Adding support for DP to LVDS bridge

Hi @WayneWWW
We are designing a custom carrier board with Xavier AGX module and we are planning to add 1280x768 LVDS display. The LVDS display is connected to Xavier AGX eDP port via an eDP-to-LVDS bridge (PS8625).

The LVDS display does not contain a EDID EEPROM, hence we have used a seperate edid eeprom connected to the bridge. I have flashed the EDID EEPROM and i am able to detect the display with the given resolution in the system settings.

But the display is up only for a half of a second and after that it goes blank(Still it is shown as connected in the system settings).I have attached the dmesg log.
dabnotworking.txt (4.9 KB)

To note there is no ddc connection to/from the display.

Can you point out what can be the issue? Do i have to make any changes in the driver since there is no ddc channel for communication from the display.


Are you saying that no connection was wired in, or that the connection is there, but fails? There is no way to get the EDID without that wire. If this has been wired in, then often such a failure would be a device tree issue. A contrived example is that perhaps a power rail is down which is required to power the device on the DDC, or perhaps an i2c device is not properly set up (the EDID is read on the DDC wire via i2c protocol). I am not particularly good at suggesting custom wiring device tree settings, but you’ll want to clarify the nature of the “no ddc” meaning.

Also, if this display has a connector and is not hard-wired, then this should be a “hot plug” device, and unplug/replug might trigger something useful in the logs.

I think i didnt explain it correctly.
The ddc channels are connected to a seperate EEPROM where I have flshed the EDID details.

But i am still getting those errors

On a “normal” HDMI the i2c components of the monitor are actually powered by the GPU card’s cable, so perhaps the error is related to something more needing to be designed in when the EEPROM substitutes for an actual DDC wire (I’m just speculating, e.g., perhaps i2c addressing is incorrect for the use of the EEPROM).

Also, for the EDID you have in the EEPROM, does it validate here:

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