linux-kernel - Re: [PATCH v2 1/2] irqchip/stm32: Add irq retrigger support

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Date:   Wed, 19 Feb 2020 14:17:35 +0100
From:   Alexandre Torgue <alexandre.torgue@...com>
To:     Marc Zyngier <maz@...nel.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Linus Walleij <linus.walleij@...aro.org>, <marex@...x.de>,
        <linux-gpio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 1/2] irqchip/stm32: Add irq retrigger support



On 2/19/20 2:13 PM, Marc Zyngier wrote:
> On 2020-02-19 13:07, Alexandre Torgue wrote:
>> On 2/19/20 12:43 PM, Marc Zyngier wrote:
>>> On 2020-02-19 11:33, Alexandre Torgue wrote:
>>>> Fix Marc email address
>>>>
>>>> On 2/18/20 2:12 PM, Alexandre Torgue wrote:
>>>>> This commit introduces retrigger support for stm32_ext_h chip.
>>>>> It consists to rise the GIC interrupt mapped to an EXTI line.
>>>>>
>>>>> Signed-off-by: Alexandre Torgue <alexandre.torgue@...com>
>>>>>
>>>>> diff --git a/drivers/irqchip/irq-stm32-exti.c 
>>>>> b/drivers/irqchip/irq-stm32-exti.c
>>>>> index e00f2fa27f00..c971d115edb4 100644
>>>>> --- a/drivers/irqchip/irq-stm32-exti.c
>>>>> +++ b/drivers/irqchip/irq-stm32-exti.c
>>>>> @@ -604,12 +604,24 @@ static void stm32_exti_h_syscore_deinit(void)
>>>>>       unregister_syscore_ops(&stm32_exti_h_syscore_ops);
>>>>>   }
>>>>>   +static int stm32_exti_h_retrigger(struct irq_data *d)
>>>>> +{
>>>>> +    struct stm32_exti_chip_data *chip_data = 
>>>>> irq_data_get_irq_chip_data(d);
>>>>> +    const struct stm32_exti_bank *stm32_bank = chip_data->reg_bank;
>>>>> +    void __iomem *base = chip_data->host_data->base;
>>>>> +    u32 mask = BIT(d->hwirq % IRQS_PER_BANK);
>>>>> +
>>>>> +    writel_relaxed(mask, base + stm32_bank->swier_ofst);
>>>>> +
>>>>> +    return irq_chip_retrigger_hierarchy(d);
>>>
>>> Calling irq_chip_retrigger_hierarchy here is really odd. If the write
>>> above has the effect of making the interrupt pending again, why do you
>>> need to force the retrigger any further?
>>
>> To be honest, as we use hierarchical irq_chip, I thought it was the
>> way to follow (to retrigger parent irq_chip). It makes maybe no sens
>> here.
> 
> Indeed, it looks perfectly pointless. What irq_chip_retrigger_hierarchy()
> does is to look for the first parent irqchip that is able to retrigger
> the interrupt. Guess what, you've just done that already. And once you've
> generated the interrupt, you don't need to ask the other irqchips in the
> chain to do the same thing.

I agree. I gonna remove it v3.

Thanks for the feeback.
Alex

>> The most important to regenerate gic interrupt (associate to the exti
>> line) is to write in SWIER register.
> 
> Quite. Hence my question.
> 
>          M.