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Date: Thu, 6 Sep 2007 14:15:05 -0500
From: Josh Boyer <jwboyer@linux.vnet.ibm.com>
To: Scott Wood <scottwood@freescale.com>
Subject: Re: finding out the processor frequency
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Cc: "Leisner, Martin" <Martin.Leisner@xerox.com>, linuxppc-embedded@ozlabs.org
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On Thu, 6 Sep 2007 13:43:08 -0500
Scott Wood <scottwood@freescale.com> wrote:

> On Thu, Sep 06, 2007 at 02:24:30PM -0400, Leisner, Martin wrote:
> > What exactly do we mean by "timebase"?
> > 
> > There a symbol in arch/powerpc/time.c:ppc_proc_freq which looks like the
> > processor frequency (derived from the dts).  But its not exported.
> > 
> > There's also ppc_tb_freq.
> 
> The timebase is the rate at which the timebase and decrementer registers
> tick.  It is not the same as the CPU core frequency.

Unless your timebase and decrementer clock source is tied to the CPU
clock. :)

So it depends on the board, and it can even depend on how the board is
initialized.  Some boards can change the timebase clock source on the
fly.

josh