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From: Thomas Gleixner <tglx@linutronix.de>
To: David Daney <ddaney@caviumnetworks.com>
Cc: linux-mips@linux-mips.org, ralf@linux-mips.org
Subject: Re: [PATCH] MIPS: Don't overflow cevt-r4k.c calculations at high clock rates.
Date: Wed, 19 May 2010 12:34:38 +0200 (CEST)	[thread overview]
Message-ID: <alpine.LFD.2.00.1005191233490.3368@localhost.localdomain> (raw)
In-Reply-To: <alpine.LFD.2.00.1005191223260.3368@localhost.localdomain>



On Wed, 19 May 2010, Thomas Gleixner wrote:

> On Tue, 18 May 2010, David Daney wrote:
> 
> > The 'mult' element of struct clock_event_device must never be wider
> > than 32-bits.  If it were, it would get truncated when used by
> > clockevent_delta2ns() when this calls do_div().
> > 
> > We meet the requirement by ensuring that the relationship:
> > 
> >  (mips_hpt_frequency >> (32 - shift)) < NSEC_PER_SEC
> > 
> > Always holds.
> 
> clocks_calc_mult_shift() is your friend :)

There are wrapper functions for clock sources and clock events as well:

clocksource_calc_mult_shift()
clockevents_calc_mult_shift()

Thanks,

	tglx

      reply	other threads:[~2010-05-19 10:34 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-05-18 22:11 [PATCH] MIPS: Don't overflow cevt-r4k.c calculations at high clock rates David Daney
2010-05-18 22:48 ` Kevin D. Kissell
2010-05-18 22:52   ` Ralf Baechle
2010-05-19  1:27 ` Wu Zhangjin
2010-05-19  9:52 ` Sergei Shtylyov
2010-05-19 10:23 ` Thomas Gleixner
2010-05-19 10:34   ` Thomas Gleixner [this message]

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