, u32 old_counter);
 
 static void AddSysClkTicks(void*, TickCount sysclk_ticks);
@@ -198,7 +198,7 @@ void Timers::SetGate(u32 timer, bool state)
       UnreachableCode();
   }
 
-  UpdateCountingEnabled(cs);
+  UpdateCountingEnabled(timer, cs);
   UpdateSysClkEvent();
 }
 
@@ -432,7 +432,7 @@ void Timers::WriteRegister(u32 offset, u32 value)
       InterruptController::SetLineState(
         static_cast<InterruptController::IRQ>(static_cast<u32>(InterruptController::IRQ::TMR0) + timer_index), false);
 
-      UpdateCountingEnabled(cs);
+      UpdateCountingEnabled(timer_index, cs);
       CheckForIRQ(timer_index, cs.counter);
       UpdateSysClkEvent();
     }
@@ -454,32 +454,41 @@ void Timers::WriteRegister(u32 offset, u32 value)
   }
 }
 
-void Timers::UpdateCountingEnabled(CounterState& cs)
+void Timers::UpdateCountingEnabled(u32 index, CounterState& cs)
 {
-  if (cs.mode.sync_enable)
+  if (index != 2)
   {
-    switch (cs.mode.sync_mode)
+    if (cs.mode.sync_enable)
     {
-      case SyncMode::PauseWhileGateActive:
-        cs.counting_enabled = !cs.gate;
-        break;
+      switch (cs.mode.sync_mode)
+      {
+        case SyncMode::PauseWhileGateActive:
+          cs.counting_enabled = !cs.gate;
+          break;
 
-      case SyncMode::ResetOnGateEnd:
-        cs.counting_enabled = true;
-        break;
+        case SyncMode::ResetOnGateEnd:
+          cs.counting_enabled = true;
+          break;
 
-      case SyncMode::ResetAndRunOnGateStart:
-      case SyncMode::FreeRunOnGateEnd:
-        cs.counting_enabled = cs.gate;
-        break;
+        case SyncMode::ResetAndRunOnGateStart:
+        case SyncMode::FreeRunOnGateEnd:
+          cs.counting_enabled = cs.gate;
+          break;
 
-      default:
-        UnreachableCode();
+        default:
+          UnreachableCode();
+      }
+    }
+    else
+    {
+      cs.counting_enabled = true;
     }
   }
   else
   {
-    cs.counting_enabled = true;
+    // Timer 2 doesn't have a gate source. With sync enabled, modes 0/3 stop counting and 1/2 free-run.
+    cs.counting_enabled = (!cs.mode.sync_enable || cs.mode.sync_mode == SyncMode::ResetOnGateEnd ||
+                           cs.mode.sync_mode == SyncMode::ResetAndRunOnGateStart);
   }
 
   cs.external_counting_enabled = cs.use_external_clock && cs.counting_enabled;