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 : a fixed clock providing input clock frequency(PWM
26	   and Fan Tach clock)
27
28fan subnode format:
29===================
30Under fan subnode there can upto 8 child nodes, with each child node
31representing a fan. If there are 8 fans each fan can have one PWM port and
32one/two Fan tach inputs.
33For PWM port can be configured cooling-levels to create cooling device.
34Cooling device could be bound to a thermal zone for the thermal control.
35
36Required properties for each child node:
37- reg : should specify PWM source port.
38	integer value in the range 0 to 7 with 0 indicating PWM port A and
39	7 indicating PWM port H.
40
41- cooling-levels: PWM duty cycle values in a range from 0 to 255
42                  which correspond to thermal cooling states.
43
44- aspeed,fan-tach-ch : should specify the Fan tach input channel.
45                integer value in the range 0 through 15, with 0 indicating
46		Fan tach channel 0 and 15 indicating Fan tach channel 15.
47		Atleast one Fan tach input channel is required.
48
49Examples:
50
51pwm_tacho_fixed_clk: fixedclk {
52	compatible = "fixed-clock";
53	#clock-cells = <0>;
54	clock-frequency = <24000000>;
55};
56
57pwm_tacho: pwmtachocontroller@1e786000 {
58	#address-cells = <1>;
59	#size-cells = <1>;
60	#cooling-cells = <2>;
61	reg = <0x1E786000 0x1000>;
62	compatible = "aspeed,ast2500-pwm-tacho";
63	clocks = <&pwm_tacho_fixed_clk>;
64	pinctrl-names = "default";
65	pinctrl-0 = <&pinctrl_pwm0_default &pinctrl_pwm1_default>;
66
67	fan@0 {
68		reg = <0x00>;
69		cooling-levels = /bits/ 8 <125 151 177 203 229 255>;
70		aspeed,fan-tach-ch = /bits/ 8 <0x00>;
71	};
72
73	fan@1 {
74		reg = <0x01>;
75		aspeed,fan-tach-ch = /bits/ 8 <0x01 0x02>;
76	};
77};
78