linux-kernel - Re: [PATCH] IIO: Adds ACPI support for ST gyroscopes

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Date:	Thu, 26 Mar 2015 12:06:45 +0200
From:	Robert Dolca <robert.dolca@...il.com>
To:	Octavian Purdila <octavian.purdila@...el.com>
Cc:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Robert Dolca <robert.dolca@...el.com>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	Jonathan Cameron <jic23@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Hartmut Knaack <knaack.h@....de>,
	Peter Meerwald <pmeerw@...erw.net>,
	Denis CIOCCA <denis.ciocca@...com>
Subject: Re: [PATCH] IIO: Adds ACPI support for ST gyroscopes

On Wed, Mar 25, 2015 at 11:12 PM, Octavian Purdila
<octavian.purdila@...el.com> wrote:
> On Wed, Mar 25, 2015 at 3:21 PM, Mika Westerberg
> <mika.westerberg@...ux.intel.com> wrote:
>> On Wed, Mar 25, 2015 at 02:25:05PM +0200, Mika Westerberg wrote:
>>> I think we can do the same for ACPI GpioInts so that we introduce
>>> acpi_gpio_irq_get() that translates from GpioInt to Linux IRQ
>>> numberspace. Then we can do something like below in I2C core:
>>>
>>>       if (client->irq <= 0) {
>>>               int irq = -ENOENT;
>>>
>>>                 if (dev->of_node)
>>>                         irq = of_irq_get(dev->of_node, 0);
>>>                 else if (ACPI_COMPANION(dev))
>>>                         irq = acpi_gpio_irq_get(ACPI_COMPANION(dev), 0);
>>>
>>>               if (irq == -EPROBE_DEFER)
>>>                         return irq;
>>>                 if (irq < 0)
>>>                         irq = 0;
>>>
>>>                 client->irq = irq;
>>>       }
>>>
>>> Now it has the drawback that the first GpioInt will not be available to
>>> the driver anymore (as a GPIO since it is locked) but if DT already does
>>> the same we should be fine.
>>
>> Below patch should take care of this.
>>
>
> One issue we noticed is that now the gpio request and set input
> directions operations are not called anymore. Some gpio controller
> drivers (dln2, adnp, lynx_point from quickly browsing the code) do not
> explicitly enable the GPIO pin nor set direction to input when the
> interrupt is enabled. Depending on hardware this may be an issue - it
> is on dln2 for example.
>
> Should the gpio controllers enable and set to input in irq_enable,
> irq_bus_sync_unlock, etc.? Or should this be done in gpiolib?

I've tested the patch and it works if the GPIO pin is enabled in the
controller (which isn't as Octavian said). I believe that the patch
should enable the pin and set the direction before it is used as IRQ.

Robert
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