Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754439AbXL3R5r (ORCPT ); Sun, 30 Dec 2007 12:57:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752065AbXL3R5j (ORCPT ); Sun, 30 Dec 2007 12:57:39 -0500 Received: from smtpq2.groni1.gr.home.nl ([213.51.130.201]:50633 "EHLO smtpq2.groni1.gr.home.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751427AbXL3R5i (ORCPT ); Sun, 30 Dec 2007 12:57:38 -0500 Message-ID: <4777DB4E.9080105@keyaccess.nl> Date: Sun, 30 Dec 2007 18:54:22 +0100 From: Rene Herman User-Agent: Thunderbird 2.0.0.9 (X11/20071031) MIME-Version: 1.0 To: Ingo Molnar CC: Alan Cox , Linus Torvalds , dpreed@reed.com, Islam Amer , hpa@zytor.com, Pavel Machek , Ingo Molnar , Andi Kleen , Thomas Gleixner , Linux Kernel Subject: Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override References: <477711DC.5030800@keyaccess.nl> <20071230144700.78f4605c@the-village.bc.nu> <20071230152835.GX16946@elte.hu> <4777BDA5.4050203@keyaccess.nl> <20071230160751.GB26221@elte.hu> <4777C6E8.7060202@keyaccess.nl> <20071230170612.GA16502@elte.hu> In-Reply-To: <20071230170612.GA16502@elte.hu> 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 Content-Length: 1231 Lines: 30 On 30-12-07 18:06, Ingo Molnar wrote: > * Rene Herman wrote: >> Real ISA systems will also generally respond faster to it than the >> unused port (this thing actually has an ISA bus but not VGA on it >> ofcourse) which means that "a perfect delay register" it is not. But >> yes, I have an actual Am386DX-40 with ISA VGA up and running which >> also doesn't care either way, about the ones in misc_32.c or anywhere >> else for that matter. > > yeah - and that's typical of most _p() use: most of them are totally > bogus, but the global existence of the delay was used as a "it _might_ > break system" boogey-man against replacing it. No delaying at all does break a few systems. > so _IF_ we do any delay in x86 platform drivers, we at most do a delay > on the order of the round-trip latency to the same piece of hardware we > are handling. Given that part of the problem is 2 MHz devices on a 8 MHz bus, you can't do this generally. Rene. -- 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/