Full-duplex SPI operation should be realized using core Transfer Initiation mode (TIMOD=0/1).
It is not possible for a SPI module to perform transmit and receive operation simultaneously when using DMA Transfer Initiation mode (TIMOD=2/3), as SPI is assigned to single DMA/interrupt source. So, SPI operation becomes half-duplex when using these modes (receiver when using TIMOD=2; and transmitter when TIMOD=3).