Re: [PATCH v4 3/7] acpi-cpufreq: Add support for disabling dynamicoverclocking

From: Matthew Garrett
Date: Sat Jul 23 2011 - 23:29:18 EST

On Sat, Jul 23, 2011 at 11:06:29PM -0400, Andy Lutomirski wrote:
> On 07/18/2011 12:37 PM, Matthew Garrett wrote:
> >One feature present in powernow-k8 that isn't present in acpi-cpufreq is
> >support for enabling or disabling AMD's core performance boost technology.
> >This patch adds that support to acpi-cpufreq, but also extends it to allow
> >Intel's dynamic acceleration to be disabled via the same interface. The
> >sysfs entry retains the cpb name for compatibility purposes.
> >
> >Signed-off-by: Matthew Garrett<mjg@xxxxxxxxxx>
> >---
> > drivers/cpufreq/acpi-cpufreq.c | 191 ++++++++++++++++++++++++++++++++++++++++
> > 1 files changed, 191 insertions(+), 0 deletions(-)
> >
> How is this different from setting 3400000 vs 3401000 as the max
> freq? (I'm probably missing something about the way that Intel's
> turbo mode works.)

It's not really, it just means that there's a shared interface to
achieve the same goal.

> >+ unsigned long val = 0;
> >+
> >+ ret = strict_strtoul(buf, 10,&val);
> >+ if (!ret&& (val == 0 || val == 1)&& cpb_supported)
> >+ cpb_toggle(val);
> Shouldn't this set the flag only on policy->cpu (as opposed to all
> online cpus?)

It's effectively a per-package MSR rather than a per-thread or per-core
one. We could make this per-package rather than system-wide, but I don't
really know of any use cases that would benefit from the extra code. If
anyone cares enough it could be added, but I'm a great believer in
letting people come up with arguments for adding something before doing

> Also, you're missing a space before &&.

Think that's a cut and paste error. I'll fix it up.

Matthew Garrett | mjg59@xxxxxxxxxxxxx
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