Visible to Intel only — GUID: llq1560470473623
Ixiasoft
Visible to Intel only — GUID: llq1560470473623
Ixiasoft
7.1.2. Debugging Data Transfer and Performance Issues
There are many possible reasons causing the PCIe link to stop transmitting data. The PCI Express base specification defines three types of errors, outlined in the table below:
Type | Responsible Agent | Description |
---|---|---|
Correctable | Hardware | While correctable errors may affect system performance, data integrity is maintained. |
Uncorrectable, non-fatal | Device software | Uncorrectable, non-fatal errors are defined as errors in which data is lost, but system integrity is maintained. For example, the fabric may lose a particular TLP, but it still works without problems. |
Uncorrectable, fatal | System software | Errors generated by a loss of data and system failure are considered uncorrectable and fatal. Software must determine how to handle such errors: whether to reset the link or implement other means to minimize the problem. |
Observation | Issue | Resolution |
---|---|---|
Data link protocol error | Data link layer error which may be due to transmitter receiving an ACK/NAK whose Seq ID does not correspond to an unacknowledged TLP or ACK sequence number. | Use the configuration output interface, Hard IP reconfiguration interface to obtain more information about the error. |
Surprise down error | Data link layer error which may be due to link_up_o getting deasserted during L0, indicating the physical layer link is going down unexpectedly. | Use the error interface, configuration output interface, Hard IP reconfiguration interface and DBI registers to obtain more information about the error. |
Flow control protocol error | Transaction layer error which can be due to the receiver reporting more than the allowed credit limit. This error occurs when a component does not receive updated flow control credits with the 200 μs limit. |
Use the TX/RX flow control interface, configuration output interface, Hard IP reconfiguration interface to obtain more information about the error. |
Poisoned TLP received | Transaction layer error which can be due to a received TLP with the EP bit set. | Use the error interface, configuration output interface, configuration intercept interface, Hard IP reconfiguration interface to obtain more information on the error and determine the appropriate action. |
Completion timeout | Transaction layer error which can be due to a completion not received within the required amount of time after a non-posted request was sent. | Use the error interface, completion timeout interface, configuration output interface, Hard IP reconfiguration interface to obtain more information on the error. |
Completer abort | Transaction layer error which can be due to a completer being unable to fulfill a request due to a problem with the requester or a failure of the completer. | Use the configuration output interface, error interface, Hard IP reconfiguration interface to obtain more information on the error. |
Unexpected completion | Transaction layer error which can be due to a requester receiving a completion that doesn’t match any request awaiting a completion. The TLP is deleted by the Hard IP and not presented to the Application Layer. |
Use the configuration output interface, error interface, Hard IP reconfiguration interface to obtain more information on the error. |
Receiver overflow | Transaction layer error which can be due to a receiver receiving more TLPs than the available receive buffer space. The TLP is deleted by the Hard IP and not presented to the Application Layer. |
Use the TX/RX flow control interface, error interface, configuration output interface, Hard IP reconfiguration interface to obtain more information on the error. |
Malformed TLP | Transaction layer error which can be due to errors in the received TLP header. The TLP is deleted by the Hard IP and not presented to the Application Layer. |
Use the error interface, configuration output interface, Hard IP reconfiguration interface to obtain more information on the error. |
ECRC error | Transaction layer error which can be due to an ECRC check failure at the receiver despite the fact that the TLP is not malformed and the LCRC check is valid. The Hard IP block handles this TLP automatically. If the TLP is a non-posted request, the Hard IP block generates a completion with a completer abort status. The TLP is deleted by the Hard IP and not presented to the Application Layer. |
Use the configuration output interface, Hard IP reconfiguration interface to obtain more information on the error. |
Unsupported request | Transaction layer error which can be due to the completer being unable to fulfill the request. The TLP is deleted in the Hard IP block and not presented to the Application Layer. If the TLP is a non-posted request, the Hard IP block generates a completion with Unsupported Request status. |
Use the configuration output interface, error interface, Hard IP reconfiguration interface to obtain more information on the error. |
ACS violation | Transaction layer error which can be due to access control error in the received posted or non-posted request. | Use the configuration output interface, error interface, Hard IP reconfiguration interface to obtain more information on the error. |
Uncorrectable internal error | Transaction layer error which can be due to an internal error that cannot be corrected by the hardware. | Use the error interface, configuration output interface, Hard IP reconfiguration interface and DBI registers to obtain more information on the error. |
Atomic egress blocked | Use the error interface, configuration output interface, Hard IP reconfiguration interface to obtain more information on the error. | |
TLP prefix blocked | EP or RP only | Use the error interface, configuration output interface, Hard IP reconfiguration interface to obtain more information on the error. |
Poisoned TLP egress blocked | EP or RP only | Use the error interface, configuration output interface, configuration intercept interface, Hard IP reconfiguration interface to obtain more information on the error. |
Use the debug tools mentioned in the next two sections for debugging link training issues observed on the PCI Express link when using the P-Tile Avalon® -ST IP for PCI Express.