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1ASPEED AST2400/AST2500 PWM and Fan Tacho controller device driver2 3The ASPEED PWM controller can support upto 8 PWM outputs. The ASPEED Fan Tacho4controller can support upto 16 Fan tachometer inputs.5 6There can be upto 8 fans supported. Each fan can have one PWM output and7one/two Fan tach inputs.8 9Required properties for pwm-tacho node:10- #address-cells : should be 1.11 12- #size-cells : should be 1.13 14- #cooling-cells: should be 2.15 16- reg : address and length of the register set for the device.17 18- pinctrl-names : a pinctrl state named "default" must be defined.19 20- pinctrl-0 : phandle referencing pin configuration of the PWM ports.21 22- compatible : should be "aspeed,ast2400-pwm-tacho" for AST2400 and23 "aspeed,ast2500-pwm-tacho" for AST2500.24 25- clocks : phandle to clock provider with the clock number in the second cell26 27- resets : phandle to reset controller with the reset number in the second cell28 29fan subnode format:30===================31Under fan subnode there can upto 8 child nodes, with each child node32representing a fan. If there are 8 fans each fan can have one PWM port and33one/two Fan tach inputs.34For PWM port can be configured cooling-levels to create cooling device.35Cooling device could be bound to a thermal zone for the thermal control.36 37Required properties for each child node:38- reg : should specify PWM source port.39 integer value in the range 0 to 7 with 0 indicating PWM port A and40 7 indicating PWM port H.41 42- cooling-levels: PWM duty cycle values in a range from 0 to 25543 which correspond to thermal cooling states.44 45- aspeed,fan-tach-ch : should specify the Fan tach input channel.46 integer value in the range 0 through 15, with 0 indicating47 Fan tach channel 0 and 15 indicating Fan tach channel 15.48 At least one Fan tach input channel is required.49 50Examples:51 52pwm_tacho: pwmtachocontroller@1e786000 {53 #address-cells = <1>;54 #size-cells = <1>;55 #cooling-cells = <2>;56 reg = <0x1E786000 0x1000>;57 compatible = "aspeed,ast2500-pwm-tacho";58 clocks = <&syscon ASPEED_CLK_APB>;59 resets = <&syscon ASPEED_RESET_PWM>;60 pinctrl-names = "default";61 pinctrl-0 = <&pinctrl_pwm0_default &pinctrl_pwm1_default>;62 63 fan@0 {64 reg = <0x00>;65 cooling-levels = /bits/ 8 <125 151 177 203 229 255>;66 aspeed,fan-tach-ch = /bits/ 8 <0x00>;67 };68 69 fan@1 {70 reg = <0x01>;71 aspeed,fan-tach-ch = /bits/ 8 <0x01 0x02>;72 };73};74