Read TCN-register in user space

Read TCN-register in user space

[Björn Östby]

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I'm currently using ELDK 3.0 (kernel 2.4.25) and a mpc823e trying to do some latency measurements for my final thesis project.

I'm wondering if there is any possibility to read the Timer Counter Register (TCN1) in user space. I have initially used gettimeofday(), which provides sufficient resolution (usec), but I suppose that solution probably adds on some kind of unknown context-switch latency. Does anyone have a clue on how to access this in user space? Could inline assembler or perhaps mmap() do the trick (I'm using C as programming language)?.


Regards,
Bjorn 





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Re: Read TCN-register in user space

[Kumar Gala]

There is a proper way to do this and hackish way.  The proper way is to=20=

eventually provide some interface via the work BenH has been doing with=20=

vDSO (while out).  The hackish way is to export it via some /proc or=20
sysfs attribute.  The hackish way will not make its way into a mainline=20=

tree.

- kumar

On Mar 7, 2005, at 5:02 AM, Bj=F6rn =D6stby wrote:

> I'm currently using ELDK 3.0 (kernel 2.4.25) and a mpc823e trying to=20=

> do some latency measurements for my final thesis project.
>
> I'm wondering if there is any possibility to read the Timer Counter=20
> Register (TCN1) in user space. I have initially used gettimeofday(),=20=

> which provides sufficient resolution (usec), but I suppose that=20
> solution probably adds on some kind of unknown context-switch latency.=20=

> Does anyone have a clue on how to access this in user space? Could=20
> inline assembler or perhaps mmap() do the trick (I'm using C as=20
> programming language)?.
>
>
>
> Regards,
>  Bjorn
>
>
>
>  <ATT07173.txt>=