linux-kernel - Re: [PATCH] pinctrl/nomadik: use irq_create

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Message-ID: <5085A7CA.3070001@wwwdotorg.org>
Date:	Mon, 22 Oct 2012 14:08:42 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	Linus Walleij <linus.walleij@...ricsson.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Stephen Warren <swarren@...dia.com>,
	Anmar Oueja <anmar.oueja@...aro.org>,
	Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH] pinctrl/nomadik: use irq_create_mapping()

On 10/22/2012 02:14 AM, Linus Walleij wrote:
> On Fri, Oct 19, 2012 at 6:22 PM, Stephen Warren <swarren@...dotorg.org> wrote:
>> On 10/19/2012 09:09 AM, Linus Walleij wrote:
>>> From: Linus Walleij <linus.walleij@...aro.org>
>>
>>> @@ -931,7 +931,7 @@ static void __nmk_gpio_irq_handler(unsigned int irq, struct irq_desc *desc,
>>>       while (status) {
>>>               int bit = __ffs(status);
>>>
>>> -             generic_handle_irq(irq_find_mapping(nmk_chip->domain, bit));
>>> +             generic_handle_irq(irq_create_mapping(nmk_chip->domain, bit));
>>
>> Surely this one can remain as irq_find_mapping() since isn't
>> nmk_gpio_to_irq() guaranteed to have been called first for this GPIO/IRQ?
> 
> It's an IRQ handler so it should be robust to spurious IRQs due to
> transient hardware states etc I believe.
> 
> So if there is a transient IRQ before gpio_to_irq() is called -> boom.

I wonder though (a) why it would be unmasked in HW, and (b) why the
software would even look at the status bit if no handler were registered?

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