Expose the TX configurable driver ports, more specifically the
TX_DIFFCTRL, TX_POSTCURSORE and TX_PRECURSORE for software. This
provides a soft tunning capability of the transmit side of the
transceivers, in cases where the insertion loss of the channel is too
high or low, comparing to the default value supported by the default
configuration of the GTs.
You can find information about these configuration ports under the
section called 'TX Configurable Driver' in the GT transceivers user
guide. (UG476, UG576)