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Commit d449991c authored by Thomas Petazzoni's avatar Thomas Petazzoni Committed by Linus Walleij
Browse files

gpio: add core support for pull-up/pull-down configuration 



This commit adds support for configuring the pull-up and pull-down
resistors available in some GPIO controllers. While configuring
pull-up/pull-down is already possible through the pinctrl subsystem,
some GPIO controllers, especially simple ones such as GPIO expanders
on I2C, don't have any pinmuxing capability and therefore do not use
the pinctrl subsystem.

This commit implements the GPIO_PULL_UP and GPIO_PULL_DOWN flags,
which can be used from the Device Tree, to enable a pull-up or
pull-down resistor on a given GPIO.

The flag is simply propagated all the way to the core GPIO subsystem,
where it is used to call the gpio_chip ->set_config callback with the
appropriate existing PIN_CONFIG_BIAS_* values.

Signed-off-by: default avatarThomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent 6581eaf0

drivers/gpio/gpiolib-of.c

+5 −0
Original line number Diff line number Diff line
@@ -345,6 +345,11 @@ struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id, 
	if (of_flags & OF_GPIO_TRANSITORY)

		*flags |= GPIO_TRANSITORY;



	if (of_flags & OF_GPIO_PULL_UP)

		*flags |= GPIO_PULL_UP;

	if (of_flags & OF_GPIO_PULL_DOWN)

		*flags |= GPIO_PULL_DOWN;



	return desc;

}

drivers/gpio/gpiolib.c

+18 −0
Original line number Diff line number Diff line
@@ -2573,6 +2573,13 @@ int gpiod_direction_input(struct gpio_desc *desc) 
	if (status == 0)

		clear_bit(FLAG_IS_OUT, &desc->flags);



	if (test_bit(FLAG_PULL_UP, &desc->flags))

		gpio_set_config(chip, gpio_chip_hwgpio(desc),

				PIN_CONFIG_BIAS_PULL_UP);

	else if (test_bit(FLAG_PULL_DOWN, &desc->flags))

		gpio_set_config(chip, gpio_chip_hwgpio(desc),

				PIN_CONFIG_BIAS_PULL_DOWN);



	trace_gpio_direction(desc_to_gpio(desc), 1, status);



	return status;
@@ -4050,6 +4057,17 @@ int gpiod_configure_flags(struct gpio_desc *desc, const char *con_id, 
	if (lflags & GPIO_OPEN_SOURCE)

		set_bit(FLAG_OPEN_SOURCE, &desc->flags);



	if ((lflags & GPIO_PULL_UP) && (lflags & GPIO_PULL_DOWN)) {

		gpiod_err(desc,

			  "both pull-up and pull-down enabled, invalid configuration\n");

		return -EINVAL;

	}



	if (lflags & GPIO_PULL_UP)

		set_bit(FLAG_PULL_UP, &desc->flags);

	else if (lflags & GPIO_PULL_DOWN)

		set_bit(FLAG_PULL_DOWN, &desc->flags);



	status = gpiod_set_transitory(desc, (lflags & GPIO_TRANSITORY));

	if (status < 0)

		return status;

drivers/gpio/gpiolib.h

+2 −0
Original line number Diff line number Diff line
@@ -219,6 +219,8 @@ struct gpio_desc { 
#define FLAG_IRQ_IS_ENABLED 10	/* GPIO is connected to an enabled IRQ */

#define FLAG_IS_HOGGED	11	/* GPIO is hogged */

#define FLAG_TRANSITORY 12	/* GPIO may lose value in sleep or reset */

#define FLAG_PULL_UP    13	/* GPIO has pull up enabled */

#define FLAG_PULL_DOWN  14	/* GPIO has pull down enabled */



	/* Connection label */

	const char		*label;

include/linux/gpio/machine.h

+2 −0
Original line number Diff line number Diff line
@@ -12,6 +12,8 @@ enum gpio_lookup_flags { 
	GPIO_OPEN_SOURCE = (1 << 2),

	GPIO_PERSISTENT = (0 << 3),

	GPIO_TRANSITORY = (1 << 3),

	GPIO_PULL_UP = (1 << 4),

	GPIO_PULL_DOWN = (1 << 5),

};



/**

include/linux/of_gpio.h

+2 −0
Original line number Diff line number Diff line
@@ -28,6 +28,8 @@ enum of_gpio_flags { 
	OF_GPIO_SINGLE_ENDED = 0x2,

	OF_GPIO_OPEN_DRAIN = 0x4,

	OF_GPIO_TRANSITORY = 0x8,

	OF_GPIO_PULL_UP = 0x10,

	OF_GPIO_PULL_DOWN = 0x20,

};



#ifdef CONFIG_OF_GPIO