Re: [PATCH v3 6/6] iio: adc: stm32: add support for EXTI trigger

[Lars-Peter Clausen]

On 03/03/2017 04:46 PM, Lars-Peter Clausen wrote:
> On 03/03/2017 02:00 PM, Fabrice Gasnier wrote:
>> On 03/03/2017 12:45 PM, Lars-Peter Clausen wrote:
>>> On 02/28/2017 05:51 PM, Fabrice Gasnier wrote:
>>>> EXTi (external interrupt) signal can be routed internally as trigger
>>>> source for ADC conversions: STM32F4 ADC can use EXTI11.
>>>>
>>>> Retrieve interrupt trigger from DT, so it can be muxed into ADC IP,
>>>> via extsel.
>>>
>>> Hi,
>>>
>>> Sorry, I have some trouble understanding the specifics of this. Is EXTI a
>>> hardware input signal into the ADC that automatically triggers a conversion
>>> when asserted? If yes how is it configured which external signal is used
>>> here. Your bindings suggest that any GPIO can be used, but the driver only
>>> differentiates between EXTI on or EXTI off.
>> Hi Lars,
>>
>> Yes, STM32 EXTI is external interrupt/event line. In case of STM32 ADC,
>> EXTI11 signal can be used to start a conversion. In this case, it must
>> be selected inside ADC IP using extsel bitfield. This EXTI11 line can
>> mapped from any GPIO bank A,B... line 11 (e.g. PA11 or PB11...) by using
>> interrupt binding.
>> This is why I expose this in DT.
> 
> How is the mapping? That's the part I don't understand. How does requesting

How is the mapping done?

> the IRQ for the GPIO as a generic software IRQ establish the hardware
> connection between the GPIO block and the ADC?
>