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

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Date:	Thu, 26 Mar 2015 14:04:35 +0200
From:	Octavian Purdila <octavian.purdila@...el.com>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Robert Dolca <robert.dolca@...il.com>,
	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 Thu, Mar 26, 2015 at 12:16 PM, Mika Westerberg
<mika.westerberg@...ux.intel.com> wrote:
> On Wed, Mar 25, 2015 at 11:12:16PM +0200, Octavian Purdila 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?
>
> Good question.
>
> In general I think that it is assumed that the boot firmware configures
> the pin upfront. However, we have seen too many times that it actually
> doesn't happen or it is configured wrong.
>
> Perhaps we could do this in GPIO core, for example in
> gpiochip_irq_reqres/gpiochip_irq_map or so.
>

That sounds good to me. We tested your patch with the patch below and
we can now directly use client->irq:

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 568aa2b..9865627 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -511,6 +511,19 @@ static const struct irq_domain_ops gpiochip_domain_ops = {
 static int gpiochip_irq_reqres(struct irq_data *d)
 {
        struct gpio_chip *chip = irq_data_get_irq_chip_data(d);
+       int ret;
+
+       ret = gpiod_request(&chip->desc[d->hwirq], "IRQ");
+       if (ret) {
+               chip_err(chip, "unable to request %lu for IRQ\n", d->hwirq);
+               return ret;
+       }
+
+       ret = gpiod_direction_input(&chip->desc[d->hwirq]);
+       if (ret) {
+               chip_err(chip, "unable to set HW IRQ %lu as input\n", d->hwirq);
+               return ret;
+       }

        if (gpiochip_lock_as_irq(chip, d->hwirq)) {
                chip_err(chip,
--
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