Article ID: 000075634 Content Type: Troubleshooting Last Reviewed: 03/05/2018

Why is my Intel® Stratix®10 GX ES device with PCIe* Hard IP unable to transmit TLP packets or show lowered bandwidth?

Environment

  • Intel® Stratix® 10 FPGAs and SoC FPGAs
  • Intel® Quartus® Prime Pro Edition
  • Avalon-ST Intel® Stratix® 10 Hard IP for PCI Express
  • Avalon-MM Intel® Stratix® 10 Hard IP for PCI Express
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    Critical Issue

    Description

    The Intel® Stratix®10 ES PCIe* Hard IP may encounter credit leakage  during TLP transmission.  When the Hard IP internal TX FIFO fills up, it may result in credit leakage. This may lead to the user interface getting throttled in conjunction with inaccurate credit consumed information being reported on the TX credit interface.
    All Gen1, Gen2, and Gen3 configurations on Intel Stratix 10 GX devices with ES1 L-Tiles, ES2 L-Tiles or ES1 H-Tiles are impacted and may observe performance degradation resulting in lowered bandwidth.

    Resolution

    To work around this errata, you must monitor and guard band the available credit for each transaction type: posted (P), non-posted (NP), and completion (Cpl) using the below formula. Do not calculate the tx_*_cdts_limit using the tx_*_cdts_consumed signal on the TX credit interface :
    Available credit = Advertised credits from partner – GB
    Where GB = 128 credits for data, 64 credits for header.
    For devices that advertise less than 128 credits, this workaround does not apply.

    Below is an example pseudo-code for NPH TLP traffic type (memory read without payload) to avoid credit leakage while it follows PCIe* ordering rule
    1a.  Track the number of outstanding NP TLPs as follows

    If (num_of_outstanding_NP_TLP < Initial_NPH_Credit) {
            Send_NPH_packet;

    }
    1b.  (OR) Guard band the available credit for the NPH TLPs as follows

    If ((tx_nph_cdts – 64) > 0) {
                Send_NPH_packet;
        }


    This errata is fixed in Intel Stratix 10 GX devices with ES3 L-Tiles, Production L-Tiles, ES2 H-Tiles, or Production H-Tiles, and all Intel Stratix 10 SX devices.

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