From 6d8dc724c2765c10b4e6f3f3e53855aa5175e6b7 Mon Sep 17 00:00:00 2001
From: Jeffrey Pfau <jeffrey@endrift.com>
Date: Tue, 11 Oct 2016 22:01:13 -0700
Subject: [PATCH] GBA BIOS: Fix MidiKey2Freq BIOS reads

---
 CHANGES        | 1 +
 src/gba/bios.c | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/CHANGES b/CHANGES
index 2789e1f3e..eecd7ed76 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,6 +1,7 @@
 0.5.2: (Future)
 Bugfixes:
  - GBA Memory: Fix misaligned BIOS reads
+ - GBA BIOS: Fix MidiKey2Freq BIOS reads
 
 0.5.1: (2016-10-05)
 Bugfixes:
diff --git a/src/gba/bios.c b/src/gba/bios.c
index 13a96cfc8..f0fd4b451 100644
--- a/src/gba/bios.c
+++ b/src/gba/bios.c
@@ -244,7 +244,12 @@ static void _ObjAffineSet(struct GBA* gba) {
 
 static void _MidiKey2Freq(struct GBA* gba) {
 	struct ARMCore* cpu = gba->cpu;
+
+	int oldRegion = gba->memory.activeRegion;
+	gba->memory.activeRegion = REGION_BIOS;
 	uint32_t key = cpu->memory.load32(cpu, cpu->gprs[0] + 4, 0);
+	gba->memory.activeRegion = oldRegion;
+
 	cpu->gprs[0] = key / powf(2, (180.f - cpu->gprs[1] - cpu->gprs[2] / 256.f) / 12.f);
 }