HP/Compaq nx6325 clock "jumping around"

[Nate Lawson]

Bruce Evans wrote:
> On Wed, 2 Jul 2008, Joerg Wunsch wrote:
> 
>> On a nx6325 running 6-stable (because I couldn't get 7.x to work with
>> ACPI at all so far), the main clock is frequently "jumping", up to a
>> level where ntpd eventually gives up:
> 
> I know of the following bugs in time on nx6325:
> - pressing the lid switch to turn the screen off makes the time jump by
>   almost precisely 1 second using any timecounter.  The system appears
>   to spend the 1 second in something like SMM mode with all interrupts
>   and all timecounters stopped.  More precisely, the jump is:
>   ACPI-fast and TSC: -1.000000 +- 10 uS
>   i8254:             -1.043000 +- 1 mS

I'm not sure how to do anything about this.  Sounds like a BIOS bug.

> - dynamic recalibration of cpu_tick_frequency has never worked.  This
>   is a MI bug, and only affects process times.  cpu_tick_frequency is
>   never adjusted downwards (except for a full recalibration).  Thus
>   any glitches in the cpu_tick clock (TSC on nx6325), e.g., from the
>   SMM bug or entering ddb) cause cpu_tick_frequency to creep or jump
>   upwards and never come down.

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?

> 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.

-- 
Nate