Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755252AbYAGTig (ORCPT ); Mon, 7 Jan 2008 14:38:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752319AbYAGTi2 (ORCPT ); Mon, 7 Jan 2008 14:38:28 -0500 Received: from moutng.kundenserver.de ([212.227.126.183]:56359 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751517AbYAGTi1 (ORCPT ); Mon, 7 Jan 2008 14:38:27 -0500 From: Bodo Eggert <7eggert@gmx.de> Subject: Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override. To: Christer Weinigel , Ingo Molnar , Alan Cox , "David P. Reed" , "H. Peter Anvin" , Rene Herman , Paul Rolland , Pavel Machek , Thomas Gleixner , linux-kernel@vger.kernel.org, Ingo Molnar , rol@witbe.net Reply-To: 7eggert@gmx.de Date: Mon, 07 Jan 2008 20:38:09 +0100 References: <9BdU5-1YW-9@gated-at.bofh.it> <9BeZN-3Gf-5@gated-at.bofh.it> <9BnTB-1As-31@gated-at.bofh.it> <9BrX4-8go-1@gated-at.bofh.it> <9BuBG-4eR-51@gated-at.bofh.it> <9BvRd-6aL-71@gated-at.bofh.it> <9GRQW-1DX-13@gated-at.bofh.it> <9GSah-23W-1@gated-at.bofh.it> <9GSDy-2GD-23@gated-at.bofh.it> <9GTpK-40d-15@gated-at.bofh.it> <9GUvy-5H2-11@gated-at.bofh.it> <9GVKU-7SS-25@gated-at.bofh.it> User-Agent: KNode/0.10.4 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7Bit Message-Id: X-be10.7eggert.dyndns.org-MailScanner-Information: See www.mailscanner.info for information X-be10.7eggert.dyndns.org-MailScanner: Found to be clean X-be10.7eggert.dyndns.org-MailScanner-From: 7eggert@gmx.de X-Provags-ID: V01U2FsdGVkX182eHdjjE751gCBrEZonaw3oI/cAesi+XMj1Ey Ymxtub4F3HF4qo7XkPJo1+pETDAtDSj+9hQEBSxVOOrkTwOyv9 6ZtAKWManf7+TewFFE2nQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1221 Lines: 20 Christer Weinigel wrote: > How do you find out the speed of the ISA bus? AFAIK there is no > standardized way to do that. On the Geode SC2200 the ISA bus speed is > usually the PCI clock divided by 4 giving 33MHz/4=8.3MHz or > 30/4=7.5MHz, but with no external ISA devices it's possible to > overclock the ISA bus to /3 to run it at 11MHz or so. But without > poking at some CPU and southbridge specific registers to find out the > PCI bus speed and the ISA bus divisor you can't really tell. If you overclock, you are on your own. IIRC I've used 13,3 MHz for some time and used a lower PIO mode to compensate. > So if you do udelay based on a 6MHz clock (I think you can safely > assume that any 386 based system runs the ISA bus at least that fast) > you'll waste at least 30% and maybe even 100% more time for the delay > after every _p call. Defaulting to 8 MHz and offering an option to set another clock speed (like idebus=) should be OK. -- 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/