From: Michael Walle <michael@walle.cc>
To: Horatiu Vultur <horatiu.vultur@microchip.com>
Cc: UNGLinuxDriver@microchip.com, andy.shevchenko@gmail.com,
linus.walleij@linaro.org, linux-gpio@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] pinctrl: ocelot: Fix interrupt controller
Date: Thu, 13 Oct 2022 09:30:25 +0200 [thread overview]
Message-ID: <994b3dfd8d5d2c0c11c2bf6f299564c1@walle.cc> (raw)
In-Reply-To: <20221007094938.qqf7exuthvz5gkdq@soft-dev3-1.localhost>
Hi Horatiu,
Am 2022-10-07 11:49, schrieb Horatiu Vultur:
> The 10/06/2022 13:43, Michael Walle wrote:
>
> Hi Walle,
>
>> Seeing 20 was definitely fishy, seeing two instead of one maybe not
>> so much. I guess it will create one spurious interrupt if none of
>> the registered handlers will care.
>>
>> OTOH, the code below won't work in all cases anyway, right? It's just
>> best effort.
>
> I was expecting to work in all cases, but if you found some cases that
> would not work, please point them out.
>
>>
>> > Below I have a diff that I tried with LAN8814 PHYs and I could see that
>> > count in /proc/interrupts is increasing correctly.
>> >
>> > > I've verified that there is only one low pulse on the interrupt line.
>> > > I've
>> > > noticed though, that the number of interrupts seem to be correlating
>> > > with
>> > > the length of the low pulse.
>> > ---
>> > diff --git a/drivers/pinctrl/pinctrl-ocelot.c
>> > b/drivers/pinctrl/pinctrl-ocelot.c
>> > index c7df8c5fe5854..105771ff82e62 100644
>> > --- a/drivers/pinctrl/pinctrl-ocelot.c
>> > +++ b/drivers/pinctrl/pinctrl-ocelot.c
>> > @@ -1863,19 +1863,28 @@ static void ocelot_irq_unmask_level(struct
>> > irq_data *data)
>> > if (val & bit)
>> > ack = true;
>> >
>> > + /* Try to clear any rising edges */
>> > + if (!active && ack)
>> > + regmap_write_bits(info->map, REG(OCELOT_GPIO_INTR, info, gpio),
>> > + bit, bit);
>>
>> Might we lose interrupts here, if the line would go active again right
>> after the read of the line state and before reading the "ack" bit?
>
> We lose the interrupt here, as the HW will not generate another one
> but at later point we read again the line status. And if the line is
> active then we kick again the interrupt handler again.
Ahh, thanks for explaining. That also explains the read below.
Will you send a proper patch?
-michael
>
>>
>> > +
>> > /* Enable the interrupt now */
>> > gpiochip_enable_irq(chip, gpio);
>> > regmap_update_bits(info->map, REG(OCELOT_GPIO_INTR_ENA, info, gpio),
>> > bit, bit);
>> >
>> > /*
>> > - * In case the interrupt line is still active and the interrupt
>> > - * controller has not seen any changes in the interrupt line, then it
>> > - * means that there happen another interrupt while the line was
>> > active.
>> > + * In case the interrupt line is still active then it means that
>> > + * there happen another interrupt while the line was active.
>> > * So we missed that one, so we need to kick the interrupt again
>> > * handler.
>> > */
>> > - if (active && !ack) {
>> > + regmap_read(info->map, REG(OCELOT_GPIO_IN, info, gpio), &val);
>> > + if ((!(val & bit) && trigger_level == IRQ_TYPE_LEVEL_LOW) ||
>> > + (val & bit && trigger_level == IRQ_TYPE_LEVEL_HIGH))
>> > + active = true;
>>
>> Why do you read the line state twice? What happens if the line state
>> changes right after you've read it?
>
> Here we need to read again the status because we might have clear the
> ack of interrupt.
> If the line becomes active right after this read, then the HW will
> generate another interrupt as the interrupt is enabled and ack is
> cleared.
>
>>
>> > +
>> > + if (active) {
>> > struct ocelot_irq_work *work;
>> >
>> > work = kmalloc(sizeof(*work), GFP_ATOMIC);
>>
>> So yes, maybe the trade-off that there will be two interrupts are
>> better than this additional patch. But it should be documented
>> somewhere, even if it's just a comment in this driver.
>>
>> -michael
next prev parent reply other threads:[~2022-10-13 7:30 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-09 14:59 [PATCH v3] pinctrl: ocelot: Fix interrupt controller Horatiu Vultur
2022-09-09 15:09 ` Andy Shevchenko
2022-09-15 11:33 ` Horatiu Vultur
2022-09-14 13:02 ` Linus Walleij
2022-09-15 11:22 ` Horatiu Vultur
2022-09-18 18:55 ` Linus Walleij
2022-09-20 12:06 ` Michael Walle
2022-09-20 12:28 ` Linus Walleij
2022-09-20 12:34 ` Michael Walle
2022-09-20 14:25 ` Michael Walle
2022-09-20 19:30 ` Horatiu Vultur
2022-10-06 11:43 ` Michael Walle
2022-10-07 9:49 ` Horatiu Vultur
2022-10-13 7:30 ` Michael Walle [this message]
2022-10-13 14:11 ` Horatiu Vultur
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