The 19-year-old impressed boss Mick McCarthy during a behind-closed-doors friendly on Monday and will be available for selection once the paperwork has been processed.
Mings came through the Southampton youth academy alongside Alex Oxlade-Chamberlain but did not make the grade at St Mary's.
After his release he moved to non-league football with Yate Town before joining Chippenham, who were then managed by his dad, Adie.
Meanwhile, Tyrone Barnett has left Portman Road and returned to parent club Peterborough after suffering a knee ligament injury in training.
The striker had made three appearances for the Tractor Boys since joining in November.
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