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Re: [PATCH] hp-timing for ppc32/64
- From: Benjamin Herrenschmidt <benh at kernel dot crashing dot org>
- To: sjmunroe at vnet dot ibm dot com
- Cc: libc-alpha at sources dot redhat dot com
- Date: Wed, 12 Oct 2005 10:11:30 +1000
- Subject: Re: [PATCH] hp-timing for ppc32/64
- References: <434AE8D0.6070602@us.ibm.com>
On Mon, 2005-10-10 at 17:18 -0500, Steve Munroe wrote:
> This patch adds hp-timing for powerpc32 and powerpc64.
A couple of questions here:
- Do you have any provision to deal with ppc32 CPUs that do not provide
the TB but different timing mecanisms ? Should we add a CPU feature bit
exposed by the kernel to userland ?
- I haven't read/found the hp-timing spec yet, but are we supposed to
be able to convert between hp-timing values/diffs & actual time units
(like nanoseconds or so) ? That would require to know the TB calibration
values, which is currently not exposed by the kernel in any way you are
supposed to use in userland afaik. I could add a vDSO entry point for
that though (and to a ppc32 vDSO which will happen soon).
Cheers,
Ben.