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