From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH] arm: omap4: allow disabling MPU local timer if 32K timer is enabled Date: Sat, 11 Feb 2012 10:26:44 +0000 Message-ID: <20120211102644.GD13587@n2100.arm.linux.org.uk> References: <1328949085-4452-1-git-send-email-tom.leiming@gmail.com> <20120211100351.GB13587@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from caramon.arm.linux.org.uk ([78.32.30.218]:58170 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753166Ab2BKK0z (ORCPT ); Sat, 11 Feb 2012 05:26:55 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Ming Lei Cc: Tony Lindgren , linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org On Sat, Feb 11, 2012 at 06:19:41PM +0800, Ming Lei wrote: > On Sat, Feb 11, 2012 at 6:03 PM, Russell King - ARM Linux > wrote: > > On Sat, Feb 11, 2012 at 04:31:25PM +0800, Ming Lei wrote: > >> With 32K gp timer, tick can be driven and system can run well, so > >> allow MPU local timer to be disabled if someone requires it, otherwise > >> MPU local timer is always chosen as the default clock_event_device. > > > > The point being? > > IMO, 32K gp timer may be more energy-saving than MPU local timer > because gp timer has much less clock frequency and only half interrupts > generated in tick mode compared with mpu local timer. > > > > > What if you want to use NO_HZ? > > 32K gp timer supports oneshot mode, so it should support NO_HZ. In my test > .config, NO_HZ is enabled and system can run well. Have you actually checked the tick rate of your timer in /proc/interrupts? Have you checked /proc/timer_list to see what mode the system is in?