[stable 9] broken hwpstate calls

[Jung-uk Kim]

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On 2012-05-25 15:39:39 -0400, Andriy Gapon wrote:
> on 25/05/2012 20:11 Jung-uk Kim said the following:
>> I just looked through the BKDG and I think you should definitely
>> check MSRC001_0071[18:16].  MSRC001_0063[2:0] is "SharedC" but
>> MSRC001_0062[2:0] and MSRC001_0071[18:15] are "Not-same-for-all".
>> I think this means writing a P-state to MSRC001_0062[2:0] will be
>> reflected in MSRC001_0070[18:16] first, then MSRC001_0071[18:16]
>> gets updated when the P-state transition is complete.
>> MSRC001_0063[2:0] will only change when all cores in a compute 
>> unit is in sync., which may be too late.
>> 
> [snip]
>> I think we should check.
> 
> Jung-uk,
> 
> if we decide so, then I think that we could still keep the things
> "simple". As we currently use the "wholesale" approach (all CPUs
> are set to the same P-state regardless of topology), then we could
> first make a pass of writing the MSR on all processors with a new
> P-state value and then make another pass of checking via MSR
> C001_0063 that the P-state is acquired.

No, I believe checking MSRC001_0071[18:16] is much simpler if it
works.  And it does not break current cpufreq(4) design principles.

Jung-uk Kim
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