From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751917Ab2GSJXB (ORCPT ); Thu, 19 Jul 2012 05:23:01 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:32795 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751473Ab2GSJW7 (ORCPT ); Thu, 19 Jul 2012 05:22:59 -0400 Date: Thu, 19 Jul 2012 10:22:39 +0100 From: Catalin Marinas To: John Stultz Cc: Andrew Morton , "linux-kernel@vger.kernel.org" , Arnd Bergmann Subject: Re: [PATCH] Allow CLOCK_TICK_RATE to be undefined Message-ID: <20120719092239.GB28942@arm.com> References: <1342543300-23460-1-git-send-email-catalin.marinas@arm.com> <20120718155141.232ae14c.akpm@linux-foundation.org> <50074287.3080802@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50074287.3080802@linaro.org> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 19, 2012 at 12:11:03AM +0100, John Stultz wrote: > On 07/18/2012 03:51 PM, Andrew Morton wrote: > > On Tue, 17 Jul 2012 17:41:40 +0100 > > Catalin Marinas wrote: > > > >> This patch allows an architecture to not define CLOCK_TICK_RATE, in > >> which case ACTHZ defaults to (HZ << 8). > > No reason was given for this change. > > > > So those people who are wondering "why don't you just define > > CLOCK_TICK_RATE" are made all sad. > > I just queued this patch with a revised commit message: > > jiffies: Allow CLOCK_TICK_RATE to be undefined > > CLOCK_TICK_RATE is a legacy constant that defines the timer > device's granularity. On hardware with particularly coarse > granularity, this constant is used to reduce accumulated > time error when using jiffies as a clocksource, by calculating > the hardware's actual tick length rather then just assuming > it is 1sec/HZ. > > However, for the most part this is unnecessary, as most modern > systems don't use jiffies for their clocksource, and their > tick device is sufficiently fine grained to avoid major error. > > Thus, this patch allows an architecture to not define > CLOCK_TICK_RATE, in which case ACTHZ defaults to (HZ << 8). > > > Let me know if you'd like to see further improvements. Looks good. Thanks for picking this up. -- Catalin