Re: [PATCH v5 1/2] dt: bindings: lm3601x: Introduce the lm3601x driver

[Jacek Anaszewski]

Dan,

On 05/11/2018 02:12 PM, Dan Murphy wrote:
> Jacek
>
> Thanks for the review
>
> On 05/10/2018 03:17 PM, Jacek Anaszewski wrote:
> > Hi Dan,
> >
> > On 05/10/2018 09:10 PM, Dan Murphy wrote:
> > > On 05/10/2018 02:06 PM, Dan Murphy wrote:
> > > > Pavel
> > > >
> > > > On 05/10/2018 01:54 PM, Pavel Machek wrote:
> > > > > Hi!
> > > > >
> > > > > > Introduce the device tree bindings for the lm3601x
> > > > > > family of LED torch, flash and IR drivers.
> > > > > >
> > > > > > Signed-off-by: Dan Murphy <dmurphy@xxxxxx>
> > > > >
> > > > > Better, thanks.
> > > > > > +++ b/Documentation/devicetree/bindings/leds/leds-lm3601x.txt
> > > > > > @@ -0,0 +1,50 @@
> > > > > > +* Texas Instruments - lm3601x Single-LED Flash Driver
> > > > >
> > > > > Ok, so is it single-LED driver, or can it driver ir & white LEDs at
> > > > > the same time?
> > > >
> > > > It is a single LED driver.  It can drive a Torch white LED or IR LED indefinitely or if the driver
> > > > is programmed to strobe mode the driver will drive the configured LED for the flash timeout specified.
> > > >
> > > > Basically a flash and a flash light. IR or White LED.
> > > >
> > > >
> > > > > > +Example:
> > > > > > +led-controller@64 {
> > > > > > +    compatible = "ti,lm36010";
> > > > > > +    #address-cells = <1>;
> > > > > > +    #size-cells = <0>;
> > > > > > +    reg = <0x64>;
> > > > > > +
> > > > > > +    led@0 {
> > > > > > +        reg = <0>;
> > > > > > +        label = "white:torch";
> > > > > > +        led-max-microamp = <10000>;
> > > > > > +    };
> > > > > > +
> > > > > > +    led@1 {
> > > > > > +        reg = <1>;
> > > > > > +        label = "white:flash";
> > > > > > +        flash-max-microamp = <10000>;
> > > > > > +        flash-max-timeout-us = <800>;
> > > > > > +    };
> > > > >
> > > > > Is this realistic config? I'd expect flash to use more power than
> > > > > torch, and would expect longer timeout than 0.8msec.
> > > >
> > > > Timeout in the spreadsheet is ms I will update this example and code
> > > > Current in the spreadsheet is mA I will update this example and code
> > > >
> > > > > Also.. if this is physically one white LED, it should not be
> > > > > spread over reg = <0> and reg = <1>...
> > > >
> > > > If the torch LED and strobe LED are the same LED how do I expose them both to the user.
> > > > It is up to consumer to configure the required interfaces they want to expose to the filesystem.
> >
> > LED flash class interface is prepared for it.
> > led_clasdev_flash_register() internally calls led_classdev_register(),
> > so there is brightness file available for torch related operations.
>
> Yes the flash class may handle this and expose the brightness node but the HW has two different registers to set the
> corresponding brightness so one set brightness node does not work.
> There is no way to differentiate between the strobe brightness (register 4) and the torch brightness (register 3).

Hmm? There is brightness file (with brightness_set{_blocking} op) from
LED class and flash_brightness file (with flash_brightness_set op) from
LED class flash.

I've only now realized that you're not using flash_brightness_set op for
the "strobe_node" in your driver. I assume that you overlooked it.
Please don't introduce "strobe_brightness" naming convention - we
already have "flash_brightness" for that.

> When the enable register is written the driver will read the corresponding register and set
> the current for the LED.
>
> This is why I separated out the strobe from the torch into 2 different LED nodes.
>
> I cannot seem to find the data sheet on line for the max77693 so I cannot verify that the device only has
> a single brightness register for both torch and strobe.

It wasn't openly available at least at the time when I had an access
to it.

But - please look at the functions max77693_set_torch_current() and
max77693_set_flash_current(). The device has separate registers
for torch and flash brightnesses.

> > > > Maybe they don't want the strobe feature and just want LED on/off and switch between IR and White.
> > > >
> > > > The IR is driven via a different output pin.
> > >
> > > Correction.  There is only one LED drive pin.  The mode selected determines how the device will drive the
> > > LED.  So you may have one device to drive a Torch and another device to drive the LED.
> >
> > But only one type of LED can be soldered on the board at a time, right?
> > If yes, then this is clearly a DT related configuration, and only
> > one child DT node should be defined for given board.
>
> But see above.  There is not a clean way to expose the torch/ir and strobe separately.
>
> Dan
>
>
> > > Strobe is available in either case but not always required if strobe is not desired by the customer hence
> > > why I have a separate DT node for it.
> > >
> > > Dan
> > >
> > > > Dan
> > > >
> > > > > Best regards,
> > > > >                                      Pavel

--
Best regards,
Jacek Anaszewski