Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758034AbXL3QI2 (ORCPT ); Sun, 30 Dec 2007 11:08:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756771AbXL3QIV (ORCPT ); Sun, 30 Dec 2007 11:08:21 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:43833 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756579AbXL3QIU (ORCPT ); Sun, 30 Dec 2007 11:08:20 -0500 Date: Sun, 30 Dec 2007 17:07:51 +0100 From: Ingo Molnar To: Rene Herman 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 Message-ID: <20071230160751.GB26221@elte.hu> References: <477711DC.5030800@keyaccess.nl> <20071230144700.78f4605c@the-village.bc.nu> <20071230152835.GX16946@elte.hu> <4777BDA5.4050203@keyaccess.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4777BDA5.4050203@keyaccess.nl> User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1320 Lines: 35 * Rene Herman wrote: > On 30-12-07 16:28, Ingo Molnar wrote: > >> Reading from the 0x3cc port does not impact the cursor position update >> sequence IIRC - i think the vidport is even ignored for the input >> direction by most hardware, there's a separate input register. The 0x3cc >> port is a well-defined VGA register which should be unused on non-VGA >> hardware. (which makes it a perfect delay register in any case) > > Hardly. Duron 1300 on AMD756: but that does not matter at all: that's not '90s era hardware that we are (slightly) worried about wrt. IO delays in misc_32.c. (i.e. on _real_ ISA systems) > rene@7ixe4:~/src/port80$ su -c ./port80 > cycles: out 2400, in 2401 > rene@7ixe4:~/src/port80$ su -c ./port3cc > cycles: out 459, in 394 of course, since VGA is implemented in the southbridge or on the video card, so it's much faster than a true ISA cycle. the only (minor) worry we have here is really ancient systems relying on delays there. Modern VGA hardware most definitely does not need any such delays. Ingo -- 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/