Date:   Sat, 12 Jan 2019 20:48:07 +0100
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Dan Murphy <dmurphy@...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

Hi Dan,

On 1/12/19 6:09 PM, Dan Murphy wrote:
> Jacek
> 
> On 1/11/19 3:52 PM, Jacek Anaszewski wrote:
>> Dan,
>>
>> On 1/11/19 1:38 PM, Dan Murphy wrote:
>>> Jacek
>>>
>>> Sorry I missed some replies
>>>
>>> On 1/10/19 4:03 PM, Jacek Anaszewski wrote:
>>>> On 1/10/19 9:43 PM, Dan Murphy wrote:
>>>>> Jacek
>>>>>
>>>>> On 1/10/19 1:57 PM, Jacek Anaszewski wrote:
>>>>>> Dan,
>>>>>>
>>>>>> On 1/10/19 8:22 PM, Dan Murphy wrote:
>>>>>>> Jacek
>>>>>>>
>>>>>>> On 1/10/19 12:44 PM, Jacek Anaszewski wrote:
>>>>>>>> Hi Dan,
>>>>>>>>
>>>>>>>> On 1/9/19 10:31 PM, Dan Murphy wrote:
>>>>>>>>> Jacek
>>>>>>>>>
>>>>>>>>> On 1/9/19 3:28 PM, Jacek Anaszewski wrote:
>>>>>>>>>> On 1/9/19 10:12 PM, Dan Murphy wrote:
>>>>>>>>>>> On 1/9/19 2:12 PM, Jacek Anaszewski wrote:
>>>>>>>>>>>> Hi Dan,
>>>>>>>>>>>>
>>>>>>>>>>>> On 1/8/19 10:22 PM, Dan Murphy wrote:
>>>>>>>>>>>>> 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.
>>>>>>>>>>>>
>>>>>>>>>>>> led-sources should map to iouts directly.
>>>>>>>>>>>> So, for RGB LED modules I would expect:
>>>>>>>>>>>>
>>>>>>>>>>>> LED0: led-sources = <0 1 2>;
>>>>>>>>>>>> LED1: led-sources = <3 4 5>;
>>>>>>>>>>>> LED2: led-sources = <6 7 8>;
>>>>>>>>>>>> and so on.
>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> for banks:
>>>>>>>>>>>>
>>>>>>>>>>>> Bank A with iouts 0,3,6,9: led-sources<0 3 6 9>;
>>>>>>>>>>>> Bank B with iouts 2,4,10:  led-sources<2 4 10>;
>>>>>>>>>>>> Bank C with iouts 5,8,11,14,17: led-sources<5 8 11 14 17>;
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Ok the led-sources would need to be different then this as I don't define the sources for banks.
>>>>>>>>>>>
>>>>>>>>>>> The led-sources for the banks and the individual groups will have different meanings within the same
>>>>>>>>>>> document.  I was attempting to keep the led-sources mapped to the LEDx_brightness registers as opposed to
>>>>>>>>>>> the hardware outputs since the RGB LEDs are controlled and grouped by a single brightness register and if banked then
>>>>>>>>>>> it would be controlled by the bank brightness register.
>>>>>>>>>>>
>>>>>>>>>>> Describing these in the DT seems wrought with potential issues as the data sheet defines what outputs map to what bank and LED
>>>>>>>>>>> registers.
>>>>>>>>>>
>>>>>>>>>> Yes, that's why I mentioned the need for validation of led-sources.
>>>>>>>>>> But they have to be iouts. This property was introduced specifically
>>>>>>>>>> for such purposes.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Yes Pavel also mentioned that as well.
>>>>>>>>>
>>>>>>>>> I will look into validating the sources.  But there will be no mapping of the sources to the output that is done
>>>>>>>>> in the hardware.  This would just be a data sheet mapping since the outputs are not configurable.
>>>>>>>>
>>>>>>>> Hmm, isn't the mapping defined in the hardware via LED_CONFIG0 register?
>>>>>>>> I have an impression that it defines whether LED belongs to an RGB LED
>>>>>>>> module or to a bank. Basing on that I created my DT example above.
>>>>>>>>
>>>>>>>
>>>>>>> Yes so if you turn on the bank control for LED0 and LED1 then
>>>>>>> out 0, 3 are mapped to BANK A
>>>>>>> out 1, 4 are mapped to BANK B
>>>>>>
>>>>>> Just noticed that I made a mistake in my example, it should have been:
>>>>>>
>>>>>> Bank B with iouts 1,4,10:  led-sources<1 4 10>;
>>>>>>
>>>>>>> out 2, 5 are mapped to BANK C
>>>>>>
>>>>>> Correct.
>>>>>>
>>>>>>> All done automatically in the hardware and the LED0_BRIGHTNESS and LED1_BRIGHTNESS registers have no affect on the brightness
>>>>>>
>>>>>> That's right.
>>>>>>
>>>>>>> If we grouped the LEDs into a bank the led-sources would look more like this
>>>>>>> led-sources = < 0 1 2 3 4 5 >;
>>>>>>
>>>>>> Why? This would be a mix of three banks. Like you listed above.
