From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacek Anaszewski Subject: Re: [PATCH 1/2] dt: bindings: lp5024: Introduce the lp5024 and lp5018 RGB driver Date: Wed, 9 Jan 2019 22:28:18 +0100 Message-ID: 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> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org 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 List-Id: linux-leds@vger.kernel.org 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. common LED bindings say: - led-sources : List of device current outputs the LED is connected to. The outputs are identified by the numbers that must be defined in the LED device binding documentation. >> We could additionally mark banks with ti,control-bank, > > We would have to keep the ti,control-bank node based on the above. > >> but I'm not sure if it would ease parsing, since >> you will have to validate iouts configuration anyway. >> >>> 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. >> >> Does the hardware allow the IOUT to belong to an RGB LED module >> and to a bank in the same time? >> > > No it does not. LED_CONFIG0 sets the bit if it is control bank or not. OK, so validation will also have to check if led-sources definitions are not mutually exclusive between child DT nodes. For consistency it would be really better if bank definitions also used led-sources. > Section 8.3.2 in the data sheet says > "When a channel is configured in > LED bank-control mode, the related color mixing and intensity control is governed by the bank control registers > (BANK_A_COLOR, BANK_B_COLOR, BANK_C_COLOR, and BANK_BRIGHTNESS) regardless of the inputs > on its own color-mixing and intensity-control registers." > -- Best regards, Jacek Anaszewski