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authorFelipe Balbi <felipe.balbi@nokia.com>2010-05-26 21:42:23 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2010-05-27 16:12:42 (GMT)
commitc4b5be98fe78508e7199d6919eb712feba9a4f01 (patch)
tree9e688dd076cea9213f8bcbda3627aa7941a01879 /drivers/gpio
parent796a8e423ac8afe9e98ad96e668f50142bdd7825 (diff)
downloadlinux-c4b5be98fe78508e7199d6919eb712feba9a4f01.tar.xz
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: Felipe Balbi <felipe.balbi@nokia.com> Cc: Tony Lindgren <tony@atomide.com> Cc: David Brownell <david-b@pacbell.net> Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/gpio')
-rw-r--r--drivers/gpio/gpiolib.c43
1 files changed, 43 insertions, 0 deletions
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 362a613..3ca3654 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -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.