linux-kernel - Re: [PATCH v2] pinctrl: queue GPIO operations instead of defering

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Message-ID: <CACRpkdasWurMctYTMZCHS+fwhvmnREaQD1vN54QYpMToTuFjsg@mail.gmail.com>
Date:	Thu, 22 Aug 2013 01:07:30 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Stephen Warren <swarren@...dia.com>,
	Haojian Zhuang <haojian.zhuang@...aro.org>,
	Lars Poeschel <poeschel@...onage.de>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Subject: Re: [PATCH v2] pinctrl: queue GPIO operations instead of defering

On Mon, Aug 19, 2013 at 9:15 PM, Stephen Warren <swarren@...dotorg.org> wrote:
> On 08/17/2013 08:56 AM, Linus Walleij wrote:

>> and the pin controller need the GPIO driver to be ready.
>
> Why does that happen?

The pin controller call back into the GPIO-side controller
functions by utilizing the GPIO ranges.
(Maybe the code is silly, I dunno, check drivers/pinctrl/pinctrl-nomadik.c)

>> This also happens if
>> pin controllers and GPIO controllers compiled as modules
>> are inserted in a certain order.
>
> Shouldn't deferred probe resolve that just fine, assuming there are no
> circular dependencies?

The above leads to circular dependencies so that is what I'm
trying to fix with this.

>> On the Nomadik we get this situation with the pinctrl
>> driver when moving to requesting GPIOs off the gpiochip
>> right after it has been added,
>
> So, the pinctrl driver calls gpio_request()? Surely the solution is
> simply not to do that?

This is what the other patch we're discussing is doing.
The one that harvests and requests interrupt GPIO's when
a gpiochip is added...

Yours,
Linus Walleij
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