> I sill need to check if the driver itself doesn't require BUS_SPACE_MAP_LINEAR.

Unfortunately, it needs linear access. Descriptors can reside
in host or adapter memory, depending on the chip version,
and the access is done by the same code.
That shouldn't be hard to change - I don't have the hardware
at the moment (let alone time).
(ti_mem() needs to be converted too - strange that it worked
at all for you, because the firmware is loaded that way.)

best regards
Matthias