[SOLVED] ADSC not rest in avr32 (adc read problem

/*
 * vmam.c
 *
 * Created: 14-Oct-15 6:44:15 PM
 *  Author: Krishna
 */ 
#define F_CPU 16000000UL
#include <avr/io.h>
#include<util/delay.h>
#include"lcd.h"


int main(void)
{
   DDRD = 0xFF;
   int adc_value=0x00;
   char ch_sec =0;
   void adc_init();
   lcd_init();
   string("ADC Reading ");
   
   adc_value = read_adc(0);  // reading adc value
   LINE2
  lcd_data(adc_value+0x30);
   while(1);
}

/*
 * adc.c
 *
 * Created: 14-Oct-15 7:39:18 PM
 *  Author: Krishna
 */ 
#include <avr/io.h>
#define F_CPU 16000000UL
#include<util/delay.h>


void adc_init()
{
ADMUX |= (REFS0); // AVcc with external capacitor at AREF
 // Set the ADC prescaler to 128 (i.e., 16MHz/128 = 125KHz)
 ADCSRA |= ( 1 << ADPS2 )|( 1 << ADPS1 ) | ( 1 << ADPS0 );
 ADCSRA |= ( 1 << ADEN ); // ADC ON    
 ADCSRA |= (1<<ADSC); 
}


unsigned int read_adc(unsigned int ch_selection)
{
    ch_selection &= 0b00000111;  // AND operation with 7
    ADMUX = (ADMUX & 0xF8)|ch_selection; // clears the bottom 3 bits before ORing
     ADCSRA |= (1<<ADSC);                //Starts a new conversion
     while(ADCSRA & (1<<ADSC));            //Wait until the conversion is done
     return ADCW;
}