[PATCH v2] pinctrl: sunxi: Implement gpiochip::get_direction()

[Chen-Yu Tsai]

After commit 471e998c0e31 ("gpiolib: remove redundant callback check"),
a warning will be printed if the gpio driver does not implement this
callback. The warning was added in commit e623c4303ed1 ("gpiolib:
sanitize the return value of gpio_chip::get_direction()"), but was
masked by the "redundant" check.

The warning can be triggered by any action that calls the callback,
such as dumping the GPIO state from /sys/kernel/debug/gpio.

Implement it for the sunxi driver. This is simply a matter of reading
out the mux value from the registers, then checking if it is one of
the GPIO functions and which direction it is.

Signed-off-by: Chen-Yu Tsai <wens@xxxxxxxxxx>
Reviewed-by: Jernej Skrabec <jernej.skrabec@xxxxxxxxx>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
---
Please merge for fixes.

Changes since v1:
- Corrected commit attribution for the warning
- Add example scenario that triggers the warning
---
 drivers/pinctrl/sunxi/pinctrl-sunxi.c | 51 +++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/drivers/pinctrl/sunxi/pinctrl-sunxi.c b/drivers/pinctrl/sunxi/pinctrl-sunxi.c
index 0fb057a07dcc..27b2a3e9d78d 100644
--- a/drivers/pinctrl/sunxi/pinctrl-sunxi.c
+++ b/drivers/pinctrl/sunxi/pinctrl-sunxi.c
@@ -204,6 +204,32 @@ sunxi_pinctrl_desc_find_function_by_pin(struct sunxi_pinctrl *pctl,
 	return NULL;
 }
 
+static struct sunxi_desc_function *
+sunxi_pinctrl_desc_find_function_by_pin_and_mux(struct sunxi_pinctrl *pctl,
+						const u16 pin_num,
+						const u8 muxval)
+{
+	for (unsigned int i = 0; i < pctl->desc->npins; i++) {
+		const struct sunxi_desc_pin *pin = pctl->desc->pins + i;
+		struct sunxi_desc_function *func = pin->functions;
+
+		if (pin->pin.number != pin_num)
+			continue;
+
+		if (pin->variant && !(pctl->variant & pin->variant))
+			continue;
+
+		while (func->name) {
+			if (func->muxval == muxval)
+				return func;
+
+			func++;
+		}
+	}
+
+	return NULL;
+}
+
 static int sunxi_pctrl_get_groups_count(struct pinctrl_dev *pctldev)
 {
 	struct sunxi_pinctrl *pctl = pinctrl_dev_get_drvdata(pctldev);
@@ -930,6 +956,30 @@ static const struct pinmux_ops sunxi_pmx_ops = {
 	.strict			= true,
 };
 
+static int sunxi_pinctrl_gpio_get_direction(struct gpio_chip *chip,
+					    unsigned int offset)
+{
+	struct sunxi_pinctrl *pctl = gpiochip_get_data(chip);
+	const struct sunxi_desc_function *func;
+	u32 pin = offset + chip->base;
+	u32 reg, shift, mask;
+	u8 muxval;
+
+	sunxi_mux_reg(pctl, offset, &reg, &shift, &mask);
+
+	muxval = (readl(pctl->membase + reg) & mask) >> shift;
+
+	func = sunxi_pinctrl_desc_find_function_by_pin_and_mux(pctl, pin, muxval);
+	if (!func)
+		return -ENODEV;
+
+	if (!strcmp(func->name, "gpio_out"))
+		return GPIO_LINE_DIRECTION_OUT;
+	if (!strcmp(func->name, "gpio_in") || !strcmp(func->name, "irq"))
+		return GPIO_LINE_DIRECTION_IN;
+	return -EINVAL;
+}
+
 static int sunxi_pinctrl_gpio_direction_input(struct gpio_chip *chip,
 					unsigned offset)
 {
@@ -1601,6 +1651,7 @@ int sunxi_pinctrl_init_with_flags(struct platform_device *pdev,
 	pctl->chip->request = gpiochip_generic_request;
 	pctl->chip->free = gpiochip_generic_free;
 	pctl->chip->set_config = gpiochip_generic_config;
+	pctl->chip->get_direction = sunxi_pinctrl_gpio_get_direction;
 	pctl->chip->direction_input = sunxi_pinctrl_gpio_direction_input;
 	pctl->chip->direction_output = sunxi_pinctrl_gpio_direction_output;
 	pctl->chip->get = sunxi_pinctrl_gpio_get;
-- 
2.47.3