linux-kernel - Re: [PATCH v1] gpio: dwapb: mask/unmask IRQ when disable/enable it

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Date: Fri, 15 Dec 2023 09:09:09 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Linus Walleij <linus.walleij@...aro.org>, Luo Jiaxing
 <luojiaxing@...wei.com>, Marc Zyngier <maz@...nel.org>
Cc: Bartosz Golaszewski <bgolaszewski@...libre.com>, Serge Semin
 <Sergey.Semin@...kalelectronics.ru>, Andy Shevchenko
 <andy.shevchenko@...il.com>, Andy Shevchenko
 <andriy.shevchenko@...ux.intel.com>, "open list:GPIO SUBSYSTEM"
 <linux-gpio@...r.kernel.org>, "linux-kernel@...r.kernel.org"
 <linux-kernel@...r.kernel.org>, Linuxarm <linuxarm@...wei.com>
Subject: Re: [PATCH v1] gpio: dwapb: mask/unmask IRQ when disable/enable it

On Sat, Dec 05 2020 at 22:58, Linus Walleij wrote:
> Sorry for top posting but I need the help of the irqchip maintainer
> Marc Z to hash this out.
>
> The mask/unmask/disable/enable semantics is something that
> you need to work with every day to understand right.

The patch is correct.

The irq_enable() callback is required to be a superset of
irq_unmask(). I.e. the core code expects it to do:

  1) Some preparatory work to enable the interrupt line

  2) Unmask the interrupt, which is why the masked state is cleared
     by the core after invoking the irq_enable() callback.

#2 is pretty obvious because if an interrupt chip does not implement the
irq_enable() callback the core defaults to irq_unmask()

Correspondingly the core expects from the irq_disable() callback:

   1) To mask the interrupt

   2) To do some extra work to disable the interrupt line

Same reasoning as above vs. #1 as the core fallback is to invoke the
irq_unmask() callback when the irq_disable() callback is not
implemented.

Thanks,

        tglx