From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763765AbZE3VA0 (ORCPT ); Sat, 30 May 2009 17:00:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756747AbZE3VAO (ORCPT ); Sat, 30 May 2009 17:00:14 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:46175 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754343AbZE3VAN (ORCPT ); Sat, 30 May 2009 17:00:13 -0400 From: "Rafael J. Wysocki" To: Kim Kyuwon Subject: Re: [PATCH] PM: suspend_device_irqs(): don't disable wakeup IRQs Date: Sat, 30 May 2009 23:00:16 +0200 User-Agent: KMail/1.11.2 (Linux/2.6.30-rc6-rjw; KDE/4.2.3; x86_64; ; ) Cc: Kim Kyuwon , Andrew Morton , linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Ingo Molnar , Kyungmin Park , Linus Torvalds , Kevin Hilman References: <1241483224-7113-1-git-send-email-khilman@deeprootsystems.com> <200905300135.07103.rjw@sisk.pl> <4d34a0a70905300034q1dee8febl60b5213082e3a5d1@mail.gmail.com> In-Reply-To: <4d34a0a70905300034q1dee8febl60b5213082e3a5d1@mail.gmail.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200905302300.17995.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Saturday 30 May 2009, Kim Kyuwon wrote: > On Sat, May 30, 2009 at 8:35 AM, Rafael J. Wysocki wrote: > > On Monday 25 May 2009, Kim Kyuwon wrote: > >> Rafael J. Wysocki wrote: > >> > On Saturday 23 May 2009, Kim Kyuwon wrote: > >> >> On Sat, May 23, 2009 at 7:29 AM, Rafael J. Wysocki wrote: > >> >>> On Saturday 23 May 2009, Kim Kyuwon wrote: > >> > [--snip--] > >> >>>> You changed the really important part of Linux, which may affect most > >> >>>> processor architectures. I think you should be careful. If some of > >> >>>> architectures can't take care of it (they can implement > >> >>>> disable_irq_wake correctly in H/W level, will you revert your changes? > >> >>> No, the changes are not going to be reverted. In fact things should have been > >> >>> done like this already much earlier. > >> >>> > >> >>> Now, do you have any particular example of a problem related to these changes > >> >>> or is it only a theoretical issue? > >> >> I'd CCing you when I'm sending a mail for this particular example of a example. > >> >> http://markmail.org/thread/fvt7d62arofon5xx > >> > > >> > Well, as I said above, reverting the changes that introduced > >> > [suspend|resume]_device_irqs() is not an option, becuase it was the only sane > >> > way to achieve the goal they were added for. So, we need to fix the wake-up > >> > problem on your platform with the assumption that > >> > [suspend|resume]_device_irqs() are going to stay. > >> > > >> > For starters, would it be possible to teach the 'disable' hook of your > >> > platform's interrupt controller not to mask the IRQs that have both > >> > IRQ_WAKEUP and IRQ_SUSPENDED set? That apparently would work around the > >> > wake-up interrupts problem. > >> > >> Thank you for considering this issue and spending your time. In order to > >> make your idea work, we need to add a dummy 'set_wake' hook which > >> returns always zero. Anyway, IMO, I think your idea is good to work > >> around this problem. But Kevin Hilman(OMAP PM Maintainer) would make > >> final decision. > >> > >> Buy the way, how can you handle the problem that a few interrupt are > >> discarded in a small window? I can be sure they are discarded, because I > >> have debugged defects which generate in sleep/resume state hundreds of > >> times on ARM Processors(PXA310, S3C6410, OMAP3430). Wake-up interrupts > >> are generated as soon as arch_suspend_enable_irqs() invoked. > > > > Sorry for the delayed response. > > > > If the wake-up interrupts are not masked, they will be delivered to the drivers > > as soon as arch_suspend_enable_irqs() has run. So, if the drivers are able to > > handle them at this point (ie. before resume_device_irqs() is called), they > > won't be lost. > > Thank you for your response! > > Your suspend_device_irqs() disables all IRQs(except timer IRQ) while > entering suspend. i.e. Before invoking resume_device_irqs() or > resume_noirq callback, all IRQs(except timer IRQ) is in IRQ_DISABLED > status. Right? > But if an IRQ is in IRQ_DISABLED status, its interrupt handler can be s/can be/can't be/ (as you noticed in the follow-up message). > invoked. (As you know, all IRQs with IRQ_DISABLE are not handled in > handle_level_irq function). Thus, even if the wake-up interrupts are > not masked, the drivers are not able to handle interrupts, because the > interrupt handler can't be invoked due to IRQ_DISABLED set by > suspend_device_irqs(). The solution to that may be to add some code that will clear the IRQ_DISABLE flag for the wake-up interrupt that caused the wake-up to happen in the early resume code of the platform. > > The only problem I see is that the drivers may expect their > > ->resume_noirq() callbacks to be executed first. > > resume_noirq() callbacks are also invoked after arch_suspend_enable_irqs(). Yes, they are, and that may be a problem, because a driver may expect resume_noirq() to be called before it can handle interrupts from the device. Best, Rafael