Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755963Ab2F1Sak (ORCPT ); Thu, 28 Jun 2012 14:30:40 -0400 Received: from gate.crashing.org ([63.228.1.57]:33050 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754557Ab2F1Sai convert rfc822-to-8bit (ORCPT ); Thu, 28 Jun 2012 14:30:38 -0400 Subject: Re: [PATCH v6 1/5] powerpc/85xx: implement hardware timebase sync Mime-Version: 1.0 (Apple Message framework v1278) Content-Type: text/plain; charset=us-ascii From: Kumar Gala In-Reply-To: <1340880651.20977.83.camel@pasglop> Date: Thu, 28 Jun 2012 13:30:26 -0500 Cc: "linuxppc-dev@lists.ozlabs.org list" , Scott Wood , "linux-kernel@vger.kernel.org list" , Li Yang , Benjamin Herrenschmidt Content-Transfer-Encoding: 8BIT Message-Id: References: <1340706359-9455-1-git-send-email-chenhui.zhao@freescale.com> <1340748634.3732.27.camel@pasglop> <20120627102138.GB10476@localhost.localdomain> <1340797732.3732.46.camel@pasglop> <20120628033815.GA11387@localhost.localdomain> <1340880651.20977.83.camel@pasglop> To: Zhao Chenhui X-Mailer: Apple Mail (2.1278) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1146 Lines: 33 On Jun 28, 2012, at 5:50 AM, Benjamin Herrenschmidt wrote: > On Thu, 2012-06-28 at 11:38 +0800, Zhao Chenhui wrote: >> >> >> The bootloader have done a timebase sync. If we do not need KEXEC or >> HOTPLUG_CPU feature, it is unnecessary to do it again at boot time of >> kernel. I only compile the timebase sync routines >> when users enable KEXEC or HOTPLUG_CPU. > > Still, how much are you really saving ? Is it worth the added mess and > loss of test coverage ? > > We have too many conditional stuff like that already. > > Cheers, > Ben. > I'd also be interested to know how long it actually takes to do time base sync this way. Since you are freezing the timers for some period how long does it really take between the freeze/unfreeze in mpc85xx_give_timebase() + mpc85xx_timebase_freeze(1); ... + mpc85xx_timebase_freeze(0); You can use ATBL/U as a way to see # of cycles taken. - k-- 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/