#Print out display kernel related message
dmesg |grep tegradc
#Print current mode in dc
sudo cat /sys/kernel/debug/tegradc.X/mode #X=0,1,2.
#Print current mode in fbcon
sudo cat /sys/class/graphics/fb0/mode #if more than one fb, just change the fbX to whatever you want.
#Capture edid
sudo cat /sys/kernel/debug/tegradc.X/edid #X=0,1,2.
Since you cannot boot up, please boot up device first without hdmi connection, then hotplug hdmi.
We’re ok for now, but I’ll outline what we ended up doing.
a) I applied the patch provided by WayneWWW found here,
it prevented the boot hangup.
b) The monitor vendor suggested that we replace the edid in the monitor
with a known good edid. We got an adapter/emulator that let us do this
and now the nvidia video system and x driver can see the modes (i.e xrandr --verbose)
shows all the modes. Not sure I agreed with this but we were in a hurry.
c) The problem was made more complex because I believe we have some marginal
wiring or cabling. The monitor is now solid on lower resolutions, but erratic
on higher resolutions.
d) I did attempt to move to the 28.2 release. There wasn’t any hang at boot but
the resolution was stuck on very low (vga) resolution, xrandr didn’t show any
other resolutions, so we gave up on that approach for now.
I did capture the EDID information for the monitor that was giving us problems.
If you want to explore this again you may want to add this to the Section “Device” of “/etc/X11/xorg.conf”:
Option "ModeDebug"
…then reboot and get a copy of “/var/log/Xorg.0.log”. The driver will tell you all EDID modes it knows about and why the other EDID modes are rejected.