From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932184AbXCQHX4 (ORCPT ); Sat, 17 Mar 2007 03:23:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752655AbXCQHX4 (ORCPT ); Sat, 17 Mar 2007 03:23:56 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:59128 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752653AbXCQHXz (ORCPT ); Sat, 17 Mar 2007 03:23:55 -0400 Date: Sat, 17 Mar 2007 08:22:27 +0100 From: Ingo Molnar To: Thomas Gleixner Cc: Maxim Levitsky , linux-kernel@vger.kernel.org, Andrew Morton , Adrian Bunk , Arjan van de Ven , Len Brown Subject: Re: [PATCH] i386: trust the PM-Timer calibration of the local APIC timer Message-ID: <20070317072227.GA12122@elte.hu> References: <200703161230.03712.maximlevitsky@gmail.com> <1174088686.13341.347.camel@localhost.localdomain> <1174089896.13341.362.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1174089896.13341.362.camel@localhost.localdomain> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.0.3 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Thomas Gleixner wrote: > When PM-Timer is available for local APIC timer calibration we can > skip the verification of the calibrated time value. The resulting > error is quite small on a bunch of evaluated platforms and is less > harming than the observed false positives. > > We need to keep the verification on systems, which have no PM-Timer to > avoid bogus local APIC timer calibrations in the range of factor 2-10, > which can be observed when swicthing off the PM-timer support in the > kernel configuration. > > The wrong calibration values are probably caused by SMM code trying to > emulate a PS/2 keyboard from a (maybe connected or not) USB keyboard. > This prohibits the accurate delivery of PIT interrupts, which are used > to calibrate the local APIC timer. Unfortunately we have no way to > disable this BIOS misfeature in the early boot process. > > Add also the dropped cpu_relax() back to the wait loops. > > Signed-off-by: Thomas Gleixner Acked-by: Ingo Molnar Ingo