Re: [PATCH v2 1/1] Input: atmel_mxt_ts - Get IRQ edge/level flags on DT booting

[Tomasz Figa <tomasz.figa@gmail.com>]

+CC Linus, as this became also pinctrl related.

On 08.08.2014 20:29, Javier Martinez Canillas wrote:
> Hello,
> 
> On 08/08/2014 06:38 PM, Javier Martinez Canillas wrote:
>>
>>
>> It seems as if the first call to exynos_irq_set_type() that is made by OF is a
>> no-op while the second call is the one that actually setups the hw correctly.
>> Does this make any sense? Maybe is related to the pin not being muxed in the
>> correct function when the "interrupts" property is parsed by OF?
>>
> 
> So after a conversation with Tomasz Figa over IRC the problem was after all that
> the pin was reconfigured. The IRQ trigger type resulted to be just a red herring
> and not a direct cause.
> 
> The pinctrl-eyxnos driver does the IRQ pinmux setup in the .irq_set_type
> function handler. So what happened was that OF parsed the "interrupts" property
> and called exynos_irq_set_type() which did the pinmux setup.
> 
> But after that, due a DTS pinctrl configuration the pin function was changed as
> a GPIO input and that happened before the atmel driver was probed. So when the
> driver called request_threaded_irq(), the correct flags were used but the pin
> was not configured as an IRQ anymore so IRQ were not fired.
> 
> Setting a trigger type just had the side effect of calling exynos_irq_set_type()
> which again setup the pin as an IRQ.
> 
> To fix the issue a variation of patch [0] will be posted that moves the IRQ
> pinmux setup from .irq_set_type to the .irq_request_resources function handler.
> That way the pin will be setup as IRQ regardless of the the trigger type [1]
> when someone calls request_[threaded]_irq().
> 
> Only the mentioned patch fixes the issue but Tomasz said that even a call to
> gpio_direction_{input,output} can change the pin configuration so he will post
> another patch that will add a bit mask to samsung_pin_bank to prevent any pinmux
> reconfiguration.

To add a bit more information about the hardware, setting up a GPIO
interrupt on Samsung SoCs is a two-step operation - in addition to
trigger configuration in a dedicated register, the pinmux must be also
reconfigured to GPIO interrupt, which is a different function than
normal GPIO input, although I/O-wise they both behave in the same way
and gpio_get_value() can be used on a pin configured as IRQ as well.

I'm afraid that such design implies that handling of this in the driver
must be done on a very low level, because it involves three possible
interfaces changing the pinmux - pinctrl, GPIO and irqchip and such
subtletes like gpio_direction_input() that shouldn't neither fail if a
pin is already configured as an interrupt nor change the configuration
to normal input.

Best regards,
Tomasz