how to get mmc interface up and running

Hi

I am looking for some initialization code for the mmc interface on the BBB.
I tried for a whole week now to get something out of the clk line but no succes so far.
I’m sure that all clocks needed are on and the pinmux should be ok
Someone any ideas what I could forget or doing wrong ? If needed I will attach some code.

Everything is welcomed !

Regards ,

Ronny