Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753462Ab3FRHcL (ORCPT ); Tue, 18 Jun 2013 03:32:11 -0400 Received: from mail-la0-f41.google.com ([209.85.215.41]:62947 "EHLO mail-la0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753087Ab3FRHcJ (ORCPT ); Tue, 18 Jun 2013 03:32:09 -0400 MIME-Version: 1.0 In-Reply-To: <20130617145352.GG6809@e106331-lin.cambridge.arm.com> References: <20130617002056.7646.54131.sendpatchset@w520> <20130617145352.GG6809@e106331-lin.cambridge.arm.com> Date: Tue, 18 Jun 2013 16:32:07 +0900 Message-ID: Subject: Re: [PATCH/RFC] arm: arch_timer: Do not set C3STOP in case CPU_IDLE=n From: Magnus Damm To: Mark Rutland Cc: "linux-kernel@vger.kernel.org" , "linux-sh@vger.kernel.org" , Marc Zyngier , Catalin Marinas , "horms@verge.net.au" , "john.stultz@linaro.org" , "shinya.kuribayashi.px@renesas.com" , "tglx@linutronix.de" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1696 Lines: 43 Hi Mark, On Mon, Jun 17, 2013 at 11:53 PM, Mark Rutland wrote: > On Mon, Jun 17, 2013 at 01:20:56AM +0100, Magnus Damm wrote: >> From: Magnus Damm >> >> Modify the ARM architected timer driver to not set C3STOP >> in case CPU_IDLE is disabled. This is a short term fix that >> allows use of high resolution timers even though no additional >> clock event is registered. >> >> Not-really-Signed-off-by: Magnus Damm >> --- >> >> If someone cares about this case then perhaps it should be >> moved up to the clock event main code. The same issue should >> in theory trigger on all architectures, perhaps x86 people >> hunting for low latency may try to disable CPU_IDLE? > > I think that changing tick_is_oneshot_capable and friends to only worry about > C3STOP when CPU_IDLE is enabled would be a nicer solution. That way you enable > all clock_event_devices with C3STOP to function as high resolution timers when > CPU_IDLE's selected. Presenting the hardware differently depending on CPU_IDLE > feels wrong. I agree that doing this in the clock event driver is a bit odd. So because of that I just posted this patch: [PATCH/RFC] clockevents: Ignore C3STOP when CPUIdle is disabled > Having some other clock_event_device would be a nicer solution still. No doubt that another clock event device helps, but mainly together with CPU Idle IMO. Thanks for your comments! / magnus -- 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/