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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: Laxman Dewangan <ldewangan@nvidia.com>
Reviwed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
This commit is contained in:
Laxman Dewangan 2012-02-17 20:26:21 +05:30 committed by Grant Likely
parent 3d2ddfdcf0
commit aca5ce14eb
2 changed files with 45 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
drivers/gpio/gpiolib.c
View File

@ -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
@ -1586,7 +1620,10 @@ void __gpio_set_value(unsigned gpio, int value)
chip = gpio_to_chip(gpio);
WARN_ON(chip->can_sleep);
trace_gpio_value(gpio, 0, value);
chip->set(chip, gpio - chip->base, 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);
@ -1653,7 +1690,10 @@ 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);
chip->set(chip, gpio - chip->base, 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);

3
include/linux/gpio.h
View File

@ -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