Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932493Ab1BYNXs (ORCPT ); Fri, 25 Feb 2011 08:23:48 -0500 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:45286 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932182Ab1BYNXq (ORCPT ); Fri, 25 Feb 2011 08:23:46 -0500 Subject: Re: [PATCH 2/4] msm: scm: Fix improper register assignment 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: <1298573085-23217-3-git-send-email-sboyd@codeaurora.org> References: <1298573085-23217-1-git-send-email-sboyd@codeaurora.org> <1298573085-23217-3-git-send-email-sboyd@codeaurora.org> Content-Type: text/plain; charset="UTF-8" Date: Fri, 25 Feb 2011 13:23:39 +0000 Message-ID: <1298640219.958.74.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: 1564 Lines: 47 On Thu, 2011-02-24 at 18:44 +0000, Stephen Boyd wrote: > Assign the registers used in the inline assembly immediately > before the inline assembly block. This ensures the compiler > doesn't optimize away dead register assignments when it > shouldn't. > > Signed-off-by: Stephen Boyd > --- > arch/arm/mach-msm/scm.c | 7 +++++-- > 1 files changed, 5 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/mach-msm/scm.c b/arch/arm/mach-msm/scm.c > index ba57b5a..5eddf54 100644 > --- a/arch/arm/mach-msm/scm.c > +++ b/arch/arm/mach-msm/scm.c > @@ -264,13 +264,16 @@ u32 scm_get_version(void) > { > int context_id; > static u32 version = -1; > - register u32 r0 asm("r0") = 0x1 << 8; > - register u32 r1 asm("r1") = (u32)&context_id; > + register u32 r0 asm("r0"); > + register u32 r1 asm("r1"); > > if (version != -1) > return version; > > mutex_lock(&scm_lock); > + > + r0 = 0x1 << 8; > + r1 = (u32)&context_id; > asm volatile( > __asmeq("%0", "r1") > __asmeq("%1", "r0") Whoa, have you seen the compiler `optimise' the original assignments away? Since there is a use in the asm block, the definition shouldn't be omitted. What toolchain are you using? 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/