From mboxrd@z Thu Jan 1 00:00:00 1970 From: Haavard Skinnemoen Subject: Re: MMIO and gcc re-ordering issue Date: Fri, 30 May 2008 08:07:00 +0200 Message-ID: <20080530080700.773a82cc@siona.local> References: <1211852026.3286.36.camel@pasglop> <20080526.184047.88207142.davem@davemloft.net> <1211854540.3286.42.camel@pasglop> <20080526.192812.184590464.davem@davemloft.net> <1211859542.3286.46.camel@pasglop> <1211922621.3286.80.camel@pasglop> <1211924335.3286.89.camel@pasglop> <20080527214241.GA22636@parisc-linux.org> <1211926636.3286.100.camel@pasglop> <20080528103648.54eb8734@hskinnemo-gx745.norway.atmel.com> <1212110003.15633.0.camel@pasglop> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from smtpeu1.atmel.com ([195.65.72.27]:37193 "EHLO bagnes.atmel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752186AbYE3GHm (ORCPT ); Fri, 30 May 2008 02:07:42 -0400 In-Reply-To: <1212110003.15633.0.camel@pasglop> Sender: linux-arch-owner@vger.kernel.org List-ID: To: benh@kernel.crashing.org Cc: Matthew Wilcox , Linus Torvalds , David Miller , linux-arch@vger.kernel.org, scottwood@freescale.com, linuxppc-dev@ozlabs.org, alan@lxorguk.ukuu.org.uk, linux-kernel@vger.kernel.org, tpiepho@freescale.com On Fri, 30 May 2008 11:13:23 +1000 Benjamin Herrenschmidt wrote: > > Currently, this is the only interface I know that can do native-endian > > accesses, so if you take it away, I'm gonna need an alternative > > interface that doesn't do byteswapping. > > Are you aware that these also don't provide any ordering guarantee ? Yes, but I am not aware of any alternative. I think the drivers I've written have the necessary barriers (or dma ops with implicit barriers) that they don't actually depend on any DMA vs. MMIO ordering guarantees. I hope MMIO vs. MMIO ordering is guaranteed though? Haavard