linux-kernel - Re: [PATCH] gpio: zynq: properly support runtime PM for GPIO used as interrupts

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Message-ID: <CACRpkdaSbcHAV=3NHYRujC7xEvVcbLJpV+k5sHdvFsRpYFsCbg@mail.gmail.com>
Date:   Wed, 13 Feb 2019 10:37:55 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Michal Simek <michal.simek@...inx.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpio: zynq: properly support runtime PM for GPIO used as interrupts

On Fri, Feb 8, 2019 at 11:40 AM Thomas Petazzoni
<thomas.petazzoni@...tlin.com> wrote:

> The Zynq GPIO driver currently implements runtime PM by:
>
>  - Enabling runtime PM support in ->probe() and letting the runtime PM
>    reference counter drop to zero at the end of ->probe().
>
>  - Increasing the runtime PM reference counter in ->request() and
>    decreasing it in ->free().
>
> However, the latter is not sufficient: when a GPIO is used as an
> interrupt, ->request() and ->free() are not called. Due to this, the
> runtime PM counter remains to zero when the only GPIOs in use are used
> as interrupts, causing them to simply not work.
>
> To address this problem, this commit implement the
> ->irq_request_resources() and ->irq_release_resources() hooks,
> ensuring that the runtime PM counter is properly
> incremented/decremented. Since we override the default hooks, we keep
> the existing behavior by making sure they call gpiochip_reqres_irq() /
> gpiochip_relres_irq() respectively.
>
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@...tlin.com>

Patch applied with Shubhrajyoti's review tag.

Yours,
Linus Walleij