Re: FRV and CPU frequency scaling

[David Howells <dhowells@redhat.com>]

> While reading through the FRV Documentation patch I stumbled across the file
> "clock.txt" file which says:
> 
> + (*) clock.txt
> +
> +     A description of the CPU clock scaling interface.
> +
> 
> Could you use the generic cpufreq core (drivers/cpufreq/) for this, please?

Maybe. I'm not sure how simple it will be to adapt, since there are several
"clocks", and the setting changes the ratios between them.

> And could you explain the difference between p0, cm and cmode settings to
> me, and how they can be combined, please? Or is the following assumption 
> correct?
> 
> The CPU core frequency can only be modified on FR405 CPUs, while p0 and cm 
> are available on all CPUs and allow for modification of the frequency of 
> some sort of external busses.

It's quite complicated. There are 16 clock ratio mode settings, a bus speed
doubler and a raw clock speed indicator. The mode table varies from CPU to
CPU, and not all modes are available on all CPUs.

David