I've fixed Metroid Prime 3 and 2 desync. And other games with desync because of FIFO Reset.

That happens because  FIFO_RW_DISTANCE_HI must be written first, for checking fifo.CPReadWriteDistance == 0, so some fifo resets was not managed in the right way.
I didn't test Metroid 2 desync reported in Issue 4336 but I think is the same.
About the flickering in MP2, I don't know for my is not related or yes, but you can test anyway.

Fixed Issue 3902

Well now the FIFO is 99.99% finished :)

1 files changed, 4 insertions, 4 deletions

diff --git a/Source/Core/VideoCommon/Src/CommandProcessor.cpp b/Source/Core/VideoCommon/Src/CommandProcessor.cpp
index 4fd7e88f5e..a6e68f6298 100644
--- a/Source/Core/VideoCommon/Src/CommandProcessor.cpp
+++ b/Source/Core/VideoCommon/Src/CommandProcessor.cpp
@@ -388,10 +388,6 @@ void Write16(const u16 _Value, const u32 _Address)
 
 	case FIFO_RW_DISTANCE_HI:
 		WriteHigh((u32 &)fifo.CPReadWriteDistance, _Value);
-		DEBUG_LOG(COMMANDPROCESSOR,"try to write to FIFO_RW_DISTANCE_HI : %04x", _Value);
-		break;
-	case FIFO_RW_DISTANCE_LO:
-		WriteLow((u32 &)fifo.CPReadWriteDistance, _Value & 0xFFE0);
 		if (fifo.CPReadWriteDistance == 0)
 		{
 			GPFifo::ResetGatherPipe();
@@ -401,6 +397,10 @@ void Write16(const u16 _Value, const u32 _Address)
 			ResetVideoBuffer();		
 		}
 		IncrementCheckContextId();
+		DEBUG_LOG(COMMANDPROCESSOR,"try to write to FIFO_RW_DISTANCE_HI : %04x", _Value);
+		break;
+	case FIFO_RW_DISTANCE_LO:
+		WriteLow((u32 &)fifo.CPReadWriteDistance, _Value & 0xFFE0);
 		DEBUG_LOG(COMMANDPROCESSOR,"try to write to FIFO_RW_DISTANCE_LO : %04x", _Value);
 		break;