Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 7/19/2024
Public

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5.3.7.10. Slave DMA Programming

Follow the next sequence to access controller’s data path using slave DMA interface:

  1. Before the host master accesses the slave DMA interface, it needs to check if data transfer is allowed. This is done by polling the sdma_trigg bit in the intr_status (0x0110) register. Alternatively, the host can unmask the interrupt associated with sdma_trigg by setting the sdma_trigg_en bit in the intr_enable (0x0114) register. Note that if sdma_paused flag in the ctrl_status (0x0118) register is set (that is, in case of detecting unexpected transaction during earlier data transfer), the controller should not request a new SDMA transaction. In this case, software must first clear the sdma_paused flag.
  2. After host discovered that data transfer is allowed, it should read the sdma_size and the sdma_trd_num registers. The sdma_size (0x0440) register provides byte aligned data block size that needs to be transferred. The sdma_trd_num (0x0444) register identifies the command associated with this data transfer which allows to select valid address and direction for data transfer.
  3. Before starting data transmission, host must clear the sdma_trigg flag by writing 1 in the corresponding bit in intr_status (0x0110) register. After clearing this flag, the host can execute data transmission on slave DMA interface.
  4. If the host ignores the requirements described above and starts to transfer data when slave DMA is not ready, then the sdma_err flag is set in the intr_status (0x0110) register. If the sdma_err_en bit is set in the intr_enable (0x0114) register, then an interrupt is triggered. When the sdma_err_rsp bit is set in the dma_settings (0x043c) register, the ERROR response is returned, and if it is cleared, the OK response is returned.
  5. If the host sends an unsupported transaction to slave interface, the slave DMA ignores this access and both the sdma_err flag in the intr_status (0x0110) register and the sdma_paused flag in the ctrl_status (0x0118) register is set.

If a system bus error is detected after the slave DMA transfer was triggered, the Fail and bus error bits are set in the last operation status register/descriptor. Performing transactions in the wrong direction (that is, write transaction to slave DMA port in case of sending read operation command to NF device) is forbidden.