Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754119AbbKLOCd (ORCPT ); Thu, 12 Nov 2015 09:02:33 -0500 Received: from hqemgate15.nvidia.com ([216.228.121.64]:17548 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753806AbbKLOCb (ORCPT ); Thu, 12 Nov 2015 09:02:31 -0500 X-PGP-Universal: processed; by hqnvupgp07.nvidia.com on Thu, 12 Nov 2015 05:51:21 -0800 Subject: Re: [RFC PATCH 1/2] genirq: Add runtime resume/suspend support for IRQ chips To: Lars-Peter Clausen , Grygorii Strashko , Thomas Gleixner References: <1447166377-19707-1-git-send-email-jonathanh@nvidia.com> <1447166377-19707-2-git-send-email-jonathanh@nvidia.com> <56421421.8070807@nvidia.com> <56421FA5.4020801@ti.com> <56423245.1040602@metafoo.de> <564314D9.9040502@nvidia.com> <564361AE.4070303@ti.com> <5644710D.7080108@nvidia.com> <5644920C.8080007@metafoo.de> <5644959D.2020207@nvidia.com> <5644986B.5030901@metafoo.de> CC: Jason Cooper , Marc Zyngier , Stephen Warren , Thierry Reding , Kevin Hilman , Geert Uytterhoeven , LKML , , Soren Brinkmann , Linus Walleij , Alexandre Courbot From: Jon Hunter Message-ID: <56449BF0.9090408@nvidia.com> Date: Thu, 12 Nov 2015 14:02:24 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <5644986B.5030901@metafoo.de> X-Originating-IP: [10.21.132.159] X-ClientProxiedBy: UKMAIL101.nvidia.com (10.26.138.13) To UKMAIL101.nvidia.com (10.26.138.13) Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7268 Lines: 160 On 12/11/15 13:47, Lars-Peter Clausen wrote: > On 11/12/2015 02:35 PM, Jon Hunter wrote: >> >> On 12/11/15 13:20, Lars-Peter Clausen wrote: >>> On 11/12/2015 11:59 AM, Jon Hunter wrote: >>>> >>>> On 11/11/15 15:41, Grygorii Strashko wrote: >>>>> On 11/11/2015 12:13 PM, Jon Hunter wrote: >>>>>> >>>>>> On 10/11/15 18:07, Lars-Peter Clausen wrote: >>>>>>> On 11/10/2015 05:47 PM, Grygorii Strashko wrote: >>>>>>> [...] >>>>>>>>> I was trying to simplify matters by placing the resume call in >>>>>>>>> __setup_irq() as opposed to requested_threaded_irq(). However, the would >>>>>>>>> mean the resume is inside the bus_lock and may be I should not assume >>>>>>>>> that I can sleep here. >>>>>>>>> >>>>>>>>>> Can you folks please agree on something which is correct and complete? >>>>>>>>> >>>>>>>>> Soren I am happy to defer to your patch and drop this. My only comment >>>>>>>>> would be what about the request_percpu_irq() path in your patch? >>>>>>>>> >>>>>>>> >>>>>>>> I have the same comment here as I asked Soren: >>>>>>>> 1) There are no restrictions to call irq set_irq_type() whenever, >>>>>>>> as result HW can be accessed before request_x_irq()/__setup_irq(). >>>>>>>> And this is used quite widely now :( >>>>>>>> >>>>>>> >>>>>>> Changing the configuration of a resource that is not owned seems to be >>>>>>> fairly broken. In the worst case this will overwrite the configuration that >>>>>>> was set by owner of the resource. >>>>>>> >>>>>>> Especially those that call irq_set_irq_type() directly before request_irq(), >>>>>>> given that you supply the trigger type to request_irq() which will make sure >>>>>>> that there are no conflicts and the configure. >>>>>>> >>>>>>> This is a bit like calling gpio_set_direction() before you call >>>>>>> gpio_request(), which will also have PM issues. >>>>>> >>>>>> Yes, I agree that this does sound a bit odd, but ... >>>>>> >>>>>>>> For example, during OF boot: >>>>>>>> >>>>>>>> [a] irq_create_of_mapping() >>>>>>>> - irq_create_fwspec_mapping() >>>>>>>> - irq_set_irq_type() >>>>>> >>>>>> The above means that if someone calls of_irq_get() (or >>>>>> platform_get_irq()), before request_irq(), then this will call >>>>>> irq_create_of_mapping() and hence, call irq_set_irq_type. So should >>>>>> irq_create_fwspec_mapping() be setting the type in the first place? I >>>>>> can see it is convenient to do it here. >>>>> >>>>> In general there is another option - save OF-flags and pass them to >>>>> __setup_irq() where they can be processed. >>>> >>>> Right, we could look at doing something like this. >>>> >>>>>>>> or >>>>> [b] >>>>>>>> irq_set_irq_type(irq, IRQ_TYPE_LEVEL_HIGH); >>>>>>>> irq_set_chained_handler(irq, mx31ads_expio_irq_handler); >>>>> >>>>> option: add "flag" parameter to irq_set_chained_handler >>>>> >>>>>>>> >>>>>>>> or >>>>> [c] >>>>>>>> irq_set_irq_type(alarm_irq, IRQ_TYPE_EDGE_BOTH); >>>>>>>> err = devm_request_irq(&pdev->dev, alarm_irq, fan_alarm_irq_handler, >>>>>>>> (there are ~200 occurrences of irq set_irq_type in Kernel) >>>>>>>> >>>>>>>> 2) if i'm not wrong, the same is valid for irq_set_irq_wake() and irq_set_affinity() >>>>>>>> >>>>>>>> I'm not saying all these code is correct, but that what's now in kernel :( >>>>>>>> I've tried to test Soren's patch with omap-gpio and immediately hit case [a] :.