RapidIO: The Next Generation Communication Fabric For Embedded Application

9.5. OPERATION ORDERING AND TRANSACTION DELIVERY

This section discusses what the RapidIO to PCI bridge must do to address the requirements of the ordering rules of the PCI specifications.

9.5.1. Operation Ordering

The RapidIO transaction ordering rules were presented in Chapter 3. The rules guarantee ordered delivery of write data and that results of read operations will contain any data that was previously written to the same location. For bridge devices, the PCI 2.2 specification has the additional requirement that the results of a read command force the completion of posted writes in both directions.

In order for the RapidIO to PCI bridge to be consistent with the PCI 2.2 ordering rules it is necessary to follow the RapidIO transaction ordering rules. In addition, the RapidIO to PCI bridge is required to adhere to the following additional rule:

• Read responses must push ahead all write requests and write responses.

9.5.2. Transaction Delivery Ordering

The RapidIO parallel physical layer specification and RapidIO serial physical layer specific-ation describe the mechanisms by which transaction ordering and delivery occur through the system. When considering the requirements for the RapidIO to PCI bridge it is first necessary to follow the transaction delivery ordering rules in these specifications. Further, it is necessary to add additional constraints to maintain programming model compatibility with PCI.

As described above, PCI has an additional transaction ordering requirement ...