FRV and CPU frequency scaling

FRV and CPU frequency scaling

[Dominik Brodowski]

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?

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.

Thanks,
	Dominik

Re: FRV and CPU frequency scaling

[David Howells]

> 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