[PATCH v2 3/3] gpiolib: Add GPIO initialization

Markus Pargmann
2015-09-21T11:01:00Z

On Sun, Aug 30, 2015 at 09:44:46AM +0200, Markus Pargmann wrote:
> This functions adds a way to initialize a GPIO without hogging it.
>
> Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
> ---
> Documentation/devicetree/bindings/gpio/gpio.txt | 29 +++++++------
> drivers/gpio/gpiolib-of.c | 9 ++++
> drivers/gpio/gpiolib.c | 55 ++++++++++++++++++++-----
> drivers/gpio/gpiolib.h | 2 +
> 4 files changed, 73 insertions(+), 22 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt
> index 5788d5cf1252..55d58983ba43 100644
> --- a/Documentation/devicetree/bindings/gpio/gpio.txt
> +++ b/Documentation/devicetree/bindings/gpio/gpio.txt
> @@ -116,29 +116,34 @@ Every GPIO controller node must contain both an empty "gpio-controller"
> property, and a #gpio-cells integer property, which indicates the number of
> cells in a gpio-specifier.
>
> -The GPIO chip may contain GPIO hog definitions. GPIO hogging is a mechanism
> -providing automatic GPIO request and configuration as part of the
> -gpio-controller's driver probe function.
> +The GPIO chip may contain GPIO definitions. These define properties for single
> +GPIOs of this controller.
>
> -Each GPIO hog definition is represented as a child node of the GPIO controller.
> +GPIO hogging is a mechanism providing automatic GPIO request and configuration
> +as part of the gpio-controller's driver probe function.
> +
> +GPIO initialization provides an automatic initialization to known save values.
> +Instead of GPIO hogging the GPIO's value and direction can be modified by other
> +users after it was initialized.
> +
> +Each GPIO definition is represented as a child node of the GPIO controller.
> Required properties:
> -- gpio-hog: A property specifying that this child node represent a GPIO hog.
> - gpios: Store the GPIO information (id, flags, ...). Shall contain the
> number of cells specified in its parent node (GPIO controller
> node).
> -Only one of the following properties scanned in the order shown below.
> -This means that when multiple properties are present they will be searched
> -in the order presented below and the first match is taken as the intended
> -configuration.
> +
> +Optional properties:
> +- line-name: The GPIO label name. If not present the node name is used.
> + Only one of gpio-hog and gpio-initval may be specified.
> +- gpio-hog: A property specifying that this child node represent a GPIO hog.
> +- gpio-initval: This GPIO should be initialized to the specified configuration.

Any feedback on this new DT binding?

