device-tree: at91: irq and gpios: problem while requesting a gpio used as an interrupt source.

[Jean-Jacques Hiblot]

Hi Boris,

2014/1/13 boris brezillon <b.brezillon at overkiz.com>:
> On 13/01/2014 11:29, Jean-Jacques Hiblot wrote:
>>
>> Hello Nicolas, Jean-Christophe,
>>
>> As I was trying to enable the touchscreen on the at91sam9261ek with
>> device-tree support, I ran into an issue. The touchscreen driver needs
>> to know the state of the pendown gpio and also needs it as an
>> interrupt source.
>>
>> The problem is that when a gpio is used as an interrupt, it's
>> requested by the pinctrl driver during the xlate stage, marking it
>> unavaliable for the other driver.
>> It looks like the at91 pinctrl driver is the only one to use
>> gpio_request() in the xlate stage. Maybe we should remove this:
>
>
> You should only request it as a GPIO and then use gpio_to_irq to get the
> related IRQ.
> Because what is done here, is to solve the case where only the irq
> is request, and in this specific case we need to request the pin as a
> GPIO.
>

That's what I did first, and was about to submit the patch for the
touchscreen driver.
However it doesn't feel right. Being able to get the state of a gpio
that is also an interrupt seems very useful to me, not only for a
touchscreen controller.

I understand why it's being done here. It's a matter of being sure
that the GPIO is an input and that it'll not be configured otherwise
latter.
But:
1) I'm wondering why the atmel pinctrl is the only one to do that.
2) I believe that configuration of the direction can be done by
describing the GPIO in the DT. (pinctrl-at91.c line 592).
3) If all the GPIOs are described in the DT with a proper pinmux
description, i believe the exclusion is also handled. It's probably
not the case today though.

>
> Best Regards,
>
> Boris
>
>>
>> diff --git a/drivers/pinctrl/pinctrl-at91.c
>> b/drivers/pinctrl/pinctrl-at91.c
>> index a7549c4..cf91a35 100644
>> --- a/drivers/pinctrl/pinctrl-at91.c
>> +++ b/drivers/pinctrl/pinctrl-at91.c
>> @@ -1463,14 +1463,6 @@ static int at91_gpio_irq_domain_xlate(struct
>> irq_domain *d,
>>          *out_hwirq = intspec[0];
>>          *out_type = intspec[1] & IRQ_TYPE_SENSE_MASK;
>>
>> -       ret = gpio_request(pin, ctrlr->full_name);
>> -       if (ret)
>> -               return ret;
>> -
>> -       ret = gpio_direction_input(pin);
>> -       if (ret)
>> -               return ret;
>> -
>>          return 0;
>>   }
>>
>> Jean-Jacques
>
>