Re: [PATCH v2 1/4] dt-bindings: hwmon: pmbus: Add Maxim MAX31785 documentation

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On Wed, Aug 02, 2017 at 04:45:38PM +0930, Andrew Jeffery wrote:
> Signed-off-by: Andrew Jeffery <andrew@xxxxxxxx>
> ---
>  .../devicetree/bindings/hwmon/pmbus/max31785.txt   | 126 +++++++++++++++++++++
>  1 file changed, 126 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/pmbus/max31785.txt
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/pmbus/max31785.txt b/Documentation/devicetree/bindings/hwmon/pmbus/max31785.txt
> new file mode 100644
> index 000000000000..8ddc4ea1958d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/pmbus/max31785.txt
> @@ -0,0 +1,126 @@
> +Bindings for the Maxim MAX31785 Intelligent Fan Controller
> +==========================================================

This is the second fan controller binding I've seen recently. The other 
being hwmon/aspeed-pwm-tacho.txt. I think some of this needs to be 
common. There's only so many types of fans, right?

And we have the thermal binding which you don't appear to tie into.

> +
> +Reference:
> +[1] https://datasheets.maximintegrated.com/en/ds/MAX31785.pdf
> +
> +Required properties:
> +- compatible     : One of "maxim,max31785" or "maxim,max31785a"
> +- reg            : I2C address, one of 0x52, 0x53, 0x54, 0x55.
> +- #address-cells : Must be 1
> +- #size-cells    : Must be 0
> +
> +Optional properties:
> +- use-stored-presence    : Do not treat the devicetree description as canon for

Is this maxim specific? If so, needs a vendor prefix.

> +                           fan presence (the 'installed' bit of FAN_CONFIG_*).
> +                           Instead, rely on the on the default value store of
> +                           the device to populate it.
> +
> +Capabilities are configured through subnodes of the controller's node.
> +
> +Fans
> +----
> +
> +Only fans with subnodes present will be considered as installed. If
> +use-stored-presence is present in the parent node, then only fans that are both
> +defined in the devicetree and have their installed bit set are considered
> +installed.
> +
> +Required subnode properties:
> +- compatible             : Must be "pmbus-fan"

What defines a pmbus-fan? Sounds generic, but then you have all these 
maxim specific properties.

> +- reg                    : The PMBus page the properties apply to.
> +- maxim,fan-rotor-input  : The type of rotor measurement provided to the
> +                           controller. Must be either "tach" for tachometer
> +                           pulses or "lock" for a locked-rotor signal.
> +- maxim,fan-lock-polarity: Required iff maxim,fan-rotor-input is "lock". Valid
> +                           values are "low" for active low, "high" for active
> +                           high.
> +
> +Optional subnode properties:
> +- fan-mode               : "rpm" or "pwm". Default value is "pwm".
> +- tach-pulses            : Tachometer pulses per revolution. Valid values are
> +                           1, 2, 3 or 4. The default is 1.
> +- maxim,fan-no-fault-ramp: Do not ramp the fan to 100% PWM duty on detecting a
> +                           fan fault
> +- maxim,fan-startup      : The number of rotations required before taking
> +                           emergency action for an unresponsive fan and driving
> +                           it with 100% or 0% PWM duty, depending on the state
> +                           of maxim,fan-no-fault-ramp. Valid values are 0
> +                           (automatic spin-up disabled), 2, 4, or 8. Default
> +                           value is 0.
> +- maxim,fan-health       : Enable automated fan health check
> +- maxim,fan-ramp         : Configures how fast the device ramps the PWM duty
> +                           cycle from one value to another. Valid values are 0
> +                           to 7 inclusive, with values 0 - 2 configuring a
> +                           1000ms update rate and 1 - 3% duty respective duty
> +                           increase, and 3 - 7 a 200ms update rate with a 1 -
> +                           5% respective duty increase. Default value is 0.
> +- maxim,fan-no-watchdog  : Do not ramp fan to 100% PWM duty on failure to
> +                           update desired fan rate inside 10s. This implies
> +                           maxim,tmp-no-fault-ramp
> +- maxim,tmp-no-fault-ramp: Do not ramp fan to 100% PWM duty on temperature
> +                           sensor fault detection. This implies
> +                           maxim,fan-no-watchdog
> +- maxim,tmp-hysteresis   : The temperature hysteresis used to determine
> +                           transitions to lower fan speed bands in the
> +                           temperature/fan rate lookup table. Valid values are
> +                           2, 4, 6 or 8 (degrees celcius). Default value is 2.
> +- maxim,fan-dual-tach    : Enable dual tachometer functionality
> +- maxim,fan-pwm-freq     : The PWM frequency. Valid values are 30, 50, 100, 150
> +                           and 25000 (Hz). Default value is 30Hz.
> +- maxim,fan-lookup-table : A 16-element cell array of alternating temperature
> +                           and rate values representing the look up table. The
> +                           rate units are set through the fan-mode property.
> +- maxim,fan-fault-pin-mon: Ramp fans to 100% PWM duty when the FAULT pin is
> +                           asserted
> +
> +Temperature
> +-----------
> +
> +Required subnode properties:
> +- compatible    : Must be "pmbus-temperature"
> +- reg           : The PMBus page the properties apply to.
> +
> +Optional subnode properties:
> +- maxim,tmp-offset      : Valid values are 0 - 30 (degrees celcius) inclusive.
> +                          Default value is 0.
> +- maxim,tmp-fans        : An array of fan indexes whose fans are controlled by
> +                          the current temperature sensor. Fans are indexed from
> +                          zero. The valid values are 0 - 5 inclusive.

Why not use a phandle here.

> +
> +Example:
> +	fan-max31785: max31785@52 {
> +		reg = <0x52>;
> +		compatible = "maxim,max31785";
> +                #address-cells = <1>;
> +                #size-cells = <0>;
> +
> +                fan@0 {
> +                        compatible = "pmbus-fan";
> +                        reg = <0>;
> +                        mode = "rpm";
> +                        tach-pulses = <1>;
> +                        maxim,fan-rotor-input = "tach";
> +                        maxim,fan-dual-tach;
> +                };
> +
> +                fan@1 {
> +                        compatible = "pmbus-fan";
> +                        reg = <1>;
> +                        mode = "rpm";
> +                        tach-pulses = <1>;
> +                        maxim,fan-rotor-input = "tach";
> +                        maxim,tmp-hysteresis = <2>;
> +                        maxim,fan-lookup-table = <
> +                        /*  Temperature    RPM  */
> +                                 0        1000
> +                                10        2000
> +                                20        3000
> +                                30        4000
> +                                40        5000
> +                                50        6000
> +                                60        7000
> +                                70        8000
> +                        >;
> +                };
> +	};
> -- 
> 2.11.0
> 
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