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[83.31.2.161]) by smtp.gmail.com with ESMTPSA id j18-v6sm15333814ljc.52.2019.01.10.11.57.51 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 10 Jan 2019 11:57:52 -0800 (PST) Subject: Re: [PATCH 1/2] dt: bindings: lp5024: Introduce the lp5024 and lp5018 RGB driver To: Dan Murphy , robh+dt@kernel.org, pavel@ucw.cz Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org References: <20181219162626.12297-1-dmurphy@ti.com> <20181219162626.12297-2-dmurphy@ti.com> <2d2d5dcd-9c23-e901-daac-9b79aa5a5e82@ti.com> <6c62956e-7789-58ba-5437-f2e033f2825c@gmail.com> <366cbf6d-94fa-fea9-be58-07ddb09cff3a@ti.com> <1702dfd6-b08f-c1ff-e46d-1366618bedb0@gmail.com> <72112839-11d4-54be-df94-b2322f77cb0f@ti.com> From: Jacek Anaszewski Message-ID: <8b126077-c200-ed34-03b7-6d43a22fb0c9@gmail.com> Date: Thu, 10 Jan 2019 20:57:50 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <72112839-11d4-54be-df94-b2322f77cb0f@ti.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >>>>>>>>>>> --- >>>>>>>>>>>       .../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. > 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. > 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. -- Best regards, Jacek Anaszewski