Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755378AbZIPIT4 (ORCPT ); Wed, 16 Sep 2009 04:19:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754658AbZIPITz (ORCPT ); Wed, 16 Sep 2009 04:19:55 -0400 Received: from gateway-1237.mvista.com ([63.81.120.158]:20308 "EHLO gateway-1237.mvista.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752011AbZIPITy (ORCPT ); Wed, 16 Sep 2009 04:19:54 -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> Content-Type: text/plain Date: Wed, 16 Sep 2009 03:26:06 -0500 Message-Id: <1253089566.3273.152.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: 2320 Lines: 73 On Wed, 2009-09-16 at 00:47 +0200, Krzysztof Halasa wrote: > Steve Chen writes: > > > If I know for sure that these are the processors that need that block of > > code, your suggestion makes perfect sense. Unfortunately, I don't know. > > Then I wouldn't write "Accurate delays". "Different", maybe. > "Accurate", we don't know. You are right. "Accurate delays" isn't appropriate. Probably want something along the lines of "try this and see if helps". > > > My primary goals are > > > > 1. Put a stop to this thread (so far I have failed miserably) > > 2. Document that block of code. > > 3. If it makes someone's life easier.. it would be a bonus. > > Uncertain comments don't make life easier. Just write what's certain, > or nothing if nothing is. Makes sense. Based on both yours and Marek's inputs, I changed the wording. The patch is below. 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 "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. + 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/