[RFC V1 1/4] cpufreq: add arm soc generic cpufreq driver

[Richard Zhao]

On Thu, Dec 15, 2011 at 08:29:11PM +0000, Russell King - ARM Linux wrote:
> On Thu, Dec 15, 2011 at 07:16:35PM +0800, Richard Zhao wrote:
> > +#ifdef CONFIG_SMP
> > +	/* loops_per_jiffy is not updated by the cpufreq core for SMP systems.
> > +	 * So update it for all CPUs.
> > +	 */
> > +	for_each_possible_cpu(cpu)
> > +		per_cpu(cpu_data, cpu).loops_per_jiffy =
> > +		cpufreq_scale(per_cpu(cpu_data, cpu).loops_per_jiffy,
> > +					freqs.old, freqs.new);
> 
> NAK.  If you think this is a good solution, you're very wrong.  If this
> is what's in the core cpufreq code, then it too is very broken.
> 
> I've seen this exact method result in the loops_per_jiffy being totally
> buggered over time by the constant scaling up and down.  The only way
> to do this _sensibly_ is to record the _initial_ loops_per_jiffy and
> _inital_ frequency, and scale from that.
> 
> That way you get consistent results irrespective of the scalings you
> do over time, rather than something which continually deteriorates with
> every frequency change.
Thanks for your comments. I'll recalculate loops_per_jiffy always based on boot
up values.

Thanks
Richard
> 
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