From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757996Ab1LNSr1 (ORCPT ); Wed, 14 Dec 2011 13:47:27 -0500 Received: from lunge.queued.net ([173.255.254.236]:34346 "EHLO lunge.queued.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757368Ab1LNSr0 (ORCPT ); Wed, 14 Dec 2011 13:47:26 -0500 Date: Wed, 14 Dec 2011 10:47:24 -0800 From: Andres Salomon To: Jens Rottmann Cc: Thomas Gleixner , linux-kernel@vger.kernel.org, linux-geode@lists.infradead.org Subject: Re: IRQF_TIMER | IRQF_SHARED ? Message-ID: <20111214104724.292b02d4@queued.net> In-Reply-To: <4EE8ECF3.6000900@LiPPERTEmbedded.de> References: <4EE620A5.7080402@LiPPERTEmbedded.de> <20111212123131.502be350@queued.net> <4EE77416.8090907@LiPPERTEmbedded.de> <4EE8ECF3.6000900@LiPPERTEmbedded.de> X-Mailer: Claws Mail 3.7.6 (GTK+ 2.20.1; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 14 Dec 2011 19:37:39 +0100 Jens Rottmann wrote: > Jens Rottmann schrieb: > > Andres Salomon schrieb: > >> Just loading cs5535-clockevt should start the periodic timer. > >> On my XO-1, IRQ 7 starts firing immediately. > > Hmm, no, doesn't work. :-| In /proc/interrupts IRQ 0 gets > > increased, not (in my case) IRQ 11. > > Update: I found that SMP-enabled kernels (like the generic one I was > using) do load cs5535-clockevt fine but ignore it and keep using the > pit timer instead. Note that there are two subsystems at work here; clockevents and clocksource. cs5535-clockevt uses clockevents (despite being in drivers/clocksource/). For you to switch away from pit (via, /sys/devices/system/clocksource/clocksource0/current_clocksource), we'd have to implement cs5535_clocksource. Something that would be worth doing, but I haven't looked into it.. > > Responsible seems kernel/time/tick-common.c: tick_check_new_device() > /* > * If the cpu affinity of the device interrupt can not > * be set, ignore it. > */ > if (!irq_can_set_affinity(newdev->irq)) > goto out_bc; > > Looks like it has been that way for quite some time, maybe > cs5535-clockevt hasn't ever worked on SMP kernels. I've only ever tested it on UP kernels. I didn't know SMP CS5536 boards existed. Gosh, I hope all of those cs5535 drivers that hadn't had their locking primitives tested aren't racy! ;) > > If I turn off SMP, cs5535-clockevt replaces the pit timer and the > MFGPT IRQ starts firing just as you said - at least on 3.0.9. 3.2-rc5 > prefers to hang instead, looks like no timer events get generated. > Sigh. > 3.2-rc4 hung on my XO-1 due to a bug that's been fixed on rc5, but I haven't tested rc5 yet. > I'll try to narrow it down tomorrow, but now I'm calling it a day. > > Cheers > Jens