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Message-ID: <alpine.LFD.2.00.1003221521440.3147@localhost.localdomain>
Date: Mon, 22 Mar 2010 15:22:12 +0100 (CET)
From: Thomas Gleixner <tglx@...utronix.de>
To: Johannes Weiner <hannes@...xchg.org>
cc: Ivan Kokshaysky <ink@...assic.park.msu.ru>,
john stultz <johnstul@...ibm.com>,
Richard Henderson <rth@...ddle.net>,
lkml <linux-kernel@...r.kernel.org>,
Matt Turner <mattst88@...il.com>
Subject: Re: [RFC][PATCH] Convert alpha to use clocksource
On Mon, 22 Mar 2010, Johannes Weiner wrote:
> > Though, even after a glance over the clocksource code, I've not
> > gotten yet to how one could estimate the "shift" value...
> > Any hints?
>
> I had the same problem with xtensa and added a comment about what I
> did in there, maybe it helps:
>
> arch/xtensa/kernel/time.c
>
> I took the upper bound of the multiplicator (nsecs per counter unit)
> and subtracted its logarithm from my available 32 bits. The result
> is the highest possible shift value that works for the clocksource.
clocks_calc_mult_shift() is what you are looking for.
Thanks,
tglx
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