gpio: samsung: add devicetree init for s3c24xx arches

Until now the EXYNOS-SoC was the only Samsung-SoC supporting the GPIOs
via the device tree. This patch implements dt-support for the
s3c24xx arches.

The controllers contain only 3 cells, as the underlying gpio controller
does not support controlling the drive strength on a gpio level.

Tested with the gpio-keys driver on a s3c2416 based machine.
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Thomas Abraham <thomas.abraham@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
[kgene.kim@samsung.com: fixed build error]
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

Documentation/devicetree/bindings/gpio/gpio-samsung.txt

@@ -39,3 +39,46 @@ Example:
 		#gpio-cells = <4>;
 		gpio-controller;
 	};
+
+
+Samsung S3C24XX GPIO Controller
+
+Required properties:
+- compatible: Compatible property value should be "samsung,s3c24xx-gpio".
+
+- reg: Physical base address of the controller and length of memory mapped
+  region.
+
+- #gpio-cells: Should be 3. The syntax of the gpio specifier used by client nodes
+  should be the following with values derived from the SoC user manual.
+     <[phandle of the gpio controller node]
+      [pin number within the gpio controller]
+      [mux function]
+      [flags and pull up/down]
+
+  Values for gpio specifier:
+  - Pin number: depending on the controller a number from 0 up to 15.
+  - Mux function: Depending on the SoC and the gpio bank the gpio can be set
+                  as input, output or a special function
+  - Flags and Pull Up/Down: the values to use differ for the individual SoCs
+                    example S3C2416/S3C2450:
+                            0 - Pull Up/Down Disabled.
+                            1 - Pull Down Enabled.
+                            2 - Pull Up Enabled.
+          Bit 16 (0x00010000) - Input is active low.
+  Consult the user manual for the correct values of Mux and Pull Up/Down.
+
+- gpio-controller: Specifies that the node is a gpio controller.
+- #address-cells: should be 1.
+- #size-cells: should be 1.
+
+Example:
+
+	gpa: gpio-controller@56000000 {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "samsung,s3c24xx-gpio";
+		reg = <0x56000000 0x10>;
+		#gpio-cells = <3>;
+		gpio-controller;
+	};

drivers/gpio/gpio-samsung.c

@@ -938,6 +938,67 @@ static void __init samsung_gpiolib_add(struct samsung_gpio_chip *chip)
 		s3c_gpiolib_track(chip);
 }
 
+#if defined(CONFIG_PLAT_S3C24XX) && defined(CONFIG_OF)
+static int s3c24xx_gpio_xlate(struct gpio_chip *gc,
+			const struct of_phandle_args *gpiospec, u32 *flags)
+{
+	unsigned int pin;
+
+	if (WARN_ON(gc->of_gpio_n_cells < 3))
+		return -EINVAL;
+
+	if (WARN_ON(gpiospec->args_count < gc->of_gpio_n_cells))
+		return -EINVAL;
+
+	if (gpiospec->args[0] > gc->ngpio)
+		return -EINVAL;
+
+	pin = gc->base + gpiospec->args[0];
+
+	if (s3c_gpio_cfgpin(pin, S3C_GPIO_SFN(gpiospec->args[1])))
+		pr_warn("gpio_xlate: failed to set pin function\n");
+	if (s3c_gpio_setpull(pin, gpiospec->args[2] & 0xffff))
+		pr_warn("gpio_xlate: failed to set pin pull up/down\n");
+
+	if (flags)
+		*flags = gpiospec->args[2] >> 16;
+
+	return gpiospec->args[0];
+}
+
+static const struct of_device_id s3c24xx_gpio_dt_match[] __initdata = {
+	{ .compatible = "samsung,s3c24xx-gpio", },
+	{}
+};
+
+static __init void s3c24xx_gpiolib_attach_ofnode(struct samsung_gpio_chip *chip,
+						 u64 base, u64 offset)
+{
+	struct gpio_chip *gc =  &chip->chip;
+	u64 address;
+
+	if (!of_have_populated_dt())
+		return;
+
+	address = chip->base ? base + ((u32)chip->base & 0xfff) : base + offset;
+	gc->of_node = of_find_matching_node_by_address(NULL,
+			s3c24xx_gpio_dt_match, address);
+	if (!gc->of_node) {
+		pr_info("gpio: device tree node not found for gpio controller"
+			" with base address %08llx\n", address);
+		return;
+	}
+	gc->of_gpio_n_cells = 3;
+	gc->of_xlate = s3c24xx_gpio_xlate;
+}
+#else
+static __init void s3c24xx_gpiolib_attach_ofnode(struct samsung_gpio_chip *chip,
+						 u64 base, u64 offset)
+{
+	return;
+}
+#endif /* defined(CONFIG_PLAT_S3C24XX) && defined(CONFIG_OF) */
+
 static void __init s3c24xx_gpiolib_add_chips(struct samsung_gpio_chip *chip,
 					     int nr_chips, void __iomem *base)
 {
@@ -962,6 +1023,8 @@ static void __init s3c24xx_gpiolib_add_chips(struct samsung_gpio_chip *chip,
 			gc->direction_output = samsung_gpiolib_2bit_output;
 
 		samsung_gpiolib_add(chip);
+
+		s3c24xx_gpiolib_attach_ofnode(chip, S3C24XX_PA_GPIO, i * 0x10);
 	}
 }