Loop back mode enabling?

I want to enable the software loop back in the MCR of UART4 instance through my (user space )application code.

I am using omap4460 panda board.

I  was able to control the baudrate ,using termios but not this as this is different when i looked into omap-serial.c for version(3.4)

How will I do it using ioctl?or any other way.How do I test it.

I tried this way.

#define DEVICE "/dev/ttyO3"

int main()
{
	int fd;
	int write_fd1;
	int read_fd;
	int status = 0;
	char buf[2];
	struct termios options;
	fd = open(DEVICE,O_RDWR | O_NONBLOCK);

	if(fd < 0)
	{
		printf("unable to open the device\n");
		return -1;
	}
	else
		printf("device opened %d \n",fd);
	tcgetattr(fd,&options);	
	cfsetospeed(&options,B300);
	cfsetispeed(&options,B300);
	tcsetattr(fd,TCSANOW,&options);	
	tcgetattr(fd,&options);	

	if((cfgetospeed(&options) != B300) || (cfgetispeed(&options)!= B300));
	{
		printf("Baud rate not set");
	}
	ioctl(fd,TIOCMGET,&status);
	status |= 0x0010;
	ioctl(fd,TIOCMSET,&status);
	/* read from file and write to device */
	while(1)
	{
		write_fd1 = write(fd,"a",2) ;
	   	read_fd = read(fd,buf,sizeof(buf)) ;
		printf("write_fd %d \n",write_fd1);
		printf("read_fd %d \n",read_fd);
	}
	close(fd);
	return 0;
}

Please share any reference code.