diff options
author | Felipe Balbi <felipe.balbi@nokia.com> | 2010-05-26 17:42:23 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-05-27 12:12:42 -0400 |
commit | c4b5be98fe78508e7199d6919eb712feba9a4f01 (patch) | |
tree | 9e688dd076cea9213f8bcbda3627aa7941a01879 /drivers/gpio/gpiolib.c | |
parent | 796a8e423ac8afe9e98ad96e668f50142bdd7825 (diff) |
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/gpiolib.c')
-rw-r--r-- | drivers/gpio/gpiolib.c | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 362a613d266e..3ca36542e338 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c | |||
@@ -1447,6 +1447,49 @@ fail: | |||
1447 | } | 1447 | } |
1448 | EXPORT_SYMBOL_GPL(gpio_direction_output); | 1448 | EXPORT_SYMBOL_GPL(gpio_direction_output); |
1449 | 1449 | ||
1450 | /** | ||
1451 | * gpio_set_debounce - sets @debounce time for a @gpio | ||
1452 | * @gpio: the gpio to set debounce time | ||
1453 | * @debounce: debounce time is microseconds | ||
1454 | */ | ||
1455 | int gpio_set_debounce(unsigned gpio, unsigned debounce) | ||
1456 | { | ||
1457 | unsigned long flags; | ||
1458 | struct gpio_chip *chip; | ||
1459 | struct gpio_desc *desc = &gpio_desc[gpio]; | ||
1460 | int status = -EINVAL; | ||
1461 | |||
1462 | spin_lock_irqsave(&gpio_lock, flags); | ||
1463 | |||
1464 | if (!gpio_is_valid(gpio)) | ||
1465 | goto fail; | ||
1466 | chip = desc->chip; | ||
1467 | if (!chip || !chip->set || !chip->set_debounce) | ||
1468 | goto fail; | ||
1469 | gpio -= chip->base; | ||
1470 | if (gpio >= chip->ngpio) | ||
1471 | goto fail; | ||
1472 | status = gpio_ensure_requested(desc, gpio); | ||
1473 | if (status < 0) | ||
1474 | goto fail; | ||
1475 | |||
1476 | /* now we know the gpio is valid and chip won't vanish */ | ||
1477 | |||
1478 | spin_unlock_irqrestore(&gpio_lock, flags); | ||
1479 | |||
1480 | might_sleep_if(extra_checks && chip->can_sleep); | ||
1481 | |||
1482 | return chip->set_debounce(chip, gpio, debounce); | ||
1483 | |||
1484 | fail: | ||
1485 | spin_unlock_irqrestore(&gpio_lock, flags); | ||
1486 | if (status) | ||
1487 | pr_debug("%s: gpio-%d status %d\n", | ||
1488 | __func__, gpio, status); | ||
1489 | |||
1490 | return status; | ||
1491 | } | ||
1492 | EXPORT_SYMBOL_GPL(gpio_set_debounce); | ||
1450 | 1493 | ||
1451 | /* I/O calls are only valid after configuration completed; the relevant | 1494 | /* I/O calls are only valid after configuration completed; the relevant |
1452 | * "is this a valid GPIO" error checks should already have been done. | 1495 | * "is this a valid GPIO" error checks should already have been done. |