From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755479Ab2LCQzH (ORCPT ); Mon, 3 Dec 2012 11:55:07 -0500 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:47313 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754358Ab2LCQzF (ORCPT ); Mon, 3 Dec 2012 11:55:05 -0500 Date: Mon, 3 Dec 2012 16:54:42 +0000 From: Will Deacon To: Armando Visconti Cc: "linux@arm.linux.org.uk" , "kgene.kim@samsung.com" , "swarren@nvidia.com" , "nico@linaro.org" , spear-devel , "linux-kernel@vger.kernel.org" , "hsweeten@visionengravers.com" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH] nommu: Enable the strict alignment (CR_A) bit only if ARCH < v6 Message-ID: <20121203165442.GJ20074@mudshark.cambridge.arm.com> References: <1354187042-28568-1-git-send-email-armando.visconti@st.com> <50BCD6DB.2030200@st.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50BCD6DB.2030200@st.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 03, 2012 at 04:44:11PM +0000, Armando Visconti wrote: > On 11/29/2012 12:04 PM, Armando VISCONTI wrote: > > This patch keeps disabled the strict alignment CP15 bit for > > all armv6 and armv7 processor without the mmu. This behaviour > > is now same as in the mmu case. > > > > Signed-off-by: Armando Visconti > > --- > > arch/arm/kernel/head-nommu.S | 2 +- > > 1 files changed, 1 insertions(+), 1 deletions(-) > > > > diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S > > index 278cfc1..2c228a0 100644 > > --- a/arch/arm/kernel/head-nommu.S > > +++ b/arch/arm/kernel/head-nommu.S > > @@ -68,7 +68,7 @@ __after_proc_init: > > * CP15 system control register value returned in r0 from > > * the CPU init function. > > */ > > -#ifdef CONFIG_ALIGNMENT_TRAP > > +#if defined(CONFIG_ALIGNMENT_TRAP)&& __LINUX_ARM_ARCH__< 6 > > orr r0, r0, #CR_A > > #else > > bic r0, r0, #CR_A > > Any feedback on this simple patch? Although this is correct, you still need some extra patches to avoid unaligned accesses to strongly-ordered memory (given that we don't currently have mainline support for the MPU). Take a look at my nommu/fixes branch: https://git.kernel.org/?p=linux/kernel/git/will/linux.git;a=shortlog;h=refs/heads/nommu/fixes I'm happy to post some of that if it's useful to you. Will