Do you mean the screen lock on the iPhone? If so, you can try to restore with iTunes or erase iPhone with iCloud. These are the two methods I know most. Also, what I get to have is a tool, Joyoshare UltFix, which is used by me to fix my iPhone boot loop issue. You can try its advanced mode to help unlock iPhone with no passcode. If need, you can enter and exit recovery mode free when need. More functions than you can guess.