[PATCH linux v3 1/3] Documentation: dt-bindings: Document binding for ASPEED AST2400/2500 PWM support

[Jaghathiswari Rankappagounder Natarajan]

This binding provides interface for adding values related to ASPEED
AST2400/2500 PWM support.
The parent node indicates a PWM controller. The parent node can have
upto 8 child nodes. Each node indicates a PWM output port.
PWM clock types M, N and 0 are three types just to have three independent
PWM sources. Each port can be assigned a different PWM clock type.
Each port can have the duty-cycle set to a different value.

Signed-off-by: Jaghathiswari Rankappagounder Natarajan <jaghu at google.com>
---
v2:
- Made binding documentation update as a separate patch.
- Included AST2500 in the description.
- Changed format to "aspeed,ast2500-pwm".
- Included explanation for types M ,N and O and calculation example to
-  determine L, H, and period bits.

v3:
- Included struct clk and phandle reference to clock node.
- Removed clock calculation description from the bindings document.
- Added some whitespace and improved style of binding document.

 .../devicetree/bindings/hwmon/aspeed-pwm.txt       | 104 +++++++++++++++++++++
 1 file changed, 104 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/aspeed-pwm.txt

diff --git a/Documentation/devicetree/bindings/hwmon/aspeed-pwm.txt b/Documentation/devicetree/bindings/hwmon/aspeed-pwm.txt
new file mode 100644
index 0000000..11a007c
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/aspeed-pwm.txt
@@ -0,0 +1,104 @@
+ASPEED AST2400/AST2500 PWM device driver
+
+The ASPEED PWM controller can support 8 PWM outputs.
+PWM clock types M, N and 0 are three types just to have three
+independent PWM sources. Each could be assigned to the 8 PWM port
+with it's own settings.
+
+Required properties:
+- #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 ASPEED PWM ports.
+
+- compatible : should be "aspeed,ast2400-pwm" for AST2400 or
+  "aspeed,ast2500-pwm" for AST2500.
+
+- clocks : phandle reference to clocks. upto three fixed clocks providing
+  three different input clock frequencies. each clock frequency indicates a
+  desired PWM frequency.
+
+   the first PWM frequency in combination with type M PWM period value
+    (described below) and source clock frequency will be used to calculate the
+    type M PWM clock division high and low values.
+   the second PWM frequency in combination with type N PWM period value and
+    source clock frequency will be used to calculate the type N PWM clock
+    division high and low values.
+   the third PWM frequency in combination with type O PWM period value and
+    source clock frequency will be used to calculate the type O PWM clock
+    division high and low values.
+
+  Since atleast one PWM frequency or one PWM clock type(type M PWM clock type)
+  is required, the first clock is required. the other two are optional.
+
+- pwm_typem_period : indicates type M PWM period. integer value in the range
+  0 to 255.
+
+Optional properties:
+- pwm_typen_period : indicates type N PWM period. integer value in the range
+  0 to 255.
+
+- pwm_typeo_period : indicates type O PWM period. integer value in the range
+  0 to 255.
+
+Each subnode represents a PWM output port.
+
+Subnode Format
+--------------
+Required properties:
+- pwm_port : indicates the PWM port. values 0 through 7 indicate PWM ports
+  A through H respectively.
+
+- pwm_enable : option to enable the PWM port indicated above. 0 is enable
+  and 1 is disable.
+
+- pwm_type : indicates the clock type for the PWM port. value 0 is type M
+  PWM clock. value 1 is type N PWM clock. value 2 is type O PWM clock.
+
+- pwm_fan_ctrl : pulse width modulation fan control. integer value
+  in the range 0 to 255. 255 is max or 100%.
+
+Additional details are available in the detailed datasheet for the device
+AST2400/AST2500.
+
+Examples:
+
+clocks {
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	pwm_typem_clock: fixedclk {
+		compatible = "fixed-clock";
+		#clock-cells = <0>;
+		clock-frequency = <25000>;
+	}
+}
+
+pwm: pwm-controller at 1e786000 {
+	#address-cells = <1>;
+	#size-cells = <1>;
+	reg = <0x1E786000 0x78>;
+	pinctrl-names = "default";
+        pinctrl-0 = <&pinctrl_pwm0_default &pinctrl_pwm1_default>
+	compatible = "aspeed,ast2500-pwm";
+	clocks = <&pwm_typem_clock>;
+	pwm_typem_period = <95>;
+	pwm_port0 {
+		pwm_port = /bits/ 8 <0x00>;
+		pwm_enable = /bits/ 8 <0x01>;
+		pwm_type = /bits/ 8 <0x00>;
+		pwm_fan_ctrl = /bits/ 8 <0x5A>;
+	};
+	pwm_port1 {
+		pwm_port = /bits/ 8 <0x01>;
+		pwm_enable = /bits/ 8 <0x01>;
+		pwm_type = /bits/ 8 <0x00>;
+		pwm_fan_ctrl = /bits/ 8 <0x5A>;
+	};
+};
+
--
2.8.0.rc3.226.g39d4020