Re: [PATCH] CPUFreq Support for PXA255

[Ian Campbell <icampbell@arcom.com>]

On Fri, 2005-07-15 at 18:41 +0200, Dominik Brodowski wrote:

Thanks for you comments. 

I've snipped the bits for changes that I've already done.

> > +static void pxa_select_freq_table(struct cpufreq_policy *policy,
> > +                               pxa_freqs_t ** settings,
> > +                               struct cpufreq_frequency_table
> **table)
> > +{
> [SNIP]
> > +}
> 
> As noted by Eric Piel already, please use a module parameter combined
> with a sysfs file instead.
> 
I've got it working with a module parameter so cpu_pxa.performance=1
allows selection of the performance table at boot time. 

This also creates /sys/module/cpu_pxa/parameters/performance which can
be written to and takes effect on the next frequency change. Is this
acceptable or should I look for a way to add a sysfs file
to /sys/devices/system/cpu/cpu0/cpufreq? The advantage would be
immediate application of the change (I think...)

> > +	cpumask_t cpus_allowed;
> 
> Is this a SMP-capable platform?

I don't really know to be honest -- there are SMP ARM's in the world but
I don't know if that will ever extend to the PXA. I doubt it, but I've
asked on the ARM kernel list.

> Is the PXA just a sub-architecture of ARM?

That's right, it's one of Intel's ARM implementations, it takes over
from their StrongARM stuff. The PXA line is quite commonly found in
PDAs.

> >  choice
> >  	prompt "Default CPUFreq governor"
> > -	default CPU_FREQ_DEFAULT_GOV_USERSPACE if CPU_FREQ_SA1100 || CPU_FREQ_SA1110
> > +	default CPU_FREQ_DEFAULT_GOV_USERSPACE if CPU_FREQ_SA1100 || CPU_FREQ_SA1110 || CPU_FREQ_PXA
> 
> Why is that?

I've no idea -- I just copied the StrongARM stuff. My guess is that
someone decided that PERFORMANCE wasn't suitable as the default for an
"embedded" platform. I think I'll probably just drop this chunk since
you can always choose via config anyway. I've pinged the ARM list just
in case there is a more pressing reason.

Ian.

-- 
Ian Campbell, Senior Design Engineer
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