Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760864Ab3GaVIv (ORCPT ); Wed, 31 Jul 2013 17:08:51 -0400 Received: from mail-wi0-f180.google.com ([209.85.212.180]:49883 "EHLO mail-wi0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753430Ab3GaVIu (ORCPT ); Wed, 31 Jul 2013 17:08:50 -0400 Message-ID: <51F97CE3.9030306@linaro.org> Date: Wed, 31 Jul 2013 23:08:51 +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: <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> <51F97842.6050200@linaro.org> <068436c6-ff98-428f-8875-bb1c6f86466b@TX2EHSMHS008.ehs.local> In-Reply-To: <068436c6-ff98-428f-8875-bb1c6f86466b@TX2EHSMHS008.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: 5049 Lines: 130 On 07/31/2013 10:58 PM, Sören Brinkmann wrote: > On Wed, Jul 31, 2013 at 10:49:06PM +0200, Daniel Lezcano wrote: >> 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 ? > > Right, that works. I forgot about that option after you mentioned, that > it is most likely not that useful. > > Anyway, this are those sysfs files with an unmodified cpuidle driver and > the gt enabled and having maxcpus=1 set. > > /proc/timer_list: > Tick Device: mode: 1 > Broadcast device > Clock Event Device: arm_global_timer > max_delta_ns: 12884902005 > min_delta_ns: 1000 > mult: 715827876 > shift: 31 > mode: 3 Here the mode is 3 (CLOCK_EVT_MODE_ONESHOT) The previous timer_list output you gave me when removing the offending cpuidle flag, it was 1 (CLOCK_EVT_MODE_SHUTDOWN). Is it possible you try to get this output again right after onlining the cpu1 in order to check if the broadcast device switches to SHUTDOWN ? > next_event: 108080000000 nsecs > set_next_event: gt_clockevent_set_next_event > set_mode: gt_clockevent_set_mode > event_handler: tick_handle_oneshot_broadcast > retries: 0 > > tick_broadcast_mask: 00000001 > tick_broadcast_oneshot_mask: 00000000 > > Tick Device: mode: 1 > Per CPU device: 0 > Clock Event Device: local_timer > max_delta_ns: 12884902005 > min_delta_ns: 1000 > mult: 715827876 > shift: 31 > mode: 3 > next_event: 106900000000 nsecs > set_next_event: twd_set_next_event > set_mode: twd_set_mode > event_handler: hrtimer_interrupt > retries: 0 > > # cat /proc/interrupts > CPU0 > 27: 252 GIC 27 gt > 29: 626 GIC 29 twd > 43: 0 GIC 43 ttc_clockevent > 82: 410 GIC 82 xuartps > IPI0: 0 CPU wakeup interrupts > IPI1: 0 Timer broadcast interrupts > IPI2: 0 Rescheduling interrupts > IPI3: 0 Function call interrupts > IPI4: 0 Single function call interrupts > IPI5: 0 CPU stop interrupts > Err: 0 > > > Sören > > -- 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/