From 33451307ae4e3a4119dd6be46b25aec03aa51b5d Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Fri, 10 May 2024 17:49:56 +0200
Subject: Ensure long irs sequencer_tick can be interrupted

---
 src/gba/gba.h        |  8 ++++++++
 src/gba/interrupts.s |  4 ++++
 src/sequencer.c      | 11 +++++------
 3 files changed, 17 insertions(+), 6 deletions(-)

(limited to 'src')

diff --git a/src/gba/gba.h b/src/gba/gba.h
index 3f629fd..1bb3afd 100644
--- a/src/gba/gba.h
+++ b/src/gba/gba.h
@@ -534,6 +534,14 @@ void irs_set(IrqIndex idx, IrsFunc func);
 // assembly and enable interrupts.
 void irq_init(void);
 
+// Only should be used inside an IrsFunc to enable it being interrupted by the
+// given interrupt (nested IRS).
+static inline void
+irs_interruptible(IrqIndex idx) {
+    IRQ_ENABLE |= (1 << idx);
+    IRQ_CTRL = 1;
+}
+
 //
 // BIOS function declarations.
 //
diff --git a/src/gba/interrupts.s b/src/gba/interrupts.s
index 67b9fe9..1d3e001 100644
--- a/src/gba/interrupts.s
+++ b/src/gba/interrupts.s
@@ -67,6 +67,10 @@ irs_main_handle_irs:
     bx      r2
     ldmfd   sp!, {lr}
 
+    @ Clear IRQ enable again just in case it was enabled from within the IRS.
+    mov r3, #0                      @ r3 = 0
+    strh r3, [ip, #8]               @ *(ip + 0x8) = r3
+
     @ Set CPU to irq mode
     mrs     r3, cpsr
     bic     r3, r3, #0xDF
diff --git a/src/sequencer.c b/src/sequencer.c
index d2a0054..a70ae85 100644
--- a/src/sequencer.c
+++ b/src/sequencer.c
@@ -628,6 +628,9 @@ env_start:
 
 void
 sequencer_tick(void) {
+    irs_interruptible(IRQ_VBLANK);  // Audio mix.
+    irs_interruptible(IRQ_TIMER_1); // Audio click sync.
+    irs_interruptible(IRQ_TIMER_3); // Link cable sync.
     // switch (settings.sync) {
     //     case SYNC_OUT_LINK_96BPQ: { gate_on(); } break;
     //     case SYNC_OUT_LINK_48BPQ: { if (sync_ticks++ % 2 == 0) { gate_on(); } } break;
@@ -647,17 +650,13 @@ sequencer_tick(void) {
     //     default: break;
     // }
     if (nseq_ticks++ == 0) {
-        if (step_counter % 16 == 0) {
-            // first_pulse = true;
-        }
-        step_counter = (step_counter + 1) % 16;
-        // play_step();
+        play_step();
     }
     if (sync_ticks++ % 4 == 0) { lsdj_pulse(); }
     if (nseq_ticks == 24) {
         nseq_ticks = 0;
     }
-    // wave_ad_tick();
+    wave_ad_tick();
 }
 
 void
-- 
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