Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754311AbcDNJgj (ORCPT ); Thu, 14 Apr 2016 05:36:39 -0400 Received: from us01smtprelay-2.synopsys.com ([198.182.60.111]:44345 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750738AbcDNJgd (ORCPT ); Thu, 14 Apr 2016 05:36:33 -0400 Subject: Re: [PATCH v4 2/5] ARC: clocksource: DT based probe To: Marc Zyngier , Thomas Gleixner , Jason Cooper , Daniel Lezcano References: <1460547605-26184-1-git-send-email-vgupta@synopsys.com> <1460547605-26184-3-git-send-email-vgupta@synopsys.com> <570E7263.8070108@arm.com> <570F623B.3000105@synopsys.com> <570F63A1.3070904@arm.com> CC: , , Noam Camus Newsgroups: gmane.linux.kernel,gmane.linux.kernel.arc From: Vineet Gupta Message-ID: <570F648A.2060307@synopsys.com> Date: Thu, 14 Apr 2016 15:06:10 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <570F63A1.3070904@arm.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.12.197.158] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 729 Lines: 12 On Thursday 14 April 2016 03:02 PM, Marc Zyngier wrote: >> This is clocksource, not clockevent. cs needs to synchronized across all cores so >> > that concurrent gtod call from threads on different cores gives you similar >> > values. This obviously is not true for the local RTC hardware timer. > Unsynchronized counters on SMP HW, who would have thought! ;-) I guess > each and every architecture has to repeat the same mistakes. Not really - hardware wise the SMP support is pretty recent and before that we only had UP cores. So transition from 32 TIMER1 to 64 bit RTC was only a natural progression in improvements and in theory SoC guys throw in this local timer into the config. We just prevent SMP linux from using it.