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+ASPEED AST2400/AST2500 PWM and Fan Tacho controller device driver
+
+The ASPEED PWM controller can support upto 8 PWM outputs. The ASPEED Fan Tacho
+controller can support upto 16 Fan tachometer inputs.
+
+There can be upto 8 fans supported. Each fan can have one PWM output and
+one/two Fan tach inputs.
+
+Required properties for pwm-tacho node:
+- #address-cells : should be 1.
+
+- #size-cells : should be 1.
+
+- #cooling-cells: should be 2.
+
+- reg : address and length of the register set for the device.
+
+- pinctrl-names : a pinctrl state named "default" must be defined.
+
+- pinctrl-0 : phandle referencing pin configuration of the PWM ports.
+
+- compatible : should be "aspeed,ast2400-pwm-tacho" for AST2400 and
+	       "aspeed,ast2500-pwm-tacho" for AST2500.
+
+- clocks : phandle to clock provider with the clock number in the second cell
+
+- resets : phandle to reset controller with the reset number in the second cell
+
+fan subnode format:
+===================
+Under fan subnode there can upto 8 child nodes, with each child node
+representing a fan. If there are 8 fans each fan can have one PWM port and
+one/two Fan tach inputs.
+For PWM port can be configured cooling-levels to create cooling device.
+Cooling device could be bound to a thermal zone for the thermal control.
+
+Required properties for each child node:
+- reg : should specify PWM source port.
+	integer value in the range 0 to 7 with 0 indicating PWM port A and
+	7 indicating PWM port H.
+
+- cooling-levels: PWM duty cycle values in a range from 0 to 255
+                  which correspond to thermal cooling states.
+
+- aspeed,fan-tach-ch : should specify the Fan tach input channel.
+                integer value in the range 0 through 15, with 0 indicating
+		Fan tach channel 0 and 15 indicating Fan tach channel 15.
+		Atleast one Fan tach input channel is required.
+
+Examples:
+
+pwm_tacho: pwmtachocontroller@1e786000 {
+	#address-cells = <1>;
+	#size-cells = <1>;
+	#cooling-cells = <2>;
+	reg = <0x1E786000 0x1000>;
+	compatible = "aspeed,ast2500-pwm-tacho";
+	clocks = <&syscon ASPEED_CLK_APB>;
+	resets = <&syscon ASPEED_RESET_PWM>;
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_pwm0_default &pinctrl_pwm1_default>;
+
+	fan@0 {
+		reg = <0x00>;
+		cooling-levels = /bits/ 8 <125 151 177 203 229 255>;
+		aspeed,fan-tach-ch = /bits/ 8 <0x00>;
+	};
+
+	fan@1 {
+		reg = <0x01>;
+		aspeed,fan-tach-ch = /bits/ 8 <0x01 0x02>;
+	};
+};