Re: [PATCH] MIPS: Don't overflow cevt-r4k.c calculations at high clock r

linux-mips

Re: [PATCH] MIPS: Don't overflow cevt-r4k.c calculations at high clock r

To:	David Daney <ddaney@caviumnetworks.com>
Subject:	Re: [PATCH] MIPS: Don't overflow cevt-r4k.c calculations at high clock rates.
From:	Thomas Gleixner <tglx@linutronix.de>
Date:	Wed, 19 May 2010 12:23:53 +0200 (CEST)
Cc:	linux-mips@linux-mips.org, ralf@linux-mips.org
In-reply-to:	<1274220676-4562-1-git-send-email-ddaney@caviumnetworks.com>
Original-recipient:	rfc822;linux-mips@linux-mips.org
References:	<1274220676-4562-1-git-send-email-ddaney@caviumnetworks.com>
Sender:	linux-mips-bounce@linux-mips.org
User-agent:	Alpine 2.00 (LFD 1167 2008-08-23)

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 :)

Thanks,

        tglx

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[PATCH] MIPS: Don't overflow cevt-r4k.c calculations at high clock rates., David Daney Re: [PATCH] MIPS: Don't overflow cevt-r4k.c calculations at high clock rates., Kevin D. Kissell Re: [PATCH] MIPS: Don't overflow cevt-r4k.c calculations at high clock rates., Ralf Baechle Re: [PATCH] MIPS: Don't overflow cevt-r4k.c calculations at high clock rates., Wu Zhangjin Re: [PATCH] MIPS: Don't overflow cevt-r4k.c calculations at high clock rates., Sergei Shtylyov Re: [PATCH] MIPS: Don't overflow cevt-r4k.c calculations at high clock rates., Thomas Gleixner <= Re: [PATCH] MIPS: Don't overflow cevt-r4k.c calculations at high clock rates., Thomas Gleixner

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