Subject: [REGRESSION] gpio hogging fails with pinctrl gpio drivers

From: Russell King - ARM Linux admin <[email-masked]>
Date: Thu, 6 Feb 2020 17:32:47 +0000

Hi Linus,

It seems that sometime between 4.20 and 5.5, something has broken the
ability to specify gpio-hogs in DT for GPIOs that are written around
pinctrl drivers.

For example:

        gpio6: sx1503@20 {
                compatible = "semtech,sx1503q";
...
                phy_rst {
                        gpio-hog;
                        gpios = <9 GPIO_ACTIVE_HIGH>;
                        output-high;
                        line-name = "10g-rstn";
                };
        };

fails with:

gpio gpiochip7: (sx1503q): setup of own GPIO 10g-rstn failed
requesting hog GPIO 10g-rstn (chip sx1503q, offset 9) failed, -517
gpiochip_add_data_with_key: GPIOs 480..495 (sx1503q) failed to register, -517

It appears that the reason for this failure is that the hogs are
requested in gpiochip_add_data_with_key(), called from
devm_gpiochip_add_data(), but as the set_config method points to
gpiochip_generic_config, it wants to look up the pinctrl pin range
via pinctrl_get_device_gpio_range(). However, that has not been setup
yet, as the following call to gpiochip_add_pin_range() has not been
reached:

        ret = devm_gpiochip_add_data(dev, &pctl->gpio, pctl);
        if (ret)
                return ret;

        ret = gpiochip_add_pin_range(&pctl->gpio, dev_name(dev),
                                     0, 0, pctl->data->npins);

and so pinctrl_get_device_gpio_range() returns -EPROBE_DEFER.

Consequently, adding a gpio-hog to DT for this driver results in the
driver endlessly returning -EPROBE_DEFER.

-- 
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