>>>>>> I'm still interpreting led-sources elements as iout identifiers.
>>>>>>
>>>>>
>>>>> I am as well but as I tried to explain that if you define OUT0 as bank controlled then OUT1 and OUT2 are also bank controlled
>>>>> within the hardware.  We have no control of that.  If BIT(0) and BIT(1) are set in the LED_CONFIG0 register then OUT0, 1, 2, 3, 4 and 5 are all bank controlled.
>>>>
>>>> There is naming conflict I noticed just now - LEDn_BANK_EN bits
>>>> in LED_CONFIG0 register enable RGB LED modules, and not BANKs (A,B,C).
>>>>
>>>>> These OUTPUTs will appear as a single RGB LED grouping.
>>>>
>>>> Single? W would rather expect that we get two RGB LED modules, whose
>>>> brightness will be controlled via LED0_BRIGHTNESS and LED1_BRIGHTNESS
>>>> registers respectively.
>>>>
>>>>>>> ti,control-bank; // But this can be omitted as led-sources is greater then 3
>>>>>>>
>>>>>>> non-banked case would be
>>>>>>> led-sources = < 0 1 2 >;
>>>>>>
>>>>>> Agreed here. It would be LED0 RGB LED module.
>>>>>>> But the actual OUT numbers don't matter in the bank case unless we do the validation.  There would need to be an algorithim
>>>>>>> that translates these output to the correct LEDx register and CONFIG0 bits.  Basically if OUT0 is mapped to the bank then OUT1 and OUT2
>>>>>>> are inherently mapped to the bank.
>>>>>>
>>>>>> To three separate banks, right?
>>>>>> OUT0 - bank A, OUT1 - bank B, OUT2 - bank C.
>>>>>
>>>>> Yes but there is no BANK output pin just like there is no dedicated LEDn output pin.  The banks are grouped internally to the device
>>>>> so again if OUT0 and OUT3 are defined as banked then 1, 2, 4, and 5 are all mapped to the bank.  1 BANK brightness register and 3 bank
>>>>> color adjustment registers.
>>>>
>>>> Here as above, I would expect two separate banks - LED0 and LED1.
>>>> Moreover - not 3 color adjustment registers, but six - one per iout:
>>>> OUT0_COLOR to OUT5_COLOR.
>>>>
>>>
>>> When the LEDs are banked the banked LEDs are controlled by the bank registers not the LEDx registers
>>> so you should only see 3 color adjustments on the banked LEDs.
>>>
>>>>>>> They cannot be separated so the device theoretically treats the RGB group as a single LED.  And
>>>>>>> when banked it treats the groups of RGBs that are defined as a single LED.
>>>>>>>
>>>>>>> This is why it was easier use the LEDx out as the virtual out as we only need to define the group number(s) that are controled by the
>>>>>>> LED file presented to the user space.
>>>>>>
>>>>>> I suspect there is logical clash here due to interpreting
>>>>>> led-sources elements as iouts in one case and LEDn modules
>>>>>> in the other case.
>>>>>>
>>>>>
>>>>> Yes.  When the RGBs are banked you have to think of them as a single RGB LED cluster and not as separate RGB LED clusters.
>>>>
>>>> We have RGB LED modules (enabled with LEDn_Bank_EN bits) and three
>>>> banks (A,B,C), which are enabled by default, am I right?
>>>
>>> No.  Independent LED modules are enabled by default.  You have to explicitly enable the banks.
>>>
>>>>
>>>> Bank A iouts: 0, 3 ,6, 9, 12, 15
>>>> Bank B iouts: 1, 4, 7, 10, 13, 16
>>>> Bank C iouts: 2, 5, 8, 11, 14, 17
>>>>
>>>> When RGB LED module is enabled (via LEDn_Bank_EN bit),
>>>> the BANK_{A.B,C}_COLOR and BANK_BRIGHTNESS registers
>>>> lose control over related IOUTs in favour of LEDn_BRIGHTNESS and
>>>> related OUTn_COLOR registers. Is it correct?
>>>
>>> No it is the opposite.  When the bit is enabled LED banking is enabled and the BANK brightness and color registers over
>>> ride the LEDx color and brightness registers.
>>>
>>> Default is independent control of the RGB via the LEDx color and brightness registers.
>>>
>>>>
>>>>> As you know the brightness is controlled by the single BANK_BRIGHTNESS register.  So identifying each output in the led-sources is
>>>>> misleading as the hardware does this all on the chip.  This is why I just mapped each output to the Virtual LEDx module.
>>>>
