This commit fixes the 16.5Gbps lane rate case where the link drops
after few seconds an initial successful link up happens.
A few seconds delayed calibration process can workaround this but with
having the differential drivers swing increased this is no longer
required.
The device clocks are AC coupled LVDS lines without external termination.
For proper operation internal differential termination must be enabled,
the DQS_BIAS will DC bias the AC coupled signal to VCCO/2 (1.8/2) 0.9V
On the Xilinx PHY the available PLL options depends on the lane rate.
Encoding is:
0 - CPLL
1 - QPLL0
2 - QPLL1
Since the selection of line rate is available from the project also the
PLL selection must be exposed.
Use over-writable parameters from the environment.
e.g.
make JESD_MODE=64B66B RX_RATE=24.75 TX_RATE=12.375 REF_CLK_RATE=375 RX_JESD_L=4 TX_JESD_L=4
make JESD_MODE=64B66B RX_RATE=16.22016 TX_RATE=16.22016 REF_CLK_RATE=245.76 RX_JESD_M=8 RX_JESD_L=2 TX_JESD_M=16 TX_JESD_L=4
make JESD_MODE=8B10B RX_JESD_L=4 RX_JESD_M=8 TX_JESD_L=4 TX_JESD_M=8