Re: [PATCH 1/2] dt: bindings: lp5024: Introduce the lp5024 and lp5018 RGB driver

From: Jacek Anaszewski
Date: Fri Jan 11 2019 - 16:52:34 EST

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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.Â The LP5024/18 can control RGB LEDs individually
or as part of a control bank group.Â 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@xxxxxx>
---
ÂÂÂÂÂÂÂ .../devicetree/bindings/leds/leds-lp5024.txtÂ | 63 +++++++++++++++++++
ÂÂÂÂÂÂÂ 1 file changed, 63 insertions(+)
ÂÂÂÂÂÂÂ 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.Â The LP5024 supports twenty four strings while the
+LP5018 supports eighteen strings.
+
+Required properties:
+ÂÂÂ - compatible:
+ÂÂÂÂÂÂÂ "ti,lp5018"
+ÂÂÂÂÂÂÂ "ti,lp5024"
+ÂÂÂ - reg :Â I2C slave address
+ÂÂÂ - #address-cells : 1
+ÂÂÂ - #size-cells : 0
+
+Optional properties:
+ÂÂÂ - enable-gpios : gpio pin to enable/disable the device.
+ÂÂÂ - vled-supply : LED supply
+
+Required child properties:
+ÂÂÂ - reg : Is the child node iteration.
+ÂÂÂ - led-sources : LP5024 - 0 - 7
+ÂÂÂÂÂÂÂÂÂÂÂ LP5018 - 0 - 5
+ÂÂÂÂÂÂÂÂÂÂÂ Declares the LED string or strings that the child node
+ÂÂÂÂÂÂÂÂÂÂÂ will control.Â If ti,control-bank is set then this
+ÂÂÂÂÂÂÂÂÂÂÂ property will contain multiple LED IDs.
+
+Optional child properties:
+ÂÂÂ - label : see Documentation/devicetree/bindings/leds/common.txt
+ÂÂÂ - linux,default-trigger :
+ÂÂÂÂÂÂ see Documentation/devicetree/bindings/leds/common.txt
+ÂÂÂ - ti,control-bank : Indicates that the LED strings declared in the
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ led-sources property are grouped within a control
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ bank for brightness and mixing control.
+
+Example:
+
+led-controller@28 {
+ÂÂÂ compatible = "ti,lp5024";
+ÂÂÂ reg = <0x28>;
+ÂÂÂ #address-cells = <1>;
+ÂÂÂ #size-cells = <0>;
+
+ÂÂÂ enable-gpios = <&gpio1 28 GPIO_ACTIVE_HIGH>;
+ÂÂÂ vled-supply = <&vbatt>;
+
+ÂÂÂ led@0 {
+ÂÂÂÂÂÂÂ reg = <0>;
+ÂÂÂÂÂÂÂ led-sources = <1>;
+ÂÂÂ };
+
+ÂÂÂ led@1 {
+ÂÂÂÂÂÂÂ reg = <1>;
+ÂÂÂÂÂÂÂ led-sources = <0 6>;
+ÂÂÂÂÂÂÂ 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.Â 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.Â 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:Â 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.Â 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.Â But there will be no mapping of the sources to the output that is done
in the hardware.Â 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:Â 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.Â We have no control of that.Â 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.Â There would need to be an algorithim
that translates these output to the correct LEDx register and CONFIG0 bits.Â 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.Â 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.Â 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.Â 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.Â 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.Â So identifying each output in the led-sources is
misleading as the hardware does this all on the chip.Â 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

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

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.

--
Best regards,
Jacek Anaszewski

Next message: Kirill A. Shutemov: "Re: [RFC PATCH] mm: align anon mmap for THP"
Previous message: Vince Weaver: "Re: perf: rdpmc bug when viewing all procs on remote cpu"
In reply to: Dan Murphy: "Re: [PATCH 1/2] dt: bindings: lp5024: Introduce the lp5024 and lp5018 RGB driver"
Next in thread: Dan Murphy: "Re: [PATCH 1/2] dt: bindings: lp5024: Introduce the lp5024 and lp5018 RGB driver"
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