linux-kernel - Re: [PATCH] gpio: pca953x: Fix warning when HW interrupts are rescheduled by the softirq tasklet

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Date:	Wed, 24 Sep 2014 13:17:12 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	Lothar Waßmann <LW@...o-electronics.de>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: [PATCH] gpio: pca953x: Fix warning when HW interrupts are
 rescheduled by the softirq tasklet

On Tue, Sep 23, 2014 at 2:26 PM, Grygorii Strashko
<grygorii.strashko@...com> wrote:
> On 09/23/2014 03:04 PM, Linus Walleij wrote:
>> On Tue, Sep 9, 2014 at 10:32 AM, Lothar Waßmann <LW@...o-electronics.de> wrote:

>>> @@ -567,6 +568,17 @@ static int pca953x_irq_setup(struct pca953x_chip *chip,
>>>                                  "could not connect irqchip to gpiochip\n");
>>>                          return ret;
>>>                  }
>>> +
>>> +               for (i = 0; i < NBANK(chip); i++) {
>>> +                       int j;
>>> +
>>> +                       for (j = 0; j < BANK_SZ; j++) {
>>> +                               int gpio = gpio_chip->base + i * BANK_SZ + j;
>>> +                               int irq = gpio_to_irq(gpio);
>>> +
>>> +                               irq_set_parent(irq, client->irq);
>>> +                       }
>>> +               }
>>
>> While this is fixing the problem, but isn't the right fix to patch
>> the function gpiochip_irq_map() in gpiolib.c to call
>> irq_set_parent() for each IRQ as it gets mapped?
>>
>> This driver is using the gpiolib irqchip helpers...
>>
>> Then you fix not just this driver but all drivers, plus the complex
>> loop and calls to gpio_to_irq() etc goes away.
>
> The problem here is that:
> - we don't know parent IRQ number inside gpiolib irqchip;
> - there can be more then one Parent IRQ per GPIO chip

We could for the simple case:

void gpiochip_set_chained_irqchip(struct gpio_chip *gpiochip,
                  struct irq_chip *irqchip,
                  int parent_irq,
                  irq_flow_handler_t parent_handler)

Note parent_irq.

Just add a field for parent_irq in struct gpio_chip so the
mapping function has this around.

But the second case with multiple parents is a valid
counterargument, gpiolib irqchip helpers
is just for the simple case of a cascaded IRQ off a single
parent, not for complex scenarios.

So PCA cannot use gpiochip_set_chained_irqchip()?

Anyway I feel I should fix this as per above for all
chips using that function, right?

Yours,
Linus Walleij
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