( >>>>>>> >>>>>>> All functions for which are part of the public API and for which it is legal >>>>>>> to call them without calling request_irq() (or similar) first will need to >>>>>>> have pm_get()/pm_put(). >>>>>> >>>>>> Right. May be we can look at the various entry points to the chip >>>>>> operators to get a feel for which public APIs need to be handled. >>>>> >>>>> >>>>> Seems yes. But we need to be very careful with this, some of functions could be >>>>> called recursively (nested), like: >>>>> [d] >>>>> static int pcf857x_irq_set_wake(struct irq_data *data, unsigned int on) >>>>> { >>>>> ... >>>>> error = irq_set_irq_wake(gpio->irq_parent, on); >>>>> >>>>> >>>>> Personally, I have nothing against irq_pm_(get|put) :) and thought about similar things >>>>> when tried to solve the same problem for omap-gpio driver. >>>>> But :(, I have to fall back to irq_bus_lock/sync_unlock, because of [a,b,c] - all above >>>>> APIs surrounded by chip_bus_lock/chip_bus_sync_unlock. ([d] - I've not hit it just because >>>>> I was lucky). >>>> >>>> I had a quick peek at the omap-gpio driver and I see that internally you >>>> are using the gpio ref-count to manage RPM and use the bus-lock hooks to >>>> invoke RPM. >>>> >>>> This can definitely be complex when considering all the potential paths, >>>> but I think that we need to a look at this from a chip-ops perspective >>>> because only the chip knows if it is accessible or not. That said, what >>>> we need to assess is: >>>> >>>> 1. Which chip-ops should ONLY be called after an IRQ has been allocated >>>> (eg, enable/disable, mask/unmask, type, etc). These chip-ops should >>>> not try to control the chip PM, but should possibly WARN if called >>>> when the chip is not accessible. >>>> 2. For chip-ops that may be called without allocating an IRQ (eg. >>>> bus_lock, irq_suspend, etc), can these be called from an atomic >>>> context? If they might be called from an atomic context then these >>>> are the chip-ops which will cause problems as we cannot guarantee >>>> that all IRQ chips can support irq-safe RPM. >>> >>> They can't. chip_bus_lock() can sleep, so anything that locks the bus can't >>> be called from atomic context. >> >> Sorry, what can't? Yes I understand that we cannot call anything that >> locks the bus from an atomic context. > > They can't be called from atomic context. The chip_bus_lock() function may > sleep and you can't access the device without previously locking the bus. > Since the device only needs to be powered up when it is accessed its safe to > assume that the places where you need pm_get()/pm_put() are only called from > non-atomic context. Right, absolutely. >>> One easy way out might be to always call pm_get/pm_but from >>> bus_lock,/bus_unlock. This way the chip is guaranteed to be powered up when >>> accessed happens. In addition pm_get is called when the IRQ is request and >>> pm_put is called when the IRQ is release, this is to ensure the chip stays >>> powered when it is actively monitoring the IRQ lines. >> >> Yes I had thought about that, but it is not quite that easy, because in >> the case of request_irq() you don't want to pm_put() after the >> bus_unlock(). However, the bus_lock/unlock() are good indicators of >> different paths. > > You'd call pm_get() twice in request_irq() once from bus_lock() and once > independently, that way you still have a reference even after the bus_unlock(). Yes that is a possibility. However, there are places such as show_interrupts() (kernel/irq/proc.c) and irq_gc_suspend() that do not call bus_lock/unlock() which would need to be handled for PM. May be these should also call bus_lock() as well? Jon -- 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/