Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751284AbaLQAov (ORCPT ); Tue, 16 Dec 2014 19:44:51 -0500 Received: from galahad.ideasonboard.com ([185.26.127.97]:49032 "EHLO galahad.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750943AbaLQAou (ORCPT ); Tue, 16 Dec 2014 19:44:50 -0500 From: Laurent Pinchart To: Daniel Lezcano Cc: Magnus Damm , linux-kernel , SH-Linux , "Simon Horman [Horms]" , Geert Uytterhoeven , Thomas Gleixner Subject: Re: [PATCH] clocksource: sh_tmu: Set cpu_possible_mask to fix SMP broadcast Date: Wed, 17 Dec 2014 02:44:54 +0200 Message-ID: <2007813.TxmaWEReSL@avalon> User-Agent: KMail/4.14.3 (Linux/3.16.5-gentoo; KDE/4.14.3; x86_64; ; ) In-Reply-To: <54901D90.1080109@linaro.org> References: <20141216094854.22639.69181.sendpatchset@w520> <54901D90.1080109@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Daniel, On Tuesday 16 December 2014 12:54:56 Daniel Lezcano wrote: > On 12/16/2014 12:46 PM, Magnus Damm wrote: > > On Tue, Dec 16, 2014 at 8:20 PM, Laurent Pinchart wrote: > >> On Tuesday 16 December 2014 12:14:40 Daniel Lezcano wrote: > >>> On 12/16/2014 10:48 AM, Magnus Damm wrote: > >>>> From: Magnus Damm > >>>> > >>>> Update the TMU driver to use cpu_possible_mask as cpumask to make > >>>> r8a7779 SMP work as expected with or without the ARM TWD timer. > >>>> > >>>> Signed-off-by: Magnus Damm > >>> > >>> Applied as a 3.18 fix. > >> > >> You're a bit too fast, I haven't had time to review the patch yet. > >> > >>> ps: May I suggest to use the CLOCK_EVT_FEAT_DYNIRQ flag for this driver > >>> ? > >>> > >>>> --- > >>>> drivers/clocksource/sh_tmu.c | 2 +- > >>>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>>> > >>>> --- 0001/drivers/clocksource/sh_tmu.c > >>>> +++ work/drivers/clocksource/sh_tmu.c 2014-12-16 > >>>> 17:49:49.000000000 +0900 @@ -428,7 +428,7 @@ static void > >>>> sh_tmu_register_clockevent(s > >>>> ced->features = CLOCK_EVT_FEAT_PERIODIC; > >>>> ced->features |= CLOCK_EVT_FEAT_ONESHOT; > >>>> ced->rating = 200; > >>>> - ced->cpumask = cpumask_of(0); > >>>> + ced->cpumask = cpu_possible_mask; > >> > >> Magnus, how thoroughly have you tested this ? The TMU is indeed usable by > >> all CPUs, so setting the CPU mask to cpu_possible_mask makes sense, but > >> last time I've tried that it broke the broadcast timer due to the > >> heuristics used by the clock events core code. > > > > Uhm, so I've tested this particular patch on r8a7779 but I do agree > > that the TMU is used on a bunch of SoCs if that's what you mean. I > > don't see how it is different from any other of our timers though, and > > those got fixed like this earlier. > > > > I wonder if you may recall an earlier issue with incorrect clock event > > priorities and code somehow working-by-accident without the mask set > > as expected? > > Could have been fixed with : ? > > commit 70e5975d3a04be5479a28eec4a2fb10f98ad2785 > Author: Stephen Boyd > Date: Thu Jun 13 11:39:50 2013 -0700 > > clockevents: Prefer CPU local devices over global devices > > On an SMP system with only one global clockevent and a dummy > clockevent per CPU we run into problems. We want the dummy > clockevents to be registered as the per CPU tick devices, but > we can only achieve that if we register the dummy clockevents > before the global clockevent or if we artificially inflate the > rating of the dummy clockevents to be higher than the rating > of the global clockevent. Failure to do so leads to boot > hangs when the dummy timers are registered on all other CPUs > besides the CPU that accepted the global clockevent as its tick > device and there is no broadcast timer to poke the dummy > devices. > > If we're registering multiple clockevents and one clockevent is > global and the other is local to a particular CPU we should > choose to use the local clockevent regardless of the rating of > the device. This way, if the clockevent is a dummy it will take > the tick device duty as long as there isn't a higher rated tick > device and any global clockevent will be bumped out into > broadcast mode, fixing the problem described above. I think I had that patch in my tree when I noticed the breakage, since my own tmu patch dates from February 2014. I'll retest it though and will let you know. > >> Could you please confirm that you've tested both CONFIG_PREEMPT_NONE and > >> CONFIG_PREEMPT with and without the ARM TWD times, and that you've booted > >> to userspace and tested timer broadcast on all CPUs ? > > > > No I have not. I've booted to user space in initramfs with DT-based > > TWD on Multiplatform for r8a7779. Without this fix (and other r8a7779 > > TWD bits) I see a lot of breakage. For instance, TWD and SMP boot is > > broken on r8a7779 - both legacy and non-legacy. I have not gotten to > > sh73a0 yet, but I assume it is busted too. > > > > Can you please explain to me how the TMU is any different compared to > > the CMT, MTU2 or STI? =) > > > > And no, I don't have any r8a7740 board anymore. Can anyone else test? -- Regards, Laurent Pinchart -- 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/