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

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Date:   Fri, 12 Feb 2021 10:37:25 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dmitry Osipenko <digetx@...il.com>,
        Android Kernel Team <kernel-team@...roid.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <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 3:07 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.

OK that seems to be the right solution. Maybe I would try to
explain the situation in the comment in gpio_bus_match
a bit more, but anyway:
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij