From c4b5be98fe78508e7199d6919eb712feba9a4f01 Mon Sep 17 00:00:00 2001
From: Felipe Balbi <felipe.balbi@nokia.com>
Date: Wed, 26 May 2010 14:42:23 -0700
Subject: [PATCH] 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>
---
drivers/gpio/gpiolib.c | 43 ++++++++++++++++++++++++++++++++++++++
include/asm-generic/gpio.h | 5 +++++
include/linux/gpio.h | 5 +++++
3 files changed, 53 insertions(+)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 362a613d266e7..3ca36542e3385 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1447,6 +1447,49 @@ int gpio_direction_output(unsigned gpio, int value)
}
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.
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index fb1ecf8baa90f..4f3d75e1ad391 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -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);
diff --git a/include/linux/gpio.h b/include/linux/gpio.h
index 4e949a5b5b85d..03f616b78cfa8 100644
--- a/include/linux/gpio.h
+++ b/include/linux/gpio.h
@@ -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 */
--
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