linux-kernel - Re: [PATCH 6/6] cpufreq: Evaluate P1 before enter turbo mode

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Message-ID: <AANLkTi=XkMqUSfO076mVqGCHv-Kw-jnuL8dZiN17ypqZ@mail.gmail.com>
Date:	Thu, 23 Dec 2010 10:13:54 -0800
From:	Venkatesh Pallipadi <venki@...gle.com>
To:	Matthew Garrett <mjg@...hat.com>
Cc:	Dominik Brodowski <linux@...inikbrodowski.net>,
	Youquan Song <youquan.song@...el.com>, davej@...hat.com,
	cpufreq@...r.kernel.org, arjan@...ux.intel.com, lenb@...nel.org,
	suresh.b.siddha@...el.com, kent.liu@...el.com,
	chaohong.guo@...el.com, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	Youquan Song <youquan.song@...ux.intel.com>
Subject: Re: [PATCH 6/6] cpufreq: Evaluate P1 before enter turbo mode

On Thu, Dec 23, 2010 at 6:38 AM, Matthew Garrett <mjg@...hat.com> wrote:
> On Thu, Dec 23, 2010 at 11:57:30AM +0100, Dominik Brodowski wrote:
>
>> NACK. First of all, why is it only a "turbo mode" if it's 1000 kHz
>> difference?
>
> I believe that that's how it's supposed to be defined for Intel systems,
> but you're right that this doesn't belong in generic code. AMD have
> support for enabling/disabling their equivalent functionality through
> sysfs - I'd say that copying that interface and using it to limit the
> set of p-states provided to the core makes more sense.
>

If this 1000kHz hack is needed, it should be in acpi-cpufreq driver
along with Intel CPU and Turbo mode capability check..
I had a change earlier and I don't think I ever pushed it out. But, it
was doing the max freq transition on turbo capable CPUs in 2 steps.
Something like:
- cpu is in one of the low freqs.
- ondemand asks for highest freq.
- acpi-cpufreq will check whether the CPU is turbo capable and will
only switch to non-turbo peak freq as first step.
- If ondemand asks for highest freq again, acpi-cpufreq will then
switch to turbo freq.

Something like that would probably help the problem here?

Thanks,
Venki


Thanks,
Venki
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