Powered USB hub not recognised after latest lubuntu 20.04 update

Hi All,
Since the latest kernel update to 5.4.0-121-generic, my powered usb hub is no longer recognized by the system. The hub is missing from the device list created by lsusb.
This is similar to my experience with a MacBook pro, which started getting sniffy about usb hubs awhile back with the MacOS Monterey update.
Any advice on how to boot it into action without rolling the kernel back?
I’m running Lubuntu 20.04.4 LTS.

thanks
Peter

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Hi,

From the grub menu at reboot please pick an older kernel to confirm older kernel works. Before we check any more details you should make sure the USB device is not broken or just my guess that connection cord or USB connector is loose. lsusb should see the device. MacOS has nothing to do with Lubuntu so that is just a coincidence but does seem to imply the USB device or USB connection is not stable.

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Hi thanks very much for your reply.
I tested with reverting the kernel back to 5.4.0-52 and the problem still existed. The earliest kernel on the grub menu (5.4.0-48) wouldn’t load. I’ve tested with another known good USB hub and experienced the same problems. Sometimes when I boot from power down, the USB hub is actually recognized and works normally, but it is a very random event.

“…Sometimes when I boot from power down, the USB hub is actually recognized and works normally, but it is a very random event.”

That is likely the key to your problem. Linux in general over the years tends to have driver issues caused by hibernations and sleep. They also tend to come and go with new kernel and or driver releases. This has been the case for decades and is really not much better even now.

It is just a very hard to find/test power management issues because new hardware is always having more odd unique cases.

I’ll be honest and post what many will not like but I avoid ALL power management on Linux. It makes Linux so much better! Some do rmmod the driver module and restart it via scripts but that is a bit complicated for any users not used to writing their own scripts. I did do this about decade ago when I only used Linux as my desktop/laptop. Now I use Windows and ChromeOS for laptop/personal desktop and printer use. I use Linux for server / NAS / tinkering / code development and code testing.

Try only booting Linux from a complete power down. Count to 30 and then power up. Likely this will solve your issue. Your Linux desktop experience will be so much better.

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yeh, I have a script that resets my usb 3.0 port for an external drive.
The horrible part is figuring out the port ID. I only ever have one drive connected to usb 3.0, so it’s easy for the script.

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Yea you always have to dig into some hardware/driver details to correctly reload kernel drivers. A decade or so ago I used Linux (Red Hat derivative) on ThinkPad T520. I remember I was able to get all the power management to work pretty good but it involved rmmod , modprobe over half dozen or so drivers and even had put some strategically placed sleeps to prevent timeouts. It was such a hack.

Then I upgraded my kernel and I had to debug my hibernation/sleep scripts with some new parameters and slightly adjusted sleeps. Argh!!! It really was horrible but I was involved in some of device driver debug for some embedded work back then. The power management special cases were such a hit and miss mess.

I do believe power management is a bit better now but there are always odd corner cases to specific hardware which can leave a new Linux user with a very bad impression of Linux.