Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751125AbWIVJht (ORCPT ); Fri, 22 Sep 2006 05:37:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751129AbWIVJhd (ORCPT ); Fri, 22 Sep 2006 05:37:33 -0400 Received: from caramon.arm.linux.org.uk ([217.147.92.249]:54031 "EHLO caramon.arm.linux.org.uk") by vger.kernel.org with ESMTP id S1751125AbWIVJhG (ORCPT ); Fri, 22 Sep 2006 05:37:06 -0400 Date: Fri, 22 Sep 2006 10:36:59 +0100 From: Russell King To: Denis Vlasenko Cc: linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [PATCH 3/3] delay: add generic udelay(), mdelay() and ssleep() Message-ID: <20060922093659.GA8609@flint.arm.linux.org.uk> Mail-Followup-To: Denis Vlasenko , linux-kernel@vger.kernel.org, Andrew Morton References: <200609220955.35826.vda.linux@googlemail.com> <200609220957.43127.vda.linux@googlemail.com> <200609220958.52736.vda.linux@googlemail.com> <200609221000.33978.vda.linux@googlemail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200609221000.33978.vda.linux@googlemail.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1472 Lines: 35 On Fri, Sep 22, 2006 at 10:00:33AM +0200, Denis Vlasenko wrote: > * __const_udelay for all arches is removed or renamed to > ? __const_delay (it did not do microsecond delays anyway) You never explained this properly - in fact I think your logic is reversed. Let me remind you of my reply (which afaics never got a response): On Wed, Aug 23, 2006 a 09:14:52AM +0100, Russell King wrote: > On Wed, Aug 23, 2006 at 07:50:24AM +0200, Denis Vlasenko wrote: > > On Tuesday 22 August 2006 18:55, Russell King wrote: > > > Please keep a "const" version in ARM. Thanks. > > > > Are you talking about this hunk? Why do you want to keep it? > > > > I mean, without it udelay(n) will become slower by the time > > needed for one extra multiply. So we will have maybe > > udelay(n) ==> udelay(n+0.1). > > Why do you think that? With the constant version, the additional > unnecessary multiply is optimised away by the compiler (since > constant * constant = constant), so it's actually slightly faster, > not sligntly slower as you seem to think. > > Since the multiply is pure overhead, it's better to get rid of it. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 Serial core - 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/