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

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Date:   Sun, 06 Dec 2020 18:50:07 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Serge Semin <fancer.lancer@...il.com>,
        luojiaxing <luojiaxing@...wei.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...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 2020-12-06 15:02, Linus Walleij wrote:
> On Sat, Dec 5, 2020 at 11:15 PM Serge Semin <fancer.lancer@...il.com> 
> wrote:
> 
>> Hmm, that sounds like a problem, but the explanation is a bit unclear
>> to me. AFAICS you are saying that the only callbacks which are
>> called during the IRQ request/release are the irq_enable(), right? If
>> so then the only reason why we haven't got a problem reported due to
>> that so far is that the IRQs actually unmasked by default.
> 
> What we usually do in cases like that (and I have discussed this
> with tglx in the past I think) is to simply mask off all IRQs in 
> probe().
> Then they will be unmasked when requested by drivers.
> 
> See e.g. gpio-pl061 that has this line in probe():
> writeb(0, pl061->base + GPIOIE); /* disable irqs */

This should definitely be the default behaviour. The code code
expects all interrupt sources to be masked until actively enabled,
usually with the IRQ being requested.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...