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

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Message-ID: <20170320161531.ob65adnqch47dvyi@rob-hp-laptop>
Date:   Mon, 20 Mar 2017 11:15:31 -0500
From:   Rob Herring <robh@...nel.org>
To:     Jaghathiswari Rankappagounder Natarajan <jaghu@...gle.com>
Cc:     joel@....id.au, jdelvare@...e.com, linux@...ck-us.net,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
        openbmc@...ts.ozlabs.org, corbet@....net,
        linux-doc@...r.kernel.org, mark.rutland@....com,
        devicetree@...r.kernel.org
Subject: Re: [PATCH linux v4 1/2] Documentation: dt-bindings: Document
 bindings for ASPEED AST2400/AST2500 PWM and Fan tach controller device
 driver

On Fri, Mar 10, 2017 at 05:53:50PM -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>
> ---
>  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”.

As I mentioned on the last version, this 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.

These 2 also need aspeed vendor prefixes.

This could become a property under the fan node as a list of tach 
channels if fan-ctrl-gpios goes away.

> +
> +Examples:
> +
> +pwmtachofixedclk: fixedclk {
> +	compatible = "fixed-clock";
> +	#clock-cells = <0>;
> +	clock-frequency = <24000000>;
> +}
> +
> +pwmtacho: pwmtachocontroller@...86000 {
> +	#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 {

fan@0

> +		reg = /bits/ 8 <0x00>;

reg is 32-bits.

> +		tach0 {
> +			fan-ctrl-gpios = <&gpio ASPEED_GPIO(O, 0) GPIO_ACTIVE_HIGH>;
> +			fan-tach-ch = /bits/ 8 <0x00>;
> +		};
> +	};
> +
> +	fan1 {

fan@1

> +		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
>