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

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Date:	Tue, 24 Sep 2013 14:17:43 +0530
From:	Sricharan R <r.sricharan@...com>
To:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
CC:	Tony Lindgren <tony@...mide.com>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Kevin Hilman <khilman@...aro.org>,
	Linus Walleij <linus.walleij@...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>,
	Jon Hunter <jgchunter@...il.com>, <linux-gpio@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [RFC] gpio/omap: auto-setup a GPIO when used as an IRQ

On Tuesday 24 September 2013 01:24 PM, Javier Martinez Canillas wrote:
> On 09/24/2013 09:39 AM, Sricharan R wrote:
>> Hi,
>> On Monday 23 September 2013 10:37 PM, Tony Lindgren wrote:
>>> * Javier Martinez Canillas <javier.martinez@...labora.co.uk> [130923 10:09]:
>>>> On 09/23/2013 06:45 PM, Tony Lindgren wrote:
>>>>> Hmm does this still work for legacy platform data based
>>>>> drivers that are doing gpio_request() first?
>>>>>
>>>> Yes it still work when booting using board files. I tested on my OMAP3 board and
>>>> it worked in both DT and legacy booting mode.
>>> OK great.
>>>  
>>>>> And what's the path for clearing things for PM when free_irq()
>>>>> gets called? It seems that this would leave the GPIO bank
>>>>> enabled causing a PM regression?
>>>>>
>>>> Indeed, I did set bank->mod_usage |= 1 << offset so the bank is enabled if the
>>>> device goes to suspended and then resumed but I completely forget about the
>>>> clearing path when the IRQ is freed.
>>>>
>>>> Which makes me think that we should probably maintain two usage variables, one
>>>> for GPIO and another one for IRQ and check both of them on the suspend/resume pm
>>>> functions.
>>> Yes that it seems that they should be treated separately.
>>  To understand, why cant the flag be cleared in gpio_irq_shutdown ?
> Hi Sricharan,
>
> Without this patch today drivers do this:
>
> gpio_request(gpio, "foo IRQ"); // bank->mod_usage |= 1 << offset
> gpio_direction_input(gpio);
>
> and then request a IRQ with:
>
> irq = gpio_to_irq(gpio);
> request_irq(irq, ...);
>
> later on its cleanup path:
>
> free_irq(irq, dev);
> gpio_free(gpio) // bank->mod_usage &= ~(1 << offset);
>
> So if you clear the flag on gpio_irq_shutdown then bank module won't be enabled
> after a suspend making drivers using the GPIO after freeing the IRQ to fail.
>
> So the idea is to have something like this:
>
> a) Drivers that request both the GPIO and IRQ
>
> gpio_request(gpio, "foo IRQ"); // bank->mod_usage |= 1 << offset
> gpio_direction_input(gpio);
>
> irq = gpio_to_irq(gpio);
> request_irq(irq, ...); // bank->irq_usage |= 1 << offset
>
> free_irq(irq, dev); // bank->irq_usage &= ~(1 << offset);
> gpio_free(gpio) // bank->mod_usage &= ~(1 << offset);
>
> b) Drivers that just request the IRQ:
>
> irq = gpio_to_irq(gpio);
> request_irq(irq, ...); // bank->irq_usage |= 1 << offset
> free_irq(irq, dev); // bank->irq_usage &= ~(1 << offset);
>
> So irq_usage or mod_usage is set means that the bank has to be enabled and if
> both are not set means that the bank module can be disabled.
>
 Ok get it. Thanks.

Regards,
 Sricharan
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