linux-kernel - Re: [PATCH 1/2] dt: bindings: lp5024: Introduce the lp5024 and lp5018 RGB driver

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Date:   Tue, 8 Jan 2019 15:22:10 -0600
From:   Dan Murphy <dmurphy@...com>
To:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        <robh+dt@...nel.org>, <pavel@....cz>
CC:     <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-leds@...r.kernel.org>
Subject: Re: [PATCH 1/2] dt: bindings: lp5024: Introduce the lp5024 and lp5018
 RGB driver

On 1/8/19 3:16 PM, Jacek Anaszewski wrote:
> On 1/8/19 9:53 PM, Dan Murphy wrote:
>> Jacek
>>
>> On 1/8/19 2:33 PM, Jacek Anaszewski wrote:
>>> Dan,
>>>
>>> On 12/19/18 5:26 PM, Dan Murphy wrote:
>>>> Introduce the bindings for the Texas Instruments LP5024 and the LP5018
>>>> RGB LED device driver.  The LP5024/18 can control RGB LEDs individually
>>>> or as part of a control bank group.  These devices have the ability
>>>> to adjust the mixing control for the RGB LEDs to obtain different colors
>>>> independent of the overall brightness of the LED grouping.
>>>>
>>>> Datasheet:
>>>> http://www.ti.com/lit/ds/symlink/lp5024.pdf
>>>>
>>>> Signed-off-by: Dan Murphy <dmurphy@...com>
>>>> ---
>>>>    .../devicetree/bindings/leds/leds-lp5024.txt  | 63 +++++++++++++++++++
>>>>    1 file changed, 63 insertions(+)
>>>>    create mode 100644 Documentation/devicetree/bindings/leds/leds-lp5024.txt
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/leds/leds-lp5024.txt b/Documentation/devicetree/bindings/leds/leds-lp5024.txt
>>>> new file mode 100644
>>>> index 000000000000..9567aa6f7813
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/leds/leds-lp5024.txt
>>>> @@ -0,0 +1,63 @@
>>>> +* Texas Instruments - LP5024/18 RGB LED driver
>>>> +
>>>> +The LM3692x is an ultra-compact, highly efficient,
>>>> +white-LED driver designed for LCD display backlighting.
>>>> +
>>>> +The main difference between the LP5024 and L5018 is the number of
>>>> +RGB LEDs they support.  The LP5024 supports twenty four strings while the
>>>> +LP5018 supports eighteen strings.
>>>> +
>>>> +Required properties:
>>>> +    - compatible:
>>>> +        "ti,lp5018"
>>>> +        "ti,lp5024"
>>>> +    - reg :  I2C slave address
>>>> +    - #address-cells : 1
>>>> +    - #size-cells : 0
>>>> +
>>>> +Optional properties:
>>>> +    - enable-gpios : gpio pin to enable/disable the device.
>>>> +    - vled-supply : LED supply
>>>> +
>>>> +Required child properties:
>>>> +    - reg : Is the child node iteration.
>>>> +    - led-sources : LP5024 - 0 - 7
>>>> +            LP5018 - 0 - 5
>>>> +            Declares the LED string or strings that the child node
>>>> +            will control.  If ti,control-bank is set then this
>>>> +            property will contain multiple LED IDs.
>>>> +
>>>> +Optional child properties:
>>>> +    - label : see Documentation/devicetree/bindings/leds/common.txt
>>>> +    - linux,default-trigger :
>>>> +       see Documentation/devicetree/bindings/leds/common.txt
>>>> +    - ti,control-bank : Indicates that the LED strings declared in the
>>>> +                led-sources property are grouped within a control
>>>> +                bank for brightness and mixing control.
>>>> +
>>>> +Example:
>>>> +
>>>> +led-controller@28 {
>>>> +    compatible = "ti,lp5024";
>>>> +    reg = <0x28>;
>>>> +    #address-cells = <1>;
>>>> +    #size-cells = <0>;
>>>> +
>>>> +    enable-gpios = <&gpio1 28 GPIO_ACTIVE_HIGH>;
>>>> +    vled-supply = <&vbatt>;
>>>> +
>>>> +    led@0 {
>>>> +        reg = <0>;
>>>> +        led-sources = <1>;
>>>> +    };
>>>> +
>>>> +    led@1 {
>>>> +        reg = <1>;
>>>> +        led-sources = <0 6>;
>>>> +        ti,control-bank;
>>>
>>> Do you really need ti,control-bank? Doesn't led-sources array size
>>> greater than 1 mean that the node describes control bank?
>>>
>>
>> That will work too.
> 
>>> Also, does it make sense to have only two LEDs in the bank?
>>
>> The array can populate all 7 LEDs in a single node.  I only show 2 here as the example.
>> See the description above of the led-sources
> 
> OK, I confused RGB LED modules with banks.
> 
> Shouldn't we allow for defining either strings or RGB LED
> triplets somehow then?
> 

Well that is what this should be doing.  If you define a single LED in LED sources then
the triplet is controlled via the associated LEDx_brightness register.

If you have multiple LED sources defined in the led-sources then those LEDs would be grouped in the bank.
I guess I need to provide some protection or a warning if a DT defines two banks because there is only one bank control.

Dan

-- 
------------------
Dan Murphy