Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753279AbXLKMIv (ORCPT ); Tue, 11 Dec 2007 07:08:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752062AbXLKMIn (ORCPT ); Tue, 11 Dec 2007 07:08:43 -0500 Received: from hawking.rebel.net.au ([203.20.69.83]:37148 "EHLO hawking.rebel.net.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751638AbXLKMIm (ORCPT ); Tue, 11 Dec 2007 07:08:42 -0500 Message-ID: <475E7DC2.4060509@davidnewall.com> Date: Tue, 11 Dec 2007 22:38:34 +1030 From: David Newall User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.2) Gecko/20070221 SeaMonkey/1.1.1 MIME-Version: 1.0 To: Rene Herman 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> In-Reply-To: <475E5D4B.8020101@keyaccess.nl> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1334 Lines: 34 Rene Herman wrote: > On 11-12-07 08:40, Paul Rolland wrote: > >> Well, if the delay is so much unspecified, what about _reading_ port >> 0x80 ? >> Will the delay be shorter ? > > The delay is completely and fully specified in terms of the ISA/LPC clock That would be the delay on the i386 (sic) architecture. In general, though, the delay is: "Some devices require that accesses to their ports are slowed down. This functionality is provided by appending a _p to the end of the function." -- Documentation/DocBook/deviceiobook.tmpl (I've not seen any other formal definition.) Most architectures (Alpha, Arm, Arm2, Blackfin, FRV, h8300, IA64, PA-RISC, PowerPC, Sparc, Sparc64, V850 and Xtensa) do no pause. M68k does no pause except in one configuration, when it's the same as i386. On m32r it's a push and a pop. On SuperH it's similar to i386, only using 16-bit input. X86-64 is the same as i386! Thinking that _p gives a pause is perhaps too PC-centric. Why, if a delay is needed, wouldn't you use a real delay; one that says how long it should be? -- 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/