audio: add Apple Sound Chip (ASC) emulation

The Apple Sound Chip was primarily used by the Macintosh II to generate sound
in hardware which was previously handled by the toolbox ROM with software
interrupts.

Implement both the standard ASC and also the enhanced ASC (EASC) functionality
which is used in the Quadra 800.

Note that whilst real ASC hardware uses AUDIO_FORMAT_S8, this implementation uses
AUDIO_FORMAT_U8 instead because AUDIO_FORMAT_S8 is rarely used and not supported
by some audio backends like PulseAudio and DirectSound when played directly with
-audiodev out.mixing-engine=off.

Co-developed-by: Laurent Vivier <laurent@vivier.eu>
Co-developed-by: Volker Rümelin <vr_qemu@t-online.de>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-ID: <20231004083806.757242-8-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

1 files changed, 84 insertions, 0 deletions

diff --git a/include/hw/audio/asc.h b/include/hw/audio/asc.h
new file mode 100644
index 0000000000..d9412815c3
--- /dev/null
+++ b/include/hw/audio/asc.h
@@ -0,0 +1,84 @@
+/*
+ * QEMU Apple Sound Chip emulation
+ *
+ * Apple Sound Chip (ASC) 344S0063
+ * Enhanced Apple Sound Chip (EASC) 343S1063
+ *
+ * Copyright (c) 2012-2018 Laurent Vivier <laurent@vivier.eu>
+ * Copyright (c) 2022 Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef HW_AUDIO_ASC_H
+#define HW_AUDIO_ASC_H
+
+#include "qemu/osdep.h"
+#include "hw/sysbus.h"
+#include "audio/audio.h"
+
+#define ASC_FREQ 22257
+
+enum {
+    ASC_TYPE_ASC    = 0,  /* original discrete Apple Sound Chip */
+    ASC_TYPE_EASC   = 1   /* discrete Enhanced Apple Sound Chip */
+};
+
+#define ASC_FIFO_OFFSET    0x0
+#define ASC_FIFO_SIZE      0x400
+
+#define ASC_REG_OFFSET     0x800
+#define ASC_REG_SIZE       0x60
+
+#define ASC_EXTREG_OFFSET  0xf00
+#define ASC_EXTREG_SIZE    0x20
+
+typedef struct ASCFIFOState {
+    int index;
+
+    MemoryRegion mem_fifo;
+    uint8_t fifo[ASC_FIFO_SIZE];
+    uint8_t int_status;
+
+    int cnt;
+    int wptr;
+    int rptr;
+
+    MemoryRegion mem_extregs;
+    uint8_t extregs[ASC_EXTREG_SIZE];
+
+    int xa_cnt;
+    uint8_t xa_val;
+    uint8_t xa_flags;
+    int16_t xa_last[2];
+} ASCFIFOState;
+
+struct ASCState {
+    SysBusDevice parent_obj;
+
+    uint8_t type;
+    MemoryRegion asc;
+    MemoryRegion mem_fifo;
+    MemoryRegion mem_regs;
+    MemoryRegion mem_extregs;
+
+    QEMUSoundCard card;
+    SWVoiceOut *voice;
+    uint8_t *mixbuf;
+    int samples;
+    int shift;
+
+    /* Time when we were last able to generate samples */
+    int64_t fifo_empty_ns;
+
+    qemu_irq irq;
+
+    ASCFIFOState fifos[2];
+
+    uint8_t regs[ASC_REG_SIZE];
+};
+
+#define TYPE_ASC "apple-sound-chip"
+OBJECT_DECLARE_SIMPLE_TYPE(ASCState, ASC)
+
+#endif