From 0e0fec3075d58fe0cc8332bd209fcc3256fd30ba Mon Sep 17 00:00:00 2001
From: booto <remornicus@gmail.com>
Date: Wed, 16 Sep 2015 03:22:01 +0800
Subject: [PATCH] AI: reduce overhead of sample counter

---
 Source/Core/Core/HW/AudioInterface.cpp | 27 +++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/Source/Core/Core/HW/AudioInterface.cpp b/Source/Core/Core/HW/AudioInterface.cpp
index 9849127e5437..f810a85fc5c0 100644
--- a/Source/Core/Core/HW/AudioInterface.cpp
+++ b/Source/Core/Core/HW/AudioInterface.cpp
@@ -133,7 +133,7 @@ void DoState(PointerWrap &p)
 static void GenerateAudioInterrupt();
 static void UpdateInterrupts();
 static void IncreaseSampleCount(const u32 _uAmount);
-static u64 GetAIPeriod();
+static int GetAIPeriod();
 static int et_AI;
 
 void Init()
@@ -205,7 +205,7 @@ void RegisterMMIO(MMIO::Mapping* mmio, u32 base)
 				g_LastCPUTime = CoreTiming::GetTicks();
 
 				CoreTiming::RemoveEvent(et_AI);
-				CoreTiming::ScheduleEvent(((int)GetAIPeriod() / 2), et_AI);
+				CoreTiming::ScheduleEvent(GetAIPeriod(), et_AI);
 			}
 
 			// AI Interrupt
@@ -238,10 +238,14 @@ void RegisterMMIO(MMIO::Mapping* mmio, u32 base)
 
 	mmio->Register(base | AI_SAMPLE_COUNTER,
 		MMIO::ComplexRead<u32>([](u32) {
-			Update(0, 0);
-			return m_SampleCounter;
+			return m_SampleCounter + static_cast<u32>((CoreTiming::GetTicks() - g_LastCPUTime) / g_CPUCyclesPerSample);
 		}),
-		MMIO::DirectWrite<u32>(&m_SampleCounter)
+		MMIO::ComplexWrite<u32>([](u32, u32 val) {
+			m_SampleCounter = val;
+			g_LastCPUTime = CoreTiming::GetTicks();
+			CoreTiming::RemoveEvent(et_AI);
+			CoreTiming::ScheduleEvent(GetAIPeriod(), et_AI);
+		})
 	);
 
 	mmio->Register(base | AI_INTERRUPT_TIMING,
@@ -250,7 +254,7 @@ void RegisterMMIO(MMIO::Mapping* mmio, u32 base)
 			DEBUG_LOG(AUDIO_INTERFACE, "AI_INTERRUPT_TIMING=%08x@%08x", val, PowerPC::ppcState.pc);
 			m_InterruptTiming = val;
 			CoreTiming::RemoveEvent(et_AI);
-			CoreTiming::ScheduleEvent(((int)GetAIPeriod() / 2), et_AI);
+			CoreTiming::ScheduleEvent(GetAIPeriod(), et_AI);
 		})
 	);
 }
@@ -308,16 +312,17 @@ void Update(u64 userdata, int cyclesLate)
 			g_LastCPUTime += Samples * g_CPUCyclesPerSample;
 			IncreaseSampleCount(Samples);
 		}
-		CoreTiming::ScheduleEvent(((int)GetAIPeriod() / 2) - cyclesLate, et_AI);
+		CoreTiming::ScheduleEvent(GetAIPeriod() - cyclesLate, et_AI);
 	}
 }
 
-u64 GetAIPeriod()
+int GetAIPeriod()
 {
-	u64 period = g_CPUCyclesPerSample * m_InterruptTiming;
+	u64 period = g_CPUCyclesPerSample * (m_InterruptTiming-m_SampleCounter);
+	u64 s_period = g_CPUCyclesPerSample * g_AISSampleRate;
 	if (period == 0)
-		period = 32000 * g_CPUCyclesPerSample;
-	return period;
+		return static_cast<int>(s_period);
+	return static_cast<int>(std::min(period, s_period));
 }
 
 } // end of namespace AudioInterface