Date:   Mon, 14 Jan 2019 06:27:03 -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

Jacek

On 1/12/19 1:48 PM, Jacek Anaszewski wrote:
> 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.
> 

A library would be overkill.
Is it just the DT that we don't want to use wild cards in naming?

leds-lp50xx.c is a fine name to me.

Dan

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

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