I have modified the PS UART clock frequency from the Clock Configuration/Advanced Clocking page of the Zynq Processing System (rev 5.5) setup GUI in IP Integrator.
There should be corresponding changes in the baud rate registers for the UART, for the unchanged baud rate setting (in this example, 115200 bps).
However, this is not happening, the PS7_init.c and ps7_init.tcl files both have the original values.
To work around this issue, change the following Vivado property to match the GUI setting of the UART reference clock.
For example if the UART reference clock is changed from 50MHz to 100MHz, the work-around is to issue the following command:
set_property CONFIG.PCW_UART_PERIPHERAL_FREQMHZ 100 [get_bd_cells processing_system7_0]