Re: Quick, Quick, Slooow

[Dominik Brodowski <linux-JhLEnvuH02M@public.gmane.org>]

Hi Al,

On Tue, Nov 05, 2002 at 12:13:59AM +0000, Al Cutter wrote:
> 	I've just started playing around with this acpi business, but the
> 	processor performance (echo 1 > /proc/acpi/.../performance) didn't seem
> 	to work on my Sony SRX41P, it'd timeout in 
> 	acpi_processor_set_performance() ("Transition failed"). 
> 
> 	The cpufreq interface seems to work fine however, so I made a little 
> 	patch against acpi-20021101 on 2.5.45 which makes :
> 		* acpi_processor_set_performance() call cpufreq to change the 
> 			clock speed, and
> 		* acpi_processor_write_performance() call ..._set_performance()
> 
> 	Don't know if this makes sense, or it's just a kludge that gets around
> 	my particular problem, but it seems to work quite well with 
> 	autospeedstep (http://gpsdrive.kraftvoll.at/speedstep.shtml).
Actually, this would be the wrong way 'round:

There are several "techniques" to switch the performance states / the CPU
freuqency. One is ACPI, others are "legacy" interfaces for Intel SpeedStep,
AMD PowerNow, Cyrix Longhaul, Transmeta Crusoe, ... 

cpufreq offers an unified interface for all these drivers (and a bit
more...) - and so you shouldn't even recognize from reading this interface,
/proc/cpufreq, what cpufreq driver (ACPI, SpeedStep, etc.) is used. 

Your patch would actually remove the ACPI cpufreq driver. Additionally,
you shouldn't try to use the ACPI generic interface to access a general
CPUfreq driver; but use /proc/cpufreq [or /proc/sys/cpu/0/] directly.

	Dominik


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