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Commit c4b5be98 authored by Felipe Balbi's avatar Felipe Balbi Committed by Linus Torvalds
Browse files

gpiolib: introduce set_debounce method 



A few architectures, like OMAP, allow you to set a debouncing time for the
gpio before generating the IRQ.  Teach gpiolib about that.

Mark said:
: This would be generally useful for embedded systems, especially where
: the interrupt concerned is a wake source.  It allows drivers to avoid
: spurious interrupts from noisy sources so if the hardware supports it
: the driver can avoid having to explicitly wait for the signal to become
: stable and software has to cope with fewer events.  We've lived without
: it for quite some time, though.

David said:
: I looked at adding debounce support to the generic GPIO calls (and thus
: gpiolib) some time back, but decided against it.  I forget why at this
: time (check list archives) but it wasn't because of lack of utility in
: certain contexts.
:
: One thing to watch out for is just how variable the hardware capabilities
: are.  Atmel GPIOs have something like a fixed number of 32K clock cycles
: for debounce, twl4030 had something odd, OMAPs were more like the Atmel
: chips but with a different clock.  In some cases debouncing had to be
: ganged, not per-GPIO.  And so forth.

Signed-off-by: default avatarFelipe Balbi <felipe.balbi@nokia.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: David Brownell <david-b@pacbell.net>
Reviewed-by: default avatarMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 796a8e42

drivers/gpio/gpiolib.c

+43 −0
Original line number Diff line number Diff line
@@ -1447,6 +1447,49 @@ fail: 
}

EXPORT_SYMBOL_GPL(gpio_direction_output);



/**

 * gpio_set_debounce - sets @debounce time for a @gpio

 * @gpio: the gpio to set debounce time

 * @debounce: debounce time is microseconds

 */

int gpio_set_debounce(unsigned gpio, unsigned debounce)

{

	unsigned long		flags;

	struct gpio_chip	*chip;

	struct gpio_desc	*desc = &gpio_desc[gpio];

	int			status = -EINVAL;



	spin_lock_irqsave(&gpio_lock, flags);



	if (!gpio_is_valid(gpio))

		goto fail;

	chip = desc->chip;

	if (!chip || !chip->set || !chip->set_debounce)

		goto fail;

	gpio -= chip->base;

	if (gpio >= chip->ngpio)

		goto fail;

	status = gpio_ensure_requested(desc, gpio);

	if (status < 0)

		goto fail;



	/* now we know the gpio is valid and chip won't vanish */



	spin_unlock_irqrestore(&gpio_lock, flags);



	might_sleep_if(extra_checks && chip->can_sleep);



	return chip->set_debounce(chip, gpio, debounce);



fail:

	spin_unlock_irqrestore(&gpio_lock, flags);

	if (status)

		pr_debug("%s: gpio-%d status %d\n",

			__func__, gpio, status);



	return status;

}

EXPORT_SYMBOL_GPL(gpio_set_debounce);



/* I/O calls are only valid after configuration completed; the relevant

 * "is this a valid GPIO" error checks should already have been done.

include/asm-generic/gpio.h

+5 −0
Original line number Diff line number Diff line
@@ -90,6 +90,9 @@ struct gpio_chip { 
						unsigned offset);

	int			(*direction_output)(struct gpio_chip *chip,

						unsigned offset, int value);

	int			(*set_debounce)(struct gpio_chip *chip,

						unsigned offset, unsigned debounce);



	void			(*set)(struct gpio_chip *chip,

						unsigned offset, int value);
@@ -123,6 +126,8 @@ extern void gpio_free(unsigned gpio); 
extern int gpio_direction_input(unsigned gpio);

extern int gpio_direction_output(unsigned gpio, int value);



extern int gpio_set_debounce(unsigned gpio, unsigned debounce);



extern int gpio_get_value_cansleep(unsigned gpio);

extern void gpio_set_value_cansleep(unsigned gpio, int value);

include/linux/gpio.h

+5 −0
Original line number Diff line number Diff line
@@ -51,6 +51,11 @@ static inline int gpio_direction_output(unsigned gpio, int value) 
	return -ENOSYS;

}



static inline int gpio_set_debounce(unsigned gpio, unsigned debounce)

{

	return -ENOSYS;

}



static inline int gpio_get_value(unsigned gpio)

{

	/* GPIO can never have been requested or set as {in,out}put */