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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 : a fixed clock providing input clock frequency(PWM
and Fan Tach clock)
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_fixed_clk: fixedclk {
compatible = "fixed-clock";
#clock-cells = <0>;
clock-frequency = <24000000>;
};
pwm_tacho: pwmtachocontroller@1e786000 {
#address-cells = <1>;
#size-cells = <1>;
#cooling-cells = <2>;
reg = <0x1E786000 0x1000>;
compatible = "aspeed,ast2500-pwm-tacho";
clocks = <&pwm_tacho_fixed_clk>;
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>;
};
};
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