1ASPEED AST2400/AST2500 PWM and Fan Tacho controller device driver
2
3The ASPEED PWM controller can support upto 8 PWM outputs. The ASPEED Fan Tacho
4controller can support upto 16 Fan tachometer inputs.
5
6There can be upto 8 fans supported. Each fan can have one PWM output and
7one/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 and
23	       "aspeed,ast2500-pwm-tacho" for AST2500.
24
25- clocks : phandle to clock provider with the clock number in the second cell
26
27- resets : phandle to reset controller with the reset number in the second cell
28
29fan subnode format:
30===================
31Under fan subnode there can upto 8 child nodes, with each child node
32representing a fan. If there are 8 fans each fan can have one PWM port and
33one/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 and
40	7 indicating PWM port H.
41
42- cooling-levels: PWM duty cycle values in a range from 0 to 255
43                  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 indicating
47		Fan tach channel 0 and 15 indicating Fan tach channel 15.
48		Atleast 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