2.8.1 PCIe master and slave restrictions and requirements

This section describes PCIe master and slave restrictions and requirements.

The restrictions and requirements are:

  • Peer-to-peer PCIe traffic, that is, one PCIe EP talking to another PCIe EP, must not pass through the CCN-502. Requests from the PCIe master can target memory only through the HN-F, MN, or an I/O slave device downstream of the HN-I, and must not target any PCIe slave downstream of the HN-I.
  • The PCIe master must not create same-AWID dependency between Non-Posted Write (NPR-Wr) and Posted Write (P-Wr) transactions that are sent on the RN-I AXI4/ACE-Lite slave port.
  • The flow control requirements are:

    CCN-502 to PCIe slave
    The PCIe slave must be able to sink at least one NPR-Wr from the CCN-502, sent on the HN-I AXI4/ACE-Lite master port. This requirement guarantees that the HN-I AW channel remains unblocked, enabling P-Wrs from PCIe master targeting the I/O slave device to make forward progress, as required by the PCIe ordering rules.
    PCIe master to CCN-502

    If a System Memory Management Unit (SMMU) is in the path between the PCIe master interface and the RN-I slave interface, there are two possible options:

    • Non-Posted Reads (NPR-Rds) from the PCIe master must not target the HN-I.
    • Use a separate master interface port in the SMMU for page table walks, such as the Translation Control Unit (TCU) in a CoreLink MMU-500, and connect this port to a different RN-I that does not send any requests to the HN-I.

      Note:

      This option is only available with the MMU-500.
  • The PCIe master can have a maximum of 256 outstanding barriers on the AW channel.
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