linux-kernel - Re: [PATCH v2 3/7] gpio: brcmstb: release the bgpio lock during irq handlers

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Message-ID: <CACRpkdaqenb0nhhMYLhT=pM=6exj71+7tqM_4G0mc2+6ATxGwQ@mail.gmail.com>
Date:   Tue, 31 Oct 2017 10:29:18 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Doug Berger <opendmb@...il.com>
Cc:     Gregory Fong <gregory.0xf0@...il.com>,
        Brian Norris <computersforpeace@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 3/7] gpio: brcmstb: release the bgpio lock during irq handlers

On Tue, Oct 24, 2017 at 9:54 PM, Doug Berger <opendmb@...il.com> wrote:

> The basic memory-mapped GPIO controller lock must be released
> before calling the registered GPIO interrupt handlers to allow
> the interrupt handlers to access the hardware.
>
> Examples of why a GPIO interrupt handler might want to access
> the GPIO hardware include an interrupt that is configured to
> trigger on rising and falling edges that needs to read the
> current level of the input to know how to respond, or an
> interrupt that causes a change in a GPIO output in the same
> bank. If the lock is not released before enterring the handler
> the hardware accesses will deadlock when they attempt to grab
> the lock.
>
> Since the lock is only needed to protect the calculation of
> unmasked pending interrupts create a dedicated function to
> perform this and hide the complexity.
>
> Fixes: 19a7b6940b78 ("gpio: brcmstb: Add interrupt and wakeup source support")
> Signed-off-by: Doug Berger <opendmb@...il.com>
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> Acked-by: Gregory Fong <gregory.0xf0@...il.com>

Patch applied.

Yours,
Linus Walleij