Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752798AbZIPOnH (ORCPT ); Wed, 16 Sep 2009 10:43:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752561AbZIPOnF (ORCPT ); Wed, 16 Sep 2009 10:43:05 -0400 Received: from gateway-1237.mvista.com ([63.81.120.158]:62539 "EHLO gateway-1237.mvista.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751742AbZIPOnD (ORCPT ); Wed, 16 Sep 2009 10:43:03 -0400 Subject: Re: [PATCH] arm: remove unused code in delay.S From: Steve Chen To: Krzysztof Halasa Cc: Felipe Contreras , Russell King - ARM Linux , Jamie Lokier , linux-kernel@vger.kernel.org, Marek Vasut , Pavel Machek , linux-arm-kernel@lists.infradead.org In-Reply-To: References: <1252875960-21512-1-git-send-email-felipe.contreras@gmail.com> <20090915103739.GA19519@elf.ucw.cz> <1253017761.3273.117.camel@linux-1lbu> <200909151541.08852.marek.vasut@gmail.com> <1253032210.3273.128.camel@linux-1lbu> <94a0d4530909151158y489a96e3x63ff932c713822b0@mail.gmail.com> <1253043875.3273.131.camel@linux-1lbu> <1253053609.3273.139.camel@linux-1lbu> <1253089566.3273.152.camel@linux-1lbu> Content-Type: text/plain Date: Wed, 16 Sep 2009 09:49:14 -0500 Message-Id: <1253112555.3273.164.camel@linux-1lbu> Mime-Version: 1.0 X-Mailer: Evolution 2.22.1.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2290 Lines: 72 On Wed, 2009-09-16 at 14:30 +0200, Krzysztof Halasa wrote: > Steve Chen writes: > > > +config OLD_CPU_DELAY > > + depends on CPU_32v3 || CPU_32v4 || CPU_32v4T > > + bool "Accurate delays for some older CPUs" > > + def_bool n > > + help > > + Try enable this if observing longer than expected delays and need > > + more accuracy. May cause instability in some CPUs. > > + > > There is still this uncertain "accurate" in the text. Why don't just > > + bool "Different delay() code for some older CPUs" Sounds good. I also update text under help to better quantify "accuracy". Updated patch below. Separately, as Russel pointed out, this should only be done by experienced people, so we even bother with this patch since the only people should touch this are the people who knows all the details. Document #if 0 code block in delay.S and make it selectable for compile. Signed-off-by: Steve Chen --- arch/arm/Kconfig | 8 ++++++++ arch/arm/lib/delay.S | 2 +- 2 files changed, 9 insertions(+), 1 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index aef63c8..ca8d535 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -813,6 +813,14 @@ config ARM_ERRATA_460075 ACTLR register. Note that setting specific bits in the ACTLR register may not be available in non-secure mode. +config OLD_CPU_DELAY + depends on CPU_32v3 || CPU_32v4 || CPU_32v4T + bool "Different delay() code for some older CPUs" + def_bool n + help + Try enable this if observing longer than expected delays. This code + improves accuracy for some CPUs while cause instability in others. + endmenu source "arch/arm/common/Kconfig" diff --git a/arch/arm/lib/delay.S b/arch/arm/lib/delay.S index 8d6a876..67e679b 100644 --- a/arch/arm/lib/delay.S +++ b/arch/arm/lib/delay.S @@ -42,7 +42,7 @@ ENTRY(__const_udelay) @ 0 <= r0 <= 0x7fffff06 @ Delay routine ENTRY(__delay) subs r0, r0, #1 -#if 0 +#ifdef CONFIG_OLD_CPU_DELAY movls pc, lr subs r0, r0, #1 movls pc, lr -- 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/