get_cycles/get_tbl on 405

get_cycles/get_tbl on 405

[andrew may]

I wanted to do some quick time measurements of some things on a driver
running of the 405GP and I eneded up using get_tbl(). It seems like
get_cycles should be the more standard way to get a tick count but
it seems to return 0. I don't get the __ftr_fixup stuff in timex.h
so I am not sure what it is trying to do differently from get_tbl.


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Re: get_cycles/get_tbl on 405

[Benjamin Herrenschmidt]

>I wanted to do some quick time measurements of some things on a driver
>running of the 405GP and I eneded up using get_tbl(). It seems like
>get_cycles should be the more standard way to get a tick count but
>it seems to return 0. I don't get the __ftr_fixup stuff in timex.h
>so I am not sure what it is trying to do differently from get_tbl.

The __ftr_fixup in timex.h adds a reference to this code in the
feature fixup section. This allow the code that access the TB to
be nop'ed out on CPUs that don't implement it (601)

Ben.


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Re: get_cycles/get_tbl on 405

[Dan Malek]

andrew may wrote:
>
> I wanted to do some quick time measurements of some things on a driver
> running of the 405GP and I eneded up using get_tbl(). It seems like
> get_cycles....

Hmmm....these look like they should work exactly the same.....
It would help me if you could disassemble a little code snippet
around the place you use these so we could have a look.

Thanks.


	-- Dan

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Re: get_cycles/get_tbl on 405

[acmay]

On Fri, Aug 24, 2001 at 10:35:10PM -0400, Dan Malek wrote:
> andrew may wrote:
> >
> > I wanted to do some quick time measurements of some things on a driver
> > running of the 405GP and I eneded up using get_tbl(). It seems like
> > get_cycles....
>
> Hmmm....these look like they should work exactly the same.....
> It would help me if you could disassemble a little code snippet
> around the place you use these so we could have a look.

They did. I just confused myself with too many kernel versions.
The 2.4.2 mvista kernel didn't have the same header file, but by
just sticking the newer header in there with the one other header
it pulls in along with it, it worked fine.

The __ftr_fixup doesn't seem to be used much in any of the other
arch's.


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Re: get_cycles/get_tbl on 405

[Dan Malek]

acmay@acmay.homeip.net wrote:

> They did. I just confused myself with too many kernel versions.

Cool.

> The __ftr_fixup doesn't seem to be used much in any of the other
> arch's.

It's a PowerPC thing that Ben recently added to make it easier
for us to manage the minor differences among the processor variations.


	-- Dan

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