linux-kernel - Re: [PATCH v3 3/3] DT: leds: Add Qualcomm Light Pulse Generator binding

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Date:   Sun, 19 Nov 2017 22:35:53 +0100
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Richard Purdie <rpurdie@...ys.net>,
        Pavel Machek <pavel@....cz>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        Fenglin Wu <fenglinw@...eaurora.org>
Subject: Re: [PATCH v3 3/3] DT: leds: Add Qualcomm Light Pulse Generator
 binding

Hi Bjorn,

Thanks for the update.

On 11/15/2017 08:13 AM, Bjorn Andersson wrote:
> This adds the binding document describing the three hardware blocks
> related to the Light Pulse Generator found in a wide range of Qualcomm
> PMICs.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---
> 
> Changes since v2:
> - Squashed all things into one node
> - Removed quirks from the binding, compatible implies number of channels, their
>   configuration etc.
> - Binding describes LEDs connected as child nodes
> - Support describing multi-channel LEDs
> - Change style of the binding document, to match other LED bindings
> 
> Changes since v1:
> - Dropped custom pattern properties
> - Renamed cell-index to qcom,lpg-channel to clarify its purpose
> 
>  .../devicetree/bindings/leds/leds-qcom-lpg.txt     | 66 ++++++++++++++++++++++
>  1 file changed, 66 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/leds-qcom-lpg.txt
> 
> diff --git a/Documentation/devicetree/bindings/leds/leds-qcom-lpg.txt b/Documentation/devicetree/bindings/leds/leds-qcom-lpg.txt
> new file mode 100644
> index 000000000000..9cee6f9f543c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/leds-qcom-lpg.txt
> @@ -0,0 +1,66 @@
> +Binding for Qualcomm Light Pulse Generator
> +
> +The Qualcomm Light Pulse Generator consists of three different hardware blocks;
> +a ramp generator with lookup table, the light pulse generator and a three
> +channel current sink. These blocks are found in a wide range of Qualcomm PMICs.
> +
> +Required properties:
> +- compatible: one of:
> +	      "qcom,pm8916-pwm",
> +	      "qcom,pm8941-lpg",
> +	      "qcom,pm8994-lpg",
> +	      "qcom,pmi8994-lpg",
> +	      "qcom,pmi8998-lpg",
> +
> +Optional properties:
> +- qcom,power-source: power-source used to drive the output, as defined in the
> +		     datasheet. Should be specified if the TRILED block is
> +		     present

Range of possible values is missing here.

> +- qcom,dtest: configures the output into an internal test line of the
> +	      pmic. Specified by a list of u32 pairs, one pair per channel,
> +	      where each pair denotes the test line to drive and the second
> +	      configures how the value should be outputed, as defined in the
> +	      datasheet
> +- #pwm-cells: should be 2, see ../pwm/pwm.txt
> +
> +LED subnodes:
> +A set of subnodes can be used to specify LEDs connected to the LPG. Channels
> +not associated with a LED are available as pwm channels, see ../pwm/pwm.txt.
> +
> +Required properties:
> +- led-sources: list of channels associated with this LED, starting at 1 for the
> +	       first LPG channel
> +
> +Optional properties:
> +- label: see Documentation/devicetree/bindings/leds/common.txt
> +- default-state: see Documentation/devicetree/bindings/leds/common.txt
> +- linux,default-trigger: see Documentation/devicetree/bindings/leds/common.txt
> +
> +Example:
> +The following example defines a RGB LED attached to the PM8941.
> +
> +&spmi_bus {
> +	pm8941@1 {
> +		lpg {
> +			compatible = "qcom,pm8941-lpg";
> +			qcom,power-source = <1>;
> +
> +			rgb {
> +				led-sources = <7 6 5>;
> +			};
> +		};
> +	};
> +};
> +
> +The following example defines the single PWM channel of the PM8916, which can
> +be muxed by the MPP4 as a current sink.
> +
> +&spmi_bus {
> +	pm8916@1 {
> +		pm8916_pwm: pwm {
> +			compatible = "qcom,pm8916-pwm";
> +
> +			#pwm-cells = <2>;

LED has to be represented as a child node -
see Documentation/devicetree/bindings/leds/common.txt

> +		};
> +	};
> +};
> 

Could you please also provide an example of the arrangement on the
board DragonBoard820c, you were describing in the discussions under
the previous version of the patch set. i.e. three green LEDs connected
to TRILED and one to the GPIO sink?

Also any other non-trivial board configurations supported by the
driver would allow to increase our comprehensions of the device
capabilities.

-- 
Best regards,
Jacek Anaszewski