HDMI not working if HDMI is not connected at boot time on Odroid xu4

[Michael Schuh]

If I boot my Odroid XU4 without the HDMI cable connected, my HDMI display does not work.  If I boot with the HDMI cable and monitor connected, the HDMI display works fine even if it is disconnected and reconnected.

 

I am running debian buster.

    deb http://deb.debian.org/debian buster main contrib non-free   
 

I have compared the dmesg output from when HDMI works and does not work and do not see a difference.  In case it helps, here are all of the dmesg lines with HDMI in them.

 

root@odroidxu4:~# grep -i hdmi dmesg_hdmi_works_usb_hdmi_plugged_in_at_boot.txt 
[    0.000000] Kernel command line: console=ttySAC2,115200n8 console=tty1 consoleblank=0 loglevel=1 root=UUID=494e7783-a94f-45f7-940d-e0ce44ea1455 rootfstype=ext4 rootwait rw  smsc95xx.macaddr=00:1e:06:61:7a:55 governor=performance hdmi_tx_amp_lvl=31 hdmi_tx_lvl_ch0=3 hdmi_tx_lvl_ch1=3 hdmi_tx_lvl_ch2=3 hdmi_tx_emp_lvl=6 hdmi_clk_amp_lvl=31 hdmi_tx_res=0 HPD=true vout=hdmi usb-storage.quirks= 
[    0.000000] hdmi: using HDMI mode
[    4.735974] OF: graph: no port node found in /soc/hdmi@14530000
[    4.737200] exynos-drm exynos-drm: bound 14530000.hdmi (ops 0xc0cb31ac)
 

I read some other posts that talked about HDMI not working if a USB device was not connected.  For both of the attached dmesg output files, the USB keyboard and mouse were connected.  In dmesg_hdmi_works_usb_hdmi_plugged_in_at_boot.txt, the HDMI display was plugged in at boot time and works and in dmesg_hdmi_fails_usb_plugged_in_at_boot_no_hdmi_at_boot.txt, the HDMI display was not plugged in at boot time and does not work after it is plugged in.

 

Has anyone seen this behavior and, if so, do you know how to configure the Odriod to boot without the HDMI cable attached and have an HDMI display work after it is attached later?

 

Thanks,

   Michael