linux-kernel - Re: [PATCH v3 2/2] pinctrl: stm32: Add level interrupt support to gpio irq chip

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Message-ID: <20200323192519.1bd1dc5f@why>
Date:   Mon, 23 Mar 2020 19:25:19 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Marek Vasut <marex@...x.de>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel@...r.kernel.org,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] pinctrl: stm32: Add level interrupt support to
 gpio irq chip

On Mon, 23 Mar 2020 20:04:23 +0100
Marek Vasut <marex@...x.de> wrote:

> On 2/20/20 10:17 AM, Marc Zyngier wrote:
> > On 2020-02-20 09:04, Linus Walleij wrote:
> >> On Wed, Feb 19, 2020 at 3:32 PM Alexandre Torgue
> >> <alexandre.torgue@...com> wrote:
> >>
> >>> 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.
> >>>
> >>> Signed-off-by: Alexandre Torgue <alexandre.torgue@...com>
> >>> Tested-by: Marek Vasut <marex@...x.de>
> >>
> >> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
> >>
> >> If Marc want to merge it with patch 1/2 go ahead!
> > 
> > I'll queue the whole thing for 5.7.
> 
> I have a feeling this doesn't work with threaded interrupts.
> 
> If the interrupt handler runs in a thread context, the EOI will happen
> almost right away (while the IRQ handler runs) and so will the code
> handling the IRQ retriggering. But since the IRQ handler still runs and
> didn't return yet, the retriggering doesn't cause the IRQ handler to be
> called again once it finishes, even if the IRQ line is still asserted.
> And that could result in some of the retriggers now happening I think.
> Or am I doing something wrong ?

Wouldn't the hardirq handler mask the interrupt? This should certainly
be the case when IRQF_ONESHOT is set.

	M.
-- 
Jazz is not dead. It just smells funny...