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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt
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ASPEED AST2400/AST2500 PWM and Fan Tacho controller device driver

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The ASPEED PWM controller can support upto 8 PWM outputs. The ASPEED Fan Tacho

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controller can support upto 16 Fan tachometer inputs.

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There can be upto 8 fans supported. Each fan can have one PWM output and

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one/two Fan tach inputs.

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Required properties for pwm-tacho node:

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- #address-cells : should be 1.

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- #size-cells : should be 1.

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- #cooling-cells: should be 2.

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- reg : address and length of the register set for the device.

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- pinctrl-names : a pinctrl state named "default" must be defined.

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- pinctrl-0 : phandle referencing pin configuration of the PWM ports.

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- compatible : should be "aspeed,ast2400-pwm-tacho" for AST2400 and

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	       "aspeed,ast2500-pwm-tacho" for AST2500.

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- clocks : phandle to clock provider with the clock number in the second cell

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- resets : phandle to reset controller with the reset number in the second cell

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fan subnode format:

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===================

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Under fan subnode there can upto 8 child nodes, with each child node

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representing a fan. If there are 8 fans each fan can have one PWM port and

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one/two Fan tach inputs.

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For PWM port can be configured cooling-levels to create cooling device.

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Cooling device could be bound to a thermal zone for the thermal control.

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Required properties for each child node:

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- reg : should specify PWM source port.

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	integer value in the range 0 to 7 with 0 indicating PWM port A and

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	7 indicating PWM port H.

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- cooling-levels: PWM duty cycle values in a range from 0 to 255

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                  which correspond to thermal cooling states.

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- aspeed,fan-tach-ch : should specify the Fan tach input channel.

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                integer value in the range 0 through 15, with 0 indicating

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		Fan tach channel 0 and 15 indicating Fan tach channel 15.

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		At least one Fan tach input channel is required.

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Examples:

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pwm_tacho: pwmtachocontroller@1e786000 {

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	#address-cells = <1>;

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	#size-cells = <1>;

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	#cooling-cells = <2>;

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	reg = <0x1E786000 0x1000>;

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	compatible = "aspeed,ast2500-pwm-tacho";

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	clocks = <&syscon ASPEED_CLK_APB>;

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	resets = <&syscon ASPEED_RESET_PWM>;

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	pinctrl-names = "default";

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	pinctrl-0 = <&pinctrl_pwm0_default &pinctrl_pwm1_default>;

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	fan@0 {

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		reg = <0x00>;

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		cooling-levels = /bits/ 8 <125 151 177 203 229 255>;

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		aspeed,fan-tach-ch = /bits/ 8 <0x00>;

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	};

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	fan@1 {

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		reg = <0x01>;

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		aspeed,fan-tach-ch = /bits/ 8 <0x01 0x02>;

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	};

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};

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