Initial commit

arm9/source/arm9Clock.s

@@ -0,0 +1,32 @@
+.section ".itcm", "ax"
+.arm
+
+#define REG_SCFG_CLK        0x04004004
+#define SCFG_CLK_CPU_SPEED  1
+
+.global scfg_setArm9Clock
+.type scfg_setArm9Clock, %function
+scfg_setArm9Clock:
+    ldr r3,= REG_SCFG_CLK
+    ldrh r2, [r3]
+    and r1, r2, #SCFG_CLK_CPU_SPEED
+    cmp r1, r0
+        bxeq lr // requested speed already set
+
+    mrs r12, cpsr
+    orr r1, r12, #0xC0 // disable irq and fiq
+    msr cpsr, r1
+
+    bic r2, r2, #SCFG_CLK_CPU_SPEED
+    orr r2, r2, r0
+
+    strh r2, [r3]
+
+    // allow the clock switch to stabilize
+    mov r0, #8
+1:
+    subs r0, r0, #1
+    bne 1b
+
+    msr cpsr, r12
+    bx lr