Virtex-5 PCIe endpoint block plus: Stay away from v1.15

While porting Xillybus to Virtex-5, I ran into nasty trouble. In the beginning, it looked like the MSI interrupt delivery mechanism was wrong, and then it turned out that the core gets locked up completely after a few packets, and refuses to send any TLPs after a few sent. I also noticed that the PCIe core has the “Fatal Error Detected” flag set in its status register (or more precisely, Xillybus banged me in the head with the bad news). Eventually, I found myself resetting the core with a debounced pushbutton connected to sys_reset_n at some very certain point in the host’s boot process to make the system work. Using just PERST_B, like the user guide suggests, simply didn’t work.

All this was with version 1.15 of the PCIe endpoint block plus, which was introduced in ISE 13.2. Quite by chance, I tried ISE 13.1, which comes with version 1.14 of the core. And guess what, suddenly PERST_B connected to sys_reset_n did the job, and the Fatal Error vanished.

I have to admit I’m quite amazed by this.

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