From 9d5f3c1306448169a3e5848c392bba3f947284a1 Mon Sep 17 00:00:00 2001
From: Connor McLaughlin <mclaughc@outlook.com>
Date: Fri, 18 Oct 2019 00:20:38 +1000
Subject: [PATCH] CPU: Support stalling CPU for bus activity such as DMA

---
 src/core/cpu_core.h | 5 +++++
 src/core/system.cpp | 5 +++++
 src/core/system.h   | 3 +++
 3 files changed, 13 insertions(+)

diff --git a/src/core/cpu_core.h b/src/core/cpu_core.h
index 7da313134..2a0abf653 100644
--- a/src/core/cpu_core.h
+++ b/src/core/cpu_core.h
@@ -35,6 +35,11 @@ public:
 
   TickCount GetPendingTicks() const { return m_pending_ticks; }
   void ResetPendingTicks() { m_pending_ticks = 0; }
+  void AddPendingTicks(TickCount ticks)
+  {
+    m_pending_ticks += ticks;
+    m_downcount -= ticks;
+  }
 
   void SetDowncount(TickCount downcount) { m_downcount = (downcount < m_downcount) ? downcount : m_downcount; }
   void ResetDowncount() { m_downcount = MAX_SLICE_SIZE; }
diff --git a/src/core/system.cpp b/src/core/system.cpp
index 4a1863570..448586bd7 100644
--- a/src/core/system.cpp
+++ b/src/core/system.cpp
@@ -296,6 +296,11 @@ void System::SetDowncount(TickCount downcount)
   m_cpu->SetDowncount(downcount);
 }
 
+void System::StallCPU(TickCount ticks)
+{
+  m_cpu->AddPendingTicks(ticks);
+}
+
 void System::SetController(u32 slot, std::shared_ptr<PadDevice> dev)
 {
   m_pad->SetController(slot, std::move(dev));
diff --git a/src/core/system.h b/src/core/system.h
index 6d6752747..10a1645ab 100644
--- a/src/core/system.h
+++ b/src/core/system.h
@@ -58,6 +58,9 @@ public:
   void SetDowncount(TickCount downcount);
   void Synchronize();
 
+  // Adds ticks to the global tick counter, simulating the CPU being stalled.
+  void StallCPU(TickCount ticks);
+
   void SetController(u32 slot, std::shared_ptr<PadDevice> dev);
   void SetMemoryCard(u32 slot, std::shared_ptr<PadDevice> dev);