ContributorIOPLL non-dedicated feedback option doesn't work correctly
In Stratix 10 and Agilex, the IOPLL supports an option for using a non-dedicated feedback path when using the normal compensation mode or source-synchronous compensation mode. However, the non-dedicated feedback option doesn't appear to work correctly.
With the non-dedicated feedback option selected, the IOPLL compensation anti-delay as reported in static timing analysis is insanely high, on the order of -30 ns, whereas it should be only a few ns for correct compensation. And consequently, this huge anti-delay causes huge clock skews of a similar magnitude, on the order of 30 ns, between the input clock and the clock generated by the IOPLL.
I'm providing a trivial design example that demonstrates this (see attached). It consists of little more than an IOPLL IP with normal mode and non-dedicated feedback option selected, and otherwise all defaults, plus a handful of registers at the top level to create timing paths to observe in STA. And note that the same design example produces reasonable compensation delays if the IOPLL is configured without the non-dedicated feedback option.
The design example provided is in the form of a Quartus Pro 24.1 project archive. But note that I've also tested older versions of Quartus Pro as far back as 21.3 -- same results.
Intel/Altera support folks, please have a look at the provided example and confirm that you can reproduce what I've reported.
And perhaps firstly can you even confirm, please: Is the non-dedicated feedback option known to work? Is it known to not work? Or am I missing something basic? Because it appears to be plainly broken.
