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Message-ID: <ed78b2fd-7ab8-d7c3-cf28-4d5b06783fb3@gmail.com> 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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