From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754579AbYE1X5j (ORCPT ); Wed, 28 May 2008 19:57:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751367AbYE1X51 (ORCPT ); Wed, 28 May 2008 19:57:27 -0400 Received: from rv-out-0506.google.com ([209.85.198.231]:61524 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751325AbYE1X5N (ORCPT ); Wed, 28 May 2008 19:57:13 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; b=E027/XBP3TAtzX0iglvHOGK3UM99MzP1AwqSZOeD5mx7BWCVEksiijioskL2Iv30TmUDoOdT08Yp/hB5jUk/dFnkFa94BzpY7mda642NEeTM2iwqCpWwtVd/h1XluSSdTU3HgDybtdtQv1OVvamhPjlFADSbDl4hFPrN16PM0uE= Message-ID: <75b66ecd0805281657k7b988bf1qa46e806810da0c17@mail.gmail.com> Date: Wed, 28 May 2008 19:57:11 -0400 From: "Lee Revell" To: Raz Subject: Re: mmap over HPET - 32 bit wrap arround Cc: "Linux Kernel" In-Reply-To: <5d96567b0805281519v7ee18eb0l27f2e4edc18af01c@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <83CA05F64804AF43B8F733C4ABDFAA5101384F73@mail1.bitband.com> <83CA05F64804AF43B8F733C4ABDFAA5101384FA4@mail1.bitband.com> <5d96567b0805281519v7ee18eb0l27f2e4edc18af01c@mail.gmail.com> X-Google-Sender-Auth: 5095e11c8f888cbd Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 28, 2008 at 6:19 PM, Raz wrote: > I am wondering wether someone can explain how hpet behaves. The bellow > is a short program that reads from a mmaped /dev/hpet the time. I am > running it and it looks that afer ~296 seconds the counter resets . I > AM RUNNING 64bi KERNEL(2.6.18-8.el5) and reading a 64BIT VARIABLE. > my hpet is 14MHZ, so I am guessing a 32bit wraparound ( ~296 * 14Mhz > ) = MAX_INT . but why ? > HPET counter can be either 32 or 64 bit. Check COUNT_SIZE_CAP. http://www.intel.com/hardwaredesign/hpetspec_1.pdf Lee