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SubjectRe: [PATCH linux v2 1/2] Documentation: dt-bindings: Document bindings for ASPEED AST2400/AST2500 PWM and Fan tach controller device driver
On Fri, Jan 27, 2017 at 01:33:59AM -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.
> Types M, N and 0 are three types just to have three independent
> PWM/Fan Tach related settings.

This still looks overly complicated to me and very specific to ASpeed.
You need to define a common structure that works for fans. To start
with, define a node for the fans themselves. This should use the
PWM binding and a -gpios property for the tach (when connected to a
GPIO).

Something like this:

ctrl: fan-controller@1234 {
...
#pwm-cells = <3>;
fan@0 {
reg = <0>; /* 'Channel' of the controller */
pwms = <&ctrl 0 ...>;
tach-gpios = <&gpio 1>;
vcc-supply = <&reg_12V>;
};
};

We already have a pwm-fan binding. This should build on or possibly
replace that.

>
> Signed-off-by: Jaghathiswari Rankappagounder Natarajan <jaghu@google.com>
> ---
> v2:
> - Removed '_' in node or property names
> - Gave some explanation for the properties used.
>
> .../devicetree/bindings/hwmon/aspeed-pwm-tacho.txt | 178 +++++++++++++++++++++
> 1 file changed, 178 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..290122bfe170
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt
> @@ -0,0 +1,178 @@
> +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 tachometer inputs.
AIUI, each fan has a PWM and a tach input. How would you use more than 8
tach inputs?

> +
> +There are three different types M, N, O. These three types are just to have
> +different PWM and Fan Tach settings. Each type can have the following settings:
> + PWM related:
> + 1) PWM period
> + 2) PWM clock division high
> + 3) PWM clock division low
> + Fan Tach related:
> + 1) Fan Tach type enable
> + 2) Fan Tach clock division
> + 3) Fan Tach mode selection
> + 4) Fan Tach period
> +
> +Each PWM port should be assigned a type which can be type M, N or O.

What is the definition of M, N, and O?

Rob

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