linux-kernel - Re: [PATCH v3] gpio: interrupt consistency check for OF GPIO IRQs

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Message-ID: <52261D2E.30306@wwwdotorg.org>
Date:	Tue, 03 Sep 2013 11:32:30 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	Alexandre Courbot <acourbot@...dia.com>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Lars Poeschel <larsi@....tu-dresden.de>,
	Lars Poeschel <poeschel@...onage.de>,
	Grant Likely <grant.likely@...aro.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ian.campbell@...rix.com>,
	Kumar Gala <galak@...eaurora.org>,
	Pawel Moll <pawel.moll@....com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Enric Balletbo i Serra <eballetbo@...il.com>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Kevin Hilman <khilman@...aro.org>,
	Balaji T K <balajitk@...com>,
	Tony Lindgren <tony@...mide.com>,
	Jon Hunter <jgchunter@...il.com>
Subject: Re: [PATCH v3] gpio: interrupt consistency check for OF GPIO IRQs

On 09/03/2013 06:43 AM, Linus Walleij wrote:
> On Fri, Aug 30, 2013 at 9:55 PM, Stephen Warren <swarren@...dotorg.org> wrote:
>> On 08/29/2013 06:24 PM, Javier Martinez Canillas wrote:
>> ...
>>> We have been trying to solve this issue for a few months by now and Linus'
>>> approach seems to be the most sensible solution to me.
>>>
>>> Drivers that request an IRQ and assume that platform code will request and setup
>>> the GPIO have been broken since the boards using these drivers were migrated to
>>> DT (e.g: smsc911x on OMAP2+ boards).
>>
>> That's only true if the driver for the GPIO controller is buggy.
>> Whatever request_irq() maps down to in the GPIO/IRQ controller driver
>> simply needs to set up the pin as an interrupt input, then it doesn't
>> matter which order the driver does things.
> 
> As mentioned it can't do that, because doing that creates a
> restriction on which order the driver does things...

I am not convinced here. Which driver (GPIO/IRQ controller driver, or
the driver which uses GPIOs/IRQs?) Which operations?

> But you mentioned that you wanted an API that would account
> for the case where the *same driver* requested the same resource
> (a GPIO line) to be used for both IRQ and GPIO, through two
> different calls.
> 
> I would be happy to see how we could do that, preferably in a
> generic way.
> 
> Since the gpio_request() does not contain the signature of the
> calling driver I don't see how we could do this without refactoring
> the whole world.
> 
> In that case it would probably be easiest to
> *first* proceed to complete Alexandre's suggested refactorings for
> GPIO descriptors, which tie down GPIOs to be requested like
> clocks and regulators and thus tied to a device, so we can from
> there proceed to implement such a conditional request,
> as we will then have the required information in the GPIO
> subsystem.

Indeed, that does seem necessary if you want the GPIO/IRQ core to be
able to implement this feature.

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