Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760778Ab3GaUtI (ORCPT ); Wed, 31 Jul 2013 16:49:08 -0400 Received: from mail-wg0-f50.google.com ([74.125.82.50]:47213 "EHLO mail-wg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757210Ab3GaUtG (ORCPT ); Wed, 31 Jul 2013 16:49:06 -0400 Message-ID: <51F97842.6050200@linaro.org> Date: Wed, 31 Jul 2013 22:49:06 +0200 From: Daniel Lezcano User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: =?UTF-8?B?U8O2cmVuIEJyaW5rbWFubg==?= CC: Stephen Boyd , John Stultz , Thomas Gleixner , Stuart Menefy , Russell King , Michal Simek , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: Enable arm_global_timer for Zynq brakes boot References: <51E72DCA.9070500@codeaurora.org> <51E7435B.3060605@codeaurora.org> <51ED8DF2.60600@codeaurora.org> <20130722201348.GI453@xsjandreislx> <0735ab8c-0f80-4b64-b2b2-8d4553482c2a@CO9EHSMHS013.ehs.local> <51F66565.7010600@linaro.org> <8d56935e-2a20-46c7-b80a-f779572dd839@CO1EHSMHS014.ehs.local> <51F77D93.4030505@linaro.org> <829dbb20-0f14-4a3b-8da9-1f7b1b5b8b59@DB8EHSMHS005.ehs.local> In-Reply-To: <829dbb20-0f14-4a3b-8da9-1f7b1b5b8b59@DB8EHSMHS005.ehs.local> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2841 Lines: 62 On 07/31/2013 12:34 AM, Sören Brinkmann wrote: > On Tue, Jul 30, 2013 at 10:47:15AM +0200, Daniel Lezcano wrote: >> On 07/30/2013 02:03 AM, Sören Brinkmann wrote: >>> Hi Daniel, >>> >>> On Mon, Jul 29, 2013 at 02:51:49PM +0200, Daniel Lezcano wrote: >>> (snip) >>>> >>>> the CPUIDLE_FLAG_TIMER_STOP flag tells the cpuidle framework the local >>>> timer will be stopped when entering to the idle state. In this case, the >>>> cpuidle framework will call clockevents_notify(ENTER) and switches to a >>>> broadcast timer and will call clockevents_notify(EXIT) when exiting the >>>> idle state, switching the local timer back in use. >>> >>> I've been thinking about this, trying to understand how this makes my >>> boot attempts on Zynq hang. IIUC, the wrongly provided TIMER_STOP flag >>> would make the timer core switch to a broadcast device even though it >>> wouldn't be necessary. But shouldn't it still work? It sounds like we do >>> something useless, but nothing wrong in a sense that it should result in >>> breakage. I guess I'm missing something obvious. This timer system will >>> always remain a mystery to me. >>> >>> Actually this more or less leads to the question: What is this >>> 'broadcast timer'. I guess that is some clockevent device which is >>> common to all cores? (that would be the cadence_ttc for Zynq). Is the >>> hang pointing to some issue with that driver? >> >> If you look at the /proc/timer_list, which timer is used for broadcasting ? > > So, the correct run results (full output attached). > > The vanilla kernel uses the twd timers as local timers and the TTC as > broadcast device: > Tick Device: mode: 1 > Broadcast device > Clock Event Device: ttc_clockevent > > When I remove the offending CPUIDLE flag and add the DT fragment to > enable the global timer, the twd timers are still used as local timers > and the broadcast device is the global timer: > Tick Device: mode: 1 > Broadcast device > Clock Event Device: arm_global_timer > > Again, since boot hangs in the actually broken case, I don't see way to > obtain this information for that case. Can't you use the maxcpus=1 option to ensure the system to boot up ? -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- 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/