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 ++++
 2 files changed, 12 insertions(+)

(limited to 'src/gba')

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
-- 
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