linux-kernel - Re: [PATCH linux v3 1/1] Documentation: dt-bindings: Document bindings for ASPEED AST2400/AST2500 PWM and Fan tach controller device driver

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Date:   Thu, 2 Mar 2017 09:07:33 -0600
From:   Rob Herring <robh@...nel.org>
To:     Jaghathiswari Rankappagounder Natarajan <jaghu@...gle.com>
Cc:     joel@....id.au, mark.rutland@....com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH linux v3 1/1] Documentation: dt-bindings: Document
 bindings for ASPEED AST2400/AST2500 PWM and Fan tach controller device
 driver

On Mon, Feb 13, 2017 at 10:19:35PM -0800, Jaghathiswari Rankappagounder Natarajan wrote:
> 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@...gle.com>
> ---
> v3:
>  Made the structure more common
> 
>  .../devicetree/bindings/hwmon/aspeed-pwm-tacho.txt | 73 ++++++++++++++++++++++
>  1 file changed, 73 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..c2de3709e554
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt
> @@ -0,0 +1,73 @@
> +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(starting from PWM A through PWM H):
> +- pwm-port : 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.
> +
> +- 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”.

This still sounds like pin muxing, not actual GPIO usage.

> +
> +- 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:
> +
> +pwm-tacho-fixed-clk: fixedclk {
> +	compatible = "fixed-clock";
> +	#clock-cells = <0>;
> +	clock-frequency = <24000000>;
> +}
> +
> +pwm-tacho: pwm-tacho-controller@...86000 {
> +	#address-cells = <1>;
> +	#size-cells = <1>;
> +	reg = <0x1E786000 0x1000>;
> +	compatible = "aspeed,aspeed2500-pwm-tacho";
> +	clocks = <&pwm-tacho-fixed-clk>;
> +	pinctrl-names = "default";
> +	pinctrl-0 = <&pinctrl_pwm0_default &pinctrl_pwm1_default>;
> +
> +	fan0 {
> +		pwm-port = /bits/ 8 <0x00>;

Since fans and pwms are 1-1, I'd just use reg here.

I still think this should probably use PWM binding, but given this is 
all self contained it is okay.

> +		fan-ctrl-gpios = <&gpio ASPEED_GPIO(O, 0) GPIO_ACTIVE_HIGH>;
> +		fan-tach-ch = /bits/ 8 <0x00>;
> +	};
> +
> +	fan1 {
> +		pwm-port = /bits/ 8 <0x01>;
> +		fan-ctrl-gpios = <&gpio ASPEED_GPIO(O, 1) GPIO_ACTIVE_HIGH>;
> +		fan-tach-ch = /bits/ 8 <0x01>;
> +	};
> +};
> --
> 2.11.0.483.g087da7b7c-goog
>