From c6dfcd1900725a366c9e646c5698a28326061b1c Mon Sep 17 00:00:00 2001
From: Sour <mesenemu@gmail.com>
Date: Sat, 29 Feb 2020 11:34:23 -0500
Subject: [PATCH] States: Prevent lockup when loading older save states taken
 when SPC sample rate was set to 32khz

---
 Core/Spc.cpp | 21 ++++++++++++++++++---
 Core/Spc.h   |  2 ++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/Core/Spc.cpp b/Core/Spc.cpp
index fd08764..bc5da1c 100644
--- a/Core/Spc.cpp
+++ b/Core/Spc.cpp
@@ -48,7 +48,7 @@ Spc::Spc(Console* console)
 	_operandB = 0;
 	_enabled = true;
 
-	_clockRatio = (double)(Spc::SpcSampleRate * 64) / _console->GetMasterClockRate();
+	UpdateClockRatio();
 }
 
 #ifndef DUMMYSPC
@@ -96,7 +96,7 @@ void Spc::SetSpcState(bool enabled)
 	if(_enabled != enabled) {
 		if(enabled) {
 			//When re-enabling, adjust the cycle counter to prevent running extra cycles
-			_state.Cycle = (uint64_t)(_memoryManager->GetMasterClock() * _clockRatio);
+			UpdateClockRatio();
 		} else {
 			//Catch up SPC before disabling it
 			Run();
@@ -105,6 +105,19 @@ void Spc::SetSpcState(bool enabled)
 	}
 }
 
+void Spc::UpdateClockRatio()
+{
+	_clockRatio = (double)(Spc::SpcSampleRate * 64) / _console->GetMasterClockRate();
+
+	//If the target cycle is off by more than 10 cycles, reset the counter to match what was expected
+	//This can happen due to overclocking (which disables the SPC for some scanlines) or if the SPC's 
+	//internal sample rate is changed between versions (e.g 32000hz -> 32040hz)
+	uint64_t targetCycle = (uint64_t)(_memoryManager->GetMasterClock() * _clockRatio);
+	if(std::abs((int64_t)targetCycle - (int64_t)_state.Cycle) > 10) {
+		_state.Cycle = targetCycle;
+	}
+}
+
 void Spc::Idle()
 {
 	IncCycleCount(-1);
@@ -359,7 +372,7 @@ void Spc::ProcessEndFrame()
 {
 	Run();
 
-	_clockRatio = (double)(Spc::SpcSampleRate * 64) / _console->GetMasterClockRate();
+	UpdateClockRatio();
 
 	int sampleCount = _dsp->sample_count();
 	if(sampleCount != 0) {
@@ -446,6 +459,8 @@ void Spc::Serialize(Serializer &s)
 	} else {
 		s.StreamArray(dspState, SPC_DSP::state_size);
 
+		UpdateClockRatio();
+
 		uint8_t *in = dspState;
 		_dsp->copy_state(&in, [](uint8_t** input, void* output, size_t size) {
 			memcpy(output, *input, size);
diff --git a/Core/Spc.h b/Core/Spc.h
index 8dff29e..8d65bcd 100644
--- a/Core/Spc.h
+++ b/Core/Spc.h
@@ -280,6 +280,8 @@ private:
 	void EndAddr();
 	void ProcessCycle();
 	void Exec();
+	
+	void UpdateClockRatio();
 
 public:
 	Spc(Console* console);