Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933720Ab3CYWxJ (ORCPT ); Mon, 25 Mar 2013 18:53:09 -0400 Received: from mail-pb0-f41.google.com ([209.85.160.41]:40225 "EHLO mail-pb0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932811Ab3CYWxF (ORCPT ); Mon, 25 Mar 2013 18:53:05 -0400 Message-ID: <5150D54D.1070004@linaro.org> Date: Mon, 25 Mar 2013 15:53:01 -0700 From: John Stultz User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130308 Thunderbird/17.0.4 MIME-Version: 1.0 To: Arnd Bergmann CC: Rob Herring , Russell King - ARM Linux , Mark Rutland , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Kukjin Kim , "linux-sh@vger.kernel.org" , Tony Lindgren , Catalin Marinas , Magnus Damm , "rob.herring@calxeda.com" , "linux-samsung-soc@vger.kernel.org" , Simon Horman , Will Deacon , Thomas Gleixner , "linux-omap@vger.kernel.org" Subject: Re: [PATCH] ARM: convert arm/arm64 arch timer to use CLKSRC_OF init References: <1363818875-15978-1-git-send-email-robherring2@gmail.com> <20130325172633.GP30923@n2100.arm.linux.org.uk> <5150C16A.3040208@gmail.com> <201303252236.23270.arnd@arndb.de> In-Reply-To: <201303252236.23270.arnd@arndb.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1634 Lines: 35 On 03/25/2013 03:36 PM, Arnd Bergmann wrote: > On Monday 25 March 2013, Rob Herring wrote: >> I count integrator-cp, realview, versatile and non-DT VExpress that do >> this (not surprisingly) and 25 platforms or timer implementations plus >> arm64 that do sched_clock setup in time_init. What's broken by not >> moving these earlier? > timekeeping_init() will leave the persistent_clock_exist variable as "false", > which is read in rtc_suspend() and timekeeping_inject_sleeptime(). Are you mixing up the persistent_clock and sched_clock here? From a generic stand-point they have different requirements. > For all I can tell, you will get a little jitter every time you > do a suspend in that case. Or perhaps it means the system clock > will be forwarded by the amount of time spent in suspend twice > after wakeup, but I'm probably misreading the code for that case. No, you shouldn't see timekeeping being incremented twice, we check in rtc_resume code if the persistent clock is present if so we won't inject any measured suspend time there. But you're probably right that we're being a little overly paranoid checking the same value twice. As far as the benefit to the persistent clock: it is just a little better to use, since we can access it earlier in resume, prior to interrupts being enabled. So we should see less time error introduced each suspend. thanks -john -- 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/