HDMI Output in i.MX 8QuadMax

[crrm]

Hello everyone,

I'm trying to get output via HDMI on a i.MX 8QuadMax but so far without any success. I've already followed the steps described here Getting an HDMI output on IMX8QMLPDDR4ARM2 for a similar problem and used two different monitors for the test: a PC monitor and a TV monitor.

The configurations I'm using are the following:

DISTRO=fsl-imx-xwayland

Yocto project image: fsl-image-qt5-validation-imx

Moreover, I tried already setting the bootargs in uboot as follows:

u-boot -> setenv mmcargs 'setenv bootargs console=${console} root=${mmcroot} video=HDMI-A-1:3840x2160-32@30'

Other errors that I noticed during boot which I'm not sure if they are indicators of other possible issues related to this problem:

During boot the following message shows up:

[FAILED] Failed to start Terminate Psplash Boot Screen.

and in dmesg:

[    2.429971] [drm] Cannot find any crtc or sizes
[    2.435001] [drm] Initialized imx-drm 1.0.0 20120507 for display-subsystem on minor 0

In addition, as this board has 8 LVDS outputs I'm not sure if I'm using the correct one. Should I use a specific one or can I plug the HDMI in any LVDS plug (obviously using the adapter)?

Can someone help me on this?

P.S. If needed I can provide more information (boot output,  uboot args, ...).

[praveenvemula]

Hello,

Is there dtb file to enable 3 displays - HDMI, LVDS-0, LVDS-1 and connect to different applications ?

Regards,

Praveen

[AldoG]

Hello,

May I ask which kernel and uboot version are you using?

Which dts are you using for your test?

As for LVDS plug, you may connect the LVDS-to-HDMI daughter card to J2/J3/J7/J8 with the Mini SAS cable.

It may be usefull if you can add your uboot log (boot output)

Thank you,

Best regards,

Aldo.

[crrm]

Hello Aldo,

Thank you very much for your reply. Here are the answers to your questions:

- Linux kernel version: Linux imx8qmmek 4.19.35-imx-4.19.35-1.0.0+ge4452f4 #1 SMP PREEMPT Thu May 14 18:09:21 UTC 2020 aarch64 aarch64 aarch64 GNU/Linux

- Uboot version: U-Boot 2019.04-imx_v2019.04_4.19.35_1.0.0+g85bdcc7 (May 15 2020 - 10:08:20 +0000)

- dts: fdt_file=fsl-imx8qm-mek-hdmi.dtb

- LVDS Plug: I have the Mini SAS Cable connected to J2 and LVDS to HDMI adapter card (green and red lights are on once Linux boots).

As of now, when I connect the board to the HDMI screen and play some video using gst-play or some graphical demo, I get no output on the HDMI screen (the screen remains on standby). Any ideas or suggestions to get this working properly?

Thank you in advance.

[AldoG · Accepted solution]

Hello,

Thank you for the information, I see that you're using the DTB for native HDMI, for LVDS you'll need to change it

fsl-imx8qm-mek-hdmi.dtb -> fsl-imx8qm-mek.dtb, you'll find this file in the FAT partition if you flashed the .wic

To do this you need to do the following:

Step 1: Power on the board and press any key to stop the boot process at U-boot.

Step 2: Type the following command to modify the default DTB

=>setenv fdt_file fsl-imx8qm-mek.dtb

Step 3: Save the environment variable by typing the command below

=> saveenv

Step 4: Boot the Linux Kernel by resetting the board or typing the command below:

=> boot

Please note that based on which DTB file is chosen then correct number of IMX-LVDS-HDMI and IMX-MIPI-

HDMI cards has to be connected for the displays to come up.

From L4.19.35_1.1.0 i.MX_Linux_Release_Notes.pdf:

• fsl-imx8qm-mek.dtb: Supports the LVDS-HDMI or MIPI-DSI-HDMI display with the LVDS-HDMI or MIPI-DSI-HDMI converts. The detection is on-the-fly by using the device-tree overlay technology.

• fsl-imx8qm-mek-hdmi.dtb: Supports native HDMI TX interface on the CPU board.

• fsl-imx8qm-mek-jdi-wuxga-lvds1-panel.dtb: Supports the dual channel LVDS panel, connecting the two mini-SAS ports with the LVDS1 CH0 and LVDS1 CH1.

If you want to use the native HDMI to run a quick test you'll need to connect your HDMI cable to the HDMI TX (J6).

Hope this helps,

Best regards,

Aldo.

[crrm]

Hello Aldo,

Somehow I've missed the information from the Linux release notes document.

Now everything works as expected. Thank you very much for your help.

Regards,

Cláudio

[albfon]

Hello,

Thanks to this post I could test both (HDMI and LVDS-2-HDMI converter outputs) by changing the dtb file. Now my questions is, Would it be possible to have both outputs working at the same time? And to run different applications on each of them. On several discussions I've seen it is possible to have two  by using two LVDS-2-HDMI converters but I'm wondering if would it be possible to have them: 1 on the HDMI TX and the other in a LVDS-2-HDMI converter.

Regards