Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758807Ab3CYR1D (ORCPT ); Mon, 25 Mar 2013 13:27:03 -0400 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:44145 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758794Ab3CYR07 (ORCPT ); Mon, 25 Mar 2013 13:26:59 -0400 Date: Mon, 25 Mar 2013 17:26:33 +0000 From: Russell King - ARM Linux To: Mark Rutland Cc: Rob Herring , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Kukjin Kim , Arnd Bergmann , "linux-sh@vger.kernel.org" , Tony Lindgren , Catalin Marinas , Magnus Damm , "rob.herring@calxeda.com" , "linux-samsung-soc@vger.kernel.org" , Simon Horman , John Stultz , Will Deacon , Thomas Gleixner , "linux-omap@vger.kernel.org" Subject: Re: [PATCH] ARM: convert arm/arm64 arch timer to use CLKSRC_OF init Message-ID: <20130325172633.GP30923@n2100.arm.linux.org.uk> References: <1363818875-15978-1-git-send-email-robherring2@gmail.com> <20130321110646.GE15279@e106331-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130321110646.GE15279@e106331-lin.cambridge.arm.com> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1262 Lines: 24 On Thu, Mar 21, 2013 at 11:06:47AM +0000, Mark Rutland wrote: > On TC2 this series leads to using the vexpress 24MHz clock as the sched clock > in preference to the architected timer: > > Architected local timer running at 24.00MHz (virt). > Switching to timer-based delay loop > Registered arch_counter_get_cntvct+0x0/0x14 as sched_clock source > sched_clock: 32 bits at 24MHz, resolution 41ns, wraps every 178956ms > Registered versatile_read_sched_clock+0x0/0x28 as sched_clock source > > As they both have the same frequency, neither overrides the other, and > whichever gets registered last is used as the sched_clock. As accesses > to the architected timer are going to have a much lower overhead, this > isn't very nice (and it could be better to use it even if it had a lower > frequency). I'll remind people that sched_clock() is supposed to be functional at the point in the boot sequence where the call to sched_init() is called. That is after setup_arch() and *before* time_init() is called. -- 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/