Re: [PATCH] 1/3 Dynamic cpufreq governor and updates to ACPI P-state driver

From: Ducrot Bruno
Date: Tue Oct 21 2003 - 12:56:52 EST


On Tue, Oct 21, 2003 at 10:15:31AM -0700, Pallipadi, Venkatesh wrote:
>
> > -----Original Message-----
> > From: Ducrot Bruno [mailto:ducrot@xxxxxxxxxxxx]


...

> > Your do not handle correctly
> > other processors
> > than Intel.
>
> I am sorry. I do not understand this comment.
> - Major part of Patch 1 is adding SMP awareness, which has
> nothing specific to Intel at all.
> - A part of patch 1 adds MSR based transition capability.
> This is based on ACPI spec.

Could you tell me where you find in ACPI spec. that FfixedHW means
always MSR? That not true for C-states definitions via _CST for
example (the first entry being always an FFixedHW, because it
is C1 and will be the single asm instruction: 'hlt').
Look 2.0b page 228.

> It will work any processor
> that is ACPI compatible and again there are no specific
> checks for Intel here.
>

On a K7 with powernow for example, perf_ctrl and perf_data will be MSR 0
with your patch, that do not make sence.
Even if you know the correct MSRs, the values for 'control' and 'status'
in _PSS packages will be only bit-fields, and they can *not* be
written nor read directly to the (correct) MSRs (again for K7 powernow).

This is because the FfixedHW is only an indication that a CPU specific
'feature' (even though already somehow defined in ACPI like P-state,
C-state, etc.) have to be handled by the OS in a non-acpi driver, as
per ACPI spec, and that will be dependant of the CPU.


--
Ducrot Bruno

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