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Subject[PATCH V2 3/3] gpio: gpiolib: Support for open source/emitter gpios
Date
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>
---
drivers/gpio/gpiolib.c | 39 +++++++++++++++++++++++++++++++++++++++
include/linux/gpio.h | 3 +++
2 files changed, 42 insertions(+), 0 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 9940777..3b089ef 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -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 */

@@ -1263,6 +1264,7 @@ 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);

@@ -1287,6 +1289,9 @@ 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
@@ -1440,6 +1445,10 @@ 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))
@@ -1601,6 +1610,32 @@ 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
@@ -1619,6 +1654,8 @@ 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);
}
@@ -1689,6 +1726,8 @@ 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);
}
diff --git a/include/linux/gpio.h b/include/linux/gpio.h
index 66a5b2e..67851bb 100644
--- a/include/linux/gpio.h
+++ b/include/linux/gpio.h
@@ -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
--
1.7.1.1


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