Completion Status Structure - 3.4 English

Versal Adaptive SoC CPM DMA and Bridge Mode for PCI Express Product Guide (PG347)

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3.4 English

The Completion Status is located at the last location of Completion ring, that is, Completion Ring Base Address + (Size of the completion length (8,16,32) * (Completion Ring Size – 1)).

In order to make the QDMA write Completion Status to the Completion ring, Completion Status must be enabled in the Completion context. In addition to affecting Interrupts, the trigger mode defined in the Completion context also moderates the writing of Completion Statuses. Subject to Interrupt/Status moderation, a Completion Status can be written when either of the following happens:
  1. A CMPT packet is written to the Completion ring.
  2. A CMPT-CIDX update from the SW is received, and indicates that more Completion entries are waiting to be read.
  3. The timer associated with the respective CMPT QID expires and is programmed in a timer-based trigger mode.
Table 1. AXI4-Stream Completion Status Structure
Bit Bit Width Field Name Description
[63:37] 27   Reserved
[36:35] 2 error


0x0: No error

0x1 Bad CIDX update received

0x2: Descriptor error

0x3: CMPT ring overflow error

[34:33] 2 int_state Interrupt State.

0: ISR


[32] 1 color Color status bit
[31:16] 16 cidx Consumer Index (RO)
[15:0] 16 pidx Producer Index