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I am seeing the following message in the Linux kernel log:

usb usb1-port5: disabled by hub (EMI?), re-enabling...

After that USB devices are disconnected. In some cases they reconnect immediately, in other cases they don't. In the latter cases, I also see:

usb usb1-port5: Cannot enable. Maybe the USB cable is bad?

What causes these issues and how to avoid the bad effects?

In this particular case, a wireless USB stick is connected directly to a USB port. The issue does not correlate to a particular time of day. Using a different USB port makes no difference. Using a different wireless USB stick makes no difference. Using a different mainboard makes a difference. Disconnecting other USB devices makes no difference.

Even though presenting details here, answer can and should try to cover more settings to be useful to others.

Ola Ström
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Helmut Grohne
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    Had this issue on a [Raspberry Pi Zero](https://www.raspberrypi.com/products/raspberry-pi-zero/) (no wifi), where Linux' USB stack [detected potential interference and re-enabled the USB ports](https://github.com/torvalds/linux/blob/53ab78cd6d5aba25575a7cfb95729336ba9497d8/drivers/usb/core/hub.c#L5571-L5580) automatically every couple of hours. Solved this by unplugging and reconnecting _all_ cables, including extension cables and adapters. Some (USB) cable _may_ have been bad, but it may also just have been badly connected after moving the tiny rpi0 around. – Joel Purra Mar 04 '22 at 10:00

1 Answers1

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I don't understand why. Physically moving the wireless USB stick from the mainboard by connecting it to an external USB hub connected with a 2 meter cable made the disconnect problems go away.

Helmut Grohne
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    Then you need to trace your EMI source... microwave, TV, other wifi in the area... – Tetsujin Sep 29 '17 at 19:07
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    Please don't add more information as an answer, instead, edit your qeustion. – dirkt Sep 30 '17 at 07:46
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    I think this is a reasonable answer to the question "how can it be avoided" even though it lacks detail on why it works. Please add better answers rather than complaining about existing ones. – Helmut Grohne Sep 30 '17 at 08:13