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Date: Mon, 14 Jan 2019 21:11:35 +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 1/14/19 1:27 PM, Dan Murphy wrote: > 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? DT is for concrete board and cpu, so it doesn't make sense to use wildcards in *.dts file names. > leds-lp50xx.c is a fine name to me. Apart of that, I've been also mulling over if we shouldn't go for single "color" sysfs file for setting r,g,b components at one go. I don't see any downsides. There is no risk that number of elements will grow, and the benefit will be an atomic way of setting color - the feature people are looking for. Vesa was mentioning the case where lack of it had been a real problem [0]. Let's check the usability of such interface. [0] https://lkml.org/lkml/2019/1/4/519 -- Best regards, Jacek Anaszewski
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