How to use HDMI Custom EDID on XU4

First, you need to check all of videoconfig in boot.ini are blocked with comment character “#“
and HPD env is TRUE.

# -----------------------------------------------
# 1920x1080 (1080P) without monitor data using generic information (1080p-noedid)
# setenv videoconfig "drm_kms_helper.edid_firmware=edid/1920x1080.bin"
# -----------------------------------------------
.....
.....
# -----------------------------------------------
# 480x320 without monitor data using generic information
# setenv videoconfig "drm_kms_helper.edid_firmware=edid/480x320.bin"
# -----------------------------------------------

#------------------------------------------------------------------------------
#
# HDMI Hot Plug detection
#
#------------------------------------------------------------------------------
setenv HPD "true"

Then, make sure to reboot your XU4.

$ sudo reboot

Now, you can read the monitor's EDID from the following node.

/sys/class/drm/card0/card0-HDMI-A-1/edid

Copy the edid binary into /lib/firmware/ directory.

$ cat /sys/class/drm/card0/card0-HDMI-A-1/edid > /lib/firmware/custom_edid.bin

Or, if you have custom edid binary that you want to use, copy it into the same directory.

Add the edid binary name in boot.ini with drm_kms_helper_parameter.

setenv videoconfig "drm_kms_helper.edid_firmware=custom_edid.bin"

setenv HPD "false"

Then, reboot.

$ sudo reboot

Now the edid is running and you can check it with these nodes.

$ cat /sys/module/drm_kms_helper/parameters/edid_firmware 
custom_edid.bin

And the display mode list from the edid is shown here.

$ cat /sys/class/drm/card0-HDMI-A-1/modes