linux-kernel - Re: [PATCH v4] gpio: Add support for Intel SoC PMIC (Crystal Cove)

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Date:	Fri, 30 May 2014 10:12:37 +0800
From:	"Zhu, Lejun" <lejun.zhu@...ux.intel.com>
To:	Linus Walleij <linus.walleij@...aro.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
CC:	Grygorii Strashko <grygorii.strashko@...com>,
	Alexandre Courbot <gnurou@...il.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	jacob.jun.pan@...ux.intel.com, bin.yang@...el.com
Subject: Re: [PATCH v4] gpio: Add support for Intel SoC PMIC (Crystal Cove)



On 5/29/2014 9:37 PM, Linus Walleij wrote:
> On Tue, May 27, 2014 at 2:04 PM, Grygorii Strashko
> <grygorii.strashko@...com> wrote:
>> On 05/27/2014 11:46 AM, Mika Westerberg wrote:
(...)
> 
> My idea is that you should call gpiochip_add() *first* and then
> add the IRQs to the chip. In succession.
> 
> Rationale: with dynamic GPIO numbers, gpio_to_irq()
> cannot reasonably be working before the gpiochip is added,
> so it should be added first, then the irqchip. Since irq_to_gpio()
> is *NOT* to be used (rather obliterated), this is the sequence
> we mandate.
> 
> This is how the new irqchip helpers work by the way. As I
> introduce this to more and more drivers it will look more and
> more like this. And attack patches tagged RFT switching the
> semantics of drivers are appreciated.
> 
> Yours,
> Linus Walleij
> 

Thanks. I'll use this sequence during probe().

(...)
	cg->regmap = pmic->regmap;

	retval = gpiochip_add(&cg->chip);
	if (retval) {
		dev_warn(&pdev->dev, "add gpio chip error: %d\n", retval);
		return ret;
	}

	gpiochip_irqchip_add(&cg->chip, &crystalcove_irqchip, 0,
			     handle_simple_irq, IRQ_TYPE_NONE);

	retval = request_threaded_irq(irq, NULL, crystalcove_gpio_irq_handler,
				      IRQF_ONESHOT, KBUILD_MODNAME, cg);

	if (retval) {
		dev_warn(&pdev->dev, "request irq failed: %d\n", retval);
		WARN_ON(gpiochip_remove(&cg->chip));
		return retval;
	}

	return 0;
}

Is the code above OK?

But this code will trigger a crash in gpiolib-acpi. Currently at the end
of gpiochip_add(), it calls:

gpiochip_add() -> acpi_gpiochip_add() -> acpi_gpiochip_request_interrupts()

acpi_gpiochip_request_interrupts() needs ->to_irq to work. Without having
called gpiochip_irqchip_add() already, this will be NULL:

        if (!chip->to_irq)
                return;    <-- It will return here.

        INIT_LIST_HEAD(&acpi_gpio->events);

In the tear down path, acpi_gpiochip_free_interrupts() will find to_irq is
no longer NULL, then it will walk an uninitialized list.

So, should this be fixed in gpiolib-acpi?

Best Regards
Lejun
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