https://github.com/enjoy-digital/litex/tree/ea8be6adcd4b76fdc7c0548a8bf9601ac8b96431/litex/soc/cores/clock https://github.com/nmigen/nmigen/issues/425
https://github.com/enjoy-digital/litex/tree/ea8be6adcd4b76fdc7c0548a8bf9601ac8b96431/litex/soc/cores/clock
amaranth-lang/amaranth#425