You will see the critical warning above when you add the "HSSI_PARAMETER" assignment for the Intel® Stratix® 10 L- and H-Tile device as per the guideline in Table 22 of the Intel® Stratix® 10 L- and H-Tile Transceiver PHY User Guide(UG-20055 | 2020.10.22) or earlier version. The assignment syntax set_instance_assignment -name HSSI_PARAMETER "pma_tx_buf_powermode_dc_tx_vod_no_jitcomp = TX_VOD_NO_JITCOMP_DC_L0" -to <serial TX pin name> is wrong.
To avoid this critical warning syntax is as below
"set_instance_assignment -name HSSI_PARAMETER "pma_tx_buf_powermode_dc_tx_vod_no_jitcomp = powerdown_tx_vod_no_jitcomp" -to <serial TX pin name> "
The new assignment syntax is fixed start with UG-20055 version 2020.10. 22.