.equ TIMER1_ADDR, 0xFF202000
.equ TIMER_STACK_SIZE, 56
.equ LED_ADDR, 0xFF200000

.global _start
_start:
    movia sp, 0x80000000

BLINK_LIGHT:
    movia r7, LED_ADDR
    movi r2, 0x1
    stwio r2,  (r7)
    movia r4, 100000000
    call Timer
    movi r2, 0x0
    stwio r2,  (r7)
    movia r4, 100000000
    call Timer
    br BLINK_LIGHT


Timer:
    subi sp, sp, TIMER_STACK_SIZE

    stw ra, 4(sp)
    stw fp, 0(sp)

    addi r2, sp, 8
    stw r16, (r2)
    addi r2, r2, 4
    stw r17, (r2)
    addi r2, r2, 4
    stw r18, (r2)
    addi r2, r2, 4
    stw r19, (r2)
    addi r2, r2, 4
    stw r20, (r2)
    addi r2, r2, 4
    stw r21, (r2)
    addi r2, r2, 4
    stw r22, (r2)
    addi r2, r2, 4
    stw r23, (r2)

    addi r2, r2, 4
    stw r4, (r2)
    addi r2, r2, 4
    stw r5, (r2)
    addi r2, r2, 4
    stw r6, (r2)
    addi r2, r2, 4
    stw r7, (r2)

    addi fp, sp, 0

    # Function starts
    movia r7, TIMER1_ADDR
    mov r2, r4
    srli r3, r2, 16     # Store upper 16
    stwio r3, 12(r7)
    andi r3, r2, 0xFFFF # Store lower 16
    stwio r3, 8(r7)

    stwio r0, (r7)

    movui r2, 4
    stwio r2, 4(r7)

WAIT:
    ldwio r2, (r7)
    andi r2, r2, 0x0001
    beq r2, r0, WAIT

EXIT:
    addi r2, sp, 8
    ldw r16, (r2)
    addi r2, r2, 4
    ldw r17, (r2)
    addi r2, r2, 4
    ldw r18, (r2)
    addi r2, r2, 4
    ldw r19, (r2)
    addi r2, r2, 4
    ldw r20, (r2)
    addi r2, r2, 4
    ldw r21, (r2)
    addi r2, r2, 4
    ldw r22, (r2)
    addi r2, r2, 4
    ldw r23, (r2)


    addi r2, r2, 4
    ldw r4, (r2)
    addi r2, r2, 4
    ldw r5, (r2)
    addi r2, r2, 4
    ldw r6, (r2)
    addi r2, r2, 4
    ldw r7, (r2)

    ldw ra, 4(sp)
    ldw fp, 0(sp)
    addi sp, sp, TIMER_STACK_SIZE

    ret