SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
As is specified in the TI DMA Architecture specification, the host initiates an optimal Rx DMA channel teardown operation by shutting down the incoming payload stream at its source (a remote peer peripheral or the Tx side of a block copy channel). Once teardown is initiated at the source, data will eventually drain from the incoming PSI-L stream and when all data is complete, the remote peer entity will send a Teardown packet (either a standalone packet or tdown asserted with eop on the last data phase of the last packet). When the UDMA receives a teardown message, the TDOWN bit will be set in RCHANRT UDMA_RRT_CTL_j. In the case where a remote peer cannot generate a teardown message, the host must ensure that all data has stopped flowing from the remote peer and will then directly set the TDOWN bit. Once the UDMA sees the TDOWN asserted it will wait for any existing packets which are currently held in the Rx Per Channel FIFO to be completed and will then de-assert the EN bit in RCHANRT UDMA_RRT_CTL_j. If the back end application continues to allow new packets to be pushed into the Rx PC FIFO, the DMA will continue to delay marking the channel as torn down as long as the Rx PC FIFO never reaches an empty state