>>>> Ekhm, I messed something here.
>>>>
>>>> So for this I would define a single LED class device.
>>>> Related DT node would not need led-sources at all,
>>>> but only ti,control-bank. The semantics would be:
>>>> controls all iouts not taken by RGB LED modules.
>>>>
>>>
>>> Hmm.  I guess I will put that on hold until you read the responses.  I am not sure that would work or
>>> that would be really clean.  I still believe that mapping led-sources to the LEDx module number is the cleanest
>>> simplest solution since the driver cannot inter mix different outputs for enablement.
>>
>> I've read the doc again more carefully and hopefully I finally have
>> proper understanding. Let's check it.
>>
>> 1. On reset LED_CONFIG0 bits are zeroed, which means
>>     LEDn module independent control mode.
>> 2. LEDn modules (i.e. IOUT triplets) are controlled independently,
>>     with use of LEDn_BRIGHTNESS registers, and each IOUT color can
>>     be adjusted using OUTn_CONTROL registers.
>> 3. LEDn_Bank_EN bits, when set to 1, assign given RGB LED module
>>     to one global bank, controlled via BANK_BRIGHTNESS and BANK_n_COLOR
>>     registers.
>>
>> Having that, I'd see led-sources definitions as follows
>> (led-sources element is IOUT identifier)
>>
>> 1.
>>
>> - LED0, LED1, LED2, LED3 modules controlled by separate
>>    LED class devices
>>
>> led-sources = <0 1 2>   // LED0
>> led-sources = <3 4 5>   // LED1
>> led-sources = <6 7 8>   // LED2
>> led-sources = <9 10 11> // LED3
>>
>> 2.
>>
>> - LED0 and LED3 modules assigned to the bank, and controlled
>>    by one LED class device,
>> - LED1 and LED2 modules controlled by separate LED class devices
>>
>> led-sources = <0 1 2 9 10 11> // Bank with LED0 and LED3
>> led-sources = <3 4 5>         // LED1
>> led-sources = <6 7 8>         // LED2
>>
>>
>> So now I see your point. It would be indeed easier
>> to switch to LEDn module identifiers for led-sources
>> elements. With that the definitions would look like
>> this:
>>
>>
>> 1.
>>
>> - LED0, LED1, LED2, LED3 modules controlled by separate
>>    LED class devices
>>
>> led-sources = <0>   // LED0
>> led-sources = <1>   // LED1
>> led-sources = <2>   // LED2
>> led-sources = <3>   // LED3
>>
>> 2.
>>
>> - LED0 and LED3 modules assigned to the bank, and controlled
>>    by one LED class device,
>> - LED1 and LED2 modules controlled by separate LED class devices
>>
>> led-sources = <0 3> // Bank with LED0 and LED3
>> led-sources = <1>   // LED1
>> led-sources = <2>   // LED2
>>
> 
> This is exactly how I submitted the code.
> 
>>
>> But, I don't think use of led-sources is justified in
>> this case. I propose to introduce device specific properties:
>>
>> ti,led-module and ti,led-bank
>>
>> With that we would have:
>>
>> ti,led-bank = <0 3>   // Bank with LED0 and LED3 modules
>> ti,led-module = <1>   // LED1
>> ti.led-module = <2>   // LED2
>>
> 
> We are now aligned.  I can change the led-sources to the TI specific if there are no further objections.
> In doing this I can eliminate the ti,control-bank property.
> 
>>
>>>> I would also add Table 1 contents (Bank Number and LED Number
>>>> Assignment) to the DT bindings.
>>>>
>>>
>>> Should I add that to the DT binding or reference the data sheet table since this driver will support 4 different devices
>>> with varying number of outputs from 18-36.
>>
>> My first thought was to show full table, but four different
>> mappings would add too much noise. So the reference to the data
>> sheet should suffice.
>>
> 
> OK
> 
> One last question I am going to add the LP5036 and 30 which have the same technology but slightly different register maps.
> Should I rename the driver to LP5036.c as the 30, 24 and 18 would technically be subsets?

How about leds-lp50xx.c ? You can also create a library like
drivers/leds/leds-lp55xx-common.c if that would simplify the code.

-- 
Best regards,
Jacek Anaszewski

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