linux-kernel - Re: [Acpi4asus-user] [PATCH 1/1] cpufreq: eeepc 900 frequency scaling driver

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Message-ID: <71cd59b00904050043u44d1cd2eu4b8d3aee9027ea17@mail.gmail.com>
Date:	Sun, 5 Apr 2009 09:43:40 +0200
From:	Corentin Chary <corentin.chary@...il.com>
To:	Cristiano Prisciandaro <cristiano.p@...net.ch>
Cc:	Thomas Renninger <trenn@...e.de>, Dave Jones <davej@...hat.com>,
	acpi4asus-user@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	cpufreq@...r.kernel.org, Tom Hughes <tom@...pton.nu>,
	linux acpi <linux-acpi@...r.kernel.org>,
	Francesco Lattanzio <f.lattanzio@...ail.it>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Grigori Goronzy <greg@...wn.ath.cx>
Subject: Re: [Acpi4asus-user] [PATCH 1/1] cpufreq: eeepc 900 frequency scaling 
	driver

>> Could it happen that upcoming machines provide this interface (the two ACPI
>> functions) and also can do real CPU frequency/volt switching, e.g. via
>> acpi-cpufreq?
>
> Probably this interface is a solution specific to machines based on the
> celeron M: I don't even know if other 'old' models provide the same
> interface.

Hi,
We I just received another patch for that (adding a cpufv file in
sysfs) and I don't really know what to do.

As Grigori Goronzy said, using cpufreq in not a good idea:

> 1) dynamic governors like "ondemand" or "conservative" are not suitable
> for SHE. It's possible to avoid usage of these by specifying a long
> (e.g. UINT_MAX) transition latency. However, the fallback governor is
> "performance" which isn't a good idea either, because it'll use the
> overclock setting always. For SHE, the default should be the "normal",
> non-overclocked frequency.
>
> 2) The SHE ACPI interface doesn't expose the clock frequencies. I'm
> using 750 / 1000 / 1500 KHz at the moment, but that's hacky. cpufreq
> does not support performance points with names, such as "powersave",
> "normal", "performance", etc.
>
> 3) It looks like it is impossible to use more than one cpufreq driver
> per CPU. This effectively means you can either use the regular ACPI
> frequency scaling, which switches between multipliers, or SHE. That's
> unacceptable. SHE is not intended to replace the regular frequency
> scaling, but to complement it.

But adding another specific file for eeepc seems ugly too.
Does someone have a great idea to solve that ?

Thanks
-- 
Corentin Chary
http://xf.iksaif.net
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