For CMOS case, lane rates are so low that reference clock of the source
synchronous interface can be routed on non-clock routes. The delays on
the clock line are adjusted by the digital interface tuning controlled
through software.
Lock down clock buffers on Rx and Tx interfaces, this avoids suboptimal
placement which causes large skew between clocks at the serdes pins.
Iulia Moldovan
Laszlo Nagy