Re: [PATCH v5 1/2] dt: bindings: lm3601x: Introduce the lm3601x driver
From: Jacek Anaszewski
Date: Mon May 14 2018 - 16:49:54 EST
Dan,
On 05/14/2018 10:07 PM, Dan Murphy wrote:
Jacek
On 05/11/2018 03:27 PM, Jacek Anaszewski wrote:
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.
I have looked at these functions and the parse dt function that dictates if there is 1 fled or 2 fled.
I am having trouble associating what these mean because the led-sources is being used to define how many LEDs.
In the common.txt it says
"- 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."
I cannot find the max77693 dt documentation or even a dt file that defines what the led-sources could be defined as.
In addition, per the common.txt, the led sources should define the current outputs the LED is connected to.
You can find more details in
Documentation/devicetree/bindings/mfd/max77693.txt.
Generally the led-sources property was introduced to solve this
particular case when there are two IOUTS that can have connected
two LEDs or a single LED which allows to feed it with greater current.
Is one to assume that it is referring to the physical current pin connection or the devices internal current routing?
When I first referenced this driver as template driver it was misleading to say fled1 and fled2 as I took it to mean, and I still do, that the
driver supports 2 LED connections and not a single output pin with different internal current routing.
Without the data sheet or the dt documentation it makes understanding a little difficult.
There are more straightforward LED flash class drivers, e.g.
drivers/leds/leds-aat1290, you can refer to.
I will fix it up how ever you would like it to be but I am thinking we need to fix up the max77693 as well so we can have 2 reference
drivers.
There is also drivers/leds/leds-as3645a.c and one greybus driver.
So we have in fact four LED flash class drivers in the tree :-)
It is very difficult to derive the driver without a public version of the data sheet.
I agree, but mfd documentation I pointed should be enough to
increase your comprehension of the subject, I hope. If not, then
we can extend it basing on your remarks and my memory.
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