Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758615AbXIKQ2V (ORCPT ); Tue, 11 Sep 2007 12:28:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752937AbXIKQ2O (ORCPT ); Tue, 11 Sep 2007 12:28:14 -0400 Received: from mailhub.linpro.no ([213.236.139.167]:48829 "EHLO mailhub.linpro.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751130AbXIKQ2N convert rfc822-to-8bit (ORCPT ); Tue, 11 Sep 2007 12:28:13 -0400 From: =?iso-8859-1?Q?Dag-Erling_Sm=F8rgrav?= To: mgross@linux.intel.com Cc: linux-kernel@vger.kernel.org Subject: Re: [RFC+PATCH] RTC calibration References: <20070911152323.GA17650@linux.intel.com> Date: Tue, 11 Sep 2007 18:28:06 +0200 In-Reply-To: <20070911152323.GA17650@linux.intel.com> (Mark Gross's message of "Tue, 11 Sep 2007 08:23:23 -0700") Message-ID: User-Agent: Gnus/5.110004 (No Gnus v0.4) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 947 Lines: 24 Mark Gross writes: > Is it necessary to change the rtc interface? Can't you detect within > your m48t59 driver that you are getting consistent time adjustments up > or down from whats in the rtc and infer it needs speeding up or slowing > down? [I didn't notice this when I first replied] Because of the RTC's low resolution and of how the calibration is implemented in the chip, you need to sample the clock at intervals of several hours in order to determine the direction of the required adjustment. Repeatedly setting the RTC to the correct time will actually prevent correct calibration. DES -- Dag-Erling Sm?rgrav Senior Software Developer Linpro AS - www.linpro.no - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/