pinctrl: rockchip: add support the get_direction

This patch adds the get_direction to support the gpio
interface.

The gpio direction is not used on rockchip platform when use the gpio
debugfs.

Tested on kylin board. (RK3036 SoCs)
The repro steps:
$/sys/class/gpio/
echo 53 > export
$/sys/class/gpio/gpio53# cat direction
in
In general, the gpio53 should be out value, but the direction is the
default value 'in',  since the get_direction didn't supported in rockchip
pinctrl.

So, we should add this patch to support it.

Cc: linux-gpio@vger.kernel.org
Cc: linux-rockchip@lists.infradead.org
Reported-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinctrl-rockchip.c

@@ -1208,6 +1208,16 @@ static int rockchip_pmx_set(struct pinctrl_dev *pctldev, unsigned selector,
 	return 0;
 }
 
+static int rockchip_gpio_get_direction(struct gpio_chip *chip, unsigned offset)
+{
+	struct rockchip_pin_bank *bank = gpiochip_get_data(chip);
+	u32 data;
+
+	data = readl_relaxed(bank->reg_base + GPIO_SWPORT_DDR);
+
+	return !(data & BIT(offset));
+}
+
 /*
  * The calls to gpio_direction_output() and gpio_direction_input()
  * leads to this function call (via the pinctrl_gpio_direction_{input|output}()
@@ -1741,6 +1751,7 @@ static const struct gpio_chip rockchip_gpiolib_chip = {
 	.free = gpiochip_generic_free,
 	.set = rockchip_gpio_set,
 	.get = rockchip_gpio_get,
+	.get_direction	= rockchip_gpio_get_direction,
 	.direction_input = rockchip_gpio_direction_input,
 	.direction_output = rockchip_gpio_direction_output,
 	.to_irq = rockchip_gpio_to_irq,