linux-kernel - Re: [PATCH v1] gpiolib: Don't probe gpio_device if it's not the primary device

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Message-ID: <CAMRc=Mci+LThvb5M5hmzjoCNSK1EAqZEqo7YU9Gp5Mo0FSRggw@mail.gmail.com>
Date:   Fri, 5 Feb 2021 11:02:04 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dmitry Osipenko <digetx@...il.com>, kernel-team@...roid.com,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] gpiolib: Don't probe gpio_device if it's not the
 primary device

On Fri, Feb 5, 2021 at 3:08 AM Saravana Kannan <saravanak@...gle.com> wrote:
>
> Dmitry reported[1] boot error messages caused by
> commit 4731210c09f5 ("gpiolib: Bind gpio_device to a driver to enable fw_devlink=on by default").
>
> gpio-1022 (cpu-pwr-req-hog): hogged as input
> max77620-pinctrl max77620-pinctrl: pin gpio4 already requested by max77620-pinctrl; cannot claim for gpiochip1
> max77620-pinctrl max77620-pinctrl: pin-4 (gpiochip1) status -22
> max77620-pinctrl max77620-pinctrl: could not request pin 4 (gpio4) from group gpio4  on device max77620-pinctrl
> gpio_stub_drv gpiochip1: Error applying setting, reverse things back
> gpio_stub_drv: probe of gpiochip1 failed with error -22
>
> This happens because when we try to probe a device, driver core calls
> into pinctrl to set up the pins. However, if the GPIO DT node already
> has a proper device created and probed, trying to probe the gpio_device
> with a stub driver makes the pins be claimed twice. pinctrl doesn't like
> this and throws an error.
>
> So, this patch makes sure the gpio_stub_drv doesn't match with a
> gpio_device if it's not the primary device for the fwnode.
>
> [1] - https://lore.kernel.org/lkml/544ad0e4-0954-274c-8e77-866aaa5661a8@gmail.com/
> Fixes: 4731210c09f5 ("gpiolib: Bind gpio_device to a driver to enable fw_devlink=on by default")
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> Tested-by: Dmitry Osipenko <digetx@...il.com>
> ---
> Greg/Linus,
>
> This will need to go into driver-core because the Fixes is in
> driver-core too.
>
> Thanks,
> Saravana
>
>  drivers/gpio/gpiolib.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 8e0564c50840..8ad679a928b0 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -56,8 +56,10 @@
>  static DEFINE_IDA(gpio_ida);
>  static dev_t gpio_devt;
>  #define GPIO_DEV_MAX 256 /* 256 GPIO chip devices supported */
> +static int gpio_bus_match(struct device *dev, struct device_driver *drv);
>  static struct bus_type gpio_bus_type = {
>         .name = "gpio",
> +       .match = gpio_bus_match,
>  };
>
>  /*
> @@ -4199,6 +4201,18 @@ void gpiod_put_array(struct gpio_descs *descs)
>  }
>  EXPORT_SYMBOL_GPL(gpiod_put_array);
>
> +
> +static int gpio_bus_match(struct device *dev, struct device_driver *drv)
> +{
> +       /*
> +        * Only match if the fwnode doesn't already have a proper struct device
> +        * created for it.
> +        */
> +       if (dev->fwnode && dev->fwnode->dev != dev)
> +               return 0;
> +       return 1;
> +}
> +
>  static int gpio_stub_drv_probe(struct device *dev)
>  {
>         /*
> --
> 2.30.0.365.g02bc693789-goog
>

Acked-by: Bartosz Golaszewski <bgolaszewski@...libre.com>