CRITICAL WARNING: [Timing 38-249] Generated clock base_i/video/hdmi_out/frontend/rgb2dvi_0/U0/SerialClk has no logical paths from master clock axi_dynclk_0_PXL_CLK_O

[dzung-hoang]

Regenerating base overlay for Pynq-Z1 results in following critical warning.

CRITICAL WARNING: [Timing 38-249] Generated clock base_i/video/hdmi_out/frontend/rgb2dvi_0/U0/SerialClk has no logical paths from master clock axi_dynclk_0_PXL_CLK_O.
Resolution: Review the path between the master clock and the generated clock with the schematic viewer and correct the -source option. If it is correct and the master clock does not have a timing path to the generated clock, define the generated clock as a primary clock by using create_clock.

The root cause is this unnecessary line in ./boards/ip/rgb2dvi_v1_2/src/rgb2dvi_clocks.xdc.

### Clock constraints ###
create_generated_clock -source [get_ports PixelClk] -multiply_by 5 [get_ports SerialClk]

Commenting out the create_generate_clock line fixes the critical warning.