[PATCH 1/4] dt-bindings: hwmon: Add Aspeed AST2600 PWM/Fan

[Troy Lee <troy_lee@aspeedtech.com>]

For supporting a new AST2600 PWM/Fan hwmon driver, we add a new binding.

Signed-off-by: Troy Lee <troy_lee@aspeedtech.com>
---
 .../bindings/hwmon/aspeed2600-pwm-tacho.txt   | 69 +++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/aspeed2600-pwm-tacho.txt

diff --git a/Documentation/devicetree/bindings/hwmon/aspeed2600-pwm-tacho.txt b/Documentation/devicetree/bindings/hwmon/aspeed2600-pwm-tacho.txt
new file mode 100644
index 000000000000..61b11914352f
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/aspeed2600-pwm-tacho.txt
@@ -0,0 +1,69 @@
+ASPEED AST2600 PWM and Fan Tacho controller device driver
+
+The ASPEED PWM controller can support upto 16 PWM outputs. The ASPEED Fan Tacho
+controller can support upto 16 Fan tachometer inputs.
+
+There can be upto 16 fans supported. Each fan can have one PWM output and
+one Fan tach inputs.
+
+Required properties for pwm-tacho node:
+- #address-cells : should be 1.
+
+- #size-cells : should be 0.
+
+- #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,ast2600-pwm-tachometer".
+
+- clocks : phandle to clock provider with the clock number in the second cell
+
+- resets : phandle to reset controller with the reset number in the second cell
+
+fan subnode format:
+===================
+Under fan subnode there can upto 16 child nodes, with each child node
+representing a fan. There are 16 fans each fan can have one PWM port and one
+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 0x00 to 0x0f with 0x00 indicating PWM port 0
+	and 0x0f indicating PWM port F.
+
+- 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.
+
+- aspeed,target-pwm : Specify the frequency of PWM. The value range from 24 to
+		      780000. Default value will be set to 25000.
+
+- aspeed,pulse-pr : Specify tacho pulse per revolution of the fan. A general
+		    parameter of pulse-pr is 2.
+
+Examples:
+
+&pwm_tacho {
+	status = "okay";
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_pwm0_default &pinctrl_tach0_default>;
+
+	fan@0 {
+		reg = <0x00>;
+		aspeed,target-pwm = <25000>;
+		cooling-levels = /bits/ 8 <125 151 177 203 229 255>;
+		aspeed,fan-tach-ch = /bits/ 8 <0x00>;
+		aspeed,pulse-pr = <2>;
+	};
+};
-- 
2.17.1