P-Credit Management Mechanism

Functional Description

According to the description of Retry in CHI protocol 2.3.2, P-Credit management follows the following rules: 1. When the RXRSP channel receives a PCrdGrant, a CAM records the PCrdType and SrcID of this operation. 2. At this point, if there is an MSHR in a certain Slice waiting for a PCredit of the same type {PCrdType, SrcID}, this PCredit is allocated to that Slice. - If multiple Slices hit simultaneously, this PCredit is allocated in a RoundRobin manner, and the corresponding record in the CAM is deleted. - If no Slice hits, the CAM saves the PCrdType and SrcID for future use (the protocol allows PCrdGrant to be issued before RetryAck). 4. For a hit Slice, if multiple MSHRs hit {PCrdType, SrcID}, it is allocated to one MSHR in a RoundRobin manner. 5. For each MSHR: - Upon receiving RetryAck, it saves PType and SrcID, while asserting the pValid signal to notify the CAM that it is waiting for PCredit. - If a matching PCredit is found in the CAM, the MSHR completes the operation by deasserting pValid and removing the matching entry from the CAM. - If no matching PCredit is found in the CAM, pValid remains asserted until the corresponding PCredit is received.