imx93EVK Yocto Backlight 12V supply

[aditya_h]

I am trying to setup Display with LVDS which uses 12V supply for backlight. I am using linux-imx-6.1.36. 12V supply is not enabled by default. How to enable it.

[AldoG]

Hello,

This is done on the hardware side, please make sure you have the correct settings for J703.
 

Used for the LVDS LCD backlight power source selection through 2.0 mm

jumper.

• Pin 1-2 shorted: BLT_VCC connects with VDD_5V power supply

• Pin 2-3 shorted: BLT_VCC connects with VDD_12V power supply (default

setting)

Also, note that J704, J705 are used for LVDS LCD power source selection through 2.0 mm jumper. LVDS_VCC connect with VDD_3V3 by default.

Best regards/Saludos,
Aldo.

[aditya_h]

Hi @AldoG thanks for the reply.

The PIN is selected properly. When I cross checked the schematics and the voltage on the board I found

EXT2_PWREN and LVDS_BLT_EN signals from IO expandars needs to be enabled. Refer below image. 

I enabled EXT2_PWREN by setting regulator-always-on; for reg_vdd_12v: regulator-vdd-12v { } in imx93-11x11-evk.dts file.

But LVDS_BLT_EN is not getting enabled by this. I could manually enable this by gpioset -c 5 8=1 in the terminal, which gets turned off after restart. What modification needed in dts file to set this IO?

[AldoG]

Hello,

I have run some test on my side to try to enable this, unfortunately I do not have an LVDS display to test it out so please help on confirmation from your side.

You first change looks correct, nice catch!

For the second thing, you may try adding the following node to your device tree:
   reg_lvds_en: regulator-lvds-en {
                compatible = "regulator-fixed";
                regulator-name = "lvds-en";
                regulator-min-microvolt = <3300000>;
                regulator-max-microvolt = <3300000>;
                gpio = <&adp5585gpio 8 GPIO_ACTIVE_HIGH>;
                enable-active-high;
                regulator-always-on;
        };

After adding this I see that the GPIO goes high correctly:

Even checked with a multimeter and it shows 3.3V correctly, please try it and let me know if this does help.

Best regards/Saludos,
Aldo.

[aditya_h]

Hi @AldoG,

The solution you suggested worked!! Thank you!

I have small doubt, While exploring on the same thing I had made some changes in imx93-11x11-evk-boe-wxga-lvds-panel.dts. I was trying to set gpio using gpio-hog. This approach was not working. What goes wrong with this approach?

&adp5585gpio {
   gpio-hog-adp5585 {
   gpio-hog;
   gpios = <8 GPIO_ACTIVE_HIGH>;
   output-high;
  };
 };

[AldoG]

Hello,

Glad to hear that it worked, regarding your last question it seems that the driver for the expander does not support this, unfortunately there is not much information about the bindings for this IC, so I would suggest to use the one above.

Best regards/Saludos.
Aldo.