linux-kernel - Re: [RFC] gpio/omap: auto-setup a GPIO when used as an IRQ

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Date:	Tue, 24 Sep 2013 07:41:08 +0200
From:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	Santosh Shilimkar <santosh.shilimkar@...com>,
	Kevin Hilman <khilman@...aro.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Lars Poeschel <larsi@....tu-dresden.de>,
	Grant Likely <grant.likely@...aro.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>,
	Balaji T K <balajitk@...com>,
	Tony Lindgren <tony@...mide.com>,
	Jon Hunter <jgchunter@...il.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Linux-OMAP <linux-omap@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] gpio/omap: auto-setup a GPIO when used as an IRQ

On 09/23/2013 10:15 PM, Linus Walleij wrote:
> On Sun, Sep 22, 2013 at 4:40 PM, Javier Martinez Canillas
> <javier.martinez@...labora.co.uk> wrote:
> 
>> To use a GPIO pin as an interrupt line, two previous configurations
>> have to be made:
>>
>> a) Map the GPIO pin as an interrupt line into the Linux irq space
>> b) Enable the GPIO bank and configure the GPIO direction as input
>>
>> Most GPIO/IRQ chip drivers just create a mapping for every single
>> GPIO pin with irq_create_mapping() on .probe so users usually can
>> assume a) and only have to do b) by using the following sequence:
>>
>> gpio_request(gpio, "foo IRQ");
>> gpio_direction_input(gpio);
>>
>> and then request a IRQ with:
>>
>> irq = gpio_to_irq(gpio);
>> request_irq(irq, ...);
> 
> I guess I have to live with this approach, but I'd like to - if possible -
> address my pet issue.
> 
> - It is OK that the HW get set up as GPIO input by the IRQ
>   request function alone. (Through gpio_irq_type I guess).
> 

Yes, this is how is made on this patch indeed.

> - When a second caller calls omap_gpio_request() it should
>   be OK as well, but only if the flags corresponds to the
>   previously enabled input mode. Else it should be
>   disallowed.
> 
> - The same should happen for _set_gpio_direction() if a pin
>   previously set up for IRQ gets a request to be used as
>   output.
> 
> If this cannot be tracked in the driver, it is certainly a candidate
> for something that gpiolib should be doing. And then I'm open to
> solutions to how we can do that.
> 

Ok, this can be tracked in the driver, will add it when posting v2 soon.

> If this needs to be applied pronto to fix the regression I'm
> happy with that too, if we add a big boilerplate stating the above
> problem and that it needs to be *fixed* at some point.
> 
> But in either case I want this to be tested on OMAP1 before
> I apply it, as in a Tested-by tag.
>

Agreed. Even though this is a fix for a long standing issue I prefer it to be
tested extensively than applying the patch in a rush just to learn that causes
regressions and have to be reverted as it happens last time.

So as you said let's wait until we have a few Tested-by tags by people using
different OMAP platforms specially OMAP1.

> Yours,
> Linus Walleij
> 

Thanks a lot and best regards,
Javier

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