I was wrong. The script works like a charm on the MC7455 too. And it is even more useful there, since that firmware doesn’t support the AT!UDUSBCOMP command. So having an AT serial port doesn’t help anymore.
Note that you’ll need to strip away the MBIM wrapping for the initial switch from QMI mode, if you want to test this on an MC74xx.
EDIT: Cancel that. Be careful. I seem to have messed up the AT command port using this switching method. Not recommended on the MC74xx.
EDIT2: Another update on this… Looks like a simple USB reset will fix things again. I have no idea why. But playing with the USB composition switching on MC74xx can be considered somewhat safe again. I’ve updated the perl script with support for USB reset to make that easier. Also added support for QMI mode. The script will now autodetect MBIM/QMI and wrap the commands with the correct headers regardless of mode, making it very easy to switch back and forth.