Best Regards,

Markus

> + Only one of input, output-low and output-high may be specified:
> - input: A property specifying to set the GPIO direction as input.
> - output-low A property specifying to set the GPIO direction as output with
> the value low.
> - output-high A property specifying to set the GPIO direction as output with
> the value high.
>
> -Optional properties:
> -- line-name: The GPIO label name. If not present the node name is used.
> -
> Example of two SOC GPIO banks defined as gpio-controller nodes:
>
> qe_pio_a: gpio-controller at 1400 {
> diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
> index f1fe5123da28..ee00c2c63f57 100644
> --- a/drivers/gpio/gpiolib-of.c
> +++ b/drivers/gpio/gpiolib-of.c
> @@ -234,6 +234,15 @@ static void of_gpiochip_scan_gpios(struct gpio_chip *chip)
>
> if (gpiod_hog(desc, lflags, dflags))
> continue;
> + } else if (of_property_read_bool(np, "gpio-initval")) {
> + if (!dflags) {
> + dev_warn(chip->dev, "GPIO line %d (%s): no initialization state specified, bailing out\n",
> + desc_to_gpio(desc), np->name);
> + continue;
> + }
> +
> + if (gpiod_initialize(desc, lflags, dflags))
> + continue;
> }
> }
> }
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index f1559fa72c36..d7aa27a92e82 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -2178,15 +2178,8 @@ struct gpio_desc *__must_check __gpiod_get_index_optional(struct device *dev,
> }
> EXPORT_SYMBOL_GPL(__gpiod_get_index_optional);
>
> -/**
> - * gpiod_hog - Hog the specified GPIO desc given the provided flags
> - * @desc: gpio whose value will be assigned
> - * @lflags: gpio_lookup_flags - returned from of_find_gpio() or
> - * of_get_gpio_hog()
> - * @dflags: gpiod_flags - optional GPIO initialization flags
> - */
> -int gpiod_hog(struct gpio_desc *desc, unsigned long lflags,
> - enum gpiod_flags dflags)
> +static int _gpiod_initialize(struct gpio_desc *desc, unsigned long lflags,
> + enum gpiod_flags dflags)
> {
> int status;
> const char *name = desc->name;
> @@ -2202,11 +2195,31 @@ int gpiod_hog(struct gpio_desc *desc, unsigned long lflags,
> status = gpiod_configure_flags(desc, name, lflags, dflags);
> if (status < 0) {
> pr_err("setup of hog GPIO %s (chip %s, offset %d) failed\n",
> - name, gpiod_to_chip(desc)->label, gpio_chip_hwgpio(desc));
> + name, gpiod_to_chip(desc)->label,
> + gpio_chip_hwgpio(desc));
> gpiochip_free_own_desc(desc);
> return status;
> }
>
> + return 0;
> +}
> +
> +/**
> + * gpiod_hog - Hog the specified GPIO desc given the provided flags
> + * @desc: gpio whose value will be assigned
> + * @lflags: gpio_lookup_flags - returned from of_find_gpio() or
> + * of_get_gpio_hog()
> + * @dflags: gpiod_flags - optional GPIO initialization flags
> + */
> +int gpiod_hog(struct gpio_desc *desc, unsigned long lflags,
> + enum gpiod_flags dflags)
> +{
> + int ret;
> +
> + ret = _gpiod_initialize(desc, lflags, dflags);
> + if (ret)
> + return ret;
> +
> /* Mark GPIO as hogged so it can be identified and removed later */
> set_bit(FLAG_IS_HOGGED, &desc->flags);
>
> @@ -2236,6 +2249,28 @@ static void gpiochip_free_hogs(struct gpio_chip *chip)
> }
>
> /**
> + * gpiod_initialize - Initialize a GPIO with a given value
> + * @desc: gpio whose value will be assigned
> + * @lflags: gpio_lookup_flags - returned from of_find_gpio() or
> + * of_get_gpio_hog()
> + * @dflags: gpiod_flags - optional GPIO initialization flags
> + *
> + * This is used to initialize GPIOs that were defined in DT
> + */
> +int gpiod_initialize(struct gpio_desc *desc, unsigned long lflags,
> + enum gpiod_flags dflags)
> +{
> + int ret;
> +
> + ret = _gpiod_initialize(desc, lflags, dflags);
> + if (ret)
> + return ret;
> +
> + __gpiod_free(desc);
> + return ret;
> +}
> +
> +/**
> * gpiod_get_array - obtain multiple GPIOs from a multi-index GPIO function
> * @dev: GPIO consumer, can be NULL for system-global GPIOs
> * @con_id: function within the GPIO consumer
> diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
> index 6c2aeff59f86..b6dfa3526e3a 100644
> --- a/drivers/gpio/gpiolib.h
> +++ b/drivers/gpio/gpiolib.h
> @@ -99,6 +99,8 @@ int gpiod_request(struct gpio_desc *desc, const char *label);
> void gpiod_free(struct gpio_desc *desc);
> int gpiod_hog(struct gpio_desc *desc, unsigned long lflags,
> enum gpiod_flags dflags);
> +int gpiod_initialize(struct gpio_desc *desc, unsigned long lflags,
> + enum gpiod_flags dflags);
>
> /*
> * Return the GPIO number of the passed descriptor relative to its chip
> --
> 2.5.0
>
>

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