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-rw-r--r--doc/device-tree-bindings/gpio/gpio-samsung.txt41
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diff --git a/doc/device-tree-bindings/gpio/gpio-samsung.txt b/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;
+ };