[PATCH V2] gpio: tegra: Implement gpio_get_direction callback

[Laxman Dewangan <ldewangan@nvidia.com>]

Implement gpio_get_direction() callback for Tegra GPIO.
The direction is only valid if the pin is configured as
GPIO. If pin is not configured in GPIO mode then this
function return error.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>

---
This patch is based on discussion on series
Re: [PATCH V5 0/4] gpio: tegra: Cleanups and support for debounce
>From Linus W:
It would be nice if you also implement .get_direction() which makes
debugfs and initial reading of the state of the lines more accurate.

V1->V2:
- Rearrange the calls to optimise the register access and avoid
 much indenting based on Stephen's and Jon review.

 drivers/gpio/gpio-tegra.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/gpio/gpio-tegra.c b/drivers/gpio/gpio-tegra.c
index b3ddd92..ec891a27 100644
--- a/drivers/gpio/gpio-tegra.c
+++ b/drivers/gpio/gpio-tegra.c
@@ -191,6 +191,21 @@ static int tegra_gpio_direction_output(struct gpio_chip *chip, unsigned offset,
 	return 0;
 }
 
+static int tegra_gpio_get_direction(struct gpio_chip *chip, unsigned offset)
+{
+	struct tegra_gpio_info *tgi = gpiochip_get_data(chip);
+	u32 pin_mask = BIT(GPIO_BIT(offset));
+	u32 cnf, oe;
+
+	cnf = tegra_gpio_readl(tgi, GPIO_CNF(tgi, offset));
+	if (!(cnf & pin_mask))
+		return -EINVAL;
+
+	oe = tegra_gpio_readl(tgi, GPIO_OE(tgi, offset));
+
+	return (oe & pin_mask) ? GPIOF_DIR_OUT : GPIOF_DIR_IN;
+}
+
 static int tegra_gpio_set_debounce(struct gpio_chip *chip, unsigned int offset,
 				   unsigned int debounce)
 {
@@ -575,6 +590,7 @@ static int tegra_gpio_probe(struct platform_device *pdev)
 	tgi->gc.get			= tegra_gpio_get;
 	tgi->gc.direction_output	= tegra_gpio_direction_output;
 	tgi->gc.set			= tegra_gpio_set;
+	tgi->gc.get_direction		= tegra_gpio_get_direction;
 	tgi->gc.to_irq			= tegra_gpio_to_irq;
 	tgi->gc.base			= 0;
 	tgi->gc.ngpio			= tgi->bank_count * 32;
-- 
2.1.4