[Linux-stm32] STM32MP1 level triggered interrupts

[Marek Vasut]

On 1/22/20 6:19 PM, Alexandre Torgue wrote:

Hi,

[...]

>>> Concerning, your question:
>>>
>>> Setting your gpioC interruption as "falling edge" should be enough. On
>>> gpioCx falling edge, a high-level signal is generated by exti and sent
>>> to GIC (which triggers GIC interrupt). This signal remains high until
>>> stm32_irq_ack is called.
>>>
>>> So you only need: (ex for gpioc 1).
>>>
>>> interrupt-parent = <&gpioc>;
>>> interrupts = <1 IRQ_TYPE_EDGE_FALLING>;
>>
>> How does this deal with the case where the device holds the interrupt
>> line low (since it's level-sensitive, active low) after the driver
>> interrupt handler finishes ? Does such condition generate another
>> interrupt and call the driver interrupt handler again ? I would expect
>> the answer is no, because the interrupt is edge-triggered and there is
>> no edge.
> 
> Your assumption is good. If your device continue to hold the line to low
> at the end of your interrupt handler, no more interrupt will be generated.

But does that basically mean that such a device cannot be used with
STM32MP1 or am I fundamentally mistaken and don't understand how a
level-triggered interrupt works ? :)

-- 
Best regards,
Marek Vasut