Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755630AbYLWEkp (ORCPT ); Mon, 22 Dec 2008 23:40:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754677AbYLWEkf (ORCPT ); Mon, 22 Dec 2008 23:40:35 -0500 Received: from hera.kernel.org ([140.211.167.34]:54908 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754514AbYLWEke (ORCPT ); Mon, 22 Dec 2008 23:40:34 -0500 Message-ID: <49506BBC.8040600@kernel.org> Date: Tue, 23 Dec 2008 13:40:28 +0900 From: Tejun Heo User-Agent: Thunderbird 2.0.0.18 (X11/20081112) MIME-Version: 1.0 To: Robert Hancock CC: ide , linux-kernel Subject: Re: [PATCH] sata_sil: add Large Block Transfer support References: <4945BDED.7050205@shaw.ca> <494F69C4.2060708@kernel.org> <49506AAF.3040400@shaw.ca> In-Reply-To: <49506AAF.3040400@shaw.ca> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Tue, 23 Dec 2008 04:40:32 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1163 Lines: 34 Hello, Robert. Robert Hancock wrote: > Tejun Heo wrote: >> >> ioread/iowrite? > > We know the register's always MMIO on this controller, so it's slightly > more optimal to avoid the conditional in there. Yeah, by a small margin but I think the consensus was to use ioread/write no matter what if it's mapped using iomap. I don't think we guarantee iomapped address == mmio address after all. >> I know it's not specific to this change but does mb() really make >> sense here? I don't think we need any barrier here. > > Not sure. Documentation/memory-barriers.txt seems rather unfortunately > vague on whether MMIO writes are strongly ordered with respect to memory > writes. I seem to recall some debate on this a while ago, did it ever > get resolved? I remember that thread too but don't really any definite conclusion. Eh... I hate barriers lying around without exact explanation. :-( Thanks. -- tejun -- 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/