RM9200 tuning

[Stanislav Sedov]

On Mon, 8 Mar 2010 21:23:38 +0100
Bernd Walter <ticso at cicely7.cicely.de> mentioned:

> Originally FreeBSD had assumed fixed clock rates.
> Knowing the peripheral rate is important for e.g. UART bps dividers.
> I think in the meantime it is possible to reconfigure the kernel to
> different clock rates - if yes what are the kernel options for it?
> Which would be the best place to reconfigure the PLL?
> I know how to do it and that it is done by the loader right now, but
> I would like to have it as a kernel tuneable.
> All I need to know is a good place in the kernel startup.
> 

I think the best place to do this would be the loader itself.  AFAIK, FreeBSD
on AT91 doesn't assume any specific clock rate except the FSB clock rate and does
the calibration of the CPU clock and xtal clock on startup.  One of solutions is to
add a loader tunable that will allow you to pass the FSB clock rate from the loader,
instead of assuming the constant value.

-- 
Stanislav Sedov
ST4096-RIPE