Lattice Diamond: How to change I/O attributes on JTAG pins?
Set JTAG_PORT to DISABLE in the software so that the I/O becomes GPIO. The user could then change the I/O attributes on that shared pin.
The JTAGEN pin will not control the IO standard and drive strength setting of the IO. If the JTAG is not persisted in user mode, those pins will follow the user setting. If the user uses the JTAGEN pin to dynamically activate the JTAG port, the user has to make sure the IO setting for those pins meet both their functionality need and JTAG standard.