Help with iMX8X DSI to HDMI in standalone setup

I have an iMX8X DSDI to HDMI adapter based on the Lontium bridge adapter. I am attempting to use it to connect a MIPI source (black box) to an external display. I have read from multiple sources that it is near impossible to get a datasheet from Lontium regarding the comms table for the LT8912B without and NDA and jumping through hoops.

However, I was able to find the Linux Kernel source from the Toradex repo:
root/drivers/gpu/drm/bridge/lt8912.c

I would like to port this driver to my system to initialize and configure the LT8912 via the I2C bus. However, I’m having trouble understanding how the config info is formatted by the Linux kernel.

	hactive = mode->hdisplay;
	hfp = mode->hsync_start - mode->hdisplay;
	hsync = mode->hsync_end - mode->hsync_start;
	hbp = mode->htotal - mode->hsync_end;
	vfp = mode->vsync_start - mode->vdisplay;
	vsync = mode->vsync_end - mode->vsync_start;
	vbp = mode->vtotal - mode->vsync_end;
	htotal = mode->htotal;
	vtotal = mode->vtotal;

where mode is type drm_display_mode (from line 56).

What I’m struggling to understand is how the data is formatted. What units are they in? What is their type/size? Is it something I can calculate from my timings without needing to reverse engineer more of the OS?

Maybe there is something else I need to understand about the initialization scheme for this mysterious chip. I’m hoping I can treat these functions as black boxes and run with with different timing configurations until I see something at the output.

Thanks in advance :slight_smile:

Hey @jrm.mendel,

A few questions to help us understand the situation.

What module and carrier board are you using?
Can you share what OS/BSP you are using?

  • Eric

Hi Eric,

Currently, we are not using a Toradex carrier board-- just attempting to use the bridge adapter to interface with another system (assume it is a black box) to get display output via HDMI. Unfortunately I don’t know enough about the Linux display drivers to take the next steps of configuring the bridge adapter as mentioned in the original post.

Thanks

Hey @jrm.mendel,

The adapter is designed to work with the Colibri modules, unfortunately we won’t be able to help much with other systems. What you might be able to do is look towards the creator of the the driver for specifics.

-Eric