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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Michael Walle <michael@walle.cc>
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Subject: Re: [PATCH v3 06/16] irqchip: add sl28cpld interrupt controller support
In-Reply-To: <87f141bce0a4fda04b550647306be296@walle.cc>
References: <20200423174543.17161-1-michael@walle.cc> <20200423174543.17161-7-michael@walle.cc> <87pnbtqhr1.fsf@nanos.tec.linutronix.de> <87f141bce0a4fda04b550647306be296@walle.cc>
Date:   Mon, 27 Apr 2020 21:00:05 +0200
Message-ID: <87sggopxe2.fsf@nanos.tec.linutronix.de>
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Michael,

Michael Walle <michael@walle.cc> writes:
> Am 2020-04-27 13:40, schrieb Thomas Gleixner:
>>> +
>>> +	ret = devm_regmap_add_irq_chip(&pdev->dev, irqchip->regmap, irq,
>>> +				       IRQF_SHARED | IRQF_ONESHOT, 0,
>> 
>> What's the point of IRQF_SHARED | IRQF_ONESHOT here?
>
> IRQF_SHARED because this interrupt is shared with all the blocks
> which can generate interrupts, i.e. the GPIO contollers.

Why are people still designing hardware with shared interrupts? Shared
interrupts are broken by design and that's well known for decades.

> IRQF_ONESHOT, because its is a threaded interrupt with no primary
> handler. But I just noticed, that regmap-irq will also set the
> IRQF_ONESHOT. But that the commit 09cadf6e088b ("regmap-irq:
> set IRQF_ONESHOT flag to ensure IRQ request") reads like it is
> just there to be sure. So I don't know if it should also be set
> here.

Ok. Wasn't aware of that magic threaded interrupt connection.

Thanks,

        tglx