From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laurent Pinchart Subject: Re: [PATCH] RFC: interrupt consistency check for OF GPIO IRQs Date: Fri, 06 Sep 2013 17:32:43 +0200 Message-ID: <2966898.neCKEkcf1e@avalon> References: <1375101368-17645-1-git-send-email-linus.walleij@linaro.org> <344239800.bDEkDg48ZQ@avalon> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: Sender: linux-omap-owner@vger.kernel.org To: Linus Walleij Cc: Grant Likely , Linux Kernel Mailing List , "linux-arm-kernel@lists.infradead.org" , Alexander Holler , Linux-OMAP , "devicetree@vger.kernel.org" , Javier Martinez Canillas , Enric Balletbo i Serra , Jean-Christophe PLAGNIOL-VILLARD , Santosh Shilimkar , Kevin Hilman , Balaji T K , Tony Lindgren , Jon Hunter List-Id: devicetree@vger.kernel.org Hi Linus, Sorry for the late reply. On Thursday 22 August 2013 00:02:39 Linus Walleij wrote: > On Tue, Aug 20, 2013 at 12:04 AM, Laurent Pinchart wrote: > > On Wednesday 31 July 2013 01:44:53 Linus Walleij wrote: > >> I don't see how sharing works here, or how another user, i.e. another one > >> than the user wanting to recieve the IRQ, can validly request such a > >> line? What would the usecase for that valid request be? > > > > When the GPIO is wired to a status signal (such as an MMC card detect > > signal) the driver might want to read the state of the signal > > independently of the interrupt handler. > > That is true. But for such a complex usecase I think it's reasonable that > we only specify the GPIO in the device tree, and the driver utilizing the > IRQ need to take that and perform gpio_to_irq() on it, and then it still > works to use it both ways. I'm pretty sure I would have had an objection a couple of weeks ago when I was looking into this, but I can't think of another use case for now, so I agree with you. > >> Basically I believe these two things need to be exclusive in the DT > >> world: > >> > >> A: request_irq(a resource passed from "interrupts"); > >> -> core implicitly performs gpio_request() > >> gpio_direction_input() > >> > >> B: gpio_request(a resource passed from "gpios"); > >> gpio_direction_input() > >> request_irq(gpio_to_irq()) > >> > >> Never both. And IIUC that was what happened in the OMAP case. > > > > Isn't the core issue that we can translate a GPIO number to an IRQ number, > > but not the other way around ? If that could be done, we could request > > the GPIO and configure it as an input when the IRQ is requested. > > That is true. It would be easier if all GPIO drivers has an irqchip and > and irqdomain, then we could implement irq_to_gpio() properly in gpiolib > and this would not be a problem. Alas, not all do. > > But I also think that the DT contains (as demonstrated by the patch) > all information about what interrupts and GPIOs may conflict, so I > also see this as something of a consistency check, but it could go > in either way. -- Regards, Laurent Pinchart