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SubjectRe: Linux 2.6.29-rc6
Linus Torvalds wrote:
>
> Jesper, here's a patch that actually tries to take teh TSC error really
> into account, and which I suspect will result (on your machine) in failing
> the fast PIT calibration.
>
> It also has a few extra printk's for debugging, and to see just what the
> values are on your machine.
>
> The idea behind the patch is to just keep track of how big the difference
> was in TSC values between two successive reads of the PIT timer. We only
> really care about the difference when the MSB turns around, and we only
> really care about the two end points. The maximum error in TSC estimation
> will simply be the sum of the differences at those points (d1 and d2).
>
> We can then compare the maximum error with the actual TSC differences
> between those points, and see if the max error is within 500 ppm. That
> _should_ mean that it all works - assuming that the PIT itself is running
> at the correct frequency, of course!
>
> Regardless of whether is succeeds or not, it will print out some debug
> messages, which will be interesting to see.


[ 0.000000] Fast TSC delta=34227730, error=6223+6219=12442
[ 0.000000] Fast TSC calibration using PIT
[ 0.000000] Detected 2312.045 MHz processor.
Using "ntpq -c peers" .. the offset steadily grows as time goes.

Full dmesg: http://krogh.cc/~jesper/dmesg-linux-2.6.29-rc8-linus1.txt

jk@quad11:~$ ntpdc -c kerninfo
pll offset: 0.085167 s
pll frequency: -18.722 ppm
maximum error: 0.137231 s
estimated error: 0.008823 s
status: 0001 pll
pll time constant: 6
precision: 1e-06 s
frequency tolerance: 500 ppm



--
Jesper




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