Trouble with USB hub in monitor

Q&A
1

I understand this is a special use case but bear with me!

Scene setting:

I have a Dell monitor with multiple inputs that includes a USB hub that dynamically changes based on the input source. My keyboard and mouse are connected to the monitor’s USB ports.

For the most part, the monitor is using the displayport on my Clear Linux desktop with a single USB cable connection between the desktop and the monitor.

From time to time, I connect my laptop to the same monitor via a USB-C connection. The keyboard and mouse now seamlessly connect to my laptop.

Problem:

It’s when switching back to the desktop (which I leave on and connected still via DP) that I start to run into troubles. If my session is still active, I have no trouble and I can continue to work seamlessly, but if the display is put to sleep either via a timeout or by locking the session, then the keyboard and mouse will not wake the display back up.

Troubleshooting

I suspect this might be a USB power saving setting that is giving me grief.

I tried the same scenario with Fedora on my desktop and did not experience this issue.

Note that I can bring the system back to life by pressing the power button on my desktop which suspends my whole system. I can then press the power button to resume the system which brings up the display and the keyboard and mouse are fully responsive.

Can anyone help me further troubleshoot this issue?

2

What monitor/model?

If your UEFI has as setting for disabling USB power save, try toggling that to see if it goes away as a quick test of your theory.

Is it possible that this is a DisplayPort “Deep Sleep” issue? I’ve seen a number of DP monitors that don’t wake up from deep sleep gracefully. It’s…annoying.

1 Like
3

This doesn’t happen to me often, but as you mentioned I want also describe my experience.

I also have a Dell monitor which connects to my workstation via HDMI port.

My keyboard is connected to the USB hub on the monitor.

My mouse is from Logitech and half of the time it’s connected to my workstation via a unifying receiver, who is connected to the USB hub of my Dell monitor. But sometimes it’s connected to the USB hub of my keyboard when I’m charging it.

Sometimes after waking up from suspension, my mouse is working, but the keyboard is not. While sometimes neither of them work and I have to press the power button to wake from the suspension.

4

Thanks for the idea, but no, it’s definitely a USB issue.

I’ve performed some additional troubleshooting and learnt the following by tailing dmesg and doing a watch lsusb:

  • If I unplug the USB hub from my USB port, I can see the hub and all USB devices disconnect immediately.
  • If I then plug the hub back in, absolutely nothing happens - the kernel doesn’t log anything and the devices do not re-appear

I have just learnt that the above occurs in my USB 3.0 ports only. If I use my USB 2.0 ports it works as expected (ie. the hub and all connected devices are detected immediately when plugging the hub cable back in)