Re: [ACPI] [PATCH] disable SMM access to SpeedStep using ACPI-FADT pstate_cnt

[Bruno Ducrot <ducrot@poupinou.org>]

On Sun, Feb 15, 2004 at 11:57:12AM +0100, Dominik Brodowski wrote:
> Disable SMM access to SpeedStep
> 
> Often, the BIOS changes the CPU frequency if a notebook is (dis)connected
> from its AC adapter. This interferes with a) an user setting the CPU frequency
> and b) kernel timing code which needs to know loops_per_jiffy, cpu_khz etc.
> 
> So, ACPI 2.0 offers a method to disable such BIOS changes -- writing
> a value contained in the FADT (pstate_cnt) to the smi_cmd port. This patch
> utilizes this method by doing this write in processor.c.
> 
> However, most current notebooks only offer 1.0 ACPI tables, where the
> pstate_cnt entry is marked as "reserved". Whenever there is a _PCT entry
> in the DSDT, though [and this is only a 2.0 object!], we assume the
> "reserved" entry to be the pstate_cnt entry [if it isn't zero].

I would prefer to name it 'take_ownership' or something like that.  I think
this is the correct naming.

-- 
Bruno Ducrot

--  Which is worse:  ignorance or apathy?
--  Don't know.  Don't care.