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gpio: gpiolib: Support for open source/emitter gpios

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Adding support for the open source gpio on which client
can specify the open source property through GPIO flag
GPIOF_OPEN_SOURCE at the time of gpio request.
The open source pins are normally pulled low and it
cannot be driven to output with value of 0 and so
when client request for setting the pin to LOW, the
gpio will be set to input direction to make pin in tristate
and hence PULL-DOWN on pins will make the state to LOW.
The open source pin can be driven to HIGH by setting output
with value of 1.

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 20:26:22 +05:30 committed by Grant Likely
parent aca5ce14eb
commit 25553ff075
2 changed files with 42 additions and 0 deletions
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39
drivers/gpio/gpiolib.c
View File

@ -59,6 +59,7 @@ struct gpio_desc {
#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 FLAG_OPEN_SOURCE 9 /* Gpio is open source type */
#define ID_SHIFT 16 /* add new flags before this one */
@ -1266,6 +1267,7 @@ void gpio_free(unsigned gpio)
clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
clear_bit(FLAG_REQUESTED, &desc->flags);
clear_bit(FLAG_OPEN_DRAIN, &desc->flags);
clear_bit(FLAG_OPEN_SOURCE, &desc->flags);
} else
WARN_ON(extra_checks);
@ -1290,6 +1292,9 @@ int gpio_request_one(unsigned gpio, unsigned long flags, const char *label)
if (flags & GPIOF_OPEN_DRAIN)
set_bit(FLAG_OPEN_DRAIN, &gpio_desc[gpio].flags);
if (flags & GPIOF_OPEN_SOURCE)
set_bit(FLAG_OPEN_SOURCE, &gpio_desc[gpio].flags);
if (flags & GPIOF_DIR_IN)
err = gpio_direction_input(gpio);
else
@ -1443,6 +1448,10 @@ int gpio_direction_output(unsigned gpio, int value)
if (value && test_bit(FLAG_OPEN_DRAIN, &desc->flags))
return gpio_direction_input(gpio);
/* Open source pin should not be driven to 0 */
if (!value && test_bit(FLAG_OPEN_SOURCE, &desc->flags))
return gpio_direction_input(gpio);
spin_lock_irqsave(&gpio_lock, flags);
if (!gpio_is_valid(gpio))
@ -1604,6 +1613,32 @@ static void _gpio_set_open_drain_value(unsigned gpio,
__func__, gpio, err);
}
/*
* _gpio_set_open_source() - Set the open source 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_source_value(unsigned gpio,
struct gpio_chip *chip, int value)
{
int err = 0;
if (value) {
err = chip->direction_output(chip, gpio - chip->base, 1);
if (!err)
set_bit(FLAG_IS_OUT, &gpio_desc[gpio].flags);
} else {
err = chip->direction_input(chip, gpio - chip->base);
if (!err)
clear_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 source gpio%d err %d\n",
__func__, gpio, err);
}
/**
* __gpio_set_value() - assign a gpio's value
* @gpio: gpio whose value will be assigned
@ -1622,6 +1657,8 @@ void __gpio_set_value(unsigned gpio, int value)
trace_gpio_value(gpio, 0, value);
if (test_bit(FLAG_OPEN_DRAIN, &gpio_desc[gpio].flags))
_gpio_set_open_drain_value(gpio, chip, value);
else if (test_bit(FLAG_OPEN_SOURCE, &gpio_desc[gpio].flags))
_gpio_set_open_source_value(gpio, chip, value);
else
chip->set(chip, gpio - chip->base, value);
}
@ -1692,6 +1729,8 @@ void gpio_set_value_cansleep(unsigned gpio, int value)
trace_gpio_value(gpio, 0, value);
if (test_bit(FLAG_OPEN_DRAIN, &gpio_desc[gpio].flags))
_gpio_set_open_drain_value(gpio, chip, value);
else if (test_bit(FLAG_OPEN_SOURCE, &gpio_desc[gpio].flags))
_gpio_set_open_source_value(gpio, chip, value);
else
chip->set(chip, gpio - chip->base, value);
}

3
include/linux/gpio.h
View File

@ -17,6 +17,9 @@
/* Gpio pin is open drain */
#define GPIOF_OPEN_DRAIN (1 << 2)
/* Gpio pin is open source */
#define GPIOF_OPEN_SOURCE (1 << 3)
/**
* struct gpio - a structure describing a GPIO with configuration
* @gpio: the GPIO number