Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755640Ab1BYMSH (ORCPT ); Fri, 25 Feb 2011 07:18:07 -0500 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:38948 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753158Ab1BYMSE (ORCPT ); Fri, 25 Feb 2011 07:18:04 -0500 X-Greylist: delayed 1259 seconds by postgrey-1.27 at vger.kernel.org; Fri, 25 Feb 2011 07:18:04 EST Subject: Re: [PATCH 1/4] msm: scm: Mark inline asm as volatile From: Will Deacon To: Stephen Boyd Cc: David Brown , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org In-Reply-To: <1298573085-23217-2-git-send-email-sboyd@codeaurora.org> References: <1298573085-23217-1-git-send-email-sboyd@codeaurora.org> <1298573085-23217-2-git-send-email-sboyd@codeaurora.org> Content-Type: text/plain; charset="UTF-8" Date: Fri, 25 Feb 2011 11:56:57 +0000 Message-ID: <1298635017.958.0.camel@e102144-lin.cambridge.arm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1487 Lines: 46 Hi Stephen, On Thu, 2011-02-24 at 18:44 +0000, Stephen Boyd wrote: > We don't want the compiler to remove these asm statements or > reorder them in any way. Mark them as volatile to be sure. > > Signed-off-by: Stephen Boyd > --- > arch/arm/mach-msm/scm.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/mach-msm/scm.c b/arch/arm/mach-msm/scm.c > index f4b9bc9..ba57b5a 100644 > --- a/arch/arm/mach-msm/scm.c > +++ b/arch/arm/mach-msm/scm.c > @@ -174,7 +174,7 @@ static u32 smc(u32 cmd_addr) > register u32 r0 asm("r0") = 1; > register u32 r1 asm("r1") = (u32)&context_id; > register u32 r2 asm("r2") = cmd_addr; > - asm( > + asm volatile( > __asmeq("%0", "r0") > __asmeq("%1", "r0") > __asmeq("%2", "r1") > @@ -271,7 +271,7 @@ u32 scm_get_version(void) > return version; > > mutex_lock(&scm_lock); > - asm( > + asm volatile( > __asmeq("%0", "r1") > __asmeq("%1", "r0") > __asmeq("%2", "r1") These asm blocks all have sensible looking output constraints. Why do they need to be marked volatile? Will -- 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/