Yes, I have done this in my younger days. I was able to get the head of my penis into my mouth....but that's as far as I got. I did cum inside my mouth though. Since those early days, I've given up the notion of ever being able to "really" suck my dick. I do still enjoy tasting my own semen though on occasion.
I heard the best way to do it is lie on your back and bring your legs and feet up over your head so you're kinda bent in two with your back on the floor... that way you have gravity's help getting your dick close to your face.