[PATCH linux v4 1/2] Documentation: dt-bindings: Document bindings for ASPEED AST2400/AST2500 PWM and Fan tach controller device driver

[Jaghathiswari Rankappagounder Natarajan <jaghu@google.com>]

This binding provides interface for adding values related to ASPEED
AST2400/2500 PWM and Fan tach controller support.
The PWM controller can support upto 8 PWM output ports.
The Fan tach controller can support upto 16 tachometer inputs.

Signed-off-by: Jaghathiswari Rankappagounder Natarajan <jaghu@google.com>
---
 v4:
- Used 'reg'

 v3:
- Made the structure more common

 v2:
- Removed '_' in node and property names
- Gave some explanation for the properties used

 .../devicetree/bindings/hwmon/aspeed-pwm-tacho.txt | 86 ++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt

diff --git a/Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt b/Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt
new file mode 100644
index 000000000000..0dfd2841ace3
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt
@@ -0,0 +1,86 @@
+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.
+
+- 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,aspeed2400-pwm-tacho" for AST2400 or
+	       "aspeed,aspeed2500-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.
+
+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.
+
+  Atleast one tach subnode is required. Each tach subnode represents a fan
+  tach input.
+  tach subnode format:
+  --------------------
+  Required properties for each child node:
+  - fan-ctrl-gpios : should specify the tachometer input GPIO pin on the hardware.
+             	     Fan Tachometer function can only work when GPIO is in
+		     ”input mode”.
+
+  - 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.
+
+Examples:
+
+pwmtachofixedclk: fixedclk {
+	compatible = "fixed-clock";
+	#clock-cells = <0>;
+	clock-frequency = <24000000>;
+}
+
+pwmtacho: pwmtachocontroller@1e786000 {
+	#address-cells = <1>;
+	#size-cells = <1>;
+	reg = <0x1E786000 0x1000>;
+	compatible = "aspeed,aspeed2500-pwm-tacho";
+	clocks = <&pwmtachofixedclk>;
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_pwm0_default &pinctrl_pwm1_default>;
+
+	fan0 {
+		reg = /bits/ 8 <0x00>;
+		tach0 {
+			fan-ctrl-gpios = <&gpio ASPEED_GPIO(O, 0) GPIO_ACTIVE_HIGH>;
+			fan-tach-ch = /bits/ 8 <0x00>;
+		};
+	};
+
+	fan1 {
+		reg = /bits/ 8 <0x01>;
+		tach0 {
+			fan-ctrl-gpios = <&gpio ASPEED_GPIO(O, 1) GPIO_ACTIVE_HIGH>;
+			fan-tach-ch = /bits/ 8 <0x01>;
+		};
+		tach1 {
+			fan-ctrl-gpios = <&gpio ASPEED_GPIO(O, 2) GPIO_ACTIVE_HIGH>;
+			fan-tach-ch = /bits/ 8 <0x02>;
+		};
+	};
+};
--
2.12.0.246.ga2ecc84866-goog