Re: Enforce _PPC limits

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

Hi Linda,

[...]

> I guess I've lost track of what intel_pstate is doing these
> days.  When it
> first came out, it totally disregarded ACPI information, which is why
> code
> was added to not load the driver on some platforms that are doing
> their
> own power management.  The rationale for not using ACPI was that ACPI
> couldn't express all the information necessary to describe the
> hardware
> capabilities.
> 
> Now it is using ACPI information for some things, but not all things?
> Perhaps intel_pstate.txt could be updated to clarify that?
>  Depending
> on what the future is for intel_pstate and ACPI, I'm wondering if
> that
> vendor-specific code is no longer needed.
> 
> This might be a nit but I'm also confused about whether it's really
> enforcing _PPC limits or _PSS.  Are you actually limiting based on
> the _PPC value?
_PPC is an index into _PSS, the max frequency we will get from _PSS. We
are not enforcing any limits in _PSS. So if some P-State is missing in
_PSS, we will still select that P-State.
I don't know what vendor specific code does. I guess it does more than
just what acpi-cpufreq would have done.

I will check on the documentation part.

Thanks,
Srinivas