Jamie Foxx -- Secret Meeting w/ Mike Tyson for Upcoming Biopic

Jamie Foxx is keeping his preparations for his upcoming Mike Tyson movie pretty close to the vest, but he did let it slip that he met with Iron Mike himself to get ready for the part.

Foxx and his adorable daughter were in Calabasas Wednesday where the Oscar winner deflected any idea that he's bulked up for the role ... by crediting his small shirt.

But the best part of the clip ... when Jamie's adorable daughter PUT HER DADDY ON BLAST as he tried to tell our photog that he's got a policy about keeping his movie details under wraps.

Seriously, one of the cutest things you're gonna see all day.