Re: [PATCH v4 1/5] Documentation: add DT bindings for ARM SCPI sensors

[Punit Agrawal <punit.agrawal@arm.com>]

Punit Agrawal <punit.agrawal@arm.com> writes:

> The System Control Processor (SCP) provides access to SoC sensors via
> the System Control and Power Interface (SCPI) Message Protocol. Add
> bindings to allow probing of these sensors. Also support referencing
> of the sensors for setting up thermal zones via the thermal DT
> bindings.
>
> Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Sudeep Holla <sudeep.holla@arm.com>

Gentle reminder for review of the below bindings. They've been updated
based on feedback on the earlier version [a].

If there are no further comments, I'd like to request an ack from the DT
reviewers.

[a] http://thread.gmane.org/gmane.linux.power-management.general/65475/focus=134976

> ---
>  Documentation/devicetree/bindings/arm/arm,scpi.txt | 38 ++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/arm/arm,scpi.txt b/Documentation/devicetree/bindings/arm/arm,scpi.txt
> index f002460..86302de 100644
> --- a/Documentation/devicetree/bindings/arm/arm,scpi.txt
> +++ b/Documentation/devicetree/bindings/arm/arm,scpi.txt
> @@ -72,8 +72,25 @@ Required sub-node properties:
>  - compatible : should be "arm,juno-scp-shmem" for Non-secure SRAM based
>  	       shared memory on Juno platforms
>  
> +Sensor bindings for the sensors based on SCPI Message Protocol
> +--------------------------------------------------------------
> +SCPI provides an API to access the various sensors on the SoC.
> +
> +Required properties:
> +- compatible : should be "arm,scpi-sensors".
> +- #thermal-sensor-cells: should be set to 1. This property follows the
> +			 thermal device tree bindings[2].
> +
> +			 Valid cell values are raw identifiers (Sensor
> +			 ID) as used by the firmware. Refer to
> +			 platform documentation for your
> +			 implementation for the IDs to use. For Juno
> +			 R0 and Juno R1 refer to [3].
> +
>  [0] http://infocenter.arm.com/help/topic/com.arm.doc.dui0922b/index.html
>  [1] Documentation/devicetree/bindings/clock/clock-bindings.txt
> +[2] Documentation/devicetree/bindings/thermal/thermal.txt
> +[3] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0922b/apas03s22.html
>  
>  Example:
>  
> @@ -122,6 +139,11 @@ scpi_protocol: scpi@2e000000 {
>  			clock-output-names = "pxlclk0", "pxlclk1";
>  		};
>  	};
> +
> +	scpi_sensors0: sensors {
> +		compatible = "arm,scpi-sensors";
> +		#thermal-sensor-cells = <1>;
> +	};
>  };
>  
>  cpu@0 {
> @@ -136,6 +158,17 @@ hdlcd@7ff60000 {
>  	clocks = <&scpi_clk 4>;
>  };
>  
> +thermal-zones {
> +	soc_thermal {
> +		polling-delay-passive = <100>;
> +		polling-delay = <1000>;
> +
> +				/* sensor         ID */
> +		thermal-sensors = <&scpi_sensors0 3>;
> +		...
> +	};
> +};
> +
>  In the above example, the #clock-cells is set to 1 as required.
>  scpi_dvfs has 3 output clocks namely: atlclk, aplclk, and gpuclk with 0,
>  1 and 2 as clock-indices. scpi_clk has 2 output clocks namely: pxlclk0
> @@ -148,3 +181,8 @@ scpi_dvfs i.e. "atlclk".
>  Similarly the second example is hdlcd@7ff60000 and it has pxlclk1 as input
>  clock. '4' in the clock specifier here points to the second entry
>  in the output clocks of scpi_clocks  i.e. "pxlclk1"
> +
> +The thermal-sensors property in the soc_thermal node uses the
> +temperature sensor provided by SCP firmware to setup a thermal
> +zone. The ID "3" is the sensor identifier for the temperature sensor
> +as used by the firmware.