From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762119AbYBRVDg (ORCPT ); Mon, 18 Feb 2008 16:03:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761734AbYBRVDN (ORCPT ); Mon, 18 Feb 2008 16:03:13 -0500 Received: from smtpq2.groni1.gr.home.nl ([213.51.130.201]:40949 "EHLO smtpq2.groni1.gr.home.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758322AbYBRVDM (ORCPT ); Mon, 18 Feb 2008 16:03:12 -0500 Message-ID: <47B9F2EC.4070308@keyaccess.nl> Date: Mon, 18 Feb 2008 22:04:44 +0100 From: Rene Herman User-Agent: Thunderbird 2.0.0.9 (X11/20071031) MIME-Version: 1.0 To: "H. Peter Anvin" CC: "David P. Reed" , Thomas Gleixner , Ingo Molnar , Alan Cox , Dmitry Torokhov , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: use explicit timing delay for pit accesses in kernel and pcspkr driver References: <6gr00g$g7qpu0@smtp01.lnh.mail.rcn.net> <47B9ECE0.70000@keyaccess.nl> <47B9EDF1.5050404@zytor.com> In-Reply-To: <47B9EDF1.5050404@zytor.com> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -0.6 (/) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18-02-08 21:43, H. Peter Anvin wrote: > Rene Herman wrote: >> >> Now with respect to the original pre port 80 "jmp $+2" I/O delay >> (which the Pentium obsoleted) I suppose it'll probably be okay even >> without fixing that specifically but do note such -- it's a vital part >> of the problem. >> > > Sorry, that paragraph didn't parse for me. I mean that before the linux kernel used a port 0x80 write as an I/O delay it used a short jump (two in a row actually...) as such and this was at the time that it actually ran on the old legacy stuff that is of most concern here. No, if I'm not mistaken, those two jumps are actually what the udelay() is going to do anyway as part of delay_loop() at that early stage so that even before loops_per_jiffy calibration, I believe we should still be okay. Yes, it's a bit of a "well, hrrm" thing, but, well... loops_per_jiffy can be initialised a bit more conservatively then today as well (and as discussed earlier, possibly per CPU family) but I believe it's actually sort of fine not too worry much about it... Rene.