Message-ID: <0140ad64-432e-7723-2415-0b3a8ac4d8dc@ti.com>
Date:   Sat, 12 Jan 2019 11:09:02 -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 1/11/19 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?



Dan

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

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