linux-kernel - Re: [PATCH 1/2] gpio: pcf857x: Propagate wake-up setting to parent irq controller

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Date:	Wed, 17 Dec 2014 09:13:39 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Alexandre Courbot <gnurou@...il.com>
Cc:	Geert Uytterhoeven <geert+renesas@...der.be>,
	Linus Walleij <linus.walleij@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Ingo Molnar <mingo@...hat.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Linux-SH <linux-sh@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] gpio: pcf857x: Propagate wake-up setting to parent
 irq controller

Hi Alexandre,

On Wed, Dec 17, 2014 at 7:01 AM, Alexandre Courbot <gnurou@...il.com> wrote:
> On Wed, Dec 10, 2014 at 10:36 PM, Geert Uytterhoeven
> <geert+renesas@...der.be> wrote:
>> The pcf857x GPIO and interrupt controller uses dummy_irq_chip, which
>> does not implement irq_chip.irq_set_wake() and does not set
>> IRQCHIP_SKIP_SET_WAKE.
>>
>> This causes two s2ram issues if wake-up is enabled for the pcf857x GPIO
>> pins:
>>   1. During resume from s2ram, the following warning is printed:
>>
>>      WARNING: CPU: 0 PID: 1046 at kernel/irq/manage.c:537 irq_set_irq_wake+0x9c/0xf8()
>>      Unbalanced IRQ 113 wake disable
>>
>>   2. Wake-up through the pcf857x GPIO pins may fail, as the parent
>>      interrupt controller may be suspended.
>>
>> Migrate the pcf857x GPIO and interrupt controller from dummy_irq_chip to
>> its own irq_chip. This irq chip implements irq_chip.irq_set_wake() to
>> propagate its wake-up setting to the parent interrupt controller.
>>
>> This fixes wake-up through gpio-keys on sh73a0/kzm9g, where the pcf857x
>> interrupt is cascaded to irq-renesas-intc-irqpin, and the latter must
>> not be suspended when wake-up is enabled.
>
> I am not very familiar with the IRQ subsystem, but wouldn't it be
> possible (and better) to try and fix/adapt dummy_irq_chip so it
> displays the right behavior? At least your first point looks like an
> issue with it.

I fixed dummy_irq_chip in the second patch of the series ("[PATCH 2/2] [RFC]
genirq: Set IRQCHIP_SKIP_SET_WAKE for no_irq_chip and dummy_irq_chip:).
But please note that that would fix the warning (issue 1) only.

Pcf857x still needs to propagate the wake-up setting to the parent interrupt
controller to avoid the parent from being suspended if wake-up is enabled
(issue 2). That cannot be done in dummy_irq_chip, as dummy_irq_chip doesn't
know it is cascaded to a parent interrupt controller, nor about the interrupt
number that is used for the cascade. That information is specific to the child
driver.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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