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.file "irs.s"
.extern irs_table;
.section .iwram, "ax", %progbits
.arm
.align
.global irs_main
irs_main:
@ Get the contents of IRQ_ENABLE, IRQ_ACK, and IRQ_CTRL
ldr ip, mem_irq_base_reg @ ip = (IRQ_ENABLE << 16) | IRQ_ACK
ldr r0, [ip] @ r0 = irq_enable
and r1, r0, r0, lsr #16 @ r1 = irq_enable & irq_ack
@ Disable IRQ_CTRL for now.
mov r3, #0 @ r3 = 0
strh r3, [ip, #8] @ *(ip + 0x8) = r3
@ r0 = irs_table address pointer
@ r2 = tmp
@ r3 = 0 (for r3; r3 < 14; r3++)
ldr r0, = irs_table
irs_main_fp_search:
@ Check that the current index is an active IRQ.
mov r2, #1
and r2, r1, r2, lsl r3
cmp r2, #0
beq irs_main_fp_search_not_enabled
@ Extract the function pointer for this IRS if available.
ldr r2, [r0]
cmp r2, #0
bne irs_main_handle_irs
irs_main_fp_search_not_enabled:
add r0, r0, #4
add r3, #1
cmp r3, #14
bne irs_main_fp_search
b irs_main_exit
irs_main_handle_irs:
@ r2: Contains IRQ function pointer.
@ r3: Stores the IRQ index.
@ Acknowledge that we are handling this interrupt writing to IRQ_ACK and
@ IRQ_ACK_BIOS.
mov r0, #1
lsl r0, r0, r3
strh r0, [ip, #2]
ldr r1, mem_irq_ack_bios @ r1 = IRQ_ACK_BIOS
str r0, [r1]
@ Store the SPSR in one of the free registers and save it along with the
@ return pointer.
mrs r3, spsr
stmfd sp!, {r3, lr}
@ Set CPU to system mode
mrs r3, cpsr
bic r3, r3, #0xDF
orr r3, r3, #0x1F
msr cpsr, r3
@ Call isr function pointer
stmfd sp!, {lr}
mov lr, pc
bx r2
ldmfd sp!, {lr}
@ Set CPU to irq mode
mrs r3, cpsr
bic r3, r3, #0xDF
orr r3, r3, #0x92
msr cpsr, r3
@ Restore the SPSR and the registers.
ldmfd sp!, {r3, lr}
msr spsr, r3
irs_main_exit:
@ Restore IRQ_CTRL.
mov r3, #1 @ r3 = 0
strh r3, [ip, #8] @ *(ip + 0x8) = r3
bx lr
mem_irq_base_reg:
.word 0x04000200 @ IRQ_ENABLE
mem_irq_ack_bios:
.word 0x03007FF8 @ IRQ_ACK_BIOS
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