linux-kernel - Re: [PATCH V4 4/5] gpio: gpio-xilinx: Add support for suspend and resume

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CACRpkdaD03pfffqiU1wMVRAu4axQL_VNqM6FrpVHxcN6Tn3XrQ@mail.gmail.com>
Date:   Sat, 9 Jan 2021 01:25:51 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Srinivas Neeli <sneeli@...inx.com>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Michal Simek <michals@...inx.com>,
        Shubhrajyoti Datta <shubhraj@...inx.com>,
        Srinivas Goud <sgoud@...inx.com>,
        Robert Hancock <hancock@...systems.ca>,
        William Breathitt Gray <vilhelm.gray@...il.com>,
        Syed Nayyar Waris <syednwaris@...il.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>,
        git <git@...inx.com>
Subject: Re: [PATCH V4 4/5] gpio: gpio-xilinx: Add support for suspend and resume

On Fri, Jan 8, 2021 at 12:41 PM Srinivas Neeli <sneeli@...inx.com> wrote:
> > On Wed, Jan 6, 2021 at 1:27 PM Srinivas Neeli <srinivas.neeli@...inx.com>
> > wrote:

> > >  /**
> > >   * xgpio_remove - Remove method for the GPIO device.
> > >   * @pdev: pointer to the platform device @@ -289,7 +323,10 @@ static
> > > int xgpio_remove(struct platform_device *pdev)  {
> > >         struct xgpio_instance *gpio = platform_get_drvdata(pdev);
> > >
> > > -       clk_disable_unprepare(gpio->clk);
> > > +       if (!pm_runtime_suspended(&pdev->dev))
> > > +               clk_disable_unprepare(gpio->clk);
> > > +
> > > +       pm_runtime_disable(&pdev->dev);
> >
> > This looks complex and racy. What if the device is resumed after you
> > executed the first part of the statement.
>
> Could you please explain more on this.
> What is the need to call pm_runtime_get_sync(); in remove API ?

I explain that on the lines right below your comment ;D

> > The normal sequence is:
> >
> > pm_runtime_get_sync(dev);
> > pm_runtime_put_noidle(dev);
> > pm_runtime_disable(dev);
> >
> > This will make sure the clock is enabled and pm runtime is disabled.
> > After this you can unconditionally call clk_disable_unprepare(gpio->clk);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Yours,
Linus Walleij