Often, a user application fails to be recognized by the system, but the AMD PIO Example design works. In these cases, the user application is often using a PCI configuration space setting that is interfering with the system systems ability to recognize and allocate resources to the card.
The AMD solutions for PCI Express handle all configuration transactions internally and generate the correct responses to incoming configuration requests. Chipsets have limits to the amount of system resources they can allocate and the core must be configured to adhere to these limitations.
The resources requested by the Endpoint are identified by the BAR settings within the Endpoint configuration space. You should verify that the resources requested in each BAR can be allocated by the chipset. Generate a core that implements a small amount of memory (approximately 2 KB) to identify if this is the root cause.
The Class Code setting selected in the Vivado IDE can also affect configuration. The Class Code informs the Chipset as to what type of device the Endpoint is. Chipsets might expect a certain type of device to be plugged into the PCI Express slot and configuration might fail if it reads an unexpected Class Code. The BIOS could be configurable to work around this issue.
Using a link analyzer, it is possible to monitor the link traffic and possibly determine when during the enumeration and configuration process problems occur.