Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754322AbXLKNrI (ORCPT ); Tue, 11 Dec 2007 08:47:08 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751960AbXLKNqy (ORCPT ); Tue, 11 Dec 2007 08:46:54 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:46980 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752430AbXLKNqy (ORCPT ); Tue, 11 Dec 2007 08:46:54 -0500 Date: Tue, 11 Dec 2007 14:47:25 +0100 From: Pavel Machek To: Andi Kleen Cc: Alan Cox , David Newall , "H. Peter Anvin" , Krzysztof Halasa , Rene Herman , "David P. Reed" , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops Message-ID: <20071211134725.GB17992@elf.ucw.cz> References: <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> <20071211131413.1079be59@the-village.bc.nu> <20071211133249.GA16750@one.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071211133249.GA16750@one.firstfloor.org> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1207 Lines: 26 On Tue 2007-12-11 14:32:49, Andi Kleen wrote: > > The LPC bus behaviour is absolutely and precisely defined. The timing of > > the inb is defined in bus clocks which is perfect as the devices needing > > delay are running at a fraction of busclock usually busclock/2. > > > > Older processors did not have a high precision timer so you couldn't > > calibrate loop based delays for 1uS. > > For newer CPUs udelay() would be probably fine though. We seem > to have several documented examples now where the bus aborts > trigger hardware bugs, and it is always better to avoid such situations. > > I still think the best strategy would be to switch based on TSC > availability. Perhaps move out*_p out of line to avoid code bloat. Why is TSC significant? udelay() based on bogomips seems to be good enough...? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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/