Hello, I am completing port to Xilinx Spartan, to do so I teared down all QSYS logic and rewrote some part of IP core.
It is no more using Avalon is not supported on, use instead native block, it seems not suffering none of issue experienced. The one are here are justified I don't know about, Its since long long time I migrated to Altera, Xilinx and Lattice too changed a lot and actual family are new to me.
I am rewriting IP as platform/vendor neutral to isolate issue. Actual issue are not similar to what I encountered on MAX10, just fresh code is not as clean as the old one used for years no more Avalon/Qsys oriented.
Think it took few day more to complete.