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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: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Thomas Petazzoni 2019-02-07 17:28:58 +01:00 committed by Linus Walleij
parent 6581eaf0e8
commit d449991c4d
5 changed files with 29 additions and 0 deletions
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5
drivers/gpio/gpiolib-of.c
View File

@ -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;
}

18
drivers/gpio/gpiolib.c
View File

@ -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;

2
drivers/gpio/gpiolib.h
View File

@ -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;

2
include/linux/gpio/machine.h
View File

@ -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),
};
/**

2
include/linux/of_gpio.h
View File

@ -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