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

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Message-ID: <8d6f6646-56e4-5218-9990-f0c96862dc83@denx.de>
Date:   Mon, 23 Mar 2020 20:19:39 +0100
From:   Marek Vasut <marex@...x.de>
To:     Marc Zyngier <maz@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     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 3/23/20 8:04 PM, Marek Vasut 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 ?

The patch below makes my usecase work, but I don't know whether it's
correct. Basically once the threaded IRQ handler finishes and unmasks
the IRQ, check whether the line is asserted and retrigger if so.

diff --git a/drivers/pinctrl/stm32/pinctrl-stm32.c
b/drivers/pinctrl/stm32/pinctrl-stm32.c
index 9ac9ecfc2f34..060dbcb7ae72 100644
--- a/drivers/pinctrl/stm32/pinctrl-stm32.c
+++ b/drivers/pinctrl/stm32/pinctrl-stm32.c
@@ -371,12 +371,26 @@ static void
stm32_gpio_irq_release_resources(struct irq_data *irq_data)
        gpiochip_unlock_as_irq(&bank->gpio_chip, irq_data->hwirq);
 }

+static void stm32_gpio_irq_unmask(struct irq_data *d)
+{
+       struct stm32_gpio_bank *bank = d->domain->host_data;
+       int level;
+
+       irq_chip_unmask_parent(d);
+
+       /* If level interrupt type then retrig */
+       level = stm32_gpio_get(&bank->gpio_chip, d->hwirq);
+       if ((level == 0 && bank->irq_type[d->hwirq] ==
IRQ_TYPE_LEVEL_LOW) ||
+           (level == 1 && bank->irq_type[d->hwirq] == IRQ_TYPE_LEVEL_HIGH))
+               irq_chip_retrigger_hierarchy(d);
+}
+
 static struct irq_chip stm32_gpio_irq_chip = {
        .name           = "stm32gpio",
        .irq_eoi        = stm32_gpio_irq_eoi,
        .irq_ack        = irq_chip_ack_parent,
        .irq_mask       = irq_chip_mask_parent,
-       .irq_unmask     = irq_chip_unmask_parent,
+       .irq_unmask     = stm32_gpio_irq_unmask,
        .irq_set_type   = stm32_gpio_set_type,
        .irq_set_wake   = irq_chip_set_wake_parent,
        .irq_request_resources = stm32_gpio_irq_request_resources,