linux-kernel - Re: [PATCH v2 0/2] Add GPIO level-sensitive interrupt support

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Message-ID: <faf55c81-e28f-20ed-ffdc-d20f00e3aefc@denx.de>
Date:   Fri, 21 Feb 2020 17:41:07 +0100
From:   Marek Vasut <marex@...x.de>
To:     Alexandre Torgue <alexandre.torgue@...com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-gpio@...r.kernel.org
Subject: Re: [PATCH v2 0/2] Add GPIO level-sensitive interrupt support

On 2/20/20 2:09 PM, Alexandre Torgue wrote:
> Hi Marek

Hi,

> On 2/19/20 6:24 PM, Marek Vasut wrote:
>> On 2/19/20 10:20 AM, Alexandre Torgue wrote:
>> Hi,
>> [...]
>>>>>>> This series adds the possibility to handle gpio interrupts on level.
>>>>>>>
>>>>>>> GPIO hardware block is directly linked to EXTI block but EXTI
>>>>>>> handles
>>>>>>> external interrupts only on edge. To be able to handle GPIO
>>>>>>> interrupt on
>>>>>>> level a "hack" is done in gpio irq chip: parent interrupt (exti irq
>>>>>>> chip)
>>>>>>> is retriggered following interrupt type and gpio line value.
>>>>>>>
>>>>>>> In exti irq chip, retrigger ops function is added.
>>>>>>
>>>>>> btw. this might be unrelated, but is it possible to have e.g. gpioC2
>>>>>> set
>>>>>> as trigger-level-low and gpioD2 set as trigger-edge-falling ? It
>>>>>> seems
>>>>>> 8eb2dfee9fb1 ("pinctrl: stm32: add lock mechanism for irqmux
>>>>>> selection")
>>>>>> prevents that.
>>>>>>
>>>>>
>>>>> No it's not possible. Each gpio line doesn't have a dedicated Exti
>>>>> line
>>>>> Each Exti line is muxing between gpio banks.
>>>>
>>>> OK, that confirms my assumption.
>>>>
>>>>> Mapping is done as following:
>>>>>
>>>>> EXTI0 = A0 or B0 or C0 .... or Z0 : selected by Mux
>>>>> EXTI1 = A1 or B1 or C1 ....or Z1 : selected by Mux
>>>>> EXTI2 = A2 or B2 or C2 ....or Z2 : selected by Mux
>>>>> ...
>>>>
>>>> Is it at least possible to have IRQs of the same type on the same exti
>>>> line? E.g. gpioA2 of trigger-edge-falling and gpioB2
>>>> trigger-edge-falling ?
>>>>
>>>
>>> Sorry I don't catch your point. If you already succeed to get gpioA2,
>>> then you will failed to get gpioB2 but looking at function call stack we
>>> could get an other issue.
>>
>> Considering the EXTI line limitations, I'd like to know what kind of IRQ
>> input configuration is allowed/valid and what kind of configuration is
>> not valid.
> 
> As a mux is used to select which GPIO[A..Z]_X has to be mapped on exti_X
> line, only one GPIO can be used on the EXTI line.
> 
> For example, on EXTI2 you could map either gpioa2 or gpiob2 or
> ....gpioz2 but not gpioa2 and gpiob2 in the same time.

Got it, thank you for the clarification.

Maybe that could be something to improve for MP2 :-)