I would like to confirm that the serial flash controller IP is only recommended to run at 25 MHz clock, as per the application note AN-736 on the website updated on 2016.05.20.
My Nios currently runs at 50 MHz, looking at how to handle this.
FJumaah, Thank you for your answer. Yes, it is helpful. I will plan to use 2 clocks, one for Nios and one for the serial flash. I trust that there will be no clock domain crossing issues here.... Thanks, James