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

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Message-ID: <CACRpkdbNh6ooBh-dhT=KKHQMZ=uK_AQMsreTg56kVXE5cE1ohQ@mail.gmail.com>
Date:	Thu, 22 Aug 2013 01:04:23 +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>,
	"linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v2] pinctrl: queue GPIO operations instead of defering

On Wed, Aug 21, 2013 at 7:45 PM, Stephen Warren <swarren@...dotorg.org> wrote:
> On 08/19/2013 01:21 PM, Stephen Warren wrote:
>> On 08/17/2013 08:56 AM, Linus Walleij wrote:
>>> We currently defer probing of the caller if a pinctrl GPIO
>>> request or direction setting comes in before the range mapping
>>> a certain GPIO to a certain pin controller is available.
>>>
>>> This can end up with a circular dependency: the GPIO driver
>>> needs the pin controller to be ready and the pin controller
>>> need the GPIO driver to be ready. This also happens if
>>> pin controllers and GPIO controllers compiled as modules
>>> are inserted in a certain order.
>>>
>>> To break this circular dependence, queue any GPIO
>>> operations coming to the framework until the range is ready,
>>> instead of deferring the probe of the caller.
>>
>> I just noticed that next-20130819 is failing on the Tegra114 Dalmore
>> board because of this patch. The kernel log is below. Reverting this
>> patch solves the problem
>
> Linus, any thoughts here?

None whatsoever, but logically it should be that your pinctrl+GPIO
driver pair depends on the GPIO driver coming first and having it's probing
deferred.

I'll rip out that patch for the time being...

Yours,
Linus Walleij
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