gpio: gpiolib: Support for open source/emitter gpios

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>

1 files changed, 39 insertions, 0 deletions

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 5d25a33d5359..58f40dfc5265 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 */
 
@@ -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);
 }