HP/Compaq nx6325 clock "jumping around"

[Nate Lawson]

Bruce Evans wrote:
> On Fri, 4 Jul 2008, Nate Lawson wrote:
> 
>>> On Wed, 2 Jul 2008, Joerg Wunsch wrote:
>>> ...
>> Bruce Evans wrote:
>>> I know of the following bugs in time on nx6325:
>> ...
>>
>> This reminds me -- the algorithm for estimating the cpu frequency 
>> needs improvement.  You had a patch you sent me that reduced its error 
>> by a lot. Would you commit it?
> 
> I'm further than ever from committing this, since I'm not set up for svn.
> 
> I never merged this to the kernel.  Running it in userland on more SMP
> machines shows the expected problems from the CPU not being pinnable in
> userland.

I used it from the kernel and it worked fine but I was scared off by 
some questions you had regarding the edge cases where calibration might 
never complete.

>>> dev.cpu.0.freq: 1985
>>> dev.cpu.0.freq_levels: 1985/-1 1736/-1 1488/-1 1240/-1 992/-1 744/-1 
>>> 496/-1 248/-1
>>>
>>> Once I used some performance/power-reduction config and got a list 
>>> like yours.
>>>
>>> 1985 actually gives 1995 MHz.
>>
>> Your freq estimation patch does better than this.
> 
> Aren't the above frequencies just read from acpi read-only data?

Depends on the back-end driver being used.  dmesg | grep cpu will reveal 
it.  Some drivers like acpi_perf and est do have their own table. 
Others like p4tcc and acpi_throttle have to estimate it.

-- 
Nate