dt-bindings: pwm: Add MediaTek display PWM bindings

Document the device-tree binding of MediaTek display PWM. The PWM has
one channel to control the backlight brightness for display. Both the
MT8173 and MT6595 are supported.

Signed-off-by: YH Huang <yh.huang@mediatek.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

diff --git a/Documentation/devicetree/bindings/pwm/pwm-mtk-disp.txt b/Documentation/devicetree/bindings/pwm/pwm-mtk-disp.txt
new file mode 100644 (file)
index 0000000..f8f59ba
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/pwm-mtk-disp.txt
@@ -0,0 +1,42 @@
+MediaTek display PWM controller
+
+Required properties:
+ - compatible: should be "mediatek,<name>-disp-pwm":
+   - "mediatek,mt8173-disp-pwm": found on mt8173 SoC.
+   - "mediatek,mt6595-disp-pwm": found on mt6595 SoC.
+ - reg: physical base address and length of the controller's registers.
+ - #pwm-cells: must be 2. See pwm.txt in this directory for a description of
+   the cell format.
+ - clocks: phandle and clock specifier of the PWM reference clock.
+ - clock-names: must contain the following:
+   - "main": clock used to generate PWM signals.
+   - "mm": sync signals from the modules of mmsys.
+ - pinctrl-names: Must contain a "default" entry.
+ - pinctrl-0: One property must exist for each entry in pinctrl-names.
+   See pinctrl/pinctrl-bindings.txt for details of the property values.
+
+Example:
+       pwm0: pwm@1401e000 {
+               compatible = "mediatek,mt8173-disp-pwm",
+                            "mediatek,mt6595-disp-pwm";
+               reg = <0 0x1401e000 0 0x1000>;
+               #pwm-cells = <2>;
+               clocks = <&mmsys CLK_MM_DISP_PWM026M>,
+                        <&mmsys CLK_MM_DISP_PWM0MM>;
+               clock-names = "main", "mm";
+               pinctrl-names = "default";
+               pinctrl-0 = <&disp_pwm0_pins>;
+       };
+
+       backlight_lcd: backlight_lcd {
+               compatible = "pwm-backlight";
+               pwms = <&pwm0 0 1000000>;
+               brightness-levels = <
+                         0  16  32  48  64  80  96 112
+                       128 144 160 176 192 208 224 240
+                       255
+               >;
+               default-brightness-level = <9>;
+               power-supply = <&mt6397_vio18_reg>;
+               enable-gpios = <&pio 95 GPIO_ACTIVE_HIGH>;
+       };