My little one saying mama

My son is 6 1/2 months old and he can say oh yeah, yeah, hi, ok! He also does loud pitch screams and shouts when he’s excited. I’ve been trying to teach him to say mama and dada.

Recently I keep noticing that when he wakes up from a nap and crys out in between the cried he say mama over and over. He doesn’t say mama or dada otherwise during the day.

I just wanted to ask has he learned how to say the word mama only when he cries, or is that sound a part of his cry?

Also if your baby does the same please let me know and can you 6-7 month old say mama and dada yet?