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>
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index e633a2a..5d25a33d 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -58,6 +58,7 @@
#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 @@
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 @@
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 @@
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 @@
}
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 @@
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 @@
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);
