From 7964e0adf80b3693072d6facf21d94d0233dafbe Mon Sep 17 00:00:00 2001
From: Patrice Mandin <patmandin@gmail.com>
Date: Sun, 13 Jan 2019 15:27:50 +0100
Subject: [PATCH] atari: Fill audio buffer with silence when too many
 interrupts triggered on same buffer

---
 src/audio/mint/SDL_mintaudio.c    |  8 +++++-
 src/audio/mint/SDL_mintaudio.h    |  4 +++
 src/audio/mint/SDL_mintaudio_it.S | 41 ++++++++++++++++++++++++++-----
 3 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/src/audio/mint/SDL_mintaudio.c b/src/audio/mint/SDL_mintaudio.c
index 159990201..61ab26763 100644
--- a/src/audio/mint/SDL_mintaudio.c
+++ b/src/audio/mint/SDL_mintaudio.c
@@ -103,6 +103,12 @@ int SDL_MintAudio_InitBuffers(SDL_AudioSpec *spec)
 	SDL_MintAudio_numbuf = SDL_MintAudio_num_its = SDL_MintAudio_num_upd = 0;
 	SDL_MintAudio_max_buf = MAX_DMA_BUF;
 
+	/* For filling silence when too many interrupts per update */
+	SDL_MintAudio_itbuffer = MINTAUDIO_audiobuf[0];
+	SDL_MintAudio_itbuflen = (dmabuflen >> 2)-1;
+	SDL_MintAudio_itsilence = (spec->silence << 24)|(spec->silence << 16)|
+		(spec->silence << 8)|spec->silence;
+
 	return (1);
 }
 
@@ -118,7 +124,7 @@ void SDL_MintAudio_FreeBuffers(void)
 	}
 	if (MINTAUDIO_audiobuf[0]) {
 		Mfree(MINTAUDIO_audiobuf[0]);
-		MINTAUDIO_audiobuf[0] = MINTAUDIO_audiobuf[1] = NULL;
+		SDL_MintAudio_itbuffer = MINTAUDIO_audiobuf[0] = MINTAUDIO_audiobuf[1] = NULL;
 	}
 }
 
diff --git a/src/audio/mint/SDL_mintaudio.h b/src/audio/mint/SDL_mintaudio.h
index e3fc73ce4..50a2d4abc 100644
--- a/src/audio/mint/SDL_mintaudio.h
+++ b/src/audio/mint/SDL_mintaudio.h
@@ -121,6 +121,10 @@ void SDL_MintAudio_WaitThread(void);
 extern volatile unsigned long SDL_MintAudio_clocktics;
 extern volatile unsigned long SDL_MintAudio_num_its;
 
+extern volatile void *SDL_MintAudio_itbuffer;
+extern volatile unsigned long SDL_MintAudio_itbuflen;
+extern volatile unsigned long SDL_MintAudio_itsilence;
+
 /* Functions */
 void SDL_MintAudio_XbiosInterruptMeasureClock(void);
 void SDL_MintAudio_XbiosInterrupt(void);
diff --git a/src/audio/mint/SDL_mintaudio_it.S b/src/audio/mint/SDL_mintaudio_it.S
index 0ffe7cccb..cb033e6be 100644
--- a/src/audio/mint/SDL_mintaudio_it.S
+++ b/src/audio/mint/SDL_mintaudio_it.S
@@ -71,22 +71,47 @@ SDL_MintAudio_EndIntMeasure:
 
 _SDL_MintAudio_XbiosInterrupt:
 _SDL_MintAudio_Dma8Interrupt:
+#if defined(__mcoldfire__)
+	lea	sp@(-12),sp
+	moveml	d0-d1/a0,sp@
+#else
+	moveml	d0-d1/a0,sp@-
+#endif
 
 	/* Clear service bit, so other MFP interrupts can work */
 #if defined(__mcoldfire__)
-	movel	d0,sp@-
-
 	moveql	#5,d0
 	bclr	d0,0xfffffa0f:w
-
-	movel	sp@+,d0
 #else
 	bclr	#5,0xfffffa0f:w
 #endif
 
 _SDL_MintAudio_StfaInterrupt:
-	addql	#1,_SDL_MintAudio_num_its
-
+	move.l	_SDL_MintAudio_num_its,d0
+	addql	#1,d0
+	move.l	d0,_SDL_MintAudio_num_its
+ 
+	cmp.l	#5,d0
+	bmi.s	_SDL_MintAudio_nosilence
+
+	move.l	_SDL_MintAudio_itbuffer,d1
+	beq.s	_SDL_MintAudio_nosilence
+	move.l	d1,a0
+
+	move.l	_SDL_MintAudio_itbuflen,d0
+	move.l	_SDL_MintAudio_itsilence,d1
+_SDL_MintAudio_fillsilence:
+	move.l	d1,a0@+
+	subq.l	#1,d0
+	bpl.s	_SDL_MintAudio_fillsilence
+
+_SDL_MintAudio_nosilence:
+#if defined(__mcoldfire__)
+	moveml	sp@,d0-d1/a0
+	lea	sp@(12),sp
+#else
+	moveml	sp@+,d0-d1/a0
+#endif
 	rte
 
 	.bss
@@ -94,3 +119,7 @@ _SDL_MintAudio_StfaInterrupt:
 	.even
 	.comm	_SDL_MintAudio_clocktics,4
 	.comm	_SDL_MintAudio_num_its,4
+
+	.comm	_SDL_MintAudio_itbuffer,4	/* Audio DMA buffer */
+	.comm	_SDL_MintAudio_itbuflen,4	/* Length in longword */
+	.comm	_SDL_MintAudio_itsilence,4	/* Silence value */