RET instruction is not returning to where it called subroutine - AVR assembly

Question

I'm writing this assembly for ATmega16 and i just want to make the LED blink for 10 times on button press. Unfortunately, when the RET instruction is reached, it brings me to the first of the code (start) instead of returning to where it left when calling the LONG_DELAY.

Could someone help me please? Thanks.

start:
    /* set the PINB0 data direction to 0 for input */
    /* This one simulates the key */
    ldi R16, (0 << PB0) ; Load 0b00000001 in R16
    out DDRB,R16    ; Configure the PINB0 as input

    /* set the PORTB7 data direction to 1 for output */
    /* this one causes the LED to be ON/OFF */
    ldi R17, (1 << PB7) ; Load 0b10000000 in R17
    out DDRB,R17    ; Configure the PORTB7 as output

OFF_MODE:
    /* Put the PORTB7 to 0 */ 
    ldi R18,(0 << PB7)
    out PORTB,R18
    /* Check the content of PINB0 */
    /* Wait for the PINB to get pressed by the user */
    sbis PINB,0
    brne OFF_MODE   ; Branch to the OFF_MODE if the key isn't pressed yet

BLINK_MODE:
    /* Define a counter */
    ldi R20,0
    /* Turn on the LED */
    /* Put the PORTB7 to 1 */
    ldi R18,(1 << PB7)
    out PORTB,R18

    /* Create a delay */
    call LONG_DELAY

    /* Turn off the LED */
    ldi R18,(0 << PB7)
    out PORTB,R18

    /* Increment the counter */
    inc R20

    /* Check the content of the counter */
    cpi R20,0x0A
    brne BLINK_MODE
    /* Clear the input to avoid duplicate press virtualization */
    cbi PINB,0
    jmp OFF_MODE
rjmp start

    /* Delay function */
LONG_DELAY:
    ldi r25,10
LOOP:
    nop
    dec R25
    cpi R25,0
    brne LOOP
    ret

Answer 1

There was some of mistakes, so here you are:

; Replace with your application code
start:
    //stack setup
    ldi r16, 0
    out SPH, r16
    ldi r16, 0xf0
    out SPL, r16
    /* set the PINB0 data direction to 0 for input */
    /* This one simulates the key */
    ldi R16, (0 << PB0) ; Load 0b00000001 in R16
    out DDRB,R16    ; Configure the PINB0 as input

    /* set the PORTB7 data direction to 1 for output */
    /* this one causes the LED to be ON/OFF */
    ldi R17, (1 << PB7) ; Load 0b10000000 in R17
    out DDRB,R17    ; Configure the PORTB7 as output

OFF_MODE:
    /* Put the PORTB7 to 0 */ 
    ldi R18,(0 << PB7)
    out PORTB,R18
    /* Check the content of PINB0 */
    /* Wait for the PINB to get pressed by the user */
    sbis PINB,0
    brne OFF_MODE   ; Branch to the OFF_MODE if the key isn't pressed yet
//Here was mistake
    ldi R20, 10

BLINK_MODE:
    /* Turn on the LED */
    /* Put the PORTB7 to 1 */
    ldi R18,(1 << PB7)
    out PORTB,R18

    /* Create a delay */
    call LONG_DELAY

    /* Turn off the LED */
    ldi R18,(0 << PB7)
    out PORTB,R18

    /* Increment the counter */
    dec R20
    brne BLINK_MODE
    /* Clear the input to avoid duplicate press virtualization */
    cbi PINB,0
    jmp OFF_MODE
rjmp start

    /* Delay function */
LONG_DELAY:
    ldi r25,10
LOOP:
    dec R25
//here was redundant instruction 
    brne LOOP
    ret