If freezing the linear equalizer and the DFE is necessary, the following ports should be driven to 1'b1:
GTX and GTH:
Cases when keeping the DFE in hold mode is recommended:
For scrambled data or for scrambled and encoded data, the adaptation algorithm provides the best equalization result in any temperature, voltage and silicon variation.
In case of non random patterns (i.e., in the very particular case when a comma is sent forever in a 8B10B encoded signal), the adaptation algorithm could bring to a wrong state and should be suspended.
The "hold" condition should follow a training period where the pattern is not random. It is difficult to know in advance when the received pattern will be random, but it is possible to check the received data and eventually repeat the DFE adaptation in case received data is a long series of the same comma which may cause an adaptation failure.