Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752226Ab3IJPBU (ORCPT ); Tue, 10 Sep 2013 11:01:20 -0400 Received: from arroyo.ext.ti.com ([192.94.94.40]:43799 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751207Ab3IJPBS (ORCPT ); Tue, 10 Sep 2013 11:01:18 -0400 Message-ID: <522F3408.6050608@ti.com> Date: Tue, 10 Sep 2013 10:00:24 -0500 From: Joel Fernandes Reply-To: User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130803 Thunderbird/17.0.8 MIME-Version: 1.0 To: Javier Martinez Canillas CC: Linus Walleij , Grant Likely , Linux Kernel Mailing List , "linux-arm-kernel@lists.infradead.org" , Alexander Holler , Linux-OMAP , "devicetree@vger.kernel.org" , Enric Balletbo i Serra , Jean-Christophe PLAGNIOL-VILLARD , Santosh Shilimkar , Kevin Hilman , Balaji T K , Tony Lindgren , Jon Hunter Subject: Re: [PATCH] RFC: interrupt consistency check for OF GPIO IRQs References: <1375101368-17645-1-git-send-email-linus.walleij@linaro.org> <51F8CC35.1070704@collabora.co.uk> <522EC392.8070002@ti.com> <522F1BF0.8080608@collabora.co.uk> In-Reply-To: <522F1BF0.8080608@collabora.co.uk> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6219 Lines: 133 On 09/10/2013 08:17 AM, Javier Martinez Canillas wrote: > On 09/10/2013 09:00 AM, Joel Fernandes wrote: >> On 07/31/2013 03:35 AM, Javier Martinez Canillas wrote: >>> On 07/31/2013 01:44 AM, Linus Walleij wrote: >>>> On Tue, Jul 30, 2013 at 6:30 AM, Grant Likely wrote: >>>>> On Mon, Jul 29, 2013 at 6:36 AM, Linus Walleij wrote: >>>>>> To solve this dilemma, perform an interrupt consistency check >>>>>> when adding a GPIO chip: if the chip is both gpio-controller and >>>>>> interrupt-controller, walk all children of the device tree, >>>>>> check if these in turn reference the interrupt-controller, and >>>>>> if they do, loop over the interrupts used by that child and >>>>>> perform gpio_reques() and gpio_direction_input() on these, >>>>>> making them unreachable from the GPIO side. >>>>> >>>>> Ugh, that's pretty awful, and it doesn't actually solve the root >>>>> problem of the GPIO and IRQ subsystems not cooperating. It's also a >>>>> very DT-centric solution even though we're going to see the exact same >>>>> issue on ACPI machines. >>>> >>>> The problem is that the patches for OMAP that I applied >>>> and now have had to revert solves it in an even uglier way, >>>> leading to breaking boards, as was noticed. >>>> >>>> The approach in this patch has the potential to actually >>>> work without regressing a bunch of boards... >>>> >>>> Whether this is a problem in ACPI or not remains to be seen, >>>> but I'm not sure about that. Device trees allows for a GPIO line >>>> to be used as an interrupt source and GPIO line orthogonally, >>>> and that is the root of this problem. Does ACPI have the same >>>> problem, or does it impose natural restrictions on such use >>>> cases? >>>> >>> >>> I agree with Linus here. The problem is that GPIO controllers that can work as >>> IRQ sources are treated in the kernel as if there where two separate controlers >>> that are rather orthogonal: an irq_chip and a gpio_chip. >>> But DT allows to use a GPIO line as an IRQ just by using an omap-gpio phandle as >>> "interrupt-parent". >>> >>> So, there should be a place where both irq_chip and gpio_chip has to be related >>> somehow to properly configure a GPIO (request it and setting it as input) when >>> used as an IRQ by DT. >>> >>> My patch for OMAP used an irq_domain_ops .map function handler to configure the >>> GPIO when a IRQ was mapped since that seemed to me as the best place to do it. >>> This worked well in OMAP2+ platforms but unfortunately broke OMAP1 platforms >>> since they are still using legacy domain mapping thus not call .map. >> >> Just wondering- why .map not called for omap1? irq_create_mapping does seem to >> call -> irq_domain_associate which calls map function. For omap case, GPIO >> driver does call irq_create_mapping, just like omap2+ no? >> > > That is what I understood too when writing the patch but I remember someone > mentioning legacy domain mapping not calling the .map function handler as a > possible cause for the OMAP1 regression and since Linus decided to revert the > patches in favor of a more general solution I didn't care to check if that was > true or not. Now looking at irq_create_mapping() I see that my assumption was > correct so I don't know what was the bug that caused the OMAP1 regression. Only stuff you deleted from the chip_init function was: - for (j = 0; j < bank->width; j++) { - int irq = irq_create_mapping(bank->domain, j); - irq_set_lockdep_class(irq, &gpio_lock_class); - irq_set_chip_data(irq, bank); - if (bank->is_mpuio) { - omap_mpuio_alloc_gc(bank, irq, bank->width); - } else { - irq_set_chip_and_handler(irq, &gpio_irq_chip, - handle_simple_irq); - set_irq_flags(irq, IRQF_VALID); - } and you moved all of it to the .map function in your patch. Not sure what could be breaking OMAP1 cases. You could potentially add that back with some #ifdef for OMAP1? Either way, map should be called looks like. If its not called, then the above block can be explicity called for OMAP1 case in omap_chip_gpio_init. What was strange is one person reported that mappings were not created for OMAP1. But I am wondering what you changed could result in not creating that mapping. Really nothing.. I think your initial patch is much better than fixing up DT but then I may be missing other problems with your patch that Linus's patch addresses. >> Further, if for any reason the .map is not called. Can you not call gpio_request >> yourself direct in omap_gpio_chip_init function? >> > > No, since you can't request a GPIO for all GPIO pins in the bank. Users have to > do it explicitly (or implicitly in the case of GPIO mapped as IRQ in DT). Ah since you split the patch up into 2, I missed the gpio_request stuff. Ok, that makes sense. >> Does it really matter if you call gpio_request from .map or from the chip_init >> function? >> > > Yes it does, because in DT the core calls irq_create_of_mapping() -> > irq_create_mapping() -> .map(). That way only are requested the GPIO pins that > are mapped as IRQ and not all of them. >> Also on a different note.. this would call gpio_request for *every* gpio line, >> but isn't that what your original patch that got reverted was doing in >> omap_gpio_chip_init: >> >> + if (!bank->chip.of_node) >> + for (j = 0; j < bank->width; j++) >> + irq_create_mapping(bank->domain, j); >> > > No it won't. This is only needed for the legacy (non-DT) boot since no one calls > irq_create_mapping() so it has to be called explicitly. > > And in that case .map will be called but gpio_request() won't since the call is > made only when bank->chip.of_node is not NULL. Ok, thanks for the explanation. That makes sense to me. Regards, -Joel -- 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/