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SubjectRE: [PATCH V4 4/5] gpio: gpio-xilinx: Add support for suspend and resume
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Hi Linus,

> -----Original Message-----
> From: Linus Walleij <linus.walleij@linaro.org>
> Sent: Thursday, January 7, 2021 3:17 PM
> To: Srinivas Neeli <sneeli@xilinx.com>
> Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>; Michal Simek
> <michals@xilinx.com>; Shubhrajyoti Datta <shubhraj@xilinx.com>; Srinivas
> Goud <sgoud@xilinx.com>; Robert Hancock <hancock@sedsystems.ca>;
> William Breathitt Gray <vilhelm.gray@gmail.com>; Syed Nayyar Waris
> <syednwaris@gmail.com>; open list:GPIO SUBSYSTEM <linux-
> gpio@vger.kernel.org>; Linux ARM <linux-arm-kernel@lists.infradead.org>;
> linux-kernel@vger.kernel.org; git <git@xilinx.com>
> Subject: Re: [PATCH V4 4/5] gpio: gpio-xilinx: Add support for suspend and
> resume
>
> On Wed, Jan 6, 2021 at 1:27 PM Srinivas Neeli <srinivas.neeli@xilinx.com>
> wrote:
>
> > Add support for suspend and resume, pm runtime suspend and resume.
> > Added free and request calls.
> >
> > Signed-off-by: Srinivas Neeli <srinivas.neeli@xilinx.com>
> (...)
>
> > +static int xgpio_request(struct gpio_chip *chip, unsigned int offset)
> > +{
> > + int ret;
> > +
> > + ret = pm_runtime_get_sync(chip->parent);
> > + /*
> > + * If the device is already active pm_runtime_get() will return 1 on
> > + * success, but gpio_request still needs to return 0.
> > + */
> > + return ret < 0 ? ret : 0;
> > +}
>
> That's clever. I think more GPIO drivers should be doing it like this, today I
> think most just ignore the return code.
>
> > +static int __maybe_unused xgpio_suspend(struct device *dev) static
> > +int __maybe_unused xgpio_resume(struct device *dev)
>
> Those look good.
>
>
> > /**
> > * 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 ?

>
> 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);
>
> It is what you are doing on the errorpath of probe().
>
> Yours,
> Linus Walleij
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