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Commit aca5ce14 authored by Laxman Dewangan's avatar Laxman Dewangan Committed by Grant Likely
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gpio: gpiolib: Support for open drain/collector gpios 



Adding support for the open drain gpio on which client
can specify the open drain property through GPIO flag
GPIOF_OPEN_DRAIN at the time of gpio request.
The open drain pins are normally pulled high and it
cannot be driven to output with value of 1 and so
when client request for setting the pin to HIGH, the
gpio will be set to input direction to make pin in tristate
and hence PULL-UP on pins will make the state to HIGH.
The open drain pin can be driven to LOW by setting output
with value of 0.

Signed-off-by: default avatarLaxman Dewangan <ldewangan@nvidia.com>
Reviwed-by: default avatarMark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: default avatarGrant Likely <grant.likely@secretlab.ca>
parent 3d2ddfdc

drivers/gpio/gpiolib.c

+42 −2
Original line number Diff line number Diff line
@@ -58,6 +58,7 @@ struct gpio_desc { 
#define FLAG_TRIG_FALL	5	/* trigger on falling edge */

#define FLAG_TRIG_RISE	6	/* trigger on rising edge */

#define FLAG_ACTIVE_LOW	7	/* sysfs value has active low */

#define FLAG_OPEN_DRAIN	8	/* Gpio is open drain type */



#define ID_SHIFT	16	/* add new flags before this one */
@@ -1264,6 +1265,7 @@ void gpio_free(unsigned gpio) 
		module_put(desc->chip->owner);

		clear_bit(FLAG_ACTIVE_LOW, &desc->flags);

		clear_bit(FLAG_REQUESTED, &desc->flags);

		clear_bit(FLAG_OPEN_DRAIN, &desc->flags);

	} else

		WARN_ON(extra_checks);
@@ -1285,6 +1287,9 @@ int gpio_request_one(unsigned gpio, unsigned long flags, const char *label) 
	if (err)

		return err;



	if (flags & GPIOF_OPEN_DRAIN)

		set_bit(FLAG_OPEN_DRAIN, &gpio_desc[gpio].flags);



	if (flags & GPIOF_DIR_IN)

		err = gpio_direction_input(gpio);

	else
@@ -1434,6 +1439,10 @@ int gpio_direction_output(unsigned gpio, int value) 
	struct gpio_desc	*desc = &gpio_desc[gpio];

	int			status = -EINVAL;



	/* Open drain pin should not be driven to 1 */

	if (value && test_bit(FLAG_OPEN_DRAIN,  &desc->flags))

		return gpio_direction_input(gpio);



	spin_lock_irqsave(&gpio_lock, flags);



	if (!gpio_is_valid(gpio))
@@ -1570,6 +1579,31 @@ int __gpio_get_value(unsigned gpio) 
}

EXPORT_SYMBOL_GPL(__gpio_get_value);



/*

 *  _gpio_set_open_drain_value() - Set the open drain gpio's value.

 * @gpio: Gpio whose state need to be set.

 * @chip: Gpio chip.

 * @value: Non-zero for setting it HIGH otherise it will set to LOW.

 */

static void _gpio_set_open_drain_value(unsigned gpio,

			struct gpio_chip *chip, int value)

{

	int err = 0;

	if (value) {

		err = chip->direction_input(chip, gpio - chip->base);

		if (!err)

			clear_bit(FLAG_IS_OUT, &gpio_desc[gpio].flags);

	} else {

		err = chip->direction_output(chip, gpio - chip->base, 0);

		if (!err)

			set_bit(FLAG_IS_OUT, &gpio_desc[gpio].flags);

	}

	trace_gpio_direction(gpio, value, err);

	if (err < 0)

		pr_err("%s: Error in set_value for open drain gpio%d err %d\n",

					__func__, gpio, err);

}



/**

 * __gpio_set_value() - assign a gpio's value

 * @gpio: gpio whose value will be assigned
@@ -1586,6 +1620,9 @@ void __gpio_set_value(unsigned gpio, int value) 
	chip = gpio_to_chip(gpio);

	WARN_ON(chip->can_sleep);

	trace_gpio_value(gpio, 0, value);

	if (test_bit(FLAG_OPEN_DRAIN,  &gpio_desc[gpio].flags))

		_gpio_set_open_drain_value(gpio, chip, value);

	else

		chip->set(chip, gpio - chip->base, value);

}

EXPORT_SYMBOL_GPL(__gpio_set_value);
@@ -1653,6 +1690,9 @@ void gpio_set_value_cansleep(unsigned gpio, int value) 
	might_sleep_if(extra_checks);

	chip = gpio_to_chip(gpio);

	trace_gpio_value(gpio, 0, value);

	if (test_bit(FLAG_OPEN_DRAIN,  &gpio_desc[gpio].flags))

		_gpio_set_open_drain_value(gpio, chip, value);

	else

		chip->set(chip, gpio - chip->base, value);

}

EXPORT_SYMBOL_GPL(gpio_set_value_cansleep);

include/linux/gpio.h

+3 −0
Original line number Diff line number Diff line
@@ -14,6 +14,9 @@ 
#define GPIOF_OUT_INIT_LOW	(GPIOF_DIR_OUT | GPIOF_INIT_LOW)

#define GPIOF_OUT_INIT_HIGH	(GPIOF_DIR_OUT | GPIOF_INIT_HIGH)



/* Gpio pin is open drain */

#define GPIOF_OPEN_DRAIN	(1 << 2)



/**

 * struct gpio - a structure describing a GPIO with configuration

 * @gpio:	the GPIO number