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Date: Thu, 20 Sep 2007 10:52:16 +1000
From: Paul Mackerras <paulus@samba.org>
To: Daniel Walker <dwalker@mvista.com>
Subject: Re: [PATCH 2/5] Implement generic time of day clocksource for
	powerpc machines.
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Cc: linuxppc-dev@ozlabs.org, Thomas Gleixner <tglx@linutronix.de>,
	johnstul@us.ibm.com, Realtime Kernel <linux-rt-users@vger.kernel.org>
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Daniel Walker writes:

> If you switch to the rtc do the shift and mult need to change?

You can't switch; any given CPU chip will have either the RTC or the
timebase but not both.

> > +       /* XXX this assumes clock->shift == 22 */
> > +       /* 4611686018 ~= 2^(20+64-22) / 1e9 */
> > +       t2x = (u64) clock->mult * 4611686018ULL;
> 
> It might make the code more readable if you put that constant into a
> macro that gives it a name.

The comment already gives more information than some arbitrary name
would.

Paul.