u-boot/doc/device-tree-bindings/gpio/gpio-samsung.txt

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Samsung Exynos4 GPIO Controller
Required properties:
- compatible: Compatible property value should be "samsung,exynos4-gpio>".
- reg: Physical base address of the controller and length of memory mapped
region.
- #gpio-cells: Should be 4. 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]
[drive strength]>
Values for gpio specifier:
- Pin number: is a value between 0 to 7.
- Flags and Pull Up/Down: 0 - Pull Up/Down Disabled.
1 - Pull Down Enabled.
3 - Pull Up Enabled.
Bit 16 (0x00010000) - Input is active low.
- Drive Strength: 0 - 1x,
1 - 3x,
2 - 2x,
3 - 4x
- gpio-controller: Specifies that the node is a gpio controller.
- #address-cells: should be 1.
- #size-cells: should be 1.
Example:
gpa0: gpio-controller@11400000 {
#address-cells = <1>;
#size-cells = <1>;
compatible = "samsung,exynos4-gpio";
reg = <0x11400000 0x20>;
#gpio-cells = <4>;
gpio-controller;
};