How to change DP0 to eDP

Hi ,

We had design carrier board with eDP for Nano (emmc).
The default HDMI (DP1) is work fine, so We would like to use eDP panel.
How to change DP0 to eDP and driver it?

Hi Karis,

DP interface is compatible with eDP. What is the problem you have here?
Could you share you hardware schematic of this part?

Hi WayneWWW,

We use two different eDP panel, but the screen is very dark, how to change it?

Hi WayneWWW,

I share our hardware schematic of edP part.
We are waiting for your confirmation.Thank you!



Hi Karis,

Sorry for late reply. We are still checking this part. Is the monitor working fine but just in very dark status?

Could you also share current dmesg with us?

Hi WayneWWW,

The monitor is no backlight. PNL_BL_EN、PNL_BL_PWM pins status are not high.
We tried to control the pins through commandline,but it’s not worked.
So we moved PNL_BL_EN、PNL_BL_PWM pins to other pins and pull high, the monitor was working fine.

Do you have any advice which pins for eDP backlight we can use ?
How to control backlight ? not just brightbacklight.Thanks!
dmesg.txt (79.5 KB)

Hi Karis,

Do you mean if you connect PNL_BL_EN and PNL_BL_PWM to some GPIO and pull it high, the monitor works fine w/o any issue?

Hi WayneWWW,

Yes,we connect those pins to other GPIO pins and pull high, the monitor is bright.

Hi Karis,

Could you share your whole step here for us to review?

Do you hog the gpio through device tree? or manually pull it up?

Could you also share the dmesg? edit: I saw it. Sorry to ask again.

BTW, I saw you have gk20a error. Please try to use latest pinmux spreadsheet which resolved this issue.

Hi WayneWWW,

We use three way to test,our step below

First

  1. We connected eDP PWM pin to GPIO7 PWM (206) and connected eDP enable pin GPIO09 AUD_MCLK (211).
  2. After flashed bsp ,I used command line to control this pins but it was not worked. commandline link below. https://devtalk.nvidia.com/default/topic/1020887/jetson-tx2/how-to-configure-a-gpio-on-tx2-/1

    Check two pins,those are low (pull down).

  3. We tried to modify dts and pull up this pins, but but it was not worked. Is should to modify u-boot.bin?

    The monitor backlight was still dark.

Second

  1. We connected eDP PWM pin to GPIO09 I2S0_FS (197) and connected eDP enable pin I2S0_DOUT (193) .
  2. After flashed bsp ,I used command line to control this pins ,and It was worked.
  3. Check the monitor, it backlight was bright.

Third

  1. We connected eDP PWM pin to GPIO14 (PWM) (230) and connected eDP enable pin I2S0_DOUT (193).
  2. After flashed bsp ,I used commandline to control this pins ,and It was worked.
  3. Check the monitor, it backlight was bright.
  4. We used commandline to control backlight commandline link below.

    https://devtalk.nvidia.com/default/topic/1047060/jetson-agx-xavier/fan-management-xavier/post/5313500/#5313500

    When we use different value,the monitor backlight is a little change.
    EX: echo 100, the backlight is dark than echo 255.

Is any advice to us?
We would like a way to control monitor’s backlight like control the fan speed.
Thank you!

I fix it. thank you!

Hi Karis,

Few questions here for you

  1. It sounds that you are only able to control the backlight through pwm in case 3, right?
  2. Do you refer to our OEM Design guide when making your own carrier board?
  3. What change did you do in case 1?

For the backlight control, I think the third case is the solution here. The display driver is not able to control the backlight directly and hence it should be done through the sysfs of pwm driver.

  1. Yes!
  2. We refer OEM Design guide to design our carrier board, Did we miss something?
  3. What you mean? We only modify dts. Before we modify the dts,the monitor is no backlight.
  1. Yes!
  1. We refer OEM Design guide to design our carrier board, Did we miss something?
    No, nothing is wrong. We just want to improve our OEM DG.
  1. What you mean? We only modify dts. Before we modify the dts,the monitor is no backlight.
    I am wondering why this does not get worked. This pin should be also pwm compatible. Need to know what you’ve change in dts.

Hi WayneWWW,

I will check again and give you a feeback. Thanks!

Hi WayneWWW,

I share our dts.
We are waiting for you update.Thanks!
dts.tar.gz (703 Bytes)

Hi Karis,

According to your previous comment, you should be able to change backlight through in case3.

When we use different value,the monitor backlight is a little change.
EX: echo 100, the backlight is dark than echo 255.

I think the only issue here is somehow the GPIO7 mentioned by design guide is not able to be a PWM pin. In your dts, the “nvidia,function” should always use lower case, so please not use “PWM0”.

You could also try to use our pinmux spreadsheet on download center to generate the correct pinmux dts.

If my understanding is not correct, please let me know your exact question.

Hi WayneWWW,

Sorry,It’s my mistake,I give you the wrong dts about gpio7.

It’s correct dts about gpio7 below,and I got dts by use pinmux spreadsheet.

lcd_bl_pwm_pv0 {
nvidia,pins = “lcd_bl_pwm_pv0”;
nvidia,function = “rsvd3”;
nvidia,pull = <TEGRA_PIN_PULL_UP>;
nvidia,tristate = <TEGRA_PIN_DISABLE>;
nvidia,enable-input = <TEGRA_PIN_DISABLE>;
};

I modify pinmux-config-p3450-porg.h and replace the u-boot.bin.
After flash bsp, the monitor’s backlight is bright.

So if I want to pull up the gpip, I need modify dts and uboot? Not just modify dts.