From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754490AbXLKOQQ (ORCPT ); Tue, 11 Dec 2007 09:16:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752782AbXLKOQE (ORCPT ); Tue, 11 Dec 2007 09:16:04 -0500 Received: from smtpq2.groni1.gr.home.nl ([213.51.130.201]:48622 "EHLO smtpq2.groni1.gr.home.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752257AbXLKOQD (ORCPT ); Tue, 11 Dec 2007 09:16:03 -0500 Message-ID: <475E9B3A.7050403@keyaccess.nl> Date: Tue, 11 Dec 2007 15:14:18 +0100 From: Rene Herman User-Agent: Thunderbird 2.0.0.9 (X11/20071031) MIME-Version: 1.0 To: David Newall CC: Paul Rolland , "H. Peter Anvin" , Krzysztof Halasa , Pavel Machek , Andi Kleen , Alan Cox , "David P. Reed" , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , rol@witbe.net Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops References: <475879CD.9080006@reed.com> <20071207160439.71b7f46a@the-village.bc.nu> <20071209125458.GB4381@ucw.cz> <20071209165908.GA15910@one.firstfloor.org> <20071209212513.GC24284@elf.ucw.cz> <475CBDD7.5050602@keyaccess.nl> <475DE37F.20706@davidnewall.com> <475DE6F4.80702@zytor.com> <475DEB23.1000304@davidnewall.com> <20071211084059.3d03e11d@tux.DEF.witbe.net> <475E5D4B.8020101@keyaccess.nl> <475E7DC2.4060509@davidnewall.com> <475E8D91.20201@keyaccess.nl> <475E95A3.3070801@davidnewall.com> In-Reply-To: <475E95A3.3070801@davidnewall.com> 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 On 11-12-07 14:50, David Newall wrote: > Rene Herman wrote: >> This particular discussion isn't about anything in general but solely >> about the delay an outb_p gives you on x86 since what is under >> discussion is not using an output to port 0x80 on that platform to >> generate it. > > That could be true if outb_p were used only in architecture dependent It not only could be, it _is_ true. Not using an output to port 0x80 is what this discussion is about. > code, but it's not. It's used in drivers that are supposed to run on > all sorts of platforms. Why does a megaraid controller need delays on > i386 but not on Sparc, PowerPC, Alpha and others? Is it buggy on most > platforms, or just unnecessarily slow on Intel? The latter probably and I don't bleedin' well care. In a discussion about removing the out to 0x80 the only thing that is relevant is what it should be replaced with. Usually, "nothing" will do but generally, udelay(1) will. >>> is needed, wouldn't you use a real delay; one that says how long it >>> should be? >> Thinking that _p gives a pause is perhaps too PC-centric. Why, if a delay >> >> Because any possible outb_p delay should be synced to the bus-clock, >> not to any wall-clock. > > You misunderstand. A delay can be counted in bus cycles. No damnit, you misunderstand. I'm saying that an outb_p _should_ be defined in terms of the bus clock since if you want a wall-clock delay you should be using just that. The _hardware_ is synced to the bus clock and therefore, having a delay available that is synced to the bus clock as well makes some sense. And again again again again not withstanding that, a udelay will still be an okay replacement in practice. Rene.