SPI Clock Frequency

Hi,

i would like to match the SPI clock frequency to some given value. From the STM32F103RCT6 hardware manual it looks like the SPI clock is generated from the AHB clock (PCLK) using a prescaler (divide by /2, /4, /8, ...). To get a more exact match to my required SPI clock, I can only think of changing the AHB clock...

I have the following questions:

1. Is it possible to change the AHB clock frequency from Javascript (or change the main PLL/clock)? If this is possible, how would that affect the other peripherals (like serial port baudrate)?
   
2. How is the PLL set up during build, i.e. would it work to recompile everything after changing chip.speed from 72 to e.g. 68 in boards/ESPURINOBOARD.py? Would then the other peripheral clocks get calculated correctly?
   
   

Thanks!