From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756766AbXLKUCf (ORCPT ); Tue, 11 Dec 2007 15:02:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756571AbXLKUCF (ORCPT ); Tue, 11 Dec 2007 15:02:05 -0500 Received: from smtpq2.groni1.gr.home.nl ([213.51.130.201]:46452 "EHLO smtpq2.groni1.gr.home.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756552AbXLKUCE (ORCPT ); Tue, 11 Dec 2007 15:02:04 -0500 Message-ID: <475EEC25.8000109@keyaccess.nl> Date: Tue, 11 Dec 2007 20:59:33 +0100 From: Rene Herman User-Agent: Thunderbird 2.0.0.9 (X11/20071031) MIME-Version: 1.0 To: Pavel Machek CC: Andi Kleen , "linux-os (Dick Johnson)" , David Newall , Paul Rolland , "H. Peter Anvin" , Krzysztof Halasa , Alan Cox , "David P. Reed" , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , rol@witbe.net Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops References: <475DE6F4.80702@zytor.com> <475DEB23.1000304@davidnewall.com> <20071211084059.3d03e11d@tux.DEF.witbe.net> <475E5D4B.8020101@keyaccess.nl> <475E7DC2.4060509@davidnewall.com> <475E8D91.20201@keyaccess.nl> <475E95A3.3070801@davidnewall.com> <20071211163017.GD16750@one.firstfloor.org> <475EBFBA.6090301@keyaccess.nl> <20071211191649.GB3437@elf.ucw.cz> In-Reply-To: <20071211191649.GB3437@elf.ucw.cz> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -1.0 (-) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11-12-07 20:16, Pavel Machek wrote: >> Pavel Machek already posted one. His udelay(8) wants to be less -- 1 or "to >> be safe" perhaps 2. >> >> http://lkml.org/lkml/2007/12/9/131 > > 2 at least; that's how long outb(0x80) takes on one of my > machines. Actually, ISA can go down to 4MHz, so maybe we should be > using 4 usec.... but I guess I'm paranoid here. 4 isn't sensible. There have been machines capable both of running Linux and their ISA bus at less than 8 MHz (if only for example by picking a 5 divisor on a system that was capable of hosting a 40 Mhz 386/486 but using a slower CPU) but not by much. And machines doing that and running Linux, even more so "today": 0. My posted test program (although there seems to be something wrong with it since it's influenced by compiler optimisation) is showing more than 1 but note that on the vast majority of machines, 0 would in fact do. 1 will on all, 2 will as well. Rene.