From a45acb282b0ba9f2dc91619b0dd20d213a426a71 Mon Sep 17 00:00:00 2001
From: Ryan Dwyer <ryandwyer1@gmail.com>
Date: Fri, 19 May 2023 21:20:08 +1000
Subject: [PATCH] Optimise DMA functions

---
 Makefile      |  2 +-
 src/lib/dma.c | 80 +++++----------------------------------------------
 2 files changed, 8 insertions(+), 74 deletions(-)

diff --git a/Makefile b/Makefile
index 91565ec0b..31f29b1a5 100644
--- a/Makefile
+++ b/Makefile
@@ -73,7 +73,7 @@ ROM_SIZE := 32
 # When enabled, press C-up and C-down simultaneously to toggle the debug menu.
 # Note that some emulators have problems displaying the crash screen text.
 
-DEBUG = 0
+DEBUG = 1
 
 # ANTIALIAS
 #
diff --git a/src/lib/dma.c b/src/lib/dma.c
index 7d3abdc8e..ed29db0a8 100644
--- a/src/lib/dma.c
+++ b/src/lib/dma.c
@@ -5,97 +5,31 @@
 #include "data.h"
 #include "types.h"
 
-volatile u32 g_DmaNumSlotsBusy;
-OSIoMesg g_DmaIoMsgs[32];
-volatile u8 g_DmaSlotsBusy[32];
-OSMesg g_DmaMesgs[32];
+OSIoMesg g_DmaIoMsgs[1];
+OSMesg g_DmaMesgs[1];
 OSMesgQueue g_DmaMesgQueue;
 
-static void dmaWait(void);
-
 void dmaInit(void)
 {
-	s32 i;
-
-	for (i = 0; i < ARRAYCOUNT(g_DmaSlotsBusy); i++) {
-		g_DmaSlotsBusy[i] = 0;
-	}
-
-	g_DmaNumSlotsBusy = 0;
-
 	osCreateMesgQueue(&g_DmaMesgQueue, g_DmaMesgs, ARRAYCOUNT(g_DmaMesgs));
 }
 
 static void dmaStart(void *memaddr, u32 romaddr, u32 len, bool priority)
 {
-	u32 numiterations;
-	u32 remainder;
-	s32 i;
-
-	if (g_DmaNumSlotsBusy) {
-		dmaWait();
-	}
-
-	if (len < 0x4000 * ARRAYCOUNT(g_DmaIoMsgs)) {
-		numiterations = len / 0x4000;
-		remainder = len % 0x4000;
-	} else {
-		// DMA size is 0x80000 or more. It won't fit in the queue, so do it
-		// all in one call to osPiStartDma using the remainder variable.
-		numiterations = 0;
-		remainder = len;
-	}
-
-	osInvalDCache(memaddr, len);
-
-	for (i = 0; i != numiterations; i++) {
-		g_DmaSlotsBusy[i] = true;
-		g_DmaNumSlotsBusy++;
-
-		osPiStartDma(&g_DmaIoMsgs[i], priority, 0, romaddr, memaddr, 0x4000, &g_DmaMesgQueue);
-
-		romaddr += 0x4000;
-		memaddr = (void *)((u32)memaddr + 0x4000);
-	}
-
-	if (remainder) {
-		g_DmaSlotsBusy[i] = true;
-		g_DmaNumSlotsBusy++;
-
-		osPiStartDma(&g_DmaIoMsgs[i], priority, 0, romaddr, memaddr, remainder, &g_DmaMesgQueue);
-	}
-}
-
-static void dmaWait(void)
-{
-	u32 stack;
 	OSIoMesg *msg;
-	s32 i;
-
-	while (g_DmaNumSlotsBusy) {
-		osRecvMesg(&g_DmaMesgQueue, (OSMesg) &msg, OS_MESG_BLOCK);
-
-		for (i = 0; i < ARRAYCOUNT(g_DmaIoMsgs); i++) {
-			if (&g_DmaIoMsgs[i] == msg) {
-				break;
-			}
-		}
-
-		g_DmaSlotsBusy[i] = false;
-		g_DmaNumSlotsBusy--;
-	}
+	osInvalDCache(memaddr, len);
+	osPiStartDma(&g_DmaIoMsgs[0], priority, 0, romaddr, memaddr, len, &g_DmaMesgQueue);
+	osRecvMesg(&g_DmaMesgQueue, (OSMesg) &msg, OS_MESG_BLOCK);
 }
 
 void dmaExec(void *memaddr, u32 romaddr, u32 len)
 {
-	dmaStart(memaddr, romaddr, len, false);
-	dmaWait();
+	dmaStart(memaddr, romaddr, len, OS_MESG_PRI_NORMAL);
 }
 
 void dmaExecHighPriority(void *memaddr, u32 romaddr, u32 len)
 {
-	dmaStart(memaddr, romaddr, len, true);
-	dmaWait();
+	dmaStart(memaddr, romaddr, len, OS_MESG_PRI_HIGH);
 }
 
 /**