Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756281AbXLOFq2 (ORCPT ); Sat, 15 Dec 2007 00:46:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751431AbXLOFqU (ORCPT ); Sat, 15 Dec 2007 00:46:20 -0500 Received: from terminus.zytor.com ([198.137.202.10]:56483 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751368AbXLOFqT (ORCPT ); Sat, 15 Dec 2007 00:46:19 -0500 Message-ID: <476369E2.8050301@zytor.com> Date: Fri, 14 Dec 2007 21:45:06 -0800 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: "David P. Reed" CC: Alan Cox , Pavel Machek , Ingo Molnar , Thomas Gleixner , linux-kernel@vger.kernel.org, Ingo Molnar , Rene Herman Subject: Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc. References: <469578CD.3080609@reed.com> <1184216528.12353.203.camel@chaos> <1184218962.12353.209.camel@chaos> <46964352.7040301@reed.com> <1184253339.12353.223.camel@chaos> <469697C6.50903@reed.com> <1184274754.12353.254.camel@chaos> <4761F193.7090400@reed.com> <20071214131502.GA14359@elte.hu> <4762C551.5070003@zytor.com> <20071214210652.GB28793@elf.ucw.cz> <4763001A.1070102@zytor.com> <20071214232955.545ab809@the-village.bc.nu> <4763442A.5020507@reed.com> In-Reply-To: <4763442A.5020507@reed.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 870 Lines: 18 David P. Reed wrote: > Just a thought for a way to fix the "very early" timing needed to set up > udelay to work in a way that works on all machines. Perhaps we haven't > exploited the BIOS enough: The PC BIOS since the PC AT (286) has > always had a standard "countdown timer" way to delay for n microseconds, > which as far as I know still works. This can be used to measure the > speed of a delay loop, without using ANY in/out instructions directly > (the ones in the BIOS are presumably correctly delayed...). If we enter from the 32-bit entrypoint, we already don't have access to the BIOS, though. -hpa -- 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/