No signal on HDMI monitor after powercycling the monitor

We are using TX2 dev board with the latest L4T28.1 kernel and having an issue with portable HDMI monitor (GeChic On-Lap 1303). This is a low power 1080p monitor that gets its power from USB, so I’m plugging it to TX2 dev board with both HDMI and USB 2.0 cables.
When the monitor is ON before TX2 boots up, everything works as expected. Also, it works fine if I disconnect the HDMI cable and then re-connect it back. However if I disconnect the USB cable that powers up the monitor and then re-connect it back to dev board (essentially power cycling the monitor while TX2 is up and running), then I’m not getting anything displayed on the monitor anymore. I have to reboot TX2 to get it working again. This is very annoying and I’m looking for any help on how to troubleshoot and fix this issue.

Here’s the EDID:

root@tx2:~# cat /sys/kernel/debug/tegradc.0/edid
 00 ff ff ff ff ff ff 00 1c a3 14 00 88 88 00 00
 00 19 01 03 80 1e 11 78 ee cd 70 a3 57 4e 9d 26
 11 50 54 21 08 00 71 40 81 00 81 80 81 c0 01 c1
 95 00 b3 00 d1 c0 e8 35 80 a0 70 38 1f 40 30 20
 25 00 25 a5 10 00 00 1a 00 00 00 ff 00 38 38 38
 38 0a 20 20 20 20 20 20 20 20 00 00 00 fc 00 4f
 6e 6c 61 70 31 33 30 33 0a 20 20 20 00 00 00 fd
 00 38 4c 1e 53 17 00 0a 20 20 20 20 20 20 01 2b
 02 03 1a 71 47 10 03 14 05 13 84 12 23 09 07 07
 83 01 00 00 65 03 0c 00 10 00 8c 0a d0 90 20 40
 31 20 0c 40 55 00 36 d4 31 00 00 18 01 1d 80 18
 71 1c 16 20 58 2c 25 00 36 d4 31 00 00 9e 01 1d
 80 d0 72 1c 16 20 10 2c 25 80 36 d4 31 00 00 9e
 01 1d 00 bc 52 d0 1e 20 b8 28 55 40 36 d4 31 00
 00 1e f3 39 80 18 71 38 2d 40 58 2c 45 00 c4 8e
 21 00 00 1e 00 00 00 00 00 00 00 00 00 00 00 54
root@tx2:~# 

root@tx2:~#  get-edid | parse-edid
This is read-edid version 3.0.2. Prepare for some fun.
Attempting to use i2c interface
No EDID on bus 0
No EDID on bus 1
No EDID on bus 2
No EDID on bus 3
No EDID on bus 4
No EDID on bus 5
No EDID on bus 6
No EDID on bus 8
1 potential busses found: 7
Bus 7 doesn't really have an EDID...
Couldn't find an accessible EDID on this computer.
I'm sorry nothing was successful. Maybe try some other arguments
if you played with them, or send an email to Matthew Kern <pyrophobicman@gmail.com>.
Partial Read... Try again
root@tx2:~#

Here’s the output from kern.log and Xorg.0.log files:

Disconnecting HDMI cable:
====================

/var/log/kern.log

Dec  6 10:00:57 tx2 kernel: [  203.070818] PD DISP2 index4 DOWN
Dec  6 10:00:57 tx2 kernel: [  203.074321] PD DISP1 index3 DOWN
Dec  6 10:00:57 tx2 kernel: [  203.077701] PD DISP0 index2 DOWN
Dec  6 10:00:57 tx2 kernel: [  203.082026] tegradc 15210000.nvdisplay: hdmi: unplugged


/var/log/Xorg.0.log

[   203.074] (II) NVIDIA(0): Setting mode "DFP-0:nvidia-auto-select"
[   203.110] (EE) NVIDIA(0): Failed to set the display configuration.



Re-connecting HDMI cable:
====================

/var/log/kern.log

Dec  6 10:02:38 tx2 kernel: [  304.023484] PD DISP0 index2 UP
Dec  6 10:02:38 tx2 kernel: [  304.028210] PD DISP1 index3 UP
Dec  6 10:02:38 tx2 kernel: [  304.031592] PD DISP2 index4 UP
Dec  6 10:02:38 tx2 kernel: [  304.035747] PD DISP2 index4 DOWN
Dec  6 10:02:38 tx2 kernel: [  304.039362] PD DISP1 index3 DOWN
Dec  6 10:02:38 tx2 kernel: [  304.042864] PD DISP0 index2 DOWN
Dec  6 10:02:38 tx2 kernel: [  304.062231] PD DISP0 index2 UP
Dec  6 10:02:38 tx2 kernel: [  304.066894] PD DISP1 index3 UP
Dec  6 10:02:38 tx2 kernel: [  304.070161] PD DISP2 index4 UP
Dec  6 10:02:38 tx2 kernel: [  304.074071] PD DISP2 index4 DOWN
Dec  6 10:02:38 tx2 kernel: [  304.077909] PD DISP1 index3 DOWN
Dec  6 10:02:38 tx2 kernel: [  304.081453] PD DISP0 index2 DOWN
Dec  6 10:02:38 tx2 kernel: [  304.100335] tegradc 15210000.nvdisplay: hdmi: plugged
Dec  6 10:02:39 tx2 kernel: [  304.109993] PD DISP0 index2 UP
Dec  6 10:02:39 tx2 kernel: [  304.111636] PD DISP1 index3 UP
Dec  6 10:02:39 tx2 kernel: [  304.111776] PD DISP2 index4 UP
Dec  6 10:02:39 tx2 kernel: [  304.115639] Parent Clock set for DC plld2
Dec  6 10:02:39 tx2 kernel: [  304.119757] tegradc 15210000.nvdisplay: hdmi: pclk:138652K, set prod-setting:prod_c_150M

/var/log/Xorg.0.log

[   304.095] (--) NVIDIA(GPU-0): GEC Onlap1303 (DFP-0): connected
[   304.095] (--) NVIDIA(GPU-0): GEC Onlap1303 (DFP-0): External TMDS
[   304.099] (II) NVIDIA(0): Setting mode "DFP-0:nvidia-auto-select"

Let me know if you need any additional info. Thank you for any hints/suggestions!

-albertr

Ok, I guess I’ve pulled the trigger too soon. Was playing with connecting/disconnecting it to different USB ports and using different USB cables, and traced the issue down to my cheap USB 2.0 HUB. Without this HUB in line, everything works as expected, so I’ll try to replace it.

-albertr

Replaced the HUB with a different model/brand and it’s all good now.

